添加劑對反應燒結氮化矽的影響及其與銅接合行為之研究

Abstract

由於氮化矽(Si3N4)陶瓷的抗化學腐蝕性及抗熱震性、及在高溫中良好的機械性質和磨耗性質，使氮化矽成為具潛力的高溫結構材。在氮化矽陶瓷的製程中，反應燒結製程能降低原料及製程成本，而反應燒結後產品能維持原有的尺寸和高溫穩定性，因此反應燒結氮化矽被廣泛的研究。在本研究中，將單獨添加氧化鋯(ZrO2)、氧化釔(Y2O3)、和同時添加氧化鋯及氧化釔的矽粉在1400oC下氮化後，觀察不同組成添加劑對反應燒結氮化矽的影響。在只添加氧化鋯的系統中，氮化率在最短的時間內可達到最高，但是由於氧化鋯在反應燒結後還留在氮化矽中，使得此系統的熱傳導係數下降。當系統中只存在氧化釔時，氧化釔會與矽粉表面的氧化矽反應成Y2Si2O7，去除留在氮化矽試片中的氧化矽。在同時添加氧化鋯和氧化釔時，會因為氧化鋯與氧化釔反應而產生鋯-釔-氧的化合物，而降低添加劑促進氮化及去除氧化矽的效應。 在本研究中，同時也探討以直接覆銅(Direct bonded of Cu)的方式將多孔的反應燒結氮化矽與銅片在預氧化後進行接合。直接覆銅的方式已被廣泛運用在氧化鋁基板與銅片的接合上，當到達接合溫度時，會因為銅-氧的共晶點在氧化鋁基板表面形成銅-氧混合物的液相，此液相可潤濕氧化鋁表面進而在氧化鋁基板與銅片之間形成銅-鋁-氧的化合物，在降溫後氧化鋁基板和銅片之間就能結合在一起。然而在銅片和氮化矽之間不會形成銅-矽-氧的化合物，因此銅片和氮化矽間的接合靠的是將氧化銅和氧化亞銅滲入氧化矽中。

Because of the superb chemical and thermal shock resistance, excellent mechanical properties at elevated temperature and good wear properties, silicon nitride (Si3N4) is a promising material for high temperature structural applications. Due to the low price of raw powders, the easy control of dimensions and good thermal stability at high temperature, the reaction bonded silicon nitride (RBSN) has been intensively investigated. In the present study, silicon powder was mixed with three different compositions of additives, ZrO2, Y2O3 and ZrO2-Y2O3, and nitrided at 1400oC. The effects of the additives on the nitridation of silicon compacts were investigated. The addition of ZrO2 shows improvement on nitridation rate and density, but decreases the thermal conductivity. The presence of Y2O3 reduces the amount of silicon oxide through the reaction of SiO2 to form Y2Si2O7. However, the co-doping ZrO2 and Y2O3 system forms the Zr-Y-O compound due to the reaction between ZrO2 and Y2O3. Therefore, the effects on improvement on nitridation are suffered. The direct bonding method was used in the present study. The porous RBSN compact and Cu plate were pre-oxidized before the direct bonding process. For the RBSN-Cu system, the Si-Cu-O compound is not formed between oxidized RBSN and Cu. The bonding is constructed by the infiltration of CuO and Cu2O into the SiO2 layer, which is formed on the RBSN surface.