微米尺寸高溫超導薄膜結構之研製 --- 直流濺鍍鈦膜遮罩對選擇性磊晶成長釔系超導薄膜之研究

Abstract

本文旨在探討選擇性磊晶成長(SEG)應用在製作微米尺寸超導薄膜元件的製程與相關之物理機制。研究顯示，SEG的主要機制係釔系薄膜中之鋇極易與形成在基板表面之鈦氧化物作用而來。觀察以直流濺鍍法形成鈦膜遮罩圖案對釔系薄膜之SEG的影響時，吾人發現，欲形成較佳之選擇成長，鈦層厚度必須大於一臨界值，才會完全破壞在其上成長之YBCO的超導性。SEG最大的特點為可在臨場(in-situ)狀態下直接製成圖案化的薄膜元件，並保有薄膜最適切的超導特性。尤有甚者，在形成鈦遮罩的前置處理中，把影響元件尺寸的瓶頸步驟—蝕刻成像—改置於鍍超導薄膜之前，將使得應用SEG的製程，具與目前之半導體製程整合的潛力。最後，我們成功地利用此製程製備了微米尺寸的微橋與陣列結構之超導薄膜元件。

We have explored the detailed processes and the physical mechanisms of the selective epitaxial growth (SEG) of Y1Ba2Cu3O7 (YBCO) films. Micron-sized superconducting thin film structures were successfully demonstrated by using dc-sputtered Ti-masks for YBCO SEG. It was found that Ti-layer reacts with the YBCO to form an amorphous Ba-Ti-O compound during the YBCO growth. For different substrates, there exist a critical thickness of the Ti-layer for obtaining entirely non-superconducting films on the masked areas. One of the outstanding features of the present SEG technique is the capability of fabricating the patterned device structure in-situ. Moreover, in the current process, all the lithography and etching processes are finished prior to YBCO deposition. As a result, not only is very compatible to semiconductor technologies, but also can eliminate completely the post-deposition etching and patterning processes.