JP2000277598A - Electrostatic chuck and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make scanty the occurrence amount of particles even when applying a high voltage and when using at high temperatures by a method wherein a support of an object to be attracted on a chuck face of an insulating substrate composed of a ceramic sintered compact is projected and fixed to the insulating substrate in a state such that the part is buried in the chuck face. SOLUTION: Heat-resistance, heat conductivity, and plasma-resistance are superior, and ceramics of an aluminum nitride sintered compact are used. An insulating substrate 2 has a multilayer structure, and is formed internally with chuck electrode layers 3, 4. The chuck electrode layer 3 of a positive pole and the chuck electrode layer 4 of a negative pole are together positioned in a layer close to a chuck face S1. Straight line parts 3a, 4a of the chuck electrode layers 3, 4 of different poles are disposed adjacently in the direction of the substrate face. A wafer support body 7 as a support of an object to be attracted Is provided on the chuck face S1. A lower face side of the wafer support body 7 is buried in the chuck face S1, so that the wafer support body 7 is fixed in a state of disabling to slip off from the insulating substrate 2. Thus, it is possible to decrease the occurrence of particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrostatic chuck and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, processes such as etching and sputtering are performed while a semiconductor wafer made of silicon or the like is fixed. In such a case, a fixing means called a chuck device is usually used. In particular, in recent years, a ceramic electrostatic chuck that attracts a semiconductor wafer by using the force of static electricity has been proposed.

In this type of electrostatic chuck, an insulating base made of a dielectric ceramic material such as an aluminum nitride sintered body is used. On the chuck surface of the insulating base material, a semiconductor wafer as an object to be attracted is supported in a state of surface contact.
Then, by supplying a current to the chuck electrode provided on the insulating base material, the wafer is electrostatically attracted to the chuck surface.

[0004]

However, in the conventional ceramic electrostatic chuck, the sintered body and the wafer are in direct contact with each other. Shear stress occurs. Then, under the influence of the shear stress, the aluminum nitride particles in the surface layer easily fall off, and there is a possibility that the aluminum nitride particles mainly become particles and adhere to the back surface of the semiconductor wafer.

It is also known that when the temperature during use is increased or when the applied voltage is increased to increase the chucking force, the generated shear stress increases, and as a result, the falling off of the aluminum nitride particles is promoted. I have.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to provide an electrostatic chuck which generates a small amount of particles even when a high voltage is applied or when a high temperature is used. It is in.

A second object of the present invention is to provide a method capable of easily and reliably manufacturing the above-mentioned preferable electrostatic chuck.

[0008]

According to the first aspect of the present invention, an object is electrostatically adsorbed on a chuck surface of an insulating base made of a ceramic sintered body. An electrostatic chuck having an object support made of carbon, wherein the object support is protrudingly fixed to the insulating base with a part of the object support being buried in the chuck surface. The gist of the present invention is as follows.

According to a second aspect of the present invention, in the first aspect, the to-be-adsorbed object support is a sheet material formed by weaving carbon fibers. According to a third aspect of the present invention, there is provided the method of manufacturing the electrostatic chuck according to the second aspect, wherein the ceramic unfired body having the sheet material disposed in the inner layer is fired, and then fired. A gist of the present invention is a method of manufacturing an electrostatic chuck in which a part of the sheet material is exposed from the ceramic sintered body by performing a chemical etching after performing a grinding process on the bonded body.

According to a fourth aspect of the present invention, in the third aspect, the sheet material is divided at a plurality of locations by grooving. Hereinafter, the “action” of the present invention will be described.

According to the first aspect of the present invention, since the object to be adsorbed is supported by the portion of the object to be adsorbed projecting from the chuck surface, the ceramic sintered body and the back surface of the object to be adsorbed are directly connected to each other. No contact. Accordingly, the ceramic sintered body is not directly affected by the shear stress, and the amount of particles generated due to the falling off of the surface crystal grains is extremely reduced. Further, since the object-to-be-adsorbed is partially fixed in a state of being buried in the ceramic sintered body, there is no fear that the object-to-be-adsorbed will fall off the chuck surface under the influence of shear stress. Furthermore, the object support made of carbon is
Low reactivity with metals even at high temperatures. Therefore, even if the object-to-be-adsorbed is brought into contact with the object-to-be-adsorbed, the object-to-be-adsorbed is not adversely affected.

According to the second aspect of the present invention, the texture of the fibers in the sheet material has irregularities,
Of these, the object to be attracted is supported in point contact by the projection projecting from the chuck surface.

According to the third aspect of the present invention, the sheet material embedded in the inner layer becomes closer to the surface layer of the ceramic sintered body by performing the grinding process. When chemical etching is further performed after the surface is exposed to some extent, the ceramic sintered body is selectively melted, and a part of the sheet material is exposed from the chuck surface. That is, through the above-described steps, a desired object-to-be-adsorbed object support is formed. Here, since chemical etching is employed, there is no possibility that the irregularities formed by the weave of the fibers constituting the sheet material are cut and damaged.

According to the fourth aspect of the present invention, the sheet material is divided at a plurality of locations by grooving, so that conduction can be established in some places. For this reason, even when, for example, a bipolar electrostatic chuck is configured, dielectric breakdown between chuck electrodes having different polarities when a high voltage is applied is less likely to occur. Therefore, the chuck force can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a bipolar type electrostatic chuck 1 according to an embodiment of the present invention will be described in detail with reference to FIGS.

FIGS. 1 and 2 schematically show an electrostatic chuck 1 according to this embodiment. The insulating base material 2 constituting the electrostatic chuck 1 is made of a sintered body of aluminum nitride which is a suitable dielectric. The reason why the aluminum nitride sintered body was selected as the ceramic sintered body is that it is excellent in heat resistance, thermal conductivity, plasma resistance and the like, and is extremely convenient as a material for the electrostatic chuck 1. Here, a disk-shaped insulating substrate having a thickness of about several mm is used. In addition, the insulating base material 2 of this embodiment is formed so as to have an area several times as large as that of the silicon wafer W1 in order to simultaneously chuck a plurality of silicon wafers W1 as the objects to be attracted.

The insulating substrate 2 of the present embodiment has a multilayer structure, in which chuck electrode layers 3 and 4 are formed. The chuck electrode layer 3 of the positive electrode and the chuck electrode layer 4 of the negative electrode are both located near the chuck surface S1. The depth from the chuck surface S1 to the lower surfaces of the chuck electrode layers 3 and 4 is set to about 0.3 mm. Each of the chuck electrode layers 3 and 4 is formed by printing using a conductive paste P1 such as a tungsten paste.

As shown in FIG. 2, the chuck electrode layer 3 of the positive electrode includes a semicircular portion located on the outer periphery of the insulating base material 2 and a plurality of straight lines extending from the semicircular portion in parallel and at equal intervals. And a portion 3a. Accordingly, the chuck electrode layer 3 has a comb-like shape as a whole. The negative electrode chuck electrode layer 4 also includes a semicircular arc-shaped portion and a large number of linear portions 4a, and also has a comb-like shape. In the present embodiment, the shapes and sizes of these two chuck electrode layers 3 and 4 are substantially equal.

The two linear portions 3a and 4a are connected to each other in FIG.
Are staggered as shown in FIG. That is, the linear portions 3a and 4a of the chuck electrode layers 3 and 4 having different polarities are
They are arranged adjacent to each other in the substrate surface direction.

The positive side of the chucking DC power supply 5 is connected to the chuck electrode layer 3 of the positive electrode through through holes and wiring (not shown). Similarly, the negative side of the DC power supply 5 is connected to the negative-electrode chuck electrode layer 4 through a through hole and a wiring (not shown).

As shown in FIGS. 1 and 7, the electrostatic chuck 1 has a wafer support 7 as a support for an object to be attracted on a chuck surface S1. This wafer support 7
Consists of a sheet material 12 formed by weaving carbon fibers 8. As shown in FIG. 7, irregularities are regularly present in the weave, which is the intersection of the warp and the weft of the carbon fiber 8. The size of the unevenness depends on the diameter, the weaving method, and the like of the carbon fiber 8. Wafer support 7
Is buried in the chuck surface S1 so that the wafer support 7 is fixed to the insulating base material 2 so as not to fall off. On the other hand, the upper surface side of the wafer support 7, specifically, the convex portion of the texture is projected from the chuck surface S1.

The protrusion of the projection on the wafer support 7 from the chuck surface S1 is 1 μm to 20 μm, and more preferably 6 μm.
It is preferably from 10 to 10 μm. If the amount of protrusion is too small, support by point contact with the wafer support 7 cannot be achieved, and support by surface contact with the insulating base material 2 may be substantially obtained. Therefore, the aluminum nitride sintered body is affected by shear stress, and the reduction in the amount of generated particles cannot be sufficiently achieved. Conversely, if the amount of protrusion is too large, the separation distance between the silicon wafer W1 and the chuck surface S1 increases, and as a result, the electrostatic force is less likely to act, and the chuck force may decrease.

Next, an example of a procedure for manufacturing the electrostatic chuck 1 of the present embodiment will be introduced. The green sheet 11, which is a material of the insulating base material 2, is formed by sheet forming a slurry containing aluminum nitride powder as a main component and a sintering aid such as yttria by a doctor blade method. At predetermined positions of the obtained green sheet 11, through holes are formed as necessary by drilling or punching.

In the next paste printing step, a conductive paste P1 containing tungsten particles as conductive particles, a dispersion solvent, a dispersant, and the like is printed on the green sheet 11 that has been subjected to the perforation processing. In this step, first, the green sheet 11 that has been subjected to the drilling step is set in a printing apparatus, and a metal mask is arranged on a printing surface. By performing printing in this state, the conductive paste P1 is filled in the through-hole forming holes. Next, the green sheet 11 on which through-hole printing or the like has been performed is set on a screen printing machine, and a screen mask is arranged on a printing surface.
In this state, the above-mentioned conductive paste P1 is pattern-printed to form chuck electrode layers 3 and 4 on the surface of the green sheet 11.

Next, the plurality of green sheets 11 having undergone the paste printing step are positioned and superimposed, and a vacuum press is performed at a predetermined pressure in this state (see FIG. 3). At that time, the sheet material 12 is interposed between predetermined green sheets 11. As a result of the vacuum pressing, each green sheet 11 and the sheet material 12 are integrated, and a green sheet laminate (that is, a ceramic unsintered body) in which the sheet material 12 is arranged in an inner layer is formed.

Then, the obtained green sheet laminate is dried by heating at a temperature of several tens of degrees C. to one hundred and several tens degrees C. for a predetermined time under normal pressure. The drying step may be performed before performing the laminating step.

The green sheet laminate after the drying step is
Before the main firing step, degreasing and preliminary firing are performed in a non-oxidizing atmosphere in advance. Thereafter, the green sheet calcined body obtained through the heat treatment step is placed in a crucible, and the periphery thereof is surrounded by a setter as needed. The crucible in this state is set in a firing furnace, and the crucible is placed in a conventional manner.
Hot press firing is performed at a temperature of 0 ° C. or higher for a predetermined time and a predetermined pressure. As a result, the aluminum nitride and the conductive paste P1 are completely co-sintered to form the insulating base 2 made of the aluminum nitride sintered body 13 as shown in FIG.

Thereafter, the outer shape of the insulating base material 2 is cut by grinding using a grinder or the like, and the surface of the sheet material 12 to be the wafer support 7 is positioned so as to be positioned near the surface layer ( (See FIG. 5). In this case, it is desirable to stop the surface exposure so that the upper surface of the sheet material 12 is not exposed.

Subsequently, chemical etching is further performed. Here, an etchant that selectively dissolves only aluminum nitride without dissolving carbon is used. Specifically, an alkali hydroxide salt such as NaOH, KOH, NH ₄ OH or the like can be used as an etchant. After this treatment, only the aluminum nitride sintered body 13 is selectively melted, so that the wafer support 7
From the chuck surface S1 of the insulating base material 2 to 3 μm to 20 μm.
It can protrude by about μm (see FIG. 6). Then, after that, a grooving process is performed by a grinder to form lattice-shaped grooves 6 on the chuck surface S1 of the insulating base material 2 as shown in FIG. As a result, the wafer support 7 obtained by dividing the sheet material 12 at a plurality of locations is completed. The groove 6 is interposed at least between the chuck electrodes 3 and 4 having different polarities, and is formed deeper than the chuck electrodes 3 and 4 here.

Thereafter, the coating and I
By performing various steps such as brazing of / O pins, a desired electrostatic chuck 1 as shown in FIGS. 1 and 2 is completed.
When a direct current is applied to the two chuck electrode layers 3 and 4 of the electrostatic chuck 1 manufactured as described above, an electric field is formed in an outer region of the chuck surface S1, and as a result, the silicon wafer W1 An electrostatic force acts on the chuck 1. As a result, the silicon wafer W1 is placed on the chuck surface S1 side.
Is attracted to fix the silicon wafer W1. At this time, the silicon wafer W1 is supported in point contact by a large number of projections on the wafer support 7.

[0031]

EXAMPLES and COMPARATIVE EXAMPLES [Preparation of Samples] Here, the following six kinds of sample samples were prepared in advance.

Samples 1 to 3 of Examples 1 to 3 are made of an insulating substrate 2 made of aluminum nitride having an outer diameter of 190 mm and a thickness of 1.5 mm, and each has the above-mentioned wafer support 7. On the other hand, Sample 4, which is Comparative Examples 1 to 3,
Nos. 5 and 6 have no wafer support 7 at all. [Comparative test and its result] The following comparative test was performed on these six types of samples.

That is, the chuck surface S1 of each electrostatic chuck 1
A silicon wafer W1 having a diameter of 20 mm was placed thereon, and energization was performed under vacuum conditions. Then, the silicon wafer W1 is
After chucking for 0 second, the operation of peeling off the silicon wafer W1 was performed five times. In this state, the number (particles / cm ² ) of particles having a diameter of 0.2 μm or more per unit area adhered to the back surface of the wafer was counted. Table 1 shows the results.
In the same table, the applied voltage (V) and the operating temperature (° C.) set for each of the samples 1 to 6 are also shown. [Conclusion] As is clear from Table 1, when the examples in which the applied voltage and the use temperature are set equal in each example and each comparative example are compared, the amount of generated particles of the sample of the example is smaller. I understand. Further, in the electrostatic chucks 1 of these examples, the amount of generated particles was small even when a high voltage was applied or when a high temperature was used.

In addition, when the sample used at 600 ° C. was observed, no particular problem such as adhesion of the wafer support 7 to the silicon wafer W1 was found. That is, even when used at a high temperature, the quality of the silicon wafer W1 was not adversely affected.

[0035]

[Table 1] When the above results are combined, according to the present embodiment, the following effects can be obtained.

(1) In the electrostatic chuck 1, the silicon wafer W1 is chucked in a state where the silicon wafer W1 is supported in point contact by a number of convex portions on the wafer support 7. Therefore, the chuck surface S1 of the aluminum nitride sintered body 13 and the back surface of the silicon wafer W1 do not come into direct surface contact.
Therefore, the aluminum nitride sintered body 13 is not directly affected by the shear stress, and the crystal grains in the surface layer are less likely to fall off. Therefore, the amount of particles generated due to the dropout of the surface crystal grains is extremely small. Further, since the wafer support 7 is fixed with its lower surface buried in the aluminum nitride sintered body 13, there is no fear that the wafer support 7 will fall off the chuck surface S1 under the influence of shear stress. As is clear from the above, according to the present embodiment, it is possible to realize an excellent electrostatic chuck 1 that can cope with high voltage application and high temperature use.

(2) Since the wafer support 7 is made of carbon, it has low reactivity with silicon even at a high temperature. Therefore, even if the wafer support 7 is brought into contact with the silicon wafer W1 at the time of chucking, in particular, the silicon wafer W1
Has no adverse effect on In this sense, the electrostatic chuck 1 according to the present embodiment is suitable for use at a high temperature of several hundred degrees Celsius.

Moreover, since carbon has conductivity,
For example, the wafer support 7 is inserted through a through hole (not shown).
Can be easily grounded by connecting to a ground wire. By doing so, the silicon wafer W1
Excess charges accumulated on the surface can be quickly released as needed, and the silicon wafer W1 can be easily removed from the electrostatic chuck 1 or the like.

(3) In the manufacturing method of the present embodiment, the aluminum nitride sintered body 13 is subjected to chemical etching after grinding in advance. In other words, the aluminum nitride sintered body 13 is melted after the surface is exposed to some extent. Therefore, there is no possibility that the irregularities formed by the weave of the carbon fiber 8 are cut and damaged by the grinding, and the preferable shape of the irregularities is maintained as it is. Therefore, the preferable electrostatic chuck 1 having the desired wafer support 7 can be easily and reliably manufactured.

(4) In the manufacturing method of the present embodiment, the sheet material 12 is groove-cut after the chemical etching, so that the sheet material 12 is divided at a plurality of locations by the grooves 6. Therefore, conduction of the sheet material 12 can be established in some places. Therefore, dielectric breakdown between the chuck electrodes 3 and 4 having different polarities when applying a high voltage is less likely to occur.
Therefore, according to this manufacturing method, the bipolar electrostatic chuck 1 having a strong chucking force can be reliably manufactured.

The embodiment of the present invention may be modified as follows. In manufacturing the insulating base material 2, a material other than the aluminum nitride sintered body 13 may be used as a ceramic sintered body, for example, a sintered body of boron nitride, silicon nitride, high-purity alumina, beryllia, magnesia, or the like. Can be selected.

In the embodiment, the chemical etching is further performed after the grinding processing is performed in advance. Alternatively, only the chemical etching may be performed without performing the grinding process, so that the convex portion of the wafer support 7 may be exposed.

The object to be adsorbed is not limited to a wafer made of silicon, but may be another object, for example, a wafer made of gallium arsenide. The groove 6 may be formed in a pattern shape different from the lattice shape, and may be omitted in some cases.

The shape, size, arrangement and the like of the wafer supports 7 are not limited to those of the embodiment, but can be arbitrarily changed. Further, it is also possible to form the wafer support 7 using a material other than the sheet material made of carbon as exemplified in the embodiment. For example,
In the wafer support 7 of the electrostatic chuck 21 shown in FIG. 8, a large number of the bottoms of the substantially cylindrical carbon pieces 22 are embedded in the chuck surface S1, and the heads thereof are projected from the same surface S1.

In the above-described embodiments and other examples, the present invention is embodied as bipolar electrostatic chucks 1 and 21. However, the present invention may be embodied as a monopolar electrostatic chuck. Next, in addition to the technical ideas described in the claims, technical ideas grasped by the above-described embodiments are listed below together with their effects.

(1) In any one of claims 1 to 4, an amount of protrusion of the projection on the object support from the chuck surface is 1 μm to 20 μm. Therefore, according to the invention described in the technical idea 1, it is possible to reliably achieve the point-to-point support of the object to be sucked while avoiding an increase in the separation distance between the object to be sucked and the chuck surface.
Therefore, it is possible to reduce the amount of generated particles without lowering the chucking force.

(2) In Claim 1, the object-to-be-adsorbed object support is a plurality of small carbon pieces whose bottoms are embedded in the chuck surface. Therefore, according to the invention described in the technical idea 2, the object to be sucked can be supported by the head projecting from the chuck surface, and the amount of generated particles can be reduced.

(3) Claims 1 to 4, technical idea 1,
2. In any one of 2., the ceramic sintered body is an aluminum nitride sintered body. Therefore, according to the invention described in the technical idea 3, a suitable electrostatic chuck having excellent heat resistance, thermal conductivity, plasma resistance and the like can be obtained.

[0049]

As described in detail above, according to the first and second aspects of the present invention, it is possible to provide an electrostatic chuck that generates a small amount of particles even when a high voltage is applied or when a high temperature is used. Can be.

According to the third aspect of the present invention, it is possible to provide a method capable of easily and surely manufacturing the above-mentioned preferable electrostatic chuck. According to the invention described in claim 4, a bipolar electrostatic chuck having a strong chucking force can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electrostatic chuck according to an embodiment of the invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the electrostatic chuck.

FIG. 4 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the electrostatic chuck.

FIG. 5 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the electrostatic chuck.

FIG. 6 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the electrostatic chuck.

FIG. 7 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the electrostatic chuck.

FIG. 8 is a partial schematic cross-sectional view of another example of an electrostatic chuck.

[Explanation of symbols]

Reference numerals 1, 21: electrostatic chuck, 2: insulating base material, 7: wafer support as a support for an object to be adsorbed, 8: carbon fiber,
12: sheet material, 13: aluminum nitride sintered body as a ceramic sintered body, 22: small carbon piece, S1: chuck surface, W1: silicon wafer as an object to be adsorbed.

Claims (4)

[Claims] 1. An electrostatic chuck wherein an object to be adsorbed is electrostatically adsorbed on a chuck surface of an insulating base made of a ceramic sintered body. The electrostatic chuck according to claim 1, wherein the support is fixedly protruded from the insulating base material with a part of the support buried in the chuck surface. 2. The electrostatic chuck according to claim 1, wherein the object support is a sheet material formed by weaving carbon fibers. 3. The method for manufacturing an electrostatic chuck according to claim 2, wherein after firing the unsintered ceramic body in which the sheet material is arranged in an inner layer, the ceramic sintered body obtained by the firing is ground. A method for manufacturing an electrostatic chuck, wherein a part of the sheet material is exposed from the ceramic sintered body by performing chemical etching after processing. 4. The method for manufacturing an electrostatic chuck according to claim 3, wherein said sheet material is divided at a plurality of positions by grooving.