CN115224066A - Image sensor and method of forming the same - Google Patents

Abstract

An image sensor and a method for forming the same, wherein the forming method includes: providing a substrate, the substrate including a pixel region; forming a plurality of deep trenches in the pixel region; forming a first doped epitaxial layer in the deep trench, the first doped epitaxial layer The hetero-epitaxial layer has first ions; the first intrinsic epitaxial layer is formed in the deep trench; the second doped epitaxial layer is formed in the deep trench, and the second doped epitaxial layer has second ions and the first ions Different electrical type from the second ion. Since the thin films in the epitaxial growth process are stacked layer by layer, and ions are added to each thin film grown, the first ion concentration distribution in the first doped epitaxial layer and the second doped epitaxial layer are formed. The uniformity of the second ion concentration distribution within is greatly improved. In addition, the formation of the first doped epitaxial layer and the second doped epitaxial layer by epitaxial growth will not cause loss to the surface of the substrate, thereby effectively improving the pixel performance of the finally formed image sensor.

Description

Image sensor and method of forming the same

technical field

The present invention relates to the technical field of semiconductor manufacturing, and in particular, to an image sensor and a method for forming the same.

Background technique

Image sensors are semiconductor devices that convert optical images into electrical signals. Because of the advantages of low power consumption and high signal-to-noise ratio, CMOS image sensors (CMOS Image Sensor, CIS) have been widely used in various fields.

The most commonly used Pixel unit in a CMOS image sensor contains a photodiode PD and four MOS transistors, including a transfer transistor TX, a reset transistor RST, a source follower transistor SF, a row select transistor RS, and a floating diffusion region FD, which can realize the photoelectric Control of selection, reset, signal output, signal amplification and readout of diode PD. The principle is that when light irradiates the photodiode PD, photo-generated carriers will accumulate in the photodiode PD, and then the transfer transistor TX is turned on through the external control circuit, and the photo-generated carriers flow from the photodiode PD to the floating diffusion area FD. The floating diffusion region FD is not only the drain of the transfer transistor TX, but also the PN junction capacitance, and the floating diffusion region FD converts photogenerated carriers into voltage signal output.

However, there are still many problems in the formation process of the prior art CMOS image sensor.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is to provide an image sensor and a method for forming the same, so as to improve the performance of the pixels in the image sensor.

In order to solve the above problems, the technical solution of the present invention provides a method for forming an image sensor, which includes: providing a substrate with first ions in the substrate, and the substrate includes a pixel area; a number of deep trenches; a first doped epitaxial layer is formed in the deep trenches, and the first doped epitaxial layer has the first ions; a first intrinsic epitaxial layer is formed in the deep trenches, so The first intrinsic epitaxial layer is located on the first doped epitaxial layer; a second doped epitaxial layer is formed in the deep trench, the second doped epitaxial layer has second ions, and the second doped epitaxial layer is formed in the deep trench. The electrical type of an ion is different from that of the second ion, the second doped epitaxial layer is located on the first intrinsic epitaxial layer; a second intrinsic epitaxial layer is formed in the deep trench, the first intrinsic epitaxial layer is formed Two intrinsic epitaxial layers are located on the second doped epitaxial layer, and the second intrinsic epitaxial layer fills the deep trench; after the second intrinsic epitaxial layer is formed, the first The doped epitaxial layer and the second doped epitaxial layer are annealed, so that the first ions in the first doped epitaxial layer and the second ions in the second doped epitaxial layer are diffused to the second doped epitaxial layer. within an intrinsic epitaxial layer.

Optionally, the first ions are P-type ions; the second ions are N-type ions.

Optionally, the doping concentration of the first ions in the first doped epitaxial layer is greater than the doping concentration of the first ions in the substrate; the doping concentration of the second ions in the second doped epitaxial layer The doping concentration is greater than the doping concentration of the first ions within the substrate.

Optionally, the doping concentration of the first ions in the first doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

Optionally, the doping concentration of the second ions in the second doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

Optionally, the thickness of the first intrinsic epitaxial layer is greater than the thickness of the first doped epitaxial layer; the thickness of the first intrinsic epitaxial layer is greater than the thickness of the second doped epitaxial layer.

Optionally, the thickness of the first doped epitaxial layer is 40 nm to 60 nm; the thickness of the second doped epitaxial layer is 40 nm to 60 nm; the thickness of the first intrinsic epitaxial layer is 90 nm nanometer to 110 nanometers.

Optionally, the substrate further includes: a marking area; in the process of forming the deep trench, further comprising: forming a marking opening in the marking area; the marking opening has a first depth dimension, the The deep trench has a second depth dimension that is greater than the first depth dimension.

Optionally, the method for forming the marked opening and the deep trench includes: forming a first patterned layer on the substrate, the first patterned layer exposing a part of the surface of the substrate; The first patterned layer is a mask to etch the substrate, the mark opening is formed in the mark area, and an initial deep trench is formed in the pixel area; the first patterned layer is removed; An epitaxial barrier layer is formed on the surface of the marking opening and the surface of the initial deep trench; after the epitaxial barrier layer is formed, a sacrificial layer is formed on the substrate, and the sacrificial layer covers the marking opening; After the sacrificial layer is formed, the initial deep trench is etched to form the deep trench; after the deep trench is formed, the sacrificial layer is removed.

Optionally, after removing the sacrificial layer, the method further includes: performing an extension etching process on the deep trench along a direction perpendicular to the sidewall of the deep trench.

Optionally, after forming the second doped epitaxial layer and before forming the second intrinsic epitaxial layer, further comprising: removing the epitaxial barrier layer located in the marking opening and the deep trench; The process of forming the second intrinsic epitaxial layer in the deep trench further includes: forming the second intrinsic epitaxial layer in the marking opening and on the substrate.

Optionally, after annealing the first doped epitaxial layer and the second doped epitaxial layer, the method further includes: forming a first lead region in the second intrinsic epitaxial layer, the first The second ions are located in the lead region, and the first lead region is respectively connected with the first doped epitaxial layer, the first intrinsic epitaxial layer and the second doped epitaxial layer; in the second intrinsic epitaxial layer A second lead region is formed within the layer and the substrate between adjacent said deep trenches, said second lead region having said first ions.

Correspondingly, the technical solution of the present invention further provides an image sensor, comprising: a substrate having first ions in the substrate, the substrate including a pixel region; a plurality of deep trenches located in the pixel region; a first doped epitaxial layer located in the deep trench, the first doped epitaxial layer has the first ions; a first intrinsic epitaxial layer located in the deep trench, the first intrinsic epitaxial layer The epitaxial layer is located on the first doped epitaxial layer; the second doped epitaxial layer is located in the deep trench, and the second doped epitaxial layer has second ions, and the first ions and the The electrical types of the second ions are different, the second doped epitaxial layer is located on the first intrinsic epitaxial layer; the second intrinsic epitaxial layer located in the deep trench, the second intrinsic epitaxial layer on the second doped epitaxial layer, and the second intrinsic epitaxial layer fills the deep trench.

Optionally, the first ions are P-type ions; the second ions are N-type ions.

Optionally, the doping concentration of the first ions in the first doped epitaxial layer is greater than the doping concentration of the first ions in the substrate; the doping concentration of the second ions in the second doped epitaxial layer The doping concentration is greater than the doping concentration of the first ions within the substrate.

Optionally, the doping concentration of the first ions in the first doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

Optionally, the doping concentration of the second ions in the second doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

Optionally, the thickness of the first intrinsic epitaxial layer is greater than the thickness of the first doped epitaxial layer; the thickness of the first intrinsic epitaxial layer is greater than the thickness of the second doped epitaxial layer.

Optionally, the thickness of the first doped epitaxial layer is 40 nm to 60 nm; the thickness of the second doped epitaxial layer is 40 nm to 60 nm; the thickness of the first intrinsic epitaxial layer is 90 nm nanometer to 110 nanometers.

Optionally, the substrate further includes: a marking area, the marking area has a marking opening, the second intrinsic epitaxial layer is also located in the marking opening and on the substrate; the marking opening has a first depth dimension, the deep trench has a second depth dimension greater than the first depth dimension.

Optionally, it further includes: a first lead region located in the second intrinsic epitaxial layer, the first lead region has the second ions, the first lead region is respectively connected to the first dopant The hetero-epitaxial layer, the first intrinsic epitaxial layer and the second doped epitaxial layer are connected; the second lead region located in the second intrinsic epitaxial layer and the substrate located between the adjacent deep trenches, so The second lead region has the first ions.

Compared with the prior art, the technical solution of the present invention has the following advantages:

In the method for forming an image sensor according to the technical solution of the present invention, the formation process of the first doped epitaxial layer and the second doped epitaxial layer adopts an epitaxial growth process, because the thin films in the epitaxial growth process are stacked layer by layer , and ions are added to each film grown, so that the first ion concentration distribution in the formed first doped epitaxial layer and the second ion concentration distribution in the second doped epitaxial layer are different from each other. Uniformity is greatly improved. In addition, the formation of the first doped epitaxial layer and the second doped epitaxial layer by epitaxial growth will not cause loss to the surface of the substrate, thereby effectively improving the pixel performance of the finally formed image sensor.

In the image sensor of the technical solution of the present invention, the formation process of the first doped epitaxial layer and the second doped epitaxial layer adopts an epitaxial growth process, because the thin films in the epitaxial growth process are stacked layer by layer, and each Growing a thin film will incorporate ions, so that the uniformity of the first ion concentration distribution in the first doped epitaxial layer and the second ion concentration distribution in the second doped epitaxial layer is greatly increased. improve. In addition, the formation of the first doped epitaxial layer and the second doped epitaxial layer by epitaxial growth will not cause loss to the surface of the substrate, thereby effectively improving the pixel performance of the finally formed image sensor.

Description of drawings

1 is a schematic structural diagram of each step of a method for forming an image sensor;

2 to 12 are schematic structural diagrams of steps of a method for forming an image sensor according to an embodiment of the present invention.

Detailed ways

As described in the background art, there are still many problems in the formation process of the prior art CMOS image sensor. The following will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic structural diagram of each step of a method for forming an image sensor.

Referring to FIG. 1, a substrate 100 is provided; an ion implantation process is used to form a first doped region 101 and a second doped region 102 adjacent to each other in the substrate 100, and the first doped region 101 has a first doped region 101. An ion, the second doped region 102 has a second ion, and the electrical type of the first ion and the second ion are different.

In this embodiment, since the electrical types of the first ions and the second ions are different, the first ions and the second ions will diffuse to a certain extent after being annealed, thereby forming a photodiode structure . Subsequently, the substrate 100 is irradiated with light on the substrate to excite electrons, and the photodiode structure is used to form an electrical signal from the excited electrons.

However, since both the first doped region 101 and the second doped region 102 are formed by ion implantation, the high-energy ion implantation may damage the surface of the substrate 100, and during the ion implantation process , the ion concentration distribution in the longitudinal direction of the first doped region 101 and the second doped region 102 will be uneven, thereby affecting the pixel performance in the image sensor.

On this basis, the present invention provides an image sensor and a method for forming the same. The formation processes of the first doped epitaxial layer and the second doped epitaxial layer both adopt an epitaxial growth process. It is stacked layer by layer, and ions are added to each film grown, so that the first ion concentration distribution in the first doped epitaxial layer and the first ion concentration distribution in the second doped epitaxial layer are formed. The uniformity of diion concentration distribution is greatly improved. In addition, the formation of the first doped epitaxial layer and the second doped epitaxial layer by epitaxial growth will not cause loss to the surface of the substrate, thereby effectively improving the pixel performance of the finally formed image sensor.

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

2 to 12 are schematic structural diagrams of steps of a method for forming a backside illuminated image sensor according to an embodiment of the present invention.

Referring to FIG. 2 , a substrate 200 is provided, the substrate 200 has first ions therein, and the substrate 200 includes the pixel region I.

In this embodiment, the material of the substrate 200 is silicon.

In other embodiments, the material of the substrate may also be germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium.

In this embodiment, the first ions are P-type ions.

The P-type ions include: boron ions or indium ions.

In this embodiment, boron ions are used as the P-type ions.

In this embodiment, the substrate 200 further includes a marking region II. The pixel area I is used to form a pixel unit, and the mark area II is used to form a mark structure, and the mark structure is used for aligning the transistors with the pixel area in the subsequent process of forming the pixel unit.

In this embodiment, after the substrate 200 is provided, the method further includes: forming a plurality of deep trenches in the pixel region I; forming a marking opening in the marking region II; the marking opening has a first depth dimension, the deep trench has a second depth dimension greater than the first depth dimension. For the specific process, please refer to FIG. 3 to FIG. 6 .

Referring to FIG. 3, a first patterned layer (not shown) is formed on the substrate 200, and the first patterned layer exposes part of the surface of the substrate 200; the first patterned layer is The substrate 200 is etched with a mask, the marking opening 201 is formed in the marking region II, and an initial deep trench 202 is formed in the pixel region I; the first patterned layer is removed.

In this embodiment, the marking opening 201 has a first depth dimension.

Referring to FIG. 4 , an epitaxial barrier layer 203 is formed on the surface of the marking opening 201 and the surface of the initial deep trench 202 .

In this embodiment, the material of the epitaxial barrier layer 203 is silicon oxide.

In this embodiment, the purpose of forming the epitaxial barrier layer 203 in the marking opening 201 is to prevent subsequent processes of forming the first doped epitaxial layer, the first intrinsic epitaxial layer and the second doped epitaxial layer , the marking opening 201 is filled.

Please refer to FIG. 5 , after the epitaxial barrier layer 203 is formed, a sacrificial layer (not shown) is formed on the substrate 200 , the sacrificial layer covers the marking opening 201 ; after the sacrificial layer is formed, The initial deep trench 202 is etched to form the deep trench 204; after the deep trench 204 is formed, the sacrificial layer is removed.

In this embodiment, since the marking openings 201 are formed at the same time in the process of forming the deep trenches 204 , it is possible to avoid using a single photomask etching to form the marking openings 201 again, thereby effectively reducing the number of processes steps, and reduce the production cost.

In this embodiment, the deep trench 204 has a second depth dimension that is greater than the first depth dimension.

Referring to FIG. 6 , after the sacrificial layer is removed, the deep trench 204 is extended and etched along the direction perpendicular to the sidewall of the deep trench 204 .

In the present embodiment, a wet etching process is used to perform the extended etching process on the deep trenches 204 along the direction perpendicular to the sidewalls of the deep trenches 204 .

Referring to FIG. 7 , a first doped epitaxial layer 205 is formed in the deep trench 204 , and the first doped epitaxial layer 205 has the first ions.

In this embodiment, the formation process of the first doped epitaxial layer 205 adopts an epitaxial growth process.

In this embodiment, the first ions are P-type ions.

The P-type ions include: boron ions or indium ions.

In this embodiment, boron ions are used as the P-type ions.

In this embodiment, the doping concentration of the first ions in the first doped epitaxial layer 205 is greater than the doping concentration of the first ions in the substrate 200 .

In this embodiment, the doping concentration of the first ions in the first doped epitaxial layer 205 is 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

In this embodiment, the thickness of the first doped epitaxial layer 205 is 40 nanometers to 60 nanometers.

Referring to FIG. 8 , a first intrinsic epitaxial layer 206 is formed in the deep trench 204 , and the first intrinsic epitaxial layer 206 is located on the first doped epitaxial layer 205 .

In this embodiment, the formation process of the first intrinsic epitaxial layer 206 adopts an epitaxial growth process.

In this embodiment, the thickness of the first intrinsic epitaxial layer 206 is greater than the thickness of the first doped epitaxial layer 205 .

In this embodiment, the thickness of the first intrinsic epitaxial layer 206 is 90 nanometers to 110 nanometers.

Referring to FIG. 9 , a second doped epitaxial layer 207 is formed in the deep trench 204 , the second doped epitaxial layer 207 has second ions, and the electrical properties of the first ions and the second ions are Different types, the second doped epitaxial layer 207 is located on the first intrinsic epitaxial layer 206 .

In this embodiment, the formation process of the second doped epitaxial layer 207 adopts an epitaxial growth process.

In this embodiment, since the thin films in the epitaxial growth process are stacked layer by layer, and ions are added to each thin film grown, the first ion concentration in the formed first doped epitaxial layer 205 is increased. The distribution and the uniformity of the second ion concentration distribution in the second doped epitaxial layer 207 are greatly improved. In addition, the formation of the first doped epitaxial layer 205 and the second doped epitaxial layer 207 by epitaxial growth will not cause loss to the surface of the substrate 200 , thereby effectively improving the pixel performance of the final image sensor.

In this embodiment, the second ions are N-type ions.

The N-type ions include: phosphorus ions or arsenic ions.

In this embodiment, phosphorus ions are used as the N-type ions.

In this embodiment, the doping concentration of the second ions in the second doped epitaxial layer 207 is greater than the doping concentration of the first ions in the substrate.

In this embodiment, the doping concentration of the second ions in the second doped epitaxial layer 207 is 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

In this embodiment, the thickness of the first intrinsic epitaxial layer 206 is greater than the thickness of the second doped epitaxial layer 207 .

In this embodiment, the thickness of the second doped epitaxial layer 207 is 40 nanometers to 60 nanometers.

Referring to FIG. 10, a second intrinsic epitaxial layer 208 is formed in the deep trench 204, the second intrinsic epitaxial layer 208 is located on the second doped epitaxial layer 207, and the second intrinsic epitaxial layer 208 is The epitaxial layer 208 fills the deep trenches 204 .

In this embodiment, the formation process of the second intrinsic epitaxial layer 208 adopts an epitaxial growth process.

In this embodiment, before forming the second intrinsic epitaxial layer 208 , the method further includes: removing the epitaxial barrier layer 203 .

In this embodiment, the process of forming the second intrinsic epitaxial layer 208 in the deep trench 204 further includes: forming the second intrinsic epitaxial layer in the marking opening 201 and on the substrate 200 Epitaxial layer 208 .

In this embodiment, the second intrinsic epitaxial layer 208 formed in the marking opening 201 is specifically located on the sidewall and bottom surface of the marking opening 201 , so the second intrinsic epitaxial layer 208 located in the marking opening 201 The surface of the two intrinsic epitaxial layers 208 is not flat, so according to this feature, it will be used as a subsequent marking structure.

Referring to FIG. 11 , after the second intrinsic epitaxial layer 208 is formed, the first doped epitaxial layer 205 and the second doped epitaxial layer 207 are annealed, so that the first doped epitaxial layer 207 is annealed. The first ions in 205 and the second ions in the second doped epitaxial inner layer 207 diffuse into the first intrinsic epitaxial layer 206 .

In this embodiment, since the electrical types of the first ions and the second ions are different, the first ions and the second ions diffuse into the first intrinsic epitaxial layer 206 after being annealed inside, and then a photodiode structure is formed. Subsequent light is irradiated on the substrate 200 to excite electrons from the substrate 200, and the photodiode structure is used to form an electrical signal from the excited electrons.

Referring to FIG. 12 , after the first doped epitaxial layer 205 and the second doped epitaxial layer 207 are annealed, a first lead region 209 is formed in the second intrinsic epitaxial layer 208 . The second ions are contained in the first lead region 209, and the first lead region 209 is respectively connected with the first doped epitaxial layer 205, the first intrinsic epitaxial layer 206 and the second doped epitaxial layer 207; A second lead region 210 is formed in the second intrinsic epitaxial layer 208 and the substrate 200 between the adjacent deep trenches 204 , and the second lead region 210 has the first ions therein.

In this embodiment, the formed photodiode structure is drawn out through the first lead region 209 for connection with the logic device structure formed subsequently.

Correspondingly, an embodiment of the present invention also provides an image sensor, please continue to refer to FIG. 12 , including: a substrate 200, the substrate 200 has first ions in it, and the substrate 200 includes a pixel region I; A plurality of deep trenches 204 located in the pixel region I; a first doped epitaxial layer 205 located in the deep trench 204, the first doped epitaxial layer 205 having the first ions; located in the deep trenches 204 The first intrinsic epitaxial layer 206 in the trench 204, the first intrinsic epitaxial layer 206 is located on the first doped epitaxial layer 205; the second doped epitaxial layer 207 located in the deep trench 204 , the second doped epitaxial layer 207 has second ions, the electrical types of the first ions and the second ions are different, and the second doped epitaxial layer 207 is located in the first intrinsic epitaxial layer 206; the second intrinsic epitaxial layer 208 located in the deep trench 204, the second intrinsic epitaxial layer 208 is located on the second doped epitaxial layer 207, and the second intrinsic epitaxial layer 208 208 fills the deep trench 204 .

In this embodiment, the first doped epitaxial layer 205 and the second doped epitaxial layer 207 are formed by an epitaxial growth process, because the thin films in the epitaxial growth process are stacked layer by layer, and each growth process A layer of thin film will be doped with ions, thereby making the first ion concentration distribution in the first doped epitaxial layer 205 and the second ion concentration distribution in the second doped epitaxial layer 207 uniform. Greatly improve. In addition, the formation of the first doped epitaxial layer 205 and the second doped epitaxial layer 207 by epitaxial growth will not cause loss to the surface of the substrate 200 , thereby effectively improving the pixel performance of the final image sensor.

In this embodiment, the first ions are P-type ions; the second ions are N-type ions.

In this embodiment, the doping concentration of the first ions in the first doped epitaxial layer 205 is greater than the doping concentration of the first ions in the substrate 200 ; The doping concentration of the second ions is greater than the doping concentration of the first ions in the substrate 200 .

In this embodiment, the doping concentration of the first ions in the first doped epitaxial layer 205 is 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

In this embodiment, the doping concentration of the second ions in the second doped epitaxial layer 207 is 1E17 atoms/cm ³ to 3E17 atoms/cm ³ .

In this embodiment, the thickness of the first intrinsic epitaxial layer 206 is greater than that of the first doped epitaxial layer 205 ; the thickness of the first intrinsic epitaxial layer 206 is greater than that of the second doped epitaxial layer 207 thickness.

In this embodiment, the thickness of the first doped epitaxial layer 205 is 40 nm to 60 nm; the thickness of the second doped epitaxial layer 207 is 40 nm to 60 nm; the thickness of the first intrinsic epitaxial layer The thickness of 206 is 90 nanometers to 110 nanometers.

In this embodiment, the substrate 200 further includes: a marking region II, with a marking opening 201 in the marking region II, and the second intrinsic epitaxial layer 208 is also located in the marking opening 201 and the liner On the bottom 200; the marking opening 201 has a first depth dimension, the deep trench 204 has a second depth dimension, and the second depth dimension is greater than the first depth dimension.

In this embodiment, it further includes: a first lead region 209 located in the second intrinsic epitaxial layer 208, the first lead region 209 has the second ions, and the first lead regions 209 are respectively Connected with the first doped epitaxial layer 205 , the first intrinsic epitaxial layer 206 and the second doped epitaxial layer 207 ; between the second intrinsic epitaxial layer 208 and the adjacent deep trench 204 The second lead region 210 in the substrate 200 of the substrate 200 has the first ions in the second lead region 210 .

Although the present invention is disclosed above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the scope defined by the claims.

Claims (21)

1. A method for forming an image sensor, comprising: providing a substrate having first ions therein, the substrate including a pixel region; forming a plurality of deep trenches in the pixel region; forming a first doped epitaxial layer in the deep trench, and the first doped epitaxial layer has the first ions; forming a first intrinsic epitaxial layer in the deep trench, the first intrinsic epitaxial layer is located on the first doped epitaxial layer; A second doped epitaxial layer is formed in the deep trench, and the second doped epitaxial layer has second ions. The electrical types of the first ions and the second ions are different. A hetero-epitaxial layer is located on the first intrinsic epitaxial layer; A second intrinsic epitaxial layer is formed in the deep trench, the second intrinsic epitaxial layer is located on the second doped epitaxial layer, and the second intrinsic epitaxial layer fills the deep trench ; After the second intrinsic epitaxial layer is formed, the first doped epitaxial layer and the second doped epitaxial layer are annealed, so that the first ions in the first doped epitaxial layer and the The second ions in the second doped epitaxial inner layer diffuse into the first intrinsic epitaxial layer. 2 . The method for forming an image sensor according to claim 1 , wherein the first ions are P-type ions; and the second ions are N-type ions. 3 . 3 . The method for forming an image sensor according to claim 1 , wherein the doping concentration of the first ions in the first doped epitaxial layer is greater than the doping concentration of the first ions in the substrate; 3 . The doping concentration of the second ions in the second doped epitaxial layer is greater than the doping concentration of the first ions in the substrate. 4 . The method for forming an image sensor according to claim 1 , wherein the doping concentration of the first ions in the first doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ . 5 . The method for forming an image sensor according to claim 1 , wherein the doping concentration of the second ions in the second doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ . 6 . 6. The method for forming an image sensor according to claim 1, wherein the thickness of the first intrinsic epitaxial layer is greater than the thickness of the first doped epitaxial layer; the thickness of the first intrinsic epitaxial layer greater than the thickness of the second doped epitaxial layer. 7 . The method for forming an image sensor according to claim 1 , wherein the thickness of the first doped epitaxial layer is 40 nanometers to 60 nanometers; the thickness of the second doped epitaxial layer is 40 nanometers to 60 nanometers. 8 . nanometer; the thickness of the first intrinsic epitaxial layer is 90 nanometers to 110 nanometers. 8 . The method for forming an image sensor according to claim 1 , wherein the substrate further comprises: a mark area; in the process of forming the deep trench, the method further comprises: forming a mark in the mark area. 9 . an opening; the marking opening has a first depth dimension and the deep trench has a second depth dimension greater than the first depth dimension. 9 . The method for forming an image sensor according to claim 8 , wherein the method for forming the marking opening and the deep trench comprises: forming a first patterned layer on the substrate, the first patterning layer being formed on the substrate. 10 . Part of the surface of the substrate is exposed by the patterned layer; the substrate is etched with the first patterned layer as a mask, the mark opening is formed in the mark area, and the initial mark is formed in the pixel area deep trenches; removing the first patterned layer; forming an epitaxial barrier layer on the surface of the marking opening and the surface of the initial deep trench; after forming the epitaxial barrier layer, forming on the substrate a sacrificial layer covering the marking opening; after forming the sacrificial layer, etching the initial deep trench to form the deep trench; after forming the deep trench, removing the sacrificial Floor. 10 . The method for forming an image sensor according to claim 9 , wherein after removing the sacrificial layer, the method further comprises: performing extended etching on the deep trench along a direction perpendicular to the sidewall of the deep trench. 11 . deal with. 11 . The method for forming an image sensor according to claim 9 , wherein after forming the second doped epitaxial layer and before forming the second intrinsic epitaxial layer, the method further comprises: removing the marking the opening and the epitaxial barrier layer in the deep trench; in the process of forming the second intrinsic epitaxial layer in the deep trench, further comprising: forming the marking opening and on the substrate The second intrinsic epitaxial layer. 12 . The method for forming an image sensor according to claim 1 , wherein after annealing the first doped epitaxial layer and the second doped epitaxial layer, the method further comprises: in the second present A first lead region is formed in the intrinsic epitaxial layer, the first lead region has the second ions, and the first lead region is respectively connected with the first doped epitaxial layer, the first intrinsic epitaxial layer and the second The doped epitaxial layer is connected; a second lead region is formed in the second intrinsic epitaxial layer and the substrate between the adjacent deep trenches, and the second lead region has the first ions. 13. An image sensor, comprising: a substrate with first ions in the substrate, and the substrate includes a pixel region; a number of deep trenches within the pixel region; a first doped epitaxial layer located in the deep trench, and the first doped epitaxial layer has the first ions; a first intrinsic epitaxial layer located in the deep trench, the first intrinsic epitaxial layer is located on the first doped epitaxial layer; a second doped epitaxial layer located in the deep trench, the second doped epitaxial layer has second ions, the electrical types of the first ions and the second ions are different, the second doped A hetero-epitaxial layer is located on the first intrinsic epitaxial layer; a second intrinsic epitaxial layer located in the deep trench, the second intrinsic epitaxial layer is located on the second doped epitaxial layer, and the second intrinsic epitaxial layer fills the deep trench . 14. The image sensor of claim 13, wherein the first ions are P-type ions; and the second ions are N-type ions. 15. The image sensor according to claim 13, wherein the doping concentration of the first ions in the first doped epitaxial layer is greater than the doping concentration of the first ions in the substrate; The doping concentration of the second ions in the double-doped epitaxial layer is greater than the doping concentration of the first ions in the substrate. 16 . The image sensor according to claim 13 , wherein the doping concentration of the first ions in the first doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ . 17 . The image sensor according to claim 13 , wherein the doping concentration of the second ions in the second doped epitaxial layer is: 1E17 atoms/cm ³ to 3E17 atoms/cm ³ . 18 . The image sensor of claim 13 , wherein the thickness of the first intrinsic epitaxial layer is greater than that of the first doped epitaxial layer; and the thickness of the first intrinsic epitaxial layer is greater than the thickness of the first intrinsic epitaxial layer. 19 . The thickness of the second doped epitaxial layer. 19. The image sensor according to claim 13, wherein the thickness of the first doped epitaxial layer is 40 nanometers to 60 nanometers; the thickness of the second doped epitaxial layer is 40 nanometers to 60 nanometers; The thickness of the first intrinsic epitaxial layer is 90 nanometers to 110 nanometers. 20 . The image sensor of claim 13 , wherein the substrate further comprises: a mark region, the mark region has a mark opening, and the second intrinsic epitaxial layer is further located in the mark opening and on the substrate; the mark opening has a first depth dimension, the deep trench has a second depth dimension, and the second depth dimension is greater than the first depth dimension. 21. The image sensor of claim 13, further comprising: a first lead region located in the second intrinsic epitaxial layer, the first lead region having the second ions, the The first lead region is respectively connected with the first doped epitaxial layer, the first intrinsic epitaxial layer and the second doped epitaxial layer; it is located between the second intrinsic epitaxial layer and the adjacent deep trenches A second lead region in the substrate, the second lead region has the first ions.

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