GB2599392A - Sputter deposition apparatus and method - Google Patents

Sputter deposition apparatus and method Download PDF

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Publication number
GB2599392A
GB2599392A GB2015460.5A GB202015460A GB2599392A GB 2599392 A GB2599392 A GB 2599392A GB 202015460 A GB202015460 A GB 202015460A GB 2599392 A GB2599392 A GB 2599392A
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Prior art keywords
plasma
sputter
helicon
deposition apparatus
sputter deposition
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GB2015460.5A
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GB202015460D0 (en
GB2599392B (en
Inventor
Gauter Sven
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Dyson Technology Ltd
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Dyson Technology Ltd
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Priority to CN202111119888.7A priority patent/CN114318259A/en
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32009Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082Radio frequency generated discharge
    • H01J37/321Radio frequency generated discharge the radio frequency energy being inductively coupled to the plasma
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34Sputtering
    • C23C14/35Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32009Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082Radio frequency generated discharge
    • H01J37/321Radio frequency generated discharge the radio frequency energy being inductively coupled to the plasma
    • H01J37/3211Antennas, e.g. particular shapes of coils
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32009Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32357Generation remote from the workpiece, e.g. down-stream
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32431Constructional details of the reactor
    • H01J37/3266Magnetic control means
    • H01J37/32669Particular magnets or magnet arrangements for controlling the discharge
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32431Constructional details of the reactor
    • H01J37/32733Means for moving the material to be treated
    • H01J37/32752Means for moving the material to be treated for moving the material across the discharge
    • H01J37/32761Continuous moving
    • H01J37/3277Continuous moving of continuous material
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/34Gas-filled discharge tubes operating with cathodic sputtering
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/34Gas-filled discharge tubes operating with cathodic sputtering
    • H01J37/3411Constructional aspects of the reactor
    • H01J37/3414Targets
    • H01J37/3417Arrangements
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/34Gas-filled discharge tubes operating with cathodic sputtering
    • H01J37/3464Operating strategies

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Analytical Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physical Vapour Deposition (AREA)
  • Plasma Technology (AREA)

Abstract

A sputter deposition apparatus (100, figure 1) comprises a process chamber (102), a substrate assembly (106) and a sputter target assembly (110) defining a deposition zone (112) therebetween, a helicon plasma source array 116 comprising a plurality of helicon plasma sources 117 each comprising a radio frequency (RF) antenna 118 for generating helicon waves that propagate away from the antenna in a launch direction 142 to generate a plasma 138. The array is preferable elongate to generate a sheet of plasma extending laterally into the deposition zone. Each plasma source may generate a plume of plasma 144 that overlaps with an adjacent plume. First and second pluralities of plasma sources (517a, 517b, figure 10) may be provided at opposite sides of the deposition zone. One or more permanent magnets (428, figure 9b) may be provided to establish a magnetic field having a direction parallel to the launch directions. The substrate assembly may comprise one or more rollers (246, 248, 250, figure 4) for transporting a flexible substrate (204) through the deposition zone.

Description

SPUTTER DEPOSITION APPARATUS AND METHOD
Field of the Invention
The present invention concerns a sputter deposition apparatus, and more particularly concerns plasma generation in a sputter deposition apparatus. The invention also concerns a method of sputter deposition.
Background of the Invention
Deposition is a process by which a 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 a target material in a condensed phase is vaporised to produce a vapour. The vapour is then condensed onto the substrate surface. An example of PVD is sputter deposition, in which particles are ejected from a sputter 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. Particles are ejected from the sputter target by bombardment by the ions of the plasma. The ejected particles may then deposit on the substrate surface. Sputter deposition has advantages over other thin film deposition methods, such as evaporation, in that the target material may be deposited without the need to heat the target, 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 sputter target. The increase of plasma density can lead to an increased deposition rate. However, use of magnetrons results in a circular "racetrack" shaped erosion profile of the sputter target, which limits the utilisation of the sputter target and can negatively affect the uniformity of the resultant -2 -deposition. It is desirable to provide uniform and/or efficient sputter deposition to allow for improved utility in industrial applications.
W02011/131921 discloses a sputter deposition apparatus in which a uniform plasma of density 1011 cm-3 is generated by an elongate gas plasma source separately from a sputter target. The plasma so generated is magnetically guided and confined to the vicinity of the sputter target. Such remotely generated plasma arrangements can provide various advantages over magnetron arrangements; for example, more uniform (less localized) sputtering of the sputter target can be obtained, which can lead to substantial increased in deposition rate, and the ability to operate and/or maintain the sputter target in conditions which would be unsuitable for the generation of plasma.
In general, the higher the plasma density in the sputter deposition apparatus, the higher the deposition rate that can be obtained. (The plasma density may also be referred to as the electron density, or the number of free electrons per unit volume). It is known that helicon plasma sources have a high ionization efficiency and can thus generate high plasma densities. In general, helicon plasma sources can produce higher plasma densities than can be produced using inductively coupled plasma (ICP) sources. In an ICP, the plasma can efficiently shield itself from the external oscillating field, and thus only skin heating of the plasma within a thin layer may be experienced. Helicon plasma sources generate helicon waves which can propagate into the plasma, which may excite the plasma to a greater depth by wave heating. It is known to use helicon plasma sources to generate plasma in a sputter deposition apparatus. However, prior art helicon plasma sources typically require a cylindrical source chamber, which can be difficult to scale up for sputter deposition onto large substrates. In particular, it can be difficult to scale-up such plasma sources whilst maintaining a uniform distribution of plasma in the process 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 sputter deposition apparatus and/or method of sputter deposition.
Summary of the Invention
The present invention provides, according to a first aspect, a sputter deposition apparatus for sputtering a sputter material from a sputter target onto a substrate, the sputter deposition apparatus comprising: a process chamber; a substrate assembly -3 -arranged to receive the substrate; a sputter target assembly arranged to receive the sputter target, the sputter target assembly being spaced apart from the substrate assembly, a deposition zone being defined between the sputter target assembly and the substrate assembly; a helicon plasma source array comprising a plurality of helicon plasma sources, each helicon plasma source comprising a radio frequency (RF) antenna arranged to be driven by a current so as to generate helicon waves that propagate away from the antenna in a launch direction and thereby generate a plasma (e.g. in a plasma generation region).
Combining the output of a plurality of helicon plasma sources may allow a relatively large region of uniformly dense plasma to be generated in the process chamber. Uniformity may be improved and/or achieved by way of adjusting and optimising the power, angle and spacing between the helicon plasma sources. Using an array of comparatively smaller helicon plasma sources to produce the plasma, rather than scaling-up one larger helicon plasma source, may provide advantages including: the ability to utilise proven and well understood plasma antenna designs, higher efficiency due to comparatively smaller losses, easier and cheaper prototyping of new sputter deposition apparatus designs, and improved flexibility of the sputter deposition apparatus, for example, the helicon plasma antennas could be rearranged to optimise the plasma generation depending on the application, and/or smaller substrates could be processed using only a subset of all the helicon plasma sources.
The plasma generated by the helicon plasma sources may have a plasma density of 10" m" or higher. The plasma generated by the helicon plasma sources may have a plasma density in the range 10" to 1019 m'. The sputter deposition apparatus may be configured such that, in use, the plasma density at the sputter target assembly (and in use at the sputter target) is 1017 m' or higher. Plasma having a plasma density of 10' m" or higher may herein be referred to as high density plasma. The helicon plasma sources of the helicon plasma source array may be arranged to collectively generate a sheet of plasma. Preferably, the sheet is a sheet of high density plasma. The sheet of plasma may have a substantially uniform plasma density. The sheet of plasma may extend into the deposition zone. The sheet of plasma may extend over the sputter target assembly. In use, the sheet of plasma preferably extends over and makes contact with a sputter target received by the sputter target assembly. The sheet of plasma may have a length, width, and thickness, -4 -whereby the length and width are at least twice, at least three times, or at least four times the thickness The sputter deposition apparatus may be configured such that the plasma density is lower at the substrate assembly than at the sputter target assembly.
Accordingly, in use, the plasma density may be lower at the substrate than at the sputter target. For example, there may be a plasma present at the substrate, but not a high density plasma. I.e. the plasma density at the substrate assembly (and in use at the substrate) may be less than 10'' m-3. It may be difficult to cool the substrate in the near vacuum environment of the process chamber Therefore such an arrangement may be advantageous where the substrate is thermally sensitive and/or could be damaged if it came into contact with high density plasma.
The helicon plasma sources may each comprise a cylindrical source chamber. The plasma may at least partly be generated in the cylindrical source chamber. The helicon plasma sources may each comprise a single loop antenna, a multi loop antenna, a helical type antenna (e.g. a fractional or integral helical type antenna), or a Nagoya type-III antenna. In alternative embodiments, other antenna types could be used, for example spiral (i.e. stove top) type antennas could be used.
The helicon plasma source array may be provided inside the process chamber, i.e. within the chamber containing the process gas (e.g. argon). The sputter deposition apparatus may comprise a housing arranged to electrically isolate the antennas from the plasma generated in the plasma generation region. The housing may be hermetically sealed, for example so process gas cannot enter the housing. The inside of the housing may be at atmospheric pressure. The cylindrical source chambers may define apertures into and/or through the housing.
In alternative embodiments, the helicon plasma source array is provided outside the process chamber. The antennas may be provided proximate a wall of the process chamber such that helicon waves generated by the antenna generate the plasma in the plasma generation region inside the process chamber. The cylindrical source chamber of each helicon source may be mounted to the wall of the process chamber, the inside of the source chamber being in fluid communication with the inside of the process chamber In alternative embodiments, the helicon plasma source array is provided within the process chamber but no housing is provided as such. The antennas may have a -5 -coating, for example a sintered ceramic coating, that electrically isolates each antenna from the plasma generated in the plasma generation region.
Each helicon plasma source may be configured to produce a plume of plasma, each plume overlapping with an adjacent plume produced by an adjacent helicon plasma source. Preferably the helicon plasma sources are arranged so as to maximise the uniformity of the plasma density generated across the helicon plasma source array. For example, the helicon plasma sources may be arranged to maximise the uniformity of the plasma density laterally across the plasma sheet.
The helicon plasma source array may be elongate in a lengthwise direction.
That is to say, the helicon plasma sources which make up the helicon plasma source array may be positioned in an arrangement having an elongate shape. The sheet of plasma may extend laterally (e.g. as between two opposing lateral edges) in the lengthwise direction.
The helicon plasma source array may comprise four or more, five or more, six or more, or ten or more helicon plasma sources. The helicon plasma sources may each have a diameter (e.g. being measured transverse to the launch direction) which is a quarter of or less, a fifth of or less, a sixth of or less, or a tenth of or less than the length (e.g. in a lengthwise direction) of the helicon plasma source array. That is, the length of the helicon plasma source array may be at least four times, five times, six times, or ten times the diameter of a single helicon plasma source. The helicon plasma sources may each have a diameter of 20cm or less, 15cm or less, 10cm or less, or 5cm or less.
The helicon plasma sources may be arranged as a linear array (e.g. in which the helicon plasma sources are provided side-by-side in a straight line). The helicon plasma sources may be provided in a plurality of rows. For example, helicon plasma sources may be arranged as two linear rows. The rows may be vertically offset from each other (e.g. the rows may be above and below each other). The helicon plasma sources in each row may be directly above and below each other, thereby forming a rectangular array. The helicon plasma sources in each row may be laterally offset from each other, the helicon plasma sources thereby may have a staggered arrangement.
The helicon plasma sources may be arranged such that at least some (e.g. at least half, and optionally all) of the helicon plasma sources have their launch direction parallel to each other. The helicon plasma sources may be arranged such that some of -6 - (e.g. at least half of) the helicon plasma sources (e.g. the plasma sources in a first row) have their launch direction parallel to a first direction, and some of (e.g. the other of) the helicon plasma sources (e.g. the plasma sources in a second row) have their launch direction parallel to a second direction, different from the first direction. The first direction and the second direction may be convergent. I.e. at least some of the helicon plasma sources may have convergent launch directions.
The helicon plasma sources may be arranged on different (e.g. opposite) sides of the deposition zone. There may be a first plurality of helicon plasma sources (e.g. arranged in a row) at a first side of the deposition zone, and a second plurality of helicon plasma sources (e.g. arranged in a row) at a second side of the deposition zone. The first and second plurality of helicon plasma sources may both have their launch directions directed towards the deposition zone. The helicon plasma sources may be staggered such that the helicon plasma sources on the first side of the deposition zone are laterally offset from the helicon plasma sources on the second side of the deposition zone. The plumes of the helicon plasma sources on the first side may overlap (e.g. the lateral edges of the plumes may overlap) with the plumes of the helicon plasma sources on the second side. Such an arrangement may contribute to improved uniformity of the plasma density.
The sputter deposition apparatus may be configured such that the current provided to each antenna can be independently controlled. In alternative embodiments, the antennas may be connected such that they are driven by the same current.
The sputter deposition apparatus may comprise one or more magnets (e.g. launch magnets) configured to establish a magnetic field having a direction that is substantially parallel to the launch direction of each helicon plasma source. The helicon waves may propagate along the magnetic field lines established by the launch magnets. There may be one or more (e.g. a pair) of such magnets provided for each helicon plasma source individually. 1.e. each helicon plasma source may have its own magnet(s) associated with it. In other embodiments, there may be one or more (e.g. a pair) of such magnets which establish a magnetic field over a plurality of (e.g. all of) the helicon plasma sources in the helicon plasma source array. The (launch) magnets may be permanent magnets. Permanent magnets may advantageously be easier to provide at a small form-factor. The (launch) magnets may be electromagnets. Electromagnets may provide a magnetic field whose strength is controllable, which -7 -may help manipulate and/or optimise the shape of the plasma so generated. At least some of the magnets may be provided within a housing of the helicon plasma array. In embodiments, the launch magnets may be on an opposite side of the deposition zone to the respective antennas. For example, each antenna may individually have a launch magnet associated with it, wherein said launch magnet is provided on the opposite side of the deposition zone to said antenna.
The deposition zone may be remote from the plasma antenna assembly. The sputter deposition apparatus may comprise a confining arrangement comprising one or more magnets arranged to provide a confining magnetic field to confine the plasma generated by the helicon plasma sources to the deposition zone. The magnets of the confining arrangement may be in addition to the launch magnets, although it will be appreciated that the launch magnets may contribute to a confining magnetic field which confines the plasma. At least some of (e.g. at least one of) the magnets of the confining arrangement may be provided in the process chamber remote from the helicon plasma source array. For example, at least some of (e.g. at least one of) the magnets may be provided at distal side of the deposition zone from the helicon plasma source array. The confining arrangement may confine the (high density) plasma to a specific region in the process chamber, there being other regions which, as a result of the confining magnetic field, do not comprise (high density) plasma.
The confining arrangement may comprise one or more magnets configured to direct (e.g. bend) the magnetic field lines towards the sputter target assembly and, in use, the surface of the sputter target. The magnetic field lines may open-up (i.e. get further apart) as they approach the sputter target.
The sputter deposition apparatus may be configured such that the distance between the helicon plasma array and the sputter target can be changed. For example, the sputter deposition apparatus may be configured such that the sputter target can be positioned within the process chamber at different distances from the helicon plasma array. In an embodiment, the helicon plasma source array may be moveable towards and away from the deposition zone. The plasma density may reduce (e.g. drop-off) with increasing distance from the helicon plasma source array. Therefore such an arrangement may provide a way to change the plasma density at the sputter target. There may be a plurality of sputter target assemblies. Each sputter target assembly may be associated with a different deposition zone. In use, each sputter -8 -target assembly need not receive the same sputter material. In embodiments, at least two sputter target assemblies receive a different sputter material There may be a plurality of helicon plasma antenna arrays. Each helicon plasma antenna array may be associated with a different sputter target assembly and/or deposition zone.
The substrate assembly may be arranged to move the substrate within the process chamber (e.g. during the sputter deposition process). The substrate assembly may be arranged to guide the substrate along a curved path. The substrate assembly may comprise one or more rollers. The roller(s) may be arranged to transport the substrate through the deposition zone(s). The deposition zone(s) may be defined between a roller and the sputter target assembly. The substrate may be flexible, for example to allow it to be passed over the roller(s). The substrate may be unwound from one roller, and wound onto another roller. A sputter deposition apparatus comprising such a roller arrangement may be known as a roll-to-roll or reel-to-reel sputter deposition apparatus. The substrate may pass over an intermediate roller (e.g. between the unwinding and winding rollers). The deposition zone(s) may be defined between the intermediate roller and the sputter target assembly.
The confining arrangement may be arranged to confine the plasma into a curved sheet. The curved sheet may extend partly around least one roller (e.g. the intermediate roller). At least part of the confining magnetic field may be concentric to the at least one roller. There may be a plurality sputter target assemblies and/or deposition zones provided circumferentially around the at least one roller.
The sputter deposition apparatus may further comprise a sputter target received by the sputter target assembly and/or a substrate received by the substrate 25 assembly.
The present invention provides, according to a second aspect, a method of sputter deposition using a sputter deposition apparatus according to the first aspect of the invention, the method comprising the following steps: driving the antenna with RF frequency current to so as to propagate helicon waves and generate plasma in the plasma generation region; generating sputtered material from one or more sputter targets using the plasma; and depositing the sputtered material onto the substrate. The one or more sputter targets may be positioned remotely from the helicon plasma source array. The method may comprise a step of confining the plasma from the helicon plasma source array to the deposition zone with a confining arrangement. -9 -
In alternative embodiments, a confining arrangement may be absent, and the plasma may diffuse and drift from the helicon plasma source array to the sputter target, without being confined and propagated there by a confining magnetic field established by such a confining arrangement.
The method may further comprise moving the substrate within the process chamber. The method may comprise rotating a roller so as to move the substrate through the deposition zone during sputtering. The method may further comprise unwinding the substrate from a first roller and winding the substrate around a second roller.
The antenna may be driven at a radio frequency of between 1MHz and 16Hz, 1NIHz and 100MHz, or 10MHz and 40MHz. For example, the antenna may be driven at a radio frequency of 13.56MHz.
The present invention provides, according to a third aspect, a method of configuring a sputter deposition apparatus according to the first aspect of the invention, the method comprising a step of determining a position of each helicon plasma source in the helicon plasma source array to provide, in use, a substantially uniform plasma density at the sputter target. The method of the second aspect may additionally comprise the method of the third aspect.
The present invention provides, according to a fourth aspect, an electronic device comprising a component which comprises a layer of material deposited using the method of the second aspect.
It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.
Description of the Drawings
Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: -10 -Figure 1 shows a schematic cross-sectional side view of a sputter deposition apparatus according to a first embodiment of the invention; Figure 2 shows a schematic front view of a helicon plasma source array of the sputter deposition apparatus according to the first embodiment of the invention; Figure 3 shows a schematic cross-sectional plan view of a sputter deposition apparatus according to the first embodiment of the invention, with magnetic field lines shown; Figure 4 shows a schematic cross-sectional side view of a sputter deposition apparatus according to a second embodiment of the invention; Figure 5 shows a schematic cross-sectional side view of the sputter deposition apparatus according to the second embodiment of the invention, with magnetic field lines shown, Figure 6 shows a schematic underside view of the sputter deposition apparatus according to the second embodiment of the invention, with certain components omitted for clarity; Figure 7 shows a schematic underside view of the sputter deposition apparatus according to the second embodiment of the invention, with certain components omitted for clarity, and with magnetic field lines shown; Figure 8a shows a schematic front view of an alternative helicon plasma source array for a sputter deposition apparatus according to the invention; Figure 8b shows a schematic cross-sectional side view of the helicon plasma source array of Figure 8a, Figure 9a shows a schematic front view of a second alternative helicon plasma source array for a sputter deposition apparatus according to the invention; Figure 9b shows a schematic cross-sectional side view of the helicon plasma source array of Figure 9a; and Figure 10 shows a schematic plan view of a third alternative helicon plasma source array for a sputter deposition apparatus according to the invention.
Detailed Description
Figure 1 shows a sputter deposition apparatus 100 according to a first embodiment of the invention. The sputter deposition apparatus comprises a process chamber 102. Within the process chamber there is provided a substrate assembly 106 and a sputter target assembly 110. The substrate assembly 106 and the sputter target assembly 110 are spaced apart, a deposition zone being defined therebetween. The deposition zone is indicated generally by arrow 112. Figure 1 shows a substrate 104 received by the substrate assembly 106, and a sputter target 108 received by the sputter target assembly 110. A process gas feed system 136 is provided for introducing one or more process gasses (e.g. argon) or process gas mixtures into the process chamber 102.
A moveable shutter assembly 114 is provided on a path between the sputter target 108 and the substrate 104. The moveable shutter assembly 114 has an 'open' position and a 'closed' position. In the open position, sputter material ejected from the sputter target 108 can coat the substrate 104. In the closed position, the sputter target 108 can be sputtered without coating the substrate 104. In embodiments, the moveable shutter assembly 114 can be removed or replaced with a fixed set of shields that define a coating aperture under which the substrate assembly 106 is translated so as to coat the substrate 104.
A helicon plasma source array 116 is also provided within the process chamber 102. The helicon plasma source array 116 comprises a plurality of individual helicon plasma sources 117. Each helicon source 117 comprises a radio frequency (RF) antenna 118. Each antenna 118 is individually connected to an impedance matching network 120 and a signal generator 122. The signal generator 122 is configured to drive the antenna 118 at an RF frequency. The signal provided to each antenna can be independently controlled by the associated signal generator 122. In alternative embodiments, all the antennas 118 are connected to the same impedance matching network 120 and signal generator 122, such that all the antennas 118 are driven by the same current.
Each antenna 118 is a single-loop antenna comprising a single closed loop of conductive material wound around a cylindrical source chamber 126. When driven by the signal generator 112, the antenna 118 generates helicon waves that propagate away from the antenna 118 in a launch direction 142. The launch direction 142 is parallel to the longitudinal axis of the source chamber 126, and is normal to the plane in which the loop of conductive antenna material is provided. The helicon waves generated by the antenna 118 ionise the process gas and generate a high density plasma 138 in a plasma generation region, indicated generally be arrow 140, within and emanating from the cylindrical source chamber 126.
-12 -The antennas 118 are provided within a housing 124 which is hermetically sealed from the rest of the process chamber 102 and which electrically isolates the antennas 118 from the high density plasma 138. In use, the inside of the housing 124 can be held at atmospheric pressure. The inside of each cylindrical source chamber is open to the process chamber 102.
Two magnets 128, 130 are further provided in the process chamber 102. In this embodiment, the magnets 128, 130 are electromagnets powered by a power supply (not shown) which allows the magnetic field strength generated by each magnet 128, 130 to be independently controlled. The first magnet 128 is a launch magnet, and is provided to a side of the helicon plasma source array 116 distal from the deposition zone 112. The magnet 128 has an elongate loop shape and is configured to establish a local magnetic field which is directed substantially parallel to the cylindrical source chambers 126. When the antennas 118 are driven by the signal generator 120, the helicon waves are launched by the antenna 118 in the launch direction 142 along the
field lines established by the magnet 128.
The second magnet 130 forms a confining arrangement and is provided at the opposite side of the deposition zone 112 to the helicon plasma source array 116. The magnet 130 has a corresponding elongate geometry to the first magnet 128. The first and second magnets 128, 130 together establish a magnetic field in the deposition zone 112, the magnetic field being directed across (i.e. parallel to) the surface of the substrate 104 and sputter target 108.
As shown in Figures 2 and 3, the helicon plasma source array 116 is a linear array of nine helicon plasma sources 117. The helicon plasma sources 117 are in a coplanar arrangement and are equispaced in a lengthwise direction (into the page in Figure 1). The helicon plasma sources 117 are also aligned such that the launch directions 142 are parallel to each other. The helicon plasma sources 117 each have a diameter D. In this case the diameter is defined by the diameter of the loop of the antenna 118. In embodiments, the diameter is 5cm and the length of the source chamber 126 is 10cm. Whilst the drawings are schematic and not to scale, the lengthwise extent (L) (measured in the lengthwise direction) of the helicon plasma source array 116 is at least nine times its thickness (i.e. at least nine times the diameter D). The helicon plasma source array 116 taken as a whole thereby has shape which is elongate in the lengthwise direction.
-13 -The helicon plasma source array 116 is oriented such that the launch direction of each helicon plasmas source 117 is directed towards the deposition zone 112. In use, the plasma generated by each helicon plasma source 117 diffuses away from the plasma generation region 140 and towards the deposition zone 112. The elongate shape of the helicon plasma source array 116 means that the high density plasma 138 collectively generated by the helicon plasma sources 117 forms into a high density plasma sheet which extends to the deposition zone 112 and over the sputter target 108. The magnetic field established by the magnets 128, 130 confines the plasma to the sheet formation. In embodiments, the high density plasma sheet is confined to a region closer to the sputter target 108 than to the substrate 104 in order to reduce or prevent high density plasma 138 contacting the substrate 104.
As can be seen, the sheet of the plasma 138 extends laterally (i.e. between its lateral edges (i.e. edges which do not adjoin the plasma generation region)) in the lengthwise direction of the helicon plasma source array 116. The helicon plasma sources 117 are spaced apart such that the sheet of plasma 138 has a substantially uniform plasma density in the lengthwise direction between the two opposing lateral edges of the sheet. Individually, the high density plasma extends from each helicon plasma source 117 to form a plume shaped region 114 of high density plasma. In this embodiment, the helicon plasma sources 117 are close enough together that adjacent plumes 144 of plasma overlap each other.
Figure 3 also shows some of the field lines of the magnetic field established by the magnets 128, 132. As can be seen, the field lines extend from the helicon plasma source array 116 to the deposition zone 112. The field lines within the deposition zone 112 are substantially parallel and the magnetic field is substantially uniform, which may promote uniform sputtering of the sputter target 108.
In alternative embodiments, the second magnet 130 is positioned above (or in alternative embodiments, within) the substrate sputter target assembly 110 so as to establish a magnetic field which is directed towards the sputter target 108.
Figure 4 shows a sputter deposition apparatus 200 according to a second embodiment of the invention. The sputter deposition apparatus 200 is a roll-to-roll (also known as a reel-to-reel) sputter deposition apparatus.
The sputter deposition apparatus 200 comprises a process chamber similar to that of the first embodiment, however the walls of the process chamber are omitted from Figures 4 and 5 for clarity. Within the process chamber is a substrate assembly -14 - 206 comprising a plurality of rollers, including a first roller 246 from which a web of substrate 204 is unwound, a second roller 248 onto which the web of substrate 204 is wound, and an intermediate roller 250 around which the web of substrate 204 is transported in a curved path (C) between the first roller 246 and the second roller 248.
A sputter target assembly 210 is provided adjacent to, but spaced apart from, the surface of intermediate roller 250. The sputter target assembly 210 is provided with a sputter target 208 suitable for plasma sputtering. A deposition zone 212 is defined between the sputter target assembly 210 and the surface of the intermediate roller 250.
A helicon plasma source array 216 is provided to one side of the intermediate roller 250. The helicon plasma source array 216 comprises a housing 224 containing a plurality of helicon plasma sources 217. The helicon plasma source array 216 has the same construction as the helicon plasma source array 116 of the first embodiment and is oriented such that the lengthwise direction of the helicon plasma source array 116 is parallel to the rotational axis of the intermediate roller 250.
The sputter deposition apparatus 200 further comprises a plurality of magnets 228, 230, 232 which are provided in the process chamber. As per the first embodiment, the magnets 228-232 are electromagnets and have an elongate geometry matching that of the helicon plasma source array 116. One of the magnets 228 is a launch magnet provided in the housing 224 and configured to establish a magnetic field local to each antenna 218 which is directed substantially parallel to the cylindrical source chamber 226. The remaining two magnets 230, 232 form a confining arrangement and are provided either side of the deposition zone 212.
As shown in Figures 5 and 7, together the magnets 228-232 establish a magnetic field having field lines which extend from the helicon plasma source array 216 and through the deposition zone 212. In doing so, the field lines pass circumferentially around a circumferential portion of the intermediate roller 250.
In use, the antennas 218 of the helicon plasma source array 216 are driven so as to launch helicon waves and generate a plasma 238 in a plasma generation region 240 remote from the deposition zone 212. The magnetic field confines and propagates the plasma 238 into a sheet which extends through the deposition zone 212. The sheet has a curved shape as it passes around the intermediate roller 250. As also shown in Figure 6, the sheet extends laterally in a direction parallel to the rotational axis 252 of the intermediate roller 250. The rollers of the substrate assembly 206 rotate and pass -15 -the substrate 204 at a constant rate through the deposition zone 212 where the substrate 204 is coated with sputter material ejected from the sputter target 208. In alternative embodiments, the sputter deposition apparatus comprises a plurality of, for example three, sputter target assemblies provided circumferentially around the intermediate roller. A deposition zone is defined between each sputter target assembly and the surface of the intermediate roller. The plasma sheet is confined so as to pass through each deposition zone. In embodiments, the sputter target assemblies each receive a different sputter material such that different material layers are deposited onto the web of substrate.
Figures 8a and 8b show an alternative helicon plasma source array 316 for use in a sputter deposition apparatus according to the invention. The helicon plasma source array 316 comprises a twelve helicon sources 317 each comprising a multi-loop antenna 318 surrounding a cylindrical source chamber 326. As per the first embodiment, the helicon plasma antennas 318 are provided in a housing and there is an elongate electromagnet configured to establish a magnetic field parallel to the longitudinal axis of the source chambers 326.
The helicon plasma sources 317 of the helicon plasma source array 316 are provided in two linear rows of six helicon plasma sources 317, the rows being vertically offset so one row is above the other row. The rows are also laterally offset from each other such that the helicon plasma sources 317 of the upper row are positioned between the helicon plasma sources 317 of the lower row. In this way, the helicon plasma sources 316 have a staggered arrangement.
As can best be seen in Figure 8b, the helicon plasma sources 317 have their launch directions 342 parallel to each other, the helicon sources 317 of the upper row having their launch direction 342 in a first plane, and the helicon plasma sources 317 of the lower row having their launch direction 342 in a second plane below and parallel to the first plane. Such an arrangement may be used to increase the thickness of the plasma sheet, for example in comparison to the linear helicon source array 116 of the first embodiment.
Figures 9a and 9b show an alternative helicon plasma source array 416 for use in a sputter deposition apparatus according to the invention. The helicon plasma source array 416 comprises eight helicon plasma sources 417 each comprising a helical antenna 418 surrounding a cylindrical source chamber 426. As per the first embodiment the antennas 418 are provided in a housing 424.
-16 -Each helicon plasma source 417 of the helicon plasma source array 416 is provided with its own launch magnet 428. The launch magnets 428 are axially magnetised permanent ring magnets (i.e. the opposing end faces of the ring have opposite poles). Each launch magnet 428 is co-axial with the cylindrical source chamber 426 and acts to establish a magnetic field local to the antenna 418 which is directed substantially parallel to the longitudinal axis of the cylindrical launch chamber 426.
The helicon plasma sources 417 of the helicon plasma source array 416 are provided in a rectangular array comprising two rows of four helicon plasma sources 417, the rows being vertically offset so one row is above the other row. The rows are laterally aligned such that the helicon plasma sources 417 of the upper row are directly above the helicon plasma sources 417 of the lower row.
As can best be seen in Figure 9b, the helicon plasma sources 417 of the upper row have their launch directions angled downwards (in a first direction), whilst the helicon plasma sources 417 of the lower row have their launch directions 442 angled straight on On a second direction), such that the launch directions converge and the high density plasma plumes 444 generated by both the upper and lower helicon plasma sources 417 overlap and also converge. This arrangement may increase the ionisation and therefore plasma density in that region of overlap and convergence.
It will be appreciated that certain features of the helicon plasma source arrays 116, 216, 316, 416 described herein may be changed or interchanged. For example, the helicon plasma source array 116 could be provided with permanent launch magnets, the helicon plasma source array 316 could have the two rows of helicon plasma sources angled such that the launch directions converge, the helicon plasma source array 416 could use single loop antennas, etc. Figure 10 shows a further alternative helicon plasma source array 516 for use in a sputter deposition apparatus according to the invention. The helicon plasma source array 516 comprises a plurality of helicon plasma sources 517a,b arranged on either side of a central deposition zone 512. The helicon plasma sources 517a,b are staggered such that the helicon plasma sources 517a on a first side of the deposition zone 512 are laterally offset from the helicon plasma sources 517b on the other side of the deposition zone 512. The plumes of the helicon plasma sources 517a on the first side overlap with the plumes of the helicon plasma sources 517b on the other side.
-17 -In the embodiment shown, the helicon plasma sources 517a,b are provided with their own launch magnet 528 to either side of a cylindrical launch chamber 526. In alternative embodiments, the launch magnet(s) could be provided on the opposite side of the deposition zone to the associated source chamber.
It will be appreciated that the precise configuration of the helicon plasma sources, in terms of the dimensions of the individual sources, the antenna type, the power, the spatial distribution, the number of sources, the launch magnet type, and the angle between them, may for each application and sputter deposition apparatus be adjusted and optimised to improve the uniformity and/or the density of the plasma within the deposition zone, in order to improve the rate and the uniformity of sputter deposition, particularly for large and very large substrates (e.g. those having dimensions in the order of one meter). The use of a plurality of smaller helicon plasma sources, as opposed to one larger and more powerful helicon plasma source, may provide flexibility in this respect which is not achievable from the use of single comparatively larger helicon plasma source. In particular, the use of a plurality of smaller helicon plasma sources may allow formation of a thinner sheet and may help control uniformity in a cross-web direction.
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. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims (4)

  1. -18 -Claims I. A sputter deposition apparatus for sputtering a sputter material from a sputter target onto a substrate, the sputter deposition apparatus comprising: a process chamber; a substrate assembly arranged to receive the substrate; a sputter target assembly arranged to receive the sputter target, the sputter target assembly being spaced apart from the substrate assembly, a deposition zone being defined between the sputter target assembly and the substrate assembly; I 0 a helicon plasma source array comprising a plurality of helicon plasma sources, each helicon plasma source comprising a radio frequency (RF) antenna arranged to be driven by a current so as to generate helicon waves that propagate away from the antenna in a launch direction and thereby generate a plasma.
  2. 2. A sputter deposition apparatus according to any preceding claim, wherein the helicon plasma sources of the helicon plasma source array are arranged to collectively generate a sheet of plasma extending into the deposition zone.
  3. 3. A sputter deposition apparatus according to claim 2, wherein the helicon plasma source array is elongate in a lengthwise direction, and the sheet of plasma extends laterally in the lengthwise direction.
  4. 4 A sputter deposition apparatus according to any preceding claim, wherein the helicon plasma source array comprises four or more helicon plasma sources A sputter deposition apparatus according to any preceding claim, wherein each helicon plasma source is configured to generate a plume of plasma, each plume overlapping with an adjacent plume.6. A sputter deposition apparatus according to any preceding claim, and wherein the plasma density is higher at the target assembly than at the substrate assembly.-19 - 7. A sputter deposition apparatus according to any preceding claim, wherein the helicon plasma sources are arranged such that at least some of the launch directions are parallel to each other.8. A sputter deposition apparatus according to any preceding claim, wherein the helicon plasma sources are arranged such that at least some of the launch directions are convergent 9. A sputter deposition apparatus according to any preceding claim, wherein a first plurality of the helicon plasma sources are provided at a first side of the deposition zone, and a second plurality of helicon plasma sources are provided at a second, opposite, side of the deposition zone.A sputter deposition apparatus according to any preceding claim, wherein the current provided to each antenna can be independently controlled 11. A sputter deposition apparatus according to any of claims 1 to 9, w-herein the antennas are connected such that they are driven by the same current.12. A sputter deposition apparatus according to any preceding claim, comprising a one or more launch magnets configured to establish a magnetic field having a direction that is substantially parallel to the launch direction of each helicon plasma source, wherein the one or more launch magnets are permanent magnets.13. A sputter deposition apparatus according to any preceding claim, wherein the sputter deposition apparatus is configured such that the distance between the helicon plasma array and the sputter target can be changed so as to change the plasma density at the sputter target.14 A sputter deposition apparatus according to any preceding claim, wherein the substrate assembly is arranged to move the substrate within the process chamber.A sputter deposition apparatus according to claim 14, wherein the substrate assembly comprises one or more rollers arranged to transport a flexible substrate through the deposition zone -20 - 16 A sputter deposition apparatus according to any preceding claim, wherein the deposition zone is remote from the plasma antenna assembly, and the sputter deposition apparatus comprises a confining arrangement comprising one or more magnets arranged to provide a confining magnetic field to confine the plasma generated by the helicon plasma sources to the deposition zone.17. A sputter deposition apparatus according to claim 16, wherein the confining arrangement is arranged to confine the plasma into a curved sheet.18. A sputter deposition apparatus according to any preceding claim, further comprising a sputter target received by the sputter target assembly, and a substrate received by the substrate assembly.19. A method of sputter deposition using a sputter deposition apparatus to any proceeding claim, the method comprising the following steps: driving the antenna with RE frequency current to so as to propagate helicon waves and generate plasma in a plasma generation region, generating sputtered material from one or more sputter targets using the plasma; and depositing the sputtered material onto the substrate.20. A method of configuring a sputter deposition apparatus according to any of claims Ito 19, the method comprising a step of: determining a position of each helicon plasma source in the helicon plasma source array to provide, in use, a substantially uniform plasma density at the sputter target.21. An electronic device comprising a component which comprises a layer of material deposited using the method of claim 20.
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