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FEOL (Front End of Line: substrate process, the first half of wafer processing)
5. Side wall spacers

How a semiconductor wafer is made

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.

5-1. Side wall oxide film growth

Side wall oxide film growth

A silicon oxide film is formed using the CVD method over the entire surface of the silicon wafer.


5-2. Side wall etching

Side wall etching

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.

Process Flow

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 |

BEOL (Back End of Line: interconnect process, the second half of wafer processing)
| 10. Metal-1 | 11. Metal-2 |

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