US3678384A
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Electron beam apparatus
Assignee: Cambridge Instruments Ltd
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Filing: 1969-08-25
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Granted: 1972-07-18
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Expires: 1989-08-25
Abstract
Abstract In electron beam apparatus in which an electron beam is caused to impinge on a specimen surface and the resulting secondary electrons are analyzed to show the distribution of electric potential on the surface, the potential on the surface is switched rapidly on and off or the potential on a grid between the specimen and collector is switched rapidly between two levels, and the signals from the collector in the two conditions are directed into two channels, from which the difference signal is used to show the potential of the surface, largely independent of topography and other factors. The beam itself can also be switched on and off at double the switching frequency. In the grid version there can be a second grid to shield the specimen from the switched grid.
Inventors
- 👤 Charles W Oatley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 16:05
CPC Classifications
H; H01; H01J; H01J49/00; H01J49/44; H01J49/46; H01J49/48; H01J49/488; H01J37/00; H01J37/26; H01J37/266; H01J37/268
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
101 words
A method of analyzing the distribution of electric potential on the surface of a specimen in which a beam of electrons is caused to impinge on that surface and the resultant stream of secondary electrons are detected by a collector to produce electrical signals which are evaluated by recording means, wherein the improvement comprises switching on and off the stream of secondary electrons from the specimen surface to the collector, switching the electrical signal from the collector into two alternate channels in synchronism with said switching, and feeding the difference in the signals in these two channels to the recording means.
Claim 2
Independent Claim
101 words
A method of analyzing the distribution of electric potential on the surface of a specimen in which a beam of electrons is caused to impinge on that surface and the resultant stream of secondary electrons are detected by a collector to produce electrical signals which are evaluated by recording means, wherein the improvement comprises switching on and off the stream of secondary electrons from the specimen surface to the collector, switching the electrical signal from the collector into two alternate channels in synchronism with said switching, and feeding the difference in the signals in these two channels to the recording means.
Claim 3
Dependent Claim
26 words
The method set forth in claim 1, wherein said electron beam is switched on and off in synchronism with said switching but at twice the frequency.
Claim 4
Dependent Claim
20 words
The method set forth in claim 2 wherein the duration for which said electron beam is switched on is variable.
Claim 5
Dependent Claim
49 words
The method set forth in claim 1 wherein said electron beam is caused to scan the surface of the specimen and said final signal is displayed on recording means scanned in synchronism with said beam, the frequency of said switching being high in relation to the frequency of scanning.
Claim 6
Independent Claim
95 words
A method of analyzing the distribution of electric potential on the surface of a specimen in which a beam of electrons is caused to impinge on that surface and the resultant stream of secondary electrons are detected by a collector to produce electrical signals which are evaluated by recording means, wherein the improvement comprises switching on and off the potential on the specimen surface, switching the electrical signal from the collector into two alternate channels in synchronism with said switching, and feeding the difference in the signals in these two channels to the recording means.
Claim 7
Independent Claim
95 words
A method of analyzing the distribution of electric potential on the surface of a specimen in which a beam of electrons is caused to impinge on that surface and the resultant stream of secondary electrons are detected by a collector to produce electrical signals which are evaluated by recording means, wherein the improvement comprises switching on and off the potential on the specimen surface, switching the electrical signal from the collector into two alternate channels in synchronism with said switching, and feeding the difference in the signals in these two channels to the recording means.
Claim 8
Independent Claim
101 words
A method of analyzing the distribution of electric potential on the surface of a specimen in which a beam of electrons is caused to impinge on that surface and the resultAnt stream of secondary electrons are detected by a collector to produce electrical signals which are evaluated by recording means, wherein the improvement comprises switching the level of the potential on a barrier electrode between the specimen and the collector, switching the electrical signal from the collector into two alternate channels in synchronism with said switching, and feeding the difference in the signals in these two channels to the recording means.
Claim 9
Independent Claim
101 words
A method of analyzing the distribution of electric potential on the surface of a specimen in which a beam of electrons is caused to impinge on that surface and the resultAnt stream of secondary electrons are detected by a collector to produce electrical signals which are evaluated by recording means, wherein the improvement comprises switching the level of the potential on a barrier electrode between the specimen and the collector, switching the electrical signal from the collector into two alternate channels in synchronism with said switching, and feeding the difference in the signals in these two channels to the recording means.
Claim 10
Dependent Claim
127 words
Apparatus for analyzing the distribution of electric potential on the surface of a specimen comprising means for forming a beam of electrons and causing said beam to impinge on said specimen surface, a collector placed to receive resultant secondary electrons from said specimen surface, a first signal channel, a second signal channel, a first gate switching signals from said collector to said first and second channels alternately, a differential device operable to produce a signal dependent on the difference in the signals in said first and second channels, evaluating means connected to said differential device, a source of potential, a second gate interposed between said source and said specimen, said second gate connecting said potential intermittently to said specimen, and said first and second gates being synchronized.
Claim 11
Dependent Claim
127 words
Apparatus for analyzing the distribution of electric potential on the surface of a specimen comprising means for forming a beam of electrons and causing said beam to impinge on said specimen surface, a collector placed to receive resultant secondary electrons from said specimen surface, a first signal channel, a second signal channel, a first gate switching signals from said collector to said first and second channels alternately, a differential device operable to produce a signal dependent on the difference in the signals in said first and second channels, evaluating means connected to said differential device, a source of potential, a second gate interposed between said source and said specimen, said second gate connecting said potential intermittently to said specimen, and said first and second gates being synchronized.
Claim 12
Dependent Claim
41 words
Apparatus as set forth in claim 7, including a third gate controlling said electron beam to switch said beam on and off said specimen said third gate being synchronized with said first and second gate but operable at twice their frequency.
Claim 13
Dependent Claim
21 words
Apparatus as set forth in claim 8 wherein said third gate includes means for varying the ''''on'''' time of said beam.
Claim 14
Dependent Claim
67 words
Apparatus as set forth in claim 7 including first scanning means operable to cause said beam to scan said specimen surface and second scanning means operable to cause the output of said differential device to scan said recording means, said first and second scanning means being synchronized, and the frequency of switching of said gates being high in relation to the scanning frequency of said scanning means.
Claim 15
Dependent Claim
125 words
Apparatus for analyzing the distribution of electric potential on the surface of a specimen comprising means for forming a beam of electrons and causing said beam to impinge on said specimen surface, a collector placed to receive resultant secondary electrons from said specimen surface, a first signal channel, a second signal channel, a gate switching signals from said collector to said first and second channels alternately, a differential device operable to produce a signal dependent on the difference in the signals in said first and second channels, evaluating means connected to said differential device, an electrode system interposed between said specimen surface and said collector, and means switching the potential on said electrode system between two levels, said switching means being synchronized with said gate.
Claim 16
Dependent Claim
125 words
Apparatus for analyzing the distribution of electric potential on the surface of a specimen comprising means for forming a beam of electrons and causing said beam to impinge on said specimen surface, a collector placed to receive resultant secondary electrons from said specimen surface, a first signal channel, a second signal channel, a gate switching signals from said collector to said first and second channels alternately, a differential device operable to produce a signal dependent on the difference in the signals in said first and second channels, evaluating means connected to said differential device, an electrode system interposed between said specimen surface and said collector, and means switching the potential on said electrode system between two levels, said switching means being synchronized with said gate.
Claim 17
Dependent Claim
20 words
Apparatus as set forth in claim 11 including a shield electrode disposed between said electrode system and said specimen surface.
Claim 18
Dependent Claim
20 words
Apparatus as set forth in claim 11 including means for varying the levels of the potential of said electrode system.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-18 | 1976-01-17 | 1976-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-18 | 1980-01-17 | 1980-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-18 | 1984-01-17 | 1984-07-18 | $7700.00 | Window Closed / Lapsed |