{'fraction_non_alphanumeric': 0.02734375, 'fraction_numerical': 0.0013020833333333333, 'mean_word_length': 4.961240310077519, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Current status and issues of X-ray mask

The X-ray mask is the most critical and most challenging element of a proximity X-ray lithography system, because the mask's dimensions must equal the final device dimensions and the mask's membrane film, which is only about 2 mm thick, must support a heavy metal absorber pattern. In NTT, we have developed fabrication technologies for highly accurate and defect-free masks, such as multiple exposure and distortion compensation methods in the electron-beam writing step, highly accurate dry etching, and inspection and repair of mask defects. In addition, the feasibility of proximity X-ray lithography was confirmed by fabricating a device. This article describes the current status of and issues with X-ray mask technology.