JP2013162084A - Electrostatic chuck regenerating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck regenerating method capable of elongating a life of a chuck body.SOLUTION: An electrostatic chuck comprises a chuck body 1 that is a dielectric body provided with a rib portion and a support portion 13 on an adsorption face to an adsorbed body, and positive and negative electrodes. In a regeneration step, a voltage is applied to both of the electrodes to electrostatically adsorb the adsorbed body on a surface. When an adsorption performance is deteriorated by repeating electrostatic adsorption of the adsorbed body, the rib portion and the support portion 13 on the adsorption face of the chuck body are removed across a predetermined thickness into a flat face, and the rib portion and the support portion are provided again. When the adsorption performance is deteriorated for the first time, instead of the regeneration step, the rib portion and a surface 13a of the support portion on the adsorption face of the chuck body are ground, so as to perform a pre-regeneration step for processing only peaks of the rib portion and the support portion into a flat plane. When the adsorption performance is deteriorated next, the above-mentioned regeneration step is performed.

Description

  The present invention relates to a method for regenerating an electrostatic chuck.

  In order to obtain a desired device structure in a semiconductor manufacturing process, plasma is generated in a processing chamber in which a silicon wafer (hereinafter referred to as “wafer”) as a processing target is placed, and film formation processing is performed on the substrate using this plasma. It is known to perform various plasma processes such as an ion implantation process and an etching process. These plasma processing apparatuses are generally provided with a substrate holding apparatus including a so-called electrostatic chuck and a base for supporting the electrostatic chuck for positioning and holding the substrate in the processing chamber. is there.

  For example, Patent Document 1 discloses an electrostatic chuck that includes a chuck body that is a dielectric having a predetermined thickness and positive and negative electrodes embedded in the chuck body. In this, a rib portion is formed on the upper surface of the chuck body so as to be in surface contact with the outer peripheral edge of the back surface of the wafer (opposite to the surface on which the predetermined processing is performed), and in the internal space surrounded by the rib portion, A plurality of support portions are concentrically provided to give a fine uneven shape. When a heating means and a cooling means are incorporated in the base and the wafer is heated or cooled, an inert gas such as argon gas or helium gas is supplied to the internal space through a gas passage formed in the chuck body. By forming an inert gas atmosphere in the inner space of the lever, heat transfer from the chuck body to the wafer is assisted so that the wafer can be efficiently heated or cooled.

  Here, contaminants such as cleaning liquid residues (mainly containing carbon and oxygen as main components) adhere to the back surface of the wafer that has undergone a plurality of processing steps. When such a wafer is attracted to the electrostatic chuck, the contaminant is transferred to the uneven shape on the surface of the chuck body. As the deposition of contaminants proceeds, a low-resistance layer made of contaminants is formed on the uneven surface of the chuck body, and the electrostatic chuck's attracting force decreases. When contaminants accumulate in this way, it is difficult to completely remove the contaminants by a cleaning process using plasma or chemicals.

  Conventionally, the chucking surface of the chuck body provided with an uneven shape is removed (cut) by a cutting process using a grinder or the like to make a flat surface, and the uneven shape is reapplied to the flat surface. A regeneration process was carried out (for example, every year). Then, by repeating the regeneration process, when the chuck body becomes thin enough to cause dielectric breakdown, the chuck body is disposed of as having a limited life. However, since the chuck body is composed of a ceramic sintered body and is expensive, there is a demand for extending its life. On the other hand, it is conceivable that the chuck body is formed thick in advance. However, in this case, the suction force per unit applied voltage may be reduced, and the required suction performance may not be obtained.

JP 2010-123810 A

  In view of the above, it is an object of the present invention to provide a method for regenerating an electrostatic chuck that can extend the life of a chuck body.

  In order to solve the above problems, a dielectric having an uneven surface on the surface to be adsorbed and an electrode are provided, and a voltage is applied to the electrode to electrostatically adsorb the adsorbed on the surface of the dielectric. When the adsorption performance decreases due to repeated electrostatic adsorption of the object to be adsorbed, the adsorption surface of the dielectric with the uneven shape is removed over a predetermined thickness to obtain a flat surface. The method for regenerating an electrostatic chuck according to the present invention including a regenerating step of re-applying the uneven shape is performed by grinding the uneven surface of the attraction surface instead of the regenerating step when the adsorption performance first decreases. A pre-regeneration step of processing only the top of the shape into a flat surface is performed, and then the regeneration step is performed when the adsorption performance is lowered.

  According to the present invention, when the adsorption performance is deteriorated by repeating electrostatic adsorption of the object to be adsorbed, the pre-regeneration step is performed instead of scraping the predetermined thickness portion including the uneven shape of the chuck body as in the past. When the adsorption performance is recovered and the adsorption performance is further reduced, the regeneration process is performed for the first time, that is, when the adsorption performance is first reduced by using the electrostatic chuck, A pre-regeneration step without removing the shape is performed, the electrostatic chuck on which the pre-regeneration step has been performed is further used, and then the regeneration step is performed when the adsorption performance is deteriorated. Thereby, a period can be lengthened until it is scraped off to a thickness that causes dielectric breakdown, and as a result, the life of the chuck body can be extended.

  In the present invention, before the regeneration step, the pre-regeneration step can be performed a plurality of times each time the adsorption performance decreases. In other words, when the suction performance is first degraded by using the electrostatic chuck, first, a preliminary regeneration process is performed without removing the uneven shape of the chuck body, and the electrostatic chuck on which the preliminary regeneration process has been performed is further performed. Use and then perform a pre-regeneration step also when the adsorption performance is reduced. However, the flatness (flatness) characteristics, surface roughness (roughness) characteristics of the upper surface of the electrostatic chuck that has been subjected to the second pre-regeneration process, verticle characteristics on the backside of the wafer, the amount of leakage of assist gas, and the temperature distribution in the substrate surface The condition is that the adsorption characteristics such as the characteristics are substantially equal to the initial state. When the adsorption performance further decreases, the regeneration process is performed when the adsorption characteristics can no longer be maintained by the pre-regeneration process. Thereby, it is possible to further increase the period until it is scraped to a thickness that causes dielectric breakdown, and as a result, it is possible to further extend the life of the chuck body.

  In the present invention, as the grinding of the uneven surface of the adsorption surface, a blasting process in which a projection material is projected and grinding is used.

The figure which illustrates typically the structure of the electrostatic chuck of embodiment of this invention. (A) And (b) is a figure explaining the reproduction | regeneration process of a chuck | zipper main body. The figure explaining a prior reproduction | regeneration process.

  Hereinafter, a method for regenerating an electrostatic chuck according to an embodiment of the present invention will be described with reference to the drawings, in which an object to be attracted is a wafer W and an electrostatic chuck EC that electrostatically attracts the wafer W is taken as an example. Hereinafter, terms indicating directions such as up and down are used with reference to FIG.

  With reference to FIG. 1, EC is an electrostatic chuck capable of performing the regeneration method of the present invention, and the electrostatic chuck EC includes a chuck body 1. The chuck body 1 is made of a ceramic sintered body that exhibits high electrical resistance, such as aluminum nitride or silicon nitride. The chuck body 1 is provided with a pair of positive and negative electrodes 2a and 2b via an insulating layer (not shown), and a DC voltage is applied from the DC power source E between the electrodes 2a and 2b. The lower surface of the chuck main body 1 is fixed to the upper surface of a cylindrical base 3 made of a metal having good thermal conductivity such as aluminum provided in a vacuum chamber (not shown).

  Further, on the upper surface of the chuck main body 1, a plurality of ribs 11 erected concentrically with an annular rib portion 11 with which the outer peripheral edge of the back surface of the wafer W can come into surface contact and an internal space 12 surrounded by the rib portion 11. And a rod-shaped support portion 13. After the wafer W is placed on the upper surface of the chuck body 1, the wafer W is attracted to the surface of the chuck plate 2 by the electrostatic force generated by applying a DC voltage between the electrodes 2 a and 2 b by the DC power source E. The Further, the chuck body 1 is provided with a gas passage 14 penetrating in the vertical direction. In this case, an assist gas made of an inert gas such as argon gas or helium gas whose flow rate is controlled is formed in the internal space 12 through a through hole 31 formed in the base 3. Although not shown and described in particular, the base 3 is provided with a heating means such as a resistance heating type heater or a cooling means by circulating a refrigerant so that the temperature of the wafer W can be controlled. In this case, by supplying an inert gas to the internal space 12 to form a gas atmosphere, heat transfer to the wafer W can be assisted and heated or cooled efficiently.

  Next, a method for manufacturing the chuck body 1 will be described. First, an aluminum nitride ceramic sintered body having a predetermined thickness is prepared, and a resist mask is formed in a predetermined pattern on the adsorption surface (upper surface in FIG. 1) of the wafer W of the ceramic sintered body. Next, by projecting a projecting material such as alumina through a resist mask, for example, by blasting and grinding the upper surface that is not covered with the resist mask, the rib portion 11 remains around the chuck body 1, and the rib portion 11 remains in the inside. Concave and convex shapes are imparted to the suction surface of the chuck body 1 so that the support portions 13 remain concentrically. In this case, the height of the rib portion 11 and the support portion 13 is set to about 10 μm, for example. Note that the uneven shape itself and its processing method are not limited to the above. Next, the upper surface of the rib portion 11 as an adsorption surface and the upper surface of each support portion 13 are made flat by a known polishing process using an abrasive or a polishing cloth. Finally, the chuck body 1 is cleaned by a known method.

  Incidentally, contaminants such as cleaning liquid residues (mainly carbon and oxygen as main components) adhere to the back surface of the wafer W that has undergone a plurality of processing steps. When such a wafer W is attracted to the electrostatic chuck EC, as shown in the uppermost drawing in FIG. 2A, the uneven shape on the surface of the chuck body 1, specifically, the rib portion 11 and the support portion 13 are formed. The pollutant P is transferred to the upper surface and side surfaces. Then, as the deposition of the contaminant P proceeds, a low resistance layer made of the contaminant P is formed on the uneven surface of the chuck body 1 and the adsorption force of the electrostatic chuck EC decreases. In such a case, a regeneration process for the chuck body 1 is performed. That is, with reference to FIG. 2B, the chucking surface of the chuck body 1 in which the chuck body 1 has a predetermined thickness (that is, the rib portion 11 and the support portion 13 are formed) by cutting using a grinder or the like. It is removed (scraped) from the upper surface over a predetermined thickness (10 μm or more). As a result, the chucking surface of the chuck body 1 becomes a flat surface 1a as shown in the second diagram from the top in FIG. Next, a resist mask MP is formed in a predetermined pattern on the flat surface 1a, and a projection material such as alumina is projected over the resist mask MP by, for example, blasting to grind the upper surface that is not covered with the resist mask MP. The rib portion 11 remains around the chuck body 1 and the support portion 13 remains concentrically in the rib body 11 so that an uneven shape is imparted to the chucking surface of the chuck body 1. Then, by repeating the regeneration process as shown in FIG. 2B (usually about three times), if the thickness of the chuck body 1 becomes thinner than a predetermined value, dielectric breakdown may occur and the adsorption performance cannot be maintained. As a result, the chuck body 1 is assumed to have a lifetime and is discarded, but it is desirable to extend the lifetime.

  In the present embodiment, when the low resistance layer made of the contaminant P is formed on the uneven surface of the chuck body 1 and the adsorption force of the electrostatic chuck EC first decreases (the uppermost state in FIG. 2A). Instead of the regeneration step, a preliminary regeneration step is performed. That is, with reference to FIG. 3, the projection material is projected onto the surfaces of the rib portion 11 and the support portion 13 by blasting to grind the uneven surface, thereby removing the contaminant P adhering to the surface. In this case, SiC or the like having a particle diameter of 200 μm is used as the projecting material, and the contaminant P is removed from the upper surface of the rib portion 11 and the support portion 13 to 2 to 3 μm (for example, 1 / of the initial height of the support portion 13). Grinding is performed only to the extent of 3). Then, when the pollutant P is removed, the convex top, that is, the upper surface of the rib portion 11 serving as the adsorption surface and the upper surface 13a of each support portion 13 are flattened by a known polishing process using an abrasive or a polishing cloth. Make a face.

  According to the experiments of the present inventors, the flatness (flatness) characteristics, the surface roughness (roughness) characteristics of the upper surface of the electrostatic chuck EC subjected to the pre-regeneration processing, the verticle characteristics on the back surface of the wafer, the amount of leakage of assist gas, It was confirmed that the adsorption characteristics such as the temperature distribution characteristic in the substrate surface are substantially equal to the initial state.

  Next, the chuck body 1 that has been subjected to the pre-regeneration process is repeatedly attracted to the wafer W (that is, by being used again as an electrostatic chuck). When the resistance layer is formed and the attractive force of the electrostatic chuck EC is next reduced, the regeneration process is performed in principle according to the above. However, as described above, even if the pre-regeneration step is further performed, the pre-regeneration step can be further performed if the adsorption characteristics can still be maintained. When these pre-regeneration steps (and further pre-regeneration steps) and the regenerative steps are repeated and become thin enough to cause dielectric breakdown, the chuck body 1 is disposed of as having a limited life.

  According to the above-described embodiment, the predetermined thickness portion including the uneven shape of the chuck body 1 is not scraped off, but the pre-regeneration process is performed to recover the adsorption performance, and then the regeneration is performed only when the adsorption performance further decreases. In order to carry out the process, that is, to perform the pre-regeneration process without removing the uneven shape of the chuck body 1 in the previous stage of the regeneration process, it is possible to lengthen the period until it is scraped to a thickness that causes dielectric breakdown, The life of the chuck body can be extended.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. In the above-described embodiment, as an example of the grinding of the uneven surface of the suction surface of the chuck body 1 using a blasting process in which a projection material is projected and ground, a low resistance layer made of a contaminant P is used. Any other grinding method can be used as long as it can efficiently grind the concavo-convex surface portion. In the present invention, a so-called bipolar type having a pair of positive and negative electrodes 2a, 2b has been described as an example. However, the present invention is not limited to this, and may be a monopolar type, for example. Further, the present invention can be widely applied as long as the dielectric layer is scraped and reproduced.

EC ... electrostatic chuck, W ... adsorbed body, 1 ... chuck body, 2a, 2b ... electrode, 11 ... rib portion (uneven shape), 13 ... support portion (uneven shape), 13a ... surface of the support portion.

Claims (3)

A dielectric having an uneven shape on the surface to be adsorbed and an electrode, and an electrode, a voltage is applied to the electrode to electrostatically adsorb the adsorbed on the surface of the dielectric, and the electrostatic of the adsorbed When the adsorption performance is deteriorated by repeating adsorption, the regeneration process of removing the adsorption surface of the dielectric provided with the uneven shape over a predetermined thickness to form a flat surface, and again applying the uneven shape to the flat surface In an electrostatic chuck regeneration method including:
When the adsorption performance first decreases, in place of the regeneration process, the uneven surface of the adsorption surface is ground, and a pre-regeneration process is performed in which only the convex top is processed into a flat surface. A method for regenerating an electrostatic chuck, wherein the regenerating step is performed when the voltage drops.   2. The method for regenerating an electrostatic chuck according to claim 1, wherein the pre-regeneration step is performed a plurality of times each time the adsorption performance is lowered before the regeneration step. The method for regenerating an electrostatic chuck according to claim 1 or 2, wherein a blasting process for projecting and projecting a projection material is used for grinding the uneven surface of the attraction surface.

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