Dual Shallow Trench Isolation Structure, Preparation Method Thereof, and CMOS Image Sensor

Abstract

The present invention belongs to the technical field of semiconductor manufacturing, and discloses a dual shallow trench isolation structure, a preparation method thereof, and a CMOS image sensor. The method includes: performing a first ion implantation on the bottom ends of a first trench opening and a second trench opening; performing a second ion implantation on the bottom end of the first trench opening; performing an annealing treatment to respectively form a first oxidation region at the bottom end of the first trench opening and a second oxidation region at the bottom end of the second trench opening; etching the first oxidation region and the second oxidation region to form a dual shallow trench isolation structure. Based on the characteristic of a high etching selectivity ratio between silicon dioxide and silicon, the present invention realizes precise control of the depth and shape of the dual shallow trench isolation structure through two ion implantation processes and one etching process of the oxidation region, improves the manufacturing efficiency while ensuring the isolation effect, and can ensure the profile continuity of the dual shallow trench isolation structure, thereby guaranteeing the overall performance and reliability of the device.

Description

Technical Field

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

[0002] A CMOS image sensor (CIS) is a solid-state imaging sensor based on CMOS (Complementary Metal-Oxide-Semiconductor) technology; in a 55-nm CMOS image sensor, it is usually required to form shallow trench isolation structures (STIs) with different depths in the logic region and the pixel region, that is, a dual shallow trench isolation structure (Dual STI).

[0003] Currently, the existing preparation process of the dual shallow trench isolation structure mainly forms shallow trench isolation structures with different depths through two photolithography and etching processes; specifically, after the first photolithography and etching, two shallower shallow trench isolation structures are formed; then, a second photolithography and etching are performed on one of the shallower shallow trench isolation structures, and thus two shallow trench isolation structures with different depths are formed; among them, due to the presence of a gap between the silicon nitride layer in the logic region and the pixel region, after chemical mechanical polishing of the shallow trench isolation structure in the logic region, 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 in the logic region, and thus seriously affecting the reliability and performance of the device. Summary of the Invention

[0004] Aiming at the technical problems existing in the prior art, the present invention provides a dual shallow trench isolation structure, a preparation method thereof, and a CMOS image sensor to solve the technical problems that the existing preparation process of the dual shallow trench isolation structure causes a discontinuous profile of the shallow trench isolation structure in the logic region, and thus seriously affects the reliability and performance of the device.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a preparation method of a dual shallow trench isolation structure, including:

[0007] Performing a first ion implantation on the bottoms of the first trench opening and the second trench opening;

[0008] Performing a second ion implantation on the bottom of the first trench opening;

[0009] Annealing is carried out to form a first oxidation region at the bottom end of the first trench opening and a second oxidation region at the bottom end of the second trench opening respectively;

[0010] The first oxidation region and the second oxidation region are etched to form a dual shallow trench isolation structure.

[0011] Further, the process of performing the first ion implantation on the bottom ends of the first trench opening and the second trench opening is as follows:

[0012] Through a photoresist layer with a dual trench pattern, oxygen ion implantation is performed on 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 dual shallow trench isolation structure to form a first ion implantation layer.

[0013] Further, the process of performing the second ion implantation on the bottom end of the first trench opening is as follows:

[0014] Through a photoresist layer with a single trench pattern, oxygen ion implantation is performed on the bottom end 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 dual shallow trench isolation structure to form a second ion implantation layer.

[0015] Further, after etching the first oxidation region and the second oxidation region to form a dual shallow trench isolation structure, it further includes:

[0016] Performing fluorine ion implantation on the dual shallow trench isolation structure;

[0017] Etching the remaining oxide in the first shallow trench isolation structure in the dual shallow trench isolation structure to form a dual shallow trench isolation structure without oxidation residue.

[0018] Further, before performing the first ion implantation on the bottom ends of the first trench opening and the second trench opening, it further includes:

[0019] Forming a photoresist layer with a dual trench pattern on a substrate having a pad oxide layer, a pad barrier layer, and a hard mask layer;

[0020] Etching to form a first trench opening and a second trench opening that penetrate through the hard mask layer, the pad barrier layer, and the pad oxide layer.

[0021] Further, during the process of performing fluorine ion implantation on the dual shallow trench isolation structure, the fluorine ions are implanted into the dual shallow trench isolation structure in a direction at a preset inclination angle with respect to the normal of the substrate; wherein, the preset inclination angle is:

[0022]

[0023] Wherein, is the preset inclination angle; is the sum of the thicknesses of the liner oxide layer and the liner barrier layer; is the depth of the second shallow trench isolation structure in the dual shallow trench isolation structure; is the width of the second shallow trench isolation structure in the dual shallow trench isolation structure.

[0024] Further, the material of the liner barrier layer is silicon nitride.

[0025] Further, the hard mask layer includes an amorphous carbon layer and a silicon oxynitride layer formed in sequence 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.

[0026] The present invention also provides a dual shallow trench isolation structure, which is prepared by applying the preparation method of the dual shallow trench isolation structure.

[0027] The present invention also provides a CMOS image sensor, which is prepared by applying the preparation method of the dual shallow trench isolation structure.

[0028] Compared with the prior art, the unexpected beneficial effects of the present invention are:

[0029] The preparation method of the dual shallow trench isolation structure provided by the present invention performs two ion implantations on the bottom end of the first trench opening, one ion implantation on the bottom end of the second trench opening, and annealing treatment to activate the implanted ions, so as to form an oxidation region with a depth adapted to the depth of the dual shallow trench isolation structure and a material of silicon dioxide on the substrate surface; based on the characteristic of a high etching selectivity ratio between silicon dioxide and silicon, etching the oxidation region once can form the dual shallow trench isolation structure; through two ion implantations and one etching process of the oxidation region, the present invention can precisely control the depth and shape of the dual shallow trench isolation structure, improve the manufacturing efficiency while ensuring the isolation effect; secondly, it can effectively avoid the interval of the silicon nitride layer between the logic region and the pixel region, ensure the profile continuity of the dual shallow trench isolation structure, and thus effectively ensure the overall performance and reliability of the device.

[0030] Further, when performing the first ion implantation, oxygen ion implantation is performed according to the depth of the second shallow trench isolation structure in the dual 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 dual shallow trench isolation structure. Then, after one etching, the second shallow trench isolation structure in the dual shallow trench isolation structure can be formed, and the shape and size of the second shallow trench isolation structure can be effectively controlled, improving the manufacturing efficiency.

[0031] Further, when performing the second ion implantation, oxygen ion implantation is carried out 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, so that the depth of the second ion implantation layer 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. Furthermore, the oxidation 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. After one etching, the first shallow trench isolation structure in the double shallow trench isolation structure can be formed, and the shape and size of the first shallow trench isolation structure can be effectively controlled, improving the manufacturing efficiency.

[0032] Further, by implanting fluorine ions and etching the remaining oxides in the first shallow trench isolation structure in the double shallow trench isolation structure, the removal of the remaining oxides in the double shallow trench isolation structure is achieved; at the same time, by implanting fluorine ions, fluorine ion doping can be formed at the interface of the shallow trench isolation structure in the logic region and the pixel region; among them, the formation of fluorine ion doping at the interface of the shallow trench isolation structure in the logic region can effectively inhibit the diffusion of boron and phosphorus and reduce the influence of the reverse narrow channel effect; while the formation of fluorine ion doping at the interface of the shallow trench isolation structure in the pixel region can fill the silicon dangling bonds and reduce the ability of interface trap electrons, thereby effectively reducing the white pixels and dark current.

[0033] The double shallow trench isolation structure and the CMOS image sensor provided by the present invention have all the advantages of the above-mentioned preparation method of the double shallow trench isolation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a flowchart of the preparation method of the double shallow trench isolation structure provided in Embodiment 1;

[0036] Figure 2 It is a schematic diagram of the substrate structure with a pad oxide layer, a pad barrier layer and a hard mask layer in Embodiment 1;

[0037] Figure 3 It is a schematic diagram of the device structure after step 2 in Embodiment 1;

[0038] Figure 4 It is a schematic diagram of the device structure after step 3 in Embodiment 1;

[0039] Figure 5Schematic diagram of the device structure after the completion of step 4 in Example 1;

[0040] Figure 6 Schematic diagram of the device structure after the completion of step 6 in Example 1;

[0041] Figure 7 Schematic diagram of the device structure after the completion of step 7 in Example 1;

[0042] Figure 8 Schematic diagram of the device structure after the completion of step 8 in Example 1;

[0043] Figure 9 Schematic diagram of the device structure after the completion of the residue treatment step in Example 2.

[0044] Among them, 1 is the substrate, 2 is the pad oxide layer, 3 is the pad barrier layer, 4 is the amorphous carbon layer, 5 is the silicon oxynitride layer, 6 is the first photoresist layer, 7 is the first trench opening, 8 is the second trench opening, 9 is the second photoresist layer, 10 is the first oxidation region, and 11 is the second oxidation region. Detailed implementation manners

[0045] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer and more understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application; obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0046] The present invention provides a preparation method for a dual shallow trench isolation structure, including the following steps:

[0047] Step 100: Perform a first ion implantation on the bottom ends of the first trench opening 7 and the second trench opening 8.

[0048] Step 200: Perform a second ion implantation on the bottom end of the first trench opening 7.

[0049] Step 300: Perform an annealing treatment to form a first oxidation region 10 at the bottom end of the first trench opening 7 and a second oxidation region 11 at the bottom end of the second trench opening 8 respectively.

[0050] Step 400: Etch the first oxidation region 10 and the second oxidation region 11 to form a dual shallow trench isolation structure.

[0051] 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 with a double trench pattern on a substrate 1 having a pad oxide layer 2, a pad barrier layer 3, and a hard mask layer; etching to form a first trench opening 7 and a second trench opening 8 that penetrate through the hard mask layer, the pad barrier layer 3, and the pad oxide layer 2.

[0052] Optionally, after etching the first oxidation region 10 and the second oxidation region 11 to form a double shallow trench isolation structure, the method further includes: performing fluorine ion implantation on the double shallow trench isolation structure; etching the remaining oxide in the first shallow trench isolation structure of the double shallow trench isolation structure to form a double shallow trench isolation structure without oxidation residue.

[0053] The method for preparing the double shallow trench isolation structure provided by the present invention is based on the characteristic of a high etching selectivity ratio between silicon dioxide and silicon. Through the processes of two ion implantations and one etching of the oxidation region, the depth and shape of the double shallow trench isolation structure can be precisely controlled, and the manufacturing efficiency can be improved while ensuring the isolation effect.

[0054] Embodiment 1

[0055] As shown in the atta Figure 1 ched drawings, Embodiment 1 of the present invention provides a method for preparing a double shallow trench isolation structure, including the following steps:

[0056] Step 1: Provide a substrate 1. As shown in the atta Figure 2 ched drawings, 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.

[0057] 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 sequentially 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 is a thermal oxidation method, and the methods for forming the pad barrier layer 3, the amorphous carbon layer 4, and the silicon oxynitride layer 5 are chemical vapor deposition methods; 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.

[0058] Step 2: Etch the hard mask layer, the pad barrier layer 3, and the pad oxide layer 2 to form a first trench opening 7 and a second trench opening 8 that penetrate through the hard mask layer, the pad barrier layer 3, and the pad oxide layer 2. Specifically, using the first photoresist layer 6 as a mask, etch the silicon oxynitride layer 5, the amorphous carbon layer 4, the pad barrier layer 3, and the pad oxide layer 2 along the opening pattern corresponding to the position of the double shallow trench isolation structure until the etching of the pad oxide layer 2 is completed, that is, the substrate 1 is exposed, as shown in the atta Figure 3As shown. Preferably, the processes of etching the silicon oxynitride layer 5, the amorphous carbon layer 4, the liner barrier layer 3, and the liner oxide layer 2 adopt dry etching processes; among them, the gas for etching the silicon oxynitride layer 5 is carbon tetrafluoride and difluoromethane, the gas for etching the amorphous carbon layer 4 is chlorine, oxygen, and hydrogen bromide, the gas for etching the liner barrier layer 3 is carbon tetrafluoride and helium, and the gas for etching the liner oxide layer 2 is carbon tetrafluoride and trifluoromethane. It should be noted that in this Embodiment 1, there is no limitation on the processes of etching the silicon oxynitride layer 5, the amorphous carbon layer 4, the liner barrier layer 3, and the liner oxide layer 2.

[0059] It should be noted that in the dual shallow trench isolation structure, it 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, taking the area where the first trench opening 7 is located as the area corresponding to the deeper shallow trench isolation structure in the dual shallow trench isolation structure, and the area where the second trench opening 8 is located as the area corresponding to the shallower shallow trench isolation structure in the dual shallow trench isolation structure as an example for illustration; among them, the deeper shallow trench isolation structure is denoted as the first shallow trench isolation structure, and the shallower shallow trench isolation structure is denoted as the second shallow trench isolation structure.

[0060] Step 3: Perform a first ion implantation on the bottom ends of the first trench opening 7 and the second trench opening 8. Specifically, as shown in the appendix Figure 4 As shown, through the first photoresist layer 6, oxygen ion implantation is performed on the surfaces of the substrate 1 and the first photoresist layer 6 according to the depth of the second shallow trench isolation structure in the dual shallow trench isolation structure, so as to form a first ion implantation layer on the surface of the substrate 1 and opposite to the bottom ends of the first trench opening 7 and the second trench opening 8.

[0061] Among them, during the first ion implantation, the injection direction of the oxygen ions forms an angle of 90° with the surfaces 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 injection dose of the oxygen ions is 1E12 - 1E16; the injection energy of the oxygen ions is such that the oxygen ions can cover the depth of the second shallow trench isolation structure in the dual shallow trench isolation structure; preferably, during the first ion implantation, a multi-channel oxygen ion implantation method with different injection energies is adopted, and the multi-channel different injection energies decrease gradually, and the lowest injection energy is not less than 1 Kev.

[0062] It should be noted that oxygen ion implantation is performed according to the depth of the second shallow trench isolation structure in the dual 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 dual shallow trench isolation structure, so as to achieve the effect that after etching the first ion implantation layer once, the second shallow trench isolation structure in the dual shallow trench isolation structure can be formed.

[0063] Step 4: Remove the first photoresist layer 6 and the hard mask layer to expose the liner stop layer 3, as shown in the attached Figure 5 figure. Among them, the process of removing the first photoresist layer 6 is specifically as follows: First, use the oxygen ashing process to remove the photoresist hard shell of the first photoresist layer 6, then use a mixture of sulfuric acid and hydrogen peroxide to wet-etch the photoresist of the first photoresist layer 6, and finally use a mixture of ammonia and hydrogen peroxide to wet-etch 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: Use carbon tetrafluoride and difluoromethane as etching gases and use the dry etching process to remove it; the process of removing the amorphous carbon layer 4 in the hard mask layer is specifically as follows: Use chlorine, oxygen and hydrogen bromide as etching gases and use the dry etching process to remove it. 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.

[0064] Step 5: After removing the first photoresist layer 6 and the hard mask layer, regrow a second photoresist layer 9 on the liner stop layer 3. Among them, there is an opening pattern on the second photoresist layer 9 corresponding to the position of the first shallow trench isolation structure in the dual shallow trench isolation structure, that is, the second photoresist layer 9 is a photoresist layer with a single trench pattern.

[0065] 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 dual shallow trench isolation structure, then 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 dual shallow trench isolation structure, then an opening pattern corresponding to the second trench opening 8 is formed on the second photoresist layer 9.

[0066] Step 6: Perform a second ion implantation on the bottom end of the first trench opening 7. Specifically, as shown in the attached Figure 6 figure, through 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 dual shallow trench isolation structure, perform oxygen ion implantation on the surfaces of the substrate 1 and the second photoresist layer 9 to form a second ion implantation layer on the surface of the substrate 1 and directly opposite the bottom end of the first trench opening 7; it should be noted that both the first ion implantation layer and the second ion implantation layer are oxygen ion implantation layers; the second ion implantation layer is formed by superimposing after the second ion implantation on the basis of the first ion implantation layer corresponding to the bottom end of the first trench opening 7.

[0067] Among them, during the second ion implantation, the implantation direction of the oxygen ions forms an angle of 90° with the surface of the substrate 1 and the second photoresist layer 9; that is, the implantation 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 implantation dose of the oxygen ions is 1E12 - 1E16; the implantation energy of the oxygen ions is such that the oxygen ions can cover the depth of the first shallow trench isolation structure in the dual shallow trench isolation structure.

[0068] Preferably, during the second ion implantation, a multi-channel oxygen ion implantation method with different implantation energies is adopted, and the different implantation energies in multiple channels decrease gradually; among them, 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 dual shallow trench isolation structure.

[0069] It should also be noted that the second ion implantation is carried out according to the depth difference between the first shallow trench isolation structure and the second shallow trench isolation structure in the dual 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 dual shallow trench isolation structure, so as to achieve the effect that after etching the second ion implantation layer once, the first shallow trench isolation structure in the dual shallow trench isolation structure can be formed.

[0070] Step 7: Remove the second photoresist layer 9 to expose the pad barrier layer 3 again; after removing the second photoresist layer 9, an annealing treatment is carried out to form a first oxidation region 10 at the bottom end of the first trench opening 7 and a second oxidation region 11 at the bottom end of the second trench opening 8, as shown in the appendix Figure 7 as shown.

[0071] Among them, the process of removing the second photoresist layer 9 is specifically as follows: first, the photoresist of the second photoresist layer 9 is removed by a wet process using a mixture of sulfuric acid and hydrogen peroxide, and then the organic matter and residual particles of the second photoresist layer 9 are removed by a wet process using a mixture of ammonia and hydrogen peroxide; the temperature of the annealing treatment is greater than 800 °C and the time is greater than 30 min to ensure that the implanted 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.

[0072] It should be noted that after oxygen ion implantation is performed on the bottom ends of the first trench opening 7 and the second trench opening 8 and an annealing treatment is carried out to activate the oxygen ions in the first ion implantation layer and the second ion implantation layer, so that the oxygen ions combine with the silicon atoms in the substrate 1 to form an oxidation region with a material of silicon dioxide and a depth adapted to the depth of the dual shallow trench isolation structure on the surface of the substrate 1. Then, based on the characteristic that the etching selectivity ratio of silicon dioxide and silicon is high, the oxidation region is etched once to form the dual shallow trench isolation structure.

[0073] Step 8: Etch the first oxidation region 10 and the second oxidation region 11 to form a dual shallow trench isolation structure, as shown in the appendix Figure 8 Shown. Preferably, the processes of etching the first oxidation region 10 and the second oxidation region 11 are both dry etching processes; among them, the gases for etching the first oxidation region 10 and the second oxidation region 11 are trifluoromethane and hydrogen; during the etching process, by adjusting the ratio of trifluoromethane to hydrogen, the etching selectivity of silicon dioxide and silicon can be improved. It should be noted that in this Embodiment 1, there is no limitation on the process of etching the first oxidation region 10 and the second oxidation region 11.

[0074] In the preparation method of the dual shallow trench isolation structure described in this Embodiment 1, by performing two oxygen ion implantations on the bottom end of the first trench opening 7, performing one oxygen ion implantation on the bottom end of the second trench opening 8, and activating the oxygen ions through annealing treatment, an oxidation region made of silicon dioxide is formed on the surface of the substrate 1; then, based on the characteristic of high etching selectivity between silicon dioxide and silicon, the oxidation region is etched once to form a dual shallow trench isolation structure, achieving precise control of the depth and shape of the dual shallow trench isolation structure, and improving the manufacturing efficiency while ensuring the isolation effect.

[0075] Embodiment 2

[0076] The preparation method of a dual shallow trench isolation structure provided in this Embodiment 2 is basically the same as the operation and principle of the preparation method of the dual shallow trench isolation structure described in the above Embodiment 1, the difference being that: after Step 8 of Embodiment 1, a residue treatment step is further included.

[0077] Specifically, the residue treatment step is as follows:

[0078] Perform fluorine ion implantation on the dual shallow trench isolation structure; etch the remaining oxides in the first shallow trench isolation structure in the dual shallow trench isolation structure to form a dual shallow trench isolation structure without oxidation residue.

[0079] As shown in the appendix Figure 9 Shown, during the process of performing fluorine ion implantation on the dual shallow trench isolation structure, the fluorine ions are implanted into the dual shallow trench isolation structure in a direction at a preset inclination angle with respect to the normal line of the substrate 1; among them, the preset inclination angle is:

[0080]

[0081] Among them, is the preset inclination angle; is the sum of the thicknesses of the pad oxide layer 2 and the pad barrier layer 3; is the depth of the second shallow trench isolation structure in the dual shallow trench isolation structure; is the width of the second shallow trench isolation structure in the dual shallow trench isolation structure.

[0082] In this Embodiment 2, when performing fluorine ion implantation, the implantation dose of fluorine ions is 1E15 - 1E16, and the implantation energy is less than 4 Kev; there is no limitation on the process of etching the remaining oxide in the first shallow trench isolation structure of the double shallow trench isolation structure.

[0083] In this Embodiment 2, by injecting fluorine ions into the double shallow trench isolation structure, the remaining oxide in the first shallow trench isolation structure in the logic region 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 remaining oxide in the first shallow trench isolation structure, the removal of the remaining oxide in the double shallow trench isolation structure is achieved; in addition, by injecting fluorine ions, fluorine ion doping is formed at the interface of the shallow trench isolation structures in the logic region and the pixel region; among them, the formation of fluorine ion doping at the interface of the shallow trench isolation structure in the logic region can effectively inhibit the diffusion of boron and phosphorus and reduce the influence of the anti-narrow channel effect; while the formation of fluorine ion doping at the interface of the shallow trench isolation structure in the pixel region can fill silicon dangling bonds and reduce the ability of interface trap electrons, thereby effectively reducing white pixels and dark current.

[0084] Embodiment 3

[0085] This Embodiment 3 provides a CMOS image sensor, including a substrate; a double shallow trench isolation structure is formed on the substrate; wherein, the double shallow trench isolation structure is prepared by using the preparation method of the double shallow trench isolation structure described in the above Embodiment 1 or 2, ensuring the profile continuity of the double shallow trench isolation structure, so that the fabricated CMOS image sensor has better reliability and performance.

[0086] It should be noted that the preparation method of the double shallow trench isolation structure is detailed in the corresponding parts of the above Embodiment 1 or 2 and will not be elaborated here.

[0087] The preparation method of the double shallow trench isolation structure described in the present invention realizes the precise control of the depth and shape of the double shallow trench isolation structure through two oxygen ion implantation processes and one etching process of the oxidation region, and can improve the manufacturing efficiency while ensuring the isolation effect; secondly, it can effectively avoid the interval of the silicon nitride layer between the logic region and the pixel region, ensure the profile continuity of the double shallow trench isolation structure, and thus effectively guarantee the overall performance and reliability of the device.

[0088] The above embodiments are only one of the implementation manners that can realize the technical solution of the present invention. The scope of protection required by the present invention is not only limited by this embodiment, but also includes any changes, substitutions and other implementation manners that are easily conceivable by any person skilled in the art within the technical scope disclosed by the present invention.

Claims

1. A method for preparing a dual shallow trench isolation structure, characterized in that Including: 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 an annealing treatment to form a first oxidation region (10) at the bottom end of the first trench opening (7) and a second oxidation region (11) at the bottom end of the second trench opening (8) respectively; Etching the first oxidation region (10) and the second oxidation region (11) to form a dual shallow trench isolation structure; Performing a fluorine ion implantation on the dual shallow trench isolation structure; Etching the oxide remaining in the first shallow trench isolation structure in the dual shallow trench isolation structure to form a dual shallow trench isolation structure without oxidation residue.

2. The preparation method of a dual 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 with a dual trench pattern, according to the depth of the second shallow trench isolation structure in the dual shallow trench isolation structure, performing an oxygen ion implantation on the bottom ends of the first trench opening (7) and the second trench opening (8) to form a first ion implantation layer.

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

4. A method for preparing a dual shallow trench isolation structure according to claim 1, wherein Before performing the first ion implantation on the bottom ends of the first trench opening (7) and the second trench opening (8), it further includes: Forming a photoresist layer with a dual trench pattern on a substrate (1) having a pad oxide layer (2), a pad barrier layer (3) and a hard mask layer; Etching to form a first trench opening (7) and a second trench opening (8) that penetrate through the hard mask layer, the pad barrier layer (3) and the pad oxide layer (2).

5. A method for preparing a dual shallow trench isolation structure according to claim 1, characterized in that, During the process of performing the fluorine ion implantation on the dual shallow trench isolation structure, injecting the fluorine ions into the dual shallow trench isolation structure in a direction at a preset inclination angle with respect to the normal of the substrate (1); wherein, the preset inclination angle is: Wherein, is a preset inclination angle; is the sum of the thicknesses of the liner oxide layer (2) and the liner barrier layer (3); is the depth of the second shallow trench isolation structure in the dual shallow trench isolation structure; is the width of the second shallow trench isolation structure in the dual shallow trench isolation structure.

6. The manufacturing method of a dual shallow trench isolation structure according to claim 4, wherein The material of the pad barrier layer (3) is silicon nitride.

7. A method for manufacturing a dual shallow trench isolation structure according to claim 4, wherein 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.

8. A dual shallow trench isolation structure, characterized in that, The described dual shallow trench isolation structure is prepared by using the preparation method of the dual shallow trench isolation structure according to any one of the above-mentioned claims 1-7.

9. A CMOS image sensor, characterized in that, The described CMOS image sensor is prepared by using the preparation method of the dual shallow trench isolation structure according to any one of the above-mentioned claims 1-7.

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