Patent ID: 8716028

Claim:
A method of detecting, measuring, and correcting the presence of free HF in a BOE composition, the method comprising the steps of: pre-determining the expected etch rate of a given BOE composition based on the interaction of temperature, surfactant type, surfactant concentration, free HF concentration, composition flow rate, composition flow direction, and proximity of the location where the BOE composition will be applied to the location of a layer-layer interface on a wafer, etching the wafer by applying the BOE composition to the wafer, simultaneous to etching, measuring the free HF concentration with the SIA process using a first chromogenic agent, simultaneous to etching, measuring the surfactant concentration with the SIA process using a second chromogenic agent, simultaneous to etching, measuring the actual etch rate occurring using a laser reflectance, and changing at least one of the temperature, surfactant type, surfactant concentration, free HF concentration, composition flow direction, and composition flow rate to alter the actual etch rate to correspond to a desired etch rate, wherein the SIA process includes utilizing a mixture of the first chromogenic agent and the second chromogenic agent, wherein the first chromogenic agent is selected from the group consisting of phenol red, chlorophenol red, and thymol blue, and wherein the second chromogenic agent is different than the first chromogenic agent, wherein the second chromogenic agent is selected from the group consisting of phenol red, chlorophenol red, and thymol blue.