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|Design and fabrication of Fresnel lens and piezoelectric transducer for ultrasonic ejectors
|2013-03-25 16:20:12 (UTC+8)
|發展超音波噴墨技術應用於商業化列印裝置中，一直呈現增長之趨勢，其技術中包括了超音波噴墨裝置的使用。超音波噴墨裝置中的兩個主要元件：四階菲涅爾透鏡與壓電換能器，將在本論文中呈現與探討因製作參數的改變而影響其特性。為了改善超音波能量之聚焦效率，本研究探討了操作頻率於100與200MHz下之菲涅爾聚焦透鏡的設計與製作方式。藉由試驗實驗，除了探討因製程參數對四階菲涅爾透鏡之外表輪廓所造成之影響，並找尋了最佳製程程序。其採用兩層光罩而無硬遮罩之製程程序首次被實行且可成形四階菲涅爾透鏡之外表輪廓，雖然結果並不理想。而菲涅爾透鏡之品質可藉由使用SiO2薄膜為硬光罩之二和三層光罩製程獲得改善；與使用二層光罩製程比較，使用三層光罩製程可獲得較佳側壁輪廓之菲涅爾透鏡。此外，觀察SU-8感光保臒膜於聚焦透鏡外表輪廓所造成之結果，可用來評估使用二層光罩製程所製作四階菲涅爾透鏡之聲能聚焦效率；有限元素法模擬結果顯示，利用表面輪廓來估測菲涅爾透鏡之效率是一種有效的評估工具。為了設計與製造壓電換能器，本研究中亦探討了影響ZnO薄膜晶元生長之影響因子，其中包括有無熱處理之鋁、鉑，射頻功率，Ar:O2氣體比，ZnO薄膜晶元生長之基板溫度。在射頻功率178瓦，基板380 ?C，10mTorr沉積壓力，與50% Ar:O2氣體比之條件下，高c軸方向性之ZnO薄膜可順利的沉積於退火後之Pt/Ti/SiO2/Si基板。此外，本研究提出兩步驟之ZnO薄膜沉積方式，可用來發展結構為Al/ZnO/Pt/Ti/SiO2/Si之壓電換能器，其分別在第一與第二步驟中，使用0.7 Pa與1.3 Pa沉積壓力，射頻功率100與178瓦，濺鍍 Ar:O2氣體比為1:3與1:1之條件。上述條件可藉由觀察沉積參數所造成的ZnO薄膜特性與高c軸方向性結構紋理，來加以確認。The tendency of developing ultrasonic printing technology is increasing in the commercialized printing devices, which incorporate with ultrasonic ejectors. In this thesis, the influences of fabrication parameters on the characteristics of four-level Fresnel lens and piezoelectric transducers, which are the two main components of an ultrasonic ejector, will be presented and discussed.The design and fabrication of Fresnel focusing lenses operating at frequencies of 100 and 200 MHz was investigated in order to enhance the focusing efficiency of ultrasonic energy. The effects of process parameters on the four-level Fresnel lens profiles were discussed to find a most feasible fabrication procedure through some trial experiments. A fabrication process employing a two-mask without using a hard mask was first carried out. The profile of four-level Fresnel lens was shaped even it was not really expected. The quality of the Fresnel lens was improved when two- and three-mask processes using a SiO2 film as the hard mask are employed. Besides, a better side-wall profile of Fresnel lens was obtained by using the three-mask process as compared to the two-mask one. In addition, a two-mask fabrication process of a four-level Fresnel lens was used to evaluate its characteristics through investigating the effect of SU-8 photoresist on the profile of the focusing lens. Besides, an investigation of the influence of surface profile on the efficiency was proposed to evaluate the acoustic energy focusing efficiency of the fabricated Fresnel lens. The simulation results of the FEM showed that it can be a useful tool to estimate the efficiency of Fresnel lenses through their surface profiles in trailed fabrications.For design and fabrication of the piezoelectric transducer, the influences of factors that can affect the crystallization growth of ZnO films were figured out and investigated. The influences of aluminum (Al), platinum (Pt) with/without heat treatment, RF power and the Ar:O2 gas ratio; substrate temperature on the crystallization growth of ZnO films wereiiiproposed and discussed. Indeed, highly c-axis (002) oriented ZnO films were successfully deposited on Pt (annealed)/Ti/SiO2/Si substrates under feasible conditions, such as RF power of 178 W, substrate temperature of 380 ?C, deposition pressure of 10mTorr and Ar:O2 gas flow ratio of 50%. Besides, a two-step deposition of ZnO films was proposed to develop a feasible fabrication of a piezoelectric transducer with the structure Al/ZnO/Pt/Ti/SiO2/Si under reasonable conditions, which include deposition pressure of 0.7 Pa and 1.3 Pa, RF power of 100 W and 178 W, and sputtering gas ratio Ar:O2 = 1:3 and 1:1 for first and second step, respectively. These conditions were applied and confirmed through investigating the influences of deposition parameters on the properties of ZnO films. Highly c-axis textured and other reasonable properties of ZnO films were confirmed.
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