Development of a fiber optic chamber wall deposition sensor for plasma etchers

Summary form only given, as follows. The ability to monitor the deposition rates and layer thicknesses on the walls of integrated circuit etching chambers is helpful in developing efficient cleaning schedules and reducing etch tool down-time. Reliable wall sensors should indicate proper conditioning times after a clean and help warn of impending particulate formation as the film flakes off of the wall and deposits on the substrate, causing damage and reduced yields. A deposition sensor has been developed which consists of an unclad quartz optical fiber which is inserted into an etching plasma. Polymer deposition occurs on the fiber and the transmitted laser signal intensity through the fiber decreases due to attenuated total internal reflection (ATR). Experiments have shown that the signal intensity decreases during CHF/sub 3/ plasma exposure and returns to 30% of its initial value in an O/sub 2/ ashing plasma indicating that the decrease in intensity is caused partially by irreversible surface roughening and partly by ATR. Further analysis of the fiber samples by scanning electron microscopy is reported.