Vertically-stacked bottom- and top- gate polycrystalline silicon TFTs for three dimensional integrated circuit

A high-performance poly-Si TFT with bottom-gate structure and a top-gate poly-Si TFT were vertically stacked for three dimensional integrated circuit. Consequently, the n-channel poly-Si TFTs with bottom-gate structure on the bottom layer showed considerably improved electrical characteristics, such as a high field effect mobility of 390 cm²/V-s due to the large lateral grain formed in the channel. The vertically stacked p-channel poly-Si TFTs with top-gate structure on the top layer showed a high field effect mobility of 131 cm²/V-s. Therefore, the proposed structure is very suitable for future 3D-IC and nano-device application.