JP2007088492A - Manufacturing method of electrostatic chuck and electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrostatic chuck with enhanced resistance to plasma and cooling performance of an object to be adsorbed. <P>SOLUTION: In the basic configuration of the electrostatic chuck 20, an insulation film 22 is formed on the surface of a metallic plate 21 by thermal spraying, a dielectric substrate 24 is joined onto the insulation film 22 via an insulating adhesive layer 23, the front side of the dielectric substrate 24 is used for a placing side of the object W to be adsorbed such as a semiconductor wafer, and the lower side is formed with electrodes 25, 25. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic chuck that attracts a semiconductor substrate, a glass substrate, and the like, and a method for manufacturing the same.

  As means for adsorbing and holding a semiconductor substrate or a glass substrate in a plasma processing chamber for performing etching, CVD, sputtering, ion implantation, ashing, etc., electrostatic chucks disclosed in Patent Documents 1 to 4 are used.

  As shown in FIG. 7, the structure of the conventional electrostatic chuck disclosed in Patent Documents 1 and 2 is a dielectric in which an electrode 102 is held on a metal plate 100 via an organic adhesive 101 such as silicone resin. The body layer 103 is bonded and integrated. And as a method of embedding the electrode 102 in the dielectric layer 103, an electrode (tungsten) is printed on the surface of the ceramic green sheet which becomes the dielectric layer by firing, and another ceramic green sheet is further formed thereon. A method of baking (hot pressing) is adopted.

Japanese Utility Model Publication No. 4-133443 JP-A-10-223742 Japanese Patent Laid-Open No. 2003-152065 JP 2001-338970 A

  Residues and products from the semiconductor wafer and coating film are attached to the inner surface of the chamber after the plasma treatment. When the plasma treatment is repeated, residues and products are gradually deposited, and eventually peel from the inner surface of the chamber and adhere to the surface of the semiconductor substrate or glass substrate, leading to a decrease in yield.

Therefore, conventionally, the inside of the chamber is periodically cleaned by plasma to remove residues and products attached to the inner surface of the chamber. At this time, conventionally, in order to prevent the surface of the electrostatic chuck from being exposed to plasma, cleaning is performed with the surface of the electrostatic chuck covered with a dummy wafer. In order to shorten and improve the production efficiency, the surface of the electrostatic chuck is not covered with a dummy wafer, and the surface of the electrostatic chuck is directly cleaned with cleaning plasma such as O ₂ gas or CF ₄ gas at the time of cleaning. Exposure, so-called waferless plasma cleaning, is an industry trend.

  By the way, the average particle diameter after firing of the electrostatic chuck manufactured using the ceramic raw material powder that is generally widely used is 5 to 50 μm. When the waferless plasma cleaning is performed on the electrostatic chuck, Defects on the surface of the ceramic and erosion of the grain boundaries increase the average roughness (Ra), causing problems such as a decrease in electrostatic adsorption force and a decrease in heat transfer coefficient at the solid contact interface with the wafer. Occurs and the electrostatic chuck must be replaced early.

  As a means for solving these problems, as disclosed in Patent Document 3, there is an electrostatic chuck in which the average particle diameter of the ceramic is suppressed to 2 μm or less. In order to insert electrodes, it requires technically sophisticated and complicated processes, such as firing and molding two dielectric substrates, and sandwiching the electrode material and integrating them by heat and pressure treatment such as hot press. Yes. For this reason, there are problems such as a decrease in reliability and a prolonged construction period.

  However, the ceramic dielectric substrate having the above average particle size suppressed to 2 μm or less is formed by laminating green sheets with the electrodes inserted into the dielectric and firing them integrally for convenience such as debinding during firing. It is not obtained. That is, in order to manufacture an electrostatic chuck having a conventional structure having plasma durability, a technique for inserting an electrode into the fired dielectric layer substrate is required.

  As disclosed in Patent Document 4, as a means for solving this problem, a method in which an electrode is formed on the surface of a dielectric layer substrate, and an insulating resin such as polyimide is pasted thereon is bonded to a metal base plate. However, in the case of this structure, there are problems in the increase in wafer temperature and the insulation reliability due to the low thermal conductivity of the insulating resin.

  The object of the present invention is to solve the above problems simultaneously, such as a simple manufacturing process, high durability of waferless plasma cleaning, high wafer cooling capability, and high reliability of electrical insulation between the electrode and the metal plate. It is to provide an electrostatic chuck that can be used.

  In order to solve the above-mentioned problems, an electrostatic chuck manufacturing method according to the present invention includes a metal plate having an insulating film formed on a surface thereof by thermal spraying, and a dielectric substrate having an electrode formed on the surface. And the electrode are opposed to each other with an insulating adhesive interposed therebetween. The present application also includes an electrostatic chuck obtained by the above method.

  As described above, even when an electrode is provided on the surface of a dielectric substrate, it is possible to cope with waferless plasma cleaning with a simple structure and high reliability by forming an insulating film by thermal spraying on the surface of a metal plate. An electrostatic chuck can be provided.

  As the particles constituting the dielectric substrate, those having an average particle diameter of 2 μm or less are preferable for improving the plasma resistance. By setting the average particle diameter to 2 μm or less, it is possible to provide an electrostatic chuck with a small change in the attracting surface roughness of the dielectric substrate even when wafer rescreening is repeated.

  The total thickness of the dielectric substrate, the insulating adhesive, and the insulating film is preferably 0.5 mm or more and 2.0 mm or less. By setting the thickness as described above, electrical insulation between the object to be adsorbed and the electrode and electrical insulation between the electrode and the metal plate can be ensured, and the heat transfer efficiency from the object to be adsorbed to the metal plate is excellent An electric chuck can be provided. As a more preferable example, the total thickness of the dielectric substrate, the insulating adhesive, and the insulating film is desirably 1.5 mm or less in order to suppress the impedance between the dielectric adsorbent and the metal plate.

  The manufacturing method of the electrostatic chuck according to the present invention and the electrostatic chuck obtained by the manufacturing method have a simple manufacturing process and a small particle diameter constituting the dielectric substrate whose surface is an attracting surface. Because it can perform waferless plasma cleaning without using a dummy wafer, the tact time can be greatly reduced, and the heat transfer efficiency is good. The reliability of electrical insulation between the metal plates can be increased.

  Specifically, FIG. 4A is a micrograph showing the surface of the dielectric substrate of the electrostatic chuck according to the present invention before plasma irradiation, and FIG. 4B is the surface of the dielectric layer of the conventional electrostatic chuck before plasma irradiation. 5A is a micrograph showing the surface of the dielectric substrate of the electrostatic chuck according to the present invention after plasma irradiation, and FIG. 5B is a dielectric of the conventional electrostatic chuck after plasma irradiation. It is a microscope picture which shows the layer surface.

  FIG. 6 shows changes in surface roughness when plasma is irradiated on the surface of the dielectric substrate of the electrostatic chuck according to the present invention and the surface of the dielectric layer of the conventional electrostatic chuck.

  As is apparent from these photographs and drawings, it can be seen that the surface roughness (Ra) of the surface of the dielectric substrate of the electrostatic chuck according to the present invention is extremely small before and after the plasma irradiation.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall view of a plasma processing apparatus incorporating an electrostatic chuck according to the present invention, FIG. 2 is a cross-sectional view of the electrostatic chuck, and FIG. 3 is a diagram illustrating an assembly procedure of the electrostatic chuck.

In the plasma processing apparatus, an upper electrode 10 for generating plasma and an electrostatic chuck 20 are disposed in a chamber 1. Also on the ceiling of the chamber 1 and the reaction gas inlet 2, such as CF ₄ or O _2, it is formed with an exhaust port 3 connected to a vacuum device.

  The basic structure of the electrostatic chuck 20 is that an insulator film 22 is formed on the surface of a metal plate 21 by thermal spraying, and a dielectric substrate 24 is bonded on the insulator film 22 via an insulating adhesive layer 23. The surface of the dielectric substrate 24 is used as a mounting surface for the object W to be adsorbed such as a semiconductor wafer, and electrodes 25 and 25 are formed on the lower surface. Lead wires 26 and 26 for supplying power to the electrodes 25 and 25 extend downward through the metal plate 21. The lead wire 26 and the metal plate 21 are insulated.

The metal plate 21 is made of a metal having excellent thermal conductivity such as an aluminum alloy or copper, a coolant passage 21a is formed inside, and the insulator film 22 formed on the upper surface of the metal plate 21 by thermal spraying includes: Inorganic materials such as alumina (Al ₂ O ₃ ) are preferred.

In addition, as a method for manufacturing the dielectric substrate 24, for example, an alumina raw material powder having an average particle diameter of 0.1 μm and a purity of 99.99% or more is a main component, and more than 0.2 wt% and 0.6 wt% or less. Titanium oxide (TiO ₂ ) is mixed and pulverized, an acrylic binder is added, and after adjustment, the mixture is granulated with a spray dryer to produce granulated powder. Then, after CIP (rubber press) or mechanical press molding, it is processed into a predetermined shape and fired in a reducing atmosphere at 1150 to 1350 ° C. Further, HIP processing (hot isostatic pressing) is performed. The HIP condition is Ar gas of 1000 atm or higher, and the temperature is 1150 to 1350 ° C., which is the same as the firing temperature. Under such conditions, the dielectric substrate 24 is extremely dense and has an average particle diameter of 2 μm or less, a volume resistivity of 10 ⁸ to 10 ¹¹ Ωcm and a relative density of 99% or more at 20 ± 3 ° C. Is obtained.

In addition, the average particle diameter shown here is a particle diameter calculated | required with the following planimetric methods. First, take a picture of the dielectric substrate with SEM, draw a circle with a known area (A) on this picture, and calculate the unit area from the number of particles nc in the circle and the number of particles ni on the circumference by equation (1). Find the number of particles per particle NG.
NG = (nc + 1/2 ni) / (A / m2)… (1)
M shown here is the magnification of the photograph. Since 1 / NG is the area occupied by one particle, the particle diameter can be obtained as 2 / √ (π NG).

  Further, the electrode 25 is obtained by grinding the surface of the dielectric substrate 24, forming a conductive film such as TiC or Ti by CVD or PVD, and sandblasting or etching the conductive film to obtain a predetermined electrode pattern.

  If the above-mentioned extremely dense dielectric substrate is used, the plasma resistance is improved, and the change in the roughness of the electrostatic chuck surface can be suppressed to a very small level without using a dummy wafer.

  In order to assemble the electrostatic chuck 20, as shown in FIG. 3, a metal plate 21 on which an insulator film 22 is formed in advance and a dielectric substrate 24 on which an electrode 25 is formed are prepared. The insulating film 22 of 21 and the electrode 25 of the dielectric substrate 24 are bonded to each other through an insulating adhesive 23 so as to face each other.

  Examples of the insulating adhesive 23 include a silicone resin having alumina or aluminum nitride as a filler and a thermal conductivity of 1 W / mk or more, preferably 1.6 W / mK or more.

Overall view of a plasma processing apparatus incorporating an electrostatic chuck according to the present invention Cross section of the electrostatic chuck The figure explaining the assembly procedure of the electrostatic chuck (A) is a photomicrograph showing the dielectric substrate surface of the electrostatic chuck according to the present invention before plasma irradiation, (b) is a photomicrograph showing the dielectric layer surface of the conventional electrostatic chuck before plasma irradiation. (A) is a photomicrograph showing the dielectric substrate surface of the electrostatic chuck according to the present invention after plasma irradiation, (b) is a photomicrograph showing the dielectric layer surface of the conventional electrostatic chuck after plasma irradiation. Changes in surface roughness when plasma is irradiated on the dielectric substrate surface of the electrostatic chuck according to the present invention and the dielectric layer surface of the conventional electrostatic chuck Cross section of conventional electrostatic chuck

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Chamber, 2 ... Reaction gas introduction port, 3 ... Exhaust port, 10 ... Upper electrode, 20 ... Electrostatic chuck, 21 ... Metal plate, 21a ... Refrigerant passage, 22 ... Insulator film, 23 ... Insulating adhesive layer 24 ... dielectric substrate, 25 ... electrode, 26 ... lead wire, 100 ... metal plate, 101 ... organic adhesive, 102 ... electrode, 103 ... dielectric layer, W ... adsorbed material.

Claims (4)

A metal plate with an insulator film formed on the surface is joined to a dielectric substrate with an electrode formed on the surface with an insulating adhesive interposed so that the insulator film and the electrode face each other. A method of manufacturing an electrostatic chuck. A metal plate with an insulator film formed on the surface and a dielectric substrate with an electrode formed on the surface are joined together with an insulating adhesive so that the insulator film and the electrode face each other. An electrostatic chuck characterized in that 3. The electrostatic chuck according to claim 2, wherein an average particle diameter of particles constituting the dielectric substrate is 2 [mu] m or less. 3. The electrostatic chuck according to claim 2, wherein a total thickness of the dielectric substrate, the insulating adhesive, and the insulator film is 0.5 mm or more and 2.0 mm or less.

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