Interface diffusion characteristics of Al–2 at.%Nd/n + a-Si:H and Al–2 at.%Nd/n + poly-Si bilayers

Abstract

In order to use Al–2 at.%Nd as the source-drain electrode of hydrogenated amorphous silicon thin film transistors (a-Si:H TFTs) without diffusion barrier, the diffusion characteristics of Al–2 at.%Nd into phosphorus-doped (n+) a-Si:H were studied, and diffusion between Al–2 at.%Nd and phosphorous-doped poly-Si (n + poly-Si) was also investigated for comparison. The electric resistance variation of Al–2 at.%Nd, n + a-Si:H, and n + poly-Si was measured by four-point probe method at every annealing step, and each surface was inspected by optical microscope. Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy were used to analyze atomic diffusion progress with the variation of annealing temperature. Through these analyses, we ascertain that the Nd element of Al–2 at.%Nd hinders the diffusion between Al and Si, and n + a-Si:H is stable up to 300 °C and n + poly-Si is stable up to 400 °C against the diffusion of Al–2 at.%Nd. Thus Al–2 at.%Nd can be utilized as the source-drain electrode of a-Si:H TFTs below 300 °C and poly-Si TFTs below 400 °C without diffusion barrier.