JPH03138383A - Method and device for plasma treatment - Google Patents

Abstract

PURPOSE:To subject a sample to a plasma etching treatment with high accuracy by providing a heating means and cooling device on the sample base of the plasma etching device and maintaining the sample under treatment at a specified temp. CONSTITUTION:A passage 10 for passing a refrigerant from a refrigerant supplying device 11 is provided on the sample base 2 in a treating chamber 1 and a heater 14 connected to a power source 15 is built therein. The sample 8 to be etched is mounted on the treating base 2 and after the inside of the treating chamber 1 is evacuated to a vacuum, treating gases are supplied to the chamber and a high frequency electric power is supplied from a high frequency power source 9 to generate an electric discharge and plasma, by which the surface of the sample 8 is etched with the plasma. The temp. of the sample 8 in contact with the sample base 2 is measured by a sensor 16 during the cooling of the sample base 2 by the refrigerant in this case and the discharge is started and the etching is started at the point of the time when the prescribed temp. is attained. The temp. of the sample is measured by a sensor 16 at all times during the etching treatment and is inputted to a controller 17 which turns on and off the heater power source 15 and corrects the temp. drop by the refrigerant by the heater 14. The etching treatment is thus executed at always the specified temp. so that the etching with the high accuracy is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma processing method and apparatus, and particularly to a plasma processing method and apparatus suitable for processing a sample by cooling it to a low temperature.

[Conventional technology]

Conventionally, samples have been processed by cooling them to a low temperature below water temperature. There is a method that heats and cools the object to be etched and processes it by controlling the temperature of the object to be etched using a thermocouple installed on a cooling sample stand.

[Problem to be solved by the invention]

The above conventional technology does not give sufficient consideration to keeping the temperature of the sample constant during plasma processing, and there is a problem that temperature changes occur in the initial stage after plasma generation, making it impossible to perform high-precision processing. . In other words, a sample is placed on a sample stage that has been cooled to a predetermined low temperature, and when the temperature of the sample has dropped sufficiently and is almost the same as the sample stage temperature, discharge is started and plasma processing of the sample begins. In the early stages of processing, there is heat input from the plasma to the sample, causing the sample temperature to rise. Thereafter, the sample temperature can be kept constant at a predetermined temperature by adjusting the heating and cooling of the sample stage. In this way, the sample temperature changes temporarily at the start of the discharge, so
There was a problem in that the reaction during processing changed, making it impossible to perform highly accurate processing.

An object of the present invention is to provide a plasma processing method and apparatus that can maintain a constant sample temperature during plasma processing and perform highly accurate processing.

[Means to solve the problem]

The above purpose is to provide a sample stage installed in a processing chamber and cooled to a low temperature, a means for placing a sample on the sample stage, and a means for generating plasma in the processing chamber while the temperature of the sample placed on the sample stage is decreasing. Equipped*! This is achieved by using a method that includes the steps of placing the sample on a sample stand cooled to a low temperature, and starting electric discharge while the sample is being cooled by the low-temperature heat of the sample stand and its temperature is decreasing. be done.

[For production]

A sample is placed on a sample stage cooled to a low temperature, and discharge is started while the temperature of the sample is decreasing.

As a result, the sample receives heat from the plasma, but the sample is still in the cooling stage due to the low-temperature heat of the sample stage, and this heat input and cooling (heat radiation) are balanced and the sample temperature at the start of discharge can be kept constant. The sample temperature can be kept constant from the beginning to the end during sample processing, and highly accurate processing can be performed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 2 shows a plasma processing apparatus, in this case a microwave plasma etching apparatus. The device is constructed as follows. A sample stage 2 is installed in the processing chamber l, and the processing chamber! A discharge tube 3 is provided in the upper part, and a processing gas is supplied from a processing gas supply device (not shown) into the space surrounded by the processing chamber 1 and the discharge tube 3, and is evacuated by a vacuum exhaust device (not shown). It is now possible to do so. A waveguide 4 is provided around the outer periphery of the discharge tube 3, and a microwave oscillator 5 is provided at the end of the waveguide 4, and the microwave oscillator 5 is ON/OFF controlled by a control device fi17. A magnetic field generating coil 6 is provided on the outer periphery of the waveguide 4 in correspondence with the discharge tube 3.
is provided so that a magnetic field can be generated within the discharge tube 3. The coil radio waves 7 connected to the magnetic field generating coil 6 are ON/OFF controlled by a control device [17].

A sample 8 can be placed on the upper part of the sample stage 2, and can be held by a holding means (not shown). Examples of the holding means include a clamp that holds down the outer periphery of the sample 8, an electrostatic chuck that attracts the entire surface of the sample 8, and the like. A high frequency power source 9 is connected to the sample stage 8, and draws in ions in the plasma to enable anisotropic etching. A refrigerant flow path 10 is provided in the sample stage 2, and the refrigerant flow jI!
A coolant supply device 11 is connected to 110 so that the sample stage 2 can be cooled to a low temperature. A heater 14 is provided between the sample placement surface of the sample stage 2 and the coolant flow path lO, so that the sample stage 2 can be heated by the heater 14. A heater section 15 connected to the heater 14 is controlled to be turned on and off and to adjust the amount of heating by a control device 17. In this case, the temperature sensor 16 is provided on the sample stage 2 so as to be in contact with the back surface of the sample 8, and the signal from the temperature sensor 16 is input to the control device 7117. In this case, the sample stage 2 should be positioned at the center of the sample 8.
A heat transfer gas supply channel is installed in the center of the heat transfer gas supply j21.
A heat transfer gas supply device 5113 is connected to 12 so that heat transfer gas, for example, He gas, can be supplied to the gap between the back surface of the sample 8 and the sample stage 2.

After the sample 8 is placed on the sample stage 2 by a transport means (not shown), the control device j17 supplies heat transfer gas! 113
A command is issued to supply a heat transfer gas to the back surface of the sample 8, and, for example, after a predetermined period of time has elapsed after the sample 8 has been placed on the sample stage 2, a command is issued to the microwave oscillator 5 and the coil power supply 7,
Plasma is generated within the discharge tube 3. Also, at this time, instead of receiving a signal of the temperature of the sample 8 from the temperature sensor 16, the command is sent to the microwave oscillator n5 and the coil power source 7 when the temperature reaches the predetermined temperature, not when a predetermined time has elapsed. Plasma may be generated within 3.

Further, the control device i17 controls the heater 15 based on the signal from the temperature sensor 16 to perform heating by the heater 14.
1, or heat transfer gas supply equipment F! 1113 to adjust the supply pressure of the heat transfer gas, the amount of low-temperature heat transmitted to the sample 8 can be adjusted t14.

The timing at which plasma is generated by the control device 17 is determined at one point shown in FIG.

FIG. 1 is a diagram showing the temperature change of the sample 8 placed on the sample stage 2, and the solid line shows the sample temperature curve of this example. The dotted line shows the sample temperature curve when the sample temperature becomes approximately equal to the sample stage temperature and discharge starts.

as indicated by the dotted line. When the sample is placed on the sample stand, the temperature of the sample approaches the sample stand temperature after a certain period of time tz (which varies depending on the heat transfer rate between the sample stand 2 and the sample 8). After this,
When the discharge for etching treatment starts, the sample temperature becomes Δ, which is determined from the heat input Q from the plasma and the thermal resistance R.
Increase by T-QR. For this reason, the sample temperature changes after the start of discharge and is not always constant. In this case, the setting conditions are: sample temperature before placement = 20°C
, sample stage temperature knee 196℃, sample heat capacity: 870J/
Heat energy per person in d-: 5682W/m' (100W/64
f'), c), heat transfer rate: 123.3 W/G·K. The discharge starting point under this condition is

That is, time t2 was 24 seconds.

In addition, as shown by the solid line, taking into consideration the temperature rise △T caused by the discharge, the sample temperature in this case is
When the discharge is started when the temperature reaches -150℃, the amount of heat input from the plasma and the amount of heat released to the sample stage are combined, and -
The temperature can be maintained at a constant temperature of 150''C. In this case, the discharge start point 1, that is, the time t1, was 10.5 seconds.

In this way, by starting the discharge during the cooling of the sample, it is possible to balance the heat input to the sample and the heat dissipated from the sample, making it possible to keep the temperature of the sample constant.

In this case, the cooling temperature of the sample is -150℃.
However, if you want to change the set temperature of the sample, you can do so by changing the temperature of the sample stage 2 with the heater 14 or by changing the gas pressure of the heat transfer gas to change the heat transfer rate. .

In the apparatus with the above configuration, if the time tl at one point of discharge start, that is, the time from when the sample is placed on the sample stage, is determined in advance, the time can be managed using the control value [17] and the discharge can be generated. Sample temperature can be kept constant with simple control.

Moreover, if the sample temperature at one point at the start of discharge is determined in advance, the signal from the temperature sensor 16 can be input to control the control value [1
If the temperature is controlled by 7 and a discharge is generated, the sample temperature can be kept constant with even higher accuracy.

Note that there is an unstable element in the contact between the sample 8 and the sample stage 2, and there is a possibility that the thermal resistance will vary to some extent depending on the placement of the sample. Therefore, by detecting the sample temperature and adding feedback control, even more excellent temperature control becomes possible. A specific example of the control system in this case is shown in Figure 3 (a
) or d).

Figure 4 (1) shows how the sample temperature is detected and the pressure is controlled by adjusting the flow rate of the heat transfer gas supplied to the back surface of the sample using the flow control valve (NFC) included in the heat transfer gas supply device j13. It is something to do. FIG. 4(b) detects the pressure of heat transfer gas and controls the pressure. Figure 4 (C) is
It detects the sample temperature and controls the sample temperature by adjusting the heater. FIG. 4(d) detects the sample stage temperature,
The sample stage temperature is controlled by adjusting the heater. (
Regarding b) and (d), it is necessary to determine the relationship between the temperature of the sample and the temperature of the heat transfer gas or sample stage.

As described above, according to this embodiment, since the discharge is started while the temperature of the sample is decreasing after the sample is placed on the sample stage, the amount of heat input from the plasma to the sample is reduced from the sample to the sample stage. The amount of heat dissipated can be taken as
Since yt does not increase, the sample temperature can be kept constant from the beginning to the end of sample processing. As a result, the reaction during processing is always stable, that is, the probability of reaction between radicals in the plasma and the sample is constant, and if the sample temperature is low, the reaction of radicals becomes small, making it possible to perform anisotropic etching with ions. Therefore, there is an effect that even fine etching can be processed with high precision.

Although this embodiment has been described using microwave plasma drop etching as an example, the same applies to other methods such as RIg.

Furthermore, although etching has been described as an example of plasma treatment, it is also applicable to layering treatments such as CVD and sputtering.

〔Effect of the invention〕

According to the present invention, the temperature of the sample in plasma can be kept constant, and highly accurate processing can be performed.

[Brief explanation of the drawing]

Figure 181 is a diagram showing the change in sample temperature over time, which is an example of when the plasma processing method of the present invention is executed;
The figure is a block diagram showing a microwave plasma etching apparatus which is an embodiment of the braz pattern processing apparatus of the present invention that implements the 's1 diagram. FIG. 2 is a configuration diagram of a control system shown in FIG. 1...Processing chamber, 2...Sample stand, 5...
...Microwave oscillator, 6...Magnetic field generating coil, 11...Refrigerant supply Figure 42 Eyes open (5)

Claims (4)

[Claims] 1. a step of placing the sample on a sample stage cooled to a low temperature;
A plasma processing method comprising the step of starting discharge while the sample is being cooled by low-temperature heat of the sample stage and its concentration is decreasing. 2. The plasma processing according to claim 1, wherein the discharge starts at a predetermined time after the sample is placed on the sample stage, or when the temperature of the sample is measured and reaches a predetermined temperature. Method. 3. A sample stand provided in a processing chamber and cooled to a low temperature, means for placing a sample on the sample stand, and means for generating plasma in the processing chamber during temperature-lowering coating of the sample placed on the sample stand. A plasma processing apparatus characterized by comprising: 4. 4. The plasma generating means generates the plasma at a predetermined time after the sample is placed on the sample stage, or generates the plasma when the temperature of the sample reaches a predetermined temperature after measuring the temperature of the sample. plasma processing equipment.