VISCOUS BEHAVIOR OF PHOSPHOSILICATE AND BOROPHOSPHOSILICATE GLASSES IN VLSI PROCESSING.

The viscous behavior of phosphosilicate and borophosphosilicate glasses in VLSI processing is reviewed. Measurements of the glass transition temperature T//g, are presented for a series of glass compositions prepared by bulk fusion of a phosphosilicate matrix to which a ternary B//2O//3 component is added. From a comparison of the measured values of T//g in bulk glasses with reported values of flow temperature, T//f, for films with corresponding compositions, a correlation factor relating these two parameters is established. These results provide guidelines for optimizing stoichiometric compositions of borophosphosilicate glass systems to match thermal budget requirements. Flow and reflow profiles of films with such optimum compositions illustrate their effectiveness in achieving desirable topographies at reduced processing temperatures as well as reduced phosphorus concentrations.