SOLID-STATE IMAGING DEVICE, METHOD FOR MANUFACTURING THE SAME, AND IMAGING APPARATUS
20170104024 ยท 2017-04-13
Inventors
- Tetsuji YAMAGUCHI (Kanagawa, JP)
- Yuko Ohgishi (Tokyo, JP)
- Takashi Ando (Kanagawa, JP)
- Harumi Ikeda (Kanagawa, JP)
Cpc classification
H10F39/806
ELECTRICITY
H10F39/011
ELECTRICITY
H10F39/18
ELECTRICITY
International classification
Abstract
Realization of an adequate hole accumulation layer and reduction in dark current are allowed to become mutually compatible. A solid-state imaging device 1 having a light-receiving portion 12 to photoelectrically convert incident light is characterized by including a film 21, which is disposed on a light-receiving surface 12s of the above-described light-receiving portion 12 and which lowers an interface state, and a film 22, which is disposed on the above-described film 21 to lower the interface state and which has a negative fixed charge, wherein a hole accumulation layer 23 is disposed on the light-receiving surface 12s side of the light-receiving portion 12.
Claims
1-19. (canceled)
20. A imaging device comprising a light receiving portion to photoelectrically convert incident light, including: a first insulating film disposed over a light receiving surface of the light receiving portion; a second insulating film disposed over the first insulating film; and a first film disposed between the first insulating film and the second insulating film, wherein the first film includes a material selected from the group consisting of a hafnium oxide, aluminum oxide, zirconium oxide, tantalum oxide, titanium oxide, lanthanum oxide, praseodymium oxide, cerium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide, hafnium nitride, aluminum nitride, hafnium oxide nitride, and aluminum oxide nitride.
21. The imaging device according to claim 20, wherein the first insulating film includes a material made of a silicon oxide.
22. The imaging device according to claim 21, further comprising: a light shield portion disposed over the second insulating film.
23. The imaging device according to claim 21, further comprising: a third insulating film disposed over the second insulting film.
24. The imaging device according to claim 21, further comprising: a color filter disposed over the second insulating film.
25. The imaging device according to claim 22, further comprising: a color filter disposed over the light shielding portion.
26. The imaging device according to claim 24, further comprising: a lens disposed over the color filter.
27. The imaging device according to claim 20, further comprising: a hole accumulation layer at the light-receiving surface side of the light receiving portion, the hole accumulation layer created due to the existence of the first film.
28. The imaging device according to claim 20, wherein the first film includes a material made of a hafnium oxide.
29. The imaging device according to claim 20, wherein a thickness of the first insulating film is less than 100 nm.
30. The imaging device according to claim 20, wherein a thickness of the first film is approximately 11 nm.
Description
BRIEF DESCRIPTION OF DRAWINGS
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BEST MODES FOR CARRYING OUT THE INVENTION
[0071] An embodiment (first example) of a solid-state imaging device (first solid-state imaging device) according to the present invention will be described with reference to a key portion configuration sectional view shown in
[0072] As shown in
[0073] In the case where the above-described solid-state imaging device 1 is a CMOS image sensor, examples of peripheral circuits of the above-described peripheral circuit portion 14 include pixel circuits composed of transistors, e.g., a transfer transistor, a reset transistor, an amplifying transistor, and a selection transistor. Furthermore, a drive circuit to effect an operation to read signals of lines to be read in a pixel array portion composed of a plurality of light-receiving portions 12, a vertical scanning circuit to transfer the signals read, a shift register or an address decoder, a horizontal scanning circuit, and the like are included.
[0074] Alternatively, in the case where the above-described solid-state imaging device 1 is a CCD image sensor, examples of peripheral circuits of the above-described peripheral circuit portion 14 include a read gate, which reads photoelectrically converted signal charges from the light-receiving portion to a vertical transfer gate, and a vertical charge transfer portion, which transfers read signal charges in the vertical direction. Furthermore, a horizontal charge transfer portion and the like are included.
[0075] The above-described film 22, which has a negative fixed charge, is formed from, for example, a hafnium oxide (HfO.sub.2) film, an aluminum oxide (Al.sub.2O.sub.3) film, a zirconium oxide (ZrO.sub.2) film, a tantalum oxide (Ta.sub.2O.sub.5) film, or a titanium oxide (TiO.sub.2) film. The above-described films of the types mentioned above have a track record in being used for gate insulating films or the like of insulated gate type field-effect transistors. Therefore, the film formation method has been established, and film formation can be conducted easily. Examples of film formation methods include a chemical vapor deposition method, a sputtering method, and an atomic layer deposition method. However, use of the atomic layer deposition method is favorable because about 1 nm of SiO.sub.2 layer, which reduces an interface state, can be formed at the same time during film formation. In this regard, examples of the materials other than those described above include lanthanum oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3), promethium oxide (Pm.sub.2O.sub.3), samarium oxide (Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3), dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide (HO.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide (Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium oxide (Lu.sub.2O.sub.3), and yttrium oxide (Y.sub.2O.sub.3). Moreover, the above-described film 22, which has a negative fixed charge, may also be formed from a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film.
[0076] Regarding the above-described film 22, which has a negative fixed charge, silicon (Si) or nitrogen (N) may be added to the film within the bounds of not impairing the insulating property. The concentration thereof is determined appropriately within the bounds of not impairing the insulating property of the film. In the case where silicon (Si) or nitrogen (N) is added as described above, it becomes possible to enhance the heat resistance of the film and the capability of preventing ion implantation during a process.
[0077] An insulating film 41 is disposed on the above-described film 22, which has a negative fixed charge, and a light-shield film 42 is disposed on the above-described insulating film 41 above the above-described peripheral circuit portion 14. A region, into which no light enters, is formed in the light-receiving portion 12 by this light-shield film 42, and a black level of the image is determined on the basis of an output of the light-receiving portion 12. Moreover, since entrance of light into the peripheral circuit portion 14 is prevented, variations in characteristics due to entrance of light into the peripheral circuit portion are suppressed. In addition, an insulating film 43, which has a transmission property with respect to the above-described incident light is disposed. It is preferable that the surface of this insulating film 43 is flattened. Furthermore, a color filter layer 44 and a condenser lens 45 are disposed on the insulating film 43.
[0078] In the above-described solid-state imaging device (first solid-state imaging device) 1, the film 22, which has a negative fixed charge, is disposed on the film 21, which lowers an interface state. Therefore, an electric field is applied to the surface of the light-receiving portion 12 by the negative fixed charge in the film of the film 22, which has a negative fixed charge, through the film 21, which lowers an interface state, and thereby, the hole accumulation (hole accumulation) layer 23 is formed on the surface of the light-receiving portion 12.
[0079] Then, as shown in
[0080] On the other hand, as shown in
[0081] Furthermore, in the above-described solid-state imaging device 1, since the film 21, which lowers the interface state, is disposed on the light-receiving surface 12s of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current, resulting from the interface state into the light-receiving portion 12 is suppressed.
[0082] Moreover, in the case where a hafnium oxide film is used as the film 22, which has a negative fixed charge, since the refractive index of the hafnium oxide film is about 2, it is possible to not only form the HAD structure, but also obtain an antireflection effect at the same time by optimizing the film thickness. Regarding materials other than the hafnium oxide film as well, as for materials having high refractive indices, it is possible to obtain an antireflection effect by optimizing the film thickness thereof.
[0083] In this regard, it is known that in the case where silicon oxide or silicon nitride, which have been previously used in solid-state imaging devices, is formed at low temperatures, the fixed charge in the film becomes positive, and it is not possible to form the HAD structure by a negative fixed charge.
[0084] Next, a modified example of the above-described solid-state imaging device (first solid-state imaging device) 1 will be described with reference to a key portion configuration sectional view shown in
[0085] In the case where regarding the above-described solid-state imaging device 1, the antireflection effect on the light-receiving portion 12 by only the film 22, which has a negative fixed charge, is inadequate, regarding a solid-state imaging device 2, as shown in
[0086] In the case where the antireflection film 46 is disposed as described above, reflection before entrance into the light-receiving portion 12 can be reduced and, thereby, the amount of light incident on the light-receiving portion 12 can be increased, so that the sensitivity of the solid-state imaging device 2 can be improved.
[0087] Next, a modified example of the above-described solid-state imaging device (first solid-state imaging device) 1 will be described with reference to a key portion configuration sectional view shown in
[0088] Regarding a solid-state imaging device 3, as shown in
[0089] In the case where the light-shield film 42 is disposed directly on the film 22, which has a negative fixed charge, as described above, the light-shield film 42 can be made close to the surface of the semiconductor substrate 11 and, thereby, the distance between the light-shield film 42 and the semiconductor substrate 11 is reduced, so that components of light incident slantingly from an upper layer of an adjacent light-receiving portion (photodiode), that is, optical color mixture components, can be reduced.
[0090] Furthermore, as shown in
[0091] Next, an embodiment (second example) of the solid-state imaging device (first solid-state imaging device) according to the present invention will be described with reference to a key portion configuration sectional view shown in
[0092] As shown in
[0093] As described above, the insulating film 24 is disposed between the surface of the above-described peripheral circuit portion 14 and the above-described film 22, which has a negative fixed charge, in such a way that the distance of the above-described film 22, which has a negative fixed charge, from the surface of the above-described peripheral circuit portion 14 becomes larger than the distance from the surface of the above-described light-receiving portion 12. Therefore, in the peripheral circuit portion 14, the influence of the electric field of a negative fixed charge in the film 22, which has a negative fixed charge, is not exerted on the peripheral circuit. Consequently, a malfunction of the peripheral circuit due to the negative fixed charge can be prevented.
[0094] Next, an embodiment (third example) of the solid-state imaging device (first solid-state imaging device) will be described with reference to a key portion configuration sectional view shown in
[0095] As shown in
[0096] As described above, the above-described film 25, which has a positive fixed charge, is disposed above the above-described peripheral circuit portion 14 and under the above-described film 22, which has a negative fixed charge. Therefore, the negative fixed charge of the film 22, which has a negative fixed charge, is reduced by the positive fixed charge in the above-described film 25, so that the influence of the electric field of a negative fixed charge in the film 22, which has the negative fixed charge, is not exerted on the peripheral circuit portion 14. Consequently, a malfunction of the peripheral circuit 14 due to the negative fixed charge can be prevented. The above-described configuration, in which the above-described film 25 having a positive fixed charge is disposed above the above-described peripheral circuit portion 14 and under the above-described film 22 having a negative fixed charge, can be applied to the above-described solid-state imaging devices 1, 2, 3, and 4, and the effects similar to those of the solid-state imaging device 5 can be obtained.
[0097] In the configuration on the film 22, which has a negative fixed charge, in the above-described solid-state imaging devices 4 and 5, the light-shield film to shield a part of the light-receiving portion 12 and the peripheral circuit portion 14 from light, the color filter layer to disperse the light incident on at least the light-receiving portion 12, the condenser lens to condense the incident light on the light-receiving portion 12, and the like are disposed. As an example of the configuration, any one of the configurations of the above-described solid-state imaging devices 1, 2, and 3 can also be applied.
[0098] Next, an embodiment (first example) of a method for manufacturing a solid-state imaging device (first manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0099] As shown in
[0100] Subsequently, as shown in
[0101] The above-described film 22, which has a negative fixed charge, is formed from, for example, a hafnium oxide (HfO.sub.2) film, an aluminum oxide (Al.sub.2O.sub.3) film, a zirconium oxide (ZrO.sub.2) film, a tantalum oxide (Ta.sub.2O.sub.5) film, or a titanium oxide (TiO.sub.2) film. The above-described films of the types mentioned above have a track record in being used for gate insulating films or the like of insulated gate type field-effect transistors. Therefore, the film formation method has been established, and film formation can be conducted easily. As for the film formation method, for example, a chemical vapor deposition method, a sputtering method, and an atomic layer deposition method can be used. However, use of the atomic layer deposition method is favorable because about 1 nm of SiO.sub.2 layer, which reduces an interface state, can be formed at the same time during film formation.
[0102] In this regard, examples of the usable materials other than those described above include lanthanum oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3), promethium oxide (Pm.sub.2O.sub.3), samarium oxide (Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3), dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide (Ho.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide (Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium oxide (Lu.sub.2O.sub.3), and yttrium oxide (Y.sub.2O.sub.3). Moreover, the above-described film 22, which has a negative fixed charge, can also be formed from a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film. As for these films, for example, the chemical vapor deposition method, the sputtering method, the atomic layer deposition method, and the like can also be used.
[0103] Furthermore, regarding the above-described film 22, which has a negative fixed charge, silicon (Si) or nitrogen (N) may be added to the film within the bounds of not impairing the insulating property. The concentration thereof is determined appropriately within the bounds of not impairing the insulating property of the film. In the case where silicon (Si) or nitrogen (N) is added as described above, it becomes possible to enhance the heat resistance of the film and the capability of preventing ion implantation during a process.
[0104] Moreover, in the case where the above-described film 22, which has a negative fixed charge, is formed from a hafnium oxide (HfO.sub.2) film, since the refractive index of the hafnium oxide (HfO.sub.2) film is about 2, it is possible to obtain an antireflection effect efficiently by adjusting the film thickness thereof. As a matter of course, regarding other types of films as well, it is possible to obtain the antireflection effect by optimizing the film thickness in accordance with the refractive index.
[0105] Subsequently, the insulating film 41 is formed on the above-described film 22, which has a negative fixed charge, and in addition, the light-shield film 42 is formed on the above-described insulating film 41. The above-described insulating film 41 is formed from, for example, a silicon oxide film. In this connection, the above-described light-shield film 42 is formed from, for example, a metal film having a light-shielding property. In the case where the light-shield film 42 is formed on the above-described film 22, which has a negative fixed charge, with the insulating film 41 therebetween, a reaction between the film 22, which is formed from a hafnium oxide film or the like and which has a negative fixed charge, and the metal in the light-shield film 42 can be prevented. In addition, since the insulating film 41 serves as an etching stopper when the light-shield film is etched, etching damage to the film 22, which has a negative fixed charge, can be prevented.
[0106] Next, as shown in
[0107] Subsequently, as shown in
[0108] Then, as shown in
[0109] At that time, a light-transmitting insulating film (not shown in the drawing) may be formed between the color filter layer 44 and the condenser lens 45 in order to prevent working damage to the color filter layer 44 during lens working. In this manner, the solid-state imaging device 1 is formed.
[0110] In the first example of the above-described method for manufacturing a solid-state imaging device (first manufacturing method), since the film 22, which has a negative fixed charge, is formed on the film 21, which lowers an interface state, the hole accumulation (hole accumulation) layer 23 is formed adequately at the interface on the light-receiving surface side of the light-receiving portion 12 by an electric field resulting from the negative fixed charge in the film 22, which has a negative fixed charge. Therefore, generation of electric charges (electrons) from the interface is suppressed and, in addition, even when electric charges (electrons) are generated, the electric charges do not flow into a charge storage portion serving as a potential well in the light-receiving portion 12, flow through the hole accumulation layer 23, in which many holes are present, and can be extinguished. Consequently, it can be prevented that a dark current due to the electric charges resulting from the interface is detected by the light-receiving portion and a dark current resulting from the interface state can be suppressed. Furthermore, since the film 21, which lowers the interface state, is disposed on the light-receiving surface of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current, resulting from the interface state into the light-receiving portion 12 is suppressed. Moreover, since the film 22, which has a negative fixed charge, is used, the HAD structure can be formed without conducting ion implantation and annealing.
[0111] Next, an embodiment (second example) of the method for manufacturing a solid-state imaging device (first manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0112] As shown in
[0113] Subsequently, as shown in
[0114] The above-described film 22, which has a negative fixed charge, is formed from, for example, a hafnium oxide (HfO.sub.2) film, an aluminum oxide (Al.sub.2O.sub.3) film, a zirconium oxide (ZrO.sub.2) film, a tantalum oxide (Ta.sub.2O.sub.5) film, or a titanium oxide (TiO.sub.2) film. The above-described films of the types mentioned above have a track record in being used for gate insulating films or the like of insulated gate type field-effect transistors. Therefore, the film formation method has been established, and film formation can be conducted easily. As for the film formation method, for example, a chemical vapor deposition method, a sputtering method, and an atomic layer deposition method can be used.
[0115] In this regard, examples of the usable materials other than those described above include lanthanum oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3), promethium oxide (Pm.sub.2O.sub.3), samarium oxide (Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3), dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide (Ho.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide (Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium oxide (Lu.sub.2O.sub.3), and yttrium oxide (Y.sub.2O.sub.3). Moreover, the above-described film 22, which has a negative fixed charge, can also be formed from a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film. As for these films, for example, the chemical vapor deposition method, the sputtering method, the atomic layer deposition method, and the like can also be used. However, use of the atomic layer deposition method is favorable because about 1 nm of SiO.sub.2 layer, which reduces an interface state, can be formed at the same time during film formation.
[0116] Furthermore, regarding the above-described film 22, which has a negative fixed charge, silicon (Si) or nitrogen (N) may be added to the film within the bounds of not impairing the insulating property. The concentration thereof is determined appropriately within the bounds of not impairing the insulating property of the film. In the case where silicon (Si) or nitrogen (N) is added as described above, it becomes possible to enhance the heat resistance of the film and the capability of preventing ion implantation during a process.
[0117] Moreover, in the case where the above-described film 22, which has a negative fixed charge, is formed from a hafnium oxide (HfO.sub.2) film, since the refractive index of the hafnium oxide (HfO.sub.2) film is about 2, it is possible to obtain an antireflection effect efficiently by adjusting the film thickness thereof. As a matter of course, regarding other types of films as well, it is possible to obtain the antireflection effect by optimizing the film thickness in accordance with the refractive index.
[0118] Subsequently, the insulating film 41 is formed on the above-described film 22, which has a negative fixed charge, and in addition, the light-shield film 42 is formed on the above-described insulating film 41. The above-described insulating film 41 is formed from, for example, a silicon oxide film. In this connection, the above-described light-shield film 42 is formed from, for example, a metal film having a light-shielding property. In the case where the light-shield film 42 is formed on the above-described film 22, which has a negative fixed charge, with the insulating film 41 therebetween, a reaction between the film 22, which is formed from a hafnium oxide film or the like and which has a negative fixed charge, and the metal in the light-shield film 42 can be prevented. In addition, since the insulating film 41 serves as an etching stopper when the light-shield film is etched, etching damage to the film 22, which has a negative fixed charge, can be prevented.
[0119] Next, as shown in
[0120] Then, as shown in
[0121] Subsequently, as shown in
[0122] According to the second example of the above-described method for manufacturing a solid-state imaging device (first manufacturing method), the effects similar to those of the above-described first example can be obtained. In addition, since the antireflection film 46 is formed, reflection before entrance into the light-receiving portion 12 can be reduced and, thereby, the amount of light incident on the light-receiving portion 12 can be increased, so that the sensitivity of the solid-state imaging device 2 can be improved.
[0123] Next, an embodiment (third example) of the method for manufacturing a solid-state imaging device (first manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0124] As shown in
[0125] Subsequently, as shown in
[0126] The above-described film 22, which has a negative fixed charge, is formed from, for example, a hafnium oxide (HfO.sub.2) film, an aluminum oxide (Al.sub.2O.sub.3) film, a zirconium oxide (ZrO.sub.2) film, a tantalum oxide (Ta.sub.2O.sub.5) film, or a titanium oxide (TiO.sub.2) film. The above-described films of the types mentioned above have a track record in being used for gate insulating films or the like of insulated gate type field-effect transistors. Therefore, the film formation method has been established, and film formation can be conducted easily. As for the film formation method, for example, a chemical vapor deposition method, a sputtering method, and an atomic layer deposition method can be used. However, use of the atomic layer deposition method is favorable because about 1 nm of SiO.sub.2 layer, which reduces an interface state, can be formed at the same time during film formation.
[0127] In this regard, examples of the usable materials other than those described above include lanthanum oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3), promethium oxide (Pm.sub.2O.sub.3), samarium oxide (Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3), dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide (Ho.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide (Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium oxide (Lu.sub.2O.sub.3), and yttrium oxide (Y.sub.2O.sub.3). Moreover, the above-described film 22, which has a negative fixed charge, can also be formed from a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film. As for these films, for example, the chemical vapor deposition method, the sputtering method, the atomic layer deposition method, and the like can also be used.
[0128] Furthermore, regarding the above-described film 22, which has a negative fixed charge, silicon (Si) or nitrogen (N) may be added to the film within the bounds of not impairing the insulating property. The concentration thereof is determined appropriately within the bounds of not impairing the insulating property of the film. In the case where silicon (Si) or nitrogen (N) is added as described above, it becomes possible to enhance the heat resistance of the film and the capability of preventing ion implantation during a process.
[0129] Moreover, in the case where the above-described film 22, which has a negative fixed charge, is formed from a hafnium oxide (HfO.sub.2) film, it is possible to obtain an antireflection effect efficiently by adjusting the film thickness of the hafnium oxide (HfO.sub.2) film. As a matter of course, regarding other types of films as well, it is possible to obtain the antireflection effect by optimizing the film thickness in accordance with the refractive index.
[0130] Then, the light-shield film 42 is formed on the above-described film 22, which has a negative fixed charge. The above-described light-shield film 42 is formed from, for example, a metal film having a light-shielding property. In the case where the light-shield film 42 is formed directly on the film 22, which has a negative fixed charge, as described above, the light-shield film 42 can be made close to the surface of the semiconductor substrate 11 and, thereby, the distance between the light-shield film 42 and the semiconductor substrate 11 is reduced, so that components of light incident slantingly from an upper layer of an adjacent photodiode, that is, optical color mixture components, can be reduced.
[0131] Next, as shown in
[0132] Thereafter, as shown in
[0133] Subsequently, as shown in
[0134] According to the third example of the above-described method for manufacturing a solid-state imaging device (first manufacturing method), the effects similar to those of the above-described first example can be obtained. In addition, since the light-shield film 42 is formed directly on the film 22, which has a negative fixed charge, the light-shield film 42 can be made close to the surface of the semiconductor substrate 11 and, thereby, the distance between the light-shield film 42 and the semiconductor substrate 11 is reduced, so that components of light incident slantingly from an upper layer of an adjacent photodiode, that is, optical color mixture components, can be reduced. Furthermore, since the antireflection film 46 is formed, the antireflection effect can be maximized in the case where the antireflection effect by only the film 22, which has a negative fixed charge, is inadequate.
[0135] Next, an embodiment (fourth example) of the method for manufacturing a solid-state imaging device (first manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0136] As shown in
[0137] Then, as shown in
[0138] Thereafter, as shown in
[0139] Next, as shown in
[0140] Then, as shown in
[0141] The above-described film 22, which has a negative fixed charge, is formed from, for example, a hafnium oxide (HfO.sub.2) film, an aluminum oxide (Al.sub.2O.sub.3) film, a zirconium oxide (ZrO.sub.2) film, a tantalum oxide (Ta.sub.2O.sub.5) film, or a titanium oxide (TiO.sub.2) film. The above-described films of the types mentioned above have a track record in being used for gate insulating films or the like of insulated gate type field-effect transistors. Therefore, the film formation method has been established, and film formation can be conducted easily. As for the film formation method, for example, a chemical vapor deposition method, a sputtering method, and an atomic layer deposition method can be used. However, use of the atomic layer deposition method is favorable because about 1 nm of SiO.sub.2 layer, which reduces an interface state, can be formed at the same time during film formation.
[0142] In this regard, examples of the usable materials other than those described above include lanthanum oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3), promethium oxide (Pm.sub.2O.sub.3), samarium oxide (Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3), dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide (Ho.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide (Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium oxide (Lu.sub.2O.sub.3), and yttrium oxide (Y.sub.2O.sub.3). Moreover, the above-described film 22, which has a negative fixed charge, can also be formed from a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film. As for these films, for example, the chemical vapor deposition method, the sputtering method, the atomic layer deposition method, and the like can also be used.
[0143] Furthermore, regarding the above-described film 22, which has a negative fixed charge, silicon (Si) or nitrogen (N) may be added to the film within the bounds of not impairing the insulating property. The concentration thereof is determined appropriately within the bounds of not impairing the insulating property of the film. In the case where silicon (Si) or nitrogen (N) is added as described above, it becomes possible to enhance the heat resistance of the film and the capability of preventing ion implantation during a process.
[0144] Moreover, in the case where the above-described film 22, which has a negative fixed charge, is formed from a hafnium oxide (HfO.sub.2) film, it is possible to obtain an antireflection effect efficiently by adjusting the film thickness thereof because the refractive index of the hafnium oxide (HfO.sub.2) film is about 2. As a matter of course, regarding other types of films as well, it is possible to obtain the antireflection effect by optimizing the film thickness in accordance with the refractive index.
[0145] In the configuration on the film 22, which has a negative fixed charge, in the above-described solid-state imaging device 4, the light-shield film to shield a part of the light-receiving portion 12 and the peripheral circuit portion 14 from light, the color filter layer to disperse the light incident on at least the light-receiving portion 12, the condenser lens to condense the incident light on the light-receiving portion 12, and the like are disposed. As an example of the configuration, any one of the configurations of the above-described solid-state imaging devices 1, 2, and 3 can also be applied.
[0146] In the fourth example of the above-described method for manufacturing a solid-state imaging device (first manufacturing method), since the film 22, which has a negative fixed charge, is formed on the film 21, which lowers an interface state, the hole accumulation (hole accumulation) layer 23 is formed adequately at the interface on the light-receiving surface side of the light-receiving portion 12 by an electric field resulting from the negative fixed charge in the film 22, which has a negative fixed charge. Therefore, generation of electric charges (electrons) from the interface is suppressed and, in addition, even when electric charges (electrons) are generated, the electric charges do not flow into a charge storage portion serving as a potential well in the light-receiving portion 12, flow through the hole accumulation layer, in which many holes are present, and can be extinguished. Consequently, it can be prevented that a dark current due to the electric charges resulting from the interface is detected by the light-receiving portion and a dark current resulting from the interface state is suppressed. Furthermore, since the film 21, which lowers the interface state, is disposed on the light-receiving surface of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current, resulting from the interface state into the light-receiving portion 12 is suppressed. Moreover, since the film 22, which has a negative fixed charge, is used, the HAD structure can be formed without conducting ion implantation and annealing.
[0147] In addition, since the insulating film 26 is disposed on the peripheral circuit portion 14, the distance to the film 22, which has a negative fixed charge, on the peripheral circuit portion 14 becomes larger than the distance to the film, which has a negative fixed charge, on the light-receiving portion 12. Therefore, the negative electric field applied from the film 22, which has a negative fixed charge, to the peripheral circuit portion 14 is mitigated. That is, the influence of the film 22, which has a negative fixed charge, exerted on the peripheral circuit portion 14 is reduced. Consequently, a malfunction of the peripheral circuit portion 14 due to the negative electric field on the basis of the film 22, which has a negative fixed charge, is prevented.
[0148] Next, an embodiment (fifth example) of the method for manufacturing a solid-state imaging device (first manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0149] As shown in
[0150] At least on the light-receiving portion 12, it is necessary that the above-described film 21, which lowers an interface state, is formed having a film thickness to allow the hole accumulation layer 23, which will be described later, to be formed on the light-receiving surface 12s side of the above-described light-receiving portion 12 by the above-described film 22, which will be described later and which has a negative fixed charge. The film thickness thereof is specified to be, for example, 1 atomic layer or more, and 100 nm or less.
[0151] Then, as shown in
[0152] Thereafter, as shown in
[0153] Next, as shown in
[0154] The above-described film 22, which has a negative fixed charge, is formed from, for example, a hafnium oxide (HfO.sub.2) film, an aluminum oxide (Al.sub.2O.sub.3) film, a zirconium oxide (ZrO.sub.2) film, a tantalum oxide (Ta.sub.2O.sub.5) film, or a titanium oxide (TiO.sub.2) film. The above-described films of the types mentioned above have a track record in being used for gate insulating films or the like of insulated gate type field-effect transistors. Therefore, the film formation method has been established, and film formation can be conducted easily. As for the film formation method, for example, a chemical vapor deposition method, a sputtering method, and an atomic layer deposition method can be used. However, use of the atomic layer deposition method is favorable because about 1 nm of SiO.sub.2 layer, which reduces an interface state, can be formed at the same time during film formation.
[0155] In this regard, examples of the usable materials other than those described above include lanthanum oxide (La.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), cerium oxide (CeO.sub.2), neodymium oxide (Nd.sub.2O.sub.3), promethium oxide (Pm.sub.2O.sub.3), samarium oxide (Sm.sub.2O.sub.3), europium oxide (Eu.sub.2O.sub.3), gadolinium oxide (Gd.sub.2O.sub.3), terbium oxide (Tb.sub.2O.sub.3), dysprosium oxide (Dy.sub.2O.sub.3), holmium oxide (Ho.sub.2O.sub.3), erbium oxide (Er.sub.2O.sub.3), thulium oxide (Tm.sub.2O.sub.3), ytterbium oxide (Yb.sub.2O.sub.3), lutetium oxide (Lu.sub.2O.sub.3), and yttrium oxide (Y.sub.2O.sub.3). Moreover, the above-described film 22, which has a negative fixed charge, can also be formed from a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film. As for these films, for example, the chemical vapor deposition method, the sputtering method, the atomic layer deposition method, and the like can also be used.
[0156] Furthermore, regarding the above-described film 22, which has a negative fixed charge, silicon (Si) or nitrogen (N) may be added to the film within the bounds of not impairing the insulating property. The concentration thereof is determined appropriately within the bounds of not impairing the insulating property of the film. In the case where silicon (Si) or nitrogen (N) is added as described above, it becomes possible to enhance the heat resistance of the film and the capability of preventing ion implantation during a process.
[0157] Moreover, in the case where the above-described film 22, which has a negative fixed charge, is formed from a hafnium oxide (HfO.sub.2) film, it is possible to obtain an antireflection effect efficiently by adjusting the film thickness of the hafnium oxide (HfO.sub.2) film. As a matter of course, regarding other types of films as well, it is possible to obtain the antireflection effect by optimizing the film thickness in accordance with the refractive index.
[0158] In the configuration on the film 22, which has a negative fixed charge, in the above-described solid-state imaging device 5, the light-shield film to shield a part of the light-receiving portion 12 and the peripheral circuit portion 14 from light, the color filter layer to disperse the light incident on at least the light-receiving portion 12, the condenser lens to condense the incident light on the light-receiving portion 12, and the like are disposed. As an example of the configuration, any one of the configurations of the above-described solid-state imaging devices 1, 2, and 3 can also be applied. In the fifth example of the above-described method for manufacturing a solid-state imaging device (first manufacturing method), since the film 22, which has a negative fixed charge, is formed on the film 21, which lowers an interface state, the hole accumulation (hole accumulation) layer 23 is formed adequately at the interface on the light-receiving surface side of the light-receiving portion 12 by an electric field resulting from the negative fixed charge in the film 22, which has a negative fixed charge. Therefore, generation of electric charges (electrons) from the interface is suppressed and, in addition, even when electric charges (electrons) are generated, the electric charges do not flow into a charge storage portion serving as a potential well in the light-receiving portion 12, flow through the hole accumulation layer 23, in which many holes are present, and can be extinguished. Consequently, it can be prevented that a dark current due to the electric charges resulting from the interface is detected by the light-receiving portion and a dark current resulting from the interface state is suppressed. Furthermore, since the film 21, which lowers the interface state, is disposed on the light-receiving surface of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current, resulting from the interface state into the light-receiving portion 12 is suppressed. Moreover, since the film 22, which has a negative fixed charge, is used, the HAD structure can be formed without conducting ion implantation and annealing.
[0159] In addition, since the film 25, which has preferably a positive fixed charge and which keeps the film having a negative fixed charge away from the surface of the light-receiving surface, is disposed above the above-described peripheral circuit portion 14 and under the above-described film 22, which has a negative fixed charge, the negative fixed charge of the film 22, which has the negative charge, is reduced by the positive fixed charge in the film 25, which has the positive fixed charge, so that the influence due to the electric field of the negative fixed charge in the film 22, which has the negative fixed charge, is not exerted on the peripheral circuit portion 14. Consequently, a malfunction of the peripheral circuit portion 14 due to the negative fixed charge can be prevented.
[0160] Here, regarding a hafnium oxide (HfO.sub.2) film as an example of the film, which has a negative fixed charge, data indicating the presence of the negative fixed charge will be described with reference to
[0161] As for a first sample, MOS capacitors, in which a gate electrode was formed on a silicon substrate with a thermal silicon oxide (SiO.sub.2) film therebetween, were prepared, where the film thicknesses of the above-described thermal silicon oxide films were changed.
[0162] As for a second sample, MOS capacitors, in which a gate electrode was formed on a silicon substrate with a CVD silicon oxide (CVD-SiO.sub.2) film therebetween, were prepared, where the film thicknesses of the above-described CVD silicon oxide films were changed.
[0163] As for a third sample, MOS capacitors, in which a gate electrode was formed on a silicon substrate with a laminated film composed of sequentially laminated ozone silicon oxide (O.sub.3SiO.sub.2) film, hafnium oxide (HfO.sub.2) film, and CVD silicon oxide (SiO.sub.2) film therebetween, were prepared, where the film thicknesses of the above-described CVD silicon oxide films were changed. In this regard, the film thicknesses of the HfO.sub.2 film and the O.sub.3SiO.sub.2 film were fixed.
[0164] In each of the above-described samples, the CVD-SiO.sub.2 film is formed by a CVD method through the use of a mixed gas of monosilane (SiH.sub.4) and oxygen (O.sub.2), and the HfO.sub.2 film is formed by an ALD method in which tetrakisethylmethyl-amino hafnium (tetrakisethylmethyl-amino hafnium: TEMAHf) and ozone (O.sub.3) serve as raw materials. The O.sub.3SiO.sub.2 film in the above-described third sample is an interfacial oxide film, which is formed between HfO.sub.2 and the silicon substrate by the ALD method in the formation of the HfO.sub.2 film and which has a thickness of about 1 nm. As for every gate electrode in the above-described individual samples, a structure, in which an aluminum (Al) film, a titanium nitride (TiN) film, and a titanium (Ti) film are laminated in that order from the upper layer, is employed.
[0165] In this connection, regarding the above-described sample structures, in the first sample and the second sample, the gate electrode is disposed immediately above the SiO.sub.2 film, whereas only the third sample including the HfO.sub.2 film has the structure, in which the CVD-SiO.sub.2 film is laminated on the HfO.sub.2 film. The reason therefor is that an occurrence of reaction between HfO.sub.2 and the gate electrode at the interface is prevented by bringing HfO.sub.2 into direct contact with the electrode.
[0166] Furthermore, in the laminated structure of the third sample, the HfO.sub.2 film thickness was fixed at 10 nm, and the film thickness of the CVD-SiO.sub.2 film serving as an upper layer was changed. The reason therefor is that HfO.sub.2 has a large specific dielectric constant and, therefore, even when a film thickness at a level of 10 nm is formed, the film thickness in terms of oxide film is several nanometers. Consequently, it is difficult to observe changes in flat band voltage Vfb versus film thickness in terms of oxide film.
[0167] Regarding the above-described first sample, second sample, and third sample, the film thickness Tox in terms of oxide film versus the flat band voltage Vfb was examined. The results thereof are shown in
[0168] As shown in
[0169] In addition, the data of interface state densities of the above-described individual samples are shown in
[0170] As a result, as shown in
[0171] Next, the film thickness Tox in terms of oxide film versus the flat band voltage Vfb was examined in the case where the film 25, which had a positive fixed charge, was formed. The results thereof are shown in
[0172] As shown in
[0173] Regarding the solid-state imaging device 1 to the solid-state imaging device 5 in the above-described individual examples, as described above, in the case where nitrogen (N) is contained in the film 22, which has a negative fixed charge, after the film 22, which has a negative fixed charge, is formed, nitrogen (N) can be contained by a nitriding treatment with high-frequency plasma or microwave plasma. Moreover, the above-described film 22, which has a negative fixed charge, is subjected to an electron beam curing treatment through electron beam irradiation after film formation and, thereby, the negative fixed charge in the film can be increased.
[0174] Next, an embodiment (first example) of a solid-state imaging device (second solid-state imaging device) according to the present invention will be described with reference to a key portion configuration sectional view shown in
[0175] As shown in
[0176] In the drawing, the above-described insulating film 27 is disposed having a thickness above the peripheral circuit portion 14 larger than the thickness above the above-described light-receiving portion 12 in such a way that the distance of the above-described film 28, which applies a negative voltage, from the surface of the above-described peripheral circuit portion 14 becomes larger than the distance from the surface of the above-described light-receiving portion 12. Furthermore, in the case where the above-described insulating film 27 is formed from, for example, a silicon oxide film, this insulating film 27 has a function similar to that of the above-described film 21, which lowers a interface state, on the light-receiving portion 12. For that purpose, it is preferable that the above-described insulating film 27 on the above-described light-receiving portion 12 is disposed having a film thickness of, for example, 1 atomic layer or more, and 100 nm or less. Consequently, when a negative voltage is applied to the film 28, which applies a negative voltage, the hole accumulation layer 23 is formed on the light-receiving surface side of the above-described light-receiving portion 12.
[0177] In the case where the above-described solid-state imaging device 6 is a CMOS image sensor, examples of peripheral circuits of the above-described peripheral circuit portion 14 include pixel circuits composed of transistors, e.g., a transfer transistor, a reset transistor, an amplifying transistor, and a selection transistor. Furthermore, a drive circuit to effect an operation to read signals of lines to be read in a pixel array portion composed of a plurality of light-receiving portions 12, a vertical scanning circuit to transfer the signals read, a shift register or an address decoder, a horizontal scanning circuit, and the like are included.
[0178] Alternatively, in the case where the above-described solid-state imaging device 6 is a CCD image sensor, examples of peripheral circuits of the above-described peripheral circuit portion 14 include a read gate, which reads photoelectrically converted signal charges from the light-receiving portion to a vertical transfer gate, and a vertical charge transfer portion, which transfers read signal charges in the vertical direction. Furthermore, a horizontal charge transfer portion and the like are included.
[0179] The above-described film 28, which applies a negative voltage, is formed from, for example, a film, which is transparent with respect to the incident light and which has electrical conductivity, and is formed from, for example, an electrically conductive film transparent with respect to the visible light. As for such a film, an indium tin oxide film, an indium zinc oxide film, or an indium oxide film, a tin oxide film, a gallium zinc oxide film, or the like can be used.
[0180] Regarding the configuration on the film 28, which applies a negative voltage, in the above-described solid-state imaging device 6, the light-shield film to shield a part of the light-receiving portion 12 and the peripheral circuit portion 14 from light, the color filter layer to disperse the light incident on at least the light-receiving portion 12, the condenser lens to condense the incident light on the light-receiving portion 12, and the like are disposed. As an example of the configuration, any one of the configurations of the above-described solid-state imaging devices 1, 2, and 3 can also be applied.
[0181] In the above-described solid-state imaging device (second solid-state imaging device) 6, since the film 28, which applies a negative voltage, is disposed on the insulating film 27 disposed on the light-receiving surface 12s of the light-receiving portion 12, the hole accumulation (hole accumulation) layer is formed adequately at the interface on the light-receiving surface 12s side of the light-receiving portion 12 by an electric field generated through application of a negative voltage to the film 28, which applies a negative voltage. Therefore, generation of electric charges (electrons) from the interface is suppressed and, in addition, even when electric charges (electrons) are generated from the interface, the electric charges do not flow into a charge storage portion serving as a potential well in the light-receiving portion, flow through the hole accumulation layer 23, in which many holes are present, and can be extinguished. Consequently, it can be prevented that the electric charges resulting from the interface serve as a dark current and are detected by the light-receiving portion 12, and a dark current resulting from the interface state can be suppressed. Moreover, since the insulating film 27 serving as a film, which lowers the interface state, is disposed on the light-receiving surface 12s of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current and which result from the interface state, into the light-receiving portion 12 is suppressed.
[0182] In addition, as shown in the drawing, the distance of the above-described film 28, which applies a negative voltage, from the surface of the above-described peripheral circuit portion 14 is made to be larger than the distance from the surface of the above-described light-receiving portion 12 by the insulating film 27. Therefore, the influence exerted on the peripheral circuit portion 14 by the electric field generated when a negative charge is applied to the film 28, which applies a negative voltage, is reduced. Consequently, a malfunction of the circuit in the peripheral circuit portion 14 can be eliminated.
[0183] Next, an embodiment (second example) of the solid-state imaging device (second solid-state imaging device) will be described with reference to a key portion configuration sectional view shown in
[0184] As shown in
[0185] An examples of the above-described film 25, which has a positive fixed charge, is a silicon nitride film.
[0186] As described above, since the film 25, which has a positive fixed charge, is disposed between the above-described peripheral circuit portion 14 and the above-described film 28, which applies a negative voltage, the negative electric field generated when a negative charge is applied to the film 28, which applies a negative voltage, is reduced by a positive fixed charge in the film 25, which has the positive fixed charge. Therefore, the influence due to this negative electric field is not exerted on the peripheral circuit portion 14. Consequently, a malfunction of the peripheral circuit portion 14 due to the negative electric field can be prevented and the reliability of the peripheral circuit portion 14 is enhanced. The above-described configuration in which the film 25, which has a positive fixed charge, is disposed above the above-described peripheral circuit portion 14 and under the above-described film 28, which applies a negative voltage, can also be applied to the above-described solid-state imaging device 6, and the effects similar to those of the solid-state imaging device 7 can be obtained.
[0187] Next, an embodiment (first example) of the method for manufacturing a solid-state imaging device (second manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0188] As shown in
[0189] Then, as shown in
[0190] Thereafter, as shown in
[0191] Next, as shown in
[0192] Then, as shown in
[0193] The above-described film 28, which applies a negative voltage, is formed from, for example, a film which is transparent with respect to the incident light and which has electrical conductivity, and is formed from, for example, an electrically conductive film transparent with respect to the visible light. As for such a film, an indium tin oxide film, an indium zinc oxide film, or an indium oxide film, a tin oxide film, a gallium zinc oxide film, or the like can be used.
[0194] In the above-described solid-state imaging device 6, the light-shield film to shield a part of the light-receiving portion 12 and the peripheral circuit portion 14 from light, the color filter layer to disperse the light incident on at least the light-receiving portion 12, the condenser lens to condense the incident light on the light-receiving portion 12, and the like are disposed on the film 28, which applies a negative voltage. As for a manufacturing method therefor, as an example, any one of the methods described in the individual examples of the above-described method for manufacturing a solid-state imaging device (first manufacturing method) can also be applied.
[0195] In the first example of the method for manufacturing the above-described solid-state imaging device 6 (second manufacturing method), since the film 28, which applies a negative voltage, is formed on the insulating film 27 disposed on the light-receiving surface 12s of the light-receiving portion 12, the hole accumulation (hole accumulation) layer is formed adequately at the interface on the light-receiving surface 12s side of the light-receiving portion 12 by an electric field generated through application of a negative voltage to the film 28, which applies a negative voltage. Therefore, generation of electric charges (electrons) from the interface is suppressed and, in addition, even when electric charges (electrons) are generated, the electric charges do not flow into a charge storage portion serving as a potential well in the light-receiving portion, flow through the hole accumulation layer 23, in which many holes are present, and can be extinguished. Consequently, it can be prevented that the electric charges resulting from the interface serve as a dark current and are detected by the light-receiving portion 12, and a dark current resulting from the interface state can be suppressed. Moreover, since the film 21, which lowers the interface state, is disposed on the light-receiving surface 12s of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current, resulting from the interface state into the light-receiving portion 12 is suppressed.
[0196] In addition, as shown in the drawing, the insulating film 27 is disposed having a thickness above the peripheral circuit portion 14 larger than the thickness of the insulating film 27 above the above-described light-receiving portion 12 in such a way that the distance of the above-described film 28, which applies a negative voltage, from the surface of the above-described peripheral circuit portion 14 becomes larger than the distance from the surface of the above-described light-receiving portion 12 by the insulating film 27. Therefore, the influence exerted by the electric field generated when a negative charge is applied to the film 28, which applies a negative voltage, on the peripheral circuit portion 14 is reduced. That is, the field strength is reduced, accumulation of holes on the surface of the peripheral circuit portion 14 is suppressed and, thereby, a malfunction of the circuit in the peripheral circuit portion 14 can be eliminated.
[0197] Next, an embodiment (second example) of the method for manufacturing a solid-state imaging device (second manufacturing method) according to the present invention will be described with reference to production step sectional views of a key portion shown in
[0198] As shown in
[0199] Then, as shown in
[0200] Thereafter, as shown in
[0201] Next, as shown in
[0202] The above-described film 28, which applies a negative voltage, is formed from, for example, a film which is transparent with respect to the incident light and which has electrical conductivity, and is formed from, for example, an electrically conductive film transparent with respect to the visible light. As for such a film, an indium tin oxide film, an indium zinc oxide film, or an indium oxide film, a tin oxide film, a gallium zinc oxide film, or the like can be used.
[0203] In the above-described solid-state imaging device 7, although not shown in the drawing, the light-shield film to shield a part of the light-receiving portion 12 and the peripheral circuit portion 14 from light, the color filter layer to disperse the light incident on at least the light-receiving portion 12, the condenser lens to condense the incident light on the light-receiving portion 12, and the like are disposed on the film 28 which applies a negative voltage. As for a manufacturing method therefor, as an example, any one of the methods described in the individual examples of the above-described method for manufacturing a solid-state imaging device (first manufacturing method) can also be applied.
[0204] In the second example of the above-described method for manufacturing the solid-state imaging device 7 (second manufacturing method), since the film 28, which applies a negative voltage, is formed on the insulating film 27 disposed on the light-receiving surface 12s of the light-receiving portion 12, the hole accumulation (hole accumulation) layer is formed adequately at the interface on the light-receiving surface 12s side of the light-receiving portion 12 by an electric field generated through application of a negative voltage to the film 28, which applies a negative voltage. Therefore, generation of electric charges (electrons) from the interface is suppressed and, in addition, even when electric charges (electrons) are generated from the interface, the electric charges do not flow into a charge storage portion serving as a potential well in the light-receiving portion, flow through the hole accumulation layer 23, in which many holes are present, and can be extinguished. Consequently, it can be prevented that the electric charges resulting from the interface serve as a dark current and are detected by the light-receiving portion 12, and a dark current resulting from the interface state can be suppressed. Moreover, since the film 21, which lowers the interface state, is disposed on the light-receiving surface 12s of the light-receiving portion 12, generation of electrons resulting from the interface state is further suppressed, so that flowing of electrons, which serve as a dark current, resulting from the interface state into the light-receiving portion 12 is suppressed.
[0205] In addition, since the film 25, which has a positive fixed charge, is disposed between the above-described peripheral circuit portion 14 and the above-described film 28, which applies a negative voltage, the negative electric field generated when a negative charge is applied to the film 28, which applies a negative voltage, is reduced by a positive fixed charge in the film 25 having the positive fixed charge. Therefore, the influence due to this negative electric field is not exerted on the peripheral circuit portion 14. Consequently, a malfunction of the peripheral circuit portion 14 due to the negative electric field can be prevented. The above-described configuration in which the film 25, which has a positive fixed charge, is disposed above the above-described peripheral circuit portion 14 and under the above-described film 28, which applies a negative voltage, can also be applied to the above-described solid-state imaging device 6, and the effects similar to those of the solid-state imaging device 7 can be obtained.
[0206] Next, an embodiment (example) of a solid-state imaging device (third solid-state imaging device) will be described with reference to a key portion configuration sectional view shown in
[0207] As shown in
[0208] Moreover, a wiring layer 73 composed of, for example, a plurality of wirings 71 and an insulating film 72 is disposed on the side opposite to the light incident side of the semiconductor substrate 11 provided with the above-described light-receiving portion 12. In addition, the wiring layer 73 is supported by a support substrate 74.
[0209] For example, since the hole accumulation layer 23 is formed from silicon (Si), the value of work function thereof is about 5.1 eV. Therefore, it is enough that the above-described hole accumulation auxiliary film 32 has the value of work function larger than 5.1.
[0210] For example, in the case where a metal film is used, according to Chronological Scientific Tables, the value of work function of an iridium (110) film is 5.42, the value of work function of an iridium (111) film is 5.76, the value of work function of a nickel film is 5.15, the value of work function of a palladium film is 5.55, the value of work function of an osmium film is 5.93, the value of work function of a gold (100) film is 5.47, the value of work function of a gold (110) film is 5.37, and the value of work function of a platinum film is 5.64. These films can be used as the above-described hole accumulation auxiliary film 32. Even films other than those described above can be used as the hole accumulation auxiliary film 32 insofar as the film is a metal film having a value of work function larger than that of the interface on the light-receiving surface 12s side of the light-receiving portion 12. In this connection, the value of work function of ITO (In.sub.2O.sub.3) used as a transparent electrode is assumed to be 4.8 eV. The work function of an oxide semiconductor can be controlled by a film formation method or impurity introduction.
[0211] The above-described hole accumulation auxiliary film 32 is disposed on the light incident side and, therefore, it is important to be formed having a film thickness suitable for transmitting the incident light. As for the incident light transmittance thereof, it is preferable to have as high transmittance as possible. For example, it is preferable that the transmittance of 95% or more is ensured.
[0212] Furthermore, it is enough that the hole accumulation auxiliary film 32 can make use of the difference in work function from that of the surface of the light-receiving portion 12, and there is no lower limit for the resistance value. Therefore, even in the case where, for example, an electrically conductive film is used, it is not necessary to form having a large film thickness. For example, when the incident light intensity is assumed to be I.sub.0 and the absorption coefficient is assumed to be (where =(4k)/, k is a Boltzmann constant, and is a wavelength of incident light), the light intensity at the position of depth z is represented by I(z)=I.sub.0exp(.Math.z). Consequently, the thickness at I(z)/I.sub.0=0.8 is determined to be, for example 1.9 nm for the iridium film, 4.8 nm for the gold film, and 3.4 nm for the platinum film, although different depending on the type of film. However, it is clear that 2 nm or less is preferable.
[0213] Moreover, the above-described hole accumulation auxiliary film 32 may be an organic film. For example, polyethylenedioxythiophene (polyethylenedioxythiophene) can also be used. As described above, the above-described hole accumulation auxiliary film 32 may be an electrically conductive film, an insulating film, or a semiconductor film insofar as the film has the value of work function higher than the value of work function of the interface on the light-receiving surface 12s side of the light-receiving portion 12.
[0214] The above-described solid-state imaging device 8 includes the film (hole accumulation auxiliary film) 32, which has a value of work function larger than that of the interface on the light-receiving surface 12s side of the above-described light-receiving portion 12 on the insulating film 31 disposed on the light-receiving portion 12 and, thereby, the hole accumulation efficiency of the hole accumulation layer 23 is increased, so that the hole accumulation layer 23 disposed at the light-receiving side interface of the light-receiving portion 12 can accumulate adequate holes. Consequently, a dark current is reduced.
[0215] Next, an example of the configuration of a solid-state imaging device including the hole accumulation auxiliary film 32 will be described with reference to
[0216] As shown in
[0217] The element isolation regions 13 are disposed in a part of the circumference of the above-described pixel portion 61, for example, between the pixel portions 61 in the longitudinal direction or the transverse direction.
[0218] In addition, the wiring layer 73 is disposed on the surface side of the semiconductor substrate 11 (in the drawing, under the semiconductor substrate 11) provided with the above-described light-receiving portions 12. This wiring layer 73 is composed of the wirings 71 and the insulating film 72 covering the wirings 71. The above-described wiring layer 73 is provided with the support substrate 74. This support substrate 74 is formed from, for example, a silicon substrate.
[0219] Furthermore, in the above-described solid-state imaging device 8 the hole accumulation layer 23 is disposed on the back surface side of the semiconductor substrate 11, and the above-described hole accumulation auxiliary film 32 is disposed on the upper surface thereof with the insulating film 31 therebetween. Moreover, an organic color filter 44 is disposed thereon with an insulating film (not shown in the drawing) therebetween. This color filter 44 is disposed in accordance with the above-described light-receiving portion 12 and is formed by, for example, arranging blue (Blue), red (Red), and green (Green) organic color filters in a checkered pattern, for example. In addition, a condenser lens 45 to condense incident light on each light-receiving portion 12 is disposed on each organic color filter 44.
[0220] Next, an embodiment (first example) of the method for manufacturing a solid-state imaging device (third manufacturing method) according to the present invention will be described with reference to a flow chart shown in
[0221] As shown in
[0222] Subsequently, as shown in
[0223] Then, as shown in
[0224] Thereafter, as shown in
[0225] Although not shown in the drawing, the above-described hole accumulation layer 23 may be formed by forming a cap film (not shown in the drawing) after removal of the insulating layer 83 from the SOI substrate 81 and conducting impurity introduction and an activation treatment. As an example, a plasma-TEOS silicon oxide film having a thickness of 30 nm is formed as the cap film and the impurity introduction is conducted through ion implantation of boron. As for the ion implantation condition, for example, implantation energy is set at 20 keV, and the amount of dose is set at 110.sup.13/cm.sup.2. In this connection, it is preferable that activation is conducted through annealing at 400 C. or lower in such a way that bonding between the wiring layer 73 and the support substrate 74 is not broken. Subsequently, the above-described cap layer is removed through, for example, a dilute hydrofluoric acid treatment. At this time, the insulating layer 83 may be removed from the SOI substrate 81.
[0226] In this manner, as shown in
[0227] Next, as shown in
[0228] Then, as shown in
[0229] In this connection, as for the material for the above-described hole accumulation auxiliary film 32 in this example, even ITO (In.sub.2O.sub.3) can also be employed because the value of work function of the interface on the light-receiving surface side of the light-receiving portion is about 5.1 eV. ITO can have a value of work function of 4.5 eV to 5.6 eV depending on the film formation process. Furthermore, as for other oxide semiconductors, since semiconductors, in which RuO.sub.2, SnO.sub.2, IrO.sub.2, OsO.sub.2, ZnO, ReO.sub.2, MoO.sub.2, and acceptor impurities are introduced, polyethylenedioxythiophene (polyethylenedioxythiophene: PEDOT), which is an organic material, and the like are allowed to have values of work function larger than 5.1 eV, they can serve as materials for the hole accumulation auxiliary film 32. Moreover, examples of film formation techniques include ALD, CVD, and vapor phase doping as film formation techniques at 400 C. or lower.
[0230] Subsequently, as shown in
[0231] Then, as shown in
[0232] In the above-described method for manufacturing a solid-state imaging device (third manufacturing method), since the hole accumulation auxiliary film 32, which is a film having a value of work function larger than that of the interface on the light-receiving surface 12s side of the above-described light-receiving portion 12, is formed on the insulating film 31 disposed on the light-receiving portion 12, the hole accumulation efficiency of the hole accumulation layer 23 is increased, so that the hole accumulation layer 23 disposed at the light-receiving surface 12s side interface of the light-receiving portion 12 can accumulate adequate holes. Consequently, a dark current is reduced. In this connection, it is enough that the above-described hole accumulation auxiliary film 32 has the value of work function higher than the value of work function of the hole accumulation layer 23 and it is not necessary to pass a current. Therefore, an electrically conductive film, an insulating film, or a semiconductor film may be employed. Hence, a material exhibiting high resistance can be selected for the hole accumulation auxiliary film 32. In addition, there is a feature that an external signal input terminal is unnecessary for the hole accumulation auxiliary film 32.
[0233] The solid-state imaging devices 1 to 8 of the above-described individual examples are provided with a plurality of pixel portions including the light-receiving portions to convert the amounts of incident light to electric signals and wiring layers on one surface side of the semiconductor substrates including the individual pixel portions, and can be applied to a back-side illumination solid-state imaging device having a configuration in which the light incident from the side opposite to the surface provided with the wiring layer is received with the above-described individual light-receiving portions. As a matter of course, it is possible to apply to a surface illumination solid-state imaging device, wherein a wiring layer is disposed on the light-receiving surface side and an optical path of the incident light incident on the light-receiving portion is specified to be a region, in which the above-described wiring layer is not disposed, in order that the incident light incident on the light-receiving portion is not interfered.
[0234] Next, an embodiment (example) according to an imaging apparatus of the present invention will be described with reference to a block diagram shown in
[0235] As shown in
[0236] The solid-state imaging device 1 or the solid-state imaging device 2 according to the present invention or the solid-state imaging device having the configuration shown in
[0237] Incidentally, the imaging apparatus 500 according to the present invention is not limited to the above-described configuration, but can be applied to an imaging apparatus having any configuration including the solid-state imaging device.
[0238] The above-described solid-state imaging device 1 to the solid-state imaging device 8 and the like may be made in the form of one chip or in the form of a module, in which an imaging portion and a signal processing portion or an optical system are integrally packaged and which has an imaging function. In addition, the present invention can be applied to not only solid-state imaging devices, but also imaging apparatuses. In this case, as for the imaging apparatus, an effect of improving image quality is obtained. Here, the imaging apparatus refers to, for example, a portable apparatus having a camera or an imaging function. In this regard, imaging includes not only picking up of image in usual photo shooting with a camera, but also fingerprint detection and the like in a broad sense.