Transistors are formed near the silicon wafer surface.
To ensure that each transistor operates independently, it is necessary to prevent interference with other neighboring transistors.
Therefore, the regions where transistors are to be formed are isolated. There are a number of methods for this isolation.
The technique introduced here is called STI (Shallow Trench Isolation).
First a silicon oxide film is formed by oxidizing a silicon wafer, and then a silicon nitride film is formed using the CVD method.
Using the resist pattern as a mask, shallow trenches are cut by etching the silicon nitride film, silicon oxide film and silicon wafer.
After trenches are cut, the resist pattern is removed.
The surface is polished to remove the excess silicon oxide film, and the silicon oxide film is left only in the trenches.
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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