Light detection device

Abstract

The present technology relates to a light detection device that makes it possible to improve sensitivity when a light-shielding film is disposed at the boundary of pixels on a semiconductor substrate. In a CMOS image sensor, a plurality of pixels are two-dimensionally arranged in a matrix in a pixel region of a semiconductor substrate. A light-shielding film is disposed between the pixels on the semiconductor substrate, and a waveguide is disposed on the upper side of the light-shielding film. A light-shielding film is disposed over a non-pixel region which is a region other than the pixel region of the semiconductor substrate. The light-shielding film in the pixel region is thinner than the light-shielding film in the non-pixel region. The present technology can be applied, for example, to CMOS image sensors.

Description

Photodetection device

[0001] The present technology relates to a photodetection device, and particularly to a photodetection device capable of further improving sensitivity in a case where a light shielding film is disposed at a boundary between pixels on a semiconductor substrate.

[0002] Along with the recent miniaturization of pixels in image sensors, quantum efficiency (Qe), that is, sensitivity, decreases, and the difficulty of processes for achieving shrinkage of an upper layer structure compatible with pixel miniaturization increases.

[0003] Therefore, a solid-state imaging device has been devised that improves color mixing and also improves sensitivity by disposing a wall including a laminated structure of a light shielding film and an oxide film at a boundary between pixels on a semiconductor substrate (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2021-158374

[0005] However, in the case where a light shielding film is disposed at a boundary between pixels on a semiconductor substrate, no consideration has been given to further improving sensitivity.

[0006] The present technology has been made in view of such circumstances, and is intended to enable further improvement in sensitivity when a light shielding film is disposed at a boundary between pixels on a semiconductor substrate.

[0007] According to one aspect of the present technology, there is provided a photodetection device including: a plurality of pixels two-dimensionally arranged in a matrix in a pixel region of a semiconductor substrate; a first light shielding film disposed between the pixels on the semiconductor substrate; a waveguide disposed above the first light shielding film; and a second light shielding film disposed on an extra-pixel region which is a region other than the pixel region of the semiconductor substrate, wherein the first light shielding film is configured to be thinner than the second light shielding film.

[0008] According to one aspect of the present technology, there are provided: a plurality of pixels two-dimensionally arranged in a matrix in a pixel region of a semiconductor substrate; a first light shielding film disposed between the pixels on the semiconductor substrate; a waveguide disposed above the first light shielding film; and a second light shielding film disposed on an extra-pixel region which is a region other than the pixel region of the semiconductor substrate. The first light shielding film is thinner than the second light shielding film.

[0009] The light detection device may be a standalone device or a module incorporated into another device.

[0010] This is a cross-sectional view showing a first structural example of a CMOS image sensor. This is a cross-sectional view showing a second structural example of a CMOS image sensor. This is a diagram illustrating the difference in light-receiving sensitivity of the CMOS image sensors in Figures 1 and 2. This is a diagram illustrating the difference in step height between the pixel region and the non-pixel region in the CMOS image sensors in Figures 1 and 2. This is a diagram showing an example configuration of a CMOS image sensor, which is one embodiment of a photodetector to which this technology is applied. This is a cross-sectional view showing an example of the structure around the phase difference detection pixel of the CMOS image sensor in Figure 5. This is a cross-sectional view showing an example of the structure around the non-pixel region of the CMOS image sensor in Figure 5. This is a diagram illustrating an example of a method for determining the thickness of the light-shielding film. This is a diagram illustrating an example of a manufacturing method for the CMOS image sensor in Figure 5. This is a diagram illustrating an example of the use of a CMOS image sensor. This is a block diagram illustrating an example configuration of an imaging device as an electronic device to which this technology is applied. This is a block diagram illustrating an example of a schematic configuration of a vehicle control system. This is an explanatory diagram showing an example of the installation position of the imaging unit.

[0011] The following describes the embodiments for implementing this technology. The description will be in the following order: 1. A first structural example of a CMOS image sensor 2. A second structural example of a CMOS image sensor 3. A comparison of the first and second structural examples of a CMOS image sensor 4. One embodiment 5. An example of using a CMOS image sensor 6. An example of application to electronic equipment 7. An example of application to mobile devices

[0012] In the drawings referenced in the following explanation, identical or similar parts are denoted by the same or similar reference numerals, thereby omitting redundant explanations as appropriate. The drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of the thickness of each layer, etc., may differ from the actual figures. Furthermore, there may be parts where the dimensional relationships and ratios differ between drawings.

[0013] Furthermore, the definitions of directions such as up and down in the following explanation are merely for explanatory convenience and do not limit the technical concept of this disclosure. For example, if an object is rotated 90° and observed, up and down will be converted to left and right and read accordingly, and if it is rotated 180° and observed, up and down will be inverted and read accordingly.

[0014] The technology disclosed herein can be applied to all types of photodetectors having a pixel array in which pixels are arranged two-dimensionally in a matrix, and which convert incident light into photoelectric signals to output a pixel signal corresponding to the amount of light. For example, the technology disclosed herein can be applied to solid-state imaging devices that generate and output an imaging signal corresponding to the amount of incident light, or to light-receiving devices (distance measuring sensors) in distance measuring systems that receive infrared light irradiated as active light and measure the distance to a subject using a direct ToF or indirect ToF method. Below, an example of applying the technology disclosed herein to a back-illuminated, XY-addressing solid-state imaging device, also known as a CMOS image sensor, will be described. In this specification, the structure of the wiring layer of the CMOS image sensor will not be described.

[0015] <1. First structural example of a CMOS image sensor> Figure 1 is a cross-sectional view showing a first structural example of the area around a phase difference detection pixel in the pixel region of a CMOS image sensor.

[0016] As shown in Figure 1A, in the pixel region of the semiconductor substrate 11 of the CMOS image sensor 10, which is made of a silicon substrate or the like, multiple photodiodes (PDs) 11a, which serve as photoelectric conversion units, are arranged in a matrix in a two-dimensional manner. An imaging pixel, which is a pixel for imaging, contains one photodiode 11a, and a phase difference detection pixel, which is a pixel for phase difference detection, contains two photodiodes 11a. In the following, unless there is a need to specifically distinguish between imaging pixels and phase difference detection pixels, they will be collectively referred to as pixels.

[0017] An SiO film 12 is placed on the semiconductor substrate 11 within the pixel region by ALD (Atomic Layer Deposition). A color filter 13 is placed on the SiO film 12 for each imaging pixel, and an on-chip lens 14 is placed on the color filter 13 of each imaging pixel. A light-shielding portion 15 is also placed on the SiO film 12 for one of the photodiodes 11a included in each phase difference detection pixel.

[0018] The light-shielding portion 15 is formed by arranging a barrier metal 15a and a light-shielding film 15b in order from the semiconductor substrate 11 side. The barrier metal 15a is composed of, for example, Ti with a thickness of 20 nm and TiN with a thickness of 10 nm. The light-shielding film 15b is formed of, for example, W (tungsten). The light-shielding portion 15 may be covered with a protective film.

[0019] A color filter 13 is placed on the SiO film 12 and light-shielding portion 15 on the other photodiode 11a included in each phase-difference detection pixel. An on-chip lens 14 is placed on the color filter 13 of each phase-difference detection pixel.

[0020] Between each pixel's color filter 13, a light-shielding portion 16 with the same thickness (height) as the light-shielding portion 15 is placed. The light-shielding portion 16 is formed by arranging a barrier metal 16a and a light-shielding film 16b in that order from the semiconductor substrate 11 side. The barrier metal 16a is made of, for example, Ti with a thickness of 20 nm and TiN with a thickness of 10 nm, similar to the barrier metal 15a. The light-shielding film 16b is made of, for example, W, similar to the light-shielding film 15b. The light-shielding portion 16 may be covered with a protective film.

[0021] As shown in Figure 1B, when each pixel of the CMOS image sensor 10 in Figure 1A is miniaturized, the photodiode 11a and on-chip lens 14 are also miniaturized. However, thinning the SiO film 12 is difficult because cracking occurs when the film is thinned. As a result, the quantum efficiency decreases. Thinning the color filter 13 is also difficult in order to ensure spectral performance. There are limits to reducing the width w of the light-shielding portion 16, that is, to making the light-shielding portion 16 thinner.

[0022] Therefore, it is desirable to improve the quantum efficiency (light-receiving sensitivity) of the CMOS image sensor 10 shown in Figure 1B.

[0023] <2. Second structural example of a CMOS image sensor> Figure 2 is a cross-sectional view showing a second structural example of the area around a phase difference detection pixel in the pixel region of a CMOS image sensor.

[0024] In Figure 2, the CMOS image sensor 30 is given the same reference numerals as the CMOS image sensor 10 in Figure 1 for parts corresponding to those parts. Therefore, explanations of those parts will be omitted as appropriate, and the explanation will focus on the parts that differ from the CMOS image sensor 10. The CMOS image sensor 30 differs from the CMOS image sensor 10 in that the color filter 13 is not placed on the light-shielding part 15, and the waveguide 31 is placed on the light-shielding part 15 and the light-shielding part 16. The CMOS image sensor 30 also differs from the CMOS image sensor 10 in that the on-chip lens 14 of the phase difference detection pixel is placed on the color filter 13 and waveguide 31 of the phase difference detection pixel. Otherwise, it is configured the same as the CMOS image sensor 10.

[0025] Waveguide 31 is formed, for example, from TEOS (tetra ethoxy silane). The height (thickness) of waveguide 31 is, for example, 400 nm.

[0026] <3. Comparison of the first and second structural examples of the CMOS image sensor> <Explanation of the difference in light receiving sensitivity> Figure 3 is a diagram illustrating the difference in light receiving sensitivity between the CMOS image sensor 10 in Figure 1 and the CMOS image sensor 30 in Figure 2.

[0027] As shown in Figure 3A, in the CMOS image sensor 10, color mixing occurs between adjacent imaging pixels due to light passing over the light-shielding portion 16, resulting in low light reception sensitivity.

[0028] In contrast, as shown in Figure 3B, the CMOS image sensor 30 can receive light that would otherwise pass through the upper part of the light-shielding section 16 and be incident on adjacent imaging pixels in the CMOS image sensor 10, via the waveguide 31, with the photodiode 11a of its own imaging pixel. As a result, the sensitivity of the CMOS image sensor 30 is improved compared to the sensitivity of the CMOS image sensor 10. For example, the quantum efficiency of the CMOS image sensor 10 with a pixel size of 0.7 μm is 73%, while the quantum efficiency of the CMOS image sensor 30 is 77%.

[0029] Furthermore, phase difference detection using the phase difference detection pixels of the CMOS image sensor 30 can be performed normally, just as with phase difference detection using the phase difference detection pixels of the CMOS image sensor 10.

[0030] <Explanation of the difference in height between the pixel area and the out-of-pixel area> Figure 4 is a diagram illustrating the difference in height between the pixel area and the out-of-pixel area in CMOS image sensors 10 and 30. The out-of-pixel area (optical black area) is an area located outside the pixel area surrounding the pixel area, used for detecting dark current components.

[0031] As shown in Figure 4A, in the CMOS image sensor 10, only a light-shielding portion 16 is placed between the color filters 13 in the pixel region 51. Therefore, in the non-pixel region 52, only a light-shielding portion 53 with the same thickness as the light-shielding portion 16 is placed on the SiO film 12. The color filters 13 and the on-chip lens 14 are then placed on top of the light-shielding portion 53 in order. Consequently, the step difference D1 between the pixel region 51 and the non-pixel region 52 is small.

[0032] The light-shielding portion 53 is formed by arranging the barrier metal 53a and the light-shielding film 53b in order from the semiconductor substrate 11 side. The barrier metal 53a is composed of, for example, Ti with a thickness of 20 nm and TiN with a thickness of 10 nm, similar to the barrier metal 15a (16a).

[0033] The light-shielding film 53b is formed of, for example, W, similar to the light-shielding film 15b (16b). The thickness of the light-shielding film 53b is the thickness necessary for detecting the dark current component, and is, for example, 200 nm or more. In this case, the thickness of the light-shielding film 16b is also the same as the thickness of the light-shielding film 53b, 200 nm. The light-shielding portion 53 may be covered with a protective film.

[0034] On the other hand, as shown in Figure 4B, in the CMOS image sensor 30, not only the light-shielding portion 16 but also the waveguide 31 is placed between the color filters 13 in the pixel region 61. Therefore, in the non-pixel region 62, not only the light-shielding portion 53 but also the waveguide 63, which has the same thickness as the waveguide 31, is placed on the SiO film 12. Then, the color filter 13 and the on-chip lens 14 are placed in order on the waveguide 63. Consequently, the step difference D2 between the pixel region 61 and the non-pixel region 62 is larger than the step difference D1.

[0035] If the step difference D2 is large, the light incident on the on-chip lens 14 of pixels located in the peripheral region close to the extra-pixel region 62 within the pixel region 61 is not focused to the center of the photodiode 11a of that pixel. As a result, sensitivity unevenness occurs, where the sensitivity of pixels in the peripheral region is lower than that of pixels in the central region within the pixel region 61.

[0036] <4. One Embodiment> <Example of CMOS Image Sensor Configuration> Figure 5 shows an example of the configuration of a CMOS image sensor, which is one embodiment of a photodetector to which this technology is applied.

[0037] The CMOS image sensor 111 includes a pixel array unit 121, a vertical drive unit 122, a column processing unit 123, a horizontal drive unit 124, a system control unit 125, a pixel drive line 126, a vertical signal line 127, a signal processing unit 128, and a data storage unit 129.

[0038] The pixel array section 121 has a pixel region and an out-of-pixel region in which a plurality of pixels, at least a portion of which are phase difference detection pixels, are arranged in a matrix in the horizontal and vertical directions in a two-dimensional manner. Each pixel has a photodiode as a photoelectric conversion unit that generates and stores charge according to the amount of light received.

[0039] In the pixel array section 121, a pixel drive line 126 is wired horizontally for each pixel arranged horizontally, that is, for each row of pixels, and a vertical signal line 127 is wired vertically for each pixel arranged vertically, that is, for each column of pixels.

[0040] One end of the pixel drive line 126 is connected to the output terminal corresponding to each row of the vertical drive unit 122, and the pixel drive line 126 supplies a drive signal to each pixel in a row-by-row manner to drive the pixels. One end of the vertical signal line 127 is connected to the signal processing circuit corresponding to each column of the column processing unit 123, and the vertical signal line 127 supplies the signal of the charge accumulated in the photodiode of the pixel driven based on its drive signal to the signal processing circuit in a column-by-column manner.

[0041] The vertical drive unit 122 consists of, for example, a shift register and an address decoder. The vertical drive unit 122 generates drive signals for each pixel of the pixel array unit 121 in row units and outputs them to the pixel drive line 126.

[0042] The column processing unit 123 has a signal processing circuit for each row of pixels. Each signal processing circuit performs predetermined signal processing on the signal supplied from the pixels of the corresponding row via the vertical signal line 127, and temporarily holds the processed signal as a pixel signal. This signal processing includes noise reduction, CDS (Correlated Double Sampling) processing, and AD (Analog to Digital) conversion processing.

[0043] The horizontal drive unit 124 consists of a shift register and an address decoder, and sequentially selects each signal processing circuit of the column processing unit 123. The signal processing circuit selected by the horizontal drive unit 124 outputs the pixel signal to the signal processing unit 128. As a result, the pixel signal of each pixel is output sequentially to the signal processing unit 128.

[0044] The system control unit 125 consists of a timing generator and other components that generate various timing signals. Based on these timing signals, the system control unit 125 controls the operation of the vertical drive unit 122, the column processing unit 123, and the horizontal drive unit 124.

[0045] The signal processing section 128 has at least an arithmetic processing function, and performs various types of signal processing such as arithmetic processing on pixel signals output from the column processing section 123. The data storage section 129 temporarily stores data required for signal processing when signal processing is performed by the signal processing section 128. The signal processing section 128 outputs a captured image and a phase difference detection signal obtained as a result of the signal processing.

[0046] <Example of Structure of CMOS Image Sensor> FIG. 6 is a cross-sectional view showing a structural example around phase difference detection pixels of the CMOS image sensor 111 in FIG. 5. FIG. 7 is a cross-sectional view showing a structural example around an out-of-pixel region of the CMOS image sensor 111.

[0047] In the CMOS image sensor 111 of FIGS. 6 and 7, portions corresponding to those of the CMOS image sensor 30 of FIGS. 3 and 4 are denoted by the same reference numerals. Therefore, description of those portions is omitted as appropriate, and description will be given focusing on portions different from FIGS. 3 and 4. The CMOS image sensor 111 differs from the CMOS image sensor 30 in that a light shielding section 15, a light shielding section 16, a waveguide 31, a pixel region 61, and an out-of-pixel region 62 are replaced with a light shielding section 140, a light shielding section 141, a waveguide 142, a pixel region 131, and an out-of-pixel region 132. The CMOS image sensor 111 also differs from the CMOS image sensor 30 in that no waveguide 63 is disposed on the light shielding section 53. Other than these points, the configuration is the same as that of the CMOS image sensor 30.

[0048] Specifically, as shown in FIG. 6, in the CMOS image sensor 111, the light shielding section 140 is disposed for one photodiode 11a included in each phase difference detection pixel on the SiO film 12 in the pixel region 131 of the semiconductor region 11. The light shielding section 140 is formed by sequentially disposing a barrier metal 15a and a light shielding film 140b from the semiconductor substrate 11 side. The light shielding section 140 may be covered with a protective film.

[0049] As shown in Figures 6 and 7, in the CMOS image sensor 111, a light-shielding portion 141 is placed between the color filters 13 of each imaging pixel on the SiO film 12 of the pixel region 131. The light-shielding portion 141 is formed by placing a barrier metal 16a and a light-shielding film 141b in that order from the semiconductor substrate 11 side. The light-shielding portion 141 may be covered with a protective film.

[0050] The thickness of the light-shielding films 140b and 141b (first light-shielding film) in the pixel region 131 is thinner than the thickness of the light-shielding film 53b (second light-shielding film) in the non-pixel region 132. Here, the thicknesses of the light-shielding films 140b and 141b in the pixel region 131 are assumed to be the same, but they may be different. The light-shielding films 140b and 141b are, for example, tungsten with a thickness of 100 nm.

[0051] As described above, the thickness of the light-shielding film 140b (141b) is thinner than that of the light-shielding film 15b (16b), which has the same thickness as the light-shielding film 53b necessary for detecting the dark current component. Therefore, the quantum efficiency of the CMOS image sensor 111 is improved compared to the quantum efficiency of the CMOS image sensor 30. For example, the quantum efficiency of the CMOS image sensor 30 is 77% when the pixel size is 0.7 μm, but the quantum efficiency of the CMOS image sensor 111 is improved to 81%.

[0052] A waveguide 142 is positioned above the light-shielding portions 140 and 141 (on the side opposite to the semiconductor substrate 11). The thickness of the waveguide 142 is set such that, for example, the sum of the thicknesses of the light-shielding portion 15 (16) and the waveguide 31 is the same as the sum of the thicknesses of the light-shielding portion 140 (141) and the waveguide 142. For example, if the sum of the thicknesses of the light-shielding portion 15 (16) and the waveguide 31 is 630 nm (= 20 + 10 + 200 + 400), the thickness of the waveguide 31 is set to 500 nm (= 630 - 20 - 10 - 100). Here, it is assumed that the thickness of the waveguide 142 positioned above the light-shielding portions 140 and 141 is the same, but it may be different.

[0053] Waveguides 142 are not placed in the out-of-pixel region 132. Therefore, the step difference D3 between the pixel region 131 and the out-of-pixel region 132 is smaller than the step difference D2 between the out-of-pixel region 62 where waveguides 63 are placed and the pixel region 61. For example, step difference D3 is about the same as step difference D1. As a result, the sensitivity unevenness described above can be improved compared to the CMOS image sensor 30.

[0054] <Explanation of method for determining the thickness of the light-shielding film within the pixel region> Figure 8 is a diagram illustrating an example of a method for determining the thickness of the light-shielding film 140b (141b) within the pixel region 131.

[0055] Figures 8A to E are graphs representing the phase difference detection signals of the CMOS image sensor 10 when the thickness (height) of the on-chip lens 14 is 1200nm, 1400nm, 1600nm, 1800nm, and 2000nm, respectively.

[0056] Specifically, in Figures 8A to E, the horizontal axis represents the angle of incidence of light, and the vertical axis represents the output value of the phase difference detection signal. In addition, in Figures 8A to E, the thick dotted line, thin dotted line, dashed line, and solid line represent the phase difference detection signals when the thickness of the light-shielding film 15b (16b) is 200 nm, 140 nm, 100 nm, and 40 nm, respectively.

[0057] As shown in Figures 8A to E, when the thickness of the light-shielding film 15b (16b) is 100 nm or more, the phase difference detection signal does not deteriorate. However, as shown in Figures 8D and E, when the thickness of the light-shielding film 15b (16b) is 40 nm, the phase difference detection signal deteriorates. Therefore, it is desirable that the thickness of the light-shielding film 15b (16b) is greater than 40 nm and 100 nm or less. That is, when the barrier metal 15a (16a) is composed of Ti with a thickness of 20 nm and TiN with a thickness of 10 nm, it is desirable that the height of the light-shielding portion 15 (16), i.e., the total metal thickness, is greater than 70 nm and 130 nm or less.

[0058] <Method for Manufacturing a CMOS Image Sensor> Figure 9 is a diagram illustrating an example of a method for manufacturing a CMOS image sensor 111.

[0059] As shown in Figure 9A, first, a photodiode 11a and the like are formed on a semiconductor substrate 11, and an SiO film 12 is formed on its upper surface. Then, a barrier metal layer 201 made of Ti and TiN and a tungsten layer 202 are sequentially sputtered onto the SiO film 12. The thicknesses of Ti and TiN in the barrier metal layer 201 are the same as the thicknesses of Ti and TiN in the barrier metal 53a. For example, the thickness of Ti in the barrier metal layer 201 is 20 nm, and the thickness of TiN is 10 nm. The thickness of the tungsten layer 202 is the thickness of the light-shielding film 53b, which is, for example, 200 nm.

[0060] Next, as shown in Figure 9B, a resist 203 is applied to the tungsten layer 202 of the out-of-pixel region 132 using a mask via lithography. Then, as shown in Figure 9C, etching (processing) is performed to remove the barrier metal layer 201 and tungsten layer 202 of the pixel region 131, as well as the resist 203 of the out-of-pixel region 132. This forms a light-shielding portion 53 in the out-of-pixel region 132.

[0061] Next, as shown in Figure 9D, a barrier metal layer 204 made of Ti and TiN, and a tungsten layer 205 are sequentially sputtered onto the SiO film 12 of the pixel region 131 and the light-shielding portion 53 of the non-pixel region 132. The thicknesses of Ti and TiN in the barrier metal layer 204 are the same as the thicknesses of Ti and TiN in the barrier metal 16a (15a). For example, the thickness of Ti in the barrier metal layer 204 is 20 nm, and the thickness of TiN is 10 nm. The thickness of the tungsten layer 205 is the thickness of the light-shielding film 141b (140b), which is, for example, 100 nm.

[0062] Next, as shown in Figure 9E, a TEOS layer 206 is formed on the tungsten layer 205 by CVD (Chemical Vapor Deposition). The thickness of the TEOS layer 206 is the thickness of the waveguide 142, for example, 500 nm. Next, as shown in Figure 9F, a resist 207 is applied to the TEOS layer 206 in the region of the pixel region 131 that will form the waveguide 142, using lithography with a mask.

[0063] Next, as shown in Figure 9G, etching is performed to remove the TEOS layer 206 and a portion of the resist 207 in the areas where the resist 207 is not applied. This forms a waveguide 142 on the tungsten layer 205 of the pixel region 131. Next, as shown in Figure 9H, further etching is performed to remove the barrier metal layer 204 and the tungsten layer 205 in the areas where the resist 207 is not applied. This forms a light-shielding portion 141 (140) on the SiO film 12 of the pixel region 131 and below the waveguide 142.

[0064] As described above, light-shielding portions 141 (140) and 53, each having a different vertical structure, are formed on the SiO film 12 in the pixel region 131 and the non-pixel region 132, respectively.

[0065] Although not shown in the diagram, the CMOS image sensor 111 is then manufactured by sequentially forming a color filter 13 and an on-chip lens 14 on the SiO film 12 of the pixel region 131 and the light-shielding portion 53 of the non-pixel region 132.

[0066] As described above, in the CMOS image sensor 111, multiple pixels are arranged in a matrix in a two-dimensional manner in the pixel region 131 of the semiconductor substrate 11. Between the pixels on the semiconductor substrate 11, a light-shielding film 140b (141b), which is thinner than the light-shielding film 53b arranged on the extra-pixel region 132, is placed. A waveguide 142 is placed above the light-shielding film 140b (141b). Therefore, compared to the CMOS image sensor 30 in which the thickness of the light-shielding film 15b (16b) in the pixel region 61 and the light-shielding film 53b in the extra-pixel region 62 are the same, sensitivity can be improved.

[0067] Furthermore, in the CMOS image sensor 111, the waveguide 142 is not located in the extra-pixel region 132. Therefore, the step difference D3 between the pixel region 131 and the extra-pixel region 132 can be made smaller than the step difference D2, and as a result, the sensitivity uniformity characteristics can be improved.

[0068] Furthermore, the comparative relationships / positional relationships such as "same length" in the above explanation include not only perfect comparative relationships / positional relationships, but also substantial comparative relationships / positional relationships within a certain margin of error.

[0069] <5. Example of CMOS Image Sensor Usage> Figure 10 shows an example of using the CMOS image sensor 111 described above.

[0070] The CMOS image sensor 111 described above can be used as an image sensor in various cases where light such as visible light, infrared light, ultraviolet light, and X-rays is sensed, for example, as follows.

[0071] - Devices that capture images for viewing purposes, such as digital cameras and portable devices with camera functions. - Devices used for traffic purposes, such as in-vehicle sensors that capture images of the front, rear, surroundings, and interior of a vehicle for safe driving such as automatic stopping and recognition of the driver's condition, surveillance cameras that monitor moving vehicles and roads, and distance measuring sensors that measure distances between vehicles. - Devices used in home appliances such as TVs, refrigerators, and air conditioners that capture user gestures and allow device operation according to those gestures. - Devices used for medical and healthcare purposes, such as endoscopes and devices that perform angiography using infrared light reception. - Devices used for security purposes, such as surveillance cameras for crime prevention and cameras for person recognition. - Devices used for beauty purposes, such as skin measuring devices that capture images of skin and microscopes that capture images of the scalp. - Devices used for sports purposes, such as action cameras and wearable cameras for sports use. - Devices used for agriculture, such as cameras that monitor the condition of fields and crops.

[0072] <6. Examples of Application to Electronic Devices> This technology is not limited to application to photodetectors. That is, the technology disclosed herein is applicable to all electronic devices that use a photodetector in the image acquisition unit, such as imaging devices like digital still cameras and video cameras, portable terminal devices with imaging functions, and photocopiers that use a photodetector in the image reading unit. The photodetector may be formed as a single chip, or it may be in the form of a module with imaging functions in which the imaging unit and the signal processing unit or optical system are packaged together.

[0073] Figure 11 is a block diagram showing an example configuration of an imaging device as an electronic device to which this technology is applied.

[0074] The imaging device 600 in Figure 11 comprises an optical unit 601 consisting of a lens group and the like, a solid-state imaging device 602 employing a CMOS image sensor 111, and a DSP (Digital Signal Processor) circuit 603 which is a camera signal processing circuit. The imaging device 600 also includes a frame memory 604, a display unit 605, a recording unit 606, an operation unit 607, and a power supply unit 608. The DSP circuit 603, frame memory 604, display unit 605, recording unit 606, operation unit 607, and power supply unit 608 are interconnected via a bus line 609.

[0075] The optical unit 601 captures incident light (image light) from the subject and forms an image on the imaging surface of the solid-state imaging device 602. The solid-state imaging device 602 converts the amount of light from the incident light formed on the imaging surface by the optical unit 601 into an electrical signal on a pixel-by-pixel basis and outputs it as a pixel signal. A CMOS image sensor 111 is used as this solid-state imaging device 602.

[0076] The display unit 605 is composed of a thin display such as an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescence) display, and displays video or still images captured by the solid-state imaging device 602. The recording unit 606 records the video or still images captured by the solid-state imaging device 602 onto a recording medium such as a hard disk or semiconductor memory.

[0077] The operation unit 607 issues operation commands for various functions of the imaging device 600 under the user's control. The power supply unit 608 appropriately supplies various power sources to the DSP circuit 603, frame memory 604, display unit 605, recording unit 606, and operation unit 607.

[0078] As described above, by using the CMOS image sensor 111 described above as the solid-state imaging device 602, the sensitivity can be further improved. Therefore, even in imaging devices 600 such as video cameras, digital still cameras, and camera modules for mobile devices such as mobile phones, it is possible to acquire, for example, highly sensitive images.

[0079] <7. Examples of Application to Mobile Devices> The technology disclosed herein (the technology) can be applied to a variety of products. For example, the technology disclosed herein may be implemented as a device mounted on any type of mobile device, such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility devices, airplanes, drones, ships, and robots.

[0080] Figure 12 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technology described herein may be applied.

[0081] The vehicle control system 12000 comprises a plurality of electronic control units connected via a communication network 12001. In the example shown in Figure 12, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an external information detection unit 12030, an internal information detection unit 12040, and an integrated control unit 12050. The functional configuration of the integrated control unit 12050 is shown in the figure, which includes a microcomputer 12051, an audio / image output unit 12052, and an in-vehicle network interface 12053.

[0082] The drivetrain control unit 12010 controls the operation of devices related to the vehicle's drivetrain according to various programs. For example, the drivetrain control unit 12010 functions as a control device for a drivetrain generating device that generates driving force for the vehicle, such as an internal combustion engine or a drive motor; a drivetrain transmission mechanism that transmits driving force to the wheels; a steering mechanism that adjusts the steering angle of the vehicle; and a braking device that generates braking force for the vehicle.

[0083] The body system control unit 12020 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window system, or various lamps such as headlights, reverse lights, brake lights, turn signals, or fog lights. In this case, the body system control unit 12020 may receive radio waves transmitted from a portable device that replaces a key or signals from various switches. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock system, power window system, lamps, etc.

[0084] The external information detection unit 12030 detects information from outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the external information detection unit 12030. The external information detection unit 12030 causes the imaging unit 12031 to capture images of the outside of the vehicle and receives the captured images. Based on the received images, the external information detection unit 12030 may perform object detection processing such as detecting people, cars, obstacles, signs, or characters on the road surface, or distance detection processing.

[0085] The imaging unit 12031 is a light sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0086] The in-vehicle information detection unit 12040 detects information inside the vehicle. The in-vehicle information detection unit 12040 is connected to, for example, a driver status detection unit 12041 that detects the driver's state. The driver status detection unit 12041 includes, for example, a camera that captures images of the driver, and the in-vehicle information detection unit 12040 may calculate the driver's level of fatigue or concentration, or determine whether the driver is drowsy, based on the detection information input from the driver status detection unit 12041.

[0087] The microcomputer 12051 can calculate control target values ​​for the drive force generator, steering mechanism, or braking device based on information inside and outside the vehicle acquired by the external information detection unit 12030 or the internal information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing ADAS (Advanced Driver Assistance System) functions, including collision avoidance or impact mitigation, following driving based on distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning.

[0088] Furthermore, the microcomputer 12051 can perform cooperative control for purposes such as autonomous driving, where the vehicle drives autonomously without driver intervention, by controlling the drive force generating device, steering mechanism, or braking device, etc., based on information about the vehicle's surroundings acquired by the external information detection unit 12030 or the internal information detection unit 12040.

[0089] Furthermore, the microcomputer 12051 can output control commands to the body system control unit 12020 based on external information acquired by the external information detection unit 12030. For example, the microcomputer 12051 can control the headlights according to the position of a preceding or oncoming vehicle detected by the external information detection unit 12030, and perform coordinated control aimed at reducing glare, such as switching from high beams to low beams.

[0090] The audio-image output unit 12052 transmits at least one of audio and image output signals to an output device capable of visually or audibly notifying information to the vehicle's occupants or to those outside the vehicle. In the example shown in Figure 12, the output devices include an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an onboard display and a head-up display.

[0091] Figure 13 shows an example of the installation position of the imaging unit 12031.

[0092] In Figure 13, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0093] The imaging units 12101, 12102, 12103, 12104, and 12105 are installed, for example, on the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the vehicle 12100. The imaging unit 12101 installed on the front nose and the imaging unit 12105 installed on the upper part of the windshield inside the vehicle mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 installed on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 installed on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 installed on the upper part of the windshield inside the vehicle is mainly used for detecting preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0094] Figure 13 shows an example of the imaging range of imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of imaging unit 12101 located on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of imaging units 12102 and 12103 located on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of imaging unit 12104 located on the rear bumper or back door. For example, by superimposing the image data captured by imaging units 12101 to 12104, an overhead view image of the vehicle 12100 can be obtained.

[0095] At least one of the imaging units 12101 to 12104 may have a function for acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera consisting of multiple image sensors, or an image sensor having pixels for phase difference detection.

[0096] For example, the microcomputer 12051, based on distance information obtained from the imaging units 12101 to 12104, can determine the distance to each object within the imaging range 12111 to 12114 and the temporal change of this distance (relative speed to the vehicle 12100). In particular, it can extract the closest object on the vehicle 12100's path that is traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or more) as the preceding vehicle. Furthermore, the microcomputer 12051 can set a predetermined distance to be maintained before the preceding vehicle and perform automatic braking control (including follow-and-stop control) and automatic acceleration control (including follow-and-start control), etc. In this way, cooperative control aimed at autonomous driving, where the vehicle drives autonomously without driver intervention, can be performed.

[0097] For example, the microcomputer 12051 can use distance information obtained from imaging units 12101 to 12104 to classify and extract three-dimensional object data related to three-dimensional objects, such as motorcycles, passenger cars, large vehicles, pedestrians, utility poles, and other three-dimensional objects, and use this data for automatic obstacle avoidance. For example, the microcomputer 12051 identifies obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines the collision risk, which indicates the degree of risk of collision with each obstacle. If the collision risk is above a set value and there is a possibility of collision, the microcomputer 12051 can provide driving assistance to avoid collisions by outputting a warning to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or evasive steering via the drive system control unit 12010.

[0098] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared light. For example, the microcomputer 12051 can recognize pedestrians by determining whether or not pedestrians are present in the images captured by the imaging units 12101 to 12104. Such pedestrian recognition is performed, for example, by a procedure to extract feature points from the images captured by the imaging units 12101 to 12104 as infrared cameras, and a procedure to perform pattern matching on a series of feature points that indicate the contour of an object to determine whether or not it is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the imaging units 12101 to 12104 and recognizes a pedestrian, the audio-image output unit 12052 controls the display unit 12062 to superimpose a rectangular contour line for emphasis on the recognized pedestrian. The audio-image output unit 12052 may also control the display unit 12062 to display an icon indicating a pedestrian at a desired position.

[0099] The above describes an example of a vehicle control system to which the technology described herein may be applied. The technology described herein can be applied to, for example, the imaging unit 12031 among the configurations described above. Specifically, the CMOS image sensor 111 can be applied to the imaging unit 12031. By applying the technology described herein to the imaging unit 12031, highly sensitive images can be obtained, thereby making it possible to better support the driver's driving operations.

[0100] The embodiments of this technology are not limited to those described above, and various modifications are possible without departing from the spirit of this technology.

[0101] The effects described herein are merely illustrative and not limited to those described herein; other effects may also occur.

[0102] The present technology can take the following configurations: (1) A light detection device comprising: a plurality of pixels arranged in a matrix in two dimensions in the pixel region of a semiconductor substrate; a first light-shielding film disposed between the pixels on the semiconductor substrate; a waveguide disposed above the first light-shielding film; and a second light-shielding film disposed on an extra-pixel region, which is a region of the semiconductor substrate other than the pixel region, wherein the first light-shielding film is configured to be thinner than the second light-shielding film. (2) The light detection device according to (1), further comprising: a color filter disposed on the semiconductor substrate for each pixel in the pixel region and also disposed on the semiconductor substrate in the extra-pixel region; and an on-chip lens disposed on the color filter for each pixel and also on the color filter in the extra-pixel region. (3) The photodetector according to (2), wherein at least a portion of the plurality of pixels are phase difference detection pixels, the phase difference detection pixels have two photoelectric conversion units, a light-shielding film for the phase difference detection pixels is disposed on the semiconductor substrate of one of the two photoelectric conversion units, a waveguide for the phase difference detection pixels is disposed above the light-shielding film for the phase difference detection pixels, the color filter of the phase difference detection pixels is disposed on the semiconductor substrate of the other of the two photoelectric conversion units, and the on-chip lens of the phase difference detection pixels is disposed on the color filter of the phase difference detection pixels and the waveguide for the phase difference detection pixels. (4) The photodetector according to (3), wherein the light-shielding film for the phase difference detection pixels has the same thickness as the first light-shielding film, and the waveguide for the phase difference detection pixels has the same height as the waveguide. (5) The photodetector according to any one of (1) to (4) above, wherein the thickness of the first light-shielding film is greater than 40 nm and less than or equal to 100 nm. (6) The photodetector according to any one of (1) to (5) above, wherein the thickness of the second light-shielding film is 200 nm or more.

[0103] 11 Semiconductor substrate, 13 Color filter, 14 On-chip lens, 16 Photodiode, 53b Light-shielding film, 111 CMOS image sensor, 131 Pixel area, 132 Out-of-pixel area, 140b, 141b Light-shielding film, 142 Waveguide

Claims

1. A photodetector comprising: a plurality of pixels arranged in a matrix in two dimensions in the pixel region of a semiconductor substrate; a first light-shielding film disposed between the pixels on the semiconductor substrate; a waveguide disposed above the first light-shielding film; and a second light-shielding film disposed on an extra-pixel region, which is a region of the semiconductor substrate other than the pixel region, wherein the first light-shielding film is configured to be thinner than the second light-shielding film.

2. The photodetector according to claim 1, further comprising: a color filter disposed on the semiconductor substrate for each pixel in the pixel region and disposed on the semiconductor substrate in the region outside the pixel; and an on-chip lens disposed on the color filter for each pixel and disposed on the color filter in the region outside the pixel.

3. The photodetector according to claim 2, wherein at least a portion of the plurality of pixels are phase difference detection pixels, the phase difference detection pixels have two photoelectric conversion units, a light-shielding film for the phase difference detection pixels is disposed on the semiconductor substrate of one of the two photoelectric conversion units, a waveguide for the phase difference detection pixels is disposed above the light-shielding film for the phase difference detection pixels, the color filter of the phase difference detection pixels is disposed on the semiconductor substrate of the other of the two photoelectric conversion units, and the on-chip lens of the phase difference detection pixels is disposed on the color filter of the phase difference detection pixels and the waveguide for the phase difference detection pixels.

4. The photodetector according to claim 3, wherein the light-shielding film for the phase difference detection pixel has the same thickness as the first light-shielding film, and the waveguide for the phase difference detection pixel has the same height as the waveguide.

5. The photodetector according to claim 1, wherein the thickness of the first light-shielding film is greater than 40 nm and less than or equal to 100 nm.

6. The photodetector according to claim 1, wherein the thickness of the second light-shielding film is 200 nm or more.

Images