Halide chemical vapour deposition of Ta2O5

Tantalum oxide, Ta2O5, has a wide range of interesting properties, for inst ance, a high dielectric constant, protonic conductivity, low leakage curren t and the material is possibly electrochromic. Tantalum oxide thin films ha ve been prepared using many deposition methods, including chemical vapour d eposition (CVD). The most widely used tantalum precursors in CVD of Ta2O5 a re Ta(OC2H5)(5) and TaCl5. A drawback with these materials is that carbon a nd chlorine, respectively, may be incorporated into the films. Furthermore, low temperature films are generally amorphous, and thermal annealing above 700 degrees C is necessary for crystallization. In the present study, Ta2O 5 is deposited by CVD using tantalum pentaiodide, TaI5, and oxygen as sourc e materials. For deposition temperatures between 300 and 800 degrees C, smo oth, well-adherent and iodine free films were deposited on Si(100) substrat es. X-ray diffraction measurements showed that the films were crystalline a s-deposited and consisted of the orthorhombic beta-Ta2O5 phase. The dielect ric constant for a film deposited at 600 degrees C was measured to be 25.8. (C) 1999 Elsevier Science S.A. All rights reserved.