Feed-Forward Run-to-Run Process Control Based on Device Array Density for LPCVD Furnace Processes

Furnace LPCVD processes have been used in Semiconductor Industry to enable high aspect ratio film deposition and for high throughput through batching of multiple lots and wafers in a single batch. Any typical wafer process will have varying levels aspect ratios or topography and each technology node will involve different device array densities due to different customer requirements. The high aspect ratio surface topography creates loading effect in the furnace that will cause thickness variation depending on the array density. This causes thickness variation when batching different density Product together. This loading effect also creates a need to segregate different array density wafers into unique processes with different levels of tuning to achieve good thickness control. But this segregation is not efficient in high volume manufacturing due to batch size limitations. In this paper, we have presented a new feed forward R2R control method based on device array density that improves thickness performance even with different density product batched together which consequently improves yield and reduces cost of operation through better throughput.