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FEOL (Front End of Line: substrate process, the first half of wafer processing)
1. Isolation

How a semiconductor wafer is made

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).

1-1. Oxide + nitride film growth

Oxide + nitride film growth

First a silicon oxide film is formed by oxidizing a silicon wafer, and then a silicon nitride film is formed using the CVD method.


1-2. Resist pattern formation

Resist pattern formation

A resist pattern is formed.


1-3. Shallow trench formation

Shallow trench formation

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.


1-4. Buried oxide film growth

Buried oxide film growth

Trenches are filled by forming a thick silicon oxide film using the CVD method.


1-5. Buried oxide film polishing

Buried oxide film polishing

The surface is polished to remove the excess silicon oxide film, and the silicon oxide film is left only in the trenches.


1-6. Nitride film removal

Nitride film removal

The silicon nitride film is removed using chemical treatment.

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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