Packaging industry leading the way
A common topic of discussion on these pages and in the industry as a whole is the convergence of wafer processing and packaging technology. This is most clear inwafer-level packaging, where, for example, wafers are bumped to prepare them for connection to the next level of assembly.There is at least one other area, though, where we in the packaging world might actually be ahead of our colleagues in the wafer fab when it comes to processing wafers. With the intense focus on thin packaging, we are fast becoming the leading experts in handling of thin wafers.
In the wafer fab, the people and equipment have the luxury of dealing with "thick" wafers, because there is typically no reason to make a wafer any thinner for the front-end processes. Handling 300-mm wafers of any thickness is non-trivial, of course, but at least the wafer is a fairly rigid item at standard thicknesses.
Recently, thin packaging has been at the forefront of increasing the functional density of electronic products, whether it is stacked chips or packages in memory modules, or just very thin bare die in smart cards, for example. The burden of handling wafers as thin as 50 µm these days has fallen squarely in the packaging court.
The news is good though, with many recent technical developments to address these significant challenges. A recent MEPTEC symposium provided a forum for sharing this work, and I was quite impressed with the achievements. Engineers are doing extensive simulations of wafer bowing when handled by different designs of tooling, and there also are efforts to integrate equipment so that the handling is minimized.
There are many clever processes out there for thinning the wafers, and all of the sophisticated approaches include steps to remove damage from the back of the thinned wafers. This strengthens the wafers significantly. There also are strategies for using the thinning process to complete the singulation process after it has been diced partially through the thickness of the wafer. This eliminates the tricky process of fully dicing a very thin wafer. There are even new kinds of shipping containers with improved designs to protect thin wafers during severe drop tests.
By the year 2002, however, no one should be surprised that the packaging engineers out there can take on such challenges successfully.Maybe even the wafer fab engineers will recognize this now, as we are taking over in one of their areas of expertise!
Thanks for reading,
Jeffrey C. Demmin