JPH04239129A - Plasma processing method of semiconductor wafer - Google Patents

Abstract

PURPOSE:To enhance the reproducibility of the process performances in the plasma processing step of semiconductor wafers by a method wherein an opposite electrode is heated so as to raise the temperature thereof at the value within a specific temperature range before starting the semiconductor wafer processing steps. CONSTITUTION:For example, within a dry-etcher of an oxide film, if the stand-by time exceeds 10 minutes, the opposite electrode 6 is cooled down at about 50 deg.C when the refrigerant temperature in a refrigerator is at 30 deg.C. When a wafer 1 is continuously processed, since the temperature of the opposite electrode 6 is normally raised up to about 110 deg.C, if 110+ or -10 deg.C is specified to be a rated value, the plasma processing step will not be started but to be advanced to the temperature stabilizing step. During the temperature stabilizing step, the plasma processing step is performed for two minutes meeting the requirements for the pressure at about 0.8Torr using Ar gas and the power of 500-700W. Resultantly, the temperature of the opposite electrode 6 is raised up to about 100-110 deg.C while the device 1 carries the first wafer 1 to a supporting electrode 2. Later the same processing steps as those of the conventional sequences are performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method for semiconductor wafers, and more particularly to a method for plasma processing semiconductor wafers using a parallel plate type plasma processing apparatus.

0002

[Prior Art] Conventionally, in a parallel plate type plasma processing apparatus, the temperature (or wafer temperature) of a holding electrode on which a semiconductor wafer (hereinafter simply referred to as wafer) is placed is controlled; Temperature control was not performed on the opposing counter electrodes. This will be explained below using the drawings.

FIG. 3 is a sectional view of an example of a conventional parallel plate type plasma processing apparatus. The wafer 1 is transferred onto the holding electrode 2 and held there. Next, the inside of the chamber 3 is evacuated by a pump connected to the exhaust port 4, and when the pressure falls below a certain limit, the reaction gas is introduced into the chamber 3 through the gas inlet 5 and maintained until the pressure stabilizes. drooping Thereafter, high frequency power is applied to either or both of the counter electrode 6 and the holding electrode 2 depending on the purpose of the treatment, and a treatment such as etching or CVD is performed.

When the wafer 1 is placed on the holding electrode 2, various parameters within the chamber (degree of vacuum, gas flow rate, temperature of the holding electrode, etc.) are checked. If there are no problems with the various parameters, high frequency power is applied to the electrodes and processing is performed for a predetermined period of time. When checking parameters before applying high-frequency power, the temperature of the holding electrode 2 is monitored, and it is possible to stop the process if necessary, but the counter electrode 6 is often only monitored or not even monitored.

[0005] Generally, when high frequency power is applied in a plasma processing apparatus, the temperature of the electrode rapidly rises. For example, in the case of an oxide film dry etcher, if the etching rate is about 500 nm/min, even if the set temperature of the coolant in the electrode cooling mechanism is about 30 °C,
The electrode reaches a temperature of over 100° C. after 2 minutes of treatment.

[0006]

[Problem to be Solved by the Invention] In this conventional wafer plasma processing method, since the temperature of the counter electrode is not controlled at all, there is a problem in that it is not possible to prevent fluctuations in process performance due to fluctuations in the temperature of the counter electrode. was there.

[0007] Fluctuations in process performance are observed, for example, in etching equipment as variations in etching rate. For example, as shown by the broken line B in FIG. 4, the etching rate of a wafer in a conventional plasma etching apparatus varies up to about 10%. For this reason, there have been problems in that the yield of semiconductor devices decreases and the characteristics vary.

[0008]

[Means for Solving the Problems] The plasma processing method for semiconductor wafers of the present invention employs a parallel plate type plasma processing apparatus having a holding electrode for holding a semiconductor wafer and a counter electrode provided opposite to this holding electrode. A plasma processing method for semiconductor wafers in which the semiconductor wafer is processed by generating plasma between both electrodes, in which the semiconductor wafer is processed after heating the counter electrode and raising its temperature within a certain temperature range. It is.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a sectional view of a plasma processing apparatus for explaining one embodiment of the present invention. The configuration of the device is basically the same as the conventional device shown in FIG. 3, but a temperature sensor 7 for monitoring the temperature of the counter electrode 6 is added. FIG. 2 is a process diagram for explaining one embodiment of the present invention.

A wafer to be processed is set in an apparatus in a standby state, and a start of processing is instructed. In this state, the device monitors the temperature of the counter electrode.

For example, in the case of an oxide film dry etcher,
When the standby time is 10 minutes or more, the counter electrode 6 is cooled to about 50°C when the temperature of the refrigerant in the cooling mechanism is 30°C. When processing wafers continuously, the temperature of the counter electrode 6 usually rises to about 110°C, so
If °C is set as the standard, the process will not start and will proceed to the temperature stabilization process. In the temperature stabilization treatment, Ar gas was used to stabilize the temperature at 0.8
Plasma processing is performed for 2 minutes under conditions of a pressure of approximately Torr and a power of 500 to 700 W. As a result, the temperature of the counter electrode 6 rises to about 110 to 110° C., and the apparatus transports the first wafer 1 onto the holding electrode 2. Thereafter, parameters such as degree of vacuum and gas flow rate are checked and processing is performed in the same manner as in the conventional processing sequence.

The relationship between the etching rate and the number of wafers processed in this way has little variation, as shown by the solid line A in FIG.

In the case of a plasma CVD apparatus as well, the temperature of the opposing electrode is raised by basically the same process as in the oxide film dry etcher. In the case of plasma CVD, the counter electrode is usually heated and the temperature is set at 200°C to 300°C. By raising the temperature of the counter electrode by about 20 to 40° C. above the set temperature by Ar plasma treatment, it is possible to reduce variations in film quality between wafers.

[0014] In the above-mentioned embodiment, a single wafer processing apparatus has been described, but it is clear that similar effects can be obtained also in a batch processing apparatus. Furthermore, if the temperature of the counter electrode 6 is monitored every time one wafer is processed, the reproducibility between wafers will be further improved, although the processing capacity will be lowered.

[0015]

As described above, the present invention has the effect of improving the reproducibility of process performance in plasma processing of semiconductor wafers by controlling the temperature of the counter electrode, which has not been controlled in the past.

Therefore, it is possible to improve the yield of semiconductor devices,
Variations in characteristics can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a plasma processing apparatus for explaining one embodiment of the present invention.

FIG. 2 is a process diagram for explaining one embodiment of the present invention.

FIG. 3 is a cross-sectional view of an example of a conventional plasma processing apparatus.

FIG. 4 is a diagram showing variations in etching rate in a conventional example and an example.

[Explanation of symbols]

1 Wafer 2 Holding electrode 3 Chamber 4 Exhaust port 5 Gas inlet 6 Counter electrode 7 Temperature sensor

Claims (2)

[Claims] 1. Processing a semiconductor wafer by generating plasma between the two electrodes using a parallel plate plasma processing apparatus having a holding electrode for holding a semiconductor wafer and a counter electrode provided opposite to the holding electrode. A plasma processing method for a semiconductor wafer, characterized in that the semiconductor wafer is processed after heating the counter electrode and raising the temperature within a certain temperature range. 2. The method of plasma processing a semiconductor wafer according to claim 1, wherein the holding electrode is heated by an inert gas plasma.