Metallo-organic low-pressure chemical vapor deposition of Ta₂O₅ using TaC₁₂H₃₀O₅N as precursor for batch fabrication of microsystems

Ta₂O₅ thin films were produced by metallo-organic low pressure chemical vapor deposition using Tantalum(V) Tetraethoxydimethylaminoethoxide (TaC₁₂H₃₀O₅N) as precursor. This liquid precursor at room temperature makes it possible to deposit thin films of Ta₂O₅ on wafer batches of up to 35 wafers. In this communication, we report on the processing and equipment development to achieve batch fabrication, and on the optimization of the deposited thin films properties for their application in microsystems. An evaporator was linked to a horizontal hot wall furnace. The deposition of Ta₂O₅ was performed at 425 °C and the influence of a post-annealing at higher temperatures on the chemical, electrical and optical properties of the films was evaluated. Annealing treatments in oxygen were found to reduce the amount of residual carbon and hydrogen in the films. An annealing in oxygen followed by an annealing in forming gas was used to improve the charge levels and hysteresis. The optical properties of the amorphous Ta₂O₅ films varied slightly with the annealing treatment. Annealing the films at a temperature of 700 °C and higher caused their crystallization, leading to a decrease of their optical bandgap. The processed films have found applications in microsystems as chemical resistant coatings, optical coatings for wave guides, and chemical sensitive layers for Ion-Sensitive Field-Effect Transistors.