Fab Area

Chemical Reaction

Reaction Equation(s)

Remarks

Epitaxy

Hydrogen reaction of SiCl₄ to deposit a silicon epitaxial layer

SiCl₄ + 2 H₂ → Si + 4 HCl

reversible process - Si may also be etched using HCl

Epitaxy

Silane (SiH₄) reaction to deposit a silicon epitaxial layer

SiH₄ → Si + 2H₂

can be done at a relatively lower temperature

SiO₂ Thermal Oxidation

Silicon dioxide (SiO₂) deposition through dry thermal oxidation

Si + O₂ → SiO₂

deposition temperature usually bet. 700-1300 deg C

SiO₂ Thermal Oxidation

Silicon dioxide (SiO₂) deposition through wet thermal oxidation

Si + H₂O → SiO₂ + 2H₂

deposition temperature usually bet. 700-1300 deg C

SiO₂ CVD

SiO₂ deposition through CVD reaction between silane (SiH₄) and O₂

SiH₄ + O₂ → SiO₂ + 2H₂

low-temperature deposition process

SiO₂ CVD

SiO₂ deposition through PECVD reaction between silane (SiH₄) and N₂O

SiH₄ + 2N₂O → SiO₂ + 2N₂ + 2H₂

deposition temperature usually bet. 200-400 deg C

SiO₂ CVD

SiO₂ deposition through LPCVD reaction between dichlorosilane (SiH₂Cl₂) and N₂O

SiH₂Cl₂ + 2 N₂O → SiO₂ + 2N₂ + 2HCl

high deposition temperature of almost 900 deg C

Si₃N₄ CVD

Silicon nitride (Si₃N₄) deposition through LPCVD reaction between dichlorosilane (SiCl₂H₂) and ammonia (NH₃)

3 SiCl₂H₂ + 4 NH₃ → Si₃N₄ + 6H₂ + 6 HCl

deposition temperature usually bet. 700-800 deg C

Si₃N₄ CVD

Si₃N₄ deposition through PECVD reaction between silane (SiH₄) and NH₃

SiH₄ +  NH₃ → Si_xN_yH_z+ H₂

deposition temperature usually bet. 200-350 deg C

Poly-Si CVD

Polysilicon deposition through LPCVD reactions of SiH₄

SiH₄ + surface site → SiH₄ (adsorbed);

SiH₄ (adsorbed) →  SiH₂ +  H₂; SiH₂ → Si +H₂

deposition temperature usually bet. 580-650 deg C;

over-all reaction:

SiH₄ → Si +2H₂

W CVD

Tungsten (W) deposition through CVD reaction between WF₆ and Si

WF₆ + 3 Si  → 2W + 3 SiF₄

deposition done between 200-400 deg C

W CVD

Tungsten (W) deposition through CVD reaction between WF₆ and H

WF₆ + 3 H₂  → W + 6HF

deposition done between 250-500 deg C

WSi₂ CVD

Tungsten silicide (WSi₂) deposition through CVD reaction between WF₆ and SiH₄

WF₆ + 2 SiH₄ +  → WSi₂ + 6HF + H₂

deposition must be done at an elevated temperature

TiSi₂ CVD

Titanium silicide (TiSi₂) deposition through CVD reaction between TiCl₄ and SiH₄

TiCl₄ + 2 SiH₄ +  → TiSi₂ + 4HCl + 2H₂

deposition must be done at an elevated temperature

Si Wet Etching

Removal of Si through wet etching with HNO₃ and HF

Si +  HNO₃ + 6 HF → H₂SiF₆ + HNO₂ + H₂ + H₂O

acetic acid is preferred as a buffering agent

SiO₂ Wet Etching

Removal of SiO₂ through wet etching with HF

SiO₂+  6 HF → SiF₆ + H₂ + 2H₂O

use at room temp to prevent HF attack of Si