The Characteristics of New n-Type Polycrystalline Silicon Thin-Film Transistors Employing Alternating Magnetic-Field-Enhanced Rapid Thermal Annealing
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 n+ amorphous silicon (n+ 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 (VTH) of -7.99 V at a drain bias of 0.1 V, a field-effect mobility of 7.14 cm2/V ldr s, a subthreshold swing (S) of 0.68 V/dec, and an ON/OFF current ratio of 107. The diffused phosphorous ions (P+ ions) in the channel reduced the VTH and increased the S value.
Uniform Poly-Si TFTs for AMOLEDs Using Field-Enhanced Rapid Thermal Annealing
Polycrystalline Si thin film transistors (TFTs) have been fabricated through solid phase crystallization using field-enhanced rapid thermal annealing (FE-RTA) system. The system consists of inline furnace modules for preheating and cooling of the glass substrates and a process module for rapid radiative heating combined with alternating magnetic field induction. The FE-RTA system enables crystallization of amorphous Si at high throughputs without any glass damages. While the typical grain structures of poly-Si by FE-RTA are similar to those of solid phase crystallization, the residual amorphous Si and intragranular defects are reduced.
The effect of hydrogen species on the electronic properties of nc-Si:H prepared in a triode PECVD system
Abstract The effect of hydrogen species on the microstructures and the electronic properties of nanometer sized crystalline silicon (nc-Si:H) prepared in a triode plasma-enhanced chemical vapor deposition (PECVD) system with a hydrogen-diluted silane plasma were investigated. It has been found that for a given set of deposition parameters there is a threshold value of dilution ratio ( H 2 H 2 + SiH 4 ) for the formation of nc-Si:H, which suggests that a minimum concentration of hydrogen atoms should be provided at the growing surface during the deposition processes. The electronic properties of nc-Si:H were changed when the H 2 dilution ratio was greater than 94%. The dark-conductivity, σ d , increased from 10 −10 to 10 −3 S/cm, although the photo-conductivity, σ ph , changed by only one order of magnitude. In addition, the drift mobility, μ d , increased from 0.8 to 16 cm 2 /V · s. The dependence of the electronic properties on the hydrogen content and structural configurations in nc-Si:H is briefly discussed.