JPH11233487A - Cleaning method for electrostatic attraction electrode and its detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect the termination of the plasma cleaning of an electrostatic attraction electrode, which supports a wafer processed by a plasma and the like with electrostatic attraction. SOLUTION: A Vpp detection circuit 16 is provided in parallel to a plasma 6, an electrode 10 having an electrostatic attraction electrode 13, a high frequency power source 14, and a high frequency apply circuit formed through a ground part. Vpp during the plasma cleaning of the electrostatic attraction electrode 13 is successively detected. When detected Vpp is matches a value which is previously set, plasma cleaning terminates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning an electrostatic chucking electrode and an apparatus for detecting the same, and more particularly to an electrostatic chucking method suitable for an electrostatic chucking electrode which supports a wafer to be processed by plasma or the like by an electrostatic chucking force. The present invention relates to an electrode cleaning method and a detection device therefor.

[0002]

2. Description of the Related Art Conventionally, in a wafer processing using plasma, for example, in an etching process, a state in which a wafer is not placed every predetermined number of processing sheets in order to remove a reaction product attached to an insulating film surface of an electrostatic chucking electrode. Plasma cleaning using oxygen gas or the like.

[0003]

In the above-mentioned prior art, the plasma cleaning is terminated based on the change in the emission intensity of the plasma or the experience of the operator, and the reaction products on the electrodes are completely removed due to insufficient plasma cleaning. However, there is a problem that the insulating film is scraped off due to the non-removal, or conversely, the termination is delayed, thereby shortening the life of the electrostatic chucking electrode.

In order to solve such a problem in connection with the present invention, for example, Japanese Patent Application Laid-Open No. 9-8113 is cited. This technique detects a change in resistance of an insulating film during plasma cleaning, and terminates plasma cleaning when the resistance drops to a preset set value.

An object of the present invention is to provide a method and an apparatus suitable for easily detecting the end of plasma cleaning.

[0006]

The object of the present invention is to provide a Vpp detection circuit in parallel with a high-frequency application circuit formed by a high-frequency power supply connected to a sample stage and comprising a plasma, an electrostatic attraction electrode and a grounding portion. The Vpp detection circuit sequentially detects a change in Vpp during plasma cleaning. Then, when Vpp drops to a preset value, the plasma cleaning is ended.

[0007] Vpp during plasma cleaning of the electrostatic attraction electrode is determined by the impedance of the reaction product adhering to the surface of the electrostatic attraction electrode and the plasma if the high frequency power applied to the electrostatic attraction electrode is constant. If the amount of the reaction product adhering to the surface of the electrostatic attraction electrode is large, the impedance increases and Vpp increases. Conversely, if it is small, Vpp will be low. Therefore, by monitoring the change in Vpp during plasma cleaning, the degree of adhesion of the reaction product on the surface of the insulating film can be detected.

Therefore, when the reaction products are removed by the plasma cleaning and the plasma cleaning is terminated when Vpp becomes equal to a preset value, the plasma cleaning is insufficient or the insulating film is scraped and the electrostatic attraction electrode is removed. Can be solved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a plasma processing apparatus equipped with an electrostatic chucking electrode, in this case, a magnetic field microwave plasma etching apparatus. 1 is a wafer, 2 is a discharge tube made of a material that transmits microwaves such as quartz, 3 is a process gas used for processing the wafer 1, 4 is a microwave for converting the process gas into plasma. Reference numeral 5 denotes a solenoid coil for forming a magnetic field in the discharge tube 2;
Is a plasma of the process gas 3, 7 is a chamber forming a vacuum processing chamber, 8 is an insulator for obtaining electrical insulation from the chamber 7, 9 is a lower part attached to the chamber 7 via the insulator 8. An electrode 10 is a material that is a good conductor of electricity and a good conductor of temperature, in this case, an electrode formed of Al, 11 is an insulating film made of Al ₂ O ₃ , 12 is an electrode 1
0 is a brazing material that joins the insulating film 11 and 13 is an electrode 10,
Lower electrode 9 composed of insulating film 11 and brazing material 12
14 is a high frequency power supply,
Reference numeral 15 denotes a switch for turning on / off the application of the high-frequency power to the lower electrode 9. Reference numeral 16 is connected to the lower electrode 9, and includes a high-frequency power supply 14, an electrostatic attraction electrode 13, a plasma 6, and a high-frequency power source. This is a high-frequency voltage Vpp detection circuit provided in parallel with the application circuit. The Vpp detection circuit 16 is configured as shown in FIG.
A diode bridge 17 for rectifying a high-frequency current and a resistor 18 for smoothing the rectified current as shown in FIG.
, A capacitor 19, an operational amplifier 20 for converting the smoothed current into a voltage, and a resistor 21. Vpp is output from the output of the operational amplifier 20 as a DC voltage. Reference numeral 22 denotes a low-pass filter including a coil 23 and a capacitor 24; 25, a DC power supply for applying a DC voltage to the electrostatic attraction electrode 13; 26, a switch for turning on and off the application of the DC voltage; This is a terminal of the switch 26. By connecting the switch 26 to the terminal 27, a DC voltage is applied to the electrostatic attraction electrode 13, and by connecting the switch 26 to the terminal 28,
The electrostatic attraction electrode 13 is grounded via a resistor 29. 30
Is a mass flow controller, and 31 is an electrostatic attraction electrode 13
A heat transfer gas supply line for supplying He gas to the back surface of the wafer 1 held thereon via a mass flow controller 30; 32, a circulator; 33, a coolant whose temperature is controlled from the circulator 32; And a refrigerant line for recovering from the lower electrode 9.
Reference numeral 34 denotes a wafer lifting device for placing the wafer 1 on the electrostatic attraction electrode 13 and removing the wafer 1 from the electrostatic attraction electrode 13.

In this apparatus having the above-described structure, the wafer 1
In the etching process, the wafer 1 is mounted on the electrostatic attraction electrode 13 by a transfer device and a wafer lifting device 34 (not shown), and the process gas 3 introduced into the discharge tube 2 is subjected to the magnetic field generated by the microwave 4 and the solenoid 5. Is made into plasma 6 by the interaction of. At this time, the switch 15 is turned on, high frequency power is applied to the lower electrode 9 by the high frequency power supply 14, and the energy of ions incident on the wafer 1 is controlled.

When the etching of the wafer 1 is completed, the etched wafer 1 is transferred from the electrostatic attraction electrode 13 to a transfer device (not shown) by the operation of the wafer lifting device 34, and then transferred to another place by the transfer device. Conveyed.

When the wafer 1 is attracted to the electrostatic attraction electrode 13 at the start of the etching process in the present apparatus,
The switch 26 is connected to the terminal 27 while the plasma 6 is generated, and a DC voltage is applied to the electrostatic attraction electrode 13 by the DC power supply 25 to perform the operation. After the etching process, the wafer 1 is released from the electrostatic attraction electrode 13 by connecting the switch 26 to the terminal 28 while the plasma 6 is being generated and grounding the electrostatic attraction electrode 13 via the resistor 29. Performed by

On the other hand, when cooling the wafer 1 to be etched, the mass flow controller 30 is opened and the He gas is supplied from the heat transfer gas supply line 31 while the wafer 1 is electrostatically attracted and held on the electrostatic attraction electrode 13. This is performed by introducing the wafer 1 to the back surface. At this time, the temperature of the lower electrode 9 is controlled by the circulator 32 and the temperature-controlled refrigerant circulating through the refrigerant line 33.

Next, a plasma cleaning method for the electrostatic attraction electrode 13 will be described with reference to FIG. The plasma cleaning is performed in a state where the wafer 1 is not placed on the electrostatic chucking electrode 13. First, an oxygen gas, for example, is introduced as a cleaning process gas 3 into the discharge tube 2, a plasma 6 is generated by the interaction between the microwave 4 and the magnetic field generated by the solenoid 5, and then the switch 15 is turned on to turn on the electrostatic switch. High-frequency power is applied to the attraction electrode 13 by the high-frequency power source 14 to start plasma cleaning. And Vp
Vpp is successively detected as a DC voltage by the p detection circuit 16. Vpp detected during plasma cleaning is
As shown in FIG. 3, when the reaction products attached to the surface of the electrostatic attraction electrode 13 are removed with the progress of the plasma cleaning, the impedance gradually decreases because the impedance decreases. After that, the detected Vpp is sequentially compared with a preset set value by a comparator or the like, and when they match, the switch 15 is turned off to stop the application of the high frequency power, and the microwave 4 and the solenoid 5 are turned off. Then, the plasma 6 is extinguished, and the plasma cleaning is completed.

As described above, by detecting the end of the plasma cleaning, insufficient removal of the reaction product due to insufficient plasma cleaning, or the insulating film 11 is scraped by the plasma cleaning to shorten the life of the electrostatic chucking electrode 13. Can solve the problem.

[0016]

According to the present invention, the end of the plasma cleaning can be easily detected.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an overall configuration of an etching apparatus which is an example of an apparatus for carrying out a method for cleaning an electrostatic chucking electrode according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a Vpp detection circuit in the device of FIG.

FIG. 3 is a diagram showing a relationship between a cleaning time and Vpp in plasma cleaning of the electrostatic chucking electrode of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 6 ... Plasma, 11 ... Insulating film, 13 ... Electrostatic attraction electrode, 14 ... High frequency power supply, 16 ... Vpp detection circuit.

Claims (2)

[Claims] An electrostatic attraction electrode for supporting a wafer to be processed by plasma with an electrostatic attraction force generated between the insulating film and an insulating film is formed through a plasma, an electrostatic attraction electrode, a high frequency power supply, and a grounding unit. Vpp of the applied high frequency application circuit
And detecting a change in Vpp during the plasma cleaning and terminating the plasma cleaning at a time when the Vpp coincides with a predetermined set value. 2. A cleaning and detecting device for an electrostatic attraction electrode for supporting a wafer to be processed by plasma with an electrostatic attraction force generated between the wafer and an insulating film. A Vpp detection circuit is provided in parallel with a high frequency application circuit formed through the device, and a means for detecting a change in the Vpp during plasma cleaning and judging the end of plasma cleaning at a time when the Vpp coincides with a predetermined set value is provided. A cleaning detection device for an electrostatic attraction electrode.