Influences of the nitrogen content on the morphological, chemical and optical properties of pulsed laser deposited silicon nitride thin films

Abstract

Silicon nitride (SiN x ) thin films of various stoichiometries ( x) were prepared on Si (100) substrates applying the Nd:YAG ( λ=1064 nm) pulsed laser deposition (PLD) process from pure Si targets in the “shaded off-axis” technique at room temperature. The specific arrangement of this technique with perpendicular target and substrate surfaces and a metallic screen in between guarantees very low particulate (droplet) deposition and, thus, excellent surface qualities. The about 80- to 100-nm-thick silicon nitride films have very smooth surfaces (∼0.5–1.5 nm roughness) and dense structures. The N 2 partial pressure strongly influences the nitrogen content and the silicon bonding structure of the films analyzed by means of secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS), resp. As a consequence, the optical properties examined by spectroscopic ellipsometry are tailorable in a wide spectral range between 250 and 1200 nm.