利用脈衝雷射沉積法在製備氧化鋅緩衝層之矽晶片上成長鈮酸鋰薄膜及表面聲波之應用

Deposition of highly c-axis oriented LiNbO3 thin films on SiO2/Si substrates with a ZnO buffer layer by pulsed laser deposition for surface acoustic wave application

孫孝湧(Shiao-yung Sun)

指導教授 ： 施文欽

大同大學/電機資訊學院/光電工程研究所/碩士(2006年)

摘要

鈮酸鋰薄膜由於晶格常數與矽基板差異很大，所以很難直接在矽基板上成長出高品質的鈮酸鋰薄膜。在本研究中我們利用脈衝雷射沉積技術在具有氧化鋅缓衝層之二氧化矽/矽基板上沉積C軸優選方向的鈮酸鋰薄膜並量測其表面聲波元件特性。我們固定基板到靶材的距離為40 mm 以及脈衝頻率為5 Hz，然後改變氧氣流量(10~40 sccm)、基板溫度(550~750 ℃)、沉積壓力(10-2~15 mbar)、雷射能量(156~183 mJ)、退火氧壓（0.75～10 mbar）、退火溫度（650～750 ℃）以及退火時間（0～120 mins.），並嘗試藉由這些不同參數的改變去成長具有c軸優選方向的鈮酸鋰薄膜。 另外，我們利用X射線繞射儀、掃描式電子顯微鏡以及原子力顯微鏡去分析鈮酸鋰薄膜的晶格結構以及表面型態。研究結果顯示，在最佳的製程參數下會有LiNbO3 (006) 優選方向的產生(膜厚約2.5 μm，半高寬約為 0.18o ) 。經由表面聲波特性的量測得到4 μm電極線寬在LiNbO3/ZnO/SiO2/Si上所量測到的頻率為188 MHz其表面聲速約為3010 m/s，接近LiNbO3 基板之表面聲速3632 m/s。

關鍵字

鈮酸鋰

並列摘要

In general, it is very difficult to deposit highly orientated LiNbO3 thin films on Si substrates since the lattice mismatch between them. In this study, ZnO film was introduced as the buffer layer between the LiNbO3 thin film and the Si substrate to avoid the above problems. Highly c-axis oriented LiNbO3 (006) thin films have been successfully grown on SiO2/Si substrates with a ZnO buffer layer by pulsed laser deposition (PLD) technique. We fixed the target-substrate spacing at 40 mm and the repetition rate of 5 Hz, then changed the oxygen flow rate (10~40 sccm), substrate temperature (550~750 ℃), deposition pressure (10-2~15 mbar), laser energy (156~183 mJ), annealing oxygen pressure (0.75~10 mbar), annealing temperature (650~750 ℃) and annealing time (0~120 mins.) to study the effect of deposition and annealing parameters on the growth of c-axis oriented LiNbO3 thin films. The as-deposited films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscopy (AFM) to analyze their crystalline structure and surface morphology, respectively. The results show that highly c-axis oriented LiNbO3 thin films with thickness of 2.5 μm have been successfully grown on SiO2/Si substrates with a ZnO buffer layer by XeCl excimer pulsed laser deposition technique and the FWHM of LiNbO3 (006) peak of the sample fabricated under optimum deposition parameters is only 0.18o. The center frequency of the LiNbO3/ZnO/SiO2/Si substrate with electrode width of 4μｍ is 188 MHz, and possesses phase velocities is 3010 m/s closed to 3632 m/s on LiNbO3 substrate.

並列關鍵字

LiNbO3

參考文獻

[1] R. M. White and F. W. Voltmer, “Direct piezoelectric coupling to surface elastic waves,” Appl. Phys. Lett, Vol.17, pp. 314-316, 1965

[2] D. W. Kim, S. H. Lee, T.W. Noh , “Structural and nonlinear optical properties of epitaxial LiNbO3 films grown by pulsed laser deposition,” Materials Science and Engineering B56 (1998) 251-255.

[3] R. I. Tomov, T. K. Kabadjova, P. A. Atanasov, S. Tonchev, M. Kaneva, A. Zherikhin, R. W. Eason, “LiNbO3 optical waveguides deposited on sapphire by electric-field-assisted pulsed laser deposition,” Vacuum 58 (2000) 396-403.

[4] H. K. Lam, J. Y. Dai, H. L. W. Chan, “Orientation controllable deposition of LiNbO3 films on sapphire and diamond substrates for surface acoustic wave device application,” Journal of Crystal Growth 268 (2004) 144-148.

[5] S. Takada, M. Ohnishi, H. Hayakawa, N. Mikoshiba, “Optical waveguides of single-crystal LiNbO3 film deposited by rf sputtering,” Appl. Phys. Lett. 24 (1974) 490-492.