Advanced Superthin Polysilicon Film Obtained by Si+ Implantation and Subsequent Annealing

Abstract

The random solid‐phase grain growth behavior of Si⁺‐implanted very thin silicon films and its related electronic properties have been investigated. Si⁺‐implanted disordered silicon films showed variable range hopping conduction and high electron spin resonance (ESR) center density of more than 10¹⁹/cm³. Two‐dimensional dendritic crystal grains grew with subsequent furnace annealing at 600°C. Nucleation time retarded for the increase of Si⁺ dose. Maximum grain size of 5 μm was obtained. Moreover, remarkable photoconductivity was seen and films changed to activated type of conduction after polycrystallization. We have fabricated a superthin film transistor using these films and obtained field effect electron mobility more than 100 cm²/V · s. Mobility value depended on grain size, i.e., the Si⁺ dose that corresponded to the ESR center density in disordered Si⁺‐implanted films.