Plasma Etching Of Sio_2 Using Remote-type Pin-to-plate Dielectric Barrier Discharge

摘要

Atmospheric pressure plasma etching of SiO_2 was examined using a modified remote-type dielectric barrier discharge (DBD), called "pin-to-plate DBD." The effect of adding four gases CF_4, C_4F_8, O_2, and Ar to the base gas mixture containing N_2 (60 slm) (slm denotes standard liters per minute)/NF_3 (600 SCCM) (SCCM denotes cubic centimeter per minute at STP) on the SiO_2 etch characteristics was investigated. The results showed that the SiO_2 etch rate decreased continuously with increasing C_4F_8 (200-800 SCCM) addition, whereas the SiO_2 etch rate increased with increasing CF_4 (1-10 slm) addition up to 7 slm CF_4. This increase in the SiO_2 etch rate up to 7 slm CF_4 was attributed to the effective removal of Si in SiO_2 by F atoms through the removal of oxygen in SiO_2 by carbon in the CF_X in the plasma. However, the decrease in SiO_2 etch rate with further increases in CF_4 flow rate above 7 slm was attributed to the formation of a thick C-F polymer layer on the SiO_2 surface. A SiO_2 etch rate of approximately 243 nm/min was obtained with a gas mixture of N_2 (60 slm)/NF_3 (600 SCCM)/CF_4 (7 slm), and an input voltage and operating frequency to the source of 10 kV and 30 kHz, respectively. The addition of 200 SCCM Ar to the above gas mixture increased the SiO_2 etch rate to approximately 263 nm/min. This is possibly due to the increased ionization and dissociation of reactive species through penning ionization of Ar.