Abstract
A symmetric eight-point van der Pauw resistor structure is described which makes it possible to determine the x- and y- axis vector components of mask superposition error on specially processed semiconductor slices. The structure is fabricated by first delineating a corner-contacted square van der Pauw resistor geometry. A second masking step adds sensor arms at the midpoints of the sides of the square body if the two masks have been correctly superimposed. The actual location of the sensor arms is determined by carrying out a series of four-point resistance measurements after doping the structure. Control geometries, in which the eight sensor arms are delineated on the same masking step, are used to investigate the accuracy and precision of the measurement technique. It is found that the vector components of mask superposition error can be determined, in the absence of mask-to-mask registration errors, with an absolute accuracy in the range ±0.10 μm and standard error below 0.015 μm. Examples of vector displacement maps are presented which illustrate the information which can be obtained when a large number of such devices is evaluated using automatic test and computing equipment.
Published Version
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