Combined Real‐Time and Run‐to‐Run Control of Etch Depth and Spatial Uniformity in Plasma Etching

Abstract

An approach for combined real‐time and run‐to‐run control is presented. Real‐time control is used to maintain plasma variables at desired set points by manipulating equipment settings. Run‐to‐run control compensates for long‐term drifts or sudden shift disturbances by suggesting new plasma set points to the real‐time controller. We demonstrate a reduction of variance in etch depth under closed‐loop feedback control of plasma variables. We also provide recent results of simultaneously controlling etch depth and spatial uniformity in reactive ion etching. Both wafer loading disturbances and oxygen leak disturbances are introduced to the process and compensated for by the integrated controller.