A method for manufacturing an image sensor and an image sensor

Abstract

The application discloses a preparation method of an image sensor and the image sensor. The preparation method comprises the following steps: forming a hard mask layer on a substrate; forming a resist mask layer on the hard mask layer, and patterning the resist mask layer by using a nanoimprint process; etching the hard mask layer and the substrate via the patterned resist mask layer to form a deep trench in the substrate; and forming an isolation layer in the deep trench to form a deep trench isolation structure. The patterned resist mask layer comprises a second protection part located at an intersection area of the first resist opening and the second resist opening, wherein the second protection part has a second thickness, and the second thickness is smaller than the first thickness; and a third protection part having the same thickness as the first protection part, which is formed between the second protection part and the first resist opening or the second protection part and the second resist opening, and one second protection part corresponds to one third protection part.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor devices, and particularly relates to a preparation method of an image sensor and the image sensor. BACKGROUND

[0002] A conventional image sensor includes a substrate and deep trench isolation structures extending from a surface of the substrate to an interior thereof, the deep trench isolation structures isolating the substrate to form a plurality of photoelectric sensing regions. Typically, the deep trench isolation structures include first deep trench isolation structures extending in a first direction and second deep trench isolation structures extending in a second direction, and the first deep trench structures and the second deep trench structures intersect.

[0003] In the process of forming the deep trench isolation structures, due to the etching loading effect, the intersection region of the first deep trench isolation structures and the second deep trench isolation structures usually forms a wider and deeper deep trench structure, and in severe cases, even contacts the opposite shallow trench isolation structure.

[0004] In the conventional technology, the etching loading effect usually needs to be corrected by OPC (Optical Proximity Correction), and even needs to redesign the mask, which is complex and cumbersome. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a preparation method of an image sensor and the image sensor to solve the above problems.

[0006] According to an aspect of the present application, a preparation method of an image sensor is provided, including: forming a hard mask layer on a substrate; forming a resist mask layer on the hard mask layer, and patterning the resist mask layer by using a nanoimprint process; etching the hard mask layer and the substrate via the patterned resist mask layer to form a deep trench in the substrate; forming an isolation layer in the deep trench to form a deep trench isolation structure; wherein the patterned resist mask layer includes: a first protection portion having a first thickness; a first resist opening extending in a first direction; a second resist opening extending in a second direction and intersecting the first resist opening; a second protection portion located at an intersection region of the first resist opening and the second resist opening, the second protection portion having a second thickness, the second thickness being smaller than the first thickness; and a third protection portion having the same thickness as the first protection portion, formed between the second protection portion and the first resist opening or the second protection portion and the second resist opening, one second protection portion corresponding to one third protection portion.

[0007] Optionally, the first resist opening and the second resist opening intersect to form a plurality of quadrilaterals, the second protection portion forms a top corner of the quadrilateral, and a third protection portion connected to the second protection portion is formed at opposite two top corners of any one of the quadrilaterals.

[0008] Optionally, the method for etching the hard mask layer and the substrate via the patterned resist mask layer comprises: etching the hard mask layer via the patterned resist mask layer to form a patterned hard mask layer; and etching the substrate via the patterned resist mask layer and the patterned hard mask layer to form deep trenches in the substrate; the patterned hard mask layer comprises: a first portion corresponding to the first protection portion; a first hard mask opening corresponding to the first resist opening, the first hard mask opening extending in a first direction; a second hard mask opening corresponding to the second resist opening, the second hard mask opening extending in a second direction and intersecting the first hard mask opening; a second portion, the second protection portion is removed, the hard mask layer covered by the second protection portion is etched by a portion to form the second portion, the second portion is located at an intersection region of the first hard mask opening and the second hard mask opening, and a thickness of the second portion is less than a thickness of the first portion; and a third portion having the same thickness as the first portion, formed between the second portion and the first hard mask opening or the second portion and the second hard mask opening, one second portion corresponding to one third portion; the first hard mask opening and the second hard mask opening intersect to form a plurality of quadrilaterals, the second portion forms a top corner of the quadrilateral, and a third portion connected to the second portion is formed at opposite two top corners of any one of the quadrilaterals.

[0009] Optionally, in the process of etching the substrate via the patterned resist mask layer and the patterned hard mask layer, the etchant etches the substrate via the first resist opening and the first hard mask opening to form a first deep trench; the etchant etches the substrate via the second resist opening and the second hard mask opening to form a second deep trench; the etchant etches the second portion and the substrate covered by the second portion to form a third deep trench; and the etchant etches the third protection portion and the third portion, so that the third deep trench is in communication with the first deep trench and the second deep trench, respectively.

[0010] Optionally, the second part is used to offset the depth etching load effect in the process of etching the substrate to form deep trenches; in the first stage of etching, the second part of the hard mask layer protects the substrate covered thereby, and the substrate under the second part is etched later than the substrate exposed by the first hard mask opening and the second hard mask opening; in the second stage of etching, the second part is etched to completion, thereby etching the substrate under the second part to form a third deep trench, the depth of the third deep trench in the second stage being less than the depths of the first deep trench and the second deep trench; in the third stage of etching, the depth load effect of etching causes the height difference between the third deep trench and the first deep trench and between the third deep trench and the second deep trench to gradually decrease until disappearing.

[0011] Optionally, the third protection part and the third part are used to offset the width etching load effect in the process of etching the substrate to form deep trenches; when the first deep trench and the second deep trench have a predetermined depth, the etchant performs lateral etching on the substrate through the sidewalls of the first deep trench and the second deep trench, so that the third deep trench is in communication with the first deep trench and the second deep trench, respectively.

[0012] Optionally, the method for patterning the resist mask layer by using the nano-imprint process comprises: placing an imprint template on the resist mask layer, applying pressure to the imprint template, and transferring the pattern on the imprint template to the resist mask layer; wherein the pattern formed on the imprint template is opposite to the pattern formed in the resist mask layer.

[0013] Optionally, the imprint template comprises: a first protrusion extending in a first direction; a second protrusion extending in a second direction, the first protrusion and the second protrusion intersecting; a third protrusion located at the intersection region formed by the intersection of the first protrusion and the second protrusion; the first protrusion and the second protrusion have the same height, the third protrusion has a height smaller than that of the first protrusion and the second protrusion, the third protrusion and the first protrusion connected thereto or the third protrusion and the second protrusion connected thereto have a break, and one third protrusion corresponds to one break.

[0014] Optionally, the first protrusion and the second protrusion intersect to form a plurality of quadrilaterals, the third protrusion forms a top corner of the quadrilateral, the break is formed at two top corners of any one quadrilateral, and the break is located at the opposite top corners of the quadrilateral.

[0015] According to another aspect of the present application, there is provided an image sensor formed by using any one of the above-mentioned methods.

[0016] The present application has the following unexpected technical effects:

[0017] In the method for manufacturing the image sensor, the resist mask layer includes a first resist opening extending in a first direction and a second resist opening extending in a second direction, and a second protection portion is formed at an intersection area of the first resist opening and the second resist opening, and the second protection portion has a second thickness smaller than the first resist opening and the second resist opening. Further, a third protection portion is formed between the second protection portion and the first resist opening or between the second protection portion and the second resist opening, and the second protection portion and the third protection portion jointly offset the etching load effect. The second protection portion is used to offset the depth etching load effect in the process of etching the substrate to form the deep trench, and the third protection portion is used to offset the width etching load effect in the process of etching the substrate to form the deep trench.

[0018] Further, one second protection portion corresponds to one third protection portion to reduce the stress of the intersection area in the process of etching the substrate.

[0019] Further, in the present application, the resist mask layer is patterned by the nano-imprint process, and compared with the traditional photoetching process which needs to repeat the process of coating, exposing, developing and etching, the nano-imprint process can form the protection portions with different heights in different areas of the resist mask layer by one process.

[0020] In the preferred embodiment, the first resist opening and the second resist opening intersect to form a plurality of quadrilaterals, the second protection portion forms a top corner of the quadrilateral, the third protection portion connected with the second protection portion is formed at two top corners of any one of the quadrilaterals, and the third protection portion is formed at opposite top corners of the quadrilateral to ensure the uniformity of the stress of the whole device. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and other objects, features and advantages of the present application will become more apparent from the following description of the preferred embodiments of the present application taken with reference to the accompanying drawings, in which:

[0022] Figure 1a A schematic cross-sectional view of a conventional image sensor is shown;

[0023] Figure 1b A schematic top view of the distribution of the deep trench isolation structure in the conventional image sensor on the substrate is shown;

[0024] Figure 1c A cross-sectional view along AA direction in a specific embodiment is shown; Figure 1b

[0025] Figure 1d A cross-sectional view along BB direction in a specific embodiment is shown; Figure 1b

[0026] Figure 2 ​​A flow chart of a method of fabricating an image sensor is shown according to embodiments of the present application;

[0027] Figure 3a A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application;

[0028] Figure 3b A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 3a A schematic cross-sectional view along the AA direction is shown;

[0029] Figure 3c A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 3a A schematic cross-sectional view along the BB direction is shown;

[0030] Figure 4a A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application;

[0031] Figure 4b A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 4a A schematic cross-sectional view along the AA direction is shown;

[0032] Figure 4c A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 4a A schematic cross-sectional view along the BB direction is shown;

[0033] Figure 4d A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application;

[0034] Figure 5a A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application;

[0035] Figure 5b A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 5a A schematic cross-sectional view along the AA direction is shown;

[0036] Figure 5c A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 5a A schematic cross-sectional view along the BB direction is shown;

[0037] Figure 6a A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application;

[0038] Figure 6b A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 6a A schematic cross-sectional view along the AA direction is shown;

[0039] Figure 6c A schematic top view of forming a hard mask layer on a first surface of a substrate is shown according to embodiments of the present application; Figure 6a A schematic cross-sectional view along the BB direction is shown;

[0040] Figure 7aA schematic top view showing a final state of etching a hard mask layer via a patterned resist mask layer according to an embodiment of the application is shown;

[0041] Figure 7b A schematic top view showing a final state of etching a hard mask layer via a patterned resist mask layer according to an embodiment of the application is shown; Figure 7a A schematic cross-sectional view along the AA-direction is shown;

[0042] Figure 7c A schematic cross-sectional view along the AA-direction is shown; Figure 7a A schematic cross-sectional view along the BB-direction is shown;

[0043] Figure 8a A schematic top view showing a final state of etching a hard mask layer via a patterned resist mask layer according to an embodiment of the application is shown;

[0044] Figure 8b A schematic cross-sectional view along the AA-direction is shown; Figure 8a A schematic cross-sectional view along the AA-direction is shown;

[0045] Figure 8c A schematic cross-sectional view along the AA-direction is shown; Figure 8a A schematic cross-sectional view along the BB-direction is shown;

[0046] Figure 9a A schematic top view showing a final state of etching a hard mask layer via a patterned resist mask layer according to an embodiment of the application is shown;

[0047] Figure 9b A schematic cross-sectional view along the AA-direction is shown; Figure 9a A schematic cross-sectional view along the AA-direction is shown;

[0048] Figure 9c A schematic cross-sectional view along the AA-direction is shown; Figure 9a A schematic cross-sectional view along the BB-direction is shown. DETAILED DESCRIPTION

[0049] The present application will be described in more detail with reference to the drawings, in which like reference numerals refer to like elements throughout. The drawings are schematic and for explanation only. They are not limiting of the scope of the application. In the drawings:

[0050] In describing the structure of the device, when a layer, a region is referred to as being "on" or "above" another layer, another region, it can be directly on the other layer, the other region, or intervening layers or regions can also be present. Also, the layer, the region can be "below" or "under" another layer, another region if the device is turned over.

[0051] If for the sake of description, the expression "directly on" or "on and adjacent to" is used, it is meant that the layer, the region is directly on the other layer, the other region.

[0052] The present application can take form in various aspects of which the following are exemplary.

[0053] Figure 1a A schematic cross-sectional view of a conventional image sensor is shown in Figure 1a As shown, the image sensor includes a substrate 110, deep trench isolation structures 120 extending from a first surface 111 of the substrate 110 into the substrate 110, and shallow trench isolation structures 130 extending from a second surface 112 of the substrate 110 into the substrate 110, the deep trench isolation structures 120 and the shallow trench isolation structures 130 being oppositely arranged to divide the substrate 110 into a plurality of photoelectric sensing regions 140. The image sensor further includes a grid structure 150 on the first surface 111 of the substrate 110 and a filter structure 160. The grid structure 150 is on the deep trench isolation structures 120, and the filter structure 160 is between adjacent grid structures 150.

[0054] Figure 1b A schematic top view of the distribution of the deep trench isolation structures in a conventional image sensor is shown in Figure 1b As shown, the deep trench isolation structures 120 include first deep trench isolation structures 121 extending in a first direction and second deep trench isolation structures 122 extending in a second direction, wherein the first direction and the second direction are intersected, and the first deep trench isolation structures 121 and the second deep trench isolation structures 122 are intersected to form third deep trench isolation structures 123. In a preferred embodiment, the first direction and the second direction are perpendicular to each other.

[0055] In a conventional technique, the method of forming the deep trench isolation structures 120 includes forming a resist mask layer on the first surface 111 of the substrate 110, patterning the resist mask layer by a photolithography process, and etching the substrate 110 via the patterned resist mask layer to transfer the pattern of the resist mask layer into the substrate 110, thereby forming trenches in the substrate 110, and filling the trenches with an isolation medium to form the deep trench isolation structures 120.

[0056] Generally, the width and depth of the first deep trench isolation structures 121 and the second deep trench isolation structures 122 are set to be the same, and the width and depth of the third deep trench isolation structures 123 are theoretically required to be the same as those of the first deep trench isolation structures 121 and the second deep trench isolation structures 122. However, due to the loading effect of etching, the third deep trench isolation structures 123 tend to have a wider width and a deeper depth relative to the first deep trench isolation structures 121 and the second deep trench isolation structures 122. Figure 1c A cross-sectional view along the AA direction in a specific embodiment is shown in Figure 1b A cross-sectional view along the BB direction in the specific embodiment is shown in Figure 1d A cross-sectional view along the BB direction in the specific embodiment is shown in Figure 1b A cross-sectional view along the BB direction in the specific embodiment is shown in Figure 1cAs shown, the width W21 of the opening of the second deep trench isolation structure 122 is, for example, 128.4 nm, the width W22 of the bottom of the second deep trench isolation structure 122 is 126.8 nm, and the depth H20 of the second deep trench isolation structure 122 is 1383 nm. As shown in FIG. 1C, the width W21 of the opening of the second deep trench isolation structure 122 is greater than the width W11 of the opening of the first deep trench isolation structure 121, and the width W22 of the bottom of the second deep trench isolation structure 122 is greater than the width W12 of the bottom of the first deep trench isolation structure 121. Figure 1d As shown, the width W31 of the opening of the third deep trench isolation structure 123 is, for example, 282.5 nm, the width W32 of the bottom of the third deep trench isolation structure 123 is 214 nm, and the depth H30 of the third deep trench isolation structure 123 is 1830 nm. As shown in FIG. 1D, the width W31 of the opening of the third deep trench isolation structure 123 is greater than the width W21 of the opening of the second deep trench isolation structure 122, and the width W32 of the bottom of the third deep trench isolation structure 123 is greater than the width W22 of the bottom of the second deep trench isolation structure 122. Figure 1c and Figure 1d As shown, in the process of etching the substrate 110 to form a trench in the substrate 110, the depth and width of the trench forming the third deep trench isolation structure 123 are both significantly increased, and the loading effect of the trench forming the third deep trench isolation structure 123 is more obvious than that of the trenches forming the first deep trench isolation structure 121 and the second deep trench isolation structure 122, and in severe cases, the third deep trench isolation structure 123 can contact the opposite shallow trench isolation structure 130.

[0057] In the conventional technology, the loading effect of etching usually needs to be corrected by OPC (Optical Proximity Correction), or even the mask needs to be redesigned, which is complex and cumbersome.

[0058] Figure 2 A flowchart of a method for manufacturing an image sensor is shown, which is provided by an embodiment of the present application, as shown in FIG. 2. Figure 2 As shown, the method for manufacturing an image sensor includes:

[0059] S110: forming a hard mask layer on a substrate;

[0060] S120: forming a resist mask layer on the hard mask layer, and patterning the resist mask layer by using a nanoimprint process;

[0061] S130: etching the hard mask layer and the substrate via the patterned resist mask layer to form a deep trench in the substrate;

[0062] S140: forming an isolation layer in the deep trench to form a deep trench isolation structure;

[0063] The patterned resist mask layer includes: a first protective portion having a first thickness; a first resist opening extending in a first direction; a second resist opening extending in a second direction and intersecting with the first resist opening; a second protective portion located at the intersection of the first resist opening and the second resist opening, the second protective portion having a second thickness less than the first thickness; and a third protective portion having the same thickness as the first protective portion, formed between the second protective portion and the first resist opening or between the second protective portion and the second resist opening, with one second protective portion corresponding to one third protective portion.

[0064] Figures 3a to 9c Cross-sectional views of various stages in the image sensor fabrication process according to embodiments of this application are shown below. Figure 2 as well as Figures 3a to 9c The fabrication method of the image sensor according to the embodiments of this application will be described.

[0065] Figure 3a A schematic top view showing a hard mask layer formed on a first surface of a substrate according to an embodiment of this application is shown. Figure 3b It shows Figure 3a Schematic cross-sectional view along the AA direction. Figure 3c It shows Figure 3a A schematic cross-sectional view along the BB direction, in which the deep trench isolation structure and the shallow trench isolation structure are clearly shown. Figure 3b and Figure 3c The dielectric layer and conductive structure formed on the second surface of the substrate are omitted in the original text, and the same applies to subsequent steps.

[0066] like Figures 3a to 3c As shown, in this step, for example, a hard mask layer 170 is formed on the first surface 111 of the substrate 110 using a deposition process. The hard mask layer 170 covers the entire first surface 111 of the substrate 110. The hard mask layer 170 may include a single film layer or a stack of multiple film layers. In this embodiment, the hard mask layer 170 includes a first hard mask layer 171 and a second hard mask layer 172. The first hard mask layer 171 is, for example, an oxide layer, and the second hard mask layer 172 is, for example, a bottom anti-reflection coating (BARC).

[0067] Before forming the hard mask layer 170 on the first surface 111 of the substrate 110, a shallow trench isolation structure 130 extending from the second surface 112 of the substrate 110 to the interior of the substrate 110 is also formed. The method of forming the shallow trench isolation structure 130 includes forming a resist mask layer on the second surface 112 of the substrate 110, patterning the resist mask layer by a photolithography process, and etching the substrate 110 via the patterned resist mask layer to transfer the pattern of the resist mask layer to the substrate 110, thereby forming a shallow trench in the substrate 110, and then filling the shallow trench with an isolation medium to form the shallow trench isolation structure 130.

[0068] Although not shown in the figure, it can be understood that after forming the shallow trench isolation structure 130, steps such as forming a dielectric layer on the second surface 112 of the substrate 110 and forming an electrical connection structure are also included.

[0069] Figure 4a A schematic top view showing the formation of a resist mask layer PR on the surface of the hard mask layer and the patterning of the resist mask layer PR by nanoimprint technology according to an embodiment of the present application is shown, Figure 4b A schematic top view showing the formation of a resist mask layer PR on the surface of the hard mask layer and the patterning of the resist mask layer PR by nanoimprint technology according to an embodiment of the present application is shown, Figure 4a A schematic cross-sectional view along the AA direction is shown, Figure 4c A schematic cross-sectional view along the AA direction is shown, Figure 4a A schematic cross-sectional view along the BB direction is shown.

[0070] As shown in 4a to Figure 4c In this step, a resist mask layer PR is formed on the hard mask layer, a stamp 50 is placed on the resist mask layer PR, pressure is applied to the stamp 50, and the pattern on the stamp 50 is transferred to the resist mask layer PR.

[0071] The stamp 50 has protrusions and recesses forming an imprint pattern on the stamp 50, Figure 4d A schematic perspective view of the stamp according to an embodiment of the present application is shown. As shown in Figure 4d The stamp 50 includes a substrate 501, a first protrusion 510, a second protrusion 520, a third protrusion 530, and a recess 540 on the substrate 501. The first protrusion 510 extends in a first direction, the second protrusion 520 extends in a second direction, and the first direction and the second direction intersect. In an embodiment, the first direction and the second direction are perpendicular to each other. The first protrusion 510 and the second protrusion 520 intersect to form an intersection region, and the third protrusion 530 is formed in the intersection region. The height of the first protrusion 510 and the second protrusion 520 is the same, and the height of the third protrusion 530 is less than the height of the first protrusion 510 and the second protrusion 520. In an embodiment, there is a height difference H between the third protrusion 530 and the first protrusion 510 and between the third protrusion 530 and the second protrusion 520.

[0072] The third protrusion 530 and the first protrusion 510 connected thereto or the third protrusion 530 and the second protrusion 520 connected thereto have a break 550, and one third protrusion 530 corresponds to one break 550.

[0073] Take the first third protrusion 531 as an example. The first protrusion 510 is connected to the first third protrusion 531 at the first side and the second side of the first third protrusion 531, and the second protrusion 520 is connected to the first third protrusion 531 at the third side and the fourth side of the first third protrusion 531. The first protrusion 510 located at the second side of the first third protrusion 531 forms a break 550 with the first third protrusion 531.

[0074] Further, the first protrusion 510 and the second protrusion 520 intersect to form a plurality of quadrilaterals, and the third protrusion 530 forms the top corners of the quadrilaterals. The breaks 550 are formed at the opposite two top corners of any one of the quadrilaterals. Take the quadrilateral S1 as an example. The second third protrusion 532, the third third protrusion 533, the fourth third protrusion 534, and the fifth third protrusion 535 successively adjacent constitute the four top corners of the quadrilateral S1, wherein the breaks 550 are formed at the opposite third third protrusion 533 and fifth third protrusion 535.

[0075] Further, the side of the imprinting template 50 formed with the imprinting pattern is contacted with the resist mask layer PR, and pressure is applied to the imprinting template 50 to transfer the pattern on the imprinting template 50 to the resist mask layer PR. The pattern formed by the resist mask layer PR is opposite to the pattern of the imprinting template 50. As shown in Figures 4a to 4c The resist mask layer PR corresponding to the recess 540 of the imprinting template 50 is not affected to form a first protection part PR1; the resist mask layer PR corresponding to the first protrusion 510 is removed to form a first resist opening PRa-1; the resist mask layer PR corresponding to the second protrusion is removed to form a second resist opening PRa-2; the resist mask layer PR corresponding to the third protrusion is removed in part, and the remaining resist mask layer forms a second protection part PR2, and the thickness of the second protection part PR2 is less than the thickness of the first protection part PR1. Further, the thickness of the second protection part PR2 is equal to the height difference H between the third protrusion 530 and the first protrusion 510. The resist mask layer PR corresponding to the break 550 is also retained to form a third protection part PR3, and the thickness of the third protection part PR3 is the same as that of the first protection part PR1.

[0076] Corresponding to the pattern of the imprinting template 50, the patterned resist mask layer includes a first resist opening PRa-1 corresponding to the first protrusion 510, a second resist opening PRa-2 corresponding to the second protrusion 520, a first protection portion PR1 corresponding to the recess 540, a second protection portion PR2 corresponding to the third protrusion 530, and a third protection portion PR3 corresponding to the break 550. The first resist opening PRa-1 and the second resist opening PRa-2 intersect, the second protection portion PR2 is located at the intersection area of the first resist opening PRa-1 and the second resist opening PRa-2, the third protection portion PR3 is formed between the second protection portion PR2 and the first resist opening PRa-1 adjacent thereto or between the second protection portion PR2 and the second resist opening PRa-2 adjacent thereto, and one second protection portion PR2 corresponds to one third protection portion PR3.

[0077] Further, the first resist opening PRa-1 and the second resist opening PRa-2 intersect to form a plurality of quadrilaterals, the second protection portion PR2 forms a top corner of the quadrilateral, and the third protection portion PR3 connected with the second protection portion PR2 is formed at the opposite two top corners of any one of the quadrilaterals. Taking the quadrilateral S2 as an example, a first second protection portion PR2a, a second second protection portion PR2b, a third second protection portion PR2c, and a fourth second protection portion PR2d successively adjacent to each other constitute four top corners of the quadrilateral S2, wherein the second second protection portion PR2b is formed with a third protection portion PR3 connected thereto, and the fourth second protection portion PR2d opposite to the second second protection portion PR2b is formed with a third protection portion PR3 connected thereto.

[0078] In an embodiment, the thickness of the first protection portion PR1 is, for example, 4100 angstroms, and the thickness of the second protection portion PR2 is, for example, 500 angstroms.

[0079] Figure 5a A schematic top view of etching the hard mask layer via the patterned resist mask layer according to an embodiment of the present application is shown, Figure 5b A schematic top view of etching the hard mask layer via the patterned resist mask layer according to an embodiment of the present application is shown, Figure 5a A schematic sectional view along the AA direction is shown, Figure 5c A schematic sectional view along the AA direction is shown, Figure 5a A schematic sectional view along the BB direction is shown. As shown in 5a to Figure 5c In this step, the pattern of the resist mask layer PR is transferred to the hard mask layer 170 by etching the hard mask layer 170 via the patterned resist mask layer PR.

[0080] In this process, the hard mask layer 170 corresponding to the first resist opening PRa-1 is etched away, forming the first hard mask opening 170a-1. The hard mask layer 170 corresponding to the second resist opening PRa-2 is etched away, forming the second hard mask opening 170a-2. The first protective part PR1 protects the hard mask layer 170 located below it, and the hard mask layer 170 covered by the first protective part PR1 is retained, forming the first part 170b. The third protective part PR3 protects the hard mask layer 170 located below it, and the hard mask layer 170 covered by the third protective part PR3 is retained, forming the third part 170d. However, it should be noted that during the etching process, the first protective part PR1 and the third protective part PR3 will also lose a portion of their contents. The second protective part PR2 also protects the hard mask layer 170 it covers, but because it is thinner than the first protective part PR1, it will be removed during the etching process. After the second protective portion PR2 is removed, a portion of the hard mask layer 170 it covers is also removed. Due to the protective effect of the second protective portion PR2, a portion of the hard mask layer 170 is retained, forming the second portion 170c. The third protective portion PR3, the third portion covered by the third protective portion PR3, and the remaining second portion 170c are used to counteract the etching load effect during the subsequent etching of the substrate 110.

[0081] In one embodiment, in the hard mask layer covered by the second protective portion PR2, the second hard mask layer 172 is completely removed, a portion of the first hard mask layer 171 is removed, and the remaining portion forms the second portion 170c.

[0082] Figure 6a A schematic top view showing an intermediate state of etching a hard mask layer via a patterned resist mask layer according to an embodiment of this application is shown. Figure 6b It shows Figure 6a Schematic cross-sectional view along the AA direction. Figure 6c It shows Figure 6a A schematic cross-sectional view along the BB direction. Figure 7a A schematic top view showing the final state of a hard mask layer etched via a patterned resist mask layer according to an embodiment of this application is shown. Figure 7b It shows Figure 7a Schematic cross-sectional view along the AA direction. Figure 7c It shows Figure 7a A schematic cross-sectional view along the BB direction.

[0083] For example, 6a to Figure 7c As shown, the substrate 110 is etched via the resist mask layer PR and the hard mask layer 170 to form a deep trench in the substrate 110.

[0084] In the process of etching the substrate 110, the etchant etches the substrate 110 via the first resist opening PRa-1 of the resist mask layer PR and the first hard mask opening 170a-1 of the hard mask layer, forming the first deep trench 110a, and etches the substrate 110 via the second resist opening PRa-2 of the resist mask layer PR and the second hard mask opening 170a-2 of the hard mask layer, forming the second deep trench 110b. The first protective portion PR1 of the resist mask layer PR and the first portion 170b of the hard mask layer 170 protect the substrate 110 located thereunder, so that the substrate 110 under the first protective portion PR1 of the resist mask layer PR and the first portion 170b of the hard mask layer is not affected by the etchant.

[0085] The etchant etches the second portion 170c and the substrate 110 covered thereby, forming the third deep trench 110c. The second portion 170c is mainly used to offset the depth etching loading effect. Specifically, the second portion 170c of the hard mask layer protects the substrate 110 covered thereby in the first stage of etching, so that the substrate 110 under the second portion 170c is etched later than the substrate exposed by the first hard mask opening 170a-1 and the second hard mask opening 170a-2; in the second stage of etching, as the etching process continues, the second portion 170c is gradually consumed, and then the substrate 110 under the second portion 170c is etched, forming the third deep trench 110c. Due to the temporary protection of the second portion 170c, the third deep trench 110c has a shallower depth relative to the first deep trench 110a and the second deep trench 110b, i.e., there is a height difference between the third deep trench 110c and the first deep trench 110a and between the third deep trench 110c and the second deep trench 110b, as shown in FIG. 2B. However, it should be understood that the third deep trench 110c is located at the intersection of the first deep trench 110a and the second deep trench 110b, and the etching loading effect is particularly obvious at this position. In the third stage of etching, as the etching process continues, the etching loading effect causes the height difference between the third deep trench 110c and the first deep trench 110a and between the third deep trench 110c and the second deep trench 110b to gradually decrease until disappearing. Figure 6c

[0086] Meanwhile, the etchant etches the third protective portion PR3 and the third portion of the hard mask layer, so that the third deep trench 110c is in communication with the first deep trench 110a and the second deep trench 110b, respectively. Specifically, the etching loading effect is not only in the depth direction but also in the width direction, and the loading effect in the width direction causes the third protective portion PR3 and the third portion 170d to also be removed. As shown in FIG. 2C. Figure 6a and Figure 6c ​As shown, due to the coverage of the third protection portion PR3 and the third portion 170d, the surface of the substrate 110 under them is not affected by the etchant, and when the first deep trench and the second deep trench have a predetermined depth, the etchant performs lateral etching on the substrate 110 through the sidewalls of the first deep trench 110a and the second deep trench 110b, and then the third protection portion PR3, the third portion 170d of the hard mask layer 170, and the substrate 110 under them are at least eroded from the sidewall of the first deep trench 110a and the sidewall of the first deep trench 110a, the third protection portion PR3, the third portion 170d of the hard mask layer 170 are finally completely etched, and the substrate 110 under them is also etched by a part, thereby forming the first deep trench 110a, the second deep trench 110b and the third deep trench 110c which are interconnected, and achieving 7a to Figure 7c The state shown.

[0087] In this embodiment, the second portion 170c of the hard mask layer 170, the third protection portion PR3 and the third portion 170d of the hard mask layer 170 are formed to offset the etching load effect in the process of etching the substrate 110 to form the deep trench. As described above, one third protection portion PR3 and third portion 170d are at least subjected to lateral erosion from two directions, and if two or more third protection portions PR3 and third portions 170d are provided, the stress on the intersection of the first deep trench and the second deep trench will be too large. In this embodiment, only one third protection portion PR3 and third portion 170d are provided at the intersection of the first deep trench and the second deep trench, and the second portion 170c with a smaller thickness is provided to cooperate with the one third protection portion PR3 and third portion 170d to offset the etching load effect and reduce the stress.

[0088] Further, in the quadrilateral formed by the first deep trench and the second deep trench, the third deep trench is a vertex of the quadrilateral, and the third protection portion PR3 connected with the second protection portion PR2 is formed at two top corners of any one of the quadrilaterals, and the third protection portion PR3 is formed on the opposite top corners to ensure the uniformity of the stress of the entire device.

[0089] After the deep trench is formed, the remaining resist mask layer and the hard mask layer are removed.

[0090] Figure 8a A schematic top view showing filling the deep trench to form a deep trench isolation structure is shown, Figure 8b A schematic top view showing Figure 8a A schematic sectional view along the AA direction is shown, Figure 8c A schematic top view showing Figure 8a A schematic sectional view along the BB direction is shown. As shown in 8a to Figure 8cAs shown, in this step, an isolation medium layer is formed, wherein the isolation medium layer covers the first surface of the substrate 110 and fills the deep trenches. Then, the portion of the isolation medium layer on the first surface of the substrate 110 is removed by, for example, a CMP (Chemical Mechanical Polishing) process or a back-etching process, and the isolation medium layer in the deep trenches is retained, thereby forming a deep trench isolation structure 120.

[0091] Figure 9a Fig. 9a shows a schematic top view of forming the grid structure 150 and the filter structure 160 according to an embodiment of the present application, Figure 9b Fig. 9b shows a schematic top view of forming the grid structure 150 and the filter structure 160 according to an embodiment of the present application, Figure 9a Fig. 9c shows a schematic cross-sectional view along AA direction, Figure 9c Fig. 9d shows a schematic cross-sectional view along BB direction. As shown in Figs. 9a to 9d, Figure 9a Fig. 9e shows a schematic cross-sectional view along CC direction. As shown in Figs. 9a to 9e, Figure 9c As shown, in this step, the grid structure 150 and the filter structure 160 are formed on the first surface 111 of the substrate 110. The grid structure 150 is located on the deep trench isolation structure 120, and the filter structure 160 is located between adjacent grid structures 150.

[0092] The present application has the following unexpected technical effects:

[0093] In the method for manufacturing the image sensor according to an embodiment of the present application, the resist mask layer includes a first resist opening extending in a first direction and a second resist opening extending in a second direction, and a second protection portion is formed at the intersection area of the first resist opening and the second resist opening, and the second protection portion has a second thickness smaller than the first thickness. Further, a third protection portion is formed between the second protection portion and the first resist opening or between the second protection portion and the second resist opening, and the second protection portion and the third protection portion jointly offset the etching loading effect. The second protection portion is used to offset the depth etching loading effect in the process of etching the substrate to form the deep trench, and the third protection portion is used to offset the width etching loading effect in the process of etching the substrate to form the deep trench.

[0094] Further, one second protection portion corresponds to one third protection portion, so as to reduce the stress of the intersection area in the process of etching the substrate.

[0095] Further, in the present application, the resist mask layer is patterned by the nanoimprint process, and compared with the traditional photoetching process which needs to repeat the process of coating, exposing, developing and etching, the nanoimprint process can form the protection portions with different heights in different areas of the resist mask layer by one process.

[0096] In a preferred embodiment, the first resist opening and the second resist opening intersect to form a plurality of quadrilaterals, the second protection portion forms a top corner of the quadrilaterals, a third protection portion connected to the second protection portion is formed at two top corners of any one of the quadrilaterals, and the third protection portion is formed at opposite top corners of the quadrilaterals to ensure uniformity of stress of the entire device.

[0097] In accordance with the embodiments of the present application as described above, these embodiments are not described in detail with all of the possible modifications and alterations. It is apparent that many modifications and changes of the embodiments can be made by one skilled in the art in light of the above description. The present description selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses on the basis of the present application. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for fabricating an image sensor, comprising: A hard mask layer is formed on the substrate; A resist mask layer is formed on the hard mask layer, and the resist mask layer is patterned using a nanoimprinting process; The hard mask layer and the substrate are etched via a patterned resist mask layer to form deep trenches in the substrate; An isolation layer is formed in the deep trench, forming a deep trench isolation structure; The patterned resist mask layer includes: The first protective section has the first thickness; The first resist opening extends in the first direction; The second resist opening extends in the second direction and intersects with the first resist opening; A second protective portion is located at the intersection of the first resist opening and the second resist opening, and the second protective portion has a second thickness, which is less than the first thickness; and The third protective portion, having the same thickness as the first protective portion, is formed between the second protective portion and the first resist opening, or between the second protective portion and the second resist opening, with one second protective portion corresponding to one third protective portion.

2. The method for fabricating an image sensor according to claim 1, wherein, The first and second resist openings intersect to form multiple quadrilaterals, the second protective part forms the vertices of the quadrilaterals, and a third protective part connected to the second protective part is formed at any two opposite vertices of the quadrilaterals.

3. The method for fabricating an image sensor according to claim 2, wherein, A method for etching the hard mask layer and the substrate via a patterned resist mask layer includes: A patterned hard mask layer is formed by etching a patterned resist mask layer; and Deep trenches are formed in the substrate by etching a patterned resist mask layer and a patterned hard mask layer. Patterned hard mask layers include: The first part corresponding to the first protection part; A first hard mask opening corresponding to the first resist opening, the first hard mask opening extending in a first direction; A second hard mask opening corresponding to the second resist opening, the second hard mask opening extending in a second direction and intersecting with the first hard mask opening; In the second part, the second protective portion is removed, and a portion of the hard mask layer covered by the second protective portion is etched away to form the second part. The second part is located at the intersection of the first hard mask opening and the second hard mask opening, and the thickness of the second part is less than the thickness of the first part. The third part, having the same thickness as the first part, is formed between the second part and the first hard mask opening, or between the second part and the second hard mask opening, with one second part corresponding to one third part; The first hard mask opening and the second hard mask opening intersect to form multiple quadrilaterals. The second part forms the vertex corners of the quadrilaterals, and a third part is formed at the two opposite vertex corners of any quadrilateral, connecting with the second part.

4. The method for fabricating an image sensor according to claim 3, wherein, During the etching process of the substrate through a patterned resist mask layer and a patterned hard mask layer, the etchant etches the substrate through the first resist opening and the first hard mask opening to form a first deep trench; The etchant etches the substrate through the second resist opening and the second hard mask opening to form a second deep trench; The etchant etches the second part and the substrate covered by the second part to form a third deep trench; The etchant etches the third protective part and the third portion, so that the third deep trench is connected to the first deep trench and the second deep trench respectively.

5. The method for fabricating an image sensor according to claim 4, wherein, The second part is used to counteract the depth etching load effect during the formation of deep trenches on the etched substrate; In the first stage of etching, the second part of the hard mask layer protects the substrate it covers, and the substrate below the second part is etched later than the substrate exposed by the first hard mask opening and the second hard mask opening. In the second stage of etching, the second part is etched, and then the substrate below the second part is etched to form a third deep trench. The depth of the third deep trench in the second stage is less than the depth of the first deep trench and the second deep trench. In the third stage of etching, the depth loading effect of etching causes the height difference between the third deep trench and the first deep trench, and between the third deep trench and the second deep trench, to gradually decrease until it disappears.

6. The method for fabricating an image sensor according to claim 4, wherein, The third protective portion and the third part are used to counteract the width etching load effect during the process of forming deep trenches on the etched substrate. When the first deep trench and the second deep trench have a predetermined depth, the etchant etches the substrate laterally through the sidewalls of the first deep trench and the second deep trench, so that the third deep trench is connected to the first deep trench and the second deep trench respectively.

7. The method for fabricating an image sensor according to claim 2, wherein, The method of patterning the resist mask layer using nanoimprint lithography includes: placing an imprint template on the resist mask layer, applying pressure to the imprint template, and transferring the pattern on the imprint template onto the resist mask layer; wherein the pattern formed on the imprint template is the opposite of the pattern formed in the resist mask layer.

8. The method for fabricating an image sensor according to claim 7, wherein, Imprinting templates include: The first protrusion extending in the first direction; A second protrusion extending in a second direction intersects the first protrusion and the second protrusion; The third protrusion is located in the intersection area formed by the first protrusion and the second protrusion; The first protrusion and the second protrusion have the same height, the third protrusion has a height less than the height of the first protrusion and the second protrusion, there is a break between the third protrusion and the first protrusion connected to it or between the third protrusion and the second protrusion connected to it, and one third protrusion corresponds to one break.

9. The method for fabricating an image sensor according to claim 8, wherein, The first protrusion and the second protrusion intersect to form multiple quadrilaterals, and the third protrusion forms the vertex of the quadrilateral. A break is formed at the two vertexes of any quadrilateral, and the break is located at the opposite vertex of the quadrilateral.

10. An image sensor formed using the method described in any one of claims 1-9.

Images