Surface Preservation Purification
After final wet cleaning, it has to be ensured that the surface is kept in this clean state to extend the mask life time as much as possible and by that to decrease customer’s cost of ownership. This became furthermore important with EUV lithography where scanner compatibility plays a critical role and any downtime of the exposure tool due to cross contamination by photomask has to be avoided.
Therefore, different surface preservation and purification processes following the final wet cleaning are required. Residual organic and inorganic ions which are still embedded in the substrate surface and the root cause for haze creation have to be removed as well as remaining molecular moisture.
SUSS MicroTec’s automated photomask cleaning equipment offers a variety of post treatments. Depending on substrate type and challenges, high temperature bake, Soft RTP or exposure of 172nm UV light can be applied to guarantee photomask pattern integrity.