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

How a semiconductor wafer is made

Silicide (compound of silicon with metal) is formed on gates (polysilicon), sources and drains (Si wafer) as three MOS transistor electrodes in order to reduce contact resistance to metal wiring layers to be formed later. This silicide formation also has the effect of lowering the resistance of each electrode.

Salicidation: A cobalt film is removed selectively by chemical etching (Self aligned silicide).

7-1. Cobalt film deposition (sputtering)

Cobalt film deposition (sputtering)

A cobalt film is formed on the silicon wafer surface using the PVD method (sputtering). Metals other than cobalt used for silicide include nickel and titanium.


7-2. Cobalt silicide formation

Cobalt silicide formation

If a silicon wafer whose surface is coated with a cobalt film is heated, the part where the silicon and cobalt are in contact changes to cobalt silicide. Cobalt on the oxide film remains as cobalt.


7-3. Cobalt removal

Cobalt removal

A cobalt film is removed selectively by chemical etching. Silicide remains on the gate, source and drain. Formation of silicide through self-alignment in this way is called salicide (self aligned silicide).

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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