Transport mechanism in borophosphosilicate glass passivation

Small and clever circuit designs are introducing challenging issues to the silicon processing industries. Interconnect performance and reliability depend upon their protection against ionic mobility through the device interlayer passivation. This passivation is accomplished by the chemical vapor deposition of the constituents of phosphosilicate glass (PSG), which is then smoothened by high temperature viscous flow. However, the low temperature softening and viscous flow of borophosphosilicate glass (BPSG) compared to phosphosilicate, along with its good step coverage, have gained popularity. The ionic mobility in this passivation can cause a serious leakage and result in a yield loss. In this glass, the boron-to-phosphorous ratio is very critical for the adsorption/absorption of sodium from the surrounding solvent. This study describes the reaction of sodium at the solid/liquid interface and its transfer into the passivation surface.