A method and apparatus for determining the presence of foreign material on a substrate chuck. The method includes: placing a bottom surface of a substrate on a top surface of the substrate chuck; applying a lateral force in a direction parallel to a top surface of the substrate chuck to the substrate; when the substrate moves partially off or moves completely off the substrate chuck in response to the applying the lateral force then a defect is present between the top surface of the substrate chuck and the bottom surface of the substrate; or when the substrate remains completely on the substrate chuck in response to the applying the lateral force then a defect is not present between the top surface of the substrate chuck and the bottom surface of the substrate.