How do I specify the tone of the photomask?
There are several different methods which people use to specify the tone (or polarity) of the photomask.
The two main strategies are:
- Trying to describe how the mask should be processed
- Trying to describe how the mask should look after processing
We have found that the first of these is the less ambiguous.
If you think about a shape drawn on your CAD system, do you want this to be Dark (Chrome) or Clear (Glass) on the photomask?
e.g. The digitized data should be Dark on the photomask.
Attempts to use descriptions such as Positive / Negative, or Field Tone can be ambiguous in many cases, and are best avoided.