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Effect of Coating Thickness and Curing Temperature on Residual Stress and Thermal Expansion Coefficients of High Glass Transition Temperature Polymides

IP.com Disclosure Number: IPCOM000105983D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Hofer, DC: AUTHOR [+3]

Abstract

A number of high glass transition temperature (T sub g s) polyimides are in use as insulators for multilevel wiring in semiconductor chip and thin film packaging applications throughout the computer industry. Each of the polyimides is thought to have a distinctive set of Young's modulus, Poisson's ratio and thermal expansion coefficient that determines the stress in a coating of the material on a substrate and that these three physical properties are characteristics of the material. Therefore, the stress in a coating should be independent of thickness. In general, it has been observed that this classic understanding is not accurate for a class of polymides which have (T sub g s) of approximately 400ºC and are processed to temperatures greater than the (T sub g)

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Effect of Coating Thickness and Curing Temperature on Residual Stress and Thermal Expansion Coefficients of High Glass Transition Temperature Polymides

      A number of high glass transition temperature (T sub g s)
polyimides are in use as insulators for multilevel wiring in
semiconductor chip and thin film packaging applications throughout
the computer industry.  Each of the polyimides is thought to have a
distinctive set of Young's modulus, Poisson's ratio and thermal
expansion coefficient that determines the stress in a coating of the
material on a substrate and that these three physical properties are
characteristics of the material.  Therefore, the stress in a coating
should be independent of thickness.  In general, it has been observed
that this classic understanding is not accurate for a class of
polymides which have (T sub g s) of approximately 400ºC and
are processed to temperatures greater than the (T sub g)

      As an example of the phenomena described above it was found
that the polyimide BPDA-PDA coated to thickness of 1.3,  7.5  and
38.7  microns on a Si substrate produced stresses of 0.8, 2.9, 4.7
and 6.2 kpsi, respectively.  Furthermore, when multiple coatings (3
to 5 coats) of the same polyimide were made with a thickness of 1.3
microns/coat the stress was largely independent of thickness when the
film was cured between each of the multiple coatings.  This phenomena
nomena exists with varying degree for the polyimides PMDA-ODA,
PMDA-PDA,...