US5330800A
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US
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High impedance plasma ion implantation method and apparatus
Assignee: The AT&T MVPD Group LLC
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Filing: 1992-11-04
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Granted: 1994-07-19
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Expires: 2012-11-04
Abstract
Abstract A high dose rate, high impedance plasma ion implantation method and apparatus to apply high voltage pulses to a target cathode within an ionization chamber to both sustain a plasma in the gas surrounding the target, and to implant ions from the plasma into the target during at least a portion of each pulse. Operating at voltages in excess of 50 kV that are too high for the reliable formation of a conventional glow discharge, the plasma is instead sustained through a beam-plasma instability interaction between secondary electrons emitted from the target and a background pulsed plasma. The voltage pulses are at least about 50 kV, and preferably 100 kV or more. Pulse durations are preferably less than 8 microseconds, with a frequency in the 50-1,000 Hz range. The preferred gas pressure range is 1×10 -4 -1×10 -3 Torr; auxiliary electrodes can be used at the lower pressures to provide sufficient seed electrons for initiating a plasma, which is sustained by the beam-plasma instability interaction.
Inventors
- 👤 Robert W. Schumacher
- 👤 Jesse N. Matossian
- 👤 Dan M. Goebel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:49
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/32; H01J37/32009; H01J37/32412
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
126 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and applying a series of time-spaced negative voltage pulses to the target at a voltage level high enough to (a) induce a 3-dimensional beam of secondary electrons from the target that sustains a plasma in the gas through a beam-plasma instability interaction for at least a first portion of each pulse, and to (b) implant ions from the plasma into the target during at least a second portion of each pulse, wherein said voltage pulses are applied to the target with a rise time rapid enough for the rise in plasma density and implant current during each pulse to lag behind the voltage pulse rise.
Claim 2
Dependent Claim
126 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and applying a series of time-spaced negative voltage pulses to the target at a voltage level high enough to (a) induce a 3-dimensional beam of secondary electrons from the target that sustains a plasma in the gas through a beam-plasma instability interaction for at least a first portion of each pulse, and to (b) implant ions from the plasma into the target during at least a second portion of each pulse, wherein said voltage pulses are applied to the target with a rise time rapid enough for the rise in plasma density and implant current during each pulse to lag behind the voltage pulse rise.
Claim 3
Dependent Claim
27 words
The method of claim 1, wherein said ionizable gas introduced into said chamber establishes a gas pressure within said chamber of approximately 1×10 -3 -1×10 -3 Torr.
Claim 4
Dependent Claim
43 words
The method of claim 1, further comprising the step of energizing an auxiliary electrode within said chamber to aid in initiating said plasma with seed electrons emitted from said auxiliary electrode, with said voltage pulses sustaining said plasma through said beam-plasma instability interaction.
Claim 5
Dependent Claim
25 words
The method of claim 3, wherein said ionizable gas introduced into said chamber establishes a gas pressure within said chamber less than 1×10 -3 Torr.
Claim 6
Dependent Claim
17 words
The method of claim 3, wherein said auxiliary electrode comprises a cold cathode suspended in said chamber.
Claim 7
Dependent Claim
32 words
The method of claim 3, further comprising the step of establishing a localized magnetic field in the vicinity of said auxiliary electrode to restrict a plasma-initiating Paschen breakdown to said auxiliary cathode.
Claim 8
Dependent Claim
36 words
The method of claim 3, wherein said auxiliary electrode is provided as an electron emitting filament, and an auxiliary energizing voltage is applied to said filament to energize it to thermionic temperatures to provide seed electrons.
Claim 9
Dependent Claim
38 words
The method of claim 7, wherein said ionizable gas introduced into said chamber establishes a gas pressure within said chamber, and the temperature of said filament controls ion current density independent of said gas pressure and voltage pulses.
Claim 10
Dependent Claim
96 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and applying a series of time-spaced negative voltage pulses to the target at a voltage level of at least about 50 kV to (a) induce a 3-dimensional beam of secondary electrons from the target that sustains a plasma in the gas through a beam-plasma instability interaction for at least a first portion of each pulse, and to (b) implant ions from the plasma into the target during at least a second portion of each pulse.
Claim 11
Dependent Claim
96 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and applying a series of time-spaced negative voltage pulses to the target at a voltage level of at least about 50 kV to (a) induce a 3-dimensional beam of secondary electrons from the target that sustains a plasma in the gas through a beam-plasma instability interaction for at least a first portion of each pulse, and to (b) implant ions from the plasma into the target during at least a second portion of each pulse.
Claim 12
Dependent Claim
15 words
The method of claim 9, wherein said pulses have durations less than about 8 microseconds.
Claim 13
Dependent Claim
20 words
The method of claim 10, wherein said voltage pulses are applied at a frequency of approximately 50-1,000 pulses per second.
Claim 14
Dependent Claim
31 words
The method of claim 11, wherein said pulse duration is on the order of about 5 microseconds and said pulse frequency is within the approximate range of 100-200 pulses per second.
Claim 15
Dependent Claim
131 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and electrically energizing said target with an energization signal that undergoes a signal rise to (a) emit secondary electrons which forms a 3-dimensional beam that establishes a background plasma in said gas in the vicinity of the target through electron-gas collisions, and a primary pulsed plasma in the vicinity of the target through a beam-plasma instability interaction between said 3-dimensional secondary electron beam and said background plasma, and to (b) produce an implantation of ions from said primary plasma into said target, with said plasma experiencing a rise in density under said beam-plasma instability interaction, and said ion implantation experiencing a rise in implantation rate, that lag said signal rise.
Claim 16
Dependent Claim
131 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and electrically energizing said target with an energization signal that undergoes a signal rise to (a) emit secondary electrons which forms a 3-dimensional beam that establishes a background plasma in said gas in the vicinity of the target through electron-gas collisions, and a primary pulsed plasma in the vicinity of the target through a beam-plasma instability interaction between said 3-dimensional secondary electron beam and said background plasma, and to (b) produce an implantation of ions from said primary plasma into said target, with said plasma experiencing a rise in density under said beam-plasma instability interaction, and said ion implantation experiencing a rise in implantation rate, that lag said signal rise.
Claim 17
Dependent Claim
107 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and electrically energizing said target is energized with negative voltage pulses of at least about 50 kV to (a) emit secondary electrons which forms a 3-dimensional beam that establishes a background plasma in said gas in the vicinity of the target through electron-gas collisions, and a primary pulsed plasma in the vicinity of the target through a beam-plasma instability interaction between said 3-dimensional secondary electron beam and said background plasma, and to (b) produce a pulsed implantation of ions from said primary plasma into said target.
Claim 18
Dependent Claim
107 words
A plasma ion implantation method, comprising: providing a target object within a plasma chamber, introducing an ionizable gas into the chamber, and electrically energizing said target is energized with negative voltage pulses of at least about 50 kV to (a) emit secondary electrons which forms a 3-dimensional beam that establishes a background plasma in said gas in the vicinity of the target through electron-gas collisions, and a primary pulsed plasma in the vicinity of the target through a beam-plasma instability interaction between said 3-dimensional secondary electron beam and said background plasma, and to (b) produce a pulsed implantation of ions from said primary plasma into said target.
Claim 19
Dependent Claim
15 words
The method of claim 14, wherein said pulses have durations less than about 8 microseconds.
Claim 20
Dependent Claim
20 words
The method of claim 15, wherein said voltage pulses are applied at a frequency of approximately 50-1,000 pulses per second.
Claim 21
Dependent Claim
27 words
The method of claim 14, wherein said ionizable gas introduced into said chamber establishes a gas pressure within said chamber of approximately 1×10 -4 -1×10 -3 Torr.
Claim 22
Dependent Claim
39 words
The method of claim 14, wherein said voltage pulses are applied to the target with a rise time rapid enough for the rise in plasma density and implant current during each pulse to lag behind the voltage pulse rise.
References Cited (Backward Citations)
US3479269A
Cited
US3732158A
Cited
US4247804A
Cited
US4596945A
Cited
US5015493A
Cited
US4764394A
Cited
US4937205A
Cited
US4912367A
Cited
US5019752A
Cited
US5126163A
Cited
US5212425A
Cited
US5218179A
Cited
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