JP2002246452A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck which has an attracting dielectric layer regardless of its thickness. SOLUTION: In the electrostatic chuck having a dielectric layer provided on an electrode, the dielectric layer contains MgO and Al2O3 as its main components, the weight ratio of MgO to Al2O3 is in the range of 0.67 to 2.33. The dielectric layer is made of a spinel sintered body which contains, in addition to the above main components, 3-30 weight % of TiO2-x or Cr2O3-x and has electrical conductivity of 10-8 to 10-14 S/cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing and transporting an object to be suctioned such as a silicon wafer in a semiconductor manufacturing apparatus or the like.
The present invention relates to an electrostatic chuck used for straightening.

[0002]

2. Description of the Related Art In an electrostatic chuck in which an electrode and a dielectric layer are provided on the upper surface thereof, insulating ceramics such as alumina and sapphire are conventionally used as the dielectric layer.

[0003]

However, in these insulating ceramics, the electrostatic attraction force generated between the charge induced in the electrode and the charge induced in the object to be attracted to the electrostatic chuck is generated. (Coulomb force), there is a problem that the thickness of the dielectric layer must be reduced to 0.1 mm or less in order to obtain a high suction force.

The present invention has been made in view of the above-mentioned problems of the electrostatic chuck, and has as its object to provide an electrostatic chuck having a dielectric layer that can be attracted regardless of the thickness of the dielectric layer. It is in.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have set the material of the dielectric layer to T.
It has been found that an electrostatic chuck having a dielectric layer that can be adsorbed regardless of the thickness of the dielectric layer can be obtained if a spinel-based sintered body containing iO _2-x or Cr ₂ O _3-x is obtained. The present invention has been completed.

That is, the present invention provides (1) an electrostatic chuck in which a dielectric layer is provided on the upper surface of an electrode, wherein the dielectric layer is
The main components are MgO and Al ₂ O ₃ , and the composition ratio is Mg
In a weight ratio of O / Al ₂ O ₃ in the range of 0.67 to 2.33, consists spinel sintered body containing TiO _2-x 3 to 30 wt% to the main components, and the electrical conductivity But 10 ^-8
(2) In an electrostatic chuck in which a dielectric layer is provided on an upper surface of an electrode, the dielectric layer mainly has a thickness of 10 to ¹⁴ S / cm. The components consist of MgO and Al ₂ O ₃ , and the composition ratio is MgO / A
The weight ratio of l ₂ O ₃ is in the range of 0.67 to 2.33, and is made of a spinel sintered body containing 3 to 30% by weight of Cr ₂ O _3-x as its main component, and its electric conductivity. But 10 ^-8 to 10
^-14 S / cm, and (3) the spinel sintered body has a corrosion resistance to a corrosive gas of 5 μm / hr at an etching rate with respect to a halogen-based plasma gas. The electrostatic chuck according to claim 1 or 2, wherein:
(4) The spinel-based sintered body is made of MgO powder, A
The l ₂ O ₃ powder and the TiO ₂ powder are blended so as to have the composition described in claim 1, mixed, molded, and sintered by sintering the molded body in a reducing atmosphere. 4. The electrostatic chuck according to claim 1, wherein the spinel-based sintered body is made of MgO powder, Al ₂ O ₃ powder, Cr ₂ O _3. And the powder are blended so as to have a composition according to claim 2, and then mixed,
The electrostatic chuck according to claim 2 or 3, wherein the molded body is formed by sintering the molded body in a reducing atmosphere.
(6) The spinel sintered body, MgO powder, Al ₂ O ₃
The powder and the TiO ₂ powder are blended so as to have the composition according to claim 1, mixed, molded, and the molded body is sintered in the air, and further heated in a reducing atmosphere. The electrostatic chuck according to claim 1 or 3, wherein the spinel sintered body is made of MgO powder, Al ₂ O. ₃ powder and Cr ₂ O ₃ powder are blended so as to have the composition described in claim 2, mixed, molded, and the molded product is sintered in air, and then further reduced in a reducing atmosphere. A gist is a sintered body produced by heat treatment in (2) or (3). This will be described in more detail below.

As described above, the electrostatic chuck of the present invention comprises a dielectric layer for adsorbing a wafer and a main component comprising Mg.
O and Al ₂ O ₃ , and its MgO / Al ₂ O ₃ ratio is in the range of 0.67 to 2.33 by weight, and its main component is T
It is made of a spinel sintered body containing 3 to 30% by weight of iO _2-x or Cr ₂ O _3-x and has an electric conductivity of 10 ^-8 to
An electrostatic chuck having a pressure of 10 ^-14 S / cm was set (claims 1 and 2).

In the electrostatic chuck, the dielectric layer is made of a spinel sintered body containing TiO _2-x or Cr ₂ O _{3-x because} it is made of conductive TiO _2-x or Cr ₂ O. _3-x
By making the dielectric layer have conductivity, the Johnsen-Rahbek force is expressed by the conductivity,
It becomes a dielectric layer that can be adsorbed regardless of the thickness of the dielectric layer,
In addition, by using spinel as a matrix, a dielectric layer having excellent corrosion resistance to halogen-based plasma gas can be obtained.

The spinel sintered body MgO / Al ₂ O ₃
Is preferably 0.67 to 2, 33. If the ratio is smaller than 0.67, the strength of the sintered body is greatly reduced. Is undesirably greatly reduced.

The content of TiO _2-x or Cr ₂ O _{3-x in} the spinel-based sintered body is preferably 3 to 30% by weight, and if it is less than 3% by weight, the electrical conductivity is 10 ^-14 S / c
it is not preferable because not a higher m, unfavorably not when it is more than 30 wt% 10 ^-8 S / cm or less and.

The electric conductivity of the spinel sintered body is preferably in the range of 10 ^-8 to 10 ^-14 S / cm because the Johnsen-Rahbek force works effectively. If it is higher than 10 ^-8 S / cm, a leak current may flow into the attracted wafer and a circuit formed on the wafer may be destroyed. If it is lower than 10 ^-14 S / cm, the Johnsen-Rahbek force works effectively. High adsorption power cannot be obtained. The electrical conductivity in such a range only needs to be obtained at least in the range of -50 to 200C.

On the other hand, the degree of corrosion resistance of the spinel sintered body
As a match, etch against halogen-based plasma gas
In terms of the rate, it is assumed to be 5 μm / hr or less.
3). This spinel sintered body is made of TiO_2-xOr Cr_TwoO
_3-xEven having such excellent corrosion resistance,
Probably TiO_2-xOr Cr_TwoO_3-xIs the spinel crystal lattice
Because of solid solution inside or MgTiO_3-x, MgT
i_TwoO_5-x, MgCr_TwoO _4-xProduces complex oxides such as
It seems to be because. This makes it extremely corrosion resistant
It becomes a strong dielectric layer.

The spinel sintered body is manufactured by blending it into a predetermined composition, mixing and molding, and sintering the formed body in a reducing atmosphere. (Claims 4 and 5). TiO
_{Since 2} or Cr ₂ O ₃ has no conductivity unless oxygen deficiency occurs, sintering it in a reducing atmosphere causes oxygen deficiency.

As another manufacturing method, a compound having a predetermined composition is blended, mixed, molded, sintered in air, and then heat-treated in a reducing atmosphere. (Claims 6 and 7). In this method, a sintered body having no oxygen deficiency is once prepared, and the sintered body is subjected to a heat treatment in a reducing atmosphere. In this method, oxygen deficiency is similarly generated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The preparation of an electrostatic chuck will be described. First, MgO powder, Al ₂ O ₃ powder, TiO ₂ powder, or MgO powder, Al ₂ O ₃ powder are used to prepare a spinel sintered body. , Cr ₂ O ₃ powder is blended to a predetermined composition. Instead of the powder described above, a composite oxide such as MAl ₂ O ₄ containing MgO and Al ₂ O ₃ may be used. These powders may be prepared according to a conventional method. For example, the powder described above is blended at a predetermined ratio, an organic solvent such as alcohol or water is added to the blended powder, mixed by a ball mill, and dried, or a salt of a predetermined blend,
There is a method of separating a coprecipitate from a solution such as an alkoxide and drying the coprecipitate.

The obtained mixed powder is formed into a predetermined shape by a uniaxial press or a cold isostatic press (CIP). The obtained molded body is sintered at a predetermined temperature in a reducing atmosphere, or the obtained molded body is sintered at a predetermined temperature in the air and further heated at a predetermined temperature in a reducing atmosphere. By performing the treatment, a spinel-based sintered body having conductivity is produced. The degree of oxygen deficiency is
Although it depends on the reducing power in the reducing atmosphere, TiO ₂ or C
Only oxygen of r ₂ O ₃ is lost, and oxygen in spinel is not lost.

The temperature for sintering the sintered body is 15
If the temperature is lower than 1500 ° C., the densification becomes insufficient. If the temperature is higher than 1650 ° C., the sintered body may be decomposed. The temperature at which the sintered body is further heated may be the same as the temperature at which it is sintered, but when hot isostatic pressure treatment (HIP treatment) is performed, 1400
1650 ° C. is preferred, lower than 1400 ° C. or 1
If the temperature is higher than 650 ° C., the effect of the HIP treatment is small, and if the pressure at that time is lower than 1800 kg / cm ² , the effect of the HIP treatment is also small.

Si contained in the obtained spinel sintered body
The impurity component such as O ₂ , CaO, Na ₂ O, and Fe ₂ O ₃ is preferably 3% by weight or less, and if it is more than 3% by weight, for example, there is a problem that insulation failure occurs in a semiconductor manufacturing apparatus. Is not preferred. The porosity of the obtained spinel-based sintered body is preferably 1% or less,
If the porosity exceeds 1%, there are many pores in the sintered body. Therefore, when the surface is processed, the pores appear on the surface, and the corrosion reaction of the halogen-based plasma gas occurs violently at the pores, and the surface is markedly remarkable. It is not preferable because it is corroded.

Next, a dielectric layer is formed by processing the obtained spinel-based sintered body, and the dielectric layer is bonded to the upper surface of the ceramic substrate on which the electrodes are formed, or the obtained dielectric layer is Is adhered to the upper surface of the electrode, or an electrode is formed on the lower surface of the dielectric layer to produce a monopolar or bipolar electrostatic chuck. In the above description, the dielectric layer is manufactured by sintering. In addition, even when the dielectric layer is formed by spraying or sputtering on the surface of a substrate such as ceramics and metal, and then reduced in a reducing atmosphere, Good.

When an electrostatic chuck is manufactured by the method described above, an electrostatic chuck having a conductive and corrosion-resistant dielectric layer formed thereon can be obtained.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples.

(Examples 1 to 7) (1) Preparation of electrostatic chuck 99% pure MgAl_TwoO_FourPowder and 99.9% pure Mg
O powder is MgO / Al _TwoO_ThreeTable 1 shows the ratio by weight.
And TiO2_TwoOr Cr_TwoO_ThreeThe powder
Add so that the addition ratio is as shown in Table 1, and add ethanol to it.
Then, it was mixed and pulverized with a ball mill for 72 hours.

The dried mixed powder was subjected to CIP treatment and formed into φ250 × 6 mmt, and the formed body was sintered at a temperature of 1500 to 1650 ° C. in a reducing atmosphere (Examples 1 to 5).
4) Alternatively, the molded body is 1500 to 1650 ° C. in the atmosphere.
Sintering at a temperature of 1400 ° C.
H at a temperature of １６1650 ° C. and a pressure of 1800 kg / cm ²
IP treatment (Examples 5 to 7) produced a spinel-based sintered body. These sintered bodies were processed into φ200 × 2 mmt to produce a dielectric layer.

An electrode is formed by printing and baking an Ag paste on one surface of the obtained dielectric layer, and the other surface is polished to have a surface roughness Ra of 0.34 μm. An electrostatic chuck was prepared by attaching the adhesive to an Al pedestal whose surface was anodized (anodized).

(2) Evaluation The bending strength of the obtained spinel sintered body was measured by a three-point bending test method. Further, the electric conductivity of the dielectric layer of the obtained electrostatic chuck was measured by a DC three-terminal method. Further, the obtained electrostatic chuck is incorporated in a parallel plate electrode type plasma etching apparatus, and a circuit formed on the silicon wafer is destroyed by applying a charge of 1 kV to determine whether or not the silicon wafer is attracted. I checked whether or not. Further, a plasma gas having a frequency of 2.45 GHz, an output of 800 W, and a volume ratio of CF ₄ to O ₂ of 4: 1 is etched on the adsorption surface for 40 minutes, and the etching rate of the dielectric layer after the etching is reduced. It was calculated from the reduced weight of the dielectric layer. Table 1 shows the results.

Comparative Examples 1 to 7 For comparison, Comparative Example 1
In Comparative Examples 3 and 4, TiO ₂ was used except that the ratio of MgO / Al ₂ O ₃ of the dielectric layer was out of the range of the present invention in 2, 5, and 6.
Comparative Example 7 except that the addition ratio of
Then, an electrostatic chuck was manufactured and evaluated in the same manner as in the example except that alumina was used as the dielectric layer. The results are also shown in Table 1.

[0027]

[Table 1]

As is apparent from Table 1, the electric conductivity of the dielectric layer was within the scope of the present invention in all the examples. Therefore, all of the silicon wafers had good adsorption properties. Further, the etching rates for the halogen-based plasma gas are all 5 μm / hr or less, which is much better than the alumina of Comparative Example 7 in the past, and the addition rate of TiO ₂ is small even when the addition rate of TiO ₂ is high. Was comparable to. This indicates that the electrostatic chuck of the present invention can be attracted irrespective of the thickness of the dielectric layer and can be formed with a corrosion-resistant dielectric layer.

On the other hand, in Comparative Examples 1, 2, 5, and 6, since the ratio of MgO / Al ₂ O ₃ was out of the range of the present invention, the strength of the dielectric layer was low. Did not. In Comparative Example 3, since the addition rate of TiO ₂ was too low, the electric conductivity was low, the silicon wafer could not be adsorbed, and the adsorbability was poor. Further, in Comparative Example 4, TiO
_Since the addition ratio of ₂ was too large, the adsorptivity was good, but the electrical conductivity was too high, and the circuit was short-circuited and the circuit was broken, and the simple TiO _2-x remained. Corrosion resistance was also bad probably because it had been. In Comparative Example 7, not only corrosion resistance was poor, but also the dielectric layer was thick,
Adsorption was poor.

[0030]

As described above, with the electrostatic chuck according to the present invention, an electrostatic chuck having a dielectric layer having conductivity and good corrosion resistance can be obtained. Thus, it is an electrostatic chuck capable of adsorbing regardless the thickness of the dielectric layer, moreover TiO _2-x or C
By adjusting the content of r ₂ O _3-x, an electrostatic chuck that can be changed to a required electric conductivity has come to be obtained.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mamoru Ishii 2-4-2 Daisaku, Sakura City, Chiba Pref. Central Research Institute of Pacific Cement Co., Ltd.

Claims (7)

[Claims] 1. An electrostatic chuck in which a dielectric layer is provided on an upper surface of an electrode, wherein the dielectric layer has a main component of MgO.
And Al ₂ O ₃ , and the ratio of MgO / Al ₂ O ₃ is in the range of 0.67 to 2.33 by weight.
It is made of a spinel sintered body containing 3 to 30% by weight of iO _2-x and has an electric conductivity of 10 ^-8 to 10 ^-14 S / cm.
An electrostatic chuck characterized by the following. 2. An electrostatic chuck in which a dielectric layer is provided on an upper surface of an electrode, wherein the dielectric layer has a main component of MgO.
And Al ₂ O ₃ , and the ratio of MgO / Al ₂ O ₃ is in the range of 0.67 to 2.33 by weight.
r ₂ O _3-x to be a spinel sintered body comprising 3 to 30 wt%, and its electrical conductivity, 10 ^-8 ~10 ^-14 S / cm
An electrostatic chuck characterized by the following. 3. The electrostatic chuck according to claim 1, wherein the corrosion resistance of the spinel sintered body to a corrosive gas is 5 μm / hr or less as an etching rate with respect to a halogen-based plasma gas. 4. The method according to claim 1, wherein the spinel-based sintered body comprises MgO powder,
An Al ₂ O ₃ powder and a TiO ₂ powder are blended so as to have the composition described in claim 1, mixed, molded, and sintered by sintering the molded body in a reducing atmosphere. The electrostatic chuck according to claim 1, wherein the electrostatic chuck is a union. 5. The method according to claim 1, wherein the spinel-based sintered body comprises MgO powder,
Al_TwoO_ThreePowder, Cr _TwoO_ThreePowder and the composition according to claim 2;
Blended, mixed, molded, and molded
Manufactured by sintering compacts in a reducing atmosphere
4. A sintered body according to claim 2, wherein the sintered body is a sintered body.
Electrostatic chuck. 6. The method according to claim 1, wherein the spinel-based sintered body comprises MgO powder,
An Al ₂ O ₃ powder and a TiO ₂ powder are blended so as to have the composition according to claim 1, mixed, molded, and the molded body is sintered in air, and then further reduced in a reducing atmosphere. The electrostatic chuck according to claim 1, wherein the electrostatic chuck is a sintered body produced by performing a heat treatment in the inside. 7. The method according to claim 1, wherein the spinel sintered body comprises MgO powder,
Al_TwoO_ThreePowder, Cr _TwoO_ThreePowder and the composition according to claim 2;
Blended, mixed, molded, and molded
After sintering the compact in air, it is further reduced
This is a sintered body produced by heat treatment in
4. The electrostatic chuck according to claim 2, wherein: