{'fraction_non_alphanumeric': 0.0202757502027575, 'fraction_numerical': 0.009732360097323601, 'mean_word_length': 5.5638297872340425, '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}}
Study on Sapphire Wafer Grinding by Chromium Oxide (Cr2O3) Wheel

Finishing process of sapphire wafer is meeting huge challenge to fulfill the strict requirement of high surface quality in semiconductor industry. Fixed abrasive process, although can guarantee the profile accuracy, leaves damaged layer on the surface or subsurface of sapphire wafer. Chemical mechanical polishing (CMP) is famous for providing great surface roughness, however, sacrifices surface geometrical accuracy. Therefore, a new chromium oxide (Cr2O3) sapphire grinding wheel based on chemical mechanical grinding (CMG) principle has been developed and its performance has also been put into examination. The experiment result has demonstrated that Cr2O3 possesses an outstanding potential in terms of a high material removal rate of sapphire wafer, meanwhile, largely reduces surface roughness from about 150nm to below 10nm in 1 hour. In addition, the design of experiment (DOE) has also been carried out to study the effect of influencing factors towards ultimate surface roughness of sapphire wafer. It reveals that the revolution speed of sapphire wafer bears twice greater influence towards surface roughness than the revolution speed of grinding wheel.