Boron-doped amorphous carbon deposited by DC sputtering for a hardmask: Microstructure and dry etching properties

[Display omitted] •Amorphous carbon-based hardmasks with high etch selectivity are essential for highly integrated semiconductor processes.•Doping the amorphous carbon film with boron enhanced its density and selectivity due to increasing the sp3 bonding ratio.•The long-term etching characteristics of high-aspect-ratio patterning found that an amorphous carbon film doped with a high boron concentration degraded with etch time increased.•Boron doping can significantly enhance the performance of the hardmask in a semiconductor process, but the bonding with oxide must be controlled. Boron-doped amorphous carbon (a-C) films have been investigated as a hardmask material for improving semiconductor integration, deposited using direct current (DC) magnetron sputtering with varying boron concentrations. Increased boron doping concentration in a-C led to a higher etch resistance but also resulted in the gradation of etch resistivity in the depth direction of the film, as confirmed by a continuous dry etching process. Scanning transmission electron microscopy electron energy loss spectroscopy showed an increase in the sp3 ratio of the film owing to boron doping as well as gradation in the B K edge region of a film doped with a high concentration of boron. This is because the high reactivity between boron and oxygen results in the reaction of residual oxygen in the chamber with boron. Time-of-flight secondary ion mass spectrometry was used to evaluate the penetration resistance to fluorine ions in the dielectric etchant. The results confirmed that B-O bonding resulted in relatively low fluorine resistance. Boron bonded with carbon can significantly improve the dry etch performance; however, bonding with oxygen needs to be effectively controlled to realize desirable film properties. Overall, this study demonstrates the potential of boron-doped a-C films as a hardmask material for the semiconductor industry.