Thermal Stress Effects on the Electrical Properties of p-Channel Polycrystalline-Silicon Thin-Film Transistors Fabricated via Metal-Induced Lateral Crystallization

Abstract

We developed a method to compact the glass sheets of a flat-panel displays that use metal-induced laterally crystallized (MILC) polycrystalline-silicon (poly-Si) thin-film transistors (TFTs), and the effects of thermal stress on the fabricated devices were compared against those of a bare-glass device. The glass substrate was exposed to a temperature of 650 • C for 40 h in order to suppress the glass shrinkage to 0.01 ppm, which suitable for a MILC poly-Si TFT process. The compressive strain that originates from glass shrinkage generally increases the size of the micro-cracks and the vacancies, and as a result, most of the electrical parameters of a bare glass device (such as the on-current, off-current, field-effect mobility, subthreshold slope, and threshold voltage) had a higher level of degradation than those of the device with the compacted glass. The increase in the on-current and the field-effect hole mobility under the compressive strain for poly-Si TFTs showed a similar behavior to that of single-crystalline-silicon (c-Si) TFTs under compressive strain. However, the increase in the off-current was the converse of that of strained c-Si TFT.Index Terms-Metal-induced lateral crystallization (MILC), polycrystalline-silicon (poly-Si) thin-film transistor (TFT), glass shrinkage, thermal stress.

Effect of dopant on metal induced lateral crystallization rate

“…Thus, the MILC rate of LPCVD intrinsic Si was higher than that of PECVD intrinsic Si because reaction (6) is faster than reaction (9). It is well reportedly known that a-Si atomic bond breaking and migration at interface 1 is more difficult in PECVD a-Si than in LPCVD a-Si because of passivated Si-H bond in PECVD a-Si.…”

“…However, there are still some problems to be solved, such as high manufacturing cost and uniformity. To address these problems, the metal-induced lateral crystallization (MILC) technique has been developed [9][10][11][12][13][14][15][16]. The MILC technique has several advantages, such as low-batch cost, simple processing method, low-temperature (under 570 °C) process, and high electrical performance of the device [17,18,19,20].…”

Compressive Stressed P-Channel Polycrystalline-Silicon Thin-Film Transistors for High Field-Effect Mobility

“…Moreover, J. H. Park et. al also showed that fabricated a metal-induced lateral crystallized (MILC) poly-Si TFT in a bare glass which induces the shrinkage during MILC growth can observe a strain-effect in the device [8]; however the microcracks originating from the grain-boundaries are also generated and lead to a poor electrical and reliability performance..…”