Photoresist Processing Trouble-Shooting Etchants and Solvents
Photoresists Ancillaries Storage/Handling/Ageing Substrate Pre-Treatment and Coating Baking Steps Exposure Development Coating and Lift-off Etching and Stripping
Wet-Chemical Etching (Adhesion and Under-Etching) Dry-Etching Stripping / Removal
Dissolubility of Processed Photoresist Films: Non cross-linked AZ® and TI photoresists can be removed easily and residual-free from the substrate in many common strippers. If not, one or more of the following reasons decreasing the removableness of resist films have to be considered:

• From temperatures of approx. 150°C on, photoresists start crosslinking thermally activated. Such temperatures can - on purpose or not - be applied during a hardbake, evaporation or sputtering of coatings, or dry-etching through the resist mask.
• Cross-linking also takes place optically activated under deep-UV radiation (wavelengths < 250 nm) which also occurs during evaporation or sputtering of coatings, or dry-etching.
• Desired cross-linking in case of negative tone resists
• Material re-deposited on the resist structures during dry-etching

Acetone is not well-suited as stripper for photoresists: The high vapour pressure of acetone causes a fast drying and thus re-deposition of stripped photoresist onto the substrate forming striations. If nevertheless acetone shall be used for this purpose, a subsequent rinse with isopropyl alcohol - immediately after the acetone step - is recommended in order to remove the resist-contaminated acetone residual-free.

NMP (1-Methyl-2-pyrrolidon) is a powerful stripper due to its physical properties: NMP yields a low vapour pressure (no striation formation), strongly solves organic impurities as well as resists, keeps the removed resist in solution, and can be heated to 80°C due to its high boiling point.

Alkaline Solutions: If the alkaline stability of the substrate is high enough, aqueous alkaline solutions such as 2-3 % KOH or NaOH (= typical developer concentrates) can be used as remover. For highly cross-linked resists, higher concentrations or/and elevated temperatures might be required.

AZ® 100 Remover is an amine-solvent mixture, and a ready-to-use standard remover for AZ® and TI photoresists. In order to improve its performance, AZ® 100 Remover can be heated to 60°C. Since AZ® 100 Remover is strongly alkaline, aluminium containing substrates might be attacked as well as copper- oder GaAs alloys/compounds. In this case, AZ® 100 Remover should be used as concentrate, any dilution or contamination (even in traces!) of AZ® 100 Remover with should be avoided.

AZ® Kwik-Strip® is an amine-free and pH-neutral stripper making it compatible with e. g. aluminium-, copper- or GaAs containing substrates. For the removal of photoresist processed under harsh conditions (high degree of cross-linking), AZ® Kwik-Strip® can be heated up to 90°C.

O2-Combustion: If a photoresist film cannot be removed wet-chemically due to its high degree of cross-linking, or dry etching is generally preferred, an O2-plasma will act as suited stripper for even highly cross-linked resists.

 Product Overview: Suited Remover/Stripper Weiterführendes Dokument (pdf) Photoresist Removal
MicroChemicals® - All you need for microstructuring with short lead times also in small sales volumes:

Photoresists (positive, negative, image reversal, thin and thick resists, spray resists, protective coating ...)
Ancillaries ( developers, thinner, adhesion promoter such as HMDS, remover)
Etchants (acids and the ready-to-use etching mixtures aluminium etch, chromium etch, gold etch und silicon etch)
Solvents (acetone, isopropyl alcohol, MEK ... in VLSI and ULSI quality)