Effect of Bias Voltage on Mechanical Properties of HiPIMS/RFMS Cosputtered Zr-Si-N Films.

Zr-Si-N films with atomic ratios of N/(Zr + Si) of 0.54-0.82 were fabricated through high-power impulse magnetron sputtering (HiPIMS)-radio-frequency magnetron sputtering (RFMS) cosputtering by applying an average HiPIMS power of 300 W on the Zr target, various RF power levels on the Si target, and negative bias voltage levels of 0-150 V connected to the substrate holder. Applying a negative bias voltage on substrates enhanced the ion bombardment effect, which affected the chemical compositions, mechanical properties, and residual stress of the Zr-Si-N films. The results indicated that Zr-Si-N films with Si content ranging from 1.4 to 6.3 atom % exhibited a high hardness level of 33.2-34.6 GPa accompanied with a compressive stress of 4.3-6.4 GPa, an H/E* level of 0.080-0.107, an H3/E*2 level of 0.21-0.39 GPa, and an elastic recovery of 62-72%.

Surface Engineering of Polycrystalline Silicon for Long-Term Mechanical Stress Endurance Enhancement in Flexible Low-Temperature Poly-Si Thin-Film Transistors.

The surface morphology in polycrystalline silicon (poly-Si) film is an issue regardless of whether conventional excimer laser annealing (ELA) or the newer metal-induced lateral crystallization (MILC) process is used. This paper investigates the stress distribution while undergoing long-term mechanical stress and the influence of stress on electrical characteristics. Our simulated results show that the nonuniform stress in the gate insulator is more pronounced near the polysilicon/gate insulator edge and at the two sides of the polysilicon protrusion. This stress results in defects in the gate insulator and leads to a nonuniform degradation phenomenon, which affects both the performance and the reliability in thin-film transistors (TFTs). The degree of degradation is similar regardless of bending axis (channel-length axis, channel-width axis) or bending type (compression, tension), which means that the degradation is dominated by the protrusion effects. Furthermore, by utilizing long-term electrical bias stresses after undergoing long-tern bending stress, it is apparent that the carrier injection is severe in the subchannel region, which confirms that the influence of protrusions is crucial. To eliminate the influence of surface morphology in poly-Si, three kinds of laser energy density were used during crystallization to control the protrusion height. The device with the lowest protrusions demonstrates the smallest degradation after undergoing long-term bending.