Plasma-enhanced chemical vapor deposition method for forming multilayer film

Abstract

The present invention relates to the field of semiconductor integrated circuit manufacturing, and provides a PECVD method for forming a multilayer film. The method of the present invention comprises: a shutdown time determination step: determining a shutdown time t of a PECVD system used in the PECVD method for forming a multilayer film; a warm-up wafer deposition step: if the shutdown time t is greater than a threshold time T, performing PECVD on a warm-up wafer; and a product wafer deposition step: after performing PECVD of the warm-up wafer, performing PECVD of a product wafer. By means of the PECVD method for forming a multilayer film provided by the present invention, the problem of greater thicknesses of films on the surfaces of the first few wafers in the process of forming multilayer films such as NON films can be solved, thereby improving the yield of chip products.

Description

Plasma-enhanced chemical vapor deposition method for forming multilayer thin films Technical Field

[0001] The present invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a plasma enhanced chemical vapor deposition method for forming a multilayer thin film. Background Art

[0002] In semiconductor integrated circuit manufacturing, the PECVD (plasma-enhanced chemical vapor deposition) process is commonly used to form NON (silicon nitride-silicon oxide-silicon nitride) thin films on wafer surfaces. Figure 2 shows the structure of the NON film layers: a first silicon nitride film 2, a silicon oxide film 3, and a second silicon nitride film 4 are sequentially formed on a wafer substrate 1. The NON film layers can be formed directly on substrate 1 or with other layers between them. However, in existing processes, when forming NON films using PECVD, the film thickness is typically higher on the first few wafers. This is because the temperature in the PECVD chamber is unstable at the beginning of the PECVD process. This chamber temperature significantly affects film thickness. This is particularly pronounced if the PECVD machine is down for a long period of time, such as more than 30 minutes, before each PECVD process.

[0003] Therefore, the industry is in urgent need of a new PECVD method that can solve the problem of thick NON films on the surfaces of the first few wafers when forming NON films. Technical issues

[0004] The present invention aims to provide a PECVD method for forming a multilayer thin film, which can solve the problem that the film thickness of the first few wafer surfaces is too thick when forming a multilayer thin film such as a NON thin film. Technical Solutions

[0005] The method of the present invention includes: a downtime confirmation step, confirming the downtime t of the plasma-enhanced chemical vapor deposition system used in the plasma-enhanced chemical vapor deposition method for forming a multilayer thin film; a warm-up control wafer deposition step, if the downtime t is greater than a threshold time T, first using the warm-up control wafer to perform the plasma-enhanced chemical vapor deposition; a product wafer deposition step, after performing the plasma-enhanced chemical vapor deposition of the warm-up control wafer, then performing the plasma-enhanced chemical vapor deposition of the product wafer. Beneficial effects

[0006] The PECVD method for forming a multilayer thin film provided by the present invention can solve the problem of thick film thickness on the surfaces of the first few wafers when forming a multilayer thin film such as a NON thin film, thereby improving the yield of chip products. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG1 is a flow chart of a PECVD method for forming a multilayer thin film according to the present invention;

[0008] And FIG2 is a schematic structural diagram of a NON film.

[0009] Explanation of symbols

[0010] 1 substrate

[0011] 2. First silicon nitride film

[0012] 3 Silicon oxide film

[0013] 4 Second silicon nitride film Best Mode for Carrying Out the Invention

[0014] The following describes the PECVD method for forming a multilayer thin film according to the present invention with reference to Figure 1. As shown in Figure 1, the PECVD method includes a downtime confirmation step ( S001 ), a warm-up control wafer deposition step ( S002 ), and a product wafer deposition step ( S003 ). Each step is described in detail below.

[0015] The downtime confirmation step S001 determines the downtime t of the PECVD system used in the PECVD method for forming a multilayer thin film. Before performing PECVD on the multilayer thin film, the downtime of the PECVD system is determined. In this embodiment, the multilayer thin film formed using the PECVD process is a non-conductive composite thin film. However, the present invention is not limited thereto; in other embodiments, the multilayer thin film may be other thin films.

[0016] In the warm-up wafer deposition step S002, if the downtime t exceeds the threshold time T, PECVD is first performed using a warm-up wafer (dummy). In this embodiment, the threshold time T is 30 minutes. That is, if the downtime t exceeds 30 minutes, PECVD is performed using a warm-up wafer before performing PECVD on the actual product wafers. However, the present invention is not limited to this. In other embodiments, the threshold time T may also be other times. In this embodiment, the warm-up wafer PECVD process can employ any conventional PECVD process and will not be further described here.

[0017] Preferably, the number of warm-up control wafers is six. According to the applicant's experiments, when forming a NON thin film using a PECVD process, the film thickness of the NON film reaches the required thickness and stabilizes after the fourth warm-up control wafer. Taking into account other relevant factors, such as the differences between the warm-up control wafers and the product wafers, the number of warm-up control wafers is ultimately set to six. That is, during product production, PECVD is performed on the six warm-up control wafers first, and then PECVD is performed on the product wafer starting with the seventh wafer.

[0018] In the product wafer deposition step S003, after the PECVD process of warming up the wafer is performed, the PECVD process of the product wafer is performed. In this embodiment, the PECVD process of the product wafer can adopt any PECVD process commonly used in the prior art, which will not be described in detail here.

[0019] The PECVD method for forming a multilayer thin film provided by the present invention can solve the problem of thick film thickness on the surface of the first few wafers when forming multilayer thin films such as NON thin films, thereby improving the yield of chip products.

[0020] Although the present invention has been disclosed in the form of embodiments as described above, they are not intended to limit the present invention. Any professional and technical personnel in this field may make various necessary changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the attached claims.

Claims

1. A plasma enhanced chemical vapor deposition method for forming a multilayer thin film, comprising: A downtime confirmation step S001 is to confirm the downtime t of the plasma enhanced chemical vapor deposition system used in the plasma enhanced chemical vapor deposition method for forming a multi-layer thin film; Warm-up and wafer-controlled deposition step S002: if the downtime t is greater than the threshold time T, the plasma enhanced chemical vapor deposition is first performed using the warm-up and wafer-controlled deposition method; The product wafer deposition step S003 is to perform plasma enhanced chemical vapor deposition on the product wafer after the plasma enhanced chemical vapor deposition on the warm-up wafer is performed.

2. The plasma enhanced chemical vapor deposition method for forming a multilayer thin film according to claim 1, characterized in that: The multilayer film is a composite film of silicon nitride-silicon oxide-silicon nitride.

3. The plasma enhanced chemical vapor deposition method for forming a multilayer thin film according to claim 2, characterized in that: The threshold time T is 30 minutes.

4. The plasma enhanced chemical vapor deposition method for forming a multilayer thin film according to claim 2, characterized in that: The number of the warm-up control sheets is 6.

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