Ion sources for ion implantation apparatus

• US 20040144932A1
• Filed: 11/07/2003
• Published: 07/29/2004
• Est. Priority Date: 12/03/2001
• Status: Active Grant

• Current Assignee: Adrian Murrell, Andrew Allen, Matthew Peter Dobson, Neil L. Clarke, Peter Michael Banks
• Original Assignee: Adrian Murrell, Andrew Allen, Matthew Peter Dobson, Neil L. Clarke, Peter Michael Banks
• Inventors: Allen, Andrew, Murrell, Adrian, Dobson, Matthew Peter, Banks, Peter Michael, Clarke, Neil L.
• Granted Patent: US 6,818,909 B2
• Time in Patent Office: Days
• US Class Current: 250/492.21
• CPC Class Codes: H01J 37/08 Ion sources; Ion guns
• CPC Class Codes: H01J 37/3171 for ion implantation

Abstract

The invention relates to an ion source for an ion implanter in which source material for providing desired ions is provided in the form of a plate or liner which can be fitted into the reactant chamber of the ion source.

Claims

1. An ion implantation apparatus including an ionization chamber having a gas inlet port and an outlet through which ions created in the chamber can exit the chamber, the chamber containing an ion source body comprising aluminium oxide, a source of etchant gas selected from the group consisting of fluorine and sulphur hexafluoride under pressure connected to the inlet port of the chamber, and an energy source to ionize etchant gas in the chamber and thereby to form a plasma containing ions of aluminium derived from said ion source body.

8. Ion implantation apparatus according to claim 1, wherein the ion source body is in rigid preshaped form, lining at least a part of an interior wall of the chamber.

10. Ion implantation apparatus according to claim 8, wherein the gas inlet port is provided in a wall of the chamber and said ion source body is positioned against said wall so that the gas flows in contact with the ion source body, in entering the chamber.

14. An ion implantation apparatus according to claim 1 wherein the chamber is formed of carbon.

15. An ion implantation apparatus according to claim 1 wherein the chamber is formed of tungsten.

16. Ion implantation apparatus according claim 8 wherein the ion source body is porous.

17. Ion implantation apparatus according to claim 8 wherein the ionization chamber is of substantially symmetrical form having an axis of symmetry and opposed end walls, with the energy source comprising a cathode and counter cathode extending through the side walls for connection to a power supply therefor, the preshaped ion source body being located adjacent said counter cathode.

2. An ion implantation apparatus including an ionization chamber having a gas inlet port and an outlet through which ions created in the chamber can exit the chamber, the chamber containing an ion source body comprising a material selected from the group consisting of aluminium, aluminium nitride, magnesium, magnesium oxide, magnesium nitride, indium, indium oxide, indium nitride, and refractory metals, and compounds thereof, capable of providing ions intended for implantation, a source of etchant gas selected from the group consisting of nitrogen trifluoride, boron trifluoride, fluorine and sulphur hexafluoride under pressure connected to the inlet port of the chamber, and an energy source to ionize etchant gas in the chamber and thereby to form a plasma containing ions of aluminium derived from said ion source body.

3. An ion implantation apparatus according to claim 2 wherein the refractory metal is selected from the group consisting of erbium, cobalt, tungsten, platinum, iridium, rhenium, nickel, niobium, tantalum, molybdenum, zirconium and titanium.

4. An ion implantation apparatus according to claim 2 wherein the ionization chamber is of substantially symmetrical form having an axis of symmetry and opposed end walls, said energy source comprising first and second electrodes providing a cathode and counter cathode extending into the chamber, the energy source further comprising a connector for electrically connecting a power source to the first and second electrodes for establishing an arc across the interior of the chamber.

5. An ion implantation apparatus according to claim 4 wherein the ionization chamber is of substantially cuboid form and has opposed side walls, end walls, a top and a base;

6. An ion implantation apparatus according to claim 5 wherein said cathode is mounted in one of said opposed end walls.

7. An ion implantation apparatus according to claim 6 wherein said counter cathode is mounted in the other of said opposed end walls.

9. Ion implantation apparatus according to claim 2, wherein the ion source body is in rigid preshaped form, lining at least a part of an interior wall of the chamber.

11. Ion implantation apparatus according to claim 9, wherein the ion source body is in the form of a plate.

12. Ion implantation apparatus according to claim 11, wherein the plate is provided with a plurality of apertures extending through the plate.

13. Ion implantation apparatus according to claim 9 wherein the ion source body comprises sheet form mesh material.

18. An ion implantation apparatus including an ion source comprising

a chamber having a gas inlet port and an outlet, the chamber containing an aluminium ion source body in the form of at least one plate having planar surfaces and a thickness, the plate being porous and formed from pure alumina,

a source of an etchant gas selected from the group consisting of fluorine and sulphur hexafluoride under pressure connected to the inlet port of the chamber,

an energy source to ionize etchant gas in the chamber and thereby to form a plasma containing ions of aluminium derived from said ion source body;

and

at least one ion extraction electrode associated with the ion source for extracting the aluminium ions from the chamber through said outlet,

said ion source body being located within the chamber and in opposed relationship to said at least one ion extraction electrode.

23. A method according to claim 18 wherein the preformed solid ion source material is porous and the gas is introduced into the chamber through the porous source material.

19. An ion implantation apparatus including an ion source comprising

a chamber having a gas inlet port and an outlet, the chamber containing an ion source body in the form of at least one plate having planar surfaces and a thickness, the plate being porous and formed from a material selected from the group consisting of aluminium nitride, magnesium, indium, and oxides and nitrides thereof, and pure refractory metals,

a source of etchant gas selected from the group consisting of nitrogen trifluoride, boron trifluoride, fluorine and sulphur hexafluoride under pressure connected to the inlet port of the chamber,

an energy source to ionize etchant gas in the chamber and thereby to form a plasma containing ions derived from said ion source body, and

at least one ion extraction electrode associated with the ion source for extracting the ions from the chamber through said outlet, said ion source body being located within the chamber, in opposed relationship to said at least one extraction electrode.

20. A method of generating aluminium ions for implantation into a substrate mounted in an ion implantation apparatus, the method comprising placing a preformed body of solid alumina as ion source material in an ionization chamber, supplying a gas selected from the group consisting of fluorine and sulphur hexafluoride to the chamber to contact the ion source material, generating a plasma in the ionization chamber to cause dissociation and ionization of the ion source material and the gas, and extracting the resultant aluminium ions from the ionization chamber for implantation.

21. A method of generating ions for implantation into a substrate mounted in an ion implantation apparatus, the method comprising placing a preformed body of solid ion source material, selected from the group consisting of aluminium nitride, magnesium, indium and oxides and nitrides thereof, and refractory metals and oxides and nitrides thereof, all capable of providing ions intended for implantation, in an ionization chamber, the ion source material being in the form of a preformed solid which at least partially lines the interior of the chamber, supplying a gas selected from the group consisting of nitrogen trifluoride, boron trifluoride, fluorine and sulphur hexafluoride to the chamber to contact the solid ion source material, generating a plasma in the ionisation chamber to cause dissociation and ionisation of the source material and the gas, and extracting the resultant ions from the ionisation chamber for implantation, the ion source material and the etchant gas being selected such that no additional ions are created having the same or similar charge/mass ratio to that of the selected ions.

22. A method according to claim 21 wherein the refractory metals are selected from the group consisting of oxides and nitrides of erbium, cobalt, tungsten, platinum, iridium, rhenium, nickel, niobium, tantalum, molybdenum, zirconium and titanium.

24. An element for use in an ionisation chamber of an ion implantation apparatus for supplying ions for implantation into a semiconductor substrate, the element being formed of a non-aluminium-containing ion source material selected from the group consisting of refractory metals and oxides and nitrides of elements providing ions intended for implantation and provided in the form of one or more solid plates locatable in said chamber.

25. An element according to claim 24 wherein said ion source material is selected from the group consisting of aluminium, magnesium, indium, erbium, cobalt, tungsten, platinum iridium, rhenium, nickel, niobium, tantalum, molybdenum, zirconium and titanium, and oxides and nitrides thereof.

29. An element according to claim 25 wherein the body of source material is about 50% porous measured against a fully dense body thereof.

30. An element according to claim 25 wherein the element is in the form of a rectangular plate of dimensions such that it can be located against an inner rectangular planar wall of said chamber.

26. An element for use in an ionisation chamber of an ion implantation apparatus for supplying aluminium ions for implantation into a semiconductor substrate, the element being preformed of an ion source material selected from the group consisting of pure alumina and pure aluminium nitride in the form of a solid and being locatable in said chamber, the source material having a purity of 99.9% or better and containing no or negligible contaminant, the source material having a purity of 99.9% or better and containing no or negligible contaminant.

27. An element according to claim 26 wherein the ion source material has a purity of 99.99% or better.

28. An element according to claim 27 and in the form of a solid body which has a surface which is complementary to an inner surface of the chamber against which the element is to be placed.

31. An element according to claim 27 wherein each plate is provided in the form of a plurality of abutting platelets.

32. An element for use in an ionisation chamber of an ion implantation apparatus for supplying aluminium ions for implantation into a semiconductor substrate, the element being formed of a source material selected from the group consisting of pure alumina and pure aluminium nitride in the form of a solid and being locatable in said chamber, the source material having a purity of at least 99.99% and containing no or negligible contaminant, the solid source material being about 50% porous measured against a fully dense body thereof, and the element being in the form of a cuboid plate of dimensions such that it can be located against an inner rectangular wall of said chamber and being so formed as to include at least surface irregularities such as to provide for stress relief when the body is subjected to operational temperatures and to maximise the surface area of the plate.