Effect of Formic Acid Vapor In Situ Treatment Process on Cu Low-Temperature Bonding

Author

Wenhua Yang ; Akaike, Masakate ; Suga, Takashi

Author_Institution

Dept. of Precision Eng., Univ. of Tokyo, Tokyo, Japan

Volume

4

Issue

6

fYear

2014

fDate

Jun-14

Firstpage

951

Lastpage

956

Abstract

Low-temperature Cu/Cu direct bonding technology using formic acid vapor in situ treatment was developed. Effect of formic acid vapor treatment conditions on Cu surface and bonding was studied. Cu surface oxide was reduced using formic acid vapor in situ treatment at 150 and 200°C, respectively. With higher temperature and longer treatment time, surface reduction is more effective. Grain boundary etching was found on chemical mechanical polished Cu film after initial treatment by formic acid. However, Cu surface roughness is minimally influenced by long-time formic acid vapor treatment. Cu film/Cu film direct bonding was realized in N₂ atmosphere with formic acid vapor in situ treatment under temperature below 200°C. For lower treatment temperature, longer treatment time is required to achieve good bonding. The bonding strength is about 9.0 MPa when Cu surface is treated at 200°C for 10 min.

Keywords

chemical mechanical polishing; copper; etching; integrated circuit bonding; surface roughness; Cu; N₂; bonding strength; chemical mechanical polishing; copper surface oxide; formic acid vapor in situ treatment; grain boundary etching; low-temperature Cu direct bonding technology; surface roughness; temperature 150 degC to 200 degC; time 10 min; Atmosphere; Bonding; Rough surfaces; Surface morphology; Surface roughness; Surface topography; Surface treatment; Cu/Cu direct bonding; formic acid vapor; low temperature;

fLanguage

English

Journal_Title

Components, Packaging and Manufacturing Technology, IEEE Transactions on

Publisher

ieee

ISSN

2156-3950

Type

jour

DOI

10.1109/TCPMT.2014.2315761

Filename

6802361