A ring chuck that holds a wafer with a vacuum uses a vacuum trough that contacts the entire outer edge of the wafer. The chuck has a base having a top surface equal to or slightly smaller than a water to be tested with vacuum channels in the base. The base provides the mechanism to connect the chuck to a measurement instrument and a vacuum source. An annulus of non-contaminant material that has concentric rings extending upward from its outer edge is fixed to the base top surface with the trough between the concentric rings connected to the vacuum channels. The vacuum trough holds the wafer securely to the chuck and minimizes vibrations when the wafer is rotated.
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