Patent ID: 7907269
Filing Date: 2011-03-15
Classification: G01N

Abstract:
1. An apparatus for detecting top scattered light from a top surface of a substrate, the apparatus comprising: a light source for directing a beam of light onto a focal position on the top surface of the substrate, where the substrate is at least partially transmissive to the beam of light, the beam of light thereby, an objective for receiving the top scattered light and an unblocked portion of the bottom scattered light, the objective having a first focal point focused on the focal position on the top surface of the substrate, and a second focal point focused on a pinhole field stop, the pinhole field stop for receiving the top scattered light and the unblocked portion of the bottom scattered light, and passing the top scattered light that is focused on the pinhole field stop and blocking the unblocked portion of the bottom scattered light, and a sensor disposed opposite the objective across the pinhole field stop for receiving and quantifying the top scattered light.