Investigation of surface pre-treatment methods for wafer-level Cu-Cu thermo-compression bonding

Koki Tanaka, Wei Shan Wang, Mario Baum, Joerg Froemel, Hideki Hirano, Shuji Tanaka, Maik Wiemer, Thomas Otto

研究成果: Article査読

5 被引用数 (Scopus)

抄録

To increase the yield of the wafer-level Cu-Cu thermo-compression bonding method, certain surface pre-treatment methods for Cu are studied which can be exposed to the atmosphere before bonding. To inhibit re-oxidation under atmospheric conditions, the reduced pure Cu surface is treated by H2/Ar plasma, NH3 plasma and thiol solution, respectively, and is covered by Cu hydride, Cu nitride and a self-assembled monolayer (SAM) accordingly. A pair of the treated wafers is then bonded by the thermo-compression bonding method, and evaluated by the tensile test. Results show that the bond strengths of the wafers treated by NH3 plasma and SAM are not sufficient due to the remaining surface protection layers such as Cu nitride and SAMs resulting from the pre-treatment. In contrast, the H2/Ar plasma-treated wafer showed the same strength as the one with formic acid vapor treatment, even when exposed to the atmosphere for 30 min. In the thermal desorption spectroscopy (TDS) measurement of the H2/Ar plasma-treated Cu sample, the total number of the detected H2 was 3.1 times more than the citric acid-treated one. Results of the TDS measurement indicate that the modified Cu surface is terminated by chemisorbed hydrogen atoms, which leads to high bonding strength.

本文言語English
論文番号234
ジャーナルMicromachines
7
12
DOI
出版ステータスPublished - 2016

ASJC Scopus subject areas

  • 制御およびシステム工学
  • 機械工学
  • 電子工学および電気工学

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