WEEK 7: Photomask #4: Metal Line Definition (Nov 21, 1995)

A. Deposit 1.3 um Photoresist Film on SIX Wafers

1) Center wafer on Headway Research Model LS 510 Spinner

2) Drip on 2/3 pipette worth of Shipley Microposit S-1813 Photoresist

3) Spin for 5 sec at 700 rpm (rids excess PR)

4) Spin for 60 sec at 4000 rpm (smooths out PR)

5) Bake at 120C for 3 min on Thermodyne Type 1900 Hot Plate

B. Expose the SIX Wafers to Mask #4

1) ALIGN alignment marks of mask #4 to those on wafer

2) Orientation of MOAT ISO DEF mask (flat and lettering to right)

3) Place wafer on Karl Suss MJB 3 UV400 Mask Aligner

4) Set spring pressure to 150 um

5) Expose wafer for 4 sec to 15 mW/cm^2 UV light

C. Develop the SIX Wafers

1) Center wafer on Headway Research Model LS 510 Spinner

2) Puddle completely with Shipley MF319 Developer Solution

3) Develop for 60 seconds

4) Spin at 700 RPM for 60 seconds to rinse

• First 10 sec -> spray with developer
• Last 50 sec -> spray with distilled water

5) Spin at 4000 RPM for 60 seconds to dry

6) Bake at 120C for 3 min on Thermodyne Type 1900 Hot Plate

D. Etch the Excess Al on the FOUR Wafers: Al + etchant -> AlPO4 + Al(NO3)3 + Alacetate + H2

1) Create etchant solution at 40C: 3:3:1:1 of 85% H3PO4, 70% HNO3, Glacial CH3COOH, DI (800 ml tot vol)

2) Keep solution warm using Pyro-Magnestir (Labline, Inc.)

3) Immerse Wafers in solution for about 1 min, 50 sec (until see Al suddenly dissolve) + 10% overetch afterwards

4) Rinse for 3 minutes under Distilled Water Spray

5) Dry with nitrogen gas spray