Precursor deposition head and system

Abstract

A precursor deposition head of a plasma source for atomic layer deposition is disclosed. The deposition head comprises a first gas inlet connected to a first gas outlet in a wall of a slotted cavity, for directing a first mass flow of gas towards an aperture. A valve arrangement is mounted inside the slotted cavity and comprises a valve member and a valve seat. The valve member interacts with the valve seat to control the first mass flow of gas through the slotted cavity. The valve seat is formed by the first gas outlet. The valve member is operable to move inside the slotted cavity between an open state, in which the valve member and the valve seat are separated by an outflow gap, and a closed state, in which the valve member seals the first gas outlet.

Description

[0001] P138063PC00

[0002] Title: PRECURSOR DEPOSITION HEAD AND SYSTEM

[0003] The invention relates to a precursor deposition head for a plasma source for spatial atomic layer deposition. The invention further relates to a system for spatial atomic layer deposition.

[0004] In spatial atomic layer deposition (ALD), a substrate is sequentially exposed to half-reactions, e.g. as in plasma enhanced ALD, where one of the half-reactions is formed by plasma species. An ALD plasma source typically comprises a precursor deposition head, to supply a mass flow of precursor gas towards the substrate as it moves with respect to the deposition head, or vice versa. In this way, the substrate can be manufactured additively by depositing various layers. By controlling the supply of precursor towards the substrate, patterns or tracks can be made on the substrate. Generally, in such depositions, it is important that the mass flow of gas is kept at a constant rate, to ensure a uniform thickness of the layer.

[0005] During the initial startup phase of a layer deposition the mass flow of precursor gas that is supplied towards the substrate may be adjusted, e.g. increased from zero, to a constant rate for obtaining a certain layer thickness. Conversely, in the end phase, the supply of precursor gas may be gradually diluted or decreased, e.g. when the layer to be obtained on the substrate is completed. As a result, a run-in and run-out section may be present in the deposited layer. To prevent a non-uniform layer thickness in the end product, dummy substrates can be placed directly before and after the substrate to be manufactured, so that the run-in and run-out is performed on the dummy substrates only.

[0006] However, a drawback of using dummy substrates is that the process is less efficient, in that the setup and throughput time is increased,and in that material is wasted. Previously used dummy substrates may need to be replaced to ensure the quality of the substrate to be manufactured. Furthermore, depending on the size of the run-in and runout section, some precursor gas and carrier gas may be wasted.

[0007] It is an object of the present invention to improve the efficiency of atomic layer deposition.

[0008] SUMMARY

[0009] Aspects of the invention provide a precursor deposition head for a plasma source for spatial atomic layer deposition, as defined in the appended claims. The deposition head comprises an aperture arranged for delivering a precursor gas from the deposition head to a substrate, and a slotted cavity extending from the aperture.

[0010] The deposition head includes a first gas inlet, arranged for receiving a first mass flow of gas, wherein the first gas inlet is fluidly connected to a first gas outlet in a first wall of the slotted cavity, the first gas outlet arranged for directing the first mass flow of gas towards the aperture.

[0011] A valve arrangement is mounted inside the slotted cavity and comprises a valve member and a valve seat. The valve member is arranged for interacting with the valve seat to control the first mass flow of gas through the slotted cavity.

[0012] The valve seat is formed by the first gas outlet. The valve member is operable to move inside the slotted cavity between an open state, in which the valve member and the valve seat are separated by an outflow gap for allowing the first mass flow of gas to flow towards the aperture, and a closed state, in which the valve member seals the first gas outlet.

[0013] The first mass flow of gas can for example comprise a carrier gas and a precursor gas. By the valve member opening and sealing the first gas outlet locally inside the slotted cavity, e.g. directly before the aperture, theflow of precursor is stopped abruptly, minimizing the amount of residual precursor left downstream the valve that could still reach the substrate.

[0014] By controlling the position of the valve member, the size of the outflow gap can be adjusted.

[0015] In conventional precursor deposition heads without an internal valve arrangement as described herein, the mass flow of the first gas is typically switched off by a valve upstream of the deposition head. As a result, a certain volume of first gas may still be present in the line section that extends between the upstream valve and the downstream deposition head, which residual volume of first gas can flow out the aperture, thereby creating a run-out section on the substrate. Conversely, when in conventional precursor deposition heads the upstream valve is opened to supply the first mass flow of gas, the presence of gas inside the line section downstream the valve will initially dilute the first mass flow of gas towards the substrate, thereby creating a run-in section in the layer deposited on the substrate.

[0016] In the precursor deposition head of the present invention, the run-in and run-out section is reduced or even eliminated completely, by the valve arrangement locally blocking the first mass flow of gas through the slotted cavity directly upstream the aperture, so that there can be virtually no volume of gas downstream the valve arrangement that affects the flow of precursor. The position of the valve member can be actively controlled, e.g. by an actuator. For example, the valve member may be pivotably slidably suspended in the slotted cavity and operable by an electromechanical or pneumatic actuator, and a controller may be arranged for controlling the actuator to move the valve member between the open and closed state.

[0017] Preferably, however, the pressure valve is passively operable, e.g. operable by a pressure difference inside the slotted cavity, rather than controlled directly by an actuator. For example, the precursor deposition head may further comprise a second gas inlet that is arranged for receivinga second mass flow of gas, wherein the second gas inlet is fluidly connected to a second gas outlet in a second wall of the slotted cavity opposite the first gas outlet. The second gas outlet may be arranged for directing the second mass flow of gas towards the aperture. By suspending the valve member inside the slotted cavity such that the valve member extends between the opposing first and second gas outlets, the valve member can be passively operable between the open and closed state by a pressure difference between the first and second gas outlets. By controlling the pressure difference, the position of the valve member of the passive pressure valve can be adjusted. In this way, the size of the outflow gap can be controlled.

[0018] The pressure difference can e.g. be created and adjusted by controlling one or more control valves in a gas supply system upstream the precursor deposition head that supplies the first and second mass flow of gas. By being passively, indirectly operated, the valve arrangement can be relatively compact and low-complex, so that it can be integrated in the precursor deposition head, in particular inside the slotted cavity between the first and second gas outlets. The valve member is preferably located directly upstream the aperture, so that only a limited volume of gas can be present between the valve member and the aperture. A passively operable pressure valve e.g. includes a leaf spring element with an inherent (bending) flexibility that allows it to move between the open state and the closed state. However, the invention is not intended to be limited to leaf spring types of passive pressure valves. Alternative variants of a passively operable pressure valve include for example a rigid valve member that is pivotably or slidably suspended between the first and second gas outlets and that is passively rotated or displaced by the pressure difference, optionally spring-loaded by a spring element for preloading the passive valve member to the open or closed position. Other variants e.g. include a membrane which, as a result of the pressure difference between opposing sides of the membrane, either seals off or opens the first or second gas outlets. Alsovariants with another type of preloaded sealing member, e.g. a ball, pin, or seat valve, may be preloaded in one direction for sealing the first or second gas outlet, and arranged for passively moving in an opposing direction for opening the respective first or second gas outlet in response to a change in pressure difference between the first and second gas outlet.

[0019] Accordingly, when the first mass flow of gas is reduced with respect to the second mass flow of gas, the thus created pressure difference between the first and second gas outlets causes the passive pressure valve to switch to the closed state, in which the first gas outlet is partially or completely sealed, limiting or preventing outflow of any further or residual portion of the first mass flow of gas into the slotted cavity.

[0020] The second mass flow of gas may comprise a carrier gas, purge gas, or any other non-reactive gas. When the valve member seals the first gas outlet in the closed state, the second gas outlet may be open so that the second mass flow of gas is free to flow towards the substrate.

[0021] The valve member does not necessarily close or seal the second gas outlet in the open state. In other words, in the open state of the valve arrangement, the first and second gas outlets may both be at least partially open simultaneously. For example, the second mass flow of gas may dilute or supplement the first mass flow of gas. In such cases, a collection chamber may be provided between the valve arrangement and the aperture, in which collection chamber the first and second mass flow of gas are able to join up and mix before flowing out the aperture and onto the substrate.

[0022] Preferably, the valve member is formed by a leaf spring that is flexibly movable between seat members at the first and second gas outlets, wherein the leaf spring is arranged for closing the second gas outlet when a working pressure of the first mass flow of gas is higher than a working pressure of the second mass flow of gas.

[0023] The leaf spring can for example be an integral part of a removable shim plate having a fixed part that is removably mounted to the depositionhead, and a cantilevered part that extends from the fixed part and provides the leaf spring, wherein the fixed part is mounted against the first wall so that the leaf spring covers the first gas outlet, and wherein a clearance is provided between the leaf spring and the second wall to allow bending of the leaf spring away from the first outlet. Preferably, the shim plate has a thickness between 50 and 300 micrometers, e.g. between 50 and 100 micrometers, or between 100-200 micrometers. By decreasing the thickness of the shim plate, the out-of-plane flexibility of the leaf spring is increased, and the pressure difference required to move the leaf spring between the open and closed state is decreased. In other words, the valve arrangement is more sensitive to pressure difference. Conversely, by increasing the thickness, i.e. bending stiffness, of the shim plate the sensitivity of the valve arrangement can be decreased.

[0024] By using a removable shim plate that provides the leaf spring, the valve arrangement can easily be serviced, e.g. to clean off residues. The removable shim plate also facilitates changing the operational properties of the valve member. For example, a thicker shim plate can be used to increase the bending stiffness of the leaf spring, to adapt the pressure valve to higher working pressures in the deposition head, and to control the outflow of the first or second mass flow of gas. Also, shim plates with different in-plane geometries can be installed interchangeably, to adapt the outflow of the gases.

[0025] In a practical embodiment that is easy to manufacture, assemble and service, the shim plate is clamped between a first part of the deposition head that defines the first wall of the slotted cavity and a second part of the deposition head that defines the second wall of the slotted cavity. These parts can e.g. be assembled by means of screws or any other type of removable fastener. Accordingly, the parts can be separated from each other, e.g. for cleaning, and rebuilt in the same configuration. Alternatively,one of the parts can be replaced by a different part to re-construct the deposition head in another configuration, when this is more appropriate.

[0026] The fixed part and the cantilevered part of the removable shim plate can e.g. be defined by one or more cutouts, or incisions, in the shim plate. Said cutouts can be arranged in a pattern that locally separates the fixed part and the cantilevered part from each other, so that the cantilevered part is only connected to the fixed part on one side of the cantilevered part, and freely suspended on other sides. Optionally, one or more cutouts may be arranged for locally weakening the connection between the cantilevered part and the fixed part, e.g. to locally increase the flexibility of the leaf spring in order to facilitate bending over a specific bend axis. In this way, the shape of the leaf spring, when moving between the open and closed position, can be controlled.

[0027] The first gas outlet may span a width of the deposition head in a lateral direction, perpendicular to a movement direction of the deposition head and the substrate relative to each other. Preferably, the valve member spans at least the same width, e.g. extends beyond the opposing lateral edges of the first gas outlet. In other words, the valve member completely covers, i.e. seals, the first gas outlet in the closed state. Accordingly, it can be prevented that a portion of the first gas is able to bypass the valve member and reach the substrate.

[0028] The flow of gas towards the substrate can be patterned by having the fixed part of a shim plate cover a section of the first gas outlet, for locally obstructing the first mass flow of gas towards the substrate regardless of the position of the valve member. In other words, a section of the first gas outlet is always closed, while one or more other sections of the first gas outlet can be selectively opened and closed by the valve arrangement as defined herein. In some embodiments, the valve arrangement comprises multiple valve members, e.g. leaf springs, that are arranged for sealing respective sections of the first gas outlet in the closedstate, and for opening said respective sections in the open state. The individual valve members may be jointly controllable between the open and closed state. Different flow patterns can be obtained by interchanging the shim plate.

[0029] The valve member is preferably biased towards the closed state, e.g. by a biasing force. The biasing force can e.g. be provided by an intrinsic elasticity of the valve member. For instance when the valve member is formed by a leaf spring, it may need to be bent out of plane in order to move the valve member from the closed state, in which the leaf spring seals the first gas outlet, to the open state in which the leaf spring is bent away from the first gas outlet so that the outflow gap is present between the first gas outlet and the leaf spring. Alternatively, or additionally, the biasing force can be provided by an elastic element, e.g. mounted between the valve member and the deposition head, or by an actuator.

[0030] Accordingly, in order to move the valve member to the open state in which the first gas outlet is opened, the working pressure of the first mass flow of gas must be larger than the working pressure of the second mass flow of gas, and must also overcome the biasing force that preloads the valve member to the closed state.

[0031] In some embodiments, the valve arrangement in the open state provides an outflow gap that is between 50 and 100 micrometer. As mentioned earlier, the size of the outflow gap can be reduced by controlling the position of the valve member, e.g. to only partially open the first gas outlet. In case of a passively operable valve member, the size of the outflow gap can be controlled by adapting the pressure difference between the first and second gas outlets.

[0032] The outflow gap preferably spans the lateral width of the deposition head, e.g. up to 10 centimeters or more. The outflow gap is preferably uniform over said lateral width. The size of the outflow gap defines a restriction for the first mass flow of gas entering the slotted cavity.In case the valve member is formed by a shim plate, e.g. leaf spring, the size of the outflow gap can be controlled by selecting a shim plate with a specific thickness relative to a distance across the slotted cavity between the first and second gas outlets. The same holds for other types of valve member, namely that the opposing first and second walls of the slotted cavity may provide end stops that define the stroke of the valve member between the first and second state, and that the thickness of the valve member thus defines the size of the outflow gap. For example, the distance between the first and second gas outlets may be 200 micrometer. When the valve member or leaf spring has a thickness of 120 micrometer, the outflow gap is 80 micrometers at most. It may be clear that in case of other interdistances between the first and second wall of the slotted cavity, and other thicknesses of the leaf spring, the size of the outflow gap can be varied accordingly.

[0033] In preferred embodiments, the valve member is arranged for sealing or closing the second gas outlet in the open state of the first gas outlet, and for opening the second gas outlet in the closed state. By sealing the second gas outlet in the open state, it can be prevented that the first mass flow of gas is diluted by the second mass flow of gas. By opening the second gas outlet in the closed state of the first gas outlet, only the second mass flow of gas is directed towards the substrate so that it can purge out any residual amount of first gas still present in the slotted cavity, to further prevent that material is deposited on the substrate.

[0034] In other aspects, the present invention provides a system for spatial atomic layer deposition. The system comprises a precursor deposition head with a passive, pressure controlled valve member as described herein, and a first and second gas supply circuit arranged for supplying the first and second mass flow of gas to the deposition head.

[0035] The first gas supply circuit comprises a first supply line that is connected to the first gas inlet of the deposition head and that is arrangedfor supplying the first mass flow of gas. The first supply line passes through a precursor gas vessel for adding precursor gas to the first mass flow of gas. Upstream the precursor gas vessel the first circuit comprises a mass flow controller arranged for controlling the first mass flow of gas in the first supply line.

[0036] The second gas supply circuit comprises a second supply line that is connected to the second gas inlet of the deposition head and that is arranged for supplying the second mass flow of gas.

[0037] The first gas supply circuit comprises a discharge line that is connected to the first supply line by a three-way valve between the mass flow controller and the precursor gas vessel. The three-way valve is controllable between a supply mode, in which the three-way valve directs the first mass flow of gas through the precursor gas vessel towards the deposition head and closes the discharge line, and a discharge mode, in which the three-way valve branches off at least a portion of the first mass flow of gas to the discharge line, thereby lowering a pressure at the first gas outlet of the deposition head.

[0038] The system further comprises a control unit arranged for controlling the three way valve between the supply mode and the discharge mode for thereby adapting a pressure difference between the first and second gas outlets of the deposition head.

[0039] For example, in the supply mode (i) the control unit may control the three-way valve so that the first supply line supplies the first mass flow of gas to the first gas inlet of the deposition head, to provide a first working pressure at the first gas outlet; and (ii) the second supply line may supply the second mass flow of gas to the second gas inlet of the deposition head, to provide a second working pressure at the second gas outlet. Preferably the first working pressure is larger than the second working pressure, so that the valve member, e.g. leaf spring, is moved to the open state in response to the pressure difference between the first and second working pressure in thesupply mode. In case the valve member is biased towards the closed state, e.g. by an internal resilience or flexibility of the leaf spring, the pressure difference is preferably large enough to overcome the biasing force. By controlling the pressure difference between the first and second gas outlet, the position of the valve member, and thus the size of the outflow gap, can be passively controlled. Alternatively, in case the valve member is directly actuated by an actuator, the size of the outflow gap can be adjusted by controlling the actuator to move the valve member to a desired position.

[0040] In the discharge mode, (i) the control unit may control the three-way valve so that the three-way branches off at least a portion of the first mass flow of gas to the discharge line; and (ii) the second supply line may supply the second mass flow of gas to the second gas inlet of the deposition head, to provide a second working pressure at the second gas outlet. The second working pressure in the discharge mode may be equal to the second working pressure in the supply mode. As a result of the first mass flow of gas being at least partially discharged, the first working pressure at the first gas outlet is reduced compared to the first working pressure in the supply mode, preferably below the second working pressure in the discharge mode. As a result, the valve member moves from the open state to the closed state, in which the first gas outlet is blocked, in response to the pressure difference between the first and second gas outlets that is induced by the discharge mode.

[0041] In practice, the first mass flow of gas may completely be discharged in the discharge mode. In other words, the three-way valve cuts off the supply of first gas towards the deposition head, e.g. to end the deposition of material on the substrate. Conversely, the first mass flow of gas may be directed entirely towards the deposition head in the supply mode, to deposit material. Nonetheless, in some embodiments the control unit may control the three-way valve to an intermediate position, i.e. a position between thesupply mode and discharge mode, to supply a first portion of gas to the deposition head and to discharge the remaining portion.

[0042] The second mass flow of gas is preferably kept constant regardless of whether the system is in the supply mode or in the discharge mode. In some embodiments, the second supply line comprises a further controllable valve or a further mass flow controller for controlling the second mass flow of gas towards the deposition head. For example, the control unit may additionally be arranged for controlling the further controllable valve and / or the further mass flow controller to increase the second mass flow of gas, thereby changing the pressure difference in order to move the passively controlled valve member inside the slotted cavity of the precursor deposition head towards the closed state, or to reduce the second mass flow of gas in order to move the valve member towards the open state.

[0043] In preferred embodiments of the system, the discharge line comprises a discharge restriction arranged for restricting discharge of the first mass flow of gas in the discharge mode, wherein a size of the discharge restriction is equal to a size of a supply restriction arranged for restricting supply of the first mass flow of gas towards the substrate in the supply mode; wherein the supply restriction is defined by the outflow gap between the first gas outlet and the valve member of the pressure valve in the open state.

[0044] For example, the supply restriction is defined by a gap width of the outflow gap that is equal to 100 micrometers and that spans a length of 10 centimeters. Hence, the supply restriction has an area of 10 millimeter squared. The discharge restriction may comprise a discharge opening or nozzle with an equal area of 10 millimeter squared. As a result, the flow resistance of the circuit remains about equal when the three-way valve is switched between the supply mode and the discharge mode. Consequently, the mass flow controller, which may have a relatively slow settling time, when configured to maintain a constant flow rate, does not detect anychanges in the circuit and therefore also does not need to adjust the flow. This increases the rehabihty of the system, and eliminates the delay caused by the mass flow controller. However, when the settling time of the mass flow controller itself is already sufficiently small, e.g. less than 0.5 seconds, the mass flow controller can alternatively, or in addition to controllable valve(s), be used to control the pressure difference by actively controlling the flow rate. In other words, the system not necessary only relies on controlling the controllable valve(s) to adapt the pressure difference and to switch the system between the supply mode and the discharge mode.

[0045] In the discharge mode, the discharged portion of the first mass flow of gas may be discharged into the surrounding atmosphere, or may be returned back to a gas source for reuse in the system.

[0046] Preferably, upstream the mass flow controller, the first supply line comprises a gas source and a pump for providing a gas flow, wherein the second supply line is fluidly coupled to the first supply line between the pump and the mass flow controller, wherein a first portion of the gas flow is directed to the mass flow controller for providing the first mass flow of gas, and wherein a second portion of the gas flow is branched off to the second supply line to provide the second mass flow of gas. In other words, the first and second gas supply circuit can be coupled to each other and the first and second mass flow of gas may be provided by a single, shared pump and gas supply source.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention will be further elucidated in the figures:

[0049] FIG. 1 illustrates an embodiment of a precursor deposition head including a valve arrangement inside the slotted cavity;FIG. 2 illustrates another or further embodiment of the precursor deposition head, in which the valve arrangement comprises a passive, pressure controlled valve member;

[0050] FIG. 3 provides a detailed view of an embodiment of the pressure controlled valve member;

[0051] FIG. 4 provides an exploded view of a preferred embodiment of the deposition head, in which the valve member is formed by a removable shim;

[0052] FIG. 5 provides another exploded view of an embodiment of the precursor deposition head;

[0053] FIG. 6 provides a detailed view of an embodiment of a valve member formed by a removable shim;

[0054] FIG. 7 illustrates a system for spatial atomic layer deposition, comprising an embodiment of the precursor deposition head described herein.

[0055] DETAILED DESCRIPTION

[0056] The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the 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 and / or cross-section illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms as well as derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise.

[0057] FIG 1 illustrates an embodiment of a precursor deposition head 100 for a plasma source, for delivering a flow of precursor gas to a substrate50. In use, the precursor deposition head 100 and the substrate 50 are moved with respect to each other in movement direction D, parallel to the plane of the substrate 50. For example, the precursor deposition head 100 may be suspended in a fixed position, while the substrate 50 is moved. The precursor deposition head may be used in combination with a plasma source to provide a flow of precursor gas to the substrate 50 during the movement, to deposit a layer of material on the substrate 50.

[0058] As illustrated, the precursor deposition head 100 comprises a body 110 with an aperture 111 arranged for delivering precursor to the substrate 50. A slotted cavity 112 extends from the aperture 111 towards an interior of the body 110.

[0059] The precursor deposition head 100 has a first gas inlet 131, arranged for receiving a first mass flow of gas Ml, e.g. from gas supply system 130. The first gas inlet 131 is fluidly connected to a first gas outlet 141 in a first wall 113 of the slotted cavity. The first gas outlet 141 is arranged for directing the first mass flow of gas Ml through the slotted cavity 112 towards the aperture 111.

[0060] A valve arrangement 150 is mounted inside the slotted cavity 112 and comprises a valve member 151 and a valve seat. The valve seat is formed by the first gas outlet 141. The valve member 151 is arranged for interacting with the valve seat to control the first mass flow of gas Ml through the slotted cavity 112.

[0061] The valve member 151 is operable to move inside the slotted cavity 112 between an open state, in which the valve member 151 and the valve seat are separated by an outflow gap G for allowing the first mass flow of gas to flow towards the aperture, and a closed state, in which the valve member 151 seals the first gas outlet 141.

[0062] In this embodiment, the valve member 151 is actuated between the open and closed state by an actuator 155 mounted to the body 110 of theprecursor deposition head. The actuator 155 may be controlled by a controller (not shown).

[0063] FIG. 2 illustrates another embodiment of the precursor deposition head 100, in which the valve member 151 is not directly actuated by an actuator, but passively or indirectly operated instead, by a pressure difference in the slotted cavity 112. In this embodiment, the precursor deposition head 100 comprises a second gas inlet 132 that is arranged for receiving a second mass flow of gas M2, e.g. an inert, non-reactive carrier gas. The second gas inlet 132 is fluidly connected to a second gas outlet 142 in a second wall 114 of the slotted cavity opposite the first wall 113.

[0064] Accordingly, the second mass flow of gas M2 can be directed towards the aperture 111.

[0065] The valve arrangement 150 includes a valve member 151 that is mounted in the slotted cavity 112 between the opposing first and second gas outlets 141, 142. The valve member 151 is passively operable between the open and closed state by a pressure difference dP = Pl - P2 between the first and second gas outlets 141, 142. In other words, the controllable parameter is Pl vs P2 at the first and second gas outlets 141, 142. In the open state, the valve member 151 opens the first gas outlet 141 for allowing the first mass flow of gas Ml to flow though the outflow gap G towards the aperture 111. In the closed state, the valve member 151 closes the first gas outlet 141. The valve member 151 is preferably biased towards the closed state. In the open state, the valve member 151 preferably provides an outflow gap G of between 50 and 100 micrometer, through which outflow gap the first mass flow of gas Ml is able to flow into the slotted cavity 112 and towards the substrate 50.

[0066] For example, the first mass flow of gas Ml may apply a first working pressure Pl on a side of the valve member 151 facing the first gas outlet 141. The second mass flow of gas M2 may apply a second working pressure P2 on an opposing side of the valve member 151 facing the secondgas outlet 142. Without any further external actuation, the position of the valve member 151 is thus dependent on the pressure difference dP between the first working pressure Pl and the second working pressure P2. For example, when the second working pressure P2 is higher than the first working pressure Pl, the resulting pressure difference dP pushes the valve member 151 towards the first gas outlet 141, thereby sealing the first gas outlet 141. Conversely, when the first working pressure Pl is higher than the second working pressure P2, the valve member 151 is moved towards the second gas outlet 142. A detailed view of such a passive, indirectly operated valve arrangement 150 is shown in FIG. 3.

[0067] The valve member 151 is preferably formed by a leaf spring 151 that is flexibly movable between the first and second gas outlets 141, 142 which provide the seat members for the leaf spring valve member 151. The leaf spring 151 is preferably arranged for closing or sealing the second gas outlet 142 in the open state, i.e. when the first working pressure Pl of the first mass flow of gas Ml is higher than the second working pressure P2 of the second mass flow of gas M2.

[0068] The leaf spring 151 is preferably an integral part of a removable shim plate 162, with a fixed part 166 that is removably mounted to the body 110 of the deposition head, and a cantilevered part 167 that extends from the fixed part 166 into the slotted cavity 112 and provides the leaf spring 151, i.e. the valve member that is movable between the first and second gas outlets 141, 142. Preferably the fixed part 166 is mounted against the first wall 113 so that the leaf spring 151 covers the first gas outlet 141. A clearance is thus provided between the leaf spring 151 and the second wall 114 to allow bending of the leaf spring 151 away from the first gas outlet 141, towards the second gas outlet 142. The leaf spring 151 may be configured such that is it pressed against the second wall 114 and seals or covers the second gas outlet 142 in the open state of the valve 150.FIGs 4 and 5 provide exploded views of an embodiment of the precursor deposition head 100, in which the body 110 has a first part 110-1 that defines the first wall 113 of the slotted cavity and a second part 110-2 that defines the second wall 114 of the slotted cavity. A stack of shim plates 161, 162, 163 may be clamped between the first and second part 110-1, 110-2 of the deposition head. The thickness of the stack of shim plates 161, 162, 163 may define the gap width of the slotted cavity. Instead of three shim plates, more or less shim plates may be mounted, e.g. to adjust the gap width. At least one of the shim plates provides a leaf spring 151 that forms the valve member. The stack of shim plates 161, 162, 163 can e.g. be clamped between the first and second part 110-1, 110-2 of the deposition head by a number of screws. Hence the shim plates 161, 162, 163 can be removed from the precursor deposition head 100, e.g. to service or clean the shim plates, as well as the valve arrangement. In case a different configuration of the precursor deposition head 100 is desired, the shim plates can be replaced by other shim plates. In this way, the properties of the valve arrangement can be adjusted, e.g. by using a leaf spring with a higher or lower bending stiffness.

[0069] As illustrated in more detail in FIG. 6 the removable shim plate 162 that provides the leaf spring valve member 151 comprises cutouts 165 that define the fixed part 166 and the cantilevered part 167 (i.e. the valve member 151). The cutouts 165 are preferably positioned such that the cantilevered part 167, i.e. leaf spring 151, extends beyond opposing lateral edges of the first gas outlet, spanning a width of the deposition head in a lateral direction, perpendicular to the movement direction D illustrated in FIG. 1.

[0070] In other words, the leaf spring 151 preferably completely covers the first gas outlet in the closed state. The other shim plate(s) 161, 163 of the stack may provide support elements 171, 173 for supporting the fixed part 166 of the leaf spring 151, e.g. on either side of the first and second gasoutlet, and one or more clearances 172, 174 for allowing movement of the cantilevered part 167, and for providing a passage for the first or second mass flow of gas to flow into the slotted cavity. For example, the other shim plate(s) 161, 163 may be provided with further cutouts to define the support elements and the clearances. In some embodiments, the fixed part 166 of the leaf spring 151 covers only a section of the first gas outlet, for locally obstructing the first mass flow of gas towards the substrate, e.g. to provide a patterned flow of precursor towards the substrate.

[0071] Instead of a stack of shims 161, 162, 163, a single removable insert 162 can be mounted between the first and second part 110-1, 110-2 of the deposition head, which single removable insert 162 integrally provides the structure and functionality of the separate shim plates discussed above. Alternatively, or additionally, the structure provided by the outermost shim plates 161, 163 can be provided by the first and second part 110-1, 110-2 of the deposition head. In other words, one or more parts of the stack of shim plates 161, 162, 163 can be combined, or integrated in other components.

[0072] FIG. 7 illustrates an embodiment of a system 500 for spatial atomic layer deposition. The system 500 comprises a precursor deposition head 100 with a passive, indirectly operated valve member 151 as described herein, a first gas supply circuit 300, and a second gas supply circuit 400.

[0073] The first gas supply circuit 300 comprises a first supply line 301 that is connected to the first gas inlet 131 of the precursor deposition head 100 and that is arranged for supplying the first mass flow of gas Ml. The first supply line 301 passes through a precursor gas vessel 330 for adding precursor gas to the first mass flow of gas Ml. Upstream the precursor gas vessel 330 the first circuit comprises a mass flow controller 350 arranged for controlling the first mass flow of gas Ml in the first supply line 301.

[0074] The second gas supply circuit 400 comprises a second supply line 401 that is connected to the second gas inlet 132 of the deposition head 100 and that is arranged for supplying the second mass flow of gas M2.The first circuit 300 comprises a discharge line 303 connected to the first supply line 301 by a three-way valve 340 between the mass flow controller 350 and the precursor gas vessel 330. The three-way valve 340 is controllable between a supply mode and a discharge mode. In the supply mode, the three-way valve 340 directs the first mass flow of gas Ml through the precursor gas vessel 330 and towards the deposition head 100 and closes the discharge line 303. In the discharge mode, the three-way valve 340 branches off at least a portion of the first mass flow of gas Ml towards the discharge line 303. As a result the working pressure Pl at the first gas outlet of the precursor deposition head 100 is reduced, preferably below the second working pressure P2. When the three-way valve 340 does not affect the second mass flow of gas M2, the second working pressure P2 is unchanged. However, the pressure difference dP, i.e. the second working pressure P2 being higher than the first working pressure Pl due to a part of the first mass flow of gas Ml being discharged causes the passive pressure valve 151 of the precursor deposition head to move to the closed state, in which the first gas outlet is blocked. Hence, only the second mass flow of gas M2 is able to flow towards the substrate. Conversely, in the supply mode, the first working pressure Pl may be higher than the second working pressure, so that the passive pressure valve is in the open state.

[0075] The system further comprises a control unit 200 arranged for controlling the three way valve 340 between the supply mode and the discharge mode for thereby adapting the pressure difference dP between the first and second gas outlets of the precursor deposition head 100.

[0076] In some embodiments the discharge line 303 comprises a discharge restriction 380 arranged for restricting discharge of the first mass flow of gas Ml in the discharge mode. The size of the discharge restriction 380 is preferably equal to the size of a supply restriction in the deposition head 100, arranged for restricting the first mass flow of gas Ml towards the substrate in the supply mode. The supply restriction may be defined by theoutflow gap between the first gas outlet and the valve member 151 in the open state. Said outflow gap can e.g. be between 50-100 micrometer, as mentioned earlier.

[0077] Upstream the mass flow controller 350, the first supply line 301 may comprise a gas source 360 and a pump 370 for providing a gas flow. The second supply line 401 may be fluidly coupled to the first supply line 301 between the pump 370 and the mass flow controller 350. Accordingly, a first portion of the gas flow delivered by the pump 370 is directed to the mass flow controller 350 for providing the first mass flow of gas Ml, and a second portion of the gas flow delivered by the pump 370 can be branched off to the second supply line 401 to provide the second mass flow of gas M2.

[0078] It will be clear to the skilled person that the invention is not limited to any embodiment herein described and that modifications are possible which may be considered within the scope of the appended claims. Also kinematic inversions are considered inherently disclosed and can be within the scope of the invention. In the claims, any reference signs shall not be construed as limiting the claim.

[0079] The terms 'comprising' and including’ when used in this description or the appended claims should not be construed in an exclusive or exhaustive sense but rather in an inclusive sense. Thus expression as 'including' or ‘comprising’ as used herein does not exclude the presence of other elements, additional structure or additional acts or steps in addition to those listed. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. Features that are not specifically or explicitly described or claimed may additionally be included in the structure of the invention without departing from its scope.

[0080] Expressions such as: "means for ...” should be read as: "component configured for ..." or "member constructed to ..." and should be construed to include equivalents for the structures disclosed. The use of expressions like:"critical", "preferred", "especially preferred" etc. is not intended to limit the invention. To the extent that structure, material, or acts are considered to be essential they are inexpressively indicated as such. Additions, deletions, and modifications within the purview of the skilled person may generally be made without departing from the scope of the invention, as determined by the claims.

Claims

23CLAIMS1. A precursor deposition head for a plasma source for spatial atomic layer deposition, the precursor deposition head comprising:- an aperture arranged for delivering a precursor gas from the deposition head to a substrate, and a slotted cavity extending from the aperture;- a first gas inlet, arranged for receiving a first mass flow of gas, wherein the first gas inlet is fluidly connected to a first gas outlet in a first wall of the slotted cavity, the first gas outlet arranged for directing the first mass flow of gas towards the aperture;- a valve arrangement, mounted inside the slotted cavity and comprising a valve member and a valve seat, wherein the valve member is arranged for interacting with the valve seat to control the first mass flow of gas through the slotted cavity;wherein the valve seat is formed by the first gas outlet; wherein the valve member is operable to move inside the slotted cavity between an open state, in which the valve member and the valve seat are separated by an outflow gap for allowing the first mass flow of gas to flow towards the aperture, and a closed state, in which the valve member seals the first gas outlet.

2. The precursor deposition head according to claim 1, further comprising a second gas inlet that is arranged for receiving a second mass flow of gas, wherein the second gas inlet is fluidly connected to a second gas outlet in a second wall of the slottedcavity opposite the first gas outlet, the second gas outlet arranged for directing the second mass flow of gas towards the aperture, wherein the valve member extends between the opposing first and second gas outlets, and wherein the valve member is passively operable between the open and closed state by a pressure difference between the first and second gas outlets.

3. The precursor deposition head according to claim 2, wherein the valve member is formed by a leaf spring that is flexibly movable between seat members at the first and second gas outlets, wherein the leaf spring is arranged for sealing the second gas outlet when a working pressure of the first mass flow of gas is higher than a working pressure of the second mass flow of gas.

4. The precursor deposition head according to claim 3, wherein the leaf spring is an integral part of a removable shim plate having a fixed part that is removably mounted to the deposition head, and a cantilevered part that extends from the fixed part and provides the leaf spring, wherein the fixed part is mounted against the first wall so that the leaf spring covers the first gas outlet, and wherein a clearance is provided between the leaf spring and the second wall to allow bending of the leaf spring away from the first outlet.

5. The precursor deposition head according to claim 4, wherein the removable shim plate is clamped between a first part of the deposition head that defines the first wall of the slotted cavity and a second part of the deposition head that defines the second wall of the slotted cavity.

6. The precursor deposition head according to claim 4 or 5, wherein the removable shim plate comprises one or more cutouts that define the fixed part and the cantilevered part.

7. The precursor deposition head according to any preceding claim, wherein the first gas outlet spans a width of the deposition head in a lateral direction, perpendicular to a movement direction of the deposition head and the substrate relative to each other, wherein the valve member extends beyond opposing lateral edges of the first gas outlet.

8. The precursor deposition head according to any of the preceding claims, wherein the valve member is biased towards the closed state.

9. The precursor deposition head according to any of the preceding claims, wherein the outflow gap between the valve member and the valve seat in the open state is between 50 and 100 micrometer.

10. The precursor deposition head according to any of claims 2-9, wherein the valve member is arranged for closing the second gas outlet in the open state, and for opening the second gas outlet in the closed state.

11. The precursor deposition head according to any preceding claim, wherein the first mass flow of gas comprises a carrier gas and a precursor.2612. The precursor deposition head according to any preceding claim, wherein the second mass flow of gas comprises a carrier gas only.

13. A system for spatial atomic layer deposition, comprising:- a precursor deposition head according to any of the preceding claims;- a first gas supply circuit, comprising a first supply line connected to the first gas inlet of the precursor deposition head and arranged for supplying the first mass flow of gas, wherein the first supply hne passes through a precursor gas vessel for adding precursor gas to the first mass flow of gas, wherein upstream the precursor gas vessel the first circuit comprises a mass flow controller arranged for controlling the first mass flow of gas in the first supply line; - a second gas supply circuit, comprising a second supply line connected to the second gas inlet of the precursor deposition head and arranged for supplying the second mass flow of gas;wherein the first circuit comprises a discharge line connected to the first supply line by a three-way valve between the mass flow controller and the precursor gas vessel;wherein the three-way valve is controllable between a supply mode, in which the three-way valve directs the first mass flow of gas through the precursor gas vessel towards the precursor deposition head and closes the discharge line, and a discharge mode, in which the three-way valve branches off at least a portion of the first mass flow of gas towards the discharge line, thereby lowering a pressure at the first gas outlet of the precursor deposition head;27wherein the system further comprises a control unit arranged for controlling the three way valve between the supply mode and the discharge mode for thereby adapting a pressure difference between the first and second gas outlets of the precursor deposition head.

14. The system according to claim 13, wherein the discharge line comprises a discharge restriction arranged for restricting discharge of the first mass flow of gas in the discharge mode, wherein a size of the discharge restriction is equal to a size of a supply restriction arranged for restricting supply of the first mass flow of gas towards the substrate in the supply mode; wherein the supply restriction is defined by the outflow gap between the first gas outlet and the valve member of the valve arrangement in the open state.

15. The system according to any of the preceding claims 13-14, wherein, upstream the mass flow controller, the first supply line comprises a gas source and a pump for providing a gas flow, wherein the second supply line is fluidly coupled to the first supply line between the pump and the mass flow controller, wherein a first portion of the gas flow is directed to the mass flow controller for providing the first mass flow of gas, and wherein a second portion of the gas flow is branched off to the second supply line to provide the second mass flow of gas.

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