Image sensor and imaging device

Abstract

To provide an imaging element capable of effectively utilizing a space between pixels.SOLUTION: An imaging element includes a semiconductor substrate, the semiconductor substrate includes a first photoelectric conversion unit that photoelectrically converts light, a second photoelectric conversion unit that is provided next to the first photoelectric conversion unit and photoelectrically converts light, and a plurality of separation units provided between the first photoelectric conversion unit and the second photoelectric conversion unit.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD

[0001] The present invention relates to an imaging element and an imaging apparatus.

BACKGROUND ART

[0002] An imaging element is known in which large-area pixels with relatively high sensitivity are arranged at one set of checkered positions, and small-area pixels with relatively low sensitivity are arranged at the other set of checkered positions (for example, see Patent Document 1). Conventionally, effective utilization of the space between pixels has been demanded.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

[0004] According to a first aspect of the present invention, an imaging element is an imaging element including a first semiconductor substrate having a plurality of photoelectric conversion units that convert light into electric charges, wherein the first semiconductor substrate includes a first photoelectric conversion unit among the plurality of photoelectric conversion units The first transfer unit includes a first transistor of a first conductivity type and transfers the charge converted by the first photoelectric conversion unit to the first storage unit. a first semiconductor portion in which is arranged, and Among the plurality of photoelectric conversion units, a second photoelectric conversion unit is arranged next to the first photoelectric conversion unit, and a second transfer unit is arranged which includes a second transistor of the first conductivity type and transfers the charge converted by the second photoelectric conversion unit to a second storage unit. the first semiconductor portion and and the second semiconductor portion of located Placed a semiconductor portion of a second conductivity type different from the first conductivity type, 3 including a transistor and electrically connected to the first storage unit. a third semiconductor portion in which a first circuit is arranged, a first isolation portion that electrically isolates the first semiconductor portion and the third semiconductor portion, and It is positioned between the first semiconductor part and the third semiconductor part a second isolation portion that electrically isolates the second semiconductor portion and the third semiconductor portion. It is positioned between the second semiconductor part and the third semiconductor part

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] [Figure 1] A cross-sectional view schematically showing the configuration of the imaging apparatus according to the first embodiment. ​ [Figure 2] A diagram showing an overview of the image sensor of the first embodiment. [Figure 3] A partially enlarged cross-sectional view of the image sensor of the first embodiment. [Figure 4] A partially enlarged cross-sectional view of the first modified image sensor. [Figure 5] A partially enlarged cross-sectional view of the second modified image sensor. [Figure 6] A partially enlarged cross-sectional view of the image sensor of the second embodiment. [Figure 7] A partially enlarged cross-sectional view of the image sensor of the third embodiment. [Figure 8] A partially enlarged cross-sectional view of the image sensor of the fourth embodiment. [Figure 9] A partially enlarged cross-sectional view of the image sensor of the fifth embodiment. [Figure 10] A partially enlarged cross-sectional view of the image sensor of the sixth embodiment. [Modes for carrying out the invention]

[0006] (First embodiment of the imaging device) Figure 1 shows an example configuration of camera 1, which is a first embodiment of the imaging device. In Figure 1, the X, Y, and Z directions indicated by arrows are considered positive directions (+). The X, Y, and Z directions are mutually orthogonal. Furthermore, the X, Y, and Z directions shown in subsequent figures are the same as those shown in Figure 1.

[0007] Camera 1 comprises an imaging optical system (imaging optical system) 2, an image sensor 3, an imaging control unit 4, a memory 6, a display unit 7, and an operation unit 8. The imaging optical system 2 has multiple lenses, including a focus adjustment lens (focus lens), and an aperture diaphragm, and forms an image of the subject on the image sensor 3. The imaging optical system 2 may be detachable from camera 1.

[0008] The image sensor 3 is an image sensor such as a CMOS image sensor or a CCD image sensor. The image sensor 3 receives the light beam that has passed through the imaging optical system 2 and captures the subject image formed by the imaging optical system 2. As will be described later, the image sensor 3 has a plurality of pixels having photoelectric conversion units arranged in a two-dimensional manner (row direction and column direction). The photoelectric conversion unit is composed of photodiodes (PDs). The image sensor 3 generates a signal by photoelectric conversion of the received light and outputs the generated signal to the imaging control unit 4.

[0009] Memory 6 is a recording medium such as a memory card. Image data, control programs, etc., are stored in Memory 6. Writing data to and reading data from Memory 6 is controlled by the image capture control unit 4. The display unit 7 displays images based on image data, shooting-related information such as shutter speed and aperture value, and menu screens, etc. The operation unit 8 includes a release button, a power switch, various setting switches such as switches for switching between various modes, and outputs signals based on each operation to the image capture control unit 4.

[0010] The image capture control unit 4 is composed of a processor such as a CPU, FPGA, or ASIC, and memory such as ROM or RAM, and controls each part of the camera 1 based on a control program. The image capture control unit 4 supplies signals to the image sensor 3 to control its operation. When taking still images, taking video, or displaying a live view image of the subject on the display unit 6, the image capture control unit 4 causes the image sensor 3 to capture an image of the subject and outputs a signal.

[0011] The imaging control unit 4 includes a generation unit 5 that generates image data by performing various image processing operations on the signal output from the image sensor 3. Image processing includes grayscale conversion and color interpolation.

[0012] (First embodiment of the image sensor) With reference to Figure 2, the configuration of the imaging element 3 according to the first embodiment will be described. Figure 2(a) is a view of the imaging element 3 according to the first embodiment viewed from the imaging surface side, that is, from the +Z side. The imaging element 3 has a plurality of pixels 9 arranged in the X direction and the Y direction. The pixels 9 may be arranged, for example, over 1000 or more in each of the X direction and the Y direction.

[0013] A horizontal control unit HC is provided at the end in the -X direction of the region where the plurality of pixels 9 are arranged (pixel region), and a vertical control unit VC is provided at the end in the +Y direction. The horizontal control unit HC and the vertical control unit VC are collectively referred to as an element control unit CU. Each of the plurality of pixels 9 may, as an example, have spectral sensitivity characteristics defined by a so-called Bayer array. Alternatively, they may have spectral sensitivity characteristics different from the Bayer array. Further, some of the pixels 9 may be so-called image plane phase difference type focus detection pixels. Since the configuration of focus detection pixels is publicly known, the description thereof is omitted in this specification.

[0014] In the following, the structure will be described by taking, as an example, four pixels (four pixels) 9Q of the pixels 9, which are arranged adjacent to each other in two rows in the X direction and two columns in the Y direction, and are enclosed by a dashed square as an example.

[0015] Figure 3(a) is an enlarged cross-sectional view showing the XY cross-section of the portion of the four pixels 9Q of the imaging element 3, and Figure 3(b) is a cross-sectional view showing the XZ cross-section along the AA cutting line in Figure 3(a). Note that Figure 3(a) shows the XY cross-section along the BB cutting line in Figure 3(b), but for ease of understanding, Figure 3(a) also shows signal processing circuits 13a to 13d, which will be described later, present on the -Z side relative to the XY cross-section corresponding to the BB cutting line in Figure 3(b). In the following, the four pixels 9 included in the four pixels 9Q are also referred to as pixels 9a to 9d, respectively.

[0016] The image sensor 3 is made of a semiconductor such as silicon and has a semiconductor substrate 10 arranged generally parallel to the XY plane. Inside the semiconductor substrate 10, there are multiple photoelectric conversion units 11a to 11d, each consisting of a photodiode as an example of a device that converts light into photoelectric energy. Hereinafter, the photoelectric conversion units 11a to 11d will be referred to collectively, individually, or simply as the photoelectric conversion unit 11. The photoelectric conversion unit 11, as an example, converts light incident on the semiconductor substrate 10 from approximately the +Z direction into photoelectric energy. Each pixel 9 is equipped with at least one photoelectric conversion unit 11. In the following, pixels 9a to 9d are assumed to be equipped with photoelectric conversion units 11a to 11d, respectively.

[0017] For example, pixel 9a includes a photoelectric conversion unit 11a, a microlens 14, a color filter 15, a transfer transistor TX, a storage unit FD, and a signal processing circuit 13a. For example, the semiconductor substrate 10 is made of a p-type semiconductor with a relatively low concentration of impurity atoms, and the photoelectric conversion unit 11a is a region having the conductive properties of an n-type semiconductor formed on a part of the p-type semiconductor substrate 10.

[0018] The photoelectric conversion unit 11a functions as a so-called embedded photodiode. The microlens 14 is provided on the side (+Z side) where light is incident on the semiconductor substrate 10, and focuses the light incident on the semiconductor substrate 10 onto the photoelectric conversion unit 11a. The color filter 15 is provided between the photoelectric conversion unit 11a and the microlens 14, and defines the wavelength characteristics of the light incident on the photoelectric conversion unit 11a.

[0019] The charge generated by the light incident on the photoelectric conversion unit 11a is transferred to the storage unit FD by the transfer transistor TX. The voltage formed by the charge transferred to the storage unit FD is converted into a current signal by the first transistor Tr1, and read out by a readout circuit (not shown) via the second transistor Tr2 and wiring W3 and W4. Therefore, the first transistor Tr1 and the second transistor Tr2 constitute part of the signal processing circuit 13a that processes the signal based on the charge generated in the photoelectric conversion unit 11a.

[0020] The transfer of charge generated in the photoelectric conversion unit 11a to the storage unit FD is controlled by the voltage of the control signal applied to the gate G0 of the transfer transistor TX. Similarly, the conduction of the first transistor Tr1 and the second transistor Tr2 is controlled by the voltage of the control signals applied to their respective gates G1 and G2.

[0021] The source region and drain region of each transistor described above (hereinafter collectively referred to as the "source and drain regions") are regions having the conductive properties of an n-type semiconductor, formed by implanting predetermined atoms such as phosphorus or arsenic near the -Z side surface of the p-type semiconductor substrate 10. Wiring W2 is a wire that electrically connects the first transistor Tr1 and the second transistor Tr2, etc., formed within the signal processing circuit 13a. Wiring W1 is a wire that electrically connects the storage unit FD and the drain of the first transistor Tr1. The signal processing circuit 13a, wiring W3, and wiring W4 are covered by an insulating film 18, except for the parts that require electrical connection to each other.

[0022] The circuit configuration of the transfer transistor TX and the signal processing circuit 13a may, for example, be the same as the circuit configuration of a typical four-transistor type CMOS image sensor, which includes a transfer transistor, an amplification transistor, a reset transistor, and a selection transistor. The configuration of the storage unit FD may be the same as the configuration of a typical floating diffusion unit. Furthermore, the signal processing circuit 13a may include more components than the circuit configuration in a typical 4-transistor CMOS image sensor. For example, it may include part of an AD converter circuit that converts analog signals to digital signals.

[0023] The configuration of pixels 9b to 9d, other than pixel 9a, is the same as that of pixel 9a described above, except that the wavelength selection characteristics of the color filter 15 are different. Each of the other pixels 9b to 9d also has signal processing circuits 13b to 13d that process signals based on the charge generated by the photoelectric conversion units 11b to 11d. Hereafter, the signal processing circuits 13a to 13d will be referred to collectively, individually, or simply as signal processing circuit 13.

[0024] As shown in Figure 3(b), a light-shielding portion 17 is provided at the boundary between adjacent pixels 9a to 9d between the semiconductor substrate 10 and the color filter 15. The light-shielding portion 17 reduces the intrusion of light transmitted through the microlens 14 and color filter 15 of one pixel 9a to 9d into the adjacent pixel.

[0025] The light-shielding portion 17 may, for example, be formed of a metal film such as tungsten. Alternatively, it may be formed of a film containing a light-absorbing material such as carbon. Furthermore, in the area between the semiconductor substrate 10 and the color filter 15 where the light-shielding portion 17 is not provided, a light-transmitting portion 16 with approximately the same thickness (length in the Z direction) as the light-shielding portion 17 is provided for the purpose of flattening.

[0026] In the image sensor 3 of the first embodiment, separation units 12a to 12d are arranged in a plane parallel to the semiconductor substrate 10 (XY plane) so as to surround the photoelectric conversion units 11a to 11d contained in each of the pixels 9a to 9d. Hereinafter, each of the separation units 12a to 12d will be referred to collectively, individually, or simply as separation unit 12.

[0027] The isolation section 12 is, for example, a deep trench isolation (DTI), which electrically separates one side of the semiconductor substrate 10 from the other side of the isolation section 12. In the image sensor 3 of the first embodiment, the isolation section 12 is arranged to surround the photoelectric conversion section 11, so that the first region 10a of the semiconductor substrate 10, which is inside each isolation section 12, and the second region 10b, which is a semiconductor region outside each isolation section 12, are electrically separated. In this specification, the second region 10b of the semiconductor substrate 10, which is separated from the first region 10a of the photoelectric conversion section 11 by the isolation section 12, is also simply referred to as the "semiconductor region".

[0028] The separation section 12 may be formed, for example, by partially carving (grooves) into the semiconductor substrate 10 from either the -Z side or the +Z side, and embedding an insulating material such as SiO2 inside the formed carving. By further embedding tungsten metal or the like within the insulating material constituting the separation section 12, in addition to electrical separation, light shielding, i.e., optical separation, can also be achieved.

[0029] The photoelectric conversion unit 11a of pixel 9a can also be called the first photoelectric conversion unit. Furthermore, the photoelectric conversion unit 11b of pixel 9b can also be called the second photoelectric conversion unit, located next to the first photoelectric conversion unit 11a. Therefore, the image sensor 3 of the first embodiment can also be said to include a first photoelectric conversion unit 11a, a second photoelectric conversion unit 11b provided next to the first photoelectric conversion unit 11a, and a plurality of separation units 12a, 12b provided between the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b.

[0030] In the image sensor 3 of the first embodiment, a signal processing circuit 13a that processes the charge based on the charge generated by the photoelectric conversion unit 11a is located in the second region 10b between the separation unit 12a and the separation unit 12b. Similarly, signal processing circuits 13b to 13d that process the charge based on the charges generated by the other photoelectric conversion units 11b to 11d are also located in the second region 10b, which is separated from the first region 10a by the separation unit 12.

[0031] Generally, the signal processing circuit 13 is a source of electrical noise that causes fluctuations in the voltage of the semiconductor substrate 10 due to fluctuations in the voltages applied to the gates G1 and G2 of the transistors Tr1 and Tr2 that constitute it. However, in the image sensor 3 of the first embodiment, a separation unit 12 is arranged between the signal processing circuit 13 and the photoelectric conversion unit 11. Therefore, even if the voltage in the second region 10b where the signal processing circuit 13 is located fluctuates, the voltage fluctuation in the first region 10a where the photoelectric conversion unit 11 is located can be reduced. Consequently, the adverse effects of electrical noise generated by the signal processing circuit 13 on the photoelectric conversion unit 11 can be reduced.

[0032] For example, the thickness of the semiconductor substrate 10 in the Z direction is approximately 3 μm or more. The separation portion 12 may be formed from the -Z end face to the +Z end face of the semiconductor substrate 10, or it may be formed within the semiconductor substrate 10 from the -Z end face to a depth of, for example, 1 μm or more, or 2 μm or more. For example, the length (depth) in the Z direction of the separation portion 12 from the -Z side edge of the semiconductor substrate 10 may be set to 2 / 3 or more of the thickness of the semiconductor substrate 10, thereby further reducing the adverse effects on the photoelectric conversion unit 11 due to electrical noise generated in the signal processing circuit 13.

[0033] Depending on the configuration of the signal processing circuit 13, it may include an element that emits visible or infrared light. For example, if the signal processing circuit 13 includes a current source circuit, that current source circuit may emit light unintentionally. For example, as described above, by further embedding tungsten metal or the like in the insulating material constituting the separation section 12, the adverse effects of light (optical noise) emitted within the signal processing circuit 13 on the photoelectric conversion section 11 can be reduced.

[0034] If it is important to reduce noise generated in the photoelectric conversion unit 11 by light emitted from the light-emitting element in the signal processing circuit 13, the isolation unit 12 may be formed from a highly light-shielding material such as metal. In this case, the electrical isolation function of the isolation unit 12 of the semiconductor substrate 10 will be reduced, but the light-shielding function, i.e., optical isolation function, will be enhanced. Alternatively, the isolation unit 12 can be made to perform both electrical and optical isolation by embedding metal in an insulating film formed by coating, for example. The separation unit 12 may be arranged to surround each of the photoelectric conversion units 11 in multiple layers.

[0035] (Image sensor modification 1) The first modified example of the image sensor 3 will be described below with reference to Figure 4. The configuration of the first modified example of the image sensor 3 is the same as that of the first embodiment of the image sensor 3 shown in Figures 2 and 3, but the configuration of the separation unit 12 is different from that of the image sensor 3 of the first embodiment.

[0036] Figure 4 is an enlarged cross-sectional view of the XY cross-section of the 4-pixel 9Q portion (see Figure 2) in the modified example 1 of the image sensor 3, and is similar to Figure 3(a) which shows the image sensor 3 of the first embodiment described above. In the following, components identical to those of the image sensor 3 of the first embodiment are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0037] As shown in Figure 4, in Modification 1 of the image sensor 3, two separation sections 12a and 12b extending in the Y direction are arranged between two adjacent photoelectric conversion sections 11a and 11b in the X direction, and between two adjacent photoelectric conversion sections 11c and 11d in the X direction. The XZ cross section of Modification 1 in the AA cross section of Figure 4 is the same as the XZ cross section of the image sensor 3 of the first embodiment shown in Figure 3(b).

[0038] The material and length in the Z direction of the separation sections 12a to 12d in Modification 1 are the same as those of the separation section 12 in the image sensor 3 of the first embodiment described above. Therefore, the first region 10a where the photoelectric conversion section 11 is located is electrically or optically separated from the second region 10b by the separation section 12.

[0039] In the modified example 1, the signal processing circuit 13 described above is located in the second region 10b of the semiconductor substrate 10. Therefore, the adverse effects of electrical noise or optical noise generated from transistors, etc., included in the signal processing circuit 13 on the photoelectric conversion unit 11 are reduced by the isolation unit 12.

[0040] Furthermore, the number of separation units 12 positioned between two adjacent photoelectric conversion units 11a and 11b in the X direction, and between two adjacent photoelectric conversion units 11c and 11d in the X direction, is not limited to the two mentioned above, but may be more than that.

[0041] In the image sensor 3 of the first embodiment and modification 1 described above, the multiple separation units 12 can also be said to be arranged along the X direction, which is the direction in which one photoelectric conversion unit 11b is arranged relative to one photoelectric conversion unit 11a. Furthermore, at least a portion of each of the multiple separation units 12 can be said to extend along the Y direction, which is the direction intersecting the X direction. Furthermore, at least a portion of each of the multiple separation sections 12 does not necessarily need to extend along the Y direction; it is sufficient if it extends in a direction intersecting the X direction.

[0042] (Image sensor modification 2) Hereinafter, a modified example 2 of the image sensor 3 will be described with reference to Figure 5. The configuration of modified example 2 of the image sensor 3 is the same as that of the image sensor 3 of the first embodiment shown in Figures 2 and 3, but the configuration of the separation unit 12 is different from that of the image sensor 3 of the first embodiment. In the following, components identical to those of the image sensor 3 of the first embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0043] Figure 5 is an enlarged cross-sectional view of the XY cross-section of the 4-pixel 9Q portion (see Figure 2) in the modified example 2 of the image sensor 3, and is similar to Figure 3(a) which shows the image sensor 3 of the first embodiment described above. As shown in Figure 5, in Modification 2 of the image sensor 3, separation units 12a to 12d are arranged to surround each of the signal processing circuits 13a to 13d that process signals based on the charge generated by the photoelectric conversion units 11a to 11d. The material and length in the Z direction of the separation units 12a to 12d in Modification 2 are the same as those of the separation unit 12 in the image sensor 3 of the first embodiment described above. Therefore, the first region 10a where the photoelectric conversion unit 11 is located is electrically or optically, or electrically and optically, separated from the second region 10b by the separation unit 12.

[0044] As a result, in the modified example 2 as well, the adverse effects of electrical noise or optical noise generated from transistors and other components in the signal processing circuit 13 on the photoelectric conversion unit 11 are reduced by the separation unit 12. The separation unit 12 may be arranged to surround each of the signal processing circuits 13 in multiple layers.

[0045] It can also be said that the image sensor 3 of the first embodiment and the modified examples 1 and 2 described above includes a plurality of separation units 12 provided between the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b, which are arranged adjacent to each other.

[0046] In the first embodiment and the modified versions 1 and 2 described above, the image sensor 3 has a signal processing circuit 13 arranged in the second region 10b of the semiconductor substrate 10. However, the signal processing circuit 13 does not necessarily have to be arranged in the second region 10b. For example, the signal processing circuit 13 may be arranged on a second semiconductor substrate stacked with the semiconductor substrate 10. Even in this case, the separation unit 12 can reduce the adverse effects of electrical noise associated with the electrical signals flowing through the wiring W3 and W4 on the photoelectric conversion unit 11.

[0047] (Effects of the image sensor in the first embodiment and modified examples 1 and 2) (1) The image sensor 3 of the first embodiment and modified example 1 and modified example 2 is an image sensor having a semiconductor substrate 10, the semiconductor substrate 10 comprising a first photoelectric conversion unit 11a that converts light into photoelectrics, a second photoelectric conversion unit 11b provided next to the first photoelectric conversion unit 11a that converts light into photoelectrics, and a plurality of separation units 12 provided between the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b. This configuration makes it possible to reduce noise introduced into the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b, thereby realizing an image sensor 3 with low noise.

[0048] (2) The separation section 12 may be a region in the semiconductor substrate 10 that electrically or optically separates the first photoelectric conversion section 11a and the second photoelectric conversion section 11b, or electrically and optically. In this case, electrical noise or optical noise mixed into the first photoelectric conversion section 11a and the second photoelectric conversion section 11b can be reduced, and an image sensor 3 with low noise can be realized.

[0049] (3) The semiconductor substrate 10 may be configured to include a signal processing circuit 13a provided in the semiconductor region (second region 10b) between two of the plurality of separation sections 12, for processing signals based on the charge generated by the first photoelectric conversion section 11a or the second photoelectric conversion section 11b. In this case, the separation section 12 can reduce the adverse effects of electrical noise or optical noise (light emission) that may be generated in the signal processing circuit 13a on the first photoelectric conversion section 11a, thereby realizing an image sensor 3 with reduced noise.

[0050] (4) The first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b are provided in the first direction (X direction), and the plurality of separation units 12 are provided in the first direction (X direction), and at least a part of each of the plurality of separation units 12 may extend in a direction (Y direction) that intersects the first direction (X direction). In this case, the semiconductor region (second region 10b) between the plurality of separation units 12 in the first direction (X direction) can be separated more effectively from the first region 10a where the first photoelectric conversion unit 11a or the second photoelectric conversion unit 11b is located, thereby realizing an image sensor 3 with further noise reduction.

[0051] (5) One of the multiple isolation units 12 (12a) may surround the first photoelectric conversion unit 11a on the semiconductor substrate 10, and the other one of the multiple isolation units 12 (12b) may surround the second photoelectric conversion unit 11b on the semiconductor substrate 10. In this case, the semiconductor region (second region 10b) can be separated even more effectively from the first region 10a on which the first photoelectric conversion unit 11a or the second photoelectric conversion unit 11b is located, thereby realizing an image sensor 3 with further reduced noise.

[0052] (Image sensor of the second embodiment) The image sensor 3 of the second embodiment will now be described with reference to Figure 6. The configuration of the image sensor 3 of the second embodiment is generally the same as that of the image sensor 3 of the first embodiment shown in Figures 2 and 3, but the shape of the light-shielding portion 17a is different from that of the light-shielding portion 17 of the image sensor 3 of the first embodiment. In the following, components identical to those of the image sensor 3 of the first embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0053] Figure 6 is an enlarged cross-sectional view of the XZ cross-section of the 4-pixel 9Q portion (see Figure 2) of the image sensor 3 of the second embodiment, and is similar to Figure 3(b) of the image sensor 3 of the first embodiment described above. Note that the XY cross-section of the image sensor 3 of the second embodiment at the BB cutting line in Figure 6 is the same as the XY cross-sectional view of the image sensor 3 of the first embodiment shown in Figure 3(a).

[0054] As shown in Figure 6, in the image sensor 3 of the second embodiment, the light-shielding portion 17a is positioned on the +Z side of the semiconductor substrate 10 so as to cover the entire surface of the second region 10b. Therefore, light incident from the +Z side of the image sensor 3 through the microlens 14 can enter the photoelectric conversion unit 11 in the first region 10a via the color filter 15 and the light-transmitting portion 16, but it cannot enter the second region 10b because it is blocked by the light-shielding portion 17a. As a result, light incident from the +Z side does not reach the signal processing circuit 13 located in the second region 10b.

[0055] In the image sensor 3 of the second embodiment, the light shielding portion 17a blocks the incidence of light to the signal processing circuit 13, thereby reducing the generation of unwanted charges, i.e., noise, due to photoelectric conversion in the signal processing circuit 13. This makes it possible to realize an image sensor 3 with low noise.

[0056] Furthermore, the shape of the separation portion 12 in the XY plane of the image sensor 3 in the second embodiment is not limited to the same shape as the separation portion 12 of the image sensor 3 in the first embodiment, but may be the same shape as the separation portion 12 in Modification 1 or Modification 2.

[0057] (Effects of the image sensor in the second embodiment) (6) The image sensor 3 of the second embodiment is equipped with a light-shielding portion 17a that blocks light incident on the semiconductor region (second region 10b), in addition to the configuration of the image sensor 3 of the second embodiment described above. With this configuration, in addition to the effects of the image sensor 3 of the embodiment, it is possible to reduce the generation of unwanted charge, i.e., noise, caused by photoelectric conversion in the signal processing circuit 13 located in the semiconductor region (second region 10b), thereby realizing an image sensor 3 with even less noise.

[0058] (Image sensor of the third embodiment) The image sensor 3 of the third embodiment will now be described with reference to Figure 7. Since the configuration of the image sensor 3 of the third embodiment is generally the same as that of the image sensor 3 of the first and second embodiments described above, the same reference numerals will be used for components identical to those of the image sensor 3 of the first embodiment, and their descriptions will be omitted as appropriate.

[0059] Figure 7(a) is an enlarged cross-sectional view of the XY cross-section of the 4-pixel 9Q portion (see Figure 2) of the image sensor 3 of the third embodiment, and is similar to the figure 3(a) described above. Figure 7(b) is a cross-sectional view showing the XZ cross-section at the AA cutting line in Figure 7(a), and is similar to the figure 3(b) described above. Figure 7(a) shows the XY cross-section at the BB cutting line in Figure 7(b), and also shows the signal processing circuits 13a to 13d.

[0060] The image sensor 3 of the third embodiment differs from the image sensor 3 of the first and second embodiments described above in that the conductive properties of the p-type or n-type semiconductor in the second region 10b of the semiconductor substrate 10 are opposite to those of the first region 10a where the photoelectric conversion unit 11 is located.

[0061] In other words, in the image sensor 3 of the third embodiment shown in Figure 7, for example, the first region 10a is a p-type semiconductor with a relatively low concentration of impurity atoms, and the second region 10b is an n-type semiconductor with a relatively low concentration of impurity atoms. The first photoelectric conversion section 11a and the second photoelectric conversion section 11b formed in the first region 10a have the conductive properties of an n-type semiconductor.

[0062] The conductivity characteristics of the p-type or n-type semiconductor in the second region 10b are imparted, for example, by implanting predetermined impurity atoms (ion implantation) from the -Z side surface of the semiconductor substrate 10. Furthermore, the conductivity characteristics of the p-type or n-type semiconductor in the entire second region 10b do not necessarily have to be the opposite of those of the first region 10a. For example, the conductivity characteristics of the p-type or n-type semiconductor in about half the thickness of the -Z side of the second region 10b may be the opposite of those of the first region 10a.

[0063] In the image sensor 3 of the third embodiment, it can also be said that a second region 10b, which is an n-type (or p-type) well, is formed on the p-type (or n-type) semiconductor substrate 10. In the image sensor 3 of the third embodiment, transistors Tr1 and Tr2, which have characteristics opposite to those of the transfer transistor TX, can be formed in the second region 10b. That is, for example, when the transfer transistor TX is an NMOS transistor, transistors Tr1 and Tr2 can be PMOS transistors. This increases the design flexibility of the signal processing circuit 13, and allows for miniaturization of the signal processing circuit 13, for example.

[0064] Furthermore, by electrically separating the first region 10a and the second region 10b with the separation unit 12, the flow of current from the p-type semiconductor region of one of the two regions to the n-type semiconductor region of the other can be suppressed. This improves the degree of freedom in the relationship between the substrate voltage of the first region 10a and the substrate voltage of the second region 10b, further improving the design freedom of the signal processing circuit 13 and enabling further miniaturization of the signal processing circuit 13.

[0065] In the above description, the image sensor 3 of the third embodiment is provided with a light-shielding portion 17a similar to that of the image sensor 3 of the second embodiment, but it may also be provided with a light-shielding portion 17 similar to that of the image sensor 3 of the first embodiment. Furthermore, the shape of the separation portion 12 in the XY plane of the image sensor 3 of the third embodiment may be the same as that of the separation portion 12 in the modified example 1 or modified example 2 described above.

[0066] (Effects of the image sensor in the third embodiment) (7) In addition to the configuration of the image sensor 3 of the first embodiment described above, the image sensor 3 of the third embodiment has the conductivity characteristics of an n-type semiconductor in the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b, and the semiconductor region (second region 10b) has the conductivity characteristics of an n-type semiconductor. That is, the first region 10a where the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b are arranged has the conductivity characteristics of a p-type semiconductor, and the semiconductor region (second region 10b) has the conductivity characteristics of an n-type semiconductor with the opposite characteristics. With this configuration, in addition to the effects of the image sensor 3 of the first embodiment described above, the degree of freedom in designing the signal processing circuit 13 arranged in the first region 10a is increased, and for example, the signal processing circuit 13 can be miniaturized.

[0067] (Image sensor of the fourth embodiment) The image sensor 3 of the fourth embodiment will now be described with reference to Figure 8. In the image sensor 3 of the fourth embodiment, as an example, the first region 10a is a p-type semiconductor with a relatively low concentration of impurity atoms, and the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b formed in the first region 10a have the conductive properties of an n-type semiconductor. Since the configuration of the image sensor 3 of the fourth embodiment is generally the same as that of the image sensor 3 of each embodiment described above, the same reference numerals will be used for components identical to those of the image sensor 3 of each embodiment described above, and their descriptions will be omitted as appropriate.

[0068] Figure 8 is an enlarged cross-sectional view of the XY cross-section of the 4-pixel 9Q portion (see Figure 2) of the image sensor 3 of the fourth embodiment, and is similar to the view shown in Figures 3(a) and 7(a) above. Note that the XZ cross-section of the image sensor 3 of the fourth embodiment at the AA cutting line in Figure 8 is the same as the XZ cross-sectional view of the image sensor 3 of the third embodiment shown in Figure 7(b). Also, signal processing circuits 13a to 13d are shown in Figure 8.

[0069] As shown in Figure 8, in the image sensor 3 of the fourth embodiment, the separation unit 12 is formed in a two-dimensional grid shape in the XY plane. The separation unit 12 separates the first region 10a of the semiconductor substrate 10, which includes the photoelectric conversion unit 11, from the semiconductor region (second region 10b), and divides the semiconductor region (second region 10b) into a plurality of sub-regions 10b1 to 10b3. The conductivity characteristics of the p-type or n-type semiconductor in at least one of the plurality of sub-regions 10b1 to 10b3 (two in the example shown in Figure 8, sub-regions 10b1 and 10b2) are inverse to the conductivity characteristics of the p-type or n-type semiconductor in the first region 10a.

[0070] Furthermore, the signal processing circuit 13 is also divided, and in the case of signal processing circuit 13a as an example, signal processing circuits 13a1 to 13a3 are arranged in each of the multiple sub-regions 10b1 to 10b3. Each of the signal processing circuits 13a1 to 13a3 is electrically connected by wiring (not shown) that spans the multiple sub-regions 10b1 to 10b3 on the -Z side surface of the semiconductor substrate 10, as shown by wiring W1 in Figure 7(b) above.

[0071] In the image sensor 3 of the fourth embodiment, NMOS transistors or PMOS transistors can be placed in each of the multiple sub-regions 10b1 to 10b3 included in the second region 10b, depending on whether the sub-region is a p-type semiconductor or an n-type semiconductor. This increases the design flexibility of the signal processing circuit 13, and for example, a signal processing circuit 13 composed of CMOS can be placed within the semiconductor substrate 10.

[0072] In the above description, the image sensor 3 of the fourth embodiment is provided with a light-shielding portion 17a similar to that of the image sensor 3 of the second embodiment, but it may also be provided with a light-shielding portion 17 similar to that of the image sensor 3 of the first embodiment. Furthermore, the separation section 12 shown in Figure 8 can be described as a plurality of separation sections, including a plurality of separation sections extending in the X direction and a plurality of separation sections extending in the Y direction.

[0073] (Effects of the image sensor in the fourth embodiment) (8) In addition to the configuration of the first embodiment of the image sensor 3 described above, the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b have the conductive properties of an n-type semiconductor, and the semiconductor region (second region 10b) is divided into a plurality of sub-regions 10b1 to 10b3 by the separation unit 12. At least one of the plurality of sub-regions 10b1 to 10b3 has the conductive properties of a p-type semiconductor. With this configuration, an NMOS transistor or a PMOS transistor can be placed in each of the plurality of sub-regions 10b1 to 10b3 included in the second region 10b, depending on whether the sub-region is a p-type semiconductor or an n-type semiconductor. As a result, in addition to the effects of the first embodiment of the image sensor 3 described above, the degree of freedom in designing the signal processing circuit 13 is increased, and for example, a signal processing circuit 13 composed of CMOS can be placed in the semiconductor substrate 10.

[0074] (9) From another viewpoint, the image sensor 3 of the fourth embodiment has, in addition to the configuration of the image sensor 3 of the first embodiment described above, the first photoelectric conversion unit 11a and the second photoelectric conversion unit 11b have the conductive properties of an n-type semiconductor, and the semiconductor region (second region 10b) is divided into a plurality of sub-regions 10b1 to 10b3 by the separation unit 12. At least one of the plurality of sub-regions 10b1 to 10b3 has the conductive properties of an n-type semiconductor. With this configuration, the same effects as those of (8) described above can be obtained.

[0075] (Image sensor of the fifth embodiment) The image sensor 3 of the fifth embodiment will now be described with reference to Figure 9. The configuration of the image sensor 3 of the fifth embodiment is generally the same as that of the image sensor 3 of the second embodiment described above, but the structure of the separation unit 12 is different from that of the image sensor 3 of the first embodiment. In the following, components identical to those of the image sensor 3 of the second embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0076] Figure 9 is an enlarged cross-sectional view of the XZ cross-section of the 4-pixel 9Q portion (see Figure 2) of the image sensor 3 of the fifth embodiment, and is similar to Figure 3(b) of the image sensor 3 of the first embodiment described above. Note that the XY cross-section of the image sensor 3 of the fifth embodiment at the BB cutting line in Figure 9 is the same as the XY cross-sectional view of the image sensor 3 of the first embodiment shown in Figure 3(a).

[0077] In the image sensor 3 of the fifth embodiment, the first region 10a and the second region 10b of the semiconductor substrate 10 separated by the separation unit 12 are both p-type semiconductors or both n-type semiconductors. As shown in Figure 9, the separation unit 12 does not separate the first region 10a and the second region 10b near the -Z side surface of the semiconductor substrate 10. Furthermore, in the image sensor 3 of the fifth embodiment, the storage unit FD, which stores the charge generated by the photoelectric conversion unit 11, is located in the second region 10b, not the first region 10a. In other words, the signal processing circuit 13 located in the second region 10b includes the storage unit FD.

[0078] As described above, light incident on the image sensor 3 from the +Z side via the microlens 14 is blocked by the light-shielding portion 17a and therefore does not enter the second region 10b. Consequently, in the image sensor 3 of the fifth embodiment, the storage unit FD located in the second region 10b is not irradiated by light incident on the semiconductor substrate 10 from the +Z side, thus reducing noise generated by unnecessary photoelectric conversion in the storage unit FD. This makes it possible to realize an image sensor 3 with even less noise.

[0079] (Effects of the image sensor in the fifth embodiment) (10) In addition to the configuration of the image sensor 3 of the second embodiment described above, the signal processing circuit 13 in the semiconductor region (second region 10b) includes a storage unit FD to which the charge generated in the first photoelectric conversion unit 11a or the second photoelectric conversion unit 11b is transferred. With this configuration, in addition to the effects of the image sensor 3 of the second embodiment described above, noise generated by unnecessary photoelectric conversion in the storage unit FD is reduced, and an image sensor 3 with even less noise can be realized.

[0080] (Image sensor of the sixth embodiment) The image sensor 3 of the sixth embodiment will now be described with reference to Figure 10. The image sensor 3 of the sixth embodiment includes the configuration of any of the image sensor 3 of the embodiments or modified examples described above. In the following, components identical to those of the image sensor 3 of the embodiments or modified examples described above will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0081] Figure 10 is an enlarged cross-sectional view of the XZ cross-section of the 4-pixel 9Q portion (see Figure 2) of the image sensor 3 of the sixth embodiment. In addition to the configuration of the image sensor 3 of each embodiment or each modified example described above, the image sensor 3 of the sixth embodiment includes a second semiconductor substrate 20 arranged parallel to the semiconductor substrate 10. A second signal processing circuit 23, enclosed by a dashed line, is arranged on the second semiconductor substrate 20. The image sensor 3 of the sixth embodiment further includes a connection portion 22 that electrically connects at least a portion of the signal processing circuit 13 on the semiconductor substrate 10 to at least a portion of the second signal processing circuit 23 arranged on the second semiconductor substrate 20.

[0082] The second signal processing circuit 23 includes a plurality of transistors Tr3 formed on the second semiconductor substrate 20, and, as an example, a plurality of layers of wiring W4, W5. The transistors Tr3, wiring W4, and wiring W5 are covered by a second insulating film 21, except for parts where electrical connection to each other is required.

[0083] The connector 22 is made of a metal such as copper, for example. The connector 22 is electrically connected to wiring W3 or W4 and wiring W5 or W6 by vertical wiring (wiring extending in the Z direction), which is not shown.

[0084] In the configuration of the image sensor 3 of the sixth embodiment shown in Figure 10, the insulating film 18 and the configuration on the +Z side of the insulating film 18 are, for example, the same as the configuration of the image sensor 3 of the first embodiment shown in Figure 3(b). Also, the XY cross-section of the image sensor 3 of the sixth embodiment at the BB cutting line in Figure 10 is the same as the XY cross-sectional view of the image sensor 3 of the first embodiment shown in Figure 3(a).

[0085] In the image sensor 3 of the sixth embodiment, a signal based on the charge generated by one photoelectric conversion unit 11 can be processed by a signal processing circuit 13 on the semiconductor substrate 10 and a second signal processing circuit 23 located on the second semiconductor substrate 20. Therefore, if the second semiconductor substrate 20 and the second signal processing circuit 23 are not present, some of the circuit elements that would normally be placed in the signal processing circuit 13 on the semiconductor substrate 10 can be placed in the second signal processing circuit 23 on the second semiconductor substrate 20. This makes it possible to reduce the size of the signal processing circuit 13 in the XY plane. As a result, it is possible to reduce the size of the pixels 9 in the XY plane and increase the integration density of the pixels 9 in the image sensor 3.

[0086] The signal processing circuit 13 and the second signal processing circuit 23 together may constitute an amplification circuit that amplifies a signal based on the charge generated by a single photoelectric conversion unit 11, and an AD conversion circuit that converts the amplified analog signal into a digital signal. The AD conversion circuit may be, for example, a slope-type (inclined) AD conversion circuit or a successive approximation type AD conversion circuit.

[0087] Furthermore, the signal processing circuit 13 and the second signal processing circuit 23 may include a current source that supplies current to the amplification circuit. By providing separate amplification circuits and AD conversion circuits for each of the multiple photoelectric conversion units 11 included in the image sensor 3, image signals can be read out from the image sensor 3 at a higher speed.

[0088] In this case, for example, at least some of the circuit elements, such as transistors, that constitute the AD conversion circuit may be provided within the signal processing circuit 13 of the semiconductor substrate 10. For example, the comparator circuit of the AD conversion circuit may be provided within the signal processing circuit 13 of the semiconductor substrate 10. Alternatively, at least some of the circuit elements, such as transistors, that constitute the amplification circuit may be provided on the second signal processing circuit 23 of the second semiconductor substrate 20.

[0089] In the configuration of the image sensor 3 of the sixth embodiment, the insulating film 18 and the configuration on the +Z side of the insulating film 18 are not limited to the same configuration as the image sensor 3 of the first embodiment described above, but may be the same configuration as the image sensor 3 of each embodiment or each modified example described above. For example, if the configuration of the image sensor 3 in the sixth embodiment, specifically the insulating film 18 and the configuration on the +Z side of the insulating film 18, is the same as that of the image sensor 3 in the third or fourth embodiment described above, a PMOS transistor can be provided in the signal processing circuit 13, further improving the freedom of circuit design. In addition, in the image sensor 3 of the sixth embodiment, the element control unit CU shown in Figure 2 may also be divided and arranged on the semiconductor substrate 10 and the second semiconductor substrate 20.

[0090] (Effects of the image sensor in the sixth embodiment) (11) The image sensor 3 of the sixth embodiment includes, in addition to the configuration of any one of the image sensor 3 of the above-described embodiments and modifications, a second semiconductor substrate 20 which is stacked on the semiconductor substrate 10 and is provided with a second signal processing circuit 23 that processes the signals processed by the signal processing circuit 13. This configuration allows, in addition to the effects of any one of the embodiments and modifications described above, some of the circuit elements of the circuit that processes the charge-based signals generated by each photoelectric conversion unit 11 to be placed in the second signal processing circuit 23 of the second semiconductor substrate 20. This makes it possible to reduce the size of the signal processing circuit 13 in the XY plane.

[0091] Furthermore, the imaging device 1 of the first embodiment described above may be equipped with any of the image sensors 3 of the embodiments and modifications described above. Although various embodiments and modifications have been described above, the present invention is not limited to these. Furthermore, each embodiment and modification may be applied individually or in combination. Other embodiments conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of Symbols]

[0092] 1: Imaging device, 2: Imaging lens, 3: Image sensor, 4: Imaging control unit, 5: Generation unit, 9: Pixel, 10: Semiconductor substrate, 10a: First region, 10b: Second region (semiconductor region), 11a~11d: Photoelectric conversion unit, 12,12a~12d: Separation unit, 13a~13d: Signal processing circuit, TX: Transfer transistor, FD: Storage unit, W3~W5: Wiring layer, 14: Microlens, 15: Color filter, 17,17a: Light shielding unit, 20: Second semiconductor substrate, 22: Connection unit, 23: Second signal processing circuit

Claims

1. An image sensor comprising a first semiconductor substrate having multiple photoelectric conversion units that convert light into electric charge, The first semiconductor substrate is A first semiconductor unit is provided, which includes a first photoelectric conversion unit among the plurality of photoelectric conversion units, and a first transfer unit that includes a first transistor of a first conductivity type and transfers the charge converted by the first photoelectric conversion unit to a first storage unit. Among the plurality of photoelectric conversion units, a second photoelectric conversion unit is arranged next to the first photoelectric conversion unit, and a second transfer unit is arranged which includes a second transistor of the first conductivity type and transfers the charge converted by the second photoelectric conversion unit to a second storage unit. A semiconductor portion located between the first semiconductor portion and the second semiconductor portion, the third semiconductor portion includes a third transistor having a second conductivity type different from the first conductivity type, and a first circuit electrically connected to the first storage portion is arranged in the third semiconductor portion, A first separation unit is positioned between the first semiconductor unit and the third semiconductor unit and electrically separates the first semiconductor unit and the third semiconductor unit. A second separation unit is positioned between the second semiconductor unit and the third semiconductor unit and electrically separates the second semiconductor unit and the third semiconductor unit. Having, Image sensor.

2. In the image sensor according to claim 1, The first circuit is used to process a first signal based on the charge transferred from the first photoelectric conversion unit to the first storage unit by the first transfer unit. Image sensor.

3. In the image sensor according to claim 2, The first circuit is used to convert the first signal into a digital signal. Image sensor.

4. In the image sensor according to any one of claims 1 to 3, The first circuit is used to read out a first signal based on the charge transferred from the first photoelectric conversion unit to the first storage unit by the first transfer unit. Image sensor.

5. In the image sensor according to any one of claims 1 to 4, The first transistor is an NMOS transistor, The third transistor mentioned above is a PMOS transistor. Image sensor.

6. In the image sensor according to any one of claims 1 to 5, The first separation unit has a first member for blocking incident light, The second separation section has a second member for blocking the incident light. Image sensor.

7. In the image sensor according to claim 6, The first member is made of tungsten, The second member is made of tungsten. Image sensor.

8. In the image sensor according to any one of claims 1 to 7, The first separation unit is arranged to surround the first semiconductor unit. The second separation section is arranged so as to surround the second semiconductor section. Image sensor.

9. In the image sensor according to any one of claims 1 to 7, The first separation section and the second separation section are arranged so as to surround the third semiconductor section. Image sensor.

10. In the image sensor according to any one of claims 1 to 9, An image sensor comprising a light-shielding portion arranged at a position different from the first separation portion and the second separation portion, for blocking light directed toward the third semiconductor portion.

11. In the image sensor according to claim 10, The light-shielding portion is arranged to cover the third semiconductor portion. Image sensor.

12. In the image sensor according to any one of claims 1 to 11, An image sensor comprising a microlens for focusing light in the first photoelectric conversion unit.

13. In the image sensor according to claim 12, The first separation portion and the second separation portion are formed on the first semiconductor substrate so as to extend in the direction of the optical axis of the microlens. Image sensor.

14. In the image sensor according to claim 13, The length of the first separation portion in the optical axis direction is 2 / 3 or more of the thickness of the first semiconductor substrate. Image sensor.

15. In the image sensor according to claim 13 or claim 14, The length of the first separation unit in the optical axis direction is 1 μm or more. Image sensor.

16. In the image sensor according to any one of claims 13 to 15, The length of the second separation portion in the optical axis direction is 2 / 3 or more of the thickness of the first semiconductor substrate. Image sensor.

17. In the image sensor according to any one of claims 13 to 16, The length of the second separation section in the optical axis direction is 1 μm or more. Image sensor.

18. In the image sensor according to any one of claims 1 to 17, An image sensor comprising a second semiconductor substrate stacked with the first semiconductor substrate.

19. In the image sensor according to claim 18, The second semiconductor substrate has a second circuit that is electrically connected to the first circuit. Image sensor.

20. In the image sensor according to claim 19, The second circuit is used to process a first signal based on the charge transferred from the first photoelectric conversion unit to the first storage unit by the first transfer unit. Image sensor.

21. An imaging device comprising an image sensor according to any one of claims 1 to 20.

22. In the imaging device according to claim 21, An imaging device comprising a generation unit that is electrically connected to the image sensor and generates image data.

23. In the imaging device according to claim 21 or claim 22, An imaging device comprising an optical system for forming an image of light on the aforementioned image sensor.

Images