Mask process flow	1 Mask data is transferred through data network (e.g. ftp) to Mikcell. Many companies need extra service in CAD design and data preparation. Mikcell has put a lot effort to ensure that our customers get all the support they need, also before sending us the final data. Normally this can be done by telephone or with e-mail messages.
	2 After the mask data is converted to an exposure file and checked for conversion errors operator loads correct size blank on the exposure table. Maximum size of the plate today is 44 x 44 inches. Computer controlled laser beam scans over photoresist and exposes those 250 x 250 nm size pixels that must be transparent on the final photomask. Smallest lines that can be processed are 1,5 µm.
	3 Photomask images are written on mask blanks that are optically high quality class plates with a thin metal film evaporated or sputtered on them (normally chrome / chrome-oxide) and coated with uniform thick photoresist (photo-sensitive polymer).
	4 Next step is to develop photoresist and inspect the result as part of the process control. After this photomask pattern is transferred into chrome film by etching and photomask will be inspected again and its CD measured. Possible defects are removed and perfect mask is cleaned and packed in a special 'clean room box' for shipping by a courier company.
	5 Mask fabrication is carried out in clean room condition where air temperature and humidity are kept constant and free from particles. Critical work areas in Mikcell clean room are at class 10. Mask laser scanner is a closed system where air is circulated through HEPA filters giving virtual 'class zero' exposure area and temperature is controlled within +- 0.02 ºC.
	6 Measurement and repair: Inspection and measuring system is Zeiss LM 100 Automated workstation. Measurement system capability and capacity: All the masks are inspected carefully and repaired in case of defects.
	7 CD calibration standards Align Rite Ltd has made the correlation plate and standards for it. Orthogonal tests Always after laser unit change and after ‘bigger services’.