Combined process for wafer direct bonding by means of the surface activation method
Combined process for wafer direct bonding by means of the surface activation method
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表面活化法晶圆直接键合组合工艺
DOI：
10.1109/ectc.2004.1319383
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
M. Howlader
中科院分区：
文献类型：
--
作者：
T. Suga;T. Kim;M. Howlader
提出了一种由氧反应离子刻蚀（RIE）等离子体和氮自由基激活组成的顺序等离子体激活工艺，用于室温下的晶片直接键合。Si晶片表面通过氧RIE等离子体活化，随后暴露于氮自由基。使通过两步法活化的晶片在空气中接触，然后将它们在空气中保持24小时。晶片在整个区域内键合，并且界面的键合强度与体硅一样强，而无需任何后退火工艺和湿化学清洗步骤。XPS研究表明，硅表面具有晶格不稳定性。红外透射图像揭示了在等离子体活化工艺之后暴露于空气期间在晶片表面中吸收了相当大量的水。高结合强度被认为是由于吸收的水扩散到晶片表面中以及相对晶片上的氮氧化硅层之间的反应。TEM图像显示，在界面处形成了厚度为15 nm的中间非晶层。结合是如此紧密，没有发现在结合界面处的微孔。此外，强结合的结晶石英和熔融石英在室温下也获得了顺序激活过程。
A sequential plasma activation process consisting of oxygen reactive ion etching (RIE) plasma and nitrogen radical activation is proposed for wafer direct bonding at room temperature. The Si wafer surface is activated by oxygen RIE plasma and subsequently exposed to nitrogen radicals. The activated wafers by the two-step process were brought into contact in air followed by keeping them in air for 24 h. The wafers were bonded throughout the whole area and the bonding strength of the interface is as strong as bulk Si without any post-annealing process and wet chemical cleaning steps. XPS study indicates that the silicon surface has thermodynamically unstable characteristics. IR transmission images reveal a considerable amount of water is absorbed in the wafer surfaces during exposure to air after the plasma activation process. The high bonding strength is thought to be due to a diffusion of absorbed water into the wafer surface and a reaction between silicon oxynitride layers on the opposing wafer. TEM images show that an intermediate amorphous layer with thickness of 15 nm is formed across the interface. The bonding is so intimate that no micro-voids are found at the bonding interface. Furthermore, strong bonding of crystalline quartz and fused quartz at room temperature was also obtained by the sequential activation process.