Image pickup element and image pickup device

Abstract

The present invention reduces the leakage of incident light into a charge retainer, etc., in a back-illuminated imaging device. The imaging element includes a photoelectric converter, a reflector, and a reflector-forming member. The photoelectric converter is formed in a semiconductor substrate and performs photoelectric conversion on incident light. The reflector is arranged on a surface of the semiconductor substrate different from the surface on which the incident light is incident and reflects light transmitted through the photoelectric converter back to the photoelectric converter. The reflector-forming member has a bottom surface adjacent to the surface of the semiconductor substrate and includes the reflector formed on a side surface thereof.

Description

Technical Field

[0001] The present invention relates to an imaging element and an imaging device, and more particularly to a back-illuminated imaging element and an imaging device including the same. Background Art

[0002] Complementary metal oxide semiconductor (CMOS) imaging elements typically use a back-illuminated imaging element. In this type of imaging element, incident light strikes the rear surface, which is different from the front surface of the semiconductor substrate where wiring areas are arranged. A photoelectric conversion unit is formed on the semiconductor substrate to perform photoelectric conversion on the incident light for each pixel. Because incident light strikes the semiconductor substrate without passing through the wiring areas, back-illuminated imaging elements can achieve improved sensitivity compared to front-illuminated imaging elements, where incident light strikes the front surface of the semiconductor substrate.

[0003] In addition, an imaging element that performs global shutter imaging is used to reduce image distortion. This imaging element includes a charge retention unit for storing charge, which is generated by photoelectric conversion of each pixel. In this global shutter imaging, imaging is performed in the following order. First, photoelectric conversion (exposure) is performed simultaneously in all pixels of the imaging element. Next, an image signal is generated and transmitted for each pixel based on the charge generated by photoelectric conversion. Multiple pixels arranged in the imaging element are arranged in a two-dimensional grid form, and image signal transmission is performed sequentially for each row of multiple pixels. The charge generated by photoelectric conversion is transferred to the charge retention unit after the exposure period ends and is retained therein. Immediately before the image signal is transmitted, the retained charge is extracted from the charge retention unit and provided for image signal generation. In this global shutter imaging element, when some incident light strikes the charge retention unit, photoelectric conversion occurs in the charge retention unit. The charge resulting from this photoelectric conversion is added to the retained charge, thereby generating noise in the image signal. As a result, the image quality deteriorates.

[0004] As an imaging element for preventing incident light from irradiating such a charge holding portion, an imaging element in which a light shielding portion is arranged around the charge holding portion has been proposed (for example, refer to Patent Document 1). The light shielding portion is composed of a cover portion and an embedded portion, and shields incident light. The cover portion is arranged on the rear side of the semiconductor substrate close to the charge holding portion, and the embedded portion is embedded in the semiconductor substrate between the photoelectric conversion portion and the charge holding portion. The embedded portion is formed from the rear side of the semiconductor substrate toward the front side thereof. The charge in the photoelectric conversion portion is transferred to the charge holding portion through a semiconductor region between the end of the embedded portion and the front surface of the semiconductor substrate.

[0005] List of citations

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Publication No. 2015-228510 Summary of the Invention

[0008] Technical problem to be solved by the invention

[0009] The above-mentioned prior art suffers from a problem of being unable to prevent incident light from leaking from the semiconductor region between the end of the embedded portion constituting the light shield and the front surface of the semiconductor substrate. Of the incident light that strikes the photoelectric converter, some that passes through the semiconductor substrate and does not contribute to photoelectric conversion is reflected by wiring and other components in the wiring area, becoming reflected light. This reflected light passes through the semiconductor region between the end of the embedded portion and the front surface of the semiconductor substrate and enters the charge retention portion, triggering photoelectric conversion and generating noise. Consequently, the above-mentioned prior art suffers from a problem of degraded image quality.

[0010] The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to reduce the leakage of incident light to a charge holding portion and the like.

[0011] Solutions to technical problems

[0012] A first aspect of the present invention designed to solve the above-mentioned problems is an imaging element, which includes a photoelectric conversion portion, which is formed in a semiconductor substrate and performs photoelectric conversion on incident light; a reflecting portion, which is arranged in a front surface of the semiconductor substrate different from the surface on which the incident light is incident, and reflects transmitted light transmitted through the photoelectric conversion portion to the photoelectric conversion portion; and a reflecting portion forming member, which has a bottom surface arranged adjacent to the front surface of the semiconductor substrate and a side surface on which the reflecting portion is formed.

[0013] Furthermore, in the first aspect, the image pickup element may further include an image signal generation circuit that generates an image signal based on the charge generated by the photoelectric conversion.

[0014] Furthermore, in the first aspect, the reflection portion forming member may be formed simultaneously with the gate of the MOS transistor arranged in the image signal generating circuit.

[0015] Furthermore, in the first aspect, the reflection portion forming member may be formed by a gate of a MOS transistor arranged in the image signal generating circuit.

[0016] Furthermore, in the first aspect, the reflection portion forming member may have a sidewall insulating film disposed on the side surface portion, and the reflection portion may be formed adjacent to the sidewall insulating film.

[0017] Furthermore, in the first aspect, the reflective portion may be arranged near a boundary of the photoelectric conversion portion in the semiconductor substrate.

[0018] Furthermore, in the first aspect, the image pickup element may further include a light shielding film formed adjacent to an upper surface of the reflection portion forming member, the upper surface being a surface opposite to the bottom surface, to shield the transmitted light.

[0019] Furthermore, in the first aspect, the image sensor may further include a charge holding portion that holds the charge generated by the photoelectric conversion.

[0020] Furthermore, in the first aspect, the image pickup element may further include a light shielding wall disposed between the photoelectric conversion portion and the charge holding portion in the semiconductor substrate.

[0021] Furthermore, in the first aspect, the light shielding wall may include an opening portion close to the front surface of the semiconductor substrate, and the reflecting portion may be arranged near the opening portion of the light shielding wall.

[0022] Furthermore, in the first aspect, the reflecting portion may be arranged so as to be offset from the opening portion of the light shielding wall toward the charge holding portion.

[0023] Furthermore, in the first aspect, the reflecting portion forming member may be formed by laminating a plurality of films.

[0024] In addition, in the first aspect, the imaging element may further include an image signal generating circuit that generates an image signal based on the charge generated by the photoelectric conversion, wherein any one of the multiple films of the reflective portion forming member may be formed simultaneously with the gate of the MOS transistor of the image signal generating circuit.

[0025] Furthermore, in the first aspect, a bias voltage may be applied to the reflection portion forming member.

[0026] Furthermore, in the first aspect, the side surface of the reflecting portion forming member may be formed in a curved shape.

[0027] Furthermore, in the first aspect, the reflecting portion forming member may include a side surface having a tapered cross section.

[0028] Furthermore, in the first aspect, the image pickup element may further include a color filter through which incident light having a predetermined wavelength is transmitted, wherein the photoelectric conversion portion may photoelectrically convert the incident light transmitted through the color filter.

[0029] In addition, in the first aspect, the imaging element may include a plurality of pixels each having the photoelectric conversion portion and the color filter, wherein the reflection portion and the reflection portion forming member are arranged in a pixel among the plurality of pixels in which the color filter that transmits the incident light having a long wavelength is arranged.

[0030] Furthermore, in the first aspect, the reflecting portion may be formed of metal.

[0031] In addition, a second aspect of the present invention is an imaging device, comprising: a photoelectric conversion portion formed in a semiconductor substrate and performing photoelectric conversion on incident light; a reflecting portion arranged in a front surface of the semiconductor substrate different from a surface on which the incident light is incident, and reflecting transmitted light transmitted through the photoelectric conversion portion to the photoelectric conversion portion, and a reflecting portion forming member having a bottom surface arranged adjacent to the front surface of the semiconductor substrate and a side surface on which the reflecting portion is formed; and a processing circuit that processes an image signal, the image signal being generated based on the charge generated by the photoelectric conversion.

[0032] By adopting the above aspects, the effect of reflecting the transmitted light of the photoelectric conversion portion toward the photoelectric conversion portion is obtained. Therefore, it is expected that the leakage of the transmitted light from the photoelectric conversion portion can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] [Figure 1]

[0034] FIG. 1 is a diagram showing a configuration example of an image pickup element according to an embodiment of the present invention.

[0035] [Figure 2]

[0036] FIG. 2 is a diagram showing an example of a circuit structure of a pixel according to a first embodiment of the present invention.

[0037] [Figure 3]

[0038] FIG. 3 is a diagram showing a configuration example of a pixel according to the first embodiment of the present invention.

[0039] [Figure 4]

[0040] FIG. 4 is a cross-sectional view showing a configuration example of a pixel according to the first embodiment of the present invention.

[0041] [Figure 5]

[0042] FIG. 5 is a diagram showing an example of reflection of transmitted light according to the first embodiment of the present invention.

[0043] [ Figure 6 ]

[0044] Figure 6: is a diagram showing an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention.

[0045] [Figure 7]

[0046] FIG. 7 is a diagram illustrating an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention.

[0047] [Figure 8]

[0048] FIG. 8 is a diagram illustrating an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention.

[0049] [Figure 9]

[0050] FIG. 9 is a diagram illustrating an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention.

[0051] [Figure 10]

[0052] FIG. 10 is a diagram illustrating an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention.

[0053] [Figure 11]

[0054] FIG. 11 is a diagram illustrating an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention.

[0055] [Figure 12]

[0056] FIG. 12 is a diagram showing a configuration example of a pixel according to a second embodiment of the present invention.

[0057] [Figure 13]

[0058] FIG. 13 is a diagram showing a configuration example of a pixel according to a third embodiment of the present invention.

[0059] [Figure 14]

[0060] FIG. 14 is a diagram showing a configuration example of a pixel according to a fourth embodiment of the present invention.

[0061] [Figure 15]

[0062] 15 is a cross-sectional view showing a configuration example of a pixel according to a fourth embodiment of the present invention.

[0063] [Figure 16]

[0064] FIG. 16 is a diagram showing a configuration example of a pixel according to a fifth embodiment of the present invention.

[0065] [Figure 17]

[0066] 17 is a cross-sectional view showing a configuration example of a pixel according to a fifth embodiment of the present invention.

[0067] [Figure 18]

[0068] 18 is a cross-sectional view showing a configuration example of a pixel according to a sixth embodiment of the present invention.

[0069] [Figure 19]

[0070] 19 is a cross-sectional view showing a configuration example of a pixel according to a seventh embodiment of the present invention.

[0071] [Figure 20]

[0072] 20 is a cross-sectional view showing a configuration example of a pixel according to an eighth embodiment of the present invention.

[0073] [Figure 21]

[0074] 21 is a cross-sectional view showing a configuration example of a pixel according to a ninth embodiment of the present invention.

[0075] [Figure 22]

[0076] 22 is a cross-sectional view showing a configuration example of a pixel according to a tenth embodiment of the present invention.

[0077] [Figure 23]

[0078] FIG 23 is a diagram showing an example of a circuit structure of a pixel according to an eleventh embodiment of the present invention.

[0079] [Figure 24]

[0080] 24 is a cross-sectional view showing a configuration example of a pixel according to an eleventh embodiment of the present invention.

[0081] [ Figure 25 ]

[0082] Figure 25 is a cross-sectional view showing a configuration example of a pixel according to a twelfth embodiment of the present invention.

[0083] [Figure 26]

[0084] FIG. 26 is a block diagram illustrating a schematic configuration example of a camera as an example of an image pickup apparatus to which the present technology can be applied. DETAILED DESCRIPTION

[0085] Next, the embodiment of the present invention (hereinafter referred to as the embodiment) will be described with reference to the accompanying drawings. In the following drawings, the same or similar parts are represented by the same or similar reference numerals. In addition, the embodiment will be described in the following order.

[0086] 1. First Implementation Method

[0087] 2. Second Implementation Plan

[0088] 3. Third Implementation Plan

[0089] 4. Fourth Implementation Plan

[0090] 5. Fifth Implementation Plan

[0091] 6. Sixth Implementation Plan

[0092] 7. Seventh Implementation Plan

[0093] 8. Eighth Implementation Plan

[0094] 9. Ninth Implementation Plan

[0095] 10. Tenth Implementation Plan

[0096] 11. Eleventh Implementation Plan

[0097] 12. Twelfth Implementation Plan

[0098] 13. Camera application examples

[0099] <1. First Implementation Method>

[0100] [Structure of the imaging element]

[0101] 1 is a diagram showing an example of the configuration of an image pickup element according to an embodiment of the present invention. In the figure, the image pickup element 1 includes a pixel array section 10, a vertical drive unit 20, a column signal processing unit 30, and a control unit 40.

[0102] Pixels 100 arranged in a two-dimensional grid form the pixel array section 10. Here, the pixels 100 generate image signals in response to irradiated light. Each pixel 100 has a photoelectric conversion unit that generates charge in response to the irradiated light. Furthermore, each pixel 100 also has an image signal generation circuit. The image signal generation circuit generates an image signal based on the charge 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 within the pixel array section 10. Signal lines 11 transmit control signals from the image signal generation circuits of the pixels 100. They are arranged for each row of the pixel array section 10 and are commonly wired for all pixels 100 arranged in each row. Signal lines 12 transmit image signals generated by the image signal generation circuits of the pixels 100. They are arranged for each column of the pixel array section 10 and are commonly wired for all pixels 100 arranged in each column. The photoelectric conversion unit and image signal generation circuit are formed on a semiconductor substrate.

[0103] The vertical drive unit 20 generates control signals for the image signal generating circuits of the pixels 100. The vertical drive unit 20 transmits the generated control signals to the pixels 100 via 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 signal lines 12 in the figure. For example, the processing in the column signal processing unit 30 corresponds to analog-to-digital conversion, converting the analog image signals generated by the pixels 100 into digital image signals. The image signals processed by the column signal processing unit 30 are output as image signals of the imaging element 1. The control unit 40 controls the entire imaging element 1. The control unit 40 generates and outputs control signals for controlling the vertical drive unit 20 and the column signal processing unit 30, thereby controlling the imaging element 1. The control signals generated by the control unit 40 are transmitted to the vertical drive unit 20 and the column signal processing unit 30 via signal lines 41 and 42. The column signal processing unit 30 is an example of the processing circuit described in the claims.

[0104] [Pixel Circuit Structure]

[0105] FIG2 is a diagram showing an example of a circuit structure of a pixel according to a first embodiment of the present invention. This figure is a circuit diagram showing the construction of pixel 100. In this figure, pixel 100 includes a photoelectric conversion unit 101, a first charge retention unit 103, a second charge retention unit 102, and MOS transistors 104 to 109. In addition, signal lines 11 and 12 consisting of signal lines OFG, TX, TR, RST, and SEL are arranged in pixel 100. The signal lines OFG, TX, TR, RST, and SEL that constitute signal line 11 are signal lines through which control signals of pixel 100 are transmitted. These signal lines are connected to the gates of MOS transistors. A voltage equal to or higher than the threshold voltage across the gate and source can be applied to the MOS transistors via the signal lines to turn on the MOS transistors. On the other hand, signal line 12 is used to transmit image signals generated by pixel 100. In addition, a power supply line Vdd is arranged in pixel 100 to provide power.

[0106] The anode of the photoelectric conversion unit 101 is grounded, and its cathode is connected to the sources of the MOS transistors 104 and 105. The drain of the MOS transistor 104 is connected to the power supply line Vdd, and its gate is connected to the signal line OFG. The drain of the MOS transistor 105 is connected to the source of the MOS transistor 106 and one end of the second charge retention unit 102. The other end of the second charge retention unit 102 is grounded. The gate of the MOS transistor 105 is connected to the signal line TX, and the gate of the MOS transistor 106 is connected to the signal line TR. The drain of the MOS transistor 106 is connected to the source of the MOS transistor 107, the gate of the MOS transistor 108, and one end of the first charge retention unit 103. The other end of the first charge retention unit 103 is grounded. The gate of the MOS transistor 107 is connected to the signal line RST. The drains of the MOS transistors 107 and 108 are commonly connected to the power supply line Vdd, and the source of the MOS transistor 108 is connected to the drain of the MOS transistor 109. The source of the MOS transistor 109 is connected to the signal line 12 and the gate thereof is connected to the signal line SEL.

[0107] The photoelectric conversion portion 101 generates electric charge in response to irradiation light and holds the electric charge as described above. A photodiode can be used for the photoelectric conversion portion 101 .

[0108] The MOS transistor 104 is a transistor that resets the photoelectric converter 101. When a power supply voltage is applied to the photoelectric converter 101, the MOS transistor 104 discharges the charge held in the photoelectric converter 101 to the power supply line Vdd, thereby resetting the photoelectric converter 101. The resetting of the photoelectric converter 101 by the MOS transistor 104 is controlled by a signal transmitted via the signal line OFG.

[0109] The MOS transistor 105 is a transistor that transfers the charge generated by the photoelectric conversion in the photoelectric conversion portion 101 to the second charge holding portion 102. The charge transfer of the MOS transistor 105 is controlled by a signal transmitted through the signal line TX.

[0110] The second charge holding portion 102 is a capacitor that holds the charge transferred by the MOS transistor 105 .

[0111] The MOS transistor 106 is a transistor that transfers the charge held in the second charge holding portion 102 to the first charge holding portion 103. The charge transfer of the MOS transistor 106 is controlled by a signal transmitted through the signal line TR.

[0112] The MOS transistor 108 generates a signal based on the charge held in the first charge holding portion 103. The MOS transistor 109 outputs the signal generated by the MOS transistor 108 as an image signal to the signal line 12. The MOS transistor 109 is controlled by a signal transmitted via the signal line SEL.

[0113] The MOS transistor 107 is a transistor that discharges the charge held in the first charge holding portion 103 to the power supply line Vdd to reset the first charge holding portion 103. This resetting of the MOS transistor 107 is controlled by a signal transmitted through the signal line RST.

[0114] The generation of the image signal of the pixel 100 in the figure can be performed as follows. First, the MOS transistor 104 is turned on to reset the photoelectric conversion unit 101. The charge generated by photoelectric conversion after the reset is accumulated in the photoelectric conversion unit. After a predetermined time, the MOS transistor 106 and the MOS transistor 107 are turned on to reset the second charge holding unit 102. Next, the MOS transistor 105 is turned on. Therefore, the charge generated in the photoelectric conversion unit 101 is transferred to the second charge holding unit 102 and held therein. The operation from resetting the photoelectric conversion unit 101 to the operation of transferring the charge by the MOS transistor 105 is performed simultaneously in all pixels 100 arranged in the pixel array unit 10. That is, a global reset of resetting simultaneously in all pixels 100 and simultaneous charge transfer in all pixels 100 are performed. Therefore, a global shutter is realized. At the same time, the time period from the resetting of the photoelectric conversion unit 101 to the charge transfer by the MOS transistor 105 corresponds to the exposure time period.

[0115] Next, the MOS transistor 107 is turned on again to reset the first charge holding portion 103. Next, the MOS transistor 106 is turned on so that the charge held in the second charge holding portion 102 is transferred to the first charge holding portion 103 and held therein. Thus, the MOS transistor 108 generates an image signal based on the charge held in the first charge holding portion 103. Next, the MOS transistor 109 is turned on so that the image signal generated by the MOS transistor 108 is output to the signal line 12. The operation from resetting the first charge holding portion 103 to outputting the image signal is sequentially performed for each pixel 100 arranged on each row of the pixel array portion 10. When the image signals in the pixels 100 of all rows of the pixel array portion 100 are output, a frame as an image signal corresponding to one screen is generated, and the frame is output from the image pickup element 1.

[0116] By performing image signal generation and image signal output in parallel in pixel 100 within the aforementioned exposure time, the time required for image capture and image signal transmission can be reduced. Furthermore, by simultaneously exposing all pixels 100 in pixel array section 10, frame distortion can be prevented, improving image quality. In this manner, second charge retention section 102 temporarily retains the charge generated by photoelectric conversion section 101 while global shutter operation is in effect. The pixel circuit is an example of the image signal generation circuit described in the claims.

[0117] [Pixel structure]

[0118] 3 is a diagram showing an example of the construction of a pixel according to a first embodiment of the present invention. The figure is a plan view showing an example of the construction of a pixel 100 and schematically shows the construction of elements such as the photoelectric conversion unit 101 described in FIG2 . In the figure, the rectangle represented by the solid line shows the gates 141 to 146 of the MOS transistor 104 to the MOS transistor 109 described in FIG2 . In addition, the rectangle represented by the long dash line and the two short dash lines alternately shows a semiconductor region formed in a semiconductor substrate (the semiconductor substrate 110 to be described later). In addition, the dotted line shows the light shielding wall 172 and the light shielding wall 173 configured on the semiconductor substrate. In addition, the rectangle filled with oblique lines shows the pseudo gate 131 to be described later.

[0119] In the pixel 100 shown in the figure, the semiconductor region 111 of the photoelectric conversion unit 101 is arranged in the center of the semiconductor substrate. The semiconductor region 112 of the second charge holding unit 102 is arranged adjacent to the upper side of the semiconductor region 111 in the figure. The gate 142 of the MOS transistor 105 shown in Figure 2 is arranged near the semiconductor region 112. The MOS transistor 105 is a MOS transistor having the semiconductor region 111 and the semiconductor region 112 as a source region and a drain region, respectively. The gate 143 of the MOS transistor 106 is arranged adjacent to the right side of the semiconductor region 112 in the figure, and the semiconductor region 113 of the first charge holding unit 103 is arranged adjacent to the gate 143. The MOS transistor 106 is a MOS transistor having the semiconductor region 112 and the semiconductor region 113 as a source region and a drain region, respectively.

[0120] Gate 144 of MOS transistor 107 is arranged adjacent to the lower side of semiconductor region 113 in the figure, and semiconductor region 114 is arranged adjacent to gate 144. MOS transistor 107 is a MOS transistor having semiconductor region 113 and semiconductor region 114 as a source region and a drain region, respectively. Gate 145 of MOS transistor 108 is arranged adjacent to the lower side of semiconductor region 114 in the figure, and semiconductor region 115 is arranged adjacent to gate 145. MOS transistor 108 is a MOS transistor having semiconductor region 114 and semiconductor region 115 as a drain region and a source region, respectively. In the figure, gate 146 of MOS transistor 109 is arranged adjacent to the lower side of semiconductor region 115 in the figure, and semiconductor region 116 is arranged adjacent to gate 146. MOS transistor 109 is a MOS transistor having semiconductor region 115 and semiconductor region 116 as a drain region and a source region, respectively.

[0121] In addition, the semiconductor region 113 and the gate 145 of the MOS transistor 108 are connected by wiring (not shown). In addition, the gate 141 of the MOS transistor 104 is arranged adjacent to the left side of the semiconductor region 111 in the figure, and the semiconductor region 117 is arranged adjacent to the lower side of the gate 141. The MOS transistor 104 is a MOS transistor having the semiconductor region 111 and the semiconductor region 117 as a source region and a drain region, respectively.

[0122] The light-shielding wall 172 is embedded in a portion of the semiconductor substrate at the boundary of the pixel 100 and shields incident light from the adjacent pixel 100. The light-shielding wall 172 is constructed in a form that penetrates the semiconductor substrate. The light-shielding wall 173 is embedded in a portion of the semiconductor substrate between the photoelectric conversion portion 101 and the second charge holding portion 102 of the pixel 100 and shields incident light from the photoelectric conversion portion 101 to the second charge holding portion 102. The light-shielding wall 173 is composed of a portion that penetrates the semiconductor substrate and a portion having an opening portion (opening portion 174 to be described later) near the front surface of the semiconductor substrate. In the figure, the dotted shaded portion in the light-shielding wall 173 shows the opening portion.

[0123] The dummy gate 131 is a member constituting a reflective portion forming member 130 to be described later. The dummy gate 131 can be configured as the same member as the gate 142 of the MOS transistor 105 or the like.

[0124] Such pixels 100 are arranged in a two-dimensional grid to form the pixel array section 10. Meanwhile, the semiconductor region 113 in the figure is shared by the pixels 100 adjacent to the right side of the pixel 100 in the figure. The gate electrode 141 and the semiconductor region 117 in the figure are shared by the pixels 100 adjacent to the left side of the pixel 100 in the figure. Meanwhile, the second charge retention portion 102 is an example of the charge retention section described in the claims.

[0125] [Cross-sectional structure of a pixel]

[0126] FIG4 is a cross-sectional view showing an example of the configuration of a pixel according to the first embodiment of the present invention. This figure shows an example of the configuration of pixel 100 and is a cross-sectional view of pixel 100 taken along line a-a' in FIG3 . Pixel 100 in the figure includes a semiconductor substrate 110, a dummy gate 131, a wiring region 160, light shielding films 150 and 170, light shielding walls 172 and 173, an insulating film 180, a color filter 191, an on-chip lens 195, and a support substrate 196.

[0127] As described above, the semiconductor substrate 110 is a semiconductor substrate in which the semiconductor portion of the element arranged in the pixel 100 is formed. For example, the semiconductor substrate 110 can be formed of silicon (Si). In addition, for example, the semiconductor substrate 110 can be formed to a thickness of 3 μm. The semiconductor portion of the element is arranged 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 semiconductor portion of the element can be formed by arranging an n-type semiconductor region in the p-type well region. The photoelectric conversion unit 101 and the second charge holding unit 102 are shown in the figure.

[0128] The photoelectric conversion unit 101 is constructed using the n-type semiconductor region 111 in the figure. Specifically, a photodiode formed using a pn junction between the n-type semiconductor region 111 and a p-type well region surrounding the n-type semiconductor region 111 corresponds to the photoelectric conversion unit 101. Light incident from the rear surface of the semiconductor substrate 110 is photoelectrically converted in the n-type semiconductor region 111. Electrons among the charges generated by the photoelectric conversion are accumulated in the n-type semiconductor region 111 during the exposure period.

[0129] The second charge holding portion 102 is constructed using the n-type semiconductor region 112 in the figure. Electrons accumulated in the n-type semiconductor region 111 during the exposure period are transferred to the n-type semiconductor region 112 after the exposure period and retained therein. In addition, a gate 142 is arranged on the front surface side of the semiconductor substrate 110 near the semiconductor region 112. This gate 142 forms the gate of the above-mentioned MOS transistor 105 and controls the potential of the semiconductor region 112. When the electrons accumulated in the above-mentioned semiconductor region 111 are transferred to the semiconductor region 112, a positive voltage is applied to the gate 142 to make the potential of the semiconductor region 112 deeper than the potential of the semiconductor region 111. Therefore, it is possible to perform complete charge transfer, transferring all the charges accumulated in the photoelectric conversion portion 101 to the second charge holding portion 102.

[0130] The gate 142 in the figure can be formed of, for example, polysilicon, and can be arranged adjacent to the semiconductor substrate 110 via a gate oxide film. In addition, a sidewall insulating film 149 can be configured on the side of the gate 142. The sidewall insulating film 149 is also called a sidewall, and is an insulating film formed in a shape that is buried in the corner sandwiched between the gate 142 and the semiconductor substrate 110. The sidewall insulating film 149 is an insulating film that serves as a mask during the ion implantation of impurities. An n-type semiconductor region that becomes a shallow drain region is formed in the semiconductor substrate 110, the gate 142 and the sidewall insulating film 149 are formed, and then ion implantation is performed to form an n-type semiconductor region that becomes a deep drain region. Therefore, a lightly doped drain (LDD) and the like can be formed in the semiconductor substrate 110.

[0131] As shown in the figure, the sidewall insulating film 149 includes a front surface having a curved cross-section. For example, the sidewall insulating film 149 can be formed of silicon oxide (SiO2) and can be formed by etching back. Specifically, the sidewall insulating film 149 can be formed by forming a SiO2 film to cover the gate 142 and performing anisotropic etching by dry etching to attach the SiO2 to the side of the gate 142 and remove the SiO2 in other portions. Here, a silicon nitride (SiN) film can be arranged as a barrier layer for dry etching.

[0132] In addition, a light-shielding wall 172 and a light-shielding wall 173 are arranged in the semiconductor substrate 110. These light-shielding walls 172 and 173 shield the second charge holding portion 102 from light and separate the photoelectric conversion portion 101 and the second charge holding portion 102 from each other. The light-shielding walls 172 and 173 can be formed by arranging a metal film 171 in a groove formed in the semiconductor substrate 110. As described above, the light-shielding wall 172 is formed in a shape that penetrates the semiconductor substrate 110 from the rear surface to the front surface of the semiconductor substrate 110. On the other hand, the light-shielding wall 173 is formed in a shape in which a portion of the light-shielding wall 173 does not penetrate the semiconductor substrate 110 from the rear surface to the front surface of the semiconductor substrate 110, and an opening portion 174 is formed at the end of the light-shielding wall 173. For example, the metal film 171 can be formed of tungsten (W), aluminum (Al), and copper (Cu).

[0133] Furthermore, a fixed charge film and an insulating film may be disposed between the metal film 171 and the trench of the semiconductor substrate 110. The fixed charge film is formed of a high-dielectric material having a negative fixed charge. The presence of the fixed charge film can reduce the impact of trap levels formed near the interface with the semiconductor substrate 110. For example, a hafnium oxide film can be used as the fixed charge film. Furthermore, the insulating film is a film that insulates the metal film 171. For example, a SiO2 film can be used as the insulating film.

[0134] Furthermore, the dummy gate 131 shown in FIG3 is arranged on the front surface side of the semiconductor substrate 110. The dummy gate 131 can be arranged near the opening 174 of the light-shielding wall 173 and between the photoelectric conversion unit 101 and the second charge retention unit 102. Furthermore, the dummy gate 131 can be arranged near the boundary of the photoelectric conversion unit 101. A sidewall insulating film 132 can be arranged at the dummy gate 131. The dummy gate 131 and the sidewall insulating film 132 can be formed from the same materials as the gate 142 and the sidewall insulating film 149, respectively, and can be formed simultaneously with the gate 142 and the sidewall insulating film 149. Furthermore, the dummy gate 131 and the sidewall insulating film 132 shown in the figure constitute the reflective portion forming member 130. The bottom surface of the reflective portion forming member 130 is arranged adjacent to the front surface of the semiconductor substrate 110, and a reflective portion 301, described later, is formed on this surface side of the semiconductor substrate 110. The dummy gate 131 can also be formed from materials other than the aforementioned polysilicon, such as SiN.

[0135] The wiring area 160 is an area arranged on the front surface side of the semiconductor substrate 110 and is composed of a wiring layer 161 and an insulating layer 169. The wiring layer 161 is a wiring through which the electrical signals of the elements of the pixel 100 are transmitted. For example, the wiring layer 161 can be formed of Cu. The insulating layer 169 insulates the wiring layer 161. For example, the insulating layer 169 can be formed of SiO2. The insulating layer 169 and the wiring layer 161 can be formed into a multilayer structure. The figure shows an example in which the insulating layer 169 and the wiring layer 161 are formed into two layers. The wiring layers 161 in different layers can be connected by via plugs (not shown). At the same time, the gate 142 of the above-mentioned MOS transistor 105 is connected to the wiring layer 161 through a contact plug 162. For example, the contact plug 162 can be formed of W or Cu.

[0136] The light shielding film 150 is arranged in the wiring area 160. The light shielding film 150 is arranged on the front surface side of the semiconductor substrate 110 and shields reflected light from the wiring layer 161. When incident light passing through the semiconductor substrate 110 is reflected by the wiring layer 161 and becomes reflected light, and is incident on the second charge retention unit 102, photoelectric conversion occurs and noise is caused in the image signal. The light shielding film 150 prevents the reflected light from being incident on the second charge retention unit 102. For example, the light shielding film 150 can be formed of metals such as Al, silver (Ag), gold (Au), Cu, platinum (Pt), molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), W, and iron (Fe). In addition, the light shielding film 150 can be formed of semiconductors such as Si, germanium (Ge), and tellurium (Te), as well as alloys of these metals. In addition, for example, the light shielding film 150 can be formed to a thickness of 200 nm. The light shielding film 150 in the drawing is arranged adjacent to the semiconductor substrate 110 , the gate electrode 142 , and the sidewall insulating film 149 via an insulating film (insulating film 122 to be described later).

[0137] Furthermore, the light shielding film 150 can extend into the region between the photoelectric conversion portion 101 and the second charge holding portion 102. In the figure, the light shielding film 150 is also arranged adjacent to the region above the side surface of the reflective portion forming member 130. The portion of the light shielding film 150 adjacent to the side surface of the reflective portion forming member 130 forms a reflective portion 301. The reflective portion 301 reflects incident light that has passed through the semiconductor substrate 110 toward the semiconductor region 111. The provision of the reflective portion 301 can reduce the incidence of transmitted light on the second charge holding portion 102. Furthermore, since the reflective portion 301 is formed adjacent to the side surface of the reflective portion forming member 130, the shape of the side surface of the reflective portion forming member 130 is transferred to the reflective portion 301. The reflective portion 301 in the figure is formed to have a curved cross-section and is formed in a shape such that a concave mirror extends along the opening 174 of the light shielding wall 173. Furthermore, as shown in the figure, the light shielding film 150 can have an opening 311 arranged near the semiconductor region 111 forming the photoelectric conversion portion 101.

[0138] Furthermore, in the wiring region 160 shown in the figure, a contact wall 167 and a cover 168 may be arranged. The contact wall 167 is formed in a wall shape, with its bottom portion abutting the light shielding film 150 and surrounding the opening 311 of the light shielding film 150. It also reflects transmitted light. The contact wall 167 can be formed from the same material as the light shielding film 150 described above. If the contact wall 167 is formed from the same material as the contact plug 162, such as W or Cu, it can be formed simultaneously with the contact plug 162 to simplify the manufacturing process of the imaging element 1. In this case, a Ti film can be arranged as the underlying metal to improve adhesion. Furthermore, the cover 168 is formed in a flat plate shape and reflects transmitted light. The cover 168 is arranged adjacent to the end of the contact wall 167 to seal the end of the contact wall 167. For example, the cover 168 can be formed from Cu and formed simultaneously with the wiring layer 161.

[0139] Contact wall 167 and cover 168 prevent transmitted light from diffusing into wiring region 160. Furthermore, contact wall 167 and cover 168 reflect transmitted light toward semiconductor region 111, forming photoelectric conversion unit 101, thereby contributing to further photoelectric conversion. This improves the efficiency of pixel 100. Furthermore, since contact wall 167 and cover 168 are positioned farther from the interface with semiconductor substrate 110 than light shielding film 150, the formation of trap levels caused by diffusion of the metal material forming them can be reduced.

[0140] Light-shielding film 170 is a film arranged on the rear side of semiconductor substrate 110 and shields incident light. Light-shielding film 170 shields the region other than photoelectric conversion unit 101 from incident light. Openings 175 are arranged in light-shielding film 170 near semiconductor region 111, where photoelectric conversion unit 101 is formed. Incident light passes through openings 175 and reaches photoelectric conversion unit 101. Light-shielding film 170 can be formed from the aforementioned metal film 171. That is, light-shielding film 170 can be formed simultaneously with light-shielding walls 172 and 173.

[0141] The insulating film 180 is a film that insulates the rear surface of the semiconductor substrate 110. The insulating film 180 also flattens the rear surface of the semiconductor substrate 110 on which the light shielding film 170 and the like are formed. Details of the structure of the insulating film 180 will be described later.

[0142] The color filter 191 is a filter that transmits incident light having a predetermined wavelength among incident light. As the color filter 191, a color filter 191 that transmits any one of red light, green light, and blue light can be arranged for each pixel 100. In addition to the color filter 191 of the primary color system, a color filter 191 of the complementary color system that transmits any one of cyan light, yellow light, and magenta light can also be used. In addition, a color filter 191 that transmits infrared light can also be used.

[0143] The on-chip lens 195 is a lens that collects incident light. The on-chip lens 195 is formed in a hemispherical shape and arranged for each pixel 100, and collects the incident light on the semiconductor region 111 of the photoelectric conversion unit 101. For example, the on-chip lens 195 can be formed of an organic material such as a styrene resin, an acrylic resin, a styrene-acrylic resin, or a silicone resin. In addition, the on-chip lens 195 can also be formed of an inorganic material such as SiN or silicon oxynitride (SiON). In addition, the on-chip lens 195 can also be formed by dispersing titanium oxide (TiO) particles in the above-mentioned organic material or polyimide resin.

[0144] The support substrate 196 is a substrate disposed adjacent to the wiring region 160. The support substrate 196 is a substrate disposed mainly to increase the strength of the semiconductor substrate 110 during the manufacturing process of the image pickup element 1.

[0145] [Reflection of transmitted light]

[0146] FIG5 is a diagram showing an example of reflection of transmitted light according to the first embodiment of the present invention. This diagram is an enlarged cross-sectional view of a portion of the semiconductor substrate 110, used to illustrate the effect of the reflective portion 301. In the diagram, the insulating film 180 is composed of a first insulating film 181 and a second insulating film 182. The first insulating film 181 is an insulating film arranged between the metal film 171 and the semiconductor substrate 110, and is formed by stacking the above-mentioned fixed charge film and an insulator such as SiO2. In addition, the second insulating film 182 is a film that is formed after the metal film 171 is arranged and insulates and flattens the metal film 171. In addition, the dummy gate 131 is arranged on the front surface of the semiconductor substrate 110 via the gate insulating film 121. In addition, the insulating film 122 is arranged below the light shielding film 150. For example, the insulating film 122 can be formed of SiN.

[0147] In the figure, A is a diagram showing an example of a case including a reflective portion 301. In the figure, the arrow represents incident light. The incident light that passes through the semiconductor substrate 110 and reaches the vicinity of the opening portion 174 of the light-shielding wall 173 is reflected by the reflective portion 301 to the side of the semiconductor region 111. In addition, due to the concave mirror shape of the reflective portion 301, the transmitted light can be concentrated on the semiconductor region 111. Therefore, it becomes possible to photoelectrically convert the transmitted light, and thus the sensitivity of the pixel 100 can be improved. In addition, when the transmitted light is photoelectrically converted and absorbed in the semiconductor region 111, the reflected light emitted from the pixel 100 is reduced. The re-incidence of the reflected light from the pixel 100 on the adjacent pixel 100 is reduced, so that flare or color mixing can be reduced.

[0148] In addition, the reflecting portion 301 can reduce the incident light on the semiconductor region 112 of the second charge holding portion 102. As described above, when the incident light leaks from the photoelectric conversion portion 101 to the second charge holding portion 102 and causes photoelectric conversion, noise is generated. The light leakage to the charge holding portion in this global shutter type imaging element is managed as parasitic sensitivity (PLS). The PLS can be improved by configuring the reflecting portion 301. In addition, since the reflecting portion forming member 130 is arranged between the light shielding film 150 forming the reflecting portion 301 and the semiconductor substrate 110, the light shielding film 150 is arranged at a position away from the semiconductor substrate 110 near the photoelectric conversion portion 101. Therefore, the influence of the light shielding film 150 on the semiconductor substrate 110 can be reduced.

[0149] Meanwhile, FIG. B illustrates an example in which the reflective portion forming member 130 and the reflective portion 301 are omitted and a light shielding film 501 is disposed in place of the light shielding film 150. The light shielding film 501 is also disposed on the front surface of the semiconductor substrate 110 near the photoelectric conversion portion 101 and shields transmitted light. The light shielding film 501 prevents transmitted light from entering the wiring region 160. However, as indicated by the arrow in FIG. B, transmitted light reaching the vicinity of the opening 174 is reflected by the light shielding film 501 toward the second charge retention portion 102. This increases noise in the image signal and increases the PLS. Furthermore, since the light shielding film 501 is disposed adjacent to the semiconductor substrate 110 near the photoelectric conversion portion 101, its effect on the semiconductor substrate 110 is increased. Specifically, trap levels on the front surface of the semiconductor substrate 110 are increased, thereby increasing dark current. Dark current is a current based on charge generated independently of incident light and represents a noise component in the image signal. Dark current is caused by discharge of charges from trap levels in the semiconductor substrate 110 or the like.

[0150] [Method for manufacturing an imaging element]

[0151] Figure 6 1 to 11 are diagrams illustrating an example of a method for manufacturing an image pickup element according to the first embodiment of the present invention. Figure 6 11 to 11 are diagrams showing the manufacturing process of the imaging element 1. First, a p-type well region and an n-type semiconductor region 111 and an n-type semiconductor region 112 are formed in the semiconductor substrate 110. This can be done by, for example, ion implantation. Next, a gate insulating film 121 is formed on the front surface of the semiconductor substrate 110. This can be done by thermal oxidation of the semiconductor substrate 110. Next, a gate 142 and a dummy gate 131 are formed. This can be done by configuring a polysilicon film as a material such as the gate 142 and etching the polysilicon film ( Figure 6 A).

[0152] Next, a SiO2 film 401 ( Figure 6 B). This can be done, for example, by chemical vapor deposition (CVD). Furthermore, a SiN film can be disposed below the film 401 as an etching barrier. Next, the film 401 is etched. This etching can be done by anisotropic etching. Thus, the sidewall insulating film 149 and the sidewall insulating film 132 ( Figure 6 Next, an insulating film 122 is disposed on the front surface of the semiconductor substrate 110. This can be performed, for example, by CVD ( Figure 6 Meanwhile, the manufacturing process of the dummy gate 131 and the sidewall insulating film 132 corresponds to the reflecting portion forming member arranging process.

[0153] Next, a metal film 403, serving as the material for the light shielding film 150, is deposited on the front surface of the semiconductor substrate 110. This can be performed, for example, by CVD or sputtering ( FIG. 7E ). Next, the metal film 403 is etched to form the opening 311. In this case, an opening 405 is formed in the region of the light shielding film 150 where the contact plug 162 is disposed near the gate 142. Thus, the light shielding film 150 can be formed, and the reflective portion 301 can be formed ( FIG. 7F ). This process corresponds to the reflective portion formation process.

[0154] Next, an insulating film 406 of the material used as the insulating layer 169 of the wiring region 160 is arranged. For example, this can be done by CVD (G in FIG. 7 ). Next, an opening 407 is formed in the region of the film 406 where the contact plug 162 and the contact wall portion 167 are to be arranged (H in FIG. 8 ). Next, a metal film 408 of the material used as the contact plug 162 is arranged. In this case, the metal film 408 is also arranged in the opening 407. A stacked film of Ti and W can be considered as the metal film 408. The metal film 408 can be arranged by forming a Ti film by sputtering and a W film by CVD so as to embed the Ti film and the W film in the opening 407. For example, the Ti film can be formed to a thickness of 30 nm (I in FIG. 8 ). Next, the metal film 408 on the front surface is removed to form the contact plug 162 and the contact wall portion 167. For example, this can be done by grinding the metal film 408 using chemical mechanical polishing (CMP) (J in FIG. 8 ).

[0155] Next, an insulating film 409 (K in FIG. 9 ) serving as the material for the insulating layer 169 is arranged. Next, the film 409 is etched to form an opening 410 (L in FIG. 9 ) in the region where the wiring layer 161 and the cover portion 168 are to be formed. Next, a metal film 411 serving as the material for the wiring layer 161 is arranged. The metal film 411 can be formed of Cu by metal electroplating (M in FIG. 9 ). A barrier layer and a seed layer for metal electroplating can also be arranged under the metal film 411. Next, the metal film 411 is polished by CMP or the like to form the wiring layer 161 and the cover portion 168 (N in FIG. 10 ). Next, an insulating film is arranged on the front surface of the wiring layer 161 and the cover portion 168 to form the insulating layer 169 (O in FIG. 10 ). The arrangement of the wiring layer 161 and the insulating film can be repeated multiple times as needed to form the wiring area 160. Then, a supporting substrate 196 (not shown) is attached to the wiring area 160.

[0156] Next, the semiconductor substrate 110 is turned upside down and thinned. Next, the area of the semiconductor substrate where the light shielding wall 173 is to be arranged is etched to form an opening 412 (P in Figure 10). Next, the first insulating film 181 is arranged (Q in Figure 11). Next, a metal film 413, which serves as the material of the light shielding film 170 and the light shielding wall 173, is arranged on the back side of the semiconductor substrate 110. In this case, the metal film 413 is embedded in the opening 412 (R in Figure 11). Thus, the light shielding wall 173 can be formed. Next, the metal film 413 is etched to form an opening 175 (S in Figure 11). Thus, the metal film 171 can be formed and the light shielding film 170 can be formed.

[0157] Then, the second insulating film 182, the color filter 191, and the on-chip lens 195 can be arranged to manufacture the image pickup element 1. The shape of the sidewall insulating film 132 can be used to form the reflecting portion 301 having a concave mirror shape.

[0158] As described above, in the image sensor 1 according to the first embodiment of the present invention, the reflection portion 301 is arranged to reflect the light transmitted through the semiconductor substrate 110. Therefore, leakage of the transmitted light to the second charge holding portion 102 is reduced. Consequently, it is possible to reduce the mixing of noise into the image signal and alleviate degradation of picture quality.

[0159] <2. Second Implementation Plan>

[0160] In the image sensor 1 of the first embodiment, the reflecting portion 301 is arranged near the opening 174 of the light shielding wall 173. On the other hand, the image sensor 1 of the second embodiment of the present invention differs from the first embodiment in that the reflecting portion is arranged offset to a position closer to the second charge holding portion 102.

[0161] [Cross-sectional structure of a pixel]

[0162] FIG12 is a cross-sectional view showing an example configuration of a pixel according to a second embodiment of the present invention. Similar to FIG4 , this figure shows an example configuration of a pixel 100. The imaging element 1 shown in the figure differs from the imaging element 1 shown in FIG4 in that a dummy gate 131 is positioned adjacent to the second charge holding portion 102 and a light shielding film 151 is provided in place of the light shielding film 150.

[0163] In the figure, the dummy gate 131 is positioned near the semiconductor region 112 forming the second charge holding portion 102 of the semiconductor substrate 110, and the sidewall insulating film 132 is positioned near the sidewall insulating film 149 of the gate 142. Therefore, the end of the reflecting portion 302 in the figure is positioned near the semiconductor region 112 forming the second charge holding portion 102. The curved portion of the reflecting portion 302 is positioned directly below the opening 174 of the light-shielding wall 173, thereby reflecting transmitted light at a greater incident angle toward the photoelectric conversion portion 101 than the reflecting portion 301 shown in FIG. 4 .

[0164] Since the configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the first embodiment of the present invention, a description thereof will be omitted.

[0165] As described above, the image sensor 1 according to the second embodiment of the present invention reflects transmitted light due to the reflecting portion 302, which is arranged so as to be offset toward the second charge holding portion 102. Therefore, of the transmitted light reaching the opening 174 of the light-shielding wall 173, the transmitted light having a wider range of incident angles can be reflected, thereby further reducing the leakage of the transmitted light into the second charge holding portion 102.

[0166] <3. Third Implementation Plan>

[0167] In the image pickup element 1 of the first embodiment, the sidewall insulating film 132 is provided at the dummy gate 131. On the other hand, the image pickup element 1 of the third embodiment of the present invention is different from the first embodiment in that the sidewall insulating film is omitted.

[0168] [Cross-sectional structure of a pixel]

[0169] FIG13 is a cross-sectional view showing an example configuration of a pixel according to a third embodiment of the present invention. Similar to FIG4 , this figure shows an example configuration of a pixel 100. The imaging element 1 shown in the figure differs from the imaging element 1 shown in FIG4 in that a dummy gate 133 and a light shielding film 152 are provided instead of the dummy gate 131 and the light shielding film 150, and the sidewall insulating film 132 is omitted.

[0170] The dummy gate 133 in the figure can be formed to have a side surface with a tapered cross-sectional shape. This can be achieved by arranging a material film as the material of the dummy gate 133 on the front surface side of the semiconductor substrate 110 and etching back. In this case, it is desirable to use SiO2 or the like suitable for etching back to form the dummy gate 133. The reflective portion 303 can be formed by arranging a light shielding film 152 on the side surface of the dummy gate 133. As shown in the figure, the reflective portion 303 is formed by the light shielding film 152 arranged obliquely relative to the semiconductor substrate 110. At the same time, in the imaging element 1 in the figure, the dummy gate 133 corresponds to the reflective portion forming member.

[0171] Since the configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the first embodiment of the present invention, a description thereof will be omitted.

[0172] As described above, the sidewall insulating film of the reflective portion forming member can be omitted in the image sensor 1 according to the third embodiment of the present invention.

[0173] <4. Fourth Implementation Plan>

[0174] In the imaging element 1 of the first embodiment, the reflecting portion 301 is arranged adjacent to the opening 174 of the light-shielding wall 173. On the other hand, the imaging element 1 of the fourth embodiment of the present invention differs from the first embodiment in that the reflecting portion is arranged on the periphery of the semiconductor region 111 of the photoelectric conversion portion 101.

[0175] [Pixel structure]

[0176] FIG14 is a diagram illustrating an example configuration of a pixel according to a fourth embodiment of the present invention. Similar to FIG3 , this diagram is a plan view illustrating an example configuration of pixel 100. Pixel 100 in the figure differs from imaging element 1 illustrated in FIG3 in that a dummy gate 134 is provided in place of dummy gate 131.

[0177] The dummy gate 134 is formed in a square shape having an opening 321 arranged at the center thereof, which is a shape along the outer periphery of the semiconductor region 111 of the photoelectric conversion unit 101 .

[0178] [Cross-sectional structure of a pixel]

[0179] FIG15 is a cross-sectional view showing an example configuration of a pixel according to a fourth embodiment of the present invention. Similar to FIG4 , this figure shows an example configuration of a pixel 100. The pixel 100 shown in the figure differs from the imaging element 1 shown in FIG4 in that the aforementioned dummy gate 134 is provided in place of the dummy gate 131, and a light shielding film 153 is provided in place of the light shielding film 150.

[0180] A sidewall insulating film 135 is arranged on the dummy gate 134 in the figure. The sidewall insulating film 135 is formed on the entire periphery of the side surface outside the dummy gate 134. The dummy gate 134 and the sidewall insulating film 135 constitute the reflective portion forming member 130. In addition, the light shielding film 153 in the figure extends at a position on the entire periphery of the side surface of the reflective portion forming member 130. Therefore, the reflective portion 304 in the figure is formed to have a curved cross-section and is formed in a "mouth" shape along the outer periphery of the semiconductor region 111 of the photoelectric conversion portion 101. The concave mirror-shaped reflective portion 304 is arranged on the entire periphery of the outer portion of the semiconductor region 111 of the photoelectric conversion portion 101, thereby concentrating more transmitted light on the semiconductor region 111 of the photoelectric conversion portion 101.

[0181] Meanwhile, the configuration of the reflective portion forming member 130 and the reflective portion 304 is not limited to this example. For example, when the semiconductor region 111 of the photoelectric conversion portion 101 is formed in a cylindrical shape, the reflective portion forming member 130 and the reflective portion 304 may be formed in a cylindrical shape.

[0182] Since the configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the first embodiment of the present invention, a description thereof will be omitted.

[0183] As described above, the image sensor 1 according to the fourth embodiment of the present invention includes the reflective portion 304 formed in a square shape along the periphery of the semiconductor region 111 of the photoelectric conversion portion 101. Therefore, the sensitivity of the pixel 100 can be further improved.

[0184] <5. Fifth Implementation Plan>

[0185] The imaging element 1 of the fourth embodiment includes a square-shaped reflector-forming member 130. On the other hand, the imaging element 1 of the fifth embodiment of the present invention differs from the fourth embodiment in that it includes a rectangular reflector-forming member 130 covering the semiconductor region 111 of the photoelectric conversion section 101.

[0186] [Pixel structure]

[0187] FIG16 is a diagram illustrating an example configuration of a pixel according to a fifth embodiment of the present invention. Similar to FIG14 , this diagram is a plan view illustrating an example configuration of pixel 100. The imaging element 1 in the figure differs from the imaging element 1 illustrated in FIG14 in that a dummy gate 136 is provided in place of dummy gate 134.

[0188] The dummy gate 136 is formed in a rectangular shape covering the semiconductor region 111 of the photoelectric conversion unit 101 .

[0189] [Cross-sectional structure of a pixel]

[0190] FIG17 is a cross-sectional view showing an example configuration of a pixel according to a fifth embodiment of the present invention. Similar to FIG15 , this figure shows an example configuration of a pixel 100. Pixel 100 shown in the figure differs from the imaging element 1 shown in FIG15 in that the aforementioned dummy gate 136 is provided in place of dummy gate 134, a light shielding film 154 is provided in place of light shielding film 153, and contact wall portion 167 and cover portion 168 are omitted.

[0191] As with the dummy gate 134 described above, the dummy gate 136 in the figure is provided with a sidewall insulating film 135. The sidewall insulating film 135 is formed along the entire periphery of the outer side surfaces of the dummy gate 136. The dummy gate 136 and the sidewall insulating film 135 constitute the reflective portion forming member 130. Furthermore, the light shielding film 154 in the figure extends above the upper surface and side surfaces of the reflective portion forming member 130, facing the bottom surface of the light shielding film 154. In other words, the light shielding film 154 is formed in a shape that covers the front surface side of the semiconductor substrate 110 where the semiconductor region 111 of the photoelectric conversion unit 101 is arranged. Since light is reflected by the light shielding film 154, the vicinity of the photoelectric conversion unit 101 of the semiconductor substrate 110 is shielded from light. The contact wall portion 167 and the cover portion 168 of the wiring region 160 can be omitted.

[0192] Furthermore, the light shielding film 154 is formed from a metal film that is continuous from the end of the reflective portion 305 to the front surface of the dummy gate 136. Therefore, variations in the amount of reflected light at the end of the reflective portion 305 of the light shielding film 154, and elsewhere, can be reduced. On the other hand, in the case of including the contact wall 167 and the cover 168 described in FIG15 , the direction of reflected light rapidly changes at the corners of the contact wall 167 and the cover 168, resulting in uneven reflected light. Furthermore, the light shielding film 154 is separated from the front surface of the semiconductor substrate 110 by the dummy gate 136, thereby reducing the effect of the light shielding film 154 on the semiconductor substrate 110. Furthermore, the reflective portion 305 shown in the figure has a cross-section having the same curved shape as the reflective portion 304 described above, and is formed in a square shape along the periphery of the semiconductor region 111 of the photoelectric converter 101. Consequently, it is expected that the amount of reflected light focused on the semiconductor region 111 of the photoelectric converter 101 is increased.

[0193] Meanwhile, the configuration of the reflective portion forming member 130 and the reflective portion 305 is not limited to this example. For example, when the semiconductor region 111 of the photoelectric conversion portion 101 is formed in a cylindrical shape, the reflective portion forming member 130 and the reflective portion 305 can be formed in the same cylindrical shape.

[0194] The configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the fourth embodiment of the present invention, and therefore a description thereof will be omitted.

[0195] As described above, in the image pickup element 1 according to the fifth embodiment of the present invention, the light shielding film 154 is formed in a shape covering the semiconductor substrate 110 near the semiconductor region 111 of the photoelectric conversion portion 101 , and thus the configuration of the image pickup element 1 can be simplified.

[0196] <6. Sixth Implementation Plan>

[0197] The imaging element 1 of the fifth embodiment includes a rectangular dummy gate 136 covering the semiconductor region 111 of the photoelectric converter 101. The imaging element 1 of the sixth embodiment differs from the fifth embodiment in that a bias voltage is applied to the dummy gate 136.

[0198] [Pixel cross-sectional configuration]

[0199] FIG18 is a cross-sectional view showing an example of the configuration of a pixel according to a sixth embodiment of the present invention. Similar to FIG17 , this figure shows an example of the configuration of a pixel 100. The pixel 100 shown in the figure differs from the imaging element 1 shown in FIG17 in that the pixel 100 shown in the figure includes a light shielding film 155 in place of the light shielding film 154, and further includes a contact plug 164 and a wiring layer 163 connected to the dummy gate 136.

[0200] The dummy gate 136 is connected to the wiring layer 163 via a contact plug 164. As with the gate 142, a predetermined voltage signal or the like can be applied to the dummy gate 136. When a negative bias voltage is applied to the dummy gate 136 via the wiring layer 163 or the like, holes can be concentrated on the front surface side of the semiconductor substrate 110, thereby forming a hole accumulation region on the surface of the semiconductor substrate 110 where holes accumulate. The holes in the hole accumulation region can pin trap levels at the front interface of the semiconductor substrate 110, thereby reducing dark current caused by the trap levels. Simultaneously, the light shielding film 155 is formed by forming an opening in the light shielding film 154 for arranging the contact plug 164.

[0201] The configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the fifth embodiment of the present invention, and therefore a description thereof will be omitted.

[0202] As described above, in the image sensor 1 according to the sixth embodiment of the present invention, a bias voltage can be applied to the dummy gate 136 having a shape covering the semiconductor substrate 110 near the semiconductor region 111 of the photoelectric conversion unit 101. Therefore, dark current can be reduced.

[0203] <7. Seventh Implementation Plan>

[0204] The image sensor 1 of the first embodiment includes the dummy gate 131. On the other hand, the image sensor 1 of the seventh embodiment of the present invention is different from the first embodiment in that the dummy gate 131 is omitted.

[0205] [Cross-sectional structure of a pixel]

[0206] FIG19 is a cross-sectional view illustrating an example configuration of a pixel according to a seventh embodiment of the present invention. Similar to FIG4 , this figure illustrates an example configuration of pixel 100. The imaging element 1 illustrated in the figure differs from the imaging element 1 illustrated in FIG4 in the following respects: dummy gate 131, sidewall insulating film 132, contact wall portion 167, and cover portion 168 are omitted. Furthermore, gate 142 and sidewall insulating film 149 are positioned near opening 174 of light-shielding wall 173. Furthermore, light-shielding film 156 is positioned in place of light-shielding film 150.

[0207] The gate 142 is positioned between the semiconductor region 111 of the photoelectric conversion unit 101 and the semiconductor region 112 of the second charge retention unit 102, and is located near the opening 174 of the light-shielding wall 173. When a voltage is applied to the gate 142 via the contact plug 162, a channel is formed in the well region between the semiconductor region 111 and the semiconductor region 112, causing the region between the photoelectric conversion unit 101 and the second charge retention unit 102 to enter a conductive state. Consequently, charge accumulated in the photoelectric conversion unit 101 is transferred to the second charge retention unit 102. Sidewall insulating films 149 are positioned on the sides of the gate 142, and the light-shielding film 156 extends to the sides of the sidewall insulating films 149. Consequently, the reflective portion 306 is formed. The gate 142 and sidewall insulating films 149 in the figure constitute the reflective portion forming member 130.

[0208] The configuration of the image sensor 1 is not limited to this example. For example, the contact plug 162 may be formed into a wall shape surrounding the semiconductor region 111 like the contact wall portion 167 and the cover portion 168 .

[0209] Since the configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the first embodiment of the present invention, a description thereof will be omitted.

[0210] As described above, in the image pickup element 1 according to the seventh embodiment of the present invention, the dummy gate 131 and the sidewall insulating film 132 can be omitted, so that the configuration of the image pickup element 1 can be simplified.

[0211] <8. Eighth Implementation Plan>

[0212] The image sensor 1 of the first embodiment includes the dummy gate 131. On the other hand, the image sensor 1 of the eighth embodiment of the present invention is different from the first embodiment in that a dummy gate is further stacked.

[0213] [Cross-sectional structure of a pixel]

[0214] FIG20 is a cross-sectional view showing an example configuration of a pixel according to an eighth embodiment of the present invention. Similar to FIG4 , this figure shows an example configuration of a pixel 100. The imaging element 1 shown in the figure differs from the imaging element 1 shown in FIG4 in that it further includes a dummy gate 137 and a light shielding film 157 in place of the light shielding film 150.

[0215] The dummy gate 137 in the figure is formed so that a portion thereof is stacked on the dummy gate 131. Specifically, the dummy gate 137 is arranged above the front surface of the semiconductor substrate 110 and a portion of the sidewall insulating film 132 and the dummy gate 131 near the second charge holding portion 102. The dummy gate 137 is arranged so as to be stacked on the sidewall insulating film 132, so that the shape of the sidewall insulating film 132 is transferred to the dummy gate 137, and the dummy gate 137 is formed to have a curved cross-section. A light shielding film 157 is arranged on the side of the dummy gate 137 to form the reflective portion 307. The reflective portion forming member 130 in the figure is composed of the dummy gate 137, the dummy gate 131, and the sidewall insulating film 132.

[0216] The dummy gate 131 and the dummy gate 137 are stacked as multiple films to form the reflective portion forming member 130. Therefore, the reflective portion forming member 130 can be formed thicker and have a side surface with a large curvature. Compared to the reflective portion 301 in Figure 4, by forming the reflective portion 307 on the side of the reflective portion forming member 130, the size of the reflective portion 307 can be increased. Therefore, more transmitted light can be reflected. In addition, the edge of the reflective portion 307 is formed on the front surface side of the dummy gate 137. Since the reflective portion 307 is formed at a position separated from the front surface of the semiconductor substrate 110, the area on the surface of the semiconductor substrate 110 used to form the reflective portion can be reduced. Specifically, the gate 142 and the sidewall insulating film 149 can extend to the area in contact with the sidewall insulating film of the dummy gate 137. Therefore, a wide configuration can be achieved in which the gate 142 is widened to cover the semiconductor region 112 of the second charge retention portion.

[0217] Meanwhile, any one of the dummy gate 131 and the dummy gate 137 may be formed simultaneously with the gate 142 .

[0218] Since the configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the first embodiment of the present invention, the description thereof will be omitted.

[0219] As described above, in the imaging element 1 according to the eighth embodiment of the present invention, the reflective portion 307 is formed on the side surface of the reflective portion forming member 130 formed by stacking a plurality of dummy gate electrodes. Therefore, the size of the reflective portion 307 can be increased, thereby reflecting more transmitted light toward the semiconductor region 111 of the photoelectric conversion portion 101. Consequently, the sensitivity of the pixel 100 can be further improved.

[0220] <9. Ninth Implementation Plan>

[0221] The imaging element 1 of the eighth embodiment includes the gate 142 and the dummy gate 137. On the other hand, the imaging element 1 of the ninth embodiment differs from the eighth embodiment in that it includes a gate obtained by connecting the gate 142 and the dummy gate 137.

[0222] [Cross-sectional structure of a pixel]

[0223] FIG21 is a cross-sectional view showing an example configuration of a pixel according to a ninth embodiment of the present invention. Similar to FIG20 , this figure shows an example configuration of a pixel 100. The imaging element 1 shown in the figure differs from the imaging element 1 shown in FIG20 in that it includes a gate electrode 148 in place of the gate electrode 142 and the dummy gate electrode 137.

[0224] The gate 148 in the figure is formed in a shape that extends from the gate 142 in FIG. 20 to the portion of the dummy gate 131 near the second charge holding portion 102. Gate 148 can be used to adjust the potential of the second charge holding portion 102 and to form a channel between the semiconductor region 111 of the photoelectric conversion portion 101 and the semiconductor region 112 of the second charge holding portion 102. Applying a positive voltage to gate 148 can cause conduction in the region between the photoelectric conversion portion 101 and the second charge holding portion 102, increasing the potential of the semiconductor region 112 of the second charge holding portion 102. This allows full transfer of charge from the photoelectric conversion portion 101 to the second charge holding portion 102.

[0225] Furthermore, the reflective portion forming member 130 in the figure is formed by stacking a plurality of films, namely, a dummy gate 131 and a gate 148. As can be seen from the figure, the gate 148 is formed after the dummy gate 131 and the sidewall insulating film 132 are formed. The reflective portion 307 can be formed by arranging the light shielding film 157 shown in FIG. 20 on the formed reflective portion forming member 130.

[0226] The configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the eighth embodiment of the present invention, and therefore a description thereof will be omitted.

[0227] As described above, in the imaging element 1 according to the ninth embodiment of the present invention, the gate electrode 148 is arranged to extend to the region between the photoelectric conversion portion 101 and the second charge holding portion 102 to constitute the reflection portion forming member 130. Therefore, the configuration of the imaging element 1 can be simplified.

[0228] <10. Tenth Implementation Plan>

[0229] In the imaging element 1 of the ninth embodiment described above, the gate electrode 148 of the second charge holding portion 102 is stacked to form the reflecting portion forming member 130 after the dummy gate electrode 131 and the sidewall insulating film 132 are formed. On the other hand, the imaging element 1 of the tenth embodiment of the present invention differs from the ninth embodiment in that the dummy gate electrode and the sidewall insulating film are formed after the gate electrode of the second charge holding portion 102 is formed.

[0230] [Cross-sectional structure of a pixel]

[0231] FIG22 is a cross-sectional view showing an example configuration of a pixel according to a tenth embodiment of the present invention. Similar to FIG21 , this figure shows an example configuration of a pixel 100. Pixel 100 shown in the figure differs from image sensor 1 shown in FIG21 in that it includes a gate electrode 147, a dummy gate electrode 138, and a sidewall insulating film 139 in place of gate electrode 148, dummy gate electrode 131, and sidewall insulating film 132.

[0232] Similar to gate 148 in FIG. 21 , gate 147 in the figure is arranged in a region extending from the vicinity of photoelectric conversion portion 101 to second charge holding portion 102. A dummy gate 138 and a sidewall insulating film 139 are stacked on gate 147. Gate 147, dummy gate 138, and sidewall insulating film 139 constitute reflection portion forming member 130. Reflection portion 307 can be formed by arranging light shielding film 157 on reflection portion forming member 130. Since dummy gate 138 and sidewall insulating film 139 are arranged after gate 147, they can be arranged without affecting the shape of gate 147.

[0233] The configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the ninth embodiment of the present invention, and therefore a description thereof will be omitted.

[0234] As described above, in the image sensor 1 according to the tenth embodiment of the present invention, the dummy gate 138 and the sidewall insulating film 139 are stacked after the gate 147 is formed. Therefore, the dummy gate 138 can be arranged at any position between the photoelectric conversion portion 101 and the second charge holding portion 102, making it possible to easily adjust the position of the reflecting portion 307.

[0235] <11. Eleventh Implementation Plan>

[0236] The image sensor 1 of the first embodiment includes the second charge holding portion 102 and performs global shutter imaging.

[0237] [Pixel Circuit Structure]

[0238] Figure 23 is a diagram showing an example of a circuit structure of a pixel according to the eleventh embodiment of the present invention. Similar to Figure 2, this figure is a circuit diagram showing the configuration of pixel 100. The difference between the pixel 100 in the figure and the pixel 100 in Figure 2 is that the second charge holding unit 102 and the MOS transistor 104 and the MOS transistor 105 are omitted. The signal line 11 in the figure is composed of a signal line TR, a signal line RST, and a signal line SEL. The cathode of the photoelectric conversion unit 101 is connected to the source of the MOS transistor 106. The connections other than the above connections are the same as those of the pixel 100 described in Figure 2, and therefore their description is omitted.

[0239] The generation of the image signal of the pixel 100 in the figure can be performed as follows. First, the MOS transistor 106 and the MOS transistor 107 are turned on to reset the photoelectric conversion unit 101 and the first charge holding portion 103. After a predetermined exposure period, the MOS transistor 106 is turned on so that the charge generated in the photoelectric conversion unit 101 is transferred to the first charge holding portion 103 and held therein. Thereby, the MOS transistor 108 generates an image signal based on the charge held in the first charge holding portion 103. Next, by turning on the MOS transistor 109, the image signal generated by the MOS transistor 108 can be output to the signal line 12. The process from the start of exposure to the output of the image signal is sequentially performed for each row of the pixel array unit 10. In this case, the image signal of one frame can be output by shifting the image signal output timing for each row.

[0240] This imaging method is called a rolling shutter method. Because the exposure time for each row varies, frame distortion (focal plane distortion) occurs and image quality degrades compared to a global shutter method. However, the second charge retention unit 102 can be omitted, thus simplifying the structure of the pixel 100.

[0241] [Cross-sectional structure of a pixel]

[0242] FIG24 is a cross-sectional view showing an example configuration of a pixel according to an eleventh embodiment of the present invention. Similar to FIG4 , this figure shows an example configuration of a pixel 100. The pixel 100 shown in the figure differs from the imaging element 1 shown in FIG4 in that the second charge holding unit 102 is omitted, a light shielding film 179 is included in place of the light shielding walls 173 and 174 and the light shielding film 170, and a light shielding film 158 is included in place of the light shielding film 150.

[0243] Since the pixel 100 shown in the figure does not need to include the second charge retention unit 102, the proportion of the photoelectric conversion unit 101 in the pixel 100 can be increased. A light shielding film 179 is arranged between the semiconductor substrate 110 and the insulating film 180 at the boundary of the pixel 100 to shield incident light. A reflective unit-forming member 130 composed of a dummy gate 136 and a sidewall insulating film 135, as shown in FIG17 , can be arranged on the front surface side of the semiconductor substrate 110. A reflective unit 308 can be formed by arranging a light shielding film 158 adjacent to the dummy gate 136 and the sidewall insulating film 135. The reflective unit 308 is arranged near the boundary with the photoelectric conversion unit 101.

[0244] Meanwhile, the configuration of pixel 100 is not limited to this example. For example, similar to dummy gate 136 shown in FIG18 , a configuration in which contact plug 164 is arranged and a bias voltage is applied thereto may be employed. Alternatively, a configuration including dummy gate 134, contact wall portion 167, and cover portion 168 as shown in FIG15 may be employed.

[0245] Since the configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the first embodiment of the present invention, the description thereof will be omitted.

[0246] As described above, in the image pickup element 1 according to the eleventh embodiment of the present invention, the configuration of the pixel 100 can be simplified by omitting the second charge holding portion 102 .

[0247] <12. Twelfth Implementation Plan>

[0248] In the image sensor 1 of the eleventh embodiment described above, the reflection portion forming member 130 and the reflection portion 308 are arranged in all pixels 100. On the other hand, the image sensor 1 of the twelfth embodiment of the present invention is different from the eleventh embodiment described above in that the reflection portion forming member 130 and the reflection portion are arranged in the pixels 100 corresponding to incident light having a long wavelength.

[0249] [Cross-sectional structure of a pixel]

[0250] Figure 25FIG24 is a cross-sectional view showing an example of the configuration of a pixel according to a twelfth embodiment of the present invention. Similar to FIG24 , this figure shows an example of the configuration of a pixel. The imaging element 1 in the figure differs from the imaging element 1 in FIG24 in that, in addition to the pixel 100, the former includes a pixel 200.

[0251] Similar to the pixel 100 described in FIG24 , the pixel 100 in the figure includes a reflective portion forming member 130 and a reflective portion 309. Furthermore, a color filter 191 that transmits incident light having a long wavelength is arranged in the pixel 100 in the figure. Specifically, a color filter 191 that transmits red light and infrared light is arranged in the pixel 100 in the figure. This long-wavelength light reaches deep portions of the semiconductor substrate 110, increasing the amount of transmitted light. Therefore, by arranging the reflective portion 309, it is possible to prevent degradation of sensitivity, etc.

[0252] Meanwhile, the pixel 200 in the figure is provided with a color filter 191, through which incident light having a relatively short wavelength passes. Specifically, a color filter 191 is provided that transmits green light and blue light. This light is absorbed in a relatively shallow area of the semiconductor substrate 110. Therefore, the reflective portion can be omitted.

[0253] Meanwhile, the configuration of the pixel 100 is not limited to this example. For example, a configuration in which the contact plug 164 is arranged or a configuration including the dummy gate 134, the contact wall portion 167, and the cover portion 168 may also be used.

[0254] The configuration of the image pickup element 1 other than the above-described configuration is the same as that of the image pickup element 1 described in the eleventh embodiment of the present invention, and therefore a description thereof will be omitted.

[0255] As described above, by omitting the reflection portion forming member 130 and the reflection portion 309 of pixels corresponding to light having a relatively short wavelength in the image pickup element 1 according to the twelfth embodiment of the present invention, the configuration of the image pickup element 1 can be simplified.

[0256] Meanwhile, the shape of the dummy gate of the third embodiment of the present invention can be applied to other embodiments. Specifically, the shape of the dummy gate 133 described in FIG13 can be applied to the dummy gates of FIG15, FIG17, FIG18, FIG20, FIG21, FIG22, FIG24 and FIG25. Figure 25 of the pseudo gate.

[0257] <13. Camera Application Example>

[0258] The technology according to the present invention (the present technology) can be applied to various products. For example, the present technology can be implemented as an image element installed in an imaging device such as a camera.

[0259] FIG26 is a block diagram showing an example of a schematic configuration of a camera as an example of an imaging device to which the present technology can be applied. The camera 1000 in the figure includes a lens 1001, an imaging element 1002, an imaging control unit 1003, a lens drive 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.

[0260] A lens 1001 is an imaging lens of the camera 1000. The lens 1001 collects light from a subject and makes the collected light incident on an image pickup element 1002 to be described later to image the subject.

[0261] The imaging element 1002 is a semiconductor element that forms an image of light collected from a subject by the lens 1001. In response to the irradiation light, the imaging element 1002 generates an analog image signal, converts the analog image signal into a digital image signal, and outputs the digital image signal.

[0262] The imaging control unit 1003 controls imaging in the imaging element 1002. The imaging control unit 1003 controls the imaging element 1002 by generating a control signal and outputting the control signal to the imaging element 1002. Furthermore, based on the image signal output from the imaging element 1002, the imaging control unit 1003 can perform autofocus in the camera 1000. Here, autofocus is a system that detects the focal position of the lens 1001 and automatically adjusts the focal position. For autofocus, a method for detecting the phase difference of the image surface using phase difference pixels configured in the imaging element 100 can be used to detect the focal position (image surface phase difference autofocus). Alternatively, a method for detecting the position with the greatest contrast in the image as the focal position (contrast autofocus) can be applied. The imaging control unit 1003 adjusts the position of the lens 1001 using the lens drive unit 1004 based on the detected focal position and performs autofocus. The imaging control unit 1003 can be configured, for example, as a digital signal processor (DSP) provided with firmware.

[0263] The lens driving unit 1004 drives the lens 1001 according to 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 motor embedded therein.

[0264] The image processing unit 1005 processes the image signal generated by the image sensor 1002. For example, this processing corresponds to demosaicing for generating a color-omitted image signal from the image signal corresponding to red, green, and blue for each pixel, noise reduction for removing noise from the image signal, image signal encoding, etc. For example, the image processing unit 1005 can be configured as a microcomputer provided with firmware.

[0265] The operation input unit 1006 receives an operation input from a user of the camera 1000. For example, a button or a touch panel can be used as the operation input unit 1006. The operation input received by the operation input unit 1006 is transmitted to the imaging control unit 1003 and the image processing unit 1005. Then, processing in response to the input operation, for example, processing such as imaging a subject, is started.

[0266] The frame memory 1007 is a memory for storing frames as image signals corresponding to one screen. The frame memory 1007 is controlled by the image processing unit 1005 and holds frames during image processing.

[0267] 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.

[0268] 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 as the recording unit 1009.

[0269] The camera to which the present invention can be applied has been described above. This technology can be applied to the imaging element 1002 in the aforementioned components. Specifically, the imaging element 1 described in FIG. 1 can be applied to the imaging element 1002. By applying the imaging element 1 to the imaging element 1002, the effects of reflected light on pixels can be reduced, thereby preventing degradation in the image quality of images produced by the camera 1000. Furthermore, 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.

[0270] Meanwhile, although a camera has been described here as an example, the technology according to the present invention can be applied to, for example, monitoring equipment, etc., in addition to electronic devices such as cameras. Furthermore, in addition to electronic devices such as cameras, the present invention can also be applied to semiconductor devices in the form of semiconductor modules. Specifically, the technology according to the present invention can also be applied to a camera module, which is a semiconductor module in which the image sensor 1002 and the image capture control unit 1003 of FIG. 26 are packaged in a single package.

[0271] Finally, the description of each of the above embodiments is an example of the present invention and the present invention is not limited to the above embodiments. Therefore, it goes without saying that, in addition to the above embodiments, various modifications can be made according to design, etc. without departing from the technical spirit of the present invention.

[0272] In addition, the drawings in the above-mentioned embodiments are schematic diagrams and the size ratios of the parts are not necessarily consistent with the actual ones. In addition, it is needless to say that the drawings include parts whose size relations and ratios are different between the drawings.

[0273] This technology can be constructed as follows:

[0274] (1) An imaging element comprising:

[0275] a photoelectric conversion portion formed in the semiconductor substrate and performing photoelectric conversion on incident light;

[0276] a reflecting portion that is arranged in a front surface of the semiconductor substrate that is different from a surface on which the incident light is incident and reflects the transmitted light transmitted through the photoelectric conversion portion to the photoelectric conversion portion, and

[0277] A reflecting portion forming member has a bottom surface disposed adjacent to the front surface of the semiconductor substrate and a side surface on which the reflecting portion is formed.

[0278] (2) The image pickup element according to (1), further including an image signal generation circuit that generates an image signal based on the charge generated by the photoelectric conversion.

[0279] (3) The image pickup element according to (2), wherein the reflection portion forming member is formed simultaneously with a gate of a MOS transistor arranged in the image signal generating circuit.

[0280] (4) The image pickup element according to (2), wherein the reflection portion forming member is formed by a gate of a MOS transistor arranged in the image signal generating circuit.

[0281] (5) The image pickup element according to any one of (1) to (4), wherein the reflection portion forming member has a side wall insulating film arranged on the side surface portion, and

[0282] The reflecting portion is formed adjacent to the sidewall insulating film.

[0283] (6) The image pickup element according to any one of (1) to (5), wherein the reflection portion is arranged near a boundary of the photoelectric conversion portion in the semiconductor substrate.

[0284] (7) The image pickup element according to (6), further including a light shielding film formed adjacent to an upper surface of the reflection portion forming member to shield the transmitted light, the upper surface being a surface opposite to the bottom surface.

[0285] (8) The image pickup element according to any one of (1) to (7), further including a charge holding portion that holds the charge generated by the photoelectric conversion.

[0286] (9) The image pickup element according to (8), further including a light shielding wall arranged between the photoelectric conversion portion and the charge holding portion in the semiconductor substrate.

[0287] (10) The image pickup element according to (9), wherein the light shielding wall includes an opening portion close to the front surface of the semiconductor substrate, and

[0288] The reflecting portion is arranged near the opening portion of the light shielding wall.

[0289] (11) The image pickup element according to (10), wherein the reflecting portion is arranged so as to be offset from the opening portion of the light shielding wall toward the charge holding portion.

[0290] (12) The image pickup element according to any one of (1) to (11), wherein the reflection portion forming member is formed by laminating a plurality of films.

[0291] (13) The image pickup element according to (12), further comprising an image signal generation circuit that generates an image signal based on the charge generated by the photoelectric conversion,

[0292] Here, any one of the plurality of films of the reflection portion forming member is formed simultaneously with the gate of the MOS transistor of the image signal generating circuit.

[0293] (14) The image pickup element according to any one of (1) to (13), wherein a bias voltage is applied to the reflection portion forming member.

[0294] (15) The image pickup element according to any one of (1) to (14), wherein the side surface of the reflection portion forming member is formed in a curved shape.

[0295] (16) The image pickup element according to any one of (1) to (14), wherein the reflection portion forming member includes a side surface having a tapered cross section.

[0296] (17) The image pickup element according to any one of (1) to (14), further including a color filter through which incident light having a predetermined wavelength is transmitted,

[0297] The photoelectric conversion unit performs photoelectric conversion on incident light transmitted through the color filter.

[0298] (18) The imaging element according to (17), comprising a plurality of pixels each having the photoelectric conversion portion and the color filter,

[0299] The reflecting portion and the reflecting portion forming member are arranged in a pixel in which the color filter that transmits the incident light having a long wavelength is arranged, among the plurality of pixels.

[0300] (19) The image pickup element according to any one of (1) to (18), wherein the reflection portion is formed of metal.

[0301] (20) A camera device comprising:

[0302] a photoelectric conversion portion formed in the semiconductor substrate and performing photoelectric conversion on incident light;

[0303] a reflecting portion that is arranged in a front surface of the semiconductor substrate that is different from a surface on which the incident light is incident and reflects the transmitted light transmitted through the photoelectric conversion portion to the photoelectric conversion portion, and

[0304] a reflecting portion forming member having a bottom surface arranged adjacent to the front surface of the semiconductor substrate and a side surface on which the reflecting portion is formed, and

[0305] A processing circuit processes an image signal generated based on the charge generated by the photoelectric conversion.

[0306] [Reference Signs List]

[0307] 1. Camera element

[0308] 10 Pixel array section

[0309] 30 columns of signal processing units

[0310] 100, 200 pixels

[0311] 101 Photoelectric Conversion Unit

[0312] 102 second charge retention unit

[0313] 103 first charge retention unit

[0314] 104-109 MOS transistors

[0315] 110 semiconductor substrate

[0316] 111~117 Semiconductor area

[0317] 121 gate insulating film

[0318] 122, 180~182 Insulation film

[0319] 130 Reflection portion forming member

[0320] 131, 133, 134, 136-138 Pseudo gate

[0321] 132, 135, 139, 149 Side wall insulation film

[0322] 141~148 gate

[0323] 150, 152~158 Light-shielding film

[0324] 151, 169 insulation layer

[0325] 160 Wiring area

[0326] 161, 163 wiring layer

[0327] 162, 164 contact plugs

[0328] 167 contact wall

[0329] 168 cover

[0330] 170, 179 Light-shielding film

[0331] 171 metal film

[0332] 172, 173 Light-shielding wall

[0333] 174, 175, 311, 321 openings

[0334] 191 Color Filter

[0335] 301~309 Reflection part

[0336] 1000 Camera

[0337] 1002 Camera Components

[0338] 1005 Image Processing Unit

Claims

1. An imaging element, comprising: a photoelectric conversion portion formed in the semiconductor substrate and performing photoelectric conversion on incident light; a reflecting portion that is arranged in a front surface of the semiconductor substrate different from a surface on which the incident light is incident and reflects transmitted light transmitted through the photoelectric conversion portion toward the photoelectric conversion portion; a reflecting portion forming member having a bottom surface arranged adjacent to the front surface of the semiconductor substrate and a side surface on which the reflecting portion is formed; a charge holding portion that holds the charge generated by the photoelectric conversion; as well as a light shielding wall arranged between the photoelectric conversion portion and the charge holding portion in the semiconductor substrate, the light shielding wall including an opening portion close to the front surface of the semiconductor substrate, The reflecting portion is arranged near the opening of the light shielding wall and offset from the opening of the light shielding wall toward the charge holding portion. 2 . The image pickup element according to claim 1 , further comprising an image signal generating circuit that generates an image signal based on the charge generated by the photoelectric conversion.

3. The imaging element according to claim 2, wherein The reflection portion forming member is formed simultaneously with the gate of the MOS transistor arranged in the image signal generating circuit.

4. The imaging element according to claim 2, wherein The reflection portion forming member is formed by a gate of a MOS transistor arranged in the image signal generating circuit.

5. The imaging element according to any one of claims 1 to 4, wherein The reflecting portion forming member has a side wall insulating film arranged on the side surface, and The reflecting portion is formed adjacent to the sidewall insulating film.

6. The imaging element according to any one of claims 1 to 4, wherein The reflecting portion is arranged near a boundary of the photoelectric conversion portion in the semiconductor substrate. 7 . The image pickup element according to claim 6 , further comprising a light shielding film formed adjacent to an upper surface of the reflection portion forming member, the upper surface being a surface opposite to the bottom surface, to shield the transmitted light.

8. The imaging element according to any one of claims 1 to 4, wherein The reflecting portion forming member is formed by laminating a plurality of films.

9. The image pickup element according to claim 8, further comprising an image signal generating circuit for generating an image signal based on the charge generated by the photoelectric conversion. in, Any one of the plurality of films of the reflection portion forming member is formed simultaneously with the gate of the MOS transistor of the image signal generating circuit.

10. The imaging element according to any one of claims 1 to 4, wherein A bias voltage is applied to the reflecting portion forming member.

11. The imaging element according to any one of claims 1 to 4, wherein The side surface of the reflecting portion forming member is formed in a curved shape.

12. The imaging element according to any one of claims 1 to 4, wherein The reflecting portion forming member includes a side surface having a tapered cross-section.

13. The image pickup element according to any one of claims 1 to 4, further comprising a color filter through which incident light having a predetermined wavelength is transmitted, in, The photoelectric conversion section performs photoelectric conversion on incident light transmitted through the color filter.

14. The image pickup element according to claim 13, comprising a plurality of pixels each having the photoelectric conversion portion and the color filter, in, The reflecting portion and the reflecting portion forming member are arranged in a pixel in which the color filter that transmits the incident light having a long wavelength is arranged, among the plurality of pixels.

15. The imaging element according to any one of claims 1 to 4, wherein The reflecting portion is formed of metal.

16. An imaging device comprising the imaging element according to any one of claims 1 to 15, and A processing circuit processes an image signal generated based on the charge generated by photoelectric conversion in the image pickup element.

Images