Interfacial adhesion of photodefinable polyimide films on passivated silicon

Martha E. Grady, Philippe H. Geubelle, Nancy R. Sottos

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. Due to the disparity of material properties between the polymer and passivated substrates, interfacial delamination is a reliability concern. Understanding the effects of surface layers and film processing on polyimide adhesion is critical for development of more reliable packages. In this paper, we examine the influence of different cure cycles and UV-exposure on the adhesion between a photodefinable polyimide (HD4100 HD Microsystems) and silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). The tensile strength of the thin film interface is measured by a laser spallation technique. Comparison of interfacial strength associated with cure cycle and UV-exposure indicates increased interfacial strength when films are processed with the exposure step as well as a longer cure cycle. Substrates including an oxygenated passivation layer have improved adhesion over nitride passivation layers. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The interfacial fracture energy for this commercially available photodefinable polyimide on silicon is on the order of 100 J/m2. The high toughness of this interface makes it difficult to use more conventional interfacial fracture testing techniques.

Original languageEnglish
Pages (from-to)116-123
Number of pages8
JournalThin Solid Films
Volume552
DOIs
StatePublished - Feb 3 2014

Bibliographical note

Funding Information:
The authors gratefully acknowledge the support of the Industrial Research Institute (IRI) , the National Science Foundation ( CMMI-1161517 ), and the Semiconductor Research Corporation (Grant SRC 2008 KJ1773 ). Experiments were carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the US Department of Energy under grants DE-FG02-07ER46453 and DE-FG02-07ER46471 .

Keywords

  • Dynamic fracture
  • Interfacial adhesion
  • Laser spallation
  • Polyimide
  • Thin films

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

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