Ultrahigh Index and Low-loss Silicon Rich Nitride Thin film for NIR HAMR Optics

Ultrahigh index and low-loss silicon rich nitride (SiNx) thin-film material is developed and studied for application in heat-assisted magnetic recording (HAMR) as light delivery system operating in the near infrared (NIR) wavelength range. The film is deposited by low-temperature inductively coupled plasma chemical vapour deposition and developed through the tuning of SiH
₄
/N
₂
/Ar gases ratio. Film characterization of SiN
_x
, including material composition, optical properties, and thermal-optics is presented. X-ray photoelectron spectroscopy shows the spectrum of binding energy and a material composition of x = 0.6. The refractive index of developed film is >3.0 with an optical bandgap around 656 nm according to ellipsometery and photospectrometery measurement. Characterization of ultra-low optical absorption is addressed with the use of ellipsometry and prism coupler waveguide loss measurement and the developed film has an absorption coefficient of about 10
^-5
in the NIR. The thermal optic characterization shows a thermal optical coefficient of 2.66 × 10
^-4
K
^-1
with a stable optical absorption at temperature up to 200 °C. The use of the developed SiNx film for HAMR as high-index contrast nanowaveguide and enabling to integrate III-V semiconductor laser for a fully integrated light delivery system is discussed.