JPH09283606A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excessive lowering of the resistance value on an insulating part even when the temperature rises in an electrostatic chuck, to improve the corrosion resisting property of the electrostatic chuck against the plasmic property of halogen gas, and to improve the mechanical strength and the thermal shock resistance of the electrostatic chuck. SOLUTION: An electrostatic chuck 8 is provided with an electrode 3 and insulating parts 1 and 2 which are formed on both sides of the electrode 3. At least the insulating part 1 on the side of attracting surface 6 consists of a composite sintered body. This composite sintered body consists of silicon carbide and aluminum oxide of 1 to 10wt.%, and the cubical intrinsic resistance value of the composite sintered body in room temperature is between 1×10<8> and 1×10<15> Ω/cm. The desired average grain diameter of the silicon carbide grains in the composite sintered body is 1μm or smaller.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor wafer,
Adheres metal wafers, glass plates, etc. by electrostatic force,
The present invention relates to an electrostatic chuck for holding.

[0002]

2. Description of the Related Art For example, when manufacturing a semiconductor, a liquid crystal, or the like, a vacuum chuck or a clamp is used as a method for fixing a semiconductor wafer or a glass plate. However, the fixing method using a vacuum chuck cannot be adopted because there is no pressure difference under vacuum conditions. In the mechanical fixing method using a clamp, the fixed part of the semiconductor wafer or glass plate cannot be used as a device, and the semiconductor wafer or glass plate is partially distorted. Have a problem.

As a solution to the above problems of the conventional technique, a ceramic electrostatic chuck utilizing electrostatic force has begun to attract attention. As a material of the ceramic electrostatic chuck, a composite sintered body containing titanium oxide in alumina (Japanese Patent Laid-Open No. 62-94953 and Japanese Patent Laid-Open No. 3-204924) and titanium nitride in ceramics such as alumina are used. Composite sintered body (Japanese Patent Laid-Open No. 6-80
No. 89) has been proposed.

[0004]

However, in an electrostatic chuck having an insulating portion made of titanium oxide contained in alumina, the temperature dependence of the resistance value of the composite sintered body is large, so that the plasma When the temperature of the electrostatic chuck rises due to such factors as described above, the resistance value of the insulating portion is lowered, an excessive current flows through the wafer, and the circuit of the wafer is broken.

Titanium oxide has poor corrosion resistance to plasma of halogen gases such as CF ₄ and BCl ₃ .
Plasma etching device using these halogen-based gases as etching or cleaning gas, CV
There are restrictions on the use of the D device. Furthermore, the alumina containing titanium oxide has lower strength than the alumina containing no titanium oxide. In addition, since the thermal expansion coefficient is large, the thermal shock resistance is poor, and there is a high risk of damage due to thermal stress when used at high temperatures.

On the other hand, in an electrostatic chuck provided with an insulating portion made by containing titanium nitride in ceramics such as alumina, surface deterioration due to oxidation of titanium nitride is remarkable in an etching gas atmosphere containing oxygen. . Further, as with the alumina containing titanium oxide, CF ₄ , BCl
Corrosion resistance of halogen-based gases such as _{3 to} plasma is poor, and there are restrictions on the use in plasma etching equipment, CVD equipment, etc., which use these gases as etching or cleaning gases.

The present invention prevents the resistance value of the insulating portion from excessively decreasing when the temperature of the electrostatic chuck rises, improves the corrosion resistance of the electrostatic chuck to the plasma of halogen gas, and It is also to improve its strength and thermal shock resistance.

[0008]

SUMMARY OF THE INVENTION The present invention is an electrostatic chuck comprising an electrode and insulating portions provided on both sides of the electrode, wherein at least the insulating portion on the suction surface side is a composite burner. The composite sintered body is substantially made of 1 wt% or more and 10 wt% or less of silicon carbide and aluminum oxide, and has a volume resistivity value at room temperature of the composite sintered body. 1 × 10 ⁸ Ω · cm or more,
The present invention relates to an electrostatic chuck, which is characterized in that it is 1 × 10 ¹⁵ Ω · cm or less.

The present inventor has conducted various studies as a result of various studies to develop an electrostatic chuck having a low temperature dependence of electric conductivity, excellent corrosion resistance to halogen gas, high strength and hardness, and excellent thermal shock resistance. As the material of the electrostatic chuck,
It has been found that certain composite sinters containing aluminum oxide and silicon carbide are suitable.

That is, at least the adsorption surface side of the insulating portion of the electrostatic chuck is substantially made up of 1% by weight or more and 10% by weight or less of silicon carbide and aluminum oxide, and has a volume resistivity value at room temperature of 1 ×. 10 ⁸ Ω · cm or more, 1 × 1
It was decided to form a composite sintered body having a resistivity of 0 ¹⁵ Ω · cm or less.

That is, the electrostatic chuck formed of this composite sintered body has less temperature dependence of electric conductivity, excellent corrosion resistance to halogen gas, and excellent strength and hardness as compared with alumina. There are few particles, and it has excellent heat resistance and thermal shock resistance, and there is no risk of damage due to thermal stress when used at high temperatures.

The volume resistivity is controlled to 1 × 10 ⁸ Ω · cm by controlling the amount of silicon carbide in the composite sintered body.
As described above, it is controlled to 1 × 10 ¹⁵ Ω · cm or less. That is, although it depends on the particle size of the sintered body and the like, when the content of silicon carbide is 1% by weight or more, the hardness and strength of the composite sintered body due to the addition of silicon carbide become remarkable, Moreover, the volume resistivity of the composite sintered body is 1 × 10 ¹⁵ Ω
・ Because it is less than cm, the responsiveness at the time of adsorption and desorption of wafers is significantly improved.

On the other hand, when the content of silicon carbide is 10% by weight or less, the volume resistivity value of the composite sintered body is 1 or less.
Since it is more than × 10 ⁸ Ω · cm, the leak current from the electrostatic chuck to the wafer or the like can be suppressed, and there is no risk of damaging the device by the leak current.

A small amount of impurities is allowed in the composite sintered body. However, the decrease in lifetime and gate voltage in the semiconductor manufacturing process is due to the transition metal element and the alkali metal. In addition, aluminum,
If the amount of metal impurities other than silicon exceeds 0.1% by weight, the semiconductor wafer is more likely to be contaminated, and the temperature dependence of the electric resistance of the electrostatic chuck increases.
Not preferred. Therefore, the content of metal impurities other than aluminum and silicon in the composite sintered body forming the insulating portion is preferably 0.1% by weight or less.

In a preferred embodiment of the present invention, the average particle size of silicon carbide particles in the composite sintered body is 1 μm or less. That is, if the average particle diameter of the silicon carbide particles exceeds 1 μm, the effect of improving the strength by the addition of silicon carbide is small, and the electric field at the time of plasma irradiation is concentrated on the silicon carbide particles, and the periphery of the silicon carbide particles is It is easily damaged. Therefore, by setting the average particle diameter of the silicon carbide particles to 1 μm or less, the corrosion resistance to plasma is further improved. From this viewpoint, it is more preferable that the average particle diameter of the silicon carbide particles in the composite sintered body be 0.2 μm or less.

In producing the composite sintered body, the raw material powder of silicon carbide has an average particle diameter of 0.5.
A raw material powder having a particle size of μm or less is preferable, and a non-oxidizing atmosphere is preferable as an atmosphere for sintering. That is, in the composite sintered body using the silicon carbide powder having an average particle diameter exceeding 0.5 μm, the average particle diameter of silicon carbide in the sintered body is 1
In addition, the effect of improving strength by adding silicon carbide is small, and when exposed to plasma, the electric field is concentrated on the silicon carbide portion and is easily damaged.

The silicon carbide raw material powder used is preferably a powder obtained by a plasma CVD method. In particular, a silane compound or silicon halide and a hydrocarbon source gas are introduced into plasma in a non-oxidizing atmosphere, and a gas phase reaction is performed while controlling the pressure of the reaction system within the range of less than 1 atm to 0.1 Torr. The obtained ultrafine powder having an average particle size of 0.1 μm or less has excellent sinterability and high purity,
Since the particle shape is spherical, the dispersibility during molding is good.

On the other hand, the aluminum oxide raw material powder is not particularly limited as long as it has a high purity. Further, by setting the atmosphere during sintering to a non-oxidizing atmosphere, excessive oxidation of silicon carbide during sintering can be suppressed. Known means can be adopted for the molding method and the sintering method during the production of the composite sintered body.

The specific form and manufacturing method of the ceramic electrostatic chuck of the present invention are not particularly limited. A suitable electrostatic chuck configuration and manufacturing method will be described with reference to FIGS. 1 and 2. FIG. 1A is a plan view showing the disc-shaped insulating portion 1 on the suction surface side, and FIG.
FIG. 6 is a plan view showing a disk-shaped insulating portion 2 on the base side of the electrostatic chuck. In order to manufacture the disk-shaped insulator 1 of FIG. 1A, first, a disk-shaped sintered body is manufactured, and the through-hole 1a is formed in this disk-shaped sintered body by machining. In order to manufacture the disk-shaped insulator 2 of FIG. 1B, first, a disk-shaped sintered body is manufactured, and the disk-shaped sintered body is machined to form the through-holes 2.
a and the electrode insertion hole 2b are formed. At least the insulator 1 is formed of the composite sintered body of the present invention.

Then, as shown in FIG. 2 (a), in a region A within a circle having a radius of 90 mm from the center of the disk-shaped insulating portion 2,
A conductive material is applied to form a coating layer 15, and an insulating material is applied to the outer peripheral edge region B outside the circular region A to form a coating layer 16. As such a conductive material, a mixed powder of a conductive ceramic powder such as tantalum carbide or titanium nitride and an aluminum oxide-silicon dioxide glass powder can be exemplified. As such an insulating material,
Various glass powders such as aluminum oxide-silicon dioxide glass can be exemplified. In this state, the disk-shaped insulating parts 1 and 2
And are superposed and heat-treated to bond them to each other to obtain an electrostatic chuck 8 as shown in FIG.

In FIG. 2B, a circular electrode 3 made of a conductive material is formed, and an insulating portion 1 is provided on the adsorption surface 6 side when viewed from the electrode 3. A lead-out electrode 14 made of a conductive ceramic such as tantalum carbide or titanium nitride is inserted into the electrode insertion hole 2b of the disk-shaped insulating portion 2, and the lead-out electrode 14 is formed on the electrode 3 by a brazing material such as active metal or silver brazing. Join to each other.

[0022]

【Example】

Example 1 <Production of Electrostatic Chuck> The electrostatic chuck shown in FIG. 2B was manufactured according to the method described with reference to FIGS. However, ultrafine silicon carbide powder having an average particle diameter of 0.05 μm was vapor-phase synthesized by the plasma CVD method. 5% by weight of this silicon carbide ultrafine powder and 95% by weight of aluminum oxide powder having an average particle diameter of 0.5 μm were mixed for 5 hours using an ultrasonic disperser, and this mixed powder was dried, molded, and subjected to argon. Two disc-shaped composite sintered bodies having a diameter of 195 mm and a thickness of 4 mm were obtained by sintering for 3 hours in an atmosphere at a temperature of 1700 ° C.

Then, the average particle diameter and volume resistivity of the silicon carbide particles in this composite sintered body were measured, and the results are shown in Table 1. The average particle diameter of the silicon carbide particles was measured by the SEM observation method, and the volume resistivity value was measured according to JIS C2141. The Vickers hardness and the room temperature 4-point bending strength (measured according to the method specified in JIS R1601) of the above-mentioned composite sintered body prepared separately were measured. Table 1 shows the results.

Then, the disc-shaped sintered body is machined,
Each disk-shaped insulating portion shown in FIGS. 1A and 1B was manufactured. However, in FIG. 1A, a through hole 1 a having a diameter of 15 mm is formed in the center of the insulating portion 1. In FIG. 1B, a through hole 2 having a diameter of 15 mm is formed at the center of the insulating portion 2.
Form a, and place a diameter of 1 mm at a location 25 mm away from the center.
An electrode insertion hole 2b of 0 mm was formed.

Then, the radius of 9 mm from the center of the disk-shaped insulating portion 2
In the circular area A within 0 mm, tantalum carbide (30 vol
%) And aluminum oxide-silicon dioxide glass powder (7
The mixed powder with 0 vol%) was applied by screen printing. Outer peripheral region B (radius 90 to radius 97.5
The area (mm) was coated with aluminum oxide-silicon dioxide glass powder by screen printing. Then
After grinding the disk-shaped insulating portion 1 for 1.3 mm, the lead-out electrode 14 made of tantalum carbide was inserted into the electrode insertion hole 2b of the insulating portion 2 and joined using a silver brazing agent.

<Measurement of Electrostatic Characteristics> The electrostatic chucking force thus manufactured, the electrostatic chucking force, the chucking time, and the desorbing time are measured at room temperature and 400 ° C. at the respective temperatures shown in FIG. Was measured using.

That is, the heater 9 is installed on the table 10,
The electrostatic chuck 8 was installed on the heater 9. The pressing member 11 was inserted into the through hole 10 a of the table 10, the through hole 9 a of the heater 9, and the through hole of the electrostatic chuck 8. An 8-inch silicon wafer 18 was placed on the attraction surface 6 of the electrostatic chuck 8. Pressing member 11 against silicon wafer 18
The upper ends of the. A voltage of 300 V DC is applied between the silicon wafer 18 and the take-out electrode 14, and the silicon wafer 18 is electrostatically adsorbed for 5 minutes.
The lifter 12 lifted the electrostatically adsorbed silicon wafer 18 to remove it. The desorption force required at this time was measured by a load cell and used as the electrostatic adsorption force.

The adsorption time is the time until the electrostatic adsorption force reaches 10 kgf / cm ² when a DC voltage of 300 V is applied, and the desorption time is a DC voltage of 300 V for 5 minutes. It is the time from when the application is stopped after the application to when the electrostatic adsorption force reaches 50 gf / cm ² .
Table 2 shows the measurement results.

Next, the electrostatic chuck was mounted in a plasma CVD apparatus, and CF ₄ 20 vol% of 1.0 Torr,
After being exposed to plasma for 20 hours in a mixed gas atmosphere of 80 vol% O _{2, the} same electrostatic adsorption test as described above was performed. Table 3 shows the results.

Further, in each electrostatic adsorption characteristic test before and after exposing the electrostatic chuck to plasma, the temperature up to 400 ° C.
The temperature was raised at a temperature rising rate of ° C / min. As a result, the electrostatic chuck was not damaged or damaged by thermal stress. Therefore, the item of thermal stress resistance in Tables 2 and 3 was described as “good”.

Example 2 A composite sintered body was obtained in the same manner as in Example 1. The composition of the composite sintered body was silicon carbide ultrafine powder 3
% By weight, aluminum oxide 97% by weight, sintering conditions are argon atmosphere, sintering temperature 1750 ° C., sintering time 7
Time. The average particle size and volume specific resistance of the silicon carbide particles in this composite sintered body were measured according to Example 1. Table 1 shows the results. The Vickers hardness and room temperature 4-point bending strength of the separately prepared composite sintered body were measured in accordance with Example 1. Table 1 shows the results.

Next, using this composite sintered body, Example 1
An electrostatic chuck was produced in accordance with Example 1, and electrostatic adsorption characteristics were measured in the same manner as in Example 1 before and after exposure to halogen gas plasma. The results are shown in Tables 2 and 3.

In the electrostatic adsorption characteristic test before and after the exposure to the halogen gas plasma, the temperature was raised to 400 ° C. at a heating rate of 80 ° C./min. In the case of No. 1, damage or damage due to thermal stress did not occur, and therefore, the item of thermal stress resistance in Tables 2 and 3 was described as “good”.

(Comparative Example 1) In accordance with Example 1, a composite sintered body was obtained. However, the composition of the composite sintered body was 15% by weight of silicon carbide and 85% by weight of aluminum oxide, and the average particle diameter of the silicon carbide raw material powder was 0.8 μm.

The average particle diameter and volume resistivity of the silicon carbide particles in this composite sintered body were measured according to Example 1.
Table 1 shows the results. In addition, the Vickers hardness and room temperature four-point bending strength of the above-mentioned composite sintered body prepared separately were determined according to Example 1
It measured according to. Table 1 shows the results.

Using this composite sintered body, Example 1
An electrostatic chuck was produced in accordance with Example 1, and electrostatic adsorption characteristics were measured in the same manner as in Example 1 before and after exposure to a halogen gas plasma. The results are shown in Tables 2 and 3.

In each of the electrostatic adsorption characteristic tests before and after the halogen gas plasma exposure, 400 ° C.
Up to 80 ° C./min. As a result, damage and damage due to thermal stress did not occur before plasma exposure. However, in the electrostatic adsorption characteristic test after the halogen gas plasma exposure, a part of the peripheral edge of the electrostatic chuck was damaged.

(Comparative Example 2) A composite sintered body was obtained in the same manner as in Example 1 except that the composition of the composite sintered body was 100% by weight of aluminum oxide.

The volume resistivity value of this composite sintered body was measured according to Example 1. Table 1 shows the results. Also,
Vickers hardness of the above composite sintered body prepared separately, room temperature 4
The point bending strength was measured according to Example 1. Table 1 shows the results. Then, using this composite sintered body, an electrostatic chuck was prepared according to Example 1, and electrostatic adsorption characteristics were measured before and after the halogen gas plasma exposure. The results are shown in Tables 2 and 3.

It is to be noted that 400 ° C. was used for each electrostatic adsorption characteristic test before and after the halogen gas plasma exposure.
The temperature was raised up to 80 ° C./min, but in each case, the peripheral edge of the electrostatic chuck was partially damaged.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

In Examples 1 and 2, both before and after plasma exposure, the electrostatic adsorption force is high, the adsorption time and desorption time are short, and the thermal stress resistance is excellent. In particular, Example 1
In the above, since the average particle diameter of the silicon carbide particles in the composite sintered body is also 0.2 μm, the electrostatic adsorption force after plasma exposure is higher, and the adsorption time and desorption time are shorter.

On the other hand, in Comparative Example 1, the content of silicon carbide was 15% by weight, and the average particle diameter of the silicon carbide particles was 1.2 μm. Therefore, all characteristics were excellent before plasma exposure. However, after the plasma exposure, the electrostatic adsorption force was remarkably reduced, the adsorption time was long, and part of the peripheral edge of the electrostatic chuck was lost when the temperature was raised to 400 ° C. In Comparative Example 2, alumina was used, the electrostatic adsorption force was low even before plasma exposure, and the peripheral portion of the electrostatic chuck was partially chipped when the temperature was raised to 400 ° C.

[0046]

As described above, according to the present invention, the electric conductivity has little temperature dependence, the corrosion resistance to halogen gas is excellent, the hardness is large, the heat resistance is excellent, and the adsorption / desorption response is high. An excellent electrostatic chuck can be provided.

[Brief description of drawings]

FIG. 1A is a plan view showing a disk-shaped insulating portion on a suction surface side, and FIG. 1B is a plan view showing a disk-shaped insulating portion on a substrate side.

FIG. 2A is a plan view showing a state in which a conductive material and an insulating material are applied onto the disk-shaped insulating portion 2,
(B) is a sectional view of the electrostatic chuck.

FIG. 3 is a schematic view showing a device for measuring the attraction force of an electrostatic chuck.

[Description of sign]

 1 Disc-shaped insulating part on adsorption side 1a Through hole 2 Disc-shaped insulating part on base side 2b Electrode insertion hole 3 Circular electrode 4 Insulating bonding layer 6 Adsorption surface 8 Electrostatic chuck 15 Coating layer of conductive material 16 Insulation Coating layer of conductive material 18 Semiconductor wafer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Inazuma 585 Tomimachi, Funabashi, Chiba Sumitomo Osaka Cement Co., Ltd.

Claims (3)

[Claims] 1. An electrostatic chuck comprising an electrode and insulating portions provided on both sides of the electrode, wherein at least the insulating portion on the suction surface side is formed of a composite sintered body. , The composite sintered body is substantially 1% by weight.
The volume resistivity of the composite sintered body at room temperature is not less than 1 × 10 ⁸ Ω · cm and not more than 1 × 10 ¹⁵ Ω · cm, which is made of 10% by weight or less of silicon carbide and aluminum oxide. Electrostatic chuck. 2. The average particle size of silicon carbide particles in the composite sintered body is 1 μm or less.
An electrostatic chuck as described. 3. The composite sintered body has an average particle diameter of 0.5 μm.
3. The electrostatic chuck according to claim 1, wherein the electrostatic chuck comprises a sintered body of a mixed powder of silicon carbide powder of m or less and aluminum oxide powder in a non-oxidizing atmosphere.