GB2360530A - High target utilisation sputtering system with remote plasma source - Google Patents

Abstract

A system for the sputter coating or sputter etching of substrates is provided by providing a source 23 of ionisable process gas in the vicinity of the target or substrate surface to be sputtered (19, Fig 1) within a vacuum system 10 which includes or has attached a remote plasma source 13, 14, 15, 16 and an arrangement of magnets 16,18,29 for confining and conducting ionising electrons from the plasma source to the vicinity of the target or substrate surface. Preferably, the remote plasma source has an additionally source 17 of ionisable process gas and is differentially pumped by a separate vacuum pump 26 with respect to the main process chamber 10. Preferably, for reactive deposition processes, a separate source 25 of the reactive gas is positioned in the vicinity of the substrate to be coated.

Description

2360530 UK Patent Application High Target Utilisation Sputtering System

This invention relates to apparatus which generate high density plasmas remotely from the process chamber in which plasma based processes are conducted, including thin film coating and etching apparatus.

Gas plasmas have been used for many years for a variety of processes including thin film coating, cleaning and etching, particularly within the semiconductor and optical industries. The plasma can provide the primary energy source for the process, as for example in the case of sputtering systems. Alternatively the plasma may be provided to assist the achievement of particular properties or reactions within the process, for example through the interaction of the plasma ions and electrons with other process materials including the growing film and substrate, as for example in plasma enhanced reactive evaporation processes.

Plasma sputtering processes are widely used for the deposition of thin films of materials onto various substrates. In general, the process takes place within a vacuum chamber in which a small quantity of ionisable process gas, for example argon, is present. At appropriate process gas pressures, a plasma may be produced through ionisation of the gas by well known means, for example the application of a high voltage between two electrodes within the chamber. A target material, which may itself form the negative (cathode) electrode, is bombarded by positive plasma ions and if the ion bombardment is of sufficient energy target atoms are ejected from the target surface into the vacuum. A substrate placed within the vacuum system, usually with line of sight to and in proximity to the target surface being bombarded, may then be coated by the released target material.

A simple plasma sputtering system, comprising for example of two metal plates separated at an appropriate distance and with a suitable DC voltage between them, is only efficient or useful under a narrow range of process conditions and therefore limited in its application. The evolution of sputtering technology has greatly improved upon such simple systems in the drive to achieve higher deposition and etch rates, better uniformity and properties of deposited films and wide ranges of materials that can be sputtered. Thus it is well known that AC voltages, usually at RF frequencies (typically 13.56 Iffiz), can be used, for example to allow the sputtering of insulators, and that magnetic fields can be used to confine or direct plasma electrons, for example to locally increase the plasma density at the target to enhance sputtering rates. It should be noted that, in general, the achievement of higher deposition and etch rates is a primary target for sputter systems.

As an example, a magnetron sputtering system has a torus shaped magnetic field penetrating the target surface to confine plasma electrons and induce a far higher local ionisation level (or 'plasma density') than would otherwise be possible. This allows high sputtering rates to be achieved at low gas pressures, typically lxIT' to 7x10-3 millibar, resulting in high deposition rates and high quality of the deposited thin films.

Page 1 As a result, the magnetron sputtering system is extensively used in the semiconductor and opto-electronic industries.

A variation of the sputter process is reactive sputtering, wherein the process gas or a component of a gas mixture reacts with the sputtered target material or the deposited film to produce a compound material. As an example, an aluminium target may be sputtered, under appropriate conditions, in a plasma struck in a gas mixture of argon and oxygen to deposit an aluminium oxide film.

A flirther variation of plasma processing is plasma etching or cleaning in which the substrate becomes the target, the plasma process thereby causing the substrate material to be sputtered or, in the case of a reactive process, converted into a volatile compound. Such plasma processes can be used to clean or prepare the surface, possibly for subsequent thin film deposition, or in conjunction with an appropriate masking material to etch a predetermined pattern into the material, for example in semiconductor wafer manufacture.

To further increase deposition or etch rates and system capability, and overcome some of the limitations imposed by magnetron sputtering systems, it is known that a high density plasma can be produced remotely from the target and then directed to its vicinity by electric or magnetic fields.

A variety of techniques are known that may be used to generate remote, high density plasmas, as summarised by Popov in 'FEgh Density Plasma Sources' (1995). For example the electron cyclotron resonance (ECR) phenomena may be used to produce a plasma by coupling a microwave source with a strong magnetic field in vacuum.

As a further example high density plasma waves may be generated by the use of an external antenna powered with 13.56 MHz radio frequency signal, as shown in original papers by Boswell and subsequently Chen. These have the advantage of using lower magnetic field strengths compared with ECR, but require careful antenna and magnetic field design to ensure the efficient production and propagation of the 'helicon wave' electrons which are used to generate the high plasma densities.

A further, more efficient plasma wave source has been invented by Thwaites (UK patent application GB 9825324.8). This utilises a helically wound coil antenna in conjunction with non-uniform magnetic fields to both produce a high density plasma wave and to direct this to a target surface out of line of sight of the plasma source. This has the advantages of a simpler, more robust antenna and magnetic field design than the 'helicon' systems and minimises contamination of the plasma source by the target material, avoiding loss of efficiency when the targets are metals or other conducting materials. The magnetic field configuration may also be used to redirect the plasma onto the substrate, for example to pre-treat or clean the surface prior to thin film deposition.

A system based upon the invention of Thwaites as described above provides an excellent basis for a versatile sputtering system. The most notable aspect of the system is that, unlike magnetron sputtering, the target is not required to produce or sustain the high plasma density. This permits the elimination of the 'toroidal' Page 2 magnetic field used in the magnetron system with the resulting major benefit that sputtering takes place over the whole target surface, not just the ring of material within the torus. Among other advantages, this increases the target material utilisation from circa 25% (or less) to in excess of 80%; as such, the system may be regarded as a High Target Utilisation Sputtering System.

Plasma processing systems need to continually replenish the gas in which the plasma is struck. This is because the vacuum systems in which the process is run are themselves continually pumped to maintain low levels of background contaminants and in the case of plasma etching and cleaning to remove volatile or gaseous reaction products which may adversely affect the process; therefore the process gas itself is also continually pumped from the chamber. Additionally, in the case of reactive processes where the gas or a component of a gas mixture is itself consumed as part of the process, for example reactive sputtering or reactive etching, there is a need to continually replenish the process gas to maintain the appropriate process conditions.

The positioning and form of the process gas feed and vacuum pumping connections in plasma processing systems are generally considered to be unimportant compared to the plasma source and target design. Many publications omit to define these elements of the configuration altogether. Work instead concentrates on the even distribution of gas into the system to improve uniformity of deposited films or in etching processes, for example through the use of 'shower head' systems to introduce the process gas uniformly across a planar surface.

In the case of high density plasma sources, it is normal to introduce the gas at or near the plasma source to permit optimum plasma densities to be generated. For remote high plasma sources normal vacuum diffusion processes are relied upon to transport the gas into the remainder of the system to permit the plasma to be maintained to the target or substrate.

For example, Thwaites introduces ionisable gas at one end of a tube, or side arm, of dielectric material around which the helically wound coil used to generate the plasma is placed. The opposite end of the tube is connected to the main vacuum chamber containing the target and / or substrate material, from where the apparatus is vacuum pumped. Magnetic fields are used not only as part of the fundamental means to generate the high density plasma but also to guide the plasma from the side arm into the main process chamber.

The invention is concerned with the provision of multiple process gas feeds, multiple vacuum pumping locations, and multiple magnets to greatly increase the efficiency of sputtering and etching systems which utilise remote plasma sources.

In accordance with the invention there is provided apparatus for forming a high density plasma at or near a target or substrate surface in a vacuum chamber comprising:

- means of generating a high density plasma remotely from the target Page 3 - means for magnetically guiding and confining electrons from the remotely generated plasma to form a high density plasma at or near the target or substrate to be treated - means for selectively introducing one or more process gases into the apparatus at one or more locations - means for vacuum pumping the apparatus at one or more locations wherein the location and amounts of process gas introduced, the location and pumping speeds of the vacuum pumping means, and the magnetic confinement arrangement of the plasma electrons having left the remote plasma source may, in addition to other process parameters, be adjusted to provide optimum conditions for the deposition of thin film materials onto a substrate or the etching of a substrate.

It has been surprisingly discovered that supplying the process gas primarily or totally at or close to the target rather than at the plasma source can more than double the target current and thereby provides the capability to realise greatly increased deposition or etching rates for the same plasma source input power.

Associated with the above, it has been discovered that the provision of additional vacuum pumping to remove process gas at the plasma source ca further increase the target current and thereby provides the capability to realise further increases in deposition or etching rates for the same plasma source input power It has also been discovered that additional magnetic confinement of the plasma electrons within the main vacuum chamber which contains the target and substrate can further substantially increase the target current and hence provides further capability to increase the deposition or etching rate for the same plasma source input power.

It has also been discovered that, when used in conjunction with a high target utilisation process, a reactive deposition process can unexpectedly be made more stable by the relocation of the inlet for the reactive gas, for example oxygen, to a position within the main process chamber remote from the target. This has a major benefit when used with the deposition of oxides in that good quality films are able to be reproducibly deposited without the usual costly optical emission spectrometry based feedback control systems used to continuously monitor and carefully adjust the reactive gas content which are normally essential in such processes.

The process of the invention is performed within a vacuum system comprising a main process chamber in which the target material and substrate and their associated support, power and cooling requirements and other systems supporting the process are installed. The necessary construction of the chamber, vacuum pumping means, controls and supporting systems, and the means of applying voltages to targets and substrates to promote sputtering or etching in the presence of a plasma are well known per se.

Page 4 A remote plasma source is attached to the main chamber with an opening between the source and the chamber such that electrons produced by the plasma source, in particular those capable of ionising the process gas, may be directed to the vicinity of the target or substrate. As a minimum the system must be vacuum pumped, preferably at the main chamber, and process gas supplied in controllable amounts at one or more preferred locations. Typically the process will be operated at process gas pressures of between 1 x10-4 and 1 X10,2 millibar.

As an example, the plasma source may comprise a helically wound antenna placed around a cylindrical quartz tube within a non-unifonn magnetic field supplied by an electromagnet as described by Thwaites. The antenna is supplied with power by a standard commercial radio frequency generator and associated impedance matching unit.

To support the process of the invention it may be necessary or desirable to 'steer' the plasma in the main process chamber onto a target or substrate positioned such that sputtered or etched materials will not be able to coat the plasma source and thereby reduce its effectiveness. This may be achieved, for example, through the use of suitably positioned electromagnets or permanent magnets.

In a preferred embodiment of the invention intended for sputtering, process gases are controllably introduced into the above described apparatus at t" distinct points; firstly at the plasma source and secondly at the target surface, the latter preferably via a gas feed ring or equivalent means of introducing the gas uniformly at the circumference of the target surface. The gas flow to each inlet is adjusted separately to achieve an optimum plasma density within the main chamber for the particular process.

In a simpler embodiment of the above, the plasma source gas feed may be dispensed with altogether if the gas conductance between the main chamber and the remote plasma source is sufficiently high to meet the plasma source supply needs by gas diffusion from the main chamber.

It will be readily appreciated that the above embodiments for sputtering may also be used for etching and cleaning processes if the target is replaced with the substrate to be etched and an appropriate process gas is used.

in a fin-ther preferred embodiment of the invention, the above described process gas feed embodiments may be supplemented by additional vacuum pumping of the remote plasma source to further enhance the plasma density in the main chamber. Ideally, this vacuum pumping is provided at a location between the opening to the main process chamber and the power input means. Ideally the plasma source input gas feed is located on the opposite side of the power input means.

For example, when using a helicon antenna or, more preferably, the helically wound coil antenna described by Thwaites, the supplementary vacuum pumping aperture will ideally be placed between the antenna and the main process chamber, and the plasma source gas feed will ideally be on the other side of the antenna.

Page 5 The opening between the plasma source and the main process chamber may optionally include a restricting aperture to enhance the efficacy of the supplementary pumping.

In an alternative embodiment of the above, the vacuum pumping of the whole system may be provided solely via the remote plasma source vacuum pumping means.

In a preferred embodiment of the invention intended for reactive sputtering, an additional reactive process gas is separately controllably introduced at a separate location into the apparatus described in the embodiments above. This additional reactive gas feed must be positioned such that the partial pressure of the reactive gas at the substrate is greater than the partial pressure of reactive gas at the target when the process is operating. This permits the establishment of process conditions which can provide unusually stable deposition of compound materials resulting from the reactive process.

As an example, it has been shown that an aluminium target may be sputtered in an argon and oxygen gas mixture to deposit thin films of good quality aluminium oxide at far higher deposition rates than are achievable from the direct sputtering of an aluminium oxide target at a fixed oxygen flow rate. The process does not require continual automatic variation of the oxygen flow to maintain the required process conditions as is the case in conventional magnetron sputtering..

More surprisingly, it has also been discovered that, for example, the above aluminium oxide process is able to be started from a state in which the target surface is already oxidised, for example as a result of establishing the required gas flows and plasma in the chamber prior to initiating sputtering. This provides further benefit in that simple start up processes can be used and the process intrinsically recovers from conditions which would normally preclude continuation without major corrective action. For example following temporary target bias shut down during arc suppression.

In alternative embodiments of the invention and irrespective of the process gas feed and vacuum pumping arrangements, one or more magnets are used to produce a magnetic field within the main process chamber such as to confine and direct the ionising electrons emitted from the plasma source and thereby increase the plasma density in the vicinity of the target or substrate.

For ease of use and optimisation of the process, electromagnets may be used to produce the required magnetic field, though permanent magnets may also be suitable.

Ideally in a preferred embodiment, the magnetic confinement scheme will be combined with the gas feed and vacuum pumping improvements described previously to provide the best possible plasma density in the process chamber under this invention.

For a better understanding of the invention, reference will now be made, by way of exemplification only, to the accompanying drawings in which:

Page 6 Figure 1 is a schematic representation of an apparatus of the invention intended generally for sputtering processes, including reactive processes.

Figure 2 is a schematic representation of an apparatus according to figure 1 including additional vacuum pumping of the plasma source.

Figure 3 is a schematic representation of an apparatus according to figure 2 including magnetic confinement of the main process chamber plasma.

The invention arose in the course of work to develop a high rate reactive sputtering process for the deposition of aluminium oxide in a High Target Utilisation Sputtering System based on the apparatus described by Thwaites. With reference to the figures, the essential differences between the conventional system and the apparatus of the invention and the advantages resulting will be described.

The apparatus shown in figures 1 to 3 provide a generic form of the invention intended for sputtering purposes, though with minor and well understood changes it could be adapted for etching processes.

With reference to figure 1, the following elements comprise a standard apparatus according to Thwaites. Figures 2 and 3 contain the same basic elements.

The system essentially comprises a main process chamber 10 of stainless steel with usual vacuum pumping, control and facilities 11 permitting the system to be evacuated to a pressure of less than 10-6 millibar, connected via a control valve 12.

A side arm plasma source comprising a quartz tube 13 with a water cooled 13.56 Nfl-1z RF supplied antenna 14 and gas feed stainless steel end plate 15 is mounted on one side of the chamber; the plasma source is completed by the provision of a 'launch' electromagnet 16 positioned co- axially around the side arm tube and positioned between the R.F antenna 14 and the main process chamber 10 in accordance with Thwaites.

The process gas mixture is supplied from separate high purity bottles of the respective gases, the mixture being controlled by commercial mass flow controllers (WCs) feeding into a stainless steel gas manifold. The manifold is connected via stainless steel tube 17 to the side arm plasma source via the gas feed end plate 15 as shown. The gas flows are set to produce the required chamber pressure and oxygen content.

At appropriate RF input power to the antenna 14, typically between 500 and 500OW, and with a DC current flowing in the launch electromagnet 16 to produce a suitable strength of magnetic field, typically 0.01 to 0.05 Tesla measured within the coil and along the coil centre line, the plasma source produces the required high density plasma in argon gas, typically at 2 x 1 W' millibar pressure, and projects this plasma into the main process chamber 10.

At the main process chamber a further externally mounted 'steering' electromagnet 18, DC powered to produce the same magnetic polarity field and similar magnetic strength as the launch electromagnet 16, is used to produce a 'bent' magnetic field

Page 7 profile to steer the plasma onto the surface of a target material 19 mounted such as to face the base of the chamber as shown. The target 19 is mounted on a water cooled holder 20 connected to a DC power supply 21 able to supply a negative potential of between 0 and 2000 volts.

With DC potentials in excess of 100 volts applied to the target 19, ions are drawn from the plasma in the vicinity of the target surface, this flux being observed as a target current and is dependent upon the plasma source power and argon gas pressure. For example, a plasma source RF power of 1. 11 kW at an argon pressure of about 2.5xl 0-3 millibar produces a target current of about 0.2 A on a 7.5 cm, diameter aluminium target.

A substrate holder 22 is installed facing the target and vertically displaced approximately 15 cm below the target surface 19, thereby remaining clear of the plasma 'beam' in the chamber. The substrate platform 22 is capable of being controllably heated, to circa 350 degrees Celcius, to support a reactive process.

The improvements according to the invention and the advantages resulting are exemplified in the apparatus of figures 1 to 3 as follows.

In the embodiment of the invention shown in figure 1, provision, is made to supply the process gases at three points.

The first and main feed is such as to admit the ionisable, usually nonreactive gas, for example argon, at or near the periphery of the target surface. A number of means have been tried to achieve this and all have proven effective. For example therefore it is possible to introduce the gas into the main process chamber 10 via suitable pipe work 23 to a distribution ring 24 placed at the periphery of the target as shown in the figure, or into the dark space gap between the target holder and earth shield and thence to the target periphery, or even simply to a location on the opposite side of the target holder to the vacuum pumping aperture(s) and thence by diffusion to the target surface.

The conventional gas feed 17 now becomes a secondary and optional gas feed and provides additional process gas to the plasma source to ensure an adequate supply of neutral gas for plasma generation. Preferably the inlet is positioned on the far side of the power input device, for example the RF antenna, from the main process chamber.

A third gas feed 25, which is also optional, is provided primarily as an inlet for the reactive gas or gases, for example oxygen, to be used in a reactive sputtering process. This is positioned so as to be closer to the substrate surface than the target surface, preferably being located between a vacuum pumping aperture and the substrate, in order to minimise the possibility of unintentionally and detrimentally contaminating the target surface.

Clearly, the use of the various gas inlets can be adapted to suit the particular process desired and gas mixtures may be introduced at one or more of the inlets if required. For example, it may be found beneficial to introduce reactive gas mixtures at the side arm inlet in order to have the mixture ionised or otherwise 'energised' by the plasma source to improve its reaction rate.

Page 8 Substantial improvements result from the use of the above gas inlet scheme.

Introducing a part or all of the process argon gas at the target gas feed 24 rather than the conventional side arm feed 17 can result in a significant increase in target current and thereby comparable increases in thin film deposition rate for the same plasma source input power.

For example, at 2.5 X10-3 millibar chamber pressure, feeding all the argon gas to the system via the target gas feed has been shown to more than double the target current for otherwise identical process conditions.

For a reactive sputtering process the third process gas feed 25 results in a more stable reactive process in situations where the target surface is readily and detrimentally reacted by the reactive gas.

For example when sputtering aluminium in an argon and oxygen gas mixture of circa 3 X10-3 millibar pressure fed into the system through the normal gas feed 17 and at a target power of circa 900 watts or more, it was found impossible to achieve an inherently stable reactive process such that good quality aluminium oxide films were deposited at the high rates associated with an unoxidised alurniniuni target surface.

When the gas inlets were provided such that the argon gas was input from the target gas feed 24 and the oxygen was input from the substrate gas feed 25, the process became inherently stable and good quality aluminium films were achieved at very high deposition rates.

The apparatus shown schematically at figure 2 exemplifies an alternative embodiment of the invention in which multiple pumping means are provided to permit deliberate vacuum pumping of the remote plasma source. The apparatus includes the gas inlet arrangements shown in the previous example and ideally requires both the target gas feed 24 and the side arm gas feed 17 to be used to obtain best performance.

The chamber is vacuum pumped normally as shown. An additional, controllable pumping means 26, having a capability to produce a vacuum of less than for example 1 x 10-4 millibar, i. e. below the required process pressure, is attached to the plasma source side arm 13 ideally between the power input means 14, for example the RF antenna, and the main process chamber 10 and on the opposite side of the power input means 14 from the side arm gas inlet 17 as shown.

An optional throttle valve 27 may be included to provide control of the secondary pump rate.

The above provides the optimum configuration to allow the gas pressure to be suffliciently high at the plasma power input 14 to avoid gas depletion effects, whilst reducing the gas pressure in the transit region between the power input region 14 and the main chamber 10 to minimise the energy loss processes resulting from electron neutral collisions in this region.

Page 9 Optionally, an annular aperture 28 of suitable high temperature material may be inserted at the side arm attachment to the main process chamber in order to increase the pressure segregation of the side arm 13 and main chamber 10 and permit a wider range of process conditions to be achieved. Clearly the aperture needs to be of sufficient size to avoid intercepting the plasma leaving the side arm, else attenuation of the main chamber plasma density will result.

In principle, it is possible to pump the apparatus solely via the side arm pumping unit 26 and thereby delete the usual chamber pumping means 11. This is not, however, a preferred configuration as it is likely to lead to process limitations due to the more restricted options for local pressure and process optimisation. Such a scheme may however prove effective in certain circumstances where design simplicity is desired. The advantage of the additional pumping arrangement is that it permits

better optimisation of the local gas pressures in the apparatus. For example it has been shown that for 3x 10-3 millibar chamber pressure and above, additional side arm pumping provides target current increases of circa 9% and correspondingly increased deposition rates.

Figure 3 shows an alternative embodiment of the invention in which an additional electromagnet 29 is used to further increase the plasma density in the main process chamber and thereby increase the target current.

The magnet 29 is positioned on the opposite side of the main process chamber 10 from the launch electromagnet 16 and has the same magnetic polarity and similar field strength- In this way it interacts with the magnetic fields of the launch electromagnet 16 and steering electromagnet 18 so as to improve the plasma containment in the vicinity of the target surface 19 and substrate and thereby increases the plasma density under otherwise identical process conditions.

It will be readily appreciated that more than one additional magnet, permanent or electro, magnets and variable field strengths and directions may be used to achieve similar effect and improvements, the key element being that the magnetic field shaping should improve the plasma density within the main process chamber in the vicinity of either the target or substrate, dependent upon the process desired.

It will also be appreciated that, whilst the preferred embodiment of the invention shown by figure 3 uses the magnetic, gas feed and pumping configurations to jointly increase the main chamber plasma density, the magnetic means can be used in isolation with any system which remotely produces a gas plasma and feeds it into a process chamber for subsequent use.

The advantage of the additional electromagnet is that increased target current and a corresponding increase therefore in deposition rate can be obtained for otherwise identical process conditions. For example, increases in target current of 10% or more have been demonstrated for a variety of deposition processes in apparatus separately utilising both an additional electromagnet and suitable permanent magnet.

Page 10 In addition there are certain processes in which the provision of a magnetic field at the substrate is of value. For example, an important aspect of the deposition of iron nitride is that the thin film should ideally be deposited in a region of uniformly directed magnetic flux to eliminate the need for later processing to induce the required magnetic alignment. This can be readily achieved using the above apparatus with additional beneficial effect on the deposition rate.

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Claims (6)

1. Apparatus for forming a high density plasma within a vacuum process chamber for use with sputter deposition or plasma etching processes comprising: means of generating a high density plasma remotely from the process chamber means for vacuum pumping the apparatus means for controllably introducing one or more process gases into the apparatus at or near the target or substrate to be treated means for magnetically guiding and confining electrons from the remotely generated plasma to form a high density plasma at or near the target or substrate to be treated means for applying a negative voltage to the target or substrate or both in order to promote sputtering, etching or other modification of the target material or substrate or both as required by the desired process wherein the process gas inlet is located and designed to provide the highest gas pressure in the vicinity of the target.

2. Apparatus for forming a high density plasma within a vacuum process chamber for use with sputter deposition or plasma etching processes comprising: apparatus as defined in claim 1 additional means for controllably introducing one or more process gases into the apparatus at the remote plasma source to provide a separate additional source of ionisable gas

3. Apparatus for forming a high density plasma within a vacuum process chamber for use with reactive sputter deposition processes comprising: apparatus as defined in claim 1 or 2 additional means for controllably introducing a reactive process gas or gas mixture into the apparatus at a location close to the substrate such that the substrate experiences a higher partial pressure of the reactive gas than the sputter target.

4. Apparatus for forming a high density plasma within a vacuum process chamber for use with sputter deposition, including reactive sputter deposition, or plasma etching processes comprising: apparatus as defined in claims 1 to 3 Page 12 additional means for separately and controllably vacuum pumping the remote plasma source to provide additional means for optimising the high density plasma in the process chamber optionally a pump speed limiting aperture between the remote plasma source and the process chamber

5. Apparatus for forming a high density plasma within a vacuum process chamber for use with sputter deposition, including reactive sputter deposition, or plasma etching processes comprising: apparatus as defined in claims 1 to 4 magnetic means for additionally confining and directing the chamber plasma such as to increase the plasma density at or near the target or substrate to be treated.

6. Apparatus for forming a high density plasma within a vacuum process chamber for use with sputter deposition, including reactive sputter deposition, or plasma etching processes comprising: apparatus as defined in claims 1 to 5 in which the remote plasma source is a system which accelerates plasma electrons to high energies and into the process chamber through the interaction of a RF antenna and magnetic field.

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