JP2003133401A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck which is capable of firmly attracting a wafer even if it is warped or deformed, keeping the surface of the wafer uniform in temperature distribution, restraining a heat conductive gas from leaking out, and excellent in response for releasing the wafer. SOLUTION: A recessed part 3 of a depth of 3 to 10 μm is provided to the one main surface of a platelike ceramic body 2 while its peripheral part 4 is left unremoved, undulations of the top surface of the peripheral part 4 are each set at 1 to 3 μm in length, a gas groove 5 is provided to the periphery of the bottom of the recessed part 3, and an electrostatic attraction electrode 7 is arranged inside the platelike ceramic body 2 beneath the recessed part 3 for the formation of an electrostatic chuck 1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to PVD, CVD,
Film forming equipment such as plasma CVD, plasma etching,
The present invention relates to an electrostatic chuck that is used in an etching apparatus such as photoexcited etching and that holds a wafer such as a semiconductor wafer by suction.

[0002]

2. Description of the Related Art Conventionally, PVD, CVD, plasma CVD
In a semiconductor manufacturing apparatus such as a film forming apparatus such as a plasma etching apparatus and an etching apparatus such as a plasma etching method, a semiconductor wafer (hereinafter, simply referred to as a wafer) is accurately held as an electrostatic holding force by electrostatic force. A chuck is used.

Most semiconductor manufacturing apparatuses perform a lot of processing in a vacuum, and in the film forming apparatus, the wafer is heated by the reaction gas at the time of film formation and the temperature distribution on the wafer surface becomes non-uniform. There was a problem that defects occurred. Also in the etching apparatus, the wafer is heated by the plasma etching gas or ultraviolet rays or visible light at the time of photoexcited etching, the temperature distribution on the wafer surface becomes non-uniform, and as a result, the etching rate varies depending on the temperature distribution,
There is a problem that the entire surface of the wafer cannot be uniformly etched. Therefore, how to make the temperature distribution on the wafer surface uniform has been a problem.

In view of this, in Japanese Patent Laid-Open No. 7-153825, as shown in FIG. 5, an electrostatic attraction electrode 23 is embedded in a plate-shaped ceramic body 22, and the plate-shaped ceramic body 22 is provided on the upper surface thereof. Is an electrostatic chuck 21 having a large number of protrusions 24 and an annular outer peripheral convex portion 25 having the same height as the protrusions 24 and having a width s of 1 mm to 5 mm provided so as to surround the protrusions 24. Is disclosed, electrostatic force is developed by applying a voltage between the electrostatic chucking electrode 23 and the wafer W while the wafer W is placed on the top surfaces of the protrusion 24 and the outer peripheral convex portion 25, and the wafer W is By adsorbing and fixing to the top surfaces of the protrusions 24 and the outer peripheral protrusions 25, and supplying a thermally conductive gas such as helium to the space formed between the wafer W and the upper surface of the plate-shaped ceramic body 22, Heat between the electrostatic chuck 21 Enhanced electric characteristics, a technique for the uniform temperature distribution of the wafer W has been proposed.

Further, Japanese Patent Laid-Open No. 7-86385 discloses that
As shown in FIG. 6, a concave portion 33 is left on the upper surface of the plate-shaped metal body 32 functioning as an electrostatic attraction electrode, leaving an outer peripheral portion 34.
And the dielectric layer 35 is deposited on the upper surface and the side surface of the plate-shaped metal body 32 including the recess 33, and the outer peripheral portion 34 is formed.
An electrostatic chuck 31 is disclosed in which the depth r from the dielectric layer surface 35a on the top surface to the dielectric layer surface 35b on the bottom surface of the recess 33 is several tens of μm to 0.1 to 0.2 mm.
The wafer W is formed on the dielectric layer surface 35a on the top surface of the outer peripheral portion 34.
By applying a voltage between the peripheral edge of the wafer W and the plate-shaped metal body 32, electrostatic force is developed, and only the peripheral edge of the wafer W is attracted to the dielectric layer surface 35a on the top surface of the outer periphery 34. While being fixed, the thermally conductive gas is supplied to the space formed by the wafer W and the concave portion 33 to enhance the thermal conductivity characteristic between the wafer W and the electrostatic chuck 31, and to make the temperature distribution of the wafer W uniform. The technology to do is proposed.

[0006]

However, in the electrostatic chuck 21 in which the wafer W is suction-held by the top surfaces of the large number of projections 24 and the outer peripheral projections 25 as in Japanese Patent Laid-Open No. 7-153825, there is a warp. When the deformed wafer W is fixed, the wafer W can only be partially adsorbed, and there is a risk that the wafer W may be displaced due to insufficient adsorption or the wafer W may drop in a severe case.

Further, in the publication, it is described that the inner area of the outer peripheral convex portion 25 is an adsorption area, and since the electrostatic adsorption electrode 23 is not buried below the outer peripheral convex portion 25, the outer peripheral convex portion 25 is not embedded. No electrostatic force is generated between the wafer 25 and the wafer W. As a result, when the warped or deformed wafer W is fixed, a large number of gaps are created between the wafer W and the top surface of the outer peripheral protrusion 25. There is a possibility that the thermally conductive gas may leak out from the gap to lower the degree of vacuum in the semiconductor manufacturing apparatus, which may adversely affect the film forming accuracy and the etching accuracy.

On the other hand, in the electrostatic chuck 31 in which a large concave portion 33 is provided in the central portion and the wafer W is attracted and held only by the convex portion of the outer peripheral portion 34 thereof as in JP-A-7-86385, the attraction force is Is small, the wafer W and the recess 33
Due to the supply pressure of the heat conductive gas supplied to the space formed by and, a gap is partially formed between the peripheral edge of the wafer W and the top surface of the outer peripheral portion 34, and the heat conductive gas leaks from this gap. There is a problem that the degree of vacuum during processing is lowered, and as a result, various processing accuracy is adversely affected.

[0009]

It is an object of the present invention to firmly adsorb even a warped or deformed wafer, to make the temperature distribution on the wafer surface uniform, and to reduce the leakage of cooling gas.
Another object is to provide an electrostatic chuck having excellent responsiveness for wafer separation.

[0010]

In view of the above problems, therefore, the electrostatic chuck of the present invention has a concave portion having a depth of 3 to 10 μm on one main surface of a plate-shaped ceramic body while leaving the outer peripheral portion thereof. Formed, and the undulation on the top surface of the outer peripheral portion is 1 to 3 μm.
m, a gas groove is provided in the peripheral portion of the bottom surface of the recess, and the electrostatic attraction electrode is arranged in the plate-shaped ceramic body below the bottom surface of the recess or on the other main surface of the plate-shaped ceramic body. To do.

Further, it is preferable that the distance from the outermost peripheral portion in the area occupied by the electrostatic attraction electrode to the inner wall surface of the outer peripheral portion is 5 to 10 mm.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

1A and 1B are views showing an example of an electrostatic chuck of the present invention. FIG. 1A is a plan view and FIG. 1B is a sectional view. Further, FIG. 2 is an enlarged cross-sectional view of the portion A of FIG.

The electrostatic chuck 1 has a concave portion 3 having a circular planar shape with an outer peripheral portion 4 left on one main surface of a disk-shaped plate-shaped ceramic body 2 having substantially the same size as a wafer. And the top surface of the outer peripheral portion 4 serves as a second holding surface 4a, and a gas groove 5 is provided in the peripheral portion of the bottom surface of the recess, and the bottom surface of the recess surrounded by the gas groove 5 is the first holding surface. 3a, a pair of semicircular electrostatic attraction electrodes 7 are arranged on the other main surface 6 of the plate-shaped ceramic body 2 below the bottom surface of the recess.

As the material for forming the plate-shaped ceramic body 2, an alumina sintered body, a silicon nitride sintered body, an aluminum nitride sintered body, a yttrium-aluminum-garnet sintered body (hereinafter referred to as YAG sintered body) And a single crystal alumina (sapphire) can be used. Among them, the aluminum nitride sintered body has a heat transfer coefficient of 50 W /
A material having a heat transfer coefficient of m · k or higher, having a heat transfer coefficient of 100 W / m · k or more, is excellent in thermal conductivity, which is preferable from the viewpoint of enhancing the thermal uniformity of the wafer. Further, the use of single crystal alumina (sapphire) does not cause voids or shedding unlike the ceramic sintered body, which is suitable when the generation of particles is avoided as much as possible.

The first holding surface 3a is a flat surface parallel to the other main surface 6 of the plate-shaped ceramic body 2, and extends from the first holding surface 3a which affects the electrostatic force to the electrostatic attraction electrode 7. The distance is kept constant.

The depth h of the recess 3 (the distance from the second holding surface 4a to the first holding surface 3a) is 3 μm to 10 μm,
A minute convex portion is formed on the outer periphery of one main surface of the plate-shaped ceramic body 2, and the waviness on the top surface of the outer peripheral portion 4 which is the second holding surface 4a is set to 1 μm to 3 μm.

Further, gas grooves 5 are formed in the plate-shaped ceramic body 2.
A plurality of gas introduction holes 8 opening in the hole are bored, and a heat transfer gas such as helium gas is supplied to the space formed by the wafer and the recess 3 from the gas introduction holes 8 through the gas grooves 5. It is supposed to do.

The electrostatic chuck 1 is made of a metal such as aluminum or stainless steel with an insulating bonding layer 14 made of glass or a resin adhesive on the other main surface side of the plate-shaped ceramic body 2. A base member 9 is bonded to the base member 9. The base member 9 is provided with gas supply holes 10 that communicate with the gas introduction holes 8 of the plate-shaped ceramic body 2, respectively, and is electrically connected to the pair of electrostatic attraction electrodes 7. An electrode extraction hole 11 for extracting the connected power supply terminal 12 is provided. Reference numeral 13 is an insulating tube provided in the electrode extraction hole 11 to prevent the elongated power supply terminal 12 from coming into contact with the metal base member 9 and causing a short circuit.

In order to fix the wafer W by the electrostatic chuck 1, as shown in FIG. 3 (a), the peripheral portion of the wafer W is the top surface of the outer peripheral portion 4 of the plate-shaped ceramic body 2, and the second surface is the second surface. In a state where the power supply terminal 12 is placed so as to be in contact with the holding surface 4a,
When a current is applied between them, an electrostatic force is developed between the electrostatic attraction electrode 7 and the wafer W, and as shown in FIG.
With the peripheral edge of the wafer W in contact with the second holding surface 4a which is the top surface of the outer peripheral portion 4 of the plate-shaped ceramic body 2. Surface 3a
It can be adsorbed so as to come into contact with, and the warped or deformed wafer W can also be adsorbed similarly.

Then, a heat transfer gas such as helium gas is supplied to the space formed by the wafer W and the concave portion 3 from the gas introduction hole 8 through the gas groove 5, so that the peripheral edge of the wafer W and the second portion. Leakage of the thermally conductive gas from between the holding surface 4a can be suppressed, and the temperature distribution on the surface of the wafer W can be made uniform. If film formation processing is performed in this state, a uniform film thickness on the wafer W can be obtained. It is possible to form a uniform thin film having the above-mentioned characteristics, and it is possible to improve various processing accuracy such that the thin film on the wafer W can be processed with high accuracy by performing etching processing.

That is, according to the present invention, the outer peripheral portion 4 on one main surface of the plate-shaped ceramic body 2 is left, and most of the outer peripheral portion 4 is the recessed portion 3, and the bottom surface of this recessed portion is the adsorption area.
Even a warped or deformed wafer W can be firmly adsorbed and fixed. Then, at the time of adsorption, the center of the wafer W is brought into contact with the first holding surface 3a, and the peripheral edge of the wafer W is held at the second holding surface 4a.
Since the heat conductive gas can be supplied to the space formed by the wafer W and the concave portion 3 while being brought into contact with a, the heat transfer characteristics of the center and the periphery of the wafer W can be approximated. The temperature distribution on the surface can be made uniform. Moreover, the center of the wafer W is the second holding surface 4a.
Since the wafer W is attracted to the first holding surface 3a located at a lower position, the wafer W can be brought into close contact with the inner peripheral edge portion of the second holding surface 4a, and can also be brought into contact with the second holding surface 4a. Therefore, it is possible to effectively prevent the thermally conductive gas supplied to the space formed by the wafer W and the recess 3 from leaking between the peripheral edge of the wafer W and the second holding surface 4a. It does not lower the degree of vacuum during processing.

Further, according to the present invention, the electrostatic attraction electrode 7 is arranged only on the other main surface 6 of the plate-shaped ceramic body 2 below the bottom surface of the recess, and the bottom surface of the recess is used as the adsorption area. The electrostatic force does not work between the holding surface 4a and the wafer W, the residual attraction force when the electrification to the electrostatic attraction electrode 7 is stopped is small, and it is forcibly curved downward. The elastic force of the wafer W allows the wafer W to be immediately released.

When the wafer W is attracted by using the electrostatic chuck 1 of the present invention, the wafer W is fixed in a curved state so that its center is convex downward as shown in FIG. 3B. However, according to the research by the present inventor, it is found that it is more important to make the temperature distribution on the surface of the wafer W uniform than to increase the flatness of the wafer W during adsorption.
The present invention has been completed.

By the way, in order to obtain such an effect, as described above, the depth h of the concave portion 3 is 3 μm to 1 μm.
It is important to set the undulation on the top surface of the outer peripheral portion 4 which is the second holding surface 4a to 1 μm to 3 μm in addition to 0 μm.

That is, if the depth h of the concave portion 3 exceeds 10 μm, the flatness of the wafer W becomes too poor at the time of adsorption, so that the film thickness becomes non-uniform during film formation and the shape deteriorates during etching. This is because the accuracy is adversely affected and the electrostatic attraction force sufficient to attract and hold the wafer W cannot be obtained. On the contrary, when the depth h of the recess 3 is less than 3 μm, the second holding surface 4a has When the waviness is 3 μm, the height of the most recessed portion of the second holding surface 4a becomes approximately the same as that of the first holding surface 3a,
Since a large gap is formed between the peripheral edge of the wafer W and the second holding surface 4a during adsorption, the amount of leakage of the thermally conductive gas becomes too large, and the degree of vacuum during film formation or etching is reduced. This is because the film forming accuracy and the etching accuracy are adversely affected.

The waviness on the top surface of the outer peripheral portion 4 is 1
This is because if the thickness is less than μm, the wafer W sticks during adsorption and cannot be separated immediately when the wafer W is detached. Conversely, the waviness on the top surface of the outer peripheral portion 4 is 3 μm.
When it exceeds m, the peripheral edge of the wafer W cannot be deformed along the waviness of the outer peripheral portion 4, so that a partial gap is formed and the thermally conductive gas easily leaks.

The waviness on the top surface of the outer peripheral portion 4 is the maximum value of this displacement measured by measuring the displacement of the entire top surface of the outer peripheral portion 4 which is the second holding surface 4a with a roundness measuring device. It is the difference between the minimum values.

Further, the width t of the outer peripheral portion 4 is 1 mm to 10 m.
It is preferably m. This is because when the width t of the outer peripheral portion 4 is less than 1 mm, the top inner peripheral edge portion of the outer peripheral portion 4 is likely to be chipped or cracked when the recess 3 is formed, and when the chipped or cracked portion is formed, the width t is narrow. This is because a gap is formed between the wafer W and the wafer W, and the heat conductive gas easily leaks from the gap. Conversely, when the width t of the outer peripheral portion 4 exceeds 10 mm,
At the time of adsorption, the center of the wafer W is less likely to curve downwardly convex, and the wafer W cannot be adsorbed to the bottom surface of the concave portion that is the first holding surface 3a, the holding force of the wafer W is reduced, and the wafer W and the concave portion 3 are separated from each other. This is because the thermally conductive gas supplied to the formed space is more likely to leak between the peripheral edge of the wafer W and the second holding surface 4a. However, the width t of the outer peripheral portion 4 does not necessarily need to be uniform over the entire circumference, and a narrow portion or a wide portion may be partially present. In such a case, the width of the narrow portion of the outer peripheral portion 4 is small. t is 1 mm or more, the outer peripheral portion 4
The width t of the wide area may be 10 mm or less.

In order to prevent the heat conductive gas from leaking more effectively, the surface roughness of the top surface of the outer peripheral portion 4 which is the second holding surface 4a is finished to be smooth so that the wafer W is held by suction. It is preferable to prevent the formation of a gap at the time of exposure, and specifically, it is preferable that the arithmetic average surface roughness (Ra) is 0.6 μm or less.

On the other hand, since the bottom surface of the recess, which is the first holding surface 3a, contacts the wafer W, it is preferable to finish the surface as smooth as possible. Specifically, the arithmetic average surface roughness (Ra) is used.
Therefore, it is preferable that the thickness is 1.2 μm or less.

The distance k from the outermost peripheral portion to the inner wall surface of the outer peripheral portion 4 in the area occupied by the electrostatic attraction electrode 7 is 5 to 1
It is preferably 0 mm. This is because when the distance k is less than 5 mm, the electrostatic attraction electrode 7 is located near the lower portion of the outer peripheral portion 4, and when the wafer W is attracted, the distance between the wafer W and the second holding surface 4a is increased. This is also because electrostatic force is generated, and the residual adsorption force when the wafer W is detached becomes large, so that the detachment response of the wafer W is impaired. Conversely, when the distance k exceeds 10 mm, the wafer W
Since a large electrostatic force cannot be obtained because the distance between the first holding surface 3a and the first holding surface 3a is too large, the peripheral edge of the wafer W is not moved to the second holding surface 4a.
Since the force pressing against a becomes small, the wafer W and the recess 3
Due to the supply pressure of the heat conductive gas supplied to the space constituted by and, a gap is partially formed between the peripheral edge of the wafer W and the second holding surface 4a, and the heat conductive gas easily leaks from this gap. Because it will be.

In order to manufacture the electrostatic chuck 1 shown in FIG. 1, a plate-shaped ceramic body 2 whose upper and lower surfaces are finished to be smooth is prepared, and the other main surface 6 of the plate-shaped ceramic body 2 is prepared.
By a film forming means such as an ion plating method, a PVD method, a CVD method, a sputtering method, and a plating method.
A pair of semi-circular electrodes 7 for electrostatic adsorption are formed by depositing a conductor layer made of a metal such as i, W, Mo, or Ni or a carbide thereof, and then removing unnecessary portions by etching. To do.

At this time, it is preferable that the outermost peripheral portion of the area occupied by the electrostatic attraction electrode 7 is located at a distance k which is 5 mm to 10 mm away from the inner wall surface of the outer peripheral portion 4 when the concave portion 3 described later is formed. .

Next, a gas groove 5 and a gas introduction hole 8 are formed at a predetermined position on one main surface of the plate-shaped ceramic body 2 by machining or blasting, and the electrostatic attraction electrode 7 is provided with a power supply terminal 12. Are fixed with a conductive adhesive or the like.

On the other main surface side of the plate-shaped ceramic body 2, a bonding layer 1 having an insulating property, such as glass or resin adhesive.
After the base member 9 is joined via 4 and the depth h is 3 on one main surface of the plate-shaped ceramic body 2, the outer peripheral portion 4 is left.
The outer peripheral part 4 is formed while forming the concave part 3 of 10 μm to 10 μm.
The electrostatic chuck 1 shown in FIG. 1 can be obtained by finishing so that the undulations on the top surface of the are 1 μm to 3 μm.

Here, as the means for forming the concave portion 3 in the plate-shaped ceramic body 2, it is possible to form it by blasting or etching, but it is preferable to produce it by grinding using a rotary machine. . This is because if a rotary processing machine is used, it is possible to consistently process from the state of rough processing where the polishing allowance remains to the outer peripheral portion 4 and the concave portion 3 to the finishing processing at the same time, and the finishing can be performed with high accuracy.

Further, the outer peripheral portion 4 can be processed by lapping only the outer peripheral portion 4 while leaving a finishing allowance for the outer peripheral portion 4 when finishing the recess 3. As the lapping conditions, when the plate-like ceramic body 2 is made of an aluminum nitride sintered body, a cast iron lapping machine having a flatness of 10 μm or less is used, and diamond abrasive grains of 10 μm or less are used, so that the peripheral portion 4 Undulation on the top surface is 1 μm ~
It can be 3 μm.

As described above, in this embodiment, the plate-shaped ceramic body 2 is used.
Although the electrostatic chuck 1 having the electrostatic attraction electrode 7 on the other main surface 6 of the above has been described as an example, as shown in FIG. 4, the electrostatic attraction electrode is provided in the plate-shaped ceramic body 2 below the bottom surface of the recess. It goes without saying that it is also applicable to the electrostatic chuck 1 in which 7 is embedded.

Further, it is needless to say that the present invention is not limited to the above-mentioned embodiments, and that modifications and changes may be made without departing from the gist of the present invention.

[0041]

EXAMPLES Example 1 The electrostatic chuck 1 shown in FIG. 1 was manufactured, and the temperature variation of the wafer surface, the amount of leakage of the heat conductive gas, and the release response when the depth h of the recess was varied. An experiment was conducted to investigate

In this experiment, a disk-shaped plate-shaped ceramic body 2 having a diameter of 200 mm and a thickness of 1 mm made of an aluminum nitride sintered body was prepared, and the other main surface of the plate-shaped ceramic body 2 was plated. After depositing the Ni film by means of etching, unnecessary portions are removed by etching to form a pair of semi-circular electrostatic attraction electrodes 7 so as to form a circle.

Next, the power supply terminal 12 is attached to each electrostatic attraction electrode 7.
After being fixed with a conductive adhesive, the aluminum-based base member 9 was bonded to the other main surface side of the plate-shaped ceramic body 2 via a bonding layer 14 made of a silicon-based adhesive.

Next, after the gas groove 5 and the gas introduction port 8 communicating with the gas groove 5 are formed at a predetermined position on one main surface of the plate-shaped ceramic body 2 by the blasting process, the plate-shaped ceramic body 2 is formed. An electrostatic chuck as each sample was manufactured by forming a concave portion 3 having a different depth h while leaving the outer peripheral portion 4 of one main surface.

The width t of the top surface of the outer peripheral portion 4 is 4 mm, the diameter of the bottom surface of the recess surrounded by the gas groove 5 is 190 mm, and the outer peripheral portion 4 to the outer peripheral portion 4 in the area occupied by the electrostatic attraction electrode 7 is from the outermost portion. The distance k to the wall surface was 5 mm.

Then, the obtained electrostatic chuck 1 is placed in a vacuum container, and as shown in FIG. 3 (a), an 8-inch silicon wafer is placed on the top surface of the outer peripheral portion 4, and then a pair of static chucks are placed. An electrostatic force is generated by energizing the electrode 7 for electroadsorption, and a silicon wafer is adsorbed to the electrostatic chuck 1 as shown in FIG. As a result, helium gas was supplied at a pressure of 2666 Pa, and the leak amount of helium gas was measured by the supply amount of helium and the differential pressure in the vacuum container. Further, the temperature variation on the surface of the silicon wafer at that time was measured. However, the set temperature of the wafer surface was 100 ° C., and the temperature variation was measured as a temperature difference ΔT between the highest temperature and the lowest temperature at 10 measurement points on the wafer surface that were arbitrarily selected.

Further, after supplying helium gas, 60
After a second, the current to the electrostatic attraction electrode 7 was stopped and the time until the wafer was detached, that is, the detachment response time was measured, and the detachment responsiveness was evaluated. However, in the time until the wafer is released, the leakage amount of helium starts to increase rapidly at the moment when the wafer is released. Therefore, the leakage amount of helium gas increases rapidly after the energization of the electrostatic attraction electrode 7 is stopped. Increased, 10 SC
The time until it became CM was measured and evaluated.

The respective results are shown in Table 1.

[0049]

[Table 1]

As can be seen from Table 1, it is understood that the release response time of each sample is 10 seconds or less and the release response is good.

However, looking at the degree of helium gas leakage, the sample No. 3 in which the depth h of the recess 3 was 0 μm.
1 is the bottom surface of the concave portion and the outer peripheral portion 4 when the wafer is sucked and fixed.
Since there is no step between it and the top surface of the wafer, the peripheral edge of the wafer cannot be strongly adhered to the top surface of the outer peripheral portion 4.
Leakage of M helium gas occurred.

Sample No. 3 having a depth h of the recess 3 of 15 μm. No. 5 is too distant from the wafer to the bottom surface of the concave portion, so that a large electrostatic force cannot be generated even when the electrostatic attraction electrode 7 is energized, and strong adsorption is not possible. By the supply pressure of 1, a gap was created between the wafer and the top surface of the outer peripheral portion 4, and 7.8 SCCM of helium gas leaked from this gap.

On the other hand, looking at the temperature variation on the wafer surface, the sample No. 3 in which the depth h of the recess 3 was 0 μm.
No. 1 could not sufficiently reach the center of the wafer due to the leakage of helium gas and could not enhance the heat transfer characteristics in the center of the wafer. As a result, the temperature variation on the wafer surface was as large as 12 ° C.

On the other hand, the depth h of the recess 3 is 3 μm to 1
Sample No. in the range of 0 μm Nos. 2 to 4 were excellent in that the leakage amount of helium gas could be suppressed to 5 SCCM or less and the temperature variation on the wafer surface could be made uniform to 5 ° C. or less.

As a result, the depth h of the recess 3 is 3 to 10 μm.
It turns out that (Example 2) Next, the depth h of the concave portion 3 is fixed to 5 μm,
An experiment was carried out under the same conditions as in Example 1 except that the undulations on the top surface of the outer peripheral portion 4 were changed to examine the temperature variation on the wafer surface, the leak amount of the thermally conductive gas, and the release response.

The results are shown in Table 2.

[0057]

[Table 2]

As can be seen from Table 2, Sample No. 6 having a waviness of 0.5 μm on the top surface of the outer peripheral portion 4 had a long detachment response time of 13.5 seconds. The cause is the outer peripheral part 4
It is considered that since the undulation of the top surface of the wafer is small, the peripheral edge of the wafer is pressed against the top surface of the outer peripheral portion 4 at the time of adsorption, resulting in a vacuum tightly contacted ringing state, which makes separation difficult.

Further, the waviness on the top surface of the outer peripheral portion 4 is 5
The sample No. 9 having a thickness of μm cannot adhere the wafer along the undulation at the time of adsorption, so that a gap is formed between the wafer and the top surface of the outer peripheral portion 4, and 12.7 S is obtained from this gap.
CCM and helium gas leaked.

On the other hand, sample Nos. 7 and 8 in which the waviness on the top surface of the outer peripheral portion 4 is in the range of 1 μm to 3 μm,
The amount of helium gas leaked could be suppressed to 5 SCCM or less, the temperature variation on the wafer surface could be made uniform to 5 ° C. or less, and the wafer release response was excellent.

As a result, it is understood that the waviness on the top surface of the outer peripheral portion 4 should be 1 μm to 3 μm.

From the results of Example 1 and Example 2, the depth h of the recess 3 was set to 3 μm to 10 μm, the undulation on the top surface of the outer peripheral portion 4 was set to 1 μm to 3 μm, and the plate shape below the bottom surface of the recess was set. The other main surface 6 of the ceramic body 2
By disposing the electrostatic attraction electrode 7 on the wafer, the temperature distribution on the wafer surface can be made uniform while suppressing the gas leakage of the heat conductive gas, and the electrostatic chuck is excellent in the responsiveness of the wafer detachment. It turns out that 1 can be provided. Also,
Since such an electrostatic chuck 1 can obtain a large attraction force, even a warped or deformed wafer can be firmly attracted and fixed. (Embodiment 3) Further, the depth h of the concave portion 3 is fixed to 5 μm, and the undulation on the top surface of the outer peripheral portion 4 is fixed to 1 μm, and the outer peripheral portion to the inner wall surface of the outer peripheral portion 4 in the area occupied by the electrostatic attraction electrode 7 are fixed. An experiment was conducted under the same conditions as in Example 1 except that the distance k to was varied with respect to the temperature variation of the wafer surface, the amount of leak of the thermally conductive gas, and the detachment response.

The results are shown in Table 3.

[0064]

[Table 3]

As can be seen from Table 3, the sample No. 3 having a distance k from the outermost peripheral portion to the inner wall surface of the outer peripheral portion 4 in the area occupied by the electrostatic attraction electrode 7 is 3 mm. No. 10 had a long wafer detachment response of 15.3 seconds. The reason for this is that since the electrostatic attraction electrode 7 is formed near the lower part of the outer peripheral portion 4, the electrostatic force also affects the outer peripheral portion 4, and when the wafer is detached, the residual attractive force acts on the outer peripheral portion 4. , It seems that it took a long time to leave.

Further, the distance k from the outermost peripheral portion to the inner wall surface of the outer peripheral portion 4 in the area occupied by the electrostatic attraction electrode 7 is 15 m.
Sample No. In No. 13, since the area occupied by the electrostatic attraction electrode 7 becomes too narrow, the attraction force of the wafer on the bottom surface of the recess is small, and the force of pressing the peripheral edge of the wafer against the top surface of the outer peripheral portion 4 becomes weak. Depending on the gas pressure,
A partial gap was created between the peripheral edge of the wafer and the top surface of the outer peripheral portion 4, causing a leak of 7.7 SCCM of helium gas.

On the other hand, in the sample No. 5 in which the distance k from the outermost peripheral portion to the inner wall surface of the outer peripheral portion 4 in the area occupied by the electrostatic attraction electrode 7 is in the range of 5 mm to 10 mm. 11, 12
Has a small helium gas leakage of less than 5 SCCM,
The time required for detaching the wafer was 10 seconds or less, which was a short and good result. Also, the temperature variation on the wafer surface is 5 ° C.
It was good as below.

As a result, the distance k from the outermost peripheral portion in the area occupied by the electrostatic attraction electrode 7 to the inner wall surface of the outer peripheral portion 4 is 5.
It can be seen that it is good if it is set to mm to 10 mm.

[0069]

As described above, according to the electrostatic chuck of the present invention, a concave portion having a depth of 3 to 10 μm is formed on one main surface of a plate-shaped ceramic body while leaving the outer peripheral portion thereof. An undulation on the top surface is set to 1 to 3 μm, a gas groove is provided in the peripheral portion of the bottom surface of the recess, and an electrostatic adsorption electrode is provided in the plate-shaped ceramic body below the bottom surface of the recess or on the other main surface of the plate-shaped ceramic body. By disposing, the warped or deformed wafer can be firmly adsorbed and fixed.

During adsorption, the center of the wafer is brought into contact with the bottom surface of the recess, which is the first holding surface, and the peripheral edge of the wafer is brought into contact with the top surface of the outer peripheral portion, which is the second holding surface. Since the heat conductive gas can be supplied to the formed space, the heat transfer characteristics at the center and the periphery of the wafer can be approximated, and the temperature distribution on the wafer surface can be made uniform.

Moreover, since the center of the wafer is adsorbed by the first holding surface which is lower than the second holding surface, the wafer can be brought into close contact with the inner peripheral edge portion of the second holding surface. Since the second holding surface can also be brought into contact with the second holding surface, the thermally conductive gas supplied to the space formed by the wafer and the recess is effectively prevented from leaking between the peripheral edge of the wafer and the second holding surface. It is possible to prevent the vacuum degree from being lowered during various processes.

Therefore, when the electrostatic chuck of the present invention is used for various processes such as film forming process and etching process, the wafer can be processed with high precision.

Moreover, since the electrostatic attraction electrode is arranged only below the bottom surface of the recess, if the energization to the electrostatic attraction electrode is stopped, the residual attraction force is small and the electrode is forced to project downward. Since the wafer can be immediately released from the holding surface by the elastic force of the curved wafer, it is possible to improve the response of detachment from the electrostatic chuck.

[Brief description of drawings]

FIG. 1 is a view showing an example of an electrostatic chuck of the present invention,
(A) is a plan view and (b) is a sectional view.

FIG. 2 is an enlarged sectional view of a portion A of FIG.

3 (a) and 3 (b) are cross-sectional views showing a process of adsorbing a wafer using the electrostatic chuck of the present invention.

FIG. 4 is a sectional view showing another example of the electrostatic chuck of the present invention.

FIG. 5 is a sectional view showing an example of a conventional electrostatic chuck.

FIG. 6 is a sectional view showing another example of a conventional electrostatic chuck.

[Explanation of symbols]

1: electrostatic chuck 2: plate-shaped ceramic body 3: concave portion
3a: 1st holding surface 4: Outer peripheral part, 4a: 2nd holding surface 5: Gas groove 6: Other main surface 7: Electrostatic attraction electrode 8: Gas introduction hole 9: Base member 10: Gas supply hole 11: Electrode extraction hole 12: Power supply terminal 13: Insulation tube 1
4: Bonding layer W: Wafer

Claims (2)

[Claims] 1. A plate-shaped ceramic body is provided with a recess having a depth of 3 .mu.m to 10 .mu.m while leaving an outer peripheral portion of the main surface, and a gas groove is provided at a peripheral edge of a bottom surface of the recess. An electrostatic chuck having an electrostatic attraction electrode in the plate-shaped ceramic body below the bottom surface or on the other main surface of the plate-shaped ceramic body, wherein the undulation on the top surface of the outer peripheral portion is 1 μm.
An electrostatic chuck having a thickness of 3 μm. 2. The distance from the outermost peripheral portion in the area occupied by the electrostatic attraction electrode to the inner wall surface of the outer peripheral portion is 5 mm to 1.
It is 0 mm, The electrostatic chuck of Claim 1 characterized by the above-mentioned.