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
Inferior resist adhesion causes lifting of the resist starting from the resist edges, with subsequent underetching. In exothermic etching solutions, this resist lifting is promoted by local heating and may further be promoted by mechanical forces if e.g. H2 evolution occurs. Resist adhesion can be improved by i) using a suited resist (we recommend the AZ® 1500 and 4500 positive resist series, or TI image reversal resists in image reversal mode), ii) a proper substrate pretreatment (e.g. TI PRIME), and iii) optimized processing (sufficient softbake, image reversal bake). On glass and ceramics, a hardbake is not generally recommended due to the different heat expansion coefficients of resist and substrate, which might cause crackles in the resist.

In isotropic etch media, even optimized resist adhesion results in underetching. If convection and diffusion of the etched medium is not the etch rate bottleneck, the lateral underetching near the substrate/resist interface is comparable to the etched depth.

In HF-containing etching solutions, F-ions diffuse through the resist to the substrate. With the resist film too thin, and/or the etching time too long, the substrate covered by the resist is also etched with large-scale resist ablation as a consequence either during etching or the subsequent rinsing. In this case, either i) a higher resist film thickness, or/and ii) an increased etching rate at fixed HF-concentration by adjusting the HF/HNO3-ratio to the specific substrate will help.
e-Mail Anfrage Resists and Etchants  Optimized Substrate Pretreatment  Recommended Softbake Conditions  Correct Hardbake e-Mail Anfrage Technical Request: Etching Solution for certain Process
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)