WHAT OPTICAL RESIST IS AVAILABLE?

Positive Resist: There are two resists that are commonly used in the lithography area.

• 3612 is used for most of our lithographys (5.5K rpm for 30 seconds = 1.0µm resist OR 2000 rpm for 30 seconds = 1.6 µm resist).
• SPR220-7 (4000 rpm for 30 seconds = 7µm resist is the standard program used for stsetch (for thicker resist you could do 1000 rpm for 30 seconds to get 18um or 2 coats =36µm, 3 coats = 54µm).

WHEN ARE THEY USED?

• For most lithographys the 3612 (1.0µm) is used, but when thicker resist is required you can use the 1.6u verson. Check the resist information data sheet for spin speeds for other thicknesses.
• When doing deep Si etches in the stsetch you need to use 7um of SPR220-7 to prevent etching through the resist and damaging the surface of the wafer. For the deep silicon trench etch (see process pages for details of this etch) you not only need the thick resist as a mask but also at is needed to keep the etch anisotropic (nitride oxide or metal layers would not give the same etch profile).

WHAT IS THE PROCESS for 3612?

• Singe 30 minutes at 150°C (unless your wafers came out of a furnace or deposition system and are coated with resist within one hour.
• Prime with C20 (50% HMDS primer) 6000 rpm for 20 seconds OR use program 1 on the svgcoat system (100% HMDS vapor prime). This helps the resist adhere to the wafer and works best over oxide or nitride films. This step is optional.
• Coat with resist using the headway coaters OR use the svgcoat program 7 (1µm 3612 resist) to coat and prebake your wafers in one easy operation.. The manual coaters give you more flexibility when using nonstandard resists or polyimides.
• Prebake for 25 minutes at 90°C (Note: svgcoat bakes on a hotplate for 60 seconds at 90°C. This can be simulated on one of the hotplates next to the headway spinner when doing a manual coat on the headway spinners).
• Exposure Chart for times(typically less than 1813) ~2.6 sec for karlusss or evalign and ~90 mj for ultratch
• Post-exposure bake (optional may be needed for 1um or less features) for 1 minute at 115C (see below for complete process details for 1um and 1.6um.

VARIATIONS?

• Backside protect: You can coat the backside of your wafers (for protection during etch) after you pattern, develop and bake the front side. This can be done on the headway spinners or on the svgcoat system (if you run it in Manual Mode and run it through the coater only OR if you run it in Auto Mode and bypass the prime/bake and prebake steps). You could then do an oven postbake at 110°C for 25 minutes.
• Front and backside align: You can run your wafers through the svgcoat (prime/bake) ONLY; then flip them over and run them through the prime/bake station, the coat station and the prebake station; you then flip them over and run them through the coater ONLY (bypass all hotplates); finally you do a prebake for 25 minutes at 90°C. They are now ready to expose the frontside, develop without bake and then do backside align, develop without bake and then oven postbake for 25 minutes at 110°C. This is useful for wet etching oxide with a pattern on both sides where you want to keep undercutting to a minimum.
• Wet Etching with 3612 resist (6:1 Buffered HF): It is recommended that you do the 60 seconds post exposure bake if you are going to do wet etching (i.e. in 6:1 Buffered HF). This will give you better adhesion and less undercutting. This step is usually done when you have 1um or less line widths.
  

3612 Procedure for 1.0 and 1.6um resist

1.0µm

1. Singe for 30 minutes at 150°C
2. Prime with HMDS program #1 on svgcoat primer station
3. Spin with svgcoat program #7 (spin 5.5K RPM, 30 seconds)
4. Prebake at 90°C for 1 minute (svgcoat bake program #1)
5. Expose (start with less time that 1813)
6. Optional: Post Exposure Bake at 115°C for 1 minute (skip this step for >1µm resolution). Use the designated 115°C degree hotplate for this step. Doing this also improves the adhesion during wet etch (6:1 Buffered HF).
7. Develop on svgdev program #3 (60 seconds in LDD26W)
8. Postbake at 110°C for 1 minute (svgdev bake program #1)

1.65µm

1. Singe for 30 minutes at 150°C
2. Prime with HMDS program #1 on svgcoat primer station.
3. Spin with svgcoat program #8 (spin 2 KRPM 30 seconds)
4. Prebake at 90°C for 2 minute (svgcoat bake program #2)
5. Expose (start with less time that 1813)
6. Optional: Post Exposure Bake at 115°C for 1 minute (skip this step for >1µm resolution). Use the designated 115°C degree hotplate for this step.
7. Develop on svgdev program #4 (120 seconds in LDD26W)
8. Postbake at 110°C for 1 minute (svgdev bake program #1) or use svgdev bake program #2 for 2 minutes.

Note PLEASE record your resist thickness, type and exposure time (and lamp setting on karlsuss) when you disable the aligners!