Optical detection device and electronic apparatus

Abstract

Provided is an optical detection device in which the number of voids generated in a plasmon filter is suppressed. This optical detection device comprises: a semiconductor layer in which one surface is a light incident surface, the other surface is an element formation surface, and a photoelectric conversion element is configured; an insulating layer that is provided on the light incident surface side of the semiconductor layer and is composed of an insulating material; a plasmon filter that has a metal film composed of a first metal and a plurality of holes provided in the metal film, and is disposed at a position overlapping the photoelectric conversion element in a plan view; and a base film in which one surface is in contact with a surface of the plasmon filter on the semiconductor layer side and the other surface is in contact with the insulating layer, wherein the base film is composed of an oxide of the first metal.

Description

Photodetector and electronic equipment

[0001] The present technology (technology related to the present disclosure) relates to a photodetector and an electronic device, and more particularly to a photodetector and an electronic device having an optical filter.

[0002] Metals such as aluminum are used for wiring in solid-state devices, but stress from insulating films (SiO2) surrounding the wiring can cause voids in the wiring. To prevent stress migration, which can cause problems such as wire breakage, a barrier metal is generally formed between the insulating layer and the wiring. For example, in Patent Document 1, a tungsten film is deposited on an insulating film formed on a semiconductor substrate, and then an aluminum film is deposited by sputtering, and then selectively etched to form wiring. Plasmon optical filters are made of metal due to their processing history and physical properties, so voids can occur in the same way as wiring.

[0003] Japanese Patent Application Publication No. 05-206136

[0004] When a barrier metal is formed between the filter and the insulating film to suppress voids, the plasmon resonance may be significantly affected.

[0005] The present technology aims to provide a photodetector and an electronic device in which the number of voids generated in a plasmon filter is suppressed.

[0006] According to one aspect of the present technology, there is provided a photodetector including: a semiconductor layer having one surface as a light incident surface and another surface as an element formation surface, and having a photoelectric conversion element configured thereon; an insulating layer provided on the light incident surface side of the semiconductor layer and made of an insulating material; a plasmon filter having a metal film made of a first metal and a plurality of holes provided in the metal film, and arranged at a position overlapping the photoelectric conversion element in a planar view; and a base film having one surface in contact with a surface of the plasmon filter facing the semiconductor layer and the other surface in contact with the insulating layer, the base film being made of an oxide of the first metal.

[0007] An electronic device according to an aspect of the present technology includes the light detection device and an optical system that forms an image light from a subject on the light detection device.

[0008] 8A is a chip layout diagram showing an example configuration of the photodetector according to the first embodiment of the present technology. FIG. 8B is a block diagram showing an example configuration of the photodetector according to the first embodiment of the present technology. FIG. 8C is an equivalent circuit diagram of a pixel of the photodetector according to the first embodiment of the present technology. FIG. 8C is a longitudinal sectional view showing a cross-sectional configuration of a pixel included in the photodetector according to the first embodiment of the present technology. FIG. 8D is a plan view showing a planar configuration of a plasmon filter included in the photodetector according to the first embodiment of the present technology. FIG. 8E is a longitudinal sectional view showing an enlarged cross-sectional configuration of the plasmon filter included in the photodetector according to the first embodiment of the present technology. FIG. 8F is a cross-sectional view showing a process of a method for manufacturing the photodetector according to the first embodiment of the present technology. FIG. 8G is a cross-sectional view showing a process of a plasmon filter included in the photodetector according to the second embodiment of the present technology. FIG. 8H is a cross-sectional view showing an enlarged cross-sectional configuration of the plasmon filter included in the photodetector according to the second embodiment of the present technology. FIG. 8H is a diagram showing a simulation result of the sensitivity of a photoelectric conversion element when the thickness of an underlayer is changed. FIG. 8I is a cross-sectional view showing a process of a method for manufacturing the photodetector according to the second embodiment of the present technology. FIG. 10 is a longitudinal cross-sectional view showing, in enlarged form, a cross-sectional configuration of a plasmon filter included in a photodetector according to a first modified example of the second embodiment of the present technology. FIG. 11 is a process cross-sectional view showing a method for manufacturing a photodetector according to a first modified example of the second embodiment of the present technology. FIG. 12 is a diagram showing a simulation result of the spectral spectrum of a plasmon filter included in a photodetector according to a fourth embodiment of the present technology. FIG. 13 is a diagram showing a simulation result of the spectral spectrum of a plasmon filter included in a photodetector according to a fifth embodiment of the present technology. FIG. 14 is a diagram showing a simulation result of the spectral spectrum of a plasmon filter included in a photodetector according to a fifth embodiment of the present technology. FIG. 15 is a diagram showing a simulation result of the spectral spectrum of a plasmon filter included in a photodetector according to a fifth embodiment of the present technology. FIG. 16 is a diagram showing a simulation result of the spectral spectrum of a plasmon filter included in a photodetector according to a fifth embodiment of the present technology. FIG. 17 is a block diagram showing an example of a schematic configuration of an electronic device.

[0009] Hereinafter, preferred embodiments for carrying out the present technology will be described with reference to the drawings. Note that the embodiments described below are examples of typical embodiments of the present technology, and the scope of the present technology should not be interpreted as being narrow.

[0010] In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc., differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined by taking into consideration the following explanation. Furthermore, it goes without saying that the drawings include parts with different dimensional relationships and ratios. Furthermore, since drawings suitable for explaining the present technology are used, there may be differences in configuration between the drawings.

[0011] Furthermore, the embodiments described below are merely examples of devices and methods for embodying the technical idea of ​​the present technology, and the technical idea of ​​the present technology does not specify the materials, shapes, structures, arrangements, etc. of the components to those described below. The technical idea of ​​the present technology can be modified in various ways within the technical scope defined by the claims.

[0012] Furthermore, the definitions of directions such as up and down in the following explanation are merely for the convenience of explanation and do not limit the technical idea of ​​the present disclosure. For example, if an object is rotated 90 degrees and observed, up and down are converted to left and right and read as such, and if an object is rotated 180 degrees and observed, up and down are obviously read as reversed.

[0013] The description will be given in the following order: 1. First embodiment 2. Second embodiment 3. Third embodiment 4. Fourth embodiment 5. Fifth embodiment 6. Sixth embodiment Application examples to electronic devices

[0014] First Embodiment In this embodiment, an example in which the present technology is applied to a photodetector device that is a back-illuminated CMOS (Complementary Metal Oxide Semiconductor) image sensor will be described.

[0015] <Overall Configuration of Photodetection Device> First, the overall configuration of the photodetection device 1 will be described. As shown in Fig. 1 , the photodetection device 1 according to the first embodiment of the present technology is mainly composed of a semiconductor chip 2 having a rectangular two-dimensional planar shape in a plan view. That is, the photodetection device 1 is mounted on the semiconductor chip 2. As shown in Fig. 20 , the photodetection device 1 captures image light (incident light 106) from a subject via an optical system (optical lens) 102, converts the amount of incident light 106 formed on an imaging surface into an electrical signal on a pixel-by-pixel basis, and outputs the electrical signal as a pixel signal.

[0016] As shown in FIG. 1, the semiconductor chip 2 on which the photodetector 1 is mounted includes, in a two-dimensional plane including an X direction and a Y direction that intersect with each other, a square-shaped pixel region 2A provided in the center, and a peripheral region 2B provided outside the pixel region 2A so as to surround the pixel region 2A.

[0017] The pixel region 2A is a light receiving surface that receives light collected by, for example, the optical system 102 shown in FIG. 20 . In the pixel region 2A, a plurality of pixels 3 are arranged in a matrix on a two-dimensional plane including the X direction and the Y direction. In other words, the pixels 3 are repeatedly arranged in each of the X direction and the Y direction that intersect with each other within the two-dimensional plane. In this embodiment, as an example, the X direction and the Y direction are orthogonal to each other. Furthermore, the direction orthogonal to both the X direction and the Y direction is the Z direction (thickness direction, stacking direction). Furthermore, the direction perpendicular to the Z direction is the horizontal direction.

[0018] 1, a plurality of bonding pads 14 are arranged in the peripheral region 2B. Each of the plurality of bonding pads 14 is arranged, for example, along each of the four sides in a two-dimensional plane of the semiconductor chip 2. Each of the plurality of bonding pads 14 is an input / output terminal used when electrically connecting the semiconductor chip 2 to an external device.

[0019] 2, the semiconductor chip 2 includes a logic circuit 13. The logic circuit 13 includes a vertical drive circuit 4, a column signal processing circuit 5, a horizontal drive circuit 6, an output circuit 7, and a control circuit 8. The logic circuit 13 is configured of a CMOS (Complementary MOS) circuit having, as field effect transistors, for example, n-channel conductivity type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and p-channel conductivity type MOSFETs.

[0020] The vertical drive circuit 4 is configured with, for example, a shift register. The vertical drive circuit 4 sequentially selects desired pixel drive lines 10, supplies pulses to the selected pixel drive lines 10 for driving the pixels 3, and drives each pixel 3 row by row. That is, the vertical drive circuit 4 sequentially selects and scans each pixel 3 in the pixel region 2A row by row in the vertical direction, and supplies pixel signals from the pixels 3 based on signal charges generated by the photoelectric conversion elements of each pixel 3 in accordance with the amount of light received to the column signal processing circuit 5 via vertical signal lines 11.

[0021] The column signal processing circuit 5 is arranged, for example, for each column of pixels 3, and performs signal processing such as noise removal for each pixel column on signals output from one row of pixels 3. For example, the column signal processing circuit 5 performs signal processing such as CDS (Correlated Double Sampling) for removing fixed pattern noise specific to the pixels and AD (Analog-Digital) conversion. A horizontal selection switch (not shown) is provided at the output stage of the column signal processing circuit 5 and connected between the output stage and the horizontal signal line 12.

[0022] The horizontal drive circuit 6 is configured by, for example, a shift register. The horizontal drive circuit 6 sequentially outputs horizontal scanning pulses to the column signal processing circuits 5, thereby selecting each of the column signal processing circuits 5 in turn and causing each column signal processing circuit 5 to output a pixel signal that has undergone signal processing to a horizontal signal line 12.

[0023] The output circuit 7 processes and outputs pixel signals sequentially supplied from each of the column signal processing circuits 5 through the horizontal signal line 12. The signal processing may include, for example, buffering, black level adjustment, column variation correction, various types of digital signal processing, etc.

[0024] Based on the vertical synchronization signal, horizontal synchronization signal, and master clock signal, the control circuit 8 generates clock signals and control signals that serve as references for the operations of the vertical drive circuit 4, column signal processing circuit 5, horizontal drive circuit 6, etc. Then, the control circuit 8 outputs the generated clock signals and control signals to the vertical drive circuit 4, column signal processing circuit 5, horizontal drive circuit 6, etc.

[0025] 3 is an equivalent circuit diagram showing an example of the configuration of a pixel 3. The pixel 3 includes a photoelectric conversion element PD, a charge accumulation region (floating diffusion) FD that accumulates (holds) signal charges photoelectrically converted by the photoelectric conversion element PD, and a transfer transistor TR that transfers the signal charges photoelectrically converted by the photoelectric conversion element PD to the charge accumulation region FD. The pixel 3 also includes a readout circuit 15 electrically connected to the charge accumulation region FD.

[0026] The photoelectric conversion element PD generates a signal charge according to the amount of light received. The photoelectric conversion element PD also temporarily accumulates (holds) the generated signal charge. The cathode side of the photoelectric conversion element PD is electrically connected to the source region of the transfer transistor TR, and the anode side is electrically connected to a reference potential line (e.g., ground). For example, a photodiode is used as the photoelectric conversion element PD.

[0027] The drain region of the transfer transistor TR is electrically connected to the charge storage region FD, and the gate electrode of the transfer transistor TR is electrically connected to a transfer transistor drive line among the pixel drive lines 10 (see FIG. 2).

[0028] The charge storage region FD temporarily stores and holds the signal charge transferred from the photoelectric conversion element PD via the transfer transistor TR.

[0029] The readout circuit 15 reads out the signal charge accumulated in the charge accumulation region FD and outputs a pixel signal based on the signal charge. The readout circuit 15 includes, but is not limited to, pixel transistors, for example, an amplification transistor AMP, a selection transistor SEL, and a reset transistor RST. These transistors (AMP, SEL, RST) are made of, for example, a silicon oxide film (SiO ２ These transistors are configured as MOSFETs having a gate insulating film made of a silicon nitride film (Si film), a gate electrode, and a pair of main electrode regions that function as a source region and a drain region. ３ N ４ Alternatively, the readout circuit 15 may be a metal insulator semiconductor field effect transistor (MISFET) made of a stack of layers such as a silicon nitride film and a silicon oxide film. The readout circuit 15 may be provided for each photoelectric conversion element PD, or one readout circuit 15 may be shared by multiple photoelectric conversion elements PD. Similarly, the charge accumulation region FD may be provided for each photoelectric conversion element PD, or one charge accumulation region FD may be shared by multiple photoelectric conversion elements PD.

[0030] The amplifier transistor AMP has a source region electrically connected to the drain region of the select transistor SEL, a drain region electrically connected to the power supply line Vdd and the drain region of the reset transistor RST, and a gate electrode electrically connected to the charge storage region FD and the source region of the reset transistor RST.

[0031] The selection transistor SEL has a source region electrically connected to the vertical signal line 11 (VSL), a drain electrically connected to the source region of the amplification transistor AMP, and a gate electrode electrically connected to a selection transistor drive line among the pixel drive lines 10 (see FIG. 2).

[0032] The reset transistor RST has a source region electrically connected to the charge storage region FD and the gate electrode of the amplifier transistor AMP, and a drain region electrically connected to the power supply line Vdd and the drain region of the amplifier transistor AMP. The gate electrode of the reset transistor RST is electrically connected to a reset transistor drive line among the pixel drive lines 10 (see FIG. 2).

[0033] <<Specific Configuration of Photodetector>> Next, a specific configuration of the photodetector 1 will be described with reference to FIGS. 4 to 6. FIG.

[0034] 4, the photodetector 1 (semiconductor chip 2) includes, for example, a semiconductor layer 20 having a first surface S1 and a second surface S2 located on opposite sides. A wiring layer 30 is laminated on the first surface S1 side of the semiconductor layer 20. On the second surface S2 side, for example, an insulating layer 40, a base film 50, a plasmon filter 60, an upper insulating layer 70, a band-pass filter 80, and a microlens Lz are laminated in order from the side closest to the second surface S2.

[0035] <Semiconductor Layer> The semiconductor layer 20 is composed of a semiconductor substrate. The semiconductor layer 20 is composed of, for example, a silicon (Si) substrate, although not limited thereto. The first surface S1 is sometimes referred to as the element formation surface or main surface, and the second surface S2 is sometimes referred to as the light incidence surface or back surface. A plurality of photoelectric conversion regions 20a are provided in the portion of the semiconductor layer 20 corresponding to the pixel region 2A, arranged in a matrix along the row direction (X direction) and column direction (Y direction) in a planar view. The semiconductor layer 20 includes, for example, a first conductivity type (e.g., p-type) semiconductor region and a second conductivity type (e.g., n-type) semiconductor region. The semiconductor layer 20, more specifically, the pixel region 2A of the semiconductor layer 20, includes the photoelectric conversion element PD, various transistors, and charge accumulation region FD shown in FIG. 3 . The photoelectric conversion element PD is configured within the photoelectric conversion region 20a, for example, for each photoelectric conversion region 20a. Then, photoelectric conversion is performed by the photoelectric conversion element PD formed in the photoelectric conversion region 20a, and signal charges are generated according to the amount of received light.

[0036] The photoelectric conversion region 20a is provided for each pixel 3, for example. More specifically, an island-shaped photoelectric conversion region 20a partitioned by an isolation region 20b is provided for each pixel 3. The number of pixels 3 is not limited to that shown in FIG. 4. The isolation region 20b has a partition structure that partitions the photoelectric conversion regions 20a from each other. The isolation region 20b has, for example, a trench structure in which a groove T is formed in the semiconductor layer 20 and an insulating film is buried in the groove T, although this is not limited thereto.

[0037] <Wiring Layer> The wiring layer 30 is a multi-layer wiring layer having, for example, an insulating film 31, wiring 32 provided in the insulating film 31, and vias 33, although not limited thereto. The wiring 32 is a horizontal wiring that extends mainly in the horizontal direction, and the vias 33 are vertical wiring that extends mainly in the thickness direction, and for example, they constitute at least a part of the wiring portion of the circuit shown in FIG. 3. The insulating film 31 is made of, for example, silicon oxide (SiO ２ , SiO) film, silicon nitride (Si ３ N ４ The wiring 32 and the via 33 are made of a known conductive material, such as a metal material, for example, copper (Cu), tungsten (W), or aluminum (Al).

[0038] <Insulating Layer> The insulating layer 40 is provided on the second surface S2 side of the semiconductor layer 20. The insulating layer 40 is made of a known insulating material, for example, silicon oxide (SiO, SiO ２ The insulating layer 40 may be made of a laminate of multiple insulating layers, and may be made of tantalum oxide (Ta) in addition to the silicon oxide layer. ２ O ５ a layer of aluminum oxide (Al ２ O ３) or the like. Even when the insulating layer 40 has multiple insulating layers, the portion in contact with the base film 50 is made of silicon oxide. That is, at least the portion of the insulating layer 40 in contact with the base film 50 is made of silicon oxide. A light-shielding layer OPB is formed within the insulating layer 40. The light-shielding layer OPB is preferably provided in a region that overlaps with the boundary between the pixels 3 (separation region 20b) in a plan view, and is made of a material that is difficult for light to transmit. The material for the light-shielding layer OPB is not limited to this, but examples thereof include tungsten (W).

[0039] <Plasmon Filter> Of the base film 50 and the plasmon filter 60, the plasmon filter 60 will be described first. The plasmon filter 60 is a filter that utilizes surface plasmon resonance. As shown in FIGS. 4 and 5 , the plasmon filter 60 includes a metal film 61 made of a first metal and a plurality of holes 62 formed in the metal film 61. The plasmon filter 60 is disposed in a position overlapping the photoelectric conversion region 20a (photoelectric conversion element PD) in a planar view. The plasmon filter 60 is provided, for example, for each pixel 3. The holes 62 penetrate the metal film 61 in the thickness direction of the semiconductor layer 20, are circular in a planar view, and are arranged at equal pitches in the metal film 61 in a planar view, forming a hole array. The surface of the metal film 61 facing the microlens Lz is covered with an upper insulating layer 70, and the interiors of the holes 62 are filled with the upper insulating layer 70. The plasmon filter 60 functions as a color filter that excites and propagates surface plasmons having a specific frequency component determined by the period of the hole array, etc., at the interface between the inner walls of the holes 62 and the upper insulating layer 70. In other words, the plasmon filter 60 is an optical element that selects specific light and supplies the selected light to the photoelectric conversion region 20a.

[0040] The photodetector 1 may have multiple types of plasmon filters 60 with different diameters, arrangement pitches, etc. of the holes 62. Fig. 5 shows, as an example, two types of plasmon filters 60 with different diameters and arrangement pitches of the holes 62. The band of light selected by the plasmon filter 60 on the right side of the page is different from the band of light selected by the plasmon filter 60 on the left side of the page. The number of types of plasmon filters 60 is not limited to two, and may be one type or three or more types.

[0041] In this embodiment, the first metal constituting the metal film 61 is aluminum (Al). The thickness of the metal film 61 is, for example, about several hundred nanometers. The thickness of the metal film 61 may be determined depending on the design of the plasmon filter 60. However, it is desirable that the metal film 61 has a thickness (at least about 100 nm or more) that does not transmit light incident on the photodetector 1. The metal film 61 is provided with a thickness of, for example, about 100 nm or more and 1 μm or less. A thickness of 1 μm can be considered relatively thick. In contrast, a thickness of about 100 nm or more and 200 nm or less can be considered relatively thin. When it is desired to make the metal film 61 thinner, for example, the thickness may be about 100 nm or more and 200 nm or less, about 100 nm or more and 150 nm or less, or about 120 nm or more and 180 nm or less. The upper insulating layer 70 is formed of, for example, silicon oxide (SiO, SiO ２ ) consists of

[0042] <Base film> One surface of the base film 50 is in contact with the surface of the plasmon filter 60 on the semiconductor layer 20 side, and the other surface is in contact with the insulating layer 40. The base film 50 is made of an oxide of a first metal. In this embodiment, since the first metal is aluminum as described above, the base film 50 is made of an oxide of aluminum (for example, Al ２ O ３ 4 and 6 , the base film 50 overlaps only the metal film 61 out of the metal film 61 and the holes 62 in a plan view. In other words, the holes 62 penetrate both the metal film 61 and the base film 50.

[0043] The base film 50 is interposed between the plasmon filter 60 and the insulating layer 40, and has the function of alleviating stress between the plasmon filter 60 and the insulating layer 40. The base film 50 has affinity with the metal film 61. More specifically, the base film 50 contains the first metal, and therefore has affinity with the metal film 61. The base film 50 having affinity with the metal film 61 means that the hardness of the base film 50 is a value between the hardness of the insulating layer 40 and the hardness of the first metal, and that the thermal expansion coefficient of the base film 50 is a value between the thermal expansion coefficient of the insulating layer 40 and the thermal expansion coefficient of the first metal, etc.

[0044] The thickness of the base film 50 may be at least the thickness corresponding to one molecule of the oxide of the first metal. From an optical perspective, the thickness of the base film 50 is preferably no more than about several hundred nanometers. The thickness of the base film 50 may also be determined depending on the characteristics of the plasmon filter 60.

[0045] <Band-pass filter> A band-pass filter 80 may be provided at a position overlapping the plasmon filter 60 in a planar view. As shown in Fig. 6 , the band-pass filter 80 has a laminated structure of, for example, a first layer 81, a second layer 82, and a third layer 83. The first layer 81 and the third layer 83 are made of, for example, silicon oxynitride, and the second layer 82 is made of, for example, silicon nitride.

[0046] <Microlens> The microlens Lz is an on-chip lens, and focuses incident light onto the semiconductor layer 20. The microlens Lz is provided for each pixel 3, for example, and is made of a resin material.

[0047] 7 shows the optical spectra of the four types of plasmon filters 60a, 60b, 60c, and 60d. In this way, even when the base film 50 is provided, the optical spectrum shown in FIG. 7 can be obtained.

[0048] 8A to 8D, a method for manufacturing the photodetector 1 will be described. Note that in this embodiment, the method for forming the base film 50 and the plasmon filter 60 will be mainly described, and descriptions of other parts will be omitted.

[0049] First, as shown in FIG. 8A , a film 50m made of an oxide of a first metal is deposited on the exposed surface of the insulating layer 40 by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), or the like. When depositing the film 50m at the molecular level, atomic layer deposition (ALD) is used to form the film 50m. When depositing a thicker film 50m, physical vapor deposition or chemical vapor deposition is used to form the film 50m. Then, as shown in FIG. 8B , a film 60m made of the first metal is deposited on the exposed surface of the film 50m by, for example, sputtering. Since the film 60m is deposited on the top surface of the film 50m, stress from the insulating layer 40 is alleviated. This reduces the number of voids that occur in the film 60m.

[0050] Next, as shown in FIG. 8C , a resist pattern R is formed using photolithography. The resist pattern R has openings Ra at positions where holes 62 are desired to be formed. Then, as shown in FIG. 8D , dry etching is performed on the films 60m and 50m using the resist pattern R as a mask. More specifically, etching is performed on the portions of the films 60m and 50m exposed through the openings Ra. This etching forms holes 62 that penetrate both the films 60m and 50m. This results in the base film 50 and the plasmon filter 60. Thereafter, although not shown, an upper insulating layer 70 is formed by atomic layer deposition, for example, to fill the holes 62 and cover the metal film 61, thereby forming the bandpass filter 80.

[0051] <<Main Effects of the First Embodiment>> Below, we will explain the main effects of the first embodiment, but first provide an overview. Generally, when forming metal wiring on an insulating film (silicon oxide), a barrier metal is typically formed between the wiring and the insulating film to prevent voids and disconnections caused by stress migration. However, in the case of a plasmon filter, forming titanium nitride (TiN) as a barrier metal between the filter and the insulating film significantly affects plasmon resonance, resulting in a decrease in plasmon propagation characteristics. For this reason, the plasmon filter was formed directly on silicon oxide. As a result, voids caused by stress migration were likely to occur in the plasmon filter. Furthermore, the occurrence of voids could result in changes in the spectral and sensitivity characteristics of the plasmon filter.

[0052] The occurrence of stress migration is thought to be related to the hardness (strength) and thermal expansion coefficient of the crystal (polycrystal). Silicon oxide has a much higher hardness than metals (such as aluminum). Silicon oxide also has a much lower thermal expansion coefficient than metals (such as aluminum). When aluminum is in contact with silicon oxide, the aluminum deforms when the temperature drops after film formation, but the silicon oxide deforms only slightly, and stress is thought to occur between the aluminum and silicon oxide.

[0053] In contrast, the photodetector 1 according to the first embodiment of the present technology includes a semiconductor layer 20 having one surface designated as a second surface S2 and the other surface designated as a first surface S1, and including a photoelectric conversion element PD, an insulating layer 40 provided on the second surface S2 side of the semiconductor layer 20 and made of an insulating material, a plasmon filter 60 having a metal film 61 made of a first metal and a plurality of holes 62 provided in the metal film 61, and arranged so as to overlap the photoelectric conversion element PD in a planar view, and an underlayer 50 having one surface in contact with the surface of the plasmon filter 60 facing the semiconductor layer 20 and the other surface in contact with the insulating layer 40, the underlayer 50 being made of an oxide of the first metal. Since the material constituting the underlayer 50 is an oxide of the first metal having an affinity for the first metal, it is possible to reduce stress between the silicon oxide and the plasmon filter 60 and to reduce the number of voids generated in the metal film 61 of the plasmon filter 60. For example, under certain experimental conditions, the amount of plasmon resonance could be reduced to about 1 / 50 when the base film 50 was provided compared to when the plasmon filter 60 was formed directly on silicon oxide. Furthermore, since the base film 50 made of an oxide of the first metal was provided instead of a material such as titanium nitride that significantly affects plasmon resonance, the significant effect on the plasmon propagation characteristics could be suppressed.

[0054] Furthermore, in the photodetector 1 according to the first embodiment of the present technology, the thickness of the base film 50 is equal to or greater than the thickness corresponding to one molecule of the oxide of the first metal. In this way, by providing even a small amount of the base film 50, stress can be alleviated and the number of voids generated in the metal film 61 of the plasmon filter 60 can be reduced.

[0055] Furthermore, it is generally known that the thinner the metal film 61, the more likely voids are to occur. Therefore, voids may be suppressed by increasing the thickness of the metal film 61. However, depending on the resonance performance required of the plasmon filter 60, it may be desirable to provide a thin metal film 61. In the photodetector 1 according to the first embodiment of the present technology, the number of voids generated in the metal film 61 is suppressed by providing the base film 50, so the thickness of the metal film 61 can be reduced, for example, to approximately 100 nm or more and 200 nm or less. This allows the metal film 61 to be provided thinly depending on the desired resonance performance, thereby increasing the degree of freedom in designing the plasmon filter 60.

[0056] In the photodetector 1 according to the first embodiment of the present disclosure, the first metal is aluminum and the base film 50 is made of an oxide of aluminum. Even in this case, the spectral characteristics shown in FIG. 7 can be obtained.

[0057] Second Embodiment A second embodiment of the present technology shown in FIG. 9 will be described below. In the first embodiment described above, the portions of the base film 50 that overlap the holes 62 of the plasmon filter 60 in a planar view were removed. In this embodiment, these portions are left unremoved. That is, the base film 50 remains on the entire lower surface of the plasmon filter 60. The rest of the configuration of the photodetector 1 is basically the same as that of the photodetector 1 of the first embodiment described above. Components that have already been described are assigned the same reference numerals, and description thereof will be omitted. Note that, as in the first embodiment described above, the first metal is aluminum, and the base film 50 is an oxide of aluminum.

[0058] In plan view, the base film 50 overlaps both the metal film 61 and the holes 62. By leaving the base film 50 in the region overlapping with the holes 62 in plan view, the sensitivity of the photoelectric conversion element PD provided in the semiconductor layer 20 is improved. For example, a portion of light that passes through the holes 62 of the plasmon filter 60 is reflected by the insulating layer 40 and returns to the plasmon filter 60 side. By leaving the base film 50 in the region overlapping with the holes 62 in plan view, a portion of the light that returns to the plasmon filter 60 side is reflected again and enters the semiconductor layer 20. This improves the sensitivity of the photoelectric conversion element PD. Furthermore, the sensitivity of the photoelectric conversion element PD can be further improved depending on the film thickness of the base film 50.

[0059] FIG. 10 shows the results of a simulation of the sensitivity of the photoelectric conversion element PD when the thickness of the underlayer film 50 is changed. In FIG. 10 , the vertical axis represents the sensitivity ratio normalized to 1 when the underlayer film 50 is not present, and the horizontal axis represents the thickness of the underlayer film 50. According to FIG. 10 , the sensitivity of the photoelectric conversion element PD is improved when the underlayer film 50 is present compared to when the underlayer film 50 is not present (thickness = 0 nm). Also, according to FIG. 10 , the sensitivity ratio is maximized when the thickness of the underlayer film 50 is approximately 70 nm. For example, a good sensitivity ratio can be obtained by setting the thickness of the underlayer film 50 to approximately 50 nm or more and 90 nm or less. More specifically, a good sensitivity ratio can be obtained by setting the thickness of the underlayer film 50 to approximately 60 nm or more and 80 nm or less.

[0060] <<Method of Manufacturing Photodetector>> Hereinafter, a method of manufacturing the photodetector 1 will be described with reference to FIG. 11 . Note that in this embodiment, only the differences from the first embodiment will be described. First, the process up to the step of forming the resist pattern R shown in FIG. 8C is the same as the first embodiment. Then, as shown in FIG. 11 , dry etching is used to etch the film 60m using the resist pattern R as a mask. More specifically, etching is performed on the portion of the film 60m exposed from the opening Ra to form a hole 62. In this case, the film 50m may be used as an etching stopper layer. Even if the film 50m is etched, it is only slightly etched. Descriptions of subsequent steps will be omitted.

[0061] <<Main Effects of Second Embodiment>> The main effects of the second embodiment will be described below. The photodetector 1 according to the second embodiment also provides the same effects as the photodetector 1 according to the first embodiment.

[0062] Furthermore, in the photodetector 1 according to the second embodiment, by leaving the base film 50 in the region that overlaps with the hole 62 in a plan view, a portion of the light that returns to the plasmon filter 60 side is reflected again and enters the semiconductor layer 20. This can improve the sensitivity of the photoelectric conversion element PD.

[0063] <Modification of Second Embodiment> A modification of the second embodiment will now be described.

[0064] <Modification 1> In the photodetector 1 according to the second embodiment, as shown in FIG. 9 , the thickness of the base film 50 is uniform or as uniform as possible, but the present technology is not limited to this. In the photodetector 1 according to Modification 1 of the second embodiment shown in FIG. 12 , the thickness of the portion of the base film 50 overlapping the hole 62 is thinner than the thickness of the portion of the base film 50 overlapping the metal film 61. Hereinafter, in order to distinguish between the portion of the base film 50 overlapping the hole 62 and the portion of the base film 50 overlapping the metal film 61, the portion of the base film 50 overlapping the hole 62 will be referred to as a first portion 51, and the portion of the base film 50 overlapping the metal film 61 will be referred to as a second portion 52. When there is no need to distinguish between the first portion 51 and the second portion 52, they will simply be referred to as the base film 50.

[0065] The thickness of the base film may be determined depending on the spectral characteristics of the plasmon filter 60. Consider a case where the thickness of the base film 50 is determined depending on the spectral characteristics, resulting in a thick film having a thickness of, for example, approximately 100 nm. Even in such a case, the sensitivity of the photoelectric conversion element PD shown in FIG. 10 can be improved by thinning the thickness of the first portion 51 by etching, as described below. More specifically, the sensitivity of the photoelectric conversion element PD can be improved by increasing the thickness of the first portion 51 to approximately 70 nm. For example, a good sensitivity ratio can be obtained by setting the thickness of the first portion 51 to approximately 50 nm or more and 90 nm or less. More specifically, a good sensitivity ratio can be obtained by setting the thickness of the first portion 51 to approximately 60 nm or more and 80 nm or less.

[0066] A method for manufacturing the photodetector 1 will be described below with reference to FIG. 13 . Note that in this modification, only the differences from the first and second embodiments will be described. First, the process up to the step of forming the resist pattern R shown in FIG. 8C is the same as the first embodiment. Then, as shown in FIG. 13 , dry etching is used to etch the films 60m and 50m using the resist pattern R as a mask. At this time, etching is performed to penetrate the film 60m, but not to penetrate the film 50m, leaving it with a desired film thickness. Description of the subsequent steps will be omitted.

[0067] The photodetector 1 according to the first modified example of the second embodiment also provides the same effects as the photodetector 1 according to the second embodiment described above.

[0068] Furthermore, in the photodetector 1 according to the first modification of the second embodiment, the sensitivity of the photoelectric conversion element PD can be improved by thinning the film thickness of the first portion 51 by etching, which will be described later, and therefore the degree of freedom in designing the plasmon filter 60 and the film thickness of the base film 50 is increased.

[0069] [Third Embodiment] A third embodiment of the present technology will be described below. Note that this embodiment will be described with reference to FIG. 4 . In the plasmon filter 60 of the photodetector 1 according to this third embodiment, the first metal constituting the metal film 61 contains an additive. Other than that, the configuration of the photodetector 1 is basically the same as that of the photodetector 1 of the first embodiment described above. Components that have already been described are assigned the same reference numerals, and description thereof will be omitted. Note that the first metal is aluminum containing an additive, and the base film 50 is an oxide of aluminum.

[0070] Examples of additives include silicon (Si) and copper (Cu). By adding copper to aluminum, the grain boundaries that make up the metal film 61 become larger, making it possible to suppress electromigration more effectively than if copper were not added. Furthermore, when the aluminum metal film 61 is connected to silicon, a phenomenon occurs in which the aluminum penetrates into the silicon in spike-like formations. By adding silicon to aluminum, it becomes more difficult for the aluminum to penetrate into the silicon.

[0071] The photodetector 1 according to the third embodiment also provides the same effects as those of the photodetector 1 according to the first embodiment.

[0072] Furthermore, in the photodetector 1 according to the third embodiment, the performance of the metal film 61 of the plasmon filter 60 can be improved.

[0073] Furthermore, in the photodetector 1 according to the third embodiment, even if the first metal contains an additive, the base film 50 has the same effect as in the first embodiment described above.

[0074] [Fourth embodiment] A fourth embodiment of the present technology will be described below. Note that this embodiment will be described with reference to FIG. 4. In the photodetector 1 according to the first embodiment, the insulating layer 40 is made of silicon oxide, but the present technology is not limited to this. In the photodetector 1 according to the fourth embodiment, the insulating layer 40 is made of silicon nitride (SiN, Si ３ N ４ ) or silicon oxynitride (SiON). More specifically, at least the portion of the insulating layer 40 that is in contact with the base film 50 is made of silicon nitride or silicon oxynitride. The other configuration of the photodetector 1 is basically the same as that of the photodetector 1 of the first embodiment described above. Components that have already been described are given the same reference numerals and their description will be omitted. Note that, as in the first embodiment described above, the first metal is aluminum, and the base film 50 is an oxide of aluminum.

[0075] 14 is a diagram showing the optical spectra of plasmon filters 60a, 60b, 60c, and 60d when base film 50 is made of silicon nitride. As such, even when base film 50 is made of silicon nitride, the optical spectrum shown in FIG. 14 is obtained.

[0076] The photodetector 1 according to the fourth embodiment also provides the same effects as those of the photodetector 1 according to the first embodiment.

[0077] Furthermore, in the photodetector 1 according to the fourth embodiment, even if the insulating layer 40 is made of an insulating material other than silicon oxide, the base film 50 has the effect of alleviating stress, similar to the first embodiment described above.

[0078] Fifth Embodiment A fifth embodiment of the present technology shown in Figures 15 to 19 will be described below. In the photodetector 1 according to the fifth embodiment, the first metal is a metal other than aluminum, and the base film 50 is an oxide of that metal. Other than that, the configuration of the photodetector 1 is basically the same as that of the photodetector 1 of the first embodiment described above. Components that have already been described are assigned the same reference numerals, and descriptions thereof will be omitted.

[0079] The first metal is, for example, any one of silver, nickel, tantalum, titanium, tungsten, and gold. When the first metal is silver (Ag), the undercoat film 50 is made of silver oxide. Even in this case, the spectral characteristics of the plasmon filters 60a, 60b, 60c, and 60d shown in FIG. 15 are obtained. When the first metal is nickel (Ni), the undercoat film 50 is made of nickel oxide. Even in this case, the spectral characteristics of the plasmon filters 60a, 60b, 60c, and 60d shown in FIG. 16 are obtained. When the first metal is tantalum (Ta), the undercoat film 50 is made of tantalum oxide. Even in this case, the spectral characteristics of the plasmon filters 60a, 60b, 60c, and 60d shown in FIG. 17 are obtained. When the first metal is titanium (Ti), the undercoat film 50 is made of titanium oxide. Even in such a case, the spectral characteristics of plasmon filters 60a, 60b, 60c, and 60d shown in Fig. 18 can be obtained. When the first metal is tungsten (W), the base film 50 is made of a tungsten oxide. Even in such a case, the spectral characteristics of plasmon filters 60a, 60b, 60c, and 60d shown in Fig. 19 can be obtained. When the first metal is gold (Au), the base film 50 is made of a gold oxide. The spectral characteristics are not shown in the figures.

[0080] The photodetector 1 according to the fifth embodiment also provides the same effects as those of the photodetector 1 according to the first embodiment.

[0081] Furthermore, in the photodetector 1 according to the fifth embodiment, the plasmon filter 60 is made of a metal other than aluminum, and the base film 50 is made of an oxide of that metal, which increases the degree of freedom in the design of the plasmon filter 60 and the base film 50.

[0082] Sixth Embodiment 1. Application Example to Electronic Devices Next, an electronic device 100 according to a sixth embodiment of the present technology will be described, as shown in Fig. 20 . The electronic device 100 includes a solid-state imaging device 101, an optical lens 102, a shutter device 103, a drive circuit 104, and a signal processing circuit 105. The electronic device 100 is, for example, an electronic device such as a camera, but is not limited thereto. The electronic device 100 also includes the above-described photodetector 1 as the solid-state imaging device 101.

[0083] An optical lens (optical system) 102 focuses image light (incident light 106) from a subject onto the imaging surface of the solid-state imaging device 101. This causes signal charges to accumulate in the solid-state imaging device 101 for a certain period of time. A shutter device 103 controls the light irradiation period and light blocking period of the solid-state imaging device 101. A drive circuit 104 supplies a drive signal that controls the transfer operation of the solid-state imaging device 101 and the shutter operation of the shutter device 103. Signal transfer from the solid-state imaging device 101 is performed in accordance with the drive signal (timing signal) supplied from the drive circuit 104. A signal processing circuit 105 performs various signal processing on signals (pixel signals) output from the solid-state imaging device 101. The processed video signals are stored in a storage medium such as a memory or output to a monitor.

[0084] With this configuration, the electronic device 100 reduces the number of voids that occur in the plasmon filter 60 of the solid-state imaging device 101, thereby improving the image quality of the video signal.

[0085] The electronic device 100 is not limited to a camera, but may be other electronic devices, such as an imaging device such as a camera module for a mobile device such as a mobile phone.

[0086] Furthermore, the electronic device 100 can be provided with, as the solid-state imaging device 101, a photodetector 1 according to any of the first to fifth embodiments and modified versions of those embodiments, or a photodetector 1 according to a combination of at least two of the first to fifth embodiments and modified versions of those embodiments.

[0087] [Other Embodiments] As described above, the present technology has been described by the first to sixth embodiments, but the descriptions and drawings that form part of this disclosure should not be understood to limit the present technology. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0088] For example, it is possible to combine the technical concepts described in the first to sixth embodiments with each other. For example, various combinations according to the technical concepts of each embodiment are possible, such as applying a metal other than aluminum according to the fifth embodiment to the configuration of the plasmon filter 60 and the base film 50 described in the first to fourth embodiments and their modifications.

[0089] Furthermore, the present technology can be applied to photodetection devices in general, including not only the solid-state imaging device as the image sensor described above but also distance measurement sensors, also known as ToF (Time of Flight) sensors, that measure distance. A distance measurement sensor emits light toward an object, detects the light reflected from the surface of the object, and calculates the distance to the object based on the time of flight between when the light is emitted and when the reflected light is received. The structure of the plasmon filter 60 and the base film 50 described above can be adopted as the structure of this distance measurement sensor.

[0090] The photodetector 1 may also be a stacked CIS (CMOS Image Sensor) in which two or more semiconductor substrates are stacked one on top of the other. In this case, elements included in at least one of the logic circuit 13 and the readout circuit 15 may be provided on a substrate different from the semiconductor substrate on which the photoelectric conversion element PD is provided.

[0091] Furthermore, for example, the materials cited as constituting the above-mentioned components may contain additives, impurities, and the like.

[0092] As such, the present technology naturally includes various embodiments not described herein. Therefore, the technical scope of the present technology is defined only by the invention-specifying matters described in the claims that are appropriate from the above description.

[0093] Furthermore, the effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0094] The present technology may be configured as follows: (1) A photodetector including: a semiconductor layer having one surface as a light incident surface and the other surface as an element formation surface, and having a photoelectric conversion element formed thereon; an insulating layer provided on the light incident surface side of the semiconductor layer and made of an insulating material; a plasmon filter having a metal film made of a first metal and a plurality of holes provided in the metal film, and positioned to overlap the photoelectric conversion element in a planar view; and an underlayer having one surface in contact with a surface of the plasmon filter facing the semiconductor layer and the other surface in contact with the insulating layer, the underlayer being made of an oxide of the first metal. (2) The photodetector according to (1), wherein the underlayer overlaps both the metal film and the holes in a planar view. (3) The photodetector according to (2), wherein a portion of the underlayer overlapping the hole is thinner than a portion of the underlayer overlapping the metal film. (4) The photodetector according to (2) or (3), wherein the portion of the underlayer film overlapping the hole has a thickness of 50 nm or more and 90 nm or less. (5) The photodetector according to (1) or (2), wherein the thickness of the underlayer film is equal to or greater than a thickness corresponding to one molecule of an oxide of the first metal. (6) The photodetector according to any one of (1) to (5), wherein the film thickness of the metal film is 100 nm or more and 200 nm or less. (7) The photodetector according to any one of (1) to (6), wherein the first metal is aluminum and the underlayer film is made of an oxide of aluminum. (8) The photodetector according to any one of (1) to (7), wherein the first metal contains an additive. (9) The photodetector according to (8), wherein the additive is copper or silicon. (10) The photodetector according to any one of (1) to (9), wherein the insulating layer is made of any one of silicon oxide, silicon nitride, and silicon oxynitride. (11) The photodetector according to any one of (1) to (6) and (8) to (10), wherein the first metal is any one of silver, nickel, tantalum, titanium, tungsten, and gold.(12) An electronic device comprising: a photodetector; and an optical system that forms an image light from a subject on the photodetector, wherein the photodetector comprises: a semiconductor layer having one surface as a light incident surface and the other surface as an element formation surface, and having a photoelectric conversion element formed thereon; an insulating layer that is provided on the light incident surface side of the semiconductor layer and is made of an insulating material; a plasmon filter that has a metal film made of a first metal and a plurality of holes provided in the metal film, and is positioned to overlap the photoelectric conversion element in a planar view; and a base film that has one surface in contact with the surface of the plasmon filter on the semiconductor layer side and the other surface in contact with the insulating layer, and the base film is made of an oxide of the first metal.

[0095] The scope of the present technology is not limited to the exemplary embodiments shown and described, but includes all embodiments that achieve equivalent effects to those intended by the present technology. Furthermore, the scope of the present technology is not limited to the combination of the features of the invention defined by the claims, but may be defined by any desired combination of specific features among all the respective disclosed features.

[0096] REFERENCE SIGNS LIST 1 Photodetector 20 Semiconductor layer 40 Insulating layer 50 Undercoat film 50m Film 51 First portion 52 Second portion 60, 60a, 60b, 60c, 60d Plasmon filter 60m Film 61 Metal film 62 Hole 102 Optical system PD Photoelectric conversion element

Claims

1. A photodetector comprising: a semiconductor layer having one surface which is a light incident surface and the other surface which is an element formation surface, and in which a photoelectric conversion element is formed; an insulating layer which is provided on the light incident surface side of the semiconductor layer and which is made of an insulating material; a plasmon filter which has a metal film made of a first metal and a plurality of holes provided in the metal film, and which is positioned so as to overlap the photoelectric conversion element in a planar view; and a base film which has one surface in contact with the surface of the plasmon filter facing the semiconductor layer and the other surface in contact with the insulating layer, wherein the base film is made of an oxide of the first metal.

2. The photodetector according to claim 1, wherein, in a plan view, the base film overlaps both the metal film and the hole.

3. The photodetector according to claim 2, wherein the portion of the base film overlapping the hole is thinner than the portion of the base film overlapping the metal film.

4. The photodetector according to claim 2, wherein the portion of the base film overlapping the hole has a thickness of 50 nm or more and 90 nm or less.

5. The photodetector according to claim 1, wherein the thickness of said undercoat film is equal to or greater than the thickness corresponding to one molecule of an oxide of said first metal.

6. The photodetector according to claim 1, wherein the metal film has a thickness of 100 nm or more and 200 nm or less.

7. The photodetector of claim 1, wherein said first metal is aluminum and said undercoat film is made of an oxide of aluminum.

8. The optical detection device of claim 7, wherein said first metal includes an additive.

9. The optical detection device of claim 8, wherein the additive is copper or silicon.

10. The photodetector device of claim 1, wherein the insulating layer is made of one of silicon oxide, silicon nitride, and silicon oxynitride.

11. The optical detection device of claim 1, wherein the first metal is one of silver, nickel, tantalum, titanium, tungsten, and gold.

12. An electronic device comprising: a photodetector; and an optical system that forms an image of light from a subject on the photodetector, wherein the photodetector comprises: a semiconductor layer having one surface as a light incident surface and the other surface as an element formation surface, and in which a photoelectric conversion element is formed; an insulating layer provided on the light incident surface side of the semiconductor layer and made of an insulating material; a plasmon filter having a metal film made of a first metal and a plurality of holes provided in the metal film, and arranged in a position overlapping the photoelectric conversion element in a planar view; and a base film having one surface in contact with the surface of the plasmon filter on the semiconductor layer side and the other surface in contact with the insulating layer, wherein the base film is made of an oxide of the first metal.

Images