Abstract:
A testing device for semiconductor components and a method of making the device is described. The testing device includes a support structure having an outer edge, and an adhesive film disposed on the support structure to hold a semiconductor wafer in position on the support structure so that neither the adhesive film nor the semiconductor wafer extends beyond the outer edge of the support structure.

Description:
FIELD OF THE INVENTION 
     This invention pertains to a testing device for semiconductor components and a method of using the device. More particularly, the inventive device that may be used to hold the wafer during processing is utilized to test the resulting wafer for viability. 
     BACKGROUND OF THE INVENTION 
     To improve the performance of semiconductor devices, particularly those devices with silicon support structures, support structures have conventionally been thinned using a chemical and mechanical polishing technique. Support structures may be thinned down to a thickness of as low as 25 μm to improve the “on” resistance; however, such thin wafers are quite fragile and susceptible to both warpage and breakage. To combat damage to the thin wafers, wafer holders were developed to transport and process the thin support structures. One type of wafer holder includes a support, and a ring that attaches to the support to hold the wafer in position. The wafer is aligned in the support after the semiconductor support structure is thinned and is further aligned once placed onto a probe chuck. 
     Accordingly, it would be advantageous to have a wafer holder that accurately aligns a wafer during the thinning process and that may be used to conduct reliable conductivity tests on the finished wafer. It would be a further advantage to provide an adhesive means for aligning the wafer on the holder in a simple and reliable manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which: 
     FIG. 1 is an enlarged isometric view of an apparatus according to the present invention; and 
     FIG. 2 is a cross sectional view of the apparatus of FIG. 1 taken along lines  1 — 1 . 
     FIG. 3 is a cross sectional view of the vacuum chuck for receiving support structure shown in FIG.  1 . 
    
    
     For simplicity and clarity of illustration, the figures illustrate the general invention, and descriptions and details of well-known features and techniques are omitted to avoid unnecessarily drawn to scale, and the same reference numerals in different figures denote the same elements. It is further understood that the embodiments of the invention described herein are capable of being manufactured or operated in other orientations than described or illustrated herein. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The testing device  10  according to the invention comprises a support structure  20  that includes a mesh material layer  25  disposed between an adhesive film  30  and the support structure  20 . The testing device  10  may be formed to fit any semiconductor substrate  50  used in the industry, but preferably exhibits a circular shape. The testing device  10  is especially effective for testing semiconductor substrates  50  that are less than about 250 μm thick. 
     Support structure  20  for example, can be fabricated from a material that is electrically conductive such as aluminum, aluminum alloy, nickel, platinum, stainless steel, titanium, copper, or gold. It is also possible to form support structure  20  from a non-conductive material such as quartz, “Delrin”, or “Teflon”. “Delrin” and “Teflon” are polymer compounds used regularly in the semiconductor industry and are registered trademarks of E. I. Du Pont De Nemours and Company of Wilmington, Del. It is also possible to plate a portion of support structure  20  using one of the above mentioned materials. If a portion of the support structure  20  or the structure  20  itself is formed of a nonconductive material, conductive plugs or portions are preferably present to provide a conductive path. 
     In a preferred embodiment, the support structure includes two conductive areas, an outer conductive area  24  and an inner conductive area  26 , separated by the mesh cavity  22  that may be made of either a conductive or nonconductive material. Preferably, areas  24  and  26  are made of a metal or metal alloy. In another embodiment of the device, both areas  24 , and  26  may be made of a nonconductive material such as plastic, and conductive plugs may be provided in areas  24  and  26  to form a conductive path between the support structure  20  and the wafer  50  being tested. 
     Support structure  20  can be formed to have a recessed portion  22  that receives and supports a porous surface-texturized sheet  25 . As illustrated in FIG. 1, the sheet  25  is supported in the recessed cavity  22  on the support  20 . A non-porous, air-impermeable, thin flexible sheet, or adhesive film  30  covers the fabric sheet  25  and extends beyond the perimeter of the sheet  25 . It is essential that the adhesive film  30  not extend beyond a conductive area  24  located on the perimeter of the support structure  20  in order to form a conductive path between the support structure  20  and the semiconductor dies on the wafer  50  to be tested. The selected diameter of the film  30  is dependent on the diameter of the wafer  50  that is supported on the structure  20 . It is further preferred that the adhesive film  30  have a top surface that is substantially planar with a top surface of the conductive areas of the support structure  20 . 
     The marginal edges of adhesive film  30  are attached to the support structure  20  by any suitable means as, for example, by use of an adhesive, such as a pressure sensitive adhesive, not shown, or simply by non-adhesive frictional and interfacial forces between a smooth portion of the base member and the marginal edges of film  30 , to provide a sealing engagement between the support structure  20  and film  30  along the marginal edges, or perimeter, thereof. In a preferred embodiment, the adhesive film is attached to the support structure  20  by means of a pressure sensitive adhesive that is provided in a groove or glue cavity  32  along the perimeter of the recessed cavity  22 . 
     As noted above, flexible sheet  25  that is sandwiched between the adhesive film  30  and support structure  20 , is porous, or permeable to allow for the passage of air through. Thus, a vacuum produced anywhere on sheet  25  is transmitted through to the adhesive film  30  supported thereon. As shown in the figures, flexible sheet  25  is adapted for connection to a low air pressure, or vacuum, source through an opening or a plurality of openings  40  formed in the support structure  20 . 
     The flexible sheet  25  includes an array of fiber crossover points and spaces between the crossovers. As a result, there is essentially point contact with the support structure  20  upon which the flexible sheet is supported, and with the adhesive film  30  supported thereby. The effect of this arrangement is to allow for an easy distribution of a vacuum through the entire surface of the fabric sheet  25 , even though the sheet  25  appears to lie flat on the support structure  20 . The sheet  25  may be made of either conductive or nonconductive material, such as metallized fiber or fabric, provided the fabric is porous to allow for the drawing of air through it. 
     A vacuum chuck, or table,  42  may be used to connect the openings  40  to a vacuum source as is conveniently known in the art. All illustrated, a chuck  42  includes vertical walls  44  which define a recess  46  in the upper face thereof. Downwardly extending walls  48  on the support structure  20  surround the walls  44  of the chuck when the support structure is positioned on the chuck, and a substantially fluid tight chamber is defined between the bottom of the support structure  20  and recess  46  in the chuck  42 . A opening  43  in the vacuum chuck is provided for connection of the recess  46  to a vacuum, or low pressure, source through a control valve  54 . Low pressure in the chamber between the chuck  42  and support structure  20  is communicated through the opening  40  in the support structure  20  and thus through the permeable, or porous, texturized fabric sheet  25  to the impermeable adhesive film  30  to draw portions of the film  30  into crevices, or interstices, in the upper face of the texturized fabric sheet  25 . 
     The adhesive film  30  may comprise, for example, an elastomeric member having a smooth upper face to provide for high interfacial retention forces between the film  30  and the device, such as chip on the wafer  50 , that is supported on the film. The selected width of the film  30  is relative to the weight of the wafer  50  to be supported on the support structure  20 . Interfacial retention forces may be increased, if desired, by use of an adhesive, such as a pressure sensitive adhesive, not shown, at the upper face of the film  30 . For decreased interfacial retention forces, a film  30  having a texturized upper face may be used. In any event, interfacial retention forces are provided for securely holding the device on the film  30  such that the device can not be readily or conveniently removed using conventional tweezers or vacuum techniques while the film  30  is in a flat position as illustrated in FIG.  2 . 
     To facilitate removal of the wafer from the film  30 , surface contact between the film  30  and device is reduced by drawing portions of the film  30  into crevices, or interstices, in the upper face of texturized fabric sheet  25  by application of a vacuum thereto. Texturized sheet  25  simply may comprise a woven, knit, braid, lace, knit-sew, or like fabric made of natural or synthetic “over and under” crossing fibers or yarns, which fabric is inherently porous and has a texturized surface. By reducing the magnitude of the force by which the wafer is attached to the film  30 , the wafer the chip, is readily removable from the sheet as by use of a vacuum wand, tweezer, or the like. 
     Support structure  20  can be further detailed to have an alignment flat  28  used to align a flat  29  of semiconductor substrate  50  to the alignment flat  28  of support structure  20 . When semiconductor substrate  50  is in support structure  20 , a vacuum pressure can be applied to the backside of semiconductor substrate  50  through vacuum openings  41 . 
     One method for using the testing device  10  is to align a wafer  50  to the alignment flat  28  and vacuum pressure is then applied through vacuum openings  40  to ensure that the top surface of wafer  50  is planar. The wafer  50  may then be thinned down and further processed during an assembly process until the wafer  50  is ready for electrical testing. To assure electrical contact between wafer  50  and the conductive area  24  during testing a vacuum or low pressure source may be applied through source  44  as illustrated in FIG. 3. A bias or ground potential is placed on the backside of semiconductor substrate  50  and the semiconductor devices on the topside of wafer  50  can then be probed. After electrical testing, the testing device can be used to transport the wafer  50  to the next fabrication process, which may include wafer bonding or final assembly. 
     By now it should be appreciated that the present invention provides a testing device  10  for the transporting, processing, or electrically testing of a thin semiconductor substrate  50 . An adhesive film  30  is disposed on a textured sheet  25  and does not extend beyond the perimeter of the sheet  20 . Thus an electrically conductive path between the support structure  20  and devices on the wafer  50  is provided to enable a bias potential to the chips during electrical testing. The testing device  10  offers a significantly improved method for processing and testing thin wafers that will significantly improve the yield of active devices produced. 
     Although the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the spirit or scope of the invention. For instance, the numerous details set forth herein such as, for example, material compositions, chemical concentrations, and layer thicknesses are provided to facilitate the understanding of the invention and are not provided to limit the scope of the invention. Accordingly, the disclosure of embodiments of the invention is intended to be illustrative of the scope of the invention and is not intended to be limiting. It is intended that the scope of the invention shall be limited only to the extent required by the appended claims.