Specific Process Knowledge/Lithography/LiftOff

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Lift-off process

Schematic of the lift-off process.

The lift-off process is used to pattern a material that can be deposited as a film on a substrate. The material is patterned by depositing the film on top of a patterned masking material, which is then dissolved, thus leaving only parts of the substrate covered in the material. Although this may in theory be done using any combination of mask and material, the most common is using photoresist as a lift-off mask for metal.

The image to the left shows a schematic of the lift off process.

• 1. The substrate is coated with the masking material.
• 2. The masking material is patterned. The mask must be a negative image of the desired material pattern. The mask sidewalls should be negative in order to prevent the material covering the sidewalls during deposition.
• 3. The material is deposited on top of both mask and substrate.
• 4. The masking matreial is dissolved, thus lifting part of the deposited material.
• 5. The remaining material forms the desired pattern on the substrate.

Comparing Lift-off equipment

Equipment		Lift-off wet bench	Lift-off (4", 6")
Purpose		AZ 5214E lift-off	AZ 5214E lift-off AZ nLOF lift-off
Bath chemical		Acetone	NMP (Remover 1165)
Process parameters	Process temperature	Room temperature	Heating of the bath is possible. The heating has been limited to 37°C
	Ultrasonic agitation	Continuous (on/off)	Continuous or pulsed The power may be varied
Substrates	Substrate size	100 mm wafers	100 mm wafers 150 mm wafers
	Allowed materials	Silicon or glass wafers Film or patterning of all but Type IV (Pb, Te)	Silicon or glass wafers Film or patterning of all but Type IV (Pb, Te)
	Batch	1 - 25	1 - 8

Lift-off wet bench

Lift-off wet bench in D-3

This bench is only for wafers with metal!

The user manual, and contact information can be found in LabManager

Process information

Lift-off wet bench is used for lift-off using resists soluble in acetone. AZ 5214E is soluble in acetone, cross linked (i.e. exposed and baked) AZ nLOF is not.

For information on image reversal of AZ 5214E, see here: Process_Flow_AZ5214_rev_vers2.docx‎

Lift-off (4", 6")

Lift-off (4", 6") in D-3

The user manual, and contact information can be found in LabManager

Process information

Lift-off (4", 6") is used for lift-off using resists that are soluble in NMP (N-Methyl-Pyrrolidone), supplied in the cleanroom as "Remover 1165". Both AZ 5214E and AZ nLOF are soluble in NMP.

For information on processing of AZ nLOF, see here: Process_Flow_AZ_nLOF_2020.docx‎