利用殘餘應力組裝之讀寫頭Fresnel 透鏡

Abstract

因為資訊技術(IT)的發展，對高速和高密度資料儲存的要求已經變得日益重要，光學資料儲存系統正是其中一種可以滿足這種需求的裝置。對於微型化和質量輕的要求推動了更輕更小的光學資料儲存系統的發展，而微光機電技術(MOEMS)是製造更輕更小的光學資料儲存系統的方法之一。但在此微光機電領域中，量產和自組裝是極重要的技術。如果量產和自組裝可實現，那這將使微光機電技術能夠更容易和以更便宜的方法來生產微型化的光學讀取頭。此研究中，設計了可以使微機電系統能夠被更容易和更便宜的方法來組裝直立元件的機構。 自組裝機構的發展使得微光學元件可以被自動組裝，但現今已開發出的數種可用於組裝直立元件的裝置皆需額外的電熱能或製程。在本論文中的組裝直立元件的機構，是利用製程中最後一道的金屬層本身的應力，設計出殘餘應力臂做為自組裝的機構，來完成了自動組裝直立元件的動作。 此研究中欲組裝的元件為光學讀取頭中的聚焦元件。聚焦透鏡有兩種，一是繞射式透鏡，另一種是折射式透鏡。每一種在光學方面都有它自己的優勢。在這裡，所採用的是繞射式的Fresnel透鏡，因為Fresnel透鏡有孔徑大､薄和輕的優點。輕薄的優點使得在這個系統中的這個結構能夠更容易的被殘餘應力臂抬起組裝。 在許多研究中，討論利用各種不同材料來製作出Fresnel透鏡，例如:多晶矽,AZ4620等等。在本論文中，討論利用厚膜光阻SU-8製作出Fresnel透鏡，因為厚膜光阻SU-8的材質對藍光雷射波長的吸收率極小，欲以此製作出極適用於藍光雷射的Fresnel透鏡。

Because of the progress of information technology (IT), the need for high speed and high density data storage has become increasingly important. The optical data storage system is one of the important devices for this need. The requirement of miniaturization and lightness pushes the development of more miniature and lighter optical data storage system. Micro Optical Electro Mechanical System (MOEMS) technology is one of methods to reach this target. If self-assembly of the MOEMS devices is realizable, it will make the technology an easier and cheaper way to produce the miniaturized pick-up head. It is important to exploit self-assembly mechanisms to assemble optical systems automatically. Until now, several methods have been developed to assemble the upright components, but extra electricity, heat or fabrication processing is needed. In this study, stress-induced beams are used to accomplish the self-assembly function to assemble a Fresnel lens. The tensile stress comes from the last metal layer in the process. The lens is the focusing component in a pick-up head. There are two kinds of lenses. One is diffractive lens, and the other is refractive. Each has its own advantage in optics. Here the diffractive lens – Fresnel lens is used because the Fresnel lens has several advantages such as much larger aperture, thin and light. The advantage of lightness makes it easier to flip up the lens structure by the stress-induced beam in this system. Different materials have been used to manufacture Fresnel lens. In this study, the thickness photoresist SU8 is adopted because the SU-8 has low absorption at blue laser wavelength.