US4665315A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for in-situ plasma cleaning of electron beam optical systems
Assignee: SK Hynix Inc
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Filing: 1985-04-01
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Granted: 1987-05-12
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Expires: 2005-04-01
Abstract
Abstract A method and apparatus for in-situ cleaning of charged particle beam optical systems such as electron microscopes, electron beam lithography systems, ion beam microscopes or lithography systems, through the use of a specially introduced plasma forming gas such as hydrogen that is excited by applying a high voltage, high frequency excitation potential between various optical elements of the electron beam optical column. Alternately, specially constructed separate plasma forming electrodes can be built into the electron beam optical system for this purpose. During the cleaning operation the plasma reacts chemically with the contaminants previously formed on the surface of the electron beam column optical elements to form gaseous reactants which then are pumped out of the electron beam column system.
Inventors
- 👤 Lawrence F. Bacchetti
- 👤 David M. Walker
- 👤 Donald O. Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 18:35
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/02
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
122 words
The method of in-situ cleaning of contaminants from the surfaces of the deflector, lens, aperture and other elements of a charged particle optical system including a source of charged particles, deflector lens and aperture elements supported within a gas-tight housing in optical alignment which comprises introducing an ionizable gas into the housing of the optical system, producing a high voltage high frequency alternating electric field between the elements of the optical system to be cleaned and an adjacent electrode member of sufficient magnitude to induce plasma discharge of the ionizable gaseous atomosphere adjacent to the elements to be cleaned, and removing reaction products produced by chemical reaction of the plasma at the surfaces of the elements to be cleaned from the housing.
Claim 2
Independent Claim
122 words
The method of in-situ cleaning of contaminants from the surfaces of the deflector, lens, aperture and other elements of a charged particle optical system including a source of charged particles, deflector lens and aperture elements supported within a gas-tight housing in optical alignment which comprises introducing an ionizable gas into the housing of the optical system, producing a high voltage high frequency alternating electric field between the elements of the optical system to be cleaned and an adjacent electrode member of sufficient magnitude to induce plasma discharge of the ionizable gaseous atomosphere adjacent to the elements to be cleaned, and removing reaction products produced by chemical reaction of the plasma at the surfaces of the elements to be cleaned from the housing.
Claim 3
Dependent Claim
34 words
The method according to claim 1 wherein the optical system housing continuously is supplied with fresh ionizable gas and pumped to remove the chemical reaction products produced by the plasma during the cleaning operation.
Claim 4
Dependent Claim
44 words
The method according to claim 1 wherein the ionizable gas reacts chemically with the contaminants on the surfaces of the optical system elements to be cleaned in the presence of the plasma and produces minimum sputtering at the surface of the optical system elements.
Claim 5
Dependent Claim
44 words
The method according to claim 2 wherein the ionizable gas reacts chemically with the contaminants on the surfaces of the optical system elements to be cleaned in the presence of the plasma and produces minimum sputtering at the surface of the optical system elements.
Claim 6
Dependent Claim
26 words
The method according to claim 1 wherein the high voltage alternating electric field is at a high frequency compatible with radio frequency electromagnetic interference emission standards.
Claim 7
Dependent Claim
26 words
The method according to claim 4 wherein the high voltage alternating electric field is at a high frequency compatible with radio frequency electromagnetic interference emission standards.
Claim 8
Dependent Claim
49 words
The method according to claim 1 further including adding at least one additional reactant gas component capable of chemically reacting with specific contaminant coatings on the surfaces of the optical system elements which otherwise would not chemically react with the ionizable gas alone in the presence of the plasma.
Claim 9
Dependent Claim
49 words
The method according to claim 6 further including adding at least one additional reactant gas component capable of chemically reacting with specific contaminant coatings on the surfaces of the optical system elements which otherwise would not chemically react with the ionizable gas alone in the presence of the plasma.
Claim 10
Dependent Claim
50 words
The method according to claim 1 further including monitoring the cleaning process to determine the time of formation of a plasma in the ionizable gaseous atmosphere and for maintaining the plasma during the cleaning process for a sufficient period of time to achieve effective cleaning of the optical system elements.
Claim 11
Dependent Claim
50 words
The method according to claim 8 further including monitoring the cleaning process to determine the time of formation of a plasma in the ionizable gaseous atmosphere and for maintaining the plasma during the cleaning process for a sufficient period of time to achieve effective cleaning of the optical system elements.
Claim 12
Dependent Claim
40 words
The method according to claim 1 further including adding a neutralizing gas such as nitrogen to the reactant gaseous products being formed in the optical system housing during the cleaning process to thereby prevent formation of hazardous combustible gaseous mixtures.
Claim 13
Dependent Claim
40 words
The method according to claim 10 further including adding a neutralizing gas such as nitrogen to the reactant gaseous products being formed in the optical system housing during the cleaning process to thereby prevent formation of hazardous combustible gaseous mixtures.
Claim 14
Dependent Claim
118 words
The method according to claim 12 wherein the ionizable gas is selected from the class consisting essentially of either hydrogen or oxygen dependent upon the nature of the material from which the optical system elements to be cleaned are fabricated, the gaseous atmosphere within the optical system housing is maintained at a pressure within the range of one milli Torr to ten Torrs, the electrodes for application of the high frequency, high voltage electric field are the optical system elements themselves and monitoring is achieved by a high impedance probe that itself does not require cleaning at the time and present in the housing in the vicinity of the plasma, said probe being connected to a suitable voltmeter.
Claim 15
Dependent Claim
131 words
Apparatus for in-situ cleaning of contaminants from the surfaces of the deflector, lens, aperture and other elements of a charged particle optical system including a source of charged particles, deflector, lens, aperture and other elements supported within a gas-tight housing in optical alignment, means for supplying an ionizable gas into the housing of the optical system, means for producing a high voltage high frequency alternating electric field between the elements of the optical system to be cleaned and an adjacent electrode, said alternating electric field being of sufficient magnitude and frequency to induce plasma discharge of the ionizable gas adjacent to the elements to be cleaned, and means for removing reaction products produced by chemical reaction of the plasma at the surfaces of the elements to be cleaned from the housing.
Claim 16
Dependent Claim
131 words
Apparatus for in-situ cleaning of contaminants from the surfaces of the deflector, lens, aperture and other elements of a charged particle optical system including a source of charged particles, deflector, lens, aperture and other elements supported within a gas-tight housing in optical alignment, means for supplying an ionizable gas into the housing of the optical system, means for producing a high voltage high frequency alternating electric field between the elements of the optical system to be cleaned and an adjacent electrode, said alternating electric field being of sufficient magnitude and frequency to induce plasma discharge of the ionizable gas adjacent to the elements to be cleaned, and means for removing reaction products produced by chemical reaction of the plasma at the surfaces of the elements to be cleaned from the housing.
Claim 17
Dependent Claim
41 words
Apparatus according to claim 14 wherein the means for removing the reaction products comprises means for continuously evacuating by pumping the optical system housing and further including means for continuously supplying fresh ionizable gas to the housing during the cleaning operation.
Claim 18
Dependent Claim
45 words
Apparatus according to claim 14 wherein the ionizable gas reacts chemically with the contaminants on the surfaces of the elements to be cleaned in the presence of the plasma with minimum occurrence of sputtering at the surfaces of the elements being cleaned during the process.
Claim 19
Dependent Claim
45 words
Apparatus according to claim 15 wherein the ionizable gas reacts chemically with the contaminants on the surfaces of the elements to be cleaned in the presence of the plasma with minimum occurrence of sputtering at the surfaces of the elements being cleaned during the process.
Claim 20
Dependent Claim
32 words
Apparatus according to claim 14 wherein the means for producing a high voltage electric field provides a high frequency alternating electric field that is compatible with radio frequency electromagnetic interference emission standards.
Claim 21
Dependent Claim
32 words
Apparatus according to claim 17 wherein the means for producing a high voltage electric field provides a high frequency alternating electric field that is compatible with radio frequency electromagnetic interference emission standards.
Claim 22
Dependent Claim
50 words
Apparatus according to claim 14 further including means for adding at least one additional reactant gas component capable of chemically reacting with specific contaminant coatings on the surfaces of the optical system elements which otherwise would not chemically react with the ionizable gas alone in the presence of the plasma.
Claim 23
Dependent Claim
50 words
Apparatus according to claim 19 further including means for adding at least one additional reactant gas component capable of chemically reacting with specific contaminant coatings on the surfaces of the optical system elements which otherwise would not chemically react with the ionizable gas alone in the presence of the plasma.
Claim 24
Dependent Claim
51 words
Apparatus according to claim 14 further including means for monitoring the cleaning process to determine the time of formation of the plasma in the ionizable gaseous atmosphere and for maintaining the plasma during the cleaning process for a sufficient period of time to achieve effective cleaning of the optical system elements.
Claim 25
Dependent Claim
51 words
Apparatus according to claim 21 further including means for monitoring the cleaning process to determine the time of formation of the plasma in the ionizable gaseous atmosphere and for maintaining the plasma during the cleaning process for a sufficient period of time to achieve effective cleaning of the optical system elements.
Claim 26
Dependent Claim
44 words
Apparatus according to claim 14 further including means for adding a neutralizing gas such as nitrogen to the reactant gaseous products being formed in the optical system housing in sufficient quantity during the cleaning process to thereby prevent formation of hazardous combustible gaseous mixtures.
Claim 27
Dependent Claim
44 words
Apparatus according to claim 23 further including means for adding a neutralizing gas such as nitrogen to the reactant gaseous products being formed in the optical system housing in sufficient quantity during the cleaning process to thereby prevent formation of hazardous combustible gaseous mixtures.
Claim 28
Dependent Claim
117 words
Apparatus according to claim 14 wherein the ionizable gas is selected from the class consisting essentially of either hydrogen or oxygen dependent upon the nature of the material from which the optical system elements to be cleaned are fabricated, the gaseous atmosphere within the optical system housing is maintained at a pressure within the range of one milli Torr to ten Torrs, the electrodes for application of the high frequency, high voltage electric field are the optical system elements themselves and monitoring is achieved by a high impedance probe that itself does not require cleaning at the time and present in the housing in the vicinity of the plasma, said probe being connected to a suitable voltmeter.
Claim 29
Dependent Claim
117 words
Apparatus according to claim 25 wherein the ionizable gas is selected from the class consisting essentially of either hydrogen or oxygen dependent upon the nature of the material from which the optical system elements to be cleaned are fabricated, the gaseous atmosphere within the optical system housing is maintained at a pressure within the range of one milli Torr to ten Torrs, the electrodes for application of the high frequency, high voltage electric field are the optical system elements themselves and monitoring is achieved by a high impedance probe that itself does not require cleaning at the time and present in the housing in the vicinity of the plasma, said probe being connected to a suitable voltmeter.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1990-05-11 | 1990-11-10 | 1991-05-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-05-11 | 1994-11-10 | 1995-05-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-05-11 | 1998-11-10 | 1999-05-12 | $7700.00 | Window Closed / Lapsed |