JP5268476B2 - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck that never varies in leak amount of cooling gas even when a large-sized body to be sucked is repeatedly attached and detached to maintain uniform controllability for a temperature distribution of a suction surface by the cooling gas, and then enhances uniformity, reproducibility, and yield of processing such as etching processing on the body to be sucked and so on. <P>SOLUTION: The electrostatic chuck 10 includes an insulating plate 11 having the suction surface 13 for sucking and fixing the body to be sucked, and an electrostatic electrode 12 provided in the insulating plate 11, wherein the insulating plate 11 is formed of ceramic having a Young's modulus of 100 to 200 GPa and surface roughness (Ra) of the suction surface 13 is 1 to 2 &mu;m. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrostatic chuck used for attracting and fixing a semiconductor wafer in a semiconductor manufacturing apparatus such as a plasma etching apparatus for etching a semiconductor wafer.

  Conventionally, in a plasma etching apparatus for etching a semiconductor wafer, an electrostatic chuck is used to attract and fix the semiconductor wafer.

  In this electrostatic chuck, an electrostatic electrode is embedded in an insulating plate, and the semiconductor wafer is attracted and fixed on the stage by an electrostatic force acting between the electrostatic electrode and the semiconductor wafer. Compared with a mechanical chuck, the back surface of a semiconductor wafer can be adhered almost entirely on the stage, and it is often used because it has excellent cooling performance of the semiconductor wafer.

  In this electrostatic chuck, in order to further improve the cooling performance of the semiconductor wafer and make the temperature distribution on the surface of the semiconductor wafer uniform, a cooling gas such as He having good thermal conductivity is applied to the back surface of the semiconductor wafer. It has been introduced. This is because when the temperature distribution is generated on the surface of the semiconductor wafer, the etching properties such as the etching shape and the etching rate vary.

  The cooling gas is introduced into the back surface of the semiconductor wafer by discharging the cooling gas from a gas supply hole provided through the insulating plate to, for example, a ring-shaped groove provided on the surface of the insulating plate serving as the suction surface of the semiconductor wafer. Is done by doing. Most of the introduced cooling gas is discharged from a gas discharge hole provided through the insulating plate, and a part is discharged as a leak gas from between the adsorption surface and the semiconductor wafer. (For example, refer to Patent Document 1).

However, in the conventional electrostatic chuck, the property of the attracting surface (especially, the surface roughness) is deteriorated due to wear or the like during repeated mounting and dismounting of the semiconductor wafer even if the temperature distribution is controlled in the initial stage. As a result, the amount of cooling gas leaking from between the semiconductor wafer and the suction surface changes, and the controllability of the temperature distribution on the suction surface by the cooling gas changes. There was a problem. When the controllability of the temperature distribution changes, the etching property changes as described above. Recently, the diameters of semiconductor wafers have become larger and larger, such as 12 inches and 18 inches. However, the larger the diameter, the larger the change in the amount of leakage of the cooling gas, and the temperature distribution on the adsorption surface. There was a tendency for the degree of change in controllability to increase.
JP-A-1-251735

  As described above, in the conventional electrostatic chuck, when the object to be adsorbed is repeatedly attached and detached, the adhesion between the object to be adsorbed and the adsorption surface of the electrostatic chuck changes, and as a result, the cooling gas leakage amount changes. Thus, there is a problem that the controllability of the temperature distribution on the adsorption surface by the cooling gas changes. As the diameter of the object to be adsorbed increases, the change in the leakage amount of the cooling gas and the degree of change in the controllability by the cooling gas of the temperature distribution on the adsorption surface tend to increase.

  The present invention has been made in response to the above-described problems of the prior art, and even for a large object to be adsorbed, the amount of cooling gas leakage does not change due to repeated attachment and detachment. Provided is an electrostatic chuck that can maintain uniform controllability of a temperature distribution with a cooling gas, thereby improving uniformity, reproducibility, and yield of processing such as etching processing on an object to be adsorbed. For the purpose.

(1) the electrostatic chuck of the present invention, have a suction surface for suction fixing the adsorbate, wherein a gas supply hole for supplying the cooling gas to the suction surface, adsorbing the adsorbate electrostatic comprising an insulating plate grooves that provided so as to form a flow path of the cooling gas, the electrostatic electrode provided inside the insulating plate between the該被adsorbate when A chuck,
The insulating plate is made of ceramic having a Young's modulus of 140 to 170 GPa , and the surface roughness (Ra) of the adsorption surface is 1.2 to 1.8 μm .
Here, the Young's modulus is a value measured at room temperature by the ultrasonic pulse method specified in JIS R 1602.

In the present invention, the insulating plate is made of ceramic with a Young's modulus of 140 to 170 GPa and the surface roughness (Ra) of the adsorption surface is 1.2 to 1.8 μm. However, the change in the surface roughness of the suction surface is small, and the change in the adhesion between the semiconductor wafer and the suction surface is small. Therefore, the change in the amount of leakage of the cooling gas can be reduced, and temperature control that is the same as in the initial stage is possible. Thereby, the uniformity of processing, such as an etching process with respect to a to-be-adsorbed object, reproducibility, a yield, etc. can be aimed at.

(2) In the electrostatic chuck of the present invention, the ceramic is mainly composed of yttria.

  The present invention exemplifies a constituent material of a preferable insulating plate. By mainly using yttria as the constituent material of the insulating plate, the change in the surface roughness of the suction surface after repeated attachment and detachment of the object to be adsorbed can be reduced, and more uniform temperature control is possible.

  According to the present invention, even for a large object to be adsorbed, the leakage amount of the cooling gas does not change by repeated attachment and detachment, and the controllability of the temperature distribution on the adsorption surface by the cooling gas is kept uniform. Accordingly, it is possible to provide an electrostatic chuck capable of improving the uniformity, reproducibility, and yield of processing such as etching processing on the object to be adsorbed.

  Embodiments according to the present invention will be described below. Although the description will be made based on the drawings, the drawings are provided for illustration only, and the present invention is not limited to the drawings. It should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Furthermore, in the following description, components having the same or substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a partially cutaway perspective view showing an electrostatic chuck device having an electrostatic chuck according to an embodiment of the present invention, and FIG. FIG. 2B is a cross-sectional view showing an enlarged main part thereof.

  As shown in FIG. 1, the electrostatic chuck 10 of this embodiment includes a disk-shaped insulating plate 11 having a constant thickness and an electrostatic electrode 12 embedded therein. The electrostatic chuck device 100 is configured by joining the back surface of the insulating plate 11 to the surface of a metal base plate 20 made of, for example, aluminum or an aluminum alloy.

The insulating plate 11 is composed of a sintered body having a laminated structure of ceramics having Young's modulus of 100 to 200 GPa, for example, yttria (Y ₂ O ₃ ) having Young's modulus of 170 GPa as a main component. The laminated structure sintered body is formed, for example, by laminating and compressing yttria green sheets mainly composed of yttria and firing them integrally. The shape of the insulating plate 11 is not particularly limited, but in the present embodiment, for example, it is a disc shape having a thickness of 2 mm and a diameter of 300 mm.

  Further, the surface of the insulating plate 11 is a suction surface (chuck surface) 13 that sucks and fixes an object (not shown) such as a semiconductor wafer. The suction surface 13 is finished to have a high flatness and a surface roughness (Ra) in the range of 1 to 2 μm by sandblasting or the like. In addition, the adsorption surface 13 communicates with a gas supply hole 15 provided through the insulating plate 11 and the base plate 20, so that when the adsorbed object is adsorbed, the cooling gas is exchanged with the adsorbed object. A groove 14 is provided to form a flow path. In the example of the drawing, the groove 14 includes a plurality of annular grooves 14a provided concentrically, and a plurality of radial grooves provided at intervals in the circumferential direction connecting the plurality of annular grooves 14a. It is comprised from the groove | channel 14b extended. A plurality of gas supply holes 15 are opened substantially uniformly in the annular groove 14a. Some of these gas supply holes 15 function as gas discharge holes.

  The electrostatic electrode 12 is for attracting an object to be attracted to the attracting surface 13 by electrostatic force, and in this embodiment, a voltage is applied to an electrode (not shown) arranged outside. Although a monopolar type that generates an electrostatic force is illustrated as an example, a bipolar type composed of a pair of electrodes may be used. For the electrostatic electrode 12, for example, a metallized paste containing a powder of a refractory metal such as tungsten, molybdenum or platinum as a main component is printed in a predetermined pattern on a ceramic green sheet, and the ceramic green sheet is laminated and bonded. Thereafter, it is formed by simultaneous firing.

  Although not shown, an electrode terminal for applying a voltage to the electrostatic electrode 12 is provided on the back surface of the insulating plate 11, and a pin terminal (not shown) is joined to the electrode terminal. Yes. The pin terminal is disposed in a through hole (not shown) provided through the base member 20 in the thickness direction, and a voltage is applied to the electrostatic electrode 12 by joining an external terminal to the pin terminal. . The pin terminal may be directly joined to the electrostatic electrode 12 by brazing or the like. In that case, a through hole is provided from the back surface of the insulator 11 toward the electrostatic electrode 12.

  For example, in the case of the insulating plate 11 made of a sintered body having a multilayer structure of ceramics whose main component is yttria, the electrostatic electrode 12 is embedded at a position separated from the attracting surface 13 by about 0.1 to 0.6 mm. .

  Furthermore, the base plate 20 is made of a metal such as aluminum or an aluminum alloy as described above, and has a larger diameter than the electrostatic chuck 10 so as to place the entire electrostatic chuck 10, for example, a thickness of 20.0 mm. It has a disc shape with a diameter of 350 mm. A flow path (not shown) for circulating cooling water is provided inside the base plate 20. The base plate 20 can be cooled by circulating cooling water through the flow path.

Next, an example of the manufacturing method of the electrostatic chuck 10 of this embodiment is demonstrated. Here, the insulating plate 11 is composed of a sintered body of a ceramic laminated structure mainly composed of yttria (Y ₂ O ₃ ) whose Young's modulus is 170 GPa, and platinum powder is used as the material of the electrostatic electrode 12. A case where the electrostatic chuck 10 is manufactured will be described.

(Production of yttria green sheet)
(1) Yttria powder: 97.9% by mass, dispersant: 2.0% by mass and calcia powder (CaO): 0.1% by mass in a mixed solvent of ethanol and toluene (weight ratio 1: 1) After wet mixing, a binder (butyral resin) is added and further mixed to obtain a fluid slurry.
(2) Next, from this slurry, a yttria green sheet having a thickness of 0.2 mm is obtained by a doctor blade method.

(Preparation of metallized paste)
(3) Further, platinum powder and yttria powder are weighed so as to have a volume ratio of 1: 1, mixed with a dispersant, a binder (ethylcellulose) and terpineol, and kneaded with three rolls to prepare a metallized paste.

(Production of laminates, etc.)
(4) After cutting the yttria green sheet into a size of 450 mm square and laminating four of the cut yttria green sheets under the conditions of 40 ° C. and 0.5 MPa, the metallized paste is used on the laminate. The pattern of the electrostatic electrode 12 is printed by a screen printing method. Further, ten cut yttria green sheets are stacked under the same conditions as described above, and a through hole for the cooling gas supply hole 15 is drilled at a predetermined position of the stacked body. Then, on the laminate (10 layers) provided with through holes, the laminate (4 layers) on which the pattern of the electrostatic electrode 12 is printed is laminated with the pattern printing surface facing the laminate (10 layers) side, Crimping is performed at 50 ° C. and 6 MPa.

  In addition, when forming a laminated body (10 layers), a through hole provided in a required yttria green sheet for an electrode terminal for applying a voltage to the electrostatic electrode 12 and a via to be connected to the electrode terminal Print the metallized paste inside. When a pin terminal is directly connected to the electrostatic electrode 12, a through hole for the pin terminal is formed toward the electrostatic electrode 12 after forming the laminated body (10 layers).

(Processing and firing of the laminate)
(5) The laminated body of yttria green sheets laminated and pressure-bonded as described above is processed into a disk having a diameter of 400 mm.
(6) Next, the processed laminate is degreased at 500 ° C. in the air, and then fired at 1550 ° C. in the air. Further, the warp is corrected at 1500 ° C. in the air, and the ceramic sintered body Get.

(Surface processing of ceramic sintered body and joining with base plate)
(7) The ceramic sintered body is subjected to parallel grinding and peripheral processing to a thickness of about 2 mm and a diameter of 300 mm, and then joined to the surface of the metal base plate 20 using, for example, a silicone-based adhesive, A pin terminal is brazed or soldered to the electrode terminal or the electrostatic electrode 12. The electrode terminal or electrostatic electrode 12 is pre-plated with nickel as necessary.
(8) Next, the surface of the ceramic sintered body is subjected to sand blasting to a surface roughness (Ra) of 1 to 2 μm, a predetermined resist pattern is formed, and the resist blasting portion is again subjected to sand blasting. The groove 14 is formed. Thereafter, by removing the resist, the electrostatic chuck device 100 including the electrostatic chuck 10 of the present embodiment having the suction surface 13 having a surface roughness (Ra) of 1 to 2 μm is completed.

The electrostatic chuck device 100 including the electrostatic chuck 10 of the present embodiment configured as described above is attached to a processing apparatus that performs various processes of semiconductor manufacturing, for example, and is used. That is, by applying a voltage to the electrostatic electrode 12, an electrostatic force is generated and an object to be adsorbed such as a semiconductor wafer is adsorbed and fixed to the adsorbing surface 13 to perform a desired process. At that time, for example, a cooling gas such as He or N ₂ is supplied from the gas supply hole 15 and discharged into the groove 14 to fill the space between the adsorption surface 13 and the object to be adsorbed. The temperature control is performed.

FIG. 2A shows a state in which the object to be adsorbed 17 is adsorbed on the adsorption surface 13, and is a cross-sectional view showing an enlarged part of the interface portion between the adsorption surface 13 and the object to be adsorbed 17. It is. FIG. 2 (b) is an enlarged view of the main part. As is clear from these FIGS. 2A and 2B, the cooling gas such as He or N ₂ is discharged from the gas supply hole 15 into the groove 14, and between the adsorption surface 13 and the object to be adsorbed 17. Part of the gas is filled and discharged as a leak gas from between the adsorption surface 13 and the object to be adsorbed 17 according to the degree of adhesion.

  In this way, a large number of objects to be adsorbed are successively adsorbed and desorbed from the adsorption surface 13, and a desired process is performed. If the amount of gas leaking from between the adsorption surface 13 and the object to be adsorbed 17 does not change even if the adsorption / removal of the object to be adsorbed is repeated in this manner, the initial object to be adsorbed 17 is obtained. In addition, the same temperature control is performed on the object to be adsorbed 17 after repeated attachment and detachment by the cooling gas. However, in the conventional electrostatic chuck, the property (particularly the surface roughness) of the suction surface changes due to wear or the like, and accordingly, the amount of gas leaking from between the suction surface 13 and the object to be attracted 17 changes. There was a problem that the temperature control by the cooling gas also changed. In the present embodiment, the insulating plate 11 is made of ceramic having a Young's modulus of 100 to 200 GPa, and the surface roughness (Ra) of the adsorption surface 13 is 1 to 2 μm. In addition, it is possible to control the temperature uniformly for the adsorbed object 17 after many attachments and detachments, and to improve the uniformity, reproducibility, and yield of the etching process and the like for the adsorbed object 17. Can do. In order to obtain such an effect, the Young's modulus of the ceramic material constituting the insulating plate 11 is preferably 130 to 180 GPa, and the surface roughness (Ra) of the adsorption surface 13 is 1.1 to More preferably, it is 1.5 μm.

  Next, experiments and experimental results performed to confirm the effects of the present embodiment will be described.

  First, according to the manufacturing method mentioned above, the electrostatic chuck apparatus which has surface roughness (Ra) as shown in Table 1 was manufactured (Examples 1-3, Comparative Examples 1-3). However, in Example 3 and Comparative Example 2, a cordierite green sheet and an alumina green sheet prepared as shown below were used, respectively, and in Example 3, the material for the electrostatic electrode 12 was prepared as shown below. Metallized paste using tungsten powder was used. In Example 3, the degreasing, firing and warping correction after the lamination were carried out by degreasing at 500 ° C. in a reducing atmosphere, then firing at 1400 ° C. in a reducing atmosphere, and further warping at 1350 ° C. in a reducing atmosphere. Made corrections. Moreover, in the comparative example 2, it carried out on the conditions similar to Example 1 grade | etc.,.

(Production of cordierite green sheet)
Cordierite powder is pulverized and mixed with a mixed solvent of ethanol and toluene (weight ratio 1: 1) using high-purity alumina spherulite (purity 99.9% or more), and then (as a ratio to the powder) , Binder (butyral resin): 10% by mass, plasticizer: 4% by mass, mixed by a ball mill to form a fluid slurry, and produced by this doctor blade method in the same manner as the yttria green sheet did.

(Production of alumina green sheet)
Alumina powder: 92% by mass, MgO: 1% by mass, CaO: 1% by mass and SiO ₂ : 6% by mass were wet pulverized in a ball mill using toluene and ethanol (weight ratio 1: 1) as a solvent. As a ratio to the powder), binder (butyral resin): 10% by mass, plasticizer: 4% by mass, mixed by a ball mill to form a fluid slurry, from this slurry, in the same manner as the yttria green sheet, It was produced by the doctor blade method.

(Preparation of tungsten metallized paste)
Tungsten powder and alumina powder were weighed so as to have a volume ratio of 1: 1, mixed with a dispersant and a binder (ethyl cellulose), and kneaded with three rolls.

  Next, each electrostatic chuck apparatus is mounted in a vacuum chamber of a plasma etching apparatus, a voltage of 2 kV is applied to the electrostatic chuck to adsorb a semiconductor wafer (silicon wafer), and then the voltage is turned off. The semiconductor wafer was removed. After repeating this 1000 times, the electrostatic chuck device was taken out from the vacuum chamber, and the surface roughness (Ra) of the attracting surface was measured. Moreover, while repeating this attachment and detachment, cooling gas (He) was supplied from the cooling gas supply hole, and the amount of cooling gas leaking from between the semiconductor wafer and the adsorption surface was measured. Further, as a semiconductor wafer to be attached and detached after the first time and 1000 times, a temperature measuring wafer having 65 measurement points was used, and the temperature distribution of the adsorption surface at each was measured, and the difference between the maximum temperature and the minimum temperature (ΔT1) for each. , ΔT2) and the change was examined.

These results are also shown in Table 1.

  As is clear from Table 1, in the examples, there was no significant change in the surface roughness (Ra) of the adsorption surface even after 1000 attachments / detachments. Therefore, the change in the amount of leakage of the cooling gas was small, and the temperature control that was the same as the initial stage was possible even after 1000 times of attachment / detachment. On the other hand, in the comparative example, the surface roughness (Ra) of the adsorption surface changes greatly. Therefore, after 1000 cycles of attachment / detachment, the change in the amount of leakage of the cooling gas was large, and the temperature control was greatly different from the initial value, confirming the effect of the present invention.

  The present invention is not limited to the description of the embodiment described above, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention.

1 is a perspective view illustrating a part of an electrostatic chuck device including an electrostatic chuck according to an embodiment of the present invention. (A) is sectional drawing which expands and shows the principal part of FIG. 1, (b) is a figure which expands and shows the principal part further.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electrostatic chuck, 11 ... Insulating plate, 12 ... Electrostatic electrode, 13 ... Adsorption surface, 14 ... Groove, 15 ... Gas supply hole, 17 ... Object to be adsorbed, 20 ... Base plate, 100 ... Electrostatic chuck apparatus.

Claims (1)

An adsorption surface for adsorbing and fixing the adsorbent, between the gas supply hole for supplying a cooling gas to the adsorption surface and the adsorbent when the adsorbent is adsorbed An electrostatic chuck comprising an insulating plate provided with a groove for forming a cooling gas flow path, and an electrostatic electrode provided inside the insulating plate,
The insulating plate is made of a ceramic mainly composed of yttria having a Young's modulus of 140 to 170 GPa, and the surface roughness (Ra) of the attracting surface is 1.2 to 1.8 μm. .

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