Control of Plasma Etching of Semiconductor Surfaces

Abstract

The current semiconductor device manufacturing requires more strict control of plasma etching. In this research, plasma etching was investigated through gas phase characterization and interface reactions. Hydrogen and nitrogen were added to Ar plasmas to manipulate the electro-physical properties that were measured by a Langmuir probe system. Hydrogen addition modified the EEDF (electron energy distribution function) by increasing the electrons in high energy range. Adding N2 formed a strong bi-Maxwellian distribution. Gas addition caused the transition between ohmic and stochastic heating. Ar-CH4-H2 and Ar-N2-H2 plasmas were also tested. Hydrogen atom beam was used on porous silicon dioxide based low-k films to remove silanol groups that were generated due to the damage of films during pattern transfer. At H2 atom beam process at 150 C moved close to 60% silanol groups were removed in less than 3 min with an etching rate of 15 A/min. The apparent activation energy was 2.4 kcal/mol. Hydrogen atoms reacted with Si-O-Si and methyl groups. The etching mechanisms of CH4/H2/Ar plasma for InP were analyzed by a beam reactor system. Sputtering yield was measured, threshold energy was approximately 60 eV. Inert ion beam assisted chemical reactions gave higher etching rate. The CH4 concentration had no strong effect on etching rate after 5%. Etching rate was not sensitive to temperature up to 150 C. The adsorption of methyl groups to the surface was proposed as rate limiting step. Chemical reaction effectively reduced the surface roughness.