介電薄膜熱傳導係數的量測與探討

Measurement and discussion of dielectric thin film thermal conductivity

賴威志(Wei-Chih Lai)

指導教授 ： 饒達仁

國立清華大學/工學院/微機電工程研究所/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00455

摘要

介電薄膜在MEMS元件設計中的應用層面非常廣泛，因此介電薄膜的熱物理特性對於產品的性能預估與設計分析十分重要，而在熱物理特性當中，熱傳導性質占了很重要的一環。然而由於尺寸效應的影響，當薄膜材料熱傳導係數值會與塊材有所不同，因此必須要利用適合此種薄膜特性之量測實驗架構，將薄膜材料之熱傳導係數值求取出來。本實驗使用3ω量測方法針對不同製程下的二氧化矽薄膜來進行量測，並結合真空低溫系統對其進行低溫的量測，量測溫度的範圍為(83K~293K)，經由實驗結果發現，由於Thermal oxide薄膜孔洞率較低的緣故，其熱傳導係數在相同條件下比PECVD oxide還低。除此之外，進行在不同溫度下，對於二氧化矽薄膜其熱傳導係數是否會造成影響?結果發現熱傳導係數會隨著溫度降低而降低，這是因為溫度越低，導致尺寸效應也就會越明顯，最後將所得到的量測數據透過計算，可以得出邊界熱阻和薄膜本質熱傳導係數的數值。經由結果發現，3ω 量測方法結合真空低溫系統，不但可以精確量測二氧化矽薄膜的熱傳導係數，也能針對在不同溫度下對於熱傳導係數是否會造成影響，未來將可以拓展其應用層面對於其他的介電薄膜進行量測。

關鍵字

3ω 量測方法 ； 熱傳導係數 ； 邊界熱阻

並列摘要

Heat transport in 30–300 nm thick dielectric films is characterized in the temperature range of 74–300 K using the 3ω method, which is a simple method to measure the cross-plane thermal conductivity of dielectric thin films. Dielectric film samples of two kinds, deposited on Si substrates using plasma enhanced chemical vapor deposition (PECVD) and grown by thermal oxidation, were measured in the cryogenics system. The apparent thermal conductivity, intrinsic thermal conductivity, and interface resistance have been analyzed in different environment temperature. The measured data with this method were verified with the measurement results from published data, which showed satisfactory agreement.
For this experiment, we discovered the thermal conductivity of PECVD SiO2 films was smaller than the conductivity of SiO2 grown by thermal oxidation, because the porosity of thermal SiO2 is smaller than PECVD SiO2. The apparent thermal conductivity of SiO2 films decreases with film thickness. The thickness dependent thermal conductivity is interpreted in terms of a small interface thermal resistance RI. For SiO2 films, the thermal conductivity decreases if the temperature decreases, because the mean free path of heater carriers increases.
3ω method combined with the cryogenics system could not only measure the thermal conductivity of SiO2 accurately, but also treat the influence of thermal conductivity on different temperature environment. In the future, we could broaden the use of this combination to measure other thin films.

並列關鍵字

3ω method ； thin film thermal conductivity ； interface resistance

參考文獻

[1]D.G.Cahill, "Thermometry and thermal transport in micro/nanoscale solid-state devices and structures". Journal of Heat Transfer, 2002. 124(2): p. 223~241.

[3]D.G.Cahill, "Heat transport in dielectric thin films and at solid-solid interfaces". Microscale Thermophysical Engineering, 1997. 1: p. 85~109.

[4]N.Taketoshi, T.Baba, and A.Ono, "Development of a thermal diffusivity measurement system for metal thin films using a picosecond thermoreflectance technique". Meas. Sci. Technol, 2001. 12(10): p. 2064~2073.

[5]D.McConnell and K.E.Goodson, "Thermal conductivity of doped polysilicon layers". Journal of Microelectromechanical systems, 2001. 10(3): p. 360~369.

[6]K.Kurabayashi, "Measurement of the thermal conductivity anisotropy in polyimide films". Journal of Microelectromechanical systems, 1999. 8(2): p. 180~191.