JP4585129B2 - Electrostatic chuck - Google Patents

Description

【００２８】
表１から明らかなように、誘電体層の電気伝導率は、実施例全てが本発明の範囲内にあった。そのため、シリコンウェハの吸着性が全て良好であった。また、ハロゲン系プラズマガスに対するエッチングレートが全て５μｍ／ｈｒ以下にあり、従前の比較例７のアルミナに比べてはるかによく、しかもＴｉＯ₂の添加率が多くてもその添加率が少ない比較例３に比べて遜色なかった。このことは、本発明の静電チャックとすれば、誘電体層の厚さに関係なく吸着でき、しかも耐食性を有する誘電体層が形成された静電チャックとすることができることを示している。
【００２９】
これに対して、比較例１、２、５、６では、ＭｇＯ／Ａｌ₂Ｏ₃の比が本発明の範囲外にあるので、誘電体層の強度が低く、以後の評価を行わなかった。また、比較例３では、ＴｉＯ₂の添加率が低すぎたため、電気伝導率が低く、シリコンウェハを吸着できず、吸着性が悪かった。さらに、比較例４では、ＴｉＯ₂の添加率が多すぎたため、吸着性は良好なものの、電気伝導率が高すぎて回路がショートし回路破壊が生じてしまっており、しかもＴｉＯ_2-xの単味のものが残存してしまったためか耐食性も悪かった。なお、比較例７では、耐食性が悪いばかりでなく、誘電体層が厚いため、吸着性が不良であった。
【００３０】
【発明の効果】
以上の通り、本発明にかかる静電チャックであれば、導電性を有し、しかも耐食性の良好な誘電体層を有する静電チャックとすることができるようになった。
このことにより、誘電体層の厚さに関係なく吸着できる静電チャックとなり、しかもＴｉＯ_2-xまたはＣｒ₂Ｏ_3-xの含有率を調整することにより、必要とする電気伝導率に変えることのできる静電チャックともなるようになった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic chuck used for fixing, transporting, and correcting an object to be adsorbed such as a silicon wafer in a semiconductor manufacturing apparatus or the like.
[0002]
[Prior art]
In an electrostatic chuck in which an electrode and a dielectric layer are provided on an upper surface of the electrode, insulating ceramics such as alumina and sapphire are conventionally used as the dielectric layer.
[0003]
[Problems to be solved by the invention]
However, these insulating ceramics are attracted by the electrostatic attraction force (Coulomb force) generated between the charge induced on the electrode and the charge induced on the object to be adsorbed to the electrostatic chuck. In order to obtain a high attractive force, there has been a problem that the thickness of the dielectric layer must be reduced to 0.1 mm or less.
[0004]
The present invention has been made in view of the problems of the electrostatic chuck described above, and an object thereof is to provide an electrostatic chuck having a dielectric layer that can be adsorbed regardless of the thickness of the dielectric layer. .
[0005]
[Means for Solving the Problems]
As a result of diligent research to achieve the above object, the present inventors have determined that the thickness of the dielectric layer can be determined if the material of the dielectric layer is a spinel sintered body containing TiO _2-x or Cr ₂ O _3-x. The present invention has been completed with the knowledge that an electrostatic chuck having a dielectric layer that can be adsorbed regardless of the thickness can be obtained.
[0006]
That is, the present invention
(1) In an electrostatic chuck in which a dielectric layer is provided on the upper surface of an electrode, the dielectric layer is mainly composed of MgO and Al ₂ O ₃ , and the composition ratio is the weight ratio of MgO / Al ₂ O ₃ . In the range of 0.67 to 2.33, and is composed of a spinel sintered body containing 3 to 30% by weight of TiO _2-x as a main component, and its electric conductivity is 10 ⁻⁸ to 10 ^−14. S / cm is an electrostatic chuck (Claim 1),
(2) In an electrostatic chuck in which a dielectric layer is provided on the upper surface of the electrode, the dielectric layer is mainly composed of MgO and Al ₂ O ₃ , and the composition ratio is the weight ratio of MgO / Al ₂ O ₃ . In the range of 0.67 to 2.33, and is composed of a spinel sintered body containing 3 to 30% by weight of Cr ₂ O _3-x as a main component and having an electric conductivity of 10 ⁻⁸ to 10 ^-14 S / cm electrostatic chuck (claim 2),
(3) The electrostatic chuck according to claim 1 or 2, wherein the corrosion resistance of the spinel sintered body to a corrosive gas is 5 μm / hr or less at an etching rate with respect to a halogen-based plasma gas. )age,
(4) The spinel sintered body is composed of MgO powder, Al ₂ O ₃ powder, and TiO ₂ powder so as to have the composition of claim 1, mixed and molded, and the molded body thus molded. The electrostatic chuck according to claim 1 or 3 (claim 4), wherein the electrostatic chuck is produced by sintering in a reducing atmosphere.
(5) The spinel sintered body is blended with MgO powder, Al ₂ O ₃ powder, and Cr ₂ O ₃ powder so as to have the composition of claim 2, mixed, molded, and molded. The electrostatic chuck according to claim 2 or 3 (claim 5), wherein the molded body is a sintered body produced by sintering in a reducing atmosphere.
(6) The spinel sintered body is composed of MgO powder, Al ₂ O ₃ powder, and TiO ₂ powder so as to have the composition according to claim 1, mixed, molded, and molded body that is molded. The electrostatic chuck (Claim 6) according to claim 1 or 3, wherein the electrostatic chuck (Claim 6) is a sintered body produced by sintering in air and then heat-treating it in a reducing atmosphere. ,
(7) The spinel sintered body is composed of MgO powder, Al ₂ O ₃ powder, and Cr ₂ O ₃ powder so as to have the composition described in claim 2, mixed, molded, and molded. 4. The electrostatic chuck according to claim 2, which is a sintered body produced by sintering a molded body in air and then heat-treating the molded body in a reducing atmosphere. ).
This will be described in more detail below.
[0007]
As described above, in the electrostatic chuck of the present invention, the dielectric layer that adsorbs the wafer is mainly composed of MgO and Al ₂ O ₃ , and the MgO / Al ₂ O ₃ ratio is 0.00 by weight. It is in the range of 67 to 2.33, and is composed of a spinel sintered body containing 3 to 30% by weight of TiO _2-x or Cr ₂ O _3-x as a main component, and has an electric conductivity of 10 ^−8. 10 to ^{14 −14} S / cm electrostatic chuck (claims 1 and 2)
[0008]
As the electrostatic chuck, the material of the dielectric layer is made of a spinel sintered body containing TiO _2-x or Cr ₂ O _3-x , and the conductive TiO _2-x or Cr ₂ O _{3-x is used.} The dielectric layer is made conductive, and the conductivity causes the Johnsen-Rahbek force to be generated, so that the dielectric layer can be adsorbed regardless of the thickness of the dielectric layer. By doing so, the dielectric layer has excellent corrosion resistance to the halogen-based plasma gas.
[0009]
The ratio of MgO / Al ₂ O ₃ of the spinel sintered body is preferably 0.67 to ₂ and 33, and if the ratio is smaller than 0.67, the strength of the sintered body is greatly reduced, which is not preferable. Even if it is higher than 2.33, the strength of the sintered body is greatly lowered, which is not preferable.
[0010]
The content of TiO _2-x or Cr ₂ O _{3-x in} the spinel sintered body is preferably 3 to 30% by weight, and if it is less than 3% by weight, the electric conductivity is 10 ⁻¹⁴ S / cm or more. It is not preferable because it does not become, and if it exceeds 30% by weight, it is not preferable because it is not 10 ⁻⁸ S / cm or less.
[0011]
As the electric conductivity of the spinel sintered body, an electric conductivity in the range of 10 ⁻⁸ to 10 ⁻¹⁴ S / cm is preferable because the Johnsen-Rahbek force works effectively, and the electric conductivity is 10 ^−8. S / cm and leakage current flows in the high and adsorbed wafer from there is a possibility that the circuit formed on the wafer is broken, 10 ^-14 S / cm lower than the Johnsen-Rahbek force is effectively exerted without high adsorption I can't get power. The electric conductivity of such a range should just be obtained in the range of -50-200 degreeC at least.
[0012]
On the other hand, the degree of corrosion resistance of the spinel sintered body is set to 5 μm / hr or less at an etching rate with respect to the halogen-based plasma gas. Even if this spinel sintered body contains TiO _2-x or Cr ₂ O _3-x , this excellent corrosion resistance is probably because TiO _2-x or Cr ₂ O _3-x is contained in the spinel crystal lattice. Probably because a solid solution, or _{MgTiO 3-x, MgTi 2 O} 5-x, is believed that it is a to produce a composite oxide such as MgCr ₂ O _4-x. As a result, the dielectric layer is extremely resistant to corrosion.
[0013]
As a method for producing the spinel sintered body, it is prepared by blending so as to have a predetermined composition, mixing, molding, and sintering the molded article in a reducing atmosphere. (Claims 4 and 5). TiO ₂ or Cr ₂ O ₃ does not have electrical conductivity unless oxygen vacancies are generated, and therefore, oxygen vacancies are generated by sintering it in a reducing atmosphere.
[0014]
Further, as another production method, it is blended so as to have a predetermined composition, mixed, molded, sintered in the air, and further heat-treated in a reducing atmosphere. It was supposed to be produced (claims 6 and 7). In this method, a sintered body having no oxygen vacancies is once produced, and the sintered body is heat-treated in a reducing atmosphere. This method similarly causes oxygen vacancies.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Regarding production of an electrostatic chuck, first, MgO powder, Al ₂ O ₃ powder, TiO ₂ powder, or MgO powder, Al ₂ O ₃ powder, Cr ₂ O ₃ powder are used to produce a spinel sintered body. Prepare to the prescribed recipe. A composite oxide such as MAl ₂ O ₄ containing MgO and Al ₂ O ₃ may be used instead of the above powder. What is necessary is just to prepare the preparation of these powders according to the conventional method. For example, the powder described above is blended at a predetermined ratio, and an organic solvent such as alcohol or water is added to the blended powder, followed by mixing with a ball mill and drying, or a solution of salts, alkoxide, or the like with a predetermined blend. There is a method of separating and drying the sediment.
[0016]
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 atmosphere and further heated at a predetermined temperature in a reducing atmosphere. By performing the treatment, a conductive spinel sintered body is produced. The degree of oxygen deficiency varies depending on the reducing power in the reducing atmosphere, but with the reducing power of the ordinary carbon atmosphere, only oxygen in TiO ₂ or Cr ₂ O ₃ is lost, and oxygen in the spinel. Will not be lost.
[0017]
The temperature at which the sintered body is sintered is preferably 1500 to 1650 ° C. If the temperature is lower than 1500 ° C., densification becomes insufficient, and if it is higher than 1650 ° C., the sintered body may be decomposed. The temperature at which the sintered sintered body is further subjected to heat treatment may be the same as the temperature at which sintering is performed, but in the case of hot isostatic pressure treatment (HIP treatment), 1400 to 1650 ° C. is preferable, and from 1400 ° C. If the pressure is lower or higher than 1650 ° 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.
[0018]
Impurity components such as SiO ₂ , CaO, Na ₂ O, Fe ₂ O _{3 and the} like contained in the obtained spinel sintered body are preferably 3% by weight or less, and more than 3% by weight, for example, a semiconductor manufacturing apparatus This is not preferable because it causes problems such as insulation failure in the device. In addition, the porosity of the obtained spinel sintered body is preferably 1% or less, and when the porosity exceeds 1%, there are many pores in the sintered body. The corrosion reaction of the halogen-based plasma gas occurs vigorously in the pores, and the surface is significantly corroded, which is not preferable.
[0019]
Next, a dielectric layer is produced by processing the obtained spinel sintered body, and the dielectric layer is adhered to the upper surface of the ceramic substrate on which the electrode is formed, or the obtained dielectric layer is attached to the electrode. A monopolar or bipolar electrostatic chuck is fabricated by bonding to the upper surface or forming an electrode on the lower surface of the dielectric layer. In addition, although the dielectric layer is manufactured by sintering in the above, it may be formed by spraying or sputtering on the surface of a substrate such as ceramics or metal, and reduced in a reducing atmosphere. Good.
[0020]
If the electrostatic chuck is manufactured by the method described above, an electrostatic chuck having a dielectric layer having conductivity and corrosion resistance can be obtained.
[0021]
【Example】
Examples of the present invention will be specifically described below together with comparative examples to describe the present invention in more detail.
[0022]
(Examples 1-7)
(1) Fabrication of electrostatic chuck A 99% pure MgAl ₂ O ₄ powder and a 99.9% pure MgO powder were prepared so that the ratio of MgO / Al ₂ O ₃ was as shown in Table 1, and TiO was used. ₂ or Cr ₂ O ₃ powder was added so that the addition ratio was as shown in Table 1, ethanol was added thereto, and the mixture was pulverized for 72 hours by a ball mill.
[0023]
The mixed powder obtained by drying the resultant is subjected to CIP treatment and molded to φ250 × 6 mmt, and the molded body is sintered at a temperature of 1500 to 1650 ° C. in a reducing atmosphere (Examples 1 to 4). And sintered at a temperature of 1500 to 1650 ° C. and further subjected to HIP treatment at a pressure of 1800 kg / cm ² at a temperature of 1400 to 1650 ° C. in a reducing atmosphere (Examples 5 to 7) to produce a spinel sintered body did. These sintered bodies were processed into φ200 × 2 mmt to produce dielectric layers.
[0024]
An electrode is formed by printing and baking Ag paste on one surface of the obtained dielectric layer, and the other surface is polished so that the surface roughness Ra is 0.34 μm. An electrostatic chuck was prepared by adhering to a dyed (anodized) Al base with an adhesive.
[0025]
(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 direct current three-terminal method. Further, the obtained electrostatic chuck is incorporated into a parallel plate electrode type plasma etching apparatus, and a circuit formed on the silicon wafer is destroyed whether or not the silicon wafer is attracted by applying a charge of 1 kV. I investigated whether or not. Furthermore, 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 adjusted. Calculation was based on the reduced weight of the dielectric layer. The results are shown in Table 1.
[0026]
(Comparative Examples 1-7)
For comparison, in Comparative Examples 1, 2, 5, and 6, except that the ratio of MgO / Al ₂ O _{3 in} the dielectric layer was out of the range of the present invention, in Comparative Examples 3 and 4, the addition rate of TiO ₂ In Comparative Example 7, an electrostatic chuck was prepared and evaluated in the same manner as in Example except that the dielectric layer was alumina. The results are also shown in Table 1.
[0027]
[Table 1]

[0028]
As is apparent from Table 1, all the examples of the electric conductivity of the dielectric layer were within the scope of the present invention. For this reason, all the adsorptivity of the silicon wafer was good. 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 the comparative example 7, and the addition rate is small even if the addition rate of TiO ₂ is large. It was not inferior to. This indicates that the electrostatic chuck according to the present invention can be attracted regardless of the thickness of the dielectric layer, and can be an electrostatic chuck on which a dielectric layer having corrosion resistance is formed.
[0029]
On the other hand, in Comparative Examples 1, 2, 5, and 6, since the ratio of MgO / Al ₂ O ₃ is outside the range of the present invention, the strength of the dielectric layer was low, and the subsequent evaluation was not performed. In Comparative Example 3, since the addition rate of TiO ₂ was too low, the electrical conductivity was low, the silicon wafer could not be adsorbed, and the adsorbability was poor. In Comparative Example 4, since the addition rate of the TiO ₂ is too large, although the adsorptive good, circuit electrical conductivity is too high has shorted circuit breakdown gone occur, yet the TiO _2-x Corrosion resistance was also bad because the simple thing remained. In Comparative Example 7, not only the corrosion resistance was poor, but also the adsorbability was poor because the dielectric layer was thick.
[0030]
【The invention's effect】
As described above, the electrostatic chuck according to the present invention can be an electrostatic chuck having a dielectric layer having conductivity and good corrosion resistance.
As a result, the electrostatic chuck can be adsorbed regardless of the thickness of the dielectric layer, and it can be changed to the required electrical conductivity by adjusting the content of TiO _2-x or Cr ₂ O _3-x. It can be used as an electrostatic chuck.

Claims (4)

In the electrostatic chuck in which the dielectric layer is provided on the upper surface of the electrode, the dielectric layer is mainly composed of MgO and Al ₂ O ₃ , and the ratio of MgO / Al ₂ O ₃ is 0.00 by weight. It is in the range of 67 to 2.33, and is composed of a spinel sintered body containing 3 to 30% by weight of TiO _2-x or Cr ₂ O _3-x as a main component, and has an electric conductivity of 10 ^−8. An electrostatic chuck characterized by having a ^{viscosity of} 10 ⁻¹⁴ S / cm.   2. The electrostatic chuck according to claim 1, wherein the corrosion resistance of the spinel sintered body against a corrosive gas is 5 μm / hr or less at an etching rate with respect to a halogen-based plasma gas. The spinel sintered body, MgO powder, _Al 2 _{O 3} powder, blended TiO ₂ powder or _Cr 2 _{O 3} so that the powder having the composition of claim 1, wherein it is mixed, molded, the molding 3. The electrostatic chuck according to claim 1, which is a sintered body produced by sintering the formed body in a reducing atmosphere. The spinel sintered body, MgO powder, _Al 2 _{O 3} powder, blended TiO ₂ powder or _Cr 2 _{O 3} so that the powder having the composition of claim 1, wherein it is mixed, molded, the molding 3. The electrostatic chuck according to claim 1, wherein the molded body is a sintered body produced by sintering the molded body in air and then heat-treating the molded body in a reducing atmosphere.