JPH11121599A - Electrostatic chuck base and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck base of extremely high suction force in vacuum and in atmosphere. SOLUTION: In an electrostatic chuck substrate, consisting of an insulator substrate 3, a conductive layer 2, and a dielectric layer 1, the dielectric layer is the electrostatic chuck substrate having a composition of Ti1-x MxO2 . Here, M is a pentavalent metal element (x=1×10<-5> -2×10<-4> ) of Ta, Nb, or Sb or a hoxavalent metal element (x=1×10<-5> -1×10<-4> ) of W or Mo. By substituting M, the volumetric specific resistivity of the dielectric can be controlled, while being set to a value of 108-1,012 Ω.cm, and attractive force is manifested. After the dielectric mixes and forms TiO2 and M2 O5 or MO3 , it is calcined at 1,200-1,600 deg.C in the atmosphere for manufacturing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck base for electrostatically holding and transporting a wafer or the like in a semiconductor manufacturing apparatus or the like.

[0002]

2. Description of the Related Art Conventionally, in semiconductor manufacturing equipment,
In order to form or etch a Si wafer or the like, it is necessary to hold the wafer while maintaining its flatness. As such means, a mechanical system, a vacuum suction system, and an electrostatic suction system have been proposed. Among them, the electrostatic chucking method is a method of holding a wafer by an electrostatic chuck, and has been used widely because it has excellent flatness of a processed surface of a wafer and can be used in a vacuum.

Conventional electrostatic chucks include those utilizing Coulomb force as an attraction force and those utilizing Johnsen-Rahbek force. For an electrostatic chuck utilizing Coulomb force, CaTiO ₃ , PbTiO ₃ −
There is one using La ₂ O ₃ system or the like (for example,
No. 31517).

[0004] The Johnsen-Rahbek force is a force generated when a minute current flows through a small gap at the interface between a dielectric and a wafer and is induced by polarization and polarization. The dielectric material has a volume resistivity of about 1012 Ω. -Occurs when the size is less than cm. Al ₂ O ₃ —TiO ₂ is used as a dielectric for an electrostatic chuck utilizing the Johnsen-Rahbek force.
A system using an AlN system or the like is known (for example, Japanese Patent Publication No. 6-97675, Japanese Patent Application Laid-Open No. H8-5589).
No. 9, etc.).

[0005]

Conventionally, an electrostatic chuck utilizing Coulomb force as an attraction force has a low attraction force, and if a ferroelectric material having a high dielectric constant is used to increase the attraction force, the residual attraction force is strong. Therefore, there is a problem that the wafer does not detach.

Further, an electrostatic chuck using the Johnsen-Rahbek force has a strong attraction force when used in a vacuum, but has a high electric current due to the adsorption of moisture on the dielectric surface when used in the air. However, there is a problem that the gas leaks and the adsorbing force is rapidly reduced.

[0007]

Means for Solving the Problems The present inventors have obtained an electrostatic chuck having a high attraction force by using, as a dielectric, a ceramic in which a trace amount of a pentavalent or hexavalent metal ion is dissolved in TiO _2. And found that the present invention was completed. That is, the gist of the present invention is as follows.

(1) An electrostatic chuck comprising a dielectric layer, a conductor layer provided on one main surface of the dielectric layer, and an insulator base covering the conductor layer, wherein the dielectric layer is made of Ti _1-x
90% relative density having a composition of M _x O ₂ (where M is at least one element selected from Ta, Nb and Sb)
X is 1 × 10 ⁻⁵ to 2 × 10
An electrostatic chuck base characterized in the range of ^-4 . (2) TiO ₂ and M ₂ O ₅ (where M is Ta, Nb,
Powder of at least one element selected from Sb)
O ₂ : M ₂ O ₅ = 1−x: x / 2 (x = 1 × 10 ⁻⁵ to 2
× 10 ^-4 ), and after molding, from 1200 to 16
The method for producing an electrostatic chuck substrate according to (1), wherein ceramics fired in the air at a temperature of 00 ° C. is used as a dielectric. (3) An electrostatic chuck including a dielectric layer, a conductor layer provided on one main surface of the dielectric layer, and an insulator base covering the conductor layer, wherein the dielectric layer is Ti _1-x A ceramic having a composition of M _x O ₂ (where M is at least one element selected from W and Mo) and having a relative density of 90% or more, and x is in the range of 5 × 10 ^-6 to 1 × 10 ^-4 . An electrostatic chuck base characterized by the following. (4) (where, M is W, at least one element selected from Mo) TiO ₂ and MO ₃ TiO powder _2: MO
₃ = 1-x: x (x = 5 × 10 ⁻⁶ to 1 × 10 ⁻⁴ ), mixed at a molar ratio, molded, and fired in the air at a temperature of 1200 to 1600 ° C. as a dielectric. (3) The method for manufacturing an electrostatic chuck substrate according to (3). (5) The electrostatic element according to the above (1) or (3), wherein the conductor layer provided on one main surface of the dielectric layer and the insulator base are joined by a joining agent. Chuck base.

[0009]

According to the above-mentioned invention, a predetermined amount of a pentavalent or hexavalent metal ion is dissolved in TiO ₂ to form a dielectric material having a volume specific resistivity of 108 to 1012 Ω · cm. , A suction force due to the Johnsen-Rahbek force is developed. In addition, since the dielectric constant of the dielectric is relatively high, such as about 100, an attractive force due to Coulomb force is also exhibited, and an electrostatic chuck having a relatively high attractive force even in the atmosphere can be obtained.

Since pure TiO ₂ is an insulator and has a specific volume resistivity of 1013 Ω · cm or more, even if it is used as a dielectric for an electrostatic chuck, the adsorption force due to the Johnsen-Rahbek force is small. However, 5 on the Ti ⁴⁺ site
When a monovalent or hexavalent metal ion is substituted and solid-dissolved, a part of Ti ⁴⁺ becomes trivalent by charge compensation, hopping conduction between Ti ⁴⁺ and Ti ³⁺ is promoted, and resistance is reduced. The present invention utilizes this.

In the present invention, the composition of the dielectric is Ti _1-x
In M _x O ₂ , x is in the range of 1 × 10 ⁻⁵ to 2 × 10 ⁻⁴ in the case of solid solution of pentavalent metal ions, and x is 5 × 10 ^{−6 in} case of solid solution of hexavalent metal ions. It needs to be in the range of 〜1 × 10 ^-4 . When x is smaller than these ranges, the volume resistivity becomes larger than 1012 Ω · cm, and the adsorption force due to the Johnsen-Rahbek force does not appear.
Adsorption force decreases. On the other hand, when x is larger than these ranges, the volume resistivity is too small, and a leak current flows to the wafer, which is not practically preferable. Further, the sintered density of the dielectric must be 90% or more in relative density. If the density is lower than this, the withstand voltage decreases, and moisture is easily adsorbed when used in the atmosphere, so that the adsorbing power is significantly reduced.

The dielectric material of the present invention is prepared by mixing a predetermined amount of TiO ₂ powder and a pentavalent or hexavalent metal oxide powder, and then molding into a predetermined shape by press molding, CIP molding, doctor blade molding or the like. It is obtained by firing at a temperature of ° C. At this time, the firing atmosphere must be in the air. When fired in a reducing atmosphere, Ti ⁴⁺
Since it is reduced to i ³⁺ ions, the resistance value drops rapidly and cannot be used. The firing temperature is 1200 to 1600 ° C, preferably 1250 to 1400 ° C. If the firing temperature is lower than 1200 ° C., metal ions do not form a solid solution in TiO ₂ , and a ceramic having a predetermined resistivity cannot be obtained. In addition, when firing at a temperature higher than 1600 ° C., the sintered density decreases.

The electrostatic chuck substrate of the present invention is, for example, provided with Pt, Pd-Pt, Ag for electrodes on the surface of a dielectric molded body.
A method of screen-printing a metal paste such as Pd or the like, then superimposing the molded body of the insulator and integrally firing in air;
Alternatively, it can be obtained by a method in which, after firing the dielectric, applying electrodes by screen printing, plating, or the like, and bonding the insulating substrate with a bonding agent. As a bonding agent, an organic bonding agent such as an epoxy resin, or a glass or oxide-based inorganic bonding agent is used. Hereinafter, the present invention will be described in detail based on examples.

[0014]

【Example】

(Examples 1 to 7, Comparative Examples 1 to 5) Ti having a purity of 99.9%
O ₂ and _{M 2 O 5 (M: Ta} , Nb or Sb) powder 1-x of: weighed so that the molar ratio of x / 2, distilled water, a binder, were mixed in a ball mill with addition of dispersants. The slurry was granulated with a spray drier to obtain granulated powder having a particle size of about 70 μm. This was CIP-molded into a disk shape, and then fired at a predetermined temperature to obtain a sintered body. The obtained sintered body was processed into a disk shape having a diameter of 90 mm and a thickness of 2 mm, for example, to obtain a dielectric.

Copper is applied to the surface of the dielectric 1 by plating,
Electrode 2 was used. The insulating substrate 3 (alumina) was bonded to this with an epoxy resin. At this time, a hole was previously formed in the center of the insulator substrate for a lead electrode.
Finally, the dielectric was ground and lapped to a thickness of 300 μm to produce an electrostatic chuck as shown in FIG.

A vacuum is applied to the electrostatic chuck (partially in the air).
, A DC voltage of 500 V was applied for 20 seconds, and the suction force when the silicon wafer was suctioned was measured. Table 1 shows the results.

[0017]

[Table 1]

(Examples 8 to 13, Comparative Examples 6 to 9) Purity 9
9.9% of TiO ₂ and MO ₃ (M: W or Mo) powder 1-x: were weighed so that the molar ratio of x, Examples 1-7
A sintered body and an electrostatic chuck were prepared in the same manner as in the above case, and the attraction force was measured. Table 2 shows the results.

From Tables 1 and 2, it can be seen that the electrostatic chuck of the present invention has a very high attraction force not only in vacuum but also in air. Although Comparative Example 2 in Table 1 and Comparative Example 6 in Table 2 exhibited relatively large attraction, they are not practically preferable because the dielectric material has a low resistance value and the leakage current flowing through the wafer increases.

[0020]

[Table 2]

[0021]

As described above, when the electrostatic chuck of the present invention is used, a high suction force can be obtained in a vacuum and in the atmosphere.
It is suitable as a component of a semiconductor manufacturing device or the like, and is extremely useful in industry.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a cross section of an electrostatic chuck according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Derivative 2 Electrode 3 Insulator 4 Silicon wafer

Claims (5)

[Claims] 1. An electrostatic chuck comprising a dielectric layer, a conductor layer provided on one principal surface of the dielectric layer, and an insulator base covering the conductor layer, wherein the dielectric layer is made of Ti. _1-x M
_x is a ceramic having a relative density of 90% or more having a composition of O ₂ (where M is at least one element selected from Ta, Nb and Sb), and x is 1 × 10 ⁻⁵ to 2 × 10 ^−4.
An electrostatic chuck base characterized in that: 2. TiO ₂ and M ₂ O ₅ (where M is T
a, Nb, and Sb) and TiO ₂ : M ₂ O ₅ = 1−x: x / 2 (x = 1 ×
After mixing at a molar ratio of 10 ^{−5 to} 2 × 10 ⁻⁴ ) and molding,
2. The method of manufacturing an electrostatic chuck base according to claim 1, wherein the ceramics fired in the air at a temperature of 00 to 1600 [deg.] C. is used as a dielectric. 3. An electrostatic chuck comprising a dielectric layer, a conductor layer provided on one main surface of the dielectric layer, and an insulator base covering the conductor layer, wherein the dielectric layer is Ti _{1 -x} M _x
O ₂ (where M is at least one selected from W and Mo)
A ceramic having a relative density of not less than 90% and a composition of x is in the range of 5 × 10 ⁻⁶ to 1 × 10 ⁻⁴ . 4. TiO ₂ and MO ₃ (where M is W, M
at least one element selected from the group consisting of TiO.
₂ : MO ₃ = 1−x: x (x = 5 × 10 ⁻⁶ to 1 × 1)
It was mixed at 0 ^-4) molar ratio, after molding, 1200-1600
4. The method of manufacturing an electrostatic chuck base according to claim 3, wherein the ceramic fired in the air at a temperature of ° C. is a dielectric. 5. The electrostatic chuck base according to claim 1, wherein the conductor layer provided on one main surface of the dielectric layer and the insulator base are joined by a bonding agent. .