Sensor device for determining the layer thickness of a thin layer

#The present disclosure relates to the subject matter disclosed in German application No. 102 17 535.7 of Apr. 16, 2002, which is incorporated herein by reference in its entirety and for all purposes.

#The invention relates to a sensor device for determining the layer thickness of a thin layer of an electrically conducting or semiconducting material.

#Such sensor devices are used if, for example, in the chemical-mechanical processing of a silicon wafer, the thickness of a copper film on the wafer has to be ascertained. The corresponding layers may in this case have a thickness of the order of magnitude of μm or less.

#FIG. 1 shows a schematic representation of a sensor device for determining the thickness of a layer on a support;

#FIG. 2 schematically shows the structure of an inductive proximity sensor, with which a layer thickness can be ascertained;

#FIG. 3 schematically shows the profile of the change in Q factor of an oscillator of the inductive proximity sensor according to FIG. 2 in dependence on a layer thickness d when the proximity sensor is positioned at a distance from this layer;

#An exemplary embodiment of a sensor device according to the invention, which is designated in FIG. 1 as a whole by 10, comprises a stationary holding device 12, which holds a sensor head 14. In the exemplary embodiment shown in FIG. 1, the sensor head 14 comprises an inductive proximity sensor 16 with an active surface area 18, which is positioned at a distance from an object being measured 20.

#The inductive proximity sensor 16 is displaceable in height with respect to the object being measured 20, for example by means of a holding arm 22, it being possible for every vertical position to be fixed.

#The object being measured 20 comprises a support 24, on which a thin electrically conducting layer, in particular a metallic layer 26, is disposed. The layer thickness of this thin layer is in this case of the order of magnitude of μm, for example between 0.005 μm and 2 μm. In particular, the support 24 is a non-conducting material, such as for example a silicon wafer, with a copper layer disposed on it as layer 26.