Modules to support mask metrology tools
Using jobdeck information and electron beam pattern file data, CATS Metrology Marking option provides a unique graphical and command-driven environment for automating off-line registration and critical dimension measurement specification. As the flow chart below indicates, CATS jobdeck viewing package may be used to display a composed photomask for any supported format. The marking option may then be used to define critical dimension and/or registration measurement locations either through a graphical point-and-click technique, or through a more automated, command-driven procedure.
Once marks are specified, they are stored in a CATS jobdeck file for later conversion to the marking script or matrix file for the appropriate tool. Marks may be defined in one pattern and quickly copied or arrayed to other similar patterns, or they may be copied from one level of the jobdeck to another. Of course, much of the procedure may be automated through CATS' user-programmable menu.
Using pattern recognition logic, CATS recognizes several standard mark types like crosses, boxes, and L-shaped features. Any arbitrary line or space may be defined as a measurement location using a mark type of CD or BAR (a "bar" is simply a CD centered on the specified line).
One approach to automation is through a CATS' include file, or command file. The user may define the location, mark type, polarity, and dimension of the marks desired. If the specified data exists, a mark is defined. If the mark does not exist, an error message is generated. Using this approach, users may define both a data and jobdeck verification procedure as well defining mark locations for future export to the measurement tool.
A second approach to automation involves a search mode. A user may specify a starting location, a search radius, and the type, polarity and size of mark required. These may also be arrayed.