Optical pump and probe measurement of the thermal conductivity of low-k dielectric thin films

We report on measurements of the thermal conductivity of a number of amorphous materials, including fluorinated silicate glass and carbon-doped oxides. These materials are of interest to the microelectronics industry for use as insulators in microprocessors. The samples measured were in the form of thin films deposited onto silicon substrates. Measurements were made using an optical technique in which the film is heated with a picosecond light pulse, and a time-delayed, probe light pulse is used to measure the temperature of the film as a function of time. We find that the thermal conductivity of these low-k dielectrics is reduced by as much as a factor of 5 with respect to amorphous ${\mathrm{SiO}}_2.$ Most measurements were made at room temperature, but for two samples we additionally report on measurements for the temperature range 150–375 K. Results for the thermal conductivity for these materials are compared to theories of heat flow in amorphous solids.