Properties of the p+ poly-Si gate fabricated using the As preamorphization method

In a deep submicon p-channel metal oxide field effect transistor (PMOSFET), the importance of the p+ poly-Si gate with less boron penetration and higher conductivity increases. With As implantation prior to B+ implantation, the conductivity of the p+ poly-Si gate was improved and the boron penetration was suppressed. These phenomena can be attributed to the enhancement of the grain growth in the As-preamorphized film and the retarded boron diffusion during annealing. DC conductivity of the film preamorphized by As+ ions at 180 keV and 4×1014 cm-2 was about 36% higher than that of the B implanted film without As preimplantation, in spite of the carrier compensation effect. Cross-sectional transmission electron microscopy (XTEM) micrographs show the bilayer with an upper layer of larger grain size (approximately 0.22 μm) and a lower layer of smaller grain size (approximately 0.03 μm) in the preamorphized and annealed film.