NMOS Fabrication Project

Fabrication Steps

The following steps were performed in the fabrication process:

1. Began with a 3" p-type silicon wafers with a resistivity of 14-16 ohm-cm and <100> crystal orientation.
2. Grew approximately 4500-5000 Angstroms of Field Oxide, and performed photolithography/etching to create space for an active area.
   • Photolithography process involved first applying a layer of Hexamethyldisilazane (HDMS) to promote adhesion between wafer and photoresist. Photoresist was then applied through a spin plate.
   • Wafers were then exposed, and immersed in a developer solution to remove the dissolved photoresist.
   • The exposed oxide was then removed with a HF solution.
3. Grew approximately 700-900 Angstroms of Field Oxide.
4. Polysilicon deposition.
5. Polysilicon was then etched to create the gate.
6. Etch away the gate oxide to expose the source/drain regions.
7. Dopant for source/drain regions implanted using Spin on Glass (SOG) method.
8. SOG strip.
9. Immediate oxidation step performed to further drive-in the dopants.
10. Contact hole photolithography.
11. Aluminum metalization using evaporator.
12. Metal photolithography and etch performed to create contacts.