Fabrication and properties of GeSi and SiON layers for above-IC integrated optics

A study is presented on silicon oxynitride material for waveguides and germanium–silicon alloys for p-i-n diodes. The materials are manufactured at low, CMOS-backend compatible temperatures, targeting the integration of optical functions on top of CMOS chips. Low-temperature germanium–silicon deposition, crystallization and doping are studied for integrated photo detection up to ∼1500 nm wavelength. An investigation of the process window for laser crystallization is presented aiming toward the localization control of crystal boundaries and the achievement of crystals larger than 2 μm. Further, an inductively-coupled-plasma chemical vapor deposition process is presented for silicon oxynitride manufacturing at 150 °C wafer temperature, yielding low-loss material in a wide optical spectral range. Integration schemes for an optical plane on top of CMOS using these materials are discussed.