System for real-time monitoring the characteristics, variations and

Abstract

A system for evaluating and measuring the performance of lithographic structures, and more particularly for monitoring the optical parameters of a projection lithography system which uses the instant electrical readout from an array of photosensitive detectors fabricated on a silicon wafer in combination with a computer for real-time characterization of lithographic devices and the evaluation of optical E-beam, ion-beam and X-ray parameters. The system includes a source radiation, such as a source of ultraviolet light, a projection mask which masks the illumination from the source. The illumination is then directed through a projection lens onto a semiconductor wafer mounted on an x-y stepping table. A standard digital data processor is provided to control the x-y drive mechanism for the stepping table. The computer also controls a Z drive mechanism for movement in a vertical direction. The semiconductor wafer contains a plurality of radiation detectors which are responsive to the radiation from the source. These detectors use a conventional power supply controlled by the computer, and employ an output signal means which obtains the radiation produced output signals from the detectors and applies them to the computer. The use of a unique mask with the radiation-sensitive detectors is employed in combination with compiling means for the purposes of evaluating image projection from a lithographic system, including the properties of intensity, modulation transfer function (MTF), focus and alignment.