ELECTRICAL PROPERTIES OF B-DOPED POLYCRYSTALLINE Si_(1-x-y)Ge_xC_y FILM DEPOSITED BY ULTRACLEAN LOW-PRESSURE CVD

摘要

The relationship between electrical properties of B-doped poly-Si_(1-x-y)Ge_xC_y and heat-treatment conditions has been investigated. Poly-Si_(1-x-y)Ge_xC_y films with average B concentration of, 1.5x10~(20) cm~(-3) were deposited on thermally oxidized Si(100) at 500-650 ℃ in a SiH_4-GeH_4-SiH_3CH_3-H_2 gas mixture by an ultraclean hot-wall low-pressure chemical vapor deposition, followed by ~(11)B~+ ion implantation and heat-treatment. The resistivity decreases with increasing Ge fraction and increases with increasing C fraction. Hall measurement and X-ray diffraction results suggest that the disordered regions near grain boundaries are reduced by the existence of Ge and density of the carrier traps at grain boundaries is increased by C segregation at grain boundaries. From the results of subsequent heat-treatment at lower temperature, it is also suggested that B segregation at grain boundaries is suppressed by the existence of C at grain boundaries.