Abstract We utilize indium tin oxide (ITO) as a material for direct bonding of Si wafers at low temperatures and without any pretreatment in order to create junctions of Si-ITO//ITO-Si. Transparent conductive oxides combine good conductivity with high optical transparency, rendering them ideal for joining III-V materials with Si based technology, e.g. to fabricate optoelectronic devices like light emitting diodes or solar cells. We found that bonded wafers did not display macroscopic defects and exhibit a bonding energy greater than 1 J/m2 determined by double cantilever beam test. This bonding strength is high enough to bear further front-of-line processing like backside grinding. The bonding interface was investigated by means of transmission electron microscopy to gain insight into the bonding mechanism. We observed that the bonding mechanism proceeds through grain growth of the ITO layers across the original bonding interface upon annealing above the crystallization temperature of ITO. To explore other factors which could influence the obtained wafer bonds, ITO layers were deposited on Si wafers and characterized before and after annealing by atomic force microscopy, scanning electron microscopy and X-Ray crystallography.

中文翻译：

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氧化铟锡的机理//氧化铟锡直接晶圆键合

摘要 我们利用氧化铟锡 (ITO) 作为在低温下直接键合 Si 晶片的材料，无需任何预处理，以创建 Si-ITO//ITO-Si 结。透明导电氧化物结合了良好的导电性和高光学透明度，使它们非常适合使用基于硅的技术连接 III-V 族材料，例如制造发光二极管或太阳能电池等光电器件。我们发现键合晶片没有显示宏观缺陷，并且通过双悬臂梁测试显示出大于 1 J/m2 的键合能量。这种结合强度足够高，可以承受进一步的前线加工，如背面研磨。通过透射电子显微镜研究键合界面以深入了解键合机制。我们观察到，当在 ITO 结晶温度以上退火时，键合机制通过 ITO 层在原始键合界面上的晶粒生长进行。为了探索可能影响获得的晶片键合的其他因素，在硅晶片上沉积 ITO 层，并通过原子力显微镜、扫描电子显微镜和 X 射线晶体学在退火前后进行表征。