2022-09-21 11:34 Status: # Fabrication Steps ## CMOS Inverter Example Start with P substrate - Put down an n-well for p-type transistors  - Then remove photo resist Then put down photoresist where transistors are etch away Fill with [Field Oxide](Field%20Oxide.md) insulator.  Next step is tricky (gate oxide) Grow thin (1nm) gate oxide across the whole wafer ([Furnace](Furnace.md)) - Be careful it doesn't get contaminated  Then deposit polycrystalline silicon which is highly doped (used as gate material)  This becomes the gate electrodes. Now etch away bits of polysilicon we don't want.  Then put down source and drain implants. Commonly use gate as a shield - ensure it is perfectly aligned for performance.  Then do the same for the p implants using [Ion implantation](Ion%20implantation.md)  Then strip the photoresist - [anneal](Furnace.md#Annealing) to reconstitute lattice. Then do the interconnects - lay down material with [Chemical Vapour Deposition](Furnace.md#Chemical%20Vapour%20Deposition) then etch holes where you want connections  Then put metal on with [Sputtering](Sputtering.md) and etch away what you don't want.  Can have 8-10 metal layers (Oxide then metal repeated for complex interconnections).  --- # References [^1]: [vr-4602-wk01-sc08-fabsteps](attachments/Lectures/W1/vr-4602-wk01-sc08-fabsteps.mp4)