Light detection device and electronic equipment

Abstract

The present disclosure pertains to a photodetector and an electronic apparatus that enable the reduction of surface reflection of an on-chip microlens and the suppression of image quality degradation. Provided is a photodetector that has a plurality of pixels having a photoelectric conversion part, an on-chip microlens formed corresponding to each pixel, and an antireflection film formed on the surface of the on-chip microlens, the antireflection film being configured by stacking a first inorganic film formed of a metal oxide film and a second inorganic film formed on the surface of the first inorganic film and having a refractive index lower than that of the first inorganic film. The present disclosure can be applied, for example, to a CMOS-type solid-state imaging device.

Description

Technical Field

[0001] The present disclosure relates to an optical detection device and an electronic device, and particularly to an optical detection device and an electronic device capable of reducing surface reflection of an on-chip microlens and suppressing deterioration of image quality.

Background Art

[0002] In a solid-state imaging device, in order to improve sensitivity characteristics, an on-chip microlens (on-chip lens) is formed on a color filter corresponding to each pixel, and incident light is condensed onto a photodiode by the on-chip microlens.

[0003] A technique of forming an antireflection film on the surface of an on-chip microlens is known. By this antireflection film, flare and the like caused by reflection can be suppressed, and sensitivity characteristics can be improved.

[0004] Patent Document 1 discloses a technique of further reducing the reflectance by laminating a layer with a high refractive index formed of a silicon nitride film (SiN film) or a silicon oxynitride film (SiON film) and a layer with a low refractive index formed of a silicon oxide film (SiO film) or a silicon oxycarbide film (SiOC film) on the surface of an on-chip microlens.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 discloses a configuration in which a silicon nitride film is used as a high refractive index layer in an anti-reflective coating. However, it has been confirmed that the silicon nitride film may oxidize at the interface between the on-chip microlens and the silicon nitride film, potentially affecting its properties.

[0007] Therefore, there was a need to reduce surface reflections of on-chip microlenses and suppress image quality degradation by using a more reliable anti-reflective coating.

[0008] This disclosure is made in light of these circumstances and aims to reduce surface reflection of on-chip microlenses and suppress image quality degradation. [Means for solving the problem]

[0009] One aspect of the present disclosure is a photodetector comprising a plurality of pixels having a photoelectric conversion unit, an on-chip microlens formed corresponding to each pixel, and an anti-reflective film formed on the surface of the on-chip microlens, wherein the anti-reflective film is constructed by laminating a first inorganic film formed of a metal oxide film and a second inorganic film formed on the surface of the first inorganic film and having a lower refractive index than the first inorganic film.

[0010] In one aspect of the present disclosure, an anti-reflective film formed on the surface of an on-chip microlens, which is formed corresponding to each pixel of a plurality of pixels having a photoelectric conversion unit, is constructed by laminating a first inorganic film made of a metal oxide film and a second inorganic film formed on the surface of the first inorganic film, which has a lower refractive index than the first inorganic film.

[0011] One aspect of the present disclosure is a photodetector comprising a plurality of pixels having a photoelectric conversion unit, an on-chip microlens formed corresponding to each pixel, and an anti-reflective film formed on the surface of the on-chip microlens, wherein the anti-reflective film is constructed by laminating a first inorganic film and a second inorganic film which is a structural film formed on the surface of the first inorganic film by processing a fine uneven shape on the surface of a workpiece having a predetermined refractive index.

[0012] In one aspect of the present disclosure, an anti-reflective film formed on the surface of an on-chip microlens, which is formed corresponding to each pixel of a plurality of pixels having a photoelectric conversion unit, is constructed by laminating a first inorganic film and a second inorganic film, which is a structural film formed on the surface of the first inorganic film and is formed by processing a fine uneven shape on the surface of a workpiece having a predetermined refractive index.

[0013] One aspect of the present disclosure is an electronic device equipped with a photodetector, which comprises a plurality of pixels having a photoelectric conversion unit, an on-chip microlens formed corresponding to each pixel, and an anti-reflective film formed on the surface of the on-chip microlens, wherein the anti-reflective film is constructed by laminating a first inorganic film formed of a metal oxide film and a second inorganic film formed on the surface of the first inorganic film and having a lower refractive index than the first inorganic film.

[0014] In one aspect of the present disclosure, an electronic device is mounted on the electronic device, and an anti-reflective film formed on the surface of an on-chip microlens, which is formed corresponding to each pixel of a plurality of pixels having a photoelectric conversion unit, is configured by laminating a first inorganic film made of a metal oxide film and a second inorganic film formed on the surface of the first inorganic film, which has a lower refractive index than the first inorganic film.

[0015] Furthermore, the photodetector and electronic equipment, which are aspects of this disclosure, may be independent devices or internal blocks constituting a single device. [Brief explanation of the drawing]

[0016] [Figure 1] It is a diagram showing a configuration example of a photodetection device to which the present disclosure is applied. [Figure 2] It is a diagram showing a cross-sectional structure example of a main part including pixels. [Figure 3] It is a diagram showing the relationship between the refractive index of the high refractive index layer and the total film thickness at the time of optimal design. [Figure 4] It is a diagram showing a cross-sectional structure example of a main part of a pixel when the number of layers of the antireflection film is four. [Figure 5] It is a diagram showing the relationship between the number of layers of the antireflection film and the reflectance. <> [Figure 6] It is a diagram showing the relationship between the center of the circle indicating the curvature of the surface of the on-chip microlens and the center of the circle indicating the curvature of the surface of the antireflection film. [Figure 7] It is a diagram showing a plane layout example when the space between on-chip microlenses is flat. [Figure 8] It is a diagram showing a cross-sectional structure example of a main part of a pixel when the space between on-chip microlenses is flat. [Figure 9] It is a diagram showing an example of a manufacturing method of a photodetection device to which the present disclosure is applied. [Figure 10] It is a diagram showing another example of the cross-sectional structure of a main part including pixels. [Figure 11] It is a diagram showing the relationship between the number of layers of the antireflection film and the reflectance. [Figure 12] It is a diagram showing the relationship between the number of layers of the antireflection film and the reflectance. [Figure 13] It is a diagram showing another example of a manufacturing method of a photodetection device to which the present disclosure is applied. [Figure 14] It is a diagram showing another example of a manufacturing method of a photodetection device to which the present disclosure is applied. [Figure 15] It is a block diagram showing a configuration example of an electronic device equipped with a photodetection device to which the present disclosure is applied. [Figure 16] It is a block diagram showing an example of a schematic configuration of a vehicle control system. [Figure 17] It is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit. [Modes for carrying out the invention]

[0017] <1. First Embodiment>

[0018] (Configuration of the light detection device) Figure 1 shows an example of the configuration of a photodetector to which this disclosure is applied.

[0019] In Figure 1, the solid-state imaging device 10 is a CMOS (Complementary Metal Oxide Semiconductor) type solid-state imaging device and is an example of a photodetector to which this disclosure is applied. The solid-state imaging device 10 consists of a pixel array unit 21, a vertical drive unit 22, a column signal processing unit 23, a horizontal drive unit 24, an output unit 25, and a control unit 26.

[0020] The pixel array section 21 has a plurality of pixels 100 arranged in a matrix in a two-dimensional manner on a silicon (Si) substrate. Each pixel 100 has a photoelectric conversion section made of a photodiode and a plurality of pixel transistors. The pixel transistors consist of a transfer transistor, a reset transistor, a selection transistor, and an amplification transistor.

[0021] In the pixel array section 21, for each row of multiple pixels 100 arranged in a two-dimensional matrix, a pixel drive line 41 is formed and connected to the vertical drive section 22, and a vertical signal line 42 is formed for each column and connected to the column signal processing section 23.

[0022] The vertical drive unit 22 is composed of a shift register, an address decoder, etc., and drives each pixel 100 arranged in the pixel array unit 21. The pixel signals output from the pixels 100 selected and scanned by the vertical drive unit 22 are supplied to the column signal processing unit 23 via the vertical signal line 42.

[0023] The column signal processing unit 23 performs predetermined signal processing on the pixel signals output from each pixel 100 in a selected row of the pixel array unit 21 through the vertical signal line 42, and temporarily holds the pixel signals after signal processing. Specifically, the column signal processing unit 23 performs at least noise reduction processing and correlated double sampling (CDS) processing as signal processing.

[0024] This correlated double sampling removes pixel-specific fixed pattern noise, such as reset noise and threshold variations of the amplification transistors. Furthermore, in addition to noise reduction processing, the column signal processing unit 23 can also be equipped with, for example, an analog / digital conversion (AD conversion) function to output the signal level as a digital signal.

[0025] The horizontal drive unit 24 is composed of a shift register, an address decoder, etc., and sequentially selects the unit circuits corresponding to the pixel rows of the column signal processing unit 23. Through the selective scanning by the horizontal drive unit 24, the pixel signals processed by the column signal processing unit 23 are output to the output unit 25 via the horizontal signal line 51.

[0026] The output unit 25 performs predetermined signal processing on the pixel signals that are sequentially input from each of the column signal processing units 23 through the horizontal signal line 51, and outputs the resulting signal.

[0027] The control unit 26 is composed of a timing generator and the like that generates various timing signals, and controls the drive of the vertical drive unit 22, the column signal processing unit 23, and the horizontal drive unit 24 based on the various timing signals generated by the timing generator.

[0028] (Pixel composition) Next, the configuration of the pixels 100 arranged in a two-dimensional manner in the pixel array section 21 of the solid-state imaging device 10 will be described.

[0029] Figure 2 shows an example of a cross-sectional structure of a key part including a pixel 100. In Figure 2, the cross-sectional structure of two adjacent pixels among the multiple pixels 100 arranged in the pixel array 21 is shown. Note that in Figure 2, a part of the photodiode and the structure formed in the layer below it are omitted.

[0030] In Figure 2, the pixel 100 has a photodiode 111 as a photoelectric conversion unit. The photodiode 111 is formed by including semiconductor regions of a first conductivity type and a second conductivity type in a well region of a first conductivity type formed on a semiconductor substrate such as a silicon substrate. Here, for example, the first conductivity type is p-type and the second conductivity type is n-type.

[0031] An insulating film 112 is formed on the upper surface of the photodiode 111, and a color filter 113 and on-chip microlenses 114 corresponding to each pixel 100 are stacked and formed on the flat surface of the insulating film 112.

[0032] As the color filter 113, for example, color filters corresponding to red (R), green (G), and blue (B) wavelengths can be used. Furthermore, as the color filter 113 formed on multiple pixels 100 arranged two-dimensionally in the pixel array section 21, color filters corresponding to a Bayer array can be used. The on-chip microlens 114 is formed, for example, from an organic film.

[0033] An anti-reflective coating 121 is formed on the surface of the on-chip microlens 114, consisting of two inorganic films, 131 and 132. The inorganic film 131 is made of a material with a higher refractive index than the on-chip microlens 114. The inorganic film 132 is made of a material with a lower refractive index than both the on-chip microlens 114 and the inorganic film 131.

[0034] The inorganic film 131 has a refractive index of N1, where N1 ≥ 1.8, and a metal oxide film with high reliability as a film type is used. For example, the film type for inorganic film 131 may be a metal oxide film such as tantalum oxide film (Ta2O5 film), niobium oxide film (Nb2O5 film), titanium oxide film (TiO2 film), or hafnium oxide film (HfO2 film).

[0035] The inorganic film 132 has a refractive index of N2, where N2 ≤ 1.55. Examples of inorganic film types used for the inorganic film 132 include silicon oxide film (SiO2 film) or silicon oxide carbide film (SiOC film).

[0036] In the anti-reflective coating 121, the inorganic film 131 has a higher refractive index than the inorganic film 132, and can therefore be described as a high refractive index layer. Furthermore, in the anti-reflective coating 121, the inorganic film 132 has a lower refractive index than the inorganic film 131, and can therefore be described as a low refractive index layer. In other words, as shown in Figure 2, the anti-reflective coating 121 has a structure in which two layers are laminated: a high refractive index layer, which is the inorganic film 131, and a low refractive index layer, which is the inorganic film 132.

[0037] In Figure 2, a light-shielding film 116 and an insulating film 117 are stacked on a well region 115 between the photodiodes 111 of each pixel 100.

[0038] (Improved reliability and thinner films) As previously mentioned, Patent Document 1 discloses a configuration in which a silicon nitride film (SiN film) is used as the high refractive index layer in an anti-reflective coating. The inventors of this disclosure have confirmed through constant temperature and humidity tests that when a silicon nitride film is used as the high refractive index layer in an anti-reflective coating, the silicon nitride film may oxidize at the interface between the on-chip microlens and the silicon nitride film, potentially affecting properties such as sensitivity characteristics.

[0039] The occurrence of such reliability failures is due to the oxidation of the silicon nitride film, which causes fluctuations (decrease) in its refractive index. As a countermeasure, it is conceivable to use a silicon nitride film with high moisture permeability, but its mass production capability is poor, making it difficult to use silicon nitride film as a high refractive index layer in anti-reflective coatings. Furthermore, from the perspective of designing the film thickness of the anti-reflective coating, if the film thickness of the high refractive index layer reaches a maximum of 450 nm, there is a concern that the quantum efficiency (QE) will decrease, especially in fine pixels, due to the increased thickness of on-chip microlenses.

[0040] On the other hand, in the solid-state imaging device 10 to which this disclosure is applied, an inorganic film 131 formed from a metal oxide film such as tantalum oxide, niobium oxide, titanium oxide, or hafnium oxide is used as the high refractive index layer in the anti-reflective coating 121 formed on the surface of the on-chip microlens 114. In other words, since a metal oxide film (such as tantalum oxide) that is originally oxidized and has the characteristic of being dense and therefore less prone to refractive index fluctuations is used as the film type for the inorganic film 131, the high refractive index layer in the anti-reflective coating 121 has high reliability.

[0041] Furthermore, since the metal oxide film (such as tantalum oxide film) used in the inorganic film 131 has a higher refractive index than the silicon nitride film, the anti-reflective film 121 can be designed to be thinner (AR (Anti-Reflection) design). For example, while the refractive index of silicon nitride film is approximately 1.85, the refractive index of metal oxide film is approximately 2 to 2.5.

[0042] Figure 3 shows the relationship between the refractive index of the high refractive index layer and the total film thickness, represented by curve L, with the horizontal axis representing the refractive index of the high refractive index layer and the vertical axis representing the film thickness of the anti-reflective coating at the optimal design (total film thickness). In the solid-state imaging device 10 to which this disclosure is applied, the refractive index of the high refractive index layer corresponds to the refractive index of the inorganic film 131, and the total film thickness corresponds to the film thickness of the anti-reflective coating 121.

[0043] As shown by curve L in Figure 3, the lower the refractive index of the high refractive index layer, the thicker the total film thickness becomes in the optimal design. Here, the refractive index of the silicon nitride film as the high refractive index layer is approximately 1.85, while the refractive index of the metal oxide film forming the inorganic film 131 is approximately 2 to 2.5. Therefore, AR design can be performed to make the film thickness of the anti-reflective coating 121 thinner.

[0044] In other words, in the solid-state imaging device 10 to which this disclosure is applied, by using a metal oxide film as the inorganic film 131, which is the high refractive index layer, as a combination of a high refractive index layer and a low refractive index layer, the refractive index can be made higher compared to the case where a silicon nitride film is used. Therefore, even when designing an AR with a thinner film, it is possible to achieve the same optical path length as when a silicon nitride film is used, thereby realizing a thinner film.

[0045] In particular, it is known that the light-gathering efficiency changes significantly depending on the distance between the top position (center) of the on-chip microlens and the silicon substrate, especially in fine pixels. However, as the thickness of the anti-reflective coating (total thickness) increases, the top position of the on-chip microlens moves away from the silicon substrate. This reduces the light-gathering efficiency, which in turn leads to a decrease in quantum efficiency (QE), thus necessitating the thinning of the anti-reflective coating. In the solid-state imaging device 10 to which this disclosure is applied, it is possible to thin the anti-reflective coating 121 formed on the surface of the on-chip microlens 114, thereby suppressing the decrease in quantum efficiency (QE) in fine pixels.

[0046] In this AR design, the thickness of the inorganic film 131, which acts as the high refractive index layer, is set to be less than or equal to the thickness of the inorganic film 132, which acts as the low refractive index layer. In other words, when the thickness of inorganic film 131 is T1 and the thickness of inorganic film 132 is T2, the design is set such that T1 ≤ T2.

[0047] Furthermore, considering the impact on the quantum efficiency (QE) characteristics at the fine pixels mentioned above, the anti-reflective coating (AR) design is performed so that the film thickness (total film thickness) of the anti-reflective coating 121 is 200 nm or less. The inventors of this disclosure have confirmed through detailed simulations that by using a metal oxide film instead of a silicon nitride film as the high refractive index layer in the anti-reflective coating, it is possible to reduce the total film thickness to about 100 nm, and that AR design with a total film thickness of 200 nm or less is possible.

[0048] Thus, in the solid-state imaging device 10 to which this disclosure is applied, by using a metal oxide film such as a tantalum oxide film as the high refractive index layer in the anti-reflective coating 121 formed on the surface of the on-chip microlens 114, reliability can be further improved and AR design can be performed with thinner films.

[0049] (Number of anti-reflective coating layers) In the above explanation, the anti-reflective coating 121 was described as consisting of two layers, a high refractive index layer and a low refractive index layer, but it is not limited to two layers. For example, it may be formed from four layers, with high refractive index layers and low refractive index layers stacked alternately.

[0050] Figure 4 shows an example of the cross-sectional structure of the main part of a pixel 100 when the number of layers of the anti-reflective coating 121 is four. In Figure 4, the same reference numerals are used for parts corresponding to those in Figure 2, and their explanations are omitted as appropriate.

[0051] In Figure 4, the anti-reflective coating 121 is formed by laminating inorganic films 141, 142, 143, and 144. In the anti-reflective coating 121, inorganic films 141 and 143 are high refractive index layers, inorganic films 142 and 144 are low refractive index layers, and the high refractive index layers and low refractive index layers are laminated alternately.

[0052] Inorganic films 141 and 143, like inorganic film 131 (Figure 2), can be made of metal oxide films such as tantalum oxide, niobium oxide, titanium oxide, or hafnium oxide. Inorganic films 141 and 143 may be made of the same type of film or different types of film. When the refractive index of inorganic film 141 and inorganic film 143 is N1, N1 ≥ 1.8 is assumed.

[0053] Inorganic films 142 and 144, like inorganic film 132 (Figure 2), can be silicon oxide films or silicon oxide carbide films. Inorganic films 142 and 144 may be the same type of film or different types of films. When the refractive indices of inorganic films 142 and 144 are N2, N2 ≤ 1.55.

[0054] In the anti-reflective coating 121, high refractive index layers (inorganic films 141, 143) and low refractive index layers (inorganic films 142, 144) are alternately stacked. The high refractive index layer (inorganic film 141) is formed on (directly above) the surface of the on-chip microlens 114, and the low refractive index layers (inorganic films 142, 144) are formed on the surface of the high refractive index layer (inorganic films 141, 143). Furthermore, in the anti-reflective coating 121, the low refractive index layer (inorganic film 144) is formed on the outermost surface.

[0055] Figure 5 shows the relationship between the number of layers of the anti-reflective coating 121 and the reflectance, represented by curves L1 to L4, with wavelength on the horizontal axis and reflectance on the vertical axis. In Figure 5, the relationship when the anti-reflective coating 121 has one layer is represented by curve L1, the relationship when it has two layers is represented by curve L2, the relationship when it has three layers is represented by curve L3, and the relationship when it has four layers is represented by curve L4.

[0056] As shown by curves L1 to L4 in Figure 5, the reflectance can be further reduced by increasing the number of layers in the anti-reflective coating 121. For example, when the number of layers in the anti-reflective coating 121 is set to four, the reflectance is lower even in the same wavelength region compared to when the number of layers is set to one to three.

[0057] Thus, in the solid-state imaging device 10 to which this disclosure is applied, by increasing the number of layers to four or more by alternately stacking high refractive index layers and low refractive index layers as the anti-reflective coating 121 formed on the surface of the on-chip microlens 114, surface reflection of the on-chip microlens 114 can be further suppressed, and image quality degradation such as flare can be suppressed.

[0058] In Figure 4, the anti-reflective coating 121 is shown as a configuration in which high-refractive-index layers and low-refractive-index layers are alternately stacked in four layers. However, more than four layers are acceptable as long as the requirements for the AR design described above are met. For example, in the case of stacking six layers, the fifth layer would be a high-refractive-index layer, the sixth layer a low-refractive-index layer, and the sixth low-refractive-index layer would be the outermost surface.

[0059] (Coverage of anti-reflective coating) Regarding the coverage of the anti-reflective coating 121, it is desirable that neither the high-refractive-index layer nor the low-refractive-index layer be conforming. For example, in the anti-reflective coating 121, the film thickness in the portion corresponding to the center (top position) of the on-chip microlens 114 should be thinner than the film thickness in the portion corresponding to the edge (bottom position) of the on-chip microlens 114. Furthermore, in the anti-reflective coating 121, the film thickness should decrease from the portion corresponding to the center of the on-chip microlens 114 towards the portion corresponding to the edge.

[0060] Figure 6 shows the relationship between the center of the circle indicating the curvature of the surface of the on-chip microlens 114 and the center of the circle indicating the curvature of the surface of the anti-reflective coating 121. In Figure 6, the same reference numerals are used for parts corresponding to those in Figure 2, and their explanations are omitted.

[0061] In Figure 6, circle C1, which represents the curvature of the surface of the on-chip microlens 114, is shown by a dashed line, and circle C2, which represents the curvature of the surface of the anti-reflective coating 121, is shown by a double-dashed line. The relationship between the center O1 of circle C1 and the center O2 of circle C2 is also shown.

[0062] Here, if the anti-reflective coating 121 is deposited conformally, the positions of the center O1 of circle C1 and the center O2 of circle C2 will coincide. In other words, although not shown in the diagram, if the anti-reflective coating 121 is deposited conformally, the film thickness will be uniform, and the film thickness will be the same in the part corresponding to the center of the on-chip microlens 114 and in the part corresponding to the edge.

[0063] However, in order to improve the characteristics, it is desirable for the anti-reflective coating 121 to be thinner near the edges of the on-chip microlens 114. Therefore, in the solid-state imaging device 10 to which this disclosure is applied, as shown in Figure 6, the center O2 of circle C2, which indicates the curvature of the surface of the anti-reflective coating 121, is located on the side where light is incident (upper side in the figure) than the center O1 of circle C1, which indicates the curvature of the surface of the on-chip microlens 114.

[0064] As a result, in the anti-reflective coating 121 (specifically the inorganic coating 132), the film thickness b in the portion corresponding to the edge of the on-chip microlens 114 is thinner than the film thickness a in the portion corresponding to the center of the on-chip microlens 114 (the relationship a > b).

[0065] Thus, in the solid-state imaging device 10 to which this disclosure is applied, the center O2 of circle C2 is located on the side where light is incident (upper side in the figure) than the center O1 of circle C1 (the positions of the center O1 of circle C1 and the center O2 of circle C2 do not coincide), and the anti-reflective film 121 formed on the surface of the on-chip microlens 114 is not conformally formed.

[0066] In other words, the anti-reflective coating 121 consists of an inorganic film 131 as a high refractive index layer and an inorganic film 132 as a low refractive index layer, but neither the inorganic film 131 nor the inorganic film 132 is conformal, and the centers of the circles indicating the curvature of the surfaces of the inorganic film 131 and the inorganic film 132 are located on the side of the incident light that is greater than the center O1 of circle C1. Therefore, in the anti-reflective coating 121 formed on the surface of the on-chip microlens 114, the film thickness at the edges is thinner than the film thickness at the center, which improves characteristics such as sensitivity compared to the case where the film thickness is uniform.

[0067] In Figure 4 above, the anti-reflective coating 121 is made up of four layers, with high refractive index layers (inorganic films 141, 143) and low refractive index layers (inorganic films 142, 144) stacked alternately. However, none of the inorganic films 141 to 144 are conformal, and it is preferable that the centers of the circles indicating the curvature of the surfaces of each inorganic film 141 to 144 are located on the side of the incident light that is greater than the center O1 of circle C1.

[0068] In Figure 6, a V-shaped recessed area, known as a recess A1 (the gap portion of the on-chip microlens 114), is formed between each on-chip microlens 114 corresponding to each pixel 100. An anti-reflective coating 121 is also formed in the recess A1, so that the anti-reflective coating 121 is not interrupted between the on-chip microlenses 114.

[0069] The region between the on-chip microlenses 114 is not limited to a V-shaped recessed region, but may also be a flat region. For example, as shown in the planar layout of Figure 7, if the on-chip microlenses 114 are arranged at predetermined intervals, the region between the on-chip microlenses 114 will be a flat region.

[0070] Figure 8 shows a cross-section of the X1-X1' plane layout shown in Figure 7. In Figure 8, parts corresponding to those in Figure 2 are denoted by the same reference numerals, and their explanations are omitted as appropriate.

[0071] In Figure 8, focusing on the flat region A2 between the on-chip microlenses 114 and the central part A3 of the on-chip microlenses 114, the thickness of the anti-reflective coating 121 is approximately the same in the portion corresponding to the flat region A2 and the portion corresponding to the central part A3. As a result, in the flat region A2, the reflectivity reduction as designed for AR is possible, and it also functions effectively against light incident between the on-chip microlenses 114. Consequently, it becomes possible to suppress image quality degradation such as flare.

[0072] Furthermore, Figure 8 also corresponds to the X2-X2' cross-section of the planar layout in Figure 7, and the thickness of the anti-reflective coating 121 is approximately the same not only for pixels 100 adjacent in the left-right and up-down directions, but also for pixels 100 adjacent in the diagonal direction, in the portion corresponding to the flat area A2 between the on-chip microlenses 114 and in the portion corresponding to the central area A3 of the on-chip microlenses 114, thus achieving a similar effect.

[0073] (Example of manufacturing method) Figure 9 shows an example of a method for manufacturing a photodetector that applies the present disclosure.

[0074] Figure 9 shows the process after the on-chip microlens 114 has been formed. Specifically, although not shown in the figure, a photodiode 111 and the like are formed on the silicon substrate to create an imaging region in which multiple pixels 100 are arranged in two dimensions. In addition, an insulating film 112 is formed on the upper surface of the photodiode 111 to flatten its surface, and a color filter 113 corresponding to red, green, or blue wavelengths is formed on top of it.

[0075] Then, as shown in Figure 9A, an on-chip microlens 114 is formed on the color filter 113.

[0076] Next, as shown in Figure 9B, an inorganic film 131 is deposited on the surface of the on-chip microlens 114. The inorganic film 131 can be deposited using methods such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD). As the inorganic film 131, for example, a metal oxide film such as tantalum oxide, niobium oxide, titanium oxide, or hafnium oxide can be deposited.

[0077] Next, as shown in Figure 9C, an inorganic film 132 is deposited on the surface of the inorganic film 131. The inorganic film 132 can be deposited using chemical vapor deposition, physical vapor deposition, or atomic layer deposition. For example, the inorganic film 132 may be a silicon oxide film or a silicon oxide carbide film.

[0078] Here, the anti-reflective film 121, which is formed by stacking inorganic films 131 and 132, is not conformal. Instead, the centers of the circles indicating the curvature of the surfaces of inorganic films 131 and 132 are located on the side where light is incident (upper side in the figure) rather than the center of the circle indicating the curvature of the surface of the on-chip microlens 114.

[0079] In this way, a solid-state imaging device 10 is obtained in which an anti-reflective coating 121 (Figure 2) consisting of two layers (a high refractive index layer and a low refractive index layer) of inorganic film 131 and inorganic film 132 is formed on the surface of the on-chip microlens 114.

[0080] Although Figure 9 shows the manufacturing method when the anti-reflective coating 121 consists of two layers, the same manufacturing method can be used when the anti-reflective coating 121 consists of four layers or more. That is, by repeating the steps shown in B and C of Figure 9, inorganic films 141, 142, 143, and 144 are sequentially formed using chemical vapor deposition, physical vapor deposition, or atomic layer deposition, etc., to obtain a solid-state imaging device 10 having an on-chip microlens 114 with an anti-reflective coating 121 (Figure 4) consisting of four layers in which high refractive index layers and low refractive index layers are alternately stacked.

[0081] <2. Second Embodiment>

[0082] Incidentally, in solid-state imaging devices having on-chip microlenses, a configuration is known in which an anti-reflective structure consisting of fine irregularities is formed on the surface of the on-chip microlens to reduce the reflection of light in the wavelength range used (see, for example, reference A below).

[0083] Document A: Japanese Patent Publication No. 2006-332433

[0084] In a configuration where an anti-reflective structure consisting of fine irregularities is formed on the surface of an on-chip microlens, there are problems with adhesion between the anti-reflective structure and the on-chip microlens because the anti-reflective structure is formed directly on the on-chip microlens, and there is a possibility that the anti-reflective structure may peel off. Furthermore, while plasma treatment is expected to improve adhesion, if plasma treatment is performed, although improved adhesion can be expected, a new problem arises in that the optical properties deteriorate.

[0085] To address these issues, the solid-state imaging device 10 to which this disclosure is applied employs an anti-reflective coating configuration as shown in Figure 10, thereby improving the adhesion between the anti-reflective coating, which includes a structural coating with fine irregularities, and the on-chip microlens, enabling high reliability while suppressing image quality degradation such as flare.

[0086] (Other components of the anti-reflective coating) Figure 10 shows another example of the cross-sectional structure of the main part including pixel 100. In Figure 10, the same reference numerals are used for parts corresponding to those in Figure 2, and their explanations are omitted as appropriate.

[0087] The cross-sectional structure in Figure 10 differs from the cross-sectional structure in Figure 2 in that an anti-reflective coating 221 is formed on the surface of the on-chip microlens 114 instead of the anti-reflective coating 121. The anti-reflective coating 221 is formed by laminating inorganic coatings 231 and 232. Inorganic coating 231 is made of a material with a higher refractive index than the on-chip microlens 114. Inorganic coating 232 is made of a material with a lower refractive index than both the on-chip microlens 114 and inorganic coating 231.

[0088] The inorganic film 231 is an adhesion layer that improves the adhesion between the on-chip microlens 114 and the inorganic film 232. The refractive index of the inorganic film 231 is set to, for example, N3 ≤ 1.55, where N3 is the refractive index. As the type of inorganic film 231, for example, an LTO (Low Temperature Oxidation) film such as a silicon oxide film (SiO2 film) is used.

[0089] The inorganic film 232 is a structural film having a moth-eye structure with a fine uneven surface. The fine uneven surface of the inorganic film 232 reduces the reflection of light in the wavelength range used. The refractive index of the inorganic film 232 is set to, for example, N4 ≤ 1.4, where N4 is the refractive index.

[0090] For example, when using an AlOx film as the film type for inorganic film 232, after the AlOx film is formed, processing treatments such as high-temperature treatment with pure water (DIW: De-Ionized Water) (e.g., 90°C treatment) are performed, which creates a fine uneven surface on the AlOx film. At this time, the refractive index of the AlOx film is said to be around 1.6, but because air layers are formed in the depressions due to the fine uneven surface, the overall refractive index decreases to around 1.3.

[0091] The thickness of the inorganic film 232 can be, for example, about 270 nm between the top and bottom. Here, the top position is the highest point of the protrusions in the fine uneven shape, and the bottom position is the interface with the inorganic film 231. In the anti-reflective film 221, the inorganic film 232 becomes a structural film with a fine uneven shape, but the inorganic film 231 as an adhesive film is not exposed, and the outermost surface is the inorganic film 232.

[0092] In the anti-reflective coating 221, the inorganic film 231 has a refractive index similar to that of the inorganic film 132, and can therefore be described as a low refractive index layer. Furthermore, in the anti-reflective coating 221, the inorganic film 232 has a lower refractive index than the inorganic film 231, and can therefore be described as an ultra-low refractive index layer with an even lower refractive index than the low refractive index layer.

[0093] In other words, the above explanation described a case in which a high refractive index layer and a low refractive index layer are alternately laminated as the anti-reflective film 121. However, as long as the structure consists of a first layer and a second layer having a lower refractive index than the first layer, other layers may be laminated. For example, as shown in Figure 10, the anti-reflective film 221 can be configured as a two-layer structure consisting of a low refractive index layer, which is an inorganic film 231, and an ultra-low refractive index layer, which is an inorganic film 232. Alternatively, the inorganic film 232 can be described as a structural film formed by processing a workpiece film having a predetermined refractive index (for example, an AlOx film having a refractive index of 1.6) with fine irregularities on its surface.

[0094] (Improvement points) Figures 11 and 12 show the relationship between the thickness of the inorganic film 231 in the anti-reflective coating 221 and the reflectance in the wavelength region, represented by curves L22 to L29, with the horizontal axis representing wavelength and the vertical axis representing reflectance. The thickness of the inorganic film 231 can be the thickness of the portion corresponding to the center (top position) of the on-chip microlens 114. For comparison, in Figures 11 and 12, the reflectance in the wavelength region when the inorganic film 231 is assumed to be a single layer as the anti-reflective coating 221 is represented by curve L20, and the reflectance in the wavelength region when the inorganic film 232 is assumed to be a single layer as the anti-reflective coating 221 is represented by curve L21.

[0095] In Figure 11, the relationship when the thickness of inorganic film 231 is 5 nm is shown by curve L22, the relationship when the thickness of inorganic film 231 is 10 nm is shown by curve L23, the relationship when the thickness of inorganic film 231 is 50 nm is shown by curve L24, and the relationship when the thickness of inorganic film 231 is 110 nm is shown by curve L25.

[0096] Furthermore, in Figure 12, the relationship when the thickness of inorganic film 231 is 200 nm is shown by curve L26, the relationship when the thickness of inorganic film 231 is 300 nm is shown by curve L27, the relationship when the thickness of inorganic film 231 is 500 nm is shown by curve L28, and the relationship when the thickness of inorganic film 231 is 1000 nm is shown by curve L29.

[0097] In Figure 11, when comparing curve L22 to curve L20, the reflectance is about 1% lower, and when compared to curve L21, the reflectance is about the same. Curve L23 shows a slight overall decrease in reflectance compared to curve L22, and curves L24 and L25 show an even further overall decrease in reflectance compared to curve L23, but the reflectance of curves L23 to L25 does not exceed the reflectance of curve L21. Thus, Figure 11 shows that even when the film thickness of the inorganic film 231 is increased to 10 nm, 50 nm, and 110 nm, the reflectance remains low in the wavelength range of 400 to 700 nm, and the reflectance does not worsen compared to when the inorganic film 231 is not stacked (when the inorganic film 232 is a single film).

[0098] In Figure 12, the reflectance of curves L26 to L29 is generally reduced and does not exceed the reflectance of curve L21. Thus, Figure 12 shows that even when the film thickness of the inorganic film 231 is further increased to 200 nm, 300 nm, 500 nm, and 1000 nm, the reflectance remains low in the 400 to 700 nm wavelength range, and the reflectance does not deteriorate compared to when the inorganic film 231 is not stacked (when the inorganic film 232 is a single film). However, the inventors of this disclosure have confirmed through detailed simulations that although the reflectance does not deteriorate when the film thickness of the inorganic film 231 is 500 nm and 1000 nm, interference occurs due to the thickness of the inorganic film 231, making it impractical. Therefore, it is preferable for the film thickness of the inorganic film 231 to be 10 nm or more and 300 nm or less.

[0099] Thus, in the anti-reflective coating 221 formed on the surface of the on-chip microlens 114, by setting the thickness of the inorganic film 231, which acts as an adhesion layer between the on-chip microlens 114 and the inorganic film 232, to 10 to 300 nm, adhesion can be improved, resulting in high reliability while suppressing image quality degradation such as flare.

[0100] Specifically, the inorganic film 231 is made of an LTO film such as a silicon oxide film, and there are no problems with adhesion to the on-chip microlens 114, nor with adhesion to the inorganic film 232. Therefore, by being placed between the on-chip microlens 114 and the inorganic film 232, adhesion can be improved. As a result, the inorganic film 231 will not peel off from the on-chip microlens 114, and consequently, the peeling of the outermost inorganic film 232 can be suppressed.

[0101] Furthermore, in the anti-reflective coating 221, inorganic films 231 and 232 are stacked, and since inorganic film 232 is a structural film with a fine uneven shape to reduce light reflection, it can reduce surface reflection of the on-chip microlens 114 and suppress flare and other issues caused by reflection. Moreover, by setting the thickness of inorganic film 231 to 10-300 nm, the reflectivity is reduced compared to when inorganic film 232 is composed as a single film, so flare and other issues can be further reduced by improving reflectivity. As a result, image quality degradation such as flare can be suppressed more reliably.

[0102] Furthermore, by forming an anti-reflective coating 221 on the surface of the on-chip microlens 114, damage to the on-chip microlens 114 can be suppressed. Note that even when the pixel 100 is a micro-pixel, the anti-reflective coating 221 can be formed on the surface of the on-chip microlens 114.

[0103] (Example of manufacturing method) Figures 13 and 14 show other examples of methods for manufacturing a photodetector that apply the present disclosure.

[0104] Figure 13 shows the process after the on-chip microlens 114 has been formed, similar to Figure 9. Specifically, a photodiode 111 and the like are formed on the silicon substrate to create an imaging region in which multiple pixels 100 are arranged in two dimensions. An insulating film 112 is then formed on the upper surface of the photodiode 111 to flatten its surface, and a color filter 113 corresponding to red, green, or blue wavelengths is formed on top of it.

[0105] Then, as shown in Figure 13A, an on-chip microlens 114 is formed on the color filter 113.

[0106] Next, as shown in Figure 13B, an inorganic film 231 is deposited on the surface of the on-chip microlens 114. The inorganic film 231 can be deposited using chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD). For example, an LTO film such as a silicon oxide film is deposited as the inorganic film 231.

[0107] Next, as shown in Figure 13C, an inorganic film 232 is deposited on the surface of the inorganic film 231. The inorganic film 232 can be deposited using methods such as atomic layer deposition (ALD). For example, an AlOx film is deposited as the inorganic film 232. The inorganic film 231 becomes an adhesion film (adhesion layer) that brings the on-chip microlens 114 and the inorganic film 232 into close contact.

[0108] Next, in Figure 14D, a high-temperature treatment (e.g., 90°C treatment) of pure water (DIW) is performed, and as shown in Figure 14E, a structural film having a fine uneven shape is formed as the inorganic film 232. In other words, the inorganic film 232 is formed of an AlOx film or the like. In this way, a solid-state imaging device 10 is obtained in which an anti-reflective film 221 consisting of two layers (a low refractive index layer and an ultra-low refractive index layer) of inorganic film 231 and inorganic film 232 is formed on the surface of the on-chip microlens 114.

[0109] <3. Variant>

[0110] (Example of a light detection device) In the above description, a CMOS-type solid-state imaging device was described as the solid-state imaging device 10. However, the CMOS-type solid-state imaging device can have a back-illuminated structure in which light is incident from the upper layer (back side) opposite to the wiring layer side (front side) formed in the lower layer when viewed from the silicon substrate on which the photodiode 111 as the photoelectric conversion unit is formed. Alternatively, the CMOS-type solid-state imaging device may have a front-illuminated structure in which the side from which light is incident is the wiring layer side (front side).

[0111] The solid-state imaging device 10 is an example of a photodetector to which this disclosure is applied. That is, a photodetector to which this disclosure is applied is not limited to the solid-state imaging device 10, but can be applied to other devices that detect light, such as a distance measuring sensor using an IR laser. Furthermore, the configuration of the anti-reflective coating to which this disclosure is applied is not limited to a CMOS type solid-state imaging device, but can also be applied to a CCD (Charge Coupled Device) type solid-state imaging device.

[0112] In the above description, the solid-state imaging device 10 is configured with a first conductivity type of p-type and a second conductivity type of n-type, but it is also acceptable for the n-type to be the first conductivity type and the p-type to be the second conductivity type. Furthermore, in the above description, the solid-state imaging device 10 is shown as using primary color filters corresponding to the wavelengths of red (R), green (G), and blue (B) as the color filter 113, but it is also acceptable to use complementary color filters corresponding to the wavelengths of cyan (C), magenta (M), and yellow (Y).

[0113] (Configuration of electronic equipment) The photodetector to which this disclosure applies can be mounted on electronic devices such as smartphones, tablet devices, mobile phones, digital still cameras, and digital video cameras. Figure 15 is a block diagram showing an example configuration of an electronic device equipped with the photodetector to which this disclosure applies.

[0114] In Figure 15, the electronic device 1000 has an imaging system consisting of an optical system 1011 including a lens group, a photodetector 1012 having a function corresponding to the solid-state imaging device 10 in Figure 1, and a camera signal processing unit DSP (Digital Signal Processor) 1013. In addition to the imaging system, the electronic device 1000 has a configuration in which a CPU (Central Processing Unit) 1010, frame memory 1014, display 1015, operation system 1016, auxiliary memory 1017, communication I / F 1018, and power supply system 1019 are interconnected via a bus 1020.

[0115] The CPU 1010 controls the operation of each part of the electronic device 1000.

[0116] The optical system 1011 captures incident light (image light) from the subject and forms an image on the photodetector surface of the photodetector element 1012. The photodetector element 1012 converts the amount of incident light formed on the photodetector surface by the optical system 1011 into an electrical signal on a pixel-by-pixel basis and outputs it as a pixel signal. The DSP 1013 performs predetermined signal processing on the signal output from the photodetector element 1012.

[0117] The frame memory 1014 temporarily records still images or video data captured by the imaging system. The display 1015 is a liquid crystal display or an organic EL display, and displays still images or video captured by the imaging system. The operating system 1016 issues operation commands for various functions of the electronic device 1000 in response to user operations.

[0118] The auxiliary memory 1017 is a storage medium including semiconductor memory such as flash memory, and records still image or video image data captured by the imaging system. The communication interface 1018 has a communication module compatible with a predetermined communication method and transmits still image or video image data captured by the imaging system to other devices via a network.

[0119] The power supply system 1019 supplies various power supplies as appropriate to the CPU 1010, DSP 1013, frame memory 1014, display 1015, operation system 1016, auxiliary memory 1017, and communication I / F 1018.

[0120] <4. Examples of applications to mobile devices>

[0121] 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 vehicle, such as an automobile, electric vehicle, hybrid electric vehicle, motorcycle, bicycle, personal mobility device, airplane, drone, ship, or robot.

[0122] Figure 16 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.

[0123] The vehicle control system 12000 comprises multiple electronic control units connected via a communication network 12001. In the example shown in Figure 16, 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] The imaging unit 12031 is an optical 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.

[0128] 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 images 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.

[0129] The microcomputer 12051 can calculate control target values ​​for the drive force generator, steering mechanism, or braking system based on information from 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 based on distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning.

[0130] 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.

[0131] 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.

[0132] 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 in Figure 16, the output devices are exemplified as 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.

[0133] Figure 17 shows an example of the installation position of the imaging unit 12031.

[0134] In Figure 17, the vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as the imaging unit 12031.

[0135] 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 forward images acquired by imaging units 12101 and 12105 are mainly used for detecting preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0136] Figure 17 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.

[0137] 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.

[0138] For example, the microcomputer 12051, based on distance information obtained from 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 vehicle 12100). In particular, it can extract the nearest object on the vehicle 12100's path that is traveling in approximately the same direction as 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.

[0139] 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, heavy 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 display unit 12062, or by performing forced deceleration or evasive steering via the drive system control unit 12010.

[0140] 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.

[0141] 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 the imaging unit 12031 of the configuration described above. Specifically, the solid-state imaging device 10 in Figure 1 can be applied to the imaging unit 12031. By applying the technology described herein to the imaging unit 12031, image quality degradation such as flare can be suppressed, and a clearer image can be obtained, thereby reducing driver fatigue.

[0142] The embodiments described herein are not limited to those described above, and various modifications are possible without departing from the spirit of this disclosure. Furthermore, the effects described herein are merely illustrative and not limiting, and other effects may also occur.

[0143] Furthermore, this disclosure can take the following form.

[0144] (1) Multiple pixels having a photoelectric conversion unit, An on-chip microlens formed corresponding to each pixel, The anti-reflective coating formed on the surface of the on-chip microlens and It has, The anti-reflective coating is A first inorganic film formed of a metal oxide film, A second inorganic film is formed on the surface of the first inorganic film and has a lower refractive index than the first inorganic film. It is constructed by stacking these elements. Light detection device. (2) The first inorganic film is a tantalum oxide film, a niobium oxide film, a titanium oxide film, or a hafnium oxide film. The light detection device described in (1) above. (3) The second inorganic film is a silicon oxide film or a silicon oxide carbide film. The light detection device described in (1) or (2) above. (4) The refractive index of the first inorganic film is 1.8 or higher. The refractive index of the second inorganic film is 1.55 or less. The light detection device according to any one of (1) to (3) above. (5) The thickness of the first inorganic film is less than or equal to the thickness of the second inorganic film. The light detection device according to any one of (1) to (4) above. (6) The thickness of the anti-reflective coating is 200 nm or less. The light detection device described in (5) above. (7) The first inorganic film is formed on the surface of the on-chip microlens, The second inorganic film is formed on the outermost surface. The light detection device according to any one of (1) to (6) above. (8) The first inorganic film and the second inorganic film are stacked alternately. The light detection device according to any one of (1) to (7) above. (9) The first inorganic film is formed on the surface of the on-chip microlens and is an adhesion film that brings the on-chip microlens and the second inorganic film into close contact. The second inorganic film described above is a structural film formed on the outermost surface and having a fine uneven surface. The light detection device described in (1) above. (10) The first inorganic film is an LTO film, The second inorganic film is formed by an AlOx film. The light detection device described in (9) above. (11) The thickness of the first inorganic film is 10 nm or more and 300 nm or less. The light detection device described in (9) or (10) above. (12) The anti-reflective coating is thinner in the portion corresponding to the edge of the on-chip microlens than in the portion corresponding to the center of the on-chip microlens. The light detection device according to any one of (1) to (8) above. (13) The anti-reflective coating becomes thinner as you move from the portion corresponding to the center of the on-chip microlens towards the portion corresponding to the edge. The light detection device described in (12) above. (14) The position of the first center of the circle indicating the curvature of the surface of the on-chip microlens and the position of the second center of the circle indicating the curvature of the surface of the anti-reflective coating do not coincide. The light detection device according to either (12) or (13) above. (15) The second center is located on the side of the first center from which light is incident. The light detection device described in (14) above. (16) The second center includes the center of the circle that represents the curvature of the surfaces of the first inorganic film and the second inorganic film, respectively. The light detection device described in (14) or (15) above. (17) The anti-reflective coating is formed between the on-chip microlenses. The light detection device according to any one of (1) to (8) or (12) to (16) above. (18) A flat portion is formed between the on-chip microlenses. The thickness of the anti-reflective coating is substantially the same in the portion corresponding to the flat area and in the portion corresponding to the center of the on-chip microlens. The light detection device described in (17) above. (19) Multiple pixels having a photoelectric conversion unit, An on-chip microlens formed corresponding to each pixel, The anti-reflective coating formed on the surface of the on-chip microlens and It has, The anti-reflective coating is The first inorganic film, A second inorganic film is formed on the surface of the first inorganic film, and is a structural film formed by processing a fine uneven shape on the surface of a workpiece film having a predetermined refractive index. It is constructed by stacking these elements. Light detection device. (20) The first inorganic film is formed on the surface of the on-chip microlens and is an adhesion film that brings the on-chip microlens and the second inorganic film into close contact. The above-mentioned second inorganic film is a structural film formed on the outermost surface. The light detection device described in (19) above. (twenty one) The first inorganic film is an LTO film, The processed film is an AlOx film. The light detection device described in (19) or (20) above. (twenty two) The thickness of the first inorganic film is 10 nm or more and 300 nm or less. The light detection device according to any one of (19) to (21) above. (twenty three) Multiple pixels having a photoelectric conversion unit, An on-chip microlens formed corresponding to each pixel, The anti-reflective coating formed on the surface of the on-chip microlens and It has, The anti-reflective coating is A first inorganic film formed of a metal oxide film, A second inorganic film is formed on the surface of the first inorganic film and has a lower refractive index than the first inorganic film. An electronic device equipped with a light detection device constructed by stacking multiple components. [Explanation of Symbols]

[0145] 10 Solid-state imaging device, 21 Pixel array unit, 22 Vertical drive unit, 23 Column signal processing unit, 24 Horizontal drive unit, 25 Output unit, 26 Control unit, 100 Pixel, 111 Photodiode, 114 On-chip microlens, 121 Anti-reflective coating, 131 Inorganic film, 132 Inorganic film, 141 Inorganic film, 142 Inorganic film, 143 Inorganic film, 144 Inorganic film, 221 Anti-reflective coating, 231 Inorganic film, 232 Inorganic film, 1000 Electronic equipment, 1012 Photodetector

Claims

1. Multiple pixels having a photoelectric conversion unit, An on-chip microlens formed corresponding to each pixel, The anti-reflective coating formed on the surface of the on-chip microlens and It has, The anti-reflective coating is A first inorganic film formed of a metal oxide film, A second inorganic film is formed on the surface of the first inorganic film and has a lower refractive index than the first inorganic film. It is constructed by stacking these, The thickness of the first inorganic film is less than or equal to the thickness of the second inorganic film. The positions of the first center of the circle indicating the curvature of the surface of the on-chip microlens and the second center of the circle indicating the curvature of the surface of the anti-reflective coating do not coincide. The second center is located on the side of the first center where light is incident, and the second center includes the center of the circle that represents the curvature of the surfaces of the first inorganic film and the second inorganic film, respectively. Light detection device.

2. The first inorganic film is a tantalum oxide film, a niobium oxide film, a titanium oxide film, or a hafnium oxide film. The light detection device according to claim 1.

3. The second inorganic film is a silicon oxide film or a silicon oxide carbide film. The light detection device according to claim 2.

4. The refractive index of the first inorganic film is 1.8 or higher. The refractive index of the second inorganic film is 1.55 or less. The light detection device according to claim 1.

5. The thickness of the anti-reflective coating is 200 nm or less. The light detection device according to claim 1.

6. The first inorganic film is formed on the surface of the on-chip microlens, The second inorganic film is formed on the outermost surface. The light detection device according to claim 1.

7. The first inorganic film and the second inorganic film are alternately stacked. The light detection device according to claim 6.

8. The anti-reflective coating is thinner in the portion corresponding to the edge of the on-chip microlens than in the portion corresponding to the center of the on-chip microlens. The light detection device according to claim 1.

9. The anti-reflective coating becomes thinner as you move from the portion corresponding to the center of the on-chip microlens towards the portion corresponding to the edge. The light detection device according to claim 8.

10. The anti-reflective coating is formed between the on-chip microlenses. The light detection device according to claim 1.

11. A flat portion is formed between the on-chip microlenses. The thickness of the anti-reflective coating is substantially the same in the portion corresponding to the flat area and in the portion corresponding to the center of the on-chip microlens. The light detection device according to claim 10.

12. Multiple pixels having a photoelectric conversion unit, An on-chip microlens formed corresponding to each pixel, The anti-reflective coating formed on the surface of the on-chip microlens and It has, The anti-reflective coating is The first inorganic film is an LTO film, A second inorganic film is a structural film formed on the surface of the first inorganic film by processing a fine uneven surface on the surface of an AlOx film having a predetermined refractive index. It is constructed by stacking these elements. Light detection device.

13. The first inorganic film is formed on the surface of the on-chip microlens and is an adhesion film that brings the on-chip microlens and the second inorganic film into close contact. The second inorganic film described above is a structural film formed on the outermost surface. The light detection device according to claim 12.

14. The thickness of the first inorganic film is 10 nm or more and 300 nm or less. The light detection device according to claim 12.

15. Multiple pixels having a photoelectric conversion unit, An on-chip microlens formed corresponding to each pixel, The anti-reflective coating formed on the surface of the on-chip microlens and It has, The anti-reflective coating is A first inorganic film formed of a metal oxide film, A second inorganic film is formed on the surface of the first inorganic film and has a lower refractive index than the first inorganic film. It is constructed by stacking these, The thickness of the first inorganic film is less than or equal to the thickness of the second inorganic film. The positions of the first center of the circle indicating the curvature of the surface of the on-chip microlens and the second center of the circle indicating the curvature of the surface of the anti-reflective coating do not coincide. The second center is located on the side of the first center where light is incident, and the second center includes the center of the circle that represents the curvature of the surfaces of the first inorganic film and the second inorganic film, respectively. An electronic device equipped with a light detection device.

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