JPH08203989A - Electrostatic chuck and its method - Google Patents

Abstract

PURPOSE: To provide an electrostatic chuck suitable for treating a wafer by multi-step etching with excellent throughput and its method. CONSTITUTION: A SiC sintered body is connected with solder 12 as an insulation film 11 on an electrode 10 to constitute an electrostatic chuck electrode. A parallel circuit 17 of a variable resistor 15 and a capacitor 16 is provided in an electrostatic chuck circuit comprising a direct current power supply 14, the insulation film 11 and a switch 18, and further resistors 21 are provided in parallel via the switch 18. A direct current voltage is applied to an electrostatic chuck electrode 13 via the parallel circuit 17 when a wafer is chucked, and an operator manipulates to grind the electrostatic chuck electrode 13 via the resistors 21 by the switch 18 when the wafer is released.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] In an electrostatic chucking device for supporting a wafer processed by plasma or the like by electrostatic chucking force,
The present invention relates to an electrostatic chucking apparatus and method suitable for processing a wafer through multi-stage etching with good throughput.

[0002]

2. Description of the Related Art As a conventional technique relating to electrostatic attraction, as disclosed in Japanese Patent Application Laid-Open No. 3-204924, an insulating film is made of Ti.
It has been proposed to adjust the specific resistance value to a range of 10 ⁹ to 10 ¹¹ Ω-cm at a use temperature of 100 ° C. or lower including O ₂ .

[0003]

Considering the application of the above-mentioned conventional technique to an electrode on which a wafer to be etched is mounted, there are the following problems to be solved. In other words, the process is becoming more complicated as the device becomes more highly integrated,
A method of etching a wafer while changing the process conditions in multiple stages has become the mainstream. In order to process the wafer well by the above-mentioned method, it is not necessary to introduce and exhaust He gas for cooling the wafer to the back surface of the wafer when the plasma is extinguished as the electrostatic attraction electrode during the process. Adhesive force is likely to remain on the other hand, and conversely, when releasing a processed wafer, it is necessary to control the residual attractive force so that the attractive force can be promptly reduced in order to carry out smoothly. . In the conventional insulating film, the specific resistance value is
Since it is in the range of 10 ⁹ to 10 ¹¹ Ω-cm, when the plasma is extinguished, a sufficient residual adsorption force for maintaining the backside pressure of the wafer cooling He gas cannot be obtained and the throughput is improved. I couldn't.

The object of the present invention is to control the residual adsorption force.
It is an object of the present invention to provide an electrostatic attraction device and method capable of treating multi-stage etching with good throughput by performing the etching.

[0005]

The above object is to provide a parallel circuit of a resistor and a capacitor in an electrostatic attraction circuit composed of a DC power source, an insulating film and a switch, and further provide a resistor in parallel via a switch. Then, a DC voltage is applied to the insulating film via the parallel circuit of the resistor and the capacitor when the wafer is adsorbed, and the insulating film is grounded without the parallel circuit of the resistor and the capacitor when releasing the wafer. It is achieved by operating the switch.

[0006]

The discharge time constant of the electric charge charged in the insulating film when the wafer is released is represented by the product of the resistance R of the insulating film and the electrostatic capacitance C in the gap between the wafer and the insulating film. On the other hand, the discharge time constant of the electric charge when the plasma is extinguished is such that the resistance value R ₁ of the resistor is higher than the resistance R of the insulating film, and the electrostatic capacitance C ₁ of the capacitor is larger than the electrostatic capacitance C of the gap between the wafer and the insulating film. By increasing the value, R ₁ C ₁ is longer than RC described above. Therefore, the residual adsorption force can be controlled, and the wafer can be processed in a good throughput by multi-stage etching.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a so-called magnetic field microwave etching apparatus to which an embodiment of the present invention is applied will be described below with reference to FIGS.
This will be described below. In FIG. 1, the wafer 1 is etched by turning the process gas 3 introduced into the discharge tube 2 into plasma 6 by the interaction of the microwave 4 and the magnetic field of the solenoid 5, and applying a high frequency to the lower electrode 7 by the high frequency power source 8. Is performed 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 transferred from the lower electrode 7 to a transfer device (not shown) by the operation of the wafer lifting device 9, and then transferred to another place by the transfer device. Also,
On the lower electrode 7, the electrode 10 is made of SiC as an insulating film 11.
An electrostatic attraction electrode 13 formed by joining a sintered body with a brazing material 12 is fixed, and a parallel circuit 17 of a variable resistor 15 and a capacitor 16 and a switch 18 are further provided between the lower electrode 7 and the DC power source 14. A DC voltage can be applied to the electrostatic attraction electrode 13 via the parallel circuit 17 by connecting the switch 18 to the terminal 19, and by connecting the switch 18 to the terminal 20, the electrostatic attraction electrode 13 via the resistor 21. So that it can be grounded.

On the other hand, the cooling of the wafer 1 to be etched occurs by connecting the switch 18 to the terminal 19 and applying a DC voltage between the insulating film 11 and the wafer 1, and then generating the plasma 6 by the method described above. With the wafer 1 supported by electrostatic attraction, the mass flow controller 22 is opened and He gas 23 is introduced to the back surface of the wafer 1. Further, the lower electrode 7 is used as the circulator 2.
The temperature is controlled by circulating the refrigerant 25 by means of 4.

Next, the case of changing the process condition to multiple stages, for example, two stages and performing the etching process will be specifically described with reference to FIG. In FIG. 3, first, when the wafer 1 to be processed is transferred onto the electrostatic attraction electrode 13, the switch 18
Is connected to the terminal 19 and a DC voltage is applied between the insulating film 11 and the wafer 1, plasma 6 is generated by the above-described method to support the wafer 1 on the electrostatic attraction electrode 13. Then, the mass flow controller 22 is opened, and He gas 23 is introduced to the back surface of the wafer 1 to start the etching process while cooling the wafer 1. After that, the plasma 6 is once extinguished until the first etching process is completed and the second etching process is started, but the introduction of the He gas 23 to the back surface of the wafer 1 is continued. When the second-stage etching process is completed, the mass flow controller 22 is closed, the introduction of the He gas 23 is stopped, and the vacuum pump 26 exhausts the gas. After that, the switch 18 is connected to the terminal 20 and both ends of the electrostatic attraction electrode 13 are grounded for a certain time, and then the plasma 6
Disappear.

The residual characteristics of the adsorption force at the time of switching the process from the first stage to the second stage when the above operation is performed will be described with reference to FIGS. 4 and 5. In the figure, first, the electric charge charged in the insulating film 11 is discharged through the parallel circuit 17 of the variable resistor 15 and the capacitor 16 when switching from the first stage to the second stage. Therefore, by adjusting the resistance value R ₁ of the variable resistor 15 to be larger than the resistance value R of the insulating film 11 and the electrostatic capacitance C ₁ of the capacitor 16 to be larger than the electrostatic capacitance C of the gap between the wafer 1 and the insulating film 11. Since the discharge time constant is R ₁ C ₁ , it is longer than RC, and even if the plasma 6 is extinguished, the pressure of the He gas 23 on the back surface of the wafer 1 can hold the wafer 1 without detaching it. Next, when the etching of the second stage is completed, both ends of the electrostatic attraction electrode 13 are grounded, so that the insulating film 1
The discharge time constant of the electric charge from 1 is the product of the resistance value R of the insulating film 11 and the electrostatic capacitance C of the gap between the wafer 1 and the insulating film 11,
Since the resistance value R of the SiC sintered body that is the insulating film 11 is set to be small, the resistance value is shortened, so that the attraction force is quickly reduced and the wafer 1 can be released from the electrostatic attraction electrode 13 in a smooth manner.

Next, FIG. 6 and FIG. 7 show the results of measuring the residual adsorption force when the plasma 6 is extinguished and when the wafer 1 is released. In the figure, the measurement shows that the insulating film 11 has a resistance of 8.1 × 1.
Using a SiC sintered body of 0 ⁴ Ω, the resistance value of the variable resistor 15 is 1 × 10 ⁷ Ω, and the capacitance of the capacitor 16 is 3 × 10 ⁶
I went as F. From this result, the residual adsorption force when the plasma 6 is extinguished depends on the applied voltage, but the adsorption force of about 0.2 N / cm ² remains even after about 60 S.
The backside pressure of the wafer 1 due to the e gas 23 could be sufficiently maintained. In addition, the residual suction force when releasing the wafer 1 was instantaneously lowered to the target value of 0.02 N / cm ² or less, and there was no problem in the transfer of the wafer 1.

In the present invention, since the residual adsorption force can be controlled as described above, the step of exhausting and introducing the He gas 23 between the first and second etching processes can be omitted, and the sulfur gas can be omitted. -The put can be improved.

[0013]

According to the present invention, it is possible to provide an electrostatic chucking device and method suitable for processing a wafer with good throughput by multi-step etching.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a configuration of an electrostatic attraction electrode to which an embodiment of the present invention is applied.

FIG. 3 is a diagram illustrating a multi-step etching method according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a residual characteristic of an attraction force according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating the residual characteristics of the suction force according to the embodiment of the present invention.

FIG. 6 is a diagram showing a measurement result of residual adsorption force according to an example of the present invention.

FIG. 7 is a diagram showing a measurement result of residual adsorption force according to an example of the present invention.

[Explanation of symbols]

11 ... Insulating film, 13 ... Electrostatic adsorption electrode, 14 ... DC power supply,
15 ... Variable resistance, 16 ... Capacitor, 17 ... Parallel circuit.

Claims (2)

[Claims] 1. An electrostatic adsorption device for supporting a sample by an electrostatic adsorption force generated between the sample and an insulating film, wherein a resistance and a capacitor are connected in parallel to an electrostatic adsorption circuit composed of a DC power supply, a switch and an insulating film. An electrostatic adsorption device characterized in that a circuit is provided and a resistor is provided in parallel via a switch. 2. When a wafer is attracted, a DC voltage is applied to the insulating film via a parallel circuit of a resistor and a capacitor, and when releasing the wafer, the insulating film is bypassed without a parallel circuit of a variable resistor and a capacitor. An electrostatic adsorption method characterized in that the switch is operated so as to be grounded.