The ShimSert System (SS) was developed at the request of several clients to simplify the S3 (Spinning Shim System). This system joins the polyurethane poromeric material and the PET (PolyEthylene Terephthalate) material into a single part. While this still provides an even polish and stock removal by rotating the wafer in the template pocket,. it greatly simplifies the handling.
If a wafer is placed in a template and held in one position, more material will be removed from the outer edge where the velocity over the polishing pad is greater. This creates several problems including a possible "wedge" condition, roll off that may exceed the limits of the EE (Edge Exclusion) zone and heat problems across the surface where the outer edge has more heat generation.
The Spinning Shim System was invented to solve this problem and the ShimSert System was developed to simplify the handling. The SS allows the wafer to rotate in the template pocket as it is polished. This rotating action will provide a more even polish.
The system works by using a template designed for wafer spinning and inserting a shim made of PET (PolyEthylene Terephthalate) and of desired thickness to provide proper wafer protrusion. The shim is bonded to an insert made of a polyurethane poromeric material. This is placed in the pocket with the poromeric material face up in the template pocket. All materials are inserted in a wet condition to take advantage of the condition known as "water adhesion" to retain the wafer.
To achieve the proper water adhesion it is important that the user press the poromeric material into the pocket and remove all air pockets, bubbles, etc. and provide a flat surface for the wafer as this helps. retain the wafer in the pocket when the polishing head is lifted
Unlike competitor templates where distortions and air pockets can remain undetected, Semisurface templates are designed to allow the user to eliminate these problems at every step with careful application and observation by the user.
Advantages of the Semisurface Shimsert System:
Spinning wafers. Wafers that rotate within the pocket receive a more even polishing. It is easier to control the edge condition with an even polishing. Care must be taken to insure that the slurry is distributed fully across the polishing pad and with the wafer rotating within the rotating polish head an even finish can be applied.
Adjustable contour. Special PET designs can be provided to adjust the polishing to correct for cupping or bow as well as some edge conditions or desired special effects. These issues should be discussed with our engineering and development team.
Replace the ShimSert, not the template. Typically the template does not deteriorate, the wear is placed on the PET material and compression on the poromeric material which, as a single assembly, is easily replaced. Reports from users state that they have been able to make several hundred runs on Silicon without replacing the template and only replacing the insert.
Adjustable protrusion. One of the most important issues for achieving proper surface finish and preventing blow outs is wafer protrusion. With this system, various thickness PET material can be used to adjust the wafer protrusion. The inserts can be supplied in virtually any thickness required by bonding various thickness PET materials to the poromeric material to keep compression to a minimum.
Limitations. Due to the loss of one PET to PET interface with this system, there is a limitation on this design and it should only be used on applications where the polish time is less than 20 minutes. For applications requiring longer periods, please see the PadSert System.
- Wafer rotating provides a more even finish.
- The ShimSert System allows for maximum flexibility for wafer protrusion.
- Special contour issues can be addressed with this system.
- The costs can be very low by replacing the ShimSert, not the template .
- Costs per run can be a fraction of the cost of a conventional template.
- Reduces lost time for template replacement as well as polish head stocking requirements.