Ammonium hydroxide effect on low-temperature wafer bonding energy enhancement

Y. L. Chao, Q. Y. Tong, T. H. Lee, M. Reiche, R. Scholz, J. C.S. Woo, U. Gösele

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Abstract

A wafer prebonding treatment by ammonium hydroxide (NH4OH) leading to a high bonding strength at low temperatures is presented in three material systems. After 200°C annealing, a surface energy of about 700 mJ/m2 for thermal silicon-oxide bonding and of 1300 mJ/m2 for plasma-enhanced chemical vapor deposition oxide bonding is realized. It is suggested that the lower ability of ammonia, the by-product of a polymerization reaction, to break the siloxane (Si-O-Si) bridging bonds appears to be responsible for the increase in surface energy in both silicon oxide bonding cases. NH4OH treatment is also effective on bare germanium/silicon- oxide bonding with a surface energy of 800 mJ/m2. A highly hydrophilic germanium surface obtained by this treatment accounts for the high bonding energy.

Original languageEnglish
Pages (from-to)G74-G77
JournalElectrochemical and Solid-State Letters
Volume8
Issue number3
DOIs
StatePublished - 2005

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