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Abstract

Apparatus (1) and method for optically measuring by interferometry the thickness of an object (2) having an external surface (16) and an internal surface (17) opposite with respect to the external surface (16). There are included: a radiation source (4) which emits a low coherence beam of radiations (I) composed of a number of wavelengths within a determined band, and comprises at least two distinct emitters (20) emitting respective radiation beams that differ from one another and are concurrently activated; a spectrometer (5) analysing the spectrum of the result of the interference between radiations (R1) that are reflected by the external surface (16) without entering the object (2) and radiations (R2) that are reflected by the internal surface (17) entering the object (2); an optical probe (6) which is connected by means of optical fibers (8, 10, 11) to the radiation source (4) and to the spectrometer (5), and is arranged in such a way to face the slice (2) of semiconductor material to be measured for directing the beam of radiations (I) emitted by the radiation source (4) towards the external surface (16) of the object (2), and for collecting the radiations (R) reflected by the object (2); and a processing unit (18) calculating the thickness of the object (2) as a function of the spectrum provided by the spectrometer (5).

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