65 E.State Street, Suit2000
Columbus, Ohio 43215
c/o Schneider Downs
Attention:Dennis R.Mowrey


"Lighting a path to the future with nano-optics."

Mask Lithography

Another of the processing methods Nalux uses in fabricating its optics is mask lithography.  The method was borrowed from the semiconductor industry where mask lithography is used to pattern the metal on printed circuit boards.  Once the method was well understood, it was realized that mask lithography was also a very useful process for patterning the microstructures that allow micro optics to alter the course of light and make the light do what we want it to do.  

Mask lithography starts with a mask.  Just like a mask for a costume covers up parts of a face and leaves other parts uncovered, masks used in mask lithography do the same thing.  Once a mask is prepared, a substrate, very often a wafer of glass that is often 150mm diameter and 1mm thick is covered with a layer of photoresist.  Photoresist is a polymer that hardens when exposed to UV light.  The wafer with the photoresist is covered with the mask.  The UV light is turned on and hardens the photoresist that is left uncovered by the mask.  The wafer, covered with areas of hardened and unhardened photoresist, is put in a solvent which attacks and dissolves the unhardened photoresist.  The unhardened photoresist gets washed away while the hardened photoresist remains on the glass wafer.  That is the short description of mask lithography.  The longer description is that sometimes the photoresist is reversed and there are methods of mask lithography where the photoresist is only washed away by the solvent if it has been exposed to UV light.  

Once a glass wafer has gone through the mask lithography process and you have areas of photoresist and areas of bare glass  on the glass wafer, then the wafer is put into a plasma etching chamber which can be compared to sandblasting with ions.  The chamber starts to etch away at the surface of the glass that is left exposed.  It also etches the surface of the hardened photoresist and the end result of the mask lithography and the etching process is a glass wafer with micro structures etched into it's surface.  

The masks used in mask lithography are very precise.  They can be used to make diffraction gratings, microlens arrays, and a wide variety of other optics.  Nalux has been using the mask lithography process for many years and is an expert in the field.  Call us today and see what we can do for you.