Plasma source and apparatus for atomic layer deposition

Abstract

A plasma source includes a plasma deposition head, an electrode plate, and a gas supply system. The plasma deposition head includes an aperture for delivering atmospheric plasma to a substrate and a slotted cavity extending from the aperture. The electrode plate is mounted in the slotted cavity and extends from an interior of the deposition head toward the aperture. The gas supply system includes a gas inlet, a gas supply chamber, and a gas outlet. The gas supply chamber is arranged to receive a gas mass flow from the gas inlets and to distribute the gas mass flow between the gas outlets. And the gas outlets are formed in two opposite sides of the electrode plate. In use, the gas mass flow is distributed to provide an atmospheric plasma flow on opposite sides of the electrode plate.

Description

Technical Field

[0001] The invention relates to a plasma source and an apparatus for atomic layer deposition comprising such a plasma source. Background Art

[0002] Spatial atomic layer deposition (S-ALD) is a thin film growth technique based on the continuous exposure of a substrate to a half-reaction. In plasma-enhanced ALD, the half-reaction is formed by a plasma species.

[0003] In order to improve the efficiency of the plasma source, it is beneficial to have a uniform mass flow of gas to the substrate. In the plasma source, the gas is supplied through a narrow gap along the high-voltage electrode. The gap is usually defined by the distance between one side of the high-voltage electrode and the opposite wall of the second electrode, and its gap width is set, for example, in the range of 0.05 mm to 0.25 mm. Due to manufacturing and / or alignment tolerances of the electrodes (the electrodes are usually ceramic plates with embedded conductors on substantially the entire plate surface), the gap width may vary along the gap length due to deviations in the flatness of the electrode plates in the direction of the gas mass flow, which may have a negative impact on the deposition quality. These changes in turn produce higher and lower flow resistance areas along the gap length, resulting in changes in the gas mass flow rate toward the substrate.

[0004] The uniformity of the gas mass flow rate toward the substrate depends heavily on the gap width variation. Gap width variation can be reduced by accurately defining the geometrical properties of the gap and high voltage electrode during manufacturing and assembly. However, variations inherent in the manufacturing process (e.g., flatness and straightness tolerances) may leave some geometric errors that remain a limiting factor in plasma source efficiency.

[0005] Furthermore, during operation of the plasma source, the plasma generated within the gap creates a high temperature environment. Thermal gradients and heterogeneous thermal expansion of components or structures of the plasma source may cause relative displacement and misalignment of components. Thus, during use of the plasma source, thermal effects may change the geometrical properties of the gap, thereby changing its resistance to gas flow, which may further limit its efficiency.

[0006] It is an object of the present invention to provide a plasma source, for example for atomic layer deposition, having an improved uniformity of the gas mass flow towards the substrate. Summary of the invention

[0007] In summary, the present invention relates to a plasma source. The plasma source comprises a plasma deposition head, an electrode plate and a gas supply system. The plasma deposition head comprises an aperture for delivering atmospheric plasma from the deposition head to a substrate, and comprises a slotted cavity having parallel walls extending from opposite edges of the aperture. The electrode plate is mounted in the slotted cavity and extends from the interior of the deposition head toward the aperture. The gas supply system comprises a gas inlet, a gas supply chamber and a gas outlet. The gas supply chamber is arranged to receive a gas mass flow from the gas inlet and distribute the gas mass flow between the gas outlets.

[0008] The gas outlets are provided on opposite sides of the electrode plate and, in use, the gas mass flow is equally distributed to provide an atmospheric plasma flow on opposite sides of the electrode plate.

[0009] By distributing the gas mass flow in the slotted cavity between the opposite sides of the electrode plate, the nominal gap width and the geometric variation of the gap width along the gap length (e.g., variation caused by flatness errors of the electrode plate) are reduced. Therefore, the uniformity of the gas mass flow through the gaps located on the opposite sides of the electrode plate is significantly improved compared to the conventional method of a single mass flow through a single gap.

[0010] For example, a flatness error of the electrode plate may result in an increase in flow resistance on one side of the electrode plate while causing a decrease in flow resistance on the other side of the electrode plate. Thus, differences in flow resistance along a slotted cavity on one side of the electrode plate may be compensated for by offsetting differences in flow resistance along a slotted cavity on the other side of the electrode plate. Compared to a conventional plasma source having a single gas mass flow, the distributed atmospheric plasma flows provided from opposite sides of the electrode plate provide a net combined atmospheric plasma flow with a more uniform mass flow, thereby effectively compensating for each other.

[0011] In order to deliver atmospheric plasma along a certain width of the substrate, the gas mass flow can be evenly distributed along the width of the plasma source. In this case, the gas supply chamber preferably extends along the width of the electrode plate and passes through opposite sides of the electrode plate. Therefore, the gas mass flow is supplied to a large volume arranged before the slotted cavity along the width of the electrode plate, and the slotted cavity can be used as a flow restriction so that the gas mass flow is evenly distributed along the width of the electrode plate.

[0012] In some embodiments, the gas supply chamber and the gas outlet are integrated into the plasma deposition head. In this way, the volume and channels defining the gas flow characteristics can be controlled during the manufacture of the plasma deposition head, thereby reducing the manufacturing and assembly tolerances of the plasma source.

[0013] In order to split the function, the gas supply chamber may include a distribution volume and a supply volume. The distribution volume may be connected to the gas inlet and may pass through opposite sides of the electrode plate, wherein the distribution volume is arranged to receive a gas mass flow from the gas inlet and distribute the gas mass flow between the opposite sides of the electrode plate. The supply volume may be connected to the distribution volume and may extend along the width of the electrode plate, wherein the supply volume is arranged to receive the distributed gas mass flow from the distribution volume and uniformly supply the gas mass flow along the width of the electrode plate towards the gas outlet.

[0014] The gas supply system may further comprise a channel-shaped section comprising a plurality of channels arranged along the width of the electrode plate and connecting the gas supply chamber to the respective gas outlets. Each of the plurality of channels may be arranged to direct a portion of the gas mass flow from the gas supply chamber to the respective gas outlets. In this way, the gas mass flow along the width of the electrode plate may be controlled, for example, to evenly distribute the gas mass flow along the width of the electrode. For example, by individually adjusting one or more specific portions of the gas mass flow through the plurality of channels, an uneven gas mass flow along the width of the electrode plate may be corrected.

[0015] In some embodiments, the channel-shaped segments are provided by a stack of shims installed between the slotted chamber wall and the electrode plate. The stack of shims can cover the gas supply chamber and the gas outlet, and multiple channels can be provided by cutouts in each shim of the stack of shims. By using shims, the channel-shaped segments are highly configurable, for example, by changing the size and shape of the cutouts, the number of shims in the stack, or the thickness of the shims. Therefore, different configurations of the channel-shaped segments can be created by using different combinations of shims, which can be manufactured and assembled with high precision, whereby the flow characteristics of the plasma source can be reliably determined.

[0016] In order to determine the gas mass flow from the gas supply chamber along the width of the electrode plate towards the gas outlet, the channel-shaped section may include a flow restriction. For example, a flow restriction may be provided in a plurality of channels, for example, to generate an increased flow resistance acting on a portion of the gas mass flow guided through one or more of the plurality of channels.

[0017] For example, the flow restriction may be formed by reducing the size of one or more cutouts in the backing plate.

[0018] Alternatively or additionally, the flow restriction may be formed by reducing the thickness of one or more shim plates.

[0019] In some other embodiments, the gas supply system includes a flow homogenizer, which is arranged between the channel-shaped section and the gas outlet and is arranged to distribute the gas mass flow equally along the width of the electrode plate. The flow homogenizer may include a hole extending from a plurality of channels into the wall at an acute angle and connected to a recess in the wall communicating with the slotted cavity. The recess may include a homogenizer plane oriented substantially perpendicular to the gas mass flow directed through the hole. By the gas mass flow hitting the homogenizer plane, the gas mass flow is diffused on the homogenizer plane and directed into the slotted cavity. Therefore, the gas mass flow is more evenly distributed by passing through the flow homogenizer.

[0020] In some preferred embodiments, the plasma deposition head includes a first component and a second component, the first component defining a first wall of the slotted cavity, and the second component defining a second wall of the slotted cavity. The electrode plate may include: a mountable component, the mountable component is mounted on the first component and / or the second component of the plasma deposition head; and a hangable component, the hangable component extends from the mountable component and is free on all other sides. In this way, the gas mass flow flowing along the slotted cavity wall and the electrode plate can be clearly defined with relatively high accuracy because the above-mentioned architecture basically separates the geometric features of the slotted cavity and the electrode plate into planar surfaces that are easily accessible to manufacturing tools.

[0021] The mountable part of the electrode plate may, for example, be clamped between the first and second parts of the plasma deposition head.

[0022] In some variations of these embodiments, the shim plate stack may be sandwiched between the first component or the second component and the electrode plate on opposite sides of the electrode plate. The shim plate stack may cover the gas supply chamber and the gas outlet. Each shim plate in the shim plate stack may be provided with a cutout, thereby forming a channel structure for directing a gas mass flow from the gas supply chamber through the shim plate stack to the gas outlet.

[0023] Preferably, the total thickness of each shim plate stack defines a respective nominal gap width between the first and second walls of the slotted cavity and the opposite sides of the electrode plate. Thus, the nominal gap width, and therefore the gap width variation, is determined by the shim plate thickness, which can be controlled, for example, by measurement and selection.

[0024] In some embodiments, the plasma deposition head comprises: an exhaust system for exhausting gas from the substrate, the exhaust system comprising an exhaust port and an exhaust channel integrated in the plasma deposition head, wherein the exhaust channel extends parallel to the slotted cavity between the substrate and the exhaust port on opposite sides of the electrode plate. Thus, after the atmospheric plasma interacts with the substrate, the gas can be exhausted through the exhaust channel located on either side of the electrode plate to limit the gas mass flow along the opposite sides of the electrode plate.

[0025] Preferably, the electrode plate comprises a distal edge which is aligned within 3 mm with the opposite edge of the aperture. In this way, the atmospheric plasma flows provided on opposite sides of the electrode plate are substantially maintained on the opposite sides of the electrode plate until they are transmitted through the aperture of the plasma deposition head to interact with the substrate. Therefore, geometric changes in the final section of the slotted cavity between the distal edge of the electrode plate and the opposite edge of the aperture have limited effect on the gas mass flow.

[0026] Preferably, the electrode plates include laminated alumina layers, and the metal electrode is printed on one of the alumina layers. Although the flatness of the electrode plates may be limited in this manufacturing technique, the present invention allows these types of electrode plates to be used in a plasma source regardless of geometric variations on the electrode plates by allowing the flow resistance differences along the slotted cavities on one side of the electrode plate to compensate for the flow resistance differences along the slotted cavities on the other side of the electrode plate.

[0027] The plasma deposition head may be made of a conductive material such as metal, for example. Thus, the plasma deposition head (particularly the wall of the slotted cavity) may form a counter electrode to the plate electrode for generating an atmospheric plasma in the slotted cavity.

[0028] Other aspects of the invention relate to an apparatus for atomic layer deposition comprising a plasma source as described herein.

[0029] The apparatus may further comprise a transport mechanism arranged to transport the substrate and the plasma source relative to each other parallel to the substrate plane. In this way, the atmospheric plasma transmitted from the plasma source may interact with the substrate region while being transported parallel to the substrate plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further illustrated in the accompanying drawings: Figure 1 A schematic illustration of one embodiment of a plasma source is provided; Figure 2 A cross-sectional view showing another or further embodiment of a plasma source; Figure 3 An exploded view of another or further embodiment of a plasma source is provided; Figure 4 Provided Figure 3 A cross-sectional view of an embodiment of the invention in an unexploded state; Figure 5 An apparatus for atomic layer deposition comprising a plasma source as described herein is shown. DETAILED DESCRIPTION

[0031] The present invention will be described more fully below with reference to the accompanying drawings, in which embodiments of the present invention are shown. In the accompanying drawings, the absolute and relative sizes of systems, components, layers and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic diagrams and / or cross-sectional diagrams of possible idealized embodiments and intermediate structures of the present invention. In the specification and the accompanying drawings, the same reference numerals always represent the same elements. Relative terms and their derivatives should be interpreted as referring to the orientation shown in the drawings described subsequently or discussed. These relative terms are for convenience of description, and unless otherwise stated, it is not required to construct or operate the system in a specific orientation.

[0032] Figure 1 A plasma source 100 is shown, which includes a plasma deposition head 110 having an aperture 111 for delivering atmospheric plasma from the deposition head 110 to the substrate 50. The plasma deposition head can be made of a conductive material, such as a metal, such as steel or an aluminum alloy, for example. The plasma deposition head 110 includes a slotted cavity 112 having parallel walls 113-1, 113-2 extending from opposite edges of the aperture 111. The plasma deposition head 110 can be manufactured as a single component, wherein the slotted cavity 112 is formed, for example, by milling, EDM or other suitable material removal processes. Alternatively, the plasma deposition head 110 can be composed of a plurality of subcomponents, which form the slotted cavity 112 in an assembled state.

[0033] The electrode plate 120 is installed in the slotted cavity 112 and extends from the inside of the deposition head 110 toward the hole 111. The electrode plate 120 may include, for example, a metal electrode, the side of which is covered with a dielectric layer. For example, the electrode plate 120 may be a ceramic plate, in which a metal conductor is buried, and the metal conductor extends below the surface of the ceramic plate. Alternatively, the metal electrode may include a laminated aluminum oxide layer, and the metal electrode may be printed on one of the aluminum oxide layers.

[0034] The plasma source 100 further comprises a gas supply system 130, which comprises a gas inlet 131, a gas supply chamber 132 and a gas outlet 133. The gas supply chamber 132 is arranged to receive a gas mass flow M from the gas inlet 131 and distribute the gas mass flow between the gas outlets 133, for example into mass flows M1 and M2. Figure 1As shown, the electrode plate 120 is mounted in the slotted cavity and extends from the inside of the deposition head towards the hole, so that the gas outlet 133 is arranged on opposite sides of the electrode plate 120, thereby effectively forming two slots 112-1 and 112-2, which respectively output plasma flows M1*, M2* after the corresponding gas flows M1, M2 are guided along the opposite sides of the plate 120. By installing the electrode (which has two electrode surfaces freely suspended in the slotted cavity), the flatness deviation of one surface of the electrode plate in one direction towards one slotted wall 113 (causing an increase in the current restriction along the electrode surface) and the corresponding reduction in the plasma flow can be compensated on its surface opposite to the opposite slotted wall 113, which will correspondingly reduce the current restriction, thereby effectively compensating each other, so that: in the hole 111, the reduction in plasma output in one slot 112-1 is compensated by the corresponding slot 112-2 opposite to the electrode plate.

[0035] like Figure 1 As shown, the electrode plate 120 includes a distal edge 121 that can be aligned with the opposite edge of the hole 111, so that the gas mass flows M1 and M2 passing through the slotted cavity remain substantially separated by the electrode plate 120 until they leave the hole 111. Preferably, the alignment between the opposite edge of the hole 111 and the distal edge 121 of the electrode plate 120 is within 3 mm, such as between 0 mm and 2 mm, and more preferably between 0 mm and 1 mm.

[0036] Figure 2 An embodiment of a plasma source 100 is shown in which a gas supply system 130 (e.g., a gas inlet 131, a gas supply chamber 132, and / or a gas outlet 133) is integrated into a plasma deposition head 110. These features may be provided, for example, by making holes, pockets, recesses, or channels in the wall structure of the plasma deposition head 110. For example, the gas outlet 133 may be formed by an array of holes, or may be formed by a groove or slit extending into the wall of the slotted cavity 112. The array, groove, or slit may be arranged along the width W of the electrode plate to evenly distribute the exhaust gas mass flow along the width of the electrode plate 120.

[0037] For similar reasons, such as Figure 2 As shown, the gas supply chamber 132 may extend along the width W of the electrode plate 120 and pass through opposite sides of the electrode plate 120. The electrode plate 120 may pass through the gas supply chamber 132, and one or more holes or cutouts may be provided in the electrode plate 120 within the gas supply chamber 132 to allow gas to pass from one side of the electrode plate 120 to the other side.

[0038] The plasma deposition head 110 may further include an exhaust system 140 for exhausting gas from the substrate. The exhaust system 140 includes, for example, an exhaust port 141 and one or more exhaust channels 142, which are integrated in the plasma deposition head 110. Figure 2 As shown, the exhaust passage 142 extends parallel to the slotted cavity 112 between the substrate and the exhaust port.

[0039] Figure 3 and Figure 4 An exemplary embodiment of a plasma source 100 is shown, wherein a plasma deposition head 110 includes: a first component 114, which defines a first wall 113-1 of a slotted cavity; and a second component 115, which defines a second wall 113-2 of the slotted cavity. An electrode plate 120 includes: a mountable component 122, which is mounted to the first component 114 and / or the second component 115 of the plasma deposition head. For example, the mountable component can be clamped between the first component 114 and the second component 115 of the plasma deposition head 110. The electrode plate 120 also includes: a hangable component 123, which extends from the mountable component 122 and is free on all other sides.

[0040] On opposite sides of the electrode plate 120, a backing plate stack 150 is sandwiched between the first component 114 or the second component 115 and the electrode plate 120. The backing plate stack 150 may include, for example, two or more backing plates, wherein the backing plates have the same or different thicknesses. Figure 3 and Figure 4 As shown, the shim plate stack 150 covers the gas supply chamber 132 and the gas outlet 133 , and each shim plate of the shim plate stack is provided with a cutout 134 , thereby forming a channel structure for guiding the gas mass flow from the gas supply chamber 132 through the shim plate stack 150 to the gas outlet 133 .

[0041] The total thickness of each shim plate stack 150 can be used to define the corresponding nominal gap widths between the first wall 113-1 and the second wall 113-2 of the slotted cavity and the opposite sides of the electrode plate 120. In this way, by varying the number of shim plates, and / or by varying the thickness of a single shim plate, the gas mass flow along the opposite sides of the electrode plate 120 can be determined.

[0042] like Figure 3 and Figure 4As shown, the functions of the gas supply system can be further separated by making the gas supply chamber 132 include a distribution volume 135 and a supply volume 136. The distribution volume 135 can be connected to the gas inlet 131 and can extend through opposite sides of the electrode plate 120. Therefore, the distribution volume 135 is arranged to receive the gas mass flow M from the gas inlet 131 and distribute the gas mass flow M between opposite sides of the electrode plate 120 into distributed gas mass flows M1, M2.

[0043] The supply volume 136 may be connected to the distribution volume 135 and may extend along the width W of the electrode plate 120. Therefore, the supply volume 136 is arranged to receive the distributed gas mass flows M1, M2 from the distribution volume 135 and uniformly supply the distributed gas mass flows along the width W of the electrode plate 120 toward the gas outlet 133.

[0044] The distribution volume 135 and the supply volume 136 may be formed, for example, by one or more recesses in the plasma deposition head 110. Figure 3 As shown, the distribution volume 135 may include a first portion and a second portion, wherein the gas mass flow is directed from the first portion in the first component 114, such as through a passage in the shim stack 150 and the electrode plate 120, to the first portion in the second component 114, then directed from the first portion in the second component 115 to the second portion in the second component 115, and then, directed from the second portion in the second component 115 to the second portion in the first component 114, such as through another passage or the same passage in the shim stack 150 and the electrode plate 120. Thus, the gas mass flow may be distributed across opposite sides of the electrode plate 120.

[0045] The supply volume 136 may include, for example, a first branch and a second branch, which are connected to the first part and the second part of the distribution volume 135, respectively. Figure 3 In this way, the gas mass flow can be evenly distributed along the width W of the electrode plate 120.

[0046] The gas supply system 130 may further include a channel-shaped section 137, which includes, for example, a plurality of channels 138, which are arranged along the width W of the electrode plate 120. The plurality of channels 138 may, for example, be arranged to connect the gas supply chamber 132 to the corresponding gas outlet 133, wherein each of the plurality of channels 138 is arranged to guide a portion of the distributed gas mass flow M1, M2 from the gas supply chamber 132 to the corresponding gas outlet 133.

[0047] like Figure 3 and Figure 4As shown, the channel-like sections 137 may be provided by a gasket stack 150 as described herein mounted between the slotted cavity walls 113 - 1 , 113 - 2 and the electrode plate 120 .

[0048] The channel-shaped section 137 may include a flow restriction 151 arranged to increase the flow resistance to determine the distributed gas mass flow M1, M2 flowing from the gas supply chamber 132 along the width W of the electrode plate 120 toward the gas outlet 133. The flow restriction 151 may be formed, for example, by reducing the size of one or more cutouts in the shim plate and / or by reducing the thickness of one or more shim plates.

[0049] like Figure 3 and Figure 4 As shown, the gas supply system 130 may also include: a flow homogenizer 139, which is arranged between the channel-shaped section 137 and the gas outlet 133 and is arranged to equally distribute the distributed gas mass flows M1, M2 along the width W of the electrode plate 120. The flow homogenizer 139 may, for example, include: a hole 139-1, which extends from the plurality of channels 138 into the walls 113-1, 113-2 at an acute angle and is connected to a recess 139-2 in the walls 113-1, 113-2 that communicates with the slotted cavity. The recess 139-2 may include: a homogenizer plane 139-3, which is oriented substantially perpendicularly to the distributed gas mass flows M1, M2 guided through the hole 139-1.

[0050] Figure 5 An embodiment of an apparatus 500 for atomic layer deposition is shown, which includes a plasma source 100 as described herein. In addition to the plasma source, the apparatus 500 may also include, for example, a system for supplying reagents and / or catalysts (such as nitrogen or metal organic precursors) to the substrate and a system for exhausting gases and materials from the substrate 50.

[0051] The apparatus 500 may further include a transport mechanism 550 arranged to transport the substrate 50 and the plasma source 100 relative to each other parallel to a plane P of the substrate 50. For example, the transport mechanism 550 may be arranged to transport the substrate 50, for example, along the plane P, while the plasma source 100 is stationary. Alternatively, the substrate 50 may remain stationary, while the transport mechanism 550 is arranged to transport the plasma source 100 parallel to the plane P.

[0052] Therefore, it is believed that the operation and construction of the present invention will be apparent from the foregoing description and its accompanying drawings. For the sake of clarity and concise description, features are described herein as part of the same or separate embodiments, however, it should be understood that the scope of the present invention may include embodiments having a combination of all or part of the features described.

[0053] The present invention is applicable not only to manufacturing applications where a plasma source is used for atomic layer deposition, but also to other technical, industrial or diagnostic applications where a plasma source is used. It should be clear to those skilled in the art that the present invention is not limited to any embodiment described herein and modifications within the scope of the appended claims may be considered possible. In addition, kinematic reversal is considered inherently disclosed and may be within the scope of the present invention. In the claims, any reference numerals shall not be construed as limiting the claim.

[0054] The term "lamination" as used in the text of this application and in the claims refers to the end result of any technique or process of manufacturing a multilayer material so that the composite material achieves improved strength, stability, sound insulation, appearance or other characteristics by using different materials. Laminated components or laminates are defined herein as permanently assembled objects, such as formed using heat, pressure, electricity, welding or adhesives. A variety of materials, techniques and equipment can be used to provide laminates. The present invention is not limited to electrode plates comprising alumina laminate layers, but may include any other dielectric material suitable for a plasma source, such as glass, quartz, ceramics (such as aluminum oxide or zirconium dioxide), polymers or combinations thereof. For example, a co-fired ceramic laminate can be manufactured by applying an electrode to a stack of layers and thereby heating the stack to form a composite material, the stack of layers, for example, comprising: a layer comprising a dielectric material (such as aluminum oxide or zirconium dioxide) and one or more layers comprising an organic binder material.

[0055] The terms "comprises" and "comprising" as used in this specification or the appended claims should not be interpreted in an exclusive or exhaustive sense, but should be interpreted in an inclusive sense. Therefore, the expression "comprises" or "comprising" as used herein does not exclude the presence of other elements, additional structures or additional actions or steps in addition to the listed elements, structures or actions or steps. In addition, the words "one" and "an" should not be interpreted as being limited to "only one", but are used to mean "at least one", and do not exclude a plurality. Features that are not specifically or explicitly described or claimed may be additionally included in the structure of the present invention without departing from the scope thereof.

[0056] Expressions such as "means for..." should be understood as "components configured for..." or "members constructed to..." and should be interpreted as including equivalents of the disclosed structures. The use of expressions such as "critical", "preferred", "particularly preferred", etc. is not intended to limit the invention. If structures, materials, or acts are considered essential, they are only non-explicitly indicated as essential. Additions, deletions, and modifications are generally possible within the purview of those skilled in the art without departing from the scope of the invention as determined by the claims.

Claims

1. A plasma source, comprising: a plasma deposition head comprising an aperture for delivering atmospheric plasma from the deposition head to a substrate and comprising a slotted cavity having parallel walls extending from opposite edges of the aperture; an electrode plate mounted in the slotted cavity and extending from the interior of the deposition head toward the hole; and a gas supply system comprising a gas inlet, a gas supply chamber and a gas outlet, wherein the gas supply chamber is arranged to: receive a gas mass flow from the gas inlet and distribute the gas mass flow between the gas outlets; Wherein the gas outlets are provided on opposite sides of the electrode plate, and wherein, in use, the gas mass flow is distributed to provide an atmospheric plasma flow on opposite sides of the electrode plate.

2. The plasma source according to claim 1, wherein The gas supply chamber extends along the width of the electrode plate and passes through opposite sides of the electrode plate.

3. A plasma source according to any one of the preceding claims, wherein: The gas supply chamber and the gas outlet are integrated in the plasma deposition head.

4. A plasma source according to any one of the preceding claims, wherein The gas supply chamber comprises: a distribution volume connected to the gas inlet and extending through opposite sides of the electrode plate, wherein the distribution volume is arranged to: receive a gas mass flow from the gas inlet and distribute the gas mass flow between opposite sides of the electrode plate; and A supply volume connected to the distribution volume and extending along the width of the electrode plate, wherein the supply volume is arranged to receive the distributed gas mass flow from the distribution volume and to supply the gas mass flow uniformly along the width of the electrode plate to the gas outlet.

5. The plasma source according to claim 4, wherein: The supply volume comprises a channel-shaped section comprising a plurality of channels arranged along the width of the electrode plate and connecting the gas supply chamber to respective gas outlets, wherein each of the plurality of channels is arranged for directing a portion of the gas mass flow from the gas supply chamber to the respective gas outlet.

6. The plasma source according to claim 5, wherein: The channel-like sections are provided by a shim plate stack mounted between the slotted cavity wall and the electrode plate, wherein the shim plate stack covers the gas supply chamber and the gas outlet, wherein the plurality of channels are provided by cutouts in each shim plate of the shim plate stack.

7. The plasma source according to any one of claims 5 to 6, wherein: The channel-shaped section comprises a flow restriction for determining a gas mass flow from the gas supply chamber along the width of the electrode plate towards the gas outlet.

8. The plasma source according to claim 7, wherein: The flow restriction is formed by reducing the size of one or more cutouts in the backing plate.

9. The plasma source according to claim 7 or 8, wherein: The flow restriction is formed by reducing the thickness of one or more shim plates.

10. The plasma source according to any one of claims 5 to 9, wherein: The gas supply system comprises a flow homogenizer arranged to equally distribute the gas mass flow along the width of the electrode plate, wherein the flow homogenizer comprises a hole extending from the plurality of channels into the wall at an acute angle and connected to a recess in the wall communicating with the slotted cavity, wherein the recess comprises a homogenizer plane oriented substantially perpendicular to the gas mass flow directed through the hole.

11. A plasma source according to any one of the preceding claims, wherein: The plasma deposition head comprises: a first component which defines a first wall of the slotted cavity; and a second component which defines a second wall of the slotted cavity, wherein the electrode plate comprises: a mountable component which is mounted to the first component and / or the second component of the plasma deposition head; and a hangable component which extends from the mountable component and is free on all other sides.

12. The plasma source according to claim 11, wherein The mountable component is sandwiched between the first and second components of the plasma deposition head.

13. The plasma source according to any one of claims 11 to 12, wherein: On each opposite side of the electrode plate, the shim plate stack is sandwiched between the first component or the second component and the electrode plate, wherein the shim plate stack covers the gas supply chamber and the gas outlet, and wherein each shim plate of the shim plate stack is provided with a cutout to form a channel structure for guiding the gas mass flow from the gas supply chamber through the shim plate stack to the gas outlet.

14. The plasma source according to claim 13, wherein: Each backing plate stack has an overall thickness that defines respective nominal gap widths between the first and second walls of the slotted cavity and opposing sides of the electrode plate.

15. A plasma source according to any one of the preceding claims, wherein: The plasma deposition head comprises an exhaust system for exhausting gas from the substrate, the exhaust system comprising an exhaust port integrated in the plasma deposition head and one or more exhaust channels, wherein the exhaust channels extend parallel to the slotted cavity between the substrate and the exhaust port.

16. A plasma source according to any one of the preceding claims, wherein: The electrode plate includes a distal edge that is aligned within 3 millimeters of an opposing edge of the aperture.

17. A plasma source according to any one of the preceding claims, wherein: The electrode plate includes laminated aluminum oxide layers, wherein a metal electrode is printed on one of the aluminum oxide layers.

18. A plasma source according to any one of the preceding claims, wherein: The plasma deposition head is made of conductive material.

19. An apparatus for atomic layer deposition, comprising: A plasma source as claimed in any preceding claim.

20. The apparatus of claim 19, further comprising: A transport mechanism is arranged to transport a substrate and the plasma source relative to each other parallel to a plane of the substrate.

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