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

Silicon nitride (SiNx:H) thin film deposited at 50 degrees C using an electron cyclotron resonance plasma-enhanced chemical deposition (ECR PECVD) system has been explored. This 50 degrees 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 degrees C silicon nitrides have a leakage current density value of 2-3 x 10(-9) A/cm(2) at electric fields of 2 MV/cm and a breakdown electric field (i.e.. held at a current density of 1 x 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 degrees 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 degrees C PECVD nitride. The lower concentration of N-H bonds may enable these low-temperature nitrides to resist BOE attack. (C) 2000 Elsevier Science Ltd. All rights reserved.