Formation method of shallow trench isolation structure and semiconductor device
By forming a hard mask layer on the substrate of the semiconductor device, forming shallow trenches, filling and planarizing the isolation material layer, and performing back etching treatment, the problem of recessed top surface of the shallow trench isolation structure is solved, and device performance is improved.
Patent Information
- Application Number
- CN202311816441.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-26
- Publication Date
- 2025-06-27
AI Technical Summary
The top surface of the shallow trench isolation structure is prone to depression defects, affecting the performance of semiconductor devices.
By forming a hard mask layer on the substrate, etching forms the first and second shallow trenches, filling the isolation material layer and performing planarization, removing part of the hard mask layer, and performing back etching to form the isolation layer, ensuring that the lateral etching rate of the initial isolation layer is greater than or equal to the longitudinal etching rate.
The top surface depression of the isolation layer in the second shallow trench is effectively avoided, and the quality of the shallow trench isolation structure and the performance of the semiconductor device are improved.
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Figure CN120221497A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and particularly to a shallow trench isolation structure and a method for forming a semiconductor device. Background Art
[0002] With the development of semiconductor technology, the insulating structure between active areas (Active Area, abbreviated as AA) is generally fabricated by using shallow trench isolation (STI) technology. During the process of forming the shallow trench isolation structure, as Figure 1 shown, usually a hard mask layer 11 is first formed on a substrate 10, and the thickness L1 of the hard mask layer 11 is 500 Å to 550 Å; then, as Figure 2 shown, the hard mask layer 11 and the substrate 10 are etched to form a first shallow trench 10a and a second shallow trench 10b, and the width of the second shallow trench 10b is greater than the width of the first shallow trench 10a; then, as Figure 3 shown, an isolation layer 12 is filled into the first shallow trench 10a and the second shallow trench 10b, and chemical mechanical polishing is performed on the isolation layer 12 to planarize the top surface of the isolation layer 12. However, during the actual chemical mechanical polishing process, the top surface of the isolation layer 12 in the second shallow trench 10b with a larger width dimension is prone to over-polishing to generate a depression (dishing), thereby causing a depression defect on the top surface of the shallow trench isolation structure formed by the isolation layer 12 in the second shallow trench (as Figure 3 shown by the dashed box), which affects the performance of the semiconductor device. Summary of the Invention
[0003] The purpose of the present invention is to provide a shallow trench isolation structure and a method for forming a semiconductor device to solve the problem of depression on the top surface of the shallow trench isolation structure.
[0004] To solve the above technical problems, the present invention provides a method for forming a shallow trench isolation structure, including:
[0005] Providing a substrate on which a hard mask layer is formed;
[0006] Sequentially etching the hard mask layer and the substrate to form a first shallow trench and a second shallow trench, wherein the width of the second shallow trench is greater than the width of the first shallow trench;
[0007] Forming an isolation material layer that fills the first shallow trench and the second shallow trench and extends to cover the hard mask layer;
[0008] Performing a planarization process on the isolation material layer until the top surface of the hard mask layer is exposed to form an initial isolation layer, and there is a height difference on the top surface of the initial isolation layer in the second shallow trench;
[0009] Remove a part of the thickness of the hard mask layer, and the top surface of the remaining hard mask layer is lower than the top surface of the initial isolation layer, and the distance from the highest point of the top surface of the initial isolation layer in the second shallow trench to the top surface of the hard mask layer is greater than the sum of the height difference between the lowest and highest points of the top surface of the initial isolation layer and half of the width of the first shallow trench; and,
[0010] Perform an etch-back on the initial isolation layer, and make the lateral etch rate of the initial isolation layer greater than or equal to the vertical etch rate until the initial isolation layer in the first shallow trench that is higher than the top surface of the hard mask layer is removed to form an isolation layer, wherein the isolation layer in the first shallow trench forms a first shallow trench isolation structure, and the isolation layer in the second shallow trench forms a second shallow trench isolation structure.
[0011] Optionally, in the method for forming the shallow trench isolation structure, the thickness of the hard mask layer is greater than or equal to 850 angstroms.
[0012] Optionally, in the method for forming the shallow trench isolation structure, the material of the hard mask layer includes silicon nitride; the material of the isolation material layer includes silicon oxide.
[0013] Optionally, in the method for forming the shallow trench isolation structure, the process of removing a part of the thickness of the hard mask layer is a first etching process, and the selectivity of the first etching process for the hard mask layer and the isolation material layer is greater than or equal to 30:1.
[0014] Optionally, in the method for forming the shallow trench isolation structure, the process of performing an etch-back on the initial isolation layer is a second etching process, and the etching selectivity of the second etching process for the initial isolation layer and the hard mask layer is greater than or equal to 30:1.
[0015] Optionally, in the method for forming the shallow trench isolation structure, the planarization process is a chemical mechanical polishing process, and the polishing liquid used includes cerium dioxide.
[0016] Optionally, in the method for forming the shallow trench isolation structure, the substrate includes a first region and a second region, the first shallow trench is formed in the first region of the substrate, the second shallow trench is formed in the second region of the substrate, and the depth of the first shallow trench is the same as the depth of the second shallow trench.
[0017] Optionally, in the method for forming the shallow trench isolation structure, after forming the isolation layer, the method for forming the shallow trench isolation structure further includes:
[0018] The hard mask layer is removed by using a dry etching process and / or a wet etching process.
[0019] Optionally, in the method for forming the shallow trench isolation structure, after forming the first shallow trench and the second shallow trench and before forming the isolation material layer, the method for forming the shallow trench isolation structure further includes:
[0020] Performing a re-etching on the hard mask layer; and,
[0021] Forming a liner oxide layer that covers sidewalls and bottom surfaces of the first shallow trench and the second shallow trench.
[0022] Based on the same inventive concept, the present invention further provides a method for forming a semiconductor device, including: forming a first shallow trench isolation structure and a second shallow trench isolation structure by using the method for forming the shallow trench isolation structure as described above.
[0023] In the method for forming the shallow trench isolation structure and the semiconductor device provided by the present invention, the width of the second shallow trench is greater than the width of the first shallow trench, such that the width of the initial isolation layer above the top surface of the hard mask layer in the second shallow trench is greater than the width of the initial isolation layer above the top surface of the hard mask layer in the first shallow trench. When performing a re-etching on the initial isolation layer, since the lateral etching rate of the initial isolation layer is greater than or equal to the longitudinal etching rate, therefore, the initial isolation layer above the top surface of the hard mask layer in the first shallow trench is more easily removed. And since the distance from the highest point of the initial isolation layer in the second shallow trench to the top surface of the hard mask layer is greater than the sum of the height difference between the lowest point and the highest point of the top surface of the initial isolation layer and half of the width of the first shallow trench, thus, after the initial isolation layer above the top surface of the hard mask layer in the first shallow trench is removed, a part of the initial isolation layer above the top surface of the hard mask layer in the second shallow trench remains, thereby avoiding the occurrence of a depression on the top surface of the isolation layer in the second shallow trench with a larger size, and further avoiding the occurrence of a depression on the top surface of the second shallow trench isolation structure. Description of the Drawings
[0024] Figures 1 to 3 is a schematic cross-sectional view of a structure formed in the method for forming a shallow trench isolation structure in the prior art;
[0025] Figure 4 is a schematic flow chart of the method for forming a shallow trench isolation structure provided by an embodiment of the present invention;
[0026] Figures 5 to 12 is a schematic cross-sectional view of a structure formed in the method for forming a shallow trench isolation structure provided by an embodiment of the present invention;
[0027] Among them, the reference numeral descriptions are as follows:
[0028] 10 - Substrate; 10a - First shallow trench; 10b - Second shallow trench; 11 - Hard mask layer; 12 - Isolation layer;
[0029] 100 - Substrate; 101 - Pad oxide layer; 110 - Hard mask layer; 111 - First shallow trench; 112 - Second shallow trench; 120 - Isolation material layer; 120a - Initial isolation layer; 120b - Isolation layer; 130 - First shallow trench isolation structure; 140 - Second shallow trench isolation structure. Detailed implementation manners
[0030] The following further elaborates on the method for forming a shallow trench isolation structure and a semiconductor device proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non - precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.
[0031] Figure 4 is a flowchart showing the method for forming a shallow trench isolation structure provided by an embodiment of the present invention. As Figure 4 shown, an embodiment of the present invention provides a method for forming a shallow trench isolation structure, including:
[0032] Step S1: Provide a substrate, on which a hard mask layer is formed;
[0033] Step S2: Etch the hard mask layer and the substrate in sequence to form a first shallow trench and a second shallow trench, the width of the second shallow trench being greater than the width of the first shallow trench;
[0034] Step S3: Form an isolation material layer, the isolation material layer filling the first shallow trench and the second shallow trench and extending to cover the hard mask layer;
[0035] Step S4: Perform a planarization process on the isolation material layer until the top surface of the hard mask layer is exposed to form an initial isolation layer, the top surface of the initial isolation layer in the second shallow trench having a height difference;
[0036] Step S5: Remove a part of the thickness of the hard mask layer, the top surface of the remaining hard mask layer being lower than the top surface of the initial isolation layer, and the distance from the highest point of the top surface of the initial isolation layer in the second shallow trench to the top surface of the hard mask layer being greater than the sum of the height difference between the lowest and highest points of the top surface of the initial isolation layer and half of the width of the first shallow trench; and,
[0037] Step S6: Perform etch-back on the initial isolation layer, and make the lateral etching rate of the initial isolation layer greater than or equal to the vertical etching rate until the initial isolation layer above the top surface of the hard mask layer in the first shallow trench is removed to form an isolation layer, where the isolation layer in the first shallow trench forms a first shallow trench isolation structure, and the isolation layer in the second shallow trench forms a second shallow trench isolation structure.
[0038] Figures 5 to 12 is a schematic cross-sectional view of the structure formed in the method for forming a shallow trench isolation structure provided by an embodiment of the present invention. The following will be combined with Figures 5 to 12 to describe in more detail the method for forming the shallow trench isolation structure provided by this embodiment.
[0039] Refer to Figure 5 , in step S1, a substrate 100 is provided, and a hard mask layer 110 is formed on the substrate 100. The substrate 100 includes a first region I and a second region II, which are respectively used to form semiconductor devices of different sizes. For example, the first region I can form semiconductor devices with smaller sizes and a larger device density; the second region II can be used to form semiconductor devices with larger sizes and a smaller device density.
[0040] Further, it is necessary to form a first shallow trench isolation structure with a smaller width in the first region I of the substrate 100 and a second shallow trench isolation structure with a larger width in the second region II subsequently.
[0041] In this embodiment, the substrate 100 provides an operation platform for subsequent processes, and can be any substrate well-known to those skilled in the art for carrying semiconductor integrated circuit components, which can be a bare chip or a wafer processed by an epitaxial growth process. The substrate 100 is, for example, a silicon-on-insulator (SOI) substrate, a bulk silicon substrate, a germanium substrate, a germanium-silicon substrate, an indium phosphide (InP) substrate, a gallium arsenide (GaAs) substrate, or a germanium-on-insulator substrate, etc.
[0042] Continue to refer to Figure 5 , before forming the hard mask layer 110, a pad oxide layer 101 can be formed on the surface of the substrate 100 by using a thermal oxidation process, a chemical vapor deposition process, or an atomic layer deposition process, etc., to reduce the etching damage to the substrate 100 during subsequent etching of the substrate 100. Among them, the material of the pad oxide layer 101 can be silicon oxide.
[0043] Then, a hard mask layer 110 with a certain thickness is deposited on the surface of the pad oxide layer 101 by using a chemical vapor deposition process, and the material of the hard mask layer 110 can be silicon nitride.
[0044] In this embodiment, the thickness L2 of the hard mask layer 110 is greater than or equal to 850 angstroms, and can be, for example, 850 angstroms, 900 angstroms, or 1000 angstroms, etc. The thickness of the existing hard mask layer 110 is generally 500 angstroms, while the thickness of the hard mask layer 110 in this embodiment is greater than or equal to 850 angstroms, which can increase the depth of the subsequently formed first shallow trench 111 and second shallow trench 112, thereby increasing the thickness of the subsequently formed isolation layer material layer.
[0045] Reference Figure 6 , in step S2, the hard mask layer 110 and the substrate 100 are etched in sequence to form a first shallow trench 111 and a second shallow trench 112, and the width L5 of the second shallow trench 112 is greater than the width L4 of the first shallow trench 111. The cross-sectional shape of the first shallow trench 111 and the second shallow trench 112 in the vertical direction can be an inverted trapezoid. Specifically, the first shallow trench 111 is formed in the first region I of the substrate 100, and multiple first shallow trenches 111 can be formed in the first region I. The second shallow trench 112 is formed in the second region II of the substrate 100, and multiple second shallow trenches 112 can be formed in the second region II. Figure 6 Only one second shallow trench 112 is taken as an example for illustration.
[0046] Specifically, the method of etching the hard mask layer 110 and the substrate 100 in sequence includes: First, the surface of the hard mask layer 110 can be coated with a photoresist (not shown), and an exposure process and a development process are performed to form a patterned photoresist layer. The patterned photoresist layer has a first pattern located on the first region I and a second pattern located on the second region II, and the width of the second pattern is greater than the width of the first pattern.
[0047] Then, using the patterned photoresist layer as a mask, the hard mask layer 110 is etched to the surface of the substrate 100 by a plasma dry etching process to transfer the pattern of the patterned photoresist layer into the hard mask layer 110, and the substrate 100 is continuously etched to form a first shallow trench 111 and a second shallow trench 112. Further, the density of the first shallow trenches 111 in the first region I is greater than the density of the second shallow trenches 112 in the second region II, that is, the spacing between adjacent first shallow trenches 111 is less than the spacing between adjacent second shallow trenches 112. Among them, the substrate 100 between adjacent first shallow trenches 111 is an active region, and the substrate 100 between adjacent second shallow trenches 112 is an active region.
[0048] After that, as Figure 7As shown, a dry etching process can be used to perform back-etching on the hard mask layer 110, so as to form a step between the sidewall of the hard mask layer 110 and the sidewall of the substrate 100, which is beneficial to the filling of the subsequent isolation material layer 120.
[0049] Next, a liner oxide layer (not shown) is formed, and the liner oxide layer covers the sidewalls and bottom surfaces of the first shallow trench 111 and the second shallow trench 112. The liner oxide layer can be formed by an in-situ steam generation process to improve the adhesion and isolation performance of the subsequent filled isolation material layer 120.
[0050] Reference Figure 8 Referring to
[0051] Next, the isolation material layer 120 is densified. For example, nitrogen ions and carbon ions are implanted and rapid annealing with an annealing time less than 60 s or high-temperature annealing with an annealing temperature greater than 500 °C (such as 900 °C to 1050 °C, etc.) is performed to eliminate the filling defects in the isolation material layer 120, make it denser, and inhibit the diffusion and migration of ions in the active region into the finally formed first shallow trench isolation structure and second shallow trench isolation structure, thereby reducing the leakage current generated between the active region and the shallow trench isolation structure and achieving an isolation structure with higher isolation performance.
[0052] In addition, due to the existence of the first shallow trench 111 and the second shallow trench 112, the top surface of the formed isolation material layer 120 has a pit A. Specifically, the top surface of the isolation material layer 120 on the first shallow trench 111 and the second shallow trench 112 is lower than the top surface of the isolation material layer 120 on the hard mask layer 110.
[0053] Reference Figure 9, perform step S4 to planarize the isolation material layer 120 until the top surface of the hard mask layer 110 is exposed to form an initial isolation layer 120a. The top surface of the initial isolation layer 120a in the second shallow trench 112 has a height difference. Wherein, the highest point of the top surface of the initial isolation layer 120a in the second shallow trench 112 may be flush with the top surface of the initial isolation layer 120a in the first shallow trench 111, or the highest point of the top surface of the initial isolation layer 120a in the second shallow trench 112 may be lower than or higher than the top surface of the initial isolation layer 120a in the first shallow trench 111. Specifically, using the hard mask layer 110 as a mask stop layer, the top surface of the isolation material layer 120 is planarized to the top surface of the hard mask layer 110 by a chemical mechanical polishing process. Wherein, the polishing slurry used in the chemical mechanical polishing process includes cerium dioxide (CeO2), whereby a relatively high polishing rate ratio can be achieved between the isolation material layer 120 and the hard mask layer 110.
[0054] During the chemical mechanical polishing process, for large-sized patterns, the middle part is prone to over-polishing and generating depression defects. The larger the size of the area to be polished, the more likely it is to generate depressions during the chemical mechanical polishing process. When polishing to the top surface of the hard mask layer 110, due to the larger width dimension of the second shallow trench 112, the polishing slurry has a faster polishing rate for the isolation material layer 120 in the second shallow trench 112, and the particle size of the polishing particles is also relatively large. The top surface of the isolation material layer 120 in the second shallow trench 112 has no support and blockage from the hard mask layer 110, and can achieve sufficient contact and collision with the polishing particles. Therefore, after polishing, the initial isolation layer 120a in the second shallow trench 112 has a structure with a convex edge and a concave middle, that is, the top surface of the initial isolation layer 120a in the second shallow trench 112 has a depression, resulting in a height difference on the top surface of the initial isolation layer 120a in the second shallow trench 112.
[0055] The lowest point of the top surface of the initial isolation layer 120a in the second shallow trench 112 is higher than the bottom surface of the hard mask layer 110. Due to the smaller width dimension of the first shallow trench 111, the initial isolation layer 120a in the first shallow trench 111 is not prone to generating depressions after planarization.
[0056] Reference Figure 10, perform step S5 to remove a partial thickness of the hard mask layer 110, and the top surface of the remaining hard mask layer 110 is lower than the top surface of the initial isolation layer 120a, and the distance from the highest point of the initial isolation layer 120a in the second shallow trench 112 to the top surface of the hard mask layer 110 is greater than the height difference between the lowest and highest points of the top surface of the initial isolation layer 120a plus half of the width L4 of the first shallow trench 111. Here, the width L4 of the first shallow trench 111 refers to the width at the top of the first shallow trench 111 (since the shape of the first shallow trench 111 is an inverted trapezoid, the width at the top of the first shallow trench 111 is greater than the width at the bottom). Among them, the thickness of the remaining hard mask layer 110 can be 50 Å to 60 Å to facilitate the subsequent removal of the hard mask layer 110.
[0057] Specifically, the process of removing a partial thickness of the hard mask layer 110 is the first etching process, and the selectivity of the first etching process for the hard mask layer 110 and the isolation material layer 120 is greater than or equal to 30:1. The first etching process includes one or a combination of a dry etching process and a wet etching process. In this embodiment, the first etching process is a wet etching process, and its parameters include: the temperature range is 160 degrees to 165 degrees, and the chemical solution is hot phosphoric acid with a concentration (volume fraction) of 86%. So that the first etching process has a large etching selectivity for the hard mask layer 110, which is beneficial to removing a partial thickness of the hard mask layer 110, while the etching amount of the initial isolation layer 120a is small, reducing the further deepening of the depression on the top surface of the initial isolation layer 120a.
[0058] In addition, after removing a partial thickness of the hard mask layer 110, a part of the initial isolation layer 120a protrudes above the top surface of the remaining hard mask layer 110. The distance from the highest point of the top surface of the initial isolation layer 120a in the second shallow trench 112 to the top surface of the hard mask layer 110 satisfies the following relational expression: L3 > (1 / 2)L4 + D1, where L3 represents the distance from the highest point of the top surface of the initial isolation layer 120a in the second shallow trench to the top surface of the hard mask layer 110, L4 represents the width of the first shallow trench 111, and D1 represents the height difference between the highest and lowest points of the top surface of the initial isolation layer 120a in the second shallow trench 112. In this way, when the initial isolation layer 120a is etched back subsequently, the depression on the top surface of the isolation layer in the second shallow trench 112 can be avoided.
[0059] Reference Figure 11, perform step S6 to perform etch-back on the initial isolation layer 120a, and make the lateral etch rate of the initial isolation layer 120a greater than or equal to the vertical etch rate until the initial isolation layer 120a above the top surface of the hard mask layer 110 in the first shallow trench is removed to form an isolation layer 120b. Among them, the isolation layer 120b in the first shallow trench 111 forms a first shallow trench isolation structure 130, and the isolation layer 120b in the second shallow trench 112 forms a second shallow trench isolation structure 140.
[0060] Preferably, the process of performing etch-back on the initial isolation layer 120a is a second etching process, and the etching selectivity of the second etching process for the initial isolation layer 120a and the hard mask layer 110 is greater than or equal to 30:1. The second etching process includes one or a combination of a dry etching process and a wet etching process.
[0061] In this embodiment, the second etching process is a wet etching process, and its etching solution includes hydrofluoric acid, hydrogen peroxide, and deionized water. Among them, the concentration of the hydrofluoric acid can be 50%, and the concentration of the hydrogen peroxide can be 30% to make the second etching process have a high etching selectivity for the initial isolation layer 120a and the hard mask layer 110.
[0062] When performing etch-back on the initial isolation layer 120a, since the width of the first shallow trench 111 is smaller than the width of the second shallow trench 112, and the lateral etch rate of the initial isolation layer 120a is greater than or equal to the vertical etch rate, therefore, the initial isolation layer 120a above the top surface of the hard mask layer 110 in the first shallow trench is more easily removed. And because the distance from the highest point of the initial isolation layer 120a in the second shallow trench 112 to the top surface of the hard mask layer 110 is greater than the sum of the height difference between the lowest and highest points of the top surface of the initial isolation layer 120a and half of the width of the first shallow trench 111. Thus, after the initial isolation layer 120a above the top surface of the hard mask layer 110 in the first shallow trench 111 is removed, a part of the initial isolation layer 120a above the top surface of the hard mask layer 110 in the second shallow trench 112 remains. This can avoid the top surface of the isolation layer 120b in the second shallow trench with a larger size from being sunken, and further avoid the top surface of the second shallow trench isolation structure 140 from being sunken.
[0063] Specifically, since the etching process etches continuously from the outermost layer of the initial isolation layer 120a towards the inside, and the part of the initial isolation layer 120a in the second shallow trench 112 that is higher than the top surface of the hard mask layer 110 has a structure with a convex edge and a concave middle, therefore, the edge of the part of the initial isolation layer 120a in the second shallow trench 112 that is higher than the top surface of the hard mask layer 110 is etched away first, so that the concave part of the initial isolation layer 120a in the second shallow trench 112 that is higher than the top surface of the hard mask layer 110 forms a protrusion, that is, after the initial isolation layer 120a in the first shallow trench that is higher than the top surface of the hard mask layer 110 is removed, the middle part of the initial isolation layer 120a in the second shallow trench 112 that is higher than the top surface of the hard mask layer 110 is retained, making the top surface of the isolation layer 120b formed in the second shallow trench 112 protrude from the top surface of the hard mask layer 110 (as Figure 12 shown).
[0064] As Figure 12 shown, after forming the isolation layer 120b, the method for forming the shallow trench isolation structure further includes: removing the hard mask layer 110 by using a dry etching process and / or a wet etching process.
[0065] This embodiment also provides a method for forming a semiconductor device. As Figure 12 shown, the first shallow trench isolation structure 130 and the second shallow trench isolation structure 140 are formed by using the method for forming the shallow trench isolation structure described in this embodiment. Among them, the width of the second shallow trench isolation structure 140 is greater than the width of the first shallow trench isolation structure 130, and the depth of the first shallow trench isolation structure 130 is the same as the depth of the second shallow trench isolation structure 140. Since there is no concave defect on the top surface of the second shallow trench isolation structure 140 with a larger width dimension, therefore, an abnormal area is not easily formed on the top surface of the second shallow trench isolation structure 140, improving the performance of the formed device.
[0066] In summary, in the method for forming the shallow trench isolation structure and the semiconductor device provided by the embodiments of the present invention, when the initial isolation layer is re-etched, since the width of the second shallow trench is greater than that of the first shallow trench, and the lateral etching rate of the initial isolation layer is greater than or equal to the vertical etching rate, therefore, the initial isolation layer in the first shallow trench that is higher than the top surface of the hard mask layer is more easily removed. And because the distance from the highest point of the initial isolation layer in the second shallow trench to the top surface of the hard mask layer is greater than the sum of the height difference between the lowest and highest points of the top surface of the initial isolation layer and half of the width of the first shallow trench, thus, after the initial isolation layer in the first shallow trench that is higher than the top surface of the hard mask layer is removed, part of the initial isolation layer in the second shallow trench that is higher than the top surface of the hard mask layer remains, so as to avoid the top surface of the isolation layer in the second shallow trench with a larger size from being sunken, and further avoid the top surface of the second shallow trench isolation structure from being sunken, thereby improving the performance of the device.
[0067] The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention according to the above disclosure shall fall within the protection scope of the claims.
Claims
1. A method for forming a shallow trench isolation structure, characterized in that Comprising: Providing a substrate on which a hard mask layer is formed; Etching the hard mask layer and the substrate in sequence to form a first shallow trench and a second shallow trench, wherein the width of the second shallow trench is greater than that of the first shallow trench; Forming an isolation material layer, which fills the first shallow trench and the second shallow trench and extends to cover the hard mask layer; Performing a planarization process on the isolation material layer until the top surface of the hard mask layer is exposed to form an initial isolation layer, and there is a height difference on the top surface of the initial isolation layer in the second shallow trench; Removing a part of the thickness of the hard mask layer, and the top surface of the remaining hard mask layer is lower than the top surface of the initial isolation layer, and the distance from the highest point on the top surface of the initial isolation layer in the second shallow trench to the top surface of the hard mask layer is greater than the sum of the height difference between the lowest point and the highest point on the top surface of the initial isolation layer and half of the width of the first shallow trench; And, Performing a re-etching process on the initial isolation layer and making the lateral etching rate of the initial isolation layer greater than or equal to the longitudinal etching rate until the initial isolation layer above the top surface of the hard mask layer in the first shallow trench is removed to form an isolation layer, wherein the isolation layer located in the first shallow trench forms a first shallow trench isolation structure, and the isolation layer located in the second shallow trench forms a second shallow trench isolation structure.
2. The method for forming a shallow trench isolation structure according to claim 1, wherein The thickness of the hard mask layer is greater than or equal to 850 angstroms.
3. The method for forming the shallow trench isolation structure according to claim 1, characterized in that, The material of the hard mask layer includes silicon nitride; the material of the isolation material layer includes silicon oxide.
4. The method for forming a shallow trench isolation structure according to claim 1, wherein The process of removing a part of the thickness of the hard mask layer is a first etching process, and the selectivity of the first etching process for the hard mask layer and the isolation material layer is greater than or equal to 30:
1.
5. The method for forming a shallow trench isolation structure according to claim 1, characterized in that The process of performing a re-etching process on the initial isolation layer is a second etching process, and the etching selectivity of the second etching process for the initial isolation layer and the hard mask layer is greater than or equal to 30:
1.
6. The method for forming a shallow trench isolation structure as claimed in claim 1, wherein The planarization process is a chemical mechanical polishing process, and the polishing liquid used includes cerium dioxide.
7. The method for forming a shallow trench isolation structure according to claim 1, wherein, The substrate includes a first region and a second region, the first shallow trench is formed in the first region of the substrate, the second shallow trench is formed in the second region of the substrate, and the depth of the first shallow trench is the same as that of the second shallow trench.
8. The method for forming a shallow trench isolation structure according to claim 1, characterized in that, After forming the isolation layer, the method for forming the shallow trench isolation structure further includes: Removing the hard mask layer by using a dry etching process and / or a wet etching process.
9. The method for forming a shallow trench isolation structure according to claim 1, wherein, After forming the first shallow trench and the second shallow trench and before forming the isolation material layer, the method for forming the shallow trench isolation structure further includes: Performing a re-etching process on the hard mask layer; and, Forming a liner oxide layer, which covers the sidewalls and the bottom surfaces of the first shallow trench and the second shallow trench.
10. A method for forming a semiconductor device, characterized in that, Comprising: Forming a first shallow trench isolation structure and a second shallow trench isolation structure by using the method for forming the shallow trench isolation structure according to any one of claims 1 to 9.