JPH0786383A - Electrostatic device and method therefor - Google Patents

Abstract

PURPOSE:To enhance an electrostatic attraction device in reliability of a wafer transfer operation by a method wherein a wafer is released after it is ascertained that a leakage current which flows when both ends of an insulating film are grounded grows less than a set value. CONSTITUTION:After an etching process is finished, a switch 14 is turned OFF and a switch 16 is turned ON before a plasma 6 is quenched, and both ends of an insulating film 12 are grounded, whereby charge stored in the insulating film 12 is discharged to grow a leakage current. The leakage current is detected by a detector 19 and converted into a digital signal through an A/D converter 24, the digital signal is compared with a set value 25 given from the outside through a comparator 26, and a wafer pushup device 9 is actuated to release a wafer 1 from a lower electrode 7 after making sure that the digital signal grows less than the set value 25. By this setup, a wafer transfer operation carried out by an electrostatic attraction device can be enhanced in reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic adsorption device and method suitable for improving the reliability of wafer transfer in an electrostatic adsorption device which supports a sample processed by plasma or the like by an electrostatic adsorption force.

[0002]

2. Description of the Related Art As a first conventional technique, Japanese Patent Laid-Open No. 62-2
As described in Japanese Patent No. 55039, when the direct-current voltage for adsorption and holding, which is applied between a pair of positive and negative electrodes of the electrostatic adsorption device, is cut off, a direct-current voltage whose polarity is opposite to that at the time of adsorption is applied between the electrodes. It has been proposed to apply the voltage for a minute time.

Further, as a second conventional technique, Japanese Patent Laid-Open No. Sho 59 is used.
As described in JP-A-67629, a measuring means for measuring the adsorption force is provided, and a charge having an electric charge amount corresponding to the measurement value of the measuring means is applied to the sample stage by applying a voltage in a direction opposite to that at the time of adsorption, It has been proposed to remove the object from the sample stage.

[0004]

Considering the application of the above-mentioned conventional technique to the electrodes on which the wafers to be successively etched are placed, there are the following problems to be solved.
As a result of an experimental study on the reduction of the residual adsorption force by applying a reverse voltage, when the resistance is low as in the case of a Si wafer and free electrons move due to dielectric polarization of the insulating film to generate an adsorption force, the reverse voltage is applied. The longer the time, the smaller the residual adsorption force, which was effective. But Si
If the SiO ₂ film by dielectric polarization of the insulating film so that the wafer where the SiO ₂ film is vapor deposited on the wafer backside also be induced polarization produces a suction force, residual adsorption force even when applying a reverse voltage is hardly removed However, it was difficult to improve the reliability of wafer transfer. In addition, the magnitude of the residual adsorption force and the speed of decay depend on the applied voltage during adsorption, the type of insulating film, the type of wafer,
It depends greatly on the electrode temperature, and it was necessary to confirm the magnitude of the residual suction force when releasing the wafer in order to improve the reliability of the transfer. A second conventional technique has been proposed as a method therefor, but it has been difficult for the etching apparatus to process the wafer while measuring the residual suction force.

An object of the present invention is to provide an electrostatic attraction device and method capable of improving the reliability of wafer transfer by detecting the magnitude of the residual attraction force by the leak current flowing when both ends of the insulating film are grounded. Especially.

[0006]

In order to achieve the above object, means for detecting a leak current flowing when both ends of an insulating film are grounded, a detected leak current and a set value from the outside are set. This is achieved by providing a means for comparison, confirming that the leak current has become equal to or less than a set value, and releasing the wafer.

[0007]

When the both ends of the insulating film are grounded after the wafer is electrostatically adsorbed, the insulating film and SiO vapor-deposited on the back surface of the Si wafer
It was clarified by experiments that the electric charge stored in the _two membranes was discharged and a leak current was generated in the direction opposite to that during adsorption, and the residual adsorption force became smaller as the leak current decreased. Therefore, by detecting this leak current, it becomes possible to confirm the magnitude of the residual attraction force, and the reliability of wafer transfer can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a magnetic field microwave etching apparatus to which an embodiment of the present invention is applied will be described below with reference to FIG.
In FIG. 1, the etching of the wafer 1 is performed by converting the process gas 3 introduced into the discharge tube 2 at a predetermined flow rate into plasma 6 by the interaction between the microwave 4 and the magnetic field of the solenoid 5.
Further, a high frequency is applied to the lower electrode 7 by a high frequency power source 8 while controlling the energy of the ions incident on the wafer 1.

When the etching of the wafer 1 is completed, the etched wafer 1 is moved from the lower electrode 7 to the transfer device (not shown) by raising the wafer push-up pin 10 by the operation of the wafer push-up device 9 such as an air cylinder. After that, the carrier is carried to another place.

An electrostatic adsorption electrode 13 formed by spraying Al ₂ O ₃ on an Al electrode 11 in a reduced pressure atmosphere to form an insulating film 12 is fixed on the lower electrode 7. , A parallel circuit of the switch 14 and the DC power supply 15, and the switch 16 and the variable resistor 17 on the lower electrode 7 is a low-pass filter.
It is connected via 18. A DC voltage can be applied to the electrostatic attraction electrode 13 by turning on the switch 14 when the wafer 1 is attracted, and can be grounded via the variable resistor 17 by turning on the switch 16 when the wafer 1 is released. The leak current flowing through the variable resistor 17 can be detected by the detector 19 as a voltage change across the variable resistor 17.

Next, a method of cooling the wafer 1 will be described. Cooling of the wafer 1 to be etched is a state in which the wafer 1 is supported by an electrostatic attraction force generated by turning on the switch 14 and applying a DC voltage across the insulating film 12 while the plasma 6 is being generated by the above-described method. Then, the mass flow controller 20 is opened and He gas 21 is supplied to the wafer 1
This is done by introducing it on the back side. The temperature of the lower electrode 7 is controlled by circulating a coolant 23 by a circulator 22.

Next, the method for releasing the wafer 1 after the etching process will be described with reference to FIGS. After the etching process is completed and before the plasma 6 is extinguished, the switch 14
Is turned off and the switch 16 is turned on to ground both ends of the insulating film 12, so that the electric charge charged in the insulating film 12 is discharged. A leak current flows in the opposite direction, and the residual attracting force gradually decreases. Then, as shown in FIG. 3, the leak current is detected by the detector 19, converted into a digital signal by the A / D converter 24, and then compared with the set value 25 from the outside by the comparator 26 to set the set value. After confirming that the number is 25 or less, the wafer pushing-up device 9 such as an air cylinder is driven to release the wafer 1 from the lower electrode 7.

As described above, in the present invention, the residual attracting force is detected by the leak current after grounding both ends of the insulating film 12 and the wafer 1 is released from the lower electrode 7. It is possible to reliably transfer the wafer 1 even if the residual adsorption force and the decay speed differ depending on the film type, the wafer type, and the electrode temperature.

[0014]

According to the present invention, it is possible to provide an electrostatic attraction device and method capable of improving the reliability of wafer transfer.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an etching apparatus to which an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram showing changes in a leak current and a residual adsorption force according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a method for releasing a wafer according to an embodiment of the present invention.

[Explanation of symbols]

9 ... Wafer lifting device, 12 ... Insulating film, 13 ... Electrostatic adsorption electrode, 17 ... Variable resistance, 19 ... Detector, 24 ... A / D
Converter, 25 ... Set value, 26 ... Comparator.

Claims (3)

[Claims] 1. An electrostatic chucking device for supporting a wafer processed by plasma by an electrostatic chucking force generated between the wafer and the insulating film, wherein a leak current flowing when both ends of the insulating film is grounded. An electrostatic chucking device comprising a detecting means and a means for comparing the leak current detected by the means with a set value from the outside. 2. A change in voltage across a variable resistor is detected as the leak current detecting means.
The electrostatic adsorption device described. 3. An electrostatic attraction method for supporting a wafer processed by plasma by an electrostatic attraction force generated between the wafer and the insulating film, wherein a leak current flowing when both ends of the insulating film are grounded. An electrostatic adsorption method characterized in that the wafer is released after reaching a set value or less.