Phosphosilicate glass flow over aluminum in integrated circuit devices

A method of planarizing multilevel metallization struc tures in the fabrication of integrated circuit devices is presented. Radiation from a tunable TEA-CO2laser, under select conditions, is found to flow a layer of phosphosilicate glass, as thin as 1 µm and with as low as 5 % wt phosphorus, over aluminum steps. The flow is accomplished without any evidence of alloying the aluminum to the underlying silicon or melting the aluminum at the glass-to-metal interfaces.