Characteristics of low-temperature silicon nitride (SiN x:H) using electron cyclotron resonance plasma

Abstract

Silicon nitride (SiN x :H) thin film deposited at 50°C using an electron cyclotron resonance plasma-enhanced chemical deposition (ECR PECVD) system has been explored. This 50°C silicon nitride deposited on a 150 mm diameter Si wafer shows an acceptable uniformity; ±0.9% of average index of refraction and ±6.5% of average thickness are maintained across 150 mm diameter of the Si wafer. As-deposited 50°C silicon nitrides have a leakage current density value of 2–3×10 −9 A/cm 2 at electric fields of 2 MV/cm and a breakdown electric field (i.e., field at a current density of 1×10 −6 A/cm 2) greater than 6 MV/cm. X-ray photoelectron spectroscopy (XPS) analysis displays that chemical bonding structure of this low-temperature ECR silicon nitride is very comparable to that of 250°C PECVD nitride. However, IR absorption data indicate that the low-temperature ECR nitride has more Si–H bonds and fewer N–H bonds than the high-temperature PECVD nitride. These ECR films manifest resistance to buffered oxide etchant (BOE) attack with the etch rates that are slower than 50% of a 250°C PECVD nitride. The lower concentration of N–H bonds may enable these low-temperature nitrides to resist BOE attack.