Photosensitive unit and forming method thereof

Abstract

The invention provides a photosensitive unit and a forming method of the photosensitive unit, the photosensitive unit comprises a substrate, an active region and a control end, the active region is arranged on a first surface of the substrate, a part of the substrate which is not covered by the active region comprises a first ion doping region and a second ion doping region from a second surface to the first surface, the first surface and the second surface of the substrate are parallel, the part, covered by the active region, of the substrate comprises a third ion doped region, and the active region comprises a fourth ion doped region, a fifth ion doped region and a sixth ion doped region from the second surface to the first surface; the control end surrounds the fourth ion doped region and the fifth ion doped region, the first surface of the active region is parallel to the second surface, the first surface of the active region is parallel to the first surface of the substrate, and an electron transmission channel extends from bottom to top, so that the influence of a short channel effect is reduced.

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 end, the active area is arranged on the first surface of the substrate, 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 part of the substrate covered by the active area includes a third ion doping area, the active area includes a fourth ion doping area, a fourth and a fifth ion doping area and a sixth ion doping area from the second surface to the first surface, the control end surrounds the fourth ion doping area and the fifth ion doping area, the first ion doping area, the third ion doping area, the fourth ion doping area and the sixth ion doping area are all N-type ion doping areas, the second ion doping area and the fifth ion doping area are all P-type ion doping areas, the first surface and the second surface of the active area are parallel, and the first surface of the active area is parallel to the first surface of the substrate.

[0008] The beneficial effect of the photosensitive unit is that the photosensitive unit includes a substrate, an active area and a control end, the active area is arranged on the first surface of the substrate, 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 part of the substrate covered by the active area includes a third ion doping area, the active area includes a fourth ion doping area, a fifth ion doping area and a sixth ion doping area from the second surface to the first surface, the control end surrounds the fourth ion doping area and the fifth ion doping area, the first ion doping area, the third ion doping area, the fourth ion doping area and the sixth ion doping area are all N-type ion doping areas, the second ion doping area and the fifth ion doping area are all P-type ion doping areas, the first surface and the second surface of the active area are parallel, the first surface of the active area is parallel to the first surface of the substrate, the electron transmission channel extends from bottom to top, reducing the influence of the short channel effect.

[0009] Optionally, the control end includes a first control end and a second control end from the active region outward, the second control end surrounds the first control end, and the first control end surrounds the fourth ion-doped region and the fifth ion-doped region.

[0010] Optionally, the first surface of the first control end and the first surface of the second control end are both flush with the first surface of the fifth ion-doped region.

[0011] Optionally, the ion doping concentration of the second ion doping region is greater than the ion doping concentration of the first ion doping region.

[0012] 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.

[0013] Optionally, the ion doping concentration of the fourth ion doping region is greater than the ion doping concentration of the third ion doping region, the ion concentration of the fifth ion doping region is less than the ion doping concentration of the fourth ion doping region, and the ion doping concentration of the fourth ion doping region is equal to the ion doping concentration of the sixth ion doping region.

[0014] Optionally, the ions doped in the fourth ion-doped region are at least one of arsenic ions and phosphorus ions, the ions doped in the fifth ion-doped region are boron ions, and the ions doped in the sixth ion-doped region are at least one of arsenic ions and phosphorus ions.

[0015] The present invention also provides a method for forming a photosensitive unit, comprising:

[0016] forming an active region on a first surface of the substrate;

[0017] 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, and a portion of the substrate covered by the active region forms a third ion-doped region, and the first surface and the second surface of the substrate are parallel;

[0018] Doping ions into the active region so that the active region forms a fourth ion-doped region, a fifth ion-doped region, and a sixth ion-doped region from the second surface to the first surface, wherein the first ion-doped region, the third ion-doped region, the fourth ion-doped region, and the sixth ion-doped region are all N-type ion-doped regions, the second ion-doped region and the fifth ion-doped region are all P-type ion-doped regions, the first surface of the active region is parallel to the second surface, and the first surface of the active region is parallel to the first surface of the substrate;

[0019] A control terminal is formed surrounding the fourth ion-doped region and the fifth ion-doped region.

[0020] The beneficial effect of the method for forming the photosensitive unit is that the method for forming the photosensitive unit includes: forming an active area on the first surface of the substrate, doping ions into the substrate so that the portion of the substrate not covered by the active area forms a first ion doping area and a second ion doping area from the second surface to the first surface, and the portion of the substrate covered by the active area forms a third ion doping area, the first surface and the second surface of the substrate are parallel, doping ions into the active area so that the active area forms a fourth ion doping area, a fifth ion doping area and a sixth ion doping area from the second surface to the first surface, the first surface and the second surface of the active area are parallel, the first surface of the active area is parallel to the first surface of the substrate, a control end surrounding the active area is formed on the first surface of the substrate, and the electron transmission channel extends from bottom to top, reducing the influence of the short channel effect.

[0021] Optionally, forming an active region on the first surface of the substrate includes:

[0022] providing a substrate;

[0023] forming a hard mask layer on the substrate;

[0024] forming an auxiliary layer on the hard mask layer;

[0025] etching the auxiliary layer to form an auxiliary layer pattern;

[0026] Using the auxiliary layer pattern as a mask, etching the hard mask layer to form a mask layer pattern, and removing the auxiliary layer pattern;

[0027] The substrate is etched using the mask layer pattern as a mask to form an active area on the substrate.

[0028] Optionally, the substrate is doped with ions 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, and a portion of the substrate covered by the active region forms a third ion-doped region, including:

[0029] The 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.

[0030] Optionally, using the 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:

[0031] Using the mask layer pattern as a mask, doping at least one of arsenic ions and phosphorus ions into a region of the substrate close to the second surface of the substrate to form a first ion-doped region;

[0032] The mask layer pattern is used as a mask to dope boron ions into a region of the substrate close to the first surface of the substrate to form a second ion doping region.

[0033] Optionally, ions are doped into the active region to form a fourth ion doping region, a fifth ion doping region and a sixth ion doping region from the second surface to the first surface of the active region, including:

[0034] doping at least one of arsenic ions and phosphorus ions into a region of the active region close to the second surface of the active region to form a fourth ion-doped region;

[0035] doping boron ions into the middle region of the active region to form a fifth ion-doped region;

[0036] At least one of arsenic ions and phosphorus ions is doped into a region of the active region close to the first surface of the active region to form a sixth ion-doped region.

[0037] Optionally, the control end includes a first control end and a second control end, forming a control end surrounding the fourth ion-doped region and the fifth ion-doped region, including:

[0038] forming a first trench surrounding the active area by photoresist;

[0039] forming an oxide material layer in the first trench;

[0040] Removing the photoresist to form a first control terminal surrounding the fourth ion-doped region and the fifth ion-doped region;

[0041] forming a second groove surrounding the first control terminal by photoresist;

[0042] forming a polysilicon material layer in the second trench;

[0043] The photoresist is removed to form a second control terminal surrounding the first control terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a circuit diagram of an image sensor in the prior art;

[0045] Figure 2 is a flow chart of a method for forming a photosensitive unit in some embodiments of the present invention;

[0046] Figure 3 Schematic diagram of silicon wafer isolation in some embodiments of the present invention;

[0047] Figure 4 is a schematic diagram of a first intermediate structure in some embodiments of the present invention;

[0048] Figure 5 is a schematic diagram of a second intermediate structure in some embodiments of the present invention;

[0049] Figure 6 is a schematic diagram of a third intermediate structure in some embodiments of the present invention;

[0050] Figure 7 is a schematic diagram of a fourth intermediate structure in some embodiments of the present invention;

[0051] Figure 8 is a schematic diagram of a fifth intermediate structure in some embodiments of the present invention;

[0052] Fig. 9 is a schematic diagram of a sixth intermediate structure in some embodiments of the present invention;

[0053] Fig.10 is a schematic diagram of a seventh intermediate structure in some embodiments of the present invention;

[0054] Fig.11 is a schematic diagram of an eighth intermediate structure in some embodiments of the present invention;

[0055] Fig.12 is a schematic diagram of a ninth intermediate structure in some embodiments of the present invention;

[0056] Fig.13 is a schematic diagram of a tenth intermediate structure in some embodiments of the present invention;

[0057] Fig.14 is a schematic diagram of an eleventh intermediate structure in some embodiments of the present invention;

[0058] Fig.15 is a schematic diagram of a twelfth intermediate structure in some embodiments of the present invention;

[0059] Fig.16 is a schematic diagram of a thirteenth intermediate structure in some embodiments of the present invention;

[0060] Fig.17 is a schematic diagram of a fourteenth intermediate structure in some embodiments of the present invention;

[0061] Fig.18 is a schematic diagram of a fifteenth intermediate structure in some embodiments of the present invention;

[0062] Fig.19 Schematic diagram of a photosensitive unit in some embodiments of the present invention;

[0063] Fig. 20In some embodiments of the present invention, a plurality of photosensitive units are formed on a silicon wafer along Fig.19 Schematic diagram of the cross-sectional structure of the pixel longitudinal section of the photosensitive unit shown. DETAILED DESCRIPTION

[0064] 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.

[0065] 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:

[0066] S1: forming an active region on a first surface of a substrate;

[0067] S2: doping ions into the substrate, so that a portion of the substrate not covered by the active region forms a first ion doping region and a second ion doping region from the second surface to the first surface, and a portion of the substrate covered by the active region forms a third ion doping region, and the first surface and the second surface of the substrate are parallel;

[0068] S3: doping ions into the active region, so that the active region forms a fourth ion doping region, a fifth ion doping region and a sixth ion doping region from the second surface to the first surface, wherein the first ion doping region, the third ion doping region, the fourth ion doping region and the sixth ion doping region are all N-type ion doping regions, the second ion doping region and the fifth ion doping region are all P-type ion doping regions, the first surface of the active region is parallel to the second surface, and the first surface of the active region is parallel to the first surface of the substrate;

[0069] S4: forming a control terminal surrounding the fourth ion-doped region and the fifth ion-doped region.

[0070] In some embodiments, forming an active region on a first surface of a substrate includes:

[0071] providing a substrate;

[0072] forming a hard mask layer on the substrate;

[0073] forming an auxiliary layer on the hard mask layer;

[0074] etching the auxiliary layer to form an auxiliary layer pattern;

[0075] Using the auxiliary layer pattern as a mask, etching the hard mask layer to form a mask layer pattern, and removing the auxiliary layer pattern;

[0076] The substrate is etched using the mask layer pattern as a mask to form an active area on the substrate. The material of the hard mask layer includes silicon nitride, and the material of the auxiliary layer includes polysilicon.

[0077] In some embodiments, ions are doped into the substrate so that a first ion-doped region and a second ion-doped region are formed in a portion of the substrate not covered by the active region from the second surface to the first surface, and a third ion-doped region is formed in a portion of the substrate covered by the active region, including: using the mask layer pattern as a mask to dope ions into a portion of the substrate not covered by the active region so that a first ion-doped region and a second ion-doped region are formed in a portion of the substrate not covered by the active region from the second surface to the first surface.

[0078] In some embodiments, using the mask layer pattern as a mask to dope ions into a portion of the substrate not covered by the active region, so that a first ion doping region and a second ion doping region are formed in the portion of the substrate not covered by the active region from the second surface to the first surface, comprising:

[0079] Using the mask layer pattern as a mask, doping at least one of arsenic ions and phosphorus ions into a region of the substrate close to the second surface of the substrate to form a first ion-doped region;

[0080] The mask layer pattern is used as a mask to dope boron ions into a region of the substrate close to the first surface of the substrate to form a second ion doping region.

[0081] In some embodiments, the concentration of ions doped into the first ion doping region is greater than the concentration of ions doped into the second ion doping region. Specifically, the concentration of ions doped into the first ion doping region is 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 The concentration of ions doped into the second ion doping region is 10 16 atoms / cm 2 Up to 10 17 atoms / cm 2 .

[0082] In some embodiments, ions are doped into the active region to form a fourth ion doping region, a fifth ion doping region, and a sixth ion doping region from the second surface to the first surface of the active region, including:

[0083] doping at least one of arsenic ions and phosphorus ions into a region of the active region close to the second surface of the active region to form a fourth ion-doped region;

[0084] doping boron ions into the middle region of the active region to form a fifth ion-doped region;

[0085] At least one of arsenic ions and phosphorus ions is doped into a region of the active region close to the first surface of the active region to form a sixth ion-doped region.

[0086] In some embodiments, the concentration of ions doped into the fourth ion doping region is greater than the concentration of ions doped into the second ion doping region, and the concentration of ions doped into the fifth ion doping region is greater than the concentration of ions doped into the fourth ion doping region. 19 atoms / cm 2 Up to 10 20 atoms / cm 2 The ion concentration doped into the fifth ion doping region is 10 18 atoms / cm 2 Up to 10 19 atoms / cm 2 The ion concentration doped into the sixth ion doping region is 10 19 atoms / cm 2 Up to 10 20 atoms / cm 2 .

[0087] In some embodiments, the control end includes a first control end and a second control end, forming a control end surrounding the fourth ion-doped region and the fifth ion-doped region, including:

[0088] forming a first trench surrounding the active area by photoresist;

[0089] forming an oxide material layer in the first trench;

[0090] Removing the photoresist to form a first control terminal surrounding the fourth ion-doped region and the fifth ion-doped region;

[0091] forming a second groove surrounding the first control terminal by photoresist;

[0092] forming a polysilicon material layer in the second trench;

[0093] The photoresist is removed to form a second control terminal surrounding the first control terminal.

[0094] In some embodiments, the control terminal includes a first control terminal and a second control terminal, forming a control terminal surrounding the active region and close to the fourth ion doping region and the fifth ion doping region, and specifically includes:

[0095] Applying photoresist to form a first photoresist layer;

[0096] Photolithography the first photoresist layer to form a first trench surrounding the active area and exposing the first surface of the substrate, wherein the exposed portion is in a ring shape;

[0097] Depositing an oxide material to form an oxide material layer, wherein the thickness of the oxide material layer is equal to the sum of the thickness of the active region close to the fourth ion doping region and the fifth ion doping region;

[0098] Removing the oxide material layer on the first photoresist layer by grinding, and removing the remaining first photoresist layer by wet method, dry method or a combination of the two, so as to form a first control terminal surrounding the active area and close to the fourth ion doping area and the fifth ion doping area;

[0099] Applying photoresist to form a second photoresist layer;

[0100] Photolithography the second photoresist layer to form a second groove surrounding the first control terminal and exposing the first surface of the substrate, wherein the exposed portion is in a ring shape;

[0101] Depositing polysilicon material to form a polysilicon material layer, wherein the thickness of the polysilicon material layer is equal to the sum of the thickness of the N-type ion doping region and the P-type ion doping region of the active region close to the second surface of the active region;

[0102] The polysilicon material layer on the second photoresist layer is removed by grinding, and the remaining second photoresist layer is removed by a wet method, a dry method or a combination of the two to form a second control terminal surrounding the first control terminal.

[0103] In some other embodiments, the control end includes a first control end and a second control end, forming a control end surrounding the fourth ion-doped region and the fifth ion-doped region, and specifically includes:

[0104] depositing a layer of oxide material;

[0105] forming a first photoresist layer;

[0106] Photolithography the first photoresist layer to form a first photoresist pattern surrounding the active area;

[0107] Using the first photoresist pattern as a mask, etching the oxide material layer, removing the first photoresist pattern, so as to form a first control terminal surrounding the fourth ion-doped region and the fifth ion-doped region;

[0108] depositing a layer of polysilicon material;

[0109] forming a second photoresist layer;

[0110] Photolithography the second photoresist layer to form a second photoresist pattern surrounding the active area;

[0111] The second photoresist pattern is used as a mask to protect the first control terminal, the polysilicon material is etched, and the second photoresist pattern is removed to form a second control terminal surrounding the first control terminal. The first control terminal and the second control terminal are concentric ring structures.

[0112] The present invention also provides a photosensitive unit, which includes a substrate, an active area and a control end, 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 type 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 part of the substrate covered by the active area includes a third ion doping area, the active area includes a fourth ion doping area, a fifth ion doping area and a sixth ion doping area from the second surface to the first surface, the control end surrounds the fourth ion doping area and the fifth ion doping area, the first ion doping area, the third ion doping area, the fourth ion doping area and the sixth ion doping area are all N-type ion doping areas, the second ion doping area and the fifth ion doping area are all P-type ion doping areas, the first surface and the second surface of the active area are parallel, and the first surface of the active area is parallel to the first surface of the substrate.

[0113] In some embodiments, the control end includes a first control end and a second control end from the active region, the second control end surrounds the first control end, and the first control end surrounds the fourth ion doping region and the fifth ion doping region, wherein the first control end and the second control end are concentric ring structures.

[0114] In some embodiments, the first surface of the first control terminal and the first surface of the second control terminal are both flush with the first surface of the fifth ion-doped region, the first surface of the fifth ion-doped region is the side of the fifth ion-doped region facing away from the substrate, and the first surface of the fifth ion-doped region is parallel to the first surface of the substrate. The material of the first control terminal includes an oxide material, the oxide material includes silicon dioxide or a high dielectric constant material, the high dielectric constant material includes tantalum oxide, titanium oxide and hafnium oxide, and the material of the second control terminal includes polysilicon material.

[0115] 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.

[0116] 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.

[0117] In some embodiments, the ion doping concentration of the fourth ion doping region is greater than the ion doping concentration of the third ion doping region, the ion concentration of the fifth ion doping region is less than the ion doping concentration of the fourth ion doping region, and the ion doping concentration of the fourth ion doping region is equal to the ion doping concentration of the sixth ion doping region.

[0118] In some embodiments, the ions doped in the fourth ion-doped region are at least one of arsenic ions and phosphorus ions, the ions doped in the fifth ion-doped region are boron ions, and the ions doped in the sixth ion-doped region are at least one of arsenic ions and phosphorus ions.

[0119] 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 200.

[0120] 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 202 to form an auxiliary layer 203, so as to form a Figure 5 The first intermediate structure is shown.

[0121] Figure 5 Schematic diagram of the second intermediate structure in some embodiments of the present invention. The auxiliary layer 203 is photolithographically formed to form a cylindrical auxiliary layer pattern, and the auxiliary layer pattern is used as a mask to etch the hard mask layer to form a mask layer pattern, so as to form a Figure 5 The second intermediate structure is shown. 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.

[0122] Figure 6The 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 200 is slightly thinned to remove surface contamination and defects, forming a Figure 6 A third intermediate structure is shown.

[0123] Figure 7 Schematic diagram of a fourth intermediate structure in some embodiments of the present invention. The substrate is etched using the mask layer pattern as a mask to form a Figure 7 The fourth intermediate structure shown.

[0124] Figure 8 Schematic diagram of the fifth intermediate structure in some embodiments of the present invention. Using the mask layer pattern as a mask, the lower substrate region of the substrate not covered by the active region 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 mask layer pattern as a mask, the upper substrate region of the portion of the substrate not covered by the active region is doped with ions at a 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.

[0125] Fig. 9 Schematic diagram of the sixth intermediate structure in some embodiments of the present invention. The mask layer pattern is removed by wet method to form Fig. 9 The sixth intermediate structure shown.

[0126] Fig.10 FIG. 1 is a schematic diagram of a seventh intermediate structure in some embodiments of the present invention. The ion concentration doped into the lower region of the 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 fourth ion doping region 206, wherein the doping ion concentration of the fourth ion doping region 206 is slightly higher than the doping ion concentration of the second ion doping region 205, so as to facilitate the subsequent formation of a conductive channel; the middle region of the active region is doped with ions at a concentration of 10 18 atoms / cm2 Up to 10 19 atoms / cm 2 boron ions to form a fifth ion doping region 207, that is, a substrate for forming a P-type channel and a floating diffusion portion FD, forming a Fig.10 The seventh intermediate structure shown.

[0127] In some embodiments, the ion concentration of the doped portion of the substrate covered by the active region is 10 19 atoms / cm 2 Up to 10 20 atoms / cm 2 At least one of arsenic ions and phosphorus ions.

[0128] Fig.11 Schematic diagram of the eighth intermediate structure in some embodiments of the present invention. The ion concentration doped into the upper region of the 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 sixth 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.

[0129] Fig.12 Schematic diagram of the ninth intermediate structure in some embodiments of the present invention. Photoresist is coated on the eighth intermediate structure to form a first photoresist layer 221, forming Fig.12 The ninth intermediate structure shown.

[0130] Fig.13 The first photoresist layer 221 is photolithographically formed to form a groove pattern surrounding the active area and exposing the first surface of the substrate, and the exposed portion is annular, forming a groove pattern as shown in FIG. Fig.13 The tenth intermediate structure shown.

[0131] Fig.14 Schematic diagram of the eleventh intermediate structure in some embodiments of the present invention. An oxidation material is deposited on the eleventh structure to form an oxidation material layer 222, and the thickness of the oxidation material layer 222 is equal to the sum of the thicknesses of the fourth ion doping region and the fifth ion doping region, forming Fig.14 The eleventh intermediate structure is shown in FIG. The oxide material includes silicon dioxide or a high dielectric constant material, and the high dielectric constant material includes tantalum oxide, titanium oxide or hafnium oxide.

[0132] Fig.15The twelfth intermediate structure is schematically shown in some embodiments of the present invention. The oxide material layer on the first photoresist layer is removed by grinding, and the remaining first photoresist layer is removed by wet method, dry method or a combination of the two to form a first control terminal 209 surrounding the fourth ion doping region and the fifth ion doping region, so as to form a Fig.15 The twelfth intermediate structure shown.

[0133] Fig.16 Schematic diagram of the thirteenth intermediate structure in some embodiments of the present invention. Photoresist is coated on the twelfth intermediate structure to form a second photoresist layer 223, forming a Fig.16 A schematic diagram of the thirteenth intermediate structure is shown.

[0134] Fig.17 Schematic diagram of the fourteenth intermediate structure in some embodiments of the present invention. The second photoresist layer 223 is photolithographically formed to form a groove pattern surrounding the first control terminal and exposing the first surface of the substrate, and the exposed portion is annular, forming a groove pattern as shown in FIG. Fig.17 The fourteenth intermediate structure shown.

[0135] Fig.18 Schematic diagram of the fifteenth intermediate structure in some embodiments of the present invention. Polysilicon material is deposited on the fourteenth intermediate structure to form a polysilicon material layer 224, and the thickness of the polysilicon material layer 224 is equal to the sum of the thickness of the fourth ion doping region and the fifth ion doping region, forming Fig.18 The fifteenth intermediate structure shown.

[0136] Fig.19 The polysilicon material layer on the second photoresist layer is removed by grinding, and the remaining second photoresist layer is removed by wet method, dry method or a combination of the two to form a second control terminal 210 surrounding the first control terminal, so as to form a Fig.19 The photosensitive unit shown.

[0137] Fig. 20 In some embodiments of the present invention, a plurality of photosensitive units are formed on a silicon wafer along Fig.19 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.

[0138] 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 from bottom to top, thereby reducing the influence of the short channel effect.

[0139] 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 photosensitive unit includes a substrate, an active area and a control end, the active area is arranged on the first surface of the substrate, 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 part of the substrate covered by the active area includes a third ion doping area, the active area includes a fourth ion doping area, a fifth ion doping area and a sixth ion doping area from the second surface to the first surface, the control end surrounds the fourth ion doping area and the fifth ion doping area, the first ion doping area, the third ion doping area, the fourth ion doping area and the sixth ion doping area are all N-type ion doping areas, the second ion doping area and the fifth ion doping area are all P-type ion doping areas, the first surface and the second surface of the active area are parallel, and the first surface of the active area is parallel to the first surface of the substrate.

2. The photosensitive unit according to claim 1, characterized in that: The control end includes a first control end and a second control end from the active region outwardly, the second control end surrounds the first control end, and the first control end surrounds the fourth ion doping region and the fifth ion doping region.

3. The photosensitive unit according to claim 2, characterized in that: The first surface of the first control end and the first surface of the second control end are both flush with the first surface of the fifth ion-doped region.

4. 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.

5. The photosensitive unit according to claim 4, characterized in that: The ions in the second ion doping region are boron ions, and the ions in the first ion doping region are at least one of arsenic ions and phosphorus ions.

6. The photosensitive unit according to claim 1, characterized in that: The ion doping concentration of the fourth ion doping region is greater than that of the third ion doping region, the ion concentration of the fifth ion doping region is less than that of the fourth ion doping region, and the ion doping concentration of the fourth ion doping region is equal to that of the sixth ion doping region.

7. The photosensitive unit according to claim 6, characterized in that: The ions doped in the fourth ion-doped region are at least one of arsenic ions and phosphorus ions, the ions doped in the fifth ion-doped region are boron ions, and the ions doped in the sixth ion-doped region are at least one of arsenic ions and phosphorus ions.

8. A method for forming a photosensitive unit, characterized in that: include: forming an active region on a 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, and a portion of the substrate covered by the active region forms a third ion-doped region, and the first surface and the second surface of the substrate are parallel; Doping ions into the active region so that the active region forms a fourth ion-doped region, a fifth ion-doped region, and a sixth ion-doped region from the second surface to the first surface, wherein the first ion-doped region, the third ion-doped region, the fourth ion-doped region, and the sixth ion-doped region are all N-type ion-doped regions, the second ion-doped region and the fifth ion-doped region are all P-type ion-doped regions, the first surface of the active region is parallel to the second surface, and the first surface of the active region is parallel to the first surface of the substrate; A control terminal is formed surrounding the fourth ion-doped region and the fifth ion-doped region.

9. The method for forming a photosensitive unit according to claim 8, characterized in that: An active region is formed on a first surface of the substrate, comprising: providing a substrate; 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, etching the hard mask layer to form a mask layer pattern, and removing the auxiliary layer pattern; The substrate is etched using the mask layer pattern as a mask to form an active area on the substrate.

10. The method for forming a photosensitive unit according to claim 9, characterized in that: Doping ions into the substrate so that a portion of the substrate not covered by the active region forms a first ion doping region and a second ion doping region from the second surface to the first surface, and a portion of the substrate covered by the active region forms a third ion doping region, including: The 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.

11. The method for forming a photosensitive unit according to claim 10, characterized in that: Using the 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 mask layer pattern as a mask, doping at least one of arsenic ions and phosphorus ions into a region of the substrate close to the second surface of the substrate to form a first ion-doped region; The mask layer pattern is used as a mask to dope boron ions into a region of the substrate close to the first surface of the substrate to form a second ion doping region.

12. The method for forming a photosensitive unit according to claim 8, characterized in that: Doping ions into the active region so that the active region forms a fourth ion doping region, a fifth ion doping region and a sixth ion doping region from the second surface to the first surface, comprising: doping at least one of arsenic ions and phosphorus ions into a region of the active region close to the second surface of the active region to form a fourth ion-doped region; doping boron ions into the middle region of the active region to form a fifth ion-doped region; At least one of arsenic ions and phosphorus ions is doped into a region of the active region close to the first surface of the active region to form a sixth ion-doped region.

13. The method for forming a photosensitive unit according to claim 8, characterized in that: The control end includes a first control end and a second control end, and forms a control end of an N-type ion doping region and a P-type ion doping region surrounding the active region and close to the second surface of the active region, including: forming a first trench surrounding the active area by photoresist; forming an oxide material layer in the first trench; Removing the photoresist to form a first control terminal surrounding the fourth ion-doped region and the fifth ion-doped region; forming a second groove surrounding the first control terminal by photoresist; forming a polysilicon material layer in the second trench; The photoresist is removed to form a second control terminal surrounding the first control terminal.

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