Method of using an electron beam.

摘要

When an electron beam (4) is used to effect a process at two adjacent surface areas (5a, 5b) of a target such as a semiconductor wafer (1) coated with an electron sensitive resist (3) various alignment errors can occur, for example, if the wafer becomes distorted. The provision of a reference marker, for example a square-etched depression (7), at the surface of the target between the areas (5a, 5b) enables the detection of any such distortion. After effecting the process at one of the areas (5a) an electron beam having substantially the same size and shape as the marker (7) is directed towards the predetermined position of the marker. The back-scattered electrons can then be detected to give a signal representative of any deviation between the actual position and the predetermined position of the marker so that the electron beam can be correctly aligned when effecting the process at the second of the two areas (5b). For increased accuracy of alignment an array (6) of markers (7) may be provided between the areas (5a, 5b).