Alignment method usable in a step-and-repeat type exposure apparatus for either global or dye-by-dye alignment

摘要

A method of aligning a semiconductor wafer, usable in a step- and- repeat type exposure apparatus for projecting, in a reduced scale, images of a pattern formed on a reticle upon different shot areas on the semiconductor wafer in a predetermined sequence. According to this alignment method, the wafer is moved stepwise before the initiation of step-and-repeat exposures of the shot areas on the wafer and in accordance with a predetermined layout grid concerning the sites of the shot areas on the wafer. While moving the wafer stepwise in this manner, any positional deviation of each of some of the shot areas with respect to the layout grid is measured by use of a reduction projection lens system and, from the results of measurement, a corrected grid is prepared according to which grid the amount of stepwise movement of the wafer to be made for the step-and-repeat exposures thereof is determined. By this, for the exposures, the wafer can be moved stepwise exactly in accordance with the actual layout of the shot areas. Sample shot areas which are the subject of measurement can be selected under predetermined conditions. Additionally, of the values obtained as a result of the measurement, any extraordinary one or ones may be determined on the basis of the variance and then are excluded at the time of calculations made to determine the corrected grid. Thus, the stepwise movement of the wafer for the step-and- repeat exposures thereof can be controlled with higher precision.