Patent US4764394A successfully refreshed from Google Patents.
US4764394A
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Method and apparatus for plasma source ion implantation
Assignee: Wisconsin Alumni Research Foundation
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Filing: 1987-01-20
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Granted: 1988-08-16
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Expires: 2007-01-20
Abstract
Abstract Ion implantation into surfaces of three-dimensional targets is achieved by forming an ionized plasma about the target within an enclosing chamber and applying a pulse of high voltage between the target and the conductive walls of the chamber. Ions from the plasma are driven into the target object surfaces from all sides simultaneously without the need for manipulation of the target object. Repetitive pulses of high voltage, typically 20 kilovolts or higher, causes the ions to be driven deeply into the target. The plasma may be formed of a neutral gas introduced into the evacuated chamber and ionized therein with ionizing radiation so that a constant source of plasma is provided which surrounds the target object during the implantation process. Significant increases in the surface hardness and wear characteristics of various materials are obtained with ion implantation in this manner.
Inventors
- 👤 John R. Conrad
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:08
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/32; H01J37/32009; H01J37/32412; C; C23; C23C; C23C14/00; C23C14/22; C23C14/48; C30; C30B; C30B31/00; C30B31/20; C30B31/22
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
94 words
A method of implanting ions from a plasma into a target object comprising the steps of: (a) positioning the target object in an enclosing chamber; (b) generating a plasma of ions which surrounds the target object; (c) then, independently from generating the plasma, applying a high negative voltage pulse to the target object to accelerate the ions in the plasma toward the target from the plasma surrounding the target at an ion energy sufficient to implant ions impacting the target object beneath the surface of and into the crystal lattice of the target object.
Claim 2
Independent Claim
94 words
A method of implanting ions from a plasma into a target object comprising the steps of: (a) positioning the target object in an enclosing chamber; (b) generating a plasma of ions which surrounds the target object; (c) then, independently from generating the plasma, applying a high negative voltage pulse to the target object to accelerate the ions in the plasma toward the target from the plasma surrounding the target at an ion energy sufficient to implant ions impacting the target object beneath the surface of and into the crystal lattice of the target object.
Claim 3
Dependent Claim
33 words
The method of claim 1 wherein the step of accelerating ions toward the target object is performed multiple times in a periodic manner composed of short pulses of ions driven toward the target.
Claim 4
Dependent Claim
22 words
The method of claim 1 wherein the ions are accelerated toward the target at an average energy of at least 20 keV.
Claim 5
Dependent Claim
22 words
The method of claim 1 wherein the plasma contains ionized gases selected from the group consisting of nitrogen, hydrogen, oxygen, and argon.
Claim 6
Dependent Claim
46 words
The method of claim 1 wherein the target object is a metal, the plasma is formed of ionized nitrogen, and the step of accelerating the ions toward the target object is performed to provide an average energy to the nitrogen ions of at least 40 keV.
Claim 7
Dependent Claim
13 words
The method of claim 1 wherein the target object is formed of silicon.
Claim 8
Dependent Claim
37 words
The method of claim 1 wherein the ions are accelerated to impact the target object at an energy sufficient to drive ions on an average at least several hundred Angstroms beneath the surface of the target object.
Claim 9
Dependent Claim
28 words
The method of claim 1 wherein the material forming the target object is selected from the group consisting of pure metals, metal alloys, semiconductors, ceramics, and organic polymers.
Claim 10
Dependent Claim
36 words
The method of claim 2 wherein the ions are accelerated toward the target in pulses of a duration of at least approximately 1 microsecond at a repetition rate of at least approximately 60 times per second.
Claim 11
Independent Claim
100 words
A method of implanting ions in a target object comprising the steps of: (a) providing an enclosing chamber having walls of electrically conductive material; (b) suspending a target object within the chamber spaced away from the walls of the chamber; (c) evacuating the interior of the chamber to a very low base pressure; (d) forming a plasma of ions in the chamber around the target object; (e) independently of forming the plasma, applying a pulse of high voltage between the chamber walls and the target object at a voltage sufficient to implant ions from the plasma into the target object.
Claim 12
Independent Claim
100 words
A method of implanting ions in a target object comprising the steps of: (a) providing an enclosing chamber having walls of electrically conductive material; (b) suspending a target object within the chamber spaced away from the walls of the chamber; (c) evacuating the interior of the chamber to a very low base pressure; (d) forming a plasma of ions in the chamber around the target object; (e) independently of forming the plasma, applying a pulse of high voltage between the chamber walls and the target object at a voltage sufficient to implant ions from the plasma into the target object.
Claim 13
Dependent Claim
40 words
The method of claim 10 wherein the step of applying a pulse of voltage between the chamber walls and the target object is performed repetitively and periodically until a desired concentration of ions in the target object has been obtained.
Claim 14
Dependent Claim
22 words
The method of claim 10 wherein, in the step of applying a pulse of voltage, the voltage is at least 20 kilovolts.
Claim 15
Dependent Claim
27 words
The method of claim 10 wherein the material of the target object is selected from the group consisting of pure metals, alloys, semiconductors, ceramics and organic polymers.
Claim 16
Dependent Claim
25 words
The method of claim 10 wherein the plasma is formed from ions of gases selected from the group consisting of nitrogen, hydrogen, oxygen and argon.
Claim 17
Dependent Claim
39 words
The method of claim 10 wherein the step of applying a pulse of voltage is performed at a voltage level sufficient to drive ions beneath the surfaces of the target object at least an average of several hundred Angstroms.
Claim 18
Dependent Claim
64 words
The method of claim 10 wherein the step of forming a plasma of ions in the chamber includes the steps of introducing a neutral gas at a controlled rate into the chamber such that a desired low pressure is maintained in the chamber and applying ionizing radiation to the interior of the chamber to ionize the neutral gas in the chamber into a plasma.
Claim 19
Dependent Claim
38 words
The method of claim 16 wherein the step of applying ionizing radiation is performed by ejecting electrons from an electron source into the chamber in a diffuse beam to ionize the neutral atoms or molecules in the chamber.
Claim 20
Dependent Claim
32 words
The method of claim 10 wherein the plasma is formed of ionized nitrogen and the target object is selected from the group consisting of metals, metal alloys, semiconductors, ceramics, and organic polymers.
Claim 21
Dependent Claim
25 words
The method of claim 18 wherein the step of applying a pulse of voltage is performed at a voltage level of at least 20 kilovolts.
Claim 22
Independent Claim
139 words
A method of implanting ions in a target object comprising the steps of: (a) providing an enclosing chamber having walls of electrically conductive material; (b) suspending a target object within the chamber spaced away from the walls of the chamber; (c) evacuating the interior of the chamber to a very low base pressure; (d) forming a plasma of ions in the chamber around the target object; (e) applying repetitive pulses of high voltage between the chamber walls and the target object independently of the forming of the plasma to draw ions in the plasma to the target object at a voltage sufficient to implant ions from the plasma into the target object, the width of the pulses being selected such that the plasma sheath surrounding the target object does not expand to contact the enclosure walls during the pulse.
Claim 23
Independent Claim
139 words
A method of implanting ions in a target object comprising the steps of: (a) providing an enclosing chamber having walls of electrically conductive material; (b) suspending a target object within the chamber spaced away from the walls of the chamber; (c) evacuating the interior of the chamber to a very low base pressure; (d) forming a plasma of ions in the chamber around the target object; (e) applying repetitive pulses of high voltage between the chamber walls and the target object independently of the forming of the plasma to draw ions in the plasma to the target object at a voltage sufficient to implant ions from the plasma into the target object, the width of the pulses being selected such that the plasma sheath surrounding the target object does not expand to contact the enclosure walls during the pulse.
Claim 24
Dependent Claim
22 words
The method of claim 20 wherein, in the steps of applying repetitive pulses of voltage, the voltage is at least 20 kilovolts.
Claim 25
Dependent Claim
64 words
The method of claim 20 wherein the step of forming a plasma of ions in the chamber includes the steps of introducing a neutral gas at a controlled rate into the chamber such that a desired low pressure is maintained in the chamber and applying ionizing radiation to the interior of the chamber to ionize the neutral gas in the chamber into a plasma.
Claim 26
Dependent Claim
38 words
The method of claim 22 wherein the step of applying ionizing radiation is performed by ejecting electrons from an electron source into the chamber in a diffuse beam to ionize the neutral atoms or molecules in the chamber.
Claim 27
Dependent Claim
31 words
The method of claim 20 wherein in the step of applying repetitive pulses of voltage, the time between pulses is selected such that thermal equilibrium of the target object is maintained.
Claim 28
Independent Claim
159 words
A method of implanting ions in a target object comprising the steps of: (a) providing an enclosing chamber having walls of electrically conductive material; (b) suspending a plurality of target objects within the chamber spaced away from the walls of the chamber and from each other; (c) evacuating the interior of the chamber to a very low base pressure; (d) forming a plasma of ions in the chamber around the target objects; (e) applying repetitive pulses of high voltage between the chamber walls and the target objects independently of the forming of the plasma to draw ions in the plasma to the target object at a voltage sufficient to implant ions from the plasma into the target objects, the width of each pulse of high voltage selected such that the plasma sheath surrounding each target object does not expand during the pulse to contact the plasma sheath surrounding another target object or to contact the walls of the chamber.
Claim 29
Independent Claim
159 words
A method of implanting ions in a target object comprising the steps of: (a) providing an enclosing chamber having walls of electrically conductive material; (b) suspending a plurality of target objects within the chamber spaced away from the walls of the chamber and from each other; (c) evacuating the interior of the chamber to a very low base pressure; (d) forming a plasma of ions in the chamber around the target objects; (e) applying repetitive pulses of high voltage between the chamber walls and the target objects independently of the forming of the plasma to draw ions in the plasma to the target object at a voltage sufficient to implant ions from the plasma into the target objects, the width of each pulse of high voltage selected such that the plasma sheath surrounding each target object does not expand during the pulse to contact the plasma sheath surrounding another target object or to contact the walls of the chamber.
Claim 30
Dependent Claim
22 words
The method of claim 25 wherein, in the step of applying repetitive pulses of voltage, the voltage is at least 20 kilovolts.
Claim 31
Dependent Claim
64 words
The method of claim 25 wherein the step of forming a plasma of ions in the chamber includes the steps of introducing a neutral gas at a controlled rate into the chamber such that a desired low pressure is maintained in the chamber and applying ionizing radiation to the interior of the chamber to ionize the neutral gas in the chamber into a plasma.
Claim 32
Dependent Claim
38 words
The method of claim 27 wherein the step of applying ionizing radiation is performed by ejecting electrons from an electron source into the chamber in a diffuse beam to ionize the neutral atoms or molecules in the chamber.
Claim 33
Dependent Claim
33 words
The method of claim 25 wherein in the step of applying repetitive pulses of high voltage, the time spacing between pulses is selected such that thermal equilibrium of the target objects is maintained.
Claim 34
Independent Claim
140 words
An apparatus for implanting ions in a target object comprising: (a) electrically conductive enclosure walls defining an enclosing chamber surrounding a sealed space; (b) means for supporting a target object within the enclosing chamber at a position spaced away from and electrically isolated from the enclosure walls of the chamber and for providing an electrical connection between the target object so supported and the exterior of the chamber; (c) means for forming a plasma of ions of a selected material within the enclosing chamber around the target object; (d) means for evacuating the interior of the enclosing chamber to a desired low pressure level; and (e) means, independent of the means for forming a plasma, for applying a pulse of voltage between the enclosure walls and the target object sufficient to implant ions from the plasma into the target object.
Claim 35
Independent Claim
140 words
An apparatus for implanting ions in a target object comprising: (a) electrically conductive enclosure walls defining an enclosing chamber surrounding a sealed space; (b) means for supporting a target object within the enclosing chamber at a position spaced away from and electrically isolated from the enclosure walls of the chamber and for providing an electrical connection between the target object so supported and the exterior of the chamber; (c) means for forming a plasma of ions of a selected material within the enclosing chamber around the target object; (d) means for evacuating the interior of the enclosing chamber to a desired low pressure level; and (e) means, independent of the means for forming a plasma, for applying a pulse of voltage between the enclosure walls and the target object sufficient to implant ions from the plasma into the target object.
Claim 36
Dependent Claim
30 words
The apparatus of claim 30 wherein the means for applying a pulse of voltage applies pulses repetitively and periodically at a peak voltage level of not less than 20 kilovolts.
Claim 37
Dependent Claim
67 words
The apparatus of claim 30 wherein the means for supporting the target object within the enclosing chamber includes a stage adapted to hold a target object and be in electrical contact therewith, and a conductive support arm extending from the conductive stage and through the conductive walls of the chamber, the conductive arm being sealed to and electrically insulated from the enclosure wall through which it extends.
Claim 38
Dependent Claim
67 words
The apparatus of claim 30 wherein the means for forming a plasma of ions includes means for supplying a selected plasma source neutral gas at a controlled rate into the interior of the enclosing chamber such that a desired low pressure level is maintained within the chamber and means for applying ionizing radiation to the neutral gas in the chamber to ionize the gas into a plasma.
Claim 39
Dependent Claim
58 words
The apparatus of claim 33 wherein the means for applying ionizing radiation to the neutral gas includes an electron beam source mounted to the chamber wall to inject a diffuse beam of electrons into the interior of the enclosing chamber wherein the electrons make contact with and ionize neutral atoms or molecules of the gas within the chamber.
Claim 40
Dependent Claim
63 words
The apparatus of claim 34 including magnets mounted on the walls of the enclosing chamber to provide a magnetic field extending into the chamber to deflect electrons ejected into the interior of the chamber away from the walls to thereby maximize the path length of the electrons within the chamber and the likelihood of collision between electrons and neutral atoms within the chamber.
Claim 41
Dependent Claim
51 words
The apparatus of claim 34 wherein the means for applying a high voltage pulse between the enclosure walls and the target object includes a high voltage pulse source connected to the means for supporting the target object within the chamber and means for grounding the conductive enclosure walls of the chamber.
Claim 42
Dependent Claim
35 words
The apparatus of claim 30 wherein the means for supporting a target object supports a plurality of target objects at positions in the enclosing chamber spaced away from the enclosure walls and from each other.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-08-16 | 1992-02-15 | 1992-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-16 | 1996-02-15 | 1996-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-16 | 2000-02-15 | 2000-08-16 | $7700.00 | Window Closed / Lapsed |