{'fraction_non_alphanumeric': 0.020535714285714286, 'fraction_numerical': 0.017857142857142856, 'mean_word_length': 4.719387755102041, '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}}
Highly Selective SiO 2 Etching Using CF 4/C 2H 4

The relationship between the chemical structure of a polymer film and SiO2/Si selectivity was studied using X-ray photoelectron spectroscopy (XPS) and Fourier transfer infrared spectroscopy (FT-IR)-attenuated total reflection (ATR) measurements to achieve a highly selective SiO2 etching using mixed gases based on CF4. The analysis of the chemical structure of the deposited polymer film revealed that the formation of a polymer film with a low F/C ratio on the Si surface is necessary for a lower etch rate of Si, and the formation of a polymer film with a low concentration of C–Hx species on the SiO2 surface is necessary to increase the etch rate of SiO2. Therefore, highly selective etching requires a deposited polymer film with a low concentration of fluorine and hydrogen atoms. The chemical structures of the deposited films depends on the exhaust rate. Based on these results, a highly selective SiO2 etching with a SiO2/Si selectivity of over 2000 was achieved at the low temperature of 20°C by controlling the exhaust rate using mixed gases of CF4 and C2H4.