David M. Gage

Short-ranged structural rearrangement and enhancement of mechanical properties of organosilicate glasses induced by ultraviolet radiation

The short-ranged bonding structure of organosilicate glasses can vary to a great extent and is directly linked to the mechanical properties of the thin film material. The combined action of ultraviolet (UV) radiation and thermal activation is shown to generate a pronounced rearrangement in the bonding structure of thin organosilicate glass films involving no significant compositional change or film densification. Nuclear magnetic resonance spectroscopy indicates loss of –OH groups and an increase of the degree of cross-linking of the organosilicate matrix for UV-treated films. Fourier transform infrared spectroscopy shows a pronounced enhancement of the Si–O–Si network bond structure, indicating the formation of more energetically stable silica bonds. Investigation with x-ray reflectivity and ellipsometric porosimetry indicated only minor film densification. As a consequence, the mechanical properties of microporous organosilicate dielectric films are substantially enhanced while preserving the organosili...

Effects of UV cure on glass structure and fracture properties of nanoporous carbon-doped oxide thin films

The effects of UV radiation curing on the glass structure and fracture properties were examined for a class of nanoporous organosilicate low dielectric constant films. A detailed characterization by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy showed significant changes in the glass structure with increasing curing time, marked by the removal of terminal organic groups and increased network-forming bonds following the initial removal of porogen material. The higher degree of film connectivity brought about by an increased cure duration is demonstrated to significantly enhance adhesive fracture properties and to moderately improve cohesive fracture resistance. Explanations for the enhanced fracture behavior are considered in terms of the glass structure. The important role of crack path selection during adhesive and cohesive fracture processes is used to rationalize the observed behavior.

Effects of friction and loading parameters on four-point bend adhesion measurements of low-k thin film interconnect structures

The four-point bend method has become an established metrology for quantitatively examining interfacial fracture energies of thin film multi-layers. However, despite the widespread use of the technique, relatively little is known about how four-point measurements are affected by loading point friction and variations in readily adjustable loading parameters. In this study, we demonstrate that four-point measurements can be sensitive to applied loading geometry and factors that affect the rate of steady state debond propagation. These effects can be experimentally significant, particularly for fracture energy measurements above /spl sim/5 J/m/sup 2/. We show that this behavior is due to a combination of Coulomb friction and stress corrosion effects. Good practice testing guidelines are suggested to systematically improve accuracy and consistency of four-point data.

Role of friction and loading parameters in four-point bend adhesion measurements

The effects of salient testing parameters on four-point adhesion measurements of thin-film structures on silicon substrates were systematically studied. These included specimen geometry, applied displacement rate, and load point separation. Measured fracture energy values, G c , were observed to increase as the ratio of applied moment arm to specimen thickness was decreased beyond a value of ∼4, particularly for specimens with G c > 5 J/m 2 . Testing parameters that affect the steady-state crack velocity were also found to affect reported G c values. The resulting trends in G c values are shown to be related to loading-point friction and environmentally assisted cracking effects. Good practice testing guidelines are suggested to improve the accuracy and precision of four-point bend measurements.

Effects of e-beam curing on glass structureand mechanical properties of nanoporous organosilicate thin films

Abstract Structural characterization techniques, including solid-state nuclear magnetic resonance and Fourier transform infrared spectroscopies, were used in conjunction with mechanical testing to study the effects of thermally activated electron bombardment curing on organosilicate thin films. The electron beam process produced significant improvements in elastic modulus and fracture resistance while still preserving low dielectric constant. Detailed and quantitative analysis was used to elucidate fundamental curing effects on glass structure, including changes in film composition and local bond rearrangements. Enhancements in fracture properties with curing are shown to be due to increased network bond density resulting from changes in network connectivity coupled with moderate film densification.