Influence of applied load on vacuum wafer bonding at low temperature

Wei Bo Yu*, Cher Ming Tan, Jun Wei, Shu Sheng Deng, Sharon Mui Ling Nai

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

16 Scopus citations

Abstract

Low temperature direct wafer bonding was performed in medium vacuum (∼10-4mbar). Different loads were applied during bonding processes. In all cases, the bond strength is above 19MPa, which is high enough for practical applications. More interestingly, in contrast to the findings by others, we found that the applied load does play a very important role in wafer bonding, the higher the applied load, the lower the bond strength. In the case of zero applied load, the cracking during pull test occurred in the silicon wafer itself rather than at the bonding interface. The bonded wafers were examined by means of scanning acoustic microscope (SAM). It was found that both the bubble size and bubble number increase with an increase in applied load. This phenomenon is contributed to the applied load. High applied load keeps two wafer surfaces in tight contact. If there are any impurities trapped during bonding process, such as air and water molecules, the tight contact prevents them from escaping out of the bonding interfaces, which results in the low bond strength. The distinctness between results from other works and our experiment were explained from the different dominant mechanisms in different wafer bonding processes.

Original languageEnglish
Pages (from-to)67-72
Number of pages6
JournalSensors and Actuators, A: Physical
Volume115
Issue number1
DOIs
StatePublished - 15 09 2004
Externally publishedYes

Keywords

  • Applied load
  • Bond strength
  • Bubble
  • Vacuum
  • Wafer bonding

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