Massive sampling involves taking and processing a massive number of measurements to reveal otherwise hidden process signatures or excursions from process equipment tools or the previous process step. Such cross-wafer variations can have huge impact on yields.
The animation example here shows the benefit of massive sampling over more limited hotspot sampling. The sparse sampling map on the left reveals no apparent signature. But as we increase the number of sampling locations, we see one clearly emerge. You can see that four areas of the wafer are darker than the others. The degree of coloration indicates the degree to which the measurement taken at that spot deviates from the desired value. This impact on the process yield would not have been detected from sparse sampling. In this example, as the number of sampling locations grows, the map reveals a signature that corresponds with a UV cure chamber.
The challenge in massive sampling is to obtain a large number of precise measurements and do it fast. The new Applied PROVision™ ebeam inspection system addresses this challenge, revealing process variation signatures in a matter of minutes, which makes it valuable for real-time process monitoring. The signature itself is helpful in analyzing possible causes of the problem, and expediting determination of the fundamental root cause, which in turn avoids further yield loss and saves on production costs.