Backside illuminated image sensor and manufacturing method thereof

Abstract

The invention relates to the technical field of semiconductor integrated circuit manufacturing, in particular to a back-illuminated image sensor and a manufacturing method thereof. The backside illuminated image sensor includes: a semiconductor substrate layer including a front surface and a back surface opposite to each other; the plurality of pixel doped regions are arranged in the semiconductor substrate layer in a mutually transverse interval manner and extend downwards from the front surface of the semiconductor substrate layer; each isolation region is arranged between two adjacent pixel doping regions, and the isolation regions extend downwards from the front surface of the semiconductor substrate layer; the back face pixel region extends upwards from the back face of the semiconductor substrate layer, and the back face pixel region covers all the pixel doping regions and the isolation regions; and a plurality of back-side deep trench isolation structures, each back-side deep trench isolation structure is formed in the back-side pixel region below each isolation region, and each back-side deep trench isolation structure penetrates through the back-side pixel region and then extends into the corresponding isolation region.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor integrated circuit manufacturing, and in particular to a back-illuminated image sensor and a manufacturing method thereof. Background Art

[0002] CMOS Image Sensor (CIS) is a sensor that can convert captured light signals into electronic signals through a lens and transmit them to a processor.

[0003] In the image sensor manufacturing process, full well capacity (FWC) is one of the indicators to measure the photosensitivity of image sensors. In recent years, with the advancement of integrated circuit manufacturing process technology and the development of 5G and artificial intelligence, CMOS image sensors have played an increasingly important role. The size of image sensors has been continuously reduced, but the performance requirements have become increasingly higher, and the application scenarios of high dynamic range have also been increasing. Therefore, it is challenging to improve the full well capacity of image sensors.

[0004] In the related art, when manufacturing a back-illuminated image sensor, the pixel region is doped on the front side first, then the isolation region is doped, and then the back side process is performed.

[0005] However, due to the small size of the pixel area, the depth-width ratio of the doping window of the pixel area formed by the photoresist is large, which is not conducive to the doping of the pixel area, resulting in a reduction in the full well capacity. Summary of the invention

[0006] The present application provides a back-illuminated image sensor and a method for manufacturing the same, which can solve the problem of reduced full well capacity caused by related technologies.

[0007] In order to solve the technical problem described in the background technology, the first aspect of the present application provides a back-illuminated image sensor, the back-illuminated image sensor comprising:

[0008] A semiconductor substrate layer, the semiconductor substrate layer comprising a front side and a back side opposite to each other;

[0009] A plurality of pixel doping regions, wherein the plurality of pixel doping regions are disposed in the semiconductor base layer at a laterally spaced interval from each other and extend downward from the front surface of the semiconductor base layer;

[0010] A plurality of isolation regions, each of which is disposed between two adjacent pixel doping regions, and the isolation region extends downward from the front side of the semiconductor substrate layer;

[0011] A back pixel region, the back pixel region extending upward from the back side of the semiconductor substrate layer, the back pixel region covering all pixel doping regions and isolation regions;

[0012] A plurality of back side deep trench isolation structures are provided, each of which is formed in a back side pixel region below each of the isolation regions, and each of the back side deep trench isolation structures respectively penetrates the back side pixel region and then extends into the corresponding isolation region.

[0013] Optionally, a thickness of the back pixel region in the longitudinal direction is smaller than a height of the back deep trench isolation structure in the longitudinal direction.

[0014] Optionally, a lateral width of the backside deep trench isolation structure is smaller than a lateral width of the isolation region.

[0015] Optionally, the backside deep trench isolation structure has a lateral width of 0.1 to 0.3 um.

[0016] Optionally, the isolation region has a lateral width of 0.4 um to 0.6 um.

[0017] Optionally, a doping impurity type of the pixel doping region is the same as a doping impurity type of the back pixel region.

[0018] In order to solve the technical problem in the background technology, the second aspect of the present application provides a method for manufacturing a back-illuminated image sensor, the method for manufacturing a back-illuminated image sensor comprising the following steps:

[0019] Providing a semiconductor substrate layer, the semiconductor substrate layer comprising a front side and a back side opposite to each other;

[0020] A pixel doping region window pattern is defined on the front side of the semiconductor substrate layer by a first photoresist layer;

[0021] Performing ion doping implantation based on the pixel doping region window pattern to form a pixel doping region in the semiconductor base layer at the position of the pixel doping region window pattern, wherein the pixel doping regions are arranged in the semiconductor base layer with a lateral spacing therebetween and extend downward from the front side of the semiconductor base layer;

[0022] Defining an isolation region window pattern on the front side of the semiconductor substrate layer through a second photoresist layer;

[0023] Performing ion doping implantation based on the isolation region window pattern to form an isolation region in the semiconductor base layer at the location of the isolation region window pattern, wherein the isolation region is arranged between two adjacent pixel doping regions and extends downward from the front side of the semiconductor base layer;

[0024] After thinning the back side of the semiconductor base layer, ion doping is implanted into the back side of the semiconductor base layer to form a back side pixel region in the semiconductor base layer, wherein the back side pixel region extends upward from the back side of the semiconductor base layer and covers all pixel doping regions and isolation regions;

[0025] A backside deep trench isolation structure is manufactured. The backside deep trench isolation structure is formed in a backside pixel region below each isolation region. Each backside deep trench isolation structure penetrates through the backside pixel region and extends into the corresponding isolation region.

[0026] Optionally, the step of performing ion doping implantation on the back side of the semiconductor base layer after thinning the back side of the semiconductor base layer to form a back side pixel region in the semiconductor base layer, wherein the back side pixel region extends upward from the back side of the semiconductor base layer, and the back side pixel region covers all pixel doping regions and isolation regions, comprises:

[0027] After thinning the back side of the semiconductor base layer, ion doping is implanted into the back side of the semiconductor base layer to cover the portion of the pixel doping region close to the back side of the semiconductor base layer, and the portion of the back side pixel region close to the back side of the semiconductor base layer is inverted to form a back side pixel region;

[0028] The back side pixel region extends upward from the back side of the semiconductor substrate layer, and the back side pixel region covers all pixel doping regions and isolation regions.

[0029] The technical solution of the present application includes at least the following advantages: by forming a back pixel area on the back side of the semiconductor substrate layer and forming a back deep trench isolation structure in the back pixel area, each of the back deep trench isolation structures respectively penetrates the back pixel area and extends into the corresponding isolation area, thereby ensuring the isolation effect while increasing the volume of the pixel unit, thereby increasing the full well capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic diagram of the structure of a back-illuminated image sensor provided by an embodiment of the present application is shown;

[0032] Figure 2 A flow chart of a method for manufacturing a back-illuminated image sensor provided by an embodiment of the present application is shown;

[0033] Figure 3 A schematic diagram of a cross-sectional structure of the device during step S3 is shown;

[0034] Figure 4 A schematic diagram of a cross-sectional structure of the device during step S5 is shown;

[0035] Figure 5 A schematic diagram of the cross-sectional structure of the device after backside thinning is shown;

[0036] Figure 6 FIG. 4 shows a schematic diagram of a cross-sectional structure of the device after step S6 is completed. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0040] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0041] Figure 1 FIG. 1 shows a schematic diagram of the structure of a back-illuminated image sensor provided in an embodiment of the present application. Figure 1It can be seen from the figure that the back-illuminated image sensor includes: a semiconductor substrate layer, a plurality of pixel doping regions 110 , a plurality of isolation regions 120 , a back pixel region 130 and a plurality of back-side deep trench isolation structures 140 .

[0042] The semiconductor substrate layer includes a front side 101 and a back side 102 opposite to each other;

[0043] The plurality of pixel doping regions 110 are disposed in the semiconductor base layer at a laterally spaced interval from each other and extend downward from the front surface 101 of the semiconductor base layer.

[0044] Each of the isolation regions 120 is disposed between two adjacent pixel doping regions 110 , and the isolation region 120 extends downward from the front side of the semiconductor substrate layer.

[0045] The back pixel region 130 extends upward from the back side of the semiconductor substrate layer, and the back pixel region 130 covers all pixel doping regions 110 and isolation regions 120 .

[0046] Each of the backside deep trench isolation structures 140 is formed in the backside pixel region 130 below each of the isolation regions 120 . Each of the backside deep trench isolation structures 140 penetrates through the backside pixel region 130 and extends into the corresponding isolation region 120 .

[0047] In this embodiment, a back pixel area is formed on the back side of the semiconductor substrate layer, and a back deep trench isolation structure is formed in the back pixel area. Each of the back deep trench isolation structures penetrates the back pixel area and extends into the corresponding isolation area, thereby ensuring the isolation effect while increasing the volume of the pixel unit, thereby increasing the full well capacity.

[0048] Exemplarily, the thickness of the back pixel region 130 in the longitudinal direction is smaller than the height of the back deep trench isolation structure 140 in the longitudinal direction.

[0049] Exemplarily, the lateral width of the back deep trench isolation structure 140 is smaller than the lateral width of the isolation region 120. Optionally, the lateral width of the back deep trench isolation structure 140 is 0.1 to 0.3 um. The lateral width of the isolation region 120 is 0.4 to 0.6 um. The back deep trench isolation structure 140 is arranged in the back pixel region 130 on the back side of the corresponding position of the isolation region 120, and the upper end of the back deep trench isolation structure 140 extends into the isolation region 120, which can ensure the isolation effect while increasing the volume of the pixel unit, thereby increasing the full well capacity.

[0050] Exemplarily, the doping impurity type of the pixel doping region is the same as the doping impurity type of the back pixel region, which is N-type, and is opposite to the doping impurity type of the isolation region 120. The doping concentration of the pixel doping region is approximately 1E12, and the doping concentration of the back pixel region is approximately 1E12. Front and back injections can use multiple gradient injections according to pixel performance requirements.

[0051] Figure 2 A flow chart of a method for manufacturing a back-illuminated image sensor according to an embodiment of the present application is shown. Figure 2 It can be seen that the manufacturing method of the back-illuminated image sensor includes the following steps:

[0052] Step S1: providing a semiconductor substrate layer, wherein the semiconductor substrate layer comprises a front side and a back side opposite to each other.

[0053] Step S2: defining a pixel doping region window pattern on the front surface of the semiconductor substrate layer through a first photoresist layer.

[0054] Step S3: Perform ion doping injection based on the pixel doping area window pattern to form a pixel doping area in the semiconductor base layer at the position of the pixel doping area window pattern, wherein the pixel doping areas are arranged in the semiconductor base layer with transverse intervals from each other and extend downward from the front side of the semiconductor base layer.

[0055] Figure 3 The schematic diagram of the device cross-sectional structure during step S3 is shown. Figure 3 It can be seen that a pixel doping region window pattern 211 is formed in the first photoresist layer 210, and N-type ion doping injection can be performed based on the pixel doping region window pattern 211 to form a pixel doping region 110 in the semiconductor base layer at the position of the pixel doping region window pattern 211. The pixel doping regions 110 are arranged in the semiconductor base layer with transverse intervals from each other, and extend downward from the front side 101 of the semiconductor base layer.

[0056] Step S4: defining an isolation region window pattern on the front surface of the semiconductor substrate layer through a second photoresist layer.

[0057] Step S5: performing ion doping implantation based on the isolation region window pattern to form an isolation region in the semiconductor substrate layer at the location of the isolation region window pattern, wherein the isolation region is located between two adjacent pixel doping regions and extends downward from the front side of the semiconductor substrate layer.

[0058] Reference Figure 4 , which shows a schematic diagram of the device cross-sectional structure when step S5 is performed, from Figure 4As can be seen, an isolation region window pattern 221 is formed in the second photoresist layer 220, and P-type ion doping implantation can be performed based on the isolation region window pattern 221 to form an isolation region 120 in the semiconductor substrate layer at the location of the isolation region window pattern 221. The isolation region 120 extends downward from the front surface 101 of the semiconductor substrate layer between two adjacent pixel doping regions 110.

[0059] Step S6: After thinning the back side of the semiconductor base layer, ion doping is performed on the back side of the semiconductor base layer to form a back side pixel region in the semiconductor base layer. The back side pixel region extends upward from the back side of the semiconductor base layer, and the back side pixel region covers all pixel doping regions and isolation regions.

[0060] Reference Figure 5 , which shows a schematic diagram of the cross-sectional structure of the device after the back side is thinned. The device after step S6 is completed can be flipped over by a flipping process, and then the back side of the semiconductor substrate layer is thinned to form Figure 5 The structure shown.

[0061] Reference Figure 6 , which shows a schematic diagram of the cross-sectional structure of the device after step S6 is completed, from Figure 6 As can be seen from the figure, N-type ion doping is performed on the back side of the semiconductor substrate layer to form a back side pixel region 130 in the semiconductor substrate layer. The back side pixel region 130 extends upward from the back side 102 of the semiconductor substrate layer. The back side pixel region 130 covers all pixel doping regions 110 and isolation regions 120. Figure 6 It can be seen from the figure that the back pixel region 130 is in contact with the pixel doping region 110 and the isolation region 120 .

[0062] Step S7: manufacturing a back side deep trench isolation structure, wherein the back side deep trench isolation structure is formed in the back side pixel region below each of the isolation regions, and each of the back side deep trench isolation structures respectively penetrates the back side pixel region and extends into the corresponding isolation region.

[0063] After step S7 is completed, Figure 1 The device structure shown.

[0064] In this embodiment, a back pixel area is formed on the back side of the semiconductor substrate layer, and a back deep trench isolation structure is formed in the back pixel area. Each of the back deep trench isolation structures penetrates the back pixel area and extends into the corresponding isolation area, thereby ensuring the isolation effect while increasing the volume of the pixel unit, thereby increasing the full well capacity.

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A back-illuminated image sensor, characterized in that: The back-illuminated image sensor comprises: A semiconductor substrate layer, the semiconductor substrate layer comprising a front side and a back side opposite to each other; A plurality of pixel doping regions, wherein the plurality of pixel doping regions are disposed in the semiconductor base layer at a laterally spaced interval from each other and extend downward from the front surface of the semiconductor base layer; A plurality of isolation regions, each of which is disposed between two adjacent pixel doping regions, and the isolation region extends downward from the front side of the semiconductor substrate layer; A back pixel region, the back pixel region extending upward from the back side of the semiconductor substrate layer, the back pixel region covering all pixel doping regions and isolation regions; A plurality of back side deep trench isolation structures are provided, each of which is formed in a back side pixel region below each of the isolation regions, and each of the back side deep trench isolation structures respectively penetrates the back side pixel region and then extends into the corresponding isolation region.

2. The back-illuminated image sensor according to claim 1, wherein: The thickness of the back pixel region in the vertical direction is smaller than the height of the back deep trench isolation structure in the vertical direction.

3. The back-illuminated image sensor according to claim 1, wherein: The lateral width of the backside deep trench isolation structure is smaller than the lateral width of the isolation region.

4. The back-illuminated image sensor according to claim 3, wherein: The backside deep trench isolation structure has a lateral width of 0.1 to 0.3 um.

5. The back-illuminated image sensor according to claim 3, wherein: The isolation region has a lateral width of 0.4 um to 0.6 um.

6. The back-illuminated image sensor according to claim 1, wherein: The doping impurity type of the pixel doping region is the same as the doping impurity type of the back pixel region.

7. A method for manufacturing a back-illuminated image sensor, characterized in that: The method for manufacturing the back-illuminated image sensor comprises the following steps: Providing a semiconductor substrate layer, the semiconductor substrate layer comprising a front side and a back side opposite to each other; A pixel doping region window pattern is defined on the front side of the semiconductor substrate layer by a first photoresist layer; Performing ion doping implantation based on the pixel doping region window pattern to form a pixel doping region in the semiconductor base layer at the position of the pixel doping region window pattern, wherein the pixel doping regions are arranged in the semiconductor base layer with a lateral spacing therebetween and extend downward from the front side of the semiconductor base layer; Defining an isolation region window pattern on the front side of the semiconductor substrate layer through a second photoresist layer; Performing ion doping implantation based on the isolation region window pattern to form an isolation region in the semiconductor base layer at the location of the isolation region window pattern, wherein the isolation region is arranged between two adjacent pixel doping regions and extends downward from the front side of the semiconductor base layer; After thinning the back side of the semiconductor base layer, ion doping and implantation are performed on the back side of the semiconductor base layer to form a back side pixel region in the semiconductor base layer, wherein the back side pixel region extends upward from the back side of the semiconductor base layer and covers all pixel doping regions and isolation regions; A backside deep trench isolation structure is manufactured. The backside deep trench isolation structure is formed in a backside pixel region below each isolation region. Each backside deep trench isolation structure penetrates through the backside pixel region and extends into the corresponding isolation region.

8. The method for manufacturing a back-illuminated image sensor according to claim 7, wherein: The step of thinning the back side of the semiconductor base layer and then performing ion doping implantation on the back side of the semiconductor base layer to form a back side pixel region in the semiconductor base layer, wherein the back side pixel region extends upward from the back side of the semiconductor base layer, and the back side pixel region covers all pixel doping regions and isolation regions, comprises: After thinning the back side of the semiconductor base layer, ion doping is implanted into the back side of the semiconductor base layer to cover the portion of the pixel doping region close to the back side of the semiconductor base layer, and the portion of the back side pixel region close to the back side of the semiconductor base layer is inverted to form a back side pixel region; The back side pixel region extends upward from the back side of the semiconductor substrate layer, and the back side pixel region covers all pixel doping regions and isolation regions.

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