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  Apparatus for use in processing a semiconductor workpieceUSPTO Application #: 20070026772Title: Apparatus for use in processing a semiconductor workpiece Abstract: The present invention provides a chuck for receiving and supporting a semiconductor workpiece for processing. The chuck includes a body for supporting the workpiece. The body is porous or has a plurality of openings, apertures or channels. A compressible corrosion resistant member is disposed around the outer periphery of the supporting body. The chuck includes a means for evacuating air from the pores or plurality of openings, apertures or channels in the body to create a vacuum. In operation, a workpiece is placed onto the supporting body. The device side of the workpiece is preferably placed on the compressible corrosion resistant member. Upon evacuating the air (or other gas) from the pores or openings in the supporting body, a vacuum is created, drawing the workpiece toward the supporting body. A seal is created and maintained between the device side of the workpiece and the compressible corrosion resistant member. Consequently, the entire backside of the workpiece is exposed for processing while at the same time the device side of the workpiece is protected from any potentially damaging process fluids. By exposing the backside of the workpiece to a chemical etchant, semiconductor workpieces can be thinned to a desired thickness. (end of abstract) Agent: Mcdermott Will & Emery LLP - Chicago, IL, US Inventors: Kert L. Dolechek, Raymon F. Thompson USPTO Applicaton #: 20070026772 - Class: 451388000 (USPTO) Related Patent Categories: Abrading, Work Holder, Vacuum The Patent Description & Claims data below is from USPTO Patent Application 20070026772. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to an apparatus for handling a workpiece, such as a semiconductor wafer, flat panel display, rigid disk or optical media, thin film heads or other workpieces formed from a substrate on which microelectronic circuits, data storage elements or layers, or micro-mechanical elements may be formed. These and similar articles are collectively referred to herein as a "wafer" or "workpiece." Specifically, the present invention relates to a chuck for use in handling, processing and treating semiconductor workpieces. BACKGROUND OF THE INVENTION [0002] State of the art electronics (e.g., cellular phones, personal digital assistants, and smart cards) demand thinner integrated circuit devices ("ICD"). In addition, advanced packaging of semiconductor devices (e.g., stacked dies or "flip-chips") provide dimensional packaging constraints which require an ultra-thin die. Moreover, as operating speeds of ICDs continue to increase heat dissipation becomes increasingly important. This is in large part due to the fact that ICDs operated at extremely high speeds tend to generate large amounts of heat. That heat must be removed from the ICD to prevent device failure due to heat stress and to prevent degradation of the frequency response due to a decrease in carrier mobility. One way to enhance thermal transfer away from the ICD, thereby mitigating any deleterious temperature effects, is by thinning the semiconductor wafer from which the ICD is fabricated. Other reasons for thinning the semiconductor wafer include: optimization of signal transmission characteristics; formation of via holes in the die; and minimization of the effects of thermal coefficient of expansion between an individual semiconductor device and a package. [0003] Semiconductor wafer thinning techniques have been developed in response to this ever increasing demand for smaller, higher performance ICDs. Typically, semiconductor devices are thinned while the devices are in wafer form. Conventional wafer thicknesses vary depending on the size of the wafer. For example, the thickness of a 150 mm diameter silicon semiconductor wafer is typically about 650 microns, while wafers having a diameter of 200 mm are generally about 725 microns thick, and 300 mm wafers generally have a thickness of 775 microns. Mechanical grinding of the back side of a semiconductor is one standard method of thinning wafers. Such thinning is referred to as "back grinding." Generally, the back grinding process employs methods to protect the front side or device side of the semiconductor wafer. Conventional methods of protection of the device side include the application of a protective tape or a photoresist layer to the device side of the wafer. The back side of the wafer is then ground until the wafer reaches a desired thickness. [0004] However, conventional back grinding processes have drawbacks. Mechanical grinding induces stress in the surface and edge of the wafer, including micro-cracks and edge chipping. This induced wafer stress can lead to performance degradation and wafer breakage resulting in low yield. In addition, there is a limit to how much a semiconductor wafer can be thinned using a back grinding process. For example, semiconductor wafers having a conventional thickness (as mentioned above) can generally be thinned to a range of approximately 250-150 microns. [0005] Accordingly, it is common to apply a wet chemical etch process to a semiconductor wafer after it has been thinned by back grinding. This process is commonly referred to as polishing. The polishing process relieves the induced stress in the wafer, removes grind marks from the back side of the wafer and results in a relatively uniform wafer thickness. Additionally, polishing after back grinding thins the semiconductor wafer beyond conventional back grinding capabilities. For example, utilizing a wet chemical etch process after back grinding allows standard 200 and 300 mm semiconductor wafers to be thinned to 100 microns or less. Wet chemical etching typically includes exposing the back side of the wafer to an oxidizing agent (e.g., HNO.sub.3, H.sub.3PO.sub.4, H.sub.2SO.sub.4) or alternatively to a caustic solution (e.g., KOH, NaOH, H.sub.2O.sub.2). Examples of wet chemical etching processes may be found in co-pending U.S. patent application Ser. No. 10/631,376, assigned to the assignee of the present invention. The teachings of patent application Ser. No. 10/631,376 are incorporated by reference. [0006] Although methods for thinning semiconductor wafers are known, they are not without limitations. For example, mounting a semiconductor wafer to a submount or "chuck" (as it is commonly known) so that the wafer can be thinned requires expensive coating and bonding equipment and materials, increased processing time, and the potential for introducing contaminates into the process area. Additionally, adhesives for bonding a wafer to a chuck that may be useful in a mechanical grinding process will not withstand the chemical process fluids used in wet chemical etching. Furthermore, the current use of a photoresist or adhesive tape fails to provide mechanical support for very thin wafers either during the back grind process or in subsequent handling and processing. The use of tape also creates obstacles in the removal process. For example, tape removal may subject a wafer to unwanted bending stresses. In the case of a photoresist, the material is washed off the device side of a wafer with a solvent, adding to the processing time and use of chemicals, and increasing the risk of contamination. [0007] Further, thinned semiconductor wafers are prone to warping and bowing. And because thinned semiconductor wafers can be extremely brittle, they are also prone to breakage when handled during further processing. Thinned semiconductor wafers (e.g., below 250 microns) also present complications in automated wafer handling because, in general, existing handling equipment has been designed to accommodate standard wafer thicknesses (e.g., 650 microns for 150 mm wafer and 725 microns for 200 and 300 mm wafers). [0008] Accordingly there is a need for equipment to secure a semiconductor workpiece for thinning, while at the same time reducing the number of processing steps necessary for thinning the semiconductor workpiece. SUMMARY OF THE INVENTION [0009] The present invention provides an apparatus for use in processing semiconductor workpieces. The apparatus allows for the entire back side of a workpiece to be thinned, yet prevents damage to the device side of the workpiece. The process and equipment of the present invention produces thinned wafers having a thickness less than about 125 microns, while reducing the number of processing steps. This results in, among other things, improved process efficiency, improved yields and a broader range of product applications. [0010] In one aspect, the present invention provides a chuck for receiving and supporting a semiconductor workpiece for processing. The chuck includes a porous body for supporting the workpiece. The porous body has a compressible corrosion resistant member disposed around its outer periphery. The chuck includes a means for evacuating air from the porous body to create a vacuum. In operation, a workpiece is placed onto the supporting body. The exclusion zone (i.e., an area having a radial width of approximately 1-5 mm around the outer periphery of the workpiece) of the device side of the workpiece is preferably placed on the compressible corrosion resistant member. Upon evacuating the air (or other gas) from the porous supporting body, a vacuum is created, drawing the workpiece toward the supporting body. Depending on the strength of the vacuum created and/or the compressibility of the corrosion resistant member, the device side of the workpiece is drawn against the supporting body (or in close proximity to the supporting body). A seal is created and maintained between the device side of the workpiece and the compressible corrosion resistant member. Consequently, the entire backside of the workpiece is exposed for processing while at the same time the device side of the workpiece is protected from any potentially damaging process fluids. By exposing the backside of the workpiece to a chemical etchant, semiconductor workpieces can be thinned to thicknesses of less than 150 microns or even less than 100 microns, resulting in a wider range of product applications. [0011] The means for evacuating air (or other gas) from the porous body can include various different configurations in the present invention. For example, a poppet valve located in a cavity in the bottom side of the porous body can be used to evacuate air from the porous body to create a vacuum. Alternatively, a diaphragm and compression assembly connected to the bottom of the porous body can be utilized. Or a pump, either connected directly to the porous body, or connected to a process vessel housing the chuck and workpiece, can be used to evacuate air from the porous body and create the desired vacuum. [0012] In another aspect of the present invention, the chuck includes a body for supporting a workpiece for processing. The body includes either a plurality of openings that extend through the body or a channel formed in the surface of the body. A compressible corrosion resistant member is attached to the outer periphery of the body. Alternatively, a retainer may be removably connected to an outer edge of the body. The compressible corrosion resistant member is attached to the retainer. Means for evacuating air (or other gases) from the openings or the channel is provided as described above to create a vacuum, securing the workpiece to the chuck and leaving the entire back side of the workpiece exposed for thinning or other processing. [0013] In yet another aspect of the invention, the chuck is comprised of an upper body removeably connected to a lower body. A cavity or opening is formed between the upper and lower bodies. At least two openings, and preferably a plurality of openings, extend through the upper body of the chuck and is in fluid communication with the cavity. A compressible corrosion resistant member is attached to the upper body at its outer periphery. The chuck is provided with means for evacuating gas from the cavity and the openings to create a vacuum (as described in the preceeding paragraphs). As a result of the vacuum, the workpiece is drawn towards the upper body and forms a seal with the compressible member. This seal protects microelectronic components formed on the device side of the workpiece from potentially damaging process fluids, resulting in improved manufacturing efficiencies. [0014] Any of the described aspects of the invention may be combined and/or repeated one or more times to achieve optimal results. The invention resides as well in sub-combinations of the aspects described. These and other objects, features and advantages of this invention are evident from the following description of preferred embodiments of this invention, with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a cross-sectional view of an embodiment of the present invention. [0016] FIG. 2 is a partial, enlarged view of FIG. 1, showing a compressible member shaped generally as a modified O-ring gasket. [0017] FIG. 3 is a partial, enlarged, cross-sectional view of the present invention, showing an alternate embodiment of the present invention where a compressible member is shaped generally as a hoop gasket. [0018] FIG. 4 is a partial, enlarged view of FIG. 1, showing the arrangement of a valve, porous body and retainer. [0019] FIG. 5 is a cross-sectional view of an embodiment of the present invention. [0020] FIG. 6 is a partial, enlarged view of FIG. 5, showing a compressible member shaped generally as a tapered gasket. Continue reading... Full patent description for Apparatus for use in processing a semiconductor workpiece Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Apparatus for use in processing a semiconductor workpiece patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Apparatus for use in processing a semiconductor workpiece or other areas of interest. ### Previous Patent Application: Edge buster series round blade sharpener and the edge tracker sharpener Next Patent Application: Tool for machining surfaces, edge areas and contours Industry Class: Abrading ### FreshPatents.com Support Thank you for viewing the Apparatus for use in processing a semiconductor workpiece patent info. 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