Constrained-film sintering of cordierite glass-ceramic on silicon substrate

Abstract

The densification behavior of cordierite glass-ceramic films constrained on a rigid silicon substrate was studied in the temperature range from 900 °C to 1000 °C. An optical setup was used to obtain the thickness versus time profiles and in-plane stresses of the constrained glass-ceramic during isothermal sintering. The thickness profiles showed a rapid shrinkage due to sintering followed by an expansion corresponding to crystallization of the glass-ceramic. Measurements of in-plane stresses in constrained-sintering films showed a rapidly rising tensile stress during densification followed by a slight drop during crystallization. In films sintered above 950 °C, the tensile stress rose rapidly again near the end of crystallization, suggesting a further densification in a mostly crystallized film. Scanning electron microscope (SEM) micrographs of the film cross sections revealed the formation and growth of large pores along the interface between the glass-ceramic and silicon substrate that may have contributed to the observed film expansion. These pores are substantially larger than the initial pore size in the films, indicating that they were formed during sintering. We believe that poor wetting of the glass-ceramic on silicon may have contributed to the formation of the porous structure at the interface.