Substrate Contact Process
Original Publication Date: 1980-Feb-01
Included in the Prior Art Database: 2005-Feb-13
In a double polysilicon process two contact masks are used to make substrate contact through the recessed silicon dioxide (ROX) regions. Two contact masks are needed because the silicon dioxide thicken the diffused regions and polysilicon layer is much less than ROX thickness. This differential in silicon dioxide thickness can be eliminated if the substrate contact is made through the thin silicon dioxide layer rather than through the thick ROX. To make the contact through thin silicon dioxide, the source-drain implant or diffusion is prevented by a non-critical blockout mask covering the area where a contact to P type material is to be made.