To allow three thickness scans during belt transport at different wafer sizes, two measuring
bars, one from top and one from bottom, hold 3 sensors each. The outer sensors pairs left
and right are mounted on a linear sledge and can be moved simultaneously equidistant to
the center by means of a manually moved lever.
Before and behind of each capacitive sensor are light barriers to validate the measurements
of a sensor only if both are covered. This assures safe measurements even with different
wafer forms or misalignments. To ensure safe start and finish of measurement the light
barriers have to be uncovered between two incoming wafers. Therefore the wafers must be
at least 30mm apart.
Optionally a one-scan resistivity measurement can be added within the same case, as well
as a one-point P/N sensor.
The electronic rack is connected to a PC which itself is linked with the host PC by an
Ethernet connection.
A simple TCP/IP based protocol is used to communicate measurement values and to
arm/disarm measurements.
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