ICMCTF2006 Session D1-2: Carbon Nitride, Boron Nitride and Group-III (Al, Ga, In) Nitride Materials

Friday, May 5, 2006 8:30 AM in Room Sunrise

Friday Morning

Start	Invited?	Item
8:30 AM		D1-2-1 Field Emission from Oriented AlN Thin Films Fabricated by Reactive Magnetron Sputtering A.P. Huang, P.K. Chu (City University of Hong Kong, PR China) Nitrides have stimulated extensive research interest due to their applications in optoelectronic devices and field emitters in recent years. Among them, aluminum nitride (AlN), an important wide band-gap semiconductor material, turns out to be a very promising candidate as a field emitter because of its very small or even negative electron affinity, high mechanical stability, high thermal conductivity, and long-term stability in harsh environment. Such a small or negative electron affinity means that an electron can be extracted from the surface easily when an electric field is applied, which results in a large field-emission current density. Recently, a variety of techniques such as radio-frequency and magnetron sputtering, spray pyrolysis, chemical vapor deposition (CVD), sol-gel process, pulse laser deposition (PLD) and so on have been explored to fabricate AlN thin films. The field emission properties of AlN nanostructures including nanotubes and nanowires have also been reported. However, there have been very few investigations on the field emission properties of oriented AlN thin films. In this work, AlN thin films were prepared with the (100) and (002) orientations by reactive magnetron sputtering, and the influence of the orientation and thickness on the field emission properties were investigated. Our results reveal that the preferential orientation of (002) is beneficial to field emission. Besides, as the thickness of the thin film decreases, the field-emission current density increases, and at a thickness of 400 nm, the current density reaches 28.6/cm² and the turn-on field is close to 5 V/m. Our study suggests that oriented AlN thin films are potentially useful in field-emission-based displays and this paper also describes the underlying mechanism.
8:50 AM		D1-2-2 A Heating and Diffusion Barrier Based on TaSiN_x for Miniaturized IC Devices H.-Y. Cheng (National Tsing Hua University, Taiwan); Y.-C. Chen, C.-M. Lee (Industrial Technology Research Institute, Taiwan); S.-H. Wang, T.-S. Chin (National Tsing Hua University, Taiwan) The simulation using a one-dimensional heat conduction model shows that by inserting a high resistive heating layer (~10 nm thick) between the bottom electrode and phase-change layer will successfully decrease the operation current of a phase- change random-access memory (PCRAM) devices. Highly resistive TaSiN_x films were investigated as candidates of such a heating layer. They were deposited by RF sputtering with TaSi₂ single target at an atmosphere of Ar+N₂ with different ratios of N₂ to Ar. The obtained resistivity, between 0.069 ~1.21 Ω-cm, fulfills the requirements as suitable heating layer suggested by simulations (0.01~1 Ω-cm) with increasing nitrogen content in films up to 52.83 %. All the as-deposited films were amorphous, while nitrogen-free Ta-Si films crystallized at 700°C, all other compositions with substantial nitrogen contents showed excellent thermal stability with amorphous structure sustaining until at least 800°C and exhibited very smooth surface examined by AFM. Besides the heating capability its amorphous structure being lack of grain boundary was found to perform a good diffusion barrier as well between W bottom electrode and Ge₂Sb₂Te₅ phase change films as determined by Auger analysis. The barrier effect was evaluated for an annealing at 400 and 500°C in Ar atmosphere for 30 minutes. The highly resistive TaSiN_x heating layer successfully obstructed the diffusion of tungsten atoms from the W bottom electrodes into Ge₂Sb₂Te₅ phase-change films even if only quite a thin TaSiN_x film of 10 nm inserted between them. With increasing N content, the barrier effect became more significant. Optimal composition of TaSiN_x films as a diffusion/barrier layer for PCRAM was proposed.