Positioning stage for quantum chip testing in a milli-kelvin environment

Abstract

The invention concerns a positioning stage with 4 degrees of freedom for use in a cryogenic environment and suited for chip probing. Special attention has been paid to completely cancel dissipation of the positioning stages during probing by applying the probe force between the wafer and the contact probes by a passive spring. The applied probe force is perfectly aligned with the probes to avoid deformation of the substrate table to maintain good probe contact. In the presented concept we introduce cryogenic compatible electromagnetic linear motors in close distance to the contacting probes which enables high speed, no wear and precise displacements. All required 4 degrees of freedom, positioning in X, Y, rotation around Z and probing action Z displacement have been integrated in a stand-alone module.

Description

[0001] P37752PC00 / TRE Text for PCT filing

[0002] Title: Positioning stage for quantum chip testing in a milli- Kelvin environment.

[0003] Field of the invention

[0004] The invention concerns a positioning stage with 4 degrees of freedom for use in a cryogenic environment and suited for chip probing.

[0005] State of the art

[0006] Chips for quantum computing need to be tested under cryogenic environmental conditions at milli-Kelvin temperatures. Testing involves accurate positioning of a substrate in X, Y and Rz position and a vertical Z motion with relatively high forces to bring each chip into contact with the test-probes.

[0007] For this a stage with four controlled degrees of freedom is needed.

[0008] Since the quantum chips must be tested at milli-Kelvin environments in a fridge with limited cooling capacity at these temperatures, the heat input from the stage needs to be zero during the test campaign.

[0009] Present cryogenic probe stages can only be used in an environment of a few Kelvin, due to their heat dissipation or thermal heat flow into the cryostat, which leads to test limitations since the quantum effects need lower temperatures.

[0010] Also due to the relatively high probe force, moments may cause tipping or tilting motion of the substrate table, which could compromise good contact of the test-probes.

[0011] An example of a cryogenic wafer testing system is disclosed in US 2023 / 0134966 A1, which discloses a cryogenic testing systems for testing electronic components such as wafers under cryogenic conditions. This known systems is disclosed to offer fast throughput by use of a cryogenically maintained test surface to which wafers may be rapidly introduced, cooled, and manipulated to contact testing elements while maintaining high quality cryogenic conditions. Thermal shielding is achieved by floating shields and / or flexible bellows that provide effective thermal shielding of the test environment while enabling manipulation of wafers with a wide range of motion.

[0012] Other known systems are disclosed in DE KRUIJF MATHIEU ET AL: "A compact and versatile cryogenic probe station for quantum device testing", REVIEW OF SCIENTIFIC INSTRUMENTS, part 94, no. 5, 19 May 2023 (2023-05-19), XP012274776, ISSN: 0034-6748, DOI: 10.1063 / 5.0139825 and in JOSHUA T WEST ET AL: "Wafer-Scale Characterization of a Superconductor Integrated Circuit Process, Using a Cryogenic Wafer Prober", CORNELL UNIVERSITY LIBRARY, 1 December 2021 (2021-12-01), XP091112885.Object of the invention

[0013] In view of the above drawbacks, it is an object of the invention to provide a positioning stage for quantum chip testing in a mil li-Kelvin environment that can cancel dissipation of the positioning stage during probing and that is able to cope with high probe forces while maintaining good probe contact, or at least to provide an alternative positioning stage.

[0014] Detailed description

[0015] The present invention provides a positioning stage for quantum chip testing in a milliKelvin environment, in which the above-mentioned disadvantages have been overcome, by substantially, e.g. completely, cancelling dissipation of the positioning stages during probing by applying the probe force between the substrate and the contact probes by a passive spring. In this way all positioning stages may be shut down during probing. Furthermore, the applied probe force may be aligned with the probes to avoid angular deformation of the positioning stages to maintain sufficient probe contact.

[0016] The positioning stage according to the invention comprises a base plate with an electromagnetically driven substrate table, wherein the base plate is rigidly connected to a holder for test probes. The substrate table is configured to be maintained at a cryogenic temperature suitable for testing quantum products and is alignable with respect to the test probes in four degrees of freedom (X, Y, Z, Rz), enabling testing of products present on the substrate table at the required temperatures. The positioning stage further comprises a positioning device for the Y direction, that is connected to the substrate table, configured to provide a substantially backlash-free Z translation of the substrate table.

[0017] By rigidly connecting the base plate to the holder of the test probes, a mechanically stable reference between the probes and the positioning mechanism may be obtained. This configuration can contribute to reproducible alignment between the substrate and the probes. The integration of four degrees of freedom in a stand-alone module may allow positioning in X, Y and rotation about Z (Rz), combined with a controlled Z displacement for probing.

[0018] The substantially backlash-free Z translation obtained by the connection between the positioning device for the Y direction and the substrate table can reduce play and hysteresis, which may be beneficial in cryogenic environments where lubrication is undesirable and thermal budgets are extremely limited.

[0019] In particular, the entire positioning device may be placed in the cryogenic environment, which may provide for a more compact system, which may improve position accuracy and which may avoid thermal heat leakage that could otherwise occur when the positioning stages are placed externally of the cryogenic environment, during which they aree physically connected to the substrate table located inside the cryogenic environment.According to the invention, the positioning stage further comprises a pressing mechanism comprising a carriage connected to the base plate via a linear guide, which only allows a translation in the Z direction. The pressing mechanism is configured to realise the Z translation, for example by means of a wedge member configured to transform movements of the carriage in the X direction or Y direction into movements of the positioning stage in the Z direction.

[0020] The pressing mechanism may form a separate mechanical path for generating the probe force between the substrate and the test probes. The carriage may be guided relative to the base plate by a linear guide that substantially enables movement to the Z direction.

[0021] Furthermore, the carriage comprises an arm having a pressure point configured to lift the substrate table at a location lying on a line coinciding with a resulting vertical force vector of the test probes.

[0022] By positioning the pressure point on a line that substantially coincides with the resulting vertical force vector of the test probes, moments about the X and Y axes of the substrate table may be reduced. This may limit tilting or angular deformation of the substrate table under high probe forces and can contribute to maintaining good probe contact and to avoid lateral displacement of the substrate table as a result of the tilting.

[0023] In embodiments, the Y-positioning device is connected to the substrate table by means of a parallel guide provided with elastic elements.

[0024] The parallel guide may comprise elastic elements, such as flexures or leaf springs, which can allow a defined translation in the Z direction while constraining motion in other directions. The elastic elements may be compliant in the Z direction and relatively stiff in X, Y and rotational directions. Because such guidance does not rely on sliding contact, frictional heat generation may be reduced, which can be advantageous in a milli-Kelvin environment, and / or the guidances may be play-free to enhance position accuracy.

[0025] In embodiments, a weight of the substrate table is substantially compensated by a force element, such as a spring, between the substrate table and the Y-positioning device.

[0026] The force element may at least partially balance the gravitational force acting on the substrate table. As a result, the net force to be delivered by Z actuator may be reduced, which can lower electrical power consumption and associated heat dissipation. The compensation may extend over at least part of the Z travel range. In addition, the weight of a substrate placed on the substrate table may also be at least partly compensated.

[0027] In embodiments, the pressing mechanism is preloaded in the Z direction by means of a preloading spring. The preloading spring may apply a defined force in the Z direction. Duringprobing, electromagnetic positioning stages may be switched off, while the contact force is maintained by the preloading spring. In this way, dissipation of the positioning stages during probing may be substantially reduced or cancelled.

[0028] In embodiments, the base plate comprises a base plate roller and the linear guide comprises a guide roller, between which rollers a cam profile can be moved to displace the substrate table in the Z direction.

[0029] The cam profile may form part of a Z positioning device. By moving the cam profile between the rollers, a vertical displacement of the carriage may be achieved. The cam profile may be shaped to provide a desired transmission ratio between actuator displacement and Z movement. The use of rollers may reduce friction and wear.

[0030] In embodiments, the cam profile is retractable to disengage from the carriage, and the substrate is pressed against the test probes by the preloading spring in the absence of substantial dissipation.

[0031] After establishing contact between the substrate and the test probes, the cam profile may be retracted such that it no longer transmits force to the carriage. The preloading spring may then maintain the pressing force. In this condition, the Z actuator may be switched off, which can minimise power consumption and heat input into the milli- Kelvin environment.

[0032] In embodiments, the cam profile is configured to maintain pressing of the substrate against the test probes after deactivation of a Z actuator.

[0033] For example, the cam profile may comprise a flat portion, such that further actuator displacement does not substantially change the Z position. In such a configuration, a mechanical equilibrium may be established without requiring continuous actuator force.

[0034] The preloading spring may serve to limit, e.g. not fully absorb but instead partially absorb, the transmission of forces between the test probes and the substrate table, for example in order to prevent that the test probes are exposed to forces that are too high.

[0035] In embodiments, the pressing mechanism comprises a frame and the carriage is connected to the frame by means of a parallel flexure mechanism configured to guide a clamp arm in the Z direction.

[0036] The parallel flexure mechanism may form a compliant guiding structure between the frame and the carriage. Such a mechanism may allow translation in the Z direction while restricting motion in other directions. The use of flexures may reduce friction, eliminate backlash and avoid the need for lubrication, which may be advantageous in cryogenic environments. The clamp arm may thereby be guided with a well-defined motion relative tothe frame while maintaining mechanical stiffness in directions other than the intended Z translation.

[0037] In embodiments, the clamp arm is configured to transmit a force to the substrate table, the force being limited by an overload preloading spring.

[0038] The clamp arm may act as a mechanical interface between the pressing mechanism and the substrate table. The force transmitted through the clamp arm may be limited by the overload preloading spring, such that the force applied between the substrate and the test probes may be controlled. This may prevent excessive loading of the probes or the substrate and may contribute to maintaining reliable probe contact during testing.

[0039] In embodiments, the overload preloading spring acts on the clamp arm through a lever mechanism defining a transmission ratio between the overload preloading spring and the force applied to the substrate table.

[0040] The lever mechanism may provide a mechanical transmission between the overload preloading spring and the clamp arm. Depending on the geometry of the lever mechanism, a desired transmission ratio may be obtained. This may allow the force exerted on the substrate table to be adjusted relative to the force generated by the overload preloading spring. Such a configuration may facilitate accurate control of the probe force while allowing the use of springs with suitable mechanical characteristics.

[0041] In embodiments, the transmission ratio is determined by a position of the overload preloading spring, a pivot point of the lever mechanism, and a roller supported by the lever mechanism.

[0042] The lever mechanism may comprise a pivot point about which the lever rotates. The position of the overload preloading spring and the position of the roller supported by the lever mechanism may determine the effective lever arm lengths. By selecting appropriate positions of these elements, the transmission ratio between the overload spring force and the force applied by the clamp arm may be defined. This may allow the probe force to be adjusted while maintaining a compact mechanical configuration.

[0043] In embodiments, a Z translation of the clamp arm is determined by a position of the cam profile which controls a distance between the base plate roller and the guide roller.

[0044] The cam profile may be displaced, for example in the X direction, between the base plate roller and the guide roller. The distance between these rollers may determine the position of the carriage and thus the Z position of the clamp arm. By shaping the cam profile appropriately, a defined relation between the actuator displacement and the Z translation maybe obtained. This arrangement may allow accurate positioning of the clamp arm and the substrate table.

[0045] In embodiments, the Z translation of the clamp arm follows the distance between the rollers only when a lever arm of the pressing mechanism is positioned against an end stop.

[0046] The lever arm may be arranged such that it normally rests against the end stop during positioning of the substrate table. In this condition, the movement imposed by the cam profile may be transmitted to the clamp arm. The end stop may thereby define a reference position of the lever mechanism during positioning.

[0047] In embodiments, when a force between the clamp arm and the test probes equals the force exerted by the overload preloading spring, the lever arm disengages from the end stop, thereby limiting the force applied to the test probes.

[0048] Once the probe force reaches the force defined by the overload preloading spring and the lever transmission ratio, the lever arm may move away from the end stop. Further movement of the cam profile may then no longer increase the force transmitted to the test probes. In this way, the mechanism may act as a force-limiting arrangement. Such a configuration may protect the probes and the substrate against excessive loading and may contribute to stable probe contact conditions during testing.

[0049] In embodiments, a preloading force exerted by the preloading spring in the Z direction as a function of the Z displacement is configured to force balance the carriage to minimize energy required to be delivered by the Z actuator.

[0050] The force-displacement characteristic of the preloading spring may be selected such that it at least partially balances the forces acting on the carriage, including probe forces and gravitational forces. This may be achieved by selecting an appropriate spring constant, by introducing a mechanism having a variable transmission ratio, by using a bistable spring, or by applying a magnet in combination with a ferromagnetic material. Such configurations may reduce the net force required from the Z actuator.

[0051] In embodiments, the pressure point configured to lift the substrate table is a thermal node configured to be maintained at an appropriate temperature and to provide substantial thermal conduction to the substrate table.

[0052] The pressure point may serve as a thermal interface between the pressing mechanism and the substrate table. By providing substantial thermal conduction, the temperature of the substrate table may be stabilised during probing. In particular, the thermal node may allow forsufficient conduction of heat out of the substrate table, in order to ensure that the substrate can be held at the lowest possible temperature during probing.

[0053] In embodiments, one or more translation stages, e.g. carriages thereof, are connected to the base frame via flexible thermal conductors.

[0054] Flexible thermal conductors may allow thermal coupling while reducing mechanical constraint. They may be formed, for example, by braided metallic elements or other high-conductivity flexible structures. In exemplary embodiments, the braids may be arranged in a U-shaped pattern.

[0055] In embodiments, the substrate table is provided with shielding configured to reduce electromagnetic interference fields at the location of a chip by applying both a magnetically highly permeable material and a superconducting material.

[0056] Such shielding may reduce magnetic and electromagnetic disturbances that could influence the operation of quantum devices under test.

[0057] In embodiments, an electromagnetic shield is provided at a fixed XY location relative to the test probes, for example on the arm of the pressing mechanism or at the pressure point.

[0058] By fixing the shield relative to the test probes, the electromagnetic environment at the probe location may remain substantially constant.

[0059] In embodiments, an electromagnetic shield is statically connected to the base plate.

[0060] In embodiments, a separate magnetic shield is configured to be moved together with the substrate table.

[0061] In embodiments, the position of the translation stages relative to their linear guides in the direction of movement, after switching off an current through magnet coils of electromagnetic actuators, is configured to be maintained by means of a frictional contact that is substantially stiff in the direction of movement, wherein the frictional force in the direction of movement can be influenced by a separate actuator.

[0062] Such frictional contact may allow the aligned position to be maintained mechanically after deactivation of the electromagnetic drives. The frictional contact may be provided between the carriage and guides of the electromagnetic actuators,

[0063] In embodiments, the frictional force in the direction of movement is present continuously, not being actively influenced.In embodiments, the substrate table, by means of the pressing mechanism with the preloading spring, forms a force equilibrium with the test probes and with at least two stops placed at a mutual distance in the XY plane in the Z direction, connected to the same frame as the test probes, whereby a frictional force in the X, Y and Rz directions is configured to be realised between the stops and the substrate table, such that the substrate table is maintained in position in X, Y and Rz relative to the test probes deactivating the current through the electromagnetic actuators, e.g. the magnet coils.

[0064] Such a force equilibrium may mechanically define the position of the substrate table during testing.

[0065] In embodiments, the substrate table, by means of the pressing mechanism with the preloading spring, forms a force equilibrium with the test probes and with at least two positioning pins placed at a mutual distance in the XY plane, connected to the same frame as the test probes, wherein during testing the positioning pins positively define the X, Y and Rz position between the test probes and the substrate table.

[0066] The positioning pins may provide a positive, e.g. geometrically confined, definition of position during probing.

[0067] In embodiments, the pressure point is configured to lift the substrate table at two or more points located at a mutual distance and lying in the same plane, whereby the position of the substrate table in the X, Y and Rz directions is fixed by friction during contact with the test probes alone.

[0068] In embodiments, piezoactuators are configured to be used for manipulating one or more of the four degrees of freedom X, Y, Z, Rz, which may offer a relatively high positioning resolution.

[0069] In embodiments, the actuators are located outside the cryogenic environment and are mechanically coupled to the substrate table that is located within the cryogenic environment required for testing the products.

[0070] In embodiments, in addition to the weight of the substrate table, the weight of the substrate is partly compensated by a force element.

[0071] In embodiments, moments resulting from a probe force are only partially compensated by the Z mechanism.In embodiments, the Rz alignment of the substrate table relative to the probes is achieved by passive adjustment, not being based on active positioning.

[0072] In embodiments, the positioning stage further comprises a compliancy mechanism that is functionally arranged in between the base plate and the holder for the test probes, configured to enable a compliancy of the test probes in one or more degrees of freedom relative to the substrate table upon contact between the test probes and the substrate table during use.

[0073] The compliancy mechanism may allow limited relative movement between the holder of the test probes and the base plate when contact occurs between the test probes and the substrate table. Such movement may occur in one or more degrees of freedom, for example translational degrees of freedom such as X, Y and / or Z, and / or rotational degrees of freedom such as rotations around the X, Y and / or Z axes. By allowing a controlled displacement in one or more of these degrees of freedom, the mechanism may accommodate small positional deviations between the substrate table and the probe holder that may arise during alignment or during the application of the probe force.

[0074] The compliancy mechanism may allow for compensation of potential inadvertent movement of the substrate table when the actuators are deactivated during use of the substrate table, which deactivation may be accompanied by minor movements and / or tilting of the substrate table. By allowing the probes to adapt to the exact position and orientation of the substrate surface, excessive local loading or tilting of the substrate table may be avoided. This may reduce the risk of loss of probe contact and may improve measurement stability and repeatability during quantum chip testing in a milli-Kelvin environment.

[0075] In embodiments, the arm configured to lift the substrate table does not perform a pure translation, but is designed as a lever having a rotation axis perpendicular to the Z axis, being offset from the pressure point.

[0076] In embodiments, the force exerted by the roller of the Z carriage on the cam profile is absorbed by the positioning device of the cam profile, not being transmitted to a roller on the base plate. Such an absorption may provide that the forces are taken up at the positioning device in order to prevent further transmission.

[0077] In embodiments, the positioning device with the cam profile does not disengage from the Z carriage, being configured to manipulate the position of the Z carriage and thereby the substrate table in the Z direction.In embodiments, the Z translation of the substrate table is enabled by coupling it to the Y positioning device by rolling elements, not being coupled by elastic elements.

[0078] In embodiments, the X, Y, Rz positioning of the substrate table is realised by coupling three actuators in parallel between the base plate and the substrate table.

[0079] The invention is not limited to the embodiments described above and shown in the drawings. Features described in relation to different embodiments may be combined within the scope of the appended claims.

[0080] Brief description of drawings

[0081] The exact nature of this invention, as well as its objectives become clear in the accompanying drawings wherein:

[0082] Fig.1 Is a cross section of an embodiment of the positioning stage according to the present invention, indicating the various components.

[0083] Fig.2 Is a top view of the system in fi. 1.

[0084] Fig.3 Is an alternative embodiment of the positioning stage according to the present invention, showing an alternative way of introduction of the preload force.

[0085] Detailed description of embodiments

[0086] A base plate (1) is rigidly connected to a probe bridge (2) holding the test-probes (3). To position the test-substrate (4) in four degrees of freedom: X, Y, Z, Rz with respect to the test-probes (3), the substrate table (5) which is holding the test substrate (4) is guided in Z direction via flexures (6).

[0087] The weight of the substrate table (5) can be off-loaded by a spring (7).

[0088] The flexures (6) are connected to the carriage (8) of the Y translation stage (9).

[0089] The pressure point configured to lift the substrate table (5) is a thermal node (24) configured to stabilise a temperature of the substrate table (5) during probing.

[0090] Each end of the Y translation stage (9) is connected to the carriage of an X translation stage (10) in such a way that on one end, only a rotation about the Z axis and rotation about the X axis is possible while the other end is mounted in such a way that only translation in Y direction and rotations about the X,Z and Y axes is possible.

[0091] To move the substrate table (5) in Z direction and to apply the probe force, a separate force-mechanism is introduced which creates a contact force between the test-probes (3) and the test-substrate (4) without introduction of ferees in the positioning mechanism.The force-mechanism comprises a frame (11) and a carriage (12), connected to each other via a parallel flexure mechanism (13) to enable a Z translation guide of the clamp arm (14).

[0092] This clamp arm (14) is able to introduce the force of spring (15) to the substrate table (5) on the same X,Y position as the X,Y position of the resulting force of the test-probes (3).

[0093] For X, Y, Rz alignment of the substrate (4) to the test-probes (3), the substrate table (5) can be moved down by pushing a profiled cam (16) between a to the base plate connected fixed roller (17) and a to the carriage (12) connected roller (18) which lowers the position in Z direction of the carriage (12) and the attached clamping arm (14).

[0094] The profiled cam (16) is attached to the carriage (19) of the Z translation stage (20). In Fig.3, an alternative way of introducing the preload force is depicted, where a base plate (1) is rigidly connected to a probe bridge (2) holding the test-probes (3).

[0095] The force-mechanism comprises a frame (11) and a carriage (12), connected to each other via a parallel flexure mechanism (13) to enable a Z translation guide of the clamp arm (14).

[0096] The force between the clamp-arm (14) and the contact springs (2) are limited by the force of an overload preload-spring (15) with a certain gear ratio caused by the position of the overload preload-spring (15), the pivot point (21) and the roller (18) on the lever arm (22).

[0097] The Z translation of the clamp-arm (14) will be determined by the X position of a profiled cam (16) which determines the distance between the fixed roller (17) and roller (18).

[0098] The Z translation only follows the distance between the fixed roller (17) and roller (18) if the lever-arm (22) is positioned against the end-stop (23).

[0099] As soon as the force between the clamp-arm (14) and the test-probes (2) equals the force of the overload preload-spring (15), additional movement of the roller (18), the end-stop (23) will lose contact with the lever-arm (22) thereby limiting the force on the test-probes (3). As such, the embodiment in figure 3 may provide for a lower energy input into the actuator, since it is not needed to overcome the force acted by the preloading spring continuously.

[0100] By introduction of a flat surface on the profiled cam (16), where there will be no vertical displacement of the roller (18) due to X translation of the profiled cam (16), no drive force or power will be needed to keep the force between the test-probes (3) and the test-substrate (4).EMBODIMENTS

[0101] E1. Device, characterised in that:

[0102] • a base plate is provided with an electromagnetically driven substrate table;

[0103] • the base plate is rigidly connected to a holder of the test probes;

[0104] • the substrate table is configured to be maintained at a cryogenic temperature suitable for testing quantum products and is alignable with respect to the test probes in four degrees of freedom (X, Y, Z, Rz), enabling testing of products present on the substrate table at the required temperatures;

[0105] • a backlash-free Z translation of the substrate table is enabled by connecting the substrate table, via a parallel guide provided with elastic elements, to a positioning device for the Y direction;

[0106] • a weight of the movable substrate table is substantially compensated by a force element, such as a spring, between the substrate table and the Y-positioning device; • the movement of said Z translation is configured to be realised by a separate pressing mechanism comprising a carriage connected to the base plate via a linear guide allowing only a translation in the Z direction and being preloaded in the Z direction by means of a preloading spring;

[0107] • a positioning device is configured to move a cam profile between a roller connected to the base plate and a roller connected to the linear guide, thereby enabling a displacement in the Z direction of the substrate table;

[0108] • the cam profile is retractable to such an extent that it disengages from the carriage, after which the positioning device can be switched off, whereby the substrate is pressed against the test probes by the preloading spring in the absence of substantial dissipation; and

[0109] • the carriage is provided with an arm having a pressure point configured to lift the substrate table at a location lying on a line coinciding with a resulting vertical force vector of the test probes, such that the test probes do not generate a moment about the X and Y axes of the substrate table resulting in tilting thereof, in order to prevent loss of probe contact.

[0110] E2. Device according to the preceding embodiment, characterised in that the force delivered by the preloading spring in the Z direction as a function of the Z displacement is such that the energy to be delivered by a Z actuator is minimised by introducing a mechanism having a variable transmission ratio, a bistable spring, or a magnet in combination with a ferromagnetic material.E3. Device according to the preceding embodiment, characterised in that the pressure point configured to lift the substrate table is a thermal node configured to be maintained at an appropriate temperature and to provide substantial thermal conduction to the substrate table.

[0111] E4. Device according to one or more of the preceding embodiments, characterised in that one or more translation stages are connected to the base frame via flexible thermal conductors.

[0112] E5. Device according to one or more of the preceding embodiments, characterised in that the substrate table is provided with shielding configured to reduce electromagnetic interference fields at the location of a chip by applying both a magnetically highly permeable material and a superconducting material.

[0113] E6. Device according to one or more of the preceding embodiments, characterised in that an electromagnetic shield is provided at a fixed XY location relative to the test probes, for example on the arm of the pressing mechanism or at the pressure point.

[0114] E7. Device according to one or more of the preceding embodiments, characterised in that an electromagnetic shield is statically connected to the base plate.

[0115] E8. Device according to one or more of the preceding embodiments, characterised in that a separate magnetic shield is configured to be moved together with the substrate table.

[0116] E9. Device according to one or more of the preceding embodiments, characterised in that the position of the translation stages relative to their linear guides in the direction of movement, after switching off the current through the magnet coils, is configured to be maintained by means of a frictional contact that is substantially stiff in the direction of movement, wherein the frictional force in the direction of movement can be influenced by a separate actuator.

[0117] E10. Device according to one or more of the preceding embodiments, characterised in that the frictional force in the direction of movement is present continuously, e.g. not being actively influenced.

[0118] E11. Device according to one or more of the preceding embodiments, characterised in that the substrate table, by means of the pressing mechanism with the preloading spring, forms a force equilibrium with the test probes and with at least two stops placed at a mutual distance in the XY plane in the Z direction, connected to the same frame as thetest probes, whereby a frictional force in the X, Y and Rz directions is configured to be realised between the stops and the substrate table, such that the substrate table is maintained in position in X, Y and Rz relative to the test probes deactivating the current through the magnet coils.

[0119] E12. Device according to one or more of the preceding embodiments, characterised in that the substrate table, by means of the pressing mechanism with the preloading spring, forms a force equilibrium with the test probes and with at least two positioning pins placed at a mutual distance in the XY plane, connected to the same frame as the test probes, wherein during testing the positioning pins positively define the X, Y and Rz position between the test probes and the substrate table.

[0120] E13. Device according to one or more of the preceding embodiments, characterised in that the pressure point is configured to lift the substrate table at two or more points located at a mutual distance and lying in the same plane, whereby the position of the substrate table in the X, Y and Rz directions is fixed by friction during contact with the test probes.

[0121] E14. Device according to one or more of the preceding embodiments, characterised in that piezoactuators are configured to be used for manipulating one or more of the four degrees of freedom X, Y, Z, Rz.

[0122] E15. Device according to one or more of the preceding embodiments, characterised in that the actuators are located outside the cryogenic environment and are mechanically coupled to the substrate table that is located within the cryogenic environment required for testing the products.

[0123] E16. Device according to one or more of the preceding embodiments, characterised in that, in addition to the weight of the substrate table, the weight of the substrate is partly compensated by a force element.

[0124] E17. Device according to one or more of the preceding embodiments, characterised in that moments resulting from a probe force are only partially compensated by the Z mechanism.

[0125] E18. Device according to one or more of the preceding embodiments, characterised in that the Rz alignment of the substrate table relative to the probes is achieved by passive adjustment, e.g. not being based on active positioning.E19. Device according to one or more of the preceding embodiments, characterised in that the arm configured to lift the substrate table does not perform a pure translation, but is designed as a lever having a rotation axis perpendicular to the Z axis, being offset from the pressure point.

[0126] E20. Device according to one or more of the preceding embodiments, characterised in that the force exerted by the roller of the Z carriage on the cam profile is absorbed by the positioning device of the cam profile, e.g. not being transmitted to a roller on the base plate.

[0127] E21. Device according to one or more of the preceding embodiments, characterised in that the positioning device with the cam profile does not disengage from the Z carriage, being configured to manipulate the position of the Z carriage and thereby the substrate table in the Z direction.

[0128] E22. Device according to one or more of the preceding embodiments, characterised in that the Z translation of the substrate table is enabled by coupling it to the Y positioning device by rolling elements, e.g. not being coupled by elastic elements.

[0129] E23. Device according to one or more of the preceding embodiments, characterised in that the X, Y, Rz positioning of the substrate table is realised by coupling three actuators in parallel between the base plate and the substrate table.

Claims

CLAIMS1. Positioning stage for quantum chip testing in a milli- Kelvin environment, comprising a base plate with an electromagnetically driven substrate table, wherein the base plate is rigidly connected to a holder for test probes;wherein the substrate table is configured to be maintained at a cryogenic temperature suitable for testing quantum products and is alignable with respect to the test probes in four degrees of freedom (X, Y, Z, Rz), enabling testing of products present on the substrate table at the required temperatures;characterized in that,the positioning stage further comprises:a positioning device for the Y direction, that is connected to the substrate table, configured to provide a substantially backlash-free Z translation of the substrate table, a pressing mechanism comprising a carriage connected to the base plate via a linear guide, which only allows a translation in the Z direction and which is configured to realise the Z translation, and in thatthe carriage comprises an arm having a pressure point configured to lift the substrate table at a location lying on a line coinciding with a resulting vertical force vector of the test probes.

2. Positioning stage according to claim 1, wherein the Y-positioning device is connected to the substrate table by means of a parallel guide provided with elastic elements3. Positioning stage according to claim 1 or 2, wherein a weight of the substrate table is substantially compensated by a force element, such as a spring, between the substrate table and the Y-positioning device.

4. Positioning stage according to any one of the preceding claims, wherein the pressing mechanism is preloaded in the Z direction by means of a preloading spring, wherein the pressing mechanism is configured to realise the Z translation.

5. Positioning stage according to any one of the preceding claims, wherein the base plate comprises a base plate roller and wherein the linear guide comprises a guide roller, between which rollers a cam profile can be moved to displace the substrate table in the Z direction.

6. Positioning stage according to claim 5, wherein the cam profile is retractable to disengage from the carriage, and wherein the substrate is pressed against the test probes by the preloading spring in the absence of substantial dissipation.

7. Positioning stage according to claim 5 or 6, wherein the cam profile is configured to maintain pressing of the substrate against the test probes after deactivation of a Z actuator.

8. Positioning stage according to any one of the preceding claims, wherein the pressing mechanism comprises a frame and the carriage is connected to the frame by means of a parallel flexure mechanism configured to guide a clamp arm in the Z direction.

9. Positioning stage according to claim 8, wherein the clamp arm is configured to transmit a force to the substrate table, the force being limited by an overload preloading spring.

10. Positioning stage according to claim 9, wherein the overload preloading spring acts on the clamp arm through a lever mechanism defining a transmission ratio between the overload preloading spring and the force applied to the substrate table.

11. Positioning stage according to claim 10, wherein the transmission ratio is determined by a position of the overload preloading spring, a pivot point of the lever mechanism, and a roller supported by the lever mechanism.

12. Positioning stage according to any one of claims 5-11, wherein a Z translation of the clamp arm is determined by a position of the cam profile which controls a distance between the base plate roller and the guide roller.

13. Positioning stage according to claim 12, wherein the Z translation of the clamp arm follows the distance between the rollers only when a lever arm of the pressing mechanism is positioned against an end stop, and wherein when a force between the clamp arm and the test probes equals the force exerted by the overload preloading spring, the lever arm disengages from the end stop, thereby limiting the force applied to the test probes.

14. Positioning stage according to any one of the preceding claims, characterised in that a preloading force exerted by the preloading spring in the Z direction as a function of theZ displacement is configured to force balance the carriage to minimize energy required to be delivered by the Z actuator.

15. Positioning stage according to any one of the preceding claims, characterised in that the pressure point configured to lift the substrate table is a thermal node configured to be maintained at an appropriate temperature and to provide substantial thermal conduction to the substrate table.

16. Positioning stage according to any one of the preceding claims, characterised in that one or more translation stages, e.g. carriages thereof, are connected to the base frame via flexible thermal conductors.

17. Positioning stage according to any one of the preceding claims, characterised in that the substrate table is provided with shielding configured to reduce electromagnetic interference fields at the location of a chip by applying both a magnetically highly permeable material and a superconducting material.

18. Positioning stage according to any one of the preceding claims, characterised in that an electromagnetic shield is provided at a fixed XY location relative to the test probes, for example on the arm of the pressing mechanism or at the pressure point.

19. Positioning stage according to any one of the preceding claims, characterised in that an electromagnetic shield is statically connected to the base plate.

20. Positioning stage according to any one of the preceding claims, characterised in that a separate magnetic shield is configured to be moved together with the substrate table.

21. Positioning stage according to any one of the preceding claims, characterised in that the position of the translation stages relative to their linear guides in the direction of movement, after switching off the current through the magnet coils, is configured to be maintained by means of a frictional contact that is substantially stiff in the direction of movement, wherein the frictional force in the direction of movement can be influenced by a separate actuator.

22. Positioning stage according to any one of the preceding claims, characterised in that the frictional force in the direction of movement is present continuously, e.g. not being actively influenced.

23. Positioning stage according to any one of the preceding claims, characterised in that the substrate table, by means of the pressing mechanism with the preloading spring, forms a force equilibrium with the test probes and with at least two stops placed at a mutual distance in the XY plane in the Z direction, connected to the same frame as the test probes, whereby a frictional force in the X, Y and Rz directions is configured to be realised between the stops and the substrate table, such that the substrate table is maintained in position in X, Y and Rz relative to the test probes deactivating the current through the magnet coils.

24. Positioning stage according to any one of the preceding claims, characterised in that the substrate table, by means of the pressing mechanism with the preloading spring, forms a force equilibrium with the test probes and with at least two positioning pins placed at a mutual distance in the XY plane, connected to the same frame as the test probes, wherein during testing the positioning pins positively define the X, Y and Rz position between the test probes and the substrate table.

25. Positioning stage according to any one of the preceding claims, characterised in that the pressure point is configured to lift the substrate table at two or more points located at a mutual distance and lying in the same plane, whereby the position of the substrate table in the X, Y and Rz directions is fixed by friction during contact with the test probes.

26. Positioning stage according to any one of the preceding claims, characterised in that piezoactuators are configured to be used for manipulating one or more of the four degrees of freedom X, Y, Z, Rz.

27. Positioning stage according to any one of the preceding claims, characterised in that the actuators are located outside the cryogenic environment and are mechanically coupled to the substrate table that is located within the cryogenic environment required for testing the products.

28. Positioning stage according to any one of the preceding claims, characterised in that, in addition to the weight of the substrate table, the weight of the substrate is partly compensated by a force element.

29. Positioning stage according to any one of the preceding claims, characterised in that moments resulting from a probe force are only partially compensated by the Z mechanism.

30. Positioning stage according to any one of the preceding claims, characterised in that the Rz alignment of the substrate table relative to the probes is achieved by passive adjustment, e.g. not being based on active positioning.

31. Positioning stage according to any one of the preceding claims, further comprising a compliancy mechanism that is functionally arranged in between the base plate and the holder for the test probes, configured to enable a compliancy of the test probes in one or more degrees of freedom relative to the substrate table upon contact between the test probes and the substrate table during use.

32. Positioning stage according to any one of the preceding claims, characterised in that the arm configured to lift the substrate table does not perform a pure translation, but is designed as a lever having a rotation axis perpendicular to the Z axis, being offset from the pressure point.

33. Positioning stage according to any one of the preceding claims, characterised in that the force exerted by the roller of the Z carriage on the cam profile is absorbed by the positioning device of the cam profile, e.g. not being transmitted to a roller on the base plate.

34. Positioning stage according to any one of the preceding claims, characterised in that the positioning device with the cam profile does not disengage from the Z carriage, being configured to manipulate the position of the Z carriage and thereby the substrate table in the Z direction.

35. Positioning stage according to any one of the preceding claims, characterised in that the Z translation of the substrate table is enabled by coupling it to the Y positioning device by rolling elements, e.g. not being coupled by elastic elements.

36. Positioning stage according to any one of the preceding claims, characterised in that the X, Y, Rz positioning of the substrate table is realised by coupling three actuators in parallel between the base plate and the substrate table.

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