JP2000216232A - Electrostatic chuck and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck made of aluminum nitride which is superior in homogeneity of electrostatic chucking force. SOLUTION: This electrostatic chuck comprises a first substrate 2 composed of an aluminum nitride sintered body, where an electrode layer 3 is formed, a second substrate 4 composed of an aluminum nitride sintered body jointed on the formed plane of the electrode layer of the first substrate 2, and a jointing layer 5 containing yttrium aluminate, which is arranged through between the first substrate 2 and the second substrate 4. In this case, at least two kinds from among the three kinds of aluminum oxide, yttrium oxide, and yttrium aluminate are made to be arranged between the first substrate 2 and the second substrate 4, or more than 0.1 g/cm2 jointing material composed of yttrium aluminate is to be interposed and arranged between the first and the second substrates. Then, the jointing material is caused to melt through heat treatment, while impressing the first substrate 2 and the second substrate 4 at 15 g/cm2 or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck used for various semiconductor manufacturing apparatuses, etching apparatuses, and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in semiconductor manufacturing, silicon wafers have been increased in diameter and fine lines. Along with this, conventional local fixing of a clamp ring or the like as a method of fixing a wafer has low uniformity of the wafer, resulting in uneven film thickness and etching rate. On the contrary,
In the fixing using the electrostatic chuck, the entire surface of the wafer can be fixed, so that the uniformity of the wafer can be greatly improved.

Further, the use of aluminum nitride having a high thermal conductivity as an electrostatic chuck can further improve the uniformity of a wafer. Therefore, an attempt has been made to use aluminum nitride as an electrostatic chuck.

Conventionally, an electrostatic chuck using aluminum nitride has a method of (1) printing an electrode on an aluminum nitride green sheet produced by a doctor blade method or the like, laminating and pressing, and then firing (2). Hot-press sintering with powder on the molded body on which the electrodes are formed, or
Alternatively, it is manufactured by a method in which a compact having an electrode formed thereon and a solid compact are pressed and sintered under pressure.

[0005]

However, the aluminum nitride electrostatic chuck manufactured by the above method has the following problems.

The method of forming an electrode on the aluminum nitride sheet produced by the doctor blade method or the like of the above (1), laminating and pressing, and then firing, the warpage occurs due to the difference in sintering shrinkage between the electrode and the aluminum nitride sheet. However, the flatness of the wafer suction surface cannot be obtained. Further, even if the flatness of the wafer suction surface is improved by processing, a thick portion and a thin portion are formed in the insulating layer, and the electrostatic attraction force becomes non-uniform.

[0007] The method of (2) hot pressing and sintering the compact on which the electrode is formed and applying the powder, or pressing the compact with the electrode and the solid compact and performing pressure sintering is as follows.
Since the electrodes are warped inside the sintered body and the electrostatic attraction force becomes non-uniform as in the technique (1), the uniformity of the wafer is reduced.

The present invention has been made in view of the above circumstances, and has as its object to provide an aluminum nitride electrostatic chuck having excellent uniformity of electrostatic chucking force and a method of manufacturing the same.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an aluminum nitride sintered body having electrodes formed thereon and an aluminum nitride sintered body
By using a structure in which a bonding layer containing yttrium aluminate is interposed, an insulating layer having a uniform thickness can be obtained, and it has been found that a uniform electrostatic attraction force can be obtained. And, between the aluminum nitride sintered body and the aluminum nitride sintered body on which the electrodes are formed, aluminum oxide, at least two kinds of yttrium oxide and yttrium aluminate, or a bonding material made of yttrium aluminate is interposed, By performing a heat treatment while applying a load under a predetermined pressure and melting the bonding material, the above-described structure is obtained, whereby the insulating layer can be formed to a uniform thickness, and the uniformity of the electrostatic attraction force can be realistically achieved. It has been found that it is possible to manufacture an aluminum nitride electrostatic chuck having excellent resistance.

[0010] The present invention has been made based on such findings, and a first substrate made of an aluminum nitride sintered body having an electrode layer formed thereon, and an electrode layer forming surface of the first substrate. A second substrate made of an aluminum nitride sintered body joined to the first substrate and a joining layer containing yttrium aluminate interposed on the entire surface between the first substrate and the second substrate. To provide an electrostatic chuck.

Further, according to the present invention, an aluminum oxide, a yttrium oxide and an yttrium oxide are provided between a first substrate made of an aluminum nitride sintered body having an electrode layer formed thereon and a second substrate made of an aluminum nitride sintered body. At least two kinds of aluminates or a bonding material made of yttrium aluminate is interposed at 0.1 g / cm ² or more, and the first substrate and the second substrate are coated with 15 g / cm ^2.
As described above, there is provided a method for manufacturing an electrostatic chuck, wherein the first substrate and the second substrate are joined to form an electrostatic chuck by performing a heat treatment while applying pressure to melt the joining material. .

In the above-described electrostatic chuck or the method of manufacturing an electrostatic chuck according to the present invention, the bonding layer or the bonding material may be 25 to 80 mol% in terms of aluminum oxide and 20 to 75 mol% in terms of yttrium oxide. preferable.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. 1 and 2 are cross-sectional views showing an electrostatic chuck according to an embodiment of the present invention. FIG. 1 shows a monopolar type, and FIG. 2 shows a bipolar type.

The single-electrode type electrostatic chuck 1 shown in FIG. 1 has a suction surface 2a of a semiconductor wafer W and is made of an aluminum nitride sintered body having an electrode layer 3 formed on a surface opposite to the suction surface 2a. A first substrate 2 is provided, and a second substrate 4 made of an aluminum nitride sintered body is bonded to an electrode forming surface of the first substrate 2 by a bonding layer 5. The bonding layer 5 is interposed on the entire surface between the second substrate 4 and the second substrate 4. A DC power supply 6 is connected to the electrode 3, and when power is supplied to the electrode 3 from the DC power supply 6, the semiconductor wafer W, which is an object to be sucked, which is placed on the suction surface 2 a of the first substrate 2. Is electrostatically attracted.

The bipolar electrostatic chuck 1 'shown in FIG. 2 similarly has a suction surface 2a of the semiconductor wafer W and an electrode layer 3 having a pair of electrode portions 3a and 3b on a surface opposite to the suction surface 2a. '
A first substrate 2 made of an aluminum nitride sintered body on which an aluminum nitride sintered body is formed. Similarly, a second substrate 4 made of an aluminum nitride sintered body is provided on the electrode forming surface of the first substrate 2 with a bonding layer 5. Are joined by Electrode part 3 of electrode layer 3 '
a, 3b are connected to a power source 6 ', and the power source 6' supplies electric charges of opposite polarities to these electrodes, respectively.
Semiconductor wafer W placed on suction surface 2a of substrate 2
Is electrostatically attracted.

The bonding layer 5 contains yttrium aluminate, and its composition is 2 in terms of aluminum oxide.
5 to 80 mol%, 20 to 75 in terms of yttrium oxide
mol% is preferred. By using such a material for the bonding layer 5, an insulating layer having a uniform thickness is formed, and an electrostatic chuck having excellent uniformity of electrostatic chucking force can be obtained. This is because the flatness of the substrate 1 is not reduced by joining the sintered bodies, and as a result, the thickness unevenness of the insulating layer can be suppressed to be low.

The bonding layer 5 can be formed by melting a bonding material composed of at least two of aluminum oxide, yttrium oxide and yttrium aluminate, or yttrium aluminate. That is, as the bonding material, (1) a mixture of aluminum oxide and yttrium oxide, (2) a mixture of aluminum oxide and yttrium aluminate, (3) a mixture of yttrium oxide and yttrium aluminate, (4) aluminum oxide, yttrium oxide A mixture of yttrium aluminate and (5) yttrium aluminate alone can be used.

At this time, the amount of the bonding material is 0.1 g /
cm ² or more, and heat treatment is performed while applying a load (pressurization) at 15 g / cm ² or more to melt the bonding material. This makes it possible to manufacture an aluminum nitride electrostatic chuck having excellent uniformity of electrostatic chucking force.

The reason why the amount of the joining material is set to 0.1 g or more is as follows.
If the amount is less than 0.1 g, the bonding material diffuses into the aluminum nitride sintered body, the bonding material is insufficient at the bonding interface, and an unbonded portion is generated, so that heat conduction is hindered and the uniformity of the wafer is reduced. is there.

The weight (pressure) during the heat treatment is 15 g /
The reason for setting to cm ² or more is that if it is less than 15 g / cm ² , a portion where the bonding material does not spread over the bonding interface may be generated, an unbonded portion may be generated, and the heat uniformity of the wafer may be reduced.

Such a bonding material partially diffuses into the grain boundaries of the aluminum nitride sintered body by melting, and functions effectively as a bonding layer by being integrated with the aluminum nitride sintered body. The composition of the bonding material is preferably 25 to 80 mol% in terms of aluminum oxide, and 20 to 75 mol% in terms of yttrium oxide. Thereby, the heat treatment temperature can be reduced to 2000 ° C. or less.
Further, it is more preferable to set the heat treatment temperature to 1900 ° C. or lower by setting the aluminum oxide equivalent to 40 to 60 mol% and the yttrium oxide equivalent to 40 to 60 mol%.

The method of inserting the bonding material between the first and second substrates 2 and 4 made of an aluminum nitride sintered body is not particularly limited, but a method of applying a bonding material paste by a printing method or A method of inserting a bonding material green sheet produced by a doctor blade method is preferable.

The materials constituting the electrode layers 3 and 3 'include:
A high melting point metal such as W or Mo is desirable. The electrode may be formed by printing the metal paste or by using a foil. In particular, when a metal paste is used, not only is it easy to form a complicated electrode pattern, but also the molten bonding material causes the metal to be sintered. It is desirable to form an electrode by a printing method because it contributes to sintering.

In the electrostatic chuck configured as described above, when the power is supplied to the electrode layer 3 or 3 ′ from the power supply 6 or 6 ′, the semiconductor wafer W is moved by the electrostatic attraction force to the suction surface 2 a of the insulating layer substrate 2. Is adsorbed. At this time, the first
By using aluminum nitride having high thermal conductivity as the second substrates 2 and 4, the uniformity of the wafer can be improved, and these are joined by the joining layer 5 containing yttrium aluminate, so that the uniform thickness is achieved. It is possible to obtain an electrostatic chuck having excellent uniformity of electrostatic attraction force.

In this case, a bonding material composed of at least two of aluminum oxide, yttrium oxide and yttrium aluminate is weighted (pressurized) under the above conditions.
If the bonding layer 5 is formed by performing the heat treatment while melting the bonding material, the warpage of the substrate and the variation in the thickness of the bonding layer 5 do not occur.
The substrate 2 can be flattened, and an electrostatic chuck having excellent uniformity of electrostatic attraction force can be manufactured in reality.

The manufacturing method according to the present invention is applicable not only to the manufacture of an electrostatic chuck but also to the manufacture of a ceramic heater and a susceptor.

[0027]

The present invention will be described below in detail with reference to examples. A single-pole W electrode was printed on one side of an aluminum nitride substrate (φ200 × 10 tmm, flatness: 0.010 to 0.020 mm) by a screen printing method. After printing the electrodes, a bonding material green sheet produced by a doctor blade method was placed thereon, and further, an aluminum nitride substrate having electrode holes processed thereon was placed thereon. Table 1 shows the composition and amount of the bonding material green sheet. Further, after the weights shown in Table 1 were applied by a W plate, degreased.
50 ° C., 1850 ° C. in Examples 3 to 5 and Comparative Examples 1 and 2.
Heat treatment was performed for 10 minutes. The adsorption surface of the obtained joined body was ground to produce an electrostatic chuck having an insulating layer thickness of 0.1 mm.

In Comparative Example 3, a single-pole W electrode was printed on a 0.3 tmm aluminum nitride green sheet produced by a doctor blade method, and a 1.5 tmm aluminum nitride green sheet was laminated thereon and pressed. It was degreased and baked at 1850 ° C. The adsorption surface of the obtained sintered body was ground to produce an electrostatic chuck having an insulating layer thickness of 0.1 mm.

In Comparative Example 4, the aluminum nitride compact having a diameter of 200 × 15 tmm and manufactured by CIP molding was treated with 0.1 μm.
After sandwiching 050tmm W foil and hot press sintering,
Grinding was performed to a depth of 0.1 mm from the position where the W foil was embedded, but the W foil was exposed due to deformation of the W foil during hot press sintering, and an electrostatic chuck was not obtained.

[0030]

[Table 1]

Next, an electrostatic chuck test of the obtained electrostatic chuck and an etching test of polysilicon were performed.
In the electrostatic chucking force test, a silicon wafer of φ30 mm is sucked (applied voltage 1 kV) at each position (center, four diagonals of φ90 mm and φ180 mm) of the electrostatic chuck suction surface shown in FIG. The force at the time of pulling and detaching was measured.

In the etching test, a silicon wafer having a polysilicon film formed thereon is attracted to an electrostatic chuck, and SF ₆ −
The polysilicon film was etched by plasma using a Cl ₂ mixed gas, and the etching depth at each position on the electrostatic chuck suction surface shown in FIG. 3 was measured. The thickness unevenness of the nine insulating layers is defined as the difference between the maximum value and the minimum value of the thickness, and the measured values of the electrostatic attraction force and the etching test are determined for uniformity using the following equation (1). The results were evaluated. The average value and the deviation at that time are shown in equations (2) and (3).

[0033]

(Equation 1)

Table 2 shows the thickness unevenness of the insulating layer, the electrostatic attraction force, and the results of the etching test. As a result, Examples 1 to 5
In this case, the thickness unevenness of the insulating layer was small, and the uniformity of the electrostatic attraction force and the uniformity of the etching were high values. In contrast, in Comparative Examples 1 and 2, the uniformity of the electrostatic attraction force was high, but the uniformity of the etching was a low value. This is considered to be because in Comparative Examples 1 and 2, an unbonded portion was present in the electrostatic chuck, where heat transfer was hindered, so that the uniformity of the wafer was reduced and the uniformity of the etching depth was reduced. Can be In Comparative Example 3, the thickness of the insulating layer was large, the uniformity of the electrostatic chucking force was reduced, and the contact between the wafer and the electrostatic chuck was uneven, and the uniformity of the etching depth was reduced.

[0035]

[Table 2]

[0036]

According to the present invention, between the aluminum nitride sintered body on which the electrode is formed and the aluminum nitride sintered body,
Since the electrostatic chuck has a structure in which a bonding layer containing yttrium aluminate is interposed, an insulating layer having a uniform thickness can be provided, and a uniform electrostatic attraction force can be obtained. Then, a bonding material composed of at least two or more of aluminum oxide, yttrium oxide and yttrium aluminate, or yttrium aluminate is interposed between the aluminum nitride sintered body having the electrodes formed thereon and the aluminum nitride sintered body. By performing a heat treatment while applying a load under a predetermined pressure and melting the bonding material, an electrostatic chuck having the above structure can be obtained. It is possible to manufacture an aluminum chuck made of aluminum nitride having excellent uniformity of the attraction force.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a monopolar electrostatic chuck to which the present invention is applied.

FIG. 2 is a cross-sectional view showing a bipolar electrostatic chuck to which the present invention is applied.

FIG. 3 is a diagram showing measurement positions of an electrostatic attraction force and an etching rate of a semiconductor wafer in an example of the present invention.

[Explanation of symbols]

 1, 1 '... electrostatic chuck 2 ... first substrate 2a ... adsorption surface 3, 3' ... electrode layer 3a, 3b ... electrode portion 4 ... second substrate 5 ... bonding layer 6, 6 '... Power supply

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Chiharu Wada 1-5-9 Nozomi Morigashi, Togane-shi, Chiba

Claims (4)

[Claims] 1. A first substrate made of an aluminum nitride sintered body having an electrode layer formed thereon, and a second substrate made of an aluminum nitride sintered body joined to an electrode layer forming surface of the first substrate. And a bonding layer including yttrium aluminate, which is interposed on the entire surface between the first substrate and the second substrate. 2. The bonding layer has an aluminum oxide equivalent of 25.
~ 80mol%, 20 ~ 75m in terms of yttrium oxide
2. The electrostatic chuck according to claim 1, wherein the electrostatic chuck comprises ol%. 3. An aluminum oxide, yttrium oxide and yttrium aluminate between a first substrate made of an aluminum nitride sintered body having an electrode layer formed thereon and a second substrate made of an aluminum nitride sintered body. at least two, or a bonding material consisting of yttrium aluminate was 0.1 g / cm ² or more interposed bonding the first substrate and the second substrate by heat treatment under pressure at 15 g / cm ² or more materials A method for manufacturing an electrostatic chuck, wherein the first substrate and the second substrate are joined to form an electrostatic chuck by melting the first and second substrates. 4. The bonding material is 2 in terms of aluminum oxide.
5 to 80 mol%, 20 to 75 in terms of yttrium oxide
The method for manufacturing an electrostatic chuck according to claim 3, comprising mol%.