Patent ID: 7112795

Claim:
A method of controlling a metallic layer etching process, the method comprising: removing alien material from a sample of an etchant; monitoring, in real time, at a predetermined temperature, absorption peaks of the etchant used for etching a metallic layer in the process of fabricating a semiconductor device or a liquid crystal display device with a near infrared spectrometer, wherein the near infrared spectrometer comprises a light source radiating a ray of wavelength range of 700–2500 nm; determining whether a concentration of each component of the etchant exceeds a corresponding reference value based on a standard calibration curve of a reference composition showing a relation of concentration and light absorption of each component to determine whether the etchant is usable; and either replacing the etchant with a new etchant in case the etchant is not usable, or using the etchant in a next metallic layer etching process in case the etchant is usable, wherein the etchant includes one or more materials selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, fluoric acid, sulfuric acid, cerium ammonium nitride, and water.