EUV mask cleaning by dry and wet processes

In the present ULSI cleaning processes, a photoresist is usually stripped by a combination of dry ashing by ozone (O3) with wet process of the piranha cleaning. The effects of cleaning process of the mask for the extreme ultraviolet lithography (EUVL) are discussed in these dry and wet processes. In dry ashing by O3, the virtual EUVL mask adhered organic contamination is tested. After removing the contamination using a dry ashing by O3, the surface roughness of the mask is decreased from -.54 nm (rms) to 0.42 nm (rms). Also, the periodic structure of the m ask is confirmed. The dry ashing by O3 is effective for removing a contamination of EUVL mask. In wet process, the piranha cleaning and typical RCA wet cleaning are employed at Mo/Si multilayer. The periodic structure of Mo/Si multilayer did not change after Piranha and RCA cleaning except FH solution in dipping long time. We confirmed the Mo/Si multilayer have enough tolerance to the Piranha and RCA cleaning.