New sensing wafer technique for artifact-free transient temperature measurements in PEB processes

Abstract

A system for monitoring the transient and steady state temperature profiles during the deep UV (DUV) post exposure bake (PEB) is described. The system, called Accura°C, consists of a sensor wafer, a wireless electronics unit and software on a laptop computer. To monitor temperature platinum resistance temperature detectors (RTDs) are embedded into silicon wafers. A flexible high temperature printed circuit (PC) ribbon cable connects the wireless electronics unit to the wafer. The system robot moves both the sensor wafer and electronics unit through the system. Communication between the electronics unit and a laptop computer is accomplished by a Bluetooth RF link. The RF link enables the laptop computer to analyze the temperature measurements in real time. The rechargeable batteries in the electronics unit allow detailed examination of all process chambers. Further the long operating time and real time data stream provide for bake chamber optimization such as tuning. The sensor integration into the wafer provides accurate, artifact free measurements of the rapid temperature changes during PEB ramps.