Method for Measuring Film Thickness
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
By rastering an ion beam having controlled variation in ion dose with position across the surface of a thin film, a hole is etched having width proportional to thickness of the thin film. Referring to the figure, ion dose is varied across a thin film from point x = 0 to point x = X, as described by the trapezoidal curve. The amount of material removed from the thin film is proportional to the ion dose. Thus, a hole of width x(d)-x(a) indicates a film of thickness t = u, and a hole of x(c)-x(b) indicates a proportionally greater thickness t = v. Controlled ion dose variation may be achieved by any of several means, e.g., varying the sweep rate as a function of beam position of a constant energy beam, or by varying the raster width in multiple sweeps of a constant, but lower energy beam.