導電薄膜材料對矽晶圓與氮化鋁基板接合之研究

Abstract

本論文主要目的是研究以導電薄膜材料對矽晶圓與氮化鋁基板接合，前後分別以無磊晶晶圓及產品晶圓接合後做微觀檢驗及破壞性測試結果，其接合後強度及對溫度信賴性測試是否可以達到如碳化矽為基板的高功率半導體元件要求。 首先，以沒有磊晶的晶圓先做可行性評估，在沒有長晶的矽晶圓背面和氮化鋁基板上濺鍍接合金屬層，之後以導電薄膜材料作為中間介質層以進行晶圓接合程序。接合後，從CSAM檢驗結果發現，燒結後的晶圓金屬層接合的品質相當良好，之後切割成不同大小接合晶粒，此導電薄膜材料對機械切割的承受能力也很好，從切割晶粒邊緣量到內部最大的碎裂長度只有26.7um。接下來，以掃描式電子顯微鏡觀察檢驗在信賴性溫度循環測試前、後，不同大小切割晶粒的縱切面都很平整，沒有破裂或是脫層的現象發生。此外，做破壞性推力測試，推力值測出來的讀值都在二十公斤以上。最後，金屬接合層所量測的熱阻值為0.46K/W。 接著，依據無磊晶晶圓的實驗製程條件及方法用實際磊晶的產品晶圓來做最後的驗證，後者的實驗結果證實與前者一致，導電薄膜材料對矽晶圓和氮化鋁基板大面積的接合性有很優良的特性。

The main purpose of this thesis is to investigate the adhesion of a silicon wafer to an aluminum nitride (AlN) substrate using a conductive adhesive thin layer. The experiments were first carried out on blank wafers. The wafer under evaluation was composed of a metallic thin film sandwiched between a silicon wafer blank and an AlN substrate. The dices from the tested wafer were carefully examined using the scanning electron microscopy (SEM) and confocal scanning acoustic microscopy (CSAM) before and after the thermal cycling and shear tests. No signs of cracks or delamination were observed on the silicon, conducting thin film, and AlN. The dices sustained under a shear force as large as 20 kg. The samples began to show cracks from the Si side at a shear force over 20 Kg. The metallic layer of the sample under test had a thermal resistance of 0.46 K/W. Finally, comparisons were made with the same measurements performed on the wafer blanks and the production wafers. The production wafer, which was composed of a metallic thin layer sandwiched between an integrated circuit (IC) silicon wafer and an AlN substrate, was examined through the same tests as the wafer blanks. The testing results from the production wafers showed excellent interface properties and were consistent with those of wafer blanks.