Perhaps the most critical control element for exposures at 193 nm and below is the Post Exposure Bake (PEB) cycle. Bake temperature is a well known variable with sensitivity varying at more than 3 nm for each degree centigrade of variation across the wafer. However what are the real control variables in the bake and what critical device elements are most strongly influenced?
Arrhenius’s Law states that increasing the temperature frequently causes a marked increase in the rate of a reaction and that reactions exhibit a threshold initiation temperature. Thermal uniformity, flow and hysteresis on the plate often prove to be more a factor in feature definition than the target temperature.
LithoWorks PEB is the only software capable of importing both thermal-sensor and critical feature metrology. Align and correlate individual features or derived variants such as rise-time, energy delivered and thermal flow to CD, Side-wall-angle, film thickness, etc.