Method of improving CDU by substrate processing

Abstract

The invention discloses a method for improving CDU through substrate treatment, which comprises the following steps of: 1, depositing a titanium nitride layer as a hard mask layer on a semiconductor substrate to be subjected to a photoetching process, and depositing a silicon oxide layer on the surface of the titanium nitride layer; 2, carrying out a one-step substrate treatment process, and carrying out O2 plasma surface treatment on the wafer in a process cavity; and 3, coating photoresist on the surface of the silicon oxide layer, and performing an exposure process. According to the invention, a one-step substrate treatment process is added, O2 plasma surface treatment is added, a nitrogen-containing layer on the surface is oxidized through O2 plasma, stable nitrogen oxide is formed, and precipitation and release of N are reduced; the plasma treatment can generate a compact inorganic layer on the surface of the substrate to prevent the internal nitrogen component from diffusing to the surface, so that the occurrence of photoresist poisoning is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit manufacturing processes, and in particular to a method for improving CDUs through substrate treatment. Background Technology

[0002] With the development of integrated circuit manufacturing processes and the shrinking of critical dimensions, CD (Critical Dimension Uniformity) control has become particularly important. Chemically amplified photoresists can improve CD resolution, but they are also very sensitive to even small changes in acid concentration. Nitrogen poisoning caused by the substrate is a typical example. For instance, in the pattern layer process, TiN is often used as a hard mask for etching, followed by a thin CAP oxide layer to cover TiN to prevent direct contact between the photoresist (PR) and TiN, which could lead to photoresist poisoning. However, in practice, it has been found that some nitrogen-active components still diffuse to the surface of the CAP oxide layer, damaging the stability of the photoresist. This is mainly because the nitrogen component in the TiN substrate material may precipitate as alkaline substances, which consume photoacids during subsequent exposure processes, reducing the dissolution rate of the photoresist during subsequent development and thus degrading CDU (Critical Dimension Uniformity). Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for improving CDU through substrate treatment, thereby solving the problem of photoresist poisoning when photoresist is covered on a titanium nitride hard mask layer.

[0004] To address the above problems, the present invention provides a method for improving CDU through substrate treatment, comprising: Step 1: Deposit a titanium nitride layer as a hard mask layer on the semiconductor substrate to be subjected to photolithography, and then deposit a silicon oxide layer on the surface of the titanium nitride layer. Step two involves a substrate processing step, in which the wafer undergoes O2 plasma surface treatment within the process chamber. Step 3: Coat the silicon oxide layer with photoresist and perform an exposure process.

[0005] Furthermore, the semiconductor substrate is a silicon substrate or a compound semiconductor; the thickness of the silicon oxide layer is less than that of the titanium nitride layer, and the silicon oxide layer isolates the photoresist from the titanium nitride layer, preventing the photoresist from directly contacting the titanium nitride layer and becoming poisoned.

[0006] Furthermore, in step two, the O2 plasma surface treatment process parameters are: chamber pressure 900±100mT, gas flow rate of N2 250~350sccm, O2 flow rate of 6400~7800sccm, and process temperature 250℃.

[0007] Furthermore, in step two, O2 plasma surface treatment can oxidize the nitrogen-containing layer on the substrate surface, forming stable nitrogen oxides and reducing the release of N; O2 plasma treatment can generate a dense inorganic layer on the substrate surface, blocking the diffusion of internal nitrogen components to the substrate surface.

[0008] The present invention provides a method for improving CDU through substrate treatment. After depositing a silicon oxide layer on the surface of a titanium nitride hard mask layer, an additional substrate treatment step is added, which includes O2 plasma surface treatment. The nitrogen-containing layer on the surface is oxidized by O2 plasma to form a stable nitrogen oxide, thereby reducing the precipitation and release of N. The plasma treatment can generate a dense inorganic layer on the substrate surface, which can block the diffusion of internal nitrogen components to the surface, thereby reducing the occurrence of photoresist poisoning. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the process steps of the present invention, which involves depositing a CAP silicon oxide layer on the surface of a TiN hard mask layer.

[0010] Figure 2 This is a schematic diagram of the O2 plasma surface treatment added to the process steps of this invention.

[0011] Figure 3 This is a schematic diagram of the process steps of the present invention, which involves coating photoresist and exposing the image.

[0012] Figure 4 This is a flowchart of the process steps of the present invention. Detailed Implementation

[0013] The following detailed description, in conjunction with the accompanying drawings, provides specific embodiments of the present invention and clearly and completely describes the technical solutions of the present invention. However, the present invention is not limited to the following embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] This invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated, and the same reference numerals denote the same elements throughout. In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0015] This invention provides a method to reduce photoresist poisoning by processing the TiN substrate, thereby improving the CDU (Current Performance Depth) of the photolithography process. This invention addresses the problem of nitride diffusion to the surface of the photolithography wafer substrate by adding a dry asher process to mitigate photoresist poisoning.

[0016] The process method of this invention involves adding an O2 plasma surface treatment (dry asher) step after forming the TiN+CAP oxide film, such as... Figures 1 to 3 As shown.

[0017] Specifically, firstly, such as Figure 1 As shown, a CAP oxide film is deposited on the substrate on which the TiN hard mask layer is formed. The CAP oxide film (CAP OX) completely covers the TiN layer.

[0018] Then, as Figure 2 As shown, a one-step substrate processing process is performed. The wafer undergoes O2 plasma surface treatment (dry asher) within the process chamber. Typical process parameters are: chamber pressure 900±100 mT, N2 flow rate 250–350 sccm, O2 flow rate 6400–7800 sccm, and process temperature 250°C. In this embodiment, the process parameters are selected as follows: pressure 900 mT, N2 flow rate 300 sccm, O2 flow rate 7200 sccm, and process temperature 250°C.

[0019] The main functions of O2 plasma surface treatment are as follows: 1. Chemical decomposition: O2 plasma treatment can oxidize the nitrogen-containing layer on the wafer surface to form stable nitrogen oxides (such as SiON), reducing the precipitation and release of N; 2. Surface densification: O2 plasma treatment can generate a dense inorganic layer (such as SiON, SiO2) on the wafer surface, blocking the diffusion of internal nitrogen components to the wafer surface.

[0020] After O2 plasma surface treatment, subsequent normal processes such as photoresist coating and exposure are carried out.

[0021] After implementing the novel process method of this invention, the performance of wafer CDU is significantly improved after O2 plasma surface treatment. Comparative tests with existing processes show a 61% improvement in CD value distribution range and a 55% improvement in Sigma. Furthermore, the method of this invention is particularly effective in improving the pixel layer in BSI devices.

[0022] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving CDU by substrate treatment, characterized in that: step one, providing a wafer to be processed by photolithography, a layer of titanium nitride is deposited on the semiconductor substrate of the wafer as a hard mask layer, and a layer of silicon oxide is further deposited on the surface of the titanium nitride layer; step two, performing a semiconductor substrate treatment process, O2 plasma surface treatment is performed on the wafer in the process chamber; step three, coating photoresist on the surface of the silicon oxide layer and performing exposure process. The semiconductor substrate is silicon substrate, or germanium-silicon, gallium nitride, silicon carbide substrate. The thickness of the silicon oxide layer is less than that of the titanium nitride layer, and the silicon oxide layer isolates the photoresist from the titanium nitride layer to prevent the photoresist from being poisoned by directly contacting the titanium nitride layer. In step two, the O2 plasma surface treatment process parameters are: chamber pressure 900±100mT, N2 flow rate 250-350sccm, O2 flow rate 6400-7800sccm, and process temperature 250℃.

2. The method of improving CDU through substrate processing of claim 1, wherein: In step two, the O2 plasma surface treatment can oxidize the nitrogen-containing layer on the substrate surface to form stable nitride oxide and reduce the release of nitrogen; after O2 plasma treatment, a dense inorganic layer is generated on the substrate surface to block the diffusion of internal nitrogen components to the substrate surface.

3. The method of improving CDU through substrate processing of claim 1, wherein: The inorganic layer contains silicon nitride oxide and silicon oxide.

4. The method of improving CDU through substrate processing of claim 1, wherein: The method is suitable for BSI devices.

5. The method of improving CDU through substrate processing of claim 1, wherein: ​ 6. The method of improving CDU through substrate processing of claim 5, wherein: ​ 7. The method of improving CDU through substrate processing of claim 1, wherein: ​

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