JPH07226431A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To stabilize wafer attracting characteristic in a temperature region to prevent the generation of residual attracting force by providing at the surface the insulating layer consisting of aluminum nitride in the particular range having a volume natural resistance ranging from a room temperature to the particular temperature. CONSTITUTION:An electrostatic chuck is composed of a base material 1 consisting of an insulating material and an electrode 2 and insulating layer 3 formed at the surface of such base material 1. The insulating layer 3 is composed of aluminium nitride and is formed at the loading surface of a silicon wafer 4 or entire part of the base material exposed in a semiconductor manufacturing apparatus with the volume natural resistance in the temperature range of room temperature to 600 deg.C set to the range of 1X10<8> to 1X10<13>OMEGA-cm. Thereby, wafer attracting characteristic in the temperature region can be stabilized and the generation of residual attracting force can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck for electrostatically holding and processing a wafer in a semiconductor manufacturing apparatus or the like for processing or carrying, and there is no residual adsorption from room temperature to high temperature. The present invention relates to an electrostatic chuck having excellent characteristics and durability.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing apparatus, in order to form and etch a semiconductor such as a silicon wafer, it is necessary to hold the silicon wafer while maintaining its flatness. A vacuum adsorption type and an electrostatic adsorption type have been proposed.

The electrostatic chuck capable of electrostatically holding the silicon wafer among these holding means easily realizes the flatness and the flatness of the processed surface required when processing the silicon wafer. Since it is possible to process a silicon wafer in a vacuum, it is most widely used in the manufacture of semiconductors.

A conventional electrostatic chuck is one in which an insulating layer made of alumina, sapphire or the like is formed on an electrode plate (JP-A-60-261377), and a conductive layer is formed on an insulating substrate. With an insulating layer formed on the surface (JP-A-4-3
No. 4953), a structure in which a conductive layer is incorporated inside an insulating substrate (Japanese Patent Laid-Open No. 62-94953), and the like.

In recent years, as the degree of integration of integrated circuits of semiconductor devices has improved, the accuracy of electrostatic chucks has become more sophisticated, and ceramic electrostatic chucks having excellent corrosion resistance, abrasion resistance, and thermal shock resistance are required. Has become.

In general, the volume resistivity of an insulator decreases with temperature. For example, in the case of aluminum nitride, it drops drastically from 10 ¹⁶ Ω-cm to 10 ⁷ Ω-cm or less at room temperature to 600 ° C., and stable operation becomes unsuccessful. It was possible and there was a limit to the operating temperature. Therefore, Japanese Laid-Open Patent Publication No. 2-160444 discloses a structure in which two or more insulating layers are laminated and electrodes and electric circuits and switchings corresponding to the respective layers are provided to withstand use from room temperature to 400 ° C. Has been done. Further, in JP-A-4-300137, a temperature detector such as a heater or a thermocouple is attached in the electrostatic chuck,
It also suggests that an external control unit be provided to control the power supply unit in response to temperature changes to stabilize the adsorption force and widen the operating temperature range.

[0007]

The material to be formed on the surface of the electrostatic chuck does not have a material having a stable adsorption force from room temperature to high temperature. I tried to widen the temperature range that can be used by various controls. However, if two or more insulating layers are laminated to increase the number of electrodes, the electric circuit becomes complicated,
Since the structure of the electrostatic chuck itself is complicated, the manufacturing process is complicated, which results in drawbacks such as reduced product reliability and increased cost. In addition, even in the method of detecting the temperature by incorporating a heater and controlling the applied voltage, the temperature detector such as a thermocouple is incorporated in the electrostatic chuck, so if the detector fails, it becomes unusable. However, since the characteristics of the material do not change essentially even in this method, the range of use is naturally limited.

[0008]

The inventors of the present invention have made repeated studies on the above problems, particularly from the viewpoint of the material constituting the electrostatic chuck, and as a result, for example, nitriding formed by a chemical vapor deposition method. Among aluminum, when an aluminum nitride film having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹³ Ω-cm at room temperature to 600 ° C. is formed on the surface as an insulating layer, it is stable in a wide temperature range of room temperature to 600 ° C. We have realized the adsorption characteristics.

That is, the electrostatic chuck of the present invention has a volume resistivity of 1 × 10 ⁸ to at least room temperature to 600 ° C.
By forming the surface with an insulating layer mainly composed of aluminum nitride of 1 × 10 ¹³ Ω-cm, it has a stable attracting force and has no residual attracting force when the applied voltage is cut off, which is good as an electrostatic chuck. It showed various characteristics.

A typical structure of the electrostatic chuck of the present invention is shown in FIG. According to FIG. 1, the electrostatic chuck is composed of a base 1 made of an insulator, and an electrode 2 and an insulating layer 3 formed on the surface of the base 1. The insulating layer 3 is formed on at least the mounting surface of the silicon wafer 4 or the entire base surface exposed in the semiconductor manufacturing apparatus. It should be noted that there is no problem even if a heater is built in the base 1.

In the present invention, the insulating layer 3 is made of aluminum nitride and has a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹³ Ω-cm at room temperature to 600 ° C., preferably 1 × 10 ⁹ to 1 × 10. It is important that it has such a characteristic that it is in the range of ¹² Ω-cm. This is because if the volume resistivity of the insulating layer is smaller than 1 × 10 ⁸ Ω-cm, the leak current becomes large, and if it is larger than 1 × 10 ¹³ Ω-cm, the residual adsorption force occurs. Of these, 1 × 10 ^{10 to} 5 × 10 ¹¹ Ω-cm is most preferable in consideration of leakage current, withstand voltage, and response. In order to perform more stable operation, the change in volume resistivity should be within 3 digits, preferably within 2 digits within the temperature range of room temperature to 600 ° C.

The film mainly composed of aluminum nitride which constitutes the insulating layer is formed by a known vapor phase method such as sputtering,
Physical vapor phase synthesis methods such as ion plating (PVD
Method), plasma CVD, photo CVD, MO (Metal)
-Organic) chemical vapor deposition (CV) such as CVD
D method), but among these, the CVD method is preferable. The volume resistivity adopted by the present invention is 1 × 10.
The film having a thickness of ⁸ to 1 × 10 ¹³ Ω-cm can be formed by using, for example, N ₂ gas, NH ₃ gas and AlCl ₃ as source gases in the CVD method.
When gases are used, the flow rate ratio of these gases is N ₂ / Al.
Cl ₃ = 5-70, NH ₃ / AlCl ₃ = 0.1-10
Then, it can be manufactured by setting the film forming temperature to a relatively high temperature of 850 ° C. or higher.

On the other hand, as the substrate 1 for forming the insulating layer 3, any one can be used except that the outermost surface is the above-mentioned insulating layer made of aluminum nitride. Specifically, Al ₂ O ₃ , AlON, Si ₃ N ₄ , diamond,
Mullite, ZrO _{2 and the} like can be mentioned, but among these, a sintered body containing aluminum nitride as a main component is most preferable in terms of excellent plasma resistance during semiconductor production. Further, a well-known metal material can be applied to the electrode 2 for applying a voltage, and for example, any of W, Mo, Mo-Mn, and Ag can be used. Also, a conductive ceramic material such as Ti
N, SiC, WC, carbon and Si semiconductor materials (n type or p type) can also be used as the electrode material. In addition, the base body may be formed of a conductive ceramic such as SiC, TiN, or WC which does not have the electrode layer 2 and has conductivity itself, a simple metal such as W or Mo, or an alloy thereof. In that case, a voltage is directly applied to the conductive substrate itself.

In order to electrostatically adsorb a silicon wafer with the electrostatic chuck having the above structure, a voltage of about 0.2 to 2.0 kV is applied to the electrode layer or the conductive substrate to electrostatically adsorb the silicon wafer. It can be carried out.

[0015]

In the present invention, the electrical characteristics of the insulating layer are from room temperature to 6
Stabilization in the temperature range of 00 ° C., and by forming a material having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹³ Ω-cm in this temperature range on the surface, the adsorption characteristics of the wafer in this temperature range are stabilized. In addition, an electrostatic chuck that does not generate residual attraction force can be obtained.

Further, according to the present invention, it is not necessary to take a particularly complicated structure, and the use of the material of the present invention simplifies the structure of the electrostatic chuck itself, so that it can be used at a low cost in a wide temperature range. It is possible to realize the simplification of the device itself including the electric circuit, and the reliability and long-term stability of the electrostatic chuck are guaranteed.

[0017]

【Example】

Example 1 An alloy of Mo and Mn was metallized as an electrode layer on the surface of a substrate made of an aluminum nitride sintered material, and then an AlN film was formed on the surface of the electrode layer by a chemical vapor deposition method. The AlN film is formed on the substrate by an external heating method at 900
The furnace was heated to 0 ° C., and a gas of 8 SLM for nitrogen and 0.5 SLM for ammonia was passed to make the pressure 40 torr. The reaction was started by flowing 300 sccm of aluminum chloride, and the reaction was continued for 6 hours to form Al having a film thickness of about 400 μm
An N film was formed. The surface roughness Ra of the AlN film is 0.
The volume resistivity of the film at 25 ° C. to 600 ° C., the attraction force as an electrostatic chuck when a voltage of 500 V is applied to the electrode and the voltage for 30 minutes are applied, and the voltage application is stopped. Immediately after, the adsorption force was measured in vacuum.

As a result of the measurement, the volume resistivity of the AlN film obtained by the vapor phase synthesis method is 5 × 10 ^{8 to} 5 in the temperature range of 25 ° C. (room temperature) to 600 ° C. as shown by the black circle in FIG. ×
It is within 10 ¹¹ Ω-cm, the adsorption force is larger than that of the comparative example as shown by the black circles in FIG. 3, and the adsorption force is the same in the temperature range of 25 to 600 ° C., and the response is good, and the residual No adsorption power was observed.

Example 2 After alloying Mo and Mn as an electrode layer on the surface of the substrate used in Example 1, an AlN film was formed by chemical vapor deposition. The AlN film is put into a furnace in which the substrate is heated to 875 ° C. by an external heating method, and a gas of 8 SLM for nitrogen and 0.5 SLM for ammonia is flowed to set the pressure at 40 to.
rr. 300 sccm of aluminum chloride there
The reaction is started by pouring and the reaction is continued for about 6 hours
A film thickness of m was obtained. Polish the surface with Ra to 0.02 mm,
The volume resistivity, adsorption force and residual adsorption force were measured in the same manner as in Example 1. The volume resistance is 25 as shown in Fig. 2.
8 × 10 ⁹ to 1 × 10 ¹¹ Ω-cm in the temperature range of up to 600 ° C.
3, the adsorption force is larger than that of the comparative example as shown in FIG. 3, and has the same adsorption force in the temperature range of 25 to 600 ° C.
In addition, the response was good, and no residual adsorption force was observed. The characteristics were the same as in Example 1, but the response at room temperature was 30% faster than in Example 1.

Comparative Example As in Example 1, an AlN film was formed as an electrode layer on an aluminum nitride substrate metallized with an alloy of Mo and Mn by a chemical vapor deposition method. At this time, the AlN film is
The substrate was placed in a furnace heated to 825 ° C. by an external heating method, and gas of 8 SLM for nitrogen and 1 SLM for ammonia was supplied to adjust the pressure to 40 torr. 300 s of aluminum chloride
The reaction was started by flowing ccm, and after about 7 hours of reaction, about 4
An AlN film having a film thickness of 00 μm was formed. After polishing the surface with Ra to 0.2 mm, volume resistance, adsorption force and residual adsorption force were measured in the same manner as in Example 1. As a result of the measurement, the volume resistance was 1 when the temperature changed from 200 ° C to 400 ° C.
Rapidly changes from 0 ⁸ Ω-cm to 10 ¹⁴ Ω-cm.
Therefore, when the adsorption force was 400 ° C. or more, the leakage current was large and the state was unusable, and at 150 and 200 ° C., it took a long time until the adsorption force was stabilized, and the residual adsorption force was observed.

[0021]

As described above in detail, the electrostatic chuck of the present invention is used in the semiconductor manufacturing process from room temperature (25 ° C.) to 60 ° C.
Has stable adsorption characteristics in a wide temperature range of 0 ° C,
It is possible to provide an electrostatic chuck that has no residual attraction force and a high attraction force. Therefore, excellent reliability and long-term stability as the electrostatic chuck can be obtained, and the manufacturing cost of the electrostatic chuck can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of an electrostatic chuck of the present invention.

FIG. 2 is a diagram showing temperature dependence of a volume resistance value of an insulating layer manufactured in an example.

FIG. 3 is a diagram showing the temperature dependence of the adsorption force of the insulating layer produced in the example.

[Explanation of symbols]

 1 substrate 2 electrode 3 insulating layer 4 silicon wafer

Claims (2)

[Claims] 1. An electrostatic chuck having an insulating layer made of aluminum nitride having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹³ Ω-cm at least at room temperature to 600 ° C. on its surface. 2. The electrostatic chuck according to claim 1, wherein the insulating layer is coated by a chemical vapor deposition method.