Spatially resolved fluorine actinometry

A method has been developed to obtain spatially resolved optical emission s pectra. This method is used ina diagnostic known as actinometry, where the relative concentration of fluorine can be obtained by examining the ratio o f two spectral lines having similar excitation thresholds and excitation cr oss sections. Generally, the etch rate of silicon is correlated to the conc entration of fluorine. In this modified actinometry method, radial emissivi ty profiles of the discharge are obtained 1 cm above the wafer surface by u sing a rotating stage to capture small wedges of light from the etching dis charge, and analyzing these wedges using a regularized reconstruction algor ithm. The relative fluorine concentration is obtained by comparing the rati o of a fluorine (703.75 nm) to argon (750.39 nm) emission line. The atomic fluorine radial profiles correlate to hard masked silicon etch radial profi les processed in a Lam TCP 9400 SE inductively coupled plasma processing to ol using an SF6/Ar chemistry. Fluorine loading on the radial fluorine conce ntration profile over the wafer surface was investigated and found to affec t the radial actinometry profile. (C) 1999 American Vacuum Society. [S0734- 2101(99)04105-6].