A method for reducing loss of critical dimension of polysilicon caused by photoresist rework

Abstract

The application discloses a method for reducing the loss of the key size of polycrystalline silicon caused by photoresist rework, which comprises the following steps: S1, providing a semiconductor device for polycrystalline silicon LEC etching, and the process immediately before polycrystalline silicon film etching has been completed; S2, performing polymer deposition; S3, performing photoresist rework and polycrystalline silicon film etching, and obtaining a device with a polycrystalline silicon key size meeting the process control standard. The application can effectively improve the problem of the reduction of the key size of polycrystalline silicon, improve the product yield and reduce the production cost by increasing the key size of the hard mask through polymer deposition on the semiconductor device immediately before the process of polycrystalline silicon film etching has been completed without changing the pattern of the polycrystalline silicon film.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for reducing the loss of critical dimensions in polycrystalline silicon caused by photolithography and photoresist rework. Background Technology

[0002] Driven by Moore's Law, semiconductor process dimensions are shrinking, making in-line control increasingly stringent. At the 28nm technology node, polysilicon etching is performed in two stages: polysilicon hard mask etching and polysilicon LEC (Litho Edgecut) etching. As is well known in the art, after the first polysilicon hard mask etching is completed, the linewidth of the polysilicon is determined; the second polysilicon LEC etching inherits the critical dimension (CD) of the polysilicon hard mask and continues etching downwards.

[0003] However, when Q-time timeouts occur during polysilicon LEC etching, requiring photolithography and photoresist rework, the rework process conditions, such as dry stripping and wet cleaning, inevitably reduce the critical dimensions of the polysilicon hard mask to some extent. It's easy to understand that during rework, the sidewalls of the oxide / silicon nitride layer serving as the hard mask are first bombarded by plasma during dry stripping, causing some linewidth loss; then, wet cleaning causes further linewidth loss. Therefore, in the case of photolithography and photoresist rework, the final polysilicon critical dimension after LEC etching will be smaller, with an actual impact of approximately 1nm and an online measurement fluctuation of about 3 sigma, directly causing yield loss.

[0004] The search for a method that achieves high process integration, ensures that the final critical size loss of polysilicon after LEC etching meets the process control range during photolithography and photoresist rework, and significantly improves product yield has become one of the technical problems that urgently need to be solved by those skilled in the art.

[0005] Therefore, in view of the problems existing in the prior art, the designer of this case, based on years of experience in this industry, actively researched and improved the technology, and thus came up with the present invention, a method to reduce the loss of critical dimensions of polysilicon caused by photolithography and photoresist rework. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies, such as the reduction in critical dimensions of polysilicon after LEC etching in traditional photolithography and photoresist rework, which results in a decrease in the final polysilicon critical dimension by approximately 1 nm and a fluctuation of about 3 sigma in online measurement, directly causing yield loss. This invention provides a method to reduce the loss of critical dimensions of polysilicon caused by photolithography and photoresist rework.

[0007] To achieve the objective of this invention, this invention provides a method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework includes:

[0008] Step S1: Provide a semiconductor device for polysilicon LEC etching, and the preceding process for polysilicon thin film etching of the semiconductor device has been completed;

[0009] Step S2: Perform polymer deposition on the semiconductor device that has completed the immediate process of polysilicon thin film etching;

[0010] Step S3: Perform photolithography and photoresist rework, and perform polysilicon thin film etching to obtain a polysilicon device with critical dimensions that meet process control standards.

[0011] Optionally, the preceding process for etching the polycrystalline silicon thin film is a photoresist stripping process.

[0012] Optionally, prior to the photoresist stripping process, which is an immediate preceding process to the polysilicon thin film etching, the process may include photoresist removal, silicon-containing anti-reflective coating and chip opening on the system, and hard mask opening.

[0013] Optionally, the polymer is a carbon- or hydrogen-containing polymer.

[0014] Optionally, the polymer is deposited on a CH4 background.

[0015] Optionally, the polymer is deposited on the sidewalls and top of the hard mask.

[0016] Optionally, the thickness of the polymer deposited on the sidewalls of the hard mask is 0.4 to 0.6 nm.

[0017] Optionally, the thickness of the polymer deposited on the sidewalls of the hard mask is 0.5 nm.

[0018] Optionally, after obtaining a polysilicon device with critical dimensions that meet process control standards by reducing the loss of critical dimensions of polysilicon caused by photolithography and photoresist rework using the method of the present invention, the subsequent process steps include breakdown, main etching, soft landing, soft landing over-etching, and overall over-etching.

[0019] Alternatively, critical dimensional variations in LEC head-to-head can be adjusted by removing photoresist undercoat during polysilicon LEC etching.

[0020] In summary, the method of the present invention for reducing the loss of critical dimensions of polysilicon caused by photolithography and photoresist rework involves polymer deposition on a semiconductor device that has completed the immediate preceding process of polysilicon thin film etching. This effectively increases the critical dimensions of the hard mask before the polysilicon thin film etching, without changing the pattern of the polysilicon thin film. This significantly improves the problem of reduced critical dimensions of polysilicon caused by photolithography and photoresist rework, increases product yield, and reduces production costs. Attached Figure Description

[0021] Figure 1 The diagram shows a flowchart of the method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework according to the present invention.

[0022] Figure 2 The diagram shown is a three-dimensional structural schematic of a semiconductor device using the method of reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework according to the present invention.

[0023] Figures 3-6 The diagram shows a phased structure of a semiconductor device using the method of reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework according to the present invention.

[0024] Figure 7 The diagram shows the changes in critical optical dimensions of polycrystalline silicon thin films caused by rework of traditional photolithography and photoresist.

[0025] Figure 8 The diagram illustrates the method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework, thereby achieving changes in critical dimensions of polysilicon that meet process control standards. Detailed Implementation

[0026] To explain in detail the technical content, structural features, objectives, and effects of this invention, the following will provide a detailed description in conjunction with embodiments and accompanying drawings.

[0027] Please see Figure 1 , Figure 1 The diagram shows a flowchart of a method for reducing critical dimension loss in polysilicon caused by photolithography and photoresist rework according to the present invention. The method for reducing critical dimension loss in polysilicon caused by photolithography and photoresist rework includes:

[0028] Step S1: Provide a semiconductor device for polysilicon LEC etching, and the preceding process for polysilicon thin film etching of the semiconductor device has been completed;

[0029] Step S2: Perform polymer deposition on the semiconductor device that has completed the immediate process of polysilicon thin film etching;

[0030] Step S3: Perform photolithography and photoresist rework, and perform polysilicon thin film etching to obtain a polysilicon device with critical dimensions that meet process control standards.

[0031] Clearly, the polysilicon critical dimension devices that meet the process control standards are the qualified products defined in production.

[0032] To more intuitively reveal the technical solution of this invention and highlight its beneficial effects, the method and principle for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework are now described in conjunction with specific embodiments. In these specific embodiments, the etching steps, process parameters, and functional material compositions of the polysilicon are merely examples and should not be considered as limitations on the technical solution of this invention.

[0033] Please see Figure 2 , Figures 3-6 and in conjunction with reference Figure 1 , Figure 2 The diagram shows a three-dimensional structure of a semiconductor device using the method of reducing the loss of critical dimensions of polysilicon caused by photolithography and photoresist rework according to the present invention. Figures 3-6 The diagram shows a phased structure of a semiconductor device using the method of reducing critical dimension loss in polysilicon caused by photolithography and photoresist rework according to the present invention. The method for reducing critical dimension loss in polysilicon caused by photolithography and photoresist rework includes:

[0034] Step S1: Provide a semiconductor device 1 for polysilicon LEC etching, and the immediate process for etching the polysilicon thin film 10 of the semiconductor device 1 has been completed;

[0035] More specifically, the immediate preceding process for etching the polysilicon thin film 10 is a photoresist stripping (PR Strip) process. Without limitation, prior to the PR Stripping process, which is the immediate preceding process for etching the polysilicon thin film 10, the following processes may also be included: removal of the photoresist 11 undercoat, opening of the silicon-containing anti-reflective coating 12 and the chip 13 on the system, and opening of the hard mask 14.

[0036] Step S2: Deposit polymer 15 on the semiconductor device 1, which has undergone the immediate preceding process of etching the polysilicon thin film 10; non-limitingly, the polymer 15 is a carbon- and hydrogen-containing polymer. The polymer 15 is deposited under a CH4 backplane. The polymer 15 is deposited on the sidewalls 141 and top 142 of the hard mask 14.

[0037] Step S3: Perform photolithography and photoresist rework, and etch the polysilicon thin film 10 to obtain a polysilicon device with critical dimensions that meet process control standards.

[0038] In this invention, by depositing polymer 15 on a semiconductor device 1 that has completed the immediate process of etching the polysilicon thin film 10, the critical dimension of the hard mask 14 is indirectly increased before the polysilicon thin film 10 is etched. Without changing the pattern of the polysilicon thin film 10, the critical dimension of the hard mask 14 is increased, thereby effectively improving the problem of the reduction of the polysilicon critical dimension caused by photolithography and photoresist rework.

[0039] Please see Figure 7 , Figure 7 The diagram illustrates the changes in critical optical dimensions of polycrystalline silicon thin films caused by traditional photolithography and photoresist rework. 2a shows the critical optical dimensions of polycrystalline silicon under normal process conditions, while 2b shows the critical optical dimensions of polycrystalline silicon after traditional photolithography and photoresist rework. Clearly, using the traditional photolithography and photoresist rework process, the final critical dimensions of the polycrystalline silicon after LEC etching will be smaller, with an actual impact of approximately 0.8–1.2 nm and a fluctuation of about 3 sigma in online measurement. This will directly cause yield loss and increase manufacturing costs.

[0040] To improve product yield and obtain polysilicon devices with critical dimensions that meet process control standards, in this invention, preferably, the thickness of the polymer 15 deposited on the sidewall 141 of the hard mask 14 is 0.4–0.6 nm. More preferably, the thickness of the polymer 15 deposited on the sidewall 141 of the hard mask 14 is 0.5 nm.

[0041] Please see Figure 8 , Figure 8 The diagram illustrates the process of obtaining polysilicon critical dimension changes that meet process control standards using the method of reducing critical dimension loss caused by photolithography and photoresist rework according to the present invention. 3a shows the polysilicon optical critical dimension under normal process conditions, and 3b shows the polysilicon optical critical dimension after photolithography and photoresist rework using the present invention. Clearly, the method of reducing critical dimension loss caused by photolithography and photoresist rework according to the present invention achieves polysilicon critical dimensions that meet process control standards with deviations controlled within ±0.1 nm.

[0042] As will be readily understood by those skilled in the art, after obtaining a polysilicon device with critical dimensions that meet process control standards through the method of reducing polysilicon critical dimension loss caused by photolithography and photoresist rework according to the present invention, subsequent process steps include, but are not limited to, breakthrough, main etching, soft landing, soft landing overetch, and total overetch. Furthermore, the head-to-head critical dimension changes that may occur in the present invention can be adjusted by removing the photoresist undercoat during polysilicon LEC etching.

[0043] In summary, the method of the present invention for reducing the loss of critical dimensions of polysilicon caused by photolithography and photoresist rework involves polymer deposition on a semiconductor device that has completed the immediate preceding process of polysilicon thin film etching. This effectively increases the critical dimensions of the hard mask before the polysilicon thin film etching, without changing the pattern of the polysilicon thin film. This significantly improves the problem of reduced critical dimensions of polysilicon caused by photolithography and photoresist rework, increases product yield, and reduces production costs.

[0044] Those skilled in the art will understand that various modifications and variations can be made to this invention without departing from its spirit or scope. Therefore, if any modification or variation falls within the scope of the appended claims and their equivalents, the invention is considered to cover such modifications and variations.

Claims

1. A method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework, characterized in that, The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework includes: Step S1: Provide a semiconductor device for polysilicon LEC etching, and the preceding process for polysilicon thin film etching of the semiconductor device has been completed; Step S2: Perform polymer deposition on the semiconductor device that has completed the immediate process of polysilicon thin film etching, wherein the polymer is deposited on the sidewalls and top of the hard mask, and the thickness of the polymer deposited on the sidewalls of the hard mask is 0.4 to 0.6 nm. Step S3: Perform photolithography and photoresist rework, and perform polysilicon thin film etching to obtain a polysilicon device with critical dimensions that meet process control standards.

2. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 1, characterized in that, The preceding process for etching the polycrystalline silicon thin film is photoresist stripping.

3. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 2, characterized in that, Prior to the photoresist stripping process, which is the immediate preceding process to the polysilicon thin film etching, the process also includes photoresist undercoat removal, silicon-containing bottom anti-reflective coating and chip opening on the system, and hard mask opening process.

4. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 1, characterized in that, The polymer is a carbon- and hydrogen-containing polymer.

5. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 4, characterized in that, The polymer is deposited on a CH4 background.

6. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 1, characterized in that, The thickness of the polymer deposited on the sidewall of the hard mask is 0.5 nm.

7. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 1, characterized in that, After obtaining a polysilicon device with critical dimensions that meets process control standards by reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework using the method of the present invention, the subsequent process steps include breakdown, main etching, soft landing, soft landing over-etching, and overall over-etching.

8. The method for reducing the loss of critical dimensions in polysilicon caused by photolithography and photoresist rework as described in claim 1, characterized in that, Key dimensional variations in LEC head-to-head are adjusted by removing photoresist undercoat during polysilicon LEC etching.

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