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Impact of SiO2 on Al–Al thermocompression wafer bonding

Abstract

Al–Al thermocompression bonding suitable for wafer level sealing of MEMS devices has been investigated. This paper presents a comparison of thermocompression bonding of Al films deposited on Si with and without a thermal oxide (SiO2 film). Laminates of diameter 150 mm containing device sealing frames of width 200 µm were realized. The wafers were bonded by applying a bond force of 36 or 60 kN at bonding temperatures ranging from 300–550 °C for bonding times of 15, 30 or 60 min. The effects of these process variations on the quality of the bonded laminates have been studied. The bond quality was estimated by measurements of dicing yield, tensile strength, amount of cohesive fracture in Si and interfacial characterization. The mean bond strength of the tested structures ranged from 18–61 MPa. The laminates with an SiO2 film had higher dicing yield and bond strength than the laminates without SiO2 for a 400 °C bonding temperature. The bond strength increased with increasing bonding temperature and bond force. The laminates bonded for 30 and 60 min at 400 °C and 60 kN had similar bond strength and amount of cohesive fracture in the bulk silicon, while the laminates bonded for 15 min had significantly lower bond strength and amount of cohesive fracture in the bulk silicon.

Category

Academic article

Client

  • Research Council of Norway (RCN) / 210601

Language

English

Author(s)

  • Nishant Malik
  • Kari Schjølberg-Henriksen
  • Erik Poppe
  • Maaike Margrete Visser Taklo
  • Terje Finstad

Affiliation

  • University of Oslo
  • SINTEF Digital / Microsystems and Nanotechnology
  • SINTEF Digital / Smart Sensor Systems

Year

2015

Published in

Journal of Micromechanics and Microengineering (JMM)

ISSN

0960-1317

Publisher

IOP Publishing

Volume

25:035025

Issue

3

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