General: Resist composition

The resists most widely used by far are the positive photo resists, followed by negative photo resists. However, there are other special resists as well.
Image reversal resists are positive resists with an additional amine. Depending on the manufacturing process, positive or negative images can be generated.

Dilution of resists

Almost all photo resists contain PMA (PGMEA) as a solvent. This solvent is therefore the most common thinner and offered by us as AR 300-12 angeboten. The PMA is often used for the removal of edge beads.

Adhesive strength

Adhesive agents serve to improve adhesion, e.g. the adhesion promoter AR 300-80, which is applied by spin coating as thin layer of approximately 15 nm immediately before the resist coating. It is also possible to evaporate HMDS on the substrate, in this process, the monomolecular coat on the wafer surface improves adhesion, because it becomes hydrophobic and better attaches to the resist.

One-layer and two-layer lift-off

Lift-off structures are needed for many technologies. There are one-layer and two-layer processes. For one-layer, only one resist is used. Typical examples are negative resists, see Resist-Wiki “Generation of undercut structures with negative resists”. However, there are also positive resists (AR-P 5300) for the lift-off. There is only a slight difference, though in most cases, which, however, is sufficient for many procedures.

Lift off (one layer – two layer)

Two procedures are principally possible to manufacture e.g. conducting paths: 1. Etching technique: A thin metal film (e.g. aluminium) is deposited on a wafer (evaporation or sputtering)