:: IPCI ::

Incomplete etch/overetch
- incomplete etch = the layer is not completely etched (picture below)
- overetch = the layer is too much etched, in this case, etching stops at the substrate due to selectivity, but continues under the photoresist ( picture below)
  - if etching continues, the resist looses its suport and can be completely lifted, exposing the whole wafer to etchant
- Causes:
  - temperature
    - with increasing temperature, the etching rate increases
    - a not suitable temperature may cause incomplete etch or overetch
  - concentration
    - with increasing the concentration of etchant components in the solvent, the etching rate increases
    - a not suitable concentration may cause incomplete etch or overetch
  - time
    - increasing the etching time causes overetch
    - too low time causes insufficent etch

Resist scuming
- If a very thin layer of resist remains after developing then the underlying layer is not etched at all due to high selectivity of resist/film
- this shows the importance of correct developing and inspection before hard baking