Abstract:
The present invention generally relates to a refurbished electrostatic chuck and a method of refurbishing a used electrostatic chuck. Initially, a predetermined amount of dielectric material is removed from the used electrostatic chuck to leave a base surface. Then, the base surface is roughened to enhance the adherence of new dielectric material thereto. The new dielectric material is then sprayed onto the roughened surface. A mask is then placed over the new dielectric material to aid in the formation of mesas upon which a substrate will sit during processing. A portion of the new dielectric layer is then removed to form new mesas. After removing the mask, edges of the mesas may be smoothed and the refurbished electrostatic chuck is ready to return to service after cleaning.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/492,692, filed Jun. 2, 2011, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to a refurbished electrostatic chuck and a method for refurbishing an electrostatic chuck. 
     2. Description of the Related Art 
     Electrostatic chucks are useful in the manufacture of semiconductor devices. The electrostatic chuck permits that substrate to remain in a fixed location on the electrostatic chuck during processing by electrostatically clamping the substrate to the chuck. 
     The electrostatic chuck typically has an electrode embedded within a dielectric material. The topmost surface of the electrostatic chuck has a plurality of mesas upon which the substrate will sit during processing. Over time, the mesas may wear down and the electrostatic chuck will not be as effective. Additionally, the electrical properties the electrostatic chuck may be jeopardized by a crack in the dielectric material or the dielectric material may be compromised by a chemical or plasma attack causing the dielectric material to breakdown. 
     When the mesas wear down, a crack forms in the dielectric material or the dielectric material breaks down, the electrostatic chuck is no longer useful and is typically discarded. It would be beneficial to refurbish the electrostatic chuck to avoid the expense of purchasing a new electrostatic chuck. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to a refurbished electrostatic chuck and a method of refurbishing a used electrostatic chuck. Initially, a predetermined amount of dielectric material is removed from the used electrostatic chuck to leave a base surface. Then, the base surface is roughened to enhance the adherence of new dielectric material thereto. The new dielectric material is then sprayed onto the roughened surface. A mask is then placed over the new dielectric material to aid in the formation of mesas upon which a substrate will sit during processing. A portion of the new dielectric layer is then removed to form new mesas. After removing the mask, edges of the mesas may be smoothed and the refurbished electrostatic chuck is ready to return to service after cleaning. 
     In one embodiment, a method for refurbishing an electrostatic chuck includes measuring a depth of an electrode below an upper surface of an electrostatic chuck, determining a thickness of a portion of the electrostatic chuck to be removed in response to the measured depth and removing the portion of the electrostatic chuck to expose a base surface. The method also includes roughening the base surface, plasma spraying dielectric material onto the roughened base surface to form a dielectric layer of sprayed material on the base surface and compressing the dielectric layer of sprayed material. The method additionally includes selectively removing material from the compressed dielectric layer of sprayed material to establish a new upper surface and polishing the new upper surface. 
     In another embodiment, a method for refurbishing an electrostatic chuck is disclosed. The method includes measuring a depth of an electrode below a top surface of an electrostatic chuck body, determining a thickness of a portion of the electrostatic chuck body to be removed in response to the measured depth, removing the portion of the electrostatic chuck body to expose a base surface, roughening the base surface and disposing dielectric material onto the roughened base surface to form a dielectric layer on the base surface. 
     In another embodiment, a refurbished electrostatic chuck includes a chuck body having one or more electrodes and one or more first dielectric layers disposed thereover and a second dielectric layer disposed over the one or more first dielectric layers. The second dielectric layer has a top surface that has a plurality of mesas extending therefrom in a direction away from the one or more first dielectric layers. The second dielectric layer and the one or more first dielectric layers are distinct layers. 
     In another embodiment, a refurbished electrostatic chuck includes a multi-layer electrostatic chuck body, wherein a first layer of the multi-layer electrostatic chuck body has one or more electrodes embedded thereon, wherein a second layer of the multi-layer electrostatic chuck body is selected from the group consisting of a sintered dielectric layer and a dielectric layer bonded to the first layer with an adhesive, wherein the second layer has a top surface that has a plurality of mesas extending therefrom in a direction away from the first layer and wherein the second layer and the first layers are distinct layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1A  is a schematic top view of a used electrostatic chuck prior to refurbishment. 
         FIG. 1B  is a cross-sectional view of the used electrostatic chuck of  FIG. 1A . 
         FIGS. 2-7  are cross-sectional views of the electrostatic chuck of  FIGS. 1A and 1B  at various stages of refurbishment according to one embodiment. 
         FIG. 8  is a cross-sectional view of the electrostatic chuck of  FIGS. 1A and 1B  at various stages of refurbishment according to another embodiment. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     The present invention generally relates to a refurbished electrostatic chuck and a method of refurbishing a used electrostatic chuck. Suitable electrostatic chucks that may be refurbished according to the embodiments discussed herein include Johnson-Rahbeck electrostatic chucks available from Applied Materials, Inc., Santa Clara, Calif. It is to be understood that the embodiments discussed herein are equally applicable to other types of electrostatic chucks, including those available from other manufacturers. 
       FIG. 1A  is a schematic top view of a used Johnson-Rahbeck type electrostatic chuck  100  prior to refurbishment.  FIG. 1B  is a cross-sectional view of the used electrostatic chuck  100  of  FIG. 1A . The electrostatic chuck  100  has a chuck body  108  that includes a top surface  112  and a bottom surface  114 . The top surface  112  includes a plurality of mesas  102  extending from the chuck body  108  of the electrostatic chuck  100 . The chuck body  108  may have one or more dielectric layers. In the embodiment shown in  FIGS. 1A and 1B , the chuck body  108  comprises a single dielectric layer. The chuck body  108  comprises a ceramic material such as aluminum nitride, however, it is to be understood that the refurbishment method discussed herein is applicable to electrostatic chucks comprising other dielectric materials. A gas retention ring  104  extends from the top surface  112  and encircles the area where the mesas  102  are disposed. Both the mesas  102  and the gas retention ring  104  comprise the same dielectric material as the chuck body  108 . Embedded within the chuck body  108  is an electrode  106  that couples to a power source through a stem  110  coupled to the bottom surface  114  of the electrostatic chuck  100 . 
     As shown in  FIG. 1B , the mesas  102  each extend a different height above the chuck body  108 . Therefore, any substrate disposed on the electrostatic chuck  100  may not be held substantially flat due to the uneven height of the mesas  102 . Additionally, the uneven mesas  102  may prevent a substrate disposed on the electrostatic chuck  100  from being uniformly chucked, which may affect the uniformity of the processing on the substrate. 
     In order to refurbish the electrostatic chuck  100 , an amount of material to be removed needs to be determined. A distance, shown by arrow “B”, between the electrode  106  and the highest point of the mesas  102  or gas retention ring  104  is determined by measuring the capacitance of the electrostatic chuck  100 . A predefined amount of material, shown by arrow “D” is desired to remain over the electrode  106  after the material is removed to prevent accidental exposure of the electrode  106 . Thus, the amount of material to be removed, shown by distance “C”, may be determined by subtracting distance “D” from distance “B”. 
     Once the amount of material to remove is determined, the electrostatic chuck  100  is then lapped and polished to remove the mesas  102 , gas retention ring  104  and additional material of the chuck body  108  to leave a base surface  202 , as shown in  FIG. 2 , which is the distance “D” above the electrode  106 . The distance “D” may be between about 20 microns to about 25 microns from the electrode  106 . The lapping removes the bulk of the material while the polishing smoothes the surface  202 . In one embodiment, lapping removes the material at a rate of between about 1 micrometers per minute to about 150 micrometers per minute, depending on the diamond size within the slurry. In one embodiment, the slurry diamond size is between about 0.05 microns to about 100 microns. It is to be understood that the slurry diamond size may be tailored to meet the desired removal rate. Lapping is beneficial for removing the material because lapping can be controlled to within 1 microns and produce as uniformly smooth a base surface  202  as possible. Other removal techniques, such as bead blasting or etching, would not be appropriate as bead blasting and etching cannot be controlled as well as lapping. 
     To enhance adhering new dielectric material to the smooth base surface  202 , the base surface  202  may be roughened. For example, the base surface  202  may be roughened to a surface roughness of between about 50 microinches to about 300 microinches, which results in roughened surface  302  as shown in  FIG. 3 . In one embodiment, the base surface  202  is roughened by bead blasting. 
     After the roughened surface  302  is formed, the new dielectric material  402  may be deposited as shown in  FIG. 4 . In one embodiment, the new dielectric material  402  is thermal plasma spray coated onto the roughened surface  302 . Most deposition processes are conformal deposition processes that replicate the surface upon which the deposition occurs. The thermal plasma spraying process is a process that achieves a non-conformal coating (i.e., the upper surface of the new coating does not replicate the roughened surface  302 ). Because of the thermal plasma spraying process, the mesas and gas retention ring to be formed later can have the desired embossment profile that reduces substrate or silicon damage and backside particles. To determine the suitable material for spray coating, the resistivity of the original dielectric material is measured and then the suitable material is selected to be both sprayable and as close to the resistivity of the original dielectric material as possible. Suitable dielectric materials that may be used include aluminum nitride powder. The dielectric material may be mixed with a dopant such as yttria, alumina, titanium oxide, samarium oxide, and combinations thereof. Once the appropriate material is selected for the Johnson-Rahbeck electrostatic chuck, the new dielectric material  402  is spray coated into the roughened surface  302 . 
     Because the new dielectric material  402  is spray coated, the grains are loosely packed. Therefore, the electrostatic chuck  100  is placed into a high pressure, inert gas environment to compress the grains so that there is less space between the grains. A suitable pressure for the compression is an environment at a pressure of greater than about 1 Torr. 
     Next, the mesas and gas retention ring are formed. To form the mesas and gas retention ring, portions of the new dielectric material  402  are selectively removed. To selectively remove portions of the new dielectric material  402 , a mask  502  is placed over the new dielectric material  402  as shown in  FIG. 5 . During the process of forming the mesas  604  and gas retention ring  602 , gas grooves, embossments and other geometries may be formed as desired. The mask  502  has openings  504  that correspond to the areas adjacent to the location where the mesas and gas retention ring will be formed. The exposed new dielectric material  402  is then bead blasted through the openings  504  formed through the mask  502 . The mask  502  is removed to leave the newly formed mesas  604  and gas retention ring  602 , as shown in  FIG. 6 . 
     The mesas  604  and gas retention ring  602  may have sharp edges or burrs that may scratch the back of the substrate during processing and create undesired particles. Therefore, the mesas  604  and gas retention ring  602  may be polished with a soft polishing pad under minimum force to round the sharp corners, to remove the burrs and to leave the finished mesas  704  and retention ring  702  as shown in  FIG. 7 . Thus, the refurbished electrostatic chuck  700  is again ready for operation. 
       FIG. 8  is a cross-sectional view of the electrostatic chuck of  FIGS. 1A and 1B  at various stages of refurbishment according to another embodiment. Rather than spray coat a dielectric layer onto the roughened surface  302 , a puck  802  of dielectric material may be bonded to the roughened surface  302  by an adhesive layer  804 . As above, suitable dielectric materials that may be used include aluminum nitride powder. The dielectric material may be mixed with a dopant such as yttria, alumina, titanium oxide, samarium oxide, and combinations thereof. Suitable materials for the adhesive layer consist of a vacuum epoxy with additives to control the resistivity and decay or discharge such as aluminum oxide, titanium oxide, tantalum oxide, samarium oxide, and combinations thereof. Once the puck  802  is adhered to the roughened surface  302 , the mesas are formed as discussed above with regards to  FIGS. 5-7 . The puck  802  need not be sintered because the grains of the puck are already closely packed. 
     The refurbished electrostatic chuck  700  comprises the original chuck body  108  having the electrode  106  embedded therein and a new dielectric material  402  disposed thereover with a top surface that has a plurality of mesas  704  extending in a direction away from the original chuck body  108 . Thus, the refurbished electrostatic chuck  700  includes multiple dielectric layers. The refurbished electrostatic chuck  700  thus has distinct portions, namely, the original chuck body  108  and the new dielectric material  402 . Both the original chuck body  108  and the new dielectric material  402  may comprise the same material such as aluminum nitride. Additionally, the new dielectric material  402  may have a dopant such as yttria, alumina, titanium oxide, samarium oxide, or combinations thereof. 
     By refurbishing the electrostatic chuck, there is no need to purchase an entirely new electrostatic chuck. The refurbished electrostatic chuck will cost less than the new electrostatic chuck, yet have essentially the same resistivity and function substantially identical as the new electrostatic chuck. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.