Preparation method of image sensor and image sensor

Abstract

The invention relates to a preparation method of an image sensor and the image sensor, and relates to the technical field of display, the image sensor is provided with a barrier layer with first doped ions in an isolation groove, and the barrier layer is high in compactness, so that external ions can be prevented from drilling into a pixel region from an interface of the isolation groove during etching, and the etching efficiency is improved. Therefore, generation of dark current caused by defects at the interface is avoided, and the problem that white pixels are generated in the local area of the pixel area is further avoided.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a method for preparing an image sensor and an image sensor. Background Art

[0002] Dark current is one of the important electrical parameters of image sensors and directly affects the optical performance of image sensor products. The generation of dark current will cause white pixels to appear in local areas of the pixel area, thus affecting image display.

[0003] In addition to the metal ion contamination that causes the intermediate energy level in the original forbidden band, which allows electrons to transition even without light, the defects at the interface of the shallow isolation trench are also an important factor in the formation of dark current. In front-illuminated image sensors, the filling of the shallow isolation trench isolation between pixel areas often uses an etching step, but during etching, some external ions will penetrate into the pixel area at the interface of the shallow isolation trench isolation, causing defects at the interface, leading to the generation of dark current, and further causing white pixels to appear in local areas of the pixel area.

[0004] Based on this, there is an urgent need for an image sensor that can reduce defects at the interface and thus improve the generation of white pixels in the pixel area. Summary of the invention

[0005] Based on this, it is necessary to provide a method for preparing an image sensor and an image sensor that reduce defects at the interface and thereby improve the generation of white pixels in the pixel area in order to solve the above problems.

[0006] In order to achieve the above object, on the one hand, the present invention provides a method for preparing an image sensor, the method comprising:

[0007] Providing a substrate, the substrate comprising a substrate and a mask layer located on the substrate, the substrate having at least two pixel regions and an isolation trench located between two adjacent pixel regions, the isolation trench penetrating the mask layer and extending into a portion of the substrate;

[0008] forming a first dielectric layer on the surface of the substrate at the sidewall and bottom of the isolation trench;

[0009] forming a barrier layer having first doping ions on a surface of the first dielectric layer and a surface of the mask layer on a sidewall of the isolation trench;

[0010] forming a first isolation material layer filling the isolation trench on a surface of the barrier layer;

[0011] Etching and removing a portion of the first isolation material layer in the isolation trench to form an opening area;

[0012] A first isolation layer and a second isolation layer are formed in the isolation trench after the opening area is formed.

[0013] In one embodiment, the step of forming a barrier layer having first doping ions on the surface of the first dielectric layer and the surface of the mask layer on the sidewall of the isolation trench comprises:

[0014] forming a first barrier material layer on a surface of the first dielectric layer and a surface of the mask layer on a sidewall of the isolation trench;

[0015] The first doping ions are implanted into the first barrier material layer by an ion implantation method to form the barrier layer having the first doping ions.

[0016] In one embodiment, before the step of forming a barrier layer having first doping ions on the surface of the first dielectric layer and the surface of the mask layer on the sidewall of the isolation trench, the step includes:

[0017] forming an injection blocking layer on the upper surface of the mask layer;

[0018] After forming the barrier layer having the first doping ions, the method further comprises:

[0019] The implantation barrier layer is removed.

[0020] In one embodiment, the step of forming a first isolation layer and a second isolation layer in the isolation trench after forming the opening area includes:

[0021] forming a second isolation material layer in the isolation trench after forming the opening area;

[0022] The second isolation material layer and the first isolation material layer on the upper surface of the mask layer are ground by a grinding process to form the first isolation layer and the second isolation layer.

[0023] In one embodiment, the step of forming a barrier layer having first doping ions on the surface of the first dielectric layer and the surface of the mask layer on the sidewall of the isolation trench further includes:

[0024] A second barrier material layer having the first doping ions is deposited on the upper surface of the mask layer, the surface of the mask layer on the sidewall of the isolation trench, and the surface of the first dielectric layer in the isolation trench.

[0025] In one embodiment, the step of forming a first isolation layer and a second isolation layer in the isolation trench after forming the opening area further includes:

[0026] forming a second isolation material layer on the surface of the first isolation material layer and in the isolation trench after the opening area is formed;

[0027] The first isolation material layer, the second isolation material layer and the second barrier material layer on the upper surface of the mask layer are ground by a grinding process to form the first isolation layer, the second isolation layer and the barrier layer.

[0028] In one embodiment, the barrier layer is a silicon nitride barrier layer, and the first doping ions are C ions; the step of etching and removing a portion of the first isolation material layer in the isolation trench to form an opening area includes:

[0029] Using a first etching gas to etch and remove a portion of the first isolation material layer in the isolation trench to form the opening area;

[0030] The first etching gas includes an etching gas containing fluorine ions.

[0031] On the other hand, the present invention further provides an image sensor, comprising:

[0032] A substrate, comprising a substrate and a mask layer located on the substrate, the substrate having at least two pixel regions and an isolation trench located between two adjacent pixel regions, the isolation trench penetrating the mask layer and extending into a portion of the substrate;

[0033] A first dielectric layer, wherein the first dielectric layer covers the sidewalls and bottom of the isolation trench and the surface of the substrate;

[0034] a barrier layer, the barrier layer covering a surface of the first dielectric layer and a surface of the mask layer on a sidewall of the isolation trench, the barrier layer having first doping ions;

[0035] a first isolation layer, the first isolation layer being located on one side of the barrier layer in the isolation trench, the first isolation layer covering the barrier layer and filling a portion of the isolation trench;

[0036] A second isolation layer is provided, wherein the second isolation layer fills the remaining isolation trench.

[0037] In one embodiment, the barrier layer includes N sub-barrier layers, N ≥ 2, and N is a positive integer;

[0038] The proportion of the first doping ions in each of the sub-blocking layers is the same.

[0039] In one embodiment, the barrier layer includes N sub-barrier layers, N ≥ 2, and N is a positive integer;

[0040] In a direction in which the barrier layer is away from the first dielectric layer, the proportion of the first doping ions in the sub-barrier layers from the 1st layer to the Nth layer gradually increases.

[0041] Compared with the prior art, the above technical solution has the following unexpected technical effects:

[0042] The substrate includes a substrate and a mask layer located on one side of the substrate, the substrate includes at least two pixel areas and an isolation groove located between the pixel areas, the isolation groove penetrates the mask layer and extends into part of the substrate, a first dielectric layer is arranged on the surface of the substrate at the sidewall and bottom of the isolation groove, and then a barrier layer is arranged on the surface of the first dielectric layer and the sidewall of the mask layer of the isolation groove, the barrier layer has first doping ions, and then a first isolation material layer filling the isolation groove is formed on the surface of the barrier layer, and part of the first isolation material layer in the isolation groove is etched away to form an opening area, and then a first isolation layer and a second isolation layer are formed in the isolation groove after the opening area is formed, thereby completing the filling of the isolation groove.

[0043] The image sensor is provided with a barrier layer having a first doped ion. Since the barrier layer has a high density, it can block external ions from penetrating into the pixel area from the interface of the isolation groove during etching, thereby avoiding the generation of dark current due to defects at the interface and further avoiding the problem of white pixels generated in local areas of the pixel area. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are 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 creative work.

[0045] Figure 1 A schematic diagram of a molecular dynamics simulation of fluorine ions drilling into a substrate during an existing etching process;

[0046] Figure 2 A schematic diagram of a process for preparing an image sensor provided in an embodiment of the present application;

[0047] Figure 3 A schematic diagram of another part of the process of a method for preparing an image sensor provided in an embodiment of the present application;

[0048] Figure 4 A schematic diagram of another part of a process for preparing an image sensor provided in an embodiment of the present application;

[0049] Figure 5A schematic structural diagram of a substrate structure during the preparation of an image sensor provided in an embodiment of the present application;

[0050] Figure 6 A schematic diagram of the structure after a first dielectric layer is formed in a manufacturing process of an image sensor provided in an embodiment of the present application;

[0051] Figure 7 A schematic diagram of the structure after forming a first barrier material layer and injecting a barrier layer in the preparation process of an image sensor provided by an embodiment of the present application;

[0052] Figure 8 A schematic diagram of the structure after a barrier layer is formed in the preparation process of an image sensor provided in an embodiment of the present application;

[0053] Fig. 9 A schematic diagram of the structure after a first isolation material layer is formed in a manufacturing process of an image sensor provided by an embodiment of the present application;

[0054] Fig.10 A schematic diagram of the structure after an opening area is formed in the manufacturing process of an image sensor provided in an embodiment of the present application;

[0055] Fig.11 A schematic diagram of the structure after a second isolation material layer is formed in the preparation process of an image sensor provided by an embodiment of the present application;

[0056] Fig.12 A schematic diagram of the structure after a second isolation layer is formed in the preparation process of an image sensor provided in an embodiment of the present application;

[0057] Fig.13 for Fig.12 A schematic diagram of a local enlarged structure;

[0058] Fig.14 A schematic diagram of the structure after a second barrier material layer is formed in the preparation process of an image sensor provided in an embodiment of the present application;

[0059] Fig.15 A schematic diagram of the structure after a second isolation material layer is formed in the preparation process of another image sensor provided in an embodiment of the present application.

[0060] Explanation of the reference numerals: 01-base; 02-substrate; 03-mask layer; 03a-first mask layer; 03b-second mask layer; 04-pixel area; 05-isolation groove; 06-first dielectric layer; 07-barrier layer; 07a-sub-barrier layer; 08-first isolation material layer; 08a-opening area; 09-first isolation layer; 10-second isolation layer; 11a-first barrier material layer; 11b-second barrier material layer; 12-injection blocking layer; 13-second isolation material layer; 111-fluoride ion; 112-Si substrate. DETAILED DESCRIPTION

[0061] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0063] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0064] Based on the content in the background technology, when preparing a front-illuminated image sensor, due to the influence of the aspect ratio of the isolation trench, hollow areas may appear in the process of filling the isolation trench. At this time, etching is used to etch away part of the isolation layer, and then the filling is continued to complete the filling of the isolation trench.

[0065] When etching the isolation layer, NF is used 3 The etching gas is used for etching, and the fluorine ions will penetrate into the Si substrate under the action of plasma, affecting the Si lattice and causing defects at the interface. Figure 1 , Figure 1 This is a schematic diagram of the molecular dynamics simulation of fluoride ions drilling into the substrate during the existing etching process. Figure 1 The fluorine ions 111 may cause defects Q at the interface of the Si substrate 112, which may lead to the generation of dark current and further to the generation of white pixels in the image sensor.

[0066] Based on this, the present application provides a method for preparing an image sensor, including providing a substrate, the substrate including a substrate and a mask layer located on one side of the substrate, the substrate including at least two pixel areas and an isolation trench located between the pixel areas, the isolation trench penetrating the mask layer and extending into part of the substrate, a first dielectric layer is arranged on the surface of the substrate at the sidewall and bottom of the isolation trench, and then a barrier layer is arranged on the surface of the first dielectric layer and the sidewall of the mask layer of the isolation trench, the barrier layer has first doped ions, and then a first isolation material layer filling the isolation trench is formed on the surface of the barrier layer, a part of the first isolation material layer in the isolation trench is etched away to form an opening area, and then a first isolation layer and a second isolation layer are formed in the isolation trench after the opening area is formed, thereby completing the filling of the isolation trench.

[0067] The image sensor is provided with a barrier layer having a first doped ion. Since the barrier layer has a high density, it can block external ions from penetrating into the substrate during etching, thereby avoiding the generation of substrate defects, reducing the generation of dark current in the image sensor, and further avoiding the generation of white pixels in the pixel area.

[0068] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0069] Please refer to Figure 2 , Figure 2 A schematic flow chart of a method for preparing an image sensor provided in an embodiment of the present application; the preparation method comprises:

[0070] S101: Provide a substrate 01 (such as Figure 5 as shown).

[0071] The base 01 includes a substrate 02 and a mask layer 03 on the substrate 02 . The substrate 01 has at least two pixel regions 04 and an isolation trench 05 between two adjacent pixel regions 04 . The isolation trench 05 penetrates the mask layer 03 and extends into a portion of the substrate 02 .

[0072] In this step, the substrate 02 in the base 01 may be a Si substrate, wherein the mask layer 03 located on the substrate 02 may include a two-layer structure. For example, it may include a first mask layer 03a located on the substrate 02 and in contact with the substrate 02, and a second mask layer 03b located on the upper side of the first mask layer 03a, wherein the first mask layer 03a may be an oxide layer, including but not limited to silicon oxide; and the second mask layer 03b may be a silicon nitride layer, which is not specifically limited and can be set as required.

[0073] In the image sensor, the substrate 01 also includes at least two pixel areas 04, and an isolation groove 05 is arranged between two adjacent pixel areas 04. The isolation groove 05 is etched by an etching process. In order to form isolation between the pixel areas 04, the isolation groove 05 needs to penetrate the mask layer 03 and extend into the substrate 02. At this time, the isolation groove 05 exposes part of the bottom surface and side wall of the substrate 02, and exposes the side wall of the mask layer 03.

[0074] S102: Form a first dielectric layer 06 (eg, Figure 6 as shown).

[0075] In this step, when etching to form the isolation trench 05, partial defects will be formed on the substrate 01. To fill the isolation layer, a first dielectric layer 06 is first formed on the sidewalls of the isolation trench 05 and the surface of the bottom substrate 02. The first dielectric layer 06 can be a pad oxide layer, including but not limited to silicon oxide materials.

[0076] S103: forming a barrier layer 07 (such as a first doping layer) having first doping ions on the surface of the first dielectric layer 06 and the surface of the mask layer 03 on the sidewall of the isolation trench 05. Figure 8 as shown).

[0077] In this step, since a hollow area will be generated due to the influence of the depth-to-width ratio of the isolation trench 05 when the isolation layer is subsequently formed, a second etching will be performed to avoid the generation of the hollow area. In order to ensure that the second etching will not generate interface defects at the substrate 02 of the isolation trench 05, a barrier layer 07 is formed before filling the isolation layer, so that the barrier layer 07 blocks the influence of external ions on the interface at the substrate 02 of the isolation trench 05 during etching, thereby reducing the generation of dark current in the image sensor and avoiding the generation of white pixels. The barrier layer 07 is a barrier layer 07 with first doped ions. Since the barrier layer 07 with the first doped ions has a higher density, the interface defects generated by the ions in the etching gas penetrating into the substrate 02 can be avoided.

[0078] It should be noted that the barrier layer 07 covers the sidewalls of the mask layer 03, which can prevent external ions from entering through the mask layer 03, and further prevent the external ions from affecting the interface of the substrate 02 at the isolation trench 05 (such as Figure 8 as shown).

[0079] When forming the barrier layer 07 having the first doping ions, the present application provides two preparation methods, which are described in turn below.

[0080] Optionally, in another embodiment of the present application, Figure 3As shown, the step of forming a barrier layer 07 having first doping ions on the surface of the first dielectric layer 06 and the surface of the mask layer 03 on the sidewall of the isolation trench 05 includes:

[0081] S201: Form a first barrier material layer 11a (eg, Figure 7 as shown).

[0082] Optionally, in another embodiment of the present application, before the step of forming the barrier layer 07 having the first doping ions on the surface of the first dielectric layer 06 and the surface of the mask layer 03 of the sidewall of the isolation trench 05, the step includes:

[0083] An injection blocking layer 12 (such as Figure 7 as shown).

[0084] Specifically, before forming the barrier layer 07 having the first doping ions, in order to ensure that the first barrier material layer 11a is not formed on the upper side of the mask layer 03, an injection barrier layer 12 is first formed on the upper surface of the mask layer 03. It should be noted that the injection barrier layer 12 can be a photoresist, which is not specifically limited, and it is sufficient to ensure that the first barrier material layer 11a is not formed on the mask layer 03.

[0085] After the injection blocking layer 12 is formed, a first barrier material layer 11a is formed on the surface of the first dielectric layer 06 and the sidewalls of the mask layer 03 of the isolation trench 05. The material of the first barrier material layer 11a can be silicon nitride material, which is not specifically limited. It should be noted that the first barrier material layer 11a covers the surface of the first dielectric layer 06 and the sidewalls of the mask layer 03 in the isolation trench 05 (such as Figure 7 as shown).

[0086] S202: implanting first doping ions into the first barrier material layer 11a by an ion implantation method to form a barrier layer 07 (eg, Figure 8 as shown).

[0087] In this step, the first doping ions are implanted into the first barrier material layer 11a by ion implantation. It should be noted that the direction of the ion implantation can be controlled during the implantation to ensure the concentration ratio of the first doping ions implanted. In addition, at this time, the first dielectric layer 06 can serve as a barrier layer for the first doping ions to prevent the first doping ions from entering the substrate 02 to avoid generating other defects.

[0088] The first barrier material layer 11a injected with the first doping ions serves as the barrier layer 07. The barrier layer 07 has improved compactness due to the injection of the first doping ions, and thus can well block ions in the etching gas and prevent them from drilling into the substrate 02. After the barrier layer 07 is formed, during the second etching, ions in the etching gas will not drill into the substrate 02, thereby avoiding defects at the interface of the substrate 02 in the isolation trench 05.

[0089] After forming the barrier layer 07 having the first doping ions, the process includes: removing the implantation blocking layer 12 .

[0090] It should be noted that after forming the barrier layer 07, if an isolation layer needs to be further formed, the injection barrier layer 12 needs to be removed first. There is no specific limitation on the method of removing the injection barrier layer 12, and it can be selected according to specific needs. For example, when the injection barrier layer 12 is a photoresist, the photoresist can be washed off.

[0091] S104: forming a first isolation material layer 08 (such as a first isolation material layer 08 ) filling the isolation trench 05 on the surface of the barrier layer 07 Fig. 9 as shown).

[0092] In this step, a first isolation material layer 08 is formed on the surface of the barrier layer 07 to fill the isolation trench 05. The material of the first isolation material layer 08 may be an oxide material, including but not limited to a silicon oxide material. Based on the aspect ratio of the isolation trench 05, when the first isolation material layer 08 is formed, a hollow area W may be formed in the center of the isolation trench 05. If the hollow area W continues to be filled, the isolation trench 05 will not be fully filled. In order to ensure the isolation effect of the isolation trench 05, a second etching is required.

[0093] S105: etching and removing a portion of the first isolation material layer 08 in the isolation trench 05 to form an opening region 08a (eg Fig.10 as shown).

[0094] In this step, a portion of the first isolation material layer 08 in the isolation trench 05 is etched away to form an opening area 08a. At this time, the isolation trench 05 has a groove, which removes the hollow area W so as to fully fill the isolation trench subsequently.

[0095] It should be noted that, in one embodiment, when forming the opening area 08a, a portion of the first isolation material layer 08 on the surface of the mask layer is etched. Fig.10 As shown, the first isolation material layer 08 may cover the mask layer 03 , and the thickness thereof is not specifically limited herein.

[0096] Optionally, in another embodiment of the present application, the barrier layer 07 is a silicon nitride barrier layer, and the first doping ions are C ions; etching and removing a portion of the first isolation material layer 08 in the isolation trench 05 to form an opening area 08a includes:

[0097] A first etching gas is used to etch away a portion of the first isolation material layer 08 in the isolation trench 05 to form an opening region 08 a.

[0098] The first etching gas includes an etching gas containing fluorine ions.

[0099] Specifically, in the present embodiment, the barrier layer 07 is a silicon nitride barrier layer, and the first doping ions are C ions. The C-doped silicon nitride barrier layer 07 has high compactness and good resistance to fluorine-containing etching gases.

[0100] When etching the first isolation material layer 08 with an etching gas containing fluorine ions, the C-doped silicon nitride barrier layer can effectively block the fluorine ions in the etching gas, so that the etching rate of the fluorine ions is greatly reduced, thereby preventing the fluorine ions from penetrating into the substrate 02 and causing interface defects.

[0101] It should be noted that this is only an example, and the material of the barrier layer 07 and the first doping ion are not specifically limited, as long as they can prevent the ions in the etching gas from penetrating into the substrate 02 during etching. 3 For example, the barrier layer 07 having the first doping ions can block the fluorine ions from penetrating into the interface of the isolation trench 05 .

[0102] S106: forming a first isolation layer 09 and a second isolation layer 10 (such as Fig.12 as shown).

[0103] Optional, reference Figure 4 In another embodiment of the present application, the step of forming the first isolation layer 09 and the second isolation layer 10 in the isolation trench 05 after forming the opening area 08a includes:

[0104] S1061: forming a second isolation material layer 13 (such as Fig.11 as shown).

[0105] S1062: grinding the second isolation material layer 13 and the first isolation material layer 08 on the upper surface of the mask layer 03 by a grinding process to form a first isolation layer 09 and a second isolation layer 10 (such as Fig.12 as shown).

[0106] Specifically, in this step, the material of the filled second isolation material layer 13 can be the same as that of the first isolation material layer 08, and the second isolation material layer 13 covers the opening area 08a and the first isolation material layer 08. Since the isolation layer only needs to fill the isolation groove 05, the first isolation material layer 08 and the second isolation material layer 13 on the upper surface of the mask layer 03 are ground by a grinding process, so that the formed first isolation layer 09 and the second isolation layer 10 are flush with the mask layer 03. At this time, due to the presence of the barrier layer 07, no interface defects will appear at the interface of the isolation groove 05 in the image sensor, thereby avoiding the generation of dark current in the image sensor and further reducing the generation of white pixels in the image sensor.

[0107] In addition to the above-mentioned method of forming the barrier layer 07 , the present application also provides another method of forming the barrier layer 07 .

[0108] Optionally, in another embodiment of the present application, refer to Fig.14 as well as Fig.15 The step of forming a barrier layer 07 having first doping ions on the surface of the first dielectric layer 06 and the surface of the mask layer 03 on the sidewall of the isolation trench 05 also includes:

[0109] A second barrier material layer 11 b having first doping ions is deposited on the upper surface of the mask layer 03 , the surface of the mask layer 03 on the sidewall of the isolation trench 05 , and the surface of the first dielectric layer 06 in the isolation trench 05 .

[0110] Specifically, the second barrier material layer 11b having the first doping ions is formed by directly depositing the second barrier material layer 11b having the first doping ions on the upper surface of the mask layer 03 and the surface of the first dielectric layer 06 in the isolation groove 05 by plasma enhanced chemical vapor deposition (PECVD). This method of forming the second barrier material layer 11b having the first doping ions does not require a second doping, thus saving preparation steps and reducing preparation costs. It should be noted that the second barrier material layer 11b is made of the same material as the barrier layer 07, and the barrier layer 07 can be obtained by subsequent grinding.

[0111] After forming the second barrier material layer 11b, an isolation layer is continuously formed in the isolation trench 05. It should be noted that in the method of directly forming the second barrier material layer 11b with the first doping ions by plasma enhanced chemical vapor deposition, the formation of the opening area 08a is the same as in the above embodiment, and will not be repeated here.

[0112] When the second barrier material layer 11 b is directly formed by PECVD, since the second barrier material layer 11 b will cover the mask layer 03 , when the second isolation layer 10 is formed, the second barrier material layer 11 b on the upper surface of the mask layer 03 will be simultaneously ground away by grinding.

[0113] Optionally, in another embodiment of the present application, the step of forming the first isolation layer 09 and the second isolation layer 10 in the isolation trench 05 after forming the opening area 08a further includes:

[0114] like Fig.15 As shown, a second isolation material layer 13 is formed on the surface of the first isolation material layer 08 and in the isolation trench 05 after the opening area 08 a is formed.

[0115] like Fig.12 As shown, the first isolation material layer 08 , the second isolation material layer 13 and the second barrier material layer 11 b on the upper surface of the mask layer 03 are ground by a grinding process to form a first isolation layer 09 , a second isolation layer 10 and a barrier layer 07 .

[0116] In this step, the material of the filled second isolation material layer 13 is the same as that of the first isolation material layer 08, and the second isolation material layer 13 covers the first isolation material layer 08 on the upper surface of the second barrier material layer 11b. Since the isolation layer only needs to fill the isolation groove 05, the first isolation material layer 08, the second isolation material layer 13 and the second barrier material layer 11b on the upper surface of the mask layer 03 are ground by a grinding process, so that the formed first isolation layer 09, the second isolation layer 10 and the barrier layer 07 are flush with the mask layer 03. At this time, due to the presence of the barrier layer 07 in the isolation groove 05, no interface defects will appear at the interface of the isolation groove 05 in the image sensor, thereby avoiding the generation of dark current in the image sensor and further reducing the generation of white pixels in the image sensor.

[0117] Based on the above-mentioned method for preparing the image sensor, this embodiment further provides an image sensor, which is prepared by the above-mentioned method, such as Fig.12 As shown, the image sensor comprises:

[0118] The substrate 01 includes a substrate 02 and a mask layer 03 located on the substrate 02 . The substrate 01 has at least two pixel regions 04 and an isolation trench 05 located between two adjacent pixel regions 04 . The isolation trench 05 penetrates the mask layer 03 and extends into a portion of the substrate 02 .

[0119] The first dielectric layer 06 covers the bottom and sidewalls of the isolation trench 05 and the surface of the substrate 02 .

[0120] The barrier layer 07 covers the surface of the first dielectric layer 06 and the sidewalls of the mask layer 03 of the isolation trench 05 , and the barrier layer 07 has first doping ions.

[0121] The first isolation layer 09 is located on one side of the barrier layer 07 in the isolation trench 05 . The first isolation layer 09 covers the barrier layer 07 and fills a portion of the isolation trench 05 .

[0122] The second isolation layer 10 fills the remaining isolation trench 05 .

[0123] Specifically, the substrate 02 may be a silicon substrate, and the mask layer 03 may include a first mask layer 03a and a second mask layer 03b sequentially disposed on the silicon substrate, wherein the first mask layer 03a may be silicon oxide, and the second mask layer 03b may be silicon nitride. The first dielectric layer 06 covers the bottom surface and sidewalls of the substrate 02 in the isolation trench 05, and the first dielectric layer 06 may be a liner oxide layer. The barrier layer 07 covers the surface of the first dielectric layer 06 in the isolation trench 05 and the sidewalls of the mask layer 03. Since the barrier layer 07 has a higher density after being doped with the first doping ions, the ions in the etching gas can be blocked from drilling into the substrate 02. Finally, the first isolation layer 09 and the second isolation layer 10 are formed to complete the filling of the isolation trench 05.

[0124] When forming the isolation layer, considering the influence of the aspect ratio of the isolation trench 05, it is necessary to first form the first isolation material layer 08, and then perform a first etching on the first isolation material layer 08. During this etching, the ions in the etching gas will enter the interface of the substrate 02, resulting in defects in the lattice of the substrate 02 material. The barrier layer 07 can block the ions in the etching gas, wherein the barrier layer 07 can be a C-doped silicon nitride layer, and the etching gas can be NF 3 The fluorine ions in the etching gas have a greater impact on the interface of the substrate 02, which will produce larger defects. The C-doped silicon nitride layer has a good barrier effect on fluorine ions, which can block the impact of fluorine ions on the interface of the substrate 02 and ensure the integrity of the interface, thereby reducing the generation of dark current and avoiding the generation of white pixels.

[0125] Optional, such as Fig.13 As shown, in another embodiment of the present application, the barrier layer 07 includes N sub-barrier layers 07a, N≥2, and N is a positive integer.

[0126] The proportion of the first doping ions in each sub-blocking layer 07a is the same.

[0127] Specifically, the barrier layer 07 may include N sub-barrier layers 07a. It should be noted that the sub-barrier layer 07a is for better illustrating the proportion of the first doping ions in the barrier layer 07. When formed, it may be an integrated structure and is not specifically limited.

[0128] Wherein, N is a positive integer greater than or equal to 2, for example, N can be 3, that is, the sub-blocking layer 07a includes 3 layers, such as Fig.14 As shown, the first doping ions in the three sub-barrier layers 07a can be C ions, and the proportion of C doping ions in each sub-barrier layer 07a in the layer is the same, that is, the proportion of C doping ions in the entire barrier layer 07 is the same.

[0129] In this embodiment, the proportion of the first doping ions in each sub-blocking layer 07a is set to be the same, so the preparation process is relatively simple and the performance is stable.

[0130] Optionally, in another embodiment of the present application, the proportion of the first doping ions in the sub-blocking layer 07a is in the range of 3%-10%.

[0131] Specifically, the doping ratio of the first doping ion is in the range of 3%-10%, including the end value, for example, the doping ratio of the first doping ion can be 3% or 6% or 7% or 9%, etc., and there is no specific limitation, and doping can be performed as needed. It should be noted that the sub-blocking layer 07a with a higher concentration ratio has a better barrier effect.

[0132] Optional, such as Fig.13 As shown, in another embodiment of the present application, the barrier layer 07 includes N sub-barrier layers 07a, N≥2, and N is a positive integer.

[0133] In the direction where the barrier layer 07 is away from the first dielectric layer 06 , the proportion of the first doping ions in the first to Nth barrier sub-layers 07 a gradually increases.

[0134] Specifically, in this embodiment, N can be 3. In the direction of the barrier layer 07 away from the first dielectric layer 06, the first doped ion ratio in the first sub-barrier layer 07a is less than the first doped ion ratio in the second sub-barrier layer 07a, and the first doped ion ratio in the second sub-barrier layer 07a is less than the first doped ion ratio in the third sub-barrier layer 07a. In other words, the first doped ion ratio in the outermost sub-barrier layer 07a is the largest. For example, the first doped ion ratio in the first sub-barrier layer 07a is 4%, the first doped ion ratio in the second sub-barrier layer 07a is 6%, and the first doped ion ratio in the third sub-barrier layer 07a is 8%. There is no specific limitation on this.

[0135] In this embodiment, the sub-barrier layer 07a with a high concentration ratio is arranged on the outside, which can better achieve the barrier of fluoride ions.

[0136] Optional, such as Fig.13As shown, in another embodiment of the present application, in the direction where the barrier layer 07 is away from the first dielectric layer 06 , the proportion of the first doping ions in the 1st to the Nth sub-barrier layers 07 a gradually decreases.

[0137] When N is 3, in the direction of the barrier layer 07 away from the first dielectric layer 06, the first doped ion ratio in the first sub-barrier layer 07a is greater than the first doped ion ratio in the second sub-barrier layer 07a, and the first doped ion ratio in the second sub-barrier layer 07a is greater than the first doped ion ratio in the third sub-barrier layer 07a. In other words, the first doped ion ratio in the innermost sub-barrier layer 07a is the largest. For example, the first doped ion ratio in the first sub-barrier layer 07a is 9%, the first doped ion ratio in the second sub-barrier layer 07a is 7%, and the first doped ion ratio in the third sub-barrier layer 07a is 3%. There is no specific limitation on this.

[0138] In this embodiment, the sub-barrier layer 07a with a high concentration ratio is arranged on the inner side, and the adhesion between the barrier layer 07 and the first dielectric layer 06 is better, thereby improving the reliability of the structure.

[0139] It should be noted that the doping ratio of the first doping ions in the sub-barrier layer 07a can be set according to the need for blocking, as long as the barrier layer 07a can block the ions in the etching gas.

[0140] In the image sensor, since the barrier layer 07 contains the first doped ions, the barrier layer 07 has a higher density, which can block the impact of ions in the etching gas, avoid defects at the interface of the substrate 02, further avoid the generation of dark current, and reduce the generation of white pixels in the pixel area 04.

[0141] In the description of this specification, the description with reference to the terms "some embodiments", "another embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0142] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features of the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing an image sensor, characterized in that: The preparation method comprises: Providing a substrate, the substrate comprising a substrate and a mask layer located on the substrate, the substrate having at least two pixel regions and an isolation trench located between two adjacent pixel regions, the isolation trench penetrating the mask layer and extending into a portion of the substrate; forming a first dielectric layer on the surface of the substrate at the sidewall and bottom of the isolation trench; forming a barrier layer having first doping ions on a surface of the first dielectric layer and a surface of the mask layer on a sidewall of the isolation trench; forming a first isolation material layer filling the isolation trench on a surface of the barrier layer; Etching and removing a portion of the first isolation material layer in the isolation trench to form an opening area; A first isolation layer and a second isolation layer are formed in the isolation trench after the opening area is formed.

2. The method for preparing an image sensor according to claim 1, characterized in that: The step of forming a barrier layer having first doping ions on the surface of the first dielectric layer and the surface of the mask layer on the sidewall of the isolation trench comprises: forming a first barrier material layer on a surface of the first dielectric layer and a surface of the mask layer on a sidewall of the isolation trench; The first doping ions are implanted into the first barrier material layer by an ion implantation method to form the barrier layer having the first doping ions.

3. The method for preparing an image sensor according to claim 2, characterized in that: Before the step of forming a barrier layer having first doping ions on the surface of the first dielectric layer and the surface of the mask layer on the sidewall of the isolation trench, the method includes: forming an injection blocking layer on the upper surface of the mask layer; After forming the barrier layer having the first doping ions, the method further comprises: The implantation barrier layer is removed.

4. The method for preparing an image sensor according to claim 2, characterized in that: The step of forming a first isolation layer and a second isolation layer in the isolation trench after forming the opening area includes: forming a second isolation material layer in the isolation trench after forming the opening area; The second isolation material layer and the first isolation material layer on the upper surface of the mask layer are ground by a grinding process to form the first isolation layer and the second isolation layer.

5. The method for preparing an image sensor according to claim 1, characterized in that: The step of forming a barrier layer having first doping ions on the surface of the first dielectric layer and the surface of the mask layer on the sidewall of the isolation trench further includes: A second barrier material layer having the first doping ions is deposited on the upper surface of the mask layer, the surface of the mask layer on the sidewall of the isolation trench, and the surface of the first dielectric layer in the isolation trench.

6. The method for preparing an image sensor according to claim 5, characterized in that: The step of forming a first isolation layer and a second isolation layer in the isolation trench after forming the opening area further includes: forming a second isolation material layer on the surface of the first isolation material layer and in the isolation trench after the opening area is formed; The first isolation material layer, the second isolation material layer and the second barrier material layer on the upper surface of the mask layer are ground by a grinding process to form the first isolation layer, the second isolation layer and the barrier layer.

7. The method for preparing an image sensor according to claim 1, characterized in that: The barrier layer is a silicon nitride barrier layer, and the first doping ions are C ions; The step of etching and removing a portion of the first isolation material layer in the isolation trench to form an opening area includes: Using a first etching gas to etch and remove a portion of the first isolation material layer in the isolation trench to form the opening area; The first etching gas includes an etching gas containing fluorine ions.

8. An image sensor, characterized in that: The image sensor comprises: A substrate, comprising a substrate and a mask layer located on the substrate, the substrate having at least two pixel regions and an isolation trench located between two adjacent pixel regions, the isolation trench penetrating the mask layer and extending into a portion of the substrate; A first dielectric layer, wherein the first dielectric layer covers the sidewalls and bottom of the isolation trench and the surface of the substrate; a barrier layer, the barrier layer covering a surface of the first dielectric layer and a surface of the mask layer on a sidewall of the isolation trench, the barrier layer having first doping ions; a first isolation layer, the first isolation layer being located on one side of the barrier layer in the isolation trench, the first isolation layer covering the barrier layer and filling a portion of the isolation trench; A second isolation layer is provided, wherein the second isolation layer fills the remaining isolation trench.

9. The image sensor according to claim 8, characterized in that: The barrier layer includes N sub-barrier layers, N ≥ 2, and N is a positive integer; The proportion of the first doping ions in each of the sub-blocking layers is the same.

10. The image sensor according to claim 8, characterized in that The barrier layer includes N sub-barrier layers, N ≥ 2, and N is a positive integer; In a direction in which the barrier layer is away from the first dielectric layer, the proportion of the first doping ions in the sub-barrier layers from the 1st layer to the Nth layer gradually increases.

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