Vacuum chuck for high warpage wafers

A vacuum chuck that supports a sample in a evaluation tool, the vacuum chuck comprising:

• a support plate having an upper planar support surface sized and shaped to retain a sample disposed thereon;
• one or more vacuum lines formed within the support plate;
• a plurality of lift pin holes formed completely through the support plate;
• a plurality of cavities formed within the support plate, wherein each cavity is fluidly coupled to a vacuum line in the one or more vacuum lines and includes an aperture at an upper surface of the planar support surface;
• and
• a plurality of vacuum pad plungers corresponding in number to the plurality of cavities, wherein each vacuum pad plunger is disposed in a unique one of the cavities and comprises a plunger body having a vacuum channel extending through its length and a biasing mechanism, wherein the plunger body is moveable between an up position in which a portion of the plunger body extends through the aperture of its respective cavity protruding above the upper planar support surface and a down position in which the plunger body is retracted into the cavity, and wherein the biasing mechanism bias the plunger body in the up position;
• and
• a moveable stage configured to move the support plate, including the vacuum pad plungers, in X, Y and Z directions;
• and
• a plurality of lift pins corresponding in number to the plurality of lift pin holes, wherein each lift pin is aligned with a unique one of the lift pin holes and configured such that as the support plate is moved up and down in the Z direction by the moveable stage while the lift pins remain in a fixed position.

A scanning laser inspection system for evaluating a sample, the system comprising:

• a vacuum chuck operable to hold a sample during a sample inspection process;
• a radiation source, adapted to irradiate a spot on the sample with coherent radiation;
• a detector, positioned to receive radiation reflected off the sample and to generate a signal responsive thereto;
• wherein the vacuum chuck comprises:
• a support plate having an upper planar support surface sized and shaped to retain a sample disposed thereon;
• one or more vacuum lines formed within the support plate;
• a plurality of cavities formed within the support plate, wherein each cavity is fluidly coupled to a vacuum line in the one or more vacuum lines and includes an aperture at an upper surface of the planar support surface;
• and
• a plurality of vacuum pad plungers corresponding in number to the plurality of cavities, wherein each vacuum pad plunger is disposed in a unique one of the cavities and comprises a plunger body having a vacuum channel extending through its length and a biasing mechanism, wherein the plunger body is moveable between an up position in which a portion of the plunger body extends through the aperture of its respective cavity protruding above the upper planar support surface and a down position in which the plunger body is retracted into the cavity, and wherein the biasing mechanism bias the plunger body in the up position.