Direct, CMOS In-Line Process Flow Compatible, Sub 100 °C Cu–Cu Thermocompression Bonding Using Stress Engineering

Panigrahi, Asisa Kumar and Ghosh, Tamal and C, Hemanth Kumar and Singh, Shiv Govind and Vanjari, Siva Rama Krishna (2018) Direct, CMOS In-Line Process Flow Compatible, Sub 100 °C Cu–Cu Thermocompression Bonding Using Stress Engineering. Electronic Materials Letters. ISSN 1738-8090

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Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10−8 Ω-cm2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.

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IITH Creators:
IITH CreatorsORCiD
Singh, Shiv Govind
Item Type: Article
Subjects: Electrical Engineering
Divisions: Department of Electrical Engineering
Depositing User: Team Library
Date Deposited: 08 Mar 2018 09:51
Last Modified: 16 Jan 2019 08:18
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