Direct-Write Lithography Recipes

Maskless Aligner (Heidelberg MLA150)

Photolithography Recipes for the Heidelberg MLA150. All recipes were characterized on blank Silicon wafers. For different substrate coatings/materials, you will likely need to run a focus-exposure matrix ("series" exposure mode), using our params as a starting point.

These recipes use the same spin and bake params as our contact aligner and stepper recipes, using built-in hotplates on the photoresist spinner benches.

Any I-Line PR is usable, although we only characterized a select few below. Run your own Focus-Exposure Matrix to characterize a new PR.

Note: On this tool, it is common to have to run a Focus-Exposure Matrix (aka. FEM), via "Series" exposure mode, for each new layer structure and/or critical feature size. The layer structure can strongly affect the exposure parameters. See the FEM Analysis Tips page for how to choose the proper exposure parameters.

Positive Resist (MLA150)

We found that positive PR's worked well with the 405nm laser - the 375nm laser would likely also work. Sub-micron features are possible. Overexposure is recommended to avoid stitching and horiz/vert discrepancies; compensate for widening/narrowing using CD Bias as described here.

Note: calibrations done with the "HIMT design" will show higher dose, due to using only dark-field line/space patterns.

Resist	Spin Cond.	Bake	Thickness	Laser (nm)	Exposure Dose (mJ/cm2)	DeFocus	Rehydrate*	PEB**	Developer	Developer Time	Comments
AZ4110	4 krpm, 30s	95°C, 60s	~ 1.1 µm	405	240	5		none	AZ400K:DI 1:4	50s	Used HIMT design (good for isolated lines 0.8-1um)
AZ4330	4 krpm, 30s	95°C, 60s	~ 3.3 µm	405	320	6		none	AZ400K:DI 1:4	90s	Used HIMT design
AZ4620
SPR 220-3.0	2.5 krpm, 30s	115°C, 90s	~ 2.7 µm	405	325	- 4		115°C, 90s	AZ300MIF	60s	Used HIMT design. 0.6-0.9µm line/space.
SPR 220-7.0	3.5 krpm, 30s	105°C/2min Cool 1min	~ 7.0µm	375	~550mJ	-20	>1hr	115°C, 90s	AZ300MiF	70s	Rehydration after exposure is necessary, to prevent bubbles at PEB.
SPR 955-CM0.9	3 krpm, 30s	95°C, 90s	~ 0.9 µm	405	250	- 7		110°C, 90s	AZ300MIF	60s	Used HIMT design
THMR-3600HP	1.5 krpm, 45s; 250 rpm/s	100°C, 60s	0.430µm	405	180–220	-4		100°C, 60s	AZ300MiF	20s	~0.4nm line/space: lower dose for clear-field, higher dose for dark-field.
*Rehydration: After exposure, leave sample in lab air (ok to cover in tray, with tinfoil). Allows water vapor in air to diffuse into PR to complete chemical reaction. **PEB: Post-exposure bake: after exposure, before develop

Negative Resist (MLA150)

We found that all the negative PR's we tested required the 375nm in order to be fully exposed with reasonable dose/time.

Resist	Spin Cond.	Bake	Thickness	Laser (nm)	Exposure Dose (mJ/cm2)	DeFocus	PEB*	Flood*	Developer	Developer Time	Comments
AZ5214	6 krpm, 30s	95°C, 60s	~ 1.0 µm	375	35	- 5	110°C, 60s	60"	AZ300MIF	60s	Used UCSB design. Good for up to ~1.3um open line space.
AZnLOF2020	4 krpm, 30s	110°C, 60s	~ 2.1µm	375	340	- 3	110°C, 60s	none	AZ300MIF	90s	Used UCSB design. Good for 2um open line space.
SU-8 2075			~70µm	375							Extremely viscous. Pour into a wide-mouthed bottle, dispense directly from bottle. Replace napkin at end.
*PEB: post-exposure bake. For AZ 5214-IR, this performs Image Reversal, and requires Flood Exposure with the MA6 or MJB aligner afterwards, before developing.

Greyscale Lithography (MLA150)

AZ4620 is the manufacturer-recommended PR for greyscale litho.

Please see the MLA150 - Greyscale Design Guidelines & Limitation

Resist	Spin Cond.	Bake	Thickness	Laser	Exposure Dose (mJ/cm2)	Focus Offset	Rehydrate*	PEB**	Developer	Developer Time	Reflow***	Comments
AZ4620	? krpm/30”	95°C, 60”							AZ300MIF	60s		TBD
SPR 220-7.0	3.5 krpm, 30s	105°C/2min Cool 1min	~ 7.0µm	375	~624mJ to clear large mm-area, 520mJ to clear ~5µm lines.	-20	≥1hr	115°C, 90s	AZ300MiF	70s	TBD	Rehydration after exposure is necessary, to prevent bubbles at PEB. Stitching leaves ridges in Y-direction with ~5% height of removed PR depth. Can be reduced via reflow. Author Credit: Patrick Curtis, 2022 & Biljana Stamenic 2023 & Demis D. John 2023
*Rehydration: After exposure, leave sample in lab air (ok to cover in tray, with tinfoil). Allows water vapor in air to diffuse into PR to complete chemical reaction. **PEB: Post-exposure bake: after exposure, before develop ***Reflow: To smooth out stitching lines. Will change sharp vertical profiles considerably, only good for gradually-sloped profiles.