Device and method for surface profilometry for the control of wafers during processing
A device or apparatus is provided for carrying out measurements of shape on a first surface of a wafer relative to structures present beneath the first surface including (i) profilometry apparatus arranged in order to carry out measurements of shape on the first surface of the wafer according to at least one measurement field; (ii) imaging apparatus facing the profilometry apparatus and arranged in order to acquire a reference image of the structures on or through a second surface of the wafer opposite to the first surface according to at least one imaging field; the profilometry apparatus and said imaging apparatus being arranged so that the measurement and imaging fields are referenced in position within a common frame of reference. A method is also provided to be implemented in this device or this apparatus.
1. A device for carrying out measurements of shape on a first surface of a wafer relative to structures present beneath said first surface, comprising:
profilometry means arranged in order to carry out measurements of shape on said first surface of the wafer according to at least one measurement field;
imaging means facing said profilometry means and arranged in order to acquire a reference image of said structures on or through a second surface of the wafer opposite to the first surface according to at least one imaging field; and
said profilometry means and said imaging means being arranged so that the measurement and imaging fields are referenced in position within a common frame of reference.
2. The device according to claim 1 , comprising imaging means capable of producing images at wavelengths in the infrared.
3. The device according to claim 1 , comprising profilometry means with a full-field interferometer.
4. The device according to claim 3 , comprising a full-field interferometer of one of the following types: Michelson, Mirau, Linnik, or Fizeau.
5. The device according to claim 3 , in which the profilometry means and the imaging means have substantially parallel optical axes.
6. The device according to claim 1 , comprising profilometry means using a point distance sensor, and scanning means for scanning the first surface with said point distance sensor.
7. The device according to claim 6 , comprising a distance sensor of the one of the following types: confocal sensor, chromatic confocal sensor, interferometry, spectral-domain low coherence interferometer, time-domain low coherence interferometer, frequency-scanning low coherence interferometer, mechanical probe, or atomic force microscopy (AFM) probe.
8. The device according to claim 1 , also comprising a support for positioning a wafer with a first face facing said profilometry means and a second face facing said imaging means.
9. A method for carrying out measurements of shape on a first surface of a wafer relative to structures present beneath said first surface, comprising the following steps:
acquiring measurements of shape according to at least one measurement field on said first surface of the wafer by implementing profilometry means;
acquiring a reference image of the structures according to at least one imaging field on or through a second surface of the wafer opposite to the first surface, implementing imaging means facing said profilometry means; and
said measurement and imaging fields are referenced in position within a common frame of reference.
10. The method according to claim 9 , also comprising a step of identification of the position of the structures in the reference image.
11. The method according to claim 10 , comprising a step of acquiring measurements of shape in proximity to at least one identified structure position.
12. The method according to claim 9 , also comprising a prior step of calibration with location of the position of the measurement and imaging fields within a common frame of reference in the form of a reference plane.