砷化鎵與矽基板之金屬接合技術研究及其在半導體雷射上的應用

Abstract

為增強單一基板的功能,不同材料間的混成整合已是一愈來愈重要的課 題. 最近的研究大多投入在基板直接整合技術上. 對flip-chip bonding 來說,使用具有多重優點的薄接合材料是一新的趨勢. 在本篇論文中,我們 提出接合材料與元件歐姆接觸的結合. 我們使用可分別作為n及p型砷化鎵 歐姆金屬的金鍺及金鈹合金. 另外,我們也嘗試兩邊用不同材料(砷化鎵用 金鍺或金鈹合金,矽用金)及在矽上用兩層材料(金鍺/金或金鈹/金)的接 合. 首先藉由研究接合溫度,時間及金屬厚度對聯結機械強度的效應,找 出最佳接合條件.為防止表面氧化,我們在幾乎無氧的環境中進行接合,同 時對介面施以壓力. 金鍺合金的最佳接合條件為450~480 C八到十分鐘,而 金鈹合金則是600~630 C八到十分鐘. 我們也觀察到互相擴散所造成的接 合金屬熔點上昇. 接著,我們將GRIN-SCH-QW雷射與表面鍍有不同金屬的 矽基板---金鍺,金,金鍺/金與金鍺細條/金進行接合. 我們得到和接合前 幾乎相同的I-V曲線及接近的L-I特性,顯示雷射特性和電性都得以維持. 與矽基板間通過聯結與歐姆接觸的電導通也建立得很好. 77K和70C間的熱 衝擊在30~35個週期內不會對電性造成衰減. 聯結的機械強度也很好. 進 一步, 我們把雷射接合在蝕刻出來的矽V形凹槽中的金表面及金鍺細條上. 凹槽的54.7度(111)平坦斜面是用來反射雷射光而達到面射的效果. 熱和 機械性質都很好,I-V曲線維持正常特性,而L-I特性也具有和原來相當的起 始電流和量子效率. 這些都証明了這個技術能可靠地產生面射的雷射光, 且有良好的電性. For enhancement of functionality and performance on a single substrate, hybrid integration of dissimilar materials has been an issue with increasingimportance. Much effort has been devoted to direct wafer bonding approachesin recent researches. For flip-chip bonding, the trend of using thin bonding materials with many advantages is reported. In this thesis, we propose the combination of bonding materials with ohmic contacts for devices. We use AU-Ge and Au-Be alloys which are ohmic metals for n- and p-type GaAs respectively. On the other hand, bonding with different materials on both sides (Au-Ge or Au-Be on GaAs with Au on Si) by wetting of low surface energymaterials (alloys) and two layer materials on Si (Au-Ge on Au on Si or Au- Beon Au on Si) are also considered. The first work is to find the optimum bonding condition for each material system by investigating the effects of bonding temperature, bonding time andmetallization thickness. Bonding is proceeded in a nearly oxygen-free ambientpreventing oxide formation with a proper pressure applied to the interfacefacilitating the reaction. Bonding is best achieved at 450~480 C for 8~10 minfor Au-Ge and 600~630 C for 8~10 min for Au-Be. The effect of melting point rise caused by interdiffusion is also observed. Second, we integrate GRIN-SCH-QW lasers to different metallizations on Sisubstrates---Au-Ge, Au, Au-Ge on Au, Au-Ge stripes on Au. Nearly identicalI-V curves and similar L-I characteristics to pre-bonding conditions are obtained, showing maintained laser performance and electrical properties. Good electrical interconnection through the formed bonds and ohmic contacts is well established. Thermal shocks between 77K and 70C cause no I- V curvedegradation up to 30~35 cycles. Further, lasers are bonded to both Au surfaces and Au-Ge stripes in etched Si V- grooves with 54.7 degree (111) smooth surfaces as reflection mirrors to exhibit surface-emitting behavior. Good thermal and mechanical properties are achieved. I-V curves that remain normal and L-I curves with comparablethreshold currents and quantum efficiencies measured right above together prove that this bonding technique is reliable in producing surface- emitting performance of laser light with good electrical properties.