CONSTRAINED-FILM SINTERING OF CORDIERITE GLASS-CERAMIC ON SILICON SUBSTRATE

The densification behavior of cordierite glass-ceramic films constrain ed on a rigid silicon substrate was studied in the temperature range f rom 900 degrees C to 1000 degrees C, An optical setup was used to obta in the thickness versus time profiles and in-plane stresses of the con strained glass-ceramic during isothermal sintering. The thickness prof iles showed a rapid shrinkage due to sintering followed by an expansio n corresponding to crystallization of the glass-ceramic. Measurements of in-plane stresses in constrained-sintering films showed a rapidly r ising tensile stress during densification followed by a slight drop du ring crystallization. In films sintered above 950 degrees C, the tensi le stress rose rapidly again near the end of crystallization, suggesti ng a further densification in a mostly crystallized film. Scanning ele ctron microscope (SEM) micrographs of the film cross sections revealed the formation and growth of large pores along the interface between t he glass-ceramic and silicon substrate that may have contributed to th e observed film expansion. These pores are substantially larger than t he initial pore size in the films, indicating that they were formed du ring sintering. We believe that poor wetting of the glass-ceramic on s ilicon may have contributed to the formation of the porous structure a t the interface.