Image pickup device, image pickup apparatus, and method for manufacturing image pickup device

Abstract

The present invention improves the sensitivity of an imaging element. This imaging element is provided with a plurality of pixels and a light-shielding wall. The plurality of pixels of the imaging element are each provided with a photoelectric conversion portion disposed on a semiconductor substrate to photoelectrically convert incident light that is shone, and an on-chip lens for focusing the incident light onto the photoelectric conversion unit. The light-shielding wall of the imaging element is disposed adjacent to the semiconductor substrate at a boundary of the plurality of pixels, wherein the side of the light-shielding wall on which the incident light is shone is configured in a tapered cross section to shield the incident light.

Description

[Technical field]

[0001] The present disclosure relates to an imaging element and an imaging device, and more particularly to an imaging element in which a plurality of pixels that generate image signals are arranged, and an imaging device that uses the imaging element. [Background technology]

[0002] Conventionally, imaging elements with improved photosensitivity have been proposed. For example, a solid-state imaging element has been proposed that is composed of a photoelectric conversion section formed in a mosaic pattern on a semiconductor substrate and performing photoelectric conversion of incident light, and a readout section for signals photoelectrically converted by the photoelectric conversion section (see, for example, Patent Document 1). This solid-state imaging element includes a lens array and a reflective layer. The lens array focuses incident light on each of the photoelectric conversion sections. The reflective layer has a function of reflecting incident light that is focused by the lens array on parts other than the photoelectric conversion sections, and focusing the light on the photoelectric conversion sections.

[0003] In this conventional technology, the photoelectric conversion units are formed on a semiconductor substrate directly below the lenses that make up the lens array, and are arranged in a relatively narrow range. The reflective layer is configured in the shape of a light guide path from near the end of the lens to the photoelectric conversion unit, and is configured in a cross-sectional shape whose diameter gradually decreases from near the end of the lens toward the photoelectric conversion unit. Incident light that is focused by the lens to a part other than the photoelectric conversion unit is reflected by the surface of the reflective layer that corresponds to the inner wall of the light guide path, and is guided to the photoelectric conversion unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 154283 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned conventional technology has a problem that the improvement in sensitivity is not sufficient. Specifically, depending on the angle of incidence of incident light focused by a lens on a portion other than the photoelectric conversion portion, the incident light is reflected by the reflective layer multiple times and enters the photoelectric conversion portion. The reflective layer can be made of metal. However, this reflective layer made of metal does not reflect 100% of the incident light, but absorbs a portion of the incident light. Therefore, when the incident light is reflected multiple times by the reflective layer, it is absorbed by the reflective layer and is significantly attenuated. Thus, the above-mentioned conventional technology has a problem that the improvement in sensitivity is not sufficient.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to improve the sensitivity of an imaging element. [Means for solving the problem]

[0007] The present disclosure has been made to solve the problems described above, and a first aspect thereof is an imaging element comprising: a plurality of pixels arranged on a semiconductor substrate, the plurality of pixels including a photoelectric conversion unit that performs photoelectric conversion of irradiated incident light and an on-chip lens that focuses the incident light onto the photoelectric conversion unit; and a light-shielding wall arranged adjacent to the semiconductor substrate at the boundary between the plurality of pixels, the side onto which the incident light is irradiated being configured with a tapered cross section, and the light-shielding wall that blocks the incident light.

[0008] Furthermore, in this first aspect, the light-shielding wall may be configured to have a tapered cross-section with an angle based on its height and width from the semiconductor substrate and the width of a light-receiving surface, which is the surface of the semiconductor substrate in the pixel onto which the incident light is irradiated.

[0009] Furthermore, in this first aspect, the light-shielding wall may be configured in a tapered shape with an elevation angle based on the inverse tangent function of a triangle including a perpendicular line drawn from the apex of the taper to the semiconductor substrate, with half of the light-shielding wall's width and the width of the light-receiving surface corresponding to the base.

[0010] In the first aspect, the light-shielding wall may be configured to have a triangular cross section having the tapered shape.

[0011] In the first aspect, each of the plurality of pixels may include a color filter that transmits incident light of a predetermined wavelength out of the collected incident light.

[0012] In the first aspect, the light-shielding wall may be configured in a shape that surrounds the color filter.

[0013] In the first aspect, the light-shielding wall may block the incident light by reflecting the incident light.

[0014] In the first aspect, the light-shielding wall may be made of metal.

[0015] In the first aspect, the light-shielding wall may be formed by etching a mask having a tapered cross section disposed on an upper surface of the light-shielding wall, thereby transferring the shape of the mask.

[0016] In the first aspect, the light-shielding wall may have the mask disposed on the upper surface thereof, the mask being etched back by plasma etching to form the tapered cross section.

[0017] Also, a second aspect of the present disclosure is an imaging device comprising: a plurality of pixels each including a photoelectric conversion unit disposed on a semiconductor substrate and performing photoelectric conversion of irradiated incident light and an on-chip lens that focuses the incident light onto the photoelectric conversion unit; a light-shielding wall disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and having a tapered cross section on the side where the incident light is irradiated, thereby blocking the incident light; and a processing circuit that processes an image signal generated based on the photoelectric conversion.

[0018] According to the aspect of the present disclosure, an effect is achieved in that the incident light entering the vicinity of the boundary of the pixel is incident on the tapered portion of the light-shielding wall. It is assumed that the incident light entering the vicinity of the boundary of the pixel is reflected by the tapered portion of the light-shielding wall. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of an imaging element according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating an example of a pixel configuration according to a first embodiment of the present disclosure. [Diagram 3] FIG. 2 is a diagram illustrating an example of light blocking according to the first embodiment of the present disclosure. [Figure 4] 3A to 3C are diagrams illustrating an example of a manufacturing method of an imaging element according to a first embodiment of the present disclosure. [Diagram 5] 3A to 3C are diagrams illustrating an example of a manufacturing method of an imaging element according to a first embodiment of the present disclosure. [Figure 6] 13 is a diagram illustrating a configuration example of a light-shielding wall according to a second embodiment of the present disclosure. FIG. [Figure 7] 13A and 13B are diagrams illustrating another configuration example of the light shielding wall according to the second embodiment of the present disclosure. [Figure 8] FIG. 13 is a diagram illustrating an example of a pixel configuration according to a third embodiment of the present disclosure. [Figure 9] FIG. 13 is a diagram illustrating an example of a pixel configuration according to a fourth embodiment of the present disclosure. [Figure 10] 1 is a block diagram showing a schematic configuration example of a camera that is an example of an imaging device to which the present technology can be applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, a mode for carrying out the present disclosure (hereinafter, referred to as an embodiment) will be described with reference to the drawings. In the following drawings, the same or similar parts are given the same or similar reference numerals. The embodiment will be described in the following order. 1. First embodiment 2. Second embodiment 3. Third embodiment 4. Fourth embodiment 5. Camera application example

[0021] <1. First embodiment> [Image sensor configuration] 1 is a diagram showing an example of the configuration of an image sensor according to an embodiment of the present disclosure. The image sensor 1 in the figure includes a pixel array section 10, a vertical drive section 20, a column signal processing section 30, and a control section 40.

[0022] The pixel array section 10 is configured by arranging pixels 100 in a two-dimensional lattice. Here, the pixel 100 generates an image signal according to irradiated light. The pixel 100 has a photoelectric conversion section that generates an electric charge according to irradiated light. The pixel 100 further has a pixel circuit. The pixel circuit generates an image signal based on the electric charge generated by the photoelectric conversion section. The generation of the image signal is controlled by a control signal generated by a vertical driving section 20 described later. In the pixel array section 10, signal lines 11 and 12 are arranged in an XY matrix. The signal line 11 is a signal line that transmits a control signal for the pixel circuit in the pixel 100, is arranged for each row of the pixel array section 10, and is commonly wired to the pixels 100 arranged in each row. The signal line 12 is a signal line that transmits an image signal generated by the pixel circuit of the pixel 100, is arranged for each column of the pixel array section 10, and is commonly wired to the pixels 100 arranged in each column. These photoelectric conversion sections and pixel circuits are formed on a semiconductor substrate.

[0023] The vertical driving unit 20 generates a control signal for the pixel circuit of the pixel 100. The vertical driving unit 20 transmits the generated control signal to the pixel 100 via a signal line 11 in the figure. The column signal processing unit 30 processes an image signal generated by the pixel 100. The column signal processing unit 30 processes an image signal transmitted from the pixel 100 via a signal line 12 in the figure. The processing in the column signal processing unit 30 corresponds to, for example, analog-to-digital conversion that converts an analog image signal generated in the pixel 100 into a digital image signal. The image signal processed by the column signal processing unit 30 is output as an image signal of the image sensor 1. The control unit 40 controls the entire image sensor 1. The control unit 40 controls the image sensor 1 by generating and outputting a control signal that controls the vertical driving unit 20 and the column signal processing unit 30. The control signal generated by the control unit 40 is transmitted to the vertical driving unit 20 and the column signal processing unit 30 via signal lines 41 and 42, respectively. The column signal processing unit 30 is an example of a processing circuit described in the claims.

[0024] [Pixel configuration] 2 is a diagram showing a configuration example of a pixel according to the first embodiment of the present disclosure. The diagram is a cross-sectional view showing a configuration example of a pixel 100 of the image sensor 1. The pixel 100 in the diagram includes a semiconductor substrate 110, a wiring region 120, a separation section 130, an insulating film 131, a color filter 140, a light-shielding wall 150, and an on-chip lens 160.

[0025] The semiconductor substrate 110 is a semiconductor substrate on which the diffusion regions of elements such as the photoelectric conversion unit and pixel circuit of the pixel 100 are disposed. Elements such as the photoelectric conversion unit are disposed in a well region formed in the semiconductor substrate 110. For convenience, it is assumed that the semiconductor substrate 110 in the figure is configured in a p-type well region. By forming an n-type semiconductor region in this p-type well region, the diffusion region of the element can be disposed. In the figure, the photoelectric conversion unit 101 is illustrated as an example. The photoelectric conversion unit 101 in the figure is configured by an n-type semiconductor region 111. Specifically, the photodiode configured by a pn junction between the n-type semiconductor region 111 and the surrounding p-type well region corresponds to the photoelectric conversion unit 101.

[0026] The wiring region 120 is a region in which wiring is formed that is disposed on the front surface side of the semiconductor substrate 110 and transmits signals to elements formed on the semiconductor substrate 110. The wiring region 120 in the figure includes a wiring layer 122 and an insulating layer 121. The wiring layer 122 is wiring that transmits signals to elements and the like. This wiring layer 122 can be made of a metal such as copper (Cu) or tungsten (W). The insulating layer 121 insulates the wiring layer 122. This insulating layer 121 can be made of an insulator such as silicon oxide (SiO2) or silicon nitride (SiN).

[0027] The separation section 130 is disposed on the semiconductor substrate 110 at the boundary between the pixels 100 to separate the pixels 100 from each other. The separation section 130 in the figure is configured in a shape that surrounds the semiconductor substrate 110 of the pixel 100, and electrically separates the pixels 100 from each other. This makes it possible to prevent the inflow of charges from the adjacent pixels 100, and to reduce the occurrence of noise. The separation section 130 in the figure can be configured by disposing an insulating material such as SiO2 or SiN in a groove formed in the semiconductor substrate 110.

[0028] The insulating film 131 is a film that insulates the back side of the semiconductor substrate 110. This insulating film 131 can be made of an insulator such as SiO2 or SiN. The insulating film 131 also protects the back side of the semiconductor substrate 110. The insulating film 131 can be formed at the same time as the separation section 130. Specifically, the above-mentioned groove is formed in the semiconductor substrate 110, and a film such as SiO2 is disposed on the back side of the semiconductor substrate 110 including the inside of the groove. This allows the insulating film 131 and the separation section 130 to be formed. When the separation section 130 is formed, a void 132 may be formed in the center of the separation section 130.

[0029] The color filter 140 is an optical filter that transmits incident light of a predetermined wavelength. For example, a color filter that transmits red light, green light, and blue light can be used as the color filter 140. The pixel 100 can be provided with a color filter 140 that corresponds to any one of these three wavelengths.

[0030] The on-chip lens 160 is a lens that collects incident light. The on-chip lens 160 is configured in a hemispherical shape and collects incident light on the photoelectric conversion unit 101. The on-chip lens 160 can be configured from an inorganic material such as SiN or an organic material such as an acrylic resin. The region below the hemispherical lens portion that constitutes the on-chip lens 160 constitutes a protective film that protects the back surface of the pixel 100. This protective film further flattens the surface on which the on-chip lens 160 is formed.

[0031] The light shielding wall 150 shields incident light. The light shielding wall 150 is disposed adjacent to the semiconductor substrate 110 at the boundary of the pixels 100, and shields incident light that passes through the adjacent pixels 100 at an angle. This can prevent crosstalk. Here, crosstalk is a phenomenon in which noise is mixed into an image signal due to the influence of incident light that has passed through the on-chip lens 160 of the pixel 100 itself and the on-chip lens 160 other than the color filter 140. The light shielding wall 150 is configured in a shape that surrounds the pixel 100, and shields incident light from the adjacent pixel 100. The light shielding wall 150 in the same figure is disposed adjacent to the semiconductor substrate 110 via the insulating film 131. The light shielding wall 150 in the same figure is disposed in the same layer as the color filter 140, and is configured in a shape that surrounds the color filter 140.

[0032] The light-shielding wall 150 can block light by reflecting incident light from the adjacent pixels 100. Such a light-shielding wall 150 can be made of a metal such as W or titanium (Ti). In this case, it is preferable that the light-shielding wall 150 is made of a material having a high reflection coefficient and a low absorption coefficient of incident light. This is because the incident light reflected by the light-shielding wall 150 can be increased, and the sensitivity can be improved when the reflected light is guided to the photoelectric conversion unit.

[0033] The light-shielding wall 150 can be configured to have approximately the same height as the film thickness of the color filter 140. Also, the light-shielding wall 150 can be configured to have approximately the same height as the film thickness of the protective film underlying the color filter 140 and the on-chip lens 160. Also, it is preferable that the light-shielding wall 150 has a width of, for example, 50 nm or more. This is because if the width of the light-shielding wall 150 is narrow, the amount of incident light that passes through the light-shielding wall 150 and enters the adjacent pixel 100 increases.

[0034] Moreover, the light-shielding wall 150 can be configured to have a tapered cross section at the upper portion. That is, the cross section of the light-shielding wall 150 is configured to have a tapered shape on the side where the incident light is irradiated. The incident light that is incident near the boundary of the pixel 100 is reflected by the inclined surface of this tapered shape and enters the photoelectric conversion unit 101 of the semiconductor substrate 110. This can further improve the sensitivity. Also, since the reflected light from the light-shielding wall 150 does not head toward the outside of the pixel 100, the occurrence of flare can be prevented.

[0035] [Shading wall configuration] 3 is a diagram showing an example of light blocking according to the first embodiment of the present disclosure. The diagram shows an example of blocking incident light by a light blocking wall 150, and is a simplified cross-sectional view of a pixel 100. In the diagram, the insulating film 131 adjacent to the semiconductor substrate 110 is omitted.

[0036] A in the figure shows how incident light is reflected by the light-shielding wall 150. The incident light of the pixel 100 is collected by the on-chip lens 160 on the semiconductor substrate 110 at the center of the pixel 100. On the other hand, when the incident light is incident on a valley of the on-chip lens 160 at the boundary of the pixel 100, a part of the incident light travels straight without being collected and reaches the light-shielding wall 150. When the upper part of the light-shielding wall 150 has a flat shape, the incident light is reflected in a direction away from the pixel 100, and the sensitivity is reduced. Therefore, by forming the upper part of the light-shielding wall 150 into a tapered shape, the incident light incident near the boundary of the pixel 100 can be reflected in the direction of the semiconductor substrate 110. Specifically, the incident light incident near the boundary of the pixel 100 is reflected in the direction of the semiconductor substrate 110 by the tapered slope 151 of the light-shielding wall 150. This allows incident light that is incident near the boundary of the pixel 100 and reaches the light-shielding wall 150 to contribute to photoelectric conversion.

[0037] The dotted line A in the figure represents an example of an on-chip lens 161 having a flat surface between adjacent on-chip lenses. An on-chip lens 161 having such a shape exhibits a more remarkable effect. This is because a large amount of incident light comes from the flat surface between adjacent on-chip lenses, and high sensitivity can be obtained by reflecting the incident light from this flat portion to the photoelectric conversion unit 101 of the semiconductor substrate 110.

[0038] The arrow A in the figure represents incident light reflected by the light-shielding wall 150. Among these, the solid arrow represents incident light 401 that is reflected by the tapered inclined surface 151 of the light-shielding wall 150 and reaches the semiconductor substrate 110. In this way, when the angle formed by the opposing tapered inclined surfaces 151 is relatively small, the reflected light directly enters the semiconductor substrate 110. In this case, the incident light excluding the incident light attenuated by the light-shielding wall 150 can be made to enter the semiconductor substrate 110. The incident light attenuated by the light-shielding wall 150 refers to the incident light that passes through the light-shielding wall 150 and the incident light that is absorbed by the light-shielding wall 150.

[0039] On the other hand, when the angle between the tapered inclined surfaces 151 facing each other is relatively large, as in the case of the light-shielding wall 150 shown by the dashed line, the reflected light reaches the light-shielding wall 150 at the boundary on the opposite side of the pixel 100. The dashed arrow A in the figure represents the incident light 402 when the angle between the tapered inclined surfaces 151 facing each other is relatively large. The incident light 402 is reflected by the inclined surface 151 of the light-shielding wall 150, and then reflected by the side surface of the other light-shielding wall 150 to enter the semiconductor substrate 110. In this case, the incident light is attenuated twice by the light-shielding wall 150, and the incident light to the semiconductor substrate 110 is reduced. For this reason, the sensitivity is not sufficiently improved. In order to further improve the sensitivity, it is necessary to allow the incident light to reach the semiconductor substrate 110 by one reflection by the inclined surface 151 of the light-shielding wall 150.

[0040] B in the figure shows an example of the angle of the tapered shape of the light-shielding wall 150. In B in the figure, h and w respectively represent the height and cross-sectional width of the light-shielding wall 150. d represents the width of the semiconductor substrate 110 portion of the light-receiving surface of the pixel 100. This d corresponds to the width of the opening of the light-shielding wall 150 on the light-receiving surface. The angle of the tapered shape of the light-shielding wall 150 can be expressed by the elevation angle θ of the inclined surface 151 from the surface of the semiconductor substrate 110. In order to allow the incident light reflected by the inclined surface 151 of the light-shielding wall 150 to directly enter the semiconductor substrate 110, it is necessary to configure the inclined surface 151 with an inclination angle larger than the angle at which the incident light reflected at the apex of the light-shielding wall 150 reaches the lower end of the opposing light-shielding wall 150.

[0041] At B in the same figure, the angle φ of point C of a triangle formed by vertex A of the light-shielding wall 150, point B drawn from this vertex A onto the surface of the semiconductor substrate 110, and point C where the opposing light-shielding wall 150 and semiconductor substrate 110 meet can be expressed as follows, assuming that the length of the base is b. φ=arctan(h / b) Here, b = w / 2 + d. The elevation angle θ to obtain this angle φ can be expressed as follows: θ = (90 + φ) / 2 (1) By making the elevation angle of the tapered inclined surface 151 of the light-shielding wall 150 larger than this θ, the incident light reflected by the inclined surface 151 can be reflected back to the semiconductor substrate 110 .

[0042] In the figure, the insulating film 131 on the back side of the semiconductor substrate 110 is omitted, but the height h of the light-shielding wall 150 can be set to a value including the thickness of the insulating film 131.

[0043] A description will be given using specific numerical values. When the width (w) and height (h) of the light-shielding wall 150 are 120 nm and 300 nm, the width (d) of the light-receiving surface of the pixel 100 is 1500 nm, and the thickness of the insulating film 131 is 100 nm, the elevation angle θ is approximately 52 degrees. By disposing the light-shielding wall 150 having the inclined surface 151 configured at an angle larger than this elevation angle θ, it is possible to prevent the incident light from being reflected by the light-shielding wall 150 more than twice.

[0044] In this way, by configuring the upper part of the light-shielding wall 150 in a tapered shape with an angle based on the height of the light-shielding wall 150, the width of the light-shielding wall 150, and the width of the light-receiving surface, it is possible to prevent incident light that has entered near the boundary of the pixel 100 from being reflected two or more times by the light-shielding wall 150. This makes it possible to improve the sensitivity of the pixel 100.

[0045] [Manufacturing method of image sensor] 4 and 5 are diagrams illustrating an example of a manufacturing method for an imaging element according to the first embodiment of the present disclosure. Figures 4 and 5 are diagrams illustrating an example of a manufacturing process for the light-shielding wall 150 of the imaging element 1. Note that a known manufacturing method can be applied to the portions of the imaging element 1 other than the light-shielding wall 150.

[0046] First, a diffusion region is formed, a wiring region 120 is formed on the front surface, and an isolation portion 130 and an insulating film 131 are arranged on the rear surface of the semiconductor substrate 110. A Ti film 301, which will be an etching stopper described later, a material film 302 for the light-shielding wall 150, and a material film 303 for the hard mask are laminated in this order on the rear surface side of the semiconductor substrate 110. A W film can be used for the material film 302 for the light-shielding wall 150. A SiN film can be used for the material film 303 for the hard mask. These films can be formed by, for example, CVD (Chemical Vapor Deposition) or the like. Next, a resist 305 having an opening 306 is arranged in an area other than the area where the light-shielding wall 150 is arranged (A in FIG. 4).

[0047] Next, the material films 302 and 303 are etched using the resist 305 as a mask. This can be performed by anisotropic etching using dry etching. For example, etching is performed using sulfur hexafluoride (SF6) and methane trifluoride (CHF3) as etching gas. At this time, the Ti film 301 acts as an etching stopper (B in FIG. 4).

[0048] Next, the resist 305 is removed. This can be done by, for example, ashing with oxygen (O2) (C in FIG. 4).

[0049] Next, the upper surface of the material film 303 is etched into a tapered shape to form a hard mask 304. This can be performed by etch-back using dry etching. For example, etching is performed using argon (Ar) and carbon tetrafluoride (CF4) as etching gas. The etching rate in this etching has an angle dependency, and the end (corner) of the cross section of the material film 303 is etched faster than the center. Therefore, as shown in the figure, a hard mask 304 having a tapered upper portion can be formed (D in FIG. 5). By this process, the hard mask 304 formed in a tapered cross section can be disposed on the upper surface of the material film 302. The hard mask 304 is an example of a mask described in the claims.

[0050] Next, the hard mask 304 and the material film 302 are etched. This can be performed by anisotropic etching using dry etching. For example, etching is performed using SF6 and CHF3 as etching gas. This anisotropic etching can transfer the shape of the hard mask 304 to the material film 302. A light-shielding wall 150 having a slope 151 can be formed (E in FIG. 5). The angle of the slope 151 can be adjusted by adjusting the selection ratio of the hard mask 304 and the material film 302. For example, by using an etching gas that has a faster etching rate for the material film 302 than for the hard mask 304, a slope 151 with a larger angle of elevation than the hard mask 304 can be formed.

[0051] Finally, the Ti film 301 is removed except for the lower part of the light-shielding wall 150. This can be done by etching the Ti film 301. Specifically, etching is performed using chlorine (Cl2) as an etching gas. This makes it possible to remove the Ti film 301 except for the lower part of the light-shielding wall 150 (F in FIG. 5). Through the process described above, it is possible to manufacture the light-shielding wall 150 having the Ti film 301 (not shown in FIG. 2) disposed in the lower layer.

[0052] Note that the imaging element 1 described in FIG. 2 is configured as a back-illuminated imaging element in which incident light is irradiated onto the back side of the semiconductor substrate 110, but it can also be configured as a front-illuminated imaging element in which incident light is irradiated onto the front side of the semiconductor substrate 110.

[0053] As described above, the image sensor 1 according to the first embodiment of the present disclosure has a light-shielding wall 150 configured with a tapered shape on the side where incident light is irradiated at the boundary of the pixel 100, and reflects incident light that is incident near the boundary of the pixel 100 to the semiconductor substrate 110. By adjusting the angle of the inclined surface 151 that constitutes the tapered shape of the light-shielding wall 150 and limiting the number of times that incident light near the boundary of the pixel 100 is reflected to one time, the sensitivity of the pixel 100 can be improved.

[0054] <2. Second embodiment> The imaging element 1 of the first embodiment described above uses a light-shielding wall 150 having a tapered shape with a pointed apex in cross section. In contrast, the imaging element 1 of the second embodiment of the present disclosure differs from the first embodiment described above in that it uses a light-shielding wall 150 having a different shape.

[0055] [Shading wall configuration] 6 is a diagram showing a configuration example of a light-shielding wall according to the second embodiment of the present disclosure, which is a cross-sectional view showing the configuration example of a light-shielding wall 150.

[0056] A in the figure shows a light-shielding wall 150 in which a tapered apex 152 formed on a flat surface is disposed. Also, B in the figure shows a light-shielding wall 150 in which a tapered apex 153 formed on a curved surface is disposed. Depending on the manufacturing method of the light-shielding wall 150, it may not be possible to form a pointed apex as shown in FIG. 2. Even in such a case, by forming a slope 151 on the upper part of the light-shielding wall 150, it is possible to reflect the incident light that is incident near the boundary of the pixel 100 to the semiconductor substrate 110. For example, by configuring the area of ​​the apex 152 and 153 to be 10% of the width of the light-shielding wall 150, it is possible to reflect most of the incident light near the boundary of the pixel 100 to the semiconductor substrate 110. Also, when the area of ​​the apex 152 and 153 is configured to be 5% of the width of the light-shielding wall 150, it is possible to reflect even more of the incident light to the semiconductor substrate 110, thereby improving the sensitivity.

[0057] C in the figure shows a light-shielding wall 150 having a bottom 154 with a curved cross section. In the light-shielding wall 150 having such a shape, it is necessary to configure the inclined surface 151 at an angle at which the incident light is incident on the end of the bottom 154. Specifically, the width d of the light-receiving surface of the pixel 100 described in B in FIG. 3 is corrected to the width from the end of the bottom 154.

[0058] [Other configurations of light-shielding walls] 7 is a diagram showing another configuration example of the light-shielding wall according to the second embodiment of the present disclosure, which is a cross-sectional view showing the configuration example of the light-shielding wall 150.

[0059] In the figure, A represents a light-shielding wall 150 configured with a triangular cross section. This light-shielding wall 150 is configured by extending a slope 151 up to the surface of the insulating film 131. When the height of the light-shielding wall 150 is relatively low, a light-shielding wall 150 having such a shape can be used. As described above, it is preferable to configure the width of the light-shielding wall 150 to be 50 nm or more. This is to reduce the transmission of incident light near the top of the light-shielding wall 150.

[0060] In the figure, B represents a light-shielding wall 150 with a wide bottom. Also, C represents a light-shielding wall 150 with a narrow bottom. In either case of the light-shielding wall 150, the sensitivity of the pixel 100 can be improved by configuring the light-shielding wall 150 to have a shape with a slope 151 at an angle based on the height and width of the light-shielding wall 150 and the width of the light-receiving surface of the pixel 100.

[0061] Other than this, the configuration of the imaging element 1 is similar to the configuration of the imaging element 1 described in the first embodiment of the present disclosure, and therefore a description thereof will be omitted.

[0062] As described above, the imaging element 1 according to the second embodiment of the present disclosure can reflect incident light onto the semiconductor substrate 110 even when using the light-shielding walls 150 having different top shapes, etc.

[0063] <3. Third embodiment> In the image sensor 1 according to the first embodiment described above, the color filter 140 is disposed in the pixel 100. In contrast, the image sensor 1 according to the third embodiment of the present disclosure differs from the first embodiment described above in that the color filter 140 in the pixel 100 is omitted.

[0064] [Pixel configuration] Fig. 8 is a diagram showing a configuration example of a pixel according to a third embodiment of the present disclosure. Similar to Fig. 2, this diagram shows a configuration example of a pixel 100. This pixel differs from the pixel 100 in Fig. 2 in that the color filter 140 is omitted.

[0065] The pixel 100 in the figure generates a monochrome image signal. For this reason, the color filter 140 is omitted. The on-chip lens 160 in the figure is disposed such that the protective film portion below it is adjacent to the insulating film 131. The light-shielding wall 150 in the figure is disposed in the protective film portion below this on-chip lens 160, and is configured in a shape that surrounds this protective film portion. This light-shielding wall 150 can reflect incident light that is incident near the boundary of the pixel 100 to the semiconductor substrate 110.

[0066] Other than this, the configuration of the imaging element 1 is similar to the configuration of the imaging element 1 described in the first embodiment of the present disclosure, and therefore a description thereof will be omitted.

[0067] As described above, the image sensor 1 according to the third embodiment of the present disclosure can improve the sensitivity of the pixels 100 that generate monochrome image signals by omitting the color filters 140.

[0068] <4. Fourth embodiment> In the image sensor 1 according to the first embodiment described above, the light-shielding wall 150 is disposed near the end of the on-chip lens 160 at the boundary of the pixel 100. In contrast, the image sensor 1 according to the fourth embodiment of the present disclosure differs from the first embodiment described above in that the on-chip lens 160 is disposed at a shifted position.

[0069] [Pixel configuration] Fig. 9 is a diagram showing a configuration example of a pixel according to a fourth embodiment of the present disclosure. Similar to Fig. 2, this diagram shows a configuration example of a pixel 100. This differs from the pixel 100 in Fig. 2 in that an on-chip lens 160 is disposed at a position shifted from the center of the pixel 100.

[0070] The pixel 100 in the figure represents the pixel 100 arranged on the periphery of the pixel array unit 10 described in FIG. 1. Incident light is incident on the pixel 100 arranged in the center of the pixel array unit 10 approximately perpendicularly. In contrast, incident light is incident on the pixel 100 arranged on the periphery of the pixel array unit 10 obliquely. Therefore, as shown in the figure, by arranging the on-chip lens 160 so as to be shifted from the center of the pixel 100, it is possible to focus the obliquely incident incident light on the photoelectric conversion unit 101 of the pixel 100 itself. Such correction of the position of the on-chip lens 160, etc. is called pupil correction.

[0071] The light-shielding wall 150 in the figure can be disposed near the end of the on-chip lens 160. Specifically, the light-shielding wall 150 can be disposed at a position where the inclined surface 151 is near the end of the on-chip lens 160. This makes it possible to reflect incident light that is incident near the end of the on-chip lens 160 to the semiconductor substrate 110.

[0072] Other than this, the configuration of the imaging element 1 is similar to the configuration of the imaging element 1 described in the first embodiment of the present disclosure, and therefore a description thereof will be omitted.

[0073] As described above, the image sensor 1 according to the fourth embodiment of the present disclosure can improve the sensitivity of the pixel 100 that performs pupil correction.

[0074] <5. Camera application example> The technology according to the present disclosure (the present technology) can be applied to various products. For example, the present technology may be realized as an imaging element mounted in an imaging device such as a camera.

[0075] 10 is a block diagram showing a schematic configuration example of a camera, which is an example of an imaging device to which the present technology can be applied. The camera 1000 in the figure includes a lens 1001, an imaging element 1002, an imaging control unit 1003, a lens driving unit 1004, an image processing unit 1005, an operation input unit 1006, a frame memory 1007, a display unit 1008, and a recording unit 1009.

[0076] A lens 1001 is a photographing lens of the camera 1000. This lens 1001 collects light from a subject and causes it to enter an image sensor 1002 (described later) to form an image of the subject.

[0077] The image sensor 1002 is a semiconductor element that captures an image of light from a subject collected by the lens 1001. The image sensor 1002 generates an analog image signal according to the irradiated light, converts it into a digital image signal, and outputs it.

[0078] The imaging control unit 1003 controls the imaging of the imaging element 1002. The imaging control unit 1003 controls the imaging element 1002 by generating a control signal and outputting it to the imaging element 1002. The imaging control unit 1003 can also perform autofocus in the camera 1000 based on an image signal output from the imaging element 1002. Here, autofocus is a system that detects the focal position of the lens 1001 and automatically adjusts it. As this autofocus, a method (image plane phase difference autofocus) can be used in which an image plane phase difference is detected by a phase difference pixel arranged in the imaging element 1002 to detect the focal position. Also, a method (contrast autofocus) can be applied in which a position where the contrast of an image is the highest is detected as the focal position. The imaging control unit 1003 adjusts the position of the lens 1001 via the lens driving unit 1004 based on the detected focal position, and performs autofocus. The imaging control unit 1003 can be configured, for example, by a DSP (Digital Signal Processor) equipped with firmware.

[0079] The lens driving unit 1004 drives the lens 1001 under the control of the imaging control unit 1003. The lens driving unit 1004 can drive the lens 1001 by changing the position of the lens 1001 using a built-in motor.

[0080] The image processing unit 1005 processes the image signal generated by the image sensor 1002. This processing includes, for example, demosaic for generating image signals of missing colors among the image signals corresponding to red, green, and blue for each pixel, noise reduction for removing noise from the image signal, and encoding of the image signal. The image processing unit 1005 can be configured, for example, by a microcomputer equipped with firmware.

[0081] The operation input unit 1006 receives an operation input from a user of the camera 1000. For example, a push button or a touch panel can be used for this operation input unit 1006. The operation input received by the operation input unit 1006 is transmitted to the imaging control unit 1003 and the image processing unit 1005. After that, a process according to the operation input, such as a process of capturing an image of a subject, is started.

[0082] The frame memory 1007 is a memory for storing frames, which are image signals for one screen. The frame memory 1007 is controlled by the image processing unit 1005, and holds frames during the image processing process.

[0083] The display unit 1008 displays the image processed by the image processing unit 1005. For this display unit 1008, for example, a liquid crystal panel can be used.

[0084] The recording unit 1009 records the image processed by the image processing unit 1005. For this recording unit 1009, for example, a memory card or a hard disk can be used.

[0085] The above describes a camera to which the present disclosure can be applied. The present technology can be applied to the imaging element 1002 among the configurations described above. Specifically, the imaging element 1 described in FIG. 1 can be applied to the imaging element 1002. By applying the imaging element 1 to the imaging element 1002, sensitivity can be improved. A clear image can be obtained even in a low-illumination environment. Note that the image processing unit 1005 is an example of a processing circuit described in the claims. The camera 1000 is an example of an imaging device described in the claims.

[0086] The configuration of the pixel 100 in the second embodiment can be combined with other embodiments. Specifically, the shape of the light-shielding wall 150 in FIGS. 6 and 7 can be applied to the light-shielding wall 150 in FIGS.

[0087] Furthermore, the configuration of the pixel 100 of the third embodiment can be combined with other embodiments. Specifically, the color filter 140 can be omitted in the pixel 100 of FIG.

[0088] Furthermore, the configuration of the pixel 100 in the fourth embodiment can be combined with other embodiments. Specifically, pupil correction can be performed in the pixel 100 in FIG.

[0089] Finally, the above-mentioned embodiments are merely examples of the present disclosure, and the present disclosure is not limited to the above-mentioned embodiments. Therefore, even if the embodiments are different from the above-mentioned embodiments, various modifications can be made depending on the design, etc., as long as they do not deviate from the technical idea of ​​the present disclosure.

[0090] In addition, the effects described in this specification are merely examples and are not limiting, and other effects may also be obtained.

[0091] In addition, the drawings in the above-mentioned embodiments are schematic, and the dimensional ratios of the various parts do not necessarily correspond to the actual ones. In addition, the drawings may include parts whose dimensional relationships and ratios differ from one another.

[0092] The present technology can also be configured as follows. (1) A plurality of pixels, each of which is disposed on a semiconductor substrate and includes a photoelectric conversion unit that performs photoelectric conversion of incident light irradiated thereon and an on-chip lens that focuses the incident light onto the photoelectric conversion unit; a light-shielding wall that is disposed adjacent to the semiconductor substrate at the boundary of the plurality of pixels and has a tapered cross section on a side where the incident light is irradiated, and that blocks the incident light; An imaging element comprising: (2) The imaging element described in (1), wherein the light-shielding wall has a tapered cross section with an angle based on its height and width from the semiconductor substrate and the width of a light-receiving surface, which is the surface of the semiconductor substrate in the pixel that is irradiated with the incident light. (3) The imaging element described in (2) above, wherein the light-shielding wall is configured in a tapered shape with an elevation angle based on the inverse tangent function of a triangle including a perpendicular line drawn from the apex of the taper to the semiconductor substrate, with half of the light-shielding wall's width and the width of the light-receiving surface corresponding to the base. (4) The imaging element according to any one of (1) to (3), wherein the light-shielding wall has a triangular cross section having the tapered shape. (5) The imaging element according to any one of (1) to (4), wherein the plurality of pixels each include a color filter that transmits incident light of a predetermined wavelength from the collected incident light. (6) The imaging element according to (5), wherein the light-shielding wall is configured in a shape surrounding the color filter. (7) The imaging element according to any one of (1) to (6), wherein the light-shielding wall blocks the incident light by reflecting it. (8) The imaging element according to (7), wherein the light-shielding wall is made of metal. (9) The image sensor according to any one of (1) to (8), wherein the light-shielding wall is formed by transferring the shape of a mask by etching the mask having a tapered cross section placed on the upper surface of the light-shielding wall. (10) The imaging element according to (9), wherein the light-shielding wall has a mask disposed on its upper surface, the mask being etched back by plasma etching to have a tapered cross section. (11) A plurality of pixels, each including a photoelectric conversion unit disposed on a semiconductor substrate and performing photoelectric conversion of incident light irradiated thereon, and an on-chip lens that focuses the incident light onto the photoelectric conversion unit; a light shielding wall disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels, the light shielding wall having a tapered cross section on a side where the incident light is irradiated, and the light shielding wall shields the incident light; a processing circuit for processing an image signal generated based on the photoelectric conversion; An imaging device comprising: [Explanation of symbols]

[0093] 1. Image sensor 10 Pixel array section 30 Column signal processing section 100 pixels 101 Photoelectric conversion unit 110 Semiconductor substrate 130 Separation section 131 Insulating film 140 Color Filter 150 Blackout Wall 151 Slope 152, 153 top 154 Bottom 160, 161 On-chip lens 304 Hard Mask 1000 Cameras 1002 Image sensor 1005 Image processing section

Claims

1. a plurality of pixels each including a photoelectric conversion unit disposed on a semiconductor substrate and performing photoelectric conversion of incident light irradiated thereon and an on-chip lens that focuses the incident light onto the photoelectric conversion unit; a light-shielding wall that is disposed adjacent to the semiconductor substrate at the boundary between the plurality of pixels and is configured to surround the pixels to form an opening, and that has a tapered cross section with an apex formed by opposing inclined surfaces on a side where the incident light is irradiated, and that blocks the incident light; a separation portion disposed on the semiconductor substrate at a boundary between the plurality of pixels to separate the pixels from each other, The light-shielding wall is formed so that an elevation angle of the inclined surface of the light-shielding wall from a surface of the semiconductor substrate in a cross-sectional view is larger than θ expressed by the following equations (1) to (3). θ=(90+φ) / 2...(1) φ=arctan(h / b)...(2) b=(w / 2)+d...(3) Here, φ is the angle formed between the surface of the semiconductor substrate and a line connecting the vertex and the point where the wall surface of the light-shielding wall facing the light-shielding wall meets the surface of the semiconductor substrate, h is the height of the light-shielding wall from the semiconductor substrate, w is the width of the light-shielding wall, and d is the width of the opening.

2. The imaging element according to claim 1; a processing circuit for processing an image signal generated based on the photoelectric conversion; An imaging device comprising:

3. a plurality of pixels each including a photoelectric conversion unit disposed on a semiconductor substrate and performing photoelectric conversion of incident light irradiated thereon and an on-chip lens that focuses the incident light onto the photoelectric conversion unit; a light-shielding wall that is disposed adjacent to the semiconductor substrate at the boundary between the plurality of pixels and is configured to surround the pixels to form an opening, and that has a tapered cross section with an apex formed by opposing inclined surfaces on a side where the incident light is irradiated, and that blocks the incident light; A method for manufacturing an image sensor comprising: The method for manufacturing an imaging element includes forming the light-shielding wall so that an elevation angle of the inclined surface of the light-shielding wall from a surface of the semiconductor substrate in a cross-sectional view is larger than θ expressed by the following equations (1) to (3): θ=(90+φ) / 2...(1) φ=arctan(h / b)...(2) b=(w / 2)+d...(3) Here, φ is the angle formed between the surface of the semiconductor substrate and a line connecting the vertex and the point where the wall surface of the light-shielding wall facing the light-shielding wall meets the surface of the semiconductor substrate, h is the height of the light-shielding wall from the semiconductor substrate, w is the width of the light-shielding wall, and d is the width of the opening.

Images