To connect electrodes such as gates, sources, and drains of transistors to metal wiring layers, contact holes are made in the dielectric film and filled with W (tungsten).
Plug-tungsten filling: Tungsten is deposited in contact holes.
Plug-tungsten polishing: The surface is polished to remove excess tungsten and leave tungsten only in the contact holes.
Using the contact hole resist pattern as a mask, contact holes are formed in the dielectric film by performing etching treatment. After etching, the resist pattern is removed. These holes are extremely small and deep (high aspect ratio), and thus great care must be taken to control hole diameter and depth.
A tungsten film is formed on the silicon wafer surface using the CVD method, and the contact holes are filled.
The surface is polished and excess tungsten film is removed. Tungsten is left only in the contact holes.
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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