ELECTRON AND CHEMICAL KINETICS IN THE LOW-PRESSURE RF DISCHARGE ETCHING OF SILICON IN SF6.

Monte Carlo simulation and Boltzmann equation solutions have been used to study the electron kinetics. All electronic excitation of SF//6 is assumed to be dissociative in analogy with the known product channels in ionization and multiphoton dissociation. The electric field to gas density ratios are high (E/n greater than equivalent to 1000 Td, where 1 Td equals 1 multiplied by 10** minus **1**7 V** minus cm**2) in low-pressure (p greater than 0. 3 torr) radio-frequency (RF) discharges. At these high E/n values, the electron energy relaxation time is much shorter than the 74-ns period at 13. 56 MHz. A rate equation model has been used to study the chemical kinetic processes. Electron-impact dissociation and ionization are the dominant sources of chemically active species. An electron density of 1 multiplied by 10**8 cm** minus **3 is estimated from the known average values of E/n and the discharge input power. Two limiting cases are studied for the positive and negative ion diffusion losses: a) trapped negative ions and positive ion loss at the ambipolar diffusion rate; and b) positive and negative ion losses at the free diffusion rates.