Patent ID: 8716039

Claim:
A monitoring apparatus for monitoring the thinning of at least one semiconductor wafer in a wet etching apparatus, said monitoring apparatus comprising: a light source configured to emit coherent light in a light wave band to which the semiconductor wafer is optically transparent; a measuring head positioned contact-free in relation to a surface of the semiconductor wafer to be etched, the measuring head being configured to irradiate the semiconductor wafer with the coherent light of the light wave band and to receive a reflected beam reflected by the semiconductor wafer; a spectrometer, the wavelengths (λ) of the reflected beam being inverted and fed to the spectrometer; a beam splitter by which the coherent light of the light wave band is directed at the measuring head and the reflected beam is directed at the spectrometer; and an evaluation unit, said evaluation unit being configured to determine the thickness d(t) of the semiconductor wafer from the beam reflected by the semiconductor wafer during the thinning of the semiconductor wafer by a method selected from a group consisting of a 1D-se FD-OCT method, a 1D-te FD-OCT method, and a 1D-se TD-OCT method.