JPH08203990A - Electrostatic chuck - Google Patents

Abstract

PURPOSE: To provide an electrostatic chuck capable of reducing a remaining chucking force expanding over a wide temperature range of a room temperature or less and excellent in reliability of wafer carriage. CONSTITUTION: An insulation film 11 is formed with a material that TiO2 is added to Al2 O3 on an electrode 10 to constitute an electrostatic chucking electrode. A film thickness and a chucking area of a wafer 1 are determined so that resistance of the insulation film 11 is within a range of 10<3> to 10<6> Ω. Further, TiO2 is added to Al2 O3 that a peculiar resistor value is in the range of 10<7> to 10<9> Ω-cm, as the insulation film 11, to form a film or a SiC sintered body to be used. Thus, it is possible to reduce a remaining chucking force when a wafer is released, expanding over a wide temperature range of a room temperature or less and enhance reliability of wafer carriage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chucking device for supporting a sample processed by plasma or the like by electrostatic chucking force to reduce the residual chucking force over a wide temperature range below room temperature and to improve wafer transfer reliability. The present invention relates to an electrostatic adsorption device suitable for improving the property.

[0002]

2. Description of the Related Art As a conventional technique relating to electrostatic attraction, an insulating film is made of T as described in JP-A-3-204924.
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 less including iO ₂ .

[0003]

Considering that the above-mentioned conventional technique is applied to an etching apparatus in which the temperature of an electrode is adjusted to an arbitrary temperature below room temperature and a wafer is continuously processed by plasma, the following problem is solved. There are two issues to be addressed. First, in the prior art, since the specific resistance value of the insulating film is optimized according to each operating temperature, the residual suction force can be reduced over a wide temperature range and the reliability of wafer transfer cannot be improved. For this reason, it is necessary to replace the electrostatic adsorption electrode each time the electrode temperature is changed and processed, and it takes time to start up the device after the electrode replacement and it is difficult to improve the throughput. Next, since the second wafer to be etched is usually sent through a thermal oxidation process, a SiO ₂ film, a Si ₃ N ₄ film or the like is formed on the back surface. Also in the above, it was necessary to lower the specific resistance value of the insulating film, that is, the resistance so that the residual adsorption force could be reduced. However, in the conventional technique, the specific resistance value is 10
Since it is in the range of ⁹ to 10 ¹¹ Ω-cm, it is necessary to reduce the film thickness of the insulating film in order to reduce the resistance, and there is a problem that dielectric breakdown easily occurs.

An object of the present invention is to provide an electrostatic chucking device which reduces the residual chucking force over a wide temperature range below room temperature and has high wafer transfer reliability.

[0005]

To achieve the above object, the film thickness and the adsorption area of the wafer are determined so that the resistance of the insulating film is in the range of 10 ³ to 10 ⁶ Ω. In addition, as an insulating film, T _{2 is used} as Al ₂ O ₃ having a specific resistance value of 10 ⁷ to 10 ⁹ Ω-cm.
A film formed by adding iO ₂ or a SiC sintered body is used.

[0006]

The discharge time constant of the electric charge from the insulating film when the wafer is released after the etching process is represented by the product of the resistance of the insulating film and the capacitance of the gap between the wafer and the insulating film. If the surface roughness of the insulating film is constant, the residual adsorption force can be reduced by lowering the resistance of the insulating film. Further, when a SiO ₂ film, a Si ₃ N ₄ film or the like is formed on the back surface, it tends to be slightly longer than the above-mentioned time constant, but similarly, by lowering the resistance of the insulating film, the residual adsorption force is reduced. Can be reduced.

Therefore, in order to reduce the residual adsorption force over a wide temperature range below room temperature, it is necessary to optimize the resistance of the insulating film in consideration of temperature dependence.

Actually, the resistance of the insulating film formed by adding TiO ₂ to Al ₂ O ₃ is 9 × 10 ⁶ Ω, 5 × 10 ⁵ Ω, 7 ×
The residual adsorption force was examined in the range of the electrode temperature of 20 to -50 ° C while changing to 10 ³ Ω. As a result, the resistance is 10 ³ to 10 ⁶
By setting the value in the range of Ω, the Si wafer and the SiO
It was found that the residual adsorption force can be reduced to the target value of 0.02 N / cm ² or less within 5 S for both Si wafers having the _two films formed to 1 μm, and the reliability of wafer transfer can be improved. Also,
In order to set the resistance value within the above range, the specific resistance value is 10
By using an insulating film in the range of ⁷ to 10 ⁹ Ω-cm, it was possible to secure a sufficient film thickness without causing dielectric breakdown. Further, similar results were obtained even when a SiC sintered body was used as an insulating film.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a so-called magnetic field microwave etching apparatus to which the first embodiment of the present invention is applied will be described below with reference to FIGS. In FIG. 1, the wafer 1 is etched by converting the process gas 3 introduced into the discharge tube 2 at a predetermined flow rate into plasma 6 by the interaction of the microwave 4 and the magnetic field of the solenoid 5, and further generating a high frequency power by the high frequency power source 8 on the lower electrode 7. Is applied to control the energy of the ions incident on the wafer 1.

When the etching of the wafer 1 is completed, the wafer 1 having been etched 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. It

Further, an electrostatic adsorption electrode 12 formed by forming an insulating film 11 on the electrode 10 by using a material obtained by adding TiO ₂ to Al ₂ O ₃ is fixed on the lower electrode 7, and further, the lower electrode. A switch 14 is provided between 7 and the DC power supply 13. Then, at the start of the etching process, the wafer 1
When the wafer 1 is released, the switch 14 is connected to the terminal 15 to apply a DC voltage to the electrostatic attraction electrode 12, and when the wafer 1 is released after the etching process is completed, the switch 14 is connected to the terminal 16 to electrostatically charge via the resistor 17. The adsorption electrode 12 is grounded.

On the other hand, the wafer 1 to be etched is cooled by connecting the switch 14 to the terminal 15 and applying a DC voltage between the insulating film 11 and the wafer 1, and then generating the plasma 6 by the above-mentioned method. With the wafer 1 supported by electrostatic attraction, the mass flow controller 18 is opened and He gas 19 is introduced to the back surface of the wafer 1. The lower electrode 7 is a circulator 20.
By circulating the refrigerant 21, the temperature is adjusted to an arbitrary temperature in the range of 20 to -50 ° C.

Next, in the first embodiment of the present invention, the resistance of the insulating film 11 is set to 9 × 10 ⁶ Ω, 5 × 10 ⁵ Ω and 7 × 10 ^3.
The electrode temperature is 20 to -50 ° C. by using the electrostatic adsorption electrode 12 manufactured by determining the film thickness and the adsorption area of the wafer 1 so as to be Ω.
3 to 5 show the results of studying the residual adsorption force in the range of. First, as shown in FIG. 3, the resistance value is 9 × 10
The residual adsorption force in the case of ⁶ Ω can be reduced to the target 0.02 N / cm ² or less within 5 S at an electrode temperature of 20 ° C., but −2
In the case of cooling to 0 ° C and -50 ° C, the adsorption force of about 0.3 N / cm ² remained even after 5S, and it was found that it cannot be applied. This is because the insulating film 1
This is because the resistance of No. 1 becomes high and the discharge time constant becomes long.
On the other hand, as shown in FIG.
It can be seen that the residual adsorption force in the case of 10 ⁵ Ω similarly increases with a decrease in the electrode temperature, but can be reduced to the target of 0.02 N / cm ² or less within 5 S within the range of 20 to -50 ° C. Further, as shown in FIG. 5, the resistance is further lowered to 7 × 10 ³ Ω, so that the residual adsorption force is reduced to 20 to 30 ° C.
It can be seen that the target value can be instantly reduced to 0.02 N / cm ² or less in the range of -50 ° C.

Further, for example, for processing a 6-inch wafer, the adsorption area of the wafer 1 is set to about 140 cm ² , and Al ₂ O _{3 having a} specific resistance value of 2 × 10 ⁹ and 3 × 10 ⁷ Ω-cm, respectively.
If the insulating film 11 with TiO ₂ added is used, the film thickness is about 30.
At 0 μm, the resistance can be made 5 × 10 ⁵ Ω and 7 × 10 ³ Ω described above, and a sufficient film thickness that does not cause dielectric breakdown even at an applied voltage of 1000 V can be secured.

Next, FIG. 6 shows the structure of the electrostatic attraction electrode 12 of the second embodiment of the present invention. The difference from the first embodiment is that the electrostatic attraction electrode 12 is formed by joining the electrode 10 and the brazing material 22 using a SiC sintered body as the insulating film 11. Determine the film thickness and the adsorption area of the wafer 1 so that the resistance of the insulating film is 8 × 10 ⁴ Ω, and the electrostatic adsorption electrode 1
2 was manufactured and the same examination as in the first embodiment was conducted. As a result, the residual adsorption force can be instantly reduced to the target value of 0.02 N / cm ² or less in the range of the electrode temperature of 20 to -50 ° C., and no problem occurs in the transportation of the wafer 1.

Further, for example, in order to process a 6-inch wafer, when the adsorption area of the wafer 1 is set to about 100 cm ^{2 and} a SiC sintered body having a specific resistance value of 8 × 10 ⁷ Ω-cm is used, the resistance is about 1 mm in film thickness. Can be set to 8 × 10 ⁴ Ω described above, and a sufficient film thickness that does not cause dielectric breakdown even at an applied voltage of 1000 V can be secured.

As described above, the specific resistance value is 10 ⁷ so that the resistance of the insulating film 11 is in the range of 10 ³ to 10 ⁶ Ω.
By manufacturing the electrostatic adsorption electrode 12 by determining the film thickness of the insulating film and the adsorption area of the wafer 1 using a material in the range of -10 ⁹ Ω-cm, the electrode temperature remains over a wide range of 20 to -50 ° C. The suction power can be reduced and the reliability of wafer transfer can be improved.

[0018]

According to the present invention, it is possible to provide an electrostatic chucking device capable of reducing the residual chucking force over a wide temperature range below room temperature and having a high wafer transfer reliability.

[Brief description of drawings]

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

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

FIG. 3 is an explanatory diagram showing the results of measuring the temperature dependence of the residual adsorption force in the first example of the present invention.

FIG. 4 is an explanatory diagram showing the results of measuring the temperature dependence of the residual adsorption force for the first example of the present invention.

FIG. 5 is an explanatory diagram showing the results of measuring the temperature dependence of the residual adsorption force for the first example of the present invention.

FIG. 6 is an explanatory diagram showing a configuration of an electrostatic attraction electrode to which a second embodiment of the present invention has been applied.

[Explanation of symbols]

11 ... Insulating film, 12 ... Electrostatic adsorption electrode, 13 ... DC power supply,
14 ... switch.

Claims (4)

[Claims] 1. An electrostatic chucking device for supporting a sample by an electrostatic chucking force generated between the sample and an insulating film, wherein the resistance of the insulating film is in the range of 10 ³ to 10 ⁶ Ω. Electrostatic adsorption device. 2. The specific resistance value of the insulating film is 10 ⁷ to 10 ⁹ Ω
The electrostatic attraction device according to claim 1, wherein the electrostatic attraction device has a range of −cm. 3. The electrostatic attraction device according to claim 1, wherein a material obtained by adding TiO ₂ to Al ₂ O ₃ is used as the insulating film. 4. The electrostatic chucking device according to claim 1, wherein a SiC sintered body is used as the insulating film.