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Method for Measuring Film Thickness

IP.com Disclosure Number: IPCOM000040307D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Atkinson, WG: AUTHOR [+3]

Abstract

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.

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Method for Measuring Film Thickness

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. Measurement of hole width may be accomplished by any of several standard methods, e.g., optical or electron beam microscopy. Measurement of relative thickness, as is required for film thickness uniformity determination, may be performed without calibration. However, measurement of actual thickness by hole size does require at least a single point of calibration by another thickness measurement for a thin film type and ion dose combination.

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