METHOD FOR IMPLANTING IONS ON A SURFACE OF AN OBJECT TO BE TREATED AND INSTALLATION FOR IMPLEMENTING THIS METHOD

Abstract

A method for the implantation of mono- or multi-charged ions on a surface of an object to be treated placed in a vacuum chamber, wherein this method includes the step that consist simultaneously of: injecting into the vacuum chamber a beam of ions produced by a source of ions and directing this beam of ions towards the surface of the object to be treated, and illuminating the surface of the object to be treated with a source of ultraviolet radiation producing ultraviolet radiation that propagates in the vacuum chamber. An ion implantation installation for implementing the implantation method.

Claims

1. A method for implanting mono- or multi-charged ions on a surface of an object to be treated placed in a vacuum chamber, this method comprising the step that consists simultaneously of: injecting into the vacuum chamber a beam of ions produced by a source of ions and directing this beam of ions towards the surface of the object to be treated, and illuminating the surface of the object to be treated by means of a source of ultraviolet radiation producing ultraviolet radiation that propagates in the vacuum chamber.

2. The method according to claim 1, wherein the source of ions is of the electron cyclotron resonance type.

3. The method according to claim 1, wherein a gas is injected into the vacuum chamber during the ion implantation process.

4. The method according to claim 2, wherein a gas is injected into the vacuum chamber during the ion implantation process.

5. The method according to claim 3, wherein the injected gas is a noble gas.

6. The method according to claim 4, wherein the injected gas is a noble gas.

7. The method according to claim 1, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

8. The method according to claim 2, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

9. The method according to claim 3, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

10. The method according to claim 4, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

11. The method according to claim 5, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

12. The method according to claim 6, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

13. The method according to claim 1, wherein the surface of the object to be treated is illuminated by means of a second source of ultraviolet radiation producing a second ultraviolet radiation that propagates in the vacuum chamber in a direction forming an angle with the first ultraviolet radiation.

14. The method according to claim 1, wherein the object to be treated is produced from a material that does not conduct electricity or is semiconductive.

15. The method according to claim 14, wherein the material from which the object to be treated is produced is chosen from the group formed by natural and synthetic sapphires, mineral glasses, polymers and ceramics.

16. The method according to claim 1, wherein the material from which the object to be treated is produced is an electrically conductive material.

17. The method according to claim 16, wherein the material from which the object to be treated is produced is chosen from the group formed by crystalline or amorphous metal alloys, ceramics and precious and non-precious metals.

18. The method according to claim 1, wherein the atoms that are implanted in the surface of the object to be treated by means of the source of ions are chosen from the group formed by nitrogen N, carbon C, oxygen O, argon Ar, helium He and neon Ne.

19. The method according to claim 1, wherein the surface of the object to be treated is treated by means of an ion implantation dose that is situated in a range lying between 1*10.sup.14 ions.Math.cm.sup.2 and 7.5.Math.10.sup.17 ions.Math.cm.sup.2, and preferably between 1*10.sup.16 ions.Math.cm.sup.2 and 15*10.sup.16 ions.Math.cm.sup.2, and wherein the acceleration voltage of the ions is between 7.5 kV and 40 kV.

20. An installation for the implantation of mono- or multi-charged ions in a surface of an object to be treated, wherein this installation comprises a vacuum chamber in which the object to be treated is disposed, wherein the installation also comprises a source of ions that injects a beam of ions into the vacuum chamber, wherein this beam of ions is directed towards the surface of the object to be treated, wherein the installation also comprises a source of ultraviolet radiation that produces ultraviolet radiation that propagates in the vacuum chamber and illuminates the object to be treated, wherein the source of ions and the source of ultraviolet radiation are arranged to function simultaneously.

21. The installation for the implantation of mono- or multi-charged ions according to claim 20, wherein the source of ions is of the electron cyclotron resonance type.

22. The installation for the implantation of mono- or multi-charged ions according to claim 20, wherein the installation comprises a source of gas that delivers gas into the vacuum chamber via an inlet valve to which the source of gas is connected.

23. The installation for the implantation of mono- or multi-charged ions according to claim 21, wherein the installation comprises a source of gas that delivers gas into the vacuum chamber via an inlet valve to which the source of gas is connected.

24. The installation for the implantation of mono- or multi-charged ions according to claim 22, wherein the gas contained in the source of gas is a noble gas.

25. The installation for the implantation of mono- or multi-charged ions according to claim 20, wherein the installation produces an ion implantation dose in a range lying between 1*10.sup.14 ions.Math.cm.sup.2 and 7.5.Math.10.sup.17 ions.Math.cm.sup.2, and preferably between 1*10.sup.16 ions.Math.cm.sup.2 and 15*10.sup.16 ions.Math.cm.sup.2, and wherein the acceleration voltage of the ions is between 7.5 kV and 40 kV.

26. The installation for the implantation of mono- or multi-charged ions according to claim 20, wherein the atmospheric pressure inside the vacuum chamber is between 10.sup.4 Pa and 10.sup.4 Pa and preferably between 10.sup.2 Pa and 10.sup.4 Pa.

27. The installation for the implantation of mono- or multi-charged ions according to claim 20, wherein the installation comprises a second source of ultraviolet radiation that illuminates the surface of the object to be treated with a second ultraviolet radiation that propagates in the vacuum chamber in a direction forming an angle with the first ultraviolet radiation.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0015] Other features and advantages of the present invention will emerge more clearly from the following detailed description of an example embodiment of the method according to the invention, this example being given purely by way of illustration and in a non-limiting manner in relation to the accompanying drawing, on which:

[0016] FIG. 1, already cited, is a schematic view of a source of ions of the electron cyclotron resonance ECR type according to the prior art;

[0017] FIG. 2, already cited, is a schematic view that illustrates a beam of ions at the exit of the source of ions of the electron cyclotron resonance ECR type illustrated in FIG. 1;

[0018] FIG. 3 is a schematic view of an installation for implanting mono- or multi-charged ions on the surface of the object to be treated according to the invention, and

[0019] FIG. 4 is a view to a larger scale of the region surrounded by a circle in FIG. 3 that illustrates the phenomenon of recombination of the free electrons that are situated in the atmosphere of the vacuum chamber with the ions present on the surface of the object to be treated.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0020] The present invention proceeds from the general inventive idea that consists of placing an object subjected to a process of ion implantation in a vacuum chamber and illuminating it by means of ultraviolet radiation at the same time as it is bombarded with a beam of mono- or multi-charged ions. In propagating in the vacuum chamber, the protons of the ultraviolet radiation extract electrons from the atoms and molecules that remain in the rarefied atmosphere of the vacuum chamber, these free electrons next recombining with the ions present on the surface of the object the surface of which is being treated. It is thus possible to control the surface potential of the object to be treated and to maintain this potential at a sufficiently low level for the new ions that arrive not to be excessively slowed down by the potential barrier and to keep sufficient kinetic energy enabling them to penetrate in depth into the object to be treated.

[0021] An ion implantation installation enabling the method according to the invention to be implemented is shown schematically in FIG. 3. Designated overall by the numerical reference 18, this ion implantation installation comprises a vacuum chamber 20 in the sealed enclosure 22 of which an object 24 intended to be subjected to an ion implantation process is placed. The object 24 to be treated may be solid or be in the powder state. It may be an amorphous or crystalline material, insulating or electrically conductive, metal or ceramic. In the case where the object 24 to be treated is in the powder state, it will preferentially be stirred throughout the ion implantation process in order to ensure that the particles that make up this powder are exposed homogeneously to the ion implantation beam.

[0022] A source of ions 26, for example of the electron cyclotron resonance ECR type, is sealingly fixed to the enclosure 22 of the vacuum chamber 20, facing a first opening 28 provided in this enclosure 22. This source of ions 26, of a type similar to that of the ECR source of ions described above, is oriented so that the beam of mono- or multi-charged ions 30 that it produces propagates in the vacuum chamber 20 and strikes the surface of the object 24 to be treated. The mono- or multi-charged ions that strike the object to be treated 24 penetrate more or less deeply under the surface of the object 24 and accumulate progressively, thus giving rise to an electrostatic potential barrier that tends to restrict and repel the ions that arrive subsequently, which poses problems of non-homogeneity of the distribution of the ions on and under the surface and in the thickness of the object 24 to be treated.

[0023] To remedy this problem, a source of ultraviolet radiation 32 is also mounted sealingly on the enclosure 22 of the vacuum chamber 20, facing a second opening 34 provided in the enclosure 22. This source of ultraviolet radiation 32 is oriented so that the ultraviolet radiation 36 that it produces propagates in the vacuum chamber 20 and falls onto the surface of the object to be treated 24 at the same time as the beam of ions 30 strikes the surface of the same object to be treated 24.

[0024] The vacuum that prevails in the sealed enclosure 22 of the vacuum chamber 20 is relatively high, typically between 10.sup.4 and 10.sup.4 Pa, preferably between 10.sup.2 Pa and 10.sup.4 Pa. Nevertheless, despite the very high vacuum that prevails in the vacuum chamber 20, there remain in the atmosphere of this vacuum chamber 20 atoms and molecules from which the photons of the ultraviolet radiation 36 will extract electrons that will be attracted by the positive potential of the surface of the object 24 and will recombine with the ions present on the surface of this object 24, so as to cancel out the electrostatic charges. The electrostatic potential of the object to be treated 24 can thus be maintained at sufficiently low values to interfere with the implantation of new ions as little as possible and to enable them to penetrate sufficiently deeply below the surface of the object to be treated 24.

[0025] In order to improve the process of implantation of ions in the object to be treated 24, enriching the atmosphere of the vacuum chamber 20 can be envisaged. For this purpose, the vacuum chamber 20 is provided with an inlet valve 38 to which a source of gas 40 is connected, for example a noble gas such as argon or xenon. This inlet valve 38 emerges close to the object to be treated 24, so as to create locally, in the vicinity of the object to be treated 24, a slight overpressure of noble gas richer in atoms.

[0026] By proceeding in this way, the atmosphere of the vacuum chamber 20 is enriched and the number of electrons extracted from the atoms present in the atmosphere that prevails in the vacuum chamber 20 (see FIG. 4) is increased. The process of recombination between the electrons in the vacuum chamber 20 and the ions on the surface of the object to be treated 24 is therefore amplified, which makes it possible to reduce even further the electrical potential of the object to be treated. This is because it has been realised with a certain amount of surprise that the electrons extracted by the photons of the ultraviolet radiation from the atoms of the noble gas, although they partly recombine with ionised atoms of the noble gas, or even with the ions of the ion implantation beam, all the same recombine in a sufficiently large number with the positive charges present on the surface of the object to be treated in order to substantially reduce the electrostatic potential of the surface of the object to be treated.

[0027] In order to improve further the process of implantation of ions in the object to be treated 24, providing a second source of ultraviolet radiation 42 can be envisaged. This second source of ultraviolet radiation 42 can be fixed sealingly to the enclosure 22 of the vacuum chamber 20, or be directly installed inside the vacuum chamber 20 while being supported by a foot 44. The second source of ultraviolet radiation 42 can be oriented so that the ultraviolet radiation 42 that it emits forms an angle, for example of approximately 90, with respect to the ultraviolet radiation 36 emitted by the first source of ultraviolet radiation 32. With such an arrangement of the sources of ultraviolet radiation 32, 42, it is possible to treat larger objects 24.

[0028] It goes without saying that the present invention is not limited to the embodiments that have just been described and that various simple modifications and variants can be envisaged by a person skilled in the art without departing from the scope of the invention as defined by the accompanying claims.

[0029] It should be noted in particular that the present invention applies especially to the surface treatment of objects made from sapphire (natural or synthetic) for producing watch glasses. By virtue of the ion implantation method according to the invention, the quantity of incident light reflected by such glasses is significantly reduced, which significantly improves the legibility of the information displayed by the indicating devices (hands, date, decoration) situated under these glasses.

[0030] The present invention also applies to the surface treatment of crystalline or amorphous metal objects or ceramics, the mechanical properties of which, in particular scratch resistance, are greatly improved when the ion implantation method with neutralisation of charges according to the invention is applied thereto.

[0031] The present invention also applies to the surface treatment of particles of a metal or ceramic material in the powder state. The metal or ceramic powder particles obtained by means of the method according to the invention are intended for the manufacture of solid parts by means of powder metallurgy methods such as the injection moulding method, better known by its English name metal injection moulding or MIM, pressing or additive manufacture such as three-dimensional laser printing.

[0032] According to particular embodiments of the method according to the invention: [0033] the source of mono- or multi-charged ions is of the electron cyclotron resonance ECR type; [0034] the ions are accelerated at a voltage of between 15,000 volts and 40,000 volts; [0035] the material from which the beam of ions is produced is chosen from nitrogen N, carbon C, oxygen O, argon Ar, helium He and neon Ne;

[0036] the dose of ions implanted is between 1*10.sup.14 ions.Math.cm.sup.2 and 7.5.10.sup.17 ions.Math.cm.sup.2, and preferably between 1*10.sup.16 ions.Math.cm.sup.2 and 15*10.sup.16 ions.Math.cm.sup.2; the depth of implantation of the ions is 150 nm to 250 nm; [0037] the metal material is a precious metal chosen from gold and platinum; [0038] the metal material is a non-precious metal chosen from magnesium, titanium and aluminium; [0039] the particles of the metal or ceramic powder are stirred throughout the ion implantation process; [0040] the granulometry of the particles of the metal powder or ceramic used is such that substantially 50% of all these particles have a dimension of less than 2 micrometres, the dimension of the particles of the metal or ceramic powder used not exceeding 60 micrometres; [0041] the ceramic material treated according to the ion implantation method in accordance with the present invention is a carbide, in particular a titanium carbide TiC or a silicon carbide SiC; [0042] the ceramic material of the carbide type is bombarded by means of nitrogen atom ions N in order to form a carbonitride, in particular titanium carbonitride TiCN or silicon carbonitride SiCN; [0043] the ceramic material treated according to the ion implantation method according to the invention is a nitride, in particular a silicon nitride Si.sub.3N.sub.4; [0044] the ceramic material treated according to the ion implantation method in accordance with the present invention is an oxide, in particular zirconia ZrO.sub.2 or alumina Al.sub.2O.sub.3; [0045] the ceramic material of the oxide type is bombarded by means of nitrogen ions in order to form an oxynitride, in particular zirconium oxynitride ZrO(NO.sub.3).sub.2, or even zirconium nitride ZrN if the ion bombardment is prolonged for sufficiently long, or aluminium oxynitride AlO.sub.xN.sub.y; [0046] the ceramic material of the oxide type is bombarded by means of carbon ions in order to form a carbonitride, in particular zirconium oxycarbide ZrO.sub.2C, or even zirconium carbide ZrC; [0047] the ceramic material of the oxide type is bombarded by means of boron ions in order to form an oxyboride, in particular zirconium oxyboride ZrO.sub.2B, or even zirconium boride ZrB.sub.2 if the ion bombardment is prolonged for sufficiently long.

LIST OF NAMES

[0048] 1. Source of ions of the electron cyclotron resonance ECR type [0049] 2. Injection stage [0050] 4. Volume of gas to be ionised [0051] 6. Microwave [0052] 8. Magnetic confinement stage [0053] 10. Plasma [0054] 12. Extraction stage [0055] 14a. Anode [0056] 14b. Cathode [0057] 16. Beam of mono- or multi-charged ions [0058] 18. Ion implantation installation [0059] 20. Vacuum chamber [0060] 22. Sealed enclosure [0061] 24. Object to be treated [0062] 26. Source of ions [0063] 28. First opening [0064] 30. Beam of mono- or multi-charged ions [0065] 32. Source of ultraviolet radiation [0066] 34. Second opening [0067] 36. Ultraviolet radiation [0068] 38. Inlet valve [0069] 40. Gas source [0070] 42. Second source of ultraviolet radiation [0071] 44. Foot [0072] 46. Ultraviolet radiation