WHAT OPTICAL RESIST IS AVAILABLE?

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

• Shipley 3612 is used for most of our lithographys (5000 rpm for 30 seconds = 1.0u resist OR 2000 rpm for 30 seconds = 1.6 u resist).
• SPR220-7 3500 rpm for 30 seconds = 7um 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 =36um, 3 coats =54um). Develop in LDD26W (see details below)

WHEN ARE THEY USED?

• For most lithographys the 3612 (1.0u) is used, but when thicker resist is required(i.e. more than 3um) SPR220-7 is a good alternative.
• When doing deep Si etches. 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 profiles)
• For DRIE in the STS 7um's of SPR220-7 with good wafer cooling should last ~ 2 hours (which is enough for >200 um ). Depending on the size of the holes, it may be adequate for through-wafer etch. .
• Etch rate of SPR220-7 resist (7um) with 30 minute bake at 90C in oven, is ~1.5um/hour (using the holder).

WHAT IS THE PROCESS for SPR220-7?

• Singe 30 minutes at 150C (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 primer station(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 4 to coat your wafers (see programs for svgcoat. The manual coaters give you more flexibility when using nonstandard resists or polyimides. (Note: Always keep resist or resist coated wafers under a ventilated exhaust hood. When using the SVGCoat, you MUST lower the two plastic panels for additional fume protection.)
• Prebake in a 90C oven or use program #4 bake (100 seconds bake) on SVGCoat.(Note:See below for suggested times). Then do an additional 100 second bake on a separate hot plate at 115C.
• Postbake for wafers getting stsetch - Oven Bake the wafers for 30 minutes at 110C (or 90C for ~45 - 60 minutes for etches longer than 2 hours)

SPR220-7 PROCESS INFORMATION?

• SPR220-7: Wafers should be singed at 150C for 30 minutes, then program 1 on the HMDS prime station.

SVGCOAT setup for 7um of SPR220-7:

prime HMDS (standard program 1)

Coat with Program 4 (see programs for svgcoat for details)

For best results Bake on svgcoat hotplate program #4 for 100 seconds at 90C . An additional bake of 100 seconds at 115C will be needed on a separate hot plate . Or you could just do program #3 bake at 90C for 200 seconds on the svgcoat. Your exposure times may vary depending on the bake you choose.

Note: SPR220-7 Fumes are toxic. Always lower the two plastic panels on the svgcoat fume hood.

Expose see chart for suggested times (these are only starting points, you should always do an exposure test).

Develop with program 6 on svgdev (see programs for svgdev in the equipment section of the webpages for details). No postbake is needed.

SVGCOAT setup for 10um of SPR220-7:

prime HMDS (standard program 1)

Coat with Program 4 (except change the spin speed to 1700 rpms. You must change the rpm back when you finish to 7um speed.

Note: SPR220-7 Fumes are toxic. Always lower the two plastic panels on the svgcoat fume hood.

For best results Bake on svgcoat hotplate program #4 for 100 seconds at 90C . An additional bake of 100 seconds at 115C will be needed on a separate hot plate .

Important: For 10um resist the best results are achieved with spinning one day and exposing the next day. If that is not possible, 3 hour delay time is a MUST.

Exposure: Your exposure times may vary depending on the bake you choose (30 seconds at 30mj/sec).

Develop with LDD26W using program 6. No postbake is needed, unless you are doing stsetch (see the note for 7um resist).

SVGCOAT setup for18um of SPR220-7:

prime HMDS (standard program 1)

Coat with Program 5 as follows using manual dispense:

 

EVENT	OPERATION	ARM	TIME	SPEED	ACCEL
1	spin	0	2.0	5.00	40
2	spin	0	5.0	0	40
3	spin	0	10.0	0.5	01
4	spin	0	40.0	1.0	01
5	end

Change the program on the coater to program #1 (skip hmds prime station ). This is the edge bead removal and for cleaning the back of the wafer and removing the edge bead.

Bake on svgcoat hotplate program #1 for 60 seconds at 90C . An additional bake of 55 minutes in the 90C oven (wafers flat) is needed. Your exposure times may vary depending on the bake you choose.

Note: SPR220-7 Fumes are toxic. Always lower the two plastic panels on the svgcoat fume hood.

It is important to let the wafers sit one day before exposure.

Expose for ~90 seconds with Karlsuss CI2 lamp intensity (these are only starting points, you should always do an exposure test).

It is a good idea to again let the wafers sit (resist side up) for at least 2 hours before develop.

Manual Develop for 5-10 minutes with constant agitation (Stirring unit is available, see Mahnaz). No postbake is needed unless you are doing stsetch (see the note for 7um above).

SVGCOAT setup for 54um of SPR220-7:

prime HMDS (standard program 1)

Coat with Program 5 (manual application) as follows (3 coats of 18um with a bake in between and a final bake give 54um):

 

EVENT	OPERATION	ARM	TIME	SPEED	ACCEL
1	spin	0	2.0	5.00	40
2	spin	0	5.0	0	40
3	spin	0	10.0	0.5	01
4	spin	0	40.0	1.0	01
5	end

Change the program on the coater to program #1 (skip hmds prime station ). This is the edge bead removal and for cleaning the back of the wafer and removing the edge bead.

After the first and second 18um layer, bake on svgcoat hotplate program #1 for 60 seconds at 90C . After the third layer an additional bake of 90 minutes in the 90C oven (wafers flat) is needed. Your exposure times may vary depending on the bake you choose.

Note: SPR220-7 Fumes are toxic. Always lower the two plastic panels on the svgcoat fume hood.

It is important to let the wafers sit one day before exposure.

Expose for ~440 seconds with Karlsuss CI2 lamp intensity (these are only starting points, you should always do an exposure test).

It is a good idea to again let the wafers sit (resist side up) for at least 2 hours before develop.

Manual Develop for 40 minutes with constant agitation (stirrer is available - see Mahnaz). No postbake is neededunless you are doing stsetch. See note for 7um above.