GB2599393A

GB2599393A - Method and apparatus for sputter deposition

Info

Publication number: GB2599393A
Application number: GB2015461.3A
Authority: GB
Inventors: Edward Rendall Michael
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
Also published as: CN114318273A; GB202015461D0

Abstract

A reactive ion source of a sputter deposition system 100 comprises an electrically powered antenna 116, wherein the antenna 116 has a substantially elongate shape. A housing 118 is provided which at least partially surrounds the antenna 116, an inlet 126 for supplying a reactive gas into the housing, and an outlet 128 from the housing configured such that reactive ions can pass through it. The antenna 116 is configured to apply an electromagnetic field to the reactive gas such that a plasma B is formed that comprises reactive ions. Magnetic assembly 108 is also provided to accelerate and focus the ions of the plasma such that the plasma and reactive ins maintain their directionality and geometry.

Description

METHOD AND APPARATUS FOR SPUT IER DEPOSITION

Field of the Invention

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

Background of the Invention I 0

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 ionised 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. Reactive sputtering involves performing sputter deposition in the presence of a reactive gas. A reactive gas is herein defined as a gas that is ionised as part of the deposition process to generate reactive ions, which react with the sputtered material as its travels through a chamber and/or is deposited on a substrate. -2 -

Alternatively, some known methods use reactive ion sources, which provide pre-ionised material into the chamber. However, neither of these methods can provide particularly dense or localised volumes of reactive ions in a deposition chamber. It is desirable to provide a reactive ion source that can provide very dense, localised regions/geometries of ions to allow for improved throughput and film quality in industrial applications of reactive sputter deposition systems.

W02011131921 discloses a sputter deposition apparatus in which a uniform plasma of density 10" cm' is generated by an elongate gas plasma source separately from a target. This source is discussed as optionally being used in reactive sputtering.

In W02011131921, the plasma is generated in an atmosphere separate from that of the plasma deposition system, and significant electromagnetic apparatus within the plasma chamber is required in order to shape and confine the plasma in the volume of the plasma chamber. It desirable to provide a reactive ion source that can produce plasma within the volume of the plasma chamber, that does not require a discreet chamber. It is also desirable to provide a reactive ion source that can provide high densities of reactive ions to locations within a plasma chamber without the need for significant electromagnetic apparatus to confine the plasma within the plasma chamber.

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 reactive ion source of a sputter deposition system. 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 method of forming a layer of electrolyte on a substrate. The invention also concerns solid state battery half-cells, solid state battery cells and solid state batteries made in accordance with such methods.

Summary of the invention

According to a first aspect of the invention there is provided an ion source, for example and ion source for producing reactive ions in a sputter deposition system. The ion source comprises an electrically powered antenna. In examples, the antenna has a substantially elongate shape. In examples, the ion source comprises a housing, for example a housing which at least partially surrounds the antenna. The ion source -3 -comprises an inlet for supplying a reactive gas, for example into the housing. The ion source comprises an outlet configured such that reactive ions pass through it, for example from the housing. The antenna is configured to apply an electromagnetic field to the reactive gas to form a plasma comprising the reactive ions.

It may be that in examples, the elongate antenna may be elongate in the sense that those parts of the antenna that actively contribute to the generation of plasma have a 3-D footprint which has a maximum dimension (i.e. "length" or "cross-sectional length") that lies along an axis, that (length) dimension being at least twice, and preferably at least three times the maximum dimension taken about any orthogonal axis (e.g. a width). It may for example be that the elongate antenna is relatively elongate and flat, such that it has a length that is more than three times its width and, optionally, also more than five times (possibly more than ten times) its depth. The antenna may have a cross sectional long dimension in excess of 400mm, optionally 1000mm in length. The cross-sectional long dimension may be no more than 1000cm in length.

According to a second aspect of the invention there is provided a reactive ion source of a sputter deposition system, comprising: an electrically powered antenna, wherein the antenna has a substantially elongate shape, a housing which at least partially surrounds the antenna, an inlet for supplying a reactive gas into the housing, and an outlet from the housing configured such that reactive ions can pass through it, wherein the antenna is configured to apply an electromagnetic field to the reactive gas such that a plasma is formed that comprises reactive ions.

For the avoidance of doubt, the statements below relate to both the reactive ion source of the first and second aspects of the present invention.

The reactive ion source may be suitable for placing in a sputter deposition chamber. The reactive ion source may have a compact design.

The terms "reactive gas" and "reactive ions" are well known to the person skilled in the art. A reactive gas refers to a gas that, once ionised, results in reactive ions. A reactive gas may not be particularly reactive in its gaseous form (for example, a diatomic gaseous form), but may be very reactive once ionised.

The plasma antenna may be substantially elongate in shape and may extend in a direction having a length. The antenna, or a part thereof, may have a length. The length of the antenna may have a shape which generally extends in a single direction. -4 -

The length of the antenna may extend between first and second locations, in a direction that is substantially linear (e.g. extending in a generally straight line). The plasma antenna may have one or more straight sections. For example, there may comprise a first straight section and a second straight section (which is optionally parallel to, or extends in the same general direction as, the first section), such that in use there is a plasma generation region which is located between the first and second straight sections.

The antenna comprises an electrical conductor, for example copper. In examples, the antenna can be considered to be such an electrical conductor, for example a wire or tube of some form. In other examples, the electrical conductor includes other materials. The plasma antenna may be a copper antenna. The plasma antenna may be enclosed in a tube casing, such as a quartz tube.

The plasma antenna may be tubular in part, which may for example, facilitate cooling of the antenna during use.

The plasma antenna may be capable of receiving a voltage of at least 1 kV, optionally at least 2 kV and optionally 5 kV. The plasma antenna may be powered by an RF power source.

The antenna may be driven at 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.

In examples, the plasma may be generated with the use of at least two lengths of plasma antenna being spaced laterally apart from each other (and for example parallel to each other). The two lengths of plasma antenna may be driven by a common RF current source and/or may be electrically coupled to each other.

It will be appreciated that in use, the plasma antenna or one or more portions thereof, is configured (i.e. typically as a result of the application of radio frequency (RF) electrical power), to excite a gaseous medium thereby generating a plasma, for example forming a plasma along the length of the antenna. Such a plasma may, for example, be generated within the housing in which the antenna is located. In examples, the plasma can be generated along the entire length of an antenna within the housing. Alternatively or additionally, the plasma may propagate throughout a process chamber in which the sputtering process (i.e. sputter deposition) takes place. The plasma may be -5 -generated in an electrically insulated cavity. The electrically insulated cavity may be defined by the housing The outlet may be shaped such that the speed at which plasma/reactive ions leave(s) the housing through the outlet is higher than the speed at which molecules of gas flow into the inlet.

The outlet may be shaped such that a plume of plasma comprising reactive ions forms from it.

The outlet may, at least in part, comprise a frustoconical shape. The outlet may be substantially "nozzle" shaped. This allows the plume of plasma to be focused onto a substrate at a high density.

The outlet may comprise a substantially elongate shape. This allows for a sheet-type geometry of plasma to propagate from the source. The outlet may be shaped in a substantially "letterbox" -type shape. Such wide-angle apertures find especial utility where large dimensioned substrates are to be processed at high throughput rates, for example, in roll-to-roll (or "web") processing.

The outlet may comprise an aperture, which is configured to be supplied with an electric charge. The aperture can be arranged such that an electrical charge can be induced onto it. The aperture can be configured to receive an electric charge, or otherwise become electrically charged, during a sputter deposition process. There may be a voltage bias applied to the aperture.

In use, supplying an electric charge to the aperture may accelerate the reactive ions through the outlet.

The aperture may be capable of being supplied with a positive charge or negative charge. The amount of charge applied to the aperture may optionally be tuneable, such that the amount of charge applied to it can be varied. The aperture may comprise an electromagnetic lens. The aperture may comprise appropriate apparatus such that an ion beam forms as the plasma passes through the aperture. Such appropriate apparatus may include an accelerator grid, a screen grid and a neutraliser.

The aperture may be capable of being supplied with a voltage bias of at least 300 V, preferably 400 V and even more preferably 500 V. Generally, it is thought that the higher the voltage applied to the aperture, the higher the exit speed of reactive ions that pass through the aperture.

An electrically charged aperture may have the effect of accelerating the ions out of the outlet. When using reactive ions from a conventional reactive ion source in a -6 -conventional sputter deposition process, the reactive ions loose their relative directionality or geometry due to the low vacuum in the sputter deposition chamber, causing the reactive ions to disperse throughout the sputter deposition chamber. In contrast, the present invention allows a directional flow of reactive ions, or a particular geometry of reactive ions (for example, a plume of reactive ions) to propagate over a longer distance in the sputter deposition chamber than would otherwise be possible, before dispersing and losing its relative directionality or geometry. Such an ion source may be an example of a linear ion source.

This is a particularly surprising finding by the applicant, as it has previously been thought that reactive ions, when introduced to a sputter deposition chamber at process vacuum (for example, a vacuum of 10' mBar or stronger) will disperse instantaneously at the point of entering the chamber. It was not previously thought possible to maintain the flow or directionality of the reactive ions as they enter the chamber without significant electromagnetic confinement of the ions within the chamber.

The ion source may, in use, (i.e. in a sputter deposition chamber under a vacuum of at least 10 mBar), produce a plume of plasma that can propagate and maintain its directionality and/or geometry over a distance of at least 1 cm. Preferably, the reactive ion source is capable of producing a plume of reactive ions that extends over a distance of at least 1 cm, preferably at least 2 cm and preferably at least 3 cm.

The housing may be configured to be supplied with a positive electrical charge. The housing may define an electrically insulated cavity.

The positive charge applied to the housing may accelerate the reactive ions through the outlet. Without wishing to be bound by theory, it is believed that plasma potential is increased, such that it is energetically favourable for the reactive ions to leave the housing through the outlet. It may be that such a lifting of the plasma potential with respect to ground can provide an acceleration voltage to the ions as they leave the chamber The acceleration of the ions may occur as a result of the ions entering a sheath in front of a grounded object (which may for example be a grounded substrate).

The apparatus may, in use, cause plasma to be generated and maintained in the gaseous medium of its surroundings. By this, what is meant is that the atmosphere in which the remotely generated plasma is created is within the volume of space defined by any chamber that contains the apparatus of the sputter deposition process. For example, this volume of space could be within a deposition chamber, and within the -7 -volume/chamber much of the apparatus necessary for sputter deposition, such as one or more targets and a substrate may be located. The apparatus may be in fluid communication with the chamber.

The plasma source may be said to be a localised plasma source located within the sputter deposition chamber. The applicant has found that, surprisingly, the high density plasma can be generated and shaped within the sputter deposition chamber without the plasma first being generated and drawn from a (discreet) plasma chamber. In other words, the plasma of the present system is generated, maintained and shaped in a working space of the sputter deposition chamber in which it is mounted, 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 chamber, as seen in the systems of the prior art. Thus, at least a part of the plasma source (i.e. antenna or housing) forms an integral or integrated element of the sputter deposition chamber, without the necessity of the housing or antenna being surrounded by a distinct plasma chamber (i.e. separate from any sputter deposition process plasma chamber), or the housing itself being part of a distinct plasma chamber. Likewise, the plasma of the present system is generated in the process atmosphere of the sputter deposition chamber, and not in a discreet, or otherwise segregated (in relation to the sputter deposition chamber) atmosphere.

The apparatus may be capable of forming and shaping a localised linear plasma formed in the sputter deposition chamber with a density greater than loll cm* Optionally, the apparatus may be capable of forming and shaping a localised linear plasma formed in the sputter deposition chamber with a density greater than 10" cm* The inlet may be fluidly connected to a source of reactive gas. Having the inlet provided with a source of reactive gas advantageously ensures that the housing and the plasma generating antenna within it are provided with a high flow rate and/or volume of reactive gas.

Alternatively, the inlet may be open to the atmosphere of the volume in which sputter deposition process takes place. The volume in which the sputter deposition process takes place may be within a sputter deposition chamber. The reactive gas may be introduced into the sputter deposition chamber, and thereafter diffuse into the housing through the inlet.

There may be an electrically conductive shield member. Such a shield member may restrict (for example prevent) the generation of plasma at one or more regions -8 -proximal to the antenna. There may be a region adjacent to the antenna between the first location and the second location at which the generation of plasma is curtailed and/or inhibited as a result of the at least one shield member. This can improve electrical efficiency as a result of reducing undesirable recombination of plasma ions and/or localise the plasma to be close to the outlet.

There may be a ferromagnetic or ferrimagnetic material arranged to partially surround the antenna, preferably so as to increase the magnetic flux density in the plasma generation region. The use of such material may enhance the generation of plasma at one or more regions and/or localise the plasma to such region(s). This can improve electrical efficiency as a result of reducing undesirable recombination of plasma ions and/or localise the plasma to those regions where it is needed (for whatever process or use the plasma is provided for). A ferromagnetic or ferrimagnetic material arranged to partially surround the antenna so as to increase the magnetic flux density in the plasma generation region may herein be referred to as a focussing member.

The focussing member may be shielded (i.e. with shielding) from external magnetic fields, i.e. magnetic fields not generated by the antenna / generated externally to the plasma antenna assembly. External magnetic fields may be present at the focussing member due to one or more magnets (e.g. electromagnets) located in the plasma generation apparatus which confine and/or propagate the plasma to a location that is remote from the plasma antenna. Hence, the focussing member may be shielded from the magnetic field generated by the one or more magnets.

It will be appreciated that the focussing member may not be completely shielded from external magnetic fields. For example, the effect of the magnetic field generated by the one or more magnets may be measurable (i.e. non-negligible) at the focussing member. However, the shielding may reduce the strength / effect of that magnetic field such that the ferromagnetic or ferrimagnetic material of the focussing member is not saturated by external magnetic fields, and can thereby effectively re-direct the magnetic field generated by the antenna in order to increase the magnetic flux density in the plasma generation region.

The focussing member may be coated with a shielding material. The shielding material may comprise nickel. The shielding material may be a nickel alloy, for example MuMetal0 alloy by Magnetic Shield Corporation, Bensenville, IL, USA. Alternatively or additionally, parts of the housing containing the antenna may be provided (e.g. coated) with shielding material. Alternatively or additionally, one or -9 -more standalone shield elements may be provided in the region between the focussing member and the one or more magnets in the plasma generation apparatus.

The ferromagnetic or ferrimagnetic material of the focussing member may be ferrite.

There may be one or more magnets provided, for example separately from the plasma antenna. Such magnet(s) may be configured such that the plasma is confined and/or propagated in an orthogonal direction relative to the length of the antenna, for example through the outlet and across a sputter deposition chamber. In the case where the antenna is at least partially located in a sputter deposition chamber, one of the one or more magnets may also be located within the deposition chamber. The magnet(s) can be positioned within the sputter deposition chamber in order to reduce the footprint of the apparatus. Furthermore, the magnets can be manipulated within the space of the deposition chamber to tune, focus, confine and/or direct the plasma formation. Thus, the plasma can be generated and shaped/confined so that it is in the correct form as necessary for the sputter deposition chamber.

The one or more magnets may be provided either inside, or outside the housing. The one or more magnets are preferably provided in close proximity to the outlet. Providing the one or more magnets in close proximity to the outlet may improve the directionality and/or geometry of the plasma as it leaves the outlet. In use, the one or more magnets may have a synergistic affect with an electrically charged aperture and or a positively charged housing in providing a plasma with exceptionally high geometry or directionality. The one or more magnets are optionally in contact with the housing.

The one or more magnets may be used to confine, shape and/or propagate the plasma generated by the antenna/antennae as a linear plasma, for example across a deposition chamber, optionally so as to take the form of a sheet or slab of thin plasma originating from the antenna. This is in contrast to inefficient large area plasma processing apparatus of the prior art where many antenna and magnets are arranged to create an unfocused plasma cloud or beam that can brought into contact with a process surface or target. It may be that the plasma is both magnetised at an appropriate level and that the magnetic field is orientated relative to the antenna such that the RE power applied by the antenna is propagated over a far greater spatial extent than is usual in other plasma generating systems. It has been surprisingly found that the plasma of embodiments of the present invention can be manipulated with a magnetic field strength as low as 4.8 gauss, which is an order of magnitude less than the operating regions of -10 -the prior art (50 -200 gauss). The manipulation of the plasma by use of a much lower magnetic field strength allows the use of multiple plasma sources within a single process chamber without detrimental or unintended cross plasma source interference, allowing multiple simultaneous plasma processes to be conducted in the same process chamber.

In examples, the plasma is shaped by one or more magnets. In examples, there is a single plasma source (i.e. reactive ion source) generating the sheet of plasma. In such a case, the plasma may have a substantially uniform density along the entire length of the antenna. This is in contrast to the multi-antenna inductively coupled plasma of the prior art that requires multiple tuned antenna and magnets to carry out wide-area plasma processing.

The reactive ion source optionally further comprises a rotatable mounting device. The rotatable mounting device allows the reactive ion source to be rotatably mounted within a sputter deposition system. The reactive ion source may be configured to be rotatably mounted within a sputter deposition system.

The reactive ion source being rotatable allows the outlet to be oriented towards the surface of a substrate positioned in a sputter deposition chamber. This allows the density of reactive ions to be higher nearer the substrate. This is particularly important during the reactive sputtering of materials which require an abundance of reactive ions in order to form. An example of one such material is lithium phosphorous oxy-nitride ("LiPON"). The sputter deposition ion source would use nitrogen as a reactive gas in this example. The quality of a LiPON film that forms as a thin-film from a reactive sputtering process depends on the availability of reactive nitrogen ions to coordinate bond into the structure of the film, as it forms. In effect, when forming a high quality film, the aim is to form as many bonds as possible between nitrogen ions and the phosphate groups of the sputtered material. Thus, the higher the density of reactive nitrogen ions near the substrate, the higher the probability of bonds forming and thus the higher the quality of film that forms.

The reactive ion source may be capable of being used additionally or alternatively as an ion implantation device. The reactive ion source being rotatable may allow it to alternatively or additionally be used as an ion implantation device. Ion implantation is a low-temperature process by which ions of one element are accelerated into a solid target (which may be the substrate and or layers of material deposited onto said substrate), thereby changing the physical, chemical, or electrical properties of the target. Ion implantation is particularly useful in preparing the surface of a deposited layer of a thin-film device, such that surface of the deposited layer provides a high quality interface for any subsequently deposited layers of material. The reactive ion source may optionally, in use, act as a reactive ion source during deposition, but also as an ion implantation device during, or pre-/post-deposition. The device being able to perform both of these roles advantageously saves space in any sputter deposition chamber in which it is located, when compared to a sputter deposition system that has both a reactive ion source and an ion implantation device. In the case where the reactive ion source is used as an ion implantation device, electrons may be removed from the plasma before it passes through the outlet, such that only positively charged reactive ions leave the outlet.

Preferably, the reactive ion source may, in use, have an ionisation efficiency of at least 40% percent. The ionisation efficiency is defined as the percentage of inert molecules of gas that are transformed into reactive ions by the apparatus. The inert molecules of gas are optionally split into atoms, before being transformed into reactive ions. The ionisation efficiency is optionally at least 60%, and preferably at least 70%.

The ionisation efficiency is optionally substantially 99%. The ionisation efficiency is optionally substantially 100%.

The reactive ion source may be an ultrapure ion source. An ultrapure ion source has a very low amount of contaminants present in it. An ion source which has a very high ionisation efficiency usually produces a volume of reactive ions with a very low number of contaminants present in it Contaminants may be, for example, stable, diatomic gas that has not been ionised.

Having a high ionisation efficiency is important when an especially pure reactive ion source is needed. For example, in the deposition of lithium phosphorous oxy-nitride "LiPON" using reactive sputtering techniques, there are two common issues. The first issue is that the density of reactive ions near the surface of the substrate/the deposited film is not high enough for sufficient nitrogen ions to be incorporated into the atomic structure that forms. This results in not all of the deposited film forming as LiPON. The second issue caused by relatively low purity reactive ion sources during the production of LiPON is that diatomic N2 implants or is otherwise included into the surface of the material as it forms. The implantation or inclusion diatomic N2 disrupts the atomic structure of UPON that forms, and results in a lower quality film, with a high number of structural and atomic defects.

-12 -The reactive ion source could also be applied to coating processes based on the technique of Plasma Enhanced Chemical Vapour Deposition (PECVD) The reactive ion source could also be used as a "plasma assist" tool for other coating processes, as is typically used in evaporative coating process tools.

The reactive ion source could also be used for plasma etching, and may be used for Reactive Ion Etching, or Inductively Coupled Etching. In this connection, the reactive gas may comprise any of methane, hydrogen, fluorine, chlorine, or sulphur hexafluori de.

In accordance with a third aspect of the invention, there is provided a method of manufacturing a layer of material, the method comprising: generating and maintaining a plasma which comprises reactive ions in the gaseous medium of a sputter deposition chamber, remote from one or more material sputter targets, from the reactive ion source the first or second aspect of the invention; generating sputtered material from the one or more targets using the plasma; and, depositing sputtered material on a substrate, thereby forming a layer of material on the substrate.

It should be understood that the method of the third aspect of the invention optionally incorporates the use of the apparatus of the first aspect or second aspect of the invention. Any features in relation to the first/second aspect of the invention are optionally also applicable and/or relevant to the third aspect of the invention.

The target may be lithium phosphate (Li3PO4). The target may alternatively be a combination of elemental lithium targets and one or more composite targets. The target assembly may include a number of targets, with distinct regions of lithium and/or phosphorous containing compounds, elemental lithium, and/or lithium oxide. In other examples, the deposition additionally occurs in a reactive oxygen atmosphere.

The reactive gas may be nitrogen. Nitrogen may be introduced through an inlet, such that a plasma comprising reactive nitrogen ions forms. The plasma may be used to deposit nitride thin films, for example, to deposit LiPON.

As mentioned above, the term reactive gas means a gas that is ionised as part of a deposition process to generate reactive ions. It may thus be the case that the reactive gas is an inert gas. The reactive gas may be a diatomic gas. For example, oxygen gas can be introduced into the sputter process in order to deposit oxide thin films, for -13 -example to deposit alumina by sputtering of an aluminium target in the presence of oxygen gas or silica by sputtering of a silicon target in the presence of oxygen gas. The reactive gas optionally comprises at least one of the following species: Mike's exhaustive list of possible use gases to be inserted here.

The substrate may be a polymer substrate, such as PEN or PET. The substrate may be especially suitable for roll-to-roll and/or "web processing" applications.

The substrate may have a thickness of from 0.1 to lOpm. The deposited so formed on the surface / the substrate may have a thickness of from 0.001 to 1 Opm. 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 1 cm', as measured on the surface opposite to said surface on which the material is deposited and as averaged over a period of 1 second, is no more than 500 degrees Celsius.

The temperature of the substrate is optionally no more than 200 °C at any point throughout the deposition process.

In accordance with a fourth aspect of the invention there is provided a method of manufacturing a layer of material, the method comprising: generating and maintaining a plasma which comprises reactive ions in the gaseous medium of a sputter deposition chamber, remote from one or more material sputter targets, accelerating at least some of the ions of the plasma through an outlet, generating sputtered material from the one or more targets from the plasma; and depositing sputtered material on a substrate, thereby forming a layer of material on the substrate which comprises the comprises the chemical species of the reactive ions.

It should be understood that the method of the fourth aspect of the invention optionally incorporates the use of the reactive ion source of the first or second aspect of the invention. Any features in relation to the first/second aspect of the invention are optionally also applicable and/or relevant to the fourth aspect of the invention.

The generating of sputtered material from the target by the plasma may be performed by plasma that originates from a plasma source that provides the reactive ions into the chamber. Alternatively, the generating of sputtered material may be performed by plasma that originates from a separate, second plasma source. The second plasma source may be a remote plasma source. The second plasma source may be -14 -provided with a process gas such as Ar. The second plasma source may provide a plasma comprising primarily process ions, such as Ar+ ions, which do not chemically react with the sputtered material or the reactive ions in the chamber.

The outlet may comprise an aperture, and the accelerating of the ions may be caused by the application of a charge to the aperture. This creates an electric field. The electrically charged aperture may be positively charged or negatively charged. The method may include generating an electric field that accelerates the ions.

The electrically charged aperture has the effect of accelerating the ions out of the outlet. When using reactive ions in a sputter deposition process, the reactive ions may lose their relative directionality or geometry due to the low vacuum in the sputter deposition chamber causing the reactive ions to disperse throughout the sputter deposition chamber. This allows a directional flow of reactive ions, or a particular geometry of reactive ions (for example, a plume of reactive ions) to propagate over a longer distance in the sputter deposition chamber, before dispersing and losing its relative directionality or geometry.

The acceleration of the ions through the outlet may be caused by the application of a positive charge to a housing that substantially surrounds an antenna that generates the plasma.

The positive charge applied to the housing may accelerate the reactive ions through the outlet. As mentioned above, it is believed that plasma potential is increased, such that it is energetically favourable for the reactive ions to leave the housing through the outlet, and that this lifting of the plasma potential is able to provide an acceleration voltage to the ions as they leave the chamber. The acceleration of the ions may occur as a result of the ions, having a lifted plasma potential, entering a sheath in front of a grounded object (which may for example be a grounded substrate).

Preferably, the remotely generated plasma has a substantially sheet like profile and shape. In such a case, the plasma may have a substantially uniform density along its entire profile. The plasma may take the form of a directional plume as it leaves the outlet. The plasma plume or sheet may maintain its directionality and/or its geometry over a distance within the sputter deposition chamber.

The distance over which the plasma plume or sheet maintains its directionality and/or geometry may be at least 1 cm, optionally at least 2 cm, and optionally at least 3 cm.

-15 -Plasma that leaves the outlet may be known as a remotely generated plasma. The remotely generated plasma may be of high energy.

The remotely generated plasma may be of high density. In this connection, the plasma may have an ion density of at least 1011 cm". The remotely generated plasma may be of high density. In this connection, the plasma may have an ion density of at least 1014 cm'.

The outlet is optionally positioned substantially proximal to the substrate. The outlet is preferably less than 3 cm away from the substrate, preferably less than 2 cm away from the substrate, and preferably less than 1 cm away from the substrate.

Positioning the outlet close to the substrate in this way results in a high density plasma being formed near the substrate.

Preferably, the ions in the plasma pass through the outlet at sufficient velocity such that they can be used for ion implantation. A sufficient velocity for ion implantation may be a velocity of an ion with an energy significantly larger than lkeV.

A step of removing electrons from the generated plasma may be performed, such that only positive ions leave the outlet. Alternatively, the electrons in the plasma may be removed after the plasma passes though the outlet.

Positioning the outlet close to the substrate optionally allows the ions in the plasma accelerated through the outlet to be used for ion implantation (ion implantation being previously described in relation to the first aspect of the invention). Ion implantation requires relatively high velocity ions. The velocity of the ions as they leave the outlet is relatively high, and remains high over distances on the order of centimetres of length.

Alternatively, the outlet may be positioned at location distal to the substrate.

This results in the plume of reactive ions dispersing somewhat within the sputter deposition chamber to create a plasma cloud or beam. This plasma cloud or beam can optionally be brought into contact with a process surface or target.

The method optionally includes the step of rotating the outlet. The outlet may be rotatably mounted and/or otherwise rotatable with respect to the surface of the substrate. Without wishing to be bound by theory, it is believed that for most materials, the depth of an ion implantation into said material varies depending on the angle of incidence of a source of reactive ions, relative to the surface of the material. Being able to rotate the outlet with respect to the substrate allows for ion implantation to be tuned for desired implantation depths for different materials which may be part of, or -16 -previously deposited onto, the substrate. This advantageously allows for the tuning of the composition of the material (i.e. how many ions are introduced) at various depths, as well as modifications to the atomic structure and/or atomic ordering of the material itself This is especially advantageous as a technique for preparing the surface of a material for the deposition of another material onto said surface. It is also especially useful for modifying materials with a high surface area to volume ratio, such as thin-films. Ion implantation therefore may have particular application to multi-layer thin film devices, such as solid state batteries.

The outlet may comprise appropriate apparatus such that an ion beam forms as the plasma passes through the outlet. Such appropriate apparatus may include an accelerator grid, a screen grid, a neutraliser, and/or one or more electromagnetic lenses. The outlet may be translatably mounted with respect to the surface of the substrate. This allows the outlet to be rastered or scanned across the surface of the substrate. This advantageously allows substrates of different size and shape to be used with the same reactive ion source.

The material sputtered from the target optionally passes through remotely generated plasma (for example, a plasma sheet, cloud, or beam) before depositing on the substrate.

The outlet is optionally positioned substantially transverse to the substrate.

Positioning the outlet substantially transverse or otherwise perpendicular to the substrate results in the plume or sheet of plasma propagating across substantially all of profile of the surface area of the substrate. This helps ensure consistent formation of the deposited material across the entire surface area of the substrate.

In accordance with a fifth aspect of the invention there is provided method of manufacturing a layer of electrolyte material for a solid state battery, the method comprising: generating and maintaining a plasma in the gaseous medium of a sputter deposition chamber, which comprises reactive nitrogen ions, remote from one or more material sputter targets, wherein said one or more targets comprise compounds or elements of lithium, generating sputtered material from the one or more targets using the plasma; and, depositing sputtered material on a substrate, thereby forming a layer of material on the substrate comprising nitrogen and lithium.

-17 -The plasma generated may comprise at least 50% ionised material. In examples, the plasma generated is an especially highly ionised plasma, that comprises a high percentage, at least 70% for example, ionised material. This percentage refers to the proportion of neutral particles that are ionized to charged particles. A pure plasma typically has such a high percentage of ionised material. The applicant has found that remotely generated plasmas are particularly useful in generating pure plasmas of reactive ions, such as nitrogen. Providing a pure reactive ion source is especially important when depositing lithium phosphorous oxy-nitride "LiPON" using reactive sputtering techniques. In depositing LiPON, there are two issues in particular that embodiments of the present invention are able to address. The first issue is that the density of reactive ions near the surface of the substrate/the deposited film is not high enough for sufficient nitrogen ions to be incorporated into the atomic structure that forms. This results in not all of the deposited film being LiPON. The second issue caused by conventional, relatively low purity reactive ion sources during the production of LiPON is that atomic N2 implants into the surface of the material as it forms. The implantation of atomic N2 disrupts the atomic structure of LiPON that forms, and results in a lower quality film, with a large number of structural and atomic defects. Proving a remotely generated plasma that comprises a high percentage of reactive nitrogen ions (and is thus is very pure) helps to mitigate these aforementioned problems, and allows for rapid deposition of high quality LiPON films using reactive sputter processes.

The generation of the plasma may result in there being substantially no diatomic N2 in the gaseous medium of the chamber (i.e. less than 1%, and optionally less than 0.1%, of the nitrogen atoms in the gaseous medium of the chamber being in this state).

In accordance with sixth aspect of the invention there is provided a method of manufacturing a half call of a solid state battery, the method comprising; making a battery cathode and forming electrolyte onto said battery cathode using the method of any of the third, fourth or fifth aspects of the invention.

The cathode is optionally an alkali metal containing compound, such as LiCo02 (lithium cobalt oxide). The method may comprise generating a plasma remote from one or more targets comprising target material (such as elemental lithium or cobalt targets, or ceramic targets of lithium and/or cobalt); exposing the plasma target or targets to the plasma, thereby generating sputtered material from the target or targets, optionally in a -18 -reactive atmosphere comprising a reactive gas (such as oxygen), thereby forming the battery cathode. If used under the reactive sputtering regime, the same apparatus used to form any reactive ions (such as nitrogen ions) required during the deposition of the electrolyte may be used to generate any reactive ions (such as oxygen ions) required during the deposition of the cathode. The apparatus may be the reactive ion source of the first or second aspects of the invention.

In accordance with a seventh aspect of the invention there is provided a cathodic half-cell made in accordance with the method of the sixth aspect of the invention.

In accordance with an eighth aspect of the invention there is provided a method of making a solid state battery cell, the method comprising making a cathodic half cell in accordance with the sixth aspect of the invention; and, contacting said cathodic half cell with an anode or depositing anode-forming material on the electrolyte.

In accordance with a ninth aspect of the present invention there is provided a solid state battery cell made in accordance with the method of the eighth aspect of the invention.

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 any other method 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 which can be briefly summarised as follows Figure 1 a is a schematic side-on view of a plasma deposition process apparatus within which, an example of both the first, and second aspects of the invention is shown; Figures lb is a schematic side-on view of a further example of both the first, and second aspects of the invention; -19 -Figure lc shows a plan view of the antenna of the remote plasma generation based reactive ion source of examples of the invention; Figure Id shows a perspective view of the plasma generation based reactive ion source of examples of the present invention; Figure 2 shows a remote ion source similar to that shown in Figure la to Id, wherein the antenna further comprises a shield member; Figure 3 shows a remote ion source similar to that shown in Figures 1 a to ld and Figure 2, wherein the antenna further comprises a focusing member; Figure 4 shows remote plasma ion source 406 similar to that shown in Figures 1 a to Id, Figure 2 and Figure 3, wherein the remote plasma ion source is rotatable, Figure 5 shows remote plasma ion source 406 similar to that shown in Figures la to Id, Figure 2 and Figure 3 and Figure 4, wherein the remote plasma ion source is translatable; Figure 6 is a schematic representation of an example of a method of manufacturing a layer of material in accordance with a third aspect of the invention; Figure 7 is a schematic representation of an example of a method of manufacturing a layer of material in accordance with a fourth aspect of the invention; Figure 8 is a schematic representation of an example of a method of manufacturing a layer of electrolyte material for a solid state battery in accordance with a fifth aspect of the invention; Figure 9 is a schematic representation of an example of a method of manufacturing a half call of a solid state batten/ in accordance with a sixth aspect of the invention, Figure 10 is a schematic representation of an example of a cathodic half-cell made in accordance with the method of the sixth aspect of the invention, the cathodic half-cell so made being an example in accordance with a seventh aspect of the invention; Figure 11 is a schematic representation of an example of a method of making a solid state battery cell in accordance with an eighth aspect of the invention; -20 -Figure 12a is a schematic representation of an example of a solid state battery cell made in accordance with the method of the eighth of the invention, the solid state battery cell so made being an example in accordance with a ninth aspect of the invention; and Figure 12b is a schematic representation of another example of a solid state battery cell made in accordance with the method of the eighth aspect of the invention, the solid state battery cell so made being an example in accordance with a ninth aspect of the invention.

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. Tt 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.

Figure 1 a is a schematic side-on view of a plasma deposition process apparatus 100. Within the plasma deposition apparatus, an example of both the first, and second aspects of the invention is shown. This example apparatus may, in some examples of the invention, be the apparatus used during the described example methods of the invention.

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 The parts of the apparatus shown in Figure 1 may be accommodated within the same process chamber 113, which accommodates a relatively large volume of space 122. The process chamber 113 may be evacuated by a pumping system (not shown) to a suitable pressure (for example less -21 -than 1x10' torr), and in use a process or sputter gas, such as argon or nitrogen, may be introduced into the process chamber 113 using to an extent such that a pressure suitable for sputter deposition is achieved (for example 3x10" toff).

With reference to Figure I a, the plasma deposition process apparatus is denoted generally by reference numeral 100 and comprises a plasma target assembly 102 comprising a target 104, a remote plasma generation based reactive ion source 106, a series of magnets 108 for confining the plasma generated by the remote plasma generator 106, a target power supply 110, a remote plasma source power supply 112 and a housing 118. Remote plasma generation based reactive ion source 106 comprises two pairs of radio frequency (RF) antennae 116, inside quartz tubing 117. Sputter deposition chamber 113 comprises a vacuum outlet 120 which is connected to a series of vacuum pumps located outside the chamber so that the chamber volume 122 defined by sputter deposition chamber 113 can be evacuated. Sputter deposition chamber 113 is also provided with a gas inlet U4 which may be connected to a gas supply (not shown) for the introduction of one or more gases into the chamber volume 122. In other examples, the gas inlet 124 may be positioned over the surface of the target assembly 102. As can be seen from Figure la, the plasma is generated remote from the target 104. As such, the plasma may be described as a remotely generated plasma.

In an example shown of the remote plasma generation based reactive ion source 106 shown in Figure la, the antenna 116 are kept inside a housing 118. The housing 118 has an inlet 126, though which the gas in the sputter deposition chamber 113 and within the chamber volume 122 can flow (through diffusion and/or magnetic based effects and gradients) into the housing 118, and into the plasma generating region 125 (not shown in Figure la) between antenna 116. The plasma generated by the antenna is then accelerated through electrostatic plates 107, and leaves the housing through outlet 128. The electrically chargeable plates 107 are formed as an aperture that surrounds the outlet 128. The electrically chargeable plates have a negative voltage bias applied to them. The negative bias applied is 500 V. As the plasma leaves the housing 118, it has a substantially plume-like, or sheet-like in shape, depending on the shape of the outlet 128, and the outlet 128 is shaped such that the plasma has a plume like shape. The plasma is then optionally confined, or further shaped by the magnets, 108. The magnets 108 are distal from the housing 118. This allows the plasma that leaves the outlet 128 to be shaped away from the housing 118. The magnet 108 is positioned proximate the antenna 114 and the housing 118 and is capable of producing an axial magnetic field -22 -strength of from 4.8 Gauss up to 500 Gauss when powered by its associated power supply Ila (e.g. a DC power supply). The magnet 108 provides a magnetic field within the process chamber volume 122 for propagating, or otherwise confining or shaping, the plasma generated by the reactive ion source 106 so that it extends or moves from the plasma generation zone 125 to and across the processing zone B of the processing chamber volume 122. The general shape of the confined plasma made from the remote plasma generator 106 is shown by the dashed lines B in Figure I a. The series of magnets 108 is used to and confine the plasma to a desired shape/volume.

In other examples of the invention, the electrically chargeable plates 107 may be not take the form of an aperture, and may take any other shape or form, whilst still being proximal to the outlet. The electrically chargeable plates 107 may have a positive bias applied to them. The voltage of the bias applied may instead be 300 V, or 400 V. In other examples, the electrically chargeable plates 107 are configured to be a variable voltage applied to the them, and the aperture may comprise a magnetic lens. In yet further examples, the aperture comprises an accelerator grid, a screen grid and a neutraliser such that an ion beam forms as the plasma passes through the aperture. A further example of the invention is shown in Figure lb. This example is similar to that described in Figure I a, however there are a number of differences, which will now be briefly described. The remote plasma generation based reactive ion source 106' is supplied by a reactive gas directly, through an inlet 126'. The inlet is not exposed to the volume of the sputter disposition chamber 122, and instead is fed from a gas feed system (not shown) separate from the sputter deposition chamber 113. This advantageously allows for a high concentration of gas to be supplied to the remote plasma generation based reactive ion source 106'. The housing 118' is positively charged. Without wishing to be bound by theory, it is thought that the positive charging of the housing 118' results in any positive ions generated by the remote plasma source being repelled out of the outlet, due to the positive charging of the housing. The gas which can be supplied though inlet 126' comprises substantially entirely a reactive gas, in this case nitrogen. A magnet assembly 108' is provided on the housing 118'. In these examples, the purpose of the magnet 108' is to accelerate and focus the ions of the plasma as they leave the outlet 128' such that the plasma of reactive ions maintains its directionality, and geometry (i.e, its sheet-like or plume-like shape) as it leaves outlet 128'. The magnet assembly 108' comprises an electromagnet in this example.

-23 -The target material 104 comprises 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 (LiPON). The target material 104 comprises LiP0 (Li3PO4) as a precursor material for the deposition of LiPON onto the substrate 135, for example via reaction with nitrogen gas emitted from the reactive ion source 101 in the region of the target material 104. The reactive ions source 101 is arranged to generate plasma B. A magnetic confining arrangement (not shown in Figure la) may also be provided to control and shape the plasma generated by the plasma generation arrangement 102. The apparatus is configured to allow for a generation of an elongate region of plasma B. In addition, the means 112 of powering the plasma source, may be of RF, (Direct Current) DC, or pulsed-DC type. The power applied to the antenna 144 is 5 kV.

For the avoidance of doubt, the target 104 of the target assembly 103 does not function as a cathode when power is applied to it from the RF, DC or pulsed DC power supply in some examples of the invention, where the reactive ion source is also used as the source of ions for the sputtering of the target 104 in a sputter deposition process. For the avoidance of doubt, in some examples, the remote plasma generation based reactive ion source 106 is simply used as a means of generation of reactive ions. In yet further examples, the remote plasma generation based reactive ion source 106 is additionally used to generate a plasma B that is used to sputter material from a target 104. In yet further examples, an additional remote plasma generation device (not shown) is used to generate the plasma used to sputter material from the target 102. Figure lc shows a plan view of the antenna of the remote plasma generation based reactive ion source of some examples of the invention. The plasma generation system 132 is located in in the sputter deposition chamber volume 122 within the plasma generation zone. The plasma generation system 3 comprises an antenna 114, and a covering 117. The plasma generation system 132 is connected to an impedance matching network 112, and a signal generator 111. These allow the antenna to be powered to specific frequencies for more efficient plasma generation. 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 system 132 of the present example resides within and is open to the volume of the sputter deposition chamber 122 where the plasma will be applied in processing of a target assembly 102 and/or substrate assembly 135. In other words, the plasma is -24 -generated locally in the atmosphere of the process chamber 122. The housing 118, which does not seal the plasma generation device from the atmosphere of the process chamber 122, is shown by the dotted outline 118. The antenna has a cross sectional long dimension L of 400mm. The inlet 126 and outlet 128 of the housing 118 are not shown in Figure lc for the sake of clarity.

The antenna 114 is shown as a single looped wire, which extends through the process chamber 113 in two straight sections 119, 121 which are connected by a curved portion 123 outside of the process chamber 113. The straight sections 119, 121 are offset in the process chamber 113 to induce plasma excitation in the region between the straight sections 119, 121 of the antenna 114. The antenna 114 is constructed from shaped metallic tubing (e.g. copper tube), although alternate electrically conducting materials, for example brass or aluminium or graphite, could be used, as can differing cross sectional shapes, for example rods, strips, wire or a combined assemblies. In an example of the invention, the antenna 114 is selected so that it can deliver RF frequency in the process chamber volume 122.

The casing 127 encloses and isolates the antenna 114 from the process chamber volume 122. The casing 117 comprises elongate tubes with a defined inner space or internal volume. The casing 117 extends through the process chamber volume 122 such that the tubes connect with the walls of the process chamber 113. The casing 127 is provided with suitable vacuum seals around the ends of casing 127 and the walls of the process chamber 113, such that the internal volume is open to atmosphere at one or both ends. The means of support and achieving vacuum seals and air cooling are omitted from the figures for the sake of clarity.

Figure Id shows a perspective view of the plasma generation based reactive ion source 106 of some examples of the present invention. It clearly shows a plasma formation region 125, which formed between the two straight sections of antenna 121 and 119, but not in the region enclosed by casing 127. Also shown is outlet 128, through which plasma generated in plasma region 125 flows. The plasma is accelerated by an electrically charged aperture 107 as it leaves the outlet 128. The outlet has a substantially elongate shape, which might also be described as a "letterbox" shape. The combination of the high density of the plasma within the housing 118, and any electrical or magnetic forces applied to the plasma cause the plasma to leave the outlet 128 with a high degree of directionality, in the direction D. The plasma as it leaves the outlet 128 in the direction D forms a substantially sheet-like shape (not shown).

-25 -When using reactive ions from a conventional reactive ion source in a conventional sputter deposition process, the reactive ions lose their relative directionality or geometry due to the low vacuum in the sputter deposition chamber, causing the reactive ions to disperse throughout the sputter deposition chamber. In contrast, some examples of the invention produce a directional flow of reactive ions, or a particular geometry of reactive ions (for example, a plume of reactive ions) that propagate over a longer distance in the chamber volume 122 than would otherwise be possible. The reactive ion source is a linear ion source.

The reactive ion source, in use, produces a plume of plasma that can propagate and maintain its directionality and/or geometry over a distance D of at least 1 cm. This is true, even where the reactive ion source is located in a sputter deposition chamber evacuated to a vacuum of 10' mBar or stronger.

In use, the reactive ion source is capable of generating a localised linear plasma formed in the sputter deposition chamber with a density greater than 1011 cm'.

The housing 118 is configured to be in fluid connection with any sputter deposition chamber volume 122 in which it resides. This allows the plasma generated by the reactive ion source to be in use, cause plasma to be generated and maintained in the gaseous medium of its surroundings. By this, what is meant is that the atmosphere in which the remotely generated plasma is created is within the volume of space defined by any chamber that contains the apparatus of the sputter deposition process. This is a much simpler set-up than that of a reactive ion source not of the invention that requires the remote plasma to be generated in an environment discreet or otherwise separate from the gaseous medium of the chamber 133 itself, such as that described in W02011131921.

In yet further examples, the reactive gas is oxygen. In another example, the gas that flows through inlet 126' is a mixture of a reactive gas, and an inert process gas (such as argon). The housing may comprise both a positively charged housing 118' and negatively charged plates 107, or merely a positively charged housing 118'. This allows such embodiments of the invention to provide maximal acceleration to the ions as they leave the outlet 128'. In some examples, the outlet 128 has a frustoconical, or "nozzle" like shape. The reactive ion source is capable of producing a plume of reactive ions that extends over a longer distance D of at least 3 cm. The apparatus is capable forming and shaping a localised linear plasma formed in the sputter deposition chamber with a density greater than 1014 cm".

-26 -In a further example, the target 104 comprises material Li31304. Briefly, the chamber U2 is evacuated until a sufficiently low pressure is reached. Power provided by power supply 112 is used to power the remote plasma generator 106 to generate a plasma. Power is applied to the target 104 such that plasma interacts with target 104, causing Li3PO4 to be sputtered from the target 104 and onto the substrate 128. In the present example, the substrate 128 comprises a polymer sheet which is placed into the plasma chamber 113. In other examples, the polymer sheet may enter the plasma chamber 113 through an input port and out an output port as part of a roll-to-roll or "web processing apparatus" (not shown). The Li3PO4is deposited onto the substrate as an amorphous material.

Figure 2 shows a remote ion source 203 similar to that shown in Figure la to Id, wherein the antenna further comprises a shield member. The principal differences between the arrangement of Figure 2, as compared to that of Figures la to Id, will now be described. There is an antenna 209 enclosed in a quartz tube casing 210 with a steel shield member 230 which prevents plasma from being generated. There is a single shield member 230 formed from a half cylinder of stainless steel material which extends circumferentially around the antenna for about 180 degrees. Thus, in the arrangement shown in Figure 2 there is, along the length of the antenna, a first location 231 at which plasma 224 is generated and a second spaced-apart location 232 at which plasma 224 is also generated. At both locations, the plasma extends -in the absence of any significant effect on the magnetic / electrical fields from other sources -circumferentially around the antenna by about 180 degrees. Along the length of the antenna between the first location 231 and the second location 232, there is a third location 233, in which plasma is also generated around about 180 degrees of the antenna. At each of the first, second and third locations along the length of the antenna, there is also a portion of the shield member 230 which restricts the generation of plasma around the other 180 degrees around the antenna. The shield member (and the region in which plasma is generated on the opposite side of the antenna to the shield member) also extends to the left (as viewed in Figure 2) of the first location 231 and to the right of the second location 232 of plasma.

It will be appreciated that, in use, particularly when the plasma generated by an antenna is to be constrained, directed or otherwise manipulated for use in a process that requires the plasma to be present at a particular desired region remote from the plasma antenna, that there will be a need for other sources of magnetic / electrical fields to -27 -affect the shape and location of the plasma. As such, in use, the shape and location of the plasma will be non-uniform and/or will be different from shown in the accompanying Figures.

Figure 3 shows a remote ion source 303 similar to that shown in Figure la to ld and Figure 2, wherein the antenna further comprises a focusing member. The principal differences between the arrangement of Figure 3, as compared to that of Figures la to Id and Figure 2, will now be described. In some examples the reactive ion source comprises a ferrite focussing member 340. The focussing member 340 is also provided in the casing 310 and partially surrounds the length of antenna 309.

The focusing member 340 and antenna 309 in the upper section 338A are arranged in mirror image to the focussing member 340 and antenna 309 in the lower section 338B, the open side of the focussing members 340 each facing generally inwards.

In use, the antenna 309 is driven by an RF current and generates a time-varying magnetic field. The magnetic field ionises gas outside the casing and an inductively coupled plasma is generated in a plasma generation region 325 between the upper section 338A and lower section 338B.

The focussing members 340 each have the effect of increasing the magnetic flux density in the angular region in which the antenna 309 is unshielded from the wall of the casing 310 (i.e. is not surrounded by the focussing member 310 / the focussing member 310 is open). The arrangement of both the focussing members 340 thereby act to increase the magnetic flux density in the plasma generation region 325.

The focussing members 340 also have the effect of reducing the magnetic field induced in the area above the upper section 338A and below the lower section 338B, and therefore less power is lost into these areas. The focussing members 340 thereby improve the efficiency of the plasma generation system as a whole. It will be appreciated that said increases and improvements are as compared to a similar antenna assembly in which the focusing members 340 are absent.

In order to take full advantage of the presence of the focussing members 340, the ferrite material of the focussing members 340 should preferably not be saturated by external magnetic fields (i.e. magnetic fields not generated by the antenna 309). In use in the remote plasma generator 106, such external magnetic fields may be generated by the magnet 108 that confines and propagates the plasma.

-28 -Accordingly, the focussing members 340 are each provided with a shield element (not shown in figure 3) to shield them from such external magnetic fields. In this embodiment, the shield element is in the form of a nickel alloy coating that is provided on the outwardly facing surfaces of the focussing member 340. An example nickel containing material that could be used is MuMetal® alloy by Magnetic Shield Corporation, Bensenville, IL, USA.

Ferrite material, which is the same ferrite material as which makes up the focussing members 340, forms a ferrite shield 346 that fully surrounds the antenna 309, thereby forming shielded sections of the plasma antenna assembly 338.

In other embodiments, alternative or additional shielding may be provided. For example, parts of the casing 310 may be provided (e.g. coated) with shielding material, and/or one or more standalone shield elements may be provided in the region between the focussing member and the magnet 108 Figure 4 shows remote plasma ion source 406 similar to that shown in Figures 1 a to Id, Figure 2 and Figure 3, wherein the remote plasma ion source is rotatable. The principal differences between the arrangement of Figure 4, as compared to that of Figure la to td, Figure 2, and Figure 3 will now be described. The same parts are labelled with reference numerals sharing the same last two digits. For example, inlet 426 in Figure 4 is the same as inlet 126 in Figure la. The examples of the invention shown in Figure 4 shows a remote plasma ion source 406 that is rotatable about axis 443. This allows the plume of ions G to be rotated through an angle a. Having the plume G being able to be angled at various angles a to the material 446 that has been deposited onto the substrate 404 allows the ion source to alternatively or additionally be used as an ion implantation device. This is because the depth at which ions in ion beam G can implant into a material 446 is dependent on the crystal structure (or lack thereof) of the material 446, and the angle alpha at which the ions are incident on the surface of material 446. Ion implantation is a low-temperature process by which ions of one element are accelerated into a solid target (which may be the substrate and or layers of material deposited onto said substrate), thereby changing the physical, chemical, or electrical properties of the target. Ion implantation is particularly useful in preparing the surface of a deposited layer of a thin-film device, such that surface of the deposited layer provides a high quality interface for any subsequently deposited layers of material. In some examples, the ion source is used as a reactive ion source during deposition, but also as an ion implantation device during, or pre-/post-deposition. The device being -29 -able to perform both of these roles advantageously saves space in any sputter deposition chamber in which it is located, when compared to a sputter deposition system that has both a reactive ion source and an ion implantation device.

Figure 5 shows remote plasma ion source 506 similar to that shown in Figs. la to id Figure 2, Figure 3, and Figure 4. The principal differences between the arrangement of Figure 5, as compared to that of Figure la to td, Figure 2, Figure 3 and Figure 4 will now be described. The same parts are labelled with reference numerals sharing the same last two digits. For example, inlet 526 in Figure 5 is the same as inlet 126 in Figure la. Figure 5 shows a remote plasma ion source 506 that is translatable along direction 545. This allows the plume of ions G to be rastered or otherwise translate or scanned across the surface of material 446. Having the plume G being able to be translated in this way allows the reactive ion source to be used with substrates 504 of different shapes and sizes.

An example of a method of manufacturing a layer of material in accordance with a third aspect of the invention will now be described with reference to Figure 6.

The method is denoted generally by reference numeral 1001 and comprises generating and maintaining 1002 a plasma which comprises reactive ions in the gaseous medium of a sputter deposition chamber, remote from one or more material sputter targets, from a reactive ion source. The example method also includes generating 1003 sputtered material from the one or more targets using the plasma; and depositing 1004 sputtered material on a substrate, thereby forming a layer of material on the substrate A reactive ion source being an example of the first aspect of the invention described herein may be used. The target is Li3PO4. The reactive gas is nitrogen. The plasma is used to deposit a thin-film of LiPON. The substrate has a thickness of 5 pm, and is made of PET. The substrate is suitable for use in a roll-to-roll or web processing" application. The maximum temperature reached at any given time by any given square of substrate material having an area of 1 cm2, as measured on the surface opposite to said surface on which the material is deposited, and averaged over a period of 1 second, is no more than 200 °C.

In other examples, a reactive ion source being an example of the second aspect of the invention may be used. The substrate has a thickness of 1 um and is made of PEN. Lithium oxide targets are used, along with targets that comprise phosphorus containing compounds. In yet further examples, elemental lithium targets are used and the deposition occurs under a reactive oxygen atmosphere. In some examples, the -30 -relative gas is one or more of Mike's exhaustive list of possible use gases to be inserted here In other examples, for example, where the layer of material deposited is alumina, the targets are aluminium, and reactive gas is oxygen. In other examples, for example where the layer of material deposited is silica, the targets are silicon, and reactive gas is oxygen.

An example of a method of manufacturing a layer of material in accordance with a fourth aspect of the invention will now be described with reference to Figure 7. The method is denoted generally by reference numeral 2001 and comprises generating and maintaining 2002 a plasma which comprises reactive ions in the gaseous medium of a sputter deposition chamber, remote from one or more material sputter targets; accelerating 2003 at least some of the ions of the plasma through an outlet; generating 2004 sputtered material from the one or more targets using the plasma; and depositing 2005 sputtered material on a substrate, thereby forming a layer of material on the substrate which comprises the comprises the chemical species of the reactive ions.

A reactive ion source being an example of the first aspect of the invention is used. The generating of sputtered material is performed by plasma that originates from a separate, second plasma source, which is a remote plasma source.

The outlet comprises an aperture, and the accelerating of the ions may be caused by the application of a charge to the aperture. The electrically charged aperture has the effect of accelerating the ions out of the outlet, such that a directional flow of reactive ions propagate over a distance within the gaseous medium of a sputter deposition chamber. In further examples, the outlet comprises an accelerator grid, a screen grid, a neutraliser, and/or one or more electromagnetic lenses such that an ion beam forms as the plasma passes through the outlet The remotely generated plasma has a substantially sheet like profile and shape. The plasma has a substantially uniform density across its profile. The sheet maintains its directionality and geometry over a distance of 1 cm (from leaving the outlet). The remotely generated plasma has an ion density of around 1011 cm* The outlet is positioned less than 1 cm away from the substrate. This results in a high density plasma forming near the substrate. The plasma source is provided with a process gas that comprises argon. The ions in the plasma can be used for ion implantation. This is because the outlet is positioned so close to the substrate (i.e. in this case less than 1 cm away), and the ions maintain their directionality, and a high -31 -velocity over a short distance within the volume of the sputter deposition chamber. Therefore, the ions strike the surface of the substrate, or the material deposited to the substrate, with such force that they implant into the material that they strike. The ions leave the outlet with an energy greater than IkeV.

The method further includes the step of rotating the outlet. The outlet is rotatably mounted with respect to the surface of the substrate. This allows for the method to be tuned such that ions implant at different depths into the surface of the substrate (or the surface of a material deposited onto the substrate. Ion implantation is described in more detail in previous paragraphs of the specification.

In other examples, the outlet is positioned at location distal to the substrate. This results in the plume of reactive ions dispersing within the sputter deposition chamber to create a plasma cloud or beam. In some examples, the sputtered material from the targets may pass through this beam before it is deposited onto the substrate. In yet further examples, the outlet is positioned transverse to the substrate, such that a large area of plasma propagated across the entire surface area of the substrate.

In other examples, a reactive ion source being an example of the second aspect of the invention is used. In yet further examples, a reactive ion source not of the first or second aspects of the invention is used, and the generating of sputtered material is performed by plasma that originates from a plasma source that is not a remote plasma source. In yet further examples the sputtering of the targets is performed by plasma that originates from a plasma source that provides the reactive ions into the chamber. The outlet is translatably mounted with respect to the substrate. The outlet is rastered, or scanned across the outlet throughout the method of manufacturing a layer of cathode. This allows for substrates of different sizes and shapes of substrate to be used. In other examples, the accelerating of the ions through the outlet is caused by the application of a positive charge to a housing that surrounds an antenna that generates the plasma. The outlet is positioned less than 3 cm away from the substrate. The remotely generated plasma may be of a higher ion density, of around 1014 cm'. The electrons may be removed from the plasma either before, or after, it leaves the outlet. The ions that leave the outlet may have an energy less than lkeV.

An example of a method of manufacturing a layer of electrolyte material for a solid state battery in accordance with a fifth aspect of the invention will now be described with reference to Figure 8. The method is denoted generally by reference numeral 3001 and comprises generating and maintaining 3002 a plasma in the gaseous -32 -medium of a sputter deposition chamber, which comprises reactive nitrogen ions, remote from one or more material sputter targets, wherein said one or more targets comprise compounds or elements of lithium,; generating 3003 sputtered material from the one or more targets using the plasma; and; depositing 3004 sputtered material on a substrate, thereby forming a layer of material on the substrate comprising nitrogen and lithium.

The plasma generated is an especially pure plasma, that comprises a very high percentage, substantially 100%, ionised material (for example, greater than 99%). This results in there being sufficient reactive nitrogen such that the layer of material deposited comprises the nitrogen co-ordinate bonds into the material that forms. The material that forms is LiPON. The number of nitrogen co-ordinate bonds that form is the number of bonds that would be necessary to form LiPON with a desired, or optimal, stoichiometry. The especially pure plasma comprises a substantially no (i.e. less than 1%) diatomic N2. Therefore, there is substantially no implantation of N2 ions into the surface of layer of material (LiPON) that forms. This results in the formation of a very high quality LiPON film.

An example of a method a method of manufacturing a half call of a solid state battery in accordance with a sixth aspect of the invention will now be described with reference to Figure 9. The method is denoted generally by reference numeral 4001 and comprises making 4002 a battery cathode and 4003 forming electrolyte onto said battery cathode using the method of an example of any of the third, fourth or fifth aspects of the invention.

The cathode is LiCo02. The method of manufacturing a cathode comprises generating a plasma remote from one or more targets comprising target material (such as elemental lithium or cobalt targets, or ceramic targets of lithium and/or cobalt); exposing the plasma target or targets to the plasma, thereby generating sputtered material from the target or targets, optionally in a reactive atmosphere comprising a reactive gas (such as oxygen), thereby forming the battery cathode. The same apparatus (i.e. the same reactive ion source) is used to produce reactive ions for the formation of the electrolyte and for the production of oxygen ions for formation of the cathode. In other examples of the present invention, the cathode is a different alkali metal containing compound.

An example of a cathodic half-cell in accordance with a seventh aspect of the invention is shown schematically with reference to Figure 10. The example cathodic -33 -half-cell is made using the method as described with reference to Figure 9. Referring to Figure 10, which shows a battery cathode 742 on a substrate 728 (which comprises a current collecting layer 729). Figure 10 additionally shows electrolyte layer 744 deposited on top of the battery cathode 742. The material deposited for the electrolyte 744 is lithium phosphorous oxy-nitride (LiPON). In other examples, the material deposited is another suitable electrolyte material.

An example of a method of making a solid state battery cell in accordance with an eighth aspect of the invention will now be described with reference to Figure 11. The method is denoted generally by reference numeral 5001 and comprises making 5002 a cathodic half cell in accordance with the sixth aspect of the invention and contacting 5003 said cathodic half cell with an anode or depositing anode-forming material on the electrolyte.

An example of a solid state battery cell made in accordance with a ninth aspect of the invention, is shown schematically with reference to Figure 12a and Figure 12b.

The example solid state battery cell is made using the method as described with reference to Figure 11. Referring to Figure 12a, reference numerals 828 and 828' are substrate materials, and reference numerals 829 and 829' are current collecting layers, reference numeral 842 is the cathode material, in this case, LiCo02, and reference numeral 844 is LiPON, which acts as both electrolyte and anode. Alternatively, in other examples the current collector material acts as an anode material.

Alternatively, in a second example of the ninth aspect of the invention a further anode material may be deposited. This is shown schematically in Figure 12b. Referring to Figure 12b, 828 and 828' are substrate materials, 829 and 829' are current collecting layers, 842 is the cathode material, in this case, LiCo02, 844 is LiPON, which acts as electrolyte, and 846 is a suitable anode material.

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 -34 -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. -35 -

Claims

Claims 1 A reactive ion source of a sputter deposition system, comprising: an electrically powered antenna, wherein the antenna has a substantially elongate shape, a housing which at least partially surrounds the antenna, an inlet for supplying a reactive gas into the housing, and an outlet from the housing configured such that reactive ions can pass through it, wherein the antenna is configured to apply an electromagnetic field I 0 to the reactive gas such that a plasma is formed that comprises reactive ions.
2. The reactive ion source of claim I wherein the outlet comprises a substantially elongate shape.
3 The reactive ion source of claim 1 or claim 2, wherein the outlet comprises an aperture, which is configured to be supplied with an electric charge.
4. The reactive ion source of any preceding claim, wherein the housing is configured to be supplied with a positive electrical charge.
5. The reactive ion source of any preceding claim wherein, in use, the plasma is generated and maintained in the gaseous medium of its surroundings.
6. The reactive ion source of any preceding claim wherein the inlet is fluidly connected to a source of reactive gas.
7 The reactive ion source of any preceding claim, wherein the antenna comprises an electrically conductive shield member.
8. The reactive ion source of any preceding claim wherein a ferromagnetic or ferrimagnetic focussing member is arranged to partially surround a length of the antenna.
9, The reactive ion source of any preceding claim, wherein the reactive ion source further comprises one or more magnets, provided separately from the antenna
10. The reactive ion source of any preceding claim, wherein the reactive ion source further comprises a rotatable mounting device, such that the reactive ion source can be rotatably mounted within a sputter deposition system.
11. The reactive ion source of any preceding claim, wherein the reactive ion source, in use, has an ionisation efficiency of at least 70 percent.
12 A method of manufacturing a layer of material, the method comprising: generating and maintaining a plasma which comprises reactive ions, in the gaseous medium of a sputter deposition chamber, remote from one or more material sputter targets, from the reactive ion source of any preceding claim; generating sputtered material from the one or more targets using the plasma; and depositing sputtered material on a substrate, thereby forming a layer of material on the substrate.
13 A method of manufacturing a layer of material, the method comprising: generating and maintaining a plasma which comprises reactive ions in the gaseous medium of a sputter deposition chamber, remote from one or more material sputter targets, accelerating at least some of the ions of the plasma through an outlet, generating sputtered material from the one or more targets from the plasma; and depositing sputtered material on a substrate, thereby forming a layer of material on the substrate which comprises the chemical species of the reactive ions.
14. The method of claim 13, wherein the outlet is optionally positioned substantially proximal to the substrate
15. The method of claim 13 or claim 14, wherein the ions pass through the outlet at sufficient velocity such that they can be used for ion implantation
16. The method of any of claims 13 to 15, wherein method includes the step of rotating the outlet.
17 A method of manufacturing a layer of electrolyte material for a solid state battery, the method comprising: generating and maintaining a plasma in the gaseous medium of a sputter deposition chamber, which comprises reactive nitrogen ions, remote from one or more material sputter targets, wherein said one or more targets comprise compounds or elements of lithium, generating sputtered material from the one or more targets using the plasma; and depositing sputtered material on a substrate, thereby forming a layer of material on the substrate comprising nitrogen and lithium.
18. A method of manufacturing a half call of a solid state battery, the method comprising; making a battery cathode and forming electrolyte onto said battery cathode using the method of any of claims 12 to 17.
19. A cathodic half cell made in accordance with the method of claim 18.
20. A method of making a solid state battery cell, the method comprising making a cathodic half cell in accordance with the method of claim 18, and contacting said cathodic half cell with an anode or depositing anode-forming material on the electrolyte.
21. A solid state battery cell made in accordance with the method of claim 20. Abstract