Thermal budget control for processes with spike-shaped temperature profiles: Application to rapid thermal annealing

Abstract

The spike-shaped temperature profile in thermal treatments is widely used in the IC industry for providing precise thermal budgets. This thermal budget control issue becomes more crucial as the technology node progressively shrinks. Therefore, rapid thermal processing (RTP), such as spike annealing has the ability to yield ultra-shallow junctions. 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, a novel methodology for designing a control system to provide a precise thermal budget is presented. By tuning controller parameters and designing the set-point profile, the method targets thermal budget indices instead of temperature servo control. Two types of controllers, PI and PI 2D, 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 that the simple PI controller performs well in spike RTP systems. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society