Precision measurement using particle beam devices

Details Precision measurement using particle beam devices Precision measurement using particle beam devices

1993-06-14

1994-07-26

Berman, Jack I.

Radiant energy

Inspection of solids or liquids by charged particles

Methods

250310, G01N 23225, H01J 37256

Patent

active

053328981

ABSTRACT:
The precision of measurements of feature dimensions of objects using a particle beam device is improved by setting upper and lower signal reference levels and a signal offset level, performing a preliminary scan of the object using the particle beam device to produce a time-quantized and level-quantized signal indicative of a surface profile of the object, determining a percentage of time intervals during which the signal lies outside a range defined by the upper and lower signal reference levels, and processing the signal by adjusting at least one of the signal reference levels and the offset level such that the foregoing percentage becomes substantially equal to a predetermined percentage. In other words, the percentage of "outliers" in a profile, that is the number of pixels that exceed full scale in a video range, is limited to a predetermined percentage, for example one percent. Clipping distortion is therefore minimized. In another embodiment of the present invention, clipping distortion is minimized by performing profile synthesis using the median of multiple profiles instead of the arithmetic mean.

REFERENCES:
patent: 3886305 (1975-05-01), Yew et al.
patent: 4099054 (1978-07-01), Okumura et al.
patent: 4907287 (1990-03-01), Homma et al.

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