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

Silicon nitride (SiNx) 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 N2 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.