Patent Description:
A scanning probe microscopy device serves to map nanostructures on a sample surface of a sample. Such a device may comprise a probe for scanning the surface of an object, and one or more motion actuators for enabling motion of the probe relative to the sample. In one embodiment a probe comprises a probing tip mounted on a cantilever arranged for bringing the probing tip in contact with the sampling surface for enabling the scanning, and a Z-position detector for determining a position of the probing tip along a Z-direction when the probing tip is in contact with the sample surface (herein the Z-direction is a direction transverse to the sample surface).

Scanning probe microscopy (SPM) devices, such as atomic force microscopy (AFM) devices as described above are for example applied in the semiconductor industry for scanning of semiconductor topologies on a surface. Other uses of this technology are found in biomedical industry, nanotechnology, and scientific applications. In particular, measurements with a microscopic probe may be used for critical metrology (CD-metrology), profilometry, particle scanning and defect review, stress- and roughness measurements. AFM microscopy allows visualization of surfaces at very high accuracy, enabling visualization of surface elements at sub-nanometer resolution.

The very high resolution and accuracy of a microscopic probe however comes at the cost of performance in terms of throughput. Throughput scales with the ratio of object area and the area of the smallest details that can be resolved with the microscopic probe. For object of macroscopic dimensions this results in significant processing time, which may be unrealistic or at least cumbersome for practical use and altogether incompatible with on line use in manufacturing processes.

High throughput scanning probe microscopy devices are nowadays available wherein a plurality of sensor heads may be positioned relative to a sample surface by means of a number of arms. Although a plurality of sensor heads may be applied simultaneously for scanning, thereby increasing the efficiency and throughput, a further increase in efficiency and throughput is desired e.g. for use in an industrial manufacturing process.

Reference is made to the following patent applications: <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

It is an object of the present invention to provide a high throughput device and method for measuring and/or modifying surface features and/or sub-surface features on or below a surface of a sample.

There is provided herewith a, in accordance with claim <NUM> a device for measuring and/or modifying surface features and/or sub-surface features on or below a surface of a sample, the system comprising: a sample carrier for supporting the sample for exposing the surface for enabling said measuring and/or modifying, one or more heads including at least one of surface measuring equipment or surface modification equipment, and a support structure for supporting the one or more heads, wherein the support structure comprises a reference surface for providing a positioning reference for enabling positioning of each of said one or more heads onto the ref erence surface at a respective working position, wherein the reference surface comprises and optical reference grid and wherein the heads are separate from the sample carrier and the support structure such as to be not connected thereto, and wherein the device further comprises a pick and place manipulator arranged for gripping of respective ones of the heads and positioning thereof at their respective working positions, wherein the manipulator comprises a gripper and an actuator for moving the gripper and the reference surface relative to each other, wherein the actuator is arranged for providing a motion in a direction transverse to the reference surface, and wherein the gripper is arranged for engaging and releasing the respective heads from the transverse motion for placing the heads on the reference surface.

The terms 'surface features' and 'sub-surface features' relates to any features that are on or below the surface of a sample and that may be sensed and/or modified. Such features may be structural features, such as height differences, ridges, holes, protrusions, indentations or the like. Such features may also include structures of different materials or internal structures or layers in a sample. The terms also include any other mechanical, electrical, and/or chemical properties of the surface or below the surface of the sample that may be measurable and/or modifiable. Examples are scanning probe microscopy (SPM) of surface or sub-surface features, such as atomic force microscopy (AFM), electrical properties measurement via scanning capacitance force microscopy, measuring elasticity and stiffness via force spectroscopy or contact resonance method, measuring the thermal properties via scanning thermal probe microscopy, etc..

In the device of the present invention, a pick and place manipulator is arranged for picking up each of the individual heads (e.g. sensor heads or processing heads) and placing them in a respective working position. The heads may be placed close to each other on the support structure such as to allow measuring or modifying the surface features in a plurality of locations simultaneously. The locations may be arranged close to each other side by side, in a dense arrangement.

In particular in the device of the present invention, the gripper of the manipulator is moved by the actuator in the direction transverse to the reference surface of the support structure. Therefore, the gripper picks up each of the heads from above, lifting the heads up and moving them to the desired working positions. In some embodiments, because the desired working positions are known (or even monitored) and the actual locations of the heads are measured, the positioning system may be a closed loop positioning system. The respective heads are then lowered (also in the transverse direction) to be placed on the support structure. The heads may for example be placed directly on the reference surface of the support structure, although placement on a different surface may also be performed where desired. As a result of enabling the lifting and lowering of the heads in a transverse direction to the reference surface, the heads can be placed close to each other side by side, because the placing of the heads is not hindered by any obstacles in this dimension. Moreover, in absence of a robotarm or any other manipulator that picks up the heads from the side, the heads do not need to be equipped with an adaptor or any other structure. This further reduces the size of the heads in the lateral direction. Therefore the footprint of the heads, and the footprint of the heads including the space required for placing of the heads can be kept as small as possible. Thus a large number of heads can be placed side by side on the reference surface, allowing simultaneous measurement in a dense formation.

In accordance with an embodiment of the present invention the support structure is movable relative to the sample carrier at least in a direction parallel to the reference surface, the device further comprising a stage actuator for moving the support structure relative to the sample carrier and the manipulator, the stage actuator being arranged for moving the support structure between at least a first position allowing said measuring and/or modifying of the surface features, and a second position allowing placement and removal of the heads onto and from said working positions.

In this embodiment, the heads may be placed by the manipulator on the support structure in the second position, after which the support structure is moved to the first position wherein the measurement and/or modifying of the surface features may be performed.

For example, in an embodiment wherein the sample carrier holds the sample with the surface to be processed facing down, the support structure on which the processing heads have been placed in a dense formation may be moved underneath the sample carrier to perform measurement and/or modifying of the surface features on the surface of the sample from below.

In accordance with a further embodiment of the present invention the gripper comprises, for engaging with the respective heads, at least one of: clamping elements such as suction clamps, magnetic clamping elements, electrostatic clamping elements or flexible clamping elements, flexible or rotatable fingers for gripping; or gravity based engagement elements, such as structural features, a ridge, a hook, an edge, a slot, for cooperating with a structure of the respective heads. As will be appreciated a gripper may be designed in a number of manners for picking and placing the heads in a vertical direction onto the surface. Also combinations of the abovementioned elements may be used together to allow gripping of the heads.

In accordance with yet other embodiments of the present invention the one or more heads comprise at least of an engagement opening or engagement element, said engagement opening or engagement element arranged on an upper side of the heads, and wherein the gripper comprises at least one other of said engagement opening or engagement element, wherein the engagement opening and engagement element are mutually corresponding such as to allow receiving of the engagement element in the engagement opening for enabling said engaging. In these embodiments, the engagement opening or engagement element on the heads is arranged on an upper side of the head. In particular, this prevents having to engage the heads from the side, and it thus even further reduces the size of the footprint of the head and the space required for placing the head on the surface. In this embodiment, the heads may in principle be placed directly adjacent one another, and potentially even in abutment against each other.

Yet in accordance with some embodiments the gripper comprises a rotatable extension comprising the engagement element, and wherein the engagement element and the engagement opening are correspondingly shaped in such a manner that the engagement element fits through the engagement opening in a first rotational position of the engagement element while enabling said engaging in a second rotational position of the engagement element. In these embodiments, the engagement element and the engagement opening, which are correspondingly shaped, are aligned with each other and the engagement element is extended through the engagement opening. Then, the engagement element and engagement opening may be rotated relative to each other such that the engagement element no longer aligns with the opening. This allows the gripper to pick up the head and move it to the respective working position. Placing of the head may be performed in the reverse order: lowering the head, rotating the engagement element relative to the engagement opening such as to align both, and moving the element back through the opening to release the head. In accordance with yet another embodiment the engagement element and the engagement opening are shaped as a polygon, such as a triangle, a square, or rectangle, a pentagon, a hexagon, a heptagon, a octagon, or another polygon.

Yet in accordance with the invention, the gripper and the heads comprise a mutually cooperating engagement structure forming a kinematic mount, the kinematic mount including at least three structural elements arranged on either one of the gripper or the heads, said at least three structural elements cooperating with at least three slots arranged on another one of the gripper or the heads. The use of a kinematic mount during placement of each of the respective heads, allows to place these heads at the respective working positions with high accuracy and prevents slipping of the heads during placement thereof. The reference surface consists of an optical reference grid that is very sensitive, and may easily damage as a result of slipping. A kinematic mount usually applies three structural elements cooperating with three slots and is designed such that during placement of the component none of the geometric dimensions is overconstrained or underconstrained, thereby preventing slipping.

In accordance with some specific embodiments wherein the engagement elements and the engagement opening are shaped as a polygon, the at least three structural elements or at least three slots are arranged in one or more corners of said polygon shape of the engagement element and the engagement opening. For example, in an embodiment wherein the engagement element and the engagement opening are shaped as a triangle, the structural elements may be located near the corners of the triangle on the engagement element. The corresponding slots of the kinematic mount may then for example be located around the periphery of the engagement opening between each two corners of the triangle. The engagement element may then be inserted into the engagement opening, and rotated such as to align the at least three structural elements with the at least three slots following the kinematic mount. These embodiments allow to combine the benefits of having a very small footprint, and enabling accurate placing of the heads without slipping.

In accordance with yet other embodiments, the gripper is arranged for maintaining the heads in the tilted orientation relative to the reference surface during motion of the heads towards and away from the support structure. By maintaining the heads in a slightly tilted orientation relative to the reference surface, upon lowering of the heads towards the support structure, the three structural elements of the kinematic mount will be released from their associated slots subsequently, depending on which part of the head touches the surface of the support structure. This allows highly accurate placement of the head onto the surface.

In accordance with yet a further embodiment thereof, the gripper comprises three fingers, each finger comprising a clamping member for defining a contact point with a respective head during said engaging, wherein each of said fingers is connected to the gripper via a releasable connection, wherein the releasable connection is operable via mechanical contact transfer through the respective finger for allowing fixation or movement of the finger with respect to the gripper dependent on contact of the respective head with the support structure. In this embodiment, the slots and structural contact elements of the kinematic mount may for example be located in the releasable connection of each of the three fingers with the gripper. The structural elements of the kinematic mount may be released from their slots by means of mechanical contact transfer: once contact is made by a part of the head with the surface of the support structure, forces between the head and the associated finger which is associated with the part being in contact with the surface may result in the releasable connection to be released such as to release the action of the finger on the head. Thus, each of the three fingers is released upon contact of an associated part of the head with the support structure. This release of the releasable connection may result in e.g. retracting of the finger or rotation away from the head, or a different action causing the head to be released.

In accordance with a specific embodiment, the releasable connection may be a magnetic or electrostatic element. The magnetic or electrostatic force of the element may be relatively weak, such as to immediately release the finger upon contact of the head with the surface of the support structure.

The device in accordance with any of the embodiments provided hereinabove, may for example, be a scanning probe microscopy device, such as an atomic force microscopy device. However, the invention is not limited to use in scanning probe microscopy devices, or microscopy devices in general, and may be applied to other type of devices wherein surface features, such as nanostructures, on the surface of a sample may be examined or modified during operation.

Furthermore, in accordance with claim <NUM>, there is provided a method of measuring and/or modifying surface features and/or sub-surface features on or below a surface of a sample, wherein the method is performed using a device comprising: a sample carrier for supporting the sample, a support structure comprising a reference surface, wherein the reference surface comprises an optical reference grid, and one or more heads including at least one of surface measuring equipment or surface modification equipment, the heads being separate from the sample carrier and the support structure; the method comprising: placing, using a pick and place manipulator, the one or more heads at a plurality of working positions on the support structure; and performing said measuring and/or modifying of surface features by said surface measuring equipment or surface modification equipment on said heads; wherein the step of placing the one or more heads comprises: engaging with a respective one of the heads using a gripper; moving the gripper and the reference surface relative to each other using an actuator of said manipulator, in a direction transverse to the reference surface; and releasing the respective heads from the gripper at the respective working position, for placing the heads on the reference surface, wherein the gripper and the heads comprise a mutually cooperating engagement structure forming a kinematic mount, the kinematic mount including at least three structural elements arranged on either one of the gripper or the heads, said at least three structural elements cooperating with at least three slots arranged on another one of the gripper or the heads.

In accordance with an embodiment of the second aspect, the method further comprises, prior to the step of performing the measurement and/or modification of the surface features, moving, using a stage actuator, the support structure relative to the sample carrier in a direction parallel to the reference surface, said moving being performed between at least a first position allowing said measuring and/or modifying of the surface features, and a second position allowing placement and removal of the heads onto and from said working positions.

Yet in accordance with further embodiments of the invention, a step of engaging comprises receiving an engagement element of at least one of the gripper or the respective head in a correspondingly shaped engagement opening in another one of the gripper or the respective head, said respective one of the engagement element or engagement opening being located on an upper side of the heads.

<FIG> schematically illustrates the working principle of a typical prior art atomic force microscope. In <FIG>, a probe head <NUM> comprises piezo type drivers <NUM> for the X-, Y-, and Z-directional motion of a probe <NUM>. The probe <NUM> consists of a cantilever <NUM> having a probe tip <NUM> arranged for scanning a sample surface <NUM> of a sample <NUM>. During scanning, a dither piezo (not shown) or other means of actuations such as photo-thermal actuation, electrostatic, etc, may drive the cantilever in vibrational mode (for example close to resonant frequency) to enable tapping of the probe tip on the surface. The manner of applying a vibrational motion to the probe tip is known to the skilled person.

Scanning of the sample surface <NUM> is performed by moving the probe tip <NUM> in the X- and Y direction parallel to the sample surface <NUM> (or alternatively, by moving the substrate surface in the X- and Y-directions while maintaining the position of the probe tip fixed in the X- and Y-directions). The probe tip <NUM> is brought in close proximity to the surface <NUM> by means of a z-directional piezo driver. Once in the position, the probe tip <NUM> is vibrated in the z-direction such that it repeatedly touches the surface <NUM> during scanning thereof. At the same time, a laser <NUM> illuminates the probe tip with laser beam <NUM>. The precise position in the z-direction is determined using photo diodes <NUM> which receive the reflected laser beam <NUM>.

The sample surface <NUM> is carried using a sample carrier <NUM>. Driving of the piezo drivers <NUM> located on the probe head <NUM> is performed using the detector and feedback electronics <NUM>. At the same time, the detector and feedback electronics <NUM> receive the detected z position as determined using photo diodes <NUM>. This principle allows for very precise mapping of surface elements, such as surface element <NUM> on the surface <NUM> of the sample <NUM>. Atomic force microscopy performed e.g. using a technique as illustrated in <FIG> allows the mapping of very small structures and features on the surface, e.g. nanostructures having typical nanometer dimensions (e.g. even <<NUM>, such as for example individual polymer strings being as thin as <NUM>). As described herein above, since the mapping of the surface has to be performed with great precision, the speed at which the method is performed is rather slow.

The present invention, however, is not limited to atomic force microscopy, but may also be applied in combination with other scanning probe microscopy methods and/or processes for modification of such small scale surface features. The present invention allows to greatly improve this performance by enabling the simultaneous mapping of surface features in a plurality of locations of a surface <NUM> of a substrate or sample <NUM>. In this respect, the invention proposes to deploy a plurality of sensor heads at multiple locations on a support structure surface, e.g. a reference surface including a reference grid. A scanning motion may then be provided by scanning the whole sample relative to the sensor heads, or in a different suitable manner.

In <FIG>, an atomic force microscopy apparatus <NUM> comprises a metrology frame <NUM>. Suspending from the metrology frame <NUM> is a sample carrier <NUM>, which is attached to the metrology frame via a plurality of positioning actuators <NUM>-<NUM> and <NUM>-<NUM> for positioning the sample carrier <NUM> e.g. at a correct height level for performing measurements. The sample carrier <NUM> carries a wafer <NUM>, the surface <NUM> of which has to be inspected by means of atomic force microscopy. Various methods are available to the skilled person for suspending the wafer <NUM> from the sample carrier <NUM>. For example, the sample carrier may comprise different types of clamps such as suction clamps or mechanic clamps or the like.

In a different part of the apparatus <NUM>, a support structure <NUM> holding a reference surface <NUM> comprising an optical reference grid is held in place underneath a manipulator <NUM>. The manipulator <NUM> comprises a movable frame structure <NUM> including a rail <NUM>. The movable frame structure <NUM> can be moved parallel to the reference surface <NUM>, e.g. in a direction out of and in to the paper. This allows a manipulator arm <NUM> comprising a gripper <NUM> to reach any desired location on the reference surface <NUM> (as long as support structure <NUM> is positioned underneath the manipulator <NUM>). The manipulator <NUM> allows to pick up each of a plurality of sensor heads <NUM> from a storage location, and place the respective head <NUM> onto a desired working position <NUM> on the reference surface <NUM>. In <FIG>, one of the sensor heads <NUM> already resides in its desired working position on the reference surface <NUM>, and the other sensor head <NUM> is being lowered towards the desired working position <NUM>.

While handling the sensor heads <NUM>, the gripper <NUM> holds the sensor heads <NUM> by means of a clamping mechanism including clamping elements <NUM> and <NUM>. In the embodiment illustrated in <FIG>, the clamping elements <NUM> and <NUM> are rotatable fingers that can rotate around a hinge located at the base of gripper <NUM>. Once the manipulator <NUM> has placed all the sensor heads <NUM> onto the reference surface <NUM>, the stage actuator <NUM> allows to move the support structure <NUM> towards the measurement position underneath the wafer <NUM>. This may be performed by the stage actuator <NUM> by extending the extension arm <NUM>. The skilled person may appreciate that a large number of alternative methods exist for moving the support structure <NUM> from its first position underneath the manipulator <NUM> towards its second position underneath the sample holder <NUM>. Thus, instead of the stage actuator <NUM> having an arm <NUM>, a complete different type of stage actuator mechanism may be implemented. For example, it is also possible that the support stage <NUM> is self propelled, or can be hovered across the surface of the lower part <NUM> of the metrology frame <NUM> by means of an air bearing or magnetic levitation. Also, the metrology frame <NUM> in its lower part <NUM> may comprise rails, with or without bearings, to move the support structure <NUM> to its second position. The skilled person may recognize alternative solutions that may be applied for moving the support structure <NUM>, without departing from the invention.

In <FIG>, the support stage <NUM> is positioned in its second position underneath the sample carrier <NUM>. As follows from <FIG>, onto the reference surface <NUM> a plurality of sensor heads <NUM> has been placed by the manipulator in a first position. Although <FIG> schematically illustrates five sensor heads, the sensor heads can be placed by the manipulator in a very compact arrangement on the reference surface, and therefore the amount of sensor heads <NUM> located on the reference surface <NUM> may be much larger than as suggested in <FIG>. For example, a dense arrangement of sensor heads <NUM> is also illustrated in <FIG> showing a reference surface <NUM> from above, wherein the sensor heads <NUM> are illustrated as squares. As can be seen, even in the dense arrangement illustrated in <FIG>, the density of the number of sensor heads <NUM> on the surface <NUM> of the wafer can be increased as long as the footprint for placing of the sensor heads <NUM> can be decreased.

Back to <FIG>, the support structure <NUM> is located underneath the sample carrier <NUM> carrying the wafer <NUM>. The sample carrier <NUM>, after positioning of the support structure <NUM> in its second position by means of the actuator <NUM> and the extension arm <NUM>, may have been lowered such that each of the probes on the sensor heads <NUM> is able to accurately perform measurements on the surface. As will be appreciated, it is very important that the surface <NUM> of the wafer <NUM> is kept level within measurable range of each of the probes of the sensor heads <NUM>. Because accuracy on a nanometer scale may be desired, various technologies may be applied for slightly adjusting the height of a probe of one of the sensor heads <NUM> to the correct level relative to the surface <NUM> of the wafer <NUM> locally at the working position of the sensor head <NUM>. For example, each of the sensor heads <NUM> may comprise an additional piezo actuator which allows to adjust the z-position of the probe. The overall levelling of the whole wafer <NUM> relative to the sensor heads <NUM> may be adjusted by means of the actuators <NUM>-<NUM> and <NUM>-<NUM> of the sample carrier <NUM>. As will be appreciated, the drawing of <FIG> is a two dimensional schematic drawings, and in reality a third or even a fourth adjustment actuator <NUM> may be used to generally align the wafer with the position of the probes or the sensor heads <NUM>.

Various methods may be applied by the manipulator <NUM> to place the sensor heads <NUM> onto the reference surface <NUM> on the support structure <NUM>. A plurality of different placement methods is schematically illustrated in <FIG> and will be discussed hereinbelow. Each of the <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> and <FIG> shows the gripper <NUM> of the manipulator <NUM> in a first mode A wherein it is holding the sensor head while placing it onto the surface <NUM>, and in a second mode B wherein it has released the sensor head <NUM> in the correct working position <NUM>. As may be appreciated, in order to move the gripper <NUM> and the reference surface <NUM> relative to each other, the manipulator may be arranged for moving either one or both of these elements. Thus, the manipulator may comprise an actuator for moving the gripper <NUM> or for moving the support structure <NUM> comprising reference surface <NUM>, or both, in a direction parallel to the reference surface <NUM>. Also the gripper <NUM> may be lowered towards the reference surface <NUM>, or the support structure <NUM> comprising the reference surface <NUM> may be raised, in order to place the heads onto the reference surface <NUM>. The skilled person is able to select a most suitable implementation of the invention without departing from the scope thereof.

The example which is not part of the claims illustrated in <FIG> shows a gripper <NUM> comprising flexible clamping elements <NUM> and <NUM> that support the sensor head <NUM> during handling around a substantial part (or all) of its periphery. To place the sensor head <NUM> onto the surface <NUM> and release the flexible clamping elements <NUM> and <NUM> from the sensor head <NUM>, a force may be applied between the sensor head <NUM> and the reference surface <NUM> which is large enough to pull the sensor head <NUM> from the clamping elements <NUM> and <NUM>. For example, a magnetic force may be applied (not shown) between the sensor head <NUM> and the support structure <NUM> through the reference frame <NUM>, once the sensor head <NUM> has been placed onto the reference surface <NUM>.

In a further example which is not part of the claims illustrated in <FIG>, the gripper <NUM> holds the sensor head <NUM> by means of clamping elements <NUM> and <NUM>. Although <FIG> is illustrated in cross section, the gripper <NUM> may comprise three clamping elements such as <NUM> and <NUM> to support the sensor head <NUM> in three positions around its periphery. In some embodiments, these three clamping locations may form a kinematic mounting structure.

In <FIG> which shows an example which is not part of the claims, the gripper <NUM> comprises rotatable fingers <NUM> and <NUM>. The fingers comprise structural elements such as ball contact <NUM> that cooperates with an edge or slot <NUM> on the sensor head <NUM>. After placing of the sensor head, as illustrated in mode B, the fingers <NUM> and <NUM> rotate outward to release the sensor head <NUM> from the gripper <NUM>.

In the example which is not part of the claims of <FIG>, gripper <NUM> also comprises rotatable fingers <NUM> and <NUM>, however these rotatable fingers <NUM> and <NUM> rotate slightly inwards after placing of the sensor head <NUM> in mode B. The engagement elements <NUM> at the ends of fingers <NUM> and <NUM> may for example cooperate with engagement openings in the upper part of the sensor head <NUM> to allow gripping by gripper <NUM>.

In the example which is not part of the claims illustrated in <FIG>, the gripper <NUM> also comprises fingers <NUM> and <NUM>, which are connected to the gripper by means of releasable connections <NUM>. In mode A, the releasable connections <NUM> retain the end parts of fingers <NUM> and <NUM>. As follows from mode B, once that one part of the sensor head <NUM>, associated with clamping element <NUM>, touches the reference surface <NUM>, the releasable connection <NUM> releases the clamping element <NUM> by means of mechanical contact transfer. Mechanical contact transfer relates to the actuation of an element responsive to a mechanical contact in a different part of that element or the device wherein it is implemented. In the present case, the sensor head <NUM> touching the reference surface <NUM> changes the force equilibrium at the clamping element <NUM> and the releasable connection <NUM>, such that the releasable connection <NUM> is released. For example, element <NUM> may be a weak magnet, and the end of contact element <NUM> is slightly biased by means of a spring force in a direction pulling it away from releasable connection <NUM>. While sensor head <NUM> is being held by the gripper <NUM> (e.g. as illustrated in mode A), the gravitational force is sufficiently strong for pulling the weakly biased contact element <NUM> towards the releasable connection <NUM>, wherein it is held in place by the magnet. Upon touching of the reference surface <NUM>, a gravitational force decreases, and the releasable connection releases the clamping element <NUM>, which is pulled back by the spring force. Damping of the spring may be added to prevent a too violent motion of the clamping element <NUM>.

In <FIG>, a more sophisticated engagement element <NUM> is illustrated. Engagement element <NUM> suspends from a rotational extension arm <NUM>. In the corners of the triangular shaped engagement element <NUM>, there is located three slots <NUM>, <NUM> and <NUM>. The upper part of sensor head <NUM> is also illustrated in <FIG>, comprising an engagement opening <NUM>. The shape of the engagement opening <NUM> corresponds with the shape of the engagement element <NUM> in such a manner that the engagement element <NUM> fits through the engagement opening <NUM>. Internally within the sensor head <NUM>, three ball contacts <NUM>, <NUM> and <NUM> are located on the periphery of the engagement opening <NUM> in the middle between the corners thereof. By extending the engagement element <NUM> through the engagement opening <NUM>, and rotating it over <NUM>°, the slots <NUM>, <NUM> and <NUM> align with the ball contacts <NUM>, <NUM> and <NUM> respectively, and pulling the engagement element <NUM> upward will lift the sensor head <NUM>. In particular, the ball of contacts <NUM>, <NUM> and <NUM> and corresponding slots <NUM>, <NUM> and <NUM> together form a kinematic mount which is designed for maintaining the sensor head <NUM> in place without over constraining or under constraining it in any dimension (x, y, z, Rx, Ry, Rz; wherein Rx through Rz are the rotation directions around axes parallel to the x, z, x axis).

<FIG> schematically illustrate how the cooperating engagements element <NUM> and engagement opening <NUM> work together to allow accurate placement of the sensor head <NUM> on the reference surface <NUM>. In mode A, gripper <NUM> has extended the engagement element <NUM> through the engagement opening <NUM>, and it is held in place by means of the kinematic mount of which the ball contacts <NUM> and <NUM> are shown in the figure. The sensor head <NUM> is held in a slightly tilted manner such that one point of the sensor head <NUM> will first touch the reference surface <NUM>. When this happens, as illustrated in mode B, the first of the ball contacts <NUM> comes free from the slot <NUM>. During placement of the sensor head <NUM> onto the reference surface <NUM>, the three ball contacts <NUM>, <NUM> and <NUM> will subsequently be released from the associated slots <NUM>, <NUM> and <NUM>.

A further embodiment is illustrated in <FIG>. Here, the gripper <NUM> comprises clamping elements consisting of a magnet <NUM> acting upon a counter element <NUM> held by the sensor head <NUM>. The gripper <NUM> further comprises ball contacts <NUM>, <NUM> (and a third ball contact (not shown)) falling into associated slots on the sensor head <NUM>. Upon placing the sensor head <NUM> onto the reference surface <NUM>, magnet <NUM> is operated to release the sensor head. Alternatively, each of the contact elements <NUM> and <NUM> is magnetic, and can be released subsequently as is illustrated in <FIG> in mode B.

Claim 1:
A device (<NUM>) for measuring and/or modifying surface features and/or sub-surface features on or below a surface (<NUM>) of a sample (<NUM>), the device comprising:
a sample carrier (<NUM>) for supporting the sample (<NUM>) for exposing the surface (<NUM>) for enabling said measuring and/or modifying, one or more heads (<NUM>) including at least one of surface measuring equipment or surface modification equipment, and a support structure (<NUM>) for supporting the one or more heads (<NUM>), wherein the support structure (<NUM>) comprises a reference surface (<NUM>) for providing a positioning reference for enabling positioning of each of said one or more heads (<NUM>) at a respective working position,
wherein the heads (<NUM>) are separate from the sample carrier (<NUM>) and the support structure (<NUM>) such as to be not connected thereto, and wherein the device (<NUM>) further comprises a pick and place manipulator arranged for gripping of respective ones of the heads (<NUM>) and positioning thereof onto the reference surface (<NUM>) at their respective working positions,
wherein the reference surface comprises an optical reference grid, and wherein the manipulator comprises a gripper (<NUM>) and an actuator for moving the gripper (<NUM>) and the reference surface (<NUM>) relative to each other, wherein the actuator is arranged for providing a motion in a direction transverse to the reference surface (<NUM>), and wherein the gripper (<NUM>) is arranged for engaging and releasing the respective heads (<NUM>) from the transverse motion for placing the heads (<NUM>) on the reference surface (<NUM>),
wherein the gripper (<NUM>) and the heads (<NUM>) comprise a mutually cooperating engagement structure forming a kinematic mount, the kinematic mount including at least three structural elements arranged on either one of the gripper (<NUM>) or the heads (<NUM>), said at least three structural elements cooperating with at least three slots arranged on another one of the gripper (<NUM>) or the heads (<NUM>).