Image sensor and manufacturing method thereof

Abstract

The invention relates to an image sensor and a manufacturing method thereof, and the method comprises the steps: providing a substrate, forming a protection layer on the substrate, forming a plurality of mutually isolated grooves in the protection layer, and enabling the grooves to extend into the substrate in a direction perpendicular to the surface of the substrate; a sacrificial layer is formed on the protective layer, the sacrificial layer fills the end portion of the side, away from the substrate, of the groove, a plurality of recesses are formed in the surface of the sacrificial layer, and projections, facing the surface of the substrate, of the recesses fall into projections, facing the surface of the substrate, of the groove; etching the sacrificial layer to enable the recess and the groove to be communicated with each other; and filling a metal material in the groove to form a metal grating. The problem of metal grating offset caused by overlay errors is reduced or avoided, the technological process is simplified, the light receiving area of the image sensor is increased, and the defect rate of the image sensor is reduced.

Description

Technical Field

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

[0002] Image sensors are devices that convert light signals into electrical signals. They are small, light, highly integrated, high resolution, low power consumption, long life, and low price. They are widely used in digital television, visual communication markets, and other industries. Currently, the most commonly used image sensor is the complementary metal oxide semiconductor (CMOS) image sensor, or CMOS image sensor (CIS).

[0003] In the manufacturing process of general image sensors, the relative position of the backside metal grid and the deep trench isolation (DTI) is affected by the yellow light overlay error (Overlapping Value). In the same yellow light exposure area (Shot), the position of part of the metal grid is offset, which will cause differences in chip specifications at different positions in the wafer. Summary of the invention

[0004] Based on this, it is necessary to provide an image sensor and a manufacturing method thereof, which can reduce or avoid the problem of metal grid deviation caused by overlay error and reduce the defect rate of the image sensor.

[0005] In a first aspect, the present application provides a method for manufacturing an image sensor, comprising:

[0006] Providing a substrate, on which a protective layer is formed, in which a plurality of mutually isolated grooves are formed, wherein the grooves extend into the substrate in a direction perpendicular to a surface of the substrate;

[0007] forming a sacrificial layer on the protective layer, the sacrificial layer filling the end of the groove away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projection of the depressions toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate;

[0008] Etching the sacrificial layer so that the recess and the groove are connected to each other;

[0009] The grooves are filled with metal material to form a metal grid.

[0010] In one embodiment, the groove forming process includes:

[0011] A plurality of mutually isolated grooves are formed in the substrate and the protective layer, and the width of a first portion of the groove formed in the substrate first expands and then decreases in a direction away from the protective layer, and the width of a second portion of the groove formed in the protective layer is smaller than the maximum width of the first portion.

[0012] In one embodiment, forming a plurality of mutually isolated trenches in the substrate and the protective layer comprises:

[0013] Etching the protective layer to form a plurality of openings in the protective layer;

[0014] The substrate is etched downward along the opening using a Bosch process to form the groove.

[0015] In one of the embodiments, the cross-sectional shape of the end of the groove away from the protective layer in a direction perpendicular to the surface of the substrate is a bowl shape that is wide at the top and narrow at the bottom.

[0016] In one embodiment, after forming a plurality of mutually isolated trenches and before forming a sacrificial layer on the protective layer, the method further includes:

[0017] forming an insulating layer on the inner wall of the groove, wherein the insulating layer extends to cover the protection layer on both sides of the groove;

[0018] The forming of a sacrificial layer on the protective layer comprises:

[0019] The sacrificial layer covers the insulating layer.

[0020] In one embodiment, the insulating layer includes a protrusion, which is formed on the inner wall of the groove and located at the junction of the substrate and the protective layer;

[0021] The step of forming a sacrificial layer on the insulating layer comprises:

[0022] The sacrificial layer is filled onto the protruding portion in the groove.

[0023] In one embodiment, forming a sacrificial layer on the protective layer, the sacrificial layer filling the end of the groove away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projection of the depressions toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate, comprises:

[0024] Using a first deposition process, a sacrificial layer material is deposited in the groove, and the width of a portion of the groove close to the protective layer is reduced;

[0025] Using a second deposition process, continue to deposit the sacrificial layer material to form the sacrificial layer covering the groove, and form the recess in the sacrificial layer;

[0026] Using a third deposition process, continue to deposit the sacrificial layer material to increase the thickness of the sacrificial layer;

[0027] Wherein, the deposition rate of the second deposition process is respectively greater than the deposition rate of the first deposition process and the deposition rate of the third deposition process.

[0028] In one embodiment, the process of filling the groove with metal material to form a metal grid includes:

[0029] Filling the groove with a metal material, wherein the metal material extends to cover the sacrificial layer on both sides of the groove;

[0030] Performing a planarization process to remove at most a portion of the sacrificial layer and the metal material on the sacrificial layer, so that the remaining metal material forms a metal grid that fills the groove and the recess;

[0031] The remaining sacrificial layer is removed.

[0032] In one of the embodiments, the metal grid includes a bottom portion, a middle portion and a top portion which are connected in sequence, wherein the bottom portion is divided into a portion of the metal grid extending into the substrate, the top portion is a portion of the metal grid that is higher than the substrate and the protective layer, the middle portion is located between the top portion and the bottom portion, and in a direction perpendicular to the surface of the substrate, the cross-sectional widths corresponding to the top portion, the middle portion and the bottom portion respectively decrease gradually.

[0033] In a second aspect, the present application also provides an image sensor manufactured using the image sensor manufacturing method.

[0034] The unexpected effect of the present application is: by forming a depression in the sacrificial layer, the projection of the depression toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate, and by connecting the groove and the depression and filling the metal material, a metal grid is formed and self-alignment of the groove and the metal grid is achieved, reducing or avoiding the risk of metal grid offset caused by overlay error, simplifying the process flow, increasing the light receiving area of ​​the image sensor, and improving the performance of the image sensor. In addition, by forming the metal grid by filling the groove and the depression with metal material, the influence of stress between each film layer on the metal grid is reduced, thereby reducing the product defect rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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.

[0036] Figure 1 The present invention is a structural schematic diagram corresponding to the step of providing a substrate in a method for manufacturing an image sensor of the related art.

[0037] Figure 2 The figure is a structural schematic diagram corresponding to the step of forming a DTI structure in a method for manufacturing an image sensor in the related art.

[0038] Figure 3 The figure is a structural schematic diagram corresponding to the step of filling a dielectric layer in a DTI structure in a method for manufacturing an image sensor in the related art.

[0039] Figure 4 The figure is a structural schematic diagram corresponding to the step of forming a silicon nitride layer on a dielectric layer in a method for manufacturing an image sensor in the related art.

[0040] Figure 5 The present invention is a structural schematic diagram corresponding to the step of planarizing a silicon nitride layer in a method for manufacturing an image sensor in the related art.

[0041] Figure 6 The figure is a schematic structural diagram corresponding to the steps of forming a metal tungsten layer and a carbide layer in a method for manufacturing an image sensor in the related art.

[0042] Figure 7 The present invention is a structural schematic diagram corresponding to the step of forming a second mask layer in a method for manufacturing an image sensor of the related art.

[0043] Figure 8 The figure is a structural schematic diagram corresponding to the step of forming a metal grid in a method for manufacturing an image sensor in the related art.

[0044] Fig. 9 The present invention is a flowchart of a method for manufacturing an image sensor according to an embodiment of the present invention.

[0045] Fig.10 This is a structural schematic diagram corresponding to the step of providing a substrate in the method for manufacturing an image sensor provided in an embodiment of the present application.

[0046] Fig.11 This is a schematic structural diagram corresponding to the step of forming a groove in a substrate in a method for manufacturing an image sensor provided in an embodiment of the present application.

[0047] Fig.12 This is a structural schematic diagram corresponding to the step of forming an insulating layer in a trench in a method for manufacturing an image sensor provided in an embodiment of the present application.

[0048] Fig.13 This is a structural schematic diagram corresponding to the step of forming a sacrificial layer in the method for manufacturing an image sensor provided in one embodiment of the present application.

[0049] Fig.14 This is a structural schematic diagram corresponding to the step of etching a sacrificial layer to connect the recess and the groove in the method for manufacturing an image sensor provided in an embodiment of the present application.

[0050] Fig.15 The present invention is a schematic structural diagram corresponding to the step of filling metal materials in grooves and recesses in a method for manufacturing an image sensor provided in an embodiment of the present application.

[0051] Fig.16 This is a structural schematic diagram corresponding to the step of performing a planarization process in a method for manufacturing an image sensor provided in an embodiment of the present application.

[0052] Fig.17 This is a structural schematic diagram corresponding to the step of removing the sacrificial layer in the method for manufacturing an image sensor provided in one embodiment of the present application.

[0053] Explanation of the reference numerals: 100-substrate; 101-DTI structure; 102-dielectric layer; 110-oxide layer; 120-first mask layer; 130-silicon nitride layer; 140-metal tungsten layer; 141-carbide layer; 142-metal grid; 150-second mask layer; A-recessed pattern; 200-substrate; 201-groove; 210-protective layer; 211-mask layer; 220-insulating layer; 221-first oxide layer; 222-high dielectric constant layer; 223-second oxide layer; 224-protrusion; 230-sacrificial layer; 231-recess; 240-metal material; 241-metal grid; 241a-top portion; 241b-middle portion; 241c-bottom portion; X1-first portion; X2-second portion. DETAILED DESCRIPTION

[0054] 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.

[0055] 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.

[0056] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, doping type or portion discussed below may be represented as a second element, component, region, layer or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0057] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0058] When used herein, the singular forms "a", "an" and " / the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like 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. At the same time, in this specification, the term "and / or" includes any and all combinations of the relevant listed items.

[0059] Figures 1 to 8 FIG. 1 is a schematic diagram of the structure corresponding to some steps in a method for manufacturing an image sensor in a related art. Figures 1 to 8 A method for manufacturing an image sensor in the related art is described.

[0060] First, see Figure 1 , providing a substrate 100, and sequentially forming an oxide layer 110 and a first mask layer 120 on the substrate 100. Optionally, the substrate 100 is a silicon substrate, and the first mask layer 120 is a photoresist layer (PR).

[0061] Next, see Figure 2 , the first mask layer 120 is patterned, and the oxide layer 110 and the substrate 100 are etched using the first mask layer 120 as a mask to form a plurality of DTI structures 101, i.e., deep trench isolation (DTI) structures, in the substrate 100. At the same time, after the DTI structures 101 are formed, the first mask layer 120 can be removed by a wet cleaning process.

[0062] Then, see Figure 3 , a dielectric layer 102 is formed in the DTI structure 101, and the dielectric layer 102 fills the DTI structure 101 and covers the oxide layer 110 on both sides of the DTI structure 101. Optionally, the dielectric layer 102 is a stacked structure formed by stacking an oxide layer, a high dielectric constant layer and an oxide layer in sequence. It should be noted that in the process of forming the dielectric layer 102 by a deposition process, the pattern of the DTI structure 101 will be transferred to the surface of the dielectric layer 102, forming a concave pattern A vertically aligned with the DTI structure 101.

[0063] See also Figure 4 , a silicon nitride layer 130 is deposited on the dielectric layer 102, and a planarization process is performed to improve the surface flatness of the silicon nitride layer 130. Optionally, a chemical mechanical polishing (CMP) process is used for the planarization process.

[0064] See also Figure 5, the silicon nitride layer 130 and the dielectric layer 102 are etched to make the surfaces of the remaining silicon nitride layer 130 flush with the surfaces of the dielectric layer 102. Optionally, the silicon nitride layer 130 just fills the recessed pattern A.

[0065] Then, see Figure 6 , a metal tungsten layer 140 and a carbide layer 141 are sequentially formed on the silicon nitride layer 130 and the dielectric layer 102. The carbide layer 141 can protect the metal tungsten layer 140 from being damaged. Optionally, the material of the metal tungsten layer 140 can also be replaced by other commonly used metals or alloy materials, such as metal copper, metal aluminum, or alloy materials containing copper, aluminum, and tungsten.

[0066] Next, see Figure 7 and Figure 8 , a patterned second mask layer 150 is formed on the carbide layer 141, and the carbide layer 141 and the metal tungsten layer 140 are etched using the second mask layer 150 as a mask to form a metal grid 142. Optionally, after the metal grid 142 is formed, a wet cleaning process may be used to remove the second mask layer 150, the carbide layer 141, and impurities and byproducts generated during the etching process.

[0067] However, since the metal grid 142 is formed by an etching process, the relative position of the metal grid 142 and the DTI structure 101 will be affected by the overlapping value. Figure 7 In the same yellow light exposure area (Shot), the position of the metal grid 142 is offset relative to the DTI structure 101, which will cause differences in chip specifications at different positions in the wafer. In addition, the metal grid 142 will be affected by the stress in the wafer surface during the formation process, and there is a risk of pattern peeling defects, which seriously affects the performance stability and product yield of semiconductor devices.

[0068] In order to solve the above problems, the present application provides an image sensor and a manufacturing method thereof, which reduces or avoids the problem of metal grid deviation caused by overlay error and reduces the defect rate of the image sensor. Fig. 9 , a method for manufacturing an image sensor provided by an embodiment of the present application includes:

[0069] Step S01: A protection layer is formed on the substrate, a plurality of mutually isolated grooves are formed in the protection layer, and the grooves extend into the substrate in a direction perpendicular to the surface of the substrate.

[0070] Step S02: forming a sacrificial layer on the protective layer, the sacrificial layer filling the end of the groove away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, the projection of the depressions toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate.

[0071] Please refer to Fig.13 Since the sacrificial layer 230 is usually prepared by a deposition process, the surface pattern of the film layer below the sacrificial layer 230 (for example, the surface pattern of the insulating layer 220) is inherited during the formation of the sacrificial layer 230, thereby forming a recess 231, and the projection of the recess 231 toward the surface of the substrate 200 falls into the projection of the groove 201 toward the surface of the substrate 200. It should be noted that, by utilizing the characteristic that the sacrificial layer 230 can inherit the pattern of the previous layer during the formation process, the recess 231 formed on the sacrificial layer 230 can be self-aligned with the groove 201, so as to reduce or avoid the problem of pattern deviation caused by overlay error when the recess 231 is formed by an etching process, thereby reducing or avoiding the deviation of the metal grid finally formed.

[0072] At the same time, since the sacrificial layer fills the end of the trench away from the substrate, a cavity is formed in the portion of the trench close to the substrate so that a metal material can be filled into the trench subsequently.

[0073] Step S03: etching the sacrificial layer to make the recess and the groove communicate with each other.

[0074] Step S04: filling the groove with metal material to form a metal grid.

[0075] It can be seen that the manufacturing method of the image sensor provided in one of the embodiments of the present application forms a depression in the sacrificial layer so that the projection of the depression toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate, and forms a metal grid by connecting the groove and the depression and filling the metal material, and realizes the self-alignment of the groove isolation and the metal grid, thereby reducing or avoiding the risk of metal grid offset caused by overlay error, simplifying the process flow, increasing the light receiving area of ​​the image sensor, and improving the performance of the image sensor. At the same time, the present application forms a metal grid by filling the groove and the depression with metal material, thereby reducing the influence of the stress between the film layers on the metal grid, thereby reducing the product defect rate.

[0076] See also Fig.10 and Fig.11In one embodiment, the process of forming the protective layer 210 and the groove 201 includes: forming a patterned mask layer 211 on the protective layer 210, and etching the protective layer 210 and the substrate 200 with the patterned mask layer 211 to form the groove 201; removing the mask layer 211 and impurities and byproducts generated during the etching process. Optionally, the mask layer 211 is removed by a wet cleaning process.

[0077] Continue reading Fig.11 In one embodiment, the protective layer 210 and the substrate 200 are etched to form the groove 201, including: etching the protective layer 210 to form a plurality of openings (not shown in the figure) in the protective layer 210; etching the substrate 200 downward along the openings using the Bosch process to form the groove 201. It should be noted that the groove 201 is mainly used to isolate the electrical signals between pixels to prevent crosstalk.

[0078] Exemplarily, a plasma etching process including carbon tetrafluoride gas (CF4 Gas) is used to etch the protective layer 210 to form a plurality of openings (not shown in the figure). Optionally, in the process of etching the substrate 200 and forming the groove 201 using a Bosch process with an etching (Etch) and a deposition (Deposition) cycle, the etching gas includes, for example, sulfur hexafluoride (SF6), and the deposition gas includes, for example, octafluorocyclobutane (C4F8).

[0079] It should be noted that, see Fig.11 In the process of forming the trench 201, due to the blocking of the protective layer 210, the width of the first part X1 of the trench 201 near the protective layer 210 is the same as or similar to the width of the second part X2; at the same time, as the number of cycles increases, the proportion of the deposition gas increases relatively, the proportion of the etching gas decreases relatively, and the process pressure gradually decreases, so that the width of the first part X1 in the trench 201 expands first and then decreases from top to bottom (i.e., in the direction away from the protective layer 210), so that the cross-sectional morphology of the bottom of the first part X1 (i.e., the end of the trench 201 away from the protective layer 210) in the direction perpendicular to the substrate 200 is a bowl-shaped pattern with a wide top and a narrow bottom. Optionally, the trench 201 is a deep trench isolation structure (Deep Trench Isolation, DTI).

[0080] In other embodiments of the present application, process parameters such as the cycle time and process pressure in the Bosch process can be adjusted according to actual needs, and the present application does not impose any restrictions on this. The etching method of the protective layer 210 and the formation method of the groove 201 can be adjusted according to needs. It is only necessary to make the first part X1 of the groove 201 located in the substrate 200 present a bowl-shaped morphology that is wide at the top and narrow at the bottom. The present application does not impose any restrictions on this.

[0081] In one embodiment, the protective layer 210 is an oxide layer, and the material of the protective layer 210 includes, for example, silicon oxide. Optionally, the thickness of the protective layer 210 ranges from 200Å to 500Å.

[0082] See also Fig.12 In one embodiment, after forming a plurality of mutually isolated trenches 201 and before forming a sacrificial layer (not shown in the figure) on the protective layer 210, the method further includes: forming an insulating layer 220 on the inner wall of the trench 201, wherein the insulating layer 220 extends to cover the protective layer 210 on both sides of the trench 201. At this time, the subsequently formed sacrificial layer (not shown in the figure) covers the insulating layer 220.

[0083] In one embodiment, the insulating layer 220 includes a high dielectric constant layer and an oxide layer, for example, may include a stacked structure formed by stacking a first oxide layer 221, a high dielectric constant layer 222 and a second oxide layer 223 in a direction perpendicular to the surface of the substrate 200, so as to improve the anti-crosstalk effect of the image sensor.

[0084] Continue reading Fig.12 In one embodiment, the insulating layer 220 further includes a protrusion 224, which is formed on the inner wall of the groove 201 and located at the junction of the substrate 200 and the protective layer 210. It should be noted that, when the protrusion 224 exists in the insulating layer 220, a sacrificial layer (not shown in the figure) formed subsequently is deposited on the protrusion 224, thereby reducing or avoiding the sacrificial layer from filling up the groove 201, so that the metal material can be filled in the groove 201 subsequently.

[0085] See also Fig.13 In one embodiment, the process of forming the sacrificial layer 230 having the recess 231 on the protective layer 210 (or the insulating layer 220) includes: using a first deposition process to deposit a sacrificial layer material (such as silicon nitride) in the trench 201, and making the portion of the trench 201 close to the protective layer 210 (i.e. Fig.11 The width of the second part X2 in the groove 201 is reduced; a second deposition process is used to continue depositing the sacrificial layer material to form a sacrificial layer 230 covering the groove 201, and a recess 231 vertically aligned with the groove 201 is formed in the sacrificial layer 230; a third deposition process is used to continue depositing the sacrificial layer material to increase the thickness of the sacrificial layer 230; wherein the deposition rate of the second deposition process is greater than the deposition rate of the first deposition process and the deposition rate of the third deposition process, respectively.

[0086] It should be noted that during the first deposition process of relatively slow deposition, a small amount of sacrificial layer material will be deposited inside the groove 201, which has little or negligible impact on the performance of the image sensor finally formed. During the second deposition process of relatively fast deposition, as the sacrificial layer material is deposited, the top width of the groove 201 (i.e. Fig.11 The width of the second portion X2 in the second deposition process is continuously reduced until the sacrificial layer material completely covers the groove 201. When the sacrificial layer material completely covers the groove 201 and forms the sacrificial layer 230, the third deposition process can be performed. In the process of continuing to use the third deposition process with relatively low deposition speed, the morphology of the sacrificial layer 230 in the second deposition process can be continued, and the thickness of the sacrificial layer 230 can be increased, so as to perform the next etching process.

[0087] In one embodiment, the material of the sacrificial layer 230 includes at least silicon nitride (SiN x ) or one of the amorphous carbons.

[0088] See also Fig.13 and Fig.14 In one embodiment, the sacrificial layer 230 is etched back by an etching process to interconnect the recess 231 and the groove 201. It should be noted that if a large amount of sacrificial layer material is filled in the groove 201 during the formation of the sacrificial layer 230, the excess sacrificial layer material in the groove 201 can be removed by this etching process to facilitate subsequent filling of metal material.

[0089] Continue reading Fig.13 and Fig.14 It should be further explained that, during the above-mentioned etching back process, the etching load effect (Load Effect) can be used to allow more etching gas to flow into the recess 231, thereby increasing the etching efficiency at the bottom of the recess 231 and achieving mutual communication between the recess 231 and the groove 201. At the same time, the sidewall of the recess 231 may also be slightly etched laterally during the etching back process, and may cause the top of the recess 231 after the etching back process (the cross-sectional morphology along the direction perpendicular to the surface of the substrate 200) to present a morphology similar to an inverted trapezoid.

[0090] In one embodiment, the process of filling the metal material 240 in the trench 201 to form the metal grid 241 includes the following process.

[0091] See also Fig.15, a metal material 240 is filled in the groove 201, and the metal material 240 extends to cover the sacrificial layer 230 on both sides of the groove 201. Optionally, the metal material 240 includes at least one of common metal conductive materials such as metal tungsten (W), metal copper (Cu), metal aluminum (Al), etc., and can also be an alloy material containing the aforementioned metal conductive materials.

[0092] See also Fig.16 , a planarization process is performed to remove at most a portion of the sacrificial layer 230 and the metal material 240 on the sacrificial layer 230, so that the remaining metal material 240 forms a metal grid 241 that fills the groove 201. Optionally, a chemical mechanical polishing (CMP) process is used for planarization. It should be noted that, due to the process of interconnecting the depression and the groove in the aforementioned step, the top of the depression may present a morphology similar to an inverted trapezoid, and the metal material 240 filled at the top of the depression also presents a morphology similar to an inverted trapezoid. At this time, if no treatment is performed, the side wall of the top part of the correspondingly formed metal grid 241 may be uneven, thereby affecting the performance of the image sensor finally formed. Therefore, in the process of planarization, the uneven angle portion of the top of the metal grid 241 can be removed by over etching (OE) to ensure that the side wall of the metal grid 241 finally formed is straight.

[0093] See also Fig.17 , remove the remaining sacrificial layer 230 so as to prepare other semiconductor structures later. Optionally, the sacrificial layer 230 is removed by a dry etching process or a wet etching process.

[0094] Continue reading Fig.17 The metal grid 241 includes a top portion 241a, a middle portion 241b and a bottom portion 241c which are connected in sequence, wherein the bottom portion 241c is a portion of the metal grid 241 extending into the substrate 200, and the top portion 241a is a portion of the metal grid 241 which is higher than the substrate 200 and the protective layer 210 ( Fig.17 The top portion 241a is higher than the insulating layer 220), the middle portion 241b is located between the top portion 241a and the bottom portion 241c, and in the direction perpendicular to the surface of the substrate 200, the cross-sectional widths corresponding to the top portion 241a, the middle portion 241b and the bottom portion 241c gradually decrease.

[0095] It should be emphasized that, since the width of the top portion 241a of the metal grid 241 is greater than the width of the bottom portion 241c, and the bottom portion 241c of the metal grid 241 is formed in the groove 201, the width of the top portion 241a of the metal grid 241 is greater than the width of the groove 201. Among them, the groove 201 is mainly used to isolate the electrical signals between pixels to prevent crosstalk; the metal grid 241 not only covers the pixel area, but also helps to reduce the alignment error of the subsequently formed color filter and the edge effect in the subsequent process manufacturing. Based on this, the width of the top portion 241a of the metal grid 241 is greater than the width of the groove 201, which can ensure that the subsequently formed color filter can accurately and completely cover the corresponding pixel, while avoiding color mixing or light leakage problems caused by process deviations.

[0096] contrast Figure 8 and Fig.17 It can be seen that the manufacturing method of the image sensor provided in the embodiment of the present application forms a recess 231 in the sacrificial layer 230, so that the projection of the recess 231 toward the surface of the substrate 200 falls into the projection of the groove 201 toward the surface of the substrate 200. By connecting the groove 201 and the recess 231 and filling the metal material, the self-alignment of the groove 201 and the metal grid 241 is achieved, reducing or avoiding the risk of the metal grid 241 being offset due to the overlay error, while reducing the influence of the stress of each film layer in the image sensor on the metal grid, and reducing the defect rate of the image sensor. In addition, the present application does not need to form a corresponding mask layer when forming the metal grid 241, which simplifies the relevant process flow and improves the manufacturing efficiency of the image sensor.

[0097] Accordingly, the present application also provides an image sensor, which is manufactured using the manufacturing method of the image sensor described above. Fig.17 The image sensor includes a substrate 200, a protective layer 210 and an insulating layer 220 stacked in sequence from bottom to top (i.e., in a direction perpendicular to the surface of the substrate 200), a plurality of mutually isolated grooves 201 are arranged in the substrate 200 and the protective layer 210, and the insulating layer 220 is arranged on the inner wall of the groove 201; a metal grid 241 is arranged in the groove 201, and the top of the metal grid 241 extends to the outside of the groove 201 and is higher than the surface of the insulating layer 220. The cross-sectional morphology of the portion of the groove 201 located in the substrate 200 in the direction perpendicular to the substrate 200 is a bowl shape that is wide at the top and narrow at the bottom.

[0098] In one embodiment, the protective layer 210 is an oxide layer, and the material of the protective layer 210 includes, for example, silicon oxide. Optionally, the thickness of the protective layer 210 ranges from 200Å to 500Å. In one embodiment, the trench 201 is a deep trench isolation structure (DTI) to isolate electrical signals between pixels and prevent crosstalk.

[0099] In one embodiment, the insulating layer 220 includes a high dielectric constant layer and an oxide layer, for example, may include a stacked structure formed by stacking a first oxide layer 221, a high dielectric constant layer 222 and a second oxide layer 223 in a direction perpendicular to the surface of the substrate 200, so as to improve the anti-crosstalk effect of the image sensor.

[0100] In one embodiment, the metal grid 241 includes a top portion 241a, a middle portion 241b and a bottom portion 241c which are connected in sequence, wherein the bottom portion 241c is a portion of the metal grid 241 extending into the substrate 200, and the top portion 241a is a portion of the metal grid 241 which is higher than the substrate 200 and the protective layer 210 ( Fig.17 The top portion 241a is higher than the insulating layer 220), the middle portion 241b is located between the top portion 241a and the bottom portion 241c, and in the direction perpendicular to the surface of the substrate 200, the cross-sectional widths corresponding to the top portion 241a, the middle portion 241b and the bottom portion 241c gradually decrease.

[0101] It should be emphasized that, since the width of the top portion 241a of the metal grid 241 is greater than the width of the bottom portion 241c, and the bottom portion 241c of the metal grid 241 is formed in the groove 201, the width of the top portion 241a of the metal grid 241 is greater than the width of the groove 201. Among them, the groove 201 is mainly used to isolate the electrical signals between pixels to prevent crosstalk; the metal grid 241 not only covers the pixel area, but also helps to reduce the alignment error of the subsequently formed color filter and the edge effect in the subsequent process manufacturing. Based on this, the width of the top portion 241a of the metal grid 241 is greater than the width of the groove 201, which can ensure that the subsequently formed color filter can accurately and completely cover the corresponding pixel, while avoiding color mixing or light leakage problems caused by process deviations.

[0102] The unexpected effect of the present application is: by forming a depression in the sacrificial layer, the projection of the depression toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate, and by connecting the groove and the depression and filling the metal material, a metal grid is formed and self-alignment of the groove isolation and the metal grid is achieved, reducing or avoiding the risk of metal grid offset caused by overlay error, simplifying the process flow, increasing the light collection area of ​​the image sensor, and improving the performance of the image sensor. In addition, by forming the metal grid by filling the groove and the depression with metal material, the influence of stress between each film layer on the metal grid is reduced, thereby reducing the product defect rate.

[0103] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", 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 application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0104] 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.

[0105] 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 application. It should be noted that, for a person of ordinary skill in the art, several modifications 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 present application shall be subject to the attached claims.

Claims

1. A method for manufacturing an image sensor, characterized in that: include: Providing a substrate, on which a protective layer is formed, in which a plurality of mutually isolated grooves are formed, wherein the grooves extend into the substrate in a direction perpendicular to a surface of the substrate; forming a sacrificial layer on the protective layer, the sacrificial layer filling the end of the groove away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projection of the depressions toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate; Etching the sacrificial layer so that the recess and the groove are connected to each other; The grooves are filled with metal material to form a metal grid.

2. The method for manufacturing an image sensor according to claim 1, wherein: The groove forming process includes: A plurality of mutually isolated grooves are formed in the substrate and the protective layer, and the width of a first portion of the groove formed in the substrate first expands and then decreases in a direction away from the protective layer, and the width of a second portion of the groove formed in the protective layer is smaller than the maximum width of the first portion.

3. The method for manufacturing an image sensor according to claim 2, wherein: The forming of a plurality of mutually isolated grooves in the substrate and the protective layer comprises: Etching the protective layer to form a plurality of openings in the protective layer; The substrate is etched downward along the opening using a Bosch process to form the groove.

4. The method for manufacturing an image sensor according to claim 1, wherein: The cross-sectional shape of the end of the groove away from the protection layer in a direction perpendicular to the surface of the substrate is a bowl shape that is wide at the top and narrow at the bottom.

5. The method for manufacturing an image sensor according to claim 1, wherein: After forming a plurality of mutually isolated trenches and before forming a sacrificial layer on the protective layer, the method further includes: forming an insulating layer on the inner wall of the groove, wherein the insulating layer extends to cover the protection layer on both sides of the groove; The forming of a sacrificial layer on the protective layer comprises: The sacrificial layer covers the insulating layer.

6. The method for manufacturing an image sensor according to claim 5, characterized in that: The insulating layer includes a protrusion, which is formed on the inner wall of the groove and located at the junction of the substrate and the protective layer; The step of forming a sacrificial layer on the insulating layer comprises: The sacrificial layer is filled onto the protruding portion in the groove.

7. The method for manufacturing an image sensor according to claim 1, wherein: The step of forming a sacrificial layer on the protective layer, wherein the sacrificial layer fills the end of the groove away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projection of the depressions toward the surface of the substrate falls into the projection of the groove toward the surface of the substrate, comprising: Using a first deposition process, a sacrificial layer material is deposited in the groove, and the width of a portion of the groove close to the protective layer is reduced; Using a second deposition process, continue to deposit the sacrificial layer material to form the sacrificial layer covering the groove, and the recess is formed in the sacrificial layer; Using a third deposition process, continue to deposit the sacrificial layer material to increase the thickness of the sacrificial layer; Wherein, the deposition rate of the second deposition process is respectively greater than the deposition rate of the first deposition process and the deposition rate of the third deposition process.

8. The method for manufacturing an image sensor according to claim 1, wherein: The process of filling the groove with metal material to form a metal grid includes: Filling the groove with a metal material, wherein the metal material extends to cover the sacrificial layer on both sides of the groove; Performing a planarization process to remove at most a portion of the sacrificial layer and the metal material on the sacrificial layer, so that the remaining metal material forms a metal grid that fills the groove and the recess; The remaining sacrificial layer is removed.

9. The method for manufacturing an image sensor according to claim 1, wherein: The metal grid includes a bottom portion, a middle portion and a top portion which are connected in sequence, wherein the bottom portion is divided into a portion of the metal grid extending into the substrate, the top portion is a portion of the metal grid higher than the substrate and the protective layer, the middle portion is located between the top portion and the bottom portion, and in a direction perpendicular to the surface of the substrate, the cross-sectional widths corresponding to the top portion, the middle portion and the bottom portion respectively decrease gradually.

10. An image sensor, characterized in that: The image sensor is manufactured using the method for manufacturing the image sensor according to any one of claims 1 to 9.

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