15min:

PATRICK J. MCCANN, I-NA CHAO AND KHOSROW NAMJOU, School of Electrical and Computer Engineering, 202 West Boyd Street, Room 219, University of Oklahoma, Norman, OK 73019.

This talk will describe the recent development of a user-friendly mid-IR laser spectrometer, one that does not need liquid nitrogen refills, and its use in the measurement of carbonyl fluoride (COF₂). COF₂ is a reaction product that is formed during fluorocarbon plasma etching of oxide insulators. Its measurement can provide etching endpoint detection information for high yield semiconductor manufacturing. A IV-VI semiconductor mid-IR laser with single mode emission in the 5.2 micron spectral range was selected to probe the R-branch of the ₁ band of COF₂. Individual rovibrational lines for COF₂ as well as an H₂O line at 1955.0 cm^-1 were easily resolved with a spectral resolution of better than 0.005 cm^-1 using second harmonic detection. Gas samples containing COF₂ were generated by burning Teflon (PTFE) with a propone torch and collected into a 10 cm long gas cell equipped with CaF₂ windows held at a pressure of 200 Torr. COF₂ concentration values higher than 200 ppm were measured using this setup, which had a minimum detection sensitivity of about 50 ppm. In addition to obtaining laser absorption spectra between 1953.5 cm^-1 and 1956.0 cm^-1, concentration values for both COF₂ and H₂O were obtained every 100 msec. Exponential fits to the data showed that both COF₂ and H₂O molecules had lifetimes of about 12 minutes suggesting that they react with each other to form HF and CO₂.