Two step rapid heating reflow of borophosphosilicate glass and estimation for a coefficient of heating delay by thermal analyses

The reflow of borophosphosilicate glass (BPSG) was studied by the rapid heating technique in two step irradiations using a halogen lamp. Pre-annealing (800? C, 30 s) during the first step irradiation, which aims to reduce the heating delay for the BPSG film, was carried out prior to high temperature heating (1050?1200? C, 20 s). The reflow angle with pre-annealing is consistently smaller than that without pre-annealing. Moreover, the reflow difference between with pre-annealing and without pre annealing decreases with increasing temperature because the heating delay for the BPSG film increases. The heating delay is primarily caused by thermal resistance between the film and the silicon wafer because, as the result obtained from the finite element method indicated, the heat conduction delay between the film surfaces was negligibly small. The equation for heat resistance can be solved analytically and the thermal resistance coefficient can be estimated by this solution, using the physical parameters of the film and the experimental results.