With project lithography light shines through the mask, goes through a reduction lens and projects onto the substrate. Since the mask never comes into contact with the sample it stays cleaner. At the LNF 500nm gratings will reliably print on [[SPR 955]], however the resolution will depend on the feature type and photoresist thickness. As feature size decreases the depth of focus also decreases so thinner resist must be used. The [[GCA AutoStep
200]] has a max die size of 14.7mm x 14.7mm and a minimum alignment tolerance of 200nm for wafers, if running pieces the tolerance will be larger. This also strongly depends on the accuracy of the artwork on the mask; mask plates produced with the [[Heidelberg µPG 501 Mask Maker]] will require larger tolerances because of this.
For prototyping and one-off jobs using the [
Heidelberg_µPG_501_Mask_Maker] to directly expose a sample can be effective.
==Methods of operation==