Anti-Sticking Strategies

More details on fused silica mold fabrication can be found elsewhere [80]. In general, a resist is patterned using electron-beam lithography and then transferred to a thin (between 8 and 20 nm) chromium layer with a CI2/O2 plasma. Afterwards, fused silica is etched in a fluorocarbon plasma using the chromium layer as a hard mask. Finally, this hard mask is removed in a wet or dry process. 

As explained before, mold inspection [81] and repair [82] is mandatory in applications like microelectronics, requiring a very low defect rate. Some specific commercial tools, derived from wafer and mask inspection equipments, are under development [83, 84]. Also, the LER is an important characteristic of fabricated templates and becomes a critical issue when the dimensions shrink. One powerful method, used in our lab, to characterize the roughness of fabricated UV-NIL molds is 

A major challenge of the nanoimprint technique is to perform a correct detachment of the mold from the cured resist. Its difficulty is inherent to the high density of nanoscale protrusions patterned on the mold surface, which effectively increases the total area in contact with the UV-cured resist. Therefore, sticking between imprinted polymeric structures and the mold surface can have the three following detrimental consequences  

Fluorinated self-assembled monolayers (F-SAM) can be deposited either in liquid phase, hy dipping the mold direcfly into a diluted solution of anti-sticking molecules [92], or in a vapor phase process. The latter can he done either by thermal evaporation of the liquid precursor at atmospheric pressure [93] or by vacuum evaporation at room temperature [94]. Chlorosilane molecules are very reactive and able to polymerize, producing particles that can precipitate onto the mold. This is why it is preferable to use the vapor phase process with this type of molecules, leading to smoother surfaces [95]. 

Compared with inorganic deposited films, F-SAMs have several advantages  

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