Effects of O_2/Ar ratio and annealing temperature on electrical properties of Ta_2O_5 film prepared by magnetron sputtering

The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies.

Temperature dependences of optical properties,chemical composition,structure,and laser damage in Ta_2O_5 films

Ta2O5 films are prepared by e-beam evaporation with varied deposition temperatures, annealing temperatures, and annealing times. The effects of temperature on the optical properties, chemical composition, structure, and laser- induced damage threshold （LIDT） are systematically investigated. The results show that the increase of deposition temperature decreases the film transmittance slightly, yet annealing below 923 K is beneficial for the transmittance. The XRD analysis reveals that the film is in the amorphous phase when annealed below 873 K and in thehexagonal phase when annealed at 1073 K. While an interesting near-crystalline phase is found when annealed at 923 K. The LIDT increases with the deposition temperature increasing, whereas it increases firstly and then decreases as the annealing temperature increases. In addition, the increase of the annealing time from 4 h to 12 h is favourable to improving the LIDT, which is mainly due to the improvement of the O/Ta ratio. The highest LIDT film is obtained when annealed at 923 K, owing to the lowest density of defect.

The Optical Properties of Nanostructured Ta_2O_5 Films

Amorphous Ta_2O_5 films were prepared on Si (100) substrates by thermal oxidization.The film consisted of amorphous Ta_2O_5 nanostructure that grew vertically and compactly at a large range.It was found that Ta_2O_5 films became crystalline when annealed at or above 650℃and remained amorphous below 650℃.The effects of annealing on the optical properties of Ta_2O_5 film were also discussed.It is estimated that the refraction indexes and the optical energy gaps of both amorphous Ta_2O_5 film and crystal one are stable.The optical energy gap of as-deposited Ta_2O_5 film is about 4.81 eV.The above results indicate that Ta_2O_5 films have a promising application in the optical devices.

离子束溅射Ta_2O_5薄膜光学性质的热处理研究

使用离子束溅射法,在熔融石英衬底上沉积Ta_2O_5薄膜,并将Ta_2O_5薄膜置入100℃到500℃的环境中退火.通过XRD、透过率光谱、面吸收测试,研究了热退火温度对Ta_2O_5薄膜折射率与面吸收的影响.总结了退火温度与薄膜折射率与面吸收的对应关系,并给出简单的理论解释.该结论对Ta_2O_5薄膜的制备及光学性能调控提供一定的参考价值.

Capacitive Microwave MEMS Switch

A novel capacitive microwave MEMS switch with a silicon/metal/dielectric as a membrane is fabricated successfully by bonding and etching-stop process. Its principal, design, and fabricating process are described in detail. A patterned dielectric layer, Ta2O5, with dielectric constant of 24 is reached. Experiment results show this novel structure,where the switch＇s dielectric layer is not prepared on the transmission line, features very low insertion loss. The insertion loss is 0.06dB at 2GHz and lower than 0.5dB in the wider range from De up to 20GHz,especially when the transmission line metal is only 0. 5μm thick.

Laser-induced damage threshold in n-on-1 regime of Ta_2O_5 films at 532,800,and 1064 nm

Ta205 films were prepared with conventional electron beam evaporation and annealed in 02 at 673 K for 12 h. Laser-induced damage thresholds （LIDTs） of the films were performed at 532 and 1064 nm in 1-on-1 regime firstly, and then were performed at 532, 800, and 1064 nm in n-on-1 regime, respectively. The results showed that the LIDTs in n-on-1 regime were higher than that in 1-on-1 regime at 532 and 1064 nm. In addition, in n-on-1 regime, the LIDT increased with the increase of wavelength. Furthermore, both the optical property and LIDT of Ta205 films were influenced by annealing in 02.