Types of CVD reactions

• Pyrolysis - thermal decomposition

• AB(g) ---> A(s) + B(g)

• ex: Sideposition from Silane at 65⁰C

• SiH₄(g) ---> Si(s) + 2H₂(g)

• use to deposit: Al, Ti, Pb , Mo, Fe, Ni, B, Zr , C, Si, Ge , SiO₂, Al₂O₃, MnO₂, BN, Si₃N₄, GaN , Si₁-xGex, . . .

Reduction

• often using H₂

• AX(g) + H₂(g) <===> A(s) + HX(g)

• often lower temperature than pyrolysis

• reversible => can use for cleaning to

• ex: Wdeposition at 30⁰C

• WF₆(g) + 3H₂(g) <===> W(s) + 6HF(g)

..........• use to deposit: Al, Ti, Sn , Ta, Nb , Cr, Mo, Fe, B, Si, Ge , TaB , TiB₂, SiO₂, BP, Nb₃Ge, Si1-xGex, . . .

Oxidation

• often using O₂

• AX(g) + O₂g) ---> AO(s) + [O]X(g)

• ex: SiO₂ deposition from silane and oxygen at 45⁰C (lower temp than thermal oxidation)

• SiH₄(g) + O₂(g) ---> SiO₂(s) + 2H₂(g)

• use to deposit: Al₂O₃, TiO₂, Ta₂O₅, SnO₂, ZnO , . . .