Reaction mechanism of TEOS and O3 atmospheric pressure CVD

The reaction mechanism of TEOS/O₃ atmospheric pressure CVD was studied for dependence of deposition rate on base material, and for step coverage. Base material dependence of TEOS/USG, PSG, BSG and BPSG (on silicon and thermal oxide) was studied. Lower deposition rates and poorer quality of TEOS/USG films have been obtained on more hydrophilic substrate surface with high ozone concentration. The mechanism was discussed in terms of hydrophile of substrate surface and deposition gases. To eliminate surface effects of thermal oxide, plasma treatment in nitrogen at 350°C for 1 min was effective. So the substrate surface plays very important role for TEOS/O₃ APCVD. In OMCTS and HMDS/USG depositions there was strong base material dependence compared with TEOS. TEOS/USG and BSG films showed base material dependence but PSG and BPSG films did not. The former showed superior step coverage, but PSG showed some overhang step coverage and BPSG showed good step coverage. TEOS is hydrophobic, TMOP is hydrophilic and TMB is not hydrophilic, so USG and BSG films showed low deposition rates on hydrophilic thermal oxide surface. Overhang step coverage in PSG deposition can be attributed to partial gas phase reaction, which is also a cause of zero base material dependence