Automation of wafer handling in legacy semiconductor fab-a true cultural change

Abstract

When yield analysis revealed extensive die losses associated with wafer scratches, our fab management commissioned a comprehensive program to completely eliminate manual handling of wafers during manufacturing. This experience constituted a true cultural change for our legacy fab, which throughout a 15-year history had excelled at low cost, low cycle time manufacturing but had neglected fundamental improvements in wafer handing automation. This paper describes a team approach to quantifying the components of scratch associated yield loss, planning for remedial actions, and completing the task. Key ingredients for success included achieving buy-in at all levels of fab operations, effectively mobilizing fab resources and developing a group of indices to measure progress. As a result of these actions, our phase-1 program eliminated all manual wafer handling in our photolithography and contiguous plasma etch areas within a seven month period, reducing scratches on resist coated wafers by 83% and setting the stage for beginning additional phases of work to extend the automation to the rest of the fab.