Image Sensor and Imaging Device

Abstract

The present invention improves the sensitivity of an image sensor. The image sensor includes a plurality of pixels and light-shielding walls. Each of the plurality of pixels included in the image sensor includes a photoelectric conversion unit disposed on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereto, and an on-chip lens that converges the incident light onto the photoelectric conversion unit. The light-shielding walls included in the image sensor are disposed adjacent to the semiconductor substrate at boundaries between the plurality of pixels and are configured such that an incident light irradiation side of the light-shielding walls has a tapered cross section to block the incident light.

Description

Technical Field

[0001] The present disclosure relates to an image sensor and an imaging device. In particular, the present disclosure relates to an image sensor in which a plurality of pixels for generating an image signal are configured, and an imaging device using the image sensor. Background Art

[0002] Heretofore, an image sensor with improved light sensitivity has been proposed. For example, a solid-state image sensor has been proposed, which is composed of a photoelectric conversion unit formed in a mosaic shape on a semiconductor substrate and performing photoelectric conversion on incident light, and a readout unit for reading out a signal obtained by the photoelectric conversion of the photoelectric conversion unit (for example, Patent Document 1). This solid-state image sensor includes a lens array and a reflective layer. The lens array converges incident light on each photoelectric conversion unit. The reflective layer serves to reflect incident light converged on a portion other than the photoelectric conversion unit by the lens array and converge it on the photoelectric conversion unit.

[0003] In the past technology, the photoelectric conversion units are formed on the semiconductor substrate directly below the lenses constituting the lens array, and thus are arranged in a relatively small range. The reflective layer is configured in the shape of a light guide path from near the edge of the lens to the photoelectric conversion unit, and is configured to have a cross section with a gradually decreasing diameter from near the edge of the lens to the photoelectric conversion unit. Incident light converged on a portion other than the photoelectric conversion unit by the lens is reflected by a surface of the reflective layer corresponding to the inner wall of the light guide path and guided to the photoelectric conversion unit.

[0004] [List of Cited References]

[0005] [Patent Documents]

[0006] [Patent Document 1] JP S61-154283A Summary of the Invention

[0007] [Technical Problem]

[0008] In the above past technology, there is a problem that the sensitivity improvement is insufficient. Specifically, according to the incident angle of the incident light converged on a portion other than the photoelectric conversion unit by the lens, it is incident on the photoelectric conversion unit that has been reflected multiple times by the reflective layer. The reflective layer may be made of metal. However, the reflective layer made of metal does not reflect 100% of the incident light, but absorbs a part of the incident light. Therefore, when the incident light is reflected multiple times by the reflective layer, the light is absorbed by the reflective layer and greatly attenuated. Therefore, in the above past technology, there is a problem that the sensitivity cannot be sufficiently improved.

[0009] In view of the above problems, an object of the present disclosure is to improve the sensitivity of the image sensor.

[0010] [Solution to the Problem]

[0011] Conceived to solve the above problems, a first aspect of the present disclosure is an image sensor, which includes: a plurality of pixels, each pixel including a photoelectric conversion unit configured on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereto, and an on-chip lens that converges the incident light onto the photoelectric conversion unit; and a light-shielding wall, the light-shielding wall being disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and configured such that an incident light irradiation side of the light-shielding wall has a conical cross-section to block incident light.

[0012] Furthermore, in this first aspect, the light-shielding wall may be configured such that the conical cross-section has a cone with an angle based on the height and width of the light-shielding wall from the semiconductor substrate and the width of the light-receiving surface, the light-receiving surface being the surface of the semiconductor substrate irradiated by incident light at the pixel.

[0013] Furthermore, in this first aspect, the light-shielding wall may be configured to have a conical shape with an elevation angle based on the arctangent function of a triangle, the triangle including a perpendicular line from the vertex of the cone downward to the semiconductor substrate, and half of the width of the light-shielding wall together with the width of the light-receiving surface corresponding to the base of the triangle.

[0014] Furthermore, in this first aspect, the light-shielding wall may be configured to have a triangular cross-section in a conical shape.

[0015] Furthermore, in this first aspect, each of the plurality of pixels may include a color filter that transmits incident light having a predetermined wavelength among the converged incident light.

[0016] Furthermore, in this first aspect, the light-shielding wall may be configured to surround the shape of the color filter.

[0017] Furthermore, in this first aspect, the light-shielding wall may block light by reflecting incident light.

[0018] Furthermore, in this first aspect, the light-shielding wall may be formed of metal.

[0019] Furthermore, in this first aspect, the light-shielding wall may be formed by transferring the shape of a mask by means of etching a mask disposed on the upper surface and having a conical cross-section.

[0020] Furthermore, in this first aspect, in the light-shielding wall, the mask disposed on the upper surface may be etched back by means of plasma etching to form the conical cross-section.

[0021] In addition, a second aspect of the present disclosure is an imaging device, which includes: a plurality of pixels, each pixel including a photoelectric conversion unit configured on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereon, and an on-chip lens that converges the incident light onto the photoelectric conversion unit; a light-shielding wall, the light-shielding wall being disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and being configured such that an incident light irradiation side of the light-shielding wall has a conical cross-section to block incident light; and a processing circuit that processes an image signal generated based on photoelectric conversion.

[0022] Aspects of the present disclosure provide an effect that incident light entering near a boundary between pixels is incident on a conical portion of the light-shielding wall. It is assumed that incident light entering near a boundary between pixels will be reflected at the conical portion of the light-shielding wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a diagram showing a configuration example of an image sensor according to an embodiment of the present disclosure.

[0024] Figure 2 is a diagram showing a configuration example of a pixel according to a first embodiment of the present disclosure.

[0025] Figure 3 is a diagram showing an example of light shielding according to a first embodiment of the present disclosure.

[0026] Figure 4 is a diagram showing an example of a manufacturing method of an image sensor according to a first embodiment of the present disclosure.

[0027] Figure 5 is a diagram showing an example of a manufacturing method of an image sensor according to a first embodiment of the present disclosure.

[0028] Figure 6 is a diagram showing a configuration example of a light-shielding wall according to a second embodiment of the present disclosure.

[0029] Figure 7 is a diagram showing another configuration example of a light-shielding wall according to a second embodiment of the present disclosure.

[0030] Figure 8 is a diagram showing a configuration example of a pixel according to a third embodiment of the present disclosure.

[0031] Figure 9 is a diagram showing a configuration example of a pixel according to a fourth embodiment of the present disclosure.

[0032] Figure 10 is a block diagram schematically showing a configuration example of a camera as an example of an imaging device to which the present technology can be applied. DETAILED DESCRIPTION

[0033] Next, embodiments for implementing the present disclosure (hereinafter referred to as embodiments) will be described with reference to the accompanying drawings. In the following drawings, the same or similar parts are denoted by the same or similar reference numerals and symbols. In addition, the embodiments will be described in the following order.

[0034] 1. First Embodiment

[0035] 2. Second Embodiment

[0036] 3. Third Embodiment

[0037] 4. Fourth Embodiment

[0038] 5. Application Example of Camera

[0039] <1. First Embodiment>

[0040] [Configuration of Image Sensor]

[0041] Figure 1 FIG. is a diagram showing a configuration example of an image sensor according to an embodiment of the present disclosure. In the figure, the image sensor 1 includes a pixel array unit 10, a vertical drive unit 20, a column signal processing unit 30, and a control unit 40.

[0042] The pixel array unit 10 is composed of pixels 100 arranged in a two-dimensional lattice. Here, the pixels 100 generate image signals in response to the irradiated light. Each pixel 100 has a photoelectric conversion unit that generates charges in response to the irradiated light. In addition, each pixel 100 also has a pixel circuit. The pixel circuit generates an image signal based on the charges generated by the photoelectric conversion unit. The generation of the image signal is controlled by a control signal generated by the vertical drive unit 20, which will be described later. Signal lines 11 and 12 are arranged in an XY matrix in the pixel array unit 10. The signal line 11 is a signal line through which the control signal of the pixel circuit in the pixel 100 is transmitted, is arranged for each row of the pixel array unit 10, and is commonly wired for the pixels 100 arranged in each row. The signal line 12 is a signal line through which the image signal generated by the pixel circuit of the pixel 100 is transmitted, is arranged for each column of the pixel array unit 10, and is commonly wired for the pixels 100 arranged in each column. The photoelectric conversion unit and the pixel circuit are formed on a semiconductor substrate.

[0043] The vertical driving unit 20 generates control signals for the pixel circuits of the pixels 100. The vertical driving unit 20 transmits the generated control signals to the pixels 100 via the signal lines 11 in the figure. The column signal processing unit 30 processes the image signals generated by the pixels 100. The column signal processing unit 30 processes the image signals transmitted from the pixels 100 via the signal lines 12 in the figure. The processing by the column signal processing unit 30 corresponds to, for example, analog-to-digital conversion of the analog image signals generated in the pixels 100. The image signals processed by the column signal processing unit 30 are output as the image signals of the image sensor 1. The control unit 40 controls the image sensor 1 as a whole. The control unit 40 generates and outputs control signals for controlling the vertical driving unit 20 and the column signal processing unit 30 to control the image sensor 1. The control signals generated by the control unit 40 are transmitted to the vertical driving unit 20 and the column signal processing unit 30 through the signal lines 41 and 42. Note that the column signal processing unit 30 is an example of the processing circuit described in the claims.

[0044] [Configuration of Pixel]

[0045] Figure 2 FIG. is a diagram showing a configuration example of a pixel according to the first embodiment of the present disclosure. This figure is a cross-sectional view showing a configuration example of the pixel 100 of the image sensor 1. In this figure, the pixel 100 includes a semiconductor substrate 110, a wiring region 120, a separation portion 130, an insulating film 131, a color filter 140, a light-shielding wall 150, and an on-chip lens 160.

[0046] The semiconductor substrate 110 is a semiconductor substrate on which diffusion regions of elements such as a photoelectric conversion portion and pixel circuits of the pixel 100 are disposed. Elements such as a 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 formed in a p-type well region. The diffusion regions of the elements can be provided by forming n-type semiconductor regions in the p-type well region. The photoelectric conversion unit 101 is shown as an example in the figure. The photoelectric conversion unit 101 is constituted by an n-type semiconductor region 111. Specifically, a photodiode constituted by the pn junction between the n-type semiconductor region 111 and the surrounding p-type well region corresponds to the photoelectric conversion unit 101.

[0047] The wiring region 120 is a region where wirings are formed, and the wirings are provided on the surface side of the semiconductor substrate 110 and transmit signals to the 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 a wiring that transmits signals to elements and the like. The wiring layer 122 can be formed of a metal such as copper (Cu) or tungsten (W). The insulating layer 121 insulates the wiring layer 122. The insulating layer 121 can be formed of an insulator such as silicon oxide (SiO2) or silicon nitride (SiN).

[0048] The isolation part 130 is disposed on the semiconductor substrate 110 at the boundary between the pixels 100 and separates the respective pixels 100 from each other. In the figure, the isolation part 130 is formed in the shape of the semiconductor substrate 110 surrounding the pixels 100 and electrically separates the respective pixels 100 from each other. This makes it possible to prevent the inflow of charges from adjacent pixels 100 and reduce the occurrence of noise. The isolation part 130 in the figure can be formed by disposing an insulator such as SiO2, SiN, etc. in a trench formed in the semiconductor substrate 110.

[0049] The insulating film 131 is a film that insulates the back side of the semiconductor substrate 110. The insulating film 131 can be formed of an insulator such as SiO2, SiN, etc. The insulating film 131 also protects the back side of the semiconductor substrate 110. Note that the insulating film 131 can be formed simultaneously with the isolation part 130. Specifically, the aforementioned trench 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 trench. Thus, the insulating film 131 and the isolation part 130 can be formed. When the isolation part 130 is formed, a cavity 132 can be formed in the central part of the isolation part 130.

[0050] The color filter 140 is an optical filter that transmits incident light of a predetermined wavelength among the incident light. For example, a color filter that transmits red light, green light, and blue light can be used as the color filter 140. The color filter 140 corresponding to any one of these three wavelengths can be disposed in the pixel 100.

[0051] The on-chip lens 160 is a lens that converges the incident light. The on-chip lens 160 is formed in a hemispherical shape and converges the incident light on the photoelectric conversion unit 101. The on-chip lens 160 can be formed of an inorganic material such as SiN or an organic material such as an acrylic resin. Note that the lower layer region of the hemispherical lens part constituting the on-chip lens 160 constitutes a protective film that protects the back side of the pixel 100. This protective film also planarizes the surface on which the on-chip lens 160 is formed.

[0052] The light-shielding wall 150 blocks incident light. The light-shielding wall 150 is disposed adjacent to the semiconductor substrate 110 at the boundary between the pixels 100, and blocks the incident light that enters through the adjacent pixels 100 at a certain angle. This makes it possible to prevent crosstalk. Here, "crosstalk" is a phenomenon in which noise is introduced into the image signal due to the influence of incident light transmitted through on-chip lenses 160 other than the on-chip lens 160 and color filters 140 through the pixel 100 itself. The light-shielding wall 150 is configured in a shape surrounding the pixel 100 and blocks the incident light from the adjacent pixels 100. In the figure, the light-shielding wall 150 is disposed adjacent to the semiconductor substrate 110 via the insulating film 131. Further, in the figure, the light-shielding wall 150 and the color filter 140 are disposed in the same layer and are configured in a shape surrounding the color filter 140.

[0053] The light-shielding wall 150 can block light by reflecting the incident light from the adjacent pixels 100. The light-shielding wall 150 can be formed of a metal such as W, titanium (Ti), etc. In this case, it is suitable that the light-shielding wall 150 is made of a material having a high reflection coefficient and a low absorption coefficient for 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.

[0054] The light-shielding wall 150 can be configured to have a height substantially the same as the thickness of the color filter 140. The light-shielding wall 150 can also be configured to have a thickness substantially the same as the protective film in the layer below the color filter 140 and the on-chip lens 160. For example, it is also suitable to configure the light-shielding wall 150 to be at least 50 nm wide. This is because when the light-shielding wall 150 is narrow, the incident light that passes through the light-shielding wall 150 and enters the adjacent pixels 100 increases.

[0055] The light-shielding wall 150 can be configured to have a tapered cross-section at its upper part. In other words, the cross-section of the light-shielding wall 150 is configured to be tapered on the incident light irradiation side. The incident light that enters near the boundary between the pixels 100 is reflected by the inclined surface of the tapered shape and enters the photoelectric conversion unit 101 of the semiconductor substrate 110. This makes it possible to further improve the sensitivity. Further, since the reflected light from the light-shielding wall 150 is not guided to the outside of the pixel 100, glare can be prevented.

[0056] [Configuration of Light-Shielding Wall]

[0057] Figure 3 is a diagram showing an example of light shielding according to the first embodiment of the present disclosure. This diagram is a diagram showing an example in which the incident light is blocked by the light-shielding wall 150, and is a simplified cross-sectional view of the pixel 100. The insulating film 13 adjacent to the semiconductor substrate 110 is omitted in the figure.

[0058] In the figure, A shows the incident light reflected by the light-shielding wall 150. The incident light of the pixel 100 is converged on the semiconductor substrate 110 at the central portion of the pixel 100 through the on-chip lens 160. On the other hand, if the incident light enters the valley between the on-chip lenses 160 at the boundary of the pixel 100, a part of the incident light will not be converged but will travel straight and reach the light-shielding wall 150. If the upper part of the light-shielding wall 150 is flat, the incident light is reflected in the direction away from the pixel 100, resulting in a reduction in sensitivity. Therefore, by forming the upper part of the light-shielding wall 150 into a conical shape, the incident light entering near the boundary between the pixels 100 can be reflected in the direction of the semiconductor substrate 110. Specifically, the conical inclined surface 151 of the light-shielding wall 150 reflects the incident light entering near the boundary between the pixels 100 in the direction of the semiconductor substrate 110. This enables the incident light that enters near the boundary between the pixels 100 and reaches the light-shielding wall 150 to contribute to photoelectric conversion.

[0059] The dashed line in A in the figure represents an example of the on-chip lens 161 having a flat surface between the on-chip lens and the adjacent on-chip lens. For the on-chip lens 161 having such a shape, the effect is more significant. This is because there is a large amount of incident light from the flat surface between the 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.

[0060] The arrow in A in the figure represents the incident light reflected by the light-shielding wall 150. Among them, the solid arrow represents the incident light 401 that is reflected by the conical inclined surface 151 of the light-shielding wall 150 and reaches the semiconductor substrate 110. In this way, when the angle formed between the inclined surfaces 151 facing each other in a conical shape is relatively small, the reflected light is directly incident on the semiconductor substrate 110. In this case, the incident light other than the incident light attenuated by the light-shielding wall 150 can be incident on the semiconductor substrate 110. The incident light attenuated by the light-shielding wall 150 is the incident light that passes through the light-shielding wall 150 and the incident light absorbed by the light-shielding wall 150.

[0061] On the other hand, when the angle formed between the opposing inclined surfaces 151 of the conical shape is relatively large, as in 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 dotted arrow in A in the figure indicates the incident light 402 when the angle formed between the opposing inclined surfaces 151 of the conical shape is relatively large. The incident light 402 is reflected by the inclined surface 151 of the light-shielding wall 150, then reflected by the side surface of another light-shielding wall 150, and then incident on the semiconductor substrate 110. In this case, the incident light is attenuated twice by the light-shielding wall 150, which reduces the incident light on the semiconductor substrate 110. Therefore, the sensitivity is not sufficiently improved. To sufficiently improve the sensitivity, it is necessary to ensure that the incident light reflected once by the inclined surface 151 of the light-shielding wall 150 reaches the semiconductor substrate 110.

[0062] B in the figure is a diagram showing an example of the angle of the conical shape of the light-shielding wall 150. In B in the figure, h and w respectively represent the height and the 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. d corresponds to the width of the opening of the light-shielding wall 150 in the light-receiving surface. The angle of the conical shape of the light-shielding wall 150 can be represented by the elevation angle θ of the inclined surface 151 from the surface of the semiconductor substrate 110. To ensure that the incident light is reflected by the inclined surface 151 of the light-shielding wall 150 and directly incident on the semiconductor substrate 110, it is necessary to construct an inclined surface 151 having an inclination angle greater than the angle at which the incident light reflected at the vertex of the light-shielding wall 150 reaches the bottom end of the light-shielding wall 150.

[0063] In B in the figure, the angle at point C of the triangle formed by the vertex A of the light-shielding wall 150, the point B from this vertex A downward to the surface of the semiconductor substrate 110, and the point C where the opposing light-shielding wall 150 is in contact with the semiconductor substrate 110 When the length of the base is represented by b, it can be expressed as follows.

[0064]

[0065] Here, b = w / 2 + d.

[0066] To obtain the angle The elevation angle θ can be expressed as follows.

[0067]

[0068] Setting the elevation angle of the conical inclined surface 151 of the light-shielding wall 150 to be greater than θ enables the incident light that has been reflected at the inclined surface 151 to be reflected onto the semiconductor substrate 110.

[0069] Although the insulating film 131 on the back side of the semiconductor substrate 110 is not shown, the height h of the light-shielding wall 150 can be set to a value including the thickness of the insulating film 131.

[0070] This will be described using specific values. If the width (w) and height (h) of the light-shielding wall 150 are 120 nm and 300 nm, respectively, 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. Setting the light-shielding wall 150 having the inclined surface 151 constructed at an angle greater than the elevation angle θ enables prevention of the incident light from being reflected more than twice by the light-shielding wall 150.

[0071] In this way, by configuring the upper part of the light-shielding wall 150 into a conical shape having 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 the incident light entering near the boundary between the pixels 100 from being reflected more than twice by the light-shielding wall 150. This enables improvement in the sensitivity of the pixel 100.

[0072] [Method of manufacturing an image sensor]

[0073] Figure 4 and Figure 5 are diagrams showing examples of a method of manufacturing an image sensor according to the first embodiment of the present disclosure. Figure 4 and Figure 5 show examples of steps for manufacturing the light-shielding wall 150 of the image sensor 1. Note that parts other than the light-shielding wall 150 of the image sensor 1 can adopt known manufacturing methods.

[0074] First, on the back side of the semiconductor substrate 110 in which a diffusion region is formed, a wiring region 120 is formed on the surface, and a separation part 130 and an insulating film 131 are disposed on the back side, a Ti film 301 serving as an etching stop layer described later, a material film 302 of the light-shielding wall 150, and a material film 303 of a hard mask are sequentially stacked. A W film can be used for the material film 302 of the light-shielding wall 150. A SiN film can be used for the material film 303 of the hard mask. Deposition of these films can be accomplished by, for example, chemical vapor deposition (CVD). Next, a resist 305 having an opening 306 is disposed in a region other than the region where the light-shielding wall 150 is to be disposed ( Figure 4 of A).

[0075] Next, using the resist 305 as a mask, the material films 302 and 303 are etched. This can be performed by anisotropic etching using dry etching. For example, etching is performed using sulfur hexafluoride (SF6) and trifluoromethane (CHF3) as etching gases. At this time, the Ti film 301 serves as an etching stop layer ( Figure 4 of B).

[0076] Then, the resist 305 is removed. For example, this can be done by ashing using oxygen (O2) ( Figure 4 C in).

[0077] Next, the upper surface of the material film 303 is etched into a conical shape to form the hard mask 304. This can be carried out by back etching using dry etching. For example, argon (Ar) and carbon tetrafluoride (CF4) are used as etching gases for etching. The etching rate in this etching has an angular dependence, and the edges (corners) of the material film 303 are etched faster than the central part of the cross-section. As a result, the hard mask 304 having a conical upper part as shown in the figure can be formed ( Figure 5 D in). This step enables the hard mask 304 formed to have a conical cross-section to be disposed on the upper surface of the material film 302. Note that the hard mask 304 is an example of the "mask" described in the claims.

[0078] Next, the hard mask 304 and the material film 302 are etched. This can be carried out by anisotropic etching using dry etching. For example, SF6 and CHF3 are used as etching gases for etching. Through this anisotropic etching, the shape of the hard mask 304 can be transferred to the material film 302. The light-shielding wall 150 having the inclined surface 151 can be formed ( Figure 5 E in). The angle of the inclined surface 151 can be adjusted by adjusting the selection ratio of the hard mask 304 and the material film 302. For example, an inclined surface 151 having a larger elevation angle than the hard mask 304 can be formed by using an etching gas having a higher etching rate for the material film 302 than for the hard mask 304.

[0079] Finally, the Ti film 301 except for the lower part of the light-shielding wall 150 is removed. This can be done by etching the Ti film 301. Specifically, chlorine (Cl2) is used as the etching gas for etching. This enables the Ti film 301 except for the lower part of the light-shielding wall 150 to be removed ( Figure 5 F in). Through the above processes, the light-shielding wall 150 having the Ti film 301 ( Figure 2 not shown) in the lower layer can be manufactured.

[0080] Although the image sensor 1 described with reference to Figure 2 is configured as a back-illuminated type image sensor in which incident light irradiates the back side of the semiconductor substrate 110, note that the image sensor 1 can also be configured as a front-illuminated type image sensor in which incident light irradiates the front side of the semiconductor substrate 110.

[0081] As described above, the image sensor 1 of the first embodiment of the present disclosure includes a light-shielding wall 150 at the boundary between pixels 100, and the incident light irradiation side is configured in a conical shape, and reflects the incident light incident near the boundary between pixels 100 toward the semiconductor substrate 110. By adjusting the angle of the inclined surface 151 that forms the conical shape of the light-shielding wall 150 to limit the number of reflections of the incident light near the boundary between pixels 100 to one, the sensitivity of the pixels 100 can be improved.

[0082] <2. Second Embodiment>

[0083] The image sensor 1 of the above-described first embodiment uses a conical light-shielding wall 150 having a sharp vertex in cross-section. In contrast, the image sensor 1 of the second embodiment of the present disclosure is different from the above-described first embodiment in that it uses a light-shielding wall 150 having a different shape.

[0084] [Configuration of Light-Shielding Wall]

[0085] Figure 6 FIG. is a diagram showing a configuration example of a light-shielding wall according to the second embodiment of the present disclosure. This figure is a cross-sectional view of a configuration example of the light-shielding wall 150.

[0086] In the figure, A represents a light-shielding wall 150 provided with a conical top 152 configured as a flat surface. In addition, B in the figure represents a light-shielding wall 150 provided with a conical top 153 configured as a curved surface. Depending on the manufacturing method of the light-shielding wall 150, it may not be possible to form a wall with a pointed top as Figure 2 shown. Even in such a case, by forming an inclined surface 151 on the upper part of the light-shielding wall 150, the incident light entering near the boundary between pixels 100 can be reflected onto the semiconductor substrate 110. For example, by configuring the areas of the tops 152 and 153 to be 10% of the width of the light-shielding wall 150, most of the incident light near the boundary between pixels 100 can be reflected onto the semiconductor substrate 110. In addition, configuring the areas of the tops 152 and 153 to be 5% of the width of the light-shielding wall 150 enables more incident light to be reflected onto the semiconductor substrate 110, thereby improving the sensitivity.

[0087] C in the figure represents a light-shielding wall 150 having a bottom 154 with a curved cross-section. In a light-shielding wall 150 having such a shape, the inclined surface 151 needs to be configured at an angle such that the incident light hits the edge of the bottom 154. Specifically, as Figure 3 illustrated in B in, the width d of the light-receiving surface of the pixel 100 is modified to the width starting from the edge of the bottom 154.

[0088] [Other Configurations of Light-Shielding Wall]

[0089] Figure 7 This is a diagram showing another structural example of the light-shielding wall according to the second embodiment of the present disclosure. This diagram is a cross-sectional view of the structural example of the light-shielding wall 150.

[0090] In the figure, A represents the light-shielding wall 150 configured to have a triangular cross-section. The light-shielding wall 150 is composed of an inclined surface 151 extending to the surface of the insulating film 131. The light-shielding wall 150 having such a shape can be used when the height of the light-shielding wall 150 is relatively low. As described above, it is suitable to configure the light-shielding wall 150 to have a width of 50 nm or more. This is to reduce the transmission of incident light near the top of the light-shielding wall 150.

[0091] In the figure, B represents the light-shielding wall 150 with a widened bottom. In addition, C in the figure represents the light-shielding wall 150 with a narrowed bottom. For any of these light-shielding walls 150, by configuring the shape to have an inclined surface 151 based on the height and width of the light-shielding wall 150 and the width of the light-receiving surface of the pixel 100, the sensitivity of the pixel 100 can be improved.

[0092] The configuration of the image sensor 1 other than the above configuration is the same as the configuration of the image sensor 1 described in the first embodiment of the present disclosure, and thus will not be described again.

[0093] As described above, the image sensor 1 of the second embodiment of the present disclosure can reflect incident light onto the semiconductor substrate 110 even when using a light-shielding wall 150 having a different shape or the like at the top.

[0094] <3. Third Embodiment>

[0095] In the image sensor 1 of the first embodiment described above, the color filter 140 is provided in the pixel 100. However, the image sensor 1 of the third embodiment of the present disclosure is different from the first embodiment described above in that the color filter 140 of the pixel 100 is omitted.

[0096] [Configuration of Pixel]

[0097] Figure 8 This is a diagram showing a structural example of a pixel according to the third embodiment of the present disclosure. Similar to Figure 2 This diagram is a diagram showing a structural example of the pixel 100. The difference between this configuration and the pixel 100 in Figure 2 is that the color filter 140 is omitted.

[0098] The pixel 100 in the figure generates a monochromatic image signal. For this purpose, the color filter 140 is omitted. In the on-chip lens 160 in the figure, the lower protective film portion is disposed adjacent to the insulating film 131. The light-shielding wall 150 in the figure is disposed in the lower protective film portion of the on-chip lens 160 and is configured to surround the shape of the protective film portion. The light-shielding wall 150 can reflect the incident light that enters near the boundary between the pixels 100 onto the semiconductor substrate 110.

[0099] The configuration of the image sensor 1 other than the above configuration is the same as that of the image sensor 1 described in the first embodiment of the present disclosure, and thus will not be described again.

[0100] As described above, the image sensor 1 according to the third embodiment of the present disclosure can improve the sensitivity of the pixel 100 that does not have the color filter 140 and generates a monochromatic image signal.

[0101] <4. Fourth Embodiment>

[0102] In the image sensor 1 of the first embodiment described above, the light-shielding wall 150 is provided near the edge of the on-chip lens 160 at the boundary between the pixels 100. However, the image sensor 1 according to the fourth embodiment of the present disclosure is different from the first embodiment described above in that the on-chip lens 160 is disposed at an offset position.

[0103] [Configuration of Pixel]

[0104] Figure 9 is a diagram showing a configuration example of a pixel according to the fourth embodiment of the present disclosure. Similar to Figure 2 This figure is a diagram showing a configuration example of the pixel 100. The difference between this configuration and the pixel 100 in Figure 2 is that the on-chip lens 160 is disposed at a position offset from the center of the pixel 100.

[0105] The pixel 100 in the figure represents a pixel 100 provided in the peripheral portion of the pixel array portion 10 shown in Figure 1 Incident light enters the pixel 100 located at the center of the pixel array portion 10 in a substantially vertical direction. In contrast, the pixel 100 provided in the peripheral portion of the pixel array portion 10 receives the incident light at a certain angle. Therefore, as shown in the figure, by disposing the on-chip lens 160 offset from the center of the pixel 100, the incident light incident at a certain angle can be converged onto the photoelectric conversion unit 101 of the pixel 100 itself. This correction of the position of the on-chip lens 160 and the like is called "pupil correction".

[0106] The light-shielding wall 150 shown in the figure can be disposed near the edge of the on-chip lens 160. Specifically, the light-shielding wall 150 can be disposed at a position where the inclined surface 151 is close to the edge of the on-chip lens 160. This enables the incident light entering near the edge of the on-chip lens 160 to be reflected onto the semiconductor substrate 110.

[0107] The configuration of the image sensor 1 other than the above-described configuration is the same as the configuration of the image sensor 1 described in the first embodiment of the present disclosure, and thus will not be described again.

[0108] 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.

[0109] <5. Application Examples of Cameras>

[0110] The technology according to the present disclosure (this technology) can be applied to various products. For example, this technology can be implemented as an image sensor installed in an imaging device such as a camera.

[0111] Figure 10 FIG. is a block diagram schematically showing a configuration example of a camera as an example of an imaging device to which this technology can be applied. The camera 1000 in the figure includes a lens 1001, an image sensor 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.

[0112] The lens 1001 is an imaging lens of the camera 1000. The lens 1001 converges the light from the subject, causes the light to enter the image sensor 1002 described later, and forms an image of the subject.

[0113] The image sensor 1002 is a semiconductor device that images the light from the subject converged by the lens 1001. The image sensor 1002 generates an analog image signal according to the irradiated light, converts the analog image signal into a digital image signal, and outputs the digital image signal.

[0114] The imaging control unit 1003 controls the imaging of the image sensor 1002. The imaging control unit 1003 controls the image sensor 1002 by generating a control signal and outputting the control signal to the image sensor 1002. In addition, the imaging control unit 1003 can perform autofocus in the camera 1000 based on the image signal output from the image sensor 1002. Here, "autofocus" is a method of detecting the focal position of the lens 1001 and automatically adjusting the focal position. As autofocus, a method of detecting the image plane phase difference to detect the focal position according to the phase difference pixels configured in the image sensor 1002 (image plane phase difference autofocus) can be used. In addition, a method of detecting the position with the maximum contrast of the image as the focal position (contrast autofocus) can also be applied. The imaging control unit 1003 performs autofocus by adjusting the position of the lens 1001 via the lens drive unit 1004 based on the detected focal position. Note that the imaging control unit 1003 can be configured as, for example, a digital signal processor (DSP) provided with firmware.

[0115] The lens drive unit 1004 drives the lens 1001 based on the control of the imaging control unit 1003. The lens drive unit 1004 can drive the lens 1001 by changing the position of the lens 1001 using a motor provided therein.

[0116] The image processing unit 1005 processes the image signal generated by the image sensor 1002. This processing corresponds to, for example, demosaicing for generating an image signal with omitted colors among the image signals corresponding to red, green, and blue of each pixel, noise reduction for removing noise in the image signal, image signal encoding, etc. The image processing unit 1005 can be configured as, for example, a microcomputer provided with firmware.

[0117] The operation input unit 1006 receives an operation input from the user of the camera 1000. For example, a button or a touchpad can be used as the operation input unit 1006. The operation input received by the operation input unit 1006 is sent to the imaging control unit 1003 and the image processing unit 1005. Thereafter, processing in response to the operation input, such as processing for imaging a subject, etc., starts.

[0118] The frame memory 1007 is a memory that stores a frame of an image signal corresponding to one picture. The frame memory 1007 is controlled by the image processing unit 1005 and holds the frame during the image processing.

[0119] The display unit 1008 displays the image processed by the image processing unit 1005. For example, a liquid crystal panel can be used as the display unit 1008.

[0120] The recording unit 1009 records the images processed by the image processing unit 1005. For example, a memory card or a hard disk can be used as the recording unit 1009.

[0121] The cameras to which the present disclosure can be applied have been described above. This technology can be applied to the image sensor 1002 in the above configuration. Specifically, Figure 1 the image sensor 1 shown can be applied to the image sensor 1002. By applying the image sensor 1 to the image sensor 1002, the sensitivity can be improved. Clear images can be obtained even in low-light environments. In addition, the image processing unit 1005 is an example of the processing circuit recited in the claims. The camera 1000 is an example of the imaging device recited in the claims.

[0122] The configuration of the pixels 100 of the second embodiment can be combined with other configurations. Specifically, Figure 6 and Figure 7 the shape of the light-shielding wall 150 in Figure 8 and Figure 9 can be applied to the light-shielding wall 150 in

[0123] In addition, the configuration of the pixels 100 of the third embodiment can be combined with other configurations. Specifically, the color filter 140 can be omitted from the pixels 100 in Figure 9 .

[0124] In addition, the configuration of the pixels 100 of the fourth embodiment can be combined with other configurations. Specifically, pupil correction can be performed on the pixels 100 in Figure 8 .

[0125] Finally, the descriptions of the above embodiments are merely examples of the present disclosure, and the present disclosure is not limited to the above embodiments. Therefore, it goes without saying that various changes other than the above embodiments can be made according to the design, etc., without departing from the technical spirit of the present disclosure.

[0126] In addition, the effects described in this specification are merely examples and not restrictive. Other effects can also be obtained.

[0127] In addition, the drawings in the above embodiments are schematic diagrams, and the dimensional ratios of each part are not necessarily the same as the actual ones. In addition, the drawings naturally include parts where the dimensional relationships and ratios vary depending on the drawings.

[0128] This technology can also have the following configuration.

[0129] (1) An image sensor, comprising:

[0130] A plurality of pixels, each pixel including a photoelectric conversion unit configured on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereto, and an on-chip lens that converges the incident light onto the photoelectric conversion unit; and

[0131] A light-shielding wall, the light-shielding wall being disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and being configured such that an incident light irradiation side of the light-shielding wall has a tapered cross-section to block incident light.

[0132] (2) The image sensor according to (1), wherein the light-shielding wall is configured such that the tapered cross-section has a taper based on an angle of a triangle having a height and a width of the light-shielding wall from the semiconductor substrate and a width of a light-receiving surface, the light-receiving surface being a surface of the semiconductor substrate irradiated with incident light at the pixel.

[0133] (3) The image sensor according to (2), wherein the light-shielding wall is configured to have a tapered shape based on an elevation angle of an arctangent function of a triangle, the triangle including a perpendicular line from a vertex of the taper downward to the semiconductor substrate, and a half of a width of the light-shielding wall together with a width of the light-receiving surface corresponding to a base of the triangle.

[0134] (4) The image sensor according to any one of (1) to (3), wherein the light-shielding wall is configured to have a triangular cross-section having a tapered shape.

[0135] (5) The image sensor according to any one of (1) to (4), wherein each of the plurality of pixels includes a color filter that transmits incident light having a predetermined wavelength among the converged incident light.

[0136] (6) The image sensor according to (5), wherein the light-shielding wall is configured to surround a shape of the color filter.

[0137] (7) The image sensor according to any one of (1) to (6), wherein the light-shielding wall blocks light by reflecting incident light.

[0138] (8) The image sensor according to (7), wherein the light-shielding wall is formed of metal.

[0139] (9) The image sensor according to any one of (1) to (8), wherein the light-shielding wall is formed by transferring a shape of a mask that is disposed on an upper surface and has a tapered cross-section by etching.

[0140] (10) The image sensor according to (9), wherein in the light-shielding wall, the mask disposed on the upper surface is etched back by plasma etching to form the tapered cross-section.

[0141] (11) An imaging device, comprising:

[0142] A plurality of pixels, each pixel including a photoelectric conversion unit configured on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereon, and an on-chip lens that converges the incident light onto the photoelectric conversion unit;

[0143] A light-shielding wall, the light-shielding wall being disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and being configured such that an incident light irradiation side of the light-shielding wall has a tapered cross section to block incident light; and

[0144] A processing circuit that processes an image signal generated based on photoelectric conversion.

[0145] [List of reference numerals]

[0146] 1 Image sensor

[0147] 10 Pixel array unit

[0148] 30 Column signal processing unit

[0149] 100 Pixel

[0150] 101 Photoelectric conversion unit

[0151] 110 Semiconductor substrate

[0152] 130 Separation unit

[0153] 131 Insulating film

[0154] 140 Color filter

[0155] 150 Light-shielding wall

[0156] 151 Inclined surface

[0157] 152, 153 Top

[0158] 154 Bottom

[0159] 160, 161 On-chip lens

[0160] 304 Hard mask

[0161] 1000 Camera

[0162] 1002 Image sensor

[0163] 1005 Image processing unit

Claims

1. An image sensor, comprising: a plurality of pixels, each pixel including a photoelectric conversion unit configured on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereon, and an on-chip lens that converges the incident light onto the photoelectric conversion unit; and a light-shielding wall, the light-shielding wall being disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and being configured such that an incident light irradiation side of the light-shielding wall has a tapered cross-section to block incident light, wherein, in a cross-sectional view, an elevation angle of a tapered slope of the light-shielding wall from a surface of the semiconductor substrate is set to be greater than θ, where θ = (90 + φ) / 2, φ = arctan(h / b), b = (w / 2) + d, wherein, in the cross-sectional view, the tapered slopes of the light-shielding wall facing each other form a vertex of the light-shielding wall, a line is connected between the vertex and a point where a wall surface on an opposite side of the light-shielding wall facing the light-shielding wall meets the surface of the semiconductor substrate, and φ is an angle formed by the line and the surface of the semiconductor substrate, h is a height of the light-shielding wall, w is a width of the light-shielding wall, d is a width of a semiconductor substrate portion of a light-receiving surface of the pixel.

2. The image sensor according to claim 1, wherein, The light-shielding wall is configured to have a triangular cross-section in a tapered shape.

3. The image sensor according to claim 1, wherein, Each of the plurality of pixels includes a color filter that transmits incident light having a predetermined wavelength among the converged incident light.

4. The image sensor according to claim 3, wherein, The light-shielding wall is configured to surround the shape of the color filter.

5. The image sensor according to claim 1, wherein, The light-shielding wall blocks light by reflecting incident light.

6. The image sensor according to claim 5, wherein, The light-shielding wall is formed of metal.

7. The image sensor according to claim 1, wherein, The light-shielding wall is formed by transferring a shape of a mask that is disposed on an upper surface and has a tapered cross-section by etching.

8. The image sensor according to claim 7, wherein, In the light-shielding wall, the mask disposed on the upper surface is etched back by plasma etching to form the tapered cross-section.

9. An imaging device, comprising: a plurality of pixels, each pixel including a photoelectric conversion unit configured on a semiconductor substrate and performing photoelectric conversion on incident light irradiated thereon, and an on-chip lens that converges the incident light onto the photoelectric conversion unit; a light-shielding wall, the light-shielding wall being disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and being configured such that an incident light irradiation side of the light-shielding wall has a tapered cross-section to block incident light; and a processing circuit that processes an image signal generated based on photoelectric conversion, wherein, in a cross-sectional view, an elevation angle of a tapered slope of the light-shielding wall from a surface of the semiconductor substrate is set to be greater than θ, where θ = (90 + φ) / 2, φ = arctan(h / b), b = (w / 2) + d, wherein, in the cross-sectional view, the tapered slopes of the light-shielding wall facing each other form a vertex of the light-shielding wall, a line is connected between the vertex and a point where a wall surface on an opposite side of the light-shielding wall facing the light-shielding wall meets the surface of the semiconductor substrate, and φ is an angle formed by the line and the surface of the semiconductor substrate, h is a height of the light-shielding wall, w is a width of the light-shielding wall, and d is a width of a semiconductor substrate portion of a light-receiving surface of the pixel.

Images