Developing Patterning Process for Homemade Microelectronics

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Final process:

  • Clean/prep wafer – Piranha, RCA 1 / 2
  • Water rinse
  • Remove native and RCA oxide – 1-2% HF dip
  • Field oxide growth – 1200 c w/ water vapor, 5000A blue film
  • If wafer in storage, dehydration bake – 10 min @ 220c
  • Check wafer hydrophobic if necessary
  • Optional spin HMDS
  • Spin 3.5mL AZ 4210 resist 30 sec @ 3500 rpm ~3.5um film
  • Soft bake resist 2 min @ 105c hotplate
  • Expose active area
  • Develop 1:3 400k KOH:H20 puddle 1 min
  • Water rinse (no solvent)
  • Inspect wafer, if defect strip resist and retry
  • Hard bake 15 min @ 125c hotplate
  • Etch active area – 1-2% HF 15 min or until surface hydrophobic
  • Water rinse
  • Resist strip – Acetone or plasma ashing 100 watts RF 5 min @ 125mTorr O2
  • IPA rinse
  • Water rinse

Tall particles can easily short out the thin gate oxide in these devices, as shown under my SEM. This poses an issue for making such devices in a garage; the gate oxides must be grown thicker to mitigate shorted devices which leads to a higher threshold voltage for the FET.

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