Image sensor and method for manufacturing the same

Abstract

The present application relates to an image sensor and a manufacturing method thereof, including: providing a substrate, a protective layer is formed on the substrate, a plurality of mutually isolated trenches are formed in the protective layer, and the trenches extend in a direction perpendicular to the surface of the substrate into the substrate; forming a sacrificial layer on the protective layer, the sacrificial layer fills the end portions of the trenches on the side away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projections of the depressions towards the surface of the substrate fall within the projections of the trenches towards the surface of the substrate; etching the sacrificial layer to communicate the depressions with the trenches; filling the trenches with a metal material to form a metal grid. The present application reduces or avoids the problem of metal grid offset caused by lithography errors, simplifies the process flow, increases the light-receiving area of the image sensor, and reduces the defect rate of the image sensor.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and particularly to an image sensor and a manufacturing method thereof. Background Art

[0002] An image sensor is a device that converts optical signals into electrical signals, and has characteristics such as small size, light weight, high integration, high resolution, low power consumption, long lifespan, and low price, and has been widely used in digital TVs, visual communication markets, and other industries. Currently, the most commonly used image sensor is a Complementary Metal Oxide Semiconductor (CMOS) image sensor, that is, a CMOS image sensor (CIS).

[0003] During the manufacturing process of a general image sensor, the relative positions of the Backside Metal Grid and the Deep Trench Isolation (DTI) are affected by the Overlapping Value of the yellow light. In the exposure area (Shot) of the same yellow light, the positions of some metal grids are shifted, which will cause differences in the chip specifications at different positions within the wafer. Summary of the Invention

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

[0005] In a first aspect, this application provides a manufacturing method of an image sensor, including:

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

[0007] Forming a sacrificial layer on the protective layer, the sacrificial layer fills the end of the trench on the side away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projection of the depression towards the surface of the substrate falls within the projection of the trench towards the surface of the substrate;

[0008] Etching the sacrificial layer to communicate the depression with the trench;

[0009] Filling a metal material in the trench to form a metal grid.

[0010] In one embodiment, the formation process of the trench includes:

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

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

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

[0014] Adopt a Bosch process to etch the substrate downward along the openings to form the trenches.

[0015] In one embodiment, the cross-sectional shape of the end of the trench away from the protective layer in a direction perpendicular to the surface of the substrate is a bowl shape with a wider top and a narrower bottom.

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

[0017] Form an insulating layer on the inner wall of the trench, and the insulating layer extends to cover the protective layer on both sides of the trench;

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

[0019] The sacrificial layer covers the insulating layer.

[0020] In one embodiment, the insulating layer includes a convex portion, and the convex portion is formed on the inner wall of the trench and at the junction of the substrate and the protective layer;

[0021] The forming of the sacrificial layer on the insulating layer includes:

[0022] The sacrificial layer is filled onto the convex portion in the trench.

[0023] In one embodiment, when forming the sacrificial layer on the protective layer, the sacrificial layer fills the end of the trench away from the substrate side, and a plurality of depressions are formed on the surface of the sacrificial layer, and the projection of the depressions onto the surface of the substrate falls within the projection of the trench onto the surface of the substrate, including:

[0024] Adopt a first deposition process to deposit sacrificial layer material in the trench and reduce the width of the part of the trench close to the protective layer;

[0025] Adopt the second deposition process to continuously deposit the sacrificial layer material to form the sacrificial layer covering the trench, and form the depression in the sacrificial layer;

[0026] Adopt the third deposition process to continuously deposit the sacrificial layer material to increase the thickness of the sacrificial layer;

[0027] 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.

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

[0029] Fill the trench with a metal material, and the metal material extends to cover the sacrificial layer on both sides of the trench;

[0030] Perform a planarization process to remove at most part of the sacrificial layer and the metal material on the sacrificial layer, so that the remaining metal material forms a metal grid filling the trench and the depression;

[0031] Remove the remaining sacrificial layer.

[0032] In one embodiment, the metal grid includes a bottom part, a middle part and a top part connected in sequence. Wherein, the bottom part is the part of the metal grid extending into the substrate, the top part is the part of the metal grid higher than the substrate and the protective layer, the middle part is located between the top part and the bottom part, and in the direction perpendicular to the surface of the substrate, the cross-sectional widths corresponding to the top part, the middle part and the bottom part gradually decrease.

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

[0034] An unexpected effect of the present application is that by forming a depression in the sacrificial layer, the projection of the depression towards the surface of the substrate falls into the projection of the trench towards the surface of the substrate. By connecting the trench and the depression and filling with a metal material, a metal grid is formed and self-alignment of the trench and the metal grid is achieved, reducing or avoiding the risk of metal grid offset caused by registration 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 a metal grid by filling the trench and the depression with a metal material, the influence of the stress between each film layer on the metal grid is reduced, thereby reducing the product defect rate. Description of the Drawings

[0035] To more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

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

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

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

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

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

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

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

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

[0044] Figure 9 It is a flowchart of the manufacturing method of an image sensor provided by an embodiment of the present application.

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

[0046] Figure 11 It is a schematic structural diagram corresponding to the step of forming trenches in the substrate in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0047] Figure 12 Schematic structural diagram corresponding to the step of forming an insulating layer in a trench in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0048] Figure 13 Schematic structural diagram corresponding to the step of forming a sacrificial layer in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0049] Figure 14 Schematic structural diagram corresponding to the step of etching the sacrificial layer to connect the depression and the trench in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0050] Figure 15 Schematic structural diagram corresponding to the step of filling a metal material in the trench and the depression in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0051] Figure 16 Schematic structural diagram corresponding to the step of performing planarization in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0052] Figure 17 Schematic structural diagram corresponding to the step of removing the sacrificial layer in the manufacturing method of an image sensor provided by an embodiment of the present application.

[0053] Description of reference numerals: 100 - substrate; 101 - DTI structure; 102 - dielectric layer; 110 - oxide layer; 120 - first mask layer; 130 - silicon nitride layer; 140 - tungsten metal layer; 141 - carbide layer; 142 - metal grid; 150 - second mask layer; A - depression pattern; 200 - substrate; 201 - trench; 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 - depression; 240 - metal material; 241 - metal grid; 241a - top part; 241b - middle part; 241c - bottom part; X1 - first part; X2 - second part. Detailed description of the embodiments

[0054] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are given 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, these embodiments are provided 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 commonly understood by one of ordinary skill in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0056] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and / or portions, these elements, components, regions, layers, doping types and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or portion from another element, component, region, layer, doping type or portion. Thus, without departing from the teachings of this application, the first element, component, region, layer, doping type or portion discussed below may be referred to 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] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. may be used herein to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, an element or feature described as "under" or "beneath" or "below" another element or feature will be oriented "on" the other element or feature. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. In addition, the device may also include additional orientations (such as rotating 90 degrees or other orientations), and the spatial descriptors used herein are to be interpreted accordingly.

[0058] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising", "including" or "having" and the like specify the presence of the stated features, integers, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, 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 related listed items.

[0059] Figures 1 to 8 It is a schematic structural diagram corresponding to some steps in the manufacturing method of an image sensor in the related art. The following will be combined with Figures 1 to 8 to illustrate the manufacturing method of the image sensor in the related art.

[0060] First, refer to Figure 1 , provide a substrate 100, and sequentially form 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, refer to Figure 2 , perform patterning on the first mask layer 120, and etch the oxide layer 110 and the substrate 100 using the first mask layer 120 as a mask to form a plurality of DTI structures 101, that is, deep trench isolation (DTI) structures, in the substrate 100. At the same time, after forming the DTI structures 101, the first mask layer 120 can be removed by a wet cleaning process.

[0062] Subsequently, refer to Figure 3 , form a dielectric layer 102 in the DTI structures 101. The dielectric layer 102 fills the DTI structures 101 and covers the oxide layer 110 on both sides of the DTI structures 101. Optionally, the dielectric layer 102 is a stacked structure formed by sequentially stacking an oxide layer, a high-k dielectric layer, and an oxide layer. It should be noted that during the process of forming the dielectric layer 102 by a deposition process, the pattern of the DTI structures 101 will be transferred to the surface of the dielectric layer 102 to form a concave pattern A vertically aligned with the DTI structures 101.

[0063] Refer to Figure 4 , deposit a silicon nitride layer 130 on the dielectric layer 102 and perform a planarization process 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] Refer to Figure 5, etch the silicon nitride layer 130 and the dielectric layer 102 to make the surfaces of the remaining silicon nitride layer 130 and the dielectric layer 102 flush. Optionally, the silicon nitride layer 130 exactly fills the recessed pattern A.

[0065] Subsequently, refer to Figure 6 , a tungsten metal layer 140 and a carbide layer 141 are sequentially formed on the silicon nitride layer 130 and the dielectric layer 102. Among them, the carbide layer 141 can protect the tungsten metal layer 140 from damage. Optionally, the material of the tungsten metal layer 140 can also be replaced with other commonly used metal or alloy materials, such as copper metal, aluminum metal or alloy materials containing copper, aluminum, and tungsten, etc.

[0066] Next, refer to 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 tungsten metal 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 can be used to remove the second mask layer 150, the carbide layer 141, and the impurities and by-products 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 yellow light overlay error (Overlapping Value). Refer to Figure 7 , in the same exposure area (Shot) of the yellow light, the position of the metal grid 142 is shifted relative to the DTI structure 101, which will cause differences in the chip specifications at different positions within the wafer. In addition, the metal grid 142 will be affected by the stress within the wafer surface during the formation process and there is a risk of pattern peeling defects, seriously affecting the performance stability of the semiconductor device and the product yield.

[0068] To solve the above problems, the present application provides an image sensor and a manufacturing method thereof, reducing or avoiding the problem of metal grid offset caused by overlay error and reducing the defect rate of the image sensor. Refer to Figure 9 , the manufacturing method of the image sensor provided by an embodiment of the present application includes:

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

[0070] Step S02: A sacrificial layer is formed on the protective layer. The sacrificial layer fills the end of the trench on the side away from the substrate, and a plurality of depressions are formed on the surface of the sacrificial layer. The projection of the depressions towards the surface of the substrate falls within the projection of the trench towards the surface of the substrate.

[0071] Please refer to Figure 13 , since the sacrificial layer 230 is usually prepared by a deposition process, during the formation of the sacrificial layer 230, the surface pattern of the film layer below the sacrificial layer 230 (such as inheriting the surface pattern of the insulating layer 220) will be inherited, thereby forming depressions 231, and the projection of the depressions 231 towards the surface of the substrate 200 falls within the projection of the trench 201 towards 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 depressions 231 formed on the sacrificial layer 230 can be self-aligned with the trench 201, so as to reduce or avoid the problem of pattern deviation caused by misregistration during the formation of the depressions 231 by etching process, thereby reducing or avoiding the deviation of the finally formed metal grid.

[0072] Meanwhile, since the sacrificial layer fills the end of the trench on the side away from the substrate, a cavity is formed in the part of the trench close to the substrate side, so as to fill the metal material in the trench subsequently.

[0073] Step S03: Etch the sacrificial layer to communicate the depressions with the trench.

[0074] Step S04: Fill the trench with a metal material to form a metal grid.

[0075] It can be seen that in the manufacturing method of the image sensor provided by one embodiment of the present application, by forming depressions in the sacrificial layer, the projection of the depressions towards the surface of the substrate falls within the projection of the trench towards the surface of the substrate. By connecting the trench and the depressions and filling the metal material, a metal grid is formed and the trench isolation and the self-alignment of the metal grid are realized, reducing or avoiding the risk of metal grid deviation caused by misregistration, 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, in the present application, the metal grid is formed by filling the trench and the depressions with the metal material, reducing the influence of the stress between the film layers on the metal grid, thereby reducing the product defect rate.

[0076] Refer to Figure 10 and Figure 11, in one embodiment, the formation process of the protective layer 210 and the trench 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 trench 201; removing the mask layer 211 and the impurities and by-products generated during the etching process. Optionally, the mask layer 211 is removed by a wet cleaning process.

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

[0078] Exemplarily, a plasma etching process including carbon tetrafluoride gas (CF 4 Gas) is used to etch the protective layer 210 to form a plurality of openings (not shown in the figure). Optionally, during the process of etching the substrate 200 and forming the trench 201 using the Bosch process with etching (Etch) and deposition (Deposition) cycles, the etching gas includes, for example, sulfur hexafluoride (SF 6 ), and the deposition gas includes, for example, octafluorocyclobutane (C 4 F 8 ).

[0079] It should be noted that referring to Figure 11 , during 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 relatively increases, the proportion of the etching gas relatively decreases, and the process pressure gradually decreases, causing the width of the first part X1 of the trench 201 to first expand and then decrease 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 wider top and a narrower bottom. Optionally, the trench 201 is a deep trench isolation (DTI) structure.

[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 places no restrictions thereon. The etching method of the protective layer 210 and the formation method of the trench 201 can both be adjusted according to requirements, as long as the first part X1 of the trench 201 located within the substrate 200 presents a bowl-shaped morphology that is wider at the top and narrower at the bottom. The present application places no restrictions thereon.

[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 range of the protective layer 210 includes 200 Å to 500 Å.

[0082] Referring to Figure 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, it further includes: forming an insulating layer 220 on the inner wall of the trench 201, and 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-k layer and an oxide layer, and for example, it may include a stacked structure formed by stacking a first oxide layer 221, a high-k 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] Continuing to refer to Figure 12 , in one embodiment, the insulating layer 220 further includes a protrusion 224, and the protrusion 224 is formed on the inner wall of the trench 201 and is located at the junction of the substrate 200 and the protective layer 210. It should be noted that when there is a protrusion 224 in the insulating layer 220, the subsequently formed sacrificial layer (not shown in the figure) is deposited on the protrusion 224, thereby reducing or avoiding the sacrificial layer filling the trench 201, so as to subsequently fill the trench 201 with a metal material.

[0085] Referring to Figure 13 , in one embodiment, the process of forming a sacrificial layer 230 having a depression 231 on the protective layer 210 (or the insulating layer 220) includes: adopting a first deposition process to deposit a sacrificial layer material (such as including silicon nitride) in the trench 201, and making the part of the trench 201 close to the protective layer 210 (i.e., Figure 11The width of the second part X2) therein decreases; a second deposition process is adopted to continue depositing the sacrificial layer material to form a sacrificial layer 230 covering the trench 201, and a depression 231 vertically aligned with the trench 201 is formed in the sacrificial layer 230; a third deposition process is adopted 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 rates of the first deposition process and the third deposition process respectively.

[0086] It should be noted that during the first deposition process with a relatively low deposition rate, a small amount of sacrificial layer material will be deposited inside the trench 201, and the impact of this situation on the performance of the finally formed image sensor is very small or negligible. During the second deposition process with a relatively high deposition rate, as the sacrificial layer material is deposited, the top width of the trench 201 (i.e., Figure 11 the width of the second part X2 therein) continuously decreases until the sacrificial layer material completely covers the trench 201. When the sacrificial layer material completely covers the trench 201 and forms the sacrificial layer 230, the third deposition process can be carried out. During the third deposition process that continues to use a relatively low deposition rate, the morphology of the sacrificial layer 230 in the second deposition process can be continued to be inherited, and the thickness of the sacrificial layer 230 can be increased for the next etching process.

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

[0088] Referring to Figure 13 and Figure 14 , in one embodiment, a re-etching process is adopted to etch the sacrificial layer 230 to make the depression 231 communicate with the trench 201. It should be noted that if there is more sacrificial layer material filled in the trench 201 during the formation of the sacrificial layer 230, the excess sacrificial layer material in the trench 201 can be removed through this etching process for subsequent filling with metal material.

[0089] Continuing to refer to Figure 13 and Figure 14 , it should be further noted that during the above re-etching process, the load effect of etching can be utilized to make more etching gas enter the depression 231, thereby increasing the etching efficiency at the bottom of the depression 231 and realizing the communication between the depression 231 and the trench 201. At the same time, the side wall of the depression 231 may also be slightly laterally etched during the re-etching process, and the top end of the depression 231 after the re-etching process (the cross-sectional morphology in the direction perpendicular to the surface of the substrate 200) may present a trapezoid-like morphology.

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

[0091] Referring to Figure 15 , the trench 201 is filled with the metal material 240, and the metal material 240 extends to cover the sacrificial layers 230 on both sides of the trench 201. Optionally, the metal material 240 includes at least one of common metal conductive materials such as tungsten (W), copper (Cu), and aluminum (Al), or may be an alloy material containing the foregoing metal conductive materials.

[0092] Referring to Figure 16 , a planarization process is performed to remove at most part of the sacrificial layer 230 and the metal material 240 on the sacrificial layer 230, so that the remaining metal material 240 forms the metal grid 241 filling the trench 201. Optionally, a chemical mechanical polishing (CMP) process is used for the planarization process. It should be noted that during the process of connecting the recess and the trench in the foregoing steps, the top of the recess may present a trapezoid-like morphology, and the metal material 240 filled at the top of the recess also presents a trapezoid-like morphology. At this time, if no treatment is performed, the side walls of the top part of the corresponding metal grid 241 may be uneven, thus affecting the performance of the finally formed image sensor. Therefore, during the planarization process, the uneven part at the top of the metal grid 241 can be removed by over-etching (OE) to ensure that the side walls of the finally formed metal grid 241 are straight.

[0093] Referring to Figure 17 , the remaining sacrificial layer 230 is removed to facilitate the preparation of other semiconductor structures subsequently. Optionally, a dry etching process or a wet etching process is used to remove the sacrificial layer 230.

[0094] Continuing to refer to Figure 17 , the metal grid 241 includes a top part 241a, a middle part 241b, and a bottom part 241c that are connected in sequence. Among them, the bottom part 241c is the part of the metal grid 241 extending into the substrate 200, and the top part 241a is the part of the metal grid 241 higher than the substrate 200 and the protective layer 210 ( Figure 17 the top part 241a of

[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 trench 201, the width of the top portion 241a of the metal grid 241 is greater than the width of the trench 201. Among them, the trench 201 is mainly used to isolate the electrical signals between pixels and prevent crosstalk; the metal grid 241 not only plays a role in covering 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 being greater than the width of the trench 201 can ensure that the subsequently formed color filter can accurately and completely cover the corresponding pixels, while avoiding color mixing or light leakage problems caused by process deviations.

[0096] Comparison Figure 8 and Figure 17 It can be seen that in the manufacturing method of the image sensor provided in the embodiment of the present application, a depression 231 is formed in the sacrificial layer 230, so that the projection of the depression 231 towards the surface of the substrate 200 falls within the projection of the trench 201 towards the surface of the substrate 200. By connecting the trench 201 and the depression 231 and filling with a metal material, self-alignment of the trench 201 and the metal grid 241 is achieved, reducing or avoiding the risk of the metal grid 241 shifting caused by registration errors, and at the same time 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 require the formation of a corresponding mask layer when forming the metal grid 241, simplifies the related process flow, and improves the manufacturing efficiency of the image sensor.

[0097] Correspondingly, the present application also provides an image sensor manufactured by using the manufacturing method of the image sensor as described above. Exemplarily, referring to Figure 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 trenches 201 are provided in the substrate 200 and the protective layer 210, and the insulating layer 220 is provided on the inner walls of the trenches 201; a metal grid 241 is provided in the trenches 201, and the top of the metal grid 241 extends outside the trenches 201 and is higher than the surface of the insulating layer 220. Among them, the cross-sectional morphology of the part of the trench 201 located in the substrate 200 is in a bowl shape with a wider top and a narrower bottom along the direction perpendicular to the substrate 200.

[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 range of the protective layer 210 includes 200 Å to 500 Å. In one embodiment, the trench 201 is a Deep Trench Isolation (DTI) structure to isolate the electrical signals between pixels and prevent crosstalk.

[0099] In one embodiment, the insulating layer 220 includes a high-k dielectric layer and an oxide layer, and may include, for example, a stacked structure formed by stacking a first oxide layer 221, a high-k dielectric 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 that are connected in sequence. Among them, the bottom portion 241c is the part of the metal grid 241 that extends into the substrate 200, and the top portion 241a is the part of the metal grid 241 that is higher than the substrate 200 and the protective layer 210 ( Figure 17 the top portion 241a is also 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 trench 201, the width of the top portion 241a of the metal grid 241 is greater than the width of the trench 201. Among them, the trench 201 is mainly used to isolate the electrical signals between pixels and prevent crosstalk; the metal grid 241 not only plays a role in covering the pixel area, but also helps to reduce the alignment error of the subsequent 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 being greater than the width of the trench 201 can ensure that the subsequent 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 as follows: By forming a depression in the sacrificial layer such that the projection of the depression onto the surface of the substrate falls within the projection of the trench onto the surface of the substrate, and by connecting the trench and the depression and filling them with a metal material, a metal grid is formed and self-alignment of trench isolation and the metal grid is achieved, reducing or avoiding the risk of misalignment of the metal grid caused by registration errors, 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 trench and the depression with a metal material, the influence of the stress between the respective film layers on the metal grid is reduced, thereby reducing the product defect rate.

[0103] In the description of this specification, the description with reference to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0104] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0105] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended 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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