Developer: SU8 (Wet Bench)

Tool description
The Developer: SU-8 (wet bench) is a manually operated wet bench for submersion development of SU-8 photoresist in PGMEA (supplied in the cleanroom as the product mr-Dev 600).

The SU-8 development is a three-stage process:

Submerge into "FIRST" bath to dissolve the bulk of the resist
Submerge into "FINAL" bath to finish the development
Submerge into "RINSE" bath to stop the development process and rinse the substrates

The development time is controlled manually by the user. After development the substrates are dried in the empty bath, which is dedicated for drying.

Product:	Arias wet bench
Year of purchase:	2023
Location:	Cleanroom E-4

User manual
The user manual and contact information can be found in LabManager - requires login

Tool training
Training on the tool requires users to complete the lithography TPT followed by online tool training and hands-on authorization training.

Equipment performance and process related parameters

Tool purpose	Development of: SU-8
Developer	mr-Dev 600 (PGMEA)
Development method	Submersion
Handling method	Multi- or single wafer holder
Process temperature	Room temperature
Process agitaion	Magnetic stirrer
Process rinse	IPA
Substrate sizes	Chips 50 mm wafers 100 mm wafers 150 mm wafers, check the liquid level in the baths 200 mm wafer, check the liquid level in the baths
Substrate materials	Silicon and glass substrates Film, or pattern, of all materials except Type IV
Substrate batch size	1-6

Process information

Several aspects of the SU-8 processing outcome 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 worse in a fresh developer bath. This effect of the developer quickly saturates after developing 5-10 wafers
The stability of fine structures (high aspect ratio structures) is affected by the rinse after development, as the lower surface tension of IPA compared to PGMEA reduces pattern collapse during drying

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

Minimum development time: 1 min per 20 µm in FIRST bath
Maximum development time: SU-8 is not very sensitive to over-development

Recommendations for development time:

≤5 µm: 2 minutes in FIRST bath, followed by 2 minutes in FINAL bath
~40 µm: 5 minutes in FIRST bath, followed by 5 minutes in FINAL bath
≥180 µm: 15 minutes in FIRST bath, followed by 15 minutes in FINAL bath