UPDATES:
- Kathryn McGill (CNF Fellow), 6/12/15
Recipe
Chip Spinning:
- spin 4% 495 PMMA (solvent anisole) @ 3000 rpm, 1000 ramp, 60 s (resist will be ~150 nm thick)
- bake @ 170 °C for 15 min
- spin 2% 950 PMMA (solvent MIBK) @ 3000 rpm, 1000 ramp, 60 s (resist will be ~50 nm thick)
- bake @ 170 °C for 15 min
E-beam Writing on the Nabity:
- Measure the current in pA for each aperture setting (typically 10 µm aperture for fine contacts & 60 µm aperture for probe (big) contact pads).
- 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
Development
45 sec in 1:3 MIBK:IPA (shake chip back-and-forth in soln) & quench in IPA; N2 dry
Liftoff
1:1 methylene chloride:acetone overnight
Walk-through
step 1 - copy gds file into this directory:
step 2 - right click to convert gds to dc2:
step 2.1 - change drawing unit size to 1 and press convert:
step 3 - right click on new dc2 file and select DesignCAD Express:
step 3.1 - click NPGS - setdump
step 3.1.1 - the dump point is green:
step 3.2 - click NPGS - MaxMag:
step 3.3 - click NPGS - save - exit when done - then re-open to double check dump existence:
step 4 - right click on dc2 - choose run file editor:
step 4.1 - for fine contacts process 2 entities - set params as shown - pattern name is name of dc2 file:
step 4.2 - 1st entity is alignment - set params as shown - insert measured beam current in pA:
step 4.2.1 - skip all non alignment layers:
step 4.3 - 2nd entity for fine contacts - skip all alignment layers - change line to area dose:
step 4.3.1 - enter params as shown - same for each layer! - skip contact pad layer - remember to update measured current
step 4.4 - save run file - extension RF6 - and exit:
step 5 - find run file - right click - process run file:
step 5.1 - click continue - the writing will start!
step 6 - set up contact pad exposure - use these params:
step 6.1 - skip all but contact pad layer - enter params - remember to update measure current - proceed as before:
