Effects of Ge Layer and Si3N4 NanoCap Layer On Metal-Induced Laterally Crystallized Polycrystalline Silicon TFTs

We known that the three major methods to recrystallize amorphous silicon are: Rapid Thermal Annealing(RTA), Excimer Laser Crystallization (ELC) and Solid Phase Crystallization(SPC)[3.1][3.2].Solid phase crystallization and RTA has several advantages over laser crystallization which include smoother surfaces, better uniformity, and batch process in furnace annealing. But in order to achieve the requirements imposed by the integrated fabrication on glass substrate, the polysilicon TFT's performance must be optimized and fabricated at a suited temperature (<600℃).So SPC and RTA, their processing temperature of around 600 still exceeds the upper temperature limit of glass substrates, are not suited to use. Nevertheless, it has been reported earlier that amorphous silicon (a-Si) thin films can be crystallized at temperatures as low as 450℃ by metal-induced crystallization (MIC) method[3.3][3.4][3.5].But the annealing temperature (>=500℃) is still too high for poly-Si TFT device to fabricated on conventional glass substrate , and the long annealing time of MILC, also increase the thermal budget in the poly-Si TFT fabrication process. However in current years, the papers are proposed that using a Ge layer can enhance MILC growth velocity three times compared with that in the a-Si single layers[3.6] and decrease nucleation temperature significantly with increasing Ge fraction[3.7].But they are still never to test the electrical characteristic.