Critical dimension management of photo resister by lens heating compensation and statistical process control

Critical dimension (CD) control of each photolithography and etching layer of the electronic devices plays an important role in creating the reliable and high yielding integrated circuits (ICs) from the semiconductor manufacturing processes. A statistical process control (SPC) method is applied to monitor the in-line product CD performance and send alarm messages immediately to the sponsors who would take emergent actions if some abnormal events occur. One of the abnormal events is a CD value out of control due to focus drift that results from the lens heating effect during photoresist exposure. A lens focus cooling curve compensation model is proposed to reduce the lens heating effect so that the CD can be controlled well.