Dicing Improvements: Yield Enhancement, Throughput Increase and Die Size Reduction in M/A-COM's GaAs Fab

Robert Fox
M/A-COM : Tyco Electronics

A strong wafer dicing operation is vital to the manufacturing process. At the dicing stage the wafer has the highest value. Everyone is aware of the wafer and die yield for the lot and they are counting on the wafers to meet customer commitments. Unfortunately, the dicing process is not trivial with GaAs. Because it is so fragile, GaAs is very sensitive to changes in the dicing tools and to drifts in the dicing machinery. These issues had to be addressed in order to meet the fab-wide drives to increase wafer throughput and increase the die count per wafer.

Over the past year, many improvements have been made in the post-fab area of the Walker building to meet the challenge. Both the saw and scribe / break processes have been streamlined. New materials are being used to dice the wafers in both methods, providing greater speeds as well as reliability. As a result of improvements in the scribe and break operation, we have been able to cut the street size of most die over 50% -- greatly increasing the number of die per wafer. Optimization of the scribing parameters has lead to more predictable separation. There are limitations to the amount of the street reduction and throughput increase that is possible - and our biggest challenge now is to raise the capability of the processing tools to meet our needs. Alignment becomes critical at smaller street sizes, as well as the ability to keep the breaks and chips within the narrow streets. This paper details these processing hindrances as well as the improvements that have been made. In addition, ongoing work with tool designers is described and the opportunities for continuous improvement are presented.