High Temperature Thin Film Strain Sensor Calibration and Mounting
High temperature thin film strain sensor accuracy depends on rigorous apparent strain polynomial correction, dielectric barrier integrity, and drift mitigation.
High Vacuum Sputtering System
Deposition Vacuum
Controlled vacuum processing equipment enables physical vapor deposition of thin film sensor grids and dielectric isolation barriers. Operating a high vacuum sputtering system maintains base pressures below one ten-thousandth of a pascal to eliminate residual atmospheric contaminants. Magnetron cathodes generate dense plasma fields that sputter target materials onto precision-cleaned structural components.
Cryogenic and turbomolecular pumps provide hydrocarbon-free pumping speeds to preserve film purity. Process gas delivery systems introduce argon and oxygen via mass flow controllers for precise reactive deposition.
Chamber Architecture
Stainless steel vacuum vessels incorporate water-cooled walls, substrate heating platens and multi-target magnetron assemblies. Substrate heaters maintain controlled deposition temperatures up to eight hundred degrees Celsius to promote film adhesion and crystalline density. Load lock chambers isolate the main processing volume to maintain vacuum integrity during part transfer.
Rotating substrate holders ensure uniform film thickness over complex aerodynamic geometries. In-situ quartz crystal microbalances monitor real-time deposition rates.
Plasma Physics
Radio frequency and direct current power supplies excite argon gas atoms into high-energy ions that bombard target materials. Target atoms eject and travel through the low-pressure chamber to condense upon the substrate surface. Magnetic field confinement increases ionization efficiency and permits low-pressure operation down to one tenth of a pascal.
Reactive sputtering with oxygen gas synthesizes stoichiometric metal oxide dielectrics such as alumina or zirconia. Sputtering power and gas ratios directly govern film stoichiometry and intrinsic growth stress.
System Boundary
Target poisoning occurs during reactive sputtering when dielectric layers form on the target surface, reducing deposition rates and causing arcing. Residual water vapor contamination elevates film resistivity and promotes film delamination during subsequent thermal cycling. Calibration routines require periodic vacuum gauge recalibration and film thickness profilometry on witness samples.
System base pressure sets the minimum achievable impurity level within deposited sensor grids. Uniformity degrades rapidly when target erosion creates deep racetrack grooves.