Passing the Test

With so many different part numbers running through a production facility, it can be difficult to know how well a process is running. One way that integrated circuit (IC) manufacturers solve this issue is to measure specific coupons (test structures) on a parametric die that is placed on each wafer in addition to special parametric wafers. Probe stations can be set up at specific process steps to test the coupons and dies and provide feedback about the condition of the process. The accumulation of process effects on a design can be measured at final test and should correlate with a specific first-pass yield (FPY).

This coupon methodology can also be applied to printed circuit board (PCB) manufacturing. There are many parametric analysis and characterization coupons available for PCBs, and they form an important part of the quality assessment process. This paper discusses six process coupon systems in detail, which cover reliability, end-product, work-in-process, and process parameter evaluations.