MICROCRYSTAL GROWTH ON BOROPHOSPHOSILICATE GLASS-FILM DURING HIGH-TEMPERATURE ANNEALING

Borophosphosilicate glass (BPSG) film with a high boron and phosphorus concentration that exceeds a certain limit shows the growth of crysta lline particles on the surface after annealing above 900 degrees C in a nitrogen atmosphere. We studied the crystalline particle growth mech anism on BPSG, and found that the particles are BPO4 crystal that grow s during the cooling step at the end of annealing. Hence, rapid coolin g of the BPSG after annealing suppresses particle growth. We also foun d that particle growth is affected by the annealing atmosphere; being more suppressed in an oxygen atmosphere than in a nitrogen atmosphere. In an oxygen-steam atmosphere, particle growth is completely suppress ed. From the measurements of boron and phosphorus out-diffusion in dif ferent annealing atmospheres, we concluded that particle growth is cau sed by the gas-phase reaction of the out-diffused phosphorus and boron from the BPSG film.