Method of measuring the thickness of the removed layer in subtractive workpiece processing

DETAILED DESCRIPTION It is the object of the invention to provide a method of measuring the removed layer thickness in subtractive workpiece processing which can be implemented reliably and very easily without affecting the process execution.
This object has been achieved with the method specified in the patent claim.
The method as disclosed by the invention permits the continuous measuring in situ of the respective removed layer thickness, and consequently the control of the process duration to such an effect that maintaining the given tolerances of the layer thickness to be removed is ensured.
According to the invention, the surface of the test sample is removed exactly like the workpiece material to be etched, the surface of the measured wedge increasing to the same extent as the layer removed from the test sample.
The method as disclosed by the invention can be implemented quite easily by observing through the microscope the distance between the gaps, and by a comparison with the original distance measured at the beginning of the process the depth reached by processing can at any time be calculated on the basis of the wedge angle.
In a particularly effective use of the present method the gap distance is automatically controlled by means of a corresponding optical measuring device whose output signals are applied to a computer storing the conversion formula as well as the original value of the gap distance.
Owing to a continuous control of the gap distance and the comparison of the calculated result with an equally stored desired value for the depth of the layer to be removed the process can take place fully automatically and does not require any specific observation.