Double-shallow-trench isolation structure, preparation method thereof and CMOS image sensor

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and discloses a double-shallow-trench isolation structure, a preparation method thereof and a CMOS image sensor, and the method comprises the steps: carrying out the first ion implantation of the bottom end of a first trench opening and the bottom end of a second trench opening; second ion implantation is carried out on the bottom end of the opening of the first groove; annealing treatment is carried out, a first oxidation region is formed at the bottom end of the first groove opening, and a second oxidation region is formed at the bottom end of the second groove opening; etching the first oxidation region and the second oxidation region to form a double-shallow-trench isolation structure; based on the characteristic that the etching selection ratio of silicon dioxide and silicon is high, the depth and the shape of the double-shallow-trench isolation structure are accurately controlled through the two-time ion implantation and one-time oxidation region etching process, and the manufacturing efficiency can be improved while the isolation effect is guaranteed; meanwhile, the contour continuity of the double-shallow-trench isolation structure can be ensured, and the overall performance and reliability of the device are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a double shallow trench isolation structure and a preparation method thereof, and a CMOS image sensor. Background Art

[0002] CMOS Image Sensor (CIS) is a solid-state imaging sensor based on CMOS (Complementary Metal-Oxide-Semiconductor) technology. In a 55nm CMOS image sensor, it is usually required that its logic area and pixel area form a shallow trench isolation structure (STI) with different depths, namely a dual shallow trench isolation structure (Dual STI).

[0003] At present, the existing preparation process of the double shallow trench isolation structure mainly forms shallow trench isolation structures with different depths through two photolithography and etching; specifically, after the first photolithography and etching, two shallow trench isolation structures with relatively shallow depths are formed; then, one of the shallower shallow trench isolation structures is subjected to a second photolithography and etching, thereby forming two shallow trench isolation structures with different depths; wherein, since there is a gap between the logic area and the pixel area of ​​the silicon nitride layer, after the shallow trench isolation structure of the logic area is subjected to chemical mechanical polishing, there is still residual oxide and the residual oxide cannot be eliminated by removing the silicon nitride layer, resulting in a discontinuous profile of the shallow trench isolation structure of the logic area, thereby seriously affecting the reliability and performance of the device. Summary of the invention

[0004] In view of the technical problems existing in the prior art, the present invention provides a dual shallow trench isolation structure and a preparation method thereof and a CMOS image sensor to solve the technical problem that the existing preparation process of the dual shallow trench isolation structure leads to a discontinuous profile of the shallow trench isolation structure in the logic area, thereby seriously affecting the reliability and performance of the device.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides a method for preparing a double shallow trench isolation structure, comprising: Performing a first ion implantation on the bottom ends of the first trench opening and the second trench opening; Performing a second ion implantation on the bottom end of the first trench opening; Performing annealing to form a first oxidized region at the bottom end of the first trench opening and a second oxidized region at the bottom end of the second trench opening; The first oxidized region and the second oxidized region are etched to form a double shallow trench isolation structure.

[0006] Furthermore, the process of performing a first ion implantation on the bottom ends of the first trench opening and the second trench opening is as follows: Through the photoresist layer with double trench patterns, oxygen ions are implanted into the bottom ends of the first trench opening and the second trench opening according to the depth of the second shallow trench isolation structure in the double shallow trench isolation structure to form a first ion implantation layer.

[0007] Furthermore, the process of performing a second ion implantation on the bottom end of the first trench opening is as follows: Through the photoresist layer with a single trench pattern, oxygen ions are implanted into the bottom of the first trench opening according to the depth difference between the first shallow trench isolation structure and the second shallow trench isolation structure in the double shallow trench isolation structure to form a second ion implantation layer.

[0008] Furthermore, after etching the first oxidized region and the second oxidized region to form a double shallow trench isolation structure, the method further includes: Performing fluorine ion implantation on the double shallow trench isolation structure; The residual oxide in the first shallow trench isolation structure of the dual shallow trench isolation structure is etched to form a dual shallow trench isolation structure without oxide residue.

[0009] Furthermore, before performing the first ion implantation on the bottom ends of the first trench opening and the second trench opening, the method further includes: forming a photoresist layer having a double groove pattern on a substrate having a pad oxide layer, a pad barrier layer and a hard mask layer; A first trench opening and a second trench opening are formed by etching through the hard mask layer, the pad barrier layer and the pad oxide layer.

[0010] Furthermore, during the process of performing fluorine ion implantation on the double shallow trench isolation structure, the fluorine ions are implanted into the double shallow trench isolation structure in a direction with a preset inclination angle to the normal line of the substrate; wherein the preset inclination angle is:

[0011] in, is the preset inclination angle; is the sum of the thickness of the pad oxide layer and the pad barrier layer; is the depth of the second shallow trench isolation structure in the double shallow trench isolation structure; is the width of the second shallow trench isolation structure in the double shallow trench isolation structure.

[0012] Furthermore, the material of the liner barrier layer is silicon nitride.

[0013] Furthermore, the hard mask layer includes an amorphous carbon layer and a silicon oxynitride layer formed sequentially from bottom to top, the material of the amorphous carbon layer is amorphous carbon, and the material of the silicon oxynitride layer is silicon oxynitride.

[0014] The present invention also provides a dual shallow trench isolation structure, and the dual shallow trench isolation structure is prepared by applying the preparation method of the dual shallow trench isolation structure.

[0015] The present invention also provides a CMOS image sensor, and the CMOS image sensor is prepared by applying the preparation method of the double shallow trench isolation structure.

[0016] Compared with the prior art, the present invention has the following unexpected beneficial effects: The present invention provides a method for preparing a double shallow trench isolation structure. The method comprises the following steps: performing two ion implantations on the bottom end of a first trench opening, performing one ion implantation on the bottom end of a second trench opening, and performing annealing to activate the implanted ions, so that an oxidation region made of silicon dioxide and having a depth corresponding to the depth of the double shallow trench isolation structure is formed on the surface of a substrate; based on the high etching selectivity of silicon dioxide and silicon, the oxidation region is etched once to form a double shallow trench isolation structure; the present invention realizes precise control of the depth and shape of the double shallow trench isolation structure through two ion implantations and one oxidation region etching process, thereby improving manufacturing efficiency while ensuring the isolation effect; secondly, the spacing of the silicon nitride layer between the logic region and the pixel region can be effectively avoided, thereby ensuring the contour continuity of the double shallow trench isolation structure, thereby effectively ensuring the overall performance and reliability of the device.

[0017] Furthermore, when the first ion implantation is performed, oxygen ion implantation is performed based on the depth of the second shallow trench isolation structure in the double shallow trench isolation structure, so that the depth of the first ion implantation layer located at the bottom end of the second trench opening is adapted to the depth of the second shallow trench isolation structure in the double shallow trench isolation structure, and then the second shallow trench isolation structure in the double shallow trench isolation structure can be formed after one etching, and the shape and size of the second shallow trench isolation structure can be effectively controlled, thereby improving manufacturing efficiency.

[0018] Furthermore, when the second ion implantation is performed, oxygen ion implantation is performed based on the depth difference between the first shallow trench isolation structure and the second shallow trench isolation structure in the double shallow trench isolation structure, so that the depth of the second ion implantation layer located at the bottom end of the first trench opening is adapted to the depth of the first shallow trench isolation structure in the double shallow trench isolation structure, and then the oxidized region formed in the region of the first shallow trench isolation structure in the double shallow trench isolation structure matches the depth of the first shallow trench isolation structure, and the first shallow trench isolation structure in the double shallow trench isolation structure can be formed after one etching, and the shape and size of the first shallow trench isolation structure can be effectively controlled, thereby improving manufacturing efficiency.

[0019] Furthermore, by injecting fluorine ions and etching the residual oxide in the first shallow trench isolation structure of the double shallow trench isolation structure, the residual oxide in the double shallow trench isolation structure is removed; at the same time, by injecting fluorine ions, fluorine ion doping can be formed at the interface of the shallow trench isolation structure in the logic area and the pixel area; wherein, fluorine ion doping is formed at the interface of the shallow trench isolation structure in the logic area, which can effectively inhibit the diffusion of boron and phosphorus and reduce the influence of the anti-narrow channel effect; and fluorine ion doping is formed at the interface of the shallow trench isolation structure in the pixel area, which can fill silicon dangling bonds and reduce the ability of interface trap electrons, thereby effectively reducing white pixels and dark currents.

[0020] The dual shallow trench isolation structure and CMOS image sensor provided by the present invention have all the advantages of the preparation method of the dual shallow trench isolation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A flow chart of a method for preparing a double shallow trench isolation structure provided in Example 1; Figure 2 Schematic diagram of the substrate structure with a liner oxide layer, a liner barrier layer and a hard mask layer in Example 1; Figure 3 This is a schematic diagram of the device structure after step 2 in Example 1 is completed; Figure 4 This is a schematic diagram of the device structure after step 3 in Example 1 is completed; Figure 5 This is a schematic diagram of the device structure after step 4 in Example 1 is completed; Figure 6 This is a schematic diagram of the device structure after step 6 in Example 1 is completed; Figure 7 This is a schematic diagram of the device structure after step 7 in Example 1 is completed; Figure 8 This is a schematic diagram of the device structure after step 8 in Example 1 is completed; Fig. 9 Schematic diagram of the device structure after the residual processing step in Example 2 is completed.

[0023] Among them, 1 is a substrate, 2 is a pad oxide layer, 3 is a pad barrier layer, 4 is an amorphous carbon layer, 5 is a silicon oxynitride layer, 6 is a first photoresist layer, 7 is a first trench opening, 8 is a second trench opening, 9 is a second photoresist layer, 10 is a first oxidation region, and 11 is a second oxidation region. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be described clearly and completely in combination with the drawings in the embodiments of this application; obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] The present invention provides a method for preparing a double shallow trench isolation structure, comprising the following steps: Step 100 , performing a first ion implantation on the bottom ends of the first trench opening 7 and the second trench opening 8 .

[0026] Step 200 , performing a second ion implantation on the bottom end of the first trench opening 7 .

[0027] Step 300 , performing annealing treatment to form a first oxidized region 10 at the bottom end of the first trench opening 7 and a second oxidized region 11 at the bottom end of the second trench opening 8 .

[0028] Step 400 , etching the first oxidized region 10 and the second oxidized region 11 to form a double shallow trench isolation structure.

[0029] Optionally, before performing the first ion implantation on the bottom ends of the first trench opening 7 and the second trench opening 8, the method further includes: forming a photoresist layer having a double trench pattern on a substrate 1 having a pad oxide layer 2, a pad barrier layer 3 and a hard mask layer; and etching to form the first trench opening 7 and the second trench opening 8 penetrating the hard mask layer, the pad barrier layer 3 and the pad oxide layer 2.

[0030] Optionally, after etching the first oxidized region 10 and the second oxidized region 11 to form a dual shallow trench isolation structure, the method further includes: implanting fluorine ions into the dual shallow trench isolation structure; and etching residual oxide in the first shallow trench isolation structure of the dual shallow trench isolation structure to form a dual shallow trench isolation structure without oxidation residue.

[0031] The preparation method of the double shallow trench isolation structure provided by the present invention is based on the high etching selectivity ratio of silicon dioxide and silicon. Through the processes of two ion implantations and one oxidation area etching, the depth and shape of the double shallow trench isolation structure can be precisely controlled, thereby improving the manufacturing efficiency while ensuring the isolation effect.

[0032] Example 1 As attached Figure 1 As shown, this embodiment 1 provides a method for preparing a double shallow trench isolation structure, comprising the following steps: Step 1, provide a substrate 1. Figure 2 As shown, a pad oxide layer 2, a pad barrier layer 3, a hard mask layer and a first photoresist layer 6 are sequentially formed on the substrate 1 from bottom to top.

[0033] Among them, the material of the substrate 1 is silicon; the material of the pad oxide layer 2 is silicon oxide, and the material of the pad barrier layer 3 is silicon nitride; the hard mask layer includes an amorphous carbon layer 4 and a silicon oxynitride layer 5 formed in sequence from bottom to top, the material of the amorphous carbon layer 4 is amorphous carbon, and the material of the silicon oxynitride layer 5 is silicon oxynitride; preferably, the method for forming the pad oxide layer 2 adopts a thermal oxidation method, and the method for forming the pad barrier layer 3, the amorphous carbon layer 4 and the silicon oxynitride layer 5 adopts a chemical vapor deposition method; an opening pattern corresponding to the position of the double shallow trench isolation structure is formed on the first photoresist layer 6, that is, the first photoresist layer 6 is a photoresist layer with a double trench pattern.

[0034] Step 2, etching the hard mask layer, the liner barrier layer 3 and the liner oxide layer 2 to form a first trench opening 7 and a second trench opening 8 penetrating the hard mask layer, the liner barrier layer 3 and the liner oxide layer 2. Specifically, using the first photoresist layer 6 as a mask, the silicon oxynitride layer 5, the amorphous carbon layer 4, the liner barrier layer 3 and the liner oxide layer 2 are etched along the opening pattern corresponding to the position of the double shallow trench isolation structure until the etching of the liner oxide layer 2 is completed, that is, the substrate 1 is exposed, as shown in the attached Figure 3 As shown. Preferably, the process of etching the silicon oxynitride layer 5, the amorphous carbon layer 4, the pad barrier layer 3 and the pad oxide layer 2 adopts a dry etching process; wherein, the gas for etching the silicon oxynitride layer 5 adopts carbon tetrafluoride and difluoromethane, the gas for etching the amorphous carbon layer 4 adopts chlorine, oxygen and hydrogen bromide, the gas for etching the pad barrier layer 3 adopts carbon tetrafluoride and helium, and the gas for etching the pad oxide layer 2 adopts carbon tetrafluoride and trifluoromethane. It should be noted that in this embodiment 1, there is no limitation on the process of etching the silicon oxynitride layer 5, the amorphous carbon layer 4, the pad barrier layer 3 and the pad oxide layer 2.

[0035] It should be noted that the double shallow trench isolation structure is divided into a deeper shallow trench isolation structure and a shallower shallow trench isolation structure according to the depth of the shallow trench isolation structure; in this embodiment 1, the area where the first trench opening 7 is located corresponds to the area of ​​the deeper shallow trench isolation structure in the double shallow trench isolation structure, and the area where the second trench opening 8 is located corresponds to the area of ​​the shallower shallow trench isolation structure in the double shallow trench isolation structure as an example for illustration; wherein the deeper shallow trench isolation structure is recorded as the first shallow trench isolation structure, and the shallower shallow trench isolation structure is recorded as the second shallow trench isolation structure.

[0036] Step 3: Perform a first ion implantation on the bottom end of the first trench opening 7 and the bottom end of the second trench opening 8. Figure 4 As shown, oxygen ion implantation is performed on the surface of the substrate 1 and the first photoresist layer 6 through the first photoresist layer 6 according to the depth of the second shallow trench isolation structure in the double shallow trench isolation structure, so as to form a first ion implantation layer on the surface of the substrate 1 and facing the bottom end of the first trench opening 7 and facing the bottom end of the second trench opening 8.

[0037] Among them, during the first ion implantation, the injection direction of the oxygen ions is at an angle of 90° to the surface of the substrate 1 and the first photoresist layer 6; that is, the injection direction of the oxygen ions forming the first ion implantation layer is perpendicular to the upper surface of the substrate 1 and the upper surface of the first photoresist layer 6; the implantation dose of the oxygen ions is 1E12-1E16; the injection energy of the oxygen ions is based on the depth that the oxygen ions can cover the second shallow trench isolation structure in the double shallow trench isolation structure; preferably, during the first ion implantation, a plurality of oxygen ion implantation methods with different injection energies are adopted, and the multiple different injection energies are gradually reduced, and the minimum injection energy is not less than 1Kev.

[0038] It should be noted that oxygen ion implantation is carried out according to the depth of the second shallow trench isolation structure in the double shallow trench isolation structure, so that the depth of the first ion implantation layer is adapted to the depth of the second shallow trench isolation structure in the double shallow trench isolation structure, so as to achieve the effect that the second shallow trench isolation structure in the double shallow trench isolation structure can be formed after the first ion implantation layer is etched once.

[0039] Step 4: remove the first photoresist layer 6 and the hard mask layer to expose the pad barrier layer 3. Figure 5 As shown. The process of removing the first photoresist layer 6 is specifically as follows: firstly, an oxygen ashing process is used to remove the photoresist hard shell of the first photoresist layer 6, and then a mixture of sulfuric acid and hydrogen peroxide is used to wet-remove the photoresist of the first photoresist layer 6, and finally, a mixture of ammonia and hydrogen peroxide is used to wet-remove the organic matter and residual particles of the first photoresist layer 6; the process of removing the silicon oxynitride layer 5 in the hard mask layer is specifically as follows: using carbon tetrafluoride and difluoromethane as etching gases, and removing it by a dry etching process; the process of removing the amorphous carbon layer 4 in the hard mask layer is specifically as follows: using chlorine, oxygen and hydrogen bromide as etching gases, and removing it by a dry etching process. It should be noted that in this embodiment 1, there is no limitation on the process of removing the first photoresist layer 6 and the hard mask layer.

[0040] Step 5: After removing the first photoresist layer 6 and the hard mask layer, a second photoresist layer 9 is regrown on the pad barrier layer 3. The second photoresist layer 9 has an opening pattern corresponding to the position of the first shallow trench isolation structure in the double shallow trench isolation structure, that is, the second photoresist layer 9 is a photoresist layer with a single trench pattern.

[0041] It should be noted that, assuming that the area where the first trench opening 7 is located corresponds to the area of ​​the first shallow trench isolation structure in the double shallow trench isolation structure, an opening pattern corresponding to the first trench opening 7 is formed on the second photoresist layer 9; on the contrary, if the area where the second trench opening 8 is located corresponds to the area of ​​the first shallow trench isolation structure in the double shallow trench isolation structure, an opening pattern corresponding to the second trench opening 8 is formed on the second photoresist layer 9.

[0042] Step 6: Perform a second ion implantation on the bottom of the first trench opening 7. Figure 6 As shown, oxygen ion implantation is performed on the surfaces of the substrate 1 and the second photoresist layer 9 according to the depth difference between the first shallow trench isolation structure and the second shallow trench isolation structure in the double shallow trench isolation structure through the second photoresist layer 9, so as to form a second ion implantation layer on the surface of the substrate 1 and directly opposite to the bottom of the first trench opening 7; it should be noted that the first ion implantation layer and the second ion implantation layer are both oxygen ion implantation layers; the second ion implantation layer is formed by superimposing the first ion implantation layer corresponding to the bottom of the first trench opening 7 after the second ion implantation.

[0043] During the second ion implantation, the injection direction of the oxygen ions is at an angle of 90° to the surfaces of the substrate 1 and the second photoresist layer 9; that is, the injection direction of the oxygen ions forming the second ion implantation layer is perpendicular to the upper surface of the substrate 1 and the upper surface of the second photoresist layer 9; the injection dose of the oxygen ions is 1E12-1E16; the injection energy of the oxygen ions is based on the depth that the oxygen ions can cover the first shallow trench isolation structure in the double shallow trench isolation structure.

[0044] Preferably, during the second ion implantation, a plurality of oxygen ion implantation methods with different implantation energies are adopted, and the plurality of different implantation energies decrease step by step; wherein the lowest implantation energy during the second ion implantation is greater than the highest implantation energy during the first ion implantation, so that the oxygen ions during the second ion implantation can evenly cover the area of ​​the first shallow trench isolation structure in the double shallow trench isolation structure.

[0045] It should also be noted that the second ion implantation is performed based on the depth difference between the first shallow trench isolation structure and the second shallow trench isolation structure in the double shallow trench isolation structure, so that the depth of the second ion implantation is adapted to the depth of the first shallow trench isolation structure in the double shallow trench isolation structure, so as to achieve the effect that the first shallow trench isolation structure in the double shallow trench isolation structure can be formed after the second ion implantation layer is etched once.

[0046] Step 7, remove the second photoresist layer 9 to expose the pad barrier layer 3 again; after removing the second photoresist layer 9, perform annealing to form a first oxidized region 10 at the bottom end of the first trench opening 7 and a second oxidized region 11 at the bottom end of the second trench opening 8, as shown in the attached Figure 7 shown.

[0047] The process of removing the second photoresist layer 9 is specifically as follows: firstly, a mixture of sulfuric acid and hydrogen peroxide is used to wet-process the photoresist of the second photoresist layer 9, and then a mixture of ammonia and hydrogen peroxide is used to wet-process the organic matter and residual particles of the second photoresist layer 9; the temperature of the annealing treatment is greater than 800° C. and the time is greater than 30 minutes to ensure that the injected oxygen ions react with the silicon atoms in the substrate 1 to form silicon dioxide. It should be noted that in this embodiment 1, there is no limitation on the process of removing the second photoresist layer 9.

[0048] It should be noted that after oxygen ion implantation is performed on the bottom end of the first trench opening 7 and the bottom end of the second trench opening 8, an annealing treatment is performed to activate the oxygen ions in the first ion implantation layer and the second ion implantation layer, so that the oxygen ions are combined with the silicon atoms in the substrate 1, and an oxidized region made of silicon dioxide and having a depth corresponding to the depth of the double shallow trench isolation structure is formed on the surface of the substrate 1. Based on the high etching selectivity of silicon dioxide and silicon, the oxidized region is etched once to form a double shallow trench isolation structure.

[0049] Step 8: Etch the first oxidized region 10 and the second oxidized region 11 to form a double shallow trench isolation structure, as shown in the attached figure. Figure 8 As shown. Preferably, the processes for etching the first oxidized region 10 and the second oxidized region 11 are both dry etching processes; wherein, the gases for etching the first oxidized region 10 and the second oxidized region 11 are trifluoromethane and hydrogen; during the etching process, the ratio of trifluoromethane to hydrogen is adjusted to improve the etching selectivity of silicon dioxide and silicon. It should be noted that in this embodiment 1, there is no limitation on the process for etching the first oxidized region 10 and the second oxidized region 11.

[0050] The preparation method of the double shallow trench isolation structure described in the present embodiment 1 implements oxygen ion implantation twice into the bottom end of the first trench opening 7, implements oxygen ion implantation once into the bottom end of the second trench opening 8, and activates the oxygen ions through annealing treatment, so as to form an oxidized region made of silicon dioxide on the surface of the substrate 1; then, based on the high etching selectivity of silicon dioxide and silicon, the oxidized region is etched once to form a double shallow trench isolation structure, thereby achieving precise control of the depth and shape of the double shallow trench isolation structure, and improving manufacturing efficiency while ensuring the isolation effect.

[0051] Example 2 The method for preparing a dual shallow trench isolation structure provided in this embodiment 2 is basically the same in operation and principle as the method for preparing a dual shallow trench isolation structure described in the above embodiment 1, except that: after step 8 of embodiment 1, a residual processing step is also included.

[0052] Specifically, the residual processing steps are as follows: Fluorine ion implantation is performed on the dual shallow trench isolation structure; residual oxide in the first shallow trench isolation structure of the dual shallow trench isolation structure is etched to form a dual shallow trench isolation structure without oxide residue.

[0053] As attached Fig. 9 As shown, during the process of fluorine ion implantation into the double shallow trench isolation structure, the fluorine ions are implanted into the double shallow trench isolation structure at a direction with a preset inclination angle to the normal line of the substrate 1; wherein the preset inclination angle is:

[0054] in, is the preset inclination angle; is the sum of the thickness of the pad oxide layer 2 and the pad barrier layer 3; is the depth of the second shallow trench isolation structure in the double shallow trench isolation structure; is the width of the second shallow trench isolation structure in the double shallow trench isolation structure.

[0055] In the second embodiment, when fluorine ion implantation is performed, the implantation dose of fluorine ions is 1E15-1E16, and the implantation energy is less than 4Kev; there is no restriction on the process of etching the residual oxide in the first shallow trench isolation structure in the double shallow trench isolation structure.

[0056] In the second embodiment, by injecting fluorine ions into the double shallow trench isolation structure, the residual oxide in the first shallow trench isolation structure in the logic area will serve as a barrier layer to prevent the injected fluorine ions from penetrating to the bottom of the first shallow trench isolation structure, thereby affecting the ion distribution in the well region and reducing the impact on isolation and leakage current; secondly, by injecting fluorine ions and etching the residual oxide in the first shallow trench isolation structure, the residual oxide in the double shallow trench isolation structure is removed; in addition, by injecting fluorine ions, fluorine ion doping is formed at the interface of the shallow trench isolation structure of the logic area and the pixel area; wherein, fluorine ion doping is formed at the interface of the shallow trench isolation structure of the logic area, which can effectively inhibit the diffusion of boron and phosphorus and reduce the impact of the anti-narrow channel effect; and fluorine ion doping is formed at the interface of the shallow trench isolation structure of the pixel area, which can fill silicon dangling bonds and reduce the ability of interface trap electrons, thereby effectively reducing white pixels and dark current.

[0057] Example 3 This embodiment 3 provides a CMOS image sensor, including a substrate; a dual shallow trench isolation structure is formed on the substrate; wherein the dual shallow trench isolation structure is prepared using the preparation method of the dual shallow trench isolation structure described in the above-mentioned embodiment 1 or 2, thereby ensuring the contour continuity of the dual shallow trench isolation structure, so that the manufactured CMOS image sensor has better reliability and performance.

[0058] It should be noted that the preparation method of the dual shallow trench isolation structure is described in detail in the corresponding part of the above-mentioned embodiment 1 or 2, and will not be repeated here.

[0059] The preparation method of the double shallow trench isolation structure described in the present invention realizes precise control of the depth and shape of the double shallow trench isolation structure through two oxygen ion implantations and one oxidation area etching process, thereby improving manufacturing efficiency while ensuring the isolation effect; secondly, it can effectively avoid the spacing of the silicon nitride layer between the logic area and the pixel area, ensuring the contour continuity of the double shallow trench isolation structure, thereby effectively ensuring the overall performance and reliability of the device.

[0060] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims

1. A method for preparing a double shallow trench isolation structure, characterized in that: include: Performing a first ion implantation on the bottom ends of the first trench opening (7) and the second trench opening (8); Performing a second ion implantation on the bottom end of the first trench opening (7); Performing annealing to form a first oxidized region (10) at the bottom end of the first trench opening (7) and a second oxidized region (11) at the bottom end of the second trench opening (8); The first oxidized region (10) and the second oxidized region (11) are etched to form a double shallow trench isolation structure.

2. The method for preparing a double shallow trench isolation structure according to claim 1, characterized in that: The process of performing the first ion implantation on the bottom ends of the first trench opening (7) and the second trench opening (8) is as follows: Through a photoresist layer having a double trench pattern, oxygen ions are implanted into the bottom ends of the first trench opening (7) and the second trench opening (8) according to the depth of the second shallow trench isolation structure in the double shallow trench isolation structure to form a first ion implantation layer.

3. The method for preparing a dual shallow trench isolation structure according to claim 1, characterized in that: The process of performing a second ion implantation on the bottom end of the first trench opening (7) is as follows: Through a photoresist layer having a single trench pattern, oxygen ions are implanted into the bottom of the first trench opening (7) according to the depth difference between the first shallow trench isolation structure and the second shallow trench isolation structure in the double shallow trench isolation structure to form a second ion implantation layer.

4. The method for preparing a double shallow trench isolation structure according to claim 1, characterized in that: After etching the first oxidized region (10) and the second oxidized region (11) to form a double shallow trench isolation structure, the method further comprises: Performing fluorine ion implantation on the double shallow trench isolation structure; The residual oxide in the first shallow trench isolation structure of the dual shallow trench isolation structure is etched to form a dual shallow trench isolation structure without oxide residue.

5. The method for preparing a double shallow trench isolation structure according to claim 4, characterized in that: Before performing the first ion implantation on the bottom ends of the first trench opening (7) and the second trench opening (8), the method further comprises: Forming a photoresist layer having a double groove pattern on a substrate (1) having a pad oxide layer (2), a pad barrier layer (3) and a hard mask layer; Etching is performed to form a first trench opening (7) and a second trench opening (8) penetrating the hard mask layer, the liner barrier layer (3) and the liner oxide layer (2).

6. The method for preparing a double shallow trench isolation structure according to claim 5, characterized in that: During the process of implanting fluorine ions into the double shallow trench isolation structure, the fluorine ions are implanted into the double shallow trench isolation structure in a direction with a preset inclination angle to the normal line of the substrate (1); wherein the preset inclination angle is: in, is the preset inclination angle; is the sum of the thickness of the liner oxide layer (2) and the liner barrier layer (3); is the depth of the second shallow trench isolation structure in the double shallow trench isolation structure; is the width of the second shallow trench isolation structure in the double shallow trench isolation structure.

7. The method for preparing a double shallow trench isolation structure according to claim 5, characterized in that: The material of the liner barrier layer (3) is silicon nitride.

8. The method for preparing a double shallow trench isolation structure according to claim 5, characterized in that: The hard mask layer comprises an amorphous carbon layer (4) and a silicon oxynitride layer (5) which are sequentially formed from bottom to top; the material of the amorphous carbon layer (4) is amorphous carbon, and the material of the silicon oxynitride layer (5) is silicon oxynitride.

9. A double shallow trench isolation structure, characterized in that: The dual shallow trench isolation structure is prepared by using the method for preparing a dual shallow trench isolation structure as described in any one of claims 1 to 8.

10. A CMOS image sensor, characterized in that: The CMOS image sensor is manufactured using the method for manufacturing a dual shallow trench isolation structure as described in any one of claims 1 to 8.

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