Etching Metal Films

Wet Chemical Etching

Ag Al, Au Cr, Cu, Ni, Pt, Sb, Ti

• Aluminum
  • "metal etch" (3:3:1:1 H3PO4:HNO3:CH3COOH:H2O) 8.7 angstrom/sec@RT "metal etch" (3:3:1:1 H3PO4:HNO3:CH3COOH:H2O)<4min/micron@40C
  • "Al fine line etch 1" (4:1:4:1 H3PO4:HNO3:CH3COOH:H2O) 30min/micron
  • "Al fine line etch 2" (1:2 HCl:H2O)
  • "Al fast etch" (17:1:3 H3PO4:HNO3:CH3COOH:H2) ~5 min/micron
• Antimony
  • "metal etch" (3:3:1:1 H3PO4:HNO3:CH3COOH:H2O) <<3min/1000A@50C
• Chromium
  • "Cyantek CR-7s" (9%ceric ammonium nitrate, 6%perchloric) 7 min/micron (24A/s new)
  • "Cr acid etch" (1:1 HCl:glycerine) 12min/micron after depassivation
  • "Cr base etch" (1:3 [50gNaOH+100mlH2O]:[30g K3Fe(CN)6+100mlH2O]) 1hr/micron
• Gold
  • "Aqua Regia" (3:1 HCl:HNO3) ~1.5 seconds/micron and ~6 seconds/micron FRESH (Note: suggest that you use an adhesion promoter for your resist to keep undecutting to a minimum. Use the Aqua Regia within about 5 min. of mixing, otherwise the etch rate goes up and it becomes harder on the photoresist. -Michael Martin U. of Louisville
  • "Au mask etch" (10g KI, 2.5g I2, 100ml H2O) 1min/micron
• Copper
  • 150g Sodium persulfate:1000ml H2O ~20s/micron @ 45C
    Use only as a last step outside of the microengineering lab. When free of Fe, this solution is selective for Cu against Ni (added iron salts will cause Ni corrosion)
• Nickel
  • "metal etch" (3:3:1:1 H3PO4:HNO3:CH3COOH:H2O) ~15min/micron@RT with air exposure every 15 seconds
• Platinum
  • use lift-off
• Silver
  • "dilute metal etch" (3:3:23:1 H3PO4:HNO3:CH3COOH:H2O) ~10min/100A
  • "silver base etch" (1:1:4 NH4OH:H2O2:CH3OH) .36micron/min resist ok but rinse rapidly after etching
• Titanium
  • Titanium etch 2 (1:9 HF:H2O) 5s/micron@32C (really that fast??) note: Titanium etch for 1 min sputtering 160W: 35s in 1%HF in DI.
  • RCA-1 ~100 min/micron

Dry Etching