Tae Kyung Won

The Latest Plasma-Enhanced Chemical-Vapor Deposition Technology for Large-Size Processing

The thin-film transistor liquid crystal display (TFT-LCD) industry has in recent years demanded ever-larger- area substrate processing capability to keep up with consumer market demands for larger and larger displays. This paper discusses the latest plasma-enhanced chemical-vapor deposition (PECVD) system, the AKT 50 K PECVD, which handles up to 2160 x 2460 mm2 substrates. As substrate size increases, lowering the processing temperature is getting even more important to improve production reliability and cost performance. The most commonly used process temperature for the so-called active layers of amorphous silicon (a-Si) TFTs is approximately 350 degC. In this paper, a newly developed single-chamber low-temperature PECVD active-layers process is discussed. In particular, our low-temperature process maintains film performance at the same level as high-temperature active layers while also maintaining system productivity and throughput.

Amorphous-silicon thin-film transistor on soda-lime glass

— Amorphous-silicon (a-Si:H) thin-film transistors (TFTs) on soda-lime glass were fabricated by using a diffusion barrier and a low-temperature process at 200°C. The silicon nitride barrier was optimized in terms of diffusion blocking effectiveness, film adhesion, and surface finish. TFTs on soda-lime glass achieved a saturation mobility 0.47 cm2/V-sec, threshold voltage of 0 V, an off-current of 7.7×10−11 A, and a sub-threshold swing of 1.0 V/dec. From diffusion experiments, a 30,000-hour lifetime for the TFT device at 80°C was estimated, and the robustness of the silicon nitride barrier against long-term migration of sodium was demonstrated.