Developer: SU8 (Wet Bench)

The SU8-Developer bench is a manually operated wet bench for submersion development of SU-8 photoresist in PGMEA (supplied in the cleanroom as mr-Dev 600). The development process is in two stages; one bath (FIRST) to dissolve the bulk of the resist, and a second, cleaner bath (FINAL) to finish the development. The development time is controlled manually by the user. After development, the substrates are rinsed with IPA in dedicated IPA bath and put for drying in the empty bath.

The user manual, user APV, and contact information can be found in LabManager: Developer: SU8(Wet Bench) - requires login

Process information

Several aspects of the outcome of SU-8 processing are affected by the development process. The lithographic resolution is affected by the time between PEB (post-exposure bake) and development, as the cross-linking process continues in the interface between exposed and unexposed regions even at room temperature. Cracks in the structures is affected by two things; the development time, and how much has previously been developed in the developer bath. Cracking is worse with longer development time, and worst in a new developer bath. The effect of the developer use quickly saturates (5-10 wafers). Finally, the stability of fine structures (high aspect ratio) is affected by the rinse after development, as the lower surface tension of IPA compared to PGMEA reduces pattern collapse during drying.

Development time is strongly dependent on the SU-8 thickness.

Minimum development time: 1 min per 20 µm in FIRST

Suggestions:

2-5µm: 2 min. in FIRST; 2 min. in FINAL
40µm: 5 min. in FIRST; 5 min. in FINAL (however, 3 min. in FIRST and 2 min. in FINAL is sufficient)
180-250µm: 15 min. in FIRST; 15 min. in FINAL

Equipment performance and process related parameters

Purpose		Development of: SU-8
Developer		mr-Dev 600 (PGMEA)
Method	Development	Submersion
Method	Handling	Single wafer holder
Process parameters	Temperature	Room temperature
	Agitation	Magnetic stirrer
	Rinse	IPA
Substrates	Substrate size	100 mm wafers 150 mm wafers, check the liquid level in the baths 200 mm wafer, check the liquid level in the baths
	Allowed materials	Silicon and glass substrates Film, or pattern, of all materials except Type IV
	Batch	1-6