氮化鋁的氧化及與銅接合後的熱性質研究

Abstract

氮化鋁的氧化行為已經過廣泛的研究，一般認為氮化鋁的氧化機制在低溫是反應控制，在高溫是擴散控制。在本研究中，氮化鋁氧化後的重量變化和氧化層的厚度皆用於活化能計算。氧化層的微結構分析指出有很多小孔洞充斥在氧化層中，孔洞的形成產生額外的表面導致進一步的反應。因此，氮化鋁氧化在低溫下由反應控制，並在高溫時繼續控制一段短時間。在氧化的過程中，擴散也同時發生，直到氧化層夠厚使得孔洞的通道無法連通時，才由擴散控制氧化。 在氮化鋁基板表面產生一層氧化層有助於後續的金屬化製程。預氧化後的氮化鋁基板和銅片接合。氮化鋁基板的氧化層是多孔的，當氧化層厚度大於6 μm時會降低熱擴散係數和抗彎強度。有一層薄氧化層的氮化鋁基板在1070°C可以和銅片接合。經過接合後薄氧化層保持穩定，但會阻礙熱傳導。銅與氮化鋁的雙層結構在25°C之熱傳導係數可達120 W/mK。

The oxidation behavior of aluminum nitride has been investigated intensively for many years. The oxidation mechanisms that have been proposed are reaction at lower temperatures and diffusion at higher temperatures. In the present study, both the weight gain and the thickness of the oxide layer formed during oxidation were monitored. Detailed microstructure analysis of the oxide surface was also conducted. The analysis indicates that the oxide layer was full of small pores. The formation of pores generates additional surface area to induce further reaction. The reaction mechanism thus controls oxidation at lower temperatures for a long time and at higher temperatures for a short time. The diffusion process takes place simultaneously and becomes dominant when the oxide layer is so thick that the pore channels are fully blocked. To introduce a surface oxide layer onto aluminum nitride substrate helps its subsequent metallization. The pre-oxidized AlN substrate is then bonded to a copper plate. The oxide layer of the substrate is porous, and its presence degrades thermal diffusivity and flexural strength at thicknesses greater than 6 μm. An AlN substrate with a thin oxide layer can bond directly to copper plate at 1070°C. The thin oxide layer remains stable after bonding with copper plate; however, it acts as a barrier to thermal conduction. After joining with copper plates, Cu/AlN bilayers exhibit a thermal conductivity around 120 W/mK at 25°C.