氮氣流量與基板偏壓對氮化鉬薄膜結構與性質之影響研究

Effects of Nitrogen Flow Rate and Substrate Bias on Structure and Properties of Molybdenum Nitride Thin Films

周卓徵(Cho-Cheng Chou)

指導教授 ： 黃嘉宏

國立清華大學/原子科學院/工程與系統科學系/碩士(2019年)

摘要

本研究的目的在於透過調控氮氣流量以及基板偏壓，探討實驗參數對於氮化鉬薄膜的結構與性質的影響，以及在氮缺乏情形下的相變化行為。本研究使用非平衡磁控濺鍍於矽(100)基板上鍍覆氮化鉬薄膜，並分別透過調控氮氣流量(N系列)與基板偏壓(B系列)製備出兩種系列的試片。由實驗結果得知薄膜的氮鉬比會隨著氮流量上升而增加(N/Mo=0.23-0.49)，而當提高基板偏壓，氮鉬比的變化是不一致的(N/Mo=0.29-0.42)。在N系列的試片中，我們發現隨著氮流量上升，會有三種不同的相成分組成，在高氮流量8 sccm時為單相的γ-Mo2N，在中等流量6 - 7 sccm為雙相的Mo 和 γ-Mo2N，在低流量 4 - 5 sccm為混相的Mo、γ-Mo2N和β-Mo2N。在B系列中，大多數的試片為雙相的Mo和γ-Mo2N，只有在高偏壓時產生混相的Mo、γ-Mo2N和β-Mo2N。鍍製出的氮化鉬薄膜皆為(200)為主的優選方向。對於薄膜的結晶度，由於氮化鉬的反應較差，在低氮流量4 sccm時的結晶度較差；在足夠的氮流量5 sccm以上時可以呈現較好的結晶度。我們發現本研究中的基板偏壓範圍所導致的離子轟擊對於氮化鉬薄膜無明顯效果，提高基板偏壓並不會造成破壞，反而會幫助反應提升結晶度。氮化鉬薄膜的殘留應力介於 +0.3至-1.2 GPa之間，而電阻係數值介於78.7至150.2 μΩ-cm之間。金屬鉬的產生有助於釋放壓應力以及降低電阻係數值。具有優良機械性質之氮化鉬薄膜製程參數範圍很大，並可以容許大量的金屬鉬存在。由於奈米晶結構的關係，薄膜變形由晶界調控機制主導，因此硬度保持在22.4至25.8 GPa小範圍之間。在本研究中，推測β-Mo2N的形成可能是在Mo與γ-Mo2N的相界面之間發生異質成核，此推測由量測接觸角實驗驗證之。

關鍵字

氮化鉬 ； 金屬氮化物 ； 陶瓷薄膜

並列摘要

The purposes of this study were to investigate the effect of nitrogen flow rate and substrate bias on the structure and properties of MoNx thin films and to explore the phase transition of MoNx under an N-deficient condition. The MoNx thin films were deposited on Si (100) substrate using DC unbalanced magnetron sputtering with varying nitrogen flow rates (N-series) and substrate bias (B-series). The N/Mo ratio increased (N/Mo=0.23-0.49) with nitrogen flow rate but varied (N/Mo=0.29-0.42) with substrate bias. For N-series, three types of MoNx thin films were found at different nitrogen flow rates, including single-phase γ-Mo2N at 8 sccm, Mo and γ-Mo2N phases at 6 - 7 sccm, and the mixed phases of Mo, γ-Mo2N, and β-Mo2N at 4 - 5 sccm. For B-series, most of the specimens are Mo and γ-Mo2N phases, while the mixture of Mo, γ-Mo2N, and β-Mo2N was also found at high substrate bias -90V. (200) preferred orientation was dominated for all specimens. Due to low reactivity between Mo and N, the crystallinity was poor at low nitrogen flow rate (4 sccm), while better crystallinity appeared at 5 sccm and above. Owing to weak ion peening effect in the range of substrate bias voltage of this study, the increasing substrate bias did not significantly damage the film structure but improve the crystallinity. The residual stress of the specimens ranged from +0.3 to -1.2GPa and the electrical resistivity ranged from 78.7 to 150.2 μΩ-cm. It was found that the existence of Mo could relieve compressive stress and decrease the electrical resistivity. The process window for maintaining good mechanical properties was quite large for the Mo2N thin films even with large fraction of metal phase. Due to the nanocrystalline structure, the hardness of the Mo2N coatings only varied in a narrow range from 22.4 to 25.8 GPa and the hardness was not significantly affected by the presence of metal phase. The finding that β-Mo2N appeared accompanying with Mo metal phase may be due to heterogeneous nucleation of β-Mo2N at the interface between γ-Mo2N and Mo phase.

並列關鍵字

Molybdenum nitride ； TMeN ； Ceramic thin film

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