Solid-state image sensor and electronic device

Abstract

Provided is a solid-state image sensor that includes a micro lens through which incident light is condensed, a photoelectrical conversion unit that generates electric charge based on the condensed incident light, and a translucent plate formed between the micro lens and the photoelectrical conversion unit and including a light-shielding wall provided between a translucent part provided for each pixel and the pixel. An antireflection film including films of two layers or more is formed between the light-shielding wall and the translucent part.

Claims

1. A solid-state image sensor, comprising: a micro lens configured to condense incident light; a photoelectrical conversion unit configured to generate electric charge based on the condensed incident light; a translucent plate between the micro lens and the photoelectrical conversion unit, wherein the translucent plate includes a light-shielding wall, a first translucent part, and a second translucent part, the first translucent part corresponds to a first pixel, the second translucent part corresponds to a second pixel, each of the first pixel and the second pixel is associated with the solid-state image sensor, and the light-shielding wall is between the first translucent part and the second translucent part; and an antireflection film between the light-shielding wall and the first translucent part, wherein the antireflection film is configured to prevent reflection of the condensed incident light having a particular wavelength, the antireflection film includes a first antireflection film layer, a second antireflection film layer, a third antireflection film layer, and a fourth antireflection film layer, the first antireflection film layer and the fourth antireflection film layer include HfO.sub.2, the second antireflection film layer includes SiO.sub.2, the third antireflection film layer includes Si, and the first antireflection film layer, the second antireflection film layer, the third antireflection film layer, and the fourth antireflection film layer are in this order from the light-shielding wall.

2. The solid-state image sensor according to claim 1, wherein the light-shielding wall includes Si.

3. The solid-state image sensor according to claim 1, wherein the antireflection film is formed by one of an ALD method or a thermal CVD method.

4. The solid-state image sensor according to claim 1, further comprising a transparent insulating layer between the translucent plate and the photoelectrical conversion unit, wherein a relation of expressions below holds, and tan 1>tan 2 holds:
tan 1=(X+Y)/B,
tan 2=(XZ)/(AB), where X represents a radius of the first translucent part of the translucent plate, Y represents a radius of the micro lens, Z represents a radius of the photoelectrical conversion unit per pixel, A represents a distance between a lower end of the micro lens and the photoelectrical conversion unit, B represents a thickness of the translucent plate, and C represents a thickness of the transparent insulating layer, 1 represents a maximum value of a first incident angle of the condensed incident light that is incident from outside a visual field of the micro lens and reflected at the light-shielding wall, and 2 represents a minimum value of a second incident angle at which reflected light of the condensed incident light at the light-shielding wall is incident on an edge of an effective radius of the photoelectrical conversion unit.

5. The solid-state image sensor according to claim 1, wherein the condensed incident light is near-infrared light, the near-infrared light has a central wavelength of 900 nm, and the solid-state image sensor is in a vein authentication device.

6. An electronic device, comprising: a solid-state image sensor that includes: a micro lens configured to condense incident light; a photoelectrical conversion unit configured to generate electric charge based on the condensed incident light; a translucent plate between the micro lens and the photoelectrical conversion unit, wherein the translucent plate includes a light-shielding wall, a first translucent part, and a second translucent part, the first translucent part corresponds to a first pixel, the second translucent part corresponds to a second pixel, each of the first pixel and the second pixel is associated with the solid-state image sensor, and the light-shielding wall is between the first translucent part and the second translucent part; and an antireflection film between the light-shielding wall and the first translucent part, wherein the antireflection film is configured to prevent reflection of the condensed incident light having a particular wavelength, the antireflection film includes a first antireflection film layer, a second antireflection film layer, a third antireflection film layer, and a fourth antireflection film layer, the first antireflection film layer and the fourth antireflection film layer include HfO.sub.2, the second antireflection film layer includes SiO.sub.2, the third antireflection film layer includes Si, and the first antireflection film layer, the second antireflection film layer, the third antireflection film layer, and the fourth antireflection film layer are in this order from the light-shielding wall.

7. A solid-state image sensor, comprising: a micro lens configured to condense incident light; a photoelectrical conversion unit configured to generate electric charge based on the condensed incident light; a translucent plate between the micro lens and the photoelectrical conversion unit, wherein the translucent plate includes a light-shielding wall, a first translucent part, and a second translucent part, the first translucent part corresponds to a first pixel, the second translucent part corresponds to a second pixel, each of the first pixel and the second pixel is associated with the solid-state image sensor, and the light-shielding wall is between the first translucent part and the second translucent part; an antireflection film between the light-shielding wall and the first translucent part, wherein the antireflection film is configured to prevent reflection of the condensed incident light having a particular wavelength, and the antireflection film includes a first antireflection film layer and a second antireflection film layer; and transparent insulating layer between the translucent plate and the photoelectrical conversion unit, wherein a relation of expressions below holds, and tan 1>tan 2 holds:
tan 1=(X+Y)/B,
tan 2=(XZ)/(AB), where X represents a radius of the first translucent part of the translucent plate, Y represents a radius of the micro lens, Z represents a radius of the photoelectrical conversion unit per pixel, A represents a distance between a lower end of the micro lens and the photoelectrical conversion unit, B represents a thickness of the translucent plate, and C represents a thickness of the transparent insulating layer, 1 represents a maximum value of a first incident angle of the condensed incident light that is incident from outside a visual field of the micro lens and reflected at the light-shielding wall, and 2 represents a minimum value of a second incident angle at which reflected light of the condensed incident light at the light-shielding wall is incident on an edge of an effective radius of the photoelectrical conversion unit.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view illustrating an exemplary configuration of a conventional solid-state image sensor in which a translucent plate is provided between a micro lens and a PD.

(2) FIG. 2 is a cross-sectional view illustrating an exemplary configuration of a conventional solid-state image sensor in which the distance between pixels is increased.

(3) FIG. 3 is a cross-sectional view illustrating an exemplary configuration of a solid-state image sensor to which the present technology is applied.

(4) FIGS. 4A, 4B, and 4C are plan views of components of the solid-state image sensor in FIG. 3.

(5) FIG. 5 is a diagram illustrating the relation between the size of each component of a solid-state image sensor and the incident angle of light.

(6) FIG. 6 is a graph illustrating the relation between the wavelength and reflectance of incident light.

(7) FIG. 7 is a graph illustrating the relation between the incident angle and reflectance of incident light.

(8) FIGS. 8A, 8B, 8C, and 8D are diagrams for description of a method of manufacturing a translucent plate of a solid-state image sensor.

(9) FIG. 9 is a diagram illustrating use examples of an electronic device to which the present technology is applied.

MODE FOR CARRYING OUT THE INVENTION

(10) Hereinafter, best modes (hereinafter, referred to as embodiments) for carrying out the present technology will be described in detail with reference to the drawings.

(11) <Exemplary Configuration of Solid-State Image Sensor According to Embodiment of Present Technology>

(12) FIG. 3 is a cross-sectional view illustrating an exemplary configuration of a solid-state image sensor according to an embodiment of the present technology. FIGS. 4A, 4B, and 4C illustrate a plan view of components of the solid-state image sensor.

(13) This solid-state image sensor 30 includes, sequentially from the light incident side, a cover glass 31, a micro lens array 32, a front light-shielding body 33, a translucent plate 34, a transparent insulating layer 38, and a PD layer 39.

(14) As illustrated in FIG. 4A, the micro lens array 32 includes a circular micro lens at the position of each pixel.

(15) As illustrated in FIG. 4B, the front light-shielding body 33 shields a region other than the micro lens of each pixel, and is formed to prevent incident light from transmitting into a substrate through the region.

(16) The translucent plate 34 includes a translucent part 35 that transmits incident light condensed through the micro lens array 32 for each pixel, and a light-shielding wall 36 that prevents light incident on the translucent part 35 from entering adjacent pixels as illustrated in FIG. 4C.

(17) In addition, an antireflection film 37 as a stack of two or more layers of predetermined material is formed on a wall surface of the light-shielding wall 36 to prevent incident light from outside of the view angle of the micro lens of the pixel from reflecting at the wall surface.

(18) In the case of FIG. 3, the antireflection film 37 includes, sequentially from a side close to the light-shielding wall 36, two layers of an antireflection-film first layer 371 and an antireflection-film second layer 372. For example, the material of the antireflection-film first layer 371 may be TiO.sub.2, and the material of the antireflection-film second layer 372 may be SiO.sub.2.

(19) Furthermore, for example, in a case where the antireflection film 37 includes four layers, the materials of the four layers may be, sequentially from the side close to the light-shielding wall 36, HfO.sub.2, SiO.sub.2, Si, and HfO.sub.2.

(20) In the solid-state image sensor 30, incident light condensed through the micro lens array 32 is received by the PD layer 39 through the translucent part 35 of the translucent plate 34. Note that incident light from outside of the visual field of the micro lens of each pixel is incident on the wall surface (light-shielding wall 36) inside the translucent plate 34, but is prevented from reflecting and reaching the PD layer 39 by the antireflection-film first layer 371 and the antireflection-film second layer 372. Accordingly, it is possible to prevent ghost image generation.

(21) <Film Thickness of Antireflection Film 37>

(22) Here, the following describes the antireflection film 37 formed on the wall surface of the light-shielding wall 36.

(23) The film thickness of the antireflection film 37 formed on the wall surface of the light-shielding wall 36 is determined in accordance with the incident angle of light from outside of the visual field of the micro lens and a light wavelength to be reduced.

(24) FIG. 5 illustrates the relation between the size of each component of the solid-state image sensor 30 and the incident angle of light from outside of the visual field of the micro lens.

(25) As illustrated in FIG. 5, X represents the radius (through-hole opening radius) of the translucent part 35 of the translucent plate 34, Y represents the radius of the micro lens, Z represents the radius of a PD effective region per pixel, A represents the distance (imaging distance) between a lower end of the micro lens and the PD layer 39, B represents the thickness (reflection region length) of the translucent plate 34, and C represents the thickness (non-reflection region length) of the transparent insulating layer 38. Furthermore, in a case where 1 represents the maximum value of the incident angle of light from outside of the visual field of the micro lens to be reflected at the light-shielding wall 36, and 2 represents the minimum value of an incident angle (=reflection angle) at which reflected light of the incident light at the light-shielding wall 36 is to be incident on the edge of the PD effective radius, the relation of Expression (1) below holds, and the present technology becomes effective when tan 1>tan 2 holds.
tan 1=(X+Y)/B
tan 2=(XZ)/(AB)(1)

(26) For example, in a case where X=55 m, Y=50 m, Z=40 m, A=500 m, B=400 m, and C=100 m, the maximum value 1 of the incident angle is 15, and the minimum value 2 of the incident angle (=reflection angle) is 8.5. This means that, in a case where the incident angle is equal to or larger than 15 and in a case where the incident angle is equal to or smaller than 8.5, incident light reflects at the wall surface of the light-shielding wall 36 but does not reach the PD effective radius or attenuates through multiple reflection.

(27) Thus, the film thickness of the antireflection film 37 needs to be determined for the incident angle of light from outside of the visual field of the micro lens in the range of 8.5 to 15.

(28) The wavelength of incident light is normally in the range of 380 nm to 830 nm approximately for visible light. Furthermore, in a case where the solid-state image sensor 30 is used to detect light having a particular wavelength, for example, used for a vein authentication device or the like using light in a near-infrared region (central wavelength of 900 nm), such a wavelength needs to be considered. The following description assumes that the solid-state image sensor 30 is used for a vein authentication device or the like using light in a near-infrared region (central wavelength of 900 nm).

(29) <Relation Between Incident Light Wavelength and Reflectance at Wall Surface of Light-Shielding Wall 36>

(30) Next, FIG. 6 illustrates the relation between the wavelength of incident light and the reflectance at the wall surface of the light-shielding wall 36 for each stacked number of an antireflection film 27.

(31) In the drawing, the horizontal axis represents the wavelength of incident light, and the vertical axis represents the reflectance. Curved line L1 corresponds to a case where no antireflection film 27 is formed. Curved line L2 corresponds to a case where the antireflection film 27 includes a material (TiO.sub.2 (121.55 nm)) of a single layer. Curved line L3 corresponds to a case where the antireflection film 27 includes materials (SiO.sub.2 (114.99 nm) and TiO.sub.2 (39.62 nm), sequentially from the light-shielding wall 36 side) of two layers. Curved line L4 corresponds to a case where the antireflection film 27 includes materials (HfO.sub.2 (53.71 nm), Si (24.20 nm), SiO.sub.2 (204.27 nm), and HfO.sub.2 (45.20 nm), sequentially from the light-shielding wall 36 side) of four layers.

(32) It is shown that, in particular, the reflectance on Curved lines L3 and L4 is low near a wavelength of 900 nm on the horizontal axis in the drawing. In other words, it is shown that, in a case where the antireflection film 27 includes two or more layers, it is possible to sufficiently prevent reflection of incident light near a wavelength of 900 nm at the wall surface of the light-shielding wall 36.

(33) FIG. 7 illustrates the relation between the incident angle of incident light having a wavelength of 900 nm and the reflectance at the wall surface of the light-shielding wall 36 for each stacking number of the antireflection film 27.

(34) In the drawing, the horizontal axis represents the incident angle of incident light, and the vertical axis represents the reflectance. Curved line L11 corresponds to a case where no antireflection film 27 is formed. Curved line L12 corresponds to a case where the antireflection film 27 includes a material (TiO.sub.2 (121.55 nm)) of a single layer. Curved line L13 corresponds to a case where the antireflection film 27 includes materials (SiO.sub.2 (114.99 nm) and TiO.sub.2 (39.62 nm), sequentially from the light-shielding wall 36 side) of two layers. Curved line L14 corresponds to a case where the antireflection film 27 includes materials (HfO.sub.2 (53.71 nm), Si (24.20 nm), SiO.sub.2 (204.27 nm), and HfO.sub.2 (45.20 nm), sequentially from the light-shielding wall 36 side) of four layers.

(35) It is shown that, in particular, the reflectance on Curved lines L13 and L14 is low near incident angle 15 on the horizontal axis in the drawing. In other words, it is shown that, in a case where the antireflection film 27 includes two or more layers, it is possible to sufficiently prevent reflection of incident light having an incident angle of 15 at the wall surface of the light-shielding wall 36.

(36) <Manufacturing Method>

(37) Next, FIGS. 8A, 8B, 8C, and 8D illustrate a method of manufacturing the translucent plate 34 included in the image sensor 30.

(38) First, as illustrated in A of the drawing, the light-shielding wall 36 is formed by opening a through-hole in a substrate of a light-shielding material such as Si. Subsequently, as illustrated in B of the drawing, the antireflection-film first layer 371 is formed on the surface of the light-shielding wall 36, and the antireflection-film second layer 372 is formed on the antireflection-film first layer 371.

(39) The formation of the antireflection-film first layer 371 and the antireflection-film second layer 372 may employ an ALD method or a thermal CVD method in accordance with the material. For example, the ALD method is employed in a case where the material is TiO.sub.2, SiO.sub.2, or HfO.sub.2. Furthermore, for example, the ALD method is employed in a case where the material is Si or SiO.sub.2.

(40) The ALD method and the thermal CVD method have superior step coverage properties to general application method and vapor deposition method, and can form a thin film on side wall surfaces with excellent controllability, so that it is possible to uniformly form the antireflection film 37. As a result, image capturing performance with stable ghost image reduction can be obtained.

(41) Subsequently, as illustrated in C of the drawing, high pressure glass to be the translucent part 35 is encapsulated in the through-hole in which the antireflection-film first layer 371 and the antireflection-film second layer 372 are formed, and thereafter, as illustrated in D of the drawing, the high pressure glass protruding above and below the through-hole is polished to form the translucent plate 34.

(42) The front light-shielding body 33 and the micro lens array 32 are formed on one surface of the translucent plate 34 formed as described above, and the PD layer 39 is stacked on the other surface through the transparent insulating layer 38, thereby forming the solid-state image sensor 30.

(43) <Summary>

(44) In the solid-state image sensor 30 according to the present embodiment, since the translucent plate 34 includes the antireflection film 37 including two or more layers, light having a particular wavelength is prevented from reflecting at a side wall of the translucent plate 34. Furthermore, since the ALD method or the thermal CVD method is employed to form the antireflection film 37 including two or more layers, the thin and uniform antireflection film 37 can be formed, thereby achieving stable antireflection performance. Accordingly, ghost image generation is reduced even when the interval between pixels is narrowed, which leads to increase in the area efficiency of the solid-state image sensor 30.

(45) <Use Example of Solid-State Image Sensor>

(46) FIG. 9 is a diagram illustrating a use example in which the above-described solid-state image sensor is used.

(47) The above-described solid-state image sensor can be used in, for example, various electronic devices configured to sense light such as visible light, infrared light, ultraviolet light, or X-ray, as described below.

(48) Devices, such as a digital camera and a portable instrument having a camera function, configured to capture images for visual appreciation.

(49) Traffic devices such as an on-board sensor configured to perform image capturing of the front and rear sides, circumference, inside, and the like of an automobile for safety driving such as automatic stopping and recognition of a driver state and the like, a monitoring camera configured to monitor a travelling vehicle or roads, and a distance measurement sensor configured to perform measurement of, for example, the distance between vehicles.

(50) Devices provided to home electronics such as a TV, a refrigerator, and an air conditioner, configured to capture an image of a user gesture to perform an instrument operation in accordance with the gesture.

(51) Medical and healthcare devices such as an endoscope, and a device configured to perform blood vessel image capturing by receiving infrared light.

(52) Security devices such as an anti-crime monitoring camera and a personal authentication camera.

(53) Beauty care devices such as a skin measurement device configured to capture an image of skin and a micro scope configured to capture an image of scalp.

(54) Sport devices such as an action camera and a wearable camera for sport usage and the like.

(55) Agricultural devices such as a camera for monitoring the states of fields and crops.

(56) It is to be noted that the embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present technology.

(57) The present technology may be configured as described below.

(58) (1)

(59) A solid-state image sensor including:

(60) a micro lens through which incident light is condensed;

(61) a photoelectrical conversion unit configured to generate electric charge in accordance with the condensed incident light; and

(62) a translucent plate formed between the micro lens and the photoelectrical conversion unit and including a light-shielding wall provided between a translucent part provided for each pixel and the pixel,

(63) in which an antireflection film including films of two layers or more is formed between the light-shielding wall and the translucent part.

(64) (2)

(65) The solid-state image sensor according to (1), in which the antireflection film prevents reflection of incident light having a particular wavelength.

(66) (3)

(67) The solid-state image sensor according to (1) or (2), in which the light-shielding wall of the translucent plate includes Si.

(68) (4)

(69) The solid-state image sensor according to any one of (1) to (3), in which the antireflection film includes a TiO.sub.2 film and an SiO.sub.2 film sequentially from the light-shielding wall side.

(70) (5)

(71) The solid-state image sensor according to any one of (1) to (3), in which the antireflection film includes an HfO.sub.2 film, an SiO.sub.2 film, an Si film, and an HfO.sub.2 film sequentially from the light-shielding wall side.

(72) (6)

(73) The solid-state image sensor according to any one of (1) to (5), in which the antireflection film is formed by an ALD method or a thermal CVD method.

(74) (7)

(75) The solid-state image sensor according to any one of (1) to (6), further including a transparent insulating layer between the translucent plate and the photoelectrical conversion unit, in which a relation of expressions below holds, and tan 1>tan 2 holds:
tan 1=(X+Y)/B
tan 2=(XZ)/(AB)

(76) in a case where X represents the radius of the translucent part of the translucent plate, Y represents the radius of the micro lens, Z represents the radius of the photoelectrical conversion unit per pixel, A represents the distance between a lower end of the micro lens and the photoelectrical conversion unit, B represents the thickness of the translucent plate, and C represents the thickness of the transparent insulating layer, and

(77) 1 represents the maximum value of an incident angle of light that is incident from outside the visual field of the micro lens and to be reflected at the light-shielding wall, and 2 represents the minimum value of an incident angle (reflection angle) at which reflected light of the incident light at the light-shielding wall is to be incident on an edge of the effective radius of the photoelectrical conversion unit.

(78) (8)

(79) The solid-state image sensor according to any one of (2) to (7), in which

(80) the incident light having the particular wavelength is near-infrared light having a central wavelength of 900 nm, and

(81) the solid-state image sensor is used in a vein authentication device.

(82) (9)

(83) An electronic device on which a solid-state image sensor is mounted, in which

(84) the solid-state image sensor includes:

(85) a micro lens through which incident light is condensed;

(86) a photoelectrical conversion unit configured to generate electric charge in accordance with the condensed incident light; and

(87) a translucent plate formed between the micro lens and the photoelectrical conversion unit and including a light-shielding wall provided between a translucent part provided for each pixel and the pixel, and

(88) an antireflection film including films of two layers or more is formed between the light-shielding wall and the translucent part.

REFERENCE SIGNS LIST

(89) 30 Solid-state image sensor 31 Cover glass 32 Micro lens array 33 Front light-shielding body 34 Translucent plate 35 Translucent part 36 Light-shielding wall 37 Antireflection film 371 Antireflection-film first layer 372 Antireflection-film second layer