HIGH-RESOLUTION INFRARED-SPECTROSCOPY APPLIED TO POWDER FORMATION, PLASMA TRANSPORT AND SURFACE PROCESSES

Infrared absorption spectroscopy using both a Fourier transform spectr ometer and a tunable diode laser arrangement has been performed to stu dy the growth of particles in an rf (13.56 MHz) plasma at pressures fr om 25 to 200 mTorr in mixtures of CF4, CF2Cl2 and CHF3 with argon. A p lanar configuration has been used, with a silicon wafer on the powered electrode. Absorption bands at 750-1300 cm(-1) have been found and at tributed to C-F, Si-F, C-Cl and Si-C absorption. Furthermore continuou s extinction due to Rayleigh and Mie scattering has been observed. The CF2 concentration appears to decrease strongly when powder growth beg ins. The SiF4 concentration shows a maximum then. Considering all thes e results, we arrive at the conclusion that particle growth is initiat ed by micromasking at the Si surface combined with a highly directiona l etching process. Due to residual isotropic etching the particles are released from the surface and enter the plasma. Furthermore, it has b een found that the powder production continues and even accelerates af ter the freon how is stopped, due to sputtering of remaining structure s on the surface.