Measuring the through-plane elastic modulus of thin polymer films in situ

Journal article (2007)

Authors

M van Soestbergen Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
L.J. Ernst Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
K.M.B. Jansen Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
W.D. van Driel Dynamics of Micro and Nano Systems - Mechanical, Maritime and Materials Engineering
Research Group
Computational Design and Mechanics (Mechanical, Maritime and Materials Engineering) (TU Delft)
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Published Date

2007

Language

Undefined/Unknown

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Precision and Microsystems Engineering

Research Group

Computational Design and Mechanics

Abstract

Due to the ongoing increase of the transistor density on a chip, industry has replaced the silicon oxide dielectric layers, traditionally used in the back-end interconnect stack, by low-K polymer films with a thickness down to several hundred nanometers. The use of these polymer dielectric films has introduced new failure modes. To have a better understanding of these failures, knowledge of the mechanical properties is necessary. Due to surface effects, the material properties of thin films may differ in the in-plane modulus. To have an in situ measurement of the through-plane modulus, a parallel plate capacitor (PPC) under hydrostatic pressure is used in combination with an interdigitated electrode (IDE) to capture the change in dielectric constant. Since it is believed to be mechanical isotropic, a benzocyclobutene (BCB) film is used to provide a reference measurement. The through-plane elastic modulus and change in permittivity for a 1 µm thick film sandwiched by two aluminum electrodes on a silicon wafer are reported. Two circular PPCs and four IDEs were tested at a pressure of 0, 5, 7.5 and 10 MPa. An initial relative dielectric constant of the film of 2.66 ± 0.05 was obtained. This yields a linear elastic behavior equal to 4.73 ± 0.46, 4.11 ± 0.39 and 3.64 ± 0.31 GPa for 20°. 50° and 75°C respectively. The modulus at room temperature is in good agreement with the values found in literature.