Thermal Budget Control for Rapid Thermal Processing Systems with Spike-Shaped Temperature Profile

Rapid thermal processing (RTP) systems with spike-shaped temperature profile is widely used in IC industry for providing precise thermal budgets. This thermal budget control issue gets more crucial as the technology node progressively shrinking. With its exceptionally stringent performance requirements (for example, high temperature uniformity and high temperature ramp-up/down rate), temperature control in RTP systems is a challenging task. In this study, we present the methodology of designing a control system for providing precise thermal budget. By tuning controller parameters and designing the setpoint profile, the method targets thermal budget indices instead of temperature servo control. Two types of controllers, PI and PI2D, are considered. Practical issues, such as the feasibility range for temperature ramp-up/down rate and the effect of model mismatch, are also discussed. The results show the simple PI controller performs well in spike RTP systems.