Cleaning method of plasma process cavity

Abstract

The invention discloses a method for cleaning a plasma process cavity, which comprises the following steps of: S1, forming a window on the cavity wall on one side of the plasma process cavity, arranging a CCD (Charge Coupled Device) image sensor and an OES (Optical Emission Spectrometer) system on the outer side of the window, and setting a certain over-etching proportion; s2, continuously introducing F-based mixed gas into the process cavity, observing the reaction proceeding degree through an OES curve, when an OES system captures a gas product concentration reduction signal, gradually reducing the etching curve, finally tending to be stable, and stopping introducing the reaction gas when the set over-etching time is reached; and S3, O2 is continuously introduced, the temperature is increased, the high-heat O2 plasma coating can remove pollution such as particles on the surface of the cavity and surface dangling bonds, and corrosion of the quartz part is reduced. The OES monitoring system is added to monitor the cleaning reaction proceeding degree, so that the damage risk to the cavity due to long-time cleaning is avoided, and the degumming problem caused by insufficient cleaning is avoided.

Description

Technical Field

[0001] The invention relates to a cleaning method, in particular to a cleaning method for a plasma process chamber. Background Art

[0002] In the semiconductor wafer manufacturing process, silicon nitride film is a common dielectric film. PECVD, as a thin film deposition technology, has the advantages of good deposition density and uniformity. However, as the process time becomes longer, the surface of the quartz cavity is gradually covered with a layer of SIN film. In the subsequent process, the surface of the cavity is prone to peeling when bombarded by plasma. If the fragments fall on the wafer surface, it will affect the yield and electrical performance of the wafer. At present, the silicon nitride film on the surface of the quartz cavity is removed by introducing F-based plasma gas, but there are certain problems in the implementation of this method. For example, if the reaction time is too long, it will bring certain corrosion risks to the quartz and other metal parts in the cavity. If the reaction time is too short, there will be a problem of incomplete removal of the silicon nitride film. Therefore, it is increasingly important to accurately determine the etching time to avoid the peeling problem caused by insufficient cleaning and the damage of parts caused by excessive cleaning. OES (optical emission spectroscopy) is currently the most commonly used endpoint monitoring method, which realizes endpoint monitoring by detecting the change in the light intensity of the wavelength emitted by a certain reactive chemical group or volatile group in the plasma. When etching to different film layers, especially when reaching the etching end point, due to the change of etching materials (gas phase and film composition), the intensity signal of the emission spectrum also changes. Therefore, by monitoring the specific emission spectrum or wavelength of a specified product or reactant in the plasma reaction, the change in the detected spectral intensity is the end point of the reaction. In the cleaning process of the quartz cavity, when the SIN film layer on the surface is cleaned, the surface of the quartz cavity is exposed, and the OES spectrum signal of the etching product changes. At this time, stop passing the gas to complete the cavity cleaning. Therefore, using the OES system to develop a cleaning method for a plasma process cavity to achieve the purpose of controllable cleaning has become a problem to be solved by those skilled in the art. Summary of the invention

[0003] The present invention is to solve the above-mentioned deficiencies and provides a method for cleaning a plasma process chamber.

[0004] The above-mentioned object of the present invention is achieved by the following technical solution: A method for cleaning a plasma process chamber comprises the following steps:

[0005] S1: A window is opened on the wall of one side of the plasma process chamber, and a CCD image sensor and an OES (optical emission spectroscopy) system are arranged outside the window. At the same time, a certain over-etching ratio is set to ensure that the SIN film is completely removed;

[0006] S2: Continue to introduce F-based mixed gas into the process chamber, and observe the degree of reaction through the OES curve. When the OES system captures the signal of gas product concentration reduction, the etching curve gradually decreases and finally tends to be stable. When the set over-etching time is reached, stop introducing the reaction gas (stop etching);

[0007] S3: Continuously introduce O2 to thermally oxidize the cavity surface and increase the temperature. The high-temperature O2 plasma coating can remove particles and other contaminants on the cavity surface and surface dangling bonds (-OH, -H), reducing the corrosion of quartz parts.

[0008] The advantages of the present invention over the prior art are: when the F-based plasma gas is introduced to etch the nitride on the surface of the cavity, the OES system is introduced to monitor the progress of the etching reaction, and the introduction of the F-based gas is stopped when the signal concentration of the product is observed to decrease to a set value. Because the OES monitoring system is added to monitor the progress of the cleaning reaction, the method avoids the risk of damage to the cavity due to long-term cleaning and the peeling problem caused by inadequate cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the method for removing the SIN film in a quartz chamber of the present invention.

[0010] Figure 2 It is a schematic diagram of the structure of the plasma device used in the present invention.

[0011] Figure 3 It is a trend diagram of the etching curve when the OES system in the present invention captures a signal of a decrease in the concentration of gas products.

[0012] Figure 4 It is a schematic diagram of a method for removing a SIN film in a quartz cavity used in the prior art. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0014] like Figure 4 The figure shows a schematic diagram of the SIN film removal method currently used in the quartz cavity (existing technology). A is the initial state of the quartz cavity surface. After a certain period of deposition process, the cavity surface is covered with a layer of SIN film. F-based mixed plasma is introduced to dry-etch the SIN film. After the reaction proceeds for a period of time, the introduction of F-based mixed gas is stopped. At this time, the removal of the SIN film on the cavity surface is unknown. Then O2 is introduced to first purge away pollutants such as metals and particles in the cavity, and then a layer of oxide film is formed on the surface to protect the cavity.

[0015] like Figure 1As shown in FIG. 1 , it is a schematic diagram of the method for removing the SIN film in the quartz chamber of the present invention. The present invention still uses the F-based mixed gas as the reaction gas, but in the process of dry etching the SIN film reaction, an OES system is added to monitor the degree of reaction, and a certain over-etching ratio is set to ensure that the SIN film is completely removed. When the OES system captures the signal of the gas product concentration reduction, the etching curve gradually decreases (such as Figure 3 As shown), it tends to be stable at last, and the etching is stopped when the set over-etching time is reached, and then O2 is introduced to thermally oxidize the chamber surface.

[0016] like Figure 2 As shown, the plasma device used in the present invention adopts an ICP type PECVD machine, a window is opened outside the reaction chamber, and a CCD image sensor and an OES system are connected. The CCD image sensor converts the captured optical signal into an electrical signal, transmits it to the OES system, and reflects it on the OES curve.

[0017] The ICP CVD data for the experimental verification work of the present invention was obtained on a Kepler 2200 machine provided by Shanghai Jet Plasma Technology Co., Ltd.

[0018] Specific usage:

[0019] Step 1: Continue to introduce mixed gases such as CH4 and CH2F2, which are ionized by the RF power source to generate F-based mixed plasma, which diffuses to the surface of the cavity and reacts with the SIN film to generate volatile products such as SIF4, which are then pumped out of the cavity by the dry pump. Using CF4 and CH2F2 gas system as reaction gas can enhance the SIN / SIO etching selectivity while increasing the SIN etching rate.

[0020] The reaction conditions were set as follows:

[0021] Use RF power: 13.5MHZ;

[0022] Operating pressure range: 500-1000mt;

[0023] Operating temperature range: 20-120℃;

[0024] CF4 gas flow range: 10sccm-1000sccm;

[0025] CH2F2 flow range: 10sccm-1000sccm.

[0026] Step 2: Observe the progress of the reaction through the OES curve. During the entire plasma reaction process, the emission spectrum of 200-800nm ​​can be observed to be released from the reaction products or the etched lower layer materials. When approaching the end point of the reaction, when the upper gas reaction products decrease and the lower gas reaction products increase, the OES system captures this signal change. Taking the SI-F signal as the benchmark, stop introducing the reaction gas when the signal is observed to decrease and stabilize.

[0027] Step 3: Continue to introduce O2 and increase the temperature. The high-temperature O2 plasma coating can remove particles and other contaminants on the surface of the cavity and surface dangling bonds (-OH, -H), reducing the corrosion of quartz parts. The reaction conditions are set as follows:

[0028] Operating pressure range: 500-1000mt;

[0029] Operating temperature range: 500-700℃;

[0030] O2 gas flow range: 10sccm-1000sccm.

[0031] In other embodiments, the laser interferometer endpoint method may be used instead of the OES system to detect the progress of the reaction, and whether the SIN film is effectively removed can be determined by detecting the change in the film thickness.

[0032] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for cleaning a plasma process chamber, characterized in that: The following steps are involved: S1: A window is opened on the wall of one side of the plasma process chamber, and a CCD image sensor and an OES system are arranged outside the window. At the same time, a certain over-etching ratio is set to ensure that the SIN film is completely removed; S2: Continue to introduce F-based mixed gas into the process chamber, and observe the degree of reaction through the OES curve. When the OES system captures the signal of gas product concentration reduction, the etching curve gradually decreases and finally tends to be stable. When the set over-etching time is reached, stop introducing the reaction gas; S3: Continuously introduce O2 to thermally oxidize the cavity surface and increase the temperature. The high-temperature O2 plasma coating can remove particles and other contaminants on the cavity surface and surface dangling bonds (-OH, -H), reducing the corrosion of quartz parts.

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