Bonding structure and etching characteristics of amorphous carbon for a hardmask deposited by DC sputtering

Abstract

An amorphous carbon hardmask was fabricated by DC sputtering to evaluate the etching characteristics for semiconductor microstructure patterning. The bonding structure of the carbon films deposited by sputtering was modified by the DC sputtering conditions and the deposition pressure. In the case of a low-pressure deposition process, an sp3-bonding-rich amorphous carbon film was fabricated and had excellent etching resistance. On the other hand, during the high-pressure deposition process, an sp2-bonding-rich amorphous carbon film was fabricated and had poor etching resistance. To understand the degradation process of the carbon hardmask induced by the penetration of fluorine ions into the film during dry etching, the phenomenon of fluorine penetration into the film and the interaction between fluorine and the carbon bonds were studied by density functional theory (DFT). Through the DFT calculations, it is unveiled that the energy barrier for the migration of a fluorine atom through the sp3 bonding path is much larger than that of a fluorine atom through the sp2 bonding path in amorphous carbon.