Aluminum Etch

This process is proven successful and very repeatable. It has been repeated over 100 wafers successfully.

  • Start etch bath with 100% Aluminum etch in Acid Hood with hotplate set to 70°C (goal liquid temp 50°C)
    • Set thermometer and teflon sample holder into glassware with Al etchant. This allows sample holder to heat up, and you can monitor and record temp
    • Al etchant etch rate varies significantly by temp. At 50C, 1um thick takes ~1min 30s to etch. Thinner layers will take even less time. Adjust bath temp to reduce etch rate if required.
  • Turn on EV620 lamp
  • Visually inspect wafers - Look for defects
  • Degrease/Dry
  • Dehydration bake - 2min 110°C
  • Test spinner with dummy wafer (wafer shouldn't fall off)
  • Spin (Recipe #3, 4500uL SPR220)
  • Check/clean mask. Load into EV620
  • Load sample into EV620
  • Blow-off sample on EV620 substrate holder
  • Align mask alignment marks (to align theta plane to crystal orientation)
  • Expose (210 mJ/cm^2 dose, hard contact)
  • Develop 917MIF 1min→ 1min sit in DI petri dish with water flowing → 1min rinse → dry → Inspect
    • If needed, 10sec more dev then rinse then inspect
    • 917MIF very slowly etches Aluminum. It won't etch enough to cause significant change in thickness. However, if you have to respin after development, you will see a shadow of the original pattern left behind in the aluminum. Therefore, if there are only minor defects, consider just leaving the defects and moving on.
  • Al Etch 1.5min-2.5min 47-51°C (ideally 50°C) (etch 10sec PAST all aluminum gone). Write down time.→ Inspect
    • If needed, 10sec more etch → Inspect
    • Use big tub w water in it to catch etchant drips when transporting wafer across benchtop.
  • Degrease/Dry
  • Strip 5min 1165
  • Degrease/Dry → Inspect

The material presented in this work was carried out by Glennys Mensing, Assistant Director of MNMS Cleanroom, within the Department of Mechanical Science and Engineering at the University of Illinois. It was provided in the spirit of cooperation to educate future generations of engineers and scientists.