Micro Crystalline Silicon TFT by the Metal Capped Diode Laser Thermal Annealing Method

Abstract

A novel crystallization method for silicon based thin film transistor (TFT) is proposed for the fabrication of high performance large size flat panel displays. In spite of using almost the same TFT fabrication process as that of hydrogenated amorphous silicon (a-Si:H) TFT, the proposed metal capped laser thermal annealing method realizes the formation of uniform and dense micro crystalline silicon (μc-Si), and provides mobility of 3.1 cm2/V•s, threshold voltage (ΔVth) of 2.3 V, and sub threshold slope (S) of 0.93 V/decade. Moreover, proposed stacked n+ amorphous silicon structure realizes extremely low off-current maintaining high on-current. As the reliability of TFT, a threshold voltage sift (ΔVth) under the high current bias stress test (BTS) condition was investigated, and realized the assumed ΔVth of +1.77 V after 100,000 hours stress of 10 μA and 50°C. This value is 2 orders smaller than that of a-Si:H TFT and only three times larger than that of low temperature poly silicon (LTPS) TFT.We believe that our μc-Si TFT technology is the suitable solution for the high quality, large size flat panel display mass-production.

An Advanced 405-nm Laser Diode Crystallization Method of a-Si Film for Fabricating Microcrystalline-Si TFTs

“…These values clearly show that the μc-Si TFT has superior parameters compared to those of the a-Si TFT. In addition, our μc-Si TFTs have higher μ, steeper S, and lower Vt than those in previous studies [4], [6], although the current on/off ratio is comparable. These excellent BG μc-Si TFT characteristics are considered the result of high crystallinity in the channel region and good source/drain contacts (as previously stated in Sect.…”