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Center of MicroNanoTechnology CMi

LOR double layer lift-off


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LOR 5A Surface preparation


Wafer Surface Preparation

When used as recommended, primers such as HMDS are typically NOT required to promote the adhesion of LOR products. Assuming wafers with clean surface without organic contamination, good adhesion of the LOR 5A polymer is observed with the following surface treatments:

Surface material (larger area) Vapor HMDS Plasma O2 Thermal dehydratation
Si √√
SiO2, fused silica, SiN, Si3N4 √√
Float glass, pyrex √√
Metal Al √√
Metals Ti, Cr, Ta X √√
III/V semiconductors (GaN, GaAs) X √√

Note: Cleanroom relative humidity control is critical for resist adhesion.



Below is the list of cleanroom equipment available for each surface treatment. Contact the staff responsible of each machine for specific questions and training requests.

Vapor HMDS

The ACS200 Gen 3 automatic coating system in Zone 1 has a built-in HMDS hotplate module. For other coating equipments, please use the standalone HMDS primer systems listed here :

Additional details about the HMDS process and control can be found here: link

Plasma O2

Thermal dehydratation

A dehydratation step is included as an option in the EVG150 and ACS200 Gen 3 automatic coaters. In addition, hotplates and ovens are available in all photolithography zones in order to perform thermal dehydratation on single or batch wafers. Please contact the photolithography staff for guidance.


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