Three-Dimensional stacked CMOS Inverters Using Laser-Crystallized Poly-Si TFTs

Abstract

High-performance three-dimensional (3-D) stacked poly-Si complementary metal-oxidesemiconductor (CMOS) inverters with a high-quality laser-crystallized channel were fabricated. Lowtemperature crystallization methods of an a-Si lm using excimer-laser annealing (ELA) and sequential lateral solidi cation (SLS) were performed. The n-channel metal-oxide-semiconductor (NMOS) thinlm transistors (TFT) at the lower CMOS layer were fabricated on an oxidized bulk Si substrate and p-channel metal-oxide semiconductor (PMOS) TFT at the upper CMOS layer were fabricated on an interlayer dielectric lm. Considerably uniform silicon grains were obtained by laser annealing. Sub-threshold swings of the fabricated NMOS TFTs at the lower layer and PMOS TFTs at the upper layer were 78 mV/dec. and 86 mV/dec., respectively. The eld e ect mobilities of the NMOS and the PMOS TFTs were 42.5 cm2/V s and 76 cm2/V s, respectively. The on/o current ratio of both TFTs was larger than 107. 3-D stacked poly-Si CMOS inverter showed excellent electrical characteristics and can be used the vertical integrated CMOS applications.