The Role of Surface Chemistry in Bonding of Standard Silicon Wafers

Q.-Y. Tong,^* T.-H. Lee, and U. Gösele^a
Wafer Bonding Laboratory, Duke University, Durham , North Carolina 27708, USA

M. Reiche^*
Max-Planck-Institute of Microstructure Physics, D-06120, Halle, Germany

J. Ramm and E. Beck
Balzers Limited, FL-9496, Liechtenstein

Abstract

Hydrophilic silicon surfaces become hydrophobic without microroughening alter 200 °C low energy hydrogen plasma cleaning. The fully hydrogen-terminated silicon surfaces do not bond to each other, not even by the application of external pressure. A subsequent 400 to 600 °C, 4 min thermal treatment in ultrahigh vacuum converts the wafer surfaces to hydrophilic and bondable which can be attributed to desorption of hydrogen from the surfaces. Hydrophobic silicon surfaces prepared by a dip in HF (without subsequent water rinse) are terminated by H and a small amount of F, or by H and a small amount of OH (alter subsequent water rinse). Hydrogen bonding of Si–F··· (HF)···H-Si or SI–OH···(HOH)···OH–Si across the two mating surfaces appears to be responsible for room temperature spontaneous hydrophobic or hydrophilic wafer bonding, respectively.

• Published in J. Electrochem. Soc. Vol. 144, No.1, January 1997
• For further information please contact UCP at ucpgroup@ucp.li 

^* Electrochemical Society Active Member.
^a Present address: Max-Planck-Institute of Microstructure Physics, Weinberg 2, D-06120, Halle/Saale, Germany

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