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Silicon Wafer Bonding: Effect of Wafer Surface Treatment on Interface Structure and Chemistry

Published online by Cambridge University Press:  02 July 2020

M.J Cox
Affiliation:
Center for Solid State Science and Science and Engineering of Materials Program, Arizona State University, Tempe, Arizona85287-1704
M.J. Kim
Affiliation:
Center for Solid State Science and Science and Engineering of Materials Program, Arizona State University, Tempe, Arizona85287-1704
Hong Xu
Affiliation:
Center for Solid State Science and Science and Engineering of Materials Program, Arizona State University, Tempe, Arizona85287-1704
R.W. Carpenter
Affiliation:
Center for Solid State Science and Science and Engineering of Materials Program, Arizona State University, Tempe, Arizona85287-1704
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Extract

The two most important characteristics of any surface considered for wafer bonding are cleanliness, surface smoothness and macroscopic flatness. Silicon wafers in the as-received condition have a native oxide on the surface several nanometers thick [1], Figure la shows that they also have a layer of hydrocarbons. While they are not clean, they are smooth. Our wafers were plasma or ion cleaned, chemically treated, and ultra high vacuum (UHV) thermal desorption annealed in different combinations to find the best method for providing smooth, contamination free substrates that will produce an atomically flat, chemically clean Si/Si bonded interface.

The first approach was a single step process to remove the contaminants and then bond the clean wafers. Cleaning was accomplished by ion bombardment of the surface in an UHV chamber with base pressure 1x109 Torr. This ion cleaning chamber is connected between the UHV (2x10-10 ) bonding chamber and UHV (1x10-10) analysis chamber, allowing wafers to be cleaned, analyzed, and bonded without breaking vacuum [2].

Type
Surfaces and Interfaces
Copyright
Copyright © Microscopy Society of America

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References

References:

1.Kim, M.J. and Carpenter, R.W., Composition and Structure of Native Oxide on Silicon by High Resolution Analytical Electron Microscopy, J. Mater. Res., 5(2)( 1990)347351CrossRefGoogle Scholar
2.Kim, M.J. et al, Controlled Planar Interface Synthesis by UHV Bonding/Deposition, J. Mater. Res., inpress (2000)CrossRefGoogle Scholar
3.Zaluzec, N.J. et al, Microscopy and Microanalysis, 3(2)(1997)983CrossRefGoogle Scholar
4. This research was supported by US DOE, OBES, Div. of Material Sciences, DE-FG03-94ER45510Google Scholar