What does Critical Dimension mean?
After a mask has been manufactured, a measurement is made of a feature on the mask to check that the exposure and processing of the mask are within the specified tolerances. The feature checked is known as the Critical Dimension. This should reflect the smallest feature size present on the mask and also the type of features (Lines or Contacts). Users are encouraged to include suitable features in their data, preferably at defined standard locations. The maximum size of Critical Dimension for our CD tools is 60um, and it must be less than 21um if the mask is to be measured on the more modern automated CD tools (LWM + M5K). If the user does not include any suitable measurement points, we can measure one of the features that we add at the edge of the mask for our SPC system.