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Abstract

A plasma assisted chemical transport system for additive or subtractive shaping of a substrate surface employs a plasma head (30) that generates a plasma (34) and is caused to scan the surface of a workpiece (51) to provide selective shaping, either by etching or depositing material. Corrosive gases of the plasma are isolated to minimize corrosive effects on the drive mechanism (20) by encompassing the plasma head within a flexible bellows (64). Scanning is in a circular path of varying radius. Acceleration induced vibrations caused by programmed varying scan velocity are avoided by use of an oppositely rotation body (56) of equal torsional inertia. Effects of linear acceleration in the radial direction are effectively avoided by making rotational scan velocity many times greater than radial scan velocity. Errors due to singularity that could exist when the scanning plasma head is at the center of its scan are kept within acceptable tolerances by stopping the scan when the center of the scanning head (30) is at a distance .DELTA.r from the center of the scan path that is equal to incremental radial steps between successive circular scan paths.

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First Claim