Controlled dose ion implantation
View Patent ↗An ion implanter for creating a ribbon or ribbon-like beam by having a scanning device that produces a side to side scanning of ions emitting by a source to provide a thin beam of ions moving into an implantation chamber. A workpiece support positions a workpiece within the implantation chamber and a drive moves the workpiece support up and down through the thin ribbon beam of ions perpendicular to the plane of the ribbon to achieve controlled beam processing of the workpiece. A control includes a first control output coupled to said scanning device to limit an extent of side to side scanning of the ion beam to less than a maximum amount and thereby limit ion processing of the workpiece to a specified region of the workpiece and a second control output coupled to the drive simultaneously limits an extent of up and down movement of the workpiece to less than a maximum amount and to cause the ion beam to impact a controlled portion of the workpiece.
1. For use with an ion implanter having an ion source and an implantation chamber; apparatus comprising:
a) beam forming structure that scans ions from side to side to produce a thin ion beam moving into an ion implantation chamber;
b) a workpiece support for positioning a workpiece within the implantation chamber;
c) a drive for moving the workpiece support back and forth through the thin ion beam to effect controlled ion beam processing of said workpiece; and
d) a control including:
i) a first control output coupled to the beam forming structure that limits an extent of side to side scanning to reduce a width of the ion beam to a width less than a width of the workpiece thereby limiting ion beam processing of the workpiece to a specified region of the workpiece; and
ii) a second control output coupled to the drive to control back and forth movement of the workpiece to a specified amount; said first and second control outputs causing the ion beam to impact less than an entire surface of the workpiece.
2. The apparatus of claim 1 wherein the second control output from said control causes the drive to move the support back and forth at a non uniform rate.
3. The apparatus of claim 1 wherein the workpiece is a generally circular workpiece and wherein the control limits a width of the ion beam to intercept approximately one half of the workpiece and further limits back and forth movement of the support to cause said beam to implant ions into a selected single quadrant of said generally circular workpiece during a scan cycle.
4. The apparatus of claim 3 wherein the control performs additional scan cycles for ion beam processing other quadrants of said workpiece.
5. The apparatus of claim 4 wherein a dose is adjusted to have different values in different quadrants of said wafer.
6. The apparatus of claim 5 wherein the dose is controlled by adjusting a back and forth workpiece speed.
7. The apparatus of claim 1 additionally comprising two current sensors spaced on opposite sides of said workpiece support for monitoring current passing through the implantation chamber in the region of the workpiece.
8. The apparatus of claim 1 additionally comprising a tilt drive for adjusting an angle at which the ions that make up the beam strike a workpiece treatment surface.
9. The apparatus of claim 1 additionally comprising a twist drive for rotating the workpiece about an axis to perform treatment of a specified portion of the workpiece.
10. For use with an ion implanter having a source and an implantation chamber; apparatus comprising:
a) structure including one or more scan electrodes that produces a thin beam of ions moving into an ion implantation chamber by deflecting ions in a scanning side to side deflection pattern;
b) a workpiece support for positioning a workpiece within the implantation chamber;
c) a drive for moving the workpiece support back and forth through the thin beam of ions to effect controlled beam processing of said workpiece; and
d) a control including a control output coupled to the scan electrodes to vary a dose received by the workpiece by changing a delay period at ends of the back and forth deflection pattern during movement of the workpiece through the thin beam of ions.
11. The apparatus of claim 10 wherein the control causes the drive to move the support back and forth at a non uniform rate.
12. The apparatus of claim 10 additionally comprising two current sensors spaced on opposite sides of said workpiece support for monitoring current passing through the implantation chamber in the region of the workpiece.
13. For use with an ion implanter having an ion source and an implantation chamber; apparatus comprising:
a) beam forming structure that produces a thin ion beam moving into an ion implantation chamber;
b) a workpiece support for positioning a workpiece within the implantation chamber;
c) a drive for moving the workpiece support back and forth through the thin ion beam to effect controlled beam treatment of said workpiece; and
d) a control including:
i) a first control output coupled to the beam forming structure that limits a width of the ion beam to less than a maximum amount and thereby limits ion processing of the workpiece to a specified region of the workpiece; and
ii) a second control output coupled to the drive to control back and forth movement of the workpiece support to a specified amount so that a controlled portion of said workpiece having a width less than an entire width of the workpiece is treated by the thin beam of ions during the back and forth movement of the workpiece.