Diffusion and oxidation of plasma-enhanced chemical-vapor-deposition silicon nitride and underlying metals

Plasma-enhanced chemical-vapor deposition (PECVD) was employed to grow sili con nitride at various temperatures to find its application in magnetic ran dom access memory. Diffusion and oxidation of PECVD nitride (SiNx : H) and underlying metals (Ta and Cu) have been studied through Auger electron spec troscopy measurements. Oxygen content on the SiNx : H surface and character istic sputtering time (t(0)), after which the oxygen signal falls below the measuring errors of the system, were used to characterize the oxidation of SiNx : H films. It is found that both oxygen content and to increase signi ficantly for decreasing deposition temperature. The oxygen content is large r for SiNx : H films with lower Si/N ratios. Cu oxidation was investigated through changing sample loading methods. Strong oxidation was observed for samples loaded at higher temperatures, while almost no oxidation was detect ed for samples loaded at room temperature and heated to the deposition temp erature after pumping the chamber to high vacuum. Strong diffusion of Si in to Cu film was detected for high-temperature-deposited layers. Independent of loading methods, the Si concentration in Cu increases dramatically as th e deposition temperature increases after exceeding 150 degreesC, whereas th ere is nearly no observable Si signal in Ta for the whole deposition temper ature range. The Cu signal was also detected in nitride films deposited at 200 degreesC, while Cu cracks were observed when the deposition temperature was larger than or equal to 250 degreesC. (C) 2001 American Vacuum Society .