FR2825298A1 - IMPROVED METHOD FOR COATING A SUPPORT, ASSOCIATED DEVICE AND STRUCTURE - Google Patents

Abstract

The invention relates to a method for covering a support (30) with a layer of particles arising from a target entity (20), said method comprising the implementation of an ion source (10) for directing an ion beam (100) towards said target entity in order to create a particle flux (F) arising from the interaction between the ion beam and the target entity, with a view to depositing at least one part of the particle flux on the support, characterized in that the method involves setting the ion beam into motion between the ion source and the target entity in order to scan the target entity in such a way that coverings are created, said coverings having a controlled thickness according to a desired profile.The invention also relates to a structure and a filter made according to said method.

Description

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 The present invention relates generally to methods and devices for covering a layer of material with a support, said layer of material being provided by spraying or by deposition of particles.

More particularly, the invention relates to a method of coating a support with a layer of particles coming from a target, the method comprising the use of an ion source to direct an ion beam towards said target. , in order to generate a flow of particles from the interaction between the ion beam and the target, with a view to depositing at least part of the flow of particles on the support,
The invention also relates to a device for implementing such a method, and a multilayer structure produced by such a method.

 Devices are already known which make it possible to implement a method of the type mentioned above for coating a support.

 These devices include an ion source for generating an ion beam.

 After being possibly electrically neutralized (for example by an electron beam crossing the ion beam), said ion beam strikes a target made of a chosen material.

 A flow of particles is then generated by the impact of the ions on the target, said ions having sufficient energy to remove particles from the target.

 The particles can be atoms taken from the target.

 Part of the flow of particles then arrives on the support, so as to coat its surface.

 In this way, these devices operate a spray (sputtering according to the popular English terminology) making it possible to coat a support.

 An advantageous, but not limiting, application of such devices is the production on a support of multilayer structures, in which layers of different materials are made to alternate.

 It is thus known to produce reflective mask blanks for extreme ultra violet lithography (EUV-corresponding to a radiation whose wavelength is between 10 and 14 nm).

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 A pattern is then formed on such mask blanks, so that the mask exposed to a source of EUV radiation reflects this radiation only according to a desired spatial pattern.

 One can for example carry out on a support an alternation of layers of Mo and Si.

 To constitute multilayer structures in this way, it is necessary to change the target when it is desired to deposit a new layer of a material different from that which constitutes the last layer deposited on the structure.

 Several solutions are known for effecting such a change of target: devices are thus known in which a mobile target support (for example in rotation) is capable of selectively presenting to the first ion beam a target among a plurality that the support of target door.

 Mechanical means are then provided to control the orientation of the target support.

 Such a device can also use a mobile shutter, which makes it possible to interrupt the bombardment of targets by the ion beam.

 Such a shutter can be used in particular when the ion source is switched on, in order to allow it to start up without however starting to coat the support. The shutter can also be used during the phases of changing the position of the target support, in order to present a new target to the ion beam.

 In such known devices, the target change and the associated operations are thus carried out by mechanical elements (target supports which is generally mobile in rotation, mobile shutter, etc.).

 The presence in the device of such mechanical elements which can be exposed to the beams constitutes a potential source of particles capable of depositing on the support, which can lead to the formation of defects in the coating of the support.

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 However, it is often desirable to be able to coat a support with a very high level of quality and a very low defect rate.

 This is the case in particular for optically reflecting multilayer structures such as those used in EUV lithography devices: one objective is to produce multilayer structures in which the largest admissible defects have a characteristic size of less than 50 nm.

 And with the limitations set out above with respect to the prior art mechanical devices, it can be problematic to achieve such quality levels.

 Furthermore, the presence in these known devices of mechanical means controlling the mobility of these elements constitutes a factor which compromises the robustness and the reliability of the devices.

 It is indeed necessary to keep perfect control of the position, orientation and kinematics of the various elements of the device, so that extremely fine adjustments and adjustments are necessary for the operation of the device.

 In addition, the devices are made fragile by the presence of these mechanical elements: any shock or vibration will thus be likely to compromise the reliability of the device.

 An object of the invention is to make it possible to produce multilayer structures which meet the quality objectives set out above.

 Another object of the invention is to further make it possible to produce spraying devices whose degree of robustness and reliability is increased.

 In order to achieve these aims, the invention proposes, according to a first aspect, a method of coating a support with a layer of particles coming from a target assembly, the method comprising the use of an ion source. for directing an ion beam towards said target set, in order to generate a flow of particles resulting from the interaction between the ion beam and the target set, with a view to depositing at least part of the particle flow on the support,

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characterized in that the method includes selectively moving the ion beam between the ion source and the target assembly
Preferred, but not limiting, aspects of the method according to the invention are as follows: said selective deflection is carried out by establishing a dedicated electromagnetic field, said selective deflection is carried out by means of a dedicated magnetic field, said selective deflection is carried out thanks to a dedicated electrostatic field, during the selective deflection, the ion beam is oriented on the desired one among a plurality of targets, the targets are fixed, any desired sequence of targets is carried out by the ion beam, targets are separated by walls, we also electrically neutralize the ion beam, we adapt the trajectory of the electron beam according to the deflection of the ion beam, * during the selective deflection we scan a target with the ion beam in order to define in a desired manner the impact link of the ion beam on the target assembly, * we thus realize a dream tely according to a desired distribution on the support, * a very homogeneous coating is thus produced over a large area,. during the selective deflection, the ion beam is momentarily oriented towards an ion reject zone in order to interrupt the flow of particles, * an ultra-fast scan of the ion beam is carried out between at least two targets, so as to constitute a coating of composites or alloys on the support,

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 the method comprises the selective movement of a second beam of ions directed towards the support so as to assist the growth of the coating.

 According to a second aspect, the invention provides a device for implementing a method according to one of the preceding claims, characterized in that it comprises a source of ions, a set of targets comprising at least one target and means for selective deflection of the ion beam from the ion source.

 Preferred, but non-limiting aspects of the device according to the invention are the following: * said selective deflection means include magnetic means such as magnets or electromagnets, * said selective deflection means include means for creating an electrostatic field, 'it is provided with means for electrically neutralizing the ion beam, * the device comprises a plurality of targets,. targets are fixed.

 According to a third aspect, the invention also provides a multilayer structure produced by a method as mentioned above, characterized in that the structure is capable of reflecting radiation of the EUV type.

 A preferred but non-limiting aspect of the multilayer structure capable of reflecting EUV radiation according to the invention is as follows: the structure constitutes a mask blank for EUV lithography.

 According to a fourth aspect, the invention also provides a filter produced by a method as carried out above.

 Other aspects, aims and advantages of the invention will appear better on the following reading of an embodiment of the invention, made with reference to the single appended figure which is a block diagram of a device according to the invention.

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 In this figure, there is shown by the general reference 1 a device according to the invention, which contains in a sealed enclosure 2 in which a vacuum has been established the elements which will be described below.

 It should be noted that this figure is a block diagram, and that the arrangement of the various elements of the device as well as their size is not necessarily representative of an actual configuration.

 The device 1 firstly contains an ion source 10 capable of generating a beam 100 of ions. The ion source can be conventional in itself, and be of any known type.

 The ions can be for example argon, krypton, xenon or other ions.

 The energy of the ion beam 100 corresponds to the energy level usually used in the ion beams used in the known coating devices as mentioned in the introduction to the present application (more precisely device of the BS- type your Beam Sputtering, which designates the devices for spraying from an ion beam according to the English terminology used).

 A plurality of fixed targets 21, 22, 23 are also provided in the device. The targets 21 to 23 form a set of targets 20.

 Each target is made from a different material. As will be seen in the description of the first preferred application of the invention, each of these targets is intended to be selectively bombarded by the ions of the beam 100, so as to produce a flow of particles F to coat a support 30.

 The support 30 can be any substrate, or assembly of substrates, intended to be coated by the particles of the flux F which result from the bombardment of one of the targets of the assembly 20 by the ions of the beam 100.

 It is specified that by deflection, is meant the operation consisting in setting in motion in a controlled manner the ions of the beam 100. It is indeed important to note that the method according to the invention allows a dynamic evolution of the orientation of the beam d '100 ions, by the means which will be described below.

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 In this way, the target assembly is scanned with the ion beam so as to define in a desired manner the place of impact of the ion beam on the target assembly.

 The targets can be separated by walls 200, in order to avoid any contamination of the flow of particles which will come from a target when the beam 100 is directed towards said target. This aspect will also be detailed in the description of the first preferred application of the invention.

 It should be noted that the number of targets shown in the figure is purely illustrative, and that the device according to the invention can operate with an assembly 20 comprising any number of targets.

 And the device can also operate according to the invention with a single target (in this case the target assembly 20 is reduced to a single target), the invention not being limited to the configuration with several targets.

 The ions of the beam 100 which comes from the source 10 are electrically charged, so that the beam 100 is not electrically neutral.

 This property is used according to the invention to selectively deflect the ions of the beam 100.

 It is specified that the support 30 can be either fixed or mobile. In particular, the support 30 can be rotatably mounted, so as to combine the movements of the support with the arrangements which will be described below and which make it possible to adapt the characteristics of the coating carried out on the support as desired.

 This deflection is carried out by selective deflection means 40 which are capable of producing a field dedicated to the deflection, which may be of an electromagnetic, magnetic or electrostatic nature.

 This deflection field interacts with the charged ions of the beam 100.

 The selective deflection means 40 can implement a dipole creating an electromagnetic field, or any other system for creating an electromagnetic or magnetic field, the characteristics of which can be controlled.

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 In this regard, it is possible to use magnets or electromagnets.

 It is also possible to use an electrostatic field to selectively deflect the ions of the beam 100.

In all cases, the selective deflection means are able to direct the beam 100 as desired, and / or to carry out any desired scanning with this beam
This makes it possible to selectively direct the beam 100 according to a beam 101, 102 or 103 onto one of the targets of the assembly 20.

 And as we will see, this also makes it possible to selectively direct the ion beam towards the desired regions of a single target, for example to generate a flow of particles F allowing a particularly homogeneous coating to be carried out over a large support surface. , or a coating according to a desired thickness profile.

 In a first preferred application of the invention, this selective deflection directs the ions of the beam 100 selectively into a beam 101, 102 or 103 directed only towards one of the targets 21, 22 or 23 respectively.

 By selectively deflecting the ions of the beam 100 towards one, chosen, of the targets 21 to 23, this allows the creation of a flux F of particles resulting from the interaction between the ions of the beam 100 and the material of said target chosen, said particle flow being directed towards the support 30 to coat it.

 It is understood that the device according to the invention thus makes it possible to selectively coat a support with particles of the desired type, the interaction of the ions of the beam 100 with the different respective targets creating fluxes of different particles.

 It is provided in association with the means 40 for selective deflection of the programmable control means making it possible to carry out any desired sequence of control of the orientation of the beam 100 towards desired targets of the assembly 20.

 It is thus possible to carry out scanning programs of the beam 100 in order to coat the support 30 with different successive layers in

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 coating materials whose particles correspond to the respective targets bombarded successively by the ions, and this according to any desired sequence of bombardments of the targets 21 to 23 by the ion beam.

 As mentioned, walls 200 are provided between the targets so as to avoid any contamination of the flow F of particles coming from a target on which the ion beam is directed by possible particles coming from a neighboring target. .

 It is also possible, according to the invention, to produce coatings in composites or in alloys, for example by having beam 100 perform an ultra-fast scanning between two targets (which may be by way of example and in an absolutely non-limiting manner in iron and in cobalt).

 Due to the rapidity of the alternation of the bombardments of the two respective targets, the flow of particles F then comprises a mixture of particles coming from the two respective targets, said mixture coming to deposit on the support.

 And by programming the parameters of such an ultra-fast scan as desired, it is possible to adjust the percentages of the various constituents of the composites or alloys thus deposited on the support as desired (it being understood that it is obviously possible to implement this variant of the invention with more than two different targets, on which the bombardment of the ion beam is alternated very rapidly).

 It is also possible to electrically neutralize the ion beam before it reaches a target, by crossing this ion beam with an electron beam E1 coming from an electron source 50.

 And the electron beam E1 can be directed selectively into the enclosure 2 to follow the movements of the ion beam 100, during its different deviations.

 In this way, it is guaranteed that the beam E 1 always crosses the ion beam in the best conditions for electrically neutralizing this beam.

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 The energy of the beam E1 can be of the order of 500 to 1000 eV for example, depending on the energy associated with the beam 100.

 In a variant of the invention which can be implemented with all the applications described here, it is also possible to direct a second ion beam 600 coming from an ion source 60 onto the support 30.

 The source 60 can, like the source 10, be of a type known per se.

 The beam 600 makes it possible to assist the growth of the coating layer on the support 30.

 And it is here again possible to electrically neutralize the ions of this beam before they reach the support 30, by crossing with this beam 600 a second electron beam E2, coming from an electron source 70.

 The energy of the beam E2 can be of the order of 20 to 50 eV for example, depending on the energy associated with the beam 600.

 It is specified according to an advantageous variant of the invention which can be implemented independently of the other aspects described in this application, the second beam 600 is also associated with selective deflection means 40 ′ allowing this beam 600 to be displaced along any desired trajectory.

 The means 40 ′ for moving the beam 600 can be similar to those, designated by the reference 40, making it possible to set the beam 100 into motion.

 It is thus possible to assist the growth of the coating layer on a large surface of the support 30.

 It is specified that by assistance of the growth, one understands in particular the fact of providing to the particles of the flow F an additional energy, in order to allow them to integrate in holes of the coating.

 Such an arrangement therefore has the consequence of improving the surface qualities of the coating which is in particular smoother.

 This arrangement thus makes it possible to avoid growth of the coating in columns of aggregated particles, providing spaces between the columns of less density.

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 And it is also specified that by increasing the energy associated with the beam 600, it is also possible to improve the coating surface qualities by bombarding said coating with the ions of the beam 100 in an operation equivalent to a spraying (the bombarded coating playing somehow the role of a target).

 In a second preferred application of the invention which can be combined with the first application described above or else implemented with a device comprising a single target, it is also possible to selectively deflect the ions of the beam 100 so as to bombard selectively regions of a single target.

 In this way, the beam 100 can be made to carry out any type of scanning desired and promote the creation of a flow of particles F of desired characteristics.

 It is thus possible to scan a target with the beam 100 according to any desired sequence to create a flow of homogeneous particles and covering a large surface, so as to produce on the support 30 a coating having high qualities of homogeneity, over a large surface.

 It is also possible to create on the support 30 any desired distribution of coating of particles, for example for producing coatings whose layer (s) has (have) a variable thickness according to a desired profile.

 It is thus possible in this second preferred application of the invention to adapt the profile of a coating, for example to produce a curved multilayer mirror on a substrate constituted by the support 30.

 To this end, it is possible to scan a target so as to obtain a desired distribution of particles on the support 30.

 In particular, it is possible to direct more or less particles onto certain regions of the support 30, and thus produce layers of variable thickness.

 Of course, in the case mentioned above of manufacturing a multilayer mirror, a target assembly is used comprising several targets so as to constitute the different layers of the mirror.

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 It appears that the invention overcomes the disadvantages mentioned in the introduction to this text.

 In fact, no movable mechanical part is present in the enclosure 2 - the only movement associated with the implementation of the invention being the introduction of the support 30 into the enclosure, with a view to coating it.

 In addition, the invention makes it possible to carry out very homogeneous coatings on large surfaces.

 In addition, the invention makes it possible to significantly increase the yield of coating operations.

 Indeed, it is possible in the case of the invention to carry out any desired sequence of bombardment of desired regions of a target, or bombardment of desired targets, and this without requiring any mechanical operation in order to interrupt the generation of the particle flow F.

 In the case where it is however desired to delay or momentarily interrupt the generation of the flux F, it is possible in the case of the invention to direct the ion beam 100 towards an ion reject zone, by means 40.

 The waste zone, bombarded by the ions of the beam 100, produces no particles capable of being deposited on the support.

 Such an area may be provided adjacent to the set of targets 20.

For example, provision may be made for placing it in the center of a ring whose different angular sectors correspond to the different targets of the assembly 20.

 It should be noted that the waste zone is particularly advantageous when the ion source 10 is switched on, in order to allow it to be put into operational service without however starting to generate a flow of particles (the quality of which would risk d '' be unstable during the transient phase of commissioning the ion source). And this advantage is obtained without a mechanical member such as a shutter.

 And in the case of the implementation of such a waste zone, the generation of particles can be interrupted at will without affecting the continuity of the coating process: no mechanical interruption takes place-and

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 we are not exposed to the drawbacks associated with such mechanical interruptions (management of the inertia of the parts, adjustment and play, vibrations, etc.).

 The invention thus makes it possible to produce coatings according to a flexible and continuous process, allowing numerous variants (changes of any targets and / or adaptation of a coating profile) without interrupting the course of the process.

 It will be noted that the invention is well suited for producing multilayer structures such as lithography mask blanks, in particular EUV lithography, which require, as has been said, a high degree of homogeneity and are associated with requirements for severe quality.

 However, the invention is not limited to the production of such multilayer structures.

 In particular, it is possible according to the invention to produce filters of the DWDM type (Dense Wavelength Division Multiplexing according to the common English terminology).

 Such filters make it possible to separate signals of different wavelengths which can be multiplexed, for example in optical filters used in telecommunications.

 Indeed, one of the advantages of the invention being to make it possible to produce coatings having very good quality of homogeneity on large surfaces, this invention finds an advantageous application in the production of large plates used for the manufacture of filters. of the type mentioned above.

 And more generally, it will be understood that the invention can be implemented to produce any type of multilayer structure.

 It should be noted that according to the invention it is also possible to inject a gas such as oxygen or nitrogen into the enclosure 2, in order to promote reactive spraying using oxides or nitrides.

 And in a variant of the latter option, it is also possible to use ions of a gas as mentioned above only in association with the second ion beam 600.

Claims (26)

 CLAIMS 1. A method of coating a support (30) with a layer of particles from a target assembly (20), the method comprising using an ion source (10) to direct a beam ions (100) towards said target set, in order to generate a flow of particles (F) resulting from the interaction between the ion beam and the target set, in order to deposit at least part of the flow of particles on the support, characterized in that the method includes selectively moving the ion beam between the ion source and the target assembly. 2. Method according to claim 1, characterized in that said selective deflection is carried out by the establishment of a dedicated electromagnetic field. 3. Method according to claim 2, characterized in that said selective deflection is carried out thanks to a dedicated magnetic field. 4. Method according to one of the preceding claims, characterized in that said selective deflection is carried out by means of a dedicated electrostatic field. 5. Method according to one of the preceding claims, characterized in that during the selective deflection, the ion beam is oriented on the desired one among a plurality of targets. 6. Method according to the preceding claim, characterized in that the targets are fixed. 7. Method according to one of the preceding claims, characterized in that any desired sequence of targets (21, 22, 23) is produced by the ion beam. <Desc / Clms Page number 15> 8. Method according to one of the preceding claims, characterized in that the targets are separated by walls (200). 9. Method according to one of the preceding claims, characterized in that the ion beam is further neutralized electrically. 10. Method according to the preceding claim, characterized in that said neutralization is carried out using an electron beam (E1). 11. Method according to the preceding claim, characterized in that the trajectory of the electron beam (E1) is adapted as a function of the deflection of the ion beam (100). 12. Method according to one of the preceding claims, characterized in that during the selective deflection a target is scanned with the ion beam so as to define in a desired manner the impact link of the ion beam on the target set. 13. Method according to the preceding claim, characterized in that a coating is thus produced according to a desired distribution on the support (30). 14. Method according to one of the preceding claims, characterized in that a very homogeneous coating is thus produced over a large surface. 15. Method according to one of the preceding claims, characterized in that during the selective deflection, the ion beam is momentarily oriented towards an ion reject zone in order to interrupt the flow of particles. 16. Method according to one of the preceding claims, characterized in that an ultra-fast scanning of the ion beam takes place between <Desc / Clms Page number 16>  at least two targets, so as to constitute a coating of composites or alloys on the support. 17. Method according to one of the preceding claims, characterized in that the method comprises the selective movement of a second ion beam (600) directed towards the support so as to assist the growth of the coating. 18. Device for implementing a method according to one of the preceding claims, characterized in that it comprises an ion source (10), a target assembly (20) comprising at least one target and means selective deflection (40) of the ion beam from the ion source. 19. Device according to the preceding claim, characterized in that said selective deflection means (40) comprise magnetic means such as magnets or electromagnets. 20. Device according to one of the two preceding claims, characterized in that said selective deflection means (40) comprise means for creating an electrostatic field. 21. Device according to one of the three preceding claims, characterized in that means are provided for electrically neutralizing the ion beam. 22. Device according to one of the four preceding claims, characterized in that the device comprises a plurality of targets. 23. Device according to the preceding claim, characterized in that the targets are fixed. <Desc / Clms Page number 17> 24. Multilayer structure produced by a method according to one of claims 1 to 17, characterized in that the structure is capable of reflecting radiation of the EUV type. 25. Multilayer structure according to the preceding claim, characterized in that the structure constitutes a mask blank for EUV lithography. 26. Multilayer structure produced by a method according to one of claims 1 to 17, characterized in that the structure is a filter of the DWDM type.