Method of forming a semiconductor structure
Through a one-step etching process and gas selection, the problems of small etching process window and poor structural morphology in semiconductor device preparation are solved, better structural morphology and mask integrity are achieved, and the process flow is simplified.
Patent Information
- Application Number
- CN202211123380.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-15
- Publication Date
- 2025-10-21
- Estimated Expiration
- 2042-09-15
AI Technical Summary
In the existing semiconductor device manufacturing process, the etching process window of the photolithography process is small, and the structural morphology after etching is poor. Especially in the process of 90 nanometers and below, the etching process of multiple dielectric layers or mask layers leads to serious photoresist loss, affecting device performance.
A one-step etching process is adopted. By selecting a suitable etching gas ratio range, the etching rate of the initial mask structure is close to that of the initial first material layer. A combination of main etching gas and protective gas is used to achieve simultaneous etching of multi-layer structures, avoid gas replacement, reduce photolithography pattern layer loss, and form a good structural morphology.
The etching process window is improved, the integrity of the mask structure is protected, the process flow is simplified, the quality of the structural morphology after etching is improved, and the loss of the photolithography pattern layer is reduced.
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Figure CN115483090B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for forming a semiconductor structure. Background Art
[0002] With the advancement of semiconductor technology, the size of semiconductor devices continues to decrease. During the semiconductor device fabrication process, photolithography plays a crucial role in determining device quality. Especially in processes of 90 nanometers and below, where the feature sizes of semiconductor structures are very small, high-quality photolithography processes are crucial for improving the process window for device fabrication and enhancing device performance.
[0003] Currently, the fabrication process of some semiconductor devices often requires the use of photolithography to etch multiple dielectric layers or mask layers composed of different materials. In existing technologies, different etching processes are typically used to sequentially etch dielectric layers or mask layers of different materials. However, existing etching processes have a small window, resulting in poor structural morphology after etching. Summary of the Invention
[0004] The technical problem solved by the present invention is to provide a method for forming a semiconductor structure, which improves the integrity of the photolithography pattern layer in the etching process, improves the etching process window and the structural morphology after etching is completed.
[0005] In order to solve the above technical problems, the technical solution of the present invention provides a method for forming a semiconductor structure, comprising: providing a substrate; forming an initial structure on the substrate, the initial structure comprising an initial first material layer and an initial mask structure located on the substrate, the material of the initial first material layer comprising polycrystalline silicon; forming a photolithography pattern layer on the initial structure; using the photolithography pattern layer as a mask, etching the initial first material layer and the initial mask structure through a one-step etching process to form an initial opening in the initial structure, the ratio of the etching rate of the initial mask structure to the etching rate of the initial first material layer in the one-step etching process is in the range of 1 to 1.2, so that the initial first material layer and the initial mask structure become a first material layer and a mask structure, and the initial opening exposes the substrate surface.
[0006] Optionally, the carbon-to-fluorine ratio of the gas used in the one-step etching process is in the range of 0.7 to 1.3.
[0007] Optionally, the gas used in the one-step etching process includes a main etching gas and a protective gas, the main etching gas includes one or more combinations of SF6, CF4, and NF3, and the protective gas includes one or more combinations of CH2F2, CHF3, CH3F, C4F6, C4F8, and C5F8.
[0008] Optionally, the main etching gas is SF6, and the protective gas is CH2F2.
[0009] Optionally, the parameters of the one-step etching process include: a gas flow rate of SF6 of 10 sccm to 30 sccm; a gas flow rate of CH2F2 of 15 sccm to 45 sccm.
[0010] Optionally, the ratio of the etching rate of the protective gas for the initial mask structure to the etching rate of the protective gas for the photolithography pattern layer is in the range of 1:1 to 2:1; the ratio of the etching rate of the protective gas for the initial first material layer to the etching rate of the protective gas for the photolithography pattern layer is in the range of 1:1 to 2:1.
[0011] Optionally, the initial mask structure includes an initial first mask layer located on the initial first material layer, and an initial second mask layer located on the initial first mask layer.
[0012] Optionally, the material of the initial first mask layer includes silicon nitride; and the material of the initial second mask layer includes silicon oxide.
[0013] Optionally, the initial structure further includes: an initial first oxide layer located between the substrate and the initial first material layer.
[0014] Optionally, the one-step etching process also etches the initial first oxide layer simultaneously.
[0015] Optionally, a bottom surface of the initial opening is lower than a top surface of the substrate.
[0016] Optionally, the distance between the bottom surface of the initial opening and the top surface of the substrate is 150 angstroms to 250 angstroms.
[0017] Optionally, the initial structure further includes: an initial anti-reflection layer located on the initial mask structure.
[0018] Optionally, before etching the initial first material layer and the initial mask structure, the method further includes: etching the initial anti-reflection layer using the photolithography pattern layer as a mask to form an anti-reflection layer.
[0019] Optionally, after forming the initial opening, the method further includes: etching the substrate using the mask structure as a mask to form a deep trench.
[0020] Optionally, the thickness of the initial mask structure ranges from 600 angstroms to 1200 angstroms.
[0021] Optionally, the thickness of the initial first material layer ranges from 200 angstroms to 400 angstroms.
[0022] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:
[0023] In the method for forming a semiconductor structure provided by the technical solution of the present invention, compared to the conventional etching process in which different processes are used sequentially to etch structures of different materials, the technical solution of the present invention changes the etching process flow and adopts a one-step etching process to etch the initial first material layer and the initial mask structure. The one-step etching process can reduce the loss of the photoresist pattern layer during the etching process, thereby improving the integrity of the photoresist pattern layer during the etching process, thereby protecting the integrity of the mask structure, and facilitating the improvement of the subsequent process window and the resulting structural morphology. In the one-step etching process, by selecting a suitable etching gas, the ratio of its etching rate for the initial mask structure to the etching rate of the initial first material layer is in the range of 1 to 1.2. Since the two different materials have similar etching rates, the initial first material layer and the initial mask structure can be etched through without changing the gas. Compared to the conventional process flow in which different gases are used to etch sequentially, the one-step etching process in the embodiment of the present invention avoids the increase in etching time due to the change of etching gas, reduces the loss of the photoresist pattern layer, and thus forms a first material layer and mask structure with good morphology after the one-step etching process is completed.
[0024] Furthermore, the gas used in the one-step etching process includes a main etching gas and a protective gas, and the etching rate of the protective gas for the initial mask structure and the etching rate of the protective gas for the photolithography pattern layer are in the range of 1:1 to 2:1; the etching rate of the protective gas for the initial first material layer and the etching rate of the protective gas for the photolithography pattern layer are in the range of 1:1 to 2:1. Therefore, compared with the etching gas in the traditional etching process, the protective gas in the embodiment of the present invention increases the etching selectivity of the initial mask structure and the photolithography pattern layer, as well as the etching selectivity of the initial first material layer and the photolithography pattern layer, thereby reducing the loss of the photolithography pattern layer in the one-step etching process.
[0025] Furthermore, the one-step etching process can simultaneously etch the initial mask structure, the initial first material layer, the initial first oxide layer and the substrate, and the bottom surface of the initial opening formed is lower than the top surface of the substrate. Therefore, the substrate is exposed after the one-step etching process is completed, thereby eliminating the additional step of opening the initial first oxide layer and simplifying the process. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figures 1 to 6 It is a schematic cross-sectional structural diagram of the formation process of the semiconductor structure according to an embodiment of the present invention. DETAILED DESCRIPTION
[0027] As described in the background technology, in the current preparation process of some semiconductor devices, due to the limitation of small-size structure, the photoresist used in the etching process is usually thinner. The thinner photoresist is easily severely damaged during the multiple etching processes of multiple dielectric layers or mask layers, resulting in incomplete etching protection, a smaller process window, and poor structural morphology after etching.
[0028] Specifically, in an embodiment of the formation process of a deep trench structure, it is usually necessary to use a photolithography process to etch multiple dielectric layers or mask layers composed of different materials. Common dielectric layer materials include polysilicon, silicon oxide, etc., and common mask layer materials include silicon nitride, silicon oxide, etc. In the prior art, different etching processes are usually used to etch dielectric layers or mask layers of different materials in sequence. The etching gases used in each etching process step are different. Therefore, the etching gas needs to be replaced in each step, resulting in a longer overall etching process time. However, due to the limitation of the small size structure, the photoresist used in the etching process is usually thinner, and the thinner photoresist is easily severely damaged during multiple etching processes over a longer time, resulting in incomplete etching protection and incomplete mask layer morphology, which in turn makes the process window smaller and the deep trench structure after etching difficult to meet the design expectations.
[0029] In order to solve the above technical problems, the technical solution of the present invention provides a method for forming a semiconductor structure, which adopts a one-step etching process to etch the initial first material layer and the initial mask structure. The etching rate of the initial mask structure and the etching rate of the initial first material layer of the one-step etching process are in the range of 1 to 1.2. Since the two different materials have similar etching rates, the initial first material layer and the initial mask structure can be etched through without changing the gas, thereby reducing the loss of the photolithography pattern layer during the etching process, and then protecting the integrity of the formed mask structure, which is conducive to improving the subsequent process window and structural morphology.
[0030] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.
[0031] Figures 1 to 6 It is a schematic cross-sectional structural diagram of the formation process of the semiconductor structure according to an embodiment of the present invention.
[0032] Please refer to Figure 1 , providing a substrate 100.
[0033] The material of the substrate 100 includes silicon, silicon germanium, silicon carbide, silicon on insulator (SOI), germanium on insulator (GOI), etc. Specifically, in this embodiment, the material of the substrate 100 is silicon.
[0034] Please refer to Figure 2An initial structure 106 is formed on the substrate 100. The initial structure 106 includes an initial first oxide layer 101 on the substrate 100, an initial first material layer 102 on the initial first oxide layer 101, and an initial mask structure 105 on the initial first material layer 102. The material of the initial first material layer 102 includes polysilicon.
[0035] In this embodiment, the initial mask structure 105 provides raw materials for subsequently formed mask structures.
[0036] In this embodiment, the initial mask structure 105 includes an initial first mask layer 103 located on the initial first material layer 102 , and an initial second mask layer 104 located on the initial first mask layer 103 .
[0037] In this embodiment, the material of the initial first mask layer 103 includes silicon nitride; the material of the initial second mask layer 104 includes silicon oxide.
[0038] In this embodiment, the material of the initial first oxide layer 101 includes silicon oxide.
[0039] In this embodiment, the initial first oxide layer 101 and the initial first material layer 102 are used as raw materials for subsequent transistor structure formation.
[0040] The material of the initial first material layer 102 includes polysilicon, which is used to form a floating gate structure or other gate structures. The initial first oxide layer 101 is used to form a gate oxide layer.
[0041] In this embodiment, the thickness of the initial first material layer 102 ranges from 200 angstroms to 400 angstroms.
[0042] In this embodiment, the thickness of the initial mask structure 105 ranges from 600 angstroms to 1200 angstroms. Specifically, the thickness of the initial first mask layer 103 ranges from 400 angstroms to 800 angstroms, and the thickness of the initial second mask layer 104 ranges from 200 angstroms to 500 angstroms.
[0043] In this embodiment, the thickness of the initial first oxide layer 101 ranges from 50 angstroms to 150 angstroms.
[0044] Therefore, the initial structure 106 has an overall thickness ranging from 1000 angstroms to 2000 angstroms, which is relatively thick. In addition, the initial structure 106 is made of multiple materials, including silicon oxide, silicon nitride, and polysilicon.
[0045] Please refer to Figure 3, forming an initial anti-reflection layer 121 on the initial mask structure 105 ; and forming a photolithography pattern layer 122 on the initial anti-reflection layer 121 .
[0046] In this embodiment, the material of the photolithography pattern layer 122 is photoresist.
[0047] In this embodiment, the photolithographic pattern layer 122 has a pattern opening (not shown), which defines the pattern of the deep trench subsequently formed in the substrate 100. Specifically, the width of the pattern opening is 0.1 micron to 0.2 micron, and the width refers to the size of the pattern opening in a direction parallel to the surface of the substrate 100.
[0048] In this embodiment, the presence of the initial anti-reflection layer 121 makes the morphology and structure of the photolithography pattern layer 122 more uniform, which is beneficial to improving the window of the subsequent etching process.
[0049] In this embodiment, the thickness of the initial anti-reflection layer 121 ranges from 800 angstroms to 1200 angstroms.
[0050] In this embodiment, the thickness of the photolithography pattern layer 122 ranges from 2500 angstroms to 3000 angstroms.
[0051] Please refer to Figure 4 , using the photolithography pattern layer 122 as a mask, etching the initial anti-reflection layer 121 to form an anti-reflection layer 131.
[0052] In this embodiment, the anti-reflection layer 131 exposes a portion of the surface of the initial mask structure 105 , thereby enabling a subsequent process of etching the initial structure 106 to proceed better.
[0053] In this embodiment, the process of etching the initial anti-reflection layer 121 includes a dry etching process or a wet etching process.
[0054] Please refer to Figure 5 , using the photolithography pattern layer 122 as a mask, the initial mask structure 105, the initial first material layer 102 and the initial first oxide layer 101 are etched through a one-step etching process to form an initial opening 140 in the initial structure 106. The ratio of the etching rate of the initial mask structure 105 to the etching rate of the initial first material layer 102 in the one-step etching process is in the range of 1 to 1.2, so that the initial first material layer 102, the initial mask structure 105 and the initial first oxide layer 101 become the first material layer 112, the mask structure 115 and the first oxide layer 111, and the initial opening 140 exposes the surface of the substrate 100.
[0055] In this embodiment, the carbon-to-fluorine ratio of the gas used in the one-step etching process is in the range of 0.7 to 1.3.
[0056] In this embodiment, by selecting a suitable etching gas, the carbon-fluorine ratio of the etching gas is controlled within a range of 0.7 to 1.3, thereby adjusting the etching selectivity of the etching gas for each different material layer in the initial structure 106, so that the etching rates of the etching gas for different material layers in the initial structure 106 are relatively close. Therefore, during the etching process, the initial mask structure 105, the initial first material layer 102, and the initial first oxide layer 101 can be etched through without changing the gas until the substrate 100 is exposed. Compared with the process flow of the traditional process of etching different material layers in sequence using different gases, the one-step etching process in the embodiment of the present invention avoids the increase in etching time due to the replacement of etching gas, reduces the loss of the photolithography pattern layer 122, and thus forms a first material layer 112, a mask structure 115, and a first oxide layer 111 with good morphology after the one-step etching process is completed, thereby improving the integrity of the mask structure 115, so that the deep trench formed by the subsequent etching of the substrate 100 has a better structural morphology.
[0057] Specifically, the ratio of the etching rate of the initial mask structure 105 to the etching rate of the initial first material layer 102 in the one-step etching process is in the range of 1 to 1.2; the ratio of the etching rate of the initial first material layer 102 to the etching rate of the initial first oxide layer 101 is in the range of 1 to 1.2; the ratio of the etching rate of the initial first oxide layer 101 to the etching rate of the substrate 100 is in the range of 1 to 1.2.
[0058] In this embodiment, the gas used in the one-step etching process includes a main etching gas and a protective gas, wherein the main etching gas is used to open the initial structure 106 to form an initial opening 140; the protective gas is used to protect the sidewall morphology of the initial opening 140, while increasing the etching selectivity of the etching gas for the initial structure 106 and the photolithography pattern layer 122.
[0059] In this embodiment, the ratio of the protective gas etching rate for the initial mask structure 105 to the protective gas etching rate for the photoresist pattern layer 122 is in the range of 1:1 to 2:1; and the ratio of the protective gas etching rate for the initial first material layer 102 to the protective gas etching rate for the photoresist pattern layer 122 is in the range of 1:1 to 2:1. Therefore, compared to the etching gas used to etch polysilicon in traditional etching processes, the protective gas in this embodiment of the present invention increases the etching selectivity between the initial mask structure 105 and the photoresist pattern layer 122, as well as the etching selectivity between the initial first material layer 102 and the photoresist pattern layer 122, thereby reducing the loss of the photoresist pattern layer 122 in the one-step etching process.
[0060] Specifically, in this embodiment, the main etching gas is SF6, and the protective gas is CH2F2.
[0061] In other embodiments, the main etching gas also includes one or more combinations of SF6, CF4, and NF3, and the protective gas also includes one or more combinations of CH2F2, CHF3, CH3F, C4F6, C4F8, and C5F8. Therefore, by selecting one or more combinations from the above-mentioned main etching gases and one or more combinations from the above-mentioned protective gases, the carbon-fluorine ratio in the etching gas composed of the main etching gas and the protective gas can be controlled within 0.7 to 1.3, thereby adjusting the etching selectivity of the etching gas for different material layers in the initial structure 106, so that the etching rates of the etching gas for different material layers in the initial structure 106 are relatively close, thereby realizing a one-step etching process.
[0062] In this embodiment, the parameters of the one-step etching process include: the SF6 gas flow rate is 10 sccm to 30 sccm; the CH2F2 gas flow rate is 15 sccm to 45 sccm.
[0063] In this embodiment, the bottom surface of the initial opening 140 is lower than the top surface of the substrate 100 .
[0064] Specifically, the etching rate of the etching gas for the initial first oxide layer 101 is similar to the etching rate of the etching gas for the substrate 100. Therefore, during the one-step etching process, after etching the initial first oxide layer 101, the substrate 100 can be directly etched to open it. Since the one-step etching process can simultaneously etch the initial mask structure 105, the initial first material layer 102, the initial first oxide layer 101, and the substrate 100, the substrate 100 is exposed after the one-step etching process is completed. This eliminates the need to additionally etch the initial first oxide layer 101 to expose the substrate 100 after forming the initial opening 140 in the traditional process, thereby simplifying the process.
[0065] In this embodiment, the distance between the bottom surface of the initial opening 140 and the top surface of the substrate 100 is 150 angstroms to 250 angstroms.
[0066] In addition, after forming the initial opening 140 , there is no need to remove the photoresist pattern layer 122 , thereby avoiding oxidation of the surface of the substrate 100 during the process of removing the photoresist pattern layer 122 and avoiding an additional step of etching the oxide layer.
[0067] Please refer to Figure 6 , using the mask structure 115 as a mask, the substrate 100 at the bottom of the initial opening 140 is etched to form a deep trench 141 .
[0068] In this embodiment, since a one-step etching process is used to etch the initial structure 106, the loss of the photolithography pattern layer 122 during the etching process is reduced, thereby improving the integrity of the photolithography pattern layer 122 during the etching process. Therefore, after the initial opening 140 is formed, the integrity of the mask structure 115 is better, which is beneficial to improving the process window for forming the deep trench 141 and the structural morphology of the deep trench 141.
[0069] In this embodiment, the depth of the deep trench 141 ranges from 1500 angstroms to 2000 angstroms, and the angle between the sidewall of the deep trench 141 and the surface of the substrate 100 ranges from 80 degrees to 90 degrees. This structural morphology meets the morphology requirements for deep trench structures in existing processes.
[0070] In this embodiment, the process of etching the substrate 100 to form the deep trench 141 includes a dry etching process, and the etching gas used in the dry etching process includes chlorine gas.
[0071] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.
Claims
1. A method for forming a semiconductor structure, characterized in that: include: providing a substrate; forming an initial structure on the substrate, the initial structure comprising an initial first material layer and an initial mask structure located on the substrate, wherein the material of the initial first material layer comprises polysilicon; forming a photolithographic pattern layer on the initial structure; Using the photolithography pattern layer as a mask, etching the initial first material layer and the initial mask structure through a one-step etching process to form an initial opening in the initial structure, wherein the ratio of the etching rate of the initial mask structure to the etching rate of the initial first material layer in the one-step etching process is in a range of 1 to 1.2, so that the initial first material layer and the initial mask structure become a first material layer and a mask structure, and the initial opening exposes the substrate surface; The initial structure further includes: an initial first oxide layer located between the substrate and the initial first material layer; the one-step etching process also simultaneously etches the initial first oxide layer; the etching rate of the etching gas for the initial first oxide layer is similar to the etching rate of the etching gas for the substrate; the bottom surface of the initial opening is lower than the top surface of the substrate; the material of the initial first oxide layer is silicon oxide; The initial mask structure includes an initial first mask layer located on a top surface of the initial first material layer, and an initial second mask layer located on a top surface of the initial first mask layer; the material of the initial first mask layer includes silicon nitride; the material of the initial second mask layer includes silicon oxide; The carbon-fluorine ratio of the gas used in the one-step etching process is in the range of 0.7 to 1.3; the main etching gas is SF6; and the protective gas is CH2F2.
2. The method for forming a semiconductor structure according to claim 1, wherein: The parameters of the one-step etching process include: the SF6 gas flow rate is 10 sccm to 30 sccm; the CH2F2 gas flow rate is 15 sccm to 45 sccm.
3. The method for forming a semiconductor structure according to claim 1, wherein: The ratio of the etching rate of the protective gas for the initial mask structure to the etching rate of the protective gas for the photolithography pattern layer is in the range of 1:1~2:1; the ratio of the etching rate of the protective gas for the initial first material layer to the etching rate of the protective gas for the photolithography pattern layer is in the range of 1:1~2:
1.
4. The method for forming a semiconductor structure according to claim 1, wherein: The distance between the bottom surface of the initial opening and the top surface of the substrate is 150 angstroms to 250 angstroms.
5. The method for forming a semiconductor structure according to claim 1, wherein: The initial structure further includes: an initial anti-reflection layer located on the initial mask structure.
6. The method for forming a semiconductor structure according to claim 5, wherein: Before etching the initial first material layer and the initial mask structure, the method further includes: etching the initial anti-reflection layer using the photolithography pattern layer as a mask to form an anti-reflection layer.
7. The method for forming a semiconductor structure according to claim 1, wherein: After forming the initial opening, the method further includes: etching the substrate using the mask structure as a mask to form a deep trench.
8. The method for forming a semiconductor structure according to claim 1, wherein: The thickness of the initial mask structure ranges from 600 angstroms to 1200 angstroms.
9. The method for forming a semiconductor structure according to claim 1, wherein: The thickness of the initial first material layer ranges from 200 angstroms to 400 angstroms.
Citation Information
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