CMOS Layout Color Codes
n-Diffusion (Green)
Represents n-type diffusion regions where nMOS source and drain are formed. These regions are silicon areas doped with donor impurities like phosphorus.
Meaning: Conducting regions for electrons (nMOS active regions)
Polysilicon (Red)
A layer of polycrystalline silicon used to form the gate of MOSFETs. It controls the ON/OFF state of the transistor.
Meaning: Controls transistor switching
Implant (Yellow / Green Outline)
Represents doping regions used to modify conductivity:
- n+ implant → increases electron concentration
- p+ implant → increases hole concentration
Meaning: Defines n-type and p-type regions
Metal (Blue)
Represents metal interconnect layers used for wiring between components. Typically made of aluminum or copper.
Meaning: Carries signals and power in the chip
Summary Table
| Layer | Color (Standard) | Function |
|---|---|---|
| n-Diffusion | Green | nMOS source and drain regions |
| Polysilicon | Red | Gate control of MOSFET |
| Implant | Yellow | Doping (n+ / p+ regions) |
| Metal 1 | Blue | Interconnections (wiring) |
These colors are only visual aids in IC design tools to help engineers distinguish different fabrication layers easily.
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