Method for controlling relative height between gate side wall and gate
By etching in the upper and lower parts during the formation of the gate side wall, the sacrificial layer and the external side wall protection are used to achieve independent adjustment of the relative height of the gate side wall and the gate, solving the problem of limited adjustment range in the prior art, and improving the flexibility and accuracy of adjustment.
Patent Information
- Application Number
- CN202510414082.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-03
- Publication Date
- 2025-07-08
AI Technical Summary
In the prior art, the adjustment range of the relative height of the gate side wall and the gate is limited, and the adjustment process has a great impact on other key result parameters, making it difficult to meet the design requirements.
During the formation of the gate side wall, it is divided into upper and lower parts for etching. The sacrificial layer is first deposited as a protective layer, and the relative height is controlled by high selectivity plasma etching, and then the external side wall is deposited as a protection to achieve independent adjustment of the relative height of the gate side wall and the gate.
Under the condition that affects other key result parameters, a large range of adjustments to the relative height of the gate side wall and the gate are achieved, improving the flexibility and accuracy of adjustment.
Smart Images
Figure CN120282528A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of semiconductor manufacturing, and particularly relates to a method for controlling the relative height between a gate sidewall and a gate. Background Art
[0002] In the process of semiconductor manufacturing, especially in relatively advanced manufacturing processes, the sidewall structures on both sides of the gate play a crucial role. They can protect the gate, prevent a large dose of source-drain implantation from being too close to the channel so that source-drain punchthrough occurs, reduce the short-channel effect, effectively improve the reliability and performance of the device, and at the same time can also reduce power consumption and noise. In the gate sidewall etching process, the relative height between the gate sidewall and the gate after the etching process is jointly determined by the sidewall film thickness and the etching process parameters.
[0003] Generally, the gate height is fixed, and the deposited film thickness of the gate sidewall and the etching process parameters need to take into account the final gate sidewall width, the gate sidewall height difference, and the silicon substrate depression at the same time. There is a lack of a method for relatively independently adjusting the result of a certain parameter, and the adjustment range is also limited. Especially for the relative height between the gate sidewall and the gate, when adjusting the relative height, it often has a more obvious impact on the width of the gate sidewall and the silicon substrate depression, and it is difficult to meet the design requirements for all results. Therefore, a method is needed that can adjust the relative height between the gate sidewall and the gate within a large range under the condition of having a small impact on other key result parameters. Summary of the Invention
[0004] The present invention is to solve all or part of the above-mentioned problems in the prior art, and provides a method for controlling the relative height between a gate sidewall and a gate. During the formation of the gate sidewall, etching is carried out in two upper and lower parts, and the position is adjusted according to the required relative height. The gate sidewall layer is divided into two upper and lower parts by controlling the etch-back amount of the sacrificial layer. First, the exposed upper part of the sidewall structure is etched to determine the relative height. Before etching the lower part, an external sidewall is deposited as a protective layer. The external sidewall always protects the upper sidewall during the subsequent sidewall etching process, avoiding the relative height being affected by etching, and realizing a large range of adjustment of the height between the gate and the gate sidewall under the condition of having a small impact on other key result parameters.
[0005] The present invention provides a method for controlling the relative height of a gate sidewall and a gate, comprising the following steps: S1: providing a substrate, on the surface of which a gate structure and a gate sidewall layer covering the upper surface of the substrate and the outer surface of the gate structure are formed; S2: depositing a sacrificial layer outside the gate sidewall layer; S3: performing a back-etching on the sacrificial layer based on the required relative height to expose a part of the gate sidewall layer structure under the sacrificial layer; S4: etching the exposed gate sidewall layer to determine the relative height, obtaining an upper sidewall, the part of the gate sidewall layer covering the outer surface of the gate structure that is not exposed is a lower sidewall, and the part covering the upper surface of the substrate is a bottom sidewall layer; S5: removing the remaining sacrificial layer; S6: depositing an external sidewall on the upper surface of the gate structure and the outer surface of the remaining gate sidewall layer as a protective layer; S7: etching at least part of the external sidewall and the bottom sidewall layer in sequence to obtain a gate sidewall including the upper sidewall and the lower sidewall. During the formation of the gate sidewall, etching is carried out in two upper and lower parts, realizing a large-range adjustment of the height of the gate and the gate sidewall under the condition of having little influence on other key result parameters.
[0006] In step S2, the material used for the sacrificial layer is spin-on carbon, which is used to protect the lower part of the gate sidewall layer in the subsequent etching process.
[0007] In step S3, the back-etching adopts a plasma etching process with a high selectivity. During the etching process, only the sacrificial layer is etched, and basically no influence is exerted on other film layers and the gate structure.
[0008] In step S5, the remaining sacrificial layer is removed by ashing, and only the remaining sacrificial layer is removed without affecting other film layers.
[0009] In step S6, the thickness of the external sidewall is The external sidewall needs to be formed with a certain thickness to protect the gate sidewall layer.
[0010] In step S6, the ratio of the thickness of the external sidewall to that of the gate sidewall layer is 1:4 - 1:8. The existence of a certain thickness ratio between the external sidewall and the gate sidewall layer ensures the normal progress of the process.
[0011] In step S7, first, a plasma etching process is used to remove the external sidewall at the top of the bottom sidewall and the top of the gate. For the etching of the external sidewall, a plasma etching process with a low selectivity or a plasma etching process with a high selectivity can be adopted; then, a plasma etching process with a high selectivity is used to etch the bottom sidewall to complete the etching of the gate sidewall.
[0012] The material used for the gate sidewall layer is silicon nitride, and the material used for the outer sidewall is silicon oxide. During the etching process of the bottom sidewall, the outer sidewall can protect the upper sidewall and the lower sidewall from being affected.
[0013] The remaining outer sidewall after step S7 can be retained or removed in subsequent process flows. Whether to retain the outer sidewall can be flexibly selected according to subsequent requirements.
[0014] The relative height between the gate and the gate sidewall can be controlled within a relatively large range of relative height adjustment intervals.
[0015] Compared with the prior art, the beneficial effects of the present invention mainly include the following: During the formation of the gate sidewall, the gate sidewall layer is etched in two parts, upper and lower. Before etching, a sacrificial layer is first deposited to adjust the position according to the required relative height. The gate sidewall layer is divided into two parts, upper and lower, by controlling the etch-back amount of the sacrificial layer. The exposed upper part of the sidewall is etched first to determine the relative height. Before etching the lower part, an outer sidewall is deposited as a protective layer to keep the relative height between the gate and the gate sidewall unchanged during the etching process. It can achieve a large range of adjustment of the height between the gate and the gate sidewall under the condition of having little impact on other key result parameters. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0017] Figure 1 It is a step schematic diagram of a method for controlling the relative height between a gate sidewall and a gate provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0018] The following description and drawings fully disclose the specific implementation schemes of the present invention, enabling those skilled in the art to practice them. Other implementation schemes may include structural, logical, electrical, process, and other changes. The embodiments only represent possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations can vary. Parts and features of some embodiments can be included in or replaced by parts and features of other embodiments.
[0019] In the current gate sidewall etching process, usually the sidewall is etched once. The setting of the sidewall deposition film thickness and etching process parameters needs to take into account the final sidewall width, sidewall height difference, and substrate silicon depression at the same time. There is a lack of a method to relatively independently adjust the results of a certain parameter, and the adjustment range is also extremely limited. Especially the relative height between the gate sidewall and the gate, the process adjustment that affects it usually has a greater impact on other result parameters.
[0020] This embodiment provides a method for controlling the relative height between the gate sidewall and the gate, as Figure 1 shown, including the following steps:
[0021] S1: Provide a substrate 1, on the surface of the substrate 1, a gate structure 2 and a gate sidewall layer 3 covering the upper surface of the substrate 1 and the outer surface of the gate structure 2 are formed; in this embodiment, the gate sidewall layer 3 is silicon nitride and is deposited by CVD (chemical vapor deposition) process.
[0022] S2: Deposit a sacrificial layer 4 outside the gate sidewall layer 3; in this embodiment, the sacrificial layer 4 used is spin-on carbon (SOC) to protect the lower gate sidewall layer 3 during the subsequent etching of the upper part of the sidewall.
[0023] S3: Back-etch the sacrificial layer 4 based on the required relative height to expose a part of the gate sidewall layer 3 structure under the sacrificial layer 4; the back-etching of the sacrificial layer 4 uses high-selectivity plasma etching, and according to the required relative height, the etching amount of the sacrificial layer 4 can be accurately controlled by controlling the etching time.
[0024] S4: Etch the exposed gate sidewall layer 3 to determine the relative height and obtain the upper sidewall 31; in the unexposed gate sidewall layer 3, the part covering the outer surface of the gate structure 2 is the lower sidewall 32, and the part covering the upper surface of the substrate 1 is the bottom sidewall layer 33; the relative height between the gate structure 2 and the gate sidewall can be controlled within During the etching process, the lower sidewall 32 and the bottom sidewall layer 33 are protected by the sacrificial layer 4 and are not affected by the etching of the upper sidewall 31;
[0025] S5: Remove the remaining sacrificial layer 4. After the upper sidewall etching is completed, the remaining sacrificial layer 4 is removed by ashing. The ashing process only removes the sacrificial layer 4 without affecting other film layers.
[0026] S6: Deposit an external sidewall 5 on the outer surfaces of the gate structure 2 and the remaining gate sidewall layer 3 as a protective layer; in this embodiment, the external sidewall 5 is silicon oxide and can be formed by atomic layer deposition (ALD) or other methods. The external sidewall 5 needs to be formed with an appropriate thickness to protect the gate sidewall layer 3, and the thickness of the external sidewall 5 is in The ratio to the thickness of the gate sidewall layer 3 is 1:4 - 1:8.
[0027] S7: Etch the outer sidewall 5 and the bottom sidewall layer 33 in sequence to complete the etching of the gate sidewall 6. First, the outer sidewall 5 is etched, and the outer sidewall 5 on the bottom sidewall layer 33 and the top 2 of the gate structure is removed by a plasma etching process. During the etching process, the outer sidewall 5 outside the upper sidewall 31 will not be completely consumed due to its morphological growth, and is used to protect the upper sidewall 31 and maintain a relative height. At the same time, the outer sidewall 5 also protects the lower sidewall 32 from being affected by the etching. The etching of the outer sidewall 5 can adopt a low-selectivity plasma etching process or a high-selectivity plasma etching process. In this embodiment, a low-selectivity plasma etching process is adopted. Then, the bottom sidewall layer 33 is etched by a plasma etching process, and its silicon nitride has a relatively high selectivity to silicon oxide. Therefore, the silicon nitride layer of the bottom sidewall layer 33 will be etched away, and the remaining part will not be affected in morphology due to the protection of the silicon oxide of the outer sidewall 5. The relative height between the gate sidewall 6 and the gate structure 2 can be precisely controlled by the back etching amount during the previous step of etching the upper sidewall 31, and can be protected during the subsequent completion of the entire sidewall etching process, thereby achieving a relatively controllable height within a larger range.
[0028] After the gate sidewall etching is completed, the remaining silicon oxide on the outer sidewall 5 after step S7 can be removed according to the subsequent process requirements. If it needs to be removed, it can be removed immediately using a wet etching method containing diluted hydrofluoric acid (DHF), or it can be removed together in the subsequent process flow; if it is compatible with the subsequent process design, it can also be retained.
[0029] The above is a multi-step process of the present invention, including specific implementations of S1 to S7. It is worth noting that steps S3 to S5 can be completed in one etching process chamber at one time, or another method can be adopted, that is, S3 and S4 are completed in one chamber, and S5 is performed in another chamber. Both methods can effectively achieve the purpose of the present invention and can be flexibly selected according to actual production conditions.
[0030] It should be understood that some commonly used English nouns or letters used in this application for the sake of clarity are only used for exemplary references rather than restrictive interpretations or specific usages, and the protection scope of this application should not be limited by their possible Chinese translations or specific letters. It should also be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.
Claims
1. A method for controlling the relative height between a gate sidewall and a gate, characterized in that It includes the following steps: S1: Provide a substrate (1), on the surface of which a gate structure (2) is formed and a gate sidewall layer (3) covering the upper surface of the substrate (1) and the outer surface of the gate structure (2) is formed; S2: Deposit a sacrificial layer (4) outside the gate sidewall layer (3); S3: Perform etch-back on the sacrificial layer (4) based on the required relative height to expose part of the gate sidewall layer (3) structure; S4: Etch the exposed gate sidewall layer (3) to determine the relative height and obtain an upper sidewall (31); in the unexposed gate sidewall layer (3), the part covering the outer surface of the gate structure (2) is a lower sidewall (32), and the part covering the upper surface of the substrate (1) is a bottom sidewall layer (33); S5: Remove the remaining sacrificial layer (4); S6: Deposit an external sidewall (5) on the outer surfaces of the gate structure (2) and the remaining gate sidewall layer (3) as a protective layer; S7: Etch at least part of the external sidewall (5) and the bottom sidewall layer (33) in sequence to obtain a gate sidewall (6) including the upper sidewall (31) and the lower sidewall (32).
2. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, wherein In step S2, the sacrificial layer (4) is made of spin-on carbon.
3. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, characterized in that, In step S3, the etch-back uses a high-selectivity plasma etching process.
4. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, wherein In step S5, the remaining sacrificial layer (4) is removed by ashing.
5. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, wherein In step S6, the thickness of the deposited outer sidewall (5) is 6. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, wherein The ratio of the thickness of the external sidewall (5) to that of the gate sidewall layer (3) is 1:4 - 1:
8.
7. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, wherein In step S7, first, use a plasma etching process to remove the external sidewall (5) on the top of the bottom sidewall layer (33) and the top of the gate structure (2); Then, use a high-selectivity plasma etching process to remove the bottom sidewall (33).
8. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, characterized in that, The gate sidewall layer (3) is made of silicon nitride, and the external sidewall (5) is made of silicon oxide.
9. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, wherein The remaining external sidewall (5) after step S7 can be retained or removed in subsequent process flows.
10. The method for controlling the relative height between the control gate sidewall and the gate according to claim 1, characterized in that, In step S4, the relative height of the gate structure (2) and the gate sidewall (6) can be controlled within