Various terminologies are used to describe the tone of both pattern and background areas of a photomask.

The terms dark field (dark background / clear pattern) and clear field, or light field (clear background / dark pattern) are common terminologies, but may be confusing as the photomask maker is required to determine between the pattern and the background. While the answer to such a question may seem obvious for a designer, technicians who are not familiar with the designer’s device can easily misinterpret it.

To avoid confusion, it is preferable to relate pattern / background tone to the digitized (drawn) and non-digitized (background) of the CAD data that is supplied to the maskmaker. Instead of “dark field”, “digitized (drawn) data dark” or “digitized (drawn) data clear” are less likely to be misunderstood.

To further avoid confusion a plot of the device or a section of the device, such as a PDF or paper plot, can be provided to the maskmaker indicating the tone of specific areas.

Photomask Tone

Example of a dark field and a clear field mask.