微奈米尺度薄膜之熱傳導量測方法研究開發

Novel Methods Development for Measuring Thermal Conductivity of Micro/Nanoscale Thin-Film

簡恒傑(Heng-Chieh Chien)

指導教授 ： 饒達仁

國立清華大學/原子科學院/工程與系統科學系/博士(2010年)

https://doi.org/10.6843/NTHU.2010.00002

摘要

本論文研究利用一組推導出來的熱源-薄膜-基板系統之數學解析解(analytical solution)，利用這組解析解，本研究開發出三種可應用於不同膜厚範圍之薄/厚膜熱傳導性能(thermal conductivity)量測方法。並且利用這些量測方法，量測估算出金屬-介電層之界面熱阻(metal-dielectric interfacial thermal resistance)。在創新量測方法研究開發方面，首先在50 nm~2 μm膜厚範圍內，本論文研究發展出一種我們稱為平行線法(parallel-strip method)的創新量測方法，同時我們量測了三種不同製程所沉積的SiO2薄膜，同時與先前之文獻值比較，結果相當吻合。在2μm ~10μm膜厚範圍內，我們修正了平行線法的部份關係式，發展出另一個薄膜量測法，並且針對電化學沉積技術(electroposition process)所沉積之Bi-Te與Sb-Te熱電薄膜(thermoelectric thin-film)進行量測。同時也針對熱電薄膜結構易碎的限制，研究出一種測試樣品製備的方法，結果成功量測出三種不同製程參數所成長的熱電薄膜。在膜厚10 μm ~1000 μm厚膜方面，我們使用相同的數學解析解，推導出一種我們稱為膜厚差異法(thickness difference method)之創新方法。該方法針對SU8厚膜進行量測，同時與文獻值比較，結果非常吻合。而在金屬-介電層之界面熱阻量測方面，我們使用平行線法，針對一種三明治薄膜結構(sandwiched film structure)進行量測。結果量測出五種不同金屬，Cr、Ti、Al、Ni、Pt，與PECVD SiO2之界面熱阻值，並研究證實連續二流體理論模型(the continuum two-fluid model)，無法完整解釋金屬-介電層界面熱阻之發生機制，同時該項研究也嘗試利用TEM觀察，與簡單的模擬估算，提出一種導因於界面不完美熱接觸之界面熱阻成因解釋。

關鍵字

薄膜 ； 熱傳導係數 ； 界面熱阻 ； 量測 ； 微機電 ； 熱電材料

並列摘要

Many methods for the measurement of the thermal conductivity of thin films have been reported in the previous scientific literatures. Because each class of thin-film structure presents an almost unique set of experimental impediments to overcome, no particular measurement method has become universally accepted. Therefore, different strategies and many techniques are needed for developing a simple, convenient and reliable measurement method for each class thin-film.
In this study, we had derived a set of mathematical analytical solution from a complete heater-film-substrate system model. Based on the analytical solutions, we had successfully developed three novel methods for three different thickness ranges of thin/thick film. In the range of film thickness between 50 nm to 2 μm, a novel method, called parallel-strip method, had been developed and three types of SiO2 been measured in that work. The measured results agree with that of the previous literatures. In the range between 2 μm to 10 μm, a modified parallel-strip method had been developed and four types of thermoelectric thin films fabricated by electrodeposition process had been measured, also an epoxy resin layer, substitute for SiO2 to serve as the dielectric layer, were introduced to the sample preparing process. For thick-film of 10 μm to 1000 μm in thickness, a novel method, called thickness difference method, had been built. The method is very simple because derived from a concise semi-empirical correlation. SU8 thick film had been tested by using the novel method and yielded a quite accurate result compared with the previous literatures.
By using parallel-strip method and a sandwiched film structure, metal-dielectric interfacial thermal resistance had also been studied in this work. A metal layer of thickness about 10 nm, including Cr (chromium), Ti (titanium), Al (aluminum), Ni (nickel) and Pt (platinum), is sandwiched between two PECVD SiO2 layers of thickness 100 nm. The estimates, 10-10~10-9 m2 K/W, calculated with a continuum two-fluid model are significantly smaller than the measured values, ~10-8 m2 K/W. The continuum two-fluid model, which according to the phenomena of electron-phonon nonequilibrium near the interface in a metal, cannot explain completely the cause of this metal-dielectric interfacial thermal resistance. From photographs of the TEM cross section, we argue that defects at an interface likely play an important role in the magnitude of the interfacial thermal resistance.

並列關鍵字

thin-film ； thermal conductivity ； interfacial thermal resistance ； measurement ； MEMS ； thermoelectric material

參考文獻

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