應用光熱效應之相變化奈米微影製程

Abstract

近幾年來，超穎材料研究發展得很快。然而，製作奈米級且反應 在可見光波段超穎材料非常的困難且昂貴。因此，我們發展高聚焦超 快雷射在相變化材料 (鍺銻碲合金)上寫下奈米結構之光熱奈米微影 術。高聚焦之雷射光斑可以將熱能侷限在很小的區域，並產生結晶化 或非晶化之過程。在實驗中，利用 AFM 來觀察相變化以及切割造成的 表面形貌及分析其生成原因，且得到最小線寬 97 nm。我們也以熱傳 導分析來研究相變化的過程以及區域，並以數值方法得出線寬和功率 的關係，當低功率時和實驗有相當好的擬合。另外，切割深度和切割 率和功率，寫線速度的關係及物理也有定性上的說明。在應用方面， 我們也製作了大小 500 奈米見方的卍字手性結構，線寬約為 100 奈 米。表示此方法有製作奈米級結構的能力，並且提供低成本和低複雜 度的優點。

In recent years, the research of metamaterials has developed quickly. However, the fabrication of metamaterials responding to visible light is still difficult and expensive. Therefore, the novel opto-thermal nanolithography is proposed. In this thesis, the opto-thermal nanolithography of as-deposited Ge2Sb2Te5 (GST) film using tightly focused femto-second pulsed laser has been studied. A focused laser spot is utilized to generate a spatially confined hot area in a Ge2Sb2Te5 film, where heat induced amorphization or crystallization of Ge2Sb2Te5 would take place. Hence, two different phases are observed. In our experiment, the topography of direct-writing lines is investigated, and the minimum line width of 97 nm is achieved by this technique. Some charecteristics of topography are studied. We also study the phenomenon theoretically by solving the heat-conduction equation to deduce the temperature distribution and to account for amorphization and crystallization. Numerical results for the relation between the line width and the laser power are obtained. In application, a planar chiral metamaterial (gammadion shape) with a unit cell size of 500×500 nm2 is fabricated. It is demonstrated that the technique provides a low-cost nanofabrication for metamaterials.