Photosensitive unit and forming method thereof
By forming a multi-part active region on the substrate of the image sensor and doping ion region, the electron transmission channel structure is optimized, and the problems of low filling rate and high process difficulty in the prior art are solved, and high dynamic range is achieved and photosensitive units with high image quality.
Patent Information
- Application Number
- CN202310780564.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-28
- Publication Date
- 2024-12-31
AI Technical Summary
In the existing stacked CMOS image sensor, the pixel array chip composed of back-illuminated pixels is stacked with the digital-to-analog hybrid circuit for data collection and processing, resulting in low photodiode filling rate and high process difficulty, and crosstalk between transistors affects the signal quantity. The maximum value of the maximum value limits the implementation of high dynamic range and high image quality.
Designing a photosensitive unit includes forming a multi-part active region on the substrate and forming different types of ion regions by doping ions, the electron transport channel extends along the substrate surface to reduce the influence of the short channel effect. The specific steps include forming an active region on the substrate surface, and forming an N-type and P-type ion region by doping ions, forming a control end covering the active region, and optimizing the structure of the electron transport channel.
It effectively reduces the impact of the short channel effect, improves the quality of signal transmission and the dynamic range of the image sensor, and reduces process difficulty and cost.
Smart Images
Figure CN119230566A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor process technology, and in particular to a photosensitive unit and a method for forming the photosensitive unit. Background Art
[0002] In the manufacturing process of conventional stacked CMOS image sensors, a pixel array chip composed of back-illuminated pixels is stacked on top of a mixed analog-digital circuit for data collection and processing. In the pixel array chip, the photodiodes for photogenerated electrons and the pixel transistors for charge transfer, charge reset, charge signal amplification, and signal row selection are on the same wafer. Such a layout reduces the photodiode fill rate; at the same time, these transistors and photodiodes use different potential well processes, which increases the process difficulty and cost; the crosstalk between transistors also affects the maximization of the saturated signal amount, which has certain limitations on achieving high dynamic range and high image quality photography.
[0003] Figure 1 FIG. 1 is a circuit diagram of an image sensor in the prior art. Figure 1 The image sensor includes a photosensitive unit 109 and a transistor unit 110. The photosensitive unit 109 includes a photodiode 100 and a charge transfer tube 101. The transistor unit 110 includes a reset tube 102, a source follower tube 103 and a row selection switch tube 104. Among them, the gate oxide of the MOS tube between the charge transfer tube 101, the reset tube 102, and the source follower tube 103, and the floating diffusion part 105 between the active areas of the far building form an integrated capacitor called FD.
[0004] In the prior art, a pixel array wafer and a peripheral circuit wafer are stacked together, wherein the photosensitive unit and the transistor unit in the pixel array wafer are distributed in parallel, and the electron transmission channel from the photodiode to the FD is a planar structure, which is easily affected by the short channel effect.
[0005] Therefore, it is necessary to provide a novel photosensitive unit and a method for forming the photosensitive unit to solve the above problems existing in the prior art. Summary of the invention
[0006] The object of the present invention is to provide a photosensitive unit and a method for forming the photosensitive unit to reduce the influence of the short channel effect.
[0007] To achieve the above-mentioned purpose, the photosensitive unit of the present invention includes a substrate, an active area and a control terminal, wherein the active area is arranged on the first surface of the substrate, and the part of the substrate not covered by the active area includes a first ion doping area and a second ion doping area from the second surface to the first surface, the first surface and the second surface of the substrate are parallel, the active area includes a first part of the active area, a second part of the active area and a third part of the active area along a first direction, the first direction is parallel to the first surface of the substrate, the part of the substrate covered by the first part of the active area includes a third ion doping area, and the part of the substrate covered by the second part of the active area and the third part of the active area from the second surface to the first surface includes a fourth ion doping area and a fifth ion-doped region, the first part of the active region includes a sixth ion-doped region, the second part of the active region includes a seventh ion-doped region, the third part of the active region includes an eighth ion-doped region and a ninth ion-doped region from the second surface to the first surface, the first surfaces of the three parts of the active region are parallel to the first surface of the substrate, the control end covers the surface of the second part of the active region, the first ion-doped region, the third ion-doped region, the fourth ion-doped region, the sixth ion-doped region and the ninth ion-doped region are all N-type ion-doped regions, and the second ion-doped region, the fifth ion-doped region, the seventh ion-doped region, and the eighth ion-doped region are all P-type ion-doped regions.
[0008] The beneficial effect of the photosensitive unit is that the active area is arranged on the first surface of the substrate, and the active area includes a first partial active area, a second partial active area and a third partial active area along a first direction, the first partial active area includes a sixth ion doping area, the second partial active area includes a seventh ion doping area, and the third partial active area includes an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, and the electron transmission channel extends along the substrate surface, reducing the influence of the short channel effect.
[0009] Optionally, the control end includes a first control end and a second control end, the first control end covers a surface of the second portion of the active area, and the second control end covers a surface of the first control end.
[0010] Optionally, the ion doping concentration of the second ion doping region is greater than the ion doping concentration of the first ion doping region.
[0011] Optionally, the ions doped into the second ion-doped region are boron ions, and the ions doped into the first ion-doped region are at least one of arsenic ions and phosphorus ions.
[0012] Optionally, the doping ion concentration of the sixth ion doping region is greater than the doping ion concentration of the second ion doping region, and the doping ion concentrations of the seventh ion doping region and the eighth ion doping region are greater than the doping ion concentration of the sixth ion doping region.
[0013] Optionally, the ions doped into the sixth ion-doped region and the ninth ion-doped region are at least one of arsenic ions and phosphorus ions, and the ions doped into the seventh ion-doped region and the eighth ion-doped region are boron ions.
[0014] The present invention also provides a method for forming a photosensitive unit, characterized by comprising:
[0015] An active region is formed on a first surface of the substrate, wherein the active region includes a first portion of the active region, a second portion of the active region, and a third portion of the active region along a first direction, wherein the first direction is parallel to the first surface of the substrate;
[0016] Doping ions into the substrate so that a portion of the substrate not covered by the active region forms a first ion-doped region and a second ion-doped region from the second surface to the first surface, a portion of the substrate covered by the first portion of the active region forms a third ion-doped region, and a portion of the substrate covered by the second portion of the active region and the third portion of the active region forms a fourth ion-doped region and a fifth ion-doped region from the second surface to the first surface, wherein the first surface and the second surface of the substrate are parallel;
[0017] Doping ions into the active area, so that the first part of the active area forms a sixth ion doping area, the second part of the active area forms a seventh ion doping area, and the third part of the active area forms an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, the first ion doping area, the third ion doping area, the fourth ion doping area, the sixth ion doping area and the ninth ion doping area are all N-type ion doping areas, the second ion doping area, the fifth ion doping area, the seventh ion doping area, and the eighth ion doping area are all P-type ion doping areas, and the first surface of the third part of the active area is parallel to the first surface of the substrate;
[0018] A control terminal is formed to cover the surface of the second active area.
[0019] The beneficial effect of the method for forming the photosensitive unit is that an active area is formed on the first surface of the substrate, the active area includes a first partial active area, a second partial active area and a third partial active area along a first direction, ions are doped into the active area so that the first partial active area forms a sixth ion doping area, the second partial active area forms a seventh ion doping area, and the third partial active area forms an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, and the electron transmission channel extends along the substrate surface, reducing the influence of the short channel effect.
[0020] Optionally, forming an active region on the first surface of the substrate includes:
[0021] forming a hard mask layer on the substrate;
[0022] forming an auxiliary layer on the hard mask layer;
[0023] etching the auxiliary layer to form an auxiliary layer pattern;
[0024] Using the auxiliary layer pattern as a mask to etch the hard mask layer to form a hard mask layer pattern, and removing the auxiliary layer pattern;
[0025] The substrate is etched using the hard mask layer pattern as a mask to form an active region on the substrate.
[0026] Optionally, doping ions into the substrate so that a portion of the substrate not covered by the active region forms a first ion-doped region and a second ion-doped region from the second surface to the first surface, comprising:
[0027] The hard mask layer pattern is used as a mask to dope ions into the portion of the substrate not covered by the active area, so that the portion of the substrate not covered by the active area forms a first ion doping region and a second ion doping region from the second surface to the first surface.
[0028] Optionally, using the hard mask layer pattern as a mask to dope ions into a portion of the substrate not covered by the active area, so that the portion of the substrate not covered by the active area forms a first ion doping region and a second ion doping region from the second surface to the first surface, comprising:
[0029] Using the hard mask layer pattern as a mask, doping at least one of arsenic ions and phosphorus ions into a portion of the substrate near the second surface that is not covered by the active area, so as to form a first ion doping area;
[0030] The hard mask layer pattern is used as a mask to dope boron ions into a portion of the substrate that is not covered by the active area and is close to the first surface, so as to form a second ion doped region.
[0031] Optionally, doping ions into the active area so that the first portion of the active area forms a sixth ion doping area, the second portion of the active area forms a seventh ion doping area, and the third portion of the active area forms an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, comprises:
[0032] doping the first active region with at least one of arsenic ions and phosphorus ions to form a sixth ion-doped region;
[0033] Doping boron ions into the second active region and the third active region to form a seventh ion-doped region and an eighth ion-doped region;
[0034] The third portion of the active region near the first surface is doped with at least one of arsenic ions and phosphorus ions to form a ninth ion-doped region.
[0035] Optionally, forming a control terminal covering the surface of the second active area includes:
[0036] Deposition of silicon dioxide or high dielectric constant materials;
[0037] Removing part of silicon dioxide or high dielectric constant material by photolithography to form a first control terminal covering the surface of the second active area;
[0038] depositing polysilicon material;
[0039] A portion of the polysilicon material is removed by photolithography to form a second control terminal covering the surface of the first control terminal. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Figure 1 is a circuit diagram of an image sensor in the prior art;
[0041] Figure 2 is a flow chart of a method for forming a photosensitive unit in some embodiments of the present invention;
[0042] Figure 3 Schematic diagram of silicon wafer isolation in some embodiments of the present invention;
[0043] Figure 4 is a schematic diagram of a first intermediate structure in some embodiments of the present invention;
[0044] Figure 5 is a schematic diagram of a second intermediate structure in some embodiments of the present invention;
[0045] Figure 6 is a schematic diagram of a third intermediate structure in some embodiments of the present invention;
[0046] Figure 7 is a schematic diagram of a fourth intermediate structure in some embodiments of the present invention;
[0047] Figure 8 is a schematic diagram of a fifth intermediate structure in some embodiments of the present invention;
[0048] Fig. 9 is a schematic diagram of a sixth intermediate structure in some embodiments of the present invention;
[0049] Fig.10 is a schematic diagram of a seventh intermediate structure in some embodiments of the present invention;
[0050] Fig.11 is a schematic diagram of an eighth intermediate structure in some embodiments of the present invention;
[0051] Fig.12 is a schematic diagram of a ninth intermediate structure in some embodiments of the present invention;
[0052] Fig.13 Schematic diagram of a photosensitive unit in some embodiments of the present invention;
[0053] Fig.14 In some embodiments of the present invention, a plurality of photosensitive units are formed on a silicon wafer along Fig.14 Schematic diagram of the cross-sectional structure of the pixel longitudinal section of the photosensitive unit shown. DETAILED DESCRIPTION
[0054] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.
[0055] In view of the problems existing in the prior art, an embodiment of the present invention provides a method for forming a photosensitive unit. Figure 2 , the method for forming the photosensitive unit comprises the following steps:
[0056] S1: forming an active region on a first surface of a substrate, wherein the active region includes a first portion of an active region, a second portion of an active region, and a third portion of an active region along a first direction, wherein the first direction is parallel to the first surface of the substrate;
[0057] S2: doping ions into the substrate, so that the portion of the substrate not covered by the active area forms a first ion doping region and a second ion doping region from the second surface to the first surface, the portion of the substrate covered by the first portion of the active area forms a third ion doping region, and the portion of the substrate covered by the second portion of the active area and the third portion of the active area forms a fourth ion doping region and a fifth ion doping region from the second surface to the first surface, and the first surface and the second surface of the substrate are parallel;
[0058] S3: doping ions into the active area, so that the first part of the active area forms a sixth ion doping area, the second part of the active area forms a seventh ion doping area, and the third part of the active area forms an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, the first ion doping area, the third ion doping area, the fourth ion doping area, the sixth ion doping area and the ninth ion doping area are all N-type ion doping areas, the second ion doping area, the fifth ion doping area, the seventh ion doping area, and the eighth ion doping area are all P-type ion doping areas, and the first surface of the third part of the active area is parallel to the first surface of the substrate;
[0059] S4: forming a control terminal covering the surface of the second active area.
[0060] In some embodiments, forming an active region on a first surface of a substrate includes:
[0061] forming a hard mask layer on the substrate;
[0062] forming an auxiliary layer on the hard mask layer;
[0063] etching the auxiliary layer to form an auxiliary layer pattern;
[0064] Using the auxiliary layer pattern as a mask to etch the hard mask layer to form a hard mask layer pattern, and removing the auxiliary layer pattern;
[0065] The substrate is etched using the hard mask layer pattern as a mask to form an active area on the substrate, wherein the material of the hard mask layer includes silicon nitride, and the material of the auxiliary layer includes polysilicon.
[0066] In some embodiments, the substrate is doped with ions to form a first ion doping region and a second ion doping region in a portion of the substrate not covered by the active region from the second surface to the first surface, including: using the hard mask layer pattern as a mask to dope ions in a portion of the substrate not covered by the active region to form a first ion doping region and a second ion doping region in a portion of the substrate not covered by the active region from the second surface to the first surface. Specifically, using the hard mask layer pattern as a mask to dope at least one of arsenic ions and phosphorus ions in a region near the second surface of a portion of the substrate not covered by the active region to form a first ion doping region, and using the hard mask layer pattern as a mask to dope boron ions in a region near the first surface of a portion of the substrate not covered by the active region to form a second ion doping region.
[0067] In some embodiments, the doping ion concentration of the second ion doping region is greater than that of the first ion doping region. Specifically, the doping ion concentration of the second ion doping region is 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 , the first ion doped region is 10 16 atoms / cm 2 Up to 10 17 atoms / cm 2 .
[0068] In some embodiments, ions are doped into the active region to form a sixth ion doping region in the first portion of the active region, a seventh ion doping region in the second portion of the active region, and an eighth ion doping region and a ninth ion doping region in the third portion of the active region from the second surface to the first surface, including:
[0069] doping the first active region with at least one of arsenic ions and phosphorus ions to form a sixth ion-doped region;
[0070] Doping boron ions into the second active region and the third active region to form a seventh ion-doped region and an eighth ion-doped region;
[0071] The third portion of the active region near the first surface is doped with at least one of arsenic ions and phosphorus ions to form a ninth ion-doped region.
[0072] In some embodiments, the doping ion concentration of the first ion doping region is greater than the doping ion concentration of the second ion doping region, and the doping ion concentration of the seventh ion doping region is greater than the doping ion concentration of the sixth ion doping region. Specifically, the doping ion concentration of the sixth ion doping region is 10 19 atoms / cm 2 Up to 1020 atoms / cm 2 The doping ion concentration of the seventh ion doping region and the eighth ion doping region is 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 The doping ion concentration of the ninth ion doping region is 10 19 atoms / cm 2 Up to 10 20 atoms / cm 2 .
[0073] In some embodiments, forming a control terminal covering the surface of the second active area portion includes:
[0074] Deposition of silicon dioxide or high dielectric constant materials;
[0075] Removing part of silicon dioxide or high dielectric constant material by photolithography to form a first control terminal covering the surface of the second active area;
[0076] depositing polysilicon material;
[0077] A portion of the polysilicon material is removed by photolithography to form a second control terminal covering the surface of the first control terminal.
[0078] The present invention also provides a photosensitive unit, comprising a substrate, an active area and a control terminal, wherein the active area is arranged on the first surface of the substrate, and the part of the substrate not covered by the active area includes a first ion doping area and a second ion doping area from the second surface to the first surface, the first surface and the second surface of the substrate are parallel, the active area includes a first part of the active area, a second part of the active area and a third part of the active area along a first direction, the first direction is parallel to the first surface of the substrate, the part of the substrate covered by the first part of the active area includes a third ion doping area, the part of the substrate covered by the second part of the active area and the third part of the active area from the second surface to the first surface includes a fourth ion doping area and a fifth ion doping area. ion doping region, the first part of the active region includes a sixth ion doping region, the second part of the active region includes a seventh ion doping region, the third part of the active region includes an eighth ion doping region and a ninth ion doping region from the second surface to the first surface, the first surfaces of the three parts of the active region are parallel to the first surface of the substrate, the control end covers the surface of the second part of the active region, the first ion doping region, the third ion doping region, the fourth ion doping region, the sixth ion doping region and the ninth ion doping region are all N-type ion doping regions, and the second ion doping region, the fifth ion doping region, the seventh ion doping region, and the eighth ion doping region are all P-type ion doping regions.
[0079] In some embodiments, the control end includes a first control end and a second control end, the first control end covers the surface of the second active area, and the second control end covers the surface of the first control end. The material of the first control end includes silicon dioxide or a high dielectric constant material, and the material of the second control end includes polysilicon material.
[0080] In some embodiments, the ion doping concentration of the second ion doping region is greater than the ion doping concentration of the first ion doping region.
[0081] In some embodiments, the ions doped in the second ion-doped region are boron ions, and the ions doped in the first ion-doped region are at least one of arsenic ions and phosphorus ions.
[0082] In some embodiments, the doping ion concentration of the sixth ion doping region is greater than the doping ion concentration of the second ion doping region, and the doping ion concentrations of the seventh ion doping region and the eighth ion doping region are greater than the doping ion concentration of the sixth ion doping region.
[0083] In some embodiments, the ions doped into the sixth ion-doped region and the ninth ion-doped region are at least one of arsenic ions and phosphorus ions, and the ions doped into the seventh ion-doped region and the eighth ion-doped region are boron ions.
[0084] Figure 3 Schematic diagram of silicon wafer isolation in some embodiments of the present invention. Figure 3 First, the silicon wafer is polished and thinned, and then the silicon wafer is doped with a concentration of 10 based on the size of the photodiode. 18 atoms / cm 2 Up to 10 19 atoms / cm 2 The boron atom concentration is reduced to form a P-type isolation region 201, and the P-type isolation region 201 isolates the silicon wafer into several substrates 100.
[0085] Figure 4 Schematic diagram of the first intermediate structure in some embodiments of the present invention. Figure 4 , silicon nitride is deposited on the substrate to form a hard mask layer 202, and polysilicon is deposited on the hard mask layer to form an auxiliary layer 203, so as to form a Figure 5 The first intermediate structure is shown.
[0086] Figure 5 Schematic diagram of the second intermediate structure in some embodiments of the present invention. The auxiliary layer 203 is photoetched to form a rectangular auxiliary layer pattern extending along the first direction, and the hard mask layer is etched using the auxiliary layer pattern as a mask to form a hard mask layer pattern, so as to form a Figure 5The second intermediate structure shown in FIG. wherein one end of the auxiliary layer pattern extends to the edge of the substrate and the other end extends to the middle of the substrate surface, and the width of the channel can be controlled by controlling the auxiliary layer pattern, and a channel of a few nanometers to several hundred nanometers, for example, 0.2 μm, can be formed.
[0087] Figure 6 The third intermediate structure in some embodiments of the present invention is schematically shown. The auxiliary layer pattern is removed by wet method, and the substrate 100 is slightly thinned to remove surface contamination and defects, forming a Figure 6 A third intermediate structure is shown.
[0088] Figure 7 The hard mask layer pattern is used as a mask to etch the substrate to form an active area extending along a first direction on the substrate, wherein the first direction is parallel to the upper surface of the portion of the substrate not covered by the active area, and the substrate is formed as shown in FIG. Figure 7 The fourth intermediate structure shown.
[0089] Figure 8 Schematic diagram of the fifth intermediate structure in some embodiments of the present invention. Using the hard mask layer pattern as a mask, the lower layer of the substrate not covered by the active area is doped with ions at a concentration of 10 16 atoms / cm 2 Up to 10 17 atoms / cm 2 At least one of arsenic ions and phosphorus ions is added to form a first ion doping region 204 for generating photogenerated electrons when the back-illuminated optical fiber is injected to record the photoelectric signal; using the hard mask layer pattern as a mask to dope the upper layer of the portion of the substrate not covered by the active region with an ion concentration of 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 boron ions to form a second ion doping region 205 to isolate the photosensitive region from the upper process curve and to form a clamping potential at the photosensitive center of the photodiode, forming a Figure 8 A fifth intermediate structure is shown.
[0090] Fig. 9 Schematic diagram of the sixth intermediate structure in some embodiments of the present invention. The hard mask layer pattern is removed by wet method to form Fig. 9 The sixth intermediate structure shown.
[0091] Fig.10 FIG. 1 is a schematic diagram of a seventh intermediate structure in some embodiments of the present invention. The first part of the active region is doped with ions at a concentration of 10 19 atoms / cm2 Up to 10 20 atoms / cm 2 At least one of arsenic ions and phosphorus ions is added to form a sixth ion doping region 206; the second active region and the third active region of the active region are doped with ions at a concentration of 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 boron ions to form the seventh ion doping region and the eighth ion doping region, that is, to form the substrate of the P-type channel and the floating diffusion portion FD, forming the following Fig.10 The seventh intermediate structure shown.
[0092] In some embodiments, the method further comprises doping a portion of the substrate covered by the first active region with ions having a concentration of 10 19 atoms / cm 2 Up to 10 20 atoms / cm 2 At least one of arsenic ions and phosphorus ions is doped into the portion of the substrate covered by the second active region and the third active region with an ion concentration of 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 of boron ions.
[0093] Fig.11 FIG. 1 is a schematic diagram of an eighth intermediate structure in some embodiments of the present invention. The ion concentration doped into the upper layer of the third active region is 10 19 atoms / cm 2 Up to 10 20 atoms / cm 2 At least one of arsenic ions and phosphorus ions is added to form a ninth ion doping region 208, forming a Fig.11 The eighth intermediate structure shown in FIG. 1 is a structure in which, due to the parasitic capacitance control of the floating diffusion FD, the depth of the N-type node here only needs to be a few nanometers to one or two hundred nanometers, and the bottom must have a P-type well.
[0094] Fig.12 Schematic diagram of the ninth intermediate structure in some embodiments of the present invention. Deposit silicon dioxide or a high dielectric constant material, remove part of the silicon dioxide or the high dielectric constant material by photolithography to form a first control terminal 209 covering the surface of the seventh ion doping region, and form a Fig.12 The ninth intermediate structure is shown, wherein the high dielectric constant material comprises tantalum oxide, titanium oxide or hafnium oxide.
[0095] Fig.13Schematic diagram of a photosensitive unit in some embodiments of the present invention. Polysilicon material is deposited, and part of the polysilicon material is removed by photolithography to form a second control terminal 210 covering the surface of the first control terminal 209. The second control terminal 210 extends to both sides to cover part of the surface of the second ion doped region 205.
[0096] Fig.14 In some embodiments of the present invention, a plurality of photosensitive units are formed on a silicon wafer along Fig.13 The schematic diagram of the cross-sectional structure of the pixel longitudinal section of the photosensitive unit shown. When the actual image sensor is used, the back incident optical fiber generates electrons in the N-region, and a high potential is applied to the gate oxide after exposure is completed, and a conductive channel is generated in the P-type silicon under the first control terminal 209. The electrons in the photodiode flow along the deep N+ electron transport region and the conductive channel to the floating diffusion part FD. The floating diffusion part FD is connected to a double-layer transistor stack, and the electronic signal is converted into a voltage signal by the stacked source follower tube SF, and is finally recognized by the third stacked circuit part.
[0097] In the present invention, the photosensitive units and transistor units in the pixel array wafer are vertically distributed, and the electron transmission channel from the photodiode to the FD extends along the substrate surface, thereby reducing the influence of the short channel effect.
[0098] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.
Claims
1. A photosensitive unit, characterized in that: The invention comprises a substrate, an active area and a control terminal, wherein the active area is arranged on the first surface of the substrate, and the part of the substrate not covered by the active area comprises a first ion doping area and a second ion doping area from the second surface to the first surface, the first surface and the second surface of the substrate are parallel, the active area comprises a first part of the active area, a second part of the active area and a third part of the active area along a first direction, the first direction is parallel to the first surface of the substrate, the part of the substrate covered by the first part of the active area comprises a third ion doping area, the part of the substrate covered by the second part of the active area and the third part of the active area comprises a fourth ion doping area and a fifth ion doping area from the second surface to the first surface, and the The first part of the active area includes a sixth ion doping area, the second part of the active area includes a seventh ion doping area, the third part of the active area includes an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, the first surfaces of the three parts of the active area are parallel to the first surface of the substrate, the control end covers the surface of the second part of the active area, the first ion doping area, the third ion doping area, the fourth ion doping area, the sixth ion doping area and the ninth ion doping area are all N-type ion doping areas, and the second ion doping area, the fifth ion doping area, the seventh ion doping area, and the eighth ion doping area are all P-type ion doping areas.
2. The photosensitive unit according to claim 1, characterized in that: The control end includes a first control end and a second control end, the first control end covers the surface of the second active area, and the second control end covers the surface of the first control end.
3. The photosensitive unit according to claim 1, characterized in that: The ion doping concentration of the second ion doping region is greater than the ion doping concentration of the first ion doping region.
4. The photosensitive unit according to claim 3, characterized in that: The ions doped into the second ion-doped region are boron ions, and the ions doped into the first ion-doped region are at least one of arsenic ions and phosphorus ions.
5. The photosensitive unit according to claim 1, characterized in that: The doping ion concentration of the sixth ion doping region is greater than the doping ion concentration of the second ion doping region, and the doping ion concentrations of the seventh ion doping region and the eighth ion doping region are greater than the doping ion concentration of the sixth ion doping region.
6. The photosensitive unit according to claim 5, characterized in that: The ions doped into the sixth ion-doped region and the ninth ion-doped region are at least one of arsenic ions and phosphorus ions, and the ions doped into the seventh ion-doped region and the eighth ion-doped region are boron ions.
7. A method for forming a photosensitive unit, characterized in that: include: An active region is formed on a first surface of the substrate, wherein the active region includes a first portion of the active region, a second portion of the active region, and a third portion of the active region along a first direction, wherein the first direction is parallel to the first surface of the substrate; Doping ions into the substrate so that a portion of the substrate not covered by the active region forms a first ion-doped region and a second ion-doped region from the second surface to the first surface, a portion of the substrate covered by the first portion of the active region forms a third ion-doped region, and a portion of the substrate covered by the second portion of the active region and the third portion of the active region forms a fourth ion-doped region and a fifth ion-doped region from the second surface to the first surface, wherein the first surface and the second surface of the substrate are parallel; Doping ions into the active area, so that the first portion of the active area forms a sixth ion doping area, the second portion of the active area forms a seventh ion doping area, and the third portion of the active area forms an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, wherein the first ion doping area, the third ion doping area, the fourth ion doping area, the sixth ion doping area, and the ninth ion doping area are all N-type ion doping areas, the second ion doping area, the fifth ion doping area, the seventh ion doping area, and the eighth ion doping area are all P-type ion doping areas, and the first surface of the third portion of the active area is parallel to the first surface of the substrate; A control terminal is formed to cover the surface of the second active area.
8. The method for forming a photosensitive unit according to claim 7, characterized in that: An active region is formed on a first surface of the substrate, comprising: forming a hard mask layer on the substrate; forming an auxiliary layer on the hard mask layer; etching the auxiliary layer to form an auxiliary layer pattern; Using the auxiliary layer pattern as a mask to etch the hard mask layer to form a hard mask layer pattern, and removing the auxiliary layer pattern; The substrate is etched using the hard mask layer pattern as a mask to form an active region on the substrate.
9. The method for forming a photosensitive unit according to claim 8, characterized in that: Doping ions into the substrate so that a portion of the substrate not covered by the active area forms a first ion doping region and a second ion doping region from the second surface to the first surface, comprising: The hard mask layer pattern is used as a mask to dope ions into the portion of the substrate not covered by the active area, so that the portion of the substrate not covered by the active area forms a first ion doping region and a second ion doping region from the second surface to the first surface.
10. The method for forming a photosensitive unit according to claim 9, characterized in that: Using the hard mask layer pattern as a mask to dope ions into a portion of the substrate not covered by the active area, so that the portion of the substrate not covered by the active area forms a first ion doping region and a second ion doping region from the second surface to the first surface, comprising: Using the hard mask layer pattern as a mask, doping at least one of arsenic ions and phosphorus ions into a portion of the substrate near the second surface that is not covered by the active area, so as to form a first ion doping area; The hard mask layer pattern is used as a mask to dope boron ions into a portion of the substrate that is not covered by the active area and is close to the first surface, so as to form a second ion doped region.
11. The method for forming a photosensitive unit according to claim 7, characterized in that: Doping ions into the active area so that the first active area forms a sixth ion doping area, the second active area forms a seventh ion doping area, and the third active area forms an eighth ion doping area and a ninth ion doping area from the second surface to the first surface, including: doping the first active region with at least one of arsenic ions and phosphorus ions to form a sixth ion-doped region; Doping boron ions into the second active region and the third active region to form a seventh ion-doped region and an eighth ion-doped region; The third portion of the active region near the first surface is doped with at least one of arsenic ions and phosphorus ions to form a ninth ion-doped region.
12. The method for forming a photosensitive unit according to claim 7, characterized in that: Forming a control terminal covering the surface of the second active area, comprising: Deposition of silicon dioxide or high dielectric constant materials; Removing part of silicon dioxide or high dielectric constant material by photolithography to form a first control terminal covering the surface of the second active area; depositing polysilicon material; A portion of the polysilicon material is removed by photolithography to form a second control terminal covering the surface of the first control terminal.