An In-Situ Measurement Technique for Through-Plane Thermal Properties of Thin Dielectric Films

In MCM-D applications, interlayer dielectrics separate and insulate metal conductors to form a threedimensional interconnection structure. Due to the three-dimensional nature of these structures, the electrical and mechanical properties of the dielectric materials must be known in all directions for proper device design. The most commonly used polymer in microelectronics, polyimide, exists in formulations which have been shown to have a high degree of orientation and exhibit anisotropic properties. mechanical proprties of thin films is diftidt due to the high resolution required to measure the small thickness changes. Existing techniques require either stacked thin films or a single cast thick film of 100 micrometers or more to achieve dimensionat changes large enough to be measwabie.740 In addition, most existing techniques require removing a large area of film, if not the whole film, from a supporting substrate to perfom the measurement. These techniques neglect the effects of the dielectric-substrate interaction, such as Poisson's effm and adhesive effects. Since most MCM-D structures utilize thin films adhered to a substrate, the measured through-plane CTEs from these other techniques may not reflect the true thermal expansion expected in real devices. Measurement of through-plane