Optical losses of multilayer stacks synthesized with silicon oxynitride by r.f. magnetron sputtering

• Published in: Thin solid films Vol. 333; no. 1; pp. 126 - 133
• Main Authors: Pinard, L., Mackowski, J.M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 23-11-1998; Elsevier Science; Elsevier
• Subjects: Astrophysics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cosmology and Extra-Galactic Astrophysics; Deposition process; Exact sciences and technology; Multilayers; Optical coatings; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Optical properties of specific thin films, surfaces, and low-dimensional structures; Physics; Multilayers; Optical coatings; Optical properties; Deposition process; Thin films; Optical losses; Refractive index; Silicon Oxynitrides; Experimental study; Antireflection coatings
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(98)00850-5

Silicon oxynitride thin films, deposited by r.f. magnetron sputtering, are used to synthesize multilayer stacks such as high reflectivity mirrors. The SiO
x
N
y
refractive index and the optical performances of these layers are measured at 1064 nm and the two compositions SiO
2 and Si
3N
4 were chosen to realize the multilayers. The losses (absorption, scattering) are measured and compared to the performances of the Ta
2O
5/SiO
2 mirrors deposited by dual ion beam sputtering. The absorption level (40 ppm) is eight times higher than that of the Ta
2O
5/SiO
2 mirrors. This is due to the high absorption coefficient of Si
3N
4. In contrast, the scattering is not governed by the material properties but by the deposition process. The r.f. sputtering increases the sample RMS roughness. Solutions are proposed to optimize optical losses of Si
3N
4/SiO
2 mirrors.