The Characteristics of New n-Type Polycrystalline Silicon Thin-Film Transistors Employing Alternating Magnetic-Field-Enhanced Rapid Thermal Annealing

摘要

We fabricated a new top-gate n-type depletion-mode polycrystalline silicon (poly-Si) thin-film transistor (TFT) employing alternating magnetic-field-enhanced rapid thermal annealing. An $hbox{n}^{bm +}$ amorphous silicon ($hbox{n}^{bm +}$ a-Si) layer was deposited to improve the contact resistance between the active Si and source/drain (S/D) metal. The proposed process was almost compatible with the widely used hydrogenated amorphous silicon (a-Si:H) TFT fabrication process. This new process offers better uniformity when compared to the conventional laser-crystallized poly-Si TFT process, because it involves nonlaser crystallization. The poly-Si TFT exhibited a threshold voltage $(V_{{rm TH}})$ of $-hbox{7.99}$ V at a drain bias of 0.1 V, a field-effect mobility of $hbox{7.14 cm}^{2}$/V$cdot$s, a subthreshold swing (S) of 0.68 V/dec, and an on/off current ratio of $hbox{10}^7$. The diffused phosphorous ions ($hbox{P}^{bm +}$ ions) in the channel reduced the $V_{{rm TH}}$and increased the S value.