Hydrogen loss and its improved retention in hydrogen plasma treated a-SiNx:H films: ERDA study with 100 MeV Ag7+ ions

TL;DR

This study investigates hydrogen loss mechanisms in a-SiNx:H films under ion irradiation and demonstrates that hydrogen plasma annealing enhances hydrogen retention by healing bonds and passivating dangling bonds, with implications for passivation applications.

Contribution

It provides a detailed ERDA analysis of hydrogen desorption processes and shows that hydrogen plasma annealing improves hydrogen retention in a-SiNx:H films.

Findings

Two distinct hydrogen diffusion processes identified with different rates.

HPA treatment results in higher hydrogen counts at high fluences.

Hydrogen radicals are confined within ~1 nm from their creation point.

Abstract

Hydrogen loss from a-SiNx:H films under irradiation with 100 MeV Ag7+ ions using elastic recoil detection analysis (ERDA) experiments is reported. The results are explained under the basic assumptions of the molecular recombination model. The ERDA hydrogen counts are composed of two distinct hydrogen desorption processes, limited by rapid molecular diffusion in the initial stages of irradiation, and as the fluence progresses a slow process limited by diffusion of atomic hydrogen takes over. Which of the aforesaid processes dominates, is determined by the continuously evolving Hydrogen concentration within the films. The ERDA measurements were also carried out for films treated with low temperature (300 degrees centigrade) hydrogen plasma annealing (HPA). The HPA treated films show an improved diffusion of atomic hydrogen, resulting from healing of weak bonds and passivation of dangling bonds. Further, upon HPA, films also show evolution of hydrogen with significantly higher counts, at advanced fluences, relative to the as-deposited films. These results indicate the potential of HPA towards improved H retention in a-SiNx:H films. The study distinguishes clearly the presence of two diffusion processes in a-SiNx:H whose diffusion rates differ by an order of magnitude, with hydrogen radicals not being able to diffuse beyond ~1 nm from the point of their creation. The results are very relevant for the passivation applications of a-SiNx:H