Bell Telephone Laboratories

James Edward Griffiths

Cyril J Mogab

Paul Zuk

John Hershel English

Eugene O Degenkolb

The endpoints of plasma discharge processing operations (e.g., plasma stripping of photoresists and plasma etching) are determined by monitoring the light produced in the space surrounding the object being processed. The optical monitor includes a wavelength selective device which is adjusted to transmit light from a selected excited species, which includes particles from the surface being processed. The surface includes a layer of one material overlaying a second material. If the selected excited species includes particles of the first material, then the endpoint of the removal operation occurs when the monitored intensity falls below a predetermined threshold level. When the selected excited species includes particles of the second material, then the endpoint occurs when the monitored intensity rises above a preselected threshold level.

Method for the optical monitoring of plasma discharge processing

Electrical equipment, such as telephone station apparatus, exposed to occasional, destructively high, voltage surges (e.g., lightning strikes) is protected by a device, placed in parallel with the equipment, including two electrodes defining a fixed narrow spark gap which breaks down (arcs over) to short the voltage surge to ground. The predominant failure mode of such devices is shorting across the narrow gap, due to electrode damage produced during the protective arcing mode. In the disclosed devices, the electrodes are contoured to define a narrow region, determining the protective breakdown voltage, and a wider region, sustaining the major part of the electrode damage. Shortly after the initiation of the protective discharge in the narrow gap region, the discharge moves into the wider gap region. Since the major portion of electrode damage is sustained by the wider gap region of the electrodes, the incidence of shorting failure is suppressed. An exemplary electrode profile includes a flat central region and a surrounding tapered region.

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Murray Hill, NJ, United States of America

James Edward Griffiths