Magnetically-enhanced plasma chamber with non-uniform magnetic field
First Claim
1. A magnetically-enhanced plasma chamber for producing an improved instantaneous spatial uniformity of ion flux from the plasma to a semiconductor workpiece, comprising:
- a chuck for holding a flat semiconductor workpiece so that the workpiece occupies a workpiece area;
a plasma source for producing a plasma in a first region above the workpiece area; and
a magnet configured to produce in a planar second region a magnetic field having a non-zero gradient such that, at every point in the second region, the magnetic field at that point has a direction that is approximately the vector cross product of (i) the gradient of the magnitude of the magnetic field at that point, and (ii) a vector extending perpendicularly from the workpiece area toward the plasma;
wherein the second region is parallel to and adjacent to the workpiece area and has a surface area substantially greater than half of the workpiece area;
wherein, at every instant, the magnetic field has a range of magnitudes in the second region which ranges between a minimum magnitude and a maximum magnitude, wherein the minimum magnitude occurs at only a single point; and
wherein, at every instant, the magnetic field has a clockwise curvature relative to said single point when viewed from above the workpiece area.
1 Assignment
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Accused Products
Abstract
A plasma chamber having a magnet which produces a magnetic field such that, within a region parallel to and adjacent to the workpiece, the direction of the magnetic field is approximately the vector cross product of (i) the gradient of the magnitude of the magnetic field, and (ii) a vector extending perpendicularly from the workpiece surface toward the plasma. Alternatively, the plasma chamber includes a north magnetic pole and a south magnetic pole located at distinct azimuths around the periphery of the workpiece. The azimuth of the south magnetic pole relative to the north magnetic pole is clockwise around the central axis, and each magnetic pole faces a direction which is more toward than away from a central axis of the workpiece area. An additional aspect of the invention is a plasma chamber having a rotating magnetic field produced by electromagnets spaced around the periphery of the workpiece which receive successive fixed amounts of electrical current during successive time intervals. During each transition between the time intervals, the current supplied to each electromagnet is changed relatively slowly or relatively quickly according to whether the current change includes a change in polarity.
140 Citations
42 Claims
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1. A magnetically-enhanced plasma chamber for producing an improved instantaneous spatial uniformity of ion flux from the plasma to a semiconductor workpiece, comprising:
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a chuck for holding a flat semiconductor workpiece so that the workpiece occupies a workpiece area; a plasma source for producing a plasma in a first region above the workpiece area; and a magnet configured to produce in a planar second region a magnetic field having a non-zero gradient such that, at every point in the second region, the magnetic field at that point has a direction that is approximately the vector cross product of (i) the gradient of the magnitude of the magnetic field at that point, and (ii) a vector extending perpendicularly from the workpiece area toward the plasma; wherein the second region is parallel to and adjacent to the workpiece area and has a surface area substantially greater than half of the workpiece area; wherein, at every instant, the magnetic field has a range of magnitudes in the second region which ranges between a minimum magnitude and a maximum magnitude, wherein the minimum magnitude occurs at only a single point; and wherein, at every instant, the magnetic field has a clockwise curvature relative to said single point when viewed from above the workpiece area. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A magnetically-enhanced plasma chamber for producing an improved instantaneous spatial uniformity of ion flux from the plasma to a semiconductor workpiece, comprising:
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a chuck for holding a semiconductor workpiece so that the workpiece occupies a workpiece area bounded by a perimeter; a plasma source for producing a plasma in a region above the workpiece area; a unitary magnet having a north magnetic pole and a south magnetic pole located at distinct azimuths around the perimeter of the workpiece area, wherein each magnetic pole faces a direction which is more toward than away from the center of the workpiece area, and the azimuth of the north magnetic pole minus the azimuth of the south magnetic pole is substantially greater than zero and substantially less than 180°
degrees in a direction counterclockwise around said perimeter when viewing the workpiece area from above. - View Dependent Claims (8)
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9. A magnetically-enhanced plasma chamber for producing an improved instantaneous spatial uniformity of ion flux from the plasma to a semiconductor workpiece, comprising:
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a chuck for holding a semiconductor workpiece so that the workpiece occupies a workpiece area bounded by a perimeter; a plasma source for producing a plasma in a region above the workpiece area; and a first north magnetic pole, a first south magnetic pole, a second south magnetic pole, and a second north magnetic pole positioned at respective azimuths around the perimeter of the workpiece area which are progressively clockwise around the perimeter of the workpiece area when viewing the workpiece area from above, wherein each magnetic pole faces a direction which is more toward than away from the center of the workpiece area, and the first north magnetic pole and first south magnetic pole in combination produce a first magnetic field between them, the second north magnetic pole and second south magnetic pole in combination produce a second magnetic field between them, and the four magnetic poles are configured so that the first magnetic field is substantially stronger than the second magnetic field. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A magnetically enhanced plasma chamber for processing a semiconductor workpiece, comprising:
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a workpiece support for holding the workpiece at a workpiece support area; a plurality of electromagnets at positions spaced around the periphery of the workpiece support area; and a power supply for providing to each respective electromagnet a respective current signal having successive fixed current values during successive time intervals so that the electromagnets in combination produce a magnetic field which rotates over time, wherein each of said time intervals is separated by a transition time period during which the power supply is configured to change the value of the current it provides to the respective electromagnets, during each transition period, to those electromagnets to which the power supply provides a current change which is a change in magnitude of current with unchanged polarity, the power supply is configured to provide said current change during a short portion of the transition period, during each transition period, to those electromagnets to which the power supply provides a current change which includes a polarity reversal, the power supply is configured to provide said current change during a long portion of the transition period, and each long portion of a transition period has a duration substantially longer than each short portion of the transition period. - View Dependent Claims (23, 24)
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25. A method of producing an ion flux from a plasma to the surface of a semiconductor workpiece, comprising the steps of:
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holding a semiconductor workpiece having a flat surface; producing a plasma in a region above the surface of the workpiece; and producing a magnetic field in a planar region such that, at any point in the planar region, the direction of the magnetic field at that point is approximately the vector cross product of (i) the gradient of the magnitude of the magnetic field at that point, and (ii) a vector extending perpendicularly from the workpiece surface toward the plasma; wherein the planar region is parallel to and adjacent to the workpiece surface and has a surface area which is at least half the surface area of the workpiece surface; wherein, at every instant, the magnetic field has a range of magnitudes in the second region which ranges between a minimum magnitude and a maximum magnitude, wherein the minimum magnitude occurs at only a single point; and wherein, at every instant, the magnetic field has a clockwise curvature relative to said single point when viewed from above the workpiece area.
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26. A method of producing an ion flux from a plasma to a semiconductor workpiece, comprising the steps of:
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holding a semiconductor workpiece having a surface bounded by a perimeter; producing a plasma in a region above the surface of the workpiece; providing a unitary magnet having a north magnetic pole and a south magnetic pole; and positioning the magnet so as to position the north magnetic pole and south magnetic pole at distinct azimuths around the perimeter of the workpiece surface, wherein each magnetic pole faces a direction which is more toward than away from the center of the workpiece surface, and the azimuth of the north magnetic pole minus the azimuth of the south magnetic pole is substantially greater than zero and substantially less than 180°
degrees in a direction counterclockwise around said perimeter when viewing the workpiece area from above.
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27. A method of producing an ion flux from a plasma to a semiconductor workpiece, comprising the steps of:
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holding a semiconductor workpiece having a surface bounded by a perimeter; producing a plasma in a region above the surface of the workpiece; and positioning a first north magnetic pole, a first south magnetic pole, a second south magnetic pole, and a second north magnetic pole at respective azimuths around the perimeter of the workpiece surface which are progressively clockwise around the perimeter of the workpiece surface when viewing the workpiece surface from above, wherein each magnetic pole faces a direction which is more toward than away from the center of the workpiece surface, and the first north magnetic pole and first south magnetic pole in combination produce a first magnetic field between them, the second north magnetic pole and second south magnetic pole in combination produce a second magnetic field between them, and the first magnetic field is substantially stronger than the second magnetic field. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method of magnetically enhancing a plasma process performed on a semiconductor workpiece, comprising the steps of:
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holding a semiconductor workpiece at a workpiece support area bounded by a perimeter; positioning a plurality of electromagnets at positions spaced around the perimeter of the workpiece support area; and supplying to each respective electromagnet a respective electrical current signal having successive fixed current values during successive time intervals so that the electromagnets in combination produce a magnetic field which rotates over time, wherein each of said time intervals is separated by a transition time period during which the respective values of the current supplied to the respective electromagnets are changed, and wherein the supplying step includes the steps of during each transition period, to those electromagnets to which the change in supplied current is a change in magnitude of current with unchanged polarity, supplying said current change during a short portion of the transition period, and during each transition period, to those electromagnets to which the change in supplied current includes a polarity reversal, supplying said current change during a long portion of the transition period, wherein each long portion of a transition period has a duration substantially longer than each short portion of the transition period. - View Dependent Claims (41, 42)
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Specification