JPH0192384A - Plasma treating device - Google Patents

Abstract

PURPOSE:To improve precision in the temp. measurement of a sample and control by providing a high-frequency voltage attenuating circuit to decrease the high-frequency voltage, and removing the obstruction due to the superimposition of the high-frequency voltages. CONSTITUTION:The plasma treating device is formed by the high-frequency voltage impressing electrode 3 provided in a vacuum vessel 1, a sample 11 placed on the electrode 3, a temp. sensor 5 in contact with the sample 11 and electrode 3, a heater 6 provided in the electrode 3 and used for heating the sample 11, a cooling mechanism, a temp. control circuit, and the high-frequency voltage attenuating circuit 7. The temp. control circuit is connected between the sensor 5 and the heater 6, and composed, for example, of a thermometer 4, an automatic temp. controller 8, and a heater power source 9. The circuit 7 is connected between the sensor 5 and heater 6 and the temp. control circuit.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasma processing apparatus that performs surface treatment on a sample placed on an electrode using plasma generated in a vacuum container by a high-frequency clasp. , especially the measurement of the temperature of the sample,
The present invention relates to a plasma processing apparatus suitable for highly accurate control.

[Conventional technology]

In conventional high-frequency discharge equipment, such as sputtering equipment and dry etching equipment, electrically measuring and controlling the temperature of the sample to be processed or the part to which a high-frequency voltage is applied, such as the cathode electrode on which the sample is placed, is a This has been extremely difficult because a high frequency voltage is superimposed on the measurement circuit or the temperature control circuit, resulting in problems such as malfunction of the circuit or unstable discharge. In order to solve this problem, conventionally 1, for example, Journal of Vacuum Society Technology A4 (5) September/1
October 1986, pp. 2392-2394 (J.

Vac, Sci, Technol, A4 (5)
5ep10at1986 p, 2392-2394)
As described in , a thermolabel that changes color depending on the temperature is attached to the sample to visually control the temperature, or a temperature sensor using an optical fiber or a non-contact radiation thermometer (infrared thermometer) is used. A method is proposed.

[Problem that the invention seeks to solve]

However, in the method using the thermolabel described above, since the temperature is detected visually, there is a problem in that the sample on which the thermolabel is attached must be removed from the processing device.

Furthermore, radiation thermometers have a problem in that measurement accuracy decreases particularly at temperatures below 0°C, and the measurement limit is 150°C.

Furthermore, temperature sensors using optical fibers are very expensive.

Even when using inexpensive contact-type temperature sensors such as thermocouples and resistance thermometers, superimposition of high-frequency voltages can be avoided if a sufficiently thick insulating material is installed between the high-frequency voltage application part, but in this case, has the problem that the response speed is significantly reduced. Therefore, it is difficult to measure temperature with a fast response speed over a wide range including -200° C. or lower without being affected by high frequency voltage.

On the other hand, in order to control the temperature of the sample, when a heater is installed inside the high-frequency voltage application electrode on which the sample is placed, the high-frequency voltage is applied to the temperature control circuit connected to the heater, similar to the temperature sensor. There is a problem in that the circuits are superimposed and the circuit malfunctions, making the discharge unstable. As with the temperature sensor above,
If an insulating material is used between the heater and the electrode to avoid superimposition of high-frequency voltages, there is a problem in that the response speed of temperature control is slow.

Electrical insulation can be achieved by using a lamp heater.

Lamp heaters have a problem of low heating efficiency and slow heating response speed.

In this way, in the conventional technology, when measuring and controlling the temperature of a part to which a high-frequency voltage is applied using a temperature sensor or a heater, sufficient consideration is not given to the attenuation of the high-frequency voltage superimposed on the electrical wiring for temperature measurement or control. has not been done,
There is a problem in that it is difficult to measure and control the temperature of the sample or electrode while discharging. This problem is particularly serious when temperature control with fast response speed is required.

The purpose of the present invention is to increase the response speed of temperature measurement and control,
Moreover, it solves the problem caused by high frequency voltages superimposed on the temperature measurement circuit or temperature control circuit.

The purpose is to stably measure and control temperature during discharge.

[Means for solving problems]

In order to achieve the above object, the plasma processing apparatus of the present invention brings a temperature sensor or a heater for temperature control into contact with a high-frequency voltage application electrode or a sample placed on the electrode without intervening an insulating material, Moreover, a circuit for attenuating high frequency voltage is installed between the temperature sensor or heater and the temperature measurement or control circuit.

The configuration of the plasma processing apparatus of the present invention will be described in more detail. In order to directly detect and measure the temperature of the sample, the temperature sensor is brought into direct contact with the high-frequency voltage application electrode or the sample placed on the electrode. The temperature sensor may be, for example, a thermocouple, or a so-called sheath type temperature sensor in which the sensor is embedded in a metal sheath tube via a thin insulating material.

Response speed of sheath type temperature sensor (time constant)
is within a few seconds, and there is no practical problem at all.

Further, in order to control the temperature of the sample, a resistance heating type sheath heater, for example, was embedded in the electrode.

No insulating material is installed between the sheath heater and the electrode. Of course, if the response speed of temperature control can be slow to some extent, it is obvious that installing an insulating material between the heater and the electrode will reduce the superimposition of high-frequency voltage on the heater wiring.

A temperature sensor installed in contact with the high-frequency voltage application part,
Alternatively, a high frequency voltage with a voltage amplitude of several hundred volts is superimposed on the heater wiring. Therefore, if the wiring is directly connected to a temperature control circuit or temperature measurement circuit consisting of a thermometer, automatic temperature controller, heater power source, etc., the circuit will malfunction due to the high frequency voltage. Therefore, in the present invention, a high frequency voltage attenuation circuit is installed in the middle of the wiring. As this high frequency voltage attenuation circuit, a filter circuit consisting of inactive elements including at least a coil and a capacitor, or a photocoupler circuit is used. This circuit uses high frequency voltage of 500kHz or more (typically 800kHz, 13.56MHz
, 2.45 GHz, etc.).

With this circuit, the high frequency voltage superimposed on the wiring can be reduced to about 1/1000 or less. As a result, malfunction of the temperature control circuit or temperature measurement circuit connected through the high-frequency voltage attenuation circuit is prevented, and the state of plasma discharge and the state of impedance matching during discharge can be stabilized.

[Effect]

As described above, by bringing the temperature sensor into direct contact with the sample, the response speed of the temperature sensor can be reduced to about 1150 or less than when contact is made through a 21 m thick sapphire substrate as an insulating material, for example.

In other words, when using sapphire, the response speed is approximately 5
By direct contact, what used to be a particle diameter,
It can be reduced within seconds. Silicon carbide (SiC) has higher thermal conductivity than sapphire, but SiC has IMH
The problem is poor insulation against high frequency voltages of z or higher.

When the plasma processing apparatus of the present invention is used, for example, in a dry etching apparatus, the processing time is often about several minutes, and when a temperature sensor is brought into contact through the sapphire, the response time is about 5 minutes. This method is impractical because of the speed required, and it is essential to contact the temperature sensor without using an insulating material.

In the present invention, as a temperature sensor without using an insulating material,
For example, even if a thermocouple or sheath type sensor is used,
The high-frequency voltage with a voltage amplitude of several hundred volts superimposed on the sensor and its wiring is reduced to approximately 1000 volts by the above-mentioned high-frequency voltage attenuation circuit.
It can be attenuated to less than one-fold.

In the case of a heater for controlling sample temperature, it is recommended to use an insulating material such as sapphire to avoid superimposition of high-frequency voltages.
The response speed of heating is slow, and highly accurate temperature control within a processing time of several minutes is impossible, and the same applies to lamp heaters. By bringing the sheath heater into direct contact with the electrode, a sufficiently practical response speed can be achieved, and by connecting a high frequency voltage attenuation circuit to the heater, malfunctions of the temperature control circuit can be prevented.

The high-frequency voltage attenuation circuit not only prevents malfunction of the circuit due to noise but also has the function of stabilizing discharge.

If this circuit is not installed, problems such as impedance matching during discharge cannot be achieved and discharge does not occur will occur, but this circuit can prevent this.

〔Example〕

Embodiment 1 FIG. 1 shows the configuration of a first embodiment of the plasma processing apparatus of the present invention. In the figure, 1 is a vacuum processing chamber (vacuum container)
, 2 is a ground electrode, 3 is a high-frequency voltage application electrode, 5 is a temperature sensor, 6 is a heater, 7 is a high-frequency voltage attenuation circuit, 4 is a thermometer, 8 is an automatic temperature controller, 9 is a heater power supply, 10 is a high-frequency power supply , 11 are samples.

A ground electrode 2 and a high frequency voltage application electrode 3 are provided in a vacuum container 1, and plasma is generated by glow discharge between the two electrodes. The output frequency of the high frequency power supply 10 is 13.56
MHz was used. A sample 11 is placed on the high frequency voltage application electrode 3.
is installed, and the temperature sensor 5 is in contact with the sample 11. A heater 6 is built inside the high-frequency voltage application electrode 3, and also has a water cooling mechanism (not shown). A temperature control circuit is configured by the thermometer 4, automatic temperature controller 8, and heater power supply 9, and a signal from the temperature sensor 5 is sent through the thermometer 4 to the automatic temperature controller 8, which changes the voltage of the heater power supply 9. It is designed to send out a signal. A DC power source was used as the heater power source 9. A high frequency voltage attenuation circuit 7 is connected between the temperature sensor 5 and the heater 6 and the temperature control circuit.

Further, a shielded insulation transformer (not shown) was installed in the power supply line of the temperature control circuit. The temperature control circuit has a ground potential.

As the temperature sensor 5, a sheath type thermocouple was used, as the heater 6, a resistance heating type sheath heater was used, and as the high frequency voltage attenuation circuit 7, a filter circuit composed of a capacitor and a coil was used.

The configuration of the filter circuit was, for example, the configuration shown in FIG. 12 is a capacitor, 13 is a coil, and 14 is a ground. Note that all of the filter circuits were installed inside a matching box.

The filter circuit having the configuration shown in FIG. 2 obtained attenuation characteristics as shown in FIG. 3. In particular, grounding to earth 14 through capacitor 13 had a remarkable effect on attenuating high frequency voltage.

Dry etching was carried out as follows using the apparatus having the above configuration.

A mixed gas of BCI&, and C112 was used as the etching gas, a layer film deposited on a Si substrate was used as the sample, and the gas pressure was 100 mTorr (13.3 Pa).
, the incident power was 400W. As a temperature sensor, a copper-constantan thermocouple was used to control the temperature of the sample at 50°C, and etching was performed. The operation of the temperature control circuit was very stable, with temperature accuracy within ±2°C. Furthermore, the discharge state was stable and good etching characteristics were obtained. At this time, the etching speed of M is 1100n
/min. When the temperature of the sample was changed from room temperature to 150° C., temperature dependence of the etching rate was observed, and it varied within 100±50 nm/min.

As the temperature sensor, a temperature measuring resistor may be used, and as the high frequency voltage attenuation circuit, a photocoupler circuit may be used with the same effect. At this time, a battery was used as a driving power source for the photocoupler circuit. However, if a photocoupler circuit was installed on the heater side, it would be difficult to transmit large amounts of power, so it was installed only on the temperature sensor l side.

Example 2 Plasma deposition was performed while controlling the temperature of the sample using an apparatus having a configuration similar to that shown in FIG. By controlling the temperature of the sample during discharge with high precision in the range of 100 to 400°C, it was possible to change the film quality of the deposition film. The temperature control accuracy at this time was ±2° C., the same as in Example 1.

In addition, it was also possible to use this device as a sputtering device.

Example 3 Etching was carried out using a low temperature dry etching apparatus as shown in FIG. 17 is a vacuum processing chamber, 18 is a sample exchange room, 29 is a sample stand, 32 is a quartz stand, 30 is a cooling gas supply port, 31 is a heating lamp, 19 is a gate valve,
41 is a gas supply control system, and 40 is a discharge mechanism.

20 is a processing gas supply port, 23 is a high frequency voltage application electrode that also serves as a cooling sample stage, 27 is a high frequency voltage power source, 26 is liquid nitrogen, 37 is a liquid nitrogen container, 24 is a sample (wafer), 3
3 is a Teflon stand, 36 is an insulator, 22 is a quartz cover, 2
1 is a metal O ring, 25 is a resistance heating type sheath heater installed in the electrode 23, 34 is a temperature sensor installed in the electrode 23, and 42 and 43 are temperature sensors 34, respectively.
, a high frequency voltage attenuation circuit connected to the heater 25, 35 a thermometer, 38 a feedback circuit, 39 a gas supply control system, and 28 a heater power source.

Using a device with such a configuration, the high frequency voltage application electrode 2
The electrode temperature was controlled within a range from room temperature to -190° C. using a temperature sensor 34 in contact with the electrode 3, a heater 25, and liquid nitrogen 26 in a cooling container integrated with the electrode 23. The temperature control system includes a high frequency voltage attenuation circuit 4 having the configuration shown in Figure 2.
2.43 is installed to prevent the effects of high frequency voltage superimposition.

Low-temperature dry etching of Si was performed using this apparatus. First, the sample 24 is placed on the cooling sample stage 23, and the sample 24 is placed on the cooling sample stage 23.
He gas was flowed into the gap between the sample 4 and the cooling sample stage 23, and the sample 24 was held down with a perforated quartz cover 22 to establish thermal contact. With this device, Si wafers can be
While controlling the temperature to 20±2℃.

Etched with SF and plasma for 5 minutes. Photoresist was used as a mask. With this etching, 1o, s
, below at, depth 3I! m, accuracy of 0.054 or less
The pattern has been formed. At this time, the etching selectivity of Si/photoresist was about 50.517 Sin, and the etching selectivity of Si/photoresist was about 40. Also, -70 to -14
Changes in the etching shape, that is, the amount of side etching, were observed in the temperature range of 0°C.

Highly accurate shape control was achieved within this temperature range.

The present invention was particularly effective because it is impossible to use a non-contact radiation thermometer in such a low temperature range.

Example 4 Using the same low temperature dry etching equipment as in Example 3,
Performed tungsten etching.

The etched shape of tungsten changed significantly between temperatures of 0 to -30°C, and high precision shape control could be achieved in this temperature range. The accuracy of the radiation thermometer in this temperature range was poor, about ±5 to 10°C.

By bringing a sheathed thermocouple into direct contact with the sample as a temperature sensor, the accuracy was improved to ±2°C. In particular, the contact position of the thermocouple is on the back side of the sample.

The parts not exposed to plasma were good, and the temperature accuracy was the highest.

In the above embodiment, a temperature sensor and a heater are provided in the high-frequency voltage application section, and a high-frequency voltage attenuation circuit is connected between each and the temperature control circuit. However, only the temperature sensor is provided, and the temperature sensor and Of course, it is also effective to install a high frequency voltage attenuation circuit between the temperature measurement circuit and the temperature measurement circuit.

〔Effect of the invention〕

As explained above, in plasma processing equipment, it has been difficult to measure and control the temperature during discharge because high-frequency voltage is conventionally superimposed on the temperature measurement or control circuit, but in the present invention, a high-frequency voltage attenuation circuit is used. By installing this, the high frequency voltage can be reduced to about 1/1000th or less, and the disturbance caused by the superimposition of high frequency voltage can be removed.
High-precision temperature measurement and control is possible even in the low temperature range below ℃, and since there is no need to use an insulating material between the temperature sensor or the heater and the electrode, the response speed of temperature control is faster than that of the insulating material. This can be reduced to several tenths of what would otherwise be the case, and the sample processing accuracy can be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a first embodiment of the plasma processing apparatus of the present invention, FIG. 2 is a circuit diagram of a filter created as an example of a high frequency voltage attenuation circuit, and FIG. 3 is a diagram shown in FIG. Figure 4 shows the high frequency voltage attenuation characteristics of the filter circuit.
1 is a schematic diagram of a low temperature dry etching apparatus to which the present invention is applied. 1... Vacuum processing chamber 2... Earth electrode 3...
High frequency voltage application electrode 4...Thermometer 5...Temperature sensor 6...
Heater 7... High frequency voltage attenuation circuit 8...
Automatic temperature controller 9... Paheater power supply 10... High frequency voltage power supply 11... Sample 12... Capacitor
13...Coil 14...Earth 17...
・Vacuum processing chamber 18...Sample exchange chamber 19...Gate valve 20...Processing gas supply port 21...Metal ring 22...Quartz cover 23...Cooled sample stage (high-frequency voltage application electrode )24...
・Sample (wafer) z5...Sheath heater 26...Liquid nitrogen 27.
...High frequency voltage power supply 28...Heater power supply 29...
・Sample stand 30...Cooling gas supply port 31...
・Heating lamp 32...Quartz stand 33...Teflon stand 34...Temperature sensor 35...Thermometer
36... Insulator 37... Liquid nitrogen container 3
8...Feedback circuit 39...Gas supply control system 40...Discharge mechanism 41...Gas supply control system 42.43...High frequency voltage attenuation circuit

Claims (1)

[Scope of Claims] 1. A vacuum container, a high-frequency voltage applying electrode provided in the vacuum container, a sample placed on the high-frequency voltage applying electrode, and contacting the sample or the high-frequency voltage applying electrode. a temperature sensor provided in the above, a heater for heating the sample provided in the high frequency voltage applying electrode, a cooling mechanism for the sample, a temperature control circuit connected to the temperature sensor and the heater; A plasma processing apparatus comprising a temperature sensor and a high frequency voltage attenuation circuit connected between the heater and the temperature control circuit. 2. The temperature control circuit includes at least a thermometer, an automatic temperature controller, and a heater power source, and a signal from the temperature sensor is sent to the automatic temperature controller through the thermometer;
2. The plasma processing apparatus according to claim 1, wherein the automatic temperature controller is configured to output a signal for changing the voltage of the heater power source. 3. The plasma processing apparatus according to claim 1, wherein the high frequency voltage attenuation circuit is a filter circuit consisting of inactive elements including at least a coil and a capacitor. 4. The plasma processing apparatus according to claim 3, wherein the filter circuit is connected to the ground through the capacitor at at least one location. 5. The plasma processing apparatus according to claim 1, wherein the high frequency voltage attenuation circuit is a photocoupler circuit. 6. The plasma processing apparatus according to claim 1, wherein the temperature sensor is a thermocouple or a resistance temperature sensor. 7. The plasma processing apparatus according to claim 1, wherein the heater is a resistance heating type heater. 8. The plasma processing apparatus according to claim 1, wherein the cooling mechanism is a cooling mechanism using liquid nitrogen. 9. A vacuum container, a high-frequency voltage application electrode provided in the vacuum container, a sample placed on the high-frequency voltage application electrode, and a sample placed in contact with the sample or the high-frequency voltage application electrode. A plasma processing apparatus comprising a temperature sensor for temperature detection, a temperature measurement circuit connected to the temperature sensor, and a high frequency voltage attenuation circuit connected between the temperature sensor and the temperature measurement circuit. .