1. spin 4% 495 PMMA (solvent anisole) @ 3000 rpm, 1000 ramp, 60 s (resist will be ~150 nm thick)
2. bake @ 170 °C for 15 min
3. spin 2% 950 PMMA (solvent MIBK) @ 3000 rpm, 1000 ramp, 60 s (resist will be ~50 nm thick)
4. bake @ 170 °C for 15 min

1. Measure the current in pA for each aperture setting (typically 10 µm aperture for fine contacts & 60 µm aperture for probe (big) contact pads).
2. Set up run files (see screenshots below).

Parameters common to all run files:

• gun @ 20 kV
• 900 magnification

General Parameters:

• Non-stop writing mode ⇒ yes
• Disable automated stage control ⇒ no
• Disable digital SEM control ⇒ no
• Disable x-y focus mode ⇒ yes
• Enable global rotation correction ⇒ no
• alignment windows: counts of 15; center-to-center & line spacing of 50 nm
• fine contacts: continuous write; center-to-center & line spacing of 5 nm; 300 µC/cm^2 area dose
• big contact pads: continuous write; center-to-center & line spacing of 30 nm; 300 µC/cm^2 area dose

45 sec in 1:3 MIBK:IPA (shake chip back-and-forth in soln) & quench in IPA; N2 dry

1:1 methylene chloride:acetone overnight