WO2020178068A1

WO2020178068A1 - Charge neutralizing apparatus

Info

Publication number: WO2020178068A1
Application number: PCT/EP2020/054842
Authority: WO
Inventors: José FERNANDES; Benjamine NAVET; Amory JACQUES
Original assignee: Agc Glass Europe; AGC Inc.; Agc Flat Glass North America, Inc.; Agc Vidros Do Brasil Ltda
Priority date: 2019-03-04
Filing date: 2020-02-25
Publication date: 2020-09-10
Also published as: WO2020178068A9; EP3935658A1; TW202103201A

Abstract

This invention relates to a charge neutralizing apparatus for a processing chamber of an ion implantation device.

Description

CHARGE NEUTRALIZING APPARATUS

FIELD OF THE INVENTION

[0001] This invention relates to a charge neutralizing apparatus for a processing chamber of an ion implantation device.

BACKGROUND

[0002] Ion implantation is a process of generating an ion beam, focusing that beam, and directing it toward a substrate to implant ions into said substrate. As fast moving particles in an ion implanter collide with the residual gas and the walls of the implanter, they generate low energy ions and free electrons. A positively charged ion beam traps these electrons and simultaneously rejects the positive ions. The positive ion beam has an inherent potential that is typically distributed non-uniformly across the beam cross-section.

[0003] When the ion beam strikes the substrate surface, low energy electrons are emitted and the substrate tends to become positively charged. Generally, the net amount of positive charge delivered to the substrate is directly proportional to the beam current. In the case of a high current beam, the positive charge on the substrate tends to become quite high, leading to surface voltage up to tens of volt and even kV depending on the impinging beam energy and the ability to discharge.

[0004] When the substrate surface is well grounded to the vacuum enclosure and free of dielectric layers obstruction, the charge mainly flows to ground. However, in some instances, the ability to discharge the electrostatic charges generated at the surface of the substrates is low as the charges cannot flow to the ground and charges may build up at the surface of the substrate.

[0005] Such a charge build-up creates problems. The electrostatic charge interacts with the beam and causes it to lose density, which is a disadvantage because variations in ion beam density results in a non-uniform implantation process and/or in a less efficient process. The surface of the substrate, while becoming positively charged, tends to repel the ions coming from the ion beam, such that the ion implantation is not homogeneously performed across the surface, and that ions initially implanted provoke a screen effect to the implantation of further ions. Pinholes may appear and/or ion implantation may be impaired.

[0006] In some instances, the beam diameter tends to expand upon coming closer to the substrate surface, as the ions all having the same electrical charge tend to repel one another. In those instances, the beam also loses in intensity and the ion implantation has a reduced homogeneity.

[0007] Also, electrostatic charge may erratically discharge and create electric arc discharges which negatively impact the ion implantation process, by either imprinting shadows or inhomogeneities at the surface of the substrates, or by damaging the surface of the substrates. If the substrate is a powder, this uncontrolled discharge can even melt or completely destroy the material. On top of that, the charged powder particles will also repel each other and this can lead to an undesired dispersion in the treatment chamber.

[0008] The erratic and unmanageable surface charge build-up during ion implantation process are thus preferably avoided.

[0009] Several solutions exist to such problems. One of these is to introduce a neutralizing charge, e.g electrons, to the surface of the substrate and/or to the beam before it contacts the substrate. One implementation of this method is to use a so-called electron shower to supply the neutralizing charge, or an electron flooding using negatively charged electrons. Another is to use plasma-generating sources to supply low energy electrons and positive ions. Both of these methods typically apply the neutralizing charge near where the beam contacts the substrate.

[0010] Electron showers, however, typically supply a large number of high energy electrons which themselves contribute to charging of the substrate surface, if not well compensated by the impinging positively charged beam.

[0011] Plasma sources, which typically supply a higher proportion of low energy electrons and ions than do electron showers, not only better neutralize the beam and the surface charge but also contribute less to negative charge buildup on the substrate. When using a plasma source, however, a large plasma density is required to neutralize the beam. The required density can increase the pressure in the vacuum enclosure and degrade the efficiency of the implantation process. Moreover, a uniform and dense plasma is necessary.

[0012] JP4998972B2 relates to an ion implantation apparatus and an ion implantation method for implanting ions extracted from plasma formed in a vacuum chamber through a grid electrode into a substrate to be processed. The grid is provided with alternative current.

[0013] These solutions require the addition of electrons and ions in a vacuum atmosphere, which may increase complexity of the processing conditions.

[0014] There is still a need for a charge neutralizing apparatus which is easy to implement and does not require complex process conditions, and which at the same time will allow for effective control of charge build-up at the surface of substrates during an ion implantation process, such that the surface treatment is homogeneous.

SUMMARY

[0015] The present invention provides for a charge neutralizing apparatus for a processing chamber of an ion implantation device, and for an ion implantation device comprising said charge neutralizing apparatus.

[0016] Also provided is the process of ion implantation using the present ion implantation device.

[0017] Last provided is the use of a charge neutralizing for a processing chamber of an ion implantation device, to reduce charge build-up at the surface of a substrate subjected to ion implantation.

[0018] The charge neutralizing apparatus allows for positive charges built up during an ion implantation process to be neutralized, such that the ion implantation can occur without unexpected or uncontrolled discharges or inhomogeneities to be created at the surface of the substrates, and is easy to implement.

FIGURES

[0019] Figure 1 : charge neutralizing apparatuses of different design (a to f), comprising at least one frame 101 , grounded via chord 102, with optional wires 103.

[0020] Figure 2: an ion implantation device, comprising a processing chamber equipped with a charge neutralizing apparatus, enclosing the path of the ion beam.

DETAILED DESCRIPTION

[0021] The present charge neutralizing apparatus is located within a processing chamber of an ion implantation device, optionally at least partially in the path of an ion beam emitted by an ion source, located in an ion source chamber, of the ion implantation device. The ion source chamber and the processing chamber of the ion implantation device are connected through a channel, which allows passage of the ion beam.

[0022] The processing chamber typically comprises a top wall, a bottom wall and at least 4 side walls, wherein at least one side wall is providing with an entry or exit port.

[0023] The charge neutralizing apparatus is typically fixed to at least one wall of the processing chamber, such that it either encloses the ion beam or such that it is encompassed within the ion beam, said ion beam being emitted by the ion source, in an ion source chamber, different from the processing chamber. The at least one wall may be the top wall of the processing chamber, or a sidewall of the processing chamber. In some instances the charge neutralizing apparatus is fixed to two walls of the processing chamber, where the two walls may be contiguous walls, or they may be opposite walls or any other configuration, suitable in the considered processing chamber.

[0024] The processing chamber of the ion implantation device may comprise a substrate holder, which may be a moveable substrate holder or a fixed substrate holder. In some instances, the charge neutralizing apparatus may be fixed to the substrate holder. It is however less typical that the charge neutralizing apparatus is fixed to a moveable substrate holder, such that the moveable substrate holder housed in the processing chamber may move independently from the charge neutralizing apparatus.

[0025] The charge neutralizing apparatus comprises at least one frame, said frame being conductive and grounded. The frame is hollow in its center to allow passage of the ion beam.

[0026] The charge neutralizing apparatus is not considered an electrode within the scope of the present invention. The charge neutralizing apparatus is not generating any beam or plasma, and merely allows passage of the ion beam exiting the ion source chamber.

[0027] The at least one frame may have any shape, defining a hollow surface.

Rectangular, square, circular or substantially circular frames may be more convenient (Figure 1 , a to f). The at least one frame may have any structure, having a diameter or width. A circular shape of the frame may allow for improved charge neutralization when the ion beam is of circular shape. A rectangular shape may allow for improved charge neutralization when the ion beam is of rectangular shape, either directly produced by a linear ion source, or by shaping or even by coupling several contiguous ion beams. A rectangular shape of the frame and a circular open area for the ion beam path may also be suitable, according to Figure 1 e. A rectangular shape of the frame and a rectangular open area for the ion beam may also be suitable, according to Figure 1f. In some instances, when using a moveable substrate holder such as a vibrating pan for powders, the charge neutralizing apparatus may be a hole in the pan cover.

[0028] The surface of the frame may be considered relative to the diameter or surface of the ion beam at the surface of the substrate holder, when considering a circular beam. The ion beam will be provided to the processing chamber through the channel, from an ion source. The ion beam will typically have a diameter defined by the size of the ion implantation device. In the present invention, the diameter of the ion beam ranges of from 0.001 to 1 m, alternatively of from 0.01 to 0.5 m, alternatively 0.01 to 0.2 m, providing for a surface ranging of from of 8 x 10⁷ to 0.8 m², alternatively of from 8 x 10 ⁵ to 0.2 m², alternatively of from 8 x 10 ⁵ to 3 x 10² m². Linear sources of up to 4 m length may provide for an ion beam of rectangular shape, having a width of from 10 to 50 cm.

[0029] In those circumstances, the surface of the frame may range of from of 5 x 10⁷ to 1 m², alternatively of from 5 x 10 ⁵ to 0.3 m², alternatively of from 5 x 10 ⁵ to 5 x 10² m². In some instances, the frame has a surface > the surface of the beam, that is, the wire is surrounding the beam; or the frame may have a surface < or equal to that of the surface of the beam, that is, the frame is encompassed within the ion beam.

[0030] The structure of the frame may have a diameter of from 0.001 to 5 cm, alternatively of 0.001 to 2 cm diameter. That is, regardless of the defined surface, the frame structure may be a wire, a plain or hollow tube of circular or square cross-section, or a plate with a hole, typically connected to the ground. When the tube is a hollow tube, it may be equipped with a cooling system.

[0031] In some instances, the charge neutralizing apparatus comprises at least one frame and at least one conductive wire. In some instances, the charge neutralizing apparatus comprises at least one frame and two or more wires, up to 150 wires. In instances where more wires and up to 150 wires are provided, the surface may account for a maximum of 20 wires/cm². In those instances, at least one of the frame or wire(s) is conductive and grounded. In most instances, the frame is conductive and grounded, and the at least one or more wire(s) are conductive, connected to the frame.

[0032] The at least one wire may have a diameter of 0.001 cm to 0.5 cm, 0.001 to 0.1 cm.

[0033] When only one wire is used in conjunction with the frame, the wire may be in any direction compared to displacement direction of the substrate holder housed within the processing chamber. Considering the substrate holder may be displaced in a X and/or a Y direction relative to the entry port of the processing chamber, the wire may thus be organized in a X or a Y axis or in any angle (of form 10 to 90°) from the direction of displacement of the substrate holder. In some instances, the Y direction for the single wire is more convenient for the organization of the substrate(s) on the substrate holder.

[0034] When there are more than one wire, that is, when there are two or more wires on the frame, these may be organized in a parallel or non-parallel design (Figure 1 , b to d). When the two or more wires are organized in a parallel design with regard to one another (Figure 1 , b), they may be parallel to the direction of displacement of the substrate holder within the processing chamber in the X and/or Y direction. In some instances, the two or more wires may be perpendicular to the direction of displacement of the substrate holder within the processing chamber.

[0035] In some instances, when the two or more wires are organized in a non-parallel design, they may intersect at any point of their geometry (Figure 1 , c and d), and form an angle of 10 to 90° from the axis of the direction of displacement of the substrate holder within the processing chamber. At least one wire of the two or more wires may be aligned in a parallel design to the direction of displacement of the substrate holder within the processing chamber.

[0036] When two or more wires are used, these may be organized in a grid format, having more or less wires forming said grid (Figure 1 , c).

[0037] A parallel or perpendicular design of the two or more wires allows for a better management of speed and alignment, avoiding for a masking effect of the wire and frame upon the ion implantation.

[0038] In some instances, the presence of at least one wire on the frame of the charge neutralizing apparatus may allow for improved reproducibility of the ion implantation.

[0039] The conductive frame or wire(s) will attract the positive charges accumulated by the substrate upon ion implantation and dissipate them without electric arc discharge.

[0040] The material composing the charge neutralizing apparatus will be advantageously chosen or treated either fully or partially to reduce or avoid sputtering during exposure to the ion beam. There is thus no major limit to the options of the composition of the charge neutralizing apparatus, as long as the ion beam is not polluted and that the implanted substrates are not contaminated. The absence of contamination will be observed if the implanted species, as measured on the substrate, contain < 10% of ions originating from the charge neutralizing apparatus, alternatively < 5%, alternatively < 1 %, alternatively < 0.1 %, alternatively < 0.01 %.

[0041] The at least one frame or wire of the charge neutralizing apparatus may independently comprise a conductive material, optionally provided with a sputtering reduction coating.

[0042] The conductive material includes graphite, or metals comprising at least one of the following metals Al, Cu, Zn, Mn, Ti, Ni, Cr, Fe, Mo, W, Au, Ag or mixtures or alloys thereof.

[0043] The sputtering reduction coating may be conductive, having a low resistivity, in particular less than 5 x 10⁷ ohm cm. Examples of sputtering reduction coatings include boron carbide, silicon oxide or carbide or nitride, aluminium carbide, zirconium oxide or carbide, titanium oxide or carbide, molybdenum oxide or carbide, niobium oxide or carbide, yttrium oxide or carbide, magnesium oxide, tin oxide, ceramic, tungsten carbide, tungsten oxide, hafnium oxide, tantalum oxide, chromium carbide or combinations of these materials.

[0044] The at least one frame or wire of the charge neutralizing apparatus may independently comprise at least one material selected from graphite, stainless steel, boron carbide, silicon oxide or carbide or nitride, aluminium carbide, zirconium oxide or carbide, titanium oxide or carbide, molybdenum oxide or carbide, niobium oxide or carbide, yttrium oxide or carbide, magnesium oxide, tin oxide, ceramic, tungsten carbide, tungsten oxide, hafnium oxide, tantalum oxide, chromium carbide, tungsten, gold coated tungsten or combinations of these materials.

[0045] Alternatively, the at least one frame or wire of the charge neutralizing apparatus may independently comprise at least one material selected from stainless steel, zirconium oxide or carbide, titanium oxide or carbide, tungsten carbide, tungsten oxide, tungsten, gold coated tungsten or combinations thereof.

[0046] In certain embodiments, the frame or at least one wire may optionally be polarized, to further improve the charge neutralizing effectiveness of the charge neutralizing apparatus. Typically, a negative polarization may prove more convenient, to attract the positive charge built up at the surface of the substrate. The frame or wire(s) are preferably not polarized. In most instances, the frame or wire(s) are not polarized.

[0047] The present ion implantation device comprises

a. a processing chamber housing at least one substrate having a surface, b. an ion source emitting an ion beam directed towards the surface of said substrate

wherein the processing chamber is equipped with a charge neutralizing apparatus located between the surface of the substrate and the ion source.

[0048] Figure 1 discloses an ion implantation device comprising an ion source (101 ), connected, via a channel (102), to a processing chamber (103), housing a substrate (104) on a substrate holder (105). The ion source emits an ion beam (106) towards said substrate (104), through a charge neutralizing apparatus (107).

[0049] The processing chamber housing the substrate may be equipped with various elements, such as substrate holder (planar or non-planar), substrate moving system (linear or rotating), precision positioning device, Faraday cup, vacuum pump, opening enclosure, possibly connecting enclosures, possibly cooling circuits, etc. Any suitable processing chamber maybe used in conjunction with the presently claimed charge neutralizing apparatus. The processing chamber may typically be provided with a fixed or moveable substrate holder.

[0050] The ion source may be an Electron Cyclotron Resonance ion source, known as an ECR source. This ECR source delivers an initial beam of ions, with parameters for ion species relative to the pressure and nature of the gas feeding the enclosure, as well as the excitation current and voltage. The chamber of the source contains a hot plasma composed of a mixture of magnetically confined ions and electrons. The ion beam is emitted and guided in the direction of the processing chamber, through the channel.

[0051] A typical ion implantation source may simultaneously produce either single charge or specific multicharge ions. Multicharge ions are ions carrying more than one positive charge, single charge ions carry one single positive charge. A typical ECR ion source may deliver a mixture of single- and multicharge ions, which makes it possible to implant multi energy ions simultaneously at the same extraction voltage. In this way, a more distributed implantation profile can be obtained simultaneously throughout the treated thickness of the substrate.

[0052] The charge neutralizing apparatus is typically aligned perpendicular to the trajectory of the ion beam, and may thus encompass at least part of the ion beam surface, or encompass the entire ion beam surface, or be partially encompassed with the ion beam surface or be fully encompassed with the ion beam surface. In most instances, the charge neutralizing apparatus encompasses the entire ion beam surface. The charge neutralizing apparatus is not designed to deviate the trajectory of the ion beam.

[0053] The distance between the charge neutralizing apparatus and the substrate may be > 0.5 mm, alternatively > 1 mm, alternatively > 2 mm, alternatively > 5 mm. There should be no physical contact between the charge neutralizing apparatus and the substrate. The distance between the charge neutralizing apparatus and the substrate is preferably such that there is no physical contact between the charge neutralizing apparatus and the substrate.

[0054] The distance should take into account the potentially uneven surface of the substrate. That is, in case of an uneven surface, the minimum distance to ensure there is no physical contact between the charge neutralizing apparatus and the substrate, is > 0.5 mm, alternatively > 1 mm, alternatively > 2 mm, alternatively > 5 mm, as from the highest detail of the surface of said uneven substrate. [0055] The distance between the charge neutralizing apparatus and the substrate may be < 80 cm, alternatively < 20 cm, alternatively < 10 cm, alternatively < 5 cm. The distance should allow for charge neutralization from the surface of the substrate.

[0056] In some instances, the charge neutralizing apparatus is located in the vicinity of the entry of the ion beam into the processing chamber. In some instances, the charge neutralizing apparatus is located in the channel connecting the ion source and the processing chamber. In those instances, the distance between the charge neutralizing apparatus and the substrate is of no direct relevance, since the charge neutralization occurs in the ion beam directly, and no longer at the surface of the substrate.

[0057] The ion implantation device may further comprise one or more of controlling apparatuses. These are used to provide control and data information about the ion source, the ion beam, the ion distribution, the location and position of the substrate in the processing chamber, the first pressure in the ion source, the second pressure in the processing chamber and so on. Such controlling apparatuses may include a mass spectrometer suitable for filtering the ions according to their charge and mass; a profiler, whose purpose is to analyse the intensity of the beam in a perpendicular intersecting plane; a current transformer, which continuously measures the intensity of the ion beam without intercepting it; a shutter, which can be a Faraday cage, the purpose of which is to interrupt the trajectory of the ions at certain times, for example when the substrate is being displaced without being treated; a numerical control machine, for positioning and moving the substrate in the processing chamber.

[0058] The ion implantation device is intended to provide for ion implantation of a substrate.

[0059] The present invention also provides for a process for ion implantation comprising the steps of

a. Providing for at least one substrate having a surface,

b. Providing for an ion implantation device,

c. Submitting the surface of the substrate to ion implantation within the ion implantation device,

wherein the ion implantation device comprises at least one charge neutralizing apparatus according to the above.

[0060] Examples of substrates include those substrates comprising glass; sapphire; alumina; polymers; elastomers; resins; metals, metal oxides or metal alloys; composite materials; ceramics; stones; or powders or mixtures of these or other material. The substrate may be conductive, or non-conductive.

[0061] Examples of polymers include polymethylmethacrylate, polyurethane, plastic, polyethylene, polypropylene, and powders, mixtures or composites thereof.

[0062] Examples of glass include clear glass or colored glass, obtained by float or other manufacturing methods. The glass may be soda lime glass, aluminosilicate glass, borosilicate glass, boroaluminosilicate glass, or any other glass composition. The glass may be in the shape of flat glass or curved glass, or the glass may be a container shape, such as bottle, drinking glass, or else.

[0063] Sapphire substrates (or corundum) mainly comprise aluminium oxide, potentially colored with elements including, but not limited to, iron, titanium, vanadium, chromium. They may be natural or synthetic sapphire substrates.

[0064] The substrate may have varying shape, from planar to non-planar surfaces. Planar surfaces include flat and/or convex and/or concave surfaces. Non-limiting examples of planar substrates include glass pieces of varying sizes, watch glasses, metal sheets, polymer sheets, or else.

[0065] Non-limiting examples of non-planar surfaces include those with holes, with indents, with generally uneven surfaces, or with substantially spherical surfaces. Non limiting examples of non-planar substrates include jewellery accessories (such as jewels, pearls, gems and stones), engineering accessories (such as pistons, valves, bolts, nails, screws, needles, pins, links, balls, or else), electronic accessories (such as chips, electronic connectors, or else), polymeric accessories (such as phone covers, ear plugs, wire encapsulants, headphones, keyboard keys, computer covers, or else), medical accessories (ortheses, prostheses, appliances, etc.), sport accessories (ping pong ball, golf ball, snooker ball, or else), and others.

[0066] Further examples of non-planar surfaces include substrates in powder form, that is, particulate matter. Such powder forms of substrates may typically be arranged as a powder layer on a planar support for ease of handling or may be arranged on a vibrating pan on a moveable substrate holder. The support may be moved or the powder layer may be re-arranged according to the end use and to the substrate holder, and if several passes of the ion implantation process are required. The powder form is considered non-planar, herein, in that the powder as spread out on the support surface may provide for an uneven surface.

[0067] The substrate is typically not polarized. [0068] The substrate may have a thickness of from 0.01 to 25 mm. For example, a glass sheet may have a thickness of from 0.1 to 8 mm, alternatively of from 0.1 to 6 mm, alternatively of from 0.1 to 2.2 mm. In other applications the substrate may have a thickness of from 10 pm to 100 pm, alternatively from 50 pm to 100 pm. Powders include those having a particle size ranging of from 0.001 pm to 1 mm, alternatively of from 0.01 to 0.7 mm.

[0069] The process for ion implantation typically occurs under vacuum atmosphere.

Vacuum may typically be classified in rough vacuum, having a pressure ranging of from atmospheric pressure to 10 ¹ Pa (= 10³ mbar); high vacuum, having a pressure ranging of from 10 ¹ to 10⁶ Pa (= 10³ to 10⁸ mbar); and ultrahigh vacuum having a pressure ranging of from 10⁶ to 10 ¹⁰ Pa (= 10⁸ to 10 ¹² mbar). Therefore, a reduction of pressure in a defined space is indicative of the reduction of gaseous matter present in said defined space

[0070] The pressure in the ion source typically ranges of from of from 0.01 x 10³ to 10² Pa, alternatively of from 0.01 x 10³ to 10³ Pa, alternatively of from 0.1 x 10³ to 10³ Pa (10 ⁵ Torr), alternatively of from 0.1 to 0.7 x 10³ Pa, alternatively of from 0.2 to 0.6 x 10³ Pa.

[0071] The pressure in the processing chamber typically ranges of from 0.01 x 10³ to 10² Pa, alternatively of from 0.01 x 10³ to 10³ Pa, alternatively of from 0.1 x 10³ to 10³ Pa, alternatively of from 0.1 to 0.7 x 10³ Pa, alternatively of from 0.2 to 0.6 x 10³ Pa.

[0072] The process for ion implantation may occur at a temperature of from 10 to 80°C, alternatively of from 10 to 50°C, alternatively of from 15 to 25°C. The process may occur in absence of any intentional heating above 25°C.

[0073] Examples of ions that may be implanted by an ECR source include one or more of the positively charged ions of N, H, O, F, C, He, Ne, Ar, Xe and Kr.

[0074] Examples of source gas include those gases that contain at least one of N, H, O, F, C, He, Ne, Ar, Xe and Kr. Such sources gases include N₂, He, 0₂, C0₂, Ar, H₂, F₂, CF₄, CH₂, CH₄ and mixtures of these.

[0075] The ions may be single charge and/or multicharge ions, wherein single charge ions are ions carrying a single positive charge, and wherein multicharge ions are ions carrying more than one positive charge. The single charge and multicharge ions generated simultaneously by the ion source make up the ions of the beam.

[0076] The dosage of said ions that are implanted by an ion implantation device as described herein may be comprised between 10¹⁴ ion/cm² and 10²² ion/cm², alternatively between 10¹⁴ ion/cm² and 10¹⁸ ion/cm², alternatively between 10¹⁵ ion/cm² and 10¹⁸ ion/cm². [0077] The acceleration voltage may range of from 5 kV to 1000 kV, alternatively of from 5 kV to 200 kV, alternatively of from 8 kV to 100 kV, alternatively of from 10 kV to 60 kV, alternatively of from 12 to 40kV alternatively at 35 ± 2 kV.

[0078] The beam power may be set at a value ranging of from 1W to 1 kW, alternatively of from 20W to 750W.

[0079] Because of their higher energy, ions carrying a higher charge will be implanted deeper into a substrate than ions carrying a lower charge. Therefore, for a given total ion dosage, a narrow depth distribution is obtained when only simple charge ions are implanted and a wider depth distribution is obtained when simple charge and multicharge ions are implanted simultaneously.

[0080] The ion dosage discussed above may be the total dosage of single charge ions and multicharge ions. The ion beam may typically provide a continuous stream of single and/or multicharge ions. The ion dosage is typically controlled by controlling the exposure time of the substrate to the ion beam.

[0081] The implantation depth of the substrate starts at the substrate surface and reaches down to a depth d, into the substrate, where typically, d is comprised within a range of from 1 to 2000 nm, alternatively of from 2 to 1000 nm, alternatively of from 4 to 700 nm, alternatively of from 4 to 500 nm. The implanted ions are spread between the substrate surface and the implantation depth. The implantation depth may be adapted by the choice of implanted ion, by the acceleration energy and varies to a certain degree depending on the substrate.

[0082] In some instances, the surface of the substrate will become positively charged upon implantation of ions. Such positive charges may redirect or repel the ion beam, which then loose in intensity, and also may provoke electrostatic discharges which may disrupt the ion implantation. The loss in intensity may be measured as a voltage at the surface of the substrate. In those instances, the ions to be implanted are decelerated and will implant at a voltage that is lower than the initial voltage, and the penetration depth will decrease. The present charge neutralizing apparatus overcomes such disruption and allows for the penetration depth to be homogeneous throughout the substrates and the process.

[0083] After completion of the ion implantation procedure, the concentration of invading ions in the substrate may be determined by secondary ion mass spectroscopy (SIMS) or nuclear analysis method like Rutherford Back Scattering (RBS), Nuclear Reaction Analysis (NRA) or ERD (Elastic Recoil Detection). [0084] The implantation of ions in a substrate will typically modify its surface properties, such as reflectance or surface hardness.

[0085] Last provided is the use of a charge neutralizing apparatus in the processing chamber of an ion implantation device, to reduce charge build-up at the surface of a substrate.

[0086] The present invention thus provides for the use of a charge neutralizing apparatus in an ion implantation device comprising:

a. a processing chamber configured to house at least one substrate having a surface

b. an ion source configured to emit an ion beam directed towards the surface of said substrate, and

c. a charge neutralizing apparatus located between the surface of the substrate and the ion source to reduce charge build-up at the surface of a substrate.

[0087] The present invention provides for a method to reduce charge build-up at the surface of a substrate, in an ion implantation device comprising a

[0088] The charge neutralizing apparatus is intended to overcome the charge build-up and electric arcs and implantation defects that may be encountered, by neutralizing the positive charges built up at surface and by reducing the occurrence of electric discharges in the vicinity of the substrate surface. Additionally, the beam does not lose in intensity upon the passage through the fractioning device.

[0089] In a glass substrate, the effectiveness of the charge neutralizing apparatus may be assessed as a reflection value for implanted substrates, or by roughness analysis.

EXAMPLES

Examples 1 to 8 and Comparative examples 1 to 3

[0090] Ion implantation was carried out using an ECR source, with nitrogen gas, at a dose of 7 x 10¹⁶ ion/cm², on soda lime glass substrates of 20 x 20 cm², in presence of charge neutralizing apparatus of different configuration. Examples 1 to 4 were implanted at an acceleration voltage of 20 kV, and Examples 5 to 8 were implanted at an acceleration voltage of 25 kV. Results are given in Tables 1 and 2. The distance between the surface of the substrate and the charge neutralizing apparatus is also indicated in Tables 1 and 2.

[0091] A first configuration of a charge neutralizing apparatus (CNA1) provided for a grounded frame having 2 wires aligned in the Y direction (compared to the movement in the X direction of the substrate holder), 50 mm from one another. The wires were made of W, and have a diameter of 50 pm.

[0092] A second configuration of a charge neutralizing apparatus (CNA2) provided for a grounded frame having 15 wires aligned in the Y direction (compared to the movement in the X direction of the substrate holder), 9 mm from one another. The wires were made of W coated with Au, and have a diameter of 25 pm.

[0093] A third configuration of a charge neutralizing apparatus (CNA3) provided for a grounded frame having 24 wires aligned in the Y direction (compared to the movement in the X direction of the substrate holder), 6 mm from one another. The wires were made of W coated with Au, and have a diameter of 25 pm.

[0094] A fourth configuration of charge neutralizing apparatus (CNA4) provided for a grounded frame complemented with 96 wires organize in a grid, with a distance of 3 mm between each wire in each direction (X and Y). The wires were made of W coated with Au, having a diameter of 25 pm.

[0095] A fifth configuration of a charge neutralizing apparatus (CNA5) provided for a grounded plain frame with a hole in the center of 12 cm diameter, according to Figure 1 e. The frame was made in aluminum. The distance of the charge neutralizing apparatus 5 from the surface of the substrate varied between 1 cm to 3.5 cm.

[0096] Comparative example 1 was the reference of soda lime glass, before the ion implantation process. The light reflection of Comparative example 1 is typically more than 8%.

[0097] Comparative example 2 was soda lime glass in samples of 5 x 5 cm², implanted according to the above described procedure, in absence of any charge neutralizing apparatus. The light reflection of Comparative example 2 is typically about 5.00 ± 0.8.

[0098] Comparative example 3 was soda lime glass in samples of 5 x 5 cm², implanted according to the above described procedure, in absence of any charge neutralizing apparatus. The light reflection of Comparative example 3 was not available, as the ion implantation process had to be interrupted, due to electric discharges and electric arcs, jeopardizing the substrates and the device. The samples incompletely processed, showed pinholes, indicative of inhomogeneous ion implantation and damages. [0099] Examples 1 to 4 and Examples 5 to 8: the ion implantation in presence of the various charge neutralizing apparatus allowed for a consistent and stable implantation, evidenced by the reduced values of reflectance, in line with the values of smaller samples (Comparative example 2), which have less issues of charge build up and electric arcs, at both doses of 20 and 25 kV.

TABLE 1

TABLE 2

Examples 9 to 11 and Comparative examples 4 and 5

[0100] Ion implantation was carried out using an ECR source, with nitrogen gas, at a dose of 7 x 10¹⁶ ion/cm², on thin aluminosilicate glass substrates (Falcon® glass) of 10 x 10 cm², for Examples 9 and 10, and on standard aluminosilicate glass for Example 1 1 , in presence of charge neutralizing apparatus of the fifth configuration. Results are given in Table 3. The acceleration voltage and the distance between the surface of the substrate and the charge neutralizing apparatus are also indicated in Table 3.

[0101] Comparative example 4 was the reference of thin aluminosilicate glass, before the ion implantation process, having a light reflection typically more than 7.8%.

[0102] Comparative example 5 was the reference of aluminosilicate glass, before the ion implantation process, having a light reflection typically more than 7.7%. TABLE 3

[0103] At larger sample sizes of non-conductive substrates, in absence of a charge neutralizing apparatus, ion implantation cannot occur without charge build-up and reduction of the ion implanted dose. In some occurrences, electric discharges provide for defects in the implanted surfaces. In other instances, the charge build-up requires to set the ion implantation process to a hold, to avoid surface breakage, or damages to the ion implanter.

[0104] The present charge neutralizing apparatus provides for the reduction or cancellation of the charge build up allowing for a reduced repellency of the ions in the beam, and in an increase in homogeneity of the beam reaching the surface of the substrate. Additionally, the beam does not lose in intensity from its emission to its arrival at the surface of the substrate. Larger sample sizes may be processed for ion implantation without any process interruption and defects on the ion implanted regions.

[0105] In the case of substrates in powder form, the present charge neutralizing apparatus allows the dissipation of energy built up on the powder substrate. This is preventing the powder either to repel from each other and generate dust in the entire chamber or to melt and be damaged trough uncontrolled arc discharge phenomena.

Claims

1. A charge neutralizing apparatus for a processing chamber of an ion implantation device, said processing chamber having at least one wall,

wherein the charge neutralizing apparatus is fixed to said at least one wall, and comprises at least one conductive frame

and wherein the charge neutralizing apparatus is not an electrode.

2. The charge neutralizing apparatus of claim 1 , wherein the frame has a surface ranging of from of 5 x 10⁷ to 1 m².

3. The charge neutralizing apparatus of claim 1 or 2, comprising a conductive frame and at least one conductive wire.

4. The charge neutralizing apparatus of anyone of claims 1 to 3, wherein the frame and optional wire independently comprise graphite, or metals comprising at least one of the following metals Al, Cu, Zn, Mn, Ti, Ni, Cr, Fe, Mo, W, Au, Ag or mixtures or alloys thereof, optionally provided with a sputtering reduction coating.

5. An ion implantation device comprising

wherein the processing chamber is equipped with a charge neutralizing apparatus according to claim 1 , located between the surface of the substrate and the ion source.

6. The ion implantation device of claim 5 wherein the distance between the charge neutralizing apparatus and the substrate > 0.5 mm.

7. The ion implantation device of claim 5 or 6, wherein the charge neutralizing apparatus encompasses at least part of the ion beam surface, or encompasses the entire ion beam surface, or is partially encompassed with the ion beam surface or is fully encompassed with the ion beam surface.

8. A process for ion implantation comprising the steps of

a. Providing for at least one substrate having a surface,

b. Providing for an ion implantation device,

c. Submitting the surface of the substrate to ion implantation within the ion implantation device at a pressure of from 0.01 x 10³ to 10² Pa,

wherein the ion implantation device comprises at least one charge neutralizing apparatus according to claim 1.

9. The process of claim 8, wherein the substrate includes those substrates comprising glass; sapphire; polymers; elastomers; resins; metals, metal oxides or metal alloys; composite materials; ceramics; or mixtures of these or other material.

10. Use of a charge neutralizing apparatus according to any of claims 1 to 4 in an ion implantation device comprising: