Patent Description:
Imprint lithography, of the type disclosed in <CIT> or in <CIT>, is gaining interest as a viable alternative to more traditional mask-based optical lithography techniques, as imprint lithography promises to be able to provide small(ler) feature sizes in a pattern to be transferred onto a substrate such as the substrate of a semiconductor device over a large area. In imprint lithography techniques such as, Substrate Conformal Imprinting Lithography ("SCIL"), a flexible stamp including a feature relief pattern on its surface is brought into contact with a substrate, which typically carries a resist material. The resist material is imprinted by the feature pattern. The resist material is subsequently developed, e.g., cured, after which the feature pattern is released from the resist material to leave a patterned resist layer on the substrate.

In this process, a curable but fluid resist layer is applied to the substrate (e.g., a wafer) supported on a chuck. The flexible stamp is for example rubber and resist layer may be cured (solidified) while being imprinted to leave the solidified relief in the resist layer which is complementary to that of the stamp relief layer after removal of the stamp from the resist. The imprint process entails arranging the thin flexible stamp, for example formed of a PDMS rubber layer adhered to a thin flexible plate such as e.g., a metal plate or glass plate with the relief surface of PDMS layer opposing the glass plate side, onto a stamp manipulator. This stamp manipulator is also known as a groove plate. This provides that the glass plate is against the stamp manipulator and the stamp's relief surface opposes the resist layer of the wafer on the chuck.

The stamp generally, but not necessarily, is held above the wafer upside down and with the two parts parallel to each other in the X-Y plane and at a small distance along the Z-axis direction from the surface of the fluidic resist layer. This small distance defines a so-called imprint gap between the relief surface of the stamp and the resist layer along the Z-axis direction.

The stamp may be locally manipulated, for example locally and sequentially released from and adhered to the stamp manipulator by the stamp manipulator. The stamp manipulator has openings, often in the form of grooves extending along the surface (X-Y plane) of the stamp manipulator, hence the name groove plate, that can be individually operated at set pressures such as over- or underpressure so as to either hold the stamp (underpressure) or release the stamp (overpressure). Thus, during the imprint process, by releasing the stamp at one X-Y location (e.g., at an edge), a first contact is made between the relief surface and resist at that location. The stamp is then gradually released from the stamp manipulator to be pulled into the resist layer mostly by capillary forces. The contact thereby grows from the first contact location along the X- and/or Y-axis direction depending on the release scheme.

To be able to attach a stamp to the manipulator it needs to be positioned up-side down beneath the manipulator. To do this, the stamp is laid down on a stamp holder (up-side down with the relief surface facing downward). The stamp manipulator is moved over the laid down stamp facing the back side of the glass plate of the stamp after which the glass plate surface of the stamp is adhered to the manipulator by operation of the manipulator openings.

A substrate is then loaded onto the chuck and positioned as desired with respect to the relief layer surface.

To set the imprint gap at the beginning of the process the distance (in the Z-axis direction) needs to be set to a desired value (e.g., in a range of <NUM> to <NUM>) and be kept within tight tolerances (e.g., with a gap variation in a range of <NUM> to <NUM>) during the imprinting process. The imprint gap is the gap between the wafer and the stamp.

During the imprinting step, the manipulator openings are switched from underpressure to slight overpressure to gradually release the stamp from the stamp manipulator such that the feature pattern is pulled into the resist layer by capillary forces, as the spacing between neighboring protrusions of such a pattern typically acts as a capillary, which therefore speeds up the wetting of the stamp by the resist. Upon and after development (e.g., solidification) of the resist layer while in contact with the stamp, the feature pattern of the flexible stamp is released from the resist layer by an opposite process in which individual manipulator openings are switched to an under pressure, thereby gradually releasing the feature pattern from the developed resist layer. The release process is typically hampered by the interaction between the stamp material and the developed (solidified) resist, which slows down the release process. This is due to the enhanced surface area between the stamp and the cured resist, which increases the van der Waals forces per unit area. Thus, it is possible on an imprinting apparatus such as the apparatus disclosed in <CIT> to set the speed of an imprinting or release step.

In current SCIL imprint machines, a <NUM> to <NUM> diameter wafer may be used. A single linear Z-stage is used for the vertical movement of the chuck in order to load and unload a wafer and to adjust the imprint gap. An adjustment of the tilt (RX and RY) between the chuck and the groove plate is for example implemented manually with three micrometer adjustment screws.

The height of the stamp landing ring in existing machines is fixed. It can only be adapted by replacing the stamp landing ring with a different height.

There is a desire to scale the design up to enable printing of larger wafers, such as <NUM> wafers. This results in an increase in the required process forces (e.g., twice as high) and a larger span width (e.g., <NUM> diameter instead of <NUM>). To maintain a required imprint gap variation such as <NUM>-<NUM> during the process load, it is not possible simply to just scale up existing designs. In particular, the support for the wafer would not have enough stiffness.

The support for the wafer for example comprises a frame of support such as for example a C-frame design of support and a chuck. The support frame may bend, because of the process load or due to warping during heating. Bending or warping results in a larger variation of the imprint gap. This reduces the quality of the imprint process significantly. A larger chuck also has large thermal mass, which results into long heating and cooling times.

One issue is thus the need to control the imprint gap quite precisely with a larger area wafer support, such as a chuck and groove plate (e.g., <NUM> diameter), while still allowing simple loading of the stamp and wafer. This loading for example requires a longer distance manipulation of the chuck with respect to the groove plate. The inventors have further found that with a larger chuck, the existing designs are difficult to manufacture with tolerances enabling sufficient stiffness to ensure imprint gap control over the entire chuck area.

Another issue is to enable precise and stable control of the position of the wafer support (known as the chuck).

Another issue is to ensure uniform process gap between the stamp and the substrate, including at the location of a stamp landing ring around the outer area of the stamp.

The invention aims to address one or more of these issues.

According to the invention, there is provided an imprinting apparatus comprising:.

This imprinting apparatus may be or comprise a substrate conformal imprinting lithography apparatus. The flexible stamp has an imprinting pattern, and the first carrier for example comprises an array of actuators (e.g., manipulator openings or apertures) for use in pulling the flexible stamp towards the first carrier and for use in pushing the flexible stamp away from the first carrier. The array of actuators may be or comprise pressure operated manipulator openings or apertures, but other types can also be used such as for example electric or electromagnetic actuators for example in combination with flexible stamps having a metal support layer.

The chuck actuators enable control of rotation of the chuck about X- and Y-axis (in-plane of the chuck/substrate) as well as in the Z-axis direction. Thus tilt and wedge compensation is enabled, and this can be manual and/or automatic based on local position sensing. Tight control of the imprint gap is enabled.

Each chuck actuator may comprise an actuator output and a lever arrangement between the actuator output and a chuck drive member. The lever arrangement enables an increase in positioning accuracy and increased stiffness, compared to the direct control of position using the actuator output.

The lever arrangement for example comprises a first pivot between a fixed lever portion and a movable lever portion, the lever arrangement providing a reduction in displacement between the actuator output and the chuck driver member.

This reduction in displacement enables increased positioning accuracy at the chuck drive member.

The first pivot for example comprises a flexure pivot between the fixed lever portion and the movable lever portion. The use of a flexure pivot provides a frictionless mounting for the lever.

The chuck drive member may comprise a second pivot where it connects to the movable lever portion. This second pivot enables the chuck drive member to adopt a suitable orientation to match the positioning of the chuck (to a position in which tilt and wedge compensation is provided).

The second pivot may also comprise a flexure pivot. The use of a flexure pivot again provides a frictionless mounting for the chuck drive member.

The lever arrangement is for example biased towards the first holder by an adjustable spring arrangement. The spring arrangement determines the required stamp release force, and this can be adjusted.

The lever arrangement preferably comprises a force sensor for monitoring a force transferred through the lever arrangement between the actuator output and the chuck drive member. This force sensor is placed in series with the chuck actuator and can be used to provide a feedback signal for detecting a sticking stamp or for providing damage protection.

The lever arrangement for example comprises a split gap which terminates at a notch flexure, and the force sensor is mounted at the split gap.

The Z-axis movement (perpendicular to the plane of the chuck/substrate) of the chuck is divided into two stages, with separate long stroke and short stroke drivers. This creates a very stiff support. The chuck actuators enable control of rotation of the chuck about X- and Y-axis (in-plane of the chuck/substrate) as well as in the Z-axis direction. Thus tilt and wedge compensation is enabled, and this can be manual and/or automatic based on local position sensing. Tight control of the imprint gap is enabled.

The main frame actuator has a large stroke (e.g. <NUM> or larger) to facilitate loading of the stamp and substrate and the chuck actuators have a small stroke for fine adjustment, e.g. to +/- <NUM> with a stroke of e.g., <NUM>.

The second carrier further may comprise a sub-frame, wherein the sub-frame is connected to the main frame and the chuck is mounted to the sub-frame, wherein the sub-frame is mounted to the main frame by a spring arrangement for biasing the sub-frame against the first carrier through a kinematic coupling during imprinting.

The chuck is then carried by a stiff sub-frame. This sub-frame can then be decoupled from the main frame and the main frame actuator. The spring arrangement provides decoupling between the sub-frame and the main frame. The sub-frame behaves as a rigid body, and deformation of the main frame and/or the main actuator will not influence the imprint gap. In particular, a separation of the force path and the position path is implemented.

The chuck may comprise a set of position sensors for measuring a distance from a surface of the chuck to the first carrier. These enable manual and/or automated control of the chuck actuators.

The apparatus may further comprise a stamp landing ring (or more generally a stamp landing device) around an outside of the chuck, wherein the stamp landing ring is for facing the first carrier outside the area of the flexible stamp. The stamp landing ring provides a support for a substrate of the flexible stamp. The flexible stamp for example comprises a glass substrate and a rubber stamp area over a central area of the glass substrate. Thus, the stamp may have edge regions with less height (thickness) than center regions. The stamp landing ring enables the same process gap to be present over the area of the area of the flexible stamp, even though it has regions of two different heights.

The second carrier may comprise a set of position sensors for measuring a distance from the stamp landing ring to the first carrier. These position sensors enable a position of the stamp landing ring to be controlled, for example to take account of different stamp thicknesses, and hence different height profiles of the flexible stamp.

The apparatus may further comprise a set of landing ring actuators, each with a third stroke, smaller than the first stroke, for translating a portion of the stamp landing ring relative to the main frame in a direction perpendicular to the plane of the second carrier. Thus, actuators for moving the stamp landing ring may also be integrated into the second carrier.

The chuck may comprise a hollow cylindrical body having a top face and a bottom face. A lattice arrangement may be provided between the top and bottom faces. This enables a reduced thermal mass of the chuck while maintaining the required stiffness for maintaining a uniform imprint gap.

The top face and the bottom face may each comprise an internal water channel arrangement for providing a flow path between a set of water inlets and a water outlet. The internal water channel arrangements mean that heating and cooling is provided at the top and bottom surfaces of the chuck rather than throughout the structure, giving effective heat control and symmetrical expansion and contraction. The heating and cooling at the top and bottom surfaces thus prevents buckling.

Embodiments of the invention are described in more detail and by way of non-limiting examples with reference to the accompanying schematic drawings, wherein:.

The figures are not drawn to scale. The he same reference numerals are used throughout the figures to indicate the same or similar parts.

The disclosure provides an imprinting apparatus which comprises a first carrier for carrying a flexible stamp and a second carrier movable relative to the first carrier. The second carrier comprises a chuck and configured to carry a substrate having a resist layer and comprises a set of chuck actuators for translating a portion of the chuck in a Z-axis direction, Each chuck actuator comprises an actuator output and a lever arrangement between the actuator output and a chuck drive member. The lever arrangement enables an increase in positioning accuracy and increased stiffness, compared to the direct control of position using the actuator output. The Z-axis movement enables at least a movement of chuck towards or away from the flexible stamp carrier.

Before describing the invention, the apparatus and method disclosed in <CIT> and <CIT> will first be described with reference to <FIG>, and then a modification of this apparatus embodying the invention will be described.

<FIG> depicts an imprinting apparatus <NUM>. The imprinting apparatus <NUM> may be a SCIL imprinting apparatus or any other suitable imprinting apparatus that can be used to transfer an imprinting pattern from a (flexible) stamp to a substrate.

The imprinting apparatus <NUM> typically comprises a first holder (e.g., a groove plate) as part of a first carrier <NUM> for holding a flexible stamp <NUM> including an imprinting pattern defined by recesses between protrusions <NUM>. The first carrier <NUM> includes a frame (not shown) to which the holder is mounted. The flexible stamp <NUM> and imprinting pattern <NUM> may be realized in any suitable material e.g., a suitable (synthetic) rubber material such as a polysiloxane-based material, e.g., polydimethylsiloxane (PDMS). The rubber layer may be applied to a flexible stamp plate (not separately shown and made of e.g., glass, plastic or metal). The feature size of the imprinting pattern may be any suitable size, and preferably is a micrometer scale or nanometer scale pattern, that is, a pattern having feature sizes as low as <NUM> up to in excess of <NUM>, with an aspect ratio (vertical dimensions divided by lateral dimensions) of the features may be <NUM> or higher. It should however be understood that other feature sizes may also be contemplated, and that the present invention equally may be applied to transfer patterns having smaller aspect ratios. For example, at least some embodiments of the present invention are suitable to transfer imprinting patterns with an aspect ratio in the range of <NUM> to <NUM>.

To this end, the first carrier <NUM> typically comprises a plurality of stamp engaging elements <NUM>, which may be arranged in an array or grid (see for example <FIG>). Such stamp engaging elements <NUM> are typically arranged to pull a portion of the flexible stamp <NUM> towards the first carrier <NUM> in a first configuration and to push the portion of the flexible stamp then away from the first carrier <NUM> in a second configuration. Such elements may be referred to a stamp actuators. In the following detailed description, the stamp engaging elements <NUM> are embodied by apertures that can be switched between an underpressure (vacuum) and an overpressure in order to provide the first and second configuration is respectively. Other actuators may be used such, as for example electromagnetic actuators.

The apertures <NUM> may have any suitable shape. For example, the apertures <NUM> may be groove-shaped, with the grooves extending over substantially the whole length of the first carrier <NUM>; or the apertures <NUM> may be circle-shaped, with the apertures <NUM> defining a two-dimensional grid, as shown in <FIG>. Other suitable shapes will be apparent to the skilled person. Groove-shaped apertures <NUM> are for example suitable in case the imprinting direction and the release direction of the flexible stamp are the same or opposite to each other. The two-dimensional grid of circular apertures <NUM> as shown in <FIG>, for example, is particularly suitable in case the imprinting direction and the release direction of the flexible stamp <NUM> are different from each other, as will be explained in more detail later.

Each aperture <NUM> comprises a valve <NUM> that can switch the aperture <NUM> between an overpressure source provided via the first channel <NUM> (referred to as "overpressure channel") and an underpressure source, e.g., vacuum pump or reservoir of air at low pressure, provided via second channel <NUM> (from here on referred to as the underpressure channel). The connection between each valve <NUM> and the underpressure channel <NUM> is shown by solid lines and the connection between each valve <NUM> and the overpressure channel <NUM> is shown by dashed lines. The underpressure may be supplied at about <NUM> mBar to <NUM> mBar below ambient, more preferably at about <NUM> to <NUM> Bar below ambient, i.e., at about <NUM>-<NUM> mBar absolute.

The respective valves <NUM> are typically controlled by a processing element (e.g., a processor) <NUM>, which may take any suitable shape or form. The processing element <NUM> typically executes computer program code that instructs the processing element <NUM> on how to control the valves <NUM> and the first carrier <NUM> during the imprinting process, as will be explained in more detail later.

The flexible stamp <NUM> may be affixed to the first carrier <NUM> by switching the apertures <NUM> to an underpressure. Additional affixing means may be provided, for example around an edge portion of the flexible stamp <NUM>. Such affixing means may for example comprise clamps clamping the edge of the flexible stamp <NUM> to the first carrier <NUM> although it should be understood that in at least some examples no additional affixing means are being used.

The imprinting apparatus <NUM> further comprises a second holder (also referred to as second carrier) <NUM> for carrying a substrate <NUM> to be imprinted.

The second carrier <NUM> for example comprises an aluminum or stainless steel chuck. The chuck is actuated for coarse alignment using micrometer spindles. The chuck is surrounded by a plate which functions as a stamp landing device or ring which functions as will be described herein below. The device may be made of aluminium, stainless steel or other solid material.

Water channels inside the chuck are used for heating and cooling of the chuck, for controlling heat based curing of the resist layer.

Any suitable substrate <NUM> may be used, e.g., any suitable semiconductor substrate such as a silicon substrate, a silicon-on-insulator substrate, a silicon germanium substrate. To this end, the substrate <NUM> may carry a resist layer <NUM>, which may be any suitable material. For example, the resist layer <NUM> may comprise a curable material that may be solidified (cured) to immobilize the imprinting pattern <NUM> in the resist layer <NUM>. In an example, the resist layer <NUM> comprises a sol-gel material. A suitable example of such a material is disclosed in <CIT>, although it should be understood that any suitable resist material may be used. Further examples of suitable resist materials for example can be found in <CIT>, <CIT>, <CIT>, <CIT> as well as in the non-patent publication <NPL>.

The first carrier <NUM> is controlled by the processing element <NUM>. To this end, the imprinting apparatus <NUM> further comprises means for positioning and repositioning the first carrier <NUM> relative to the second carrier <NUM> including in three dimensions represented by the three Cartesian coordinates X, Y, Z under control of the processing element <NUM>. Furthermore, there may be provided means for adjusting the relative positions laterally (in a direction parallel to the second carrier <NUM>), vertically (in a direction perpendicular to the second carrier <NUM>) both using translation and orientation. In this example the apparatus includes automated displacement means under control of the processing element <NUM>. The automated displacement means may include for example mechanical or electrical units providing mechanical or electrical feedback mechanisms for precisely controlling the relative XYZ positions and orientation of the first carrier <NUM> relative to the second carrier <NUM>. Such displacement means are known per se and are therefore not described in any further detail for the sake of brevity only.

The second carrier <NUM>) optionally may also be controlled by the processing element <NUM> in a manner analogous to the above control means for the first carrier <NUM>, to increase the degrees of freedom of the imprinting apparatus <NUM>. However, it is equally feasible to provide an imprinting apparatus <NUM> having a stationary or fixed second carrier <NUM>.

The first carrier <NUM> is separated from the second carrier <NUM> by a gap <NUM>, the size of which may be controlled by the processing element <NUM>, e.g., by engaging the means for positioning and repositioning the first carrier <NUM> relative to the second carrier <NUM>. In a particular example, the processing element <NUM> may be programmed to alter the gap size in between the imprinting step and the release step. Specifically, the processing element <NUM> may be programmed to increase the gap size upon completion of the imprinting step (and after developing the resist layer <NUM>) as increasing the gap size can aid the release of the imprinting pattern <NUM> from the developed resist layer <NUM>.

The overpressure channel <NUM> may include a pressure regulator <NUM> under control of the processing element <NUM>. This facilitates varying the overpressure during an imprinting or release step.

The imprinting apparatus <NUM> may have a user interface, e.g., a user terminal including at least one instruction input device such as a keyboard, mouse, trackball, and so on for allowing the user to configure the imprinting apparatus <NUM> in accordance with the desired imprinting process. It should be understood that any suitable user interface may be used.

As mentioned above, the processing element <NUM> is arranged to control the first carrier <NUM>, the valves <NUM> and/or the pressure regulator <NUM>. To this end, the imprinting apparatus <NUM> further comprises a computer-readable data storage medium (not shown), such as a memory device, e.g., Flash memory, RAM or ROM, a solid state disk, a magnetic disk and so on. The data storage medium comprises computer program code for execution by the processing element <NUM>, which computer program code causes the processing element <NUM> to implement the various steps of the imprinting method. The data storage medium may be located in any suitable location of the imprinting apparatus <NUM>. The he data storage medium may be integral to the processing element <NUM> or may be a discrete component accessible by the processing element <NUM> in any suitable manner, e.g., over a data communication bus or a point-to-point connection between the processing element <NUM> and the data storage medium.

A typical imprinting process using the imprinting apparatus <NUM> is as follows. A flexible stamp <NUM> comprising an imprinting pattern <NUM> is affixed to the first carrier <NUM>, for example by switching the valves <NUM> such that the apertures <NUM> are connected to an underpressure channel <NUM>, which channel may be connected to an underpressure-providing source such as a vacuum pump. The first carrier <NUM> is subsequently positioned over the second carrier <NUM> carrying the substrate <NUM> coated with resist layer <NUM>, such that the imprinting pattern <NUM> faces the resist layer <NUM>. The first carrier <NUM> is typically positioned relative to the second carrier <NUM> such that a gap <NUM> exists between the first carrier <NUM> and the second carrier <NUM>, which gap <NUM> may be defined by the user of the imprinting apparatus <NUM> to ensure a good conformal contact between the flexible stamp <NUM> and the substrate <NUM> during imprinting. The gap <NUM> may be chosen in any suitable range; for example, in a typical SCIL process in which the imprinting pattern <NUM> is a nanoscale pattern, the gap <NUM> may be chosen in a range from <NUM>-<NUM> µm, preferably in a range from <NUM>-<NUM>, more preferably in the range from <NUM>-<NUM>.

Upon positioning the first carrier <NUM> relative to the second carrier <NUM>, the imprinting process proceeds with an imprinting step, in which a contact area is created between the flexible stamp <NUM> and the substrate <NUM>, which contact area is gradually expanded until the entire imprinting pattern <NUM> intended to contact the substrate <NUM> is brought into contact with this substrate.

<FIG> shows the imprinting process. In <FIG> the imprinting pattern <NUM> has been omitted for the sake of clarity only.

As can be seen in the upper pane of <FIG>, an initial contact area <NUM> is created between the flexible stamp <NUM> and the substrate <NUM> by individually switching selected apertures <NUM> from underpressure to overpressure in the direction of the horizontal arrow <NUM> over the overpressure channel <NUM>. In <FIG>, only the selected connections between the valves <NUM> and the respective channels <NUM> and <NUM> are shown, for reasons of clarity. This bulges part of the flexible stamp <NUM> away from the first carrier <NUM> towards the second carrier <NUM> to establish the contact area <NUM> between the flexible stamp <NUM> and the second carrier <NUM> including the substrate <NUM> carrying the resist layer <NUM>. A space <NUM> is formed between the first carrier <NUM> and the flexible stamp <NUM>.

The contact area <NUM> is typically expanded by moving the contact front of the contact area <NUM> in the direction of the aforementioned arrow by periodically switching the next aperture <NUM> from the underpressure to the overpressure by controlling its valve <NUM>, as shown in the bottom pane of <FIG>. This process is repeated until the contact area <NUM> is established over the entire desired area of the substrate <NUM>, i.e., the desired portion of the imprinting pattern <NUM> has been brought into contact with the resist layer <NUM>. The rate of expansion of the contact area <NUM> is typically determined by the rate at which the next apertures <NUM> are switched to the overpressure, as well as by the gap <NUM>. The associated bridge width W where the stamp is not contacted by either the first carrier <NUM> or the substrate <NUM> may for example be chosen between <NUM> and <NUM>.

Once the desired contact area <NUM> between the imprinting pattern <NUM> and the substrate <NUM> has been established, the resist layer <NUM> is subsequently developed, e.g., cured, in any suitable manner, for example by exposure to an external stimulus such as UV or visible light, heat and so on. This solidifies the resist layer <NUM>, which immobilizes the imprinting pattern <NUM> in the developed resist layer <NUM>.

At this stage, the gap <NUM> may be adjusted, i.e., increased, in order to reduce the duration of the release step in which the imprinting pattern <NUM> is released from the developed resist layer <NUM>. Not all gap settings facilitate automatic release of the stamp. Depending on the type of imprinting pattern <NUM> and resist layer <NUM>, the stamp <NUM> can be attached to the imprinted developed resist layer <NUM> by a relatively high contact area <NUM>, and thus force. The release force that can be generated is higher for larger gaps <NUM>. For example, it is possible that a stamp <NUM> cannot be released from the developed resist layer <NUM> if the gap <NUM> is set to <NUM> micron but can be released if this gap is <NUM> micron.

<FIG> is used to show how the stamp is released. During the release step, individual apertures <NUM> are switched from overpressure channel <NUM> to underpressure channel (vacuum) <NUM> by the processing element <NUM> controlling the respective valves <NUM>, which causes the flexible stamp <NUM> to move up, i.e., the flexible stamp <NUM> is peeled away from the developed resist layer <NUM>, thereby sealing the vacuum and shortening the bridge length W by one aperture pitch. This increases the force on the contact surface <NUM> and as more apertures <NUM> are switched to underpressure to displace the contact front of the contact area <NUM> in the direction of the horizontal arrow <NUM>, as shown in the bottom pane of <FIG>, the bridge is further shortened. The bridge is shortened until the force is equal to the release force of the imprinting pattern <NUM> of the flexible stamp <NUM> from the developed resist layer <NUM> on the substrate <NUM> carried by the second carrier <NUM>. This then relaxes by release of the stamp. With a larger gap <NUM>, the forces normal to the substrate wafer are higher, thereby easing the stamp release. Also, the longer bridge length caused by this larger gap <NUM> allows more force to be applied before the vacuum seal is lost between the portion of the stamp <NUM> and the apertures <NUM> of the first carrier <NUM> holding the flexible stamp <NUM> in place, e.g., the apertures <NUM> in contact with the outer edge of the flexible stamp <NUM>.

It is noted that during stamp release from the solidified resist layer, the flexible stamp <NUM> is in equilibrium with the force required to release the stamp. The next aperture <NUM> can only be switched to underpressure, e.g., vacuum, after a portion of the flexible stamp <NUM> (on average) has released that has a size comparable to an aperture-to-aperture distance. Consequently, the rate of release of the flexible stamp <NUM> from the substrate <NUM> will be determined by the gap setting as well. For the example, if a flexible stamp <NUM> can be released using a gap of <NUM> and <NUM> microns, the release speed for a gap of <NUM> micron will be higher than that of a <NUM> micron gap, such that a higher release rate, i.e., the rate at which individual apertures <NUM> are switched to the underpressure along the direction indicated by the horizontal line, can be applied by the processing element <NUM>, i.e., by periodically switching the corresponding valves <NUM> to the underpressure channel <NUM>. For the highest throughput of the overall imprinting process, the gap <NUM> setting for the imprinting step may be different from the gap <NUM> required for optimal stamp release during the release step shown in <FIG>.

Further details of the known printing process are disclosed in <CIT> and <CIT>.

As mentioned above, there is a desire to scale the design up to enable printing of larger wafers, such as <NUM> wafers. This results in an increase in the required process forces (e.g., twice as high) and a larger span width (e.g., <NUM> diameter instead of <NUM>). To maintain a required imprint gap variation such as <NUM>-<NUM> during the process load, it is not possible simply to scale up existing designs. In particular the second carrier <NUM> (which comprises a chuck and a supporting chuck frame) would not have sufficient stiffness.

In particular, a conventional C-frame design implemented by the coupling between the chuck frame and the groove plate will bend, because of the process load. Bending results in a larger variation of the imprint gap. This reduces the quality of the imprint process significantly.

The chuck frame can also warp during heating. While some warping is permitted to a small extent, after cooling down to room temperature warping is not accepted.

The chuck frame also has a large thermal mass, which results in long heating and cooling times. A thermal temperature gradient across the chuck can also be too high when the size is scaled up.

There is a need to control the imprint gap with a larger area chuck and groove plate (e.g., <NUM> diameter) while still allowing simple loading of the stamp and wafer. This for example requires a longer distance manipulation of the chuck with respect to the groove plate (i.e., as part of the first carrier <NUM>). With a larger chuck, the existing designs are difficult to manufacture with tolerances enabling sufficient stiffness to ensure gap control over the entire chuck area.

A first aspect of the invention relates to the chuck manipulator.

<FIG> shows the design of the chuck manipulator.

It shows the chuck <NUM> surrounded by a stamp landing ring <NUM>. The chuck <NUM> comprises a chuck frame <NUM>. The position of the chuck frame is adjustable by micrometer adjustment screws <NUM>.

The Z-axis position control of the chuck is controlled by a single Z-stage actuator <NUM>.

This first aspect of the invention provides a two-component frame chuck manipulator.

<FIG> shows the overall system, comprising a sub-frame <NUM> on which the chuck <NUM> and stamp landing ring <NUM> is mounted. The chuck <NUM> is held by the sub-frame <NUM> and is manipulated relative to this sub-frame <NUM> using a set of three short stroke manipulators <NUM>, discussed in further below. The three short stroke manipulators <NUM> (i.e., chuck actuators) are spaced angularly around the chuck <NUM>.

The sub-frame <NUM> may be considered to be the main structural part of the second carrier and hence may be considered to be equivalent to the support <NUM> in <FIG>.

The chuck is designed to hold either a <NUM> wafer or a <NUM> wafer in this example. The chuck for example has a spillage channel around the outside of a <NUM> diameter and another spillage channel around the outside of a <NUM> diameter.

The sub-frame <NUM> may be a bolted assembly, but it could also be a welded or a 3D-printed construction. The sub-frame <NUM>, including the chuck, is manipulated as a sub-assembly mounted to a main frame <NUM>. The main frame <NUM> is manipulated relative to the fixed world, i.e., a reference frame <NUM>, using a long stroke driver <NUM> (i.e., a main actuator). The manipulation using the main actuator <NUM> allows long distance chuck manipulation (e.g., <NUM> or larger, for example between <NUM> and <NUM>) for loading of the stamp and/or wafer or servicing of parts of the chuck. In addition, the main actuator <NUM> stiffly fixes (i.e., presses) the sub-frame <NUM> to the groove plate (i.e., as part of the first carrier <NUM>), in particular against a groove plate holder <NUM> that holds the groove plate and the frame <NUM>, so that the chuck may be short-stroke manipulated relative to the groove plate <NUM> to control the imprint gap. The short stroke may be around <NUM> or less such as for example <NUM> or less.

At the same time, the sub-assembly of the sub-frame <NUM> and chuck <NUM> is biased towards the groove plate via a buffer spring arrangement <NUM>, discussed below. This allows design imperfections of parts that lead to errors in relative orientation of the sub-frame <NUM> with respect to the groove plate. Errors that originate from movement can also be compensated.

<FIG> shows that the sub-frame <NUM> has a set of contact buffers <NUM> through which the sub-frame <NUM> is pressed against a groove plate holder <NUM>. These are discussed further below. The three chuck actuators <NUM> are also discussed in greater detail below. They are located at corners of a triangle (preferably an equilateral triangle), and a triangular frame defines the sub-frame <NUM> which supports the chuck <NUM>. The chuck actuators each include a lever arrangement <NUM> which is discussed below.

The three independent actuators and associated lever arrangements inside the sub-frame <NUM> support the chuck. In this way, the imprint gap is automatically adjustable in the Z-axis direction as well as for rotation about the X-axis and Y-axis directions (e.g., to +/- <NUM>). As will be shown below, the support for the chuck is formed using flexure mechanisms which are free of play and friction.

There are also three independent actuators and levers inside the sub-frame for supporting the stamp landing ring (i.e., landing ring actuators). They are for translating a portion of the stamp landing ring in the Z-axis direction.

The position of the stamp landing ring relative to the chuck is thus also automatically adjustable in Z-axis direction as well for rotation about the X-axis and Y-axis directions (to +/- <NUM>). This enables adjustment to the thickness of the stamp, and/or any taper in the stamp thickness, since the stamp landing ring is contacted by the glass carrier plate of the stamp.

The setup described above in the figure allows for tight control of the imprint gap and associated wedge orientation of the stamp surface with respect to the chuck surface while loading long stroke manipulation of the chuck is still possible.

Note that in-plane (XY) alignment of stamp surface with respect to chuck surface, namely translation in X-axis and or Y-axis direction and/or Z-axis rotation of the stamp surface with respect to the chuck surface, is implemented via manipulation of the groove plate <NUM> with respect to its holder <NUM>. The groove plate <NUM> has a groove plate frame <NUM> which is driven by three linear actuators (shown further below) and the groove plate frame is supported by the groove plate holder <NUM> by air bearings <NUM>. This is described further below. The groove plate alignment is separate from the gap (Z-axis direction) alignment.

The use of separate long stroke (main) and short stroke (chuck) actuators creates a very stiff support for the chuck in the Z-axis direction.

Three distance sensors are used to measure (and to calibrate) the distance between the top of the chuck and the glass plate of the stamp, i.e., the groove plate. Three distance (and hence position) sensors are also used to measure (and to calibrate) the distance between the top of the stamp landing ring and the glass plate of the stamp. These sensors enable automated control of the chuck actuators and the landing ring actuators, instead of requiring manual adjustment.

<FIG> shows a plan view of the sub-frame <NUM>.

The sub-frame <NUM> behaves as a rigid body, which deals internally with the process forces. The sub-frame <NUM> is a structure which extends around the chuck, such as a ring <NUM>, although it may be a polygon.

The sub-frame <NUM> is stiff and holds the chuck <NUM> and the stamp landing ring <NUM>. Landing ring actuators 620a are between the stamp landing ring <NUM> and the sub-frame <NUM> and chuck actuators 620b are between the chuck and the sub-frame <NUM>. The actuators can independently translate three edges of the chuck/stamp landing ring in the Z-axis direction (e.g., perpendicular to the chuck top surface) relative to the sub-frame <NUM>. These allow for the ultimate gap control over the entire chuck area and over the stamp landing ring <NUM>.

Fixations are also used for ensuring the thermal centers of the chuck and the sub-frame <NUM> stay in position during homogeneous explanation. The fixations define the coupling between the chuck and the sub-frame <NUM>. They have sufficient play to allow differential thermal expansion between the two parts, but once the kinematic coupling discussed above is formed, this play does not allow any relative movement.

Returning to <FIG>, the sub frame <NUM> is attached to (in this case rests on) the main frame <NUM>. The main frame <NUM> is slidably supported on the reference frame <NUM> (the outside world). The main actuator <NUM> is between the main frame <NUM> and the reference frame <NUM> to manipulate the main frame <NUM> (and also the sub-frame <NUM> and chuck) with respect to the reference frame <NUM>.

The groove plate holder <NUM> and the groove plate <NUM> are also attached to the reference frame <NUM>.

The attachment of the sub-frame <NUM> to the main frame <NUM> is spring buffered at three locations. Two spring arrangements <NUM> are shown in <FIG>. Although not shown, the spring arrangements <NUM> may comprise an outer, larger diameter, buffer spring and an inner smaller diameter buffer spring (not visible). The buffer springs serve to compensate for alignment errors while providing a pressing force. They create a rigid coupling between the sub-frame <NUM> and the groove plate <NUM>.

As mentioned above, the sub-frame <NUM> has three (spherical top half with circular base) contact buffers <NUM> at its top surface (opposite to the side resting on the main frame <NUM>). The contact buffers are spherical with a circular base These contact buffers are for pressing the sub-frame <NUM> against the groove plate holder (at a kinematic coupling location) when the imprint machine is in the imprinting stage.

The buffers <NUM> are disconnected when loading wafers or stamps as then the sub-frame <NUM> is lowered from the groove plate by manipulation of the main frame <NUM> using the main actuator <NUM>. The pressing is so stiff that the groove plate holder and sub-frame <NUM> effectively have become one stiff part. The spring-loaded connectors <NUM> between the sub-frame <NUM> and the main frame <NUM> ensure that any alignment errors (with any cause) between the groove plate and the sub-frame <NUM> are compensated for, by these connections. The spring arrangements <NUM> push the sub-frame <NUM> against the groove plate holder.

In this way, the gap control is independent of instabilities in the main frame <NUM> and the reference frame <NUM> as the gap control is only dependent on the ensemble of the groove plate and sub-frame <NUM>, which functions as a single part.

The kinematic coupling between the sub-frame <NUM> and the groove plate holder may instead be based on balls and grooves, instead of projections with flat surfaces.

The sub-frame <NUM> is mounted to the main frame <NUM> by three pins and three slots in region <NUM>.

The slots are oriented at <NUM>°,<NUM>° and <NUM>° angles. The pins and slots have play of a few micrometers. However, this play will not cause any movements during the imprint process, because of the high friction forces within the kinematic coupling provided by the buffers <NUM>. The forces that the alignment motors can produce are much lower than the friction within the kinematic coupling.

As mentioned above, each of the spring arrangements <NUM> has a smaller diameter inner spring <NUM> within each of the larger diameter springs <NUM> for automatic mechanical overload protection. The two-spring design is optional. During normal processing, the main actuator (long stroke driver) runs at high speed. The impact of a collision could seriously damage the groove plate. Collisions can occur if there are substances on the chuck that do not belong there, or for example, if a too thick wafer is being used.

The spring arrangement means that the sub-frame <NUM> is pressed up to the kinematic coupling by two springs in series at each corner of the sub-frame <NUM>. The two springs have different force characteristics. First, only the weaker springs are used to lift the sub-frame <NUM>. After contacting the kinematic mount, the stiffer springs push the sub-frame <NUM> against the kinematic mount. This two-step approach provides the necessary time to slow down the spindle drive motor of the main actuator.

As explained above, the chuck actuators <NUM> provide Z-axis position (i.e., perpendicular to a plane of the substrate and stamp). The Z-axis positioning at three locations provides <NUM> degrees of freedom ("DOF"), in that Z-axis translation and rotation about the X- and Y-axes can be controlled.

The groove plate has in-plane positioning control, and provides X- and Y-axis translation and can provide rotation about the Z-axis. Thus, <NUM> DOF position adjustment is enabled with a simple structure which maintains a desired stiffness of the carriers. The position control is split between the groove plate and the chuck.

In the design described above, deflection of the reference frame <NUM> and/or main (long stroke) actuator will not have any influence on the imprint gap. In particular, the sub-frame <NUM> is decoupled from the main actuator by the contact buffers <NUM>. In this way, a separation of the force path and the position path has been established.

The example above makes use of separate chuck actuators to move the chuck relative to the sub-frame <NUM> and actuators for moving the groove plate. As an alternative, the chuck could be supported with a hexapod inside the sub-frame <NUM>. The hexapod would replace the three chuck actuators <NUM> of the chuck. A hexapod can move in <NUM>-axes. So-called overlay alignment for X- and Y-axis translation and rotation about the Z-axis (for stamp to wafer adjustment) is implemented in the design shown above by moving the groove plate <NUM> and <NUM> inside the groove plate holder <NUM> or <NUM> in <FIG>, which functions as an alignment station (see <FIG>). With a hexapod, this could then also be done by moving the chuck with <NUM> DOF. However, this may introduce additional difficulties in enabling sufficiently accurate overlay alignment as well as sufficient Z-axis stiffness of the chuck support. A hexapod will also result in a lower stiffness and less accurate alignment capability, but it can simplify the module so that manufacturing and development cost can be lower. Linear actuators, air bearings, short stroke manipulators, or flexible hoses for the grooves would then not be needed.

As an alternative for the pins and slots <NUM> used for mounting the sub-frame <NUM>, also flexures could be used such as folded sheet flexures.

The arrangement shown enables automatic tilt adjustments of the chuck for rotations about the X-and Y-axes. In some designs, the position of the stamp landing ring relative to the chuck can also automatically be adjusted using position sensing. Wedge compensation is also possible (i.e., the parallelism error of the stamp).

A second aspect of the invention relates to a design of the chuck, again to enable the dimension increases discussed above.

<FIG> shows the chuck <NUM>. The top image shows a perspective view showing the top and bottom image shows a partially cut away perspective view to show the internal structure. The chuck <NUM> has a flat top face for receiving a wafer. It is designed to receive a <NUM> diameter wafer or a <NUM> diameter wafer. Vacuum openings <NUM> are located at the approximate locations of the outer periphery of the wafers. These vacuum openings are for clamping the wafer. Radially outside the vacuum openings <NUM>, there are annular spillage grooves <NUM> for catching overspill of resist which may happen during the imprinting step. The overspill grooves <NUM> prevent that the chuck is polluted by the wet resist on top of the wafer. If the resist doesn't contact the chuck <NUM>, it will not stick to the chuck <NUM>.

The top face also has openings <NUM> which enable the passage of lifting pins to lower the wafer on the chuck and raise the wafer off the chuck <NUM>.

The chuck <NUM> is formed as a hollow structure. This enables it to have low thermal mass while also having a large thickness to provide the required stiffness. The chuck <NUM> is generally cylindrical. Mounting points <NUM> are formed around the outer periphery, and these engage with the chuck actuators <NUM>. At each of these mounting points, there is also a sensor <NUM> for measuring a spacing to the groove plate.

A hollow lattice structure is defined between top and bottom faces. These top and bottom faces include a water channel arrangement for temperature control. The same temperature control is provided to the top and bottom faces to provide symmetry and prevent buckling. For example, the structure and water channel layout may be the same.

The water channel arrangement for example covers the full area of the chuck. The temperature control of the top face is for the heating and cooling of the wafer and hence the resist layer provided over the wafer.

Within the hollow area between the top and bottom faces, there is a lattice structure <NUM> to provide stiffness and rigidity. Thus, there is a sandwich design with a lattice structure inside to provide the desired stiffness. The lattice structure is for example a cubic lattice (simple, or body centered or face centered) or a hexagonal lattice. The cell size and beam size is chosen to provide the required stiffness.

Connections for the water channels (e.g., a set of water entry ports and a single water exist port) as well as the vacuum connections are all placed at the bottom face of the chuck.

The chuck <NUM> is for example designed to be manufactured by powder bed fusion for metal 3D printing. It is made of stainless steel. After the 3D-printing and removal of the powder, finishing is performed with a milling machine. With a lapping process at the end, the required flatness of <NUM> for the top surface is fulfilled.

<FIG> shows the internal structure in more detail. The top part of <FIG> is a cross section showing the top face <NUM> and the bottom face <NUM>, which each enclose a channel arrangement. The thickness of each of the faces is for example <NUM> with a <NUM> skin above and below a <NUM> water layer.

The total thickness of the chuck is for example in the range <NUM> to <NUM> thick.

Two vacuum openings <NUM> are shown as well as the overspill channels <NUM>. Two alignment pin slots <NUM> are also shown.

The bottom part of <FIG> is another cross section to show how heating water (e.g., at <NUM> to <NUM> degrees) or cooling water (e.g., at <NUM> degrees) is supplied to the channel arrangements in the top and bottom faces. One water supply duct <NUM> is shown. There are for example six such supply ducts around an outer periphery of the chuck.

The supply duct <NUM> opens at its base to the channel arrangement within the bottom face <NUM> and also has a conduit <NUM> between the bottom face <NUM> and the top face <NUM>, which terminates at the channel arrangement within the top face <NUM>.

The top and bottom faces <NUM> and <NUM> enclose their respective channel arrangements. The central lattice area of the chuck is sealed from the water supply.

The conduit <NUM> has a bellows structure so that axial stresses in the conduit can be compensated by deformation of the conduit rather than inducing deformation of the surrounding parts of the chuck which could lead to a loss of flatness. However, the bellows of the conduits are an integral part of the structure of the chuck.

The chuck for example has a single water exit duct at the center of the chuck for collecting water after passing through the channel arrangement.

<FIG> shows a cross section of the entire chuck. It shows that the water exit duct <NUM> in the center also has the same bellows design as shown in <FIG>.

<FIG> shows a set of ridges <NUM> within the upper face or lower face to define the channel arrangement. Thus, it shows an opened-up area of the top or bottom channel arrangement. The top image is a plan view and the bottom image is a perspective view to show the three dimension nature of the ridges and projections. The six fluid entry ducts <NUM> are spaced around the periphery, the locations of two of which are shown in <FIG>, and the single fluid exit duct <NUM> is shown at the center. The ridges <NUM> mean the water has to follow a meandering path from the locations of the fluid entry ducts to the fluid exit duct, with circumferential path sections and radial path sections. The ridges <NUM> form a set of discontinuous annular paths, and the gaps in one annular path are staggered with respect to the gaps in the adjacent paths to define the meandering path. In addition to the ridges, which function as dams, there are pillars <NUM> around the annular paths which serve to support the skin to remain flat and, additionally or alternatively may increase turbulence.

This design provides a homogeneous water temperature distribution covering the full area of the chuck, caused by multiple mixing locations for the water.

Connections for the supply of water, the removal of water and vacuum connections are all placed at (beneath) the bottom face of the chuck. This leaves the place free for a movable stamp landing ring around the chuck.

Thermal sensors may be additionally mounted at the bottom face. Thus, there may be sensors to measure temperature in the top and bottom surfaces.

<FIG> shows the underside of the bottom face, and shows water inlet connections <NUM> around the periphery, a central water outlet connection <NUM>, vacuum connections VAC1 and VAC2, and cavity connections CAV1 to CAV6.

These cavity connections lead to openings at different locations of the chuck surface, and they connect to a pressure source for applying an under- or overpressure.

The cavities are used to enable printing on both sides of a wafer. After the first side has been printed, the pattern should not be touched and in particular not pressed over a flat surface once turned over.

To enable two-sided printing, an interface plate <NUM> as shown in <FIG> may be provided over the chuck. The interface plate is a metal or aluminum plate that can be removably positioned on top of the chuck. <FIG> shows an example of the interface plate in perspective view (upper drawing) as well as in cross section view (lower drawing) over the chuck <NUM>.

The interface plate <NUM> has a grid of openings <NUM> so that when a printed wafer <NUM> is placed over the interface plate <NUM> (with a first already-printed side facing down) the printed areas of the wafer (which will be diced to form separate products) align with the openings, and the grid lines <NUM> of the interface plate <NUM> are over (aligned with) non-patterned areas of the wafer.

The openings may extend straight through (e.g. 872a) the plate <NUM> or they may have offset shapes (e.g. 872b) as can be seen in the cross section of <FIG>. A sufficient depth is required to receive the printed substrate layer so that the surface is not contacted. The extension of the openings <NUM> to the side of the plate facing the chuck are arranged such that when the plate is attached to the chuck, the openings line up with pressure lines <NUM> within the chuck.

By providing pressure lines <NUM> through the chuck <NUM> to the openings <NUM>, the pressure in the cavities (openings) can be controlled in synchronism with the printing process. In particular, by providing a positive pressure when the printing bulge of a stamp is present, a counter pressure is used via the pressure lines to support the wafer against the pressure of the printing bulge during the printing process, instead of using a solid chuck surface. If the printing bulge advances in the direction of the arrow <NUM>, a supporting pressure may be applied in sequence to a first to fourth columns C1 to C4 of openings <NUM>. Thus, for example, the interface plate of <FIG> uses four cavity (opening) connections. However, there may be more columns of independently operable cavities, and <FIG> indeed shows six cavity connections CAV1 to CAV <NUM> at the bottom of the chuck that may be independently operated. The cavity connections lead to openings in the chuck via the pressure lines <NUM> and the openings in the chuck are located within the openings <NUM>. If no positive pressure is applied, an underpressure can be or is applied to those openings (which are closed at the top side of the interface plate by the wafer). Underpressure provision helps adhere the wafer to the plate and plate to the chuck via a clamping effect.

The interface plate <NUM> is for example a <NUM> thick stainless steel plate with a set of cut outs preferably formed by chemical etching. To mount the interface plate over the chuck, the interface plate for example has a set of, e.g. <NUM>, openings which slide over receiving pins of the chuck <NUM>. The interface plate also has vacuum grooves <NUM> for areas between the openings <NUM>. The vacuum grooves <NUM> in between and around the cavities clamp the wafer to the cavity plate.

Note that the interface plate may instead be an integral part of the chuck. In such case the plate is not removable from the chuck.

The openings <NUM> prevent contact of already imprinted structures with the wafer support as mentioned above. The interface plate also makes it possible to support, or to clamp, a wafer at any desired positions. The openings are connected via the chuck to pressurized air and/or vacuum. Openings and channels in the bottom of the interface plate connect the supplies of the chuck to the cavities.

The interface plate <NUM> has a low thermal mass and a high thermal conductivity, so that it slows down the printing process as little as possible. The plate is preferably made of aluminium, but other materials such as stainless steel can also be used. Stainless steel has a lower thermal conductivity than aluminium (which is less preferred), but since the plate is thin, such lower thermal conductivity can be used. Those skilled in the art will know how to balance thermal properties of materials in question and the geometric design to arrive at useful plates.

The required flatness and parallelism of the cavity plate is around +/- <NUM>. For a stainless steel plate, this can be achieved by using an etching process for creating the cavities. Milling causes stresses in the material which can lead to involuntary deformations.

The interface plate <NUM> gives more flexibility for implementing further designs. The chuck <NUM> itself cannot be exchanged for imprinting different designs. However, for each stamp design, a separate interface plate <NUM> can be designed and manufactured.

Thus use of a pin and slot coupling (e.g., <NUM> or more, preferably <NUM> or more, pins and slots combinations) between the interface plate <NUM> and the chuck <NUM> prevents shifts due to thermal expansion and additionally may prevent or reduce warping.

Some design options will now be explained.

A stainless steel plate is preferred. For a stainless steel plate, the plate is preferably thinner than <NUM>. A thin plate has a low thermal mass and high thermal conductivity compared to a thicker plate. A thin plate also has low stiffness so it can easily bend. The plate will align itself with the flattened top of the chuck under the vacuum force. A thin plate also gives good thermal transition from the chuck to the cavity plate. The flatness requirement, which can be important for the imprint gap, is also met. A thin plate is also preferred, because of the range of the short stroke manipulators of the chuck, such as <NUM>.

The plate should however also not be too thin. The vacuum channels cannot then be made deep enough, resulting in too many flow losses and an insufficiently strong vacuum. The force to hold the wafer onto the cavity plate will then be too small. The cavities and grooves can be or are made by a chemical etching process.

Stainless steel has a much lower thermal conductivity than aluminum. Nevertheless, the stainless steel plate will approximately add less than <NUM> seconds of heating time and <NUM> seconds of cooling time.

An aluminum plate is a possible but less preferred option. For an aluminum interface plate, aluminum has a better thermal conductivity and a lower thermal mass then stainless steel. It could therefore be made thicker for better manufacturability. Stress free casted aluminum is only available from <NUM> thickness and higher. Normal aluminum sheet material already has too many internal stresses because of the rolling processes of the raw material.

With the thicker plate, the vacuum channels can be made deep enough, resulting in enough flow and a sufficiently strong vacuum to hold the wafer. Cavities and grooves cannot in this case be made by a chemical etching process. Chemical etching is not possible using aluminum. The alternative, milling, causes stresses in the material. This leads to involuntary deformations. Tension-free annealing may be used.

The thicker aluminum plate will be stiffer than a thin stainless steel plate. However, it will not align itself with the flattened top of the chuck. This can lead to a gap between the chuck and the cavity plate and therefore leakages of the vacuum, resulting in no vacuum to hold the cavity plate to the chuck. Furthermore, such gap may reduce heat transfer between the plate and chuck thus reducing heating and cooling rate during use of the apparatus.

It is, however, difficult with an aluminum plate to provide the desired thermal transition from the chuck to the cavity plate and to meet the flatness requirement, which is important for controlling the imprint gap. The thicker plate is also not preferred due to the short stroke manipulators of the chuck. However, in printing machines with only one Z-stage, the thicker plate could be used.

As mentioned above, the short stroke manipulator (i.e., the chuck actuator <NUM>) is another aspect of the design of the invention.

The same design of short stroke manipulator may be used as a stiff support and drive arrangement for the chuck as well as for the stamp landing ring. The short stroke manipulator is used to position the chuck and the stamp landing ring with <NUM> degrees of freedom (i.e., <NUM> translations and <NUM> rotations) when combined with the positioning of the groove plate as explained above.

The chuck, groove plate and stamp landing ring each have to be supported and correctly aligned with <NUM> DOF.

The groove plate can be moved in <NUM> DOF (X-axis translation, Y-axis, translation and rotation about the Z-axis), and the other <NUM> are fixed (Z-axis translation and rotations about X- and Y-axis.

The chuck and stamp landing ring can be moved in <NUM> DOF (Z-axis translation, and rotation about the X- and Y-axis), and the other <NUM> are fixed (X-axis and Y-axis translations and rotation about the Z-axis). One short stroke manipulator supports <NUM> DOF (Z-axis translation and fixed X-axis translation).

The manipulators are used as fine adjustment of the chuck and the stamp landing ring in the Z-axis direction and for rotation about the X- and Y-axes. As will be described further below, the chuck actuators are also used for force measurement and for shock absorbing.

Thus, the aligning and manipulating of the <NUM> DOF between the stamp and the wafer is realized by two separate aligning systems:.

For two-sided imprinting of a wafer (as discussed above), in addition to controlling the imprint gap, the overlay alignment is essential. The overlay alignment specification requires a very high position accuracy. Friction and hysteresis free overlay alignment are critical. A large alignment range also needs to be covered in the horizontal plane, such as up to <NUM> or even up to <NUM> of linear movement. The allowed forces of the piezo stepper drives are also limited such as a maximum of <NUM> N.

Controlling the imprint gap is achieved by the two-stage chuck support described above. For overlay alignment, two markers on the stamp and two markers on the wafer are used. A camera system on top of the groove plate measures the coordinates of these four markers. The groove plate is transparent for this purpose. Both the markers of the wafer and the markers on the stamp need to be in focus (i.e., at the correct height) of the camera system.

The system compares the coordinates of the four markers and a transformation matrix is used, to calculate the desired movements for the three short stroke actuators. For reaching a better accuracy, this control loop can be repeated several times.

As mentioned above, one option to control all <NUM> DOF is to manipulate only the chuck. A hexapod could be used for that as explained above. However, a hexapod that meets the requirements is not commercially available. Splitting the alignment functions in the manner outlined above makes it possible to meet the requirements.

One aspect of the invention makes use of an alignment stage which contains a movable groove plate carrier <NUM>. The groove plate carrier can be positioned by translation in the X-axis and Y-axis directions and Z-axis rotation (Rz) without any friction or backlash. A large alignment range in the horizontal plane of the desired <NUM> (or even <NUM>) linear movement is possible.

<FIG> shows the drive arrangement for the groove plate <NUM> (i.e., as part of the first carrier <NUM>). This functions as an alignment stage. The groove plate <NUM> has a groove plate frame <NUM> as also shown in <FIG> which is driven by three linear actuators <NUM>, each coupled to an associated pair of air bearings <NUM> via a flexure <NUM>. While this is a preferred construction, the association is not necessary per se. The actuators can also be placed at different positions or angels such as for example three times <NUM> degrees rotated with respect to each other and <NUM> degrees rotated with respect to the air bearings. These may be named "carrier actuators" to distinguish from the chuck actuators and the stamp landing ring actuators. A pneumatic valve terminal <NUM> couples to the groove plate via flexible air tubes to provide the printing pressures explained above.

The groove plate frame can be positioned in X-axis direction, Y-axis direction, and Z-axis rotation (Rz)without any friction or backlash.

The translations in X-axis and Y-axis directions and the rotation around the Z-axis are established by the three actuators <NUM>. The required forces for the linear actuators for example do not exceed <NUM> N. The actuators are mounted to the fixed world (i.e., a base <NUM>) and are connected via the three flexures <NUM> to the groove plate frame <NUM>. The three flexures allow lateral movement orthogonal to the actuator movement. The lateral shift prevents an over constrained groove plate frame <NUM>.

The set of three pairs <NUM> of air bearings are used for Z, Rx and Ry fixation of the groove plate frame <NUM> inside the alignment stage. The air bearings are mounted to the fixed world <NUM>. At each of three corners, a set <NUM> of two air bearings clamp the groove plate frame. One air bearing is on top of the groove plate frame and one is at the bottom (as can be seen in <FIG>, but shown as a single unit in <FIG>). The groove plate frame <NUM> is clamped between the air bearings above and below, so that the air pressure is equalized (in the Z-axis direction). The three corners set a fixed horizontal frame, and movement within that plane is allowed by each pair of air bearings. The allowed movement is for example around <NUM>, and is needed primarily for Rzadjustment.

One air bearing of each pair may be pre-loaded using a spring mechanism as can be seen in <FIG>. This pre-load makes it possible to keep the air gap constant under all circumstances. The height of the air gap is a dominant factor for the stiffness of the groove plate support in the Z-direction.

The displacement coordinates of the frame <NUM> are calculated with a translation matrix.

In use, the markers of the wafer are positioned at the correct focus depth by operating the chuck support, which provides Z-axis positioning. After this, the horizontal alignment can be implemented.

Note that an alternative for the <NUM> air bearings is a set of (for example <NUM> or <NUM>) folded leaf springs for Z-axis, Rx and Ry fixation. A disadvantage compared to the air bearings is that folded leaf springs require additional force of the linear actuators to move the groove plate. Leaf springs (e. g folded leaf springs) must be high, long and thick enough to provide the required movement in the X-axis direction, Y-axis direction, and Rotation around the Z-axis (Rz) and the stiffness of the groove plate frame <NUM>, resulting in a larger force requirement for the (e.g., groove plate) actuators.

<FIG> shows in more detail the design of the short stroke actuator <NUM> for use as the chuck actuator. The same actuator may be used for the stamp landing ring, and again the sensor (described below) may be used for machine damage protection.

The chuck actuator comprises a drive element <NUM> such as a piston which drives an actuator tip <NUM> up and down. The actuator tip <NUM> position is fixed relative to the sub-frame at connection <NUM> and this is rigidly coupled to the real world (i.e., the reference frame <NUM>) during printing as discussed below, so operating the actuator results in an actuator output <NUM>, in the form of a drive coupling, moving up and down. A tension spring <NUM> pulls the short stroke actuator up. The top of the tension spring connects to pin <NUM> which is also connected to the sub-frame. The spring compression varies over the same distance as the stroke of the short stroke manipulators.

The tension spring <NUM> is adjustable and ensures a pre-loaded manipulator, free of play. The adjustment may be made by a threaded tube <NUM> which adjusts the position of one end of the spring (e.g., opposite the pin <NUM>). The pretension of the tension spring <NUM> defines the allowed stamp release force. The higher the spring force, the higher the release force can be. The pretension of the spring may not be too high, because of the limited allowed load on an integrated force sensor <NUM> discussed below.

The actuator <NUM> comprises a lever arrangement with the actuator output <NUM> at one end and a chuck driver <NUM> at the other end. A pivot point <NUM> is along the lever arrangement and this is formed as a cross flexure pivot. A fixed part <NUM> of the lever arrangement connects to the reference frame (e.g., the sub frame <NUM>), and the main body <NUM> of the lever arrangement is a movable part of the pivot point <NUM> which rocks about the pivot location. A lever ratio is defined as the ratio of the distance (d2) between pivot point <NUM> and actuator output <NUM> over the distance (d1) between pivot point <NUM> and chuck driver <NUM>. The lever ratio (d2:d1) is for example <NUM>:<NUM>.

The lever, e.g., with lever ratio <NUM>:<NUM>, ensures that the support provided at the chuck driver <NUM> is <NUM> times more accurate and <NUM> times stiffer in the Z-axis direction than the actuator <NUM> would be without the lever arrangement. Thus, by using a lever, the imprint gap is better controlled.

The force sensor <NUM> is for measuring the process load and is integrated inside the lever. This enables better monitoring of the imprint process. The force sensor <NUM> is part of the stiffness loop, and the force sensor is placed in series with the actuator.

The main body <NUM> of the lever is split by a groove <NUM> for example of <NUM>. The moment created inside the lever by the force of the actuator is transmitted without any hysteresis via the senor <NUM> and a notch flexure <NUM>. The sensor in this example measures a force of <NUM> times the load based on the ratio of d1:d3 (e.g., <NUM> to <NUM>). d3 is the rotational arm length from the notch flexure to the force sensor.

The connection <NUM>, pin <NUM>, and fixed part <NUM> all connect to the sub-frame <NUM>. However, in use with the sub-frame pressed against the groove plate, the sub-frame becomes rigidly coupled to the reference frame (through the kinematic coupling). Thus, sub frame <NUM> is pushed against part <NUM> via the kinematic coupling <NUM>.

The force sensor <NUM> comprises a force sensor element <NUM> which is biased by a compression spring <NUM> against a seat above the split <NUM>.

The seat provides overload protection for the sensor. The force sensor element <NUM> is pushed against the seat by a pre-compressed spring <NUM>. The seat will only move against the bias of the spring if the force on the sensor exceeds for example <NUM> N.

As long as the force sensor element is pushed against the seat when there is not an excessive force), the overload protection will have no impact on the stiffness loop.

The actuator tip <NUM> of the drive element <NUM> is limited by a stopper <NUM> fixed relative to the reference frame.

The stopper <NUM> comprises a ring which is pushed against the tip by a spring <NUM>. The ring can move against the bias of the spring if the force on the sensor exceeds for example <NUM> N. As long as the tip is against the stopper with the spring not compressed, the spring will have no impact on the stiffness loop. This prevents the spindle of the actuator being damaged by an impact force.

The force sensor and the actuator are in this way protected against overload by shock, for example the load of the force sensor should be limited between -<NUM> and +<NUM> N, otherwise the sensor or actuator can be damaged.

A negative force to the sensor is prevented by the split groove design. The split groove inside the lever will become wider in the event of a negative force, so that the sensor will lift from its contact point. The force will thus be zero. A positive force, however, can be higher than <NUM> N due to shock, and therefore the force limiting arrangement described above is used.

The force sensor is also able to detect a stamp that is sticking, and can be used to prevent machine damage.

Stamp sticking is a problem which is preferably detected. It happens when the stamp release sequence after the imprint process does not work. This situation can occur when a stamp is being used too many times. The rubber relief part of the stamp will no longer be removed from the wafer.

At the end of the imprint process, the support (e.g., glass or metal plate) of the stamp is held by a vacuum against the groove plate and the wafer is held by a vacuum against the chuck. The groove plate, stamp, wafer, and chuck function as one monolithic body at this point. Normally after the imprint and stamp release sequence, the chuck is lowered, in this case by the chuck actuators and the main actuator. At this moment, the chuck will be lifted and the actuators lose contact.

In such a case, a gap between the actuator tip <NUM> and the stopper <NUM> can result, for example with a dimension of <NUM> to <NUM>. If the chuck suddenly drops, it can fall down by around <NUM> to <NUM>. This generates a shock with an impact force of around <NUM> N on the actuator. This shock will result in a broken force sensor and a damaged spindle of the actuator.

Lifting the chuck is necessary to protect the groove plate from an excessively large load. The main actuator <NUM> can easily cause too much pulling force via the stamp on the groove plate. Thus, by detecting a sticking stamp, the main actuator can be stopped. The groove plate may thus be protected from damage.

<FIG> shows the chuck driver <NUM>, mounted between the lever and the chuck, as an end view. It has a cross flexure <NUM> in the middle of its width (e.g., perpendicular to the Z-axis). This allows some rotational movement in the width direction of the chuck driver, e.g., rotation about the Y-axis direction for the example shown.

The purpose of this movement is to allow the chuck driver <NUM> to adopt a correct position after the tilt of the chuck has been adjusted.

The chuck driver <NUM> comprises a shortening compensation leaf spring.

When the lever rotates around pivot <NUM>, the right side of the lever (the shorter side) shortens as seen from the center of the chuck. This shortening is a parasitic movement of the lever. The length when projected onto the plane of the chuck is shorted so that it becomes L (<NUM>-cos(φ)) where φ is the rotation angle of the lever. The lever arrangement compensates for this so that the position of the chuck in the X-axis and Y-axis directions does not change in response to an adjustment of the Z-axis direction position.

This design allows the three chuck actuators to individually move over the complete stroke of the lever. This enables zeroing of each actuator and prevents over constraining the chuck.

The forces on the chuck in the X-axis and Y-axis directions (parallel to the wafer) are routed via the cross flexures <NUM> and <NUM> of the three levers and the chuck driver <NUM>. Each lever thereby provides two degrees of freedom; translation along the Z-axis and the X-axis.

The short stroke manipulator design may be used as the chuck actuator for movement of the chuck and as the landing ring actuator for movement of the stamp landing ring. Thus two short stroke manipulators may be placed at each corner of the triangular sub-frame <NUM>, one constituting a chuck actuator and the other constituting a landing ring actuator. This provides a modular design.

Note that in this design, the tension spring <NUM> both pulls the senor tip to the lever and pulls the actuator tip to the stopper. However, two separate springs could be used. This would mean that the load on the sensor would not be (or less) influenced by adjusting the pretension of the tension spring and/or by a different position of the lever.

As mentioned above, another aspect of the invention is the ability to control the position of the stamp landing ring. Some further refinements relating to the stamp landing ring are discussed below.

As explained above, before starting the imprint process, the substrate (wafer) is brought into close proximity e.g., <NUM> to <NUM> to the stamp, providing a process gap. The groves of the groove plate are successively pressurized and the stamp bulges out from the groove plate towards the substrate spanning the process gap until it contacts the substrate, and is supported by the substrate. The resist layer of the substrate is solidified during contact and the stamp is removed after such solidification by supplying vacuum to the grooves again. Thus, the process of stamp application to the substrate uses a pressure difference between areas of the stamp that are held to the groove plate and areas that are pushed towards the substrate. Such differences arise at the edges of the stamp. The difference is a cause of pressure leakage and may result in uncontrolled stamp application and/or removal. In general, the larger the process gap between the groove plate and the substrate (or chuck), the larger the leakage and therewith the larger the loss of pressure under the stamp. Thus, the process gap needs to be controlled accurately over the whole area of the stamp.

Different stamps differ from one to the other at the edges. There will be an area of the support (the groove plate) not covered by stamp material at the edges. Hence this area is not supported during stamp manipulation because only the stamp is contacting the wafer that is supported. This lack of support allows bulging of the stamp beyond the set process gap at these areas and this may induce additional leakage.

The stamp landing ring mentioned above surrounds the chuck to provide stamp support at this edge area such that the whole flexible stamp area that bulges can be prevented from bulging out beyond the set process gap. However, different stamp and substrate (wafer) combinations require different actively controlled thicknesses and gaps, with a different area outside the stamp and different thickness of stamp.

The stamp landing ring is an additional edge support structure which prevents the stamp at the edges from bulging beyond the set process gap by supporting that part of the composite stamp.

<FIG> shows the process using a stamp landing ring.

The top image shows the substrate <NUM> raised above the chuck <NUM> by supporting wafer lift pins <NUM> and the chuck spaced from the groove plate <NUM> on which the stamp <NUM> is mounted. The chuck <NUM> is driven relative to a chuck assembly, such as the sub-frame <NUM>, by the chuck actuators 620a.

A stamp landing ring <NUM> is driven relative to the sub-frame <NUM> by the landing ring actuators 620b.

The configuration at the top allows the substrate <NUM> and the stamp <NUM> to be loaded and unloaded.

The imprint position is shown at the bottom.

The process gap between the substrate <NUM> and the stamp <NUM> is the same as the process gap between the stamp landing ring <NUM> and the groove plate (or more particularly the glass supporting plate of the stamp) outside the area where the stamp material is present.

The use of separate chuck actuators and landing ring actuators enables different combinations of substrate (wafer) thickness and stamp thickness to be tolerated.

In addition, further refinements discussed below enable different imprint configurations for various stamp size (in plan view) and wafer size (in plan view) combinations, e.g., combinations of <NUM> or <NUM> substrates with <NUM> or <NUM> stamps.

<FIG> shows a substrate <NUM> supported on a chuck <NUM>. The stamp landing ring <NUM> supports the area outside the actual stamping area. <FIG> shows a stamp landing ring adapter <NUM> over the stamp landing ring. The adapter design has the same shape and size as the stamp landing ring, and hence it provides a thickness adaptation. For example, <FIG> shows a <NUM> wafer <NUM> with a <NUM> PDMS stamp <NUM>. The process gap will be defined by the distance between the wafer and the stamp and the adapter <NUM> and the thin glass support of the stamp.

However, the stamp landing ring adapter may also adapt the stamp landing ring in dependence on a size of the substrate.

<FIG> shows an example where the stamp landing ring <NUM> is for fitting around a substrate of a first size (e.g., <NUM>) and the stamp landing ring adapter <NUM> is for extending the size of the stamp landing ring <NUM> to fit around a substrate <NUM> of a second, smaller size (e.g., <NUM>).

In <FIG>, the stamp landing ring <NUM> is for fitting around a flexible stamp <NUM> of a first size (e.g., <NUM>), and the stamp landing ring adapter is also for extending the size of the stamp landing ring to fit around a flexible stamp <NUM> of a second, smaller size (e.g., <NUM>).

<FIG> thus shows a <NUM> substrate (wafer) with a <NUM> PDMS stamp. The process gap will be defined by the distance between the wafer and the stamp and the adapter and the thin glass. The adapter extended over and beyond the <NUM> chuck to support the PDMS stamp outside the wafer area. As the ring is relatively thin it can bend down due to the pressure under the stamp. This can be compensated by moving the stamp landing ring up relative to the chuck.

<FIG> shows an example where the chuck <NUM> is for fitting around a flexible stamp <NUM> of a first size (e.g., <NUM>) and there is a second stamp landing ring <NUM> for fitting over the chuck around a substrate <NUM> of a second, smaller size.

<FIG> shows a <NUM> PDMS stamp is to be used on relatively thin wafers (e.g., <NUM> to <NUM>). The overhanging stamp landing ring might not have a sufficiently high bending stiffness to compensate the pressure exerted by the stamp. The maximum thickness for such a stamp landing ring would be the thickness of the wafer.

The stamp would bend down the free hanging part too much, so that the stamp does not nicely transition on the wafer and cause imprint defects at or around the wafer edge, and stamp/pattern deformations deteriorating overlay alignment.

By having a stationary second stamp landing ring around the wafer as shown, with the same thickness as the substrate (wafer), the movable stamp landing ring <NUM> can be used to compensate for variation is stamp thickness and wedge by the chuck, and the whole stamp is still properly suspended over the whole area. The stationary ring <NUM> does not have to be changed as the wafer thickness is typically within +/-<NUM> or even +/-<NUM>, which is not an issue and the stamp can transition from the stationary ring <NUM> to the wafer smoothly.

<FIG> shows an example suitable for imprinting relatively thick <NUM> wafers (e.g., <NUM> to <NUM>) using a <NUM> stamp which thus also needs to be correspondingly thick. The stamp landing ring adapter <NUM> can have enough stiffness to counteract the pressure from the stamp on the overhanging part. Still the area of the stamp outside the rubber needs to be supported such that the stamp does not bulge out further than the process gap. This can be achieved by using a stamp landing ring with two thicknesses. The additional outside thickness provided by second adapter <NUM> compensates for the stamp thickness.

The adjustable drive provided by the landing ring actuators reduced the need to replace the stamp landing ring to accommodate different stamp and substrate combinations. This allows (on the fly) adjustment to a wide variety of wafer thicknesses and stamp thicknesses and wedge angles and lead to an optimized imprint process for each case.

The optimized process gap leads to reduced pressure loss and an improved reproducibility in imprint quality with lessened pattern distortions and improved overlay alignment.

The stamp and wafer thickness for example need to have a known thickness to within around <NUM>, as it is desired that the process gap is defined to within this range. The same tool and stamp hardware and size may be used to handle a variety of wafer and stamp size combinations.

The chuck actuators and landing ring actuators enable dynamic changes to the gap between the stamp and substrate during separate stages of the process (e.g., alignment, imprint, release).

The printing process requires loading of a stamp onto the groove plate. In existing machines, the stamp is loaded by pivoting open a top cover which carries the groove plate. The cover could be manually turned by <NUM>° so that the groove plate is presented upside-down. The stamp can then be placed with the glass plate side on the groove plate. The grooves have a small overpressure at this time, which creates an air bearing for the stamp. The stamp could thus easily be moved and aligned manually.

The position is then fixed by switching the grooves to vacuum. After this, the cover is closed again and the imprinting process can start. In case of a power down or a vacuum loss, the stamp will drop on top of the chuck. To remove the stamp, the top cover could easily be opened manually in the same way.

The design described above, with the groove plate alignment stage for overlay alignment, as well as the increased size of the wafer, means it is not desirable to have a pivotable cover, because it is too large, too heavy and too fragile).

Another design aspect thus relates to a semi-automatic stamp loading function, in which the stamp loading takes place from below the groove plate. The design approach described below also means that if the hold on a stamp is lost, (by power or vacuum loss) the machine does not need to be opened. An integrated stamp drop protection prevents the stamp from dropping, and the stamp can be unloaded via the normal unloading sequence.

<FIG> shows a design with semi-automatic stamp loading.

<FIG> shows the groove plate <NUM> above the stamp <NUM>. The stamp <NUM> is mounted on a stamp carrier <NUM> which is positioned on a frame, in particular a sliding telescopic drawer <NUM>. Together, the stamp carrier <NUM> and the drawer may be considered to comprise a stamp loader. The stamp carrier <NUM> comprises a frame with a central opening to avoid contact with the rubber stamp material (PDMS). Thus, the stamp carrier <NUM> supports the glass substrate of the stamp and the stamp does not move or sag, because the outside rim of the stamp is held by vacuum. The telescopic drawer <NUM> transfers the stamp carrier <NUM> in the horizontal direction, from the load position (outside the module), to a park position and then to the transfer position.

The long stroke driver <NUM> of the module, described above, is used for the vertical lifting of the stamp carrier <NUM>.

The stamp <NUM> is shown above the chuck <NUM> and the stamp landing ring <NUM>. The stamp landing ring is positioned by the stamp landing actuator 620a and the chuck is positioned by the chuck actuator 620b.

This stamp loading mechanism loads and unloads a stamp <NUM> automatically from below, without opening a top cover. The groove plate <NUM> is positioned with the grooves facing downwards. A stamp drop protection <NUM> is also integrated inside the frame of the groove plate <NUM>.

The stamp <NUM> is held by vacuum on the outside rim of the stamp carrier <NUM> by vacuum channels <NUM>. The stamp carrier <NUM>, for example, has two separate vacuum channels. One channel is used when the carrier is placed on the telescopic drawer <NUM>, the other channel is used when the stamp carrier is placed on the stamp landing ring <NUM>. The presence of the stamp is detected by measuring the vacuum pressure.

The stamp loading sequence will now be described.

The loaded stamp is then ready to be used. The stamp is unloaded via a reverse procedure.

The integrated stamp drop protection prevents the stamp from uncontrolled dropping onto the chuck.

Typically, three or four clamps support the stamp at the corners or outside rim of the stamp. The stamp drop protection for example comprises a spring force loaded mechanism to keep the stamp clamped, during power, vacuum or air pressure loss. As outlined above, the stamp drop protection needs to be opened for loading and unloading a stamp. In a closed (clamped) position it will interfere with the stamp carrier.

During normal production cycling (i.e., not stamp loading), the stamp drop protection remains closed (i.e., clamped). It is designed not to interfere with the stamp landing device ring during the normal cycling. Openings inside or around the stamp landing ring may be used to allow all movements (linear and rotation) of the clamps.

If the stamp is not fixed to groove plate (because of an incident etc.) and it is only clamped by the stamp drop protection, the stamp can be removed by executing the normal stamp unload sequence with the stamp carrier. Manual intervention by the operator (opening the module as in the past) is not needed.

The stamp loading process is described as semi-automatic, in that the stamp is loaded manually into the drawer. However, the drawer design may be used as a step towards full automation of stamp loading and unloading in the future. In the current situation, an operator places the stamp on the carrier manually, the telescopic drawer moves the carrier in and out. In the future, this could be done by the robot of the cluster tool. This could be the robot that is now used for loading and unloading the wafers or an additional robot. The end-effector of the robot needs to be adapted to handle the stamp carrier and to supply vacuum for holding the stamp. The robot can then take over the role of the drawer. Inside the cluster tool, a stacking system can then be installed which contains stamp carriers loaded with new stamps, and empty stamp carriers.

There are various design aspects described above. They may be used alone or in combination. Notably, these design aspects are:.

In the examples above, the first carrier comprises an array of apertures for use in pulling the flexible stamp towards the first carrier and for use in pushing the flexible stamp away from the first carrier. A pressure source in combination with the apertures provides an actuator function. However, other actuators may be used, for example electromagnetic actuators or other actuators may be used to provide the pulling and pushing function.

Claim 1:
An imprinting apparatus (<NUM>) comprising:
a first carrier (<NUM>) for carrying a flexible stamp (<NUM>); and
a second carrier (<NUM>) movable relative to the first carrier,
wherein the second carrier comprises:
a chuck (<NUM>) configured to carry a substrate (<NUM>) having a resist layer (<NUM>); and
a set of chuck actuators (<NUM>) for translating a portion of the chuck in a direction perpendicular to the plane of the second carrier, wherein each chuck actuator comprises a chuck drive member (<NUM>), an actuator output (<NUM>) and a lever arrangement (<NUM>,<NUM>) between the actuator output (<NUM>) and said chuck drive member (<NUM>);
characterized in that the lever arrangement comprises a first pivot (<NUM>) between a fixed lever portion (<NUM>) and a movable lever portion (<NUM>), the lever arrangement providing a reduction in displacement between the actuator output and the chuck driver member.