Bpsg reflow method to reduce thermal budget for next generation device including heating in a steam ambient

Abstract

A multistep method for planarizing a silicon oxide insulating layer such as a deposited borophosphosilicate glass (BPSG) layer. The method includes several different planarization stages. During an initial, pre-planarization stage, a substrate having a BPSG layer deposited over it is loaded into a substrate processing chamber. Then, during a first planarization stage after the pre-planarization stage, oxygen and hydrogen are flowed into the substrate processing chamber to form a steam ambient in said chamber and the substrate is heated in the steam ambient from a first temperature to a second temperature. The first temperature is below a reflow temperature of the BPSG layer and the second temperature is sufficient to reflow the layer. After the substrate is heated to the second temperature during a second planarization stage, the temperature of the substrate and the conditions within the substrate processing chamber are maintained at conditions sufficient to reflow the BPSG layer in the steam ambient. In a more preferred embodiment, the multistep planarization method also includes a third planarization stage, after the second stage. In the third planarization stage, the flow of hydrogen is stopped while the flow of oxygen is maintained, thereby forming an oxygen ambient in the substrate processing chamber. The substrate temperature is maintained in the oxygen ambient at a temperature above the reflow temperature of the BPSG layer. It is believed that this additional step minimizes the amount of moisture incorporated into the reflowed BPSG layer.