Investigation of charge‐trapping centers in low‐pressure chemical vapor deposition Si₃N₄ thin films

Abstract

Defects in Si3N4 films formed by low‐pressure chemical vapor deposition (LPCVD) were investigated by election spin resonance measurement. At room temperature, no electron spin resonance signal was observed in as‐deposited films. When the films were illuminated by ultraviolet ray (UV), signals of dangling bonds of Si (Si‐DB, N3  Si) are detected, where the g‐values were 2.0028 and the half‐value width was 14 G. This means there are N vacancies of weak Si: Si bonds (N3  Si : Si  N3) and/or dipolar‐type defects (N3  Si : Si  N3) caused by redistribution of electrons in N vacancies which cause pairs of defects (N3  Si:−, +Si  N3) by UV illumination. It is proposed that these vacancies can become dipolar‐amphoteric charge‐trapping centers of electrons and holes. The trap density and the charge‐trapping behaviors were investigated by evaluating the characteristics of MNOS nonvolatile memory devices with Si3N4 gate dielectrics.