LPCVD Technology for Oxides

Both undoped as well as doped oxides can be deposited using LPCVD. Undoped oxides are used as an insulator between multilevel metalization, implantation or diffusion mask, increase thermal oxide thickness for high voltage devices., P-doped is used as a multilevel metalization insulator, final passivation layer (prevents ionic diffusion), or as a gettering source. Either Silane or Dichlorosilane known as DCS {SiCl₂H₂} or Tetraethoxysilane known as TEOS {Si(OC₂H₅)₄} are used as silicon sources. The following reactions occur during undoped oxide deposition.

1. < 500°C
   Contain H₂O, SiH, and SiOH impurities
2.    ~900°C
   contains Cl
3. 650-750 °C
4. TEOS + Ozone (O₃)     ~400°C
   Ozone is more reactive and lowers deposition temperatures to ~400°C