Investigation of airborne molecular contamination adsorption rate as storage materials in mask

Abstract

The haze issue has gradually increased in the 65 nm node technology and beyond. This issue has been reporting that it is caused by chemical reaction among ions like SO42-, NH4+ and aromatic hydrocarbon compounds (AHCs) such as butylated hydroxy toluene (BHT), toluene and etc. on mask by 193 nm laser in general. This haze growth causes defects with accumulation of exposure energy. Finally, it decreases the lifetime of photomask with an increase in defects. The source of this haze is generated from storage materials as well as chemical residue in the photomask process. Therefore, we investigated the adsorption rate of airborne molecular contamination (AMC) on each layer with storage materials which were assumed to be the source of the haze. We analyzed adsorbed ions and volatile organic compounds (VOCs) on each layer to verify the effects of storage materials for some storage periods by automatic thermal desorption gas chromatography/mass spectrometer (ATD GC/MS) and ion chromatography (IC). Also, we investigated the contact angle of each layer as AMC concentration of storage materials. From the experimental results, we confirmed that the adsorption rate of AMC was different on each layer as storage materials.