Practical Fractional-Order Variable-Gain Super-Twisting Control with Application to Wafer Stages of Photolithography Systems

TL;DR

This paper introduces a practical fractional-order variable-gain super-twisting control algorithm to enhance wafer stage tracking in photolithography, reducing chattering, improving response, and compensating disturbances for semiconductor manufacturing.

Contribution

It proposes a novel fractional-order sliding surface and variable-gain super-twisting algorithm tailored for wafer stage control, with stability analysis and practical validation.

Findings

Enhanced tracking accuracy compared to conventional methods

Reduced chattering and overshoot in control responses

Effective disturbance compensation demonstrated in experiments

Abstract

In this paper, a practical fractional-order variable-gain super-twisting algorithm (PFVSTA) is proposed to improve the tracking performance of wafer stages for semiconductor manufacturing. Based on the sliding mode control (SMC), the proposed PFVSTA enhances the tracking performance from three aspects: 1) alleviating the chattering phenomenon via super-twisting algorithm and a novel fractional-order sliding surface~(FSS) design, 2) improving the dynamics of states on the sliding surface with fast response and small overshoots via the designed novel FSS and 3) compensating for disturbances via variable-gain control law. Based on practical conditions, this paper analyzes the stability of the controller and illustrates the theoretical principle to compensate for the uncertainties caused by accelerations. Moreover, numerical simulations prove the effectiveness of the proposed sliding surface and control scheme, and they are in agreement with the theoretical analysis. Finally, practice-based comparative experiments are conducted. The results show that the proposed PFVSTA can achieve much better tracking performance than the conventional methods from various perspectives.