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 degrees 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 degrees 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. (c) 2005 Elsevier B.V. All rights reserved.