Effects of process history and aging on the properties of polyimide films

Polyimide is used extensively in a variety of integrated circuit packaging applications. It is a good dielectric material with excellent planarizing capabilities, but like most polymers, it absorbs moisture. This hygroscopic behavior can lead to reliability problems in integrated circuit packages. The effects of variations in process history on moisture uptake are examined using gravimetric measurement techniques. In particular, the effects of cure schedule and exposure to high temperature/high humidity environments (85 °C/85% RH) on steady state moisture uptake are reported. Steady state moisture uptake is shown to be a decreasing function of cure temperature. Samples cured at 250 °C absorb 25% more moisture by weight than do samples cured at 400 °C. Moreover, the steady state moisture uptake in polyimide is greater after the samples have been “aged” in a high temperature and humidity ambient. The bulk and surface chemical composition are also monitored as a function of aging using Fourier transform infrared spectroscopy (FTIR) and electron spectroscopy for chemical analysis (ESCA), respectively. The PI surface chemistry degrades after 700 h in an 85 °C/85% RH environment. The bulk chemical composition appears to be unaffected.

[1]  H. Meyer,et al.  Dynamics of polyimide curing and degradation: An in situ x‐ray photoemission study , 1988 .

[2]  C. Pryde,et al.  IR studies of polyimides. I. Effects of chemical and physical changes during cure , 1989 .

[3]  K. L. Mittal,et al.  Polyimides : synthesis, characterization, and applications , 1984 .

[4]  D. Campbell,et al.  Surface analysis of aromatic polyimide films using ESCA , 1979 .

[5]  A. Wilson.  Polyimide insulators for multilevel interconnections , 1981 .

[6]  G. Turban,et al.  Dry Etching of Polyimide in O 2 ‐ CF 4 and O 2 ‐ SF 6 Plasmas , 1983 .

[7]  R. Jensen,et al.  Copper/polyimide Materials System for High Performance Packaging , 1984 .

[8]  Homer D. Hagstrum,et al.  Photoelectron and Auger Spectroscopy , 1975 .

[9]  R. Ginsburg,et al.  Polyimide Cure Determination , 1984 .

[10]  David F. Eggers,et al.  Infrared spectra of complex molecules , 1959 .

[11]  M. Grunze,et al.  Preparation and adhesion of ultrathin polyimide films on polycrystalline silver , 1987 .

[12]  L. Rothman.  Properties of Thin Polyimide Films , 1980 .

[13]  A. Theuwissen,et al.  Linear CCD-Imagers with a polyimide insulation for double level metallization , 1982, IEEE Electron Device Letters.

[14]  N. Teneketges,et al.  Multichip Packaging Design for VLSI-Based Systems , 1987 .

[15]  P. Ho,et al.  Origin of the carbon 1s-core level shifts in polyimide model compounds , 1985 .

[16]  T. Russell,et al.  A small‐angle X‐ray scattering study of an aromatic polyimide , 1984 .

[17]  Y. Homma,et al.  Feature size limit of liftoff metallization technology , 1982 .

[18]  Stephen D. Senturia,et al.  Moisture diffusion in poltimide films in integrated circuits , 1985 .

[19]  J. Clabes,et al.  Molecular orbital analysis of the XPS spectra of PMDA‐ODA polymide and its polyamic acid precursor , 1986 .

[20]  L. P. Buchwalter,et al.  X-ray photoelectron spectroscopy analysis of hexafluorodianhydride-oxydianiline polyimide: Substantiation for substituent effects on aromatic carbon 1s binding energies , 1987 .

[21]  S. Greenbaum,et al.  Dielectric relaxation and deuteron NMR of water in polyimide films , 1989 .

[22]  D. D. Denton,et al.  Gravimetric measurements of steady-state moisture uptake in spin-coated polyimide films , 1991 .

[23]  P. Ho,et al.  Complex formation and growth at the Cr– and Cu–polyimide interface , 1988 .

[24]  Wen‐Yaung Lee,et al.  Solventless polyimide films by vapor deposition , 1986 .