Patent ID: 8440094

Claim:
A method for chemical mechanical polishing of a substrate, comprising: providing a substrate, wherein the substrate comprises a polysilicon overburden deposited over silicon dioxide; providing a chemical mechanical polishing composition concentrate, wherein the chemical mechanical polishing composition concentrate consists essentially of: water, 0.1 to 25 wt % of a colloidal silica abrasive having an average particle size of ≦100 nm; 0.01 to 1 wt % of a diquaternary cation according to formula (I): wherein R 1 is a C 2 -C 6 alkyl group; and, wherein R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently selected from a C 2 -C 6 alkyl group; providing a first diluent; providing a second diluent; adding the first diluent to a first portion of the chemical mechanical polishing composition concentrate to form a first polishing formulation, wherein the first polishing formulation exhibits a pH of >4.2 to 11, wherein the first polishing formulation is tuned to exhibit a first polysilicon removal rate of ≧2,000 Å/min and a first polysilicon to silicon dioxide removal rate selectivity of 20:1 to 600:1; providing a chemical mechanical polishing pad; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; dispensing the first polishing formulation onto the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; removing the polysilicon overburden from the substrate; adding the second diluent to a second portion of the chemical mechanical polishing composition concentrate to form a second polishing formulation, wherein the second polishing formulation exhibits a pH of 2 to 4.2, wherein the second polishing formulation is tuned to exhibit a second polysilicon removal rate of ≧1,500 Å/min and a second polysilicon to silicon dioxide removal rate selectivity of 1:2 to 10:1; dispensing the second polishing formulation onto the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; and, removing at least some more of the polysilicon and at least some of the silicon dioxide from the substrate.