Hi All,
1) Do you know how long a coated wafer can be kept (in a closed box) without exposure considering humidity variations of the cleanroom? After how long it should be reworked?
2) How long the resist is good after exposure and before development? When should it be reworked if not developed? Is there an effect on the LW if the exposed resist wasn't developed long time (1 week)?
Thanks!
Hello Olga,
the upper limit for the interruption of process steps is the lifetime of the resist in the bottle (see charge number). The aging limits the storing time for some years.
The separate steps 1) and 2) can be compared with the conventional (analogous) photography.
1) The light sensitive film can be stored within the camera for nearly 2 years. Then the sensitivity decreases and colour layers mix by diffusion. So you get a wrong colour picture.
2) The exposed film changes within the same period provided the storage conditions are followed. This is especially the temperature. The wafer must be cooled but T > 0C.
From colour-photography you know - a long storage gives gaudy pictures. But I expect, if the wafer is illuminated with blue light, the information holds.
Nevertheless, fine details can change remarkable and a structure can fail.
With regard
R. Mitdank
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Coating