Molybdenum Silicide

Molybdenum silicide (MoSiᵪ, commonly MoSi₂ or amorphous Mo₀․₇₅Si₀․₂₅) is a refractory compound that couples very high melting and oxidation resistance with good electrical conductivity and moderate hardness. In contrast, its amorphous variants retain uniformity and internal stress control at nanometre scales. Thin films are formed chiefly by magnetron sputtering or e‑beam evaporation; adjusting power, silicide target composition, and substrate temperature lets engineers switch between dense amorphous layers for superconducting devices and polycrystalline MoSi₂ for high‑temperature structural coatings. In semiconductor process flows, MoSi serves as a self‑aligned silicide contact, local interconnect, diffusion barrier, and stable gate or resistor film, while poly‑MoSi₂ provides oxidation‑resistant heaters and protective MEMS coatings that tolerate >1000 °C. Optically, MoSi-based stacks act as durable mid-IR absorbers, high-temperature plasmonic and selective-emitter coatings, and soft-X-ray mirror multilayers when paired with Si, supporting beamline monochromators and compact Göbel mirrors. Amorphous MoSi becomes superconducting near 6–8 K, enabling state‑of‑the‑art superconducting nanowire single‑photon detectors, kinetic‑inductance detectors, low‑loss microwave resonators, and rapid single‑flux‑quantum circuitry for cryogenic logic. Its radiation tolerance, thermal stability, and moderate density also suit MoSi films for space optics, shielding components, and harsh‑environment sensors, underscoring their versatility wherever robust, high‑temperature, or superconducting thin‑film performance is required.

Deposition of MoSi using sputtering method

Molybdenum silicide is particularly attractive for optical coatings because co-sputtering Mo with Si allows precise control of MoSi stoichiometry—and, in turn, the film’s refractive index at the design wavelength.

MoSi alloy can be deposited by DC co-sputtering in either Sputter-System Metal-Oxide(PC1) or Sputter-System Metal-Nitride (PC3)—collectively referred to as the Cluster Lesker. The process uses two 3-inch targets:

Mo (unbonded)

Si (indium-bonded)

Achieving the desired composition and optical properties requires careful tuning of three key parameters:

Magnetron power on each target

Substrate temperature

Deposition pressure

Below is a link summarizing process results obtained with the Metal-Oxide (PC1) system:

MoSi Co-sputtering in Sputter-System Metal-Oxide(PC1)