In this work electroless nickel-phosphorous coatings were used as the micro heaters for scanning thermal microscopy. The deposition of Ni-P alloys not only simplified the microelectromechanical system fabrication steps but also provided flexibility in the tuning of the resistance of the heating elements. Ni-P films were plated on patterned silicon substrates and silicon with a silicon nitride film. The pre-deposition reactive ion etch (RIE) treatment caused a change in surface roughness that enhanced the adhesion of Ni-P coatings. Optimization of RIE parameters and pH values could achieve selective deposition of Ni-P, thus helped the lift-off of a serpentine circuit pattern. The chemical composition and microstructure of Ni-P films affect the electrical properties of micro heaters. Energy-dispersive X-ray spectroscopy identified the Ni-P composition and confirmed its insignificant level of oxidation. The high-temperature X-ray diffraction indicated that the as-deposited film was crystalline Ni, which later transformed into Ni3P at higher temperature. The resistivity of Ni-P films was tailored between 10- 5 and 10- 7 Ω m via a post-deposition annealing, which also obtained a stable temperature coefficient of resistance. Consequently, the performance of micro heaters could be designed with a high degree of flexibility.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry