Nanoindentation Behaviour of As-Deposited and Annealed CuO/GaAs Thin Films

退火在氧化銅／砷化鎵薄膜奈米壓痕行為上之效應分析

李偉賢(Woei-Shyan Lee) ； 張家源(Chia-Yuan Chang)

《中國機械工程學刊》 41卷2期 (2020/04) Pp. 107-120

摘要

CuO thin films with thicknesses of 200 nm and 300 nm, respectively, are deposited on GaAs substrates. The mechanical properties of the CuO/GaAs thin-film systems are evaluated under room temperature conditions by nanoidentation tests performed to depths ranging from 150 to 350 nm. The tests are performed using both as-deposited samples and samples annealed at 500℃ for 30 minutes. The results show that for the as-deposited specimens, a pop-in effect occurs in the loading curve for all film thicknesses and nanoindentation depths (150 nm, 250 nm and 350 nm) due to a delamination of the thin film from the substrate. However, for the annealed samples, no pop-in events are observed, irrespective of the film thickness or nanoindentation depth. For both samples (as-deposited and annealed), the maximum indentation load increases with an increasing indentation depth and film thickness. However, the shape of the hardness-depth curve for the annealed specimens is different from that of the as-deposited specimens. Moreover, the hardness of the annealed specimens is less than that of the as-deposited specimens at the maximum indentation depth. Similar tendencies are observed for the variation of the Young's modulus with the indentation depth. Scanning electron microscopy (SEM) observations show that the indentation area increases with an increasing indentation depth and thin film thickness, but decreases in the annealed condition. Furthermore, the transmission electron microscopy (TEM) observations reveal that no delamination occurs for the annealed specimen with the maximum thickness of 300 nm under indentation depths of 150 nm and 350 nm. In addition, dislocations within the GaAs substrate are apparent only in the annealed specimen with a thickness of 300 nm and an indentation depth of 350 nm. The selected area (electron) diffraction (SAED) patterns confirm that the as-deposited and annealed CuO film has a polycrystalline structure, while the GaAs substrate has a single crystal structure. Finally, the high-resolution TEM (HRTEM) micrographs show that the asdeposited and annealed CuO film and GaAs substrate have lattice spacings of 0.25 nm and 0.283 nm, respectively.

關鍵字

Nanoindentation ； GaAs ； Microstructural evolution ； Annealing ； CuO thin films

並列摘要

本研究主要是探討退火在銅／砷化鎵薄膜系統之奈米壓痕行為及薄膜顯微結構上的效應。本實驗首先利用電子束蒸鍍法在砷化鎵晶圓上製作200nm及300nm厚度之銅薄膜，經過退火處理，條件為加熱至500℃，並持溫30分鐘，再分別對200nm試片進行150nm及250nm深度；對300nm試片進行150nm 350nm深度之奈米壓痕試驗，藉以瞭解退火對奈米壓痕行為及微觀結構之影響。奈米壓痕試驗結果顯示，硬度及楊氏模數受退火影響甚鉅，退火前及退火候後之硬度-深度曲線有很大的不同，且在最大壓深下，退火後的硬度值較未退火的低。楊氏模數則有相同的趨勢。負載-深度曲線顯示在對200nm試片進行150nm及250nm深度；及對300nm試片進行150nm 350nm深度時，退火與未退火的荷載曲線皆有pop-in的現象發生；而所有的卸載曲線則都是連續而無pop-out的現象發生。掃描式電子顯微鏡之觀測結果顯示，壓痕的區域隨著壓痕深度及薄膜厚度的增加而增加。穿透式電子顯微鏡之觀測結果證實，薄膜的分離僅發生在膜厚300nm，壓深150nm與350nm。而差排僅形成於膜厚300nm，壓深350nm之退火試片。為結構分析證實CuO薄膜是屬多晶結構，而GaAs為單晶結構。高解析穿透式電子顯微鏡分析顯示，CuO薄膜和GaAs基材的晶格間距分別為0.25nm和0.283nm。