Processing control for 0.25 μm x‐ray exposures of commercially available resists: The potential for adaptive control

The processing of chemically amplified resists to yield 0.25 μm structures requires control of a number of key parameters. Some of these may be at the limits of the control range or at the limits of achievable uniformity. Where it may not be possible to improve the control or the uniformity, it may be possible to use adaptive control to compensate. The focus of this article is to explore what is needed for adaptive control with two commercial x‐ray resists, Shipley SAL 605 (negative tone) and Hoechst AZ PF‐514 (positive tone) and to explore the feasibility of adaptive control with the SAL 605 resist. Statistical optimization has been used previously to provide robust process latitude by focusing on the preexposure bake temperature and time, the x‐ray dose, and the postexposure bake temperature and time. To determine the required control and the slope of the linewidth change with the change in each variable, a statistical model of the response surface was constructed. The statistical results and new work w...