GB2599394A

GB2599394A - Method and apparatus for sputter deposition

Info

Publication number: GB2599394A
Application number: GB2015462.1A
Authority: GB
Inventors: Gauter Sven
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2022-04-06
Anticipated expiration: 2040-09-30
Also published as: CN114318260A; GB202015462D0; CN114318260B; GB2599394B

Abstract

A helicon plasma reactor (100, figure 1) comprises a process chamber, a device for holding a substrate (118) or a target material 206 or both, a helicon plasma source (102a) defining a plasma generating zone and comprising one or more antennae 230, and one or more permanent magnets 240 arranged to generate a unidirectional magnetic field of uniform strength and having an average flux density of between 50 and 100 gauss across the plasma generating zone. The permanent magnets preferably comprise a ring magnet 240 or a ring of magnets (544, figure 12) defining an interior region extending radially inwardly of the rings in which the plasma generating zone is at least partially located. The one or more magnets may be arranged to generate a magnetic field that includes a field-reversal region (262, figure 3) acting as a boundary to generated plasma. The apparatus may be used to sputter deposit a layer of conducting or semiconducting material forming part of a multilayer sheet of an electronic component, preferably a battery or an energy storage device.

Description

METHOD AND APPARATUS FOR SPUTTER DEPOSITION

Technical Field

The present invention relates to sputter deposition, and more particularly to methods and apparatuses for sputter deposition of target material to a surface using a remotely generated plasma.

Background

Deposition is a process by which target material is deposited on a surface, for example a substrate. An example of deposition is thin film deposition in which a thin layer (typically from around a nanometre or even a fraction of a nanometre up to several micrometres or even tens of micrometres) is deposited on a substrate, such as a silicon wafer or web. An example technique for thin film deposition is Physical Vapour Deposition (PVD), in which target material in a condensed phase is vaporised to produce a vapour, which vapour is then condensed onto the substrate surface. An example of PVD is sputter deposition, in which particles are ejected from the target as a result of bombardment by energetic particles, such as ions. In examples of sputter deposition, a sputter gas, such as an inert gas, such as Argon, is introduced into a vacuum chamber at low pressure, and the sputter gas is ioni sed using energetic electrons to create a plasma. Bombardment of the target by ions of the plasma eject target material which may then deposit on the substrate surface. Sputter deposition has advantages over other thin film deposition methods such as evaporation in that target materials may be deposited without the need to heat the target material, which may in turn reduce or prevent thermal damage to the substrate. A known sputter deposition technique employs a magnetron, in which a glow discharge is combined with a magnetic field that causes an increase in plasma density in a circular shaped region close to the target. The increase of plasma density can lead to an increased deposition rate. However, use of magnetrons results in a circular "racetrack" shaped erosion profile of the target, which limits the utilisation of the target and can negatively affect the uniformity of the resultant deposition. It is desirable to provide uniform and/or efficient sputter deposition to allow for improved utility in industrial applications.

W02011131921 discloses a sputter deposition apparatus in which a uniform plasma of density 1011 cm' (i.e. 1017 m-1) is generated by an elongate gas plasma source separately from a target. The plasma so generated is magnetically guided and confined to the vicinity of the target. It is desirable to have higher plasma densities The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of depositing or otherwise manufacturing a layer of material on a surface. Alternatively or additionally, the present invention seeks to provide an improved plasma reactor.

Summary

According to a first aspect of the present invention, there is provided a method of manufacturing, for example depositing, a layer of material on a surface, for example of a substrate. The method includes generating a plasma, in a plasma generating zone, with the use of a helicon plasma source. The helicon plasma source comprises one or more antennae and one or more magnets, preferably permanent magnets. There may be a plasma generating axis. The one or more antennae may define the plasma generating axis. The one or more magnets may define the plasma generating axis. In examples, the plasma is launched in or along the direction of the plasma generating axis. The one or more permanent magnets are arranged to generate a magnetic field, for example both proximate to the magnet(s) and in the plasma generating zone, which is along the plasma generating axis. In examples, the magnetic field needs to be along the plasma generating axis in order for plasma to be generated in the helicon mode. The plasma so generated causes material to eject from one or more sputter target(s).

The plasma may be generated remotely, that is, remotely from such sputter targets. Material ejected from the sputter target(s) may then deposit onto a surface of or supported by a substrate. The material may be deposited directly on the surface so that it forms a crystalline layer in situ.

In embodiments, the one or more permanent magnets and the one or more antennae may be arranged such that the magnetic field in the plasma generating zone is relatively uniform, substantially constant field strength, has field lines that are evenly distributed and substantially aligned with the plasma generating axis, and is strong enough to support helicon waves. In embodiments, the permanent magnets are sufficiently near to the plasma generating zone that the far-field magnetic field lines, which tend to be conveniently parallel and uniformly distributed (and otherwise potentially suitable for plasma generation) are spaced apart from the plasma generating zone and thus not used, or indeed needed, for plasma generation. Instead, by taking care over the geometry and set-up of the component parts of the helicon plasma source of such example embodiments, it has been found that the magnetic field nearer to the magnets (e.g. the near-field magnetic field) can be engineered to be suitable for plasma generation, thus resulting in certain examples of the present invention having a conveniently small and compact footprint.

Example helicon plasma sources of the present invention may be able to produce plasma, in the helicon mode, having a plasma density of 10's m', or greater, for example without the need for bulky electromagnets for the generation of the plasma. Plasma of such high density may allow for effective and/or high rate sputter deposition. The volume of the plasma generating zone may be greater than 10cm3, may optionally be greater than 250cm' and may possibly be greater than 500cm3. The volume of plasma generated, having a density of 1018 m' or greater, may be greater than 10cm3 and may be greater than 500cm3. It may be that there is a volume (e.g. greater than 0cm' and optionally greater than 500cm3) of plasma having a density of 1019m", possibly at least 1020m-3. The plasma in the plasma generating zone may have a density of at least 10' m".

The magnetic flux density in all points within the plasma generating zone may be at least 10 gauss, and may be greater than 25 gauss. It may be that a magnetic flux density of less than 5 gauss is insufficient to support helicon waves and that may act as a virtual boundary to the generation of helicon-mode plasma. In some examples, the magnetic flux density in the plasma generating zone is at least 50 gauss. In some examples, the magnetic flux density in the plasma generating zone may be less than 250 gauss. In an example, a plasma of density of at least 5 x 10'7 m' is supported by a magnetic field having an average flux density of 50 to 100 gauss, for example about 65 gauss.

The afore-mentioned plasma densities may be sustained in a region where the local gas pressure is in the range of 10 mBar (for example, at least 10' mBar, but less than 10' mBar, optionally less than 8 x 10-3 mBar).

The antenna may be positioned near to the permanent magnet(s). The antenna may be less than 200mm away from the nearest permanent magnet, optionally less than 150mm away, and possibly less than 100mm away. This may allow for a compact design of helicon plasma source.

The target may be positioned near to the antenna. The antenna may be less than 200mm away from the nearest target, optionally less than 150mm away, and possibly less than 100mm away. This may allow for a compact design of helicon plasma source.

In examples, the method includes driving the one or more antennae with RF frequency current to generate plasma, typically at an electrical power of at least lkW, and possibly 2 kW or more. When there are multiple antennae the power needed to drive each antenna may be lower, for example being between 100W and lkW. The antennae may be driven at a frequency that is at least 1 MHz, and optionally at a frequency of 13.56 MHz, or multiples thereof The antenna may be driven at a lower frequency than 13.56 MHz; for example, the antenna may be driven at a frequency in the range 1 MHz to 10 MHz, for example at about 2N/Hz.

It will be understood that the magnetic field of the magnets need not be exactly parallel to the plasma generating axis for examples of the invention to have the benefits mentioned herein. Indeed, small divergence or convergence might be beneficial. In examples, it may be that the magnetic field of the magnets have field lines that are sufficiently close to parallel to the plasma generating axis that the lines that touch or pass through the antenna continue from the antenna and out from the helicon plasma source without termination to any wall or part of the source. With such an arrangement, it is more likely that the plasma generated by the antenna will follow the direction of the field lines and avoid undesirable interactions with any such walls. In examples, it may be that the magnetic field of the magnets have field lines that are sufficiently close to parallel that the maximum divergence between field lines in the plasma generating zone is less than 20 degrees when resolved onto a notional horizontal plane.

In an example, the one or more permanent magnets comprise a ring magnet. In an example, the one or more permanent magnets comprise a ring of magnets. The ring may be elongate, thus having a generally tubular shape. A (magnetic) ring of the source may have a length (along its axis) that is greater than its diameter. The magnetic field generated by a ring magnet or a ring of magnets, particularly for example the field within an interior region of the ring(s), which extends radially inwardly of the ring(s) may have properties that are particularly well suited to generating plasma in the helicon mode. The plasma generating zone may be located at least partially, and possibly entirely, in the interior region of the ring. The antenna may be located at least partially, and possibly entirely, in the interior region of the ring. Such a ring typically has a corresponding exterior region extending radially outwardly of the ring(s). When the ring is formed of multiple magnets spaced apart circumferentially around the ring there may be at least three magnets forming the ring. In some examples, there may still be benefit to having a notional ring formed of only two circumferentially spaced apart magnets. The interior region may be considered to extend in the direction of the axis of the ring beyond the top and/or bottom of the ring. In examples, using the internal field of a ring magnet and/or a ring of magnets may enable a reduction in the amount of necessary magnetic material needed to support the generation of plasma in the helicon mode, as compared to other geometries (for example those utilising the far-field region of the magnetic field). This may enable the overall dimension of the helicon plasma source to be reduced, thus resulting in a compact source. In an example, the helicon plasma source comprises a ring magnet with a wall thickness of less than lOmm, and possibly less than 5mm.

The plasma generating axis defined by the one or more antennae may be oriented to be along, for example substantially aligned with and/or parallel to, the central axis of the ring(s) (the axis that is perpendicular to the notional plane on which the ring lies).

It may be that the antenna is spaced apart from the one or more permanent magnets in the direction of the plasma generation axis.

In an example, the plasma is launched in a particular direction. Such a direction may for example be along the plasma generation axis. The plasma may be launched in a direction 15 towards the one or more permanent magnets, for example towards a ring magnet / ring of magnets.

In some examples there may be multiple different rings of magnets and/or ring magnets. The rings may be aligned along the same axis. One ring of the helicon plasma source may have a different diameter from another ring of the same helicon plasma source. In examples, having multiple such rings (e.g. tubes of different radii) allow the magnetic field shape to be engineered / shaped to suit a particular application. For example, there may be two or more such ring(s), including a first ring having a first radius and a second ring having a second radius that is different from the first radius (at least 5% greater).

In the case where there is more than one ring magnet, the interior region (of the ring(s)) may be considered to extend from one ring to the next, via a notional surface created by the loci of the shortest straight lines joining one ring to the next. The interior region may also be considered to extend from the distal end of the end ring magnet, away from the permanent magnets, via the notional cylindrical surface created defined by the inner diameter of the ring magnet If part of the arrangement of permanent magnets includes a ring of magnets, then the interior region may be defined by the loci of smallest diameter circles that touch all of the magnets that form the ring.

In examples, it may be that the one or more permanent magnets are arranged to generate a magnetic field in the plasma generating zone with magnetic field lines which are aligned (for example, substantially parallel to -or at least, close enough to parallel to support the helicon mode) with the plasma generating axis defined by the one or more antennae. The magnetic field lines which are aligned with the plasma generating axis may be those in the near-field (as opposed, for example, to those in the far-field). It may be that the one or more permanent magnets are arranged to generate a magnetic field with one or more regions having a local magnetic field which defines a boundary to the plasma generating zone. Such a boundary may, at least in part, be defined by those points at which the magnetic flux density drops below a certain threshold minimum value. Such a threshold minimum value may be greater than I gauss. Such a threshold minimum value may be less than 20 gauss. Such a boundary may, at least in part, be defined by those points at which the magnetic field lines change direction, for example where there is a field reversal point and/or where the direction as resolved along the plasma generating axis reverses. The one or more permanent magnets may be arranged to generate a magnetic field that includes such a field-reversal region, which may then effectively act as a boundary to the plasma. Such a field-reversal region may be relatively close to the magnet surface on the magnet. It may be that a sudden drop in field strength and/or a field reversal region limits the expansion of the helicon wave and may thus act as an axial boundary to the plasma.

There may be a step of launching the plasma in the direction of converging magnetic field lines (for example towards one of the permanent magnets). It may be a magnetic field with converging field lines allow more intense coupling close to the antenna.

The helicon plasma source may comprise two or more permanent magnets, for example two or more permanent magnets per each antenna. The helicon plasma source may comprise at least three permanent magnets, for example per antenna. The helicon plasma may comprise only one antenna, in examples. Such multiple permanent magnets may be positioned spaced apart from each other, for example by a gap with no other solid material in that gap. It may be that at least two of the spaced-apart permanent magnets are spaced apart, in direction of the plasma generating axis. It may be that at least two of the permanent magnets are spaced apart in a circumferential direction about the plasma generating axis. Such circumferentially spaced apart magnets may form a ring of magnets. It may be that one of the spaced-apart permanent magnets is in the form of a stick magnet (for example a bar magnet), for example having a generally elongate form. It may be that the antenna is located between at least two of the spaced apart magnets. For example, there may be a ring magnet (or ring of magnets) and at least one stick magnet spaced apart therefrom along the central axis of the ring, the antenna being positioned between the ring and the stick.

There may be further electromagnetic field generating elements, such as electromagnets and/or further permanent magnets. Such further electromagnetic field generating elements may be arranged to extend the region where the RF is coupling into the plasma (for example, if the helicon waves can be sustained there will be coupling into the plasma in such an extended region). Such further electromagnetic field generating elements may, alternatively or additionally, be arranged to shape and control the movement of plasma once generated. Such further electromagnetic field generating elements may act to generate a plasma confining field. In some embodiments, it may be unnecessary for further electromagnetic field generating elements to be provided in order to confine the plasma. For example, the electromagnetic field generated at least in part by the helicon plasma source may be sufficient to control the extent and shape of the plasma. Additionally or alternatively, the or each helicon plasma source may be provided sufficiently close to the target that the plasma does not need extra confinement and/or additional control over how far, and to where, it extends. The plasma generation zone may be located directly adjacent to the target, with the plasma being generated separately from the target (i.e. the plasma is not generated as a result of, or with a need for, striking the target).

The target may be positioned between an antenna and a permanent magnet, at least when viewed in at least one direction. The target may be positioned directly adjacent to a permanent magnet, at least when viewed in at least one direction.

The one or more antennae defining a plasma generating axis, may each follow a path having a curvature, the curved path being transverse to the plasma generating axis. For example, at least part of the path of an antennae may form at least part of a helical, spiral, and/or circular shape and/or follow a notional surface that is cylindrical or conical, The plasma generating axis may for example be parallel to an axis defined by the shape of the path of the antenna (e.g, the axis of the helical, spiral, circular, cylindrical, and/or conical shape). The or each antenna may be in the form of a stove top antenna, for example with its plane perpendicular to the magnetic field and/or the plasma generating axis. Other geometries of antenna are also envisaged including geometries such as a half of a Boswell (double saddle) antenna. The antenna need not have a symmetrical shape.

There may be a region adjacent to the antenna at which the generation of helicon waves is restricted and/or reflected, for example as a result of at least one boundary member. Such a boundary member may be configured to reflect the wave that is initially propagated in one direction so that it is superimposed onto the wave initially launched in the opposite direction.

There may be a region adjacent to the antenna at which the generation of plasma is restricted, for example as a result of at least one shield member.

In examples, the plasma is generated, maintained and shaped in a working space of a process chamber, and is not generated in a separate, discrete, or non-integrated plasma chamber (usually referred to as a discharge tube), which is subsequently drawn into the working space of the process chamber, as seen in the systems of the prior art. Thus, at least a part of the plasma source (for example the antenna or optionally its housing or a part thereof) may form an integral or integrated element of the process chamber, without the necessity of the housing or antenna being surrounded by a plasma chamber, or the housing itself being part of a plasma chamber. In contrast, certain examples of the present invention generate and maintain the high density plasma in the gaseous medium of the process chamber. It has been found that, in certain examples, it may be adequate merely to house or enclose the antenna itself within the process chamber, thus greatly simplifying the design requirements of a plasma processing apparatus.

It may be that at least part of the substrate is carried by a rotating drum.

As mentioned above, the method may result in the manufacture of a crystalline layer of material on the surface. The crystalline layer may comprise lithium, at least one transition metal and at least one counter-ion. The substrate may have a thickness of from 0.1 to 10p.m. The crystalline layer so formed on the surface / the substrate may have a thickness of from 0.001 to 10jtm. It may be that the steps of sputtering material onto the surface are so performed that the maximum temperature reached at any given time by any given square of substrate material having an area of 1cm2, as measured on the surface opposite to said surface on which the material is deposited and as averaged over a period of I second, is no more than 500 degrees Celsius.

There is also provided a method of manufacturing at least part of an electronic component for use in an electronic product, utilising the sputter deposition method of the present invention as described or claimed herein. Such a method may include forming a multilayer sheet of different materials. Such a method may include a multilayer sheet of different materials, or a part thereof, in the electronic component (or part thereof). At least one of the layers of material in the electronic product so formed is a layer of conducting or semiconducting material made by performing the sputter deposition method of the present invention as described or claimed herein The substrate may be retained as a part of the electronic component in certain examples. In other examples, the material may be lifted off, or otherwise removed, from the substrate. The electronic component may be a battery. The electronic component may be a functional layer of a battery. The electronic component may be an energy storage device. The electronic component may be a cell of battery. The electronic component may comprise one or more layers of crystalline material. A battery may for example comprise multiple stacked cathode layers, multiple stacked electrolyte layers, and multiple stacked anode layers. It may be that at least two of the multiple stacked cathode layers are made by performing the sputter deposition method of the present invention as described or claimed herein.

According to a further aspect of the invention, there is also provided a helicon plasma reactor, for example being suitable for use in the sputter deposition method of the present invention as described or claimed herein. Such a helicon plasma reactor may for example include a process chamber. The plasma reactor may comprise a helicon plasma source, for example located in the process chamber, for generating plasma with helicon waves. The helicon plasma source may define a plasma generating zone. The helicon plasma source may comprise one or more antennae. The helicon plasma source may comprise one or more permanent magnets. The one or more permanent magnets may be arranged to generate a unidirectional magnetic field, for example of substantially uniform strength, across the entire extent of the plasma generating zone (e.g, substantially the same strength, give or take, say, 20% with a variation in direction of less than, say, +/-15 degrees). The magnetic flux density of the field in the plasma generating zone may have an average value that it between 50 to 100 gauss. The plasma reactor may comprise a device for holding a substrate. The plasma reactor may comprise a device for holding a target material. The helicon plasma reactor may be configured to perform the sputter deposition method of the present invention as described or claimed herein. The plasma reactor may also include a radio frequency (RF) power source, and optionally an associated control unit, for driving the antenna.

According to a further aspect of the invention, there is also provided an apparatus for generating plasma in the helicon mode, for example being suitable for use as the helicon plasma source as required in the sputter deposition method of the present invention as described or claimed herein. Such an apparatus may have applications in other methods, not being sputter deposition for example. The apparatus may define a plasma generating zone. The apparatus may comprise one or more antennae defining a plasma generating axis and, and one or more permanent magnets arranged to generate a magnetic field along the plasma generating axis.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 is a schematic diagram that illustrates a cross section of an apparatus according to an example; Figure 2 is a perspective view of a helicon plasma source with a first configuration; Figure 3 shows some magnetic field lines of a part of the helicon plasma source of Figure 2; Figure 4 is a diagram showing the direction of the magnetic field at various locations in the helicon plasma source of Figure 2, Figure 5 is a diagram showing the contours of constant magnetic flux density of the field of part of the helicon plasma source of Figure 2; Figure 6 is a perspective view of a helicon plasma source with a second configuration; Figure 7 is a diagram showing the direction of the magnetic field at various locations in the helicon plasma source of Figure 6; Figure 8 is a diagram showing the contours of constant magnetic flux density of the field of part of the helicon plasma source of Figure 6; Figure 9 is a perspective view of a helicon plasma source with a third configuration, Figure 10 is a diagram showing the direction of the magnetic field at various locations in the helicon plasma source of Figure 9, Figure 11 is a diagram showing the contours of constant magnetic flux density of the field of part of the helicon plasma source of Figure 9, Figure 12 is a perspective view of a helicon plasma source with a third configuration; Figure 13 is a diagram showing the direction of the magnetic field at various locations in the helicon plasma source of Figure 12; Figure 14 is a diagram showing the contours of constant magnetic flux density of the field of part of the helicon plasma source of Figure 12; and Figure 15 is a flow diagram illustrating a method of using the apparatus of Figure 1 to form a thin film crystalline layer of material on a substrate.

Detailed Description

Reference in the specification to "an example" (or to "an embodiment" or similar language) means that a particular feature, structure, or characteristic described in connection with the example is included in at least that one example, but not necessarily in other examples.

It should further be noted that certain examples are described schematically with certain features omitted and/or necessarily simplified for ease of explanation and understanding of the concepts underlying the examples.

Referring to Figure 1, an example apparatus 100 for sputter deposition of target material 108 to a substrate 116 is illustrated. The apparatus 100 may be considered as an example of a plasma reactor. The apparatus 100 may be used for plasma-based sputter deposition for a wide number of industrial applications, such as those which have utility for the deposition of thin films, such as in the production of optical coatings, magnetic recording media, electronic semiconductor devices, LEDs, energy generation devices such as thin-film solar cells, and energy storage devices such as thin-film batteries. Therefore, while the context of the present disclosure may in some cases relate to the production of energy storage devices or portions thereof, it will be appreciated that the apparatus 100 and method described herein are not limited to the production thereof Although not shown in the Figures for clarity, it is to be appreciated that the apparatus 100 may be provided within a housing (not shown), which in use may be evacuated to a low pressure suitable for sputter deposition, for example 3x10' torr (1 torr 1.333 mBar) For example, the housing (not shown) may be evacuated by a pumping system (not shown) to a suitable pressure (for example less than lx10' torr), and in use a process or sputter gas, such as argon or nitrogen, may be introduced into the housing (not shown) using a gas feed system (not shown) to an extent such that a pressure suitable for sputter deposition is achieved (for example 3x10' torr). The parts of the apparatus shown in Figure 1 may be accommodated within the same housing / process chamber, which accommodates a relatively large volume of space 122.

Returning to the apparatus 100 illustrated in Figure 1, in broad overview, plasma generated by one or more plasma generation arrangements 102 causes material to eject from one or more sputter targets 106 which is then deposited onto a substrate 116 thus forming a layer of material. In some embodiments, crystalline material may be formed directly on the substrate (in situ) as it is deposited, without the need for further post-deposition processing or re-heating. The apparatus, and some of the possible variations/modifications thereof will now be described in more detail.

The apparatus 100 comprises a substrate guide 118 and a target portion 106. The substrate guide 118 is arranged to guide a web of substrate 116 along a curved path (the curved path being indicated by arrow C in Figure 1). In some examples, the substrate guide 118 may be provided by a curved member 118. The curved member 118 may be arranged to rotate about an axis 120, for example provided by an axle 120, which may also be a longitudinal axis of the curved member 118. In some examples, including the example illustrated in Figure 1, the curved member 118 may be provide by a substantially cylindrical drum or roller 118 of an overall web feed assembly 119. The web feed assembly 119 may be arranged to feed the web of substrate 116 onto and from the roller 118 such that the web of substrate 116 is carried by at least part of a curved surface of the roller 118. In some examples, the web feed assembly comprises a first roller 110a arranged to feed the web of substrate 116 onto the drum 118, and a second roller 1106 arranged to feed the web of substrate 116 from the drum 118, after the web of substrate 116 has followed the curved path C. The web feed assembly 119 may be part of a -reel-to-reel" process arrangement (not shown), where the web of substrate 116is fed from a first reel or bobbin (not shown) of substrate web 116, passes through the apparatus 100, and is then fed onto a second reel or bobbin (not shown) to form a loaded reel of processed substrate web (not shown). In some examples, the web of substrate 116 may be or comprise a polymer.

In some examples, for example for the production of an energy storage device, the web of substrate 116 may be or comprise nickel foil, but it will be appreciated that any suitable metal could be used instead of nickel, such as aluminium, copper or steel, or a metallised material including metallised plastics such as aluminium on polyethylene terephthalate (PET).

The target portion 106 is arranged to support the target material 108. In some examples, the target portion 106 may comprise a plate or other support structure that supports or holds the target material 108 in place during sputter deposition. The target material 108 may be a material on the basis of which the sputter deposition onto the substrate 116 is to be performed. For example, the target material 108 may be or comprise material that is to be deposited onto the web of substrate 116 by sputter deposition. In some examples, for example for the production of an energy storage device, the target material 108 may be or comprise, or may be or comprise a precursor material for, a cathode layer of an energy storage device, such as a material which is suitable for storing Lithium ions, such as Lithium Cobalt Oxide, Lithium Iron Phosphate or alkali metal polysulphide salts. Additionally or alternatively, the target material 108 may be or comprise, or may be or comprise a precursor material for, an anode layer of an energy storage device, such as Lithium metal, Graphite, Silicon or Indium Tin Oxides.

Additionally or alternatively, the target material 108 may be or comprise, or may be or comprise a precursor material for, an electrolyte layer of an energy storage device, such as material which is ionically conductive, but which is also an electrical insulator, such as lithium phosphorous oxynitride (Li PON). For example, the target material 108 may be or comprise LiP0 as a precursor material for the deposition of LiPON onto the substrate 116, for example via reaction with nitrogen gas in the region of the target material 108. The target portion 106 and the substrate guide 118 are spaced apart from one another and define between them a deposition zone 114. The deposition zone 114 may be taken as the area or volume between the substrate guide 118 and the target portion 106 in which sputter deposition from the target material 108 onto the web of substrate 116 occurs in use. In some examples, such as those illustrated, the apparatus may comprise a plasma generation arrangement 102. The plasma generation arrangement 102 is arranged to generate plasma 112. A magnetic confining arrangement (not shown in Figure 1) may also be provided to control and shape the plasma 112 generated by the plasma generation arrangement 102. The apparatus is configured to allow for a generation of an elongate region of plasma 112 which may be confined to the deposition zone 114.

Additionally or alternatively, the apparatus 100 may be configured for sputter deposition of target material 108 to a substrate 116 to form a crystalline material, for example taking the form AB02. Such an ABO2 crystalline material may take the form of a layered oxide structure. The ABO2 material may be LiCo02. In other examples, the crystalline material structure may comprise at least one of the following compounds (described here with nonspecific stoichiometry): LiCoO, LiCoA10, LiNiCoA10, LiMnO, LiNiMnO, Li NiNftiCoO, LiNi0 and LiNiCo0. These materials are potential candidates for manufacturing a battery cathode. Those skilled in the art will realise that the stoichiometry may be varied.

The details of the possible plasma generation arrangements 102 are described with reference to Figures 2 to 13, which all relate to plasma generation using the helicon mode, which enables a much higher density of plasma to be created. Plasma of high density may allow for effective and/or high rate sputter deposition.

The plasma generation arrangement 102 is located in the housing / process chamber (not shown). In contrast to prior art examples of process chambers, where plasmas are generated within contained plasma generation systems and then drawn out into the processing chamber, the plasma generation arrangement 102 of the present invention resides within and is open to the same space 122 of process chamber where the plasma will be applied in processing of a target assembly and/or substrate assembly. In other words, the plasma is generated locally in the atmosphere of the process chamber.

The location in the housing of the plasma generation arrangement 102a as shown in Figure 1 may be varied. There may be more than the single plasma generation arrangement 102a, as shown in Figure 1. For example a further plasma source may be added at the position shown by the box 102b, shown in broken line in Figure 1. Additionally or alternatively, one or more plasma generation arrangements may be provided in other locations, for example there being multiple plasma sources arranged along the width of the roller 118 (parallel to the roller axis 120). In some examples, the plasma generation arrangement 102 may be disposed remotely of the substrate guide or roller 118. For example, the plasma generation arrangement 102a may be disposed at a distance radially away from the substrate guide 118. As such, plasma 112 may be generated remotely of the substrate guide 118, and remotely from the deposition zone 114.

In some examples, the plasma generation arrangements 102 may individually or collectively be similar in length to the substrate guide 118, and accordingly similar to the width of the web of substrate 116 carried by the substrate guide 118. The plasma generation arrangement(s) 102 may provide for plasma 112 to be generated across a region having a length corresponding to the length of the substrate guide 118 (and hence corresponding to the width of the web of substrate 116), and hence may allow for plasma 112 to be available evenly or uniformly across the width of the web of substrate 116. This may in turn help provide for even or uniform sputter deposition.

The configuration and arrangement of the one or more plasma generation arrangements 102 may be such that plasma is generated in one or more zones very near the target material. The plasma may be launched in a particular direction that, with appropriate biasing of the target, allows for sputter deposition to take place without needing further permanent magnets or electromagnets for shaping, confining or repositioning of the plasma once generated In other examples, the plasma 112 may be confined at least in part by a magnetic field generated by one or more additional magnetic elements (not shown in Figure 1) into the deposition zone 114, in order to provide for sputter deposition of target material 108 to the web of substrate 116 in use In cases where a confining magnetic field is provided, the confining magnetic field may is have magnetic field lines arranged to, at least in the deposition zone 114, substantially follow or be parallel to a curve of the curved path C so as to confine the plasma 112 around the curved path C. In use, the generated plasma 112 tends to follow the magnetic field lines. Confining the generated plasma 112 in this way may allow for more uniform distribution of plasma density at the web of substrate 116, at least in a direction around curve of the curved path C. This may in turn allow for a more uniform sputter deposition onto the web of substrate 116 in a direction around the curved path C. The sputter deposition may therefore, in turn, be performed more consistently. This may, for example, improve the consistency of the processed substrate, and may for example, reduce the need for quality control. Alternatively or additionally, confining the generated plasma 112 in this way may allow for an increased area of the substrate 116 to be exposed to the plasma 112, and hence for an increased area in which sputter deposition may be effected. This may allow, for example, for the web of substrate 116 to be fed through a reel-to-reel type apparatus at a faster rate for a given degree of deposition, and hence for more efficient sputter deposition.

A confining magnetic field may in some examples be provided, in part, by magnetic elements that form part of the plasma generation arrangements 102.

A confining magnetic field may in some examples be provided, at least in part, by one or more electromagnets, for example with the use of a controller (also not shown) arranged to control a strength of the magnetic field provided. This may allow for the arrangement of the magnetic field lines characterising the confining magnetic field to be controlled. This may allow for adjustment of the plasma density at the substrate 116 and or the target material 108 and hence for improved control over the sputter deposition. This may allow for improved flexibility in the operation of the apparatus 100. In some examples, one or more of the electromagnets may be provided by a solenoid, for example defining an opening through which plasma 112 passes (is confined) in use.

In some examples, one or more magnetic elements are arranged to provide the confining magnetic field so as to confine the plasma 112 in the form of a curved sheet. In some examples, one or more magnetic elements are arranged to provide the confining magnetic field so as to confine the plasma 112 in the form of a sheet having, at least in the deposition zone 114, a substantially uniform density. Such a sheet of plasma has a form in which the depth (or thickness) of the plasma 112 is substantially less than its length or width. The thickness of the sheet of plasma 112 may be substantially constant along the length and width of the sheet. The density of the sheet of plasma 112 may be substantially uniform in one or both of its width and length directions.

In some examples, the plasma 112 may, at least in the deposition zone 114, be high density plasma. For example, the plasma 112 (in the form of a curved sheet or otherwise) may have, at least in the deposition zone 114, a density (e.g. electron density or equivalent) of 1011 cm' (i.e. 1017 m-3) or more, for example. Plasma 112 of high density in the deposition zone 114 may allow for effective and/or high rate sputter deposition.

In the example illustrated in Figure 1, the target portion 106 and the target material 108 supported thereby is substantially planar. However, in some examples, the target portion may be arranged, or may be configurable to be arranged, such that at least one part of the target portion defines a supporting surface forming an obtuse angle with respect to a supporting surface of another part of the target portion. For example, the target portion may be substantially curved. For example, the target portion may be arranged to substantially follow the curve of the curved path C. The target portion may be arranged, or configurable to be arranged, such that at least one part of the target portion defines a planar surface forming an obtuse angle with respect to a planar surface of another part of the target portion. The target portion may comprise multiple, for example three, substantially planar parts with each part making an obtuse angle with respect an adjacent part, the multiple planar parts together being arranged so as to approximate the curve of the curved path C. In some examples, the target portion is configurable so that an angle that a first part of the target portion makes with a second, for example adjacent, part of the target portion is configurable. For example, the first part and the second part may be mechanically connected by a hinge element or other such component that allows the angle therebetween to be changed, optionally by an actuator and suitable controller provided for that purpose. This may allow for control of the plasma density experienced by the target material of different parts of the target portion, to be controlled during use, thus allowing control over the rate of ejection of material from respective parts of the target portion. Alternatively or additionally, the confining magnetic field may be controlled by a controller (not shown) to alter the curvature of the plasma 112 and thereby control the density of plasma experienced by different respective parts of the target portion.

In some examples, the target material provided on one part of the target portion may be different from the target material provided on another part of the target portion. This may allow for a desired arrangement or composition of target material to be sputter deposited onto the web of substrate 116.

Various example helicon plasma sources, which may be used as the plasma generation arrangement 102 shown in Figure 1, will now be described with reference to Figures 2 to 13. Each of the helicon plasma sources described and illustrated have antennae for generating plasma in a magnetic field created by one or more permanent magnets. The plasma 20 is generated by helicon waves from the process or sputter gas in the housing (not shown separately in the Figures). Helicon plasma sources are known in the prior art in various other fields of application. Typically, bulky electromagnets and associated control systems are used in order to generate the magnetic fields in the manner needed to generate helicon waves. Such bulky arrangement would be impractical for many arrangements where the plasma is being generated by apparatus inside a process chamber. Having a helicon plasma source with a smaller footprint may be beneficial in other applications for other reasons, it is proposed in US 8,179,050 that a helicon plasma source can be made using permanent magnets, but only by creating the plasma in the weaker remote far-field of the permanent magnets where the field lines are closer to parallel. The present embodiments utilise the near-field of one or more permanent magnets as a result of the realisation that the problems identified in US 8,179,050 of using permanent magnets in a helicon source can be mitigated by techniques other than only utilising the far-field of the magnets. Such techniques include using different topologies of magnets and/or magnetic fields and confining the plasma so generated in various ways so as to avoid undesirable interactions between the plasma and other objects/walls in the process chamber.

In the present embodiments, the antennae are shaped to have a helical, spiral and/or circular shape (shown in the schematic figures simply as circular), and thus all tend to have a well-defined axis. Other geometries of antennae may also be used. Plasma may be generated by a radio frequency power supply system (not shown) driving a radio frequency current through the one or more antennae for example at a frequency between 1MHz and 10Hz; a frequency between 1 MHz and 100MHz; a frequency between 10 MHz and 40 MHz; or at a frequency of approximately 13.56 MHz or multiples thereof In examples, the antenna may be driven at electrical powers of at least IkW, and possibly 2 kW or more.

Plasma is generated within a high strength magnetic field configured so as to generate a wave heated plasma using helicon waves (also referred to as helicon plasma, helicon discharge, or plasma in the helicon mode). It will be understood that helicon waves travel most efficiently in a direction along the magnetic field lines. For a high density helicon plasma to be generated the magnetic field needs to be both strong enough and aligned with the antenna axis.

It will be appreciated that magnetic field lines may be used to characterise or describe the arrangement or geometry of a magnetic field. The one or more permanent magnets are configured to create magnetic field lines which, in the near field of the magnetic field, are evenly distributed and aligned with a plasma generating axis. Within the plasma generating zone there is therefore a magnetic field of substantially constant field strength. In order to generate and maintain a plasma in the plasma generating zone, the magnetic flux density needs to be above a certain level which may for example be about 5 gauss. Where the field drops 25 below such a minimum level may act as a virtual boundary to the plasma generation zone As mentioned above, by generating plasma utilising the helicon mode it may in certain examples be possible to generate plasmas with relatively high densities. The term "plasma density" as used herein will be understood as referring to the density of positive ions per unit volume in the plasma -which may of course be substantially equal to the density of free electrons in the plasma. It may be that in the plasma generating zone, at least 10% of the gas will be ionised, possibly at least 50% of the gas will be ionised, and optionally more. The plasma density may be measured by using a Langmuir probe. A Langmuir probe is essentially an electrode which can be exposed to the plasma and, by sweeping a voltage on the electrode and drawing a characteristic current from the plasma, can be used to calculate electron temperature and an ion saturation current, from which the ion density may be calculated.

It will be understood that the maximum plasma density achievable will relate to the amount of gas locally and therefore the process pressure. For example at a relatively low pressure of say, 0.01 Pa (=10-4mBar or -7.5x10-5 torr), the gas density is only -10's m-3 so even if all of that gas is ionized, the maximum achievable plasma density would be -1018 m". Thus, the higher the pressures gets the easier it will be to achieve higher plasma densities. However, for efficient sputtering, the pressure might be of the order of -10' mBar, which would correspond to -10" m", if fully ionized. Useful sputtering may be achievable using plasmas with densities of 5 x 1017 m' or more, preferably of the order of a few 1018 m', or so. By way of comparison, conventional magnetrons would typically achieve plasma densities up to a maximum of 1016 ni".

By generating plasma utilising the helicon mode it may in certain examples be possible to generate plasmas with a density of 10" m' or more, and possibly 1020 m" or more. The volume of plasma generated in the plasma generation zone having a density of 10" m" or more may be greater than 10cm1 and may be greater than 500cm1. There may be an interrelationship between the plasma density and the magnetic field. In certain embodiments, the plasma in the plasma generating zone has a density of at least 1017 m-11 corresponding to a magnetic field average flux density of between 50 to 100 gauss. In one embodiment, the plasma has a density of at least 5 x 1017 m" corresponding to a magnetic field average flux density of about 65 gauss. A first configuration of antenna and permanent magnets is illustrated by, and will now be described with reference to, Figures 2 to 5. Figure 2 shows a plasma generation arrangement 202 comprising an antenna 230, which has a longitudinal axis 232 aligned with a notional z-axis. In this example, the antenna is a loop antenna using copper, coated with an insulator such as anodised aluminium and/or a ceramic insulating material.

A single ring magnet 240 aligned with the same axis 232 is spaced apart from the antenna 230 in the direction along the axis 232 (by about 90mm). The target material 206 is off-set from the z-axis 232 in the y-direction and positioned (in the direction of the z-axis) between the antenna 230 and the magnet 240. The substrate (not shown) is off-set from the z-axis 232 in the opposite direction along the y-axis and faces the target. The substrate is thus also positioned (in the direction of the z-axis) between the antenna 230 and the magnet 240. The antenna axis 232 may be considered to represent a plasma generation axis.

The arrangement shown in Figure 2 thus has a permanent ring magnet 240 defining an interior region 250 extending radially inwardly of the ring and an exterior region 252 extending radially outwardly of the ring.

Figures 3, 4 and 5 show schematically the shape of the magnetic field of the arrangement of Figure 2. Figures 3 and 4 show some magnetic field lines/field direction arrows, and Figure 5 shows some contours of constant magnetic flux density. With reference to Figure 3, plasma 212 is primarily generated in a zone which is located within the notional cylinder aligned along the z-axis and having a cross-section that envelopes the antenna 230.

The field lines 260 in the plasma generation zone are evenly spaced and aligned with (substantially parallel to) the z axis. The flux density in this zone is relatively uniform, at around 150 gauss (1.5 x 10' Testa). Figure 4 shows a grid of field directions, each small triangle 264 in the grid indicating the direction of the field at that point. Very generally, the field is stronger closer to the ring magnet, and reduces in flux density with distance from the magnet. The field varies in strength in the region shown in Figure 4 from a maximum of almost 1,000 gauss in the immediate vicinity of the magnet to less than 60 gauss in the region on the opposite side of the antenna from the magnet The shape and intensity of such fields is of course readily understood by those skilled in the art.

The plasma is launched by the antenna in the direction of the block arrows 270 shown in Figure 5. The launch direction of the helicon wave can be influenced by the shape and direction of the antenna used, in the case where the waves are designed to couple into the m=1 mode of the helicon wave (e.g. Nagoya, half helical, Boswell etc). In the case of a symmetric antenna, waves may be launched evenly in both directions. To achieve a stronger launch in one direction, an axial boundary may be placed at a certain distance defined by the axial wavelength of the helicon wave. This boundary will allow the wave which is launched in this direction to be reflected and superimpose on the wave launched in the other direction. This then results effectively in the wave being launched preferentially away from the side with the boundary.

The field generated by a ring magnet typically has a region in which the direction of the field reverses, this region being indicated in Figures 3 and 5 by means of a double-headed arrow 262. The reversal of the direction of the magnetic field at this point may act as a boundary to the zone in which plasma 212 is generated by the antenna. Such a (virtual) boundary may be of use in reducing undesirable plasma-wall interactions. It will also be seen that the field lines, while generally aligned with the plasma generation axis 232 converge slightly within the plasma generation zone in the direction from the antenna to the magnet. The plasma generating arrangement 202 shown in Figures 2 to 5 thus uses the close field (near field) of an annular magnet 240, with plasma 212 being launched (arrows 270) in the direction of converging field lines (towards the magnet 240). The converging field lines allow more intense coupling close to the antenna 230. The sudden drop and field reversal close to the magnet 240 limits the expansion of the helicon wave and effectively acts as a boundary to the plasma generating zone. Magnet topologies can be designed that shape the magnetic field lines where plasma is being generated in a manner that follow paths -where the plasma is likely to be guided/confined -which avoid walls. Such techniques can be used to avoid or reduce undesirable plasma-wall interactions.

The antenna 230 may include on surfaces facing away from the magnet 240 shielding material, so as to prevent the generation of plasma in a region on the side of the antenna opposite from the magnet. There may thus be a region adjacent to the antenna at which the generation of plasma is restricted, for example as a result of at least one shield member and/or as a result of shielding material.

A second configuration of antenna and permanent magnets is illustrated by, and will now be described with reference to, Figures 6 to 8. Similar parts will be labelled with reference numbers the same as those used in Figures 2 to 5, but being one hundred higher (so that the reference numeral 2nn becomes 3nn). Figure 6 shows a plasma generation arrangement 302 comprising an antenna 330, with a plasma generation axis 332, which is located in the internal magnetic field generated by a split ring magnet arrangement. The split ring magnet arrangement consists of two ring magnets 340 aligned with the same axis 332 and which are spaced apart from each other in the direction along the axis 332. In this case, the magnets have thin walls, being less than 10mm in thickness. The diameter of the magnets is more than ten times the wall thickness. The antenna 330 is positioned halfway down, in the direction along the axis 332, the split ring magnet arrangement. The outer diameter of the antenna 330 is about 70mm. The outer diameter of the ring magnets 340 is greater than the outer diameter of the antenna by at least 20%. The target material 306 is off-set from the z-axis 332 in the y-direction and positioned (in the direction of the z-axis) immediately above, in the z-axis direction, the upper ring magnet 340. The substrate (not shown) is off-set from the z-axis 332 in the opposite direction along the y-axis and faces the target. The substrate is thus also positioned (in the direction of the z-axis) immediately above the upper ring magnet 340.

The arrangement shown in Figure 6 has a permanent ring magnet arrangement defining an interior region 350 extending radially inwardly and an exterior region 352 extending radially outwardly from the rings. The antenna 330 and the plasma generating zone is wholly located in the interior region 350.

Figures 7 and 8 show schematically the shape of the magnetic field of the arrangement of Figure 6. With reference to Figure 7, a grid of field directions shown by the array of small triangles 364 shows that the field in the plasma generation zone is substantially along parallel lines aligned with the axis 332. The field varies in strength in the region shown by the triangles 364 shown in Figure 7 by less than 10% from a value that may for example be about 65 gauss, which is sufficient to support helicon waves. The plasma generated has a density of about 5 x 101' m-3. Figure 8 shows some contours of constant magnetic flux density. It will be appreciated that the white zones directly adjacent to the ring magnets 340 are regions of relatively very high magnetic flux and have no contours drawn there separately, for the sake of clarity. It will also be appreciated that the field direction is not necessarily perpendicular to the contours of constant flux (as can be seen from Figure 7 for example).

There are regions where the field strength is much greater than 100 gauss, particularly in the regions very close to the magnet walls. The plasma is launched by the antenna in the direction of the block arrows 370 shown in Figure 7. The substantially parallel field lines effectively confines the plasma so as to avoid interaction with the magnet walls.

In other examples, the split ring magnet arrangement could be replaced by a single ring magnet, in which the antenna is accommodated. Splitting the magnets in this manner has the benefit however of the magnetic field strength varying less along the z-axis, as there might otherwise be a peak midway along the axis 332 within the ring magnet arrangement. Using the internal field of a ring magnet arrangement reduces the amount of necessary magnetic material and may allow the overall dimension of the plasma generation arrangement to be reduced. The arrangement 302 shown in Figures 6 to 8 has a height of about 100mm and a diameter of less than 150mm. The volume of the space it occupies is less than 2,000cm3.

In a variation of the split ring magnet arrangement, there may be two or more such ring magnets, with differing diameters and/or magnetic field strengths, so as to allow for better control over the shape and properties of the magnetic field in the plasma generating zone and/or allowing for the field to confine the plasma appropriately.

A third configuration of antenna and permanent magnets is illustrated by, and will now be described with reference to, Figures 9 to 11. Similar parts will be labelled with reference numbers the same as those used in Figures 2 to 5, but being two hundred higher (so that the reference numeral 2nn becomes 4nn). Figure 9 shows a plasma generation arrangement 402 comprising an antenna 430, with a plasma generation axis 432, aligned with a single ring magnet 440. The antenna 430 is positioned, in the z-axis direction, between the ring magnet 440 and a further stick magnet 442, which lies along and is aligned with the same axis 432.

The upper end of the ring magnet 440 is less than 50mm from the bottom end of the stick magnet 442, as measured in the z-axis direction. In this case, the ring magnet has thin walls, being less than lOmm in thickness, and is less than 50mm in height, as measured in the z-direction. The diameter of the ring magnet is more than ten times the wall thickness. The outer diameter of the antenna 430 is about 50mm. The outer diameter of the ring magnets 440 is greater than the outer diameter of the antenna by at least 20%. The target material 406 is off-set from the z-axis 432 in the y-direction and positioned immediately below, in the z-axis direction, the ring magnet 440. The substrate (not shown) is off-set from the z-axis 432 in the opposite direction along the y-axis and faces the target. The substrate is thus also positioned fin the direction of the z-axis) immediately below the ring magnet 440.

The arrangement shown in Figure 9 has a permanent ring magnet arrangement defining an interior region 450 extending radially inwardly and an exterior region 452 extending radially outwardly from the rings. If the interior region is considered to extend in the z-axis beyond the top and bottom of the ring magnet, to form an infinitely long notional cylinder, then the antenna 430 and the plasma generating zone would be wholly located in such a notional cylinder.

Figures 10 and 11 show schematically the shape of the magnetic field of the arrangement of Figure 9. With reference to Figure 10, a grid of field directions shown by the array of small triangles 464 shows that the field in the plasma generation zone is substantially along parallel lines aligned with the axis 432. The field varies in strength in the plasma generating from about 50 gauss to about 75 gauss. The plasma generated has a density of the order of 1017 m'. Figure 11 shows some contours of constant magnetic flux density, relative to the location of the antenna and the magnets, by way of comparison with the other figures showing such contours. It will be appreciated that the white zones directly adjacent to the permanent magnets 440, 442 are regions of relatively very high magnetic flux have no contours drawn there separately.

The plasma is launched by the antenna in the direction of the block arrow 470 shown in Figure 10, which is thus in the direction of the ring magnet 440. It will be seen that in this case, the launch direction is with the direction of the field lines, in contrast to other illustrated examples, in which the launch direction is against the direction of the field lines.

The substantially parallel field lines effectively confine the plasma so as to avoid interaction with the magnet walls. The stick magnet 442 has a magnetic North at one end and a magnetic South at the opposite end and is oriented such that the magnetic field lines from the end of the stick magnet 442 nearest the ring magnet 440 are in the same direction as the internal magnetic field in the ring magnet 440. Such a combination of a relatively small stick magnet with a single ring magnet enables the field on the opening of the ring magnet between the antenna and the ring magnet to be opened up to create more uniform parallel field lines. This in turn allows for the use of a relatively small ring magnet.

A fourth configuration of antenna and permanent magnets is illustrated by, and will now be described with reference to, Figures 12 to 14. Similar parts will be labelled with reference numbers the same as those used in Figures 2 to 5, but being three hundred higher (so that the reference numeral 2nn becomes 5nn). Figure 12 shows a plasma generation arrangement 502 comprising an antenna 530, with a plasma generation axis 532. The antenna is surrounded by three stick magnets 544 arranged in a notional ring 546. The magnets 544 in the ring are spaced apart by at least 30mm in the circumferential direction around the ring. The antenna 530 is positioned, in the z-axis direction, near to the midway along the height of the stick magnets (in some examples, the antenna may be off-set slightly from this midway point to be at the 25% to 45% region, so as to enable more of the uniform magnetic field to be used).

The plasma is launched upwards (in the orientation shown in Figures 12 to 14). The diameter of the notional ring 546 of magnets is less than 100mm. The diameter of the notional ring 546 is greater than the outer diameter of the antenna -such that the outer diameter of the antenna is spaced apart from the notional ring 546 from each of the stick magnets. The target material 506 is off-set from the z-axis 532 in the y-direction and positioned immediately above, in the z-axis direction, the magnets 544. The substrate (not shown) is off-set from the z-axis 532 in the opposite direction along the y-axis and faces the target. The substrate is thus also positioned (in the direction of the z-axis) immediately above the ring of magnets 544.

The arrangement shown in Figure 12 has a ring of magnets 544 defining an interior region 550 extending radially inwardly from the infinitely long notional cylinder having as its cross-section the circle 546 and having axis 532 as its longitudinal axis. There is thus an exterior region 552 extending radially outwardly from such a notional cylinder. The antenna 530 and the plasma generating zone are both located in that notional cylinder.

Figures 13 and 14 show schematically the shape of the magnetic field of the arrangement of Figure 12. With reference to Figure 13, a grid of field directions shown by the array of small triangles 564 shows that the field in the plasma generation zone is substantially along parallel lines aligned with the axis 532. The field in the plasma generating zone is a constant 80 gauss (within +1-10%) along the central axis 532 for at least 30mm in the z-direction over a diameter of at least 20mm. The plasma generated has a density of the order of 101' ni-3. Figure 14 shows some contours of constant magnetic flux density, relative to the location of the antenna and the magnets, by way of comparison with the other figures showing such contours. It will be appreciated that the white zones directly adjacent to the permanent magnets 550, 552 are regions of relatively very high magnetic flux have no contours drawn there separately.

The plasma is launched by the antenna in the direction of the block arrow 570 shown in Figure 13, towards the target 506 (in the z-axis direction). The substantially parallel field lines effectively confine the plasma so as to avoid interaction with the stick magnet walls. The field produce by the stick magnets arranged in a ring results in a similar field to a ring magnet.

However, the field requirements can readily be achieved using as little as three stick magnets (possibly only two in some examples) as shown by Figures 12 to 14. Combination of different sizes and positions of multiple stick magnets may allow the shape and strength of the magnetic field to be tailored for specific applications such, for example, reducing/minimizing plasma expansion in one direction while increasing/optimizing for another.

Other arrangements of magnets and antennae are of course with the scope of the present invention, and there will be other topologies that provide evenly distributed field lines, aligned with a helicon plasma generation direction, the magnetic field with the plasma generation zone having a substantially constant field strength. One such example not presently illustrated may comprise two spaced apart parallel plate magnets with field lines extending normal to the plate surfaces for the majority of the region directly between the two plates.

It will be noted from the above examples, that it has been found that small divergence or convergence of field lines might be beneficial. However, in such cases it is desirable to arrange the apparatus such that field lines from the region near the antenna leave the plasma generating zone without termination to any nearby wall or solid surface. Regions with field strength of less than a minimum threshold level, say 5 gauss for example, may act as a virtual boundary to the plasma and should preferably be designed outside of the desired plasma generating zone. Such a virtual boundary may be of use in avoiding undesirable plasma-wall interactions.

Referring to Figure 15, there is illustrated schematically an example method 1000 of sputter deposition of target material to form a thin film crystalline layer (i.e. non-amorphous layer) on a web of substrate. The method uses an apparatus as shown in Figure 1, and may incorporate any of the helicon plasma generating arrangements as shown in Figures 2 to 13. In the method, the web (e.g. comprising a polymer sheet) of substrate is guided by a substrate guide, such as a roller, along a curved path. A deposition zone is defined between the substrate guide and a target portion supporting the target material. The process chamber is evacuated until a sufficiently low pressure is reached. In this example, the working pressure of the system is 0.0050 mBar (different working pressures may be appropriate depending on the requirements of the particular application). The method comprises a step 1002 of generating a helicon plasma remotely from a plasma target or targets, that is generating plasma without using the target in the generation of the plasma. It will be understood that the plasma may be remotely generated in this sense, yet be generated directly adjacent to the target. The plasma is generated for the purpose of plasma sputtering. There is a step 1004 of exposing the plasma target or targets to the plasma, thereby generating sputtered material to be ejected from the target or targets. Power may be applied to the target(s) to encourage the plasma to interact with the target to cause sputtering. The sputtered material is then (step 1006) deposited directly onto the substrate to form a crystalline layer in situ.

The method of depositing a crystalline layer of material on the substrate surface may form part of a method of manufacturing an electronic component for use in an electronic product. Such a method may include forming a multilayer sheet of different materials, one of which being the crystalline layer formed by step 1006. There may be a further step 1008 of integrating such a multilayer sheet, or a part thereof, in the electronic component. The electronic component may be a solid state battery for example, and the crystalline layer of material may be LiCo02. In such an example, the target(s) may each comprise LiCo02 material.

In this example, the use of high energy high density uniform plasma enables the material to be deposited as a crystalline material in a relatively high energy state. In the case where the material deposited is LiCo02, the material is optionally deposited with a hexagonal and/or rhombohedral lattice structure, optionally haying a form which is in the RIn space group (also referred to as the "R 3(bar) 2/m" space group or space group 166). This structure has a number of benefits, particularly when the LiCo02 material is being used as the cathode of an energy cell or battery, such as having a relatively greater accessible capacity and high rate of charging and discharging compared to the low energy structure of LiCo02, which has a structure in the Fd3m space group (a face centred cubic structure). The Rin space group is regarded as having better performance in typical battery applications due to enhanced reversibility and fewer structural changes on lithium intercalation and de-intercalation.

Therefore crystalline LiCo02 in the R-3m space group is favoured for solid state battery applications.

During performance of the method, crystalline material may grow substantially epitaxially from the surface on or supported by the substrate. Epitaxial growth is favoured, particularly when the crystalline material is being used for electrical devices, as it allows for ions to intercalate and de-intercalate more easily. The crystals of the crystalline material are optionally aligned with the (101) and (110) planes substantially parallel to the substrate. This may be beneficial as it means that the ion channels of a thin film crystalline material are orientated perpendicular to the substrate, making for easier intercalation and de-intercalation of the ions. With a lithium ion battery for example, this can improve the working capacity and the speed of charging of the battery.

The material may be deposited as a layer that is approximately 1 micron thick. In other examples, the material is deposited as layer that is approximately 5 microns thick. In yet further examples, the material is deposited as a layer that is approximately 10 microns thick.

In this example, the working pressure is above a lower bound below which crystalline material in the layered oxide structure does not form, but below an upper bound above which observable damage is caused to the substrate. The working distance is shorter than an upper bound above which crystalline material in the layered oxide structure does not form, and longer than a lower bound below which the energy of the deposition causes observable damage to the substrate, or unfavourable oxide states to form.

The average crystallite size of the crystallites which form on the film in this example is around 20 nm. In other examples, the average crystallite size of the crystallites which form on the film is around 50 nm.

Whilst the forgoing description has been described and illustrated with reference to particular examples, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. Some such variations will now be described, by way of example only.

In relation to the embodiment shown in Figure 12, a further stick magnet could be positioned on the z-axis, but spaced apart in the z-axis direction, from the ring of magnets, in a manner similar to the stick magnet of Figure 9 being spaced apart from the ring magnet of Figure 9.

The working pressure of the system may be 10-3 mBar or less.

In other examples the deposited material may take a semi-crystalline form, or be amorphous.

There may be example embodiments where multiple successive layers of different material are deposited on a substrate. At least some of those multiple layers may be semiconducting layers. Such layers may be deposited as part of a method of manufacturing a semi-conducting device or part thereof In some possible examples, it may be that deposition of one or more of the layers is performed by another appropriate deposition technology such as thermal evaporation, electron beam evaporation, pulsed laser deposition, or other thin film deposition technology.

It may be that in certain examples deposition occurs under a reactive gas atmosphere, such as ionised nitrogen or oxygen gas.

In some examples, it may be that plasma generating source could be operated without a continuous supply of process gas. In such a case, the process may be started with process gas, but then once sputtering has been initiated, the evaporated sputter material in the gas phase may itself provide enough density to act as an alternative to the process gas. Such a mode of operation may be referred to as gas-less self-sputtering and would require highly ionized high rate sputtering.

The use of plasma generated using helicon waves and/or with antenna capable of generating helicon waves has been described with reference to the figures in relation to a method of manufacturing a crystalline layer of material on a surface via sputter deposition. Plasma generated by the antennae and permanent magnet arrangements could be used in other applications, such as for example etching or other processes that would benefit from the generation of the high density plasma.

The above examples are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments. Equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

CLAIMS1. A method of manufacturing a layer of material on a surface, wherein the method comprises the following steps: a helicon plasma source generating, in a plasma generating zone and along a plasma generating axis, a plasma remote from at least one sputter target, the helicon plasma source comprising (a) one or more antennae and (b) one or more permanent magnets arranged to generate a magnetic field, proximate to the magnet(s), which is along the plasma generating axis and in the plasma generating zone, the plasma causing material to eject from the sputter target(s), and depositing material ejected from the sputter target(s) onto a surface of or supported by a substrate to form the layer of material on the surface.
2. A method according to claim 1, wherein the one or more permanent magnets comprises a ring magnet or a ring of magnets defining an interior region extending radially inwardly of the ring(s) and an exterior region extending radially outwardly of the ring(s).
3. A method according to claim 2, wherein the plasma generating zone is located at least partially in the interior region.
4. A method according to claim 2 or claim 3, wherein the plasma generating axis defined by the one or more antennae is along an axis defined by the ring(s).
5. A method according to any of claims 2 to 4, wherein the plasma is launched in a direction towards the ring(s)
6. A method according to any of claims 2 to 5, wherein there are two or more such ring(s), including a first ring haying a first radius and a second ring having a second radius that is different from the first radius.
7. A method according to any preceding claim, wherein the one or more permanent magnets are arranged to generate a magnetic field in the plasma generating zone with magnetic field lines, in the near-field region, which are aligned with the plasma generating axis defined by the one or more antennae.
8. A method according to any preceding claim, wherein the one or more permanent magnets are arranged to generate a magnetic field with one or more regions having a local magnetic field which defines a boundary to plasma generating zone
9. A method according to any preceding claim, wherein the one or more permanent magnets are arranged to generate a magnetic field that includes a field-reversal region which acts as a boundary to the plasma so generated.
10. A method according to any preceding claim, wherein the magnetic field is generated 15 by two or more spaced-apart permanent magnets.
11. A method according to claim 10, wherein at least two of the spaced-apart permanent magnets are spaced apart in the direction of the plasma generating axis.
12. A method according to claim 10 or 11, wherein at least two of the spaced-apart permanent magnets are spaced apart in a circumferential direction about the plasma generating axis.
13. A method according to any of claims 10 to 12, wherein one of the spaced-apart 25 permanent magnets is in the form of a stick magnet
14. A method according to any of claims 10 to 13, wherein at least one of the antennae is located between at least two of the spaced apart magnets.
15. A method according to any preceding claim, wherein the plasma in the plasma generating zone has a density of at least 1018111-3.
16. A method of manufacturing at least part of an electronic component for use in an electronic product, the method including forming a multilayer sheet of different materials, integrating the multilayer sheet or a part thereof in the electronic component, or part thereof, wherein at least one of the layers of the sheet is a layer of conducting or semiconducting material made by performing the method of any preceding claim.
17. A method according to claim 16, wherein the electronic component is a battery, a functional layer of a battery, an energy storage device or a cell of battery.
18. A helicon plasma reactor including a a process chamber, a helicon plasma source for generating plasma with helicon waves, the helicon plasma source defining a plasma generating zone and comprising (a) one or more antennae and (b) one or more permanent magnets arranged to generate a unidirectional magnetic field of uniform strength across the entire extent of the plasma generating zone, the magnetic field in the plasma generating zone having an average flux density of between 50 to 100 gauss, and a device for holding a substrate and/or a target material, and wherein the helicon plasma reactor is configured to perform the method of any preceding claim.
19. A helicon plasma reactor according to claim 18, wherein the one or more antennae of the helicon plasma source are located within the process chamber.
20. A helicon plasma source configured for use as the helicon plasma source referred to in any preceding claim.