The effects of minute impurities (H, OH, F) on the SiO2/Si interface investigated by nuclear resonant reaction and electron spin resonance

The effects of minute amounts of impurities (H, OH, and F) in SiO ₂ are investigated to obtain a guideline for improving the reliability of MOS devices. To examine the behavior of hydrogen, deuterium (D) is adopted as a tracer. The quantity of deuterium dissolved in SiO₂ is measured by the D(³He,p)⁴He nuclear resonant reaction (NRR) technique. The SiO₂/Si interface structure is examined by electron spin resonance (ESR) measurement. Hot-carrier injection with MOS capacitors and transistors are examined to determine the effects of minute impurities on the electrical characteristics of gate SiO₂ and the correlation of this effect with the NRR and ESR experimental results. Significant amounts of D₂O are dissolved into SiO₂, even at 200°C, and the dissolved D ₂O is eliminated at temperatures above 700°C. The disappearance of the interface traps at temperatures higher than 800°C is thought to be due to the viscous flow of SiO₂ or due to the interface reoxidation, since in both cases the interface strain is relaxed. Reduced hydrogen concentration and relaxation of the interface strain are essential for improving the MOS device endurance against hot carriers