WO2004061893A2

WO2004061893A2 - Machine for uniform treatment of sample surfaces by multicharged ion projection

Info

Publication number: WO2004061893A2
Application number: PCT/FR2003/003744
Authority: WO
Inventors: Gilles Borsoni; Bruno Simon
Original assignee: Qplus
Priority date: 2002-12-18
Filing date: 2003-12-16
Publication date: 2004-07-22
Also published as: FR2849266A1; WO2004061893A3; AU2003300625A1; AU2003300625A8

Abstract

The invention relates to a machine for uniform treatment of sample surfaces by projection of multicharged low kinetic energy ions. The inventive machine comprises a unit which produces ion beam, is electrically insulated from the remaining part thereof and polarisable, electorstatic deceleration means which decelerates ions approaching the surface of a treated sample, scanning means for scanning the surface of the sample by a ion beam in order to obtain a desired uniformity of the treatment, mechanical supporting means for keeping the sample in such position that the surface thereof can be treated by the ion beam, and vacuum producing means arranged on vacuum chambers in which the treated sample is arranged and the ion beam circulates.

Description

UNIFORM TREATMENT MACHINE FOR SAMPLE SURFACES

BY MULTICHARGE ION PROJECTION.

The subject of the invention is a machine for uniform treatment of surfaces of materials, using ultra-charged slow ion beams of very low kinetic energy, these treatments making it possible to induce nanometric or sub-nanometric, physical or chemical modifications, on the surface of samples exposed to the ion beam. Various pieces of equipment are known in the state of the art for projecting multicharged ions. By way of example, European patent EP0483004 describes a source of highly charged positive ions with electronic cyclotron resonance comprising: - a microwave cavity having an axis of symmetry (X); a high frequency input opening into the cavity to create a high frequency electromagnetic field there; - introduction of gas into the cavity; means for producing a magnetic field along the axis in said cavity; means for producing a multipolar radial magnetic field in this cavity, the superposition of these axial and radial magnetic fields forming a resulting magnetic field distributed throughout the cavity and defining at least one equimagnetic surface (S) completely closed inside of the cavity; means for extracting the ions at the end of the cavity, a voltage polarizable probe to improve the ionization of the gas and thus increase the flow of extracted ions, made of metal emitting electrons, placed upstream of the means extraction and having no contact with the equimagnetic surface. Another patent of the prior art, the German patent DE4226299 describes an equipment comprising a plasma chamber in which a vacuum is created to be able to produce plasma and in which the microwaves are introduced, a plasma electrode and an electrode extraction process through which the ions produced are extracted from the plasma. An extraction field is generated between the plasma electrode and the extraction electrode, due to the voltage difference (around 20 kV). The plasma chamber is provided with one or more material evaporation furnace (s) which make it possible to produce plasmas and thus ions of any elements. An electrically or magnetically launched electron beam produced in the extraction electrode is superimposed on the ion beam coming from the plasma chamber and passing through the plasma electrode and the extraction electrode, so that it an extraction channel is formed with space charge compensation for the ions. In general, prior art multi-charged ion beam production systems used in research or industry are equipped with different types of ion sources, including:

- ion sources with Electronic Cyclotronic Resonance, called ECR sources (Electron Cyclotron Resonance in English), in which the ions are created in a plasma confined by magnetic field and whose electrons are heated by radio frequency. These sources are capable in particular of producing intense currents of lightly to moderately charged ion beams. electron beam ion sources, called Electron Beam Ion Sources (EBIS), in which the ions are produced by collision with an electron beam of kinetic energy adjustable and compressed in a magnetic field. These sources are capable of producing in particular weak currents of very highly charged ions.

- ion discharge sources, in which the ions are created by collision with the electrons of an electronic discharge.

- laser ion sources in which the ions are created during the impact of a laser beam on a material. The disadvantage of these ion sources is that they do not make it possible to produce multicharged ions in sufficient quantity to allow rapid processes to be carried out when the ions are extracted from these sources directly at very low kinetic energy. Another disadvantage of these ion sources is that the ion beams which they produce do not have sufficient uniformity to allow the carrying out of surface treatments of the quality necessary for the surface treatments envisaged. A disadvantage of the ion beams created by such sources, when they are intense and when the samples are not very conductive, is that they generate undesirable positive charges on the surface of the treated sample, inducing sometimes undesirable modifications of the physical properties of the surface. Another disadvantage of these ion beams, when they are intense, is that they can generate during their transport under vacuum a large number of particles which it is impossible to decelerate correctly, which can cause defects under the surface of the sample to be treated. These problems mean that the existing machines making it possible to use ions of very low kinetic energy cannot carry out with sufficient quality the targeted surface treatment processes, that is to say the production of physical or chemical modifications, nanometric or sub-nanometric dimensions, on the surface of the treated samples.

The present invention aims to overcome these drawbacks by proposing to couple a system for producing ion beams to a first decelerating system making it possible to obtain ions of very low kinetic energy at the surface of the sample to be treated. , and to a second system for scanning the ion beam on the edge of the sample to be treated, making it possible to obtain a satisfactory uniformity of treatment for the targeted processes. In the semiconductor industry, for example, a standard surface treatment process has a uniformity generally between 95% and 99.99%, and this over the entire surface of the sample to be treated.

To do this, the subject of the invention is a machine for uniform treatment of sample surfaces by projection of multicharged ions of very low kinetic energy, comprising: - an ion beam production assembly, making it possible to produce under vacuum a beam of multicharged ions, sorted or not according to the ratio of their mass to their charge; electrostatic deceleration means allowing the deceleration of the ions when approaching the surface of the sample to be treated,

- scanning means allowing the surface of the sample to be treated to be scanned by the ion beam to obtain the desired uniformity of treatment, - mechanical holding means for samples making it possible to present the surface of the samples to be treated in front of the ion beam during the treatment,

- vacuum production means, such as vacuum pumps, mounted on vacuum chambers inside which is located the sample to be treated and the ion beam circulates.

According to particular embodiments: - the machine comprises a system making it possible to neutralize the positive charges appearing on said surface during the treatment. An objective of this system is to allow the ions not to be prevented from reaching the surface by undergoing an electrostatic repulsion caused by the presence of positive charges on said surface, these charges having been created by the ions having previously interacted with said surface , the consequence being that the energy distribution of the ions reaching the surface is as small as possible. Another objective of this system is to improve the quality of the treatment, in the case where the presence of positive charges on the surface of the sample is undesirable. This neutralization can be carried out by bombardment of the surface by electrons slow enough not to induce undesirable modifications of the surface. In one version of the machine, these electrons can be produced by one or more electron guns, placed near the surface of the sample to be treated, between the electrodes of the decelerator system and the surface of the sample, so as not to hinder the passage of ions from the beam. In a different version of the machine, the electrons can be produced by an electron gun with cylindrical symmetry, located near the surface of the sample to be treated, in the axis of which the ion beam passes. This electron gun can for example comprise a circular polarized filament. the machine includes a system making it possible to remove from the ion beam the ions which have changed charge by capturing one or more electrons by interaction with the residual gas present in the chambers empty. This system acts by subjecting a deflection of any angle not zero to the ion beam. This deflection being less intense when the charge of the ions is weaker, this makes it possible to remove the parasitic particles from the beam, whose charge is weaker, and to stop them with mechanical means such as metal plates. In one version of the machine, the beam-induced deflection is achieved by imposing on the ion beam an electric field created by the electrodes of an electrostatic deflection system. In another version of the machine, this deflection is achieved by imposing a magnetic field produced by a magnet or an electromagnet. In the case of an electric field, this may be produced by polarized and facing electrodes, in the middle of which the beam circulates. These electrodes can have, among other possibilities, flat, or semi-cylindrical, or hemispherical shapes, these types of electrodes respectively making it possible to obtain, after deflection, a beam of better optical quality.

According to a variant, the machine comprises a control system, using an image acquisition system, and making it possible to measure the spatial intensity distribution of the photons emitted from the interaction zone of the ion beam with the surface to be treat. The image acquisition system can include, for example, one or more CCD cameras (Charge Coupled Devices, in English). This system can also include optical filters, making it possible to observe only the photons which are emitted from the surface, at a wavelength or in a given wavelength range. This system makes it possible to follow the surface treatment process, insofar as it makes it possible to measure the thickness of the layers of materials which can cover the surface of the sample, as well as to know the nature of the material present on the surface. - the machine comprises a control system using an optical filter coupled to a photon counter to measure the evolution of the flux of photons emitted from the surface of the sample during the treatment, in a range of given wavelengths or at a given wavelength. This system can for example consist of optical lenses concentrating the photons, an optical fiber guiding the photons towards an optical monochromator, coupled to a photon detector allowing the counting. A filter can be added to this system to allow detection only of photons emitted from the surface at a given wavelength or in one or more given wavelength ranges.

- the machine includes a thermal modulation system associated with the sample maintenance system making it possible to adjust the temperature of the sample to be treated. In one version of the machine, this system consists of a heating resistor located near the sample to be treated. In another version of the machine, this system makes it possible to cool the sample, consisting of a hollow tube, such as a coil, also located near or in contact with the sample to be treated and in which a cooling fluid circulates, such as those known to those skilled in the art, such as for example liquid nitrogen. The temperature of the sample can be measured using systems known to those skilled in the art such as a thermocouple probe brought into contact with the sample, or a system for measuring the radiation emitted by the sample, for example in the infrared domain. - The machine has a mechanical system for changing the orientation of the surface of the sample to be treated, this in order to make the machine compatible with a sample transfer mode which uses a different orientation. In the machine, the surface of the sample to be treated can be oriented in all possible directions, because the orientation of the different sub-assemblies of the machine can be arbitrary. The orientation of the machine can be chosen according to different criteria. In one version of the machine, the surface of the sample to be treated is oriented downwards, so as to make it compatible with certain existing systems for transferring samples under vacuum which use this orientation, in particular those used in certain machines. deposit under ultra-vacuum by molecular beam epitaxy (MBE, or Molecular Beam Epitaxy, in English). Another objective of this downward orientation is that it makes it possible to prevent dust from depositing by gravity on the surface of the sample. In another version of the machine, the surface of the sample to be treated is oriented upwards so as to make it compatible with certain existing systems for transferring samples under vacuum which use this orientation, in particular those used in the silicon industry. Another objective of this upward orientation is that it allows the sample, in particular when it is large and of small thickness, to rest entirely by gravity on its support and thus to remain flat. Other sample transfer systems exist in which the surface of the samples is vertical. The machine can also process samples whose surface is vertical, by changing the orientation of the sub-assemblies that constitute it. An objective of the mechanical system provided for in the invention is that it makes it possible to adapt the machine to any sample transfer system, by changing the orientation of the surface of the sample in its transfer from the machine to the transfer, and vice versa.

- the machine includes a control unit composed of electronic modules and software, making it possible in particular to adjust the parameters of the machine and to carry out the treatment of the surface of the sample using only the parameters of the process that the user wishes to see carried out. Thus, users do not need to know the operation of the machine covered by the invention in detail. This control unit can also manage the operation of other parts of the machine, such as those relating to user safety and the operation of the gas pumping groups.

- The machine's ion production assembly includes an ion source of the ECR type. This ion source can be electrically isolated from the rest of the machine, so as to be brought to an electrical voltage chosen by the user. It is the value of this voltage, combined with the values of the voltages of other parts of the machine, which fixes the kinetic energy of the ions in the beam. This voltage can be variable, adjustable by the user, so as to vary the kinetic energy of the ions. Other ion sources generating multicharged ions can also be used on the machine. When these ion sources are brought to voltage, they are isolated from the rest of the machine by an enclosure, in order to protect the user against the risk of electric shock. Similarly, when these ion sources emit ionizing radiation during their operation, the protective enclosure can comprise a material absorbing these ionizing radiation in order to protect the user. - The ion production assembly of the machine comprises, connected to the ion source, an ion extraction system with several electrodes. This system makes it possible to extract the ions from the ion source at high speed, in order to optimize the ion current produced by the source and the optical qualities of the beam, then to remove them. decelerate so that they are transported in the beam line at lower speed.

the machine's ion production assembly includes magnetic means making it possible to sort the ions as a function of the ratio of their mass to their charge, and to select the ionic species with which the user wishes to carry out the surface treatment . In one version of the machine, these magnetic means include an electromagnet, the ion beam circulating in the vacuum chamber located in the air gap of this magnet, the magnetic field in the air gap being adjusted by adjusting the electric current which flows through the magnet coils. The vacuum chamber of the electromagnet can be electrically isolated therefrom in order to be polarized at a voltage which, combined with the voltages of the other parts of the machine, regulate the speed of the ions in their passage in the middle of the 1 ' electro magnet. The magnetic means can also include a permanent magnet, when the user wishes to use only one ionic species for the surface treatments he wishes to perform, or when the user wishes to choose the working ionic species by varying the speed of the ions in the air gap of the magnet, and not by varying the magnetic field as in the previous case. The advantage of a permanent magnet is that it reduces the cost and the size of the machine. When the magnetic means are absent, the surface treatment uses all the ions which are produced by the ion source. The advantage, in the latter case, is that the current available for surface treatments can be greater.

- the machine's ion beam production assembly comprises vacuum chambers provided with sets of slots, the latter being composed of mounted metal plates, making it possible to reduce the transverse dimensions of the ion beam, the enclosures and the sets of slots being electrically isolable from the rest of the machine, and polarizable, so as to allow the ion speed of the beam to be varied. One objective of these sets of slits is that they make it possible to improve the sorting of the ions and the optical qualities of the ion beam. The plates constituting the sets of slots can be fixed, or mounted on mechanical translation systems allowing the user of the machine targeted by the invention to adjust their dimensions. Travel systems can also be motorized. Diaphragms can be used in place of the slots.

- the machine's ion beam production assembly includes image acquisition systems arranged along the beam line, making it possible to observe the photons emitted when the ions of the beam strike the plates of which they are made slot games. One objective of this device is to allow the user to adjust the path of the ion beam. Another objective is to allow the uniformity of the ion beam to be measured at different locations along its path in the beam line.

- the ion beam deceleration system is composed of one or more polarizable electrodes with cylindrical symmetry, inside which the ion beam circulates. An objective of this device is to decelerate the ions of the beam to a very low kinetic energy, in such a way that their trajectory can remain as perpendicular as possible to the surface of the sample. In another version of the machine covered by the invention, there is a space between the electrode of the deceleration system which is located closest to the surface of the sample, and the surface of the sample, space in which are installed the means neutralization. An objective of this configuration is that the electrons circulate in an area where the electrostatic potential is little different from the electrostatic potential of the surface, which aims to minimize the acceleration undergone by these same electrons when they go towards the surface of the sample. In another version of the machine covered by the invention, the first electrode through which the ion beam passes when it enters the deceleration system is polarized so that the electrons which would be produced downstream of the system are repelled , and cannot penetrate inside the deceleration system or reach the surface of the sample. This first electrode has the effect of accelerating the ions entering the deceleration system, the ions then being decelerated by the electric field created by the difference in electrostatic potential existing between the electrode (s) of the deceleration system, and the surface of the 'sample. - In one version of the machine, the scanning system includes electromagnetic means which make it possible to deflect the path of the beam so that it can interact with any part of the surface. These electromagnetic means may consist of one or more electromagnets, surrounding a vacuum chamber in which the ion beam circulates, the magnetic field of the electromagnet having a component perpendicular to the primary direction of the ion beam. The path of the ion beam is deflected by this magnetic field, the intensity of the magnetic field being varied by varying the current flowing in the coils of the electromagnet, which allows the ion beam to sweep all or part of the sample surface. In another version of the machine, the scanning system is provided with electrostatic means, which also make it possible to deflect the path of the ion beam so as to make it interact with all or part of the surface. These electrostatic means may consist of one or more sets of metal electrodes of any shape, polarized and facing each other, in the middle of which the beam circulates. In another version of the machine, the scanning system is provided with mechanical, motorized means which make it possible to scroll the surface under the ion beam, so as to make the ion beam interact with all or part of the area. These mechanical means may include a motorized translation table, making it possible for the sample to make two movements in directions orthogonal to them and to the direction of the ion beam. Other versions of the machine are envisaged, in which the different means, electrostatic, magnetic and mechanical, are combined, allowing the ion beam to interact with all or part of the surface, which constitutes the first objective of this system. Another objective of this scanning system is to allow the user to choose the uniformity of the treatment of the surface of the sample, by choosing the modalities of the different scanning modes, in particular the scanning pitch. Another objective of this scanning system is to allow the user to choose the number of ions that will interact with the surface, by adjusting in particular the speed of the different scanning modes and the scanning pitch.

- the mechanical sample holding system is replaced by a holding system using electrostatic force, such as for example a system, known to those skilled in the art, in which the face of the electrostatic holding system, on which is placed the sample, is polarized, so as to induce a polarization on the rear face of the sample, which has the effect of inducing an attractive force between the face of the electrostatic holding system on which the sample is placed and the rear face of the sample. An objective of this system is that it makes it possible not to have recourse to mechanical means, certain parts of which would come onto the surface of the sample to be treated, while allowing the surface of the sample to be treated to be oriented in any direction .

- near the sample holding system and the surface of the sample to be treated, are added means for measuring the ion beam currents and electron beams. When the beam or sample to be processed is in a particular position, this device intercepts the ion and / or electron beam. These means may include charge collection devices, such as faraday cages, known to those skilled in the art, for example coupled to one or more ammeters.

- Near the sample holding system and the surface of the sample to be treated, are added means for measuring the uniformity of the ion and electron beams. When the beam or the sample to be treated is in a particular position, these means intercept the beam of ions and / or electrons. In a version of the machine, these means may include devices, such as plates of any material, allowing the emission of photons when they intercept ions or electrons, coupled to image acquisition systems, making it possible to obtain the intensity of the photons emitted at different points in the ion and / or electron beam. In another version of the machine, these means may include charge collection devices, such as networks of conductive wires which collect the current, coupled to one or more ammeters, so as to allow measurement at different points. the intensity of the ion beam and / or the electron beam. the sample holding system and the sample itself are electrically isolated from the rest of the machine to allow them to be polarized. One objective is to vary the kinetic energy of the ions and / or of the electrons when they interact with the surface, this kinetic energy being controlled mainly by the difference between the potentials of the area where the ions are created, in the source d 'ions, and the surface of the sample to be treated. the machine includes a system making it possible to inject one or more types of gas in a controlled manner inside the enclosure in which the sample to be treated is located. One objective is to allow this or these gases to participate in the chemical reactions which may take place on the surface of the sample to be treated. In order to control the partial pressures of the injected gas or gases, as well as their purity, a residual gas analyzer, known to a person skilled in the art, can be used as a means of complementary control of this injection system.

- The ion beam production system of the machine includes means for electrostatic or magnetic deflection of the ion beam, in order to optimize its trajectory.

- The ion beam production system of the machine includes retractable means for measuring the ion beam current, acting by intercepting the ion beam and collecting its charges.

- the ion and electron beams are pulsed in intensity, allowing the ions and electrons to reach the surface of the sample to be treated alternately, in order to prevent certain ions from the beam to be neutralized directly by the electrons in the electron capture neutralization system.

- photons a beam of photons is directed towards the surface of the sample to be treated, in order to activate the surface of the sample to be treated in order to promote the chemical or physical reaction caused by the treatment, the length of wave of these photons being chosen according to the chemical or physical reaction desired by the user. Other features and benefits of

1 the invention will appear in the light of the detailed description which follows, relating to preferred embodiments, with reference to the appended figures representing respectively: - Figure 1 shows the block diagram of the machine in a straight line configuration.

- Figure 2, an improved variant of the previous embodiment in which the ion beam production assembly comprises an electromagnet which curves the path of the beam, the machine being provided with an elimination system which curves also the beam path, giving the machine a U-shaped configuration; Figure 3, a variant of the previous embodiment in which the machine has a U-shaped configuration and uses process control means using an image acquisition system and a photon counting system; Figure 4, a variant of the previous embodiment in which the machine has an S configuration.

Figure 1 shows an overview of an embodiment of a machine according to the invention. It includes an ion production system 1, capable of producing multi-charged ion beams 2. The ion beam circulates inside a system of electrostatic deceleration 3, which reduces the kinetic energy of the ions by using the electric field created by the electrostatic deceleration system. The beam then enters the vacuum enclosure 4 where the process for processing the sample 5 is carried out. The sample is mounted on a mechanical support 6 allowing it to be maintained. The ion beam 2 is scanned on the surface of the sample 5 using scanning means 7. A set of pumping means 8 makes it possible to maintain the various chambers which make up the machine under vacuum.

These examples describe variants of machines intended for studying and developing methods for treating surfaces with slow, multi-charged ions. The preferred embodiment for the research equipment corresponds to FIG. 2 illustrating a machine according to a U-shaped configuration. In this example embodiment of the machine, the ion beam production assembly includes an ion source 9 of ECR type, in which multicharged ions are created. Such an ion source produces several milliamps of charge ions and of varied nature, depending on the gases injected into the enclosure of the source. The states of charge can range, for argon, up to the maximum charge, Arl8 +. The body of the ion source is electrically isolated from the rest of the machine, and is brought to a voltage which can be varied by the user between -100 V and +100 V, in order to cancel the effect of the potential of the plasma from the ECR source.

A three-electrode extractor 10 makes it possible to extract the ions produced in the source at high speed, and to focus the beam to allow it to keep good optical characteristics after its deceleration at the exit of the extractor. The first electrode is polarized at -35 kV, the second electrode at -25 kV, the third electrode at -35 kV. At the exit of the extractor, the ion beam enters a vacuum enclosure polarized at -15 kV, in which are placed 2 movable plates 12 defining a vertical slit relative to the plane of the figure, making it possible to reduce the width of the beam at 10 mm. A CCD camera 13 makes it possible to obtain a beam intensity profile when the slit is closed, from the photons emitted by the ions when they strike the plates 12.

The ion beam then enters an enclosure 14 polarized at -15 kV, placed in the air gap of an electromagnet. The magnetic field B perpendicular to the plane of the beam, produced by the electromagnet curves the trajectories of the ions of the beam. The radius of curvature R of the trajectory of an ion of charge q and of mass m, having been accelerated by a difference of potential DU and subjected to a magnetic field B is given by the formula: R ² = 2 * DU * m / (q * B ² )

Depending on the magnetic field chosen by the user, the ions, whose mass-to-charge ratio is different, will have a trajectory with a different radius of curvature, which makes it possible to select the ion with which the user of the machine wishes carry out the process. In the radius of curvature of the magnet is 250 mm, and the magnetic field of 0.135 Tesla allows to select the Arll + ions among the other ions of the beam.

The ion beam then enters a vacuum chamber 15 polarized at -15 kV in which sets of plates 16 polarized at voltages varying between -14 kV and -16 kV make it possible to modify its trajectory. In this enclosure, sets of movable plates 12 define horizontal and vertical slots with respect to the plane of the figure, making it possible to modify the shape of the envelope of the bundle. A mobile and retractable faraday cage 17 makes it possible to intercept the ion beam in order to measure its intensity by measuring using of an ammeter the current of charges collected. A CCD camera 13 makes it possible to measure the characteristics of the beam when it is intercepted by the plates defining the slits. The ion beam then enters a vacuum enclosure 18 polarized at -15 kV in which an electrostatic deflector 19 is installed, which constitutes a first part of the system for eliminating parasitic particles from the machine. This deflector is composed of two electrodes facing each other, whose surface has the shape of a part of a sphere and in the middle of which the beam circulates. The potential difference between the two electrodes is 4200 Volts, to allow the Ar ¹¹⁺ ions to exit this enclosure. The ions having lost one or more charges by collision with the molecules of the residual gas are less deflected and their trajectory does not have the same axis as that of the Ar ¹¹⁺ ions.

The ion beam then enters a vacuum enclosure 20 polarized at -15 kV in which sets of plates 12 define horizontal and vertical slots relative to the plane of the figure, which constitute the second part of the elimination system. machine particles. These plates make it possible to intercept the ions which have changed charge by collision with the residual gas of the vacuum chambers, and whose trajectory at the outlet of the electrostatic deflector 19 is different from that of the Arll + ions. This vacuum enclosure is provided with a CCD camera 13 which makes it possible to measure the characteristics of the beam when it is intercepted by the plates defining the slots.

The beam then enters a two-part vacuum enclosure (21, 22) in which the cylindrical electrodes 23 of the electrostatic deceleration system are placed. The first part of the vacuum chamber 21 is polarized at -15 kV. It is isolated by an insulator 24 from the second part of the vacuum enclosure 22, which is at the potential of the electrical ground of the machine (0V). The beam passes through the middle of a first electrode 25 polarized at -16 kV, which prevents the electrons which would be produced by collision of the ions of the beam with the objects present in the vacuum chambers from entering the decelerator system. This setting allows you to get rid of all the electrons created with an initial kinetic energy of 1 kV. The following electrodes 23 are polarized at different voltages, gradually going from -15 kV to -30 V for the last electrode 26, the closest to the sample to be treated 5.

The ion beam then enters a space in which the potential difference with the surface of the sample to be treated does not exceed 30 V. An electron gun 27 produces slow electrons 28 which are directed towards the area of impact of the ion beam on the surface of the sample to be treated, the energy of these electrons not exceeding 30 eV when they collide with the surface of the sample. The ions have a kinetic energy of a few eV / q, where q represents their charge, when they hit the surface of the sample. This kinetic energy, expressed in this unit, is equal to the potential difference between the place where the ions are created and the surface of the sample, which is at the potential of the mass of the machine (0 V) in this example of achievement.

Sample 5 is held facing the _. ion beam by a mechanical system 29 on a mobile and motorized stage 30, which allows the ion and electron beams to scan the surface of the sample. The first scan is carried out in the plane of the figure, perpendicular to the ion beam at a displacement speed of 113 mm / s. The direction of the second movement is in the plane perpendicular to the figure and to the ion beam. It is a step by step movement, the displacement being carried out at the end of the stroke of the first scan, each step displacing the sample by 0.5 mm. The intensity of the Arll + ion beam interacting with the surface of the sample is 10 micro-amps. The sample in the example is a silicon wafer, in the form of a 100 mm diameter disc. An ion dose of 10 ^Λ 13 ions / cm ² is thus deposited over the entire surface of the sample with uniformity better than 99% and in 270 seconds.

A gas injection system 31 makes it possible to inject oxygen inside the enclosure 22 during the treatment of the surface of the sample, at a pressure of 10 ^Λ -7 Torr, so that the oxygen can react with the surface of the sample chemically activated by the ions.

FIG. 3 illustrates another version of the machine in which the electromagnet 32 deflects the ions at an angle other than 90 °. In this version of the machine, the elimination system 33 includes planar electrodes 34 for deflecting the ion beam with an angle greater than 90 °. The scanning system comprises electromagnets in Helmholtz 35 coils producing an alternating magnetic field B. The neutralization system consists of a cylindrical filament 36 in the middle of which the ion beam circulates. A CCD camera 37 makes it possible to observe the photons emitted during the interaction of the ions with the surface of the sample, in order to measure the uniformity of the treatment, and its state of progress. A photon counting system 38 makes it possible to measure the intensity of the photons emitted in the wavelength range which is not absorbed by the optical filter 39. The sample to be treated 5 is held facing the ion beam by the action of an electrostatic sample holding system 40. This sample is cooled to contact of a coil 41 in which a coolant circulates. A mechanical system makes it possible to transfer the sample from its position on its support, to position 42 then 43, in which the orientation of the surface of the sample is different.

FIG. 4 illustrates another version of the machine, in which the elimination system 44 uses the magnetic field produced by a magnet. In this version, scanning uses the alternating magnetic field produced by two Helmholtz 45 coils to move the beam in a plane perpendicular to the plane of the figure and to the ion beam, then the alternating electric field produced by two polarized metal plates 46 to scan the beam quickly and at small amplitudes in the plane of the figure and perpendicular to the ion beam, then a motorized mechanical table 47 making it possible to scan the surface of the sample under the ion beam in a direction parallel to the plane of the figure and perpendicular to the ion beam. A metal plate 48 located near the sample 5 makes it possible to measure the uniformity of the ion beam and of the electron beam, when it is placed in the position to intercept them, using a CCD camera 49. A heating resistor 50 located under the sample makes it possible to raise its temperature, according to the needs of the process. The sample is electrically isolated from the rest of the machine by two isolators 51, and is polarized by means of a voltage generator 52. The neutralization system uses, in this version of the machine, two electron guns 27, producing electrons of low kinetic energy 28 towards the surface of the sample to be treated. A system 53 using an ammeter makes it possible to measure the current of the ion and electron beams incident on the sample to be treated. A production system 54 of photons allows to project photons of given wavelength on the surface of the sample to be treated.

The machine according to the invention makes it possible to use the ultra slow multicharged ions, of only a few electron volts per charge, to modify the surface of materials on the atomic scale, in particular, but not exclusively, the surface of semiconductor materials. The processes permitted by the machine targeted by the invention are the etching of materials, the cleaning of surfaces, the manufacture of nanostructures, the production of physical or chemical, nanometric, surface modifications, the chemical modification of surfaces on an atomic scale. , and the manufacture of ultra-thin layers.

Claims

1. Machine for uniform treatment of sample surfaces by projection of multicharged ions of very low kinetic energy, characterized in that it comprises

- an ion beam production assembly electrically isolable from the rest of the machine and polarizable, - electrostatic deceleration means allowing the deceleration of the ions when approaching the surface of the sample to be treated,

- scanning means allowing the surface of the sample to be treated to be scanned by the ion beam to obtain the desired uniformity of treatment,

- mechanical means for holding samples making it possible to present the surface of the samples to be treated facing the ion beam during the treatment;

- vacuum production means mounted on vacuum chambers inside which the sample to be treated is located and the ion beam circulates.

2. Uniform surface treatment machine according to claim 1, characterized in that it comprises means for neutralizing the positive charges brought to the surface by the ions.

3. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it comprises means for removing from the ion beam ions which have changed charge during their transport to the surface of the sample to be processed.

4. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it comprises a process control system, using an image acquisition system, and making it possible to measure the spatial distribution of intensity of photons emitted from the interaction zone of the ion beam with the surface to be treated.

5. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it includes a process control system, using an optical filter coupled to a photon counter to measure the evolution of the photon flux. emitted from the surface of the sample during processing, in a given wavelength range or at a given wavelength.

6. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it is planned to add to the mechanical system for maintaining samples, a thermal modulation system making it possible to adjust the temperature of the sample to be processed.

7. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it comprises a mechanical system making it possible to change the orientation of the surface of the sample to be treated in order to make the machine compatible with a sample transfer mode that uses a different orientation.

8. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it comprises a control assembly composed of electronic modules and software, making it possible in particular to adjust the parameters of the machine and to carry out the treatment of the surface of the sample using only the parameters of the process that the user wishes to see carried out.

9. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the ion beam production assembly comprises an ion source with Electronic Cyclotronic Resonance electrically isolable from the rest of the machine and polarizable .

10. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the ion beam production assembly comprises a multi-electrode electrostatic extractor, connected via an isolator to the ion source, to optimize the quality and intensity of the ion beam, electrically isolable from the rest of the machine and polarizable.

11. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the ion beam production assembly comprises a system making it possible to sort the ions of the beam according to their mass ratio by their load, consisting of a vacuum enclosure electrically isolable from the rest of the machine, polarizable and provided with magnetic means.

12. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the ion beam production assembly comprises vacuum chambers provided with sets of slots, the latter being composed of metal plates, making it possible to reduce the transverse dimensions of the ion beam, the enclosures and the sets of slots being electrically isolable from the rest of the machine, and polarizable.

13. Uniform surface treatment machine according to the preceding claim, characterized in that the ion beam production assembly comprises image acquisition means, making it possible to observe the photons emitted when the ions of the beam strike the plates of which the sets of slots are made.

14. Uniform surface treatment machine according to any one of claims 3 to 13, characterized in that the elimination system comprises electrodes of the planar, hemispherical or semi-cylindrical, polarizable type, between which the beam circulates.

15. Uniform surface treatment machine according to any one of claims 3 to 14, characterized in that the elimination system is provided with magnetic means producing a magnetic field inside the vacuum chamber in which the ion beam.

16. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the deceleration system is composed of one or more polarizable electrodes with cylindrical symmetry, inside which the ion beam circulates.

17. Uniform surface treatment machine according to the preceding claim, characterized in that the position and the shape of the electrodes of the deceleration system provide space for the neutralization system.

18. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the deceleration system comprises a polarized electrode so as to repel the secondary electrons produced downstream from the deceleration system.

19. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the scanning system comprises electromagnetic means.

20. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the scanning system comprises electrostatic means.

21. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the scanning system comprises motorized mechanical means.

22. Uniform surface treatment machine according to any one of claims 1 to 18, characterized in that the scanning system is mechanical and motorized, allowing the surface of the sample to be treated to pass in front of the ion beam. , in two directions perpendicular to the ion beam.

23. Uniform surface treatment machine according to any one of claims 2 to 22, characterized in that the neutralization system uses one or more sources of electrons arranged around the sample to be treated and in front of its surface.

24. Uniform surface treatment machine according to any one of claims 2 to 22, characterized in that the neutralization system uses an electron source with cylindrical symmetry, placed in front of the surface of the sample to be treated, at l inside which the ion beam circulates.

25. A uniform surface treatment machine according to any one of the preceding claims, characterized in that the mechanical system for holding samples is replaced by a system for using electrostatic force.

26. Uniform surface treatment machine according to any one of claims 6 to 25, characterized in that the thermal modulation system comprises a heating resistor making it possible to raise the temperature of the sample.

27. Uniform surface treatment machine according to any one of claims 6 to 26, characterized in that the thermal modulation system comprises a coil in which a fluid circulates allowing the temperature of the sample to be lowered.

28. Uniform surface treatment machine according to any one of the preceding claims, characterized in that are added near the system of maintenance of samples, means for measuring the current of ion and electron beams.

29. Uniform surface treatment machine according to any one of the preceding claims, characterized in that are added, close to the sample holding system, a system composed of a plate of any material from which photons can be emitted when ions and electrons strike it, to allow the uniformity of ion and electron beams to be measured using an image acquisition system.

30. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the sample holding system and the sample are electrically isolable from the rest of the machine, and polarizable.

31. Uniform surface treatment machine according to any one of the preceding claims, characterized in that its orientation is such that the surface of the sample to be treated is oriented downwards, in order to prevent dust from settling down. by gravity, and in order to make it compatible with a sample transfer mode which uses this orientation.

32. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the orientation of the sub-assemblies which constitute it is such that the surface of the sample to be treated is oriented upwards, in order to make it compatible with a particular sample transfer mode which uses this orientation.

33. Uniform surface treatment machine according to any one of the preceding claims, characterized in that it comprises means for the controlled injection of gas into the vacuum enclosure in which the sample to be treated is located.

34. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the ion beam production system includes means for electrostatic or magnetic deflection of the ion beam, with the aim of optimizing its trajectory.

35. Uniform surface treatment machine according to any one of the preceding claims, characterized in that the ion beam production system comprises retractable means for measuring the ion beam current.

36. Uniform surface treatment machine according to any one of claims 23 to 35, characterized in that the electron beam and the ion beam are pulsed, the ions and the electrons arriving alternately on the surface.