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US 3,937,958 AGranted
Charged particle beam apparatus
AssigneeMinnesota Mining and Manufacturing Company
InventorsThomas W. Rusch, Jerry A. Sievers
Life of this patent
Estimating the term…
Abstract
A charged particle beam (e.g., ions or electrons) apparatus including two electrostatic focusing lenses and an electrode having a diameter limiting aperture positioned between the lenses is further provided with two electrode assemblies which interact with an extractor electrode and with a source of charged particles such that the trajectories of the particles in the beam passing through the second of the two assemblies are substantially parallel. This feature and other disclosed improvements facilitate the production of a substantially monoenergetic beam which under a first set of conditions can be focused to provide a small-diameter, spherical-aberration limited beam and which under another set of conditions, can be focused to provide a high current beam.
Claims31
A charged particle beam apparatus comprising:
- (a) means for generating a charged particle beam including a source of charged particles and a primary extractor electrode having an aperture defining the effective diameter of said generated beam, (b) means for accelerating said charged particles in said beam, (c) a first focusing means for focusing said beam at a cross-over point, (d) means for limiting the diameter of said focused beam, and (e) a second focusing means for focusing said beam at a target, each of said means being located along a beam axis downstream from previously recited means, THE IMPROVEMENT WHEREIN:
- said accelerating means comprises
- a first electrode assembly including said primary extractor electrode at the upstream end thereof and means for providing a circularly-symmetric axially-centered unipotential surface extending a first predetermined distance downstream from said extractor electrode,
- a second electrode assembly the upstream end of which is spaced a second predetermined distance downstream from the downstream end of said first electrode assembly and including means for providing a circularly-symmetric axially-centered unipotential surface extending axially a third predetermined distance,
- means for applying a given potential between said source of charged particles and said second electrode assembly, and
- means for applying a given fraction of said given potential to said first electrode assembly in order to establish an electrostatic lens, a focal point of which is approximately in the plane of the aperture of said primary extractor electrode such that the trajectories of charged particles passing through said second electrode assembly are substantially parallel, thereby enhancing the current density of the beam at said target under a given set of focusing conditions.
3 more elements
A method of surface analysis using a dual mode charged particle beam apparatus comprising
- positioning a sample, a surface of which is to be analyzed,
- generating a beam of charged particles,
- accelerating and directing said beam of charged particles into substantially parallel trajectories,
- focusing said parallel beam at a first cross-over point,
- refocusing substantially all of the particles emerging from the cross-over point in a high current beam which impinges on a portion of said surface,
- converting emissions resulting from the high current beam into a spectrum indicative of characteristics of said surface portion,
- changing the focus of said parallel beam to a second cross-over point substantially upstream from said first cross-over point,
- blocking all but a small center portion of said beam,
- focusing the said center portion of said beam into a small-diameter, spherical-aberration limited beam to produce emissions,
- deflecting the small-diameter beam to scan said surface,
- converting emissions resulting from the small-diameter beam into an electronic signal and in turn into an image indicative of spacial concentrations of a characteristic shown in said spectrum.
8 more elements
A method of surface analysis using a dual mode charged particle beam apparatus comprising
- positioning a sample, a surface of which is to be analyzed,
- generating a beam of charged particles,
- accelerating and directing said beam of charged particles into substantially parallel trajectories,
- focusing said parallel beam at a first cross-over point,
- refocusing substantially all of the particles emerging from the cross-over point in a high current beam which impinges on a portion of said surface, and which sputters atoms therefrom, resulting in a crater in said surface portion,
- converting emissions resulting from the high current beam into a spectrum indicative of characteristics of the surface portion within said crater,
- changing the focus of said parallel beam to a second cross-over point substantially upstream from said first cross-over point, blocking all but a small center portion of said beam,
- focusing the said center portion into a small diameter spherical aberration limited beam to produce emissions,
- deflecting the small diameter beam to scan a portion of said surface including said crater,
- converting emissions resulting from the small diameter beam into an electronic signal and in turn into an image indicative of spacial concentrations of a characteristic shown in said spectrum, whereby changes in the concentration of said characteristic as a function of depth into said crater may be compared with the concentration of said characteristics on said surface within the scanned portion.
7 more elements
A method of surface analysis using a dual mode charged particle beam apparatus comprising
- positioning a sample, a surface of which is to be analyzed,
- generating a beam of electrons,
- accelerating and directing said beam of electrons into substantially parallel trajectories,
- focusing said parallel beam of electrons to impinge on a portion of said surface,
- converting a first type of emissions resulting from said electron impingement into an indication of certain characteristics of said impinged upon surface portion,
- supplying gas atoms into said apparatus, whereby electrons from said supply of electrons collide with and ionize said gas atoms,
- generating a beam of positive ions,
- accelerating and directing said beam of positive ions into substantially parallel trajectories,
- focusing said parallel beam of positive ions to impinge on the same portion of said surface,
- converting a second type of emissions resulting from said ion impingement into an indication of said another characteristic,
- whereby said another characteristic is determined without repositioning or altering said sample.
8 more elements
Dependencies are inferred from the claim text.