Envelope apparatus for localized vacuum processing

Output device for use with a vacuum processing system for treating the surface of a thin, flexible workpiece and for use with a first vacuum source and a second vacuum source providing a lower vacuum than said first source, said device comprising:

• first vacuum envelope means adapted for connection to said first vacuum source;
• second vacuum envelope means adapted for connection to said second vacuum source;
• said first and second envelope means having respective first and second apertures;
• said second aperture surrounding said first aperture in evenly spaced relationship thereto;
• said first and second apertures lying in a plane and having sufficiently small areas relative to the workpiece area to permit treatment of the workpiece surface close to its edge without breaking vacuum in the apertures and to minimize bowing of the thin, flexible workpiece caused by differential pressure thereacross;
• means for maintaining said apertures within a predetermined range of close spacing to said surface without any contact between the device and the surface;
• said first aperture and at least a portion of said first envelope means transmitting the output of said vacuum processing system to said surface;
• said first and second vacuum envelopes being of a truncated conical form extending from said apertures;
• and
• means for causing relative lateral motion between said surface and said apertures.

Charged particle beam apparatus wherein a semiconductor wafer workpiece surface is treated by the beam comprising a high vacuum envelope in a first vacuum and having a tip containing an aperture, a charged particle beam source located in the vacuum envelope for deriving a charged particle beam that is directed through the aperture as a treating beam for the workpiece surface, means for maintaining only a portion of the workpiece surface in approximate registration with the aperture in a vacuum such that the beam can propagate from the source to the workpiece surface portion exclusively in a first passage, the first passage terminating at the aperture and being in a second vacuum having a value that is only somewhat lower than the high vacuum, said maintaining means including:

• (a) means for holding the workpiece so that all of the workpiece, except said workpiece surface portion, is in an ambient environment not subjected to the vacuum;
• (b) means for forming a gap between the tip and the workpiece without contacting the workpiece so that the tip is positioned opposite from the workpiece surface, the gap being dimensioned to minimize the flow of gas through it and to enable the workpiece to be moved so that the workpiece surface can move generally transversely of the beam propagation direction without contacting any of the tip to enable different portions of the workpiece surface to be treated in vacuo by the beam at differing times, and (c) means forming a vacuum seal in the gap for minimizing degradation of the vacuum through the gap;
• said means for forming the vacuum seal including:
• vacuum pump means connected to a second passage surrounding the first passage for providing a third vacuum between the tip and the workpiece surface in the gap, the second fluid passage causing the third vacuum to surround the second vacuum, the third vacuum being a lower vacuum than the second vacuum, whereby a radial graded vacuum seal is formed in the gap, the tip terminating in a plane forming one side of the gap, the passages terminating at said plane, at least one of the passages having a cross sectional area that increases as the distance of said one passage increases from said plane, the area of the tip being sufficiently small relative to the workpiece surface area to permit treatment close to the workpiece edge without loss of the vacuum in the gap and to minimize bowing of the semiconductor wafer workpiece caused by differenial pressure thereacross.

A method of treating the surface of a thin, flexible workpiece with a charged particle beam, comprising the steps of:

• directing a beam from a source located in a vacuum envelope through an aperture in a vacuum tip of the envelope onto a first portion of the workpiece surface that is approximately in registration with the aperture;
• maintaining a gap between the vacuum tip and the first portion of the workpiece surface sufficient to prevent contact therebetween;
• maintaining the first portion of the workpiece surface in vacuum while maintaining the remainder of the workpiece surface in an ambient environment outside of the vacuum, the vacuum being formed by using vacuum pump means to form a graded vacuum seal in the gap while the first portion of the workpiece surface is being treated by the charged particle beam, the gap and seal being such that the beam is exclusively in vacuum while propagating from the envelope to the first portion of the surface;
• limiting the aperture and the first portion of the workpiece surface to a sufficiently small area relative to the workpiece area to minimize bowing of the workpiece caused by differential pressure thereacross and to permit treatment close to the workpiece edge without loss of vacuum in the gap while providing high vacuum in the gap by connecting the graded seal in the gap to the vacuum pump means through high vacuum conductance passages which increase in cross-sectional area as the distance from the gap increases;
• and
• moving the workpiece surface relative to the aperture so that different portions of the surface are successively in registration with the aperture while maintaining the gap between the workpiece surface and the aperture and without breaking the vacuum seal between the workpiece surface and the vacuum envelope interior so as to treat selected portions of the workpiece surface.