DIAGNOSTICS AND CONTROL OF RADIOFREQUENCY GLOW-DISCHARGE

The diagnostics of 13.56 MHz planar radio-frequency (rf) plasma were carried out using spatially resolved optical emission spectroscopy between the parallel electrodes. Plasma sheath thickness d evaluated from the optical emission profiles depends on gas pressure P, and a relationship of P n d = const, was obtained for CH 4, CF 4, and 0 2 plasmas with n ≤ 1/3, and for He and Ar plasmas with n ≤ 1/2. The etching rate and the etching profile of silicon in CF 4 plasma were also examined as a function of gas pressure. A novel technique for controlling rf plasmas using the optical sheath thickness and maximum optical emission intensity is presented. This technique was applied to dry etching of silicon in CF 4 plasma. When this novel control technique was used, the deviation in the etched depth for a constant etching time became smaller than that obtained using conventional power control methods. © 1994, American Vacuum Society. All rights reserved.