Use of Virtual Metrology for in-situ Visualization of Thermal Uniformity and Handoff Adjustment in RTP Critical Anneals

Applied materials rapid thermal processing (RTP) systems are unique in providing high resolution process data particularly wafer rotation angle and wafer rotation speed as a function of time. This work explores how this information can be used to predict on-wafer process results using an advanced analysis package known as WISR (wafer interdiction and scrap reduction). WISR is an advanced process control platform for the collection, storage, visualization, and analysis of process parameters from production tools. One of the main analysis features of WISR is the ability to create virtual sensors. Virtual sensors are calculated parameters derived from physical sensors that can provide real-time and statistical representation of process health. The focus of this paper is the ability of WISR to transform time series chamber parameters from the pyrometers and the magnetic levitation controller into thermal wafer images at any time during the recipe execution and provide wafer-to-wafer handoff correction. These abilities constitute a virtual sensor module in WISR known as Virtual metrology (VM). We describe the implementation of the VM-analysis and show how temperature maps and handoff corrections correlate with offline metrology in RTP critical anneals. This is an innovative new method to significantly reduce wafer processing errors, enhance yield, and minimize production cost.