Apparatus and method for determining the elemental compositions and

Abstract

An apparatus and method are presented for determining the elemental compositions and relative locations of particles on a surface of a semiconductor wafer. An exposed region of the surface of the semiconductor wafer is subjected to a beam of primary X-ray photons, and secondary X-ray photons emitted by atoms of elements on and just under the surface of the semiconductor wafer are detected by an X-ray detector array which includes multiple X-ray detectors. Each X-ray detector produces an output signal which is proportional to energy levels of incident X-ray photons. The X-ray detectors are laterally displaced from one another, and arranged to allow two-dimensional resolution of detected secondary X-ray photons emitted by atoms of elements on the surface of the semiconductor wafer. The X-ray detector array is preferably an electronic area image sensor including a two-dimensional array of photosensor elements formed upon a monolithic semiconductor substrate. With adequate resolution, the X-ray detector array may also provide information as to the relative sizes of particles on the surface of the semiconductor wafer. By virtue of an employed total reflection X-ray fluorescence (TXRF) technique, substantially all of the detected X-ray photons are secondary X-ray photons emitted by atoms of elements located on and just under the exposed surface of the semiconductor wafer.