JP2000306986A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrostatic chuck that can increase the plasma- resistance property of an electrostatic chuck base, without damaging attraction force by the Johnson-Rahbek effect, can suppress generation of impurity elements that become the contamination source for a body to be attracted and generation leakage current accompanying reduction of resistivity, and can be used over a wide temperature range. SOLUTION: A plasma-resistant protection film 2, consisting of a low-impurity dielectric, is provided onto the surface of an electrostatic chuck base 3 made of one of ceramics, silicone resin, and polyimide. Furthermore, more specifically, on the surface of a ceramics sintering body 3 having resistivity of 1010-1015 Ωcm, an aluminum nitride film 2 formed by the gaseous phase synthesis method is provided. Also, the aluminum nitride film 2 preferably contains titanium with a ratio of 10 atom.% or less with respect to aluminum element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck for holding a wafer substrate such as a silicon wafer by using electrostatic force in a semiconductor manufacturing process or the like.

[0002]

2. Description of the Related Art An electrostatic chuck is a dielectric chuck as shown in FIG.
Structure with one pole on the body and opposite pole on the body to be adsorbed
Only the positive electrode is formed in a dielectric as shown in FIG.
A monopolar structure in which the plasma potential is negative, or as shown in FIG.
Bipolar formed by paralleling positive and negative poles in such a dielectric
Those having a mold structure are typical. Also, its dielectric
Polymers and ceramics are roughly classified according to the material used.
In the Lamix series, aluminum nitride sintered as a dielectric
The one that uses body or alumina has large electrostatic attraction,
Also, it has excellent plasma resistance. In particular, aluminum nitride
Sintered body has excellent thermal conductivity, and the wafer to be adsorbed
There is an advantage that the temperature distribution in the substrate can be made uniform. This
Here, the chucking force of the electrostatic chuck is a voltage as shown in FIG.
By applying voltage, a dielectric material is placed between the electrode and the electrode.
And the coulomb force that works when the capacitor is formed
A minute current flows through a minute gap at the interface between the adherend and the dielectric,
Synthesis with Johnson-Rahbek force induced by electric polarization
It is known to appear as force,
As shown in FIG. 5, the resistivity increases as the resistivity of the dielectric decreases.
You. Therefore, it is difficult to use high
Resistance ceramics (resistivity 10¹⁵Ωcm or more)
Coulomb force is dominant and the adsorption force is small. The resistivity is 1
0^TenΩcm-10¹⁵Ωcm for ceramics
Very large due to the addition of suction force due to
Demonstrate the best adsorption power. However, if the resistivity is 10 ^TenΩcm
If it falls below, the gap between the electrostatic chuck and the wafer that is
Circuit current increases and circuit elements formed on the wafer break.
There is a risk of being destroyed.

In ceramics having a relatively low resistivity, a sintering aid is added in order to lower the melting point and produce a dense ceramic, and this aid is adsorbed on a silicon wafer or the like. May be a source of contamination for the body. Specifically, it is pointed out that impurity elements such as Ba and Ca in the sintering aid are easily sputtered by plasma, and such impurity elements contaminate a silicon wafer or the like. In addition, many ceramic materials decrease in resistivity at high temperatures, and the resistivity decreases at high temperatures, increasing the above-described leakage current, and is not suitable for use at high temperatures regardless of the heat resistance of the electrostatic chuck itself. There is a problem.

The present invention has been made in view of the above-mentioned problems, and has as its object to solve the above-mentioned problems and to reduce the resistance of the electrostatic chuck base material without impairing the suction force due to the Johnson-Rahbek force. An object of the present invention is to provide an electrostatic chuck that can enhance plasma properties, suppress generation of an impurity element that becomes a contamination source for an object to be adsorbed, and generation of a leak current due to a decrease in resistivity, and can be used in a wide temperature range. .

[0004]

A first feature of the electrostatic chuck according to the present invention for achieving the above object is as described in claim 1 of the claims. In addition, a plasma-resistant protective film made of a low-impurity dielectric is provided on the surface of an electrostatic chuck base made of any one of polyimide and polyimide.

[0005] The second characteristic configuration is that the resistivity is 10 ¹⁰ Ωcm to ¹ Ωcm, as described in claim 2 of the claims.
The point is that an aluminum nitride film formed by a vapor phase synthesis method is provided on the surface of the ceramic sintered body of 0 ¹⁵ Ωcm. Here, as the vapor phase synthesis method, for example, thermal CVD
Method, MOCVD method (organic metal CVD method), plasma CV
D method, plasma MOCVD method, laser CVD method, laser MOCVD method and the like.

[0006] The third feature is that, in addition to the second feature, the aluminum nitride film is not more than 10 atomic% with respect to aluminum element, in addition to the second feature. In that it contains titanium in the proportion of

The operation and effect will be described below. ADVANTAGE OF THE INVENTION According to the 1st characteristic structure of the electrostatic chuck which concerns on this invention, the plasma resistance of the conventional electrostatic chuck base material surface with low plasma resistance can be improved, As a result, the semiconductor exposed to plasma This can be used as a wafer chuck in the manufacturing process, and the problem that impurities such as Ca and Ba contained in the base material of the electrostatic chuck are sputtered and mixed into the wafer is eliminated. Also, the service life of the electrostatic chuck is improved.

According to the second feature, the aluminum nitride film formed on the surface has excellent plasma resistance, so that the etching rate when exposed to oxygen plasma or fluorine plasma is low, and the ceramic base The generation of contaminant elements from the material can be prevented. Furthermore, by using the gas phase synthesis method, the raw material purity is high, and
Since the contamination of impurities is greatly suppressed, the aluminum nitride film can be formed with extremely high purity. As a result, the aluminum nitride film itself formed on the surface itself is a source of impurities such as Ba and Ca which is a polluting source for the substance to be adsorbed. It does not contain any elements. Further, the aluminum nitride film formed by the vapor phase synthesis method has a resistivity of about 2 × 10 ¹³ Ωcm, and as shown in FIG. Since a film having a film thickness can be formed, a decrease in the attraction force is also suppressed.

[0009] According to the third characteristic configuration, by adding titanium to the aluminum nitride film, the resistivity of the aluminum nitride film falls below 2 × 10 ¹³ Ωcm, and the attraction force due to the Johnson-Rahbek force increases. In addition, it is possible to further suppress a decrease in the attraction force due to the aluminum nitride film.
Further, when the content of titanium is 10 atomic% or less with respect to the aluminum element, there is no possibility that the resistivity is significantly lower than 10 ¹⁰ Ωcm from the experimental results shown in FIG.
It is possible to prevent the resistance from being lowered to such an extent that a circuit breakage or the like is induced in the object to be attracted by the leak current.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrostatic chuck according to the present invention is manufactured by forming an aluminum nitride film on the surface of a ceramic electrostatic chuck substrate by using a laser MOCVD method which is a kind of a vapor phase synthesis method. For one embodiment,
This will be described with reference to the drawings.

As shown in FIG. 1, the conventional electrostatic chuck 1a has an electrode layer 4 formed on an alumina substrate 5 and a ceramic sintered body 3 formed thereon. Aluminum nitride film 2 on the surface of the electrostatic chuck base material, that is, the surface of the ceramic sintered body 3
Is formed. The formation of the aluminum nitride film 2 includes:
This is performed by using a laser MOCVD method which is a kind of a gas phase synthesis method.

The ceramic sintered body 3 includes Ca, Z
It contains contaminants such as n and Ba that contaminate a silicon wafer or the like as an object to be adsorbed. Therefore, the electrostatic chuck 1
Is used without coating the aluminum nitride film 2, that is, when used as a conventional ceramic-based electrostatic chuck 1a, the ceramic sintered body 3 is sputtered from the surface in a plasma atmosphere, and the contaminant element is removed. There is a possibility that it may be mixed into the wafer which is the object to be attracted. This can be seen from the comparison table of etching rates by oxygen plasma shown in Table 1 because the etching rate of the ceramic sintered body 3 is higher than that of a high-purity Al ₂ O ₃ sintered body or the like.

[0013]

[Table 1]

Next, a method of forming the aluminum nitride film 2 will be described. As shown in FIG. 2, a general laser MOCVD apparatus 6 is used, and an electrostatic chuck 1a before an aluminum nitride film is formed is placed on a support 8 having a built-in heater in a reaction vessel 7. The raw material Al (CH
₃ ) ₃ , NH ₃ is supplied into the reaction vessel 7 through the source gas introduction path 9. Al (CH ₃ ) ₃ flow rate 1cc
m, a pipe temperature of 40 ° C., and a nitrogen source NH ₃ at a flow rate of 2 to 50 sccm. The film forming operation pressure in the reaction vessel 7 is 3 Torr, and ArF excimer laser light (wavelength 193 nm, output 100 Hz,
00mJ). In addition, Al (CH
_{3) 3} instead of AlCl _3, N ₂ in place of NH ₃ as a nitrogen source may be a hydrazine.

Another embodiment for lowering the resistance by incorporating titanium into the aluminum nitride film 2 will be described.
In order to add titanium, in the CVD process, Ti [N (CH ₃ ) _{3 is used} together with Al (CH ₃ ) ₃ as a raw material.
₂ ] Supply ₄ etc. In this case, Ti [N (CH ₃ )
₂ ] ₄ is a flow rate of 1 to 100 using nitrogen gas as a carrier gas.
Ccm at a pipe temperature of 25 ° C. Other conditions are the same as in the case where titanium is not contained. In this embodiment, as the aluminum nitride film 2, an AlN—TiN film containing 2.4 atomic% of titanium with respect to the aluminum element was formed.

The etching rates of the two kinds of aluminum nitride films 2 by oxygen plasma were measured. The measurement results are shown in Table 1 above in comparison with those of various sintered bodies.
From Table 1, it can be seen that the two types of aluminum nitride films 2 function as plasma-resistant protective films on the ceramic sintered body 3, that is, the surface of the electrostatic chuck base of the conventional ceramic electrostatic chuck 1a. I understand.

Further, the two kinds of aluminum nitride films 2
The temperature characteristics of the resistivity were measured. As shown in FIG. 3, the measurement result shows that the characteristics are sufficiently flat in a temperature range up to 400 ° C., and that a high-quality aluminum nitride film whose resistivity does not decrease even at a high temperature is formed. As a result,
Even if the resistivity of the ceramic sintered body 3 is lowered at a high temperature, the ceramics sintered body 3 is insulated by the aluminum nitride film 2, so that the generation of a leak current is suppressed.

An experiment was also conducted on the relationship between the titanium content and the resistivity of the aluminum nitride film, and the results are shown in FIG. From FIG. 4, it has been found that the content of titanium is desirably about 10 atomic% or less with respect to the aluminum element in order to secure a resistivity of 10 ¹⁰ Ωcm or more. Also, the resistivity of the aluminum nitride film 2 not containing titanium is about 2 × 10 ¹³ Ωcm, and the resistivity is 10 ¹⁰ to 2 × 1 by containing titanium.
Since it can be controlled within the range of 0 ¹³ Ωcm, the chucking force of the electrostatic chuck 1 in which the surface of the ceramic sintered body 3 is coated with the aluminum nitride film 2 is independent of the resistivity of the ceramic sintered body 3. The ceramic sintered body 3
Can be made equal to or more than the adsorption force of Note that the chucking force of the electrostatic chuck 1 in which the surface of the ceramic sintered body 3 is coated with the aluminum nitride film 2 not containing titanium shows a good chucking force even after being treated with oxygen plasma for 8 hours. It was confirmed that.

Hereinafter, another embodiment will be described. <1> In the above embodiment, the ceramic-based electrostatic chuck in which the electrostatic chuck base material whose surface is coated with the aluminum nitride film 2 is a ceramic sintered body is intended.
The same effect as in the above embodiment can be expected for a polymer electrostatic chuck whose electrostatic chuck base is a polymer material such as silicone resin or polyimide.

<2> In the above embodiment, the laser MOCVD method is used for forming the aluminum nitride film 2, but another gas phase synthesis method may be used. Further, in addition to titanium, a 3d transition metal such as Cr or a noble metal such as Pt, Au, or Ag may be contained in the aluminum nitride film in order to reduce the resistance.

<3> The structure and material of the electrostatic chuck 1 are not limited to the above embodiment. For example, in FIG. 1, the electrostatic chuck 1 has a bipolar structure, but may have a monopolar structure.

[0022]

According to the present invention, by using an aluminum nitride film formed by a vapor phase synthesis method as a plasma-resistant protective film, it has excellent plasma resistance, has a large adsorption force by the action of Johnson-Rahbek force, and has an adsorption-desorption response. An electrostatic chuck which was excellent in retentivity, did not decrease in resistivity even at high temperatures, and exhibited a large attraction force over a wide temperature range was obtained. In addition, an electrostatic chuck having plasma resistance comparable to that of a high-purity aluminum nitride sintered body can be manufactured at a low cost. This solves the problem that impurities such as Ca and Ba contained in the chuck base material are sputtered and mixed into the wafer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one structure of an electrostatic chuck according to the present invention.

FIG. 2 is a schematic configuration diagram of a laser MOCVD apparatus used for manufacturing the electrostatic chuck according to the present invention.

FIG. 3 is a characteristic diagram showing temperature characteristics of resistivity of an aluminum nitride film of the electrostatic chuck according to the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the resistivity of the aluminum nitride film and the titanium content of the electrostatic chuck according to the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a resistivity of a dielectric and an attraction force.

FIG. 6 is a cross-sectional view illustrating a basic structure of a conventional electrostatic chuck.

FIG. 7 is a cross-sectional view illustrating a monopolar structure of a conventional electrostatic chuck.

FIG. 8 is a cross-sectional view illustrating a bipolar structure of a conventional electrostatic chuck.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrostatic chuck 2 aluminum nitride film (anti-plasma protective film) 3 ceramic sintered body (electrostatic chuck base material) 4 electrode layer 5 alumina substrate 6 laser MOCVD device 7 reaction vessel 8 support base 9 source gas introduction path

Continued on the front page (72) Inventor Kayu Kayu 2-9-1-2 Ikuta, Tama-ku, Kawasaki-shi, Kanagawa Japan Engineering Co., Ltd. (72) Inventor Shigeru Morikawa 17 Kyoto-shi, Shimoda-ku, Kyoto, Kyoto Kyoto research Park Science Center Building Co., Ltd.Kansai New Technology Research Institute (72) Inventor Takamitsu Fujii 17 Kyoto Research Park Science Center Building Co., Ltd.Kansai New Technology Research Co., Ltd. (72) Inventor Atsuko Kajimura 17 Kyoto University Research Park Science Center Building, Shimogyo-ku, Kyoto Shimogyo-ku Kyoto Research Park Science and Technology Research Institute Kansai New Technology Research Institute F-term (reference) 5F004 BB22 BB29 BB30 5F031 CA02 HA02 HA10 HA16 MA28 MA32

Claims (3)

[Claims] 1. An electrostatic chuck base made of any one of ceramics, silicone resin and polyimide,
An electrostatic chuck having a plasma-resistant protective film made of a low-impurity dielectric. 2. An electrostatic chuck comprising a ceramic sintered body having a resistivity of 10 ¹⁰ Ωcm to ^{10 15} Ωcm and an aluminum nitride film formed by a vapor phase synthesis method on a surface of the ceramic sintered body. 3. The electrostatic chuck according to claim 2, wherein said aluminum nitride film contains titanium in a ratio of 10 atomic% or less with respect to aluminum element.