JP2021034405A - Imaging element and imaging apparatus - Google Patents

Abstract

To prevent a decrease in sensitivity of pixels that acquire polarization information.SOLUTION: An imaging element includes a polarizing portion, and a semiconductor substrate on which a photoelectric conversion portion is formed. The polarizing portion polarizes incident light in a specific polarization direction. The surface of the semiconductor substrate is formed with a slope that is inclined at a predetermined angle with respect to the incident surface which is the surface on which the polarized incident light is incident, and is inclined in an inclined direction that is substantially parallel to a specific polarization direction. The photoelectric conversion portion is formed on the semiconductor substrate and performs photoelectric conversion of the polarized light incident through the slope.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an image pickup device and an image pickup apparatus. More specifically, the present invention relates to an image pickup device that acquires polarization information of a subject and an image pickup device that uses the image pickup device.

Conventionally, an image sensor that acquires polarization information of a subject has been used. By acquiring the polarization information, it is possible to detect incident light in a specific polarization direction, for example, reflected light from a water pool or a glass surface, and remove the incident light in the specific polarization direction. It is possible to improve the image quality of the image captured by the image sensor. Polarization information can be acquired by arranging a polarizing portion that transmits incident light in a specific polarization direction on the pixels of the image sensor. As this polarizing portion, a polarizing portion configured by a wire grid can be used. This wire grid is formed by arranging a plurality of strip-shaped conductors based on a predetermined pitch. The incident light in the polarization direction parallel to the arrangement direction of the plurality of band-shaped conductors is transmitted through the polarizing part by the wire grid, and the incident light in the polarization direction perpendicular to the arrangement direction of the plurality of band-shaped conductors is reflected and attenuated by the polarization part. Will be done. An image pickup device in which such a polarizing portion is arranged has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-076644

The above-mentioned conventional technique has a problem that the sensitivity of the image sensor is lowered. As described above, in the image sensor in which the polarizing portion is arranged, incident light different from the desired polarization direction is reflected and attenuated by the polarizing portion, so that the sensitivity is higher than that in the image sensor having no polarizing portion. Halve. A part of the incident light transmitted through the polarizing portion is reflected by the surface of the semiconductor substrate or the like when it is incident on the semiconductor substrate. Therefore, the above-mentioned conventional technique has a problem that the sensitivity is significantly lowered as compared with a normal image sensor.

The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to prevent a decrease in sensitivity of a pixel that acquires polarization information.

The present disclosure has been made to solve the above-mentioned problems, and the first aspect thereof is a polarizing portion that polarizes incident light in a specific polarization direction and a surface on which the polarized incident light is incident. A semiconductor substrate having a surface formed with a slope inclined at a predetermined angle with respect to the incident surface and inclined in a direction of inclination substantially parallel to the specific polarization direction, and the slope formed on the semiconductor substrate. It is an image pickup device including a photoelectric conversion unit that performs photoelectric conversion of the polarized incident light incident through the light.

Further, in this first aspect, the polarizing portion may polarize the incident light by transmitting the incident light in a specific polarization direction among the incident lights.

Further, in the first aspect, the polarizing portion may be composed of a wire grid composed of a plurality of strip-shaped conductors arranged at a predetermined pitch.

Further, in the first aspect, the surface of the semiconductor substrate may be formed with peaks and valleys in which a plurality of the slopes having different inclination directions are alternately arranged adjacent to each other.

Further, in the first aspect, the semiconductor substrate may have the slope formed on the surface thereof, which is inclined at the predetermined angle of 20 to 70 degrees.

Further, in the first aspect, the semiconductor substrate may have the slope formed on the surface thereof, which is inclined at the predetermined angle of 50 to 65 degrees.

Further, in the first aspect, the semiconductor substrate is configured to have the slope width according to the wavelength of the incident light when the width in the inclination direction obtained by projecting the slope onto the incident surface is defined as the slope width. The slope may be formed on the surface.

Further, in the first aspect, a protective film arranged adjacent to the incident surface of the semiconductor substrate is further provided, and the semiconductor substrate corresponds to the wavelength of the incident light and the refractive index of the protective film. The slope formed by the slope width may be formed on the surface.

Further, in the first aspect, the color filter that transmits the incident light having a predetermined wavelength among the incident light is further provided, and the semiconductor substrate corresponds to the wavelength of the incident light that has passed through the color filter. The slope formed by the slope width may be formed on the surface.

Further, in the first aspect, the semiconductor substrate may have the slope formed on the surface formed of a flat surface.

Further, in this first aspect, a plurality of pixels including the polarization unit and the photoelectric conversion unit may be arranged and configured.

Further, in the first aspect, the plurality of pixels may be respectively arranged with the polarization portion for polarizing the incident light in different specific polarization directions.

Further, in the first aspect, a light-shielding wall arranged at the boundary of the pixels to block the incident light may be further provided.

Further, in the second aspect of the present disclosure, the polarizing portion that polarizes the incident light in a specific polarization direction and the incident surface, which is the surface on which the polarized incident light is incident, are inclined at a predetermined angle and described above. Photoelectric conversion of a semiconductor substrate having a surface formed with a slope inclined in an inclined direction substantially parallel to a specific polarization direction and the polarized incident light formed on the semiconductor substrate and incident through the slope. It is an image pickup apparatus including a photoelectric conversion unit for performing the photoelectric conversion and a processing circuit for processing an image signal generated based on the photoelectric conversion.

By adopting the above aspect, the incident light in a specific polarization direction transmitted through the polarizing portion is obliquely incident on the semiconductor substrate. It is expected that the reflection of incident light on the surface of the semiconductor substrate will be reduced.

It is a figure which shows the structural example of the image pickup device which concerns on embodiment of this disclosure. It is sectional drawing which shows the structural example of the pixel which concerns on 1st Embodiment of this disclosure. It is a figure which shows an example of the polarization of the incident light which concerns on embodiment of this disclosure. It is a figure which shows the structural example of the mountain valley part which concerns on 1st Embodiment of this disclosure. It is a figure which shows an example of the reflectance of the surface of the semiconductor substrate which concerns on embodiment of this disclosure. It is a figure which shows the structural example of the pixel array part which concerns on 1st Embodiment of this disclosure. It is sectional drawing which shows the structural example of the image pickup device which concerns on the modification of 1st Embodiment of this disclosure. It is sectional drawing which shows the structural example of the pixel which concerns on the 2nd Embodiment of this disclosure. It is sectional drawing which shows the structural example of the pixel which concerns on 3rd Embodiment of this disclosure. It is a figure which shows the structural example of the pixel array part which concerns on 3rd Embodiment of this disclosure. It is sectional drawing which shows the structural example of the pixel which concerns on 4th Embodiment of this disclosure. It is a block diagram which shows the schematic configuration example of the camera which is an example of the image pickup apparatus to which this technology can be applied.

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 drawings below, the same or similar parts are designated by the same or similar reference numerals. In addition, the embodiments will be described in the following order.
1. 1. First Embodiment 2. Second embodiment 3. Third embodiment 4. Fourth Embodiment 5. Application example to camera

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

The pixel array unit 10 is configured by arranging the pixels 100 in a two-dimensional grid pattern. Here, the pixel 100 generates an image signal according to the irradiated light. The pixel 100 has a photoelectric conversion unit that generates an electric charge according to the irradiated light. Further, the pixel 100 further has a pixel circuit. This pixel circuit generates an image signal based on the electric charge generated by the photoelectric conversion unit. The generation of the image signal is controlled by the control signal generated by the vertical drive unit 20 described later. The signal lines 11 and 12 are arranged in the pixel array unit 10 in an XY matrix. The signal line 11 is a signal line that transmits a control signal of the pixel circuit in the pixel 100, is arranged for each line of the pixel array unit 10, and is commonly wired to the pixel 100 arranged in each line. The signal line 12 is a signal line for transmitting an image signal generated by the pixel circuit of the pixel 100, is arranged in each row of the pixel array unit 10, and is commonly wired to the pixel 100 arranged in each row. To. These photoelectric conversion units and pixel circuits are formed on a semiconductor substrate.

The vertical drive unit 20 generates a control signal for the pixel circuit of the pixel 100. The vertical drive unit 20 transmits the generated control signal to the pixel 100 via the signal line 11 in the figure. The column signal processing unit 30 processes the image signal generated by the pixel 100. The column signal processing unit 30 processes the image signal transmitted from the pixel 100 via the 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 for controlling the vertical drive unit 20 and the column signal processing unit 30. The control signal generated by the control unit 40 is transmitted to the vertical drive unit 20 and the column signal processing unit 30 by the signal lines 41 and 42, respectively. The column signal processing unit 30 is an example of the processing circuit described in the claims.

[Pixel composition]
FIG. 2 is a cross-sectional view showing a configuration example of a pixel according to the first embodiment of the present disclosure. The figure is a cross-sectional view showing a configuration example of the pixel 100. The pixel 100 in the figure includes a semiconductor substrate 120, a wiring region 130, protective films 143 and 144, a polarizing portion 150, an on-chip lens 190, and a support substrate 199.

The semiconductor substrate 120 is a semiconductor substrate on which a diffusion region of a photoelectric conversion unit or an element of a pixel circuit is formed. For the semiconductor substrate 120, for example, a semiconductor substrate made of silicon (Si) or germanium (Ge) can be used. Further, a substrate of a compound semiconductor containing gallium (Ga) and arsenic (As) can also be used. The diffusion region of the elements of the photoelectric conversion unit and the pixel circuit is formed in the well region formed on the semiconductor substrate 120. For convenience, the semiconductor substrate 120 in the figure is assumed to be configured in a p-type well region. By arranging the n-type semiconductor region in the p-type well region, it is possible to form a diffusion region of the elements of the photoelectric conversion unit and the pixel circuit.

In the figure, the photoelectric conversion unit 101 is shown as an example of these. The photoelectric conversion unit 101 is composed of an n-type semiconductor region 121 arranged on the semiconductor substrate 120 in the figure. Specifically, a photodiode formed by a pn junction at the interface between the n-type semiconductor region 121 and the surrounding p-type well region corresponds to the photoelectric conversion unit 101. When the pn junction portion is irradiated with incident light, an electric charge is generated by photoelectric conversion. The electrons of this charge are accumulated in the n-type semiconductor region 121. Based on the accumulated charges (electrons), an image signal is generated by a pixel circuit (not shown).

A light-shielding wall 141 is arranged at the boundary of the pixels 100 of the semiconductor substrate 120. The light-shielding wall is configured to surround the semiconductor substrate 120 of the pixel 100 and separates the pixel 100. Further, the light-shielding wall 141 prevents leakage of incident light from adjacent pixels 100 and reduces crosstalk. It is possible to prevent the incident light refracted by the slope 123, which will be described later, from being incident on the adjacent pixel 100. The light-shielding wall 141 can be formed, for example, by embedding a metal such as tungsten (W) in a groove formed in the semiconductor substrate 120.

A light-shielding film 142 is arranged on the back surface of the semiconductor substrate 120. This light-shielding film is a film that blocks the boundary between the pixels 100. The light-shielding film 142 can be made of a metal such as tungsten (W) like the light-shielding wall 141, and can be formed at the same time as the light-shielding wall 141.

The wiring area 130 is an area that is arranged adjacent to the front surface of the semiconductor substrate 120 and forms a wiring that transmits a signal to an element or the like of the pixel circuit of the pixel 100. The wiring area 130 in the figure is composed of a wiring layer 132 and an insulating layer 131. The wiring layer 132 is a wiring for transmitting a signal. The wiring layer 132 can be made of, for example, a metal such as copper (Cu). The insulating layer 131 insulates the wiring layer 132. The insulating layer 131 can be made of, for example, silicon oxide (SiO ₂ ) or silicon nitride (SiN).

The protective film 143 is a film that is arranged adjacent to the surface of the back side of the semiconductor substrate 120 and protects the back side of the semiconductor substrate 120. The protective film 143 can be made of, for example, SiO ₂ . A fixed charge film that pins the interface state of the semiconductor substrate 120 can also be arranged between the semiconductor substrate 120 and the protective film 143.

The polarizing unit 150 is arranged on the surface of the protective film 143 to polarize the incident light from the subject in a specific polarization direction. For the polarizing unit 150, for example, a polarizing unit that polarizes the incident light by transmitting the incident light in a specific polarization direction can be used. The polarizing unit 150 in the figure represents an example of a polarizing unit composed of a wire grid. This wire grid is a polarizing portion formed by arranging a plurality of strip-shaped conductors at a predetermined pitch. The polarizing portion 150 in the figure is configured by arranging strip-shaped conductors 151. A dielectric material such as air can be arranged in the region between the plurality of strip conductors 151.

The incident light in the polarization direction perpendicular to the arrangement direction of the band-shaped conductors 151, that is, the polarization direction parallel to the band-shaped conductors 151 is attenuated by the polarizing unit 150. This is because the electric charge inside the band-shaped conductor 151 vibrates due to the incident light to generate reflected light. On the other hand, the incident light in the polarization direction parallel to the arrangement direction of the band-shaped conductors 151, that is, the polarization direction perpendicular to the band-shaped conductors 151, passes through the polarizing portion 150. This is because the vibration of the electric charge inside the strip conductor 151 is limited. The polarization direction transmitted through the polarizing unit 150 is referred to as a transmission axis. Details of the polarization of the incident light by the polarizing unit 150 will be described later.

The protective film 144 is a film that protects the polarizing portion 150. The protective film 144 can be made of, for example, SiO ₂ or SiN.

The on-chip lens 190 is a lens that is arranged for each pixel 100 and collects incident light. The on-chip lens 190 is configured in a hemispherical shape and collects incident light on a photoelectric conversion unit 101 (n-type semiconductor region 121). The on-chip lens 190 can be made of, for example, an organic material such as acrylic resin or an inorganic material such as SiN.

The support substrate 199 is a substrate that is arranged adjacent to the wiring region 130 and supports the image pickup device 1. The support substrate 199 improves the strength of the image pickup device 1 during manufacturing.

A mountain valley portion 122 is formed on the back surface of the semiconductor substrate 120. The mountain valley portion 122 is composed of an uneven portion in which the shape of the cross section of the mountain or valley shown in the figure is extended in the depth direction of the paper surface in the figure to form a ridge line or a valley line. The uneven portion is composed of slopes 123 formed at different inclination angles on the surface of the semiconductor substrate 120. The slope 123 is a surface on the back side of the semiconductor substrate 120, and is inclined at a predetermined angle with respect to an incident surface, which is a surface on which incident light is incident. Further, the slope 123 is inclined in an inclined direction substantially parallel to the transmission axis of the above-mentioned polarizing portion 150. That is, the slope 123 is formed in an inclined direction substantially parallel to a specific polarization direction of the incident light transmitted through the polarizing portion 150. By arranging the mountain valley portion 122, it is possible to reduce the reflection of the incident light transmitted through the polarizing portion 150. The mountain valley portion 122 can be formed, for example, by etching the 111 surface of the back surface of the semiconductor substrate 120. The details of the configuration of the Yamatani portion 122 will be described later.

[Polarization of incident light]
FIG. 3 is a diagram showing an example of polarization of incident light according to the embodiment of the present disclosure. The figure is a diagram for explaining the state of polarization by the polarizing unit 150. As shown in the figure, the strip-shaped conductor 151 of the polarizing portion 150 can be formed in the shape of a rectangular parallelepiped. The strip-shaped conductors 151 are arranged at a predetermined pitch. The polarization of the polarizing unit 150 will be described by taking as an example the case where the polarizing unit 150 is irradiated with the incident lights 401 and 402. The incident light 401 is incident light in the polarization direction parallel to the arrangement direction of the plurality of strip-shaped conductors 151. The incident light 402 is incident light in the polarization direction perpendicular to the arrangement direction of the plurality of strip-shaped conductors 151. As described above, the incident light 402 is reflected because free electrons vibrate in the longitudinal direction of the rectangular parallelepiped-shaped strip conductor 151. Therefore, the incident light 402 cannot pass through the polarizing unit 150.

On the other hand, in the incident light 401, the vibration of the free electrons of the band-shaped conductor 151 is restricted and the reflection is reduced. Therefore, the incident light 401 transmits through the polarizing unit 150. The incident light 401', which is the incident light transmitted through the polarizing portion 150, is incident on the surface on the back side of the semiconductor substrate 120. A mountain valley portion 122 is formed on the surface on the back side of the semiconductor substrate 120, and the incident light 401'is incident on the slope 123 constituting the mountain valley portion 122. As described above, the slope 123 is inclined at a predetermined angle with respect to the incident surface which is the surface on the back side of the semiconductor substrate 120. Further, the slope 123 is inclined in a direction substantially parallel to the polarization direction of the incident light 401'. That is, the ridgeline of the mountain portion of the mountain valley portion 122 is formed in a direction substantially perpendicular to the polarization direction of the incident light 401'.

[Composition of Sanya]
FIG. 4 is a diagram showing a configuration example of a mountain valley portion according to the first embodiment of the present disclosure. In the figure, A is a plan view showing a configuration example of the mountain valley portion 122, and is a diagram showing the configuration of the surface on the back side of the semiconductor substrate 120. The dotted line A in the figure represents the boundary of the pixel 100. A mountain valley portion 122 is formed on the surface of the semiconductor substrate 120 in the region where the light-shielding film 142 is opened. The mountain valley portion 122 is formed by connecting mountain portions formed by slopes 123 having different inclination directions. The solid line and the alternate long and short dash line of the mountain valley portion 122 in the figure represent the ridge line 127 and the valley line 128, respectively.

FIG. B in the figure is a cross-sectional view showing a configuration example of the mountain valley portion 122, and is a cross-sectional view showing the configuration of the surface on the back side of the semiconductor substrate 120. On the ridge line 127 and the valley line 128, a plurality of slopes 123 that incline in opposite directions are alternately arranged adjacent to each other to form a mountain valley portion 122. As described above, the slope 123 constituting the mountain valley portion 122 is inclined at a predetermined angle with respect to the incident surface which is the surface on the back side of the semiconductor substrate 120. Assuming that this angle is the inclination angle θ, the incident angle of the incident light 401'is also equal to θ, as shown in B in the figure. The reflection of the incident light when the incident light is obliquely incident on the surface of the semiconductor substrate 120 depends on the incident angle. The width of the slope 123 projected onto the incident surface 129 is represented by the slope width W.

[Reflectance on the surface of the semiconductor substrate]
FIG. 5 is a diagram showing an example of the reflectance of the surface of the semiconductor substrate according to the embodiment of the present disclosure. The figure shows the relationship between the reflectance of the surface of the semiconductor substrate 120 and the incident angle of the incident light. The vertical axis in the figure represents the reflectance. The unit is%. The horizontal axis in the figure represents the incident angle of the incident light. The incident angle of this incident light is a value equal to the above-mentioned inclination angle θ. Further, the solid line graph 411 in the figure is a graph showing the reflectance of incident light in the polarization direction parallel to the inclination direction. Further, the solid line graph 412 is a graph showing the reflectance of incident light in the polarization direction perpendicular to the inclination direction. The dotted line graph 413 is a graph showing the average value of the graphs 411 and 412. It is assumed that the reflectance is 8% when the incident light is vertically incident on the surface of the semiconductor substrate 120 (incident angle is 0 degrees).

It is known that the reflection of incident light depends on the polarization direction in addition to the incident angle. As is clear from Graph 412, the reflectance of the incident light in the polarization direction perpendicular to the tilt direction increases exponentially as the incident angle increases. On the other hand, the reflectance of the incident light in the polarization direction parallel to the inclination direction of the graph 411 decreases once and then increases as the incident angle increases. Therefore, the reflectance can be lowered as compared with the case where the incident light is vertically incident on the surface of the semiconductor substrate 120. From the figure, when the incident angle (tilt angle) is in the range of 20 to 70, the reflectance of the incident light in the polarization direction parallel to the tilt direction is lowered and the reflectance of the incident light in the polarization direction perpendicular to the tilt direction is reduced. Can be increased. As a result, it is possible to reduce the reflection of the incident light on the transmission axis of the polarizing unit 150 and increase the reflection of the incident light in the polarization direction different from the transmission axis of the polarizing unit 150. As a result, it is possible to reduce the decrease in sensitivity of the pixel 100 including the polarizing unit 150 and reduce the error in the polarization information. Further, by setting the incident angle (tilt angle) in the range of 50 to 65, the reflectance of the incident light on the transmission axis of the polarizing portion 150 can be made substantially 0%, and a more remarkable effect can be obtained. ..

In this way, it is possible to reduce the reflection of the incident light 401'parallel to the inclination direction of the slope 123 formed on the surface of the semiconductor substrate 120. It is possible to reduce the decrease in sensitivity due to reflection from the surface of the semiconductor substrate 120. By forming the slope 123 flat, the inclination angle becomes a constant value, and more accurate reflection characteristics can be obtained.

The incident characteristics of the incident light according to the polarization direction are based on the geometrical optics behavior of the incident light. In order to obtain the geometrical optics behavior of the incident light, it is necessary to make the slope width W of the slope 123 of the mountain valley portion 122 larger than the wavelength of the incident light. When the slope width W of the slope 123 is smaller than the wavelength of the incident light, the behavior of the incident light becomes wave-optical, and the above-mentioned incident characteristics are impaired. Specifically, when imaging blue light (wavelength 436 nm) having a short wavelength among visible light, it is necessary to arrange a slope 123 having a slope width W having a size exceeding 436 nm.

When the incident light passes through the dielectric, the phase velocity decreases and the wavelength becomes shorter. Therefore, the slope width W of the slope 123 can be adjusted according to the refractive index of the dielectric through which the incident light is transmitted. Specifically, the slope width W of the slope 123 can be adjusted based on the value obtained by dividing the wavelength of the incident light by the refractive index of the protective film 143 adjacent to the semiconductor substrate 120. For example, when the protective film 143 is made of a material having a refractive index of 2 or more and less than 3, a slope 123 having a slope width W of 200 nm can be arranged with respect to blue light.

Further, when imaging long wavelength light, for example, infrared light (wavelength 850 nm), it is necessary to further increase the slope width W.

[Structure of pixel array section]
FIG. 6 is a diagram showing a configuration example of a pixel array unit according to the first embodiment of the present disclosure. The figure is a plan view which shows the arrangement example of the pixel 100 in the pixel array part 10, and is the figure which shows the arrangement example of the mountain valley part 122 and the polarization part 150. The dotted rectangle in the figure represents the pixel 100. The solid rectangle represents the peaks and valleys 122 on the surface of the semiconductor substrate 120 described with reference to FIG. The broken line rectangle represents the strip conductor 151.

The figure shows an example of a pixel 100 in which a polarizing portion 150 having a polarization direction different by 90 degrees is arranged. The direction of the ridgeline of the mountain valley portion 122 is also configured to be 90 degrees different depending on the polarization direction of the polarizing portion 150.

[Modification example]
In the image pickup device 1 described above, the mountain valley portion 122 having a plurality of ridge lines is generated on the surface of the semiconductor substrate 120, but the mountain valley portion 122 composed of a single peak and valley may be arranged.

FIG. 7 is a cross-sectional view showing a configuration example of a pixel according to a modified example of the first embodiment of the present disclosure. Similar to FIG. 2, FIG. 2 is a cross-sectional view showing a configuration example of the pixel 100. It differs from the peaks and valleys 122 described in FIG. 2 in that the peaks and valleys 122 on the back surface of the semiconductor substrate 120 are composed of a single peak or valley. In the figure, the description of the wiring area 130 and the support substrate 199 is omitted.

In the figure, A represents an example of a pixel 100 in which a mountain valley portion 122 composed of a single valley is formed. Further, B in the figure represents an example of the pixel 100 in which the mountain valley portion 122 composed of a single mountain is formed. These mountain valleys 122 are composed of two slopes 123.

The configuration of the image sensor 1 according to the first embodiment of the present disclosure is not limited to this example. For example, it can be applied to a surface-illuminated image sensor in which incident light is emitted from the front side of the semiconductor substrate. In this case, the polarizing portion 150 is arranged on the front side of the semiconductor substrate 120, and the mountain valley portion 122 is formed on the front surface of the semiconductor substrate 120.

As described above, in the image pickup device 1 of the first embodiment of the present disclosure, a slope inclined at a predetermined angle with respect to the incident surface is formed on the surface of the semiconductor substrate 120 of the pixel 100 including the polarizing unit 150. , The inclination direction of this slope is arranged parallel to the transmission axis of the polarizing portion 150. As a result, it is possible to reduce the reflection of the incident light transmitted through the polarizing portion 150 on the surface of the semiconductor substrate 120, and it is possible to reduce the decrease in the sensitivity of the pixel 100.

<2. Second Embodiment>
In the image pickup device 1 of the first embodiment described above, a plurality of slopes 123 are formed on the surface of the semiconductor substrate 120 of the pixel 100. On the other hand, the image sensor 1 of the second embodiment of the present disclosure is different from the above-described first embodiment in that a single slope 123 is formed on the surface of the semiconductor substrate 120.

[Pixel composition]
FIG. 8 is a cross-sectional view showing a configuration example of a pixel according to the second embodiment of the present disclosure. Similar to FIG. 2, FIG. 2 is a cross-sectional view showing a configuration example of the pixel 100. It differs from the pixel 100 described in FIG. 2 in that a single slope 123 is formed on the surface of the semiconductor substrate 120.

One slope 123 is arranged on the back surface of the semiconductor substrate 120 of the pixel 100 in the figure. The slope 123 is inclined at a predetermined angle with respect to the incident surface 129 of the semiconductor substrate 120 and is inclined in a direction parallel to the arrangement direction of the strip-shaped conductors 151 of the polarizing portion 150. Therefore, it is possible to reduce the reflection of the incident light transmitted through the polarizing unit 150. Since the slope width W can be widened, it is possible to reduce the decrease in sensitivity even when imaging long-wavelength light such as infrared light.

Since the other configurations of the image sensor 1 are the same as the configurations of the image sensor 1 described in the first embodiment of the present disclosure, the description thereof will be omitted.

As described above, in the image pickup device 1 of the second embodiment of the present disclosure, a single slope 123 is formed on the surface of the semiconductor substrate 120 of the pixel 100. As a result, it is possible to reduce the decrease in sensitivity even when imaging long-wavelength light.

<3. Third Embodiment>
The image sensor 1 of the first embodiment described above generates a monochrome image signal at the pixel 100. On the other hand, the image sensor 1 of the third embodiment of the present disclosure is different from the above-described first embodiment in that it generates a color image signal.

[Pixel composition]
FIG. 9 is a cross-sectional view showing a configuration example of a pixel according to a third embodiment of the present disclosure. Similar to FIG. 2, FIG. 2 is a cross-sectional view showing a configuration example of the pixel 100. It differs from the pixel 100 described in FIG. 2 in that it includes a color filter 180.

The color filter 180 is an optical filter that transmits incident light having a predetermined wavelength among the incident light. The color filter 180 can be arranged between the protective film 144 and the on-chip lens 190. As the color filter 180, for example, a color filter 180 that transmits red light, green light, and blue light can be used, and any one of these color filters 180 can be arranged in each pixel 100. The polarizing unit 150 in the figure polarizes the incident light transmitted through the color filter 180, and the photoelectric conversion unit 101 of the semiconductor substrate 120 performs photoelectric conversion of the incident light transmitted through the color filter 180 and the polarizing unit 150.

[Structure of pixel array section]
FIG. 10 is a diagram showing a configuration example of a pixel array unit according to a third embodiment of the present disclosure. Similar to FIG. 6, FIG. 6 is a plan view showing an example of arrangement of pixels 100 in the pixel array unit 10. In the pixel array unit 10 of the figure, polarization units 150 having different polarization directions by 45 degrees are arranged on four pixels 100 in 2 rows and 2 columns. Depending on the polarization direction, the direction of the ridgeline of the mountain valley portion 122 on the surface of the semiconductor substrate 120 is also configured to be different by 45 degrees. The characters attached to the central portion of the pixel 100 in the figure represent the type of the color filter 180 arranged in each pixel. Specifically, the letters "R", "G" and "B" represent a color filter 180 that transmits red light, green light and blue light, respectively. The same type of color filter 180 is arranged for each of the four pixels 100 in the two rows and two columns described above, and these four pixels 100 are arranged in a Bayer array. Here, the Bayer arrangement is an arrangement method in which color filters corresponding to green light are arranged in a checkered pattern, and color filters corresponding to red light and blue light are arranged between the color filters corresponding to the green light. ..

Since the other configurations of the image sensor 1 are the same as the configurations of the image sensor 1 described in the first embodiment of the present disclosure, the description thereof will be omitted.

As described above, in the image pickup device 1 of the third embodiment of the present disclosure, the color filter 180 is arranged on the pixel 100, and a color image signal can be generated.

<4. Fourth Embodiment>
In the image pickup device 1 of the third embodiment described above, a mountain valley portion 122 composed of slopes 123 of the same size is arranged on the surface of the semiconductor substrate 120 of the pixel 100. On the other hand, the image sensor 1 of the fourth embodiment of the present disclosure is different from the above-described third embodiment in that slopes 123 of different sizes are formed on the surface of the semiconductor substrate 120.

[Pixel composition]
FIG. 11 is a cross-sectional view showing a configuration example of a pixel according to a fourth embodiment of the present disclosure. Similar to FIG. 9, FIG. 9 is a cross-sectional view showing a configuration example of the pixel 100. It differs from the pixel 100 described in FIG. 9 in that slopes of different sizes are formed on the surface of the semiconductor substrate 120.

The pixel 100a in the figure is a pixel that captures a relatively short wavelength, for example, blue light. Further, the pixel 100b in the figure is a pixel that captures a relatively long wavelength, for example, red light. A color filter 180 that transmits blue light and red light is arranged in the pixel 100a and the pixel 100b, respectively.

On the back surface of the semiconductor substrate 120 of the pixel 100a, a mountain valley portion 122a having a slope 124 is arranged. The slope 124 is a slope having a relatively small slope width W in response to blue light having a short wavelength. The slope width W of the slope 124 can be configured to be 200 nm as described above in FIG. As a result, light having a long wavelength such as red light (700 nm) cannot obtain the effect of reducing the reflectance on the surface of the semiconductor substrate 120, and the amount of light incident on the semiconductor substrate 120 is reduced. The error of the image signal in the pixel 100a can be reduced.

Further, the n-type semiconductor region 121a of the photoelectric conversion unit 101 of the pixel 100a can be formed from a relatively shallow region on the back side of the semiconductor substrate 120 to the vicinity of the surface on the front side. This is because the incident light having a short wavelength is absorbed in a relatively shallow region of the semiconductor substrate 120 to cause photoelectric conversion.

On the back surface of the semiconductor substrate 120 of the pixel 100b, a mountain valley portion 122b having a slope 125 is arranged. The slope 125 is a slope having a relatively large slope width W in response to red light having a long wavelength. Further, the n-type semiconductor region 121b of the photoelectric conversion unit 101 of the pixel 100b is formed in a relatively deep region on the back side of the semiconductor substrate 120, and performs photoelectric conversion of red light reaching a relatively deep portion. Light having a short wavelength, such as blue light, is absorbed in a shallow region of the semiconductor substrate 120, and therefore does not contribute to photoelectric conversion in the pixel 100b. Therefore, like the pixel 100a, the error of the image signal of the pixel 100b can be reduced.

Since the other configurations of the image sensor 1 are the same as the configurations of the image sensor 1 described in the third embodiment of the present disclosure, the description thereof will be omitted.

As described above, in the image sensor 1 of the fourth embodiment of the present disclosure, a slope having a slope width corresponding to the incident light transmitted through the color filter 180 arranged in the pixel 100 is formed on the surface of the semiconductor substrate 120. Therefore, the error of the image signal can be reduced.

<5. Application example to camera>
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 image pickup device mounted on an image pickup device such as a camera.

FIG. 12 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 image pickup element 1002, an image pickup control unit 1003, a lens drive unit 1004, an image processing unit 1005, an operation input unit 1006, a frame memory 1007, a display unit 1008, and the like. A recording unit 1009 is provided.

The lens 1001 is a photographing lens of the camera 1000. The lens 1001 collects light from the subject and causes the light to be incident on the image pickup device 1002 described later to form an image of the subject.

The image pickup device 1002 is a semiconductor device that captures light from a subject focused 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 the signal.

The image pickup control unit 1003 controls the image pickup in the image pickup device 1002. The image pickup control unit 1003 controls the image pickup device 1002 by generating a control signal and outputting the control signal to the image pickup device 1002. Further, the image pickup control unit 1003 can perform autofocus on the camera 1000 based on the image signal output from the image pickup device 1002. Here, the 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) in which the image plane phase difference is detected by the phase difference pixels arranged in the image sensor 1002 to detect the focal position can be used. It is also possible to apply a method (contrast autofocus) of detecting the position where the contrast of the image is highest as the focal position. The image pickup control unit 1003 adjusts the position of the lens 1001 via the lens drive unit 1004 based on the detected focal position, and performs autofocus. The image pickup control unit 1003 can be configured by, for example, a DSP (Digital Signal Processor) equipped with firmware.

The lens driving unit 1004 drives the lens 1001 based on 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.

The image processing unit 1005 processes the image signal generated by the image sensor 1002. This processing includes, for example, demosaic to generate an image signal of a color that is insufficient among the image signals corresponding to red, green, and blue for each pixel, noise reduction to remove noise of the image signal, and coding of the image signal. Applicable. In addition, the image processing unit 1005 can process the polarization information generated by the image sensor 1002. The image processing unit 1005 can be configured by, for example, a microcomputer equipped with firmware.

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

The frame memory 1007 is a memory for storing a frame which is an image signal for one screen. The frame memory 1007 is controlled by the image processing unit 1005 and holds the frame in the process of image processing.

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.

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

The cameras to which the present disclosure can be applied have been described above. The present technology can be applied to the image pickup device 1002 among the configurations described above. Specifically, the image pickup device 1 described with reference to FIG. 1 can be applied to the image pickup device 1002. By applying the image sensor 1 to the image sensor 1002, it is possible to reduce a decrease in sensitivity when acquiring polarization information. The image processing unit 1005 is an example of the processing circuit described in the claims. The camera 1000 is an example of the imaging device described in the claims.

Finally, the description of each of the embodiments described above is an example of the present disclosure, and the disclosure is not limited to the embodiments described above. Therefore, it goes without saying that various changes can be made according to the design and the like as long as the technical idea according to the present disclosure is not deviated from the above-described embodiments.

Moreover, the effects described in the present specification are merely examples and are not limited. It may also have other effects.

Further, the drawings in the above-described embodiment are schematic, and the ratio of the dimensions of each part and the like do not always match the actual ones. In addition, it goes without saying that the drawings include parts having different dimensional relationships and ratios from each other.

The present technology can have the following configurations.
(1) A polarizing unit that polarizes incident light in a specific polarization direction,
A semiconductor substrate having a surface formed with a slope inclined at a predetermined angle with respect to an incident surface, which is a surface on which the polarized incident light is incident, and an inclined direction substantially parallel to the specific polarization direction. ,
An image pickup device including a photoelectric conversion unit formed on the semiconductor substrate and incident via the slope to perform photoelectric conversion of the polarized incident light.
(2) The image pickup device according to (1), wherein the polarizing unit polarizes the incident light by transmitting the incident light in a specific polarization direction of the incident light.
(3) The image pickup device according to (2) above, wherein the polarizing portion is composed of a wire grid composed of a plurality of strip-shaped conductors arranged at a predetermined pitch.
(4) The image pickup device according to any one of (1) to (3) above, wherein the semiconductor substrate has peaks and valleys formed on the surface of a plurality of slopes having different inclination directions alternately arranged adjacent to each other. ..
(5) The image pickup device according to any one of (1) to (4), wherein the semiconductor substrate has a slope formed on the surface thereof, which is inclined at a predetermined angle of 20 to 70 degrees.
(6) The image pickup device according to (5), wherein the semiconductor substrate has a slope formed on the surface thereof, which is inclined at a predetermined angle of 50 to 65 degrees.
(7) In the semiconductor substrate, when the width in the inclination direction obtained by projecting the slope onto the incident surface is defined as the slope width, the slope formed on the slope width according to the wavelength of the incident light is formed on the surface. The image pickup device according to any one of (1) to (6) above.
(8) Further provided with a protective film arranged adjacent to the incident surface of the semiconductor substrate,
The image pickup device according to (7), wherein the semiconductor substrate has a slope formed on the surface having the slope width corresponding to the wavelength of the incident light and the refractive index of the protective film.
(9) A color filter that transmits incident light having a predetermined wavelength among the incident light is further provided.
The image pickup device according to (7), wherein the semiconductor substrate has the slope formed on the surface having the slope width corresponding to the wavelength of the incident light transmitted through the color filter.
(10) The image pickup device according to any one of (1) to (9) above, wherein the semiconductor substrate has the slope formed on the flat surface formed on the surface.
(11) The image pickup device according to any one of (1) to (10), wherein a plurality of pixels including the polarizing unit and the photoelectric conversion unit are arranged.
(12) The image pickup device according to (11), wherein the plurality of pixels are arranged with the polarizing portion that polarizes incident light in different specific polarization directions.
(13) The image pickup device according to (11), further comprising a light-shielding wall arranged at the boundary of the pixels to block incident light.
(14) A polarizing unit that polarizes the incident light in a specific polarization direction,
A semiconductor substrate having a surface formed with a slope inclined at a predetermined angle with respect to an incident surface, which is a surface on which the polarized incident light is incident, and an inclined direction substantially parallel to the specific polarization direction. ,
A photoelectric conversion unit formed on the semiconductor substrate and performing photoelectric conversion of the polarized incident light incident through the slope, and a photoelectric conversion unit.
An image pickup apparatus including a processing circuit for processing an image signal generated based on the photoelectric conversion.

1 Image sensor 10 Pixel array unit 30 Column signal processing unit 100, 100a, 100b Pixel 101 Photoelectric conversion unit 120 Semiconductor substrate 121, 121a, 121b Semiconductor area 122 Mountain valley 123-125 Slope 127 Ridge line 129 Incident surface 141 Light-shielding wall 142 Light-shielding film 143, 144 Protective film 150 Polarizing part 151 Band-shaped conductor 180 Color filter 1002 Image sensor 1005 Image processing part

Claims (14)

A polarizing part that polarizes the incident light in a specific polarization direction,
A semiconductor substrate having a surface formed with a slope inclined at a predetermined angle with respect to an incident surface, which is a surface on which the polarized incident light is incident, and an inclined direction substantially parallel to the specific polarization direction. ,
An image pickup device including a photoelectric conversion unit formed on the semiconductor substrate and incident via the slope to perform photoelectric conversion of the polarized incident light. The image pickup device according to claim 1, wherein the polarizing unit polarizes the incident light by transmitting the incident light in a specific polarization direction of the incident light. The image pickup device according to claim 2, wherein the polarizing portion is composed of a wire grid composed of a plurality of strip-shaped conductors arranged at a predetermined pitch. The image pickup device according to claim 1, wherein the semiconductor substrate is formed with peaks and valleys on the surface in which a plurality of slopes having different inclination directions are alternately arranged adjacent to each other. The image pickup device according to claim 1, wherein the semiconductor substrate has the slope formed on the surface thereof, which is inclined at the predetermined angle of 20 to 70 degrees. The image pickup device according to claim 5, wherein the semiconductor substrate has the slope formed on the surface thereof, which is inclined at the predetermined angle of 50 to 65 degrees. In the semiconductor substrate, when the width in the inclination direction in which the slope is projected onto the incident surface is defined as the slope width, the slope formed on the slope width according to the wavelength of the incident light is formed on the surface. Item 1. The imaging element according to Item 1. Further provided with a protective film arranged adjacent to the incident surface of the semiconductor substrate,
The image pickup device according to claim 7, wherein the semiconductor substrate has the slope formed on the surface having the slope width corresponding to the wavelength of the incident light and the refractive index of the protective film. A color filter that transmits incident light of a predetermined wavelength among the incident light is further provided.
The image pickup device according to claim 7, wherein the semiconductor substrate has the slope formed on the surface having the slope width corresponding to the wavelength of the incident light transmitted through the color filter. The image pickup device according to claim 1, wherein the semiconductor substrate has a slope formed on a flat surface. The image pickup device according to claim 1, wherein a plurality of pixels including the polarizing unit and the photoelectric conversion unit are arranged. The image pickup device according to claim 11, wherein the plurality of pixels are arranged with the polarizing portion that polarizes incident light in different specific polarization directions. The image pickup device according to claim 11, further comprising a light-shielding wall arranged at the boundary of the pixels to block incident light. A polarizing part that polarizes the incident light in a specific polarization direction,
A semiconductor substrate having a surface formed with a slope inclined at a predetermined angle with respect to an incident surface, which is a surface on which the polarized incident light is incident, and an inclined direction substantially parallel to the specific polarization direction. ,
A photoelectric conversion unit formed on the semiconductor substrate and performing photoelectric conversion of the polarized incident light incident through the slope, and a photoelectric conversion unit.
An image pickup apparatus including a processing circuit for processing an image signal generated based on the photoelectric conversion.

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