Coherence Analysis of Wafer Process Measurements from Chamber and Optical Emission Spectrum : APC: Advanced Process Control

Coherency analysis is adopted in this paper to examine the linear dependence between measurements of three processing parameters during wafer fabrication process. They are power, pressure and voltage measurements and three channels from optical emission spectrum data. The measurement data were divided into consecutive short data segments to provide time-stamped coherence signatures. Our results observe significant linear dependence appeared in multiple harmonic frequencies. The linear dependence appears in the beginning of the processing step and continues toward the end. The verified linear relationship between process parameters sheds the light for redundancy reduction and more compact data representation.