An oxide film is formed only at side wall portions of gates for LDD formation (above mentioned) and salicidation (described below) of gates, sources, and drains.
Side wall oxide film: A silicon oxide film is formed on the entire wafer surface.
Side wall etching: Anisotropic etching (vertical direction) is performed on the oxide film so that the oxide film may be left only on gate side walls.
If anisotropic etching is performed on the oxide film formed over the entire surface, it is possible to leave an oxide film only at the gate side walls. This sort of etching which does not use a resist pattern is called etching back.
FEOL (Front End of Line: substrate process, the first half of wafer processing)
| 1. Isolation | 2. Well and channel formation | 3. Gate oxidation and gate formation
| 4. LDD formation | 5. Side wall spacers | 6. Source/drain | 7. Silicide | 8. Dielectric film |
9. Contact holes |
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