Composite substrate, semiconductor chip having a composite substrate and method for producing composite substrates and semiconductor chips

Abstract

A composite substrate has a carrier and a utility layer. The utility layer is attached to the carrier by means of a dielectric bonding layer and the carrier contains a radiation conversion material. Other embodiments relate to a semiconductor chip having such a composite substrate, a method for producing a composite substrate and a method for producing a semiconductor chip with a composite substrate.

Claims

1. A composite substrate comprising: a carrier; a dielectric bonding layer; and a utility layer attached to the carrier by the dielectric bonding layer, wherein the utility layer is thinner than the carrier, wherein the composite substrate comprises a radiation conversion material, and wherein a refractive index of the dielectric bonding layer decreases from the utility layer towards the carrier, wherein the dielectric bonding layer directly adjoins the carrier and the utility layer, wherein the utility layer comprises a nitride compound semiconductor material, and wherein the dielectric bonding layer comprises an oxynitride, a nitrogen content of the oxynitride varying such that the refractive index of the dielectric bonding layer decreases towards the carrier.

2. The composite substrate according to claim 1, wherein the utility layer has a thickness of, at most, 1 m.

3. The composite substrate according to claim 1, wherein the dielectric bonding layer comprises an oxide, a nitride or an oxynitride.

4. The composite substrate according to claim 1, wherein on at least one side the dielectric bonding layer adjoins a boundary surface with patterning.

5. A semiconductor chip with a composite substrate according to claim 1, wherein a semiconductor body with an active region configured to generate radiation is arranged on the utility layer, and wherein the radiation generated by the active region during operation is converted, at least in part, by the radiation conversion material.

6. The semiconductor chip according to claim 5, wherein the carrier comprises a mirror layer on a side of the carrier that is remote from a semiconductor layer sequence of the semiconductor body.

7. The semiconductor chip according to claim 5, wherein a major face of the carrier that is remote from the semiconductor body forms a radiation exit face.

8. The semiconductor chip according to claim 5, wherein the refractive index of the dielectric bonding layer decreases from the utility layer towards the carrier in one of a continuous manner and a staged manner, and wherein the refractive index of a first portion of the dielectric bonding layer adjacent to the utility layer is larger than the refractive index of a second portion of the dielectric bonding layer adjacent of the carrier.

9. The semiconductor chip according to claim 5, wherein the carrier is thicker than all layers on the carrier.

10. The semiconductor chip according to claim 5, wherein a thickness of the carrier amounts to between 10 m inclusive and 200 m inclusive.

11. The composite substrate according to claim 1, wherein the carrier is thicker than all layers on the carrier.

12. The composite substrate according to claim 1, wherein a thickness of the carrier amounts to between 10 m inclusive and 200 m inclusive.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features, configurations and convenient aspects are revealed by the following description of the exemplary embodiments in conjunction with the figures, in which:

(2) FIGS. 1A and 1B respectively show first and second exemplary embodiments of a composite substrate, in schematic sectional view;

(3) FIGS. 2A to 2E show an exemplary embodiment of a method for producing a composite substrate, by means of intermediate steps shown schematically in sectional view;

(4) FIGS. 3A and 3B show an exemplary embodiment of a semiconductor chip with a composite substrate (FIG. 3A) and a component with such a semiconductor chip (FIG. 3B);

(5) FIGS. 4A and 4B show a second exemplary embodiment of a semiconductor chip with a composite substrate (FIG. 4A) and a component with such a semiconductor chip (FIG. 4B), in each case in schematic sectional view; and

(6) FIGS. 5A to 5C show an exemplary embodiment of a method for producing a plurality of semiconductor chips, by means of intermediate steps shown schematically in sectional view.

(7) Identical, similar or identically acting elements are provided with the same reference numerals in the figures. The figures and the size ratios of the elements illustrated in the figures relative to one another are not to be regarded as being to scale. Rather, individual elements may be illustrated on an exaggeratedly large scale for greater ease of depiction and/or better comprehension.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(8) A first exemplary embodiment of a composite substrate is illustrated schematically in sectional view in FIG. 1A. The composite substrate 1 comprises a carrier 2 and a utility layer 5. Between the carrier and the utility layer a dielectric bonding layer 3 is arranged. A surface of the utility layer remote from the carrier 2 takes the form of a deposition surface for epitaxial deposition.

(9) The carrier 2 comprises a radiation conversion material, for example a luminescent or phosphorescent material. The carrier may take the form of a ceramic, the radiation conversion material, in the form of luminescent material particles, being joined together into a ceramic, for example, by sintering, to produce the carrier. To produce the ceramic, further particles and/or additives may be admixed, in addition to the radiation conversion material. The additives may exit completely from the carrier during production or remain at least in part in the carrier.

(10) A ceramic-based carrier is preferably formed for the most part by the radiation conversion material. The carrier preferably contains a proportion by volume of the radiation conversion material of at least 75%, particularly preferably of at least 90%.

(11) A ceramic having a radiation conversion material and a method for producing such a ceramic is described in International Patent Publication No. WO 2010/045915, the disclosure content of which is hereby included explicitly by reference in this respect in the present application.

(12) A suitable radiation conversion material is in particular a garnet, for example, Y.sub.3(Al, Ga).sub.5O.sub.12, doped with rare earth metals, for example, Ce.

(13) Alternatively or in addition, the carrier may contain at least one of the following materials: rare earth metal-activated alkaline earth metal sulfides, rare earth metal-activated thiogallates, rare earth metal-activated aluminates, rare earth metal-activated orthosilicates, rare earth metal-activated chlorosilicates, rare earth metal-activated alkaline earth metal silicon nitrides, rare earth metal-activated oxynitrides and rare earth metal-activated aluminum oxynitrides, rare earth metal-activated silicon nitrides.

(14) Alternatively or in addition, the carrier may comprise a matrix material, for example, a glass, in which the radiation conversion material is embedded. In this case, the radiation conversion material and the glass are conveniently adapted to one another in such a way that the radiation conversion material is not degraded or destroyed on introduction into the glass melt. The proportion by volume of the radiation conversion material amounts in this case preferably to between 5% and 30% inclusive.

(15) The dielectric bonding layer 3 preferably contains an oxide, for example, silicon oxide, a nitride, for example, silicon nitride, or an oxynitride, for example, silicon oxynitride. In the case of silicon oxynitride, the refractive index can be adjusted by varying the nitrogen content between approximately 1.45 and 2.5, the refractive index being higher, the greater the nitrogen content.

(16) The composition of the dielectric bonding layer 3 may vary in the perpendicular direction, i.e., in a direction extending perpendicular to a main plane of extension of the composite substrate 1. Preferably, the dielectric bonding layer 3 exhibits a higher refractive index on the side facing the utility layer 5 than on the side facing the carrier 2. The refractive index may reduce continuously or in steps towards the carrier.

(17) For silicon oxynitride it is not only the refractive index, but also the absorption coefficient which increases as the nitrogen content increases. A dielectric bonding layer with a nitrogen content decreasing towards the carrier is therefore distinguished in comparison with a pure silicon oxide layer by better refractive index adaptation to semiconductor material and in comparison with a pure silicon nitride layer by lower absorption for the same thickness.

(18) The utility layer 5 is preferably constructed such that it is suitable for the deposition of III-V compound semiconductor material. The utility layer 5 is preferably based on a nitride compound semiconductor material. In contrast thereto, the utility layer may however also contain another material, in particular, another semiconductor material such as, for example, silicon, silicon carbide, gallium phosphide or gallium arsenide or consist of such a material.

(19) The second exemplary embodiment, illustrated in FIG. 1B, of a composite substrate corresponds substantially to the first exemplary embodiment described in connection with FIG. 1A.

(20) In contrast thereto, the composite substrate 1 exhibits patterning 25, which is formed by way of example at a boundary surface between the carrier 2 and the dielectric bonding layer 3. Alternatively or in addition, a boundary surface between the utility layer and the dielectric bonding layer 3 may also be patterned.

(21) The patterning 25 may, for example, be formed irregularly by means of roughening. Regular, in particular periodically repeating patterning may also be used. The patterning is provided in particular for the purpose of reducing waveguide effects of radiation irradiated into the composite substrate 1 and/or radiation converted by means of the radiation conversion material. Alternatively or in addition, the patterning 25 may fulfill the function of an optical element, for example, a lens or a diffraction grating. Furthermore, the patterning and/or the optical element may alternatively or in addition also be formed on the side of the carrier 2 remote from the utility layer 5.

(22) FIGS. 2A to 2E show a first exemplary embodiment of production of a composite substrate by way of intermediate steps shown schematically in sectional view.

(23) As shown in FIG. 2A, a semiconductor material 50 is provided on an auxiliary carrier 4. The auxiliary carrier 4 serves in particular in epitaxial deposition of the semiconductor material 50, for example, by means of MBE or MOCVD.

(24) Separation nuclei 51 are formed in the semiconductor material 50 by implanting ions, for example, hydrogen ions (shown by arrows in FIG. 2B). The separation nuclei extend in a plane extending parallel to a surface of the semiconductor material 50 remote from the auxiliary carrier 4. The energy of the ions determines the penetration depth of the ions into the semiconductor material and thus the thickness of the semiconductor material subsequently to be transferred.

(25) The thickness preferably amounts to at most 1 m, preferably between 10 nm and 500 nm inclusive, particularly preferably between 10 nm and 200 nm inclusive.

(26) A first dielectric sublayer 31 is deposited on the semiconductor material 50, said sublayer constituting part of the dielectric bonding layer 3 in the finished composite substrate.

(27) The carrier 2 is coated with a second dielectric sublayer 32. As shown in step 2D, the carrier 2 and the auxiliary carrier 4 are positioned relative to one another in such a way that the first dielectric sublayer 31 and the second dielectric sublayer 32 adjoin one another directly. The dielectric sublayers 31, 32 are joined together by direct bonding, for example, by pressing together at a temperature of between 700 C. and 1200 C., and together form the dielectric bonding layer 3. An adhesion layer such as a glue layer or a solder layer is not required to produce the bond.

(28) Once the directly bonded joint has been produced, the auxiliary carrier 4 is detached along the separation nuclei, with part of the semiconductor material 50. This is preferably thermally induced. The semiconductor material remaining on the carrier 2 forms the utility layer 5 of the composite substrate 1 (FIG. 2E). The auxiliary carrier can be reused after detachment to produce further composite substrates.

(29) Unlike in the exemplary embodiment described, it is also feasible for the semiconductor material 50 for the utility layer 5 to stem directly from the auxiliary carrier 4. Epitaxial deposition on the auxiliary carrier is not necessary in this case.

(30) A first exemplary embodiment of a semiconductor chip is shown in schematic sectional view in FIG. 3A. By way of example, the semiconductor chip 10 comprises a composite substrate 1 constructed as described in relation to FIG. 1A.

(31) A semiconductor body 7 with a semiconductor layer sequence 700 is arranged on the composite substrate 1. The semiconductor layer sequence, which forms the semiconductor body, comprises an active region 70, which is arranged between a first semiconductor layer 71 and a second semiconductor layer 72. The first semiconductor layer 71 and the second semiconductor layer 72 conveniently differ from one another with regard to their conduction type. For example, the first semiconductor layer 71 may be n-conductive and the second semiconductor layer 72 p-conductive or vice versa.

(32) The first semiconductor layer 71 and the second semiconductor layer 72 are each connected electrically conductively to a first contact 81 and a second contact 82 respectively. The contacts 81, 82 are intended for external electrical contacting of the semiconductor chip 10. When the semiconductor chip 10 is in operation, charge carriers can be injected from different sides via the contacts into the active region 70 and there recombine, with emission of radiation of a first wavelength range.

(33) The radiation of the first wavelength range is converted in the composite substrate 1, in particular in the carrier 2, partially into radiation of a second wavelength range different from the first wavelength range.

(34) For example, the active region 70 may be intended for generating radiation in the blue spectral range and the radiation conversion material in the carrier 2 may be intended for converting radiation into radiation in the yellow spectral range, such that mixed light which appears white to the human eye emerges from the semiconductor chip 10. Radiation thus proceeds in the semiconductor chip itself. In contrast to a component in which radiation conversion material is embedded in an enclosure or in which a radiation conversion element is attached to the semiconductor chip by means of an adhesion layer, the radiation does not pass through any material with a comparatively low refractive index, such as, for example, silicone, prior to radiation conversion. Because the refractive index of the dielectric bonding layer 3 is high compared with silicone, said bonding layer separating the radiation conversion material of the carrier 2 from the semiconductor material of the semiconductor chip 10, the radiation conversion material is coupled optically particularly efficiently to the semiconductor material. Furthermore, thermal resistance is reduced by the dielectric bonding layer compared with a semiconductor chip to which a conversion element is attached using an adhesion layer. The heat conduction of a 250 nm thick dielectric bonding layer 3 of silicon oxide is, for example, approximately ten times that of a 1 m thick silicone layer.

(35) One exemplary embodiment of a radiation-emitting component 100 with such a semiconductor chip is illustrated schematically and in sectional view in FIG. 3B. The semiconductor chip 10 is attached to a connection carrier 9. The first contact 81 and the second contact 82 are each connected electrically conductively with the connection carrier by a first land 91 and a second land 92 respectively.

(36) The connection carrier 9 may for example be a circuit board, in particular a printed circuit board (PCB), an intermediate carrier (sub-mount), for example, a ceramic carrier, or a housing body in particular for a surface-mountable component. In particular, the first land 91 and the second land 92 may be formed by a lead frame.

(37) The semiconductor chip 10 is embedded in an encapsulation 95. The encapsulation is conveniently transparent or at least translucent to the radiation emitted by the semiconductor chip 10. In particular, the encapsulation may be free of radiation conversion material, since this is already contained in the carrier 2 of the composite substrate 1. A silicone, an epoxide or a hybrid material with a silicone and an epoxide is particularly suitable for the encapsulation.

(38) Alternatively, a further radiation conversion material and/or diffuser material may be contained in the encapsulation, in addition to the radiation conversion material in the carrier 2. The further radiation conversion material may in particular be provided to adjust the color locus of the radiation emitted by the radiation-emitting component 100.

(39) The semiconductor chip 10 is arranged in flip-chip geometry on the connection carrier 9, i.e., the composite substrate 1 is arranged on the side of the semiconductor layer sequence 7 remote from the connection carrier 9. When the semiconductor chip is in operation, the carrier 2 thus forms on the top, i.e., remote from the connection carrier, a radiation exit face of the semiconductor chip 10.

(40) In contrast with a thin-film semiconductor chip, in which the growth substrate is removed, the composite substrate remains completely or at least in part in the semiconductor chip. The carrier 2 may thus mechanically stabilize the semiconductor body 7, so reducing the risk of breakage.

(41) The thickness of the carrier 2 preferably amounts to between 10 m and 200 m inclusive, particularly preferably between 20 m and 100 m inclusive, for example, 50 m. During epitaxial deposition of the semiconductor layer sequence, the carrier may also exhibit a greater thickness. This makes it possible to reduce the risk of warping of the carrier at the comparatively high temperatures used in epitaxial deposition. The thickness of a thick carrier is reduced to the stated thickness after deposition. By way of the thickness it is possible to adjust the color locus of the radiation emitted by the finished semiconductor chip.

(42) On production of the component 100, the semiconductor chip 10 may be electrically contacted to determine the color locus of the emitted radiation prior to formation of the encapsulation. To adapt the color locus, in particular to reduce the proportion of the radiation converted in the carrier 2, the thickness of the carrier may be reduced, for example, mechanically, for instance using grinding, lapping or polishing, or chemically, for instance, wet chemically or dry chemically or by means of material abrasion by coherent radiation, for instance, laser radiation. It is thus possible individually to adjust the color locus of the radiation emitted by the semiconductor chip, in particular even separately for each individual semiconductor chip. If necessary, the semiconductor chip may also be provided with a coating to adjust the color locus, which coating may likewise contain radiation conversion material.

(43) The second exemplary embodiment, illustrated in FIG. 4A, of a semiconductor chip 10 corresponds substantially to the first exemplary embodiment described in connection with FIG. 3A. In contrast thereto, on the side of the composite substrate 1 remote from the semiconductor body 7 a mirror layer 96 is formed, which is intended to reflect the radiation generated in the active region 70. The preferably metallic mirror layer 96 conveniently exhibits high reflectivity for the radiation generated in the active region 70 and/or the radiation converted in the carrier 2 by means of the radiation conversion material. In the visible spectral range, aluminum or silver are suitable examples.

(44) Furthermore, unlike in the first exemplary embodiment, a radiation-transmissive contact layer 821 is formed on the second semiconductor layer 72, via which contact layer the charge carriers injected into the second contact 82 may be impressed uniformly and over a large area into the second semiconductor layer 72.

(45) The radiation-transmissive contact layer 821 preferably contains a transparent conductive oxide (TCO), for example, indium-tin oxide (ITO) or zinc oxide (ZnO). Alternatively or in addition, the radiation-transmissive contact layer may comprise a metal layer, which is so thin that it transmits radiation generated in the semiconductor chip.

(46) As shown in FIG. 4B, such a semiconductor chip is suitable, in particular, for mounting in which the mirror layer 96 faces the connection carrier 9.

(47) The contacts 81, 82 may be connected electrically conductively to the lands 91, 92 by way of connecting leads 97, for example, via wire bond connections.

(48) One exemplary embodiment of a method for producing a semiconductor chip is shown schematically in FIGS. 5A to 5C by way of intermediate steps.

(49) As FIG. 5A shows, a composite substrate is provided, with a carrier 2 which contains radiation conversion material, a dielectric bonding layer 3 and a utility layer 5.

(50) For simplified representation, a region of the composite substrate 1 is shown in the figures which, on production of the semiconductor chips, results in two semiconductor chips, the method being described by way of example for semiconductor chips which are constructed as described in relation to FIG. 4A.

(51) A semiconductor layer sequence consisting of a first semiconductor layer 71, an active region and a second semiconductor layer 72 is deposited epitaxially on the utility layer 5 of the composite substrate 1, for instance using MBE or MOCVD (FIG. 5B). In contrast to an adhesion layer such as a glue layer or a solder layer, the dielectric bonding layer withstands the temperatures typical of epitaxy, for example, temperatures of between 700 C. and 1100 C., such that the carrier 2 is able to mechanically stabilize the semiconductor layer sequence during deposition.

(52) To form the first contact 81, the first semiconductor layer 71 is exposed in places. This may be performed in particular chemically, for instance, wet chemically or dry chemically.

(53) Deposition of the contacts 81, 82 and the radiation-transmissive contact layer and the mirror layer 96 preferably proceeds by means of vapor deposition or sputtering.

(54) This is followed by singulation into semiconductor chips, for example, by means of laser radiation, mechanically, for instance, by means of sawing, or chemically, for instance, by means of wet chemical or dry chemical etching.

(55) In the above-described method, the semiconductor layers are deposited epitaxially on a composite substrate which already contains the radiation conversion material.

(56) When singulating into semiconductor chip, therefore, semiconductor chips are obtained which already contain the radiation conversion material.

(57) The invention is not restricted by the description given with reference to the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or the exemplary embodiments.