Image sensor and method of forming the same

Abstract

An image sensor and a forming method thereof, wherein the method comprises: providing a substrate; performing a patterning process on the substrate to form a plurality of columnar structures arranged in an array, the columnar structures arranged along a first direction have first deep trenches therebetween, the columnar structures arranged along a second direction have second deep trenches therebetween, the columnar structures arranged along a third direction have cross deep trenches therebetween, a sidewall of the columnar structure perpendicular to the first direction is a (110) crystal face, and a bevel surface of the columnar structure perpendicular to the third direction is a (100) crystal face; and forming a doped epitaxial layer in the first deep trenches, the second deep trenches, and the cross deep trenches. By arranging the sidewall of the columnar structure perpendicular to the first direction as the (110) crystal face and the bevel surface of the columnar structure perpendicular to the third direction as the (100) crystal face, defects when the cross deep trenches are finally sealed and filled can be obviously improved, and generation of white noise can be effectively reduced, so as to improve performance of the finally formed image sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular to an image sensor and a forming method thereof. BACKGROUND

[0002] An image sensor is a semiconductor device for converting an optical image into an electrical signal. CMOS image sensors (CIS) have been widely used in various fields due to their low power consumption and high signal-to-noise ratio.

[0003] The most commonly used pixel unit in a CMOS image sensor includes a photodiode PD and four MOS tubes, including a transfer transistor TX, a reset transistor RST, a source follower transistor SF, a row selection transistor RS, and a floating diffusion region FD, which can realize the control of selection, reset, signal output, signal amplification and reading of the photodiode PD. The principle is that when light shines on the photodiode PD, photo-generated carriers will accumulate in the photodiode PD, and then the photo-generated carriers will flow from the photodiode PD to the floating diffusion region FD by opening the transfer transistor TX through an external control circuit. The floating diffusion region FD is both the drain of the transfer transistor TX and a PN junction capacitor, which converts the photo-generated carriers into a voltage signal output.

[0004] However, the prior art CMOS image sensor still has many problems in the forming process. SUMMARY

[0005] The technical problem solved by the present application is to provide an image sensor and a forming method thereof, which can effectively reduce white noise to improve image quality.

[0006] To solve the above problems, the present application provides a forming method of an image sensor, comprising: providing a substrate, the substrate having a first ion therein; performing a patterned treatment on the substrate to form a plurality of columnar structures arranged in an array, the columnar structures arranged along a first direction having a first deep trench between them, the columnar structures arranged along a second direction having a second deep trench between them, and the columnar structures arranged along a third direction having a cross deep trench between them, the first direction being perpendicular to the second direction, the third direction having an angle of 45° with the first direction and the second direction, respectively, a sidewall of the columnar structure perpendicular to the first direction being a (110) crystal plane, and a bevel surface of the columnar structure perpendicular to the third direction being a (100) crystal plane; forming a doped epitaxial layer in the first deep trench, the second deep trench and the cross deep trench, and the doped epitaxial layer filling the first deep trench, the second deep trench and the cross deep trench, the doped epitaxial layer having a second ion therein, the second ion being different in electrical type from the first ion.

[0007] Optionally, the substrate material is monocrystalline silicon, and the crystal orientation of the substrate surface is <110> crystal orientation.

[0008] Optionally, before the patterning process of the substrate, the method further comprises: forming a mask material layer on the substrate; and during the patterning process of the substrate, the method further comprises: etching and removing part of the mask material layer to form a mask layer.

[0009] Optionally, the thickness of the mask material layer is 100-800 nm.

[0010] Optionally, the material of the mask layer is different from the material of the doped epitaxial layer; and the material of the mask layer comprises silicon oxide or silicon nitride.

[0011] Optionally, the forming method of the doped epitaxial layer comprises: forming an epitaxial material layer on the surfaces of the first deep trench, the second deep trench, and the intersecting deep trench, and on the surface of the mask layer; performing a first planarization process on the epitaxial material layer until the surface of the mask layer is exposed, to form an initial doped epitaxial layer; removing the mask layer; and performing a second planarization process on the initial doped epitaxial layer until the top surface of the columnar structure is exposed, to form the doped epitaxial layer.

[0012] Optionally, the process of the first planarization process comprises a chemical mechanical polishing process.

[0013] Optionally, the process of the second planarization process comprises a chemical mechanical polishing process.

[0014] Optionally, before the forming of the doped epitaxial layer, the method further comprises: forming an intrinsic epitaxial layer on the sidewall of the columnar structure, and the doped epitaxial layer is located on the intrinsic epitaxial layer.

[0015] Optionally, the first ions are N-type ions, and the second ions are P-type ions.

[0016] Optionally, after the forming of the doped epitaxial layer, the method further comprises: forming a cover layer on the columnar structure and the doped epitaxial layer.

[0017] Optionally, the forming method of the cover layer comprises: forming a cover material layer on the columnar structure and the doped epitaxial layer by an epitaxial growth process; and performing a third planarization process on the cover material layer to form the cover layer.

[0018] Optionally, the process of the third planarization process comprises a chemical mechanical polishing process.

[0019] Correspondingly, the technical scheme of the present application also provides an image sensor, comprising: a substrate, the substrate having first ions therein, the substrate comprising a plurality of columnar structures arranged in an array, the columnar structures arranged along a first direction having first deep trenches therebetween, the columnar structures arranged along a second direction having second deep trenches therebetween, the columnar structures arranged along a third direction having intersecting deep trenches therebetween, the first direction being perpendicular to the second direction, the third direction having an angle of 45 degrees with the first direction and the second direction respectively, a sidewall of the columnar structure perpendicular to the first direction being a (110) crystal plane, and a bevel surface of the columnar structure perpendicular to the third direction being a (100) crystal plane; a doped epitaxial layer located in the first deep trenches, the second deep trenches and the intersecting deep trenches, and the doped epitaxial layer filling the first deep trenches, the second deep trenches and the intersecting deep trenches, the doped epitaxial layer having second ions therein, the second ions being different in electrical type from the first ions.

[0020] Optionally, the substrate material is monocrystalline silicon, and a crystal direction of the substrate surface is a <110> crystal direction.

[0021] Optionally, the technical scheme further comprises: an intrinsic epitaxial layer located on a sidewall of the columnar structure, and the doped epitaxial layer being located on the intrinsic epitaxial layer.

[0022] Optionally, the first ions are N-type ions, and the second ions are P-type ions.

[0023] Optionally, the technical scheme further comprises: a cover layer located on the columnar structure and the doped epitaxial layer.

[0024] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0025] In the forming method of the image sensor of the technical scheme of the present application, since the sidewall of the columnar structure perpendicular to the first direction is a (110) crystal plane, and the bevel surface of the columnar structure perpendicular to the third direction is a (100) crystal plane, in the process of forming the doped epitaxial layer, the epitaxial growth rate in the first deep trench is greater than the epitaxial growth rate in the intersecting deep trench, that is, the first deep trench is sealed first. When the epitaxial filling is continued, a "cylinder" structure is gradually formed in the intersecting deep trench. With the epitaxial growth, the "cylinder" structure in the intersecting deep trench is gradually filled and sealed, and a (111) crystal plane prone to dislocation accumulation is not generated in the upper part of the intersecting deep trench. Therefore, the defects in the upper part are obviously improved when the final sealing is filled, and the generation of white noise is effectively reduced, so as to improve the performance of the finally formed image sensor.

[0026] Further, before forming the doped epitaxial layer, an intrinsic epitaxial layer is formed on the sidewall of the columnar structure, and the doped epitaxial layer is located on the intrinsic epitaxial layer. The intrinsic epitaxial layer can repair defects on the sidewall of the columnar structure, thereby improving the performance of the image sensor.

[0027] In the image sensor of the technical solution, the sidewall of the columnar structure perpendicular to the first direction is a (110) crystal plane, and the bevel surface of the columnar structure perpendicular to the third direction is a (100) crystal plane. Therefore, during formation of the doped epitaxial layer, the epitaxial growth rate in the first deep trench is greater than the epitaxial growth rate in the cross deep trench, that is, the first deep trench is sealed first. When the epitaxial filling continues, a "cylinder" structure is gradually formed in the cross deep trench. With the epitaxial process, the "cylinder" structure in the cross deep trench is gradually filled and sealed, and no (111) crystal plane prone to stacking faults is generated on the upper part of the cross deep trench. Therefore, the defects on the upper part are obviously improved when the sealing and filling are completed, and the generation of white noise is effectively reduced, thereby improving the performance of the finally formed image sensor.

[0028] Further, an intrinsic epitaxial layer is located on the sidewall of the columnar structure, and the doped epitaxial layer is located on the intrinsic epitaxial layer. The intrinsic epitaxial layer can repair defects on the sidewall of the columnar structure, thereby improving the performance of the image sensor. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figures 1 to 4 is a structural schematic diagram of each step of the forming method of the image sensor;

[0030] Figure 5 is a schematic diagram of a forming process of a doped epitaxial layer of the image sensor;

[0031] Figures 6 to 15 is a structural schematic diagram of each step of the forming method of the image sensor in the embodiment of the present application. DETAILED DESCRIPTION

[0032] As described in the background, the CMOS image sensor of the prior art still has many problems in the forming process. The following will be specifically described with reference to the drawings.

[0033] Figures 1 to 4 is a structural schematic diagram of each step of the forming method of the image sensor; Figure 5 is a schematic diagram of a forming process of a doped epitaxial layer of the image sensor.

[0034] Please refer to Figure 1 and Figure 2 , Figure 2 is Figure 1As shown in the enlarged view of the structure in part A, a substrate 100 is provided, which has first ions therein; the substrate 100 is subjected to a patterning process to form a plurality of columnar structures 101 arranged in an array, the columnar structures 101 arranged along a first direction a have first deep trenches 102 therebetween, the columnar structures 101 arranged along a second direction b have second deep trenches 103 therebetween, and the columnar structures 101 arranged along a third direction c have cross deep trenches 104 therebetween, the first direction a is perpendicular to the second direction b, the third direction c forms an angle of 45° with the first direction a and the second direction b respectively, the sidewall of the columnar structure 101 perpendicular to the first direction a is a (100) crystal plane, and the bevel surface of the columnar structure 101 perpendicular to the third direction c is a (110) crystal plane.

[0035] Please refer to Figure 3 and Figure 4 , Figure 3 and Figure 2 , the view directions are consistent, Figure 4 is Figure 3 As shown in the cross-sectional view along line A-A in FIG. 1, a doped epitaxial layer 105 is formed in the first deep trenches 102, the second deep trenches 103 and the cross deep trenches 104, and the doped epitaxial layer 105 fills the first deep trenches 102, the second deep trenches 103 and the cross deep trenches 104, and the doped epitaxial layer 105 has second ions therein, which are different from the first ions in electrical type.

[0036] In the present embodiment, the substrate 100 is a <100> crystal silicon substrate, and in the process of forming the doped epitaxial layer in the first deep trenches 102, the second deep trenches 103 and the cross deep trenches 104, since the width size d1 of the first deep trenches 102 is smaller than the diagonal width size d2 of the cross deep trenches 104, and the sidewall of the columnar structure 101 perpendicular to the first direction a is a (100) crystal plane, and the bevel surface of the columnar structure 101 perpendicular to the third direction c is a (110) crystal plane, since the growth rate of the (110) crystal plane is faster than that of the (100) crystal plane, (111) crystal planes are easily formed in the upper portions of the first deep trenches 102 and the cross deep trenches 104 in the unsealing process (as shown in FIG. 2). Figure 4 Since the growth rate of the (111) crystal plane is the slowest, as the epitaxial growth continues, the growth speed of the third direction c is the fastest, and the merging growth is performed from four directions, and the first deep trenches 102 are also gradually merged, and finally the merging is performed from eight directions in the upper portions of the cross deep trenches 104 (as shown in FIG. 3). Figure 5As shown in Fig. 1 (b), according to the single-atom nucleation Si-Si stacking arrangement of the silicon epitaxial method, the eight faces formed during the continued growth of the eight faces have different growth rates, and the dislocation is accumulated on the uppermost (111) crystal face during the final sealing (as shown in Fig. 1 (c)). Figure 4 As shown in Part B of Fig. 1.

[0037] The lattice dislocation phenomenon causes the subsequent formed part of the pixel points to also generate charges in the absence of light, and the accumulation of the charges will generate a dark current. For a pixel unit, if the dark current value exceeds the photocurrent generated by capturing photoelectrons, the pixel unit will be considered as a white pixel, thereby affecting the performance of the finally formed image sensor.

[0038] On this basis, the application provides an image sensor and a forming method thereof. The sidewall perpendicular to the first direction of the columnar structure is a (110) crystal face, and the bevel perpendicular to the third direction of the columnar structure is a (100) crystal face. Therefore, during the formation of the doped epitaxial layer, the epitaxial growth rate in the first deep trench is greater than the epitaxial growth rate in the cross deep trench, that is, the first deep trench is sealed first. When the epitaxial filling is continued, a "cylinder" structure is gradually formed in the cross deep trench. With the epitaxial process, the "cylinder" structure in the cross deep trench is gradually filled and sealed, and the (111) crystal face prone to dislocation accumulation is not generated on the upper part of the cross deep trench. Therefore, the defects on the upper part are obviously improved when the final sealing is filled, thereby effectively reducing the generation of white noise and improving the performance of the finally formed image sensor.

[0039] In order to make the above-mentioned purposes, characteristics and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below with reference to the drawings.

[0040] Figures 6 to 15 Fig. 1 is a structural schematic diagram of each step of the forming method of the image sensor in the embodiment of the application.

[0041] Please refer to Figure 6 and Figure 7 , Figure 7 is Figure 6 Fig. 1 (b) is a schematic diagram of the cross section along the B-B line in Fig. 1 (a), which provides a substrate 200 having first ions in the substrate 200.

[0042] In the embodiment, the substrate 200 includes a base, a first P-type epitaxial layer on the base, a first intrinsic epitaxial layer on the first P-type epitaxial layer, and an N-type epitaxial layer (not marked) on the first intrinsic epitaxial layer.

[0043] It should be noted that the first ions in the substrate 200 are N-type ions doped in the N-type epitaxial layer.

[0044] The N-type ions include phosphorus ions or arsenic ions. In this embodiment, the N-type ions are phosphorus ions.

[0045] In this embodiment, the material of the substrate is silicon doped with P-type ions. In other embodiments, the material of the substrate can also be germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium.

[0046] In this embodiment, the material of the substrate 200 is single crystal silicon, and the crystal orientation of the surface of the substrate 200 is <110> crystal orientation.

[0047] Please refer to the same view direction of Figure 8 , Figure 8 and Figure 7 , a mask material layer 201 is formed on the substrate 200.

[0048] In this embodiment, the mask material layer 201 is a single layer structure, and the material of the mask material layer 201 is silicon oxide or silicon nitride.

[0049] In other embodiments, the mask material layer can also be a multi-layer structure, specifically a first mask material layer, a second mask material layer located on the first mask material layer, and a third mask material layer located on the second mask material layer. The materials of the first mask material layer and the third mask material layer are silicon oxide, and the material of the second mask material layer is silicon nitride.

[0050] In this embodiment, the thickness of the mask material layer 201 is 100-800 nm.

[0051] In this embodiment, the material of the mask material layer 201 is different from the material of the subsequently formed doped epitaxial layer, which is used as a polishing stop layer for subsequent planarization treatment of the epitaxial material layer.

[0052] Please refer to the same view direction of Figure 9 and Figure 10 , Figure 10 is Figure 9The structure diagram of the mask layer omitted in the middle C part is shown. The substrate 200 is subjected to a patterning process to form a plurality of columnar structures 202 arranged in an array. The columnar structures 202 arranged along a first direction a have first deep trenches 203 therebetween. The columnar structures 202 arranged along a second direction b have second deep trenches 204 therebetween. The columnar structures 202 arranged along a third direction c have intersecting deep trenches 205 therebetween. The first direction a is perpendicular to the second direction b. The third direction c forms an angle of 45° with the first direction a and the second direction b, respectively. A sidewall of the columnar structure 202 perpendicular to the first direction a is a (110) crystal plane. An inclined surface of the columnar structure 202 perpendicular to the third direction c is a (100) crystal plane.

[0053] In the embodiment, the mask material layer 201 is etched to form a mask layer 206 during the patterning process of the substrate 200.

[0054] In the embodiment, the line width of the first deep trench 203 is 0.3-0.5 microns. The line width of the second deep trench 204 is 0.3-0.5 microns.

[0055] In the embodiment, the first deep trench 203, the second deep trench 204, and the intersecting deep trench 205 are subjected to a cleaning process to remove residues formed in the first deep trench 203, the second deep trench 204, and the intersecting deep trench 205 during the etching process.

[0056] In the embodiment, the wet etching process is used in the patterning process of the substrate 200.

[0057] Please refer to Figure 11 and Figure 12 , Figure 12 are Figure 11 The intrinsic epitaxial layer 207 is formed on the sidewalls of the first deep trench 203, the second deep trench 204, and the intersecting deep trench 205.

[0058] In the embodiment, the intrinsic epitaxial layer 207 can repair defects on the sidewalls of the first deep trench 203, the second deep trench 204, and the intersecting deep trench 205 to improve the performance of the image sensor finally formed.

[0059] In the embodiment, the epitaxial growth process is used in the formation of the intrinsic epitaxial layer 207.

[0060] Please refer to Figure 13 , Figure 13and Figure 12 The direction of view is consistent with the first direction a, a doped epitaxial layer 208 is formed in the first deep trench 203, the second deep trench 204 and the cross deep trench 205, and the doped epitaxial layer 208 fills the first deep trench 203, the second deep trench 204 and the cross deep trench 205, and the doped epitaxial layer 208 has second ions, and the second ions are different from the first ions in electrical type.

[0061] In the embodiment, since the sidewall perpendicular to the first direction a of the columnar structure 202 is a (110) crystal plane, and the bevel perpendicular to the third direction c of the columnar structure 202 is a (100) crystal plane, in the process of forming the doped epitaxial layer 208, the epitaxial growth rate in the first deep trench 203 is greater than that in the cross deep trench 205, that is, the first deep trench 203 is sealed first. When the epitaxial filling continues, a "cylinder 210" structure is gradually formed in the cross deep trench 205. As the epitaxial process continues, the "cylinder 210" structure in the cross deep trench 205 is gradually filled and sealed (the epitaxial growth process is as shown in FIG. 8B), and no (111) crystal plane prone to stacking faults is generated on the upper part of the cross deep trench 205. When the final sealing and filling are completed, the defects on the upper part are obviously improved, and the generation of white noise is effectively reduced, so as to improve the performance of the finally formed image sensor. Figure 14

[0062] It should be noted that the crystal plane of the sidewall perpendicular to the second direction b of the columnar structure 202 belongs to the same crystal system as the (110) crystal plane, and the growth rate is consistent with that of the (110) crystal plane. Therefore, the second deep trench 204 is also sealed first.

[0063] In the embodiment, the doped epitaxial layer 208 is located on the intrinsic epitaxial layer 207.

[0064] In the embodiment, the forming method of the doped epitaxial layer 208 includes: forming an epitaxial material layer (not shown) in the first deep trench 203, the second deep trench 204 and the cross deep trench 205, and on the surface of the mask layer 206; performing first planarization treatment on the epitaxial material layer until the surface of the mask layer 206 is exposed, to form an initial doped epitaxial layer (not shown); removing the mask layer 206; and performing second planarization treatment on the initial doped epitaxial layer until the top surface of the columnar structure 202 is exposed, to form the doped epitaxial layer 208.

[0065] In the embodiment, the process of the first planarization treatment adopts a chemical mechanical polishing process.

[0066] ​In the embodiment, the second planarization process adopts a chemical mechanical polishing process.

[0067] In the embodiment, the first ion and the second ion are both diffused due to the difference in the electrical type of the first ion and the second ion, and a photodiode structure is formed in the intrinsic epitaxial layer 207. Subsequently, the substrate 200 is excited by electrons by irradiating light on the substrate, and the photodiode structure is used to form an electrical signal from the excited electrons.

[0068] In the embodiment, the second ion adopts a P-type ion.

[0069] The P-type ion includes a boron ion or an indium ion. In the embodiment, the P-type ion adopts a boron ion.

[0070] Please refer to Figure 15 After the doped epitaxial layer 208 is formed, a cover layer 209 is formed on the columnar structure 202 and the doped epitaxial layer 208.

[0071] In the embodiment, the forming method of the cover layer 209 includes: forming a cover material layer (not shown) on the columnar structure 202 and the doped epitaxial layer 208 by using an epitaxial growth process; and performing a third planarization process on the cover material layer to form the cover layer 209.

[0072] In the embodiment, the third planarization process adopts a chemical mechanical polishing process.

[0073] Correspondingly, the embodiment of the present application also provides an image sensor, please continue to refer to Figure 15, comprising: a substrate 200, the substrate 200 having first ions therein, the substrate 200 comprising a plurality of columnar structures 202 arranged in an array, the columnar structures 202 arranged along a first direction a having first deep trenches 203 therebetween, the columnar structures 202 arranged along a second direction b having second deep trenches 204 therebetween, the columnar structures 202 arranged along a third direction c having cross deep trenches 205 therebetween, the first direction a being perpendicular to the second direction b, the third direction c being at an angle of 45° with respect to the first direction a and the second direction b respectively, a sidewall of the columnar structures 202 perpendicular to the first direction a being a (110) crystal plane, and a bevel of the columnar structures 202 perpendicular to the third direction c being a (100) crystal plane; a doped epitaxial layer 208 located in the first deep trenches 203, the second deep trenches 204 and the cross deep trenches 205, and the doped epitaxial layer 208 filling the first deep trenches 203, the second deep trenches 204 and the cross deep trenches 205, the doped epitaxial layer 208 having second ions therein, the second ions being different in electrical type from the first ions.

[0074] In the embodiment, since the sidewall of the columnar structures 202 perpendicular to the first direction a is a (110) crystal plane, and the bevel of the columnar structures 202 perpendicular to the third direction c is a (100) crystal plane, in the process of forming the doped epitaxial layer 208, the epitaxial growth rate in the first deep trenches 203 is greater than that in the cross deep trenches 205, that is, the first deep trenches 203 are sealed first. When the epitaxial filling continues, a "cylinder 210" structure is gradually formed in the cross deep trenches 205. With the epitaxial growth, the "cylinder 210" structure in the cross deep trenches 205 is gradually filled and sealed (the epitaxial growth process is as shown in FIG. 8), and no (111) crystal plane prone to stacking faults is generated on the upper part of the cross deep trenches 205. This makes the defects on the upper part significantly improved when the final sealing is filled, and further effectively reduces the generation of white noise, so as to improve the performance of the finally formed image sensor. Figure 14

[0075] In the embodiment, the material of the substrate 200 is single crystal silicon, and the crystal direction of the surface of the substrate 200 is <110> crystal direction.

[0076] In the embodiment, the intrinsic epitaxial layer 207 located on the sidewall of the columnar structures 202 is further included, and the doped epitaxial layer 208 is located on the intrinsic epitaxial layer 207. The intrinsic epitaxial layer 207 can be used to repair defects on the sidewall of the first deep trenches 203, the second deep trenches 204 and the cross deep trenches 205, so as to improve the performance of the finally formed image sensor.

[0077] ​In the embodiment, the first ions are N-type ions; and the second ions are P-type ions.

[0078] In the embodiment, a cover layer 209 is further included on the columnar structure 202 and the doped epitaxial layer 208.

[0079] Although the present application has been disclosed with reference to the above embodiments, the present application is not limited to the above embodiments. Any person skilled in the art, without departing from the spirit and scope of the present application, can make various modifications and changes, and the scope of protection of the present application should be limited by the scope defined in the claims.

Claims

1. A method of forming an image sensor, characterized by, The application relates to a substrate and a method for manufacturing the substrate. The substrate is provided with a first ion; The substrate is subjected to a patterning process to form a plurality of columnar structures arranged in an array, the columnar structures arranged along a first direction have first deep trenches between the columnar structures, the columnar structures arranged along a second direction have second deep trenches between the columnar structures, and the columnar structures arranged along a third direction have cross deep trenches between the columnar structures, the first direction is perpendicular to the second direction, the third direction forms an angle of 45 degrees with the first direction and the second direction respectively, the sidewall of the columnar structure perpendicular to the first direction is a (110) crystal face, and the bevel of the columnar structure perpendicular to the third direction is a (100) crystal face; A doped epitaxial layer is formed in the first deep trenches, the second deep trenches and the cross deep trenches, and the doped epitaxial layer fills the first deep trenches, the second deep trenches and the cross deep trenches, the doped epitaxial layer has a second ion, and the second ion is different from the first ion in electrical type.

2. The method for forming an image sensor according to claim 1, wherein The substrate material is monocrystalline silicon, and the crystal direction of the substrate surface is a <110> crystal direction.

3. The method of forming an image sensor of claim 1, wherein, Before the substrate is subjected to the patterning process, a mask material layer is formed on the substrate; and during the patterning process, part of the mask material layer is etched and removed to form a mask layer.

4. The method for forming an image sensor according to claim 3, wherein The thickness of the mask material layer is 100-800 nm.

5. The method of forming an image sensor of claim 3, wherein, The material of the mask layer is different from that of the doped epitaxial layer, and the material of the mask layer comprises silicon oxide or silicon nitride.

6. The method for forming an image sensor according to claim 3, wherein The forming method of the doped epitaxial layer comprises the following steps: forming an epitaxial material layer on the surface of the mask layer and in the first deep trenches, the second deep trenches and the cross deep trenches; performing first planarization treatment on the epitaxial material layer until the surface of the mask layer is exposed, thereby forming an initial doped epitaxial layer; removing the mask layer; and performing second planarization treatment on the initial doped epitaxial layer until the top surface of the columnar structure is exposed, thereby forming the doped epitaxial layer.

7. The method for forming an image sensor according to claim 6, wherein The first planarization treatment process comprises a chemical mechanical polishing process.

8. The method for forming an image sensor according to claim 6, wherein The second planarization treatment process comprises a chemical mechanical polishing process.

9. The method of claim 1, wherein Before the doped epitaxial layer is formed, an intrinsic epitaxial layer is formed on the sidewall of the columnar structure, and the doped epitaxial layer is located on the intrinsic epitaxial layer.

10. The method of claim 1, wherein The first ion is an N-type ion, and the second ion is a P-type ion.

11. The method of claim 1, wherein After the doped epitaxial layer is formed, a cover layer is formed on the columnar structure and the doped epitaxial layer.

12. The method for forming an image sensor according to claim 11, wherein The forming method of the cover layer comprises the following steps: forming a cover material layer on the columnar structure and the doped epitaxial layer by using an epitaxial growth process; and performing third planarization treatment on the cover material layer, thereby forming the cover layer.

13. The method for forming an image sensor according to claim 12, wherein The third planarization treatment process comprises a chemical mechanical polishing process.

14. An image sensor, comprising: The application relates to a substrate and a method for manufacturing the substrate. A substrate having first ions therein, the substrate comprising a plurality of columnar structures arranged in an array, the columnar structures arranged along a first direction having first deep trenches therebetween, the columnar structures arranged along a second direction having second deep trenches therebetween, the columnar structures arranged along a third direction having intersecting deep trenches therebetween, the first direction being perpendicular to the second direction, the third direction being at an angle of 45° with respect to the first direction and the second direction respectively, a sidewall of the columnar structure perpendicular to the first direction being a (110) crystal plane, a bevel of the columnar structure perpendicular to the third direction being a (100) crystal plane; A doped epitaxial layer located in the first deep trenches, the second deep trenches and the intersecting deep trenches, the doped epitaxial layer filling the first deep trenches, the second deep trenches and the intersecting deep trenches, the doped epitaxial layer having second ions therein, the second ions being of a different electrical type from the first ions.

15. The image sensor of claim 14, wherein, The substrate material is monocrystalline silicon, and a crystal orientation of a surface of the substrate is a <110> crystal orientation.

16. The image sensor of claim 14, wherein, Further comprising: An intrinsic epitaxial layer located on sidewalls of the columnar structures, the doped epitaxial layer being located on the intrinsic epitaxial layer.

17. The image sensor of claim 14, wherein, The first ions are N-type ions, and the second ions are P-type ions.

18. The image sensor of claim 14, wherein, Further comprising: A cover layer located on the columnar structures and the doped epitaxial layer.

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