Ultra-low temperature wafer inspection system

Abstract

A cryogenic inspection system is provided for inspecting electronic components, such as wafers, under cryogenic conditions. The novel design enables high-speed throughput by using a cryogenically maintained inspection surface that allows wafers to be rapidly introduced, cooled, and manipulated into contact with the inspection element while maintaining high-quality cryogenic conditions. Thermal shielding is achieved through a floating shield and / or flexible bellows that provide effective thermal shielding of the inspection environment while allowing manipulation of the wafer over a wide range of motion. Also provided are novel door assemblies, chuck configurations, and vacuum plate bases that enable effective maintenance of cryogenic conditions and high throughput. TIFF2023501007000002.tif188153

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 937,443, filed November 19, 2019, entitled "System for High Throughput Testing of Electronic Components Under Cryogenic Conditions"; U.S. Provisional Patent Application No. 62 / 978,766, filed February 19, 2020, entitled "Precision Vacuum Chamber Surfaces"; and U.S. Provisional Patent Application No. 62 / 020,069, filed May 5, 2020, entitled "Efficient Low Temperature Wafer Probe Station". The contents of these applications are hereby incorporated by reference into this specification.

[0002] Statement Regarding Federally Sponsored Research or Development Not Applicable

Background Art

[0003] Background of the Invention Driven by the demand for increased processing power and the processing needs of quantum computing circuits, substantial efforts are currently underway to develop cryogenic computers. In cryogenic computing, the operation of processing components at extremely low temperatures provides conditions for eliminating electrical resistance, thereby significantly reducing the power required for computer processing. The cryogenic technology platform uses cryogenic elements fabricated on a silicon wafer or similar substrate. An important process in the manufacture and distribution of cryogenic computers is wafer inspection. Wafer inspection or wafer probing involves inspecting the electronic components located on the wafer and identifying functional defects. Wafer inspection can also provide verification information for improving the manufacturing process. The wafer is usually placed on the inspection surface. A wafer prober makes electrical contact with one or more fabricated circuits located on the wafer surface to identify usable circuits. After the wafer is cut into individual dice, unusable dice can be separated from the usable components and further processed or excluded from manufacturing.

[0004] In the case of cryogenic elements, the wafer must be inspected at the appropriate conditions under which the circuits are utilized, for example, at extremely low temperatures of 0K to 6K. Due to the extremely low temperature requirements, there are significant challenges associated with cooling the wafer to these temperatures and maintaining the thermal environment during inspection.

[0005] Currently, in one common method, the wafer is cooled in parallel with the working environment. For example, currently available solutions involve placing the wafer on a carrier or plate and cooling the carrier, wafer, and inspection environment together to a specified temperature. Repeatedly cooling the working environment to cryogenic temperatures for each wafer requires substantial time and results in a very low throughput.

[0006] Another known approach involves direct cooling of the wafer in an inspection environment maintained at cryogenic temperatures. In a standard direct cooling embodiment, the wafer is either mechanically constrained to a carrier or adhered to the carrier by an adhesive grease or other material (e.g., indium). The constrained or adhered wafer is introduced into the cryogenic inspection environment where it is cooled from ambient temperature to cryogenic temperature. In this embodiment, the adhesive must be removed after inspection, and additional cumbersome steps are required during the process. Additional handling and process steps also pose a risk of device loss due to damage. Further, significant thermal mass is potentially added to the wafer, resulting in throughput degradation and higher energy and / or helium consumption to cool the system.

[0007] Another obstacle to the effective inspection of certain cryogenic devices is the need for effective magnetic shielding. In the case of these cryogenic devices, stray magnetic fields can change the conductivity of the devices on the wafer, trap troublesome magnetic fluxes at critical spots, degrade device performance, or even inhibit functions all at once. Therefore, the wafer must be shielded from stray magnetic fields during the inspection process. Maintaining high-quality magnetic shielding while simultaneously maintaining cryogenic conditions in the inspection environment presents a serious engineering problem.

[0008] Yet another obstacle in the case of effective inspection of certain devices is the need to maintain a flat and horizontal inspection surface within a vacuum environment. In particular, in order to achieve and maintain a vacuum environment under cryogenic conditions, the outer housing of such inspection equipment may be exposed to significant vacuum forces. Due to those vacuum forces, it is necessary to reduce the warping of certain surfaces, especially the surfaces that support sensitive inspection equipment such as precision actuators or motion stages.

[0009] In some embodiments, it is desirable to use a "dry" probe station in which a closed-loop cooling element is utilized to maintain the desired inspection environment temperature while preventing leakage of expensive liquid helium or other coolants.

[0010] A variety of cryogenic wafer inspection systems are known in the art. For example, U.S. Patent No. 8,497,693 B2 to Kiesewetter et al. (Patent Document 1) entitled "Method for testing a test substrate under defined thermal conditions and thermally conditionable prober" describes a system in which a temperature-controllable chuck is set to a defined temperature and a test substrate is positioned relative to a test probe by at least one positioning device. U.S. Patent No. 8,692,567 to Teich et al. (Patent Document 2) entitled "Method for verifying a test substrate in a prober under defined thermal conditions" discloses a system in which a housing has at least two housing sections, in one of which (hereinafter referred to as the inspection chamber) a test substrate to be verified is held by a chuck and set to a defined temperature, and in the other housing section (hereinafter referred to as the probe chamber) a probe is held. U.S. Patent No. 7,046,025 to Schneidewind et al. (Patent Document 3) entitled "Test apparatus for testing substrates at low temperatures" discloses a system in which a vacuum chamber surrounds the working area of a chuck, the chuck is thermally isolated from a non-cooled chuck drive and cooled, and the cooled chuck and the cooled test substrate are shielded from the thermal radiation of the surrounding non-cooled assembly by a directly cooled thermal radiation shield. Despite the contributions of these prior systems, achieving high throughput and high-quality wafer positioning while maintaining thermal and magnetic shielding through efficient use of cryogens remains a substantial challenge.

[0011] Accordingly, in the art, some unmet needs remain. There is a need for wafer inspection apparatuses and methods that consistently and efficiently maintain a probing environment at cryogenic temperatures, such as from 0K to 6K. There is a need for wafer inspection apparatuses and methods that enable high-throughput inspection of wafers while eliminating the occurrence of structural damage to the wafers due to thermal expansion and contraction stresses under these cryogenic conditions. There is a need for wafer inspection apparatuses and methods that support rapid and direct cooling of wafers to cryogenic conditions in order to improve the efficiency of the wafer inspection process. In the art, there is a need for systems that provide high-quality magnetic shielding and cryogenic conditions in the same inspection chamber. Further, in the art, there is a need for improved dry wafer inspection systems that reduce the consumption of expensive coolants.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0013] The scope of the present invention encompasses novel systems, devices, and methods that enable high-throughput and high-quality inspection of wafers under magnetically shielded cryogenic conditions. The systems of the present invention provide significantly improved throughput, higher-quality inspection conditions, and substantially reduced inspection costs.

[0014] In a first aspect, the scope of the present invention includes a novel wafer inspection apparatus or "probe station". Conventional probe station systems suffer from problems of insufficient magnetic shielding (or lack thereof) and inefficient maintenance of very low temperature cryogenic conditions such as about 4K. The novel probe station of the present invention provides, in certain embodiments, a magnetically isolated shell where the inspection system can be maintained at a desired cryogenic temperature. In some embodiments, the novel probe station system of the present invention utilizes concentric thermal buffer zones to surround the inspection environment, maintain it at a tightly controlled cryogenic temperature, and optionally also provide excellent magnetic shielding. In the probe station of the present invention, the wafer can be moved with high precision within the inspection chamber by connection to a movement system. Maintenance of the desired cryogenic temperature and magnetically shielded state is assisted by a "floating shield" that maintains chamber temperature and magnetic isolation while allowing accurate movement of the wafer for effective inspection by the probe station.

[0015] In another aspect, the scope of the present invention relates to a novel method for directly cooling a wafer for inspection under cryogenic conditions. The novel method of the present invention enables inspection of bare wafers without the need for a carrier structure or adhesive. Direct cooling of the bare wafer by the device of the present invention allows for greatly improved throughput and avoids the problem of wafer cracking. The novel system of the present invention enables direct cooling of the bare wafer through the use of a novel receiving element located within a cryogenic isolation environment that holds the wafer in place during inspection without thermally shock-induced wafer breakage.

[0016] In another aspect, the scope of certain embodiments of the present invention relates to maintaining a flat and horizontal surface within a vacuum environment. Through the use of a novel combination of materials, the novel system of the present invention enables inspection of wafers under cryogenic and vacuum conditions on a precision actuator or motion system that relies on a sufficiently flat surface.

[0017] In another aspect, the scope of the present invention includes a novel dry wafer inspection system in which a flexible thermal conductivity strap connects the mobile stage and the static stage of the inspection device, and a large cooler operates on the static stage. The use of such elements is difficult because it imposes conflicting requirements on the strap. To be conductive, it should be thick, short, and made of a highly conductive material such as pure copper or pure aluminum; on the other hand, to be flexible, it should be long, thin, and made of a stronger material. The resulting design problems are very difficult and are prone to subtle failure modes such as work hardening of the strap, which leads to a decrease in thermal conductivity. The inventors of the present disclosure have advantageously determined that a specific flexible material that experiences a substantial increase in thermal conductivity over a critical temperature range can be used as the strap material. In the novel dry system of the present invention, the strap includes materials such as pure alloys of copper and aluminum, is cooled to a temperature range of about 15 - 25K, resulting in a substantial increase in thermal conductivity. Such embodiments solve the flexibility vs. thermal conduction problem and enable the use of thin straps with sufficient flexibility to allow the wide range of movement required in a wafer inspection system.

[0018] [The present invention 1001] An apparatus for inspecting a device under specified thermal conditions, comprising an outer housing, within a chamber defined by the outer housing, a chuck including a surface for receiving the device and one or more clamping elements configured to receive the device and act to hold it on the surface of the chuck, the chuck being connected to a motion stage via a column, the motion stage being configured to operate the column at least in lateral and vertical directions, the chuck; a probe card configured to bring the device into contact with one or more terminals; an inspection zone surrounded by an inspection zone casing is located; the inspection zone casing surrounding the chuck and the probe card; the probe card being attached to the inspection zone casing by one or more support elements and disposed above the inspection surface of the chuck; the inspection zone casing and the outer housing including aligned slots on the same plane through which a wafer can be introduced to the chuck, the inspection zone casing including a heat shielding material, the inspection zone casing including a bottom surface having an opening through which the inspection zone is accessed by the column; the inspection zone including one or more cooling elements located within the casing, on the casing, and / or in the column, the bottom opening of the inspection zone casing being thermally shielded by a shielding element circumscribing the column; the shielding element being a floating shield; a flexible bellows; or a combination of a floating shield and a flexible bellows including, the apparatus. [The present invention 1002] The shielding element includes a floating shield; the floating shield includes a heat shielding material; the floating shield has a horizontal upper surface wider than the bottom opening of the inspection zone casing, and the column is configured to operate laterally while maintaining coverage of the bottom opening of the inspection zone casing by the floating shield, the apparatus of the present invention 1001. [The present invention 1003] The apparatus of the present invention 1001, wherein the shielding element includes a flexible bellows. [The present invention 1004] The bellows includes a concertina-shaped or pleated tube, ring, skirt, or funnel having an upper edge and a lower edge; The upper edge is connected to the inspection zone casing around the bottom opening thereof, and the lower edge is connected to a floating shield or a central column, The apparatus of the present invention 1003. [The present invention 1005] The apparatus of the present invention 1001, wherein one or more cooling elements of the inspection zone include a heat exchanger through which a liquid cryogen flows. [The present invention 1006] The apparatus of the present invention 1005, wherein the cryogen includes liquid helium. [The present invention 1007] The apparatus of the present invention 1001, wherein one or more cooling elements of the inspection zone include one or more flexible straps connected to a cooling stage of a cryocooler by heat conducting elements. [The present invention 1008] The apparatus of the present invention 1007, wherein the one or more thermal straps include a plurality of layers of metal foil. [The present invention 1009] The apparatus of the present invention 1008, wherein the foil includes copper, aluminum, or an alloy thereof. [The present invention 1010] The apparatus of the present invention 1001, configured to maintain the device in the inspection zone at a temperature of 1 to 6K. [The present invention 1011] The inspection zone is A magnetic shielding casing that includes a magnetic shielding material, is located within the inspection zone casing, surrounds the chuck, and has a bottom opening; The floating shield and / or bellows that include a magnetic shielding material The apparatus of the present invention 1001, magnetically shielded by a combination of. [The present invention 1012] The apparatus includes a magnetic shielding casing; The magnetic shielding casing includes a magnetic shielding material; The magnetic shielding casing surrounds the chuck and the probe card; The magnetic shielding casing is surrounded by the inspection zone casing; The magnetic shielding casing includes a bottom surface having an opening, through which the column is connected to the chuck; The magnetic shielding casing includes a slot covered by a door operable to open and close the slot, the slot being aligned with the aligned slots of the outer housing and the inspection zone casing; The floating shield and / or flexible bellows include a magnetic shielding material, The apparatus of the present invention 1011. [The present invention 1013] The inspection zone casing is surrounded within one or more thermal buffer casings; Each of the thermal buffer casings contacts or houses one or more cooling elements; Each of the one or more thermal buffer casings includes a bottom opening through which the column connecting the chuck to the motion stage passes; Each of the one or more thermal buffer casings includes a thermal shielding material; The bottom opening of the inspection zone casing is thermally shielded by a shielding element that circumscribes the column; The shielding element is a floating shield; a flexible bellows; or a combination of a floating shield and a flexible bellows The apparatus of the present invention 1001 including. [The present invention 1014] The apparatus includes one or more thermal buffer zones; Each of the one or more thermal buffer zones is defined by a thermal buffer casing; Each of the one or more thermal buffer casings includes a thermal shielding material; One or more cooling elements contact or are present inside each of the one or more thermal buffer casings; Each of the one or more thermal buffer casings surrounds the inspection zone casing; Each of the one or more thermal buffer casings includes a slot covered by a door operable to open and close the slot, the slot being aligned with the aligned slots of the outer housing and the inspection zone casing and, if any, the magnetic shielding casing; Each of the one or more thermal buffer casings includes a bottom opening through which a central column passes; For each of the one or more thermal buffer casings, a thermal buffer floating shield disposed below the bottom surface of the associated thermal buffer casing circumscribes the central column; Each thermal buffer floating shield includes a thermal shielding material; Each thermal buffer floating shield has a horizontal upper surface wider than the bottom opening of the associated thermal buffer casing, and the column is operable horizontally while maintaining the covering of the bottom opening by the thermal buffer floating shield. The apparatus of the present invention 1013. [The present invention 1015] The apparatus of the present invention 1013 including a single thermal buffer casing. [The present invention 1016] An apparatus of the present invention 1015 including an inspection zone casing configured to be maintained at a temperature of 1 to 6K and a thermal buffer casing configured to be maintained at a temperature of 35 to 80K. [The present invention 1017] The apparatus of the present invention 1016, wherein the thermal buffer casing is configured to be maintained at a temperature of about 50K. [The present invention 1018] The apparatus of the present invention 1013, wherein the one or more cooling elements of the inspection zone include a heat exchanger through which a liquid refrigerant flows. [The present invention 1019] The apparatus of the present invention 1018, wherein the refrigerant includes liquid helium. [The present invention 1020] The apparatus of the present invention 1013, wherein the one or more cooling elements of the inspection zone include one or more flexible straps connected to a cooling stage of a cryocooler via a heat conducting element. [The present invention 1021] The chuck includes a receiving surface and one or more spring-type clamping elements surrounding the receiving surface of the chuck, and the one or more clamping elements are configured to hold a wafer at its edge to the chuck; The operation of the one or more clamping elements is achieved by connection to a push bar within a central column connected to one or more electric actuators; the operation of the push bar with respect to the spring-type clamp lifts the one or more spring-type clamps above the surface of the chuck to create a receiving space for the wafer, and release of the push bar pulls the spring-type clamp downward to clamp the wafer to the chuck surface, in the apparatus of the present invention 1001. [The present invention 1022] The apparatus includes a thermal buffer casing, and a door assembly is located between the adjacent thermal buffer casing and the inspection zone casing, The door assembly includes a first door including a planar body sized and shaped to cover a slot of the thermal buffer casing, and an opposing second door including a planar body sized and shaped to cover a slot of the inspection zone casing; The door includes a heat shielding material; One or more spring elements between the doors stretch the door elements in opposite directions and press them against the casing, and the ends of the one or more springs are separated from the doors by intervening heat insulating elements; The one or more springs are connected to an element connected to the push bar, and the push bar is mechanically connected to an actuator so as to be able to move the push bar to move the door assembly; The apparatus of the present invention 1001, wherein the door assembly is configured such that the actuation of the push bar slides the door so that the aligned slots of the thermal buffer casing and the inspection zone casing are exposed. [The present invention 1023] The apparatus includes a magnetic shielding casing within the inspection zone casing, The second door includes a layer of magnetic shielding material, The apparatus of the present invention 1022. [The present invention 1024] The outer housing is attached to the base, The base is, A slab including a high-rigidity material; A vacuum vessel plate attached to the upper part of the slab by a plurality of fasteners and includes; The upper surface of the vacuum vessel plate has a high flatness, The apparatus of the present invention 1001. [The present invention 1025] The apparatus of the present invention 1024, wherein the slab includes rock. [The present invention 1026] The apparatus of the present invention 1025, wherein the slab includes granite. [The present invention 1027] The apparatus of the present invention 1025, wherein the flatness of the upper surface of the vacuum vessel plate is 1 to 15 microns. [The present invention 1028] The apparatus of the present invention 1027, wherein the flatness tolerance of the upper surface of the vacuum vessel plate is less than 6 microns. [The present invention 1029] A method for inspecting an electronic component under specified thermal conditions, A step of introducing the electronic component by an arm of an external component supply system into a chuck in a thermally isolated inspection zone of any one of the apparatuses of the present invention 1001 to 1028, wherein the electronic component is introduced through aligned slots of an outer casing, and if any, any intervening thermal buffer casing, an inspection zone casing, and if any, a magnetic shielding casing; Engaging a clamping element with the chuck to hold the electronic component on the chuck surface; Moving the central column, the connected chuck, and the held electronic component horizontally to a selected position under the probe card by a motion stage; Moving the central column, the connected chuck, and the held electronic component vertically by the motion stage so that the electronic component contacts one or more terminals of the probe card; The step of engaging the probe card to generate an input to the electronic component and record an output from the electronic component A method comprising the same. [Invention 1030] The method of Invention 1029, wherein the electronic component is a wafer. [Invention 1031] The method of Invention 1030, wherein the wafer includes a plurality of cryogenic elements. [Invention 1032] The method of Invention 1030, wherein the inspection process is performed while the wafer is maintained at a temperature of 1 to 6K. Next, various devices, systems, and methods of the present invention will be described in detail.

Brief Description of the Drawings

[0019]

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DETAILED DESCRIPTION OF THE INVENTION

[0020] Detailed Description of the Invention The various inventions disclosed herein include novel and improved devices for inspecting electronic components under tightly maintained cryogenic conditions and, optionally, under magnetically shielded conditions. The system is referred to herein as a "probe station".

[0021] The various probe stations and their components disclosed herein can be described with reference to the drawings. Numerical keys indicating the structures, components, and elements shown by various reference numerals in the figures are listed below. 100: Apparatus 101: Central vertical column 102: Chuck 103: Motion stage 104: Inspection zone casing 105: Magnetic shielding casing 106: Horizontal gap 107: Bridge 108: Probe card 109: First floating shield 110: Strut 111: Magnetic shielding layer 112: Vertical gap 113: Inspection zone 114: Moving radius 115: Horizontal gap 116a, 116b, 116c, 116d: Slotted gates 117a, 117b, 117c, 117d: Optical apertures or windows 118: Optical element 119: Second floating shield 120: Vertical gap 121: Second thermal buffer zone 122: Moving radius 123: Cooling element 124: Outer housing 125: Thermal buffer casing 126: Clamping element 127: Wafer 129 and 130: Structural members 150: Door assembly 151: First door 152: Second door 153: Support rod 154: Actuator 155: Heat insulation element 156a and 156b: Thermal strips 157: Spring 159: Heat insulation element 201: Service line 202: Heat insulation material 203: Inlet 204: Outlet 300: Clamp 301: Vertical support 302: Spring 303: Aperture 304: Push bar 305: Platform 306: Cross member 307: Wafer supply arm 308: Bellows 309: Bellows 310: Upper edge of the bellows 311: Lower edge of the bellows 400: Base 401: Vacuum vessel plate 402: Adjustable leg 403: Fastener 404: Load distribution plate 405: Stud 406: First end of stud 407: Second end of stud 408: Washer 409: Nut 410: First surface of vacuum vessel plate 411: Second surface of vacuum vessel plate 412: Through hole 413: Fastening hole 414: Bolt 415: First end of fastener 416: First side of base 417: Second end of fastener 418: Second side of base 500: Flattening area 501: Grid 502: Reference plane 503: Dial indicator 504: Support block 505: Reference block 506: Relative distance 601: Base structure 602: Motion system 603: Medium-temperature mobile stage 604: Low-temperature mobile stage 605: Wafer chuck 606: Gate valve 607: Outer housing 608: Medium-temperature static shell 609: Thermal insulation support 610: Low-temperature static shell 611: Window 612: Low-temperature compatible two-stage cryocooler 613a and 613b: Temperature stages a and b of cryocooler 614: Low-temperature thermal link 615: Low-temperature thermal equilibration block 616: Low-temperature flexible strap 617: Medium-temperature cryocooler 618: Low-temperature stage 619: Medium-temperature link 620: Medium-temperature thermal equilibration block 621: Medium-temperature flexible thermal strap 700: Thermal equilibration block 701: Flexible thermal link 702: Mobile stage cross-section at the center of the movement range 703: Flexible thermal link at one limit of the movement 704: Mobile stage cross-section at one limit of the movement 800: Mobile stage 801: Flexible thermal composed of foil 802: Static thermal equilibration block

[0022] The novel structures disclosed herein can be fabricated from any number of materials. The devices described herein are not limited to any particular material, and it will be understood by those skilled in the art that they can select materials suitable for the ultra-low temperature (and, in some embodiments, magnetically shielded) operation described herein. The various materials described herein are referred to as "high-purity" materials. Exemplary high-purity materials can include materials of 99% purity, 3N (99.9% purity), 4N (99.99% purity), 5N (99.999% purity), and 6N (99.9999% purity). Various metals are described herein together with their "alloys". As used herein, "alloy" can include materials that are primarily the described metal combined with other metals, as is known in the art (e.g., an "aluminum alloy" can primarily include aluminum combined with other metals). References to steel alloys can include, for example, steel alloys 304 and 310 and alloys containing chromium and / or nickel. For example, a steel alloy can include a nickel content of 20% - 25% and can further include cobalt, molybdenum, titanium, aluminum, or niobium. Aluminum alloys can include, for example, alloys of the 2000 and 5000 series, 1100, 2014, 2024, 2219, 3003, 5083, 5456, 6061, 7005, 7039, 7075, 5083-O, 2219-T87, 5052-H38, 5083-1138, 2024-T6, 7039-T6, 2219-T87, and 6061-T6. Nickel alloys can include, for example, alloys containing nickel combined with copper, iron, manganese, carbon, and silicon, such as Monel, K-Monel, electroforming nickel, hardened nickel, Inconel X, Inconel 718, René 41, and Hastelloy B. Copper alloys can include, for example, 70-30 brass, copper beryllium, iron silicon, and aluminum bronze.

[0023] Next, various elements of the probe station system of the present invention will be described.

[0024] Outer housing The first element of the probe station is the outer housing. The outer housing surrounds the various elements of the system, provides insulation to the component inspection zone, and in some aspects, defines a vacuum chamber where the elements of the present invention are enclosed. The housing includes a storage container. In the main aspect, as in the exemplary probe station of the present invention shown in FIGS. 1 and 2, the housing 124 includes a cylindrical container, but a cubic housing, a rectangular box, or a housing of other shape dimensions is within the scope of the present invention.

[0025] The outer housing provides a barrier between the external ambient conditions and the internal components. In some aspects, the outer housing defines a vacuum chamber in which a vacuum is created and maintained within the chamber defined by the housing. The outer housing may include ports or other physical elements that connect the internal elements of the housing to components outside the device. For example, the outer housing may include one or more ports connected to a vacuum source, one or more ports for piping to direct liquid cryogen into and out of the device, and one or more conduits or wires that connect the probe card, motion stage, door actuator, chuck actuator, and other elements to a power source and control and data collection components located outside the processor or device.

[0026] In one aspect, the outer housing includes a vacuum boundary material and design that can maintain an internal vacuum and withstand external pressure. Exemplary outer casing materials include metals such as aluminum, stainless steel, and their alloys, for example, a single layer of aluminum with a thickness of 2 - 15 mm. In certain aspects, the outer housing further includes a magnetic shielding material for changing the orientation of the ambient magnetic field and keeping it away from the interior of the housing.

[0027] The outer housing may include a removable lid, door, or other structure that allows access to internal components. The outer housing may also include a gated slot, i.e., a slot and a related door that can be actuated to cover and uncover the slot. This gated slot allows for the introduction of the wafer or other component to be inspected into the device and the retrieval from the device.

[0028] In one embodiment, the outer housing includes a cylindrical body attached to a rigid base and including a removable circular lid, which, when attached to the top of the cylindrical body by a closure element (such as a latch, bolt, etc.), can create an airtight chamber.

[0029] A thermally defined and magnetically isolated working zone for wafer inspection The main element of the device of the present invention is an inspection chamber that can be maintained under precisely controlled conditions, including cryogenic conditions. This inspection chamber, referred to herein as the "inspection zone," includes a thermally defined and optionally magnetically isolated chamber in which a plurality of elements are housed, as described below.

[0030] As used herein, "thermally defined" means that the elements within the chamber are maintained within a selected temperature or selected temperature range. In the main embodiment of the present invention where the inspection chamber is maintained under vacuum conditions, the thermally defined conditions are achieved by the use of heat conducting elements that are in contact with one or more cooling elements or are otherwise cooled by one or more cooling elements, as described herein.

[0031] The inspection zone is defined by a casing, herein referred to as an "inspection zone casing", for the role of defining the area of the inspection zone and maintaining the desired conditions of the inspection zone. Referring to the exemplary embodiments shown in FIGS. 1 and 2, inspection zone 113 is an area within inspection zone casing 104. The inspection zone casing includes a hollow body including an internal space as well as an outer wall, top surface, and bottom surface. The inspection zone casing includes various openings including a bottom opening, an upper portion, an upper optical access opening, and side openings including a slotted gate.

[0032] The inspection zone casing includes a thermal shielding material to resist the intrusion of heat from outside the casing. As used herein, a thermal shielding material is a material including a pure material or a composite or alloy of multiple materials that can thermally isolate or insulate the area enclosed by the material. Preferred thermal shielding materials for the inspection zone casing include materials having a high thermal conductivity and a structural strength suitable to withstand extreme cooling. In one embodiment, the inspection zone casing includes aluminum, such as 1100, 3003, 6063, or 6061 type aluminum. Alternative materials include metals such as magnesium and copper. For example, in one embodiment, the inspection zone casing includes 3003 aluminum or copper. The thickness of the inspection zone casing can be, for example, 0.25 - 10 mm, such as about 3 mm (as used herein, "about" means within 10% of the recited value), although other thicknesses may be considered. Generally, the inspection zone casing includes a single layer of material, although in alternative embodiments, the casing includes multiple layers.

[0033] In a main embodiment, the inspection zone casing includes circular / cylindrical as shown in FIGS. 1 and 2. However, it will be understood that the inspection zone casing may have any shape, such as a cube, rectangular box, triangular box, or irregular shape.

[0034] The bottom opening of the inspection zone casing is covered by a shielding element, as described below. The inspection zone casing also houses, surrounds, or contacts one or more cooling elements, as also described below. By the action of the one or more cooling elements, the elements within the inspection zone can be maintained under tightly controlled thermal conditions within any selected temperature range between the base temperature of the device and room temperature. In a main aspect, the inspection zone casing 104 is maintained at an extremely low temperature, for example, a temperature in the range of 0K to 6K, for example, about 4K.

[0035] Magnetic isolation In certain aspects of the invention, the successful inspection of electronic components requires an environment substantially free of ambient or other magnetic fields and magnetic fluxes. In such cases, the probe station can be configured to have a magnetically isolated inspection zone. This is achieved by the use of a casing, herein referred to as a magnetic shielding casing. The magnetic shielding casing is a hollow structure disposed inside the inspection zone casing. The magnetic shielding casing includes a bottom opening that is aligned with the bottom opening of the inspection zone casing.

[0036] To maintain a thermally defined temperature, the magnetic shielding casing is cooled by a thermally conductive connection to the inspection zone casing along one or more surfaces, such as the bottom surface, as shown in FIGS. 1 and 2. In one aspect, the magnetic shielding casing is connected to the inner surface of the inspection zone casing by struts, beams, or other thermally conductive support structures. In one configuration, the magnetic shielding casing and the inspection zone casing in which it is located are composed of different materials having different coefficients of thermal expansion. In such aspects of the invention, one or more flexible thermally conductive members can optionally be utilized to connect the inspection zone casing 104 and the magnetic shielding casing 105. In one aspect, the magnetic shielding casing is located on (or connected to, for example, by welding or screws) the bottom surface of the inspection zone casing, as shown, for example, in FIG. 1 or FIG. 2. In one aspect, the magnetic casing includes an inner layer of material that lines the inner surface of the inspection zone casing.

[0037] The magnetic shielding casing can include any shape, but generally it is advantageous for it to have the same shape as the inspection zone casing in which it is located. For example, referring to the exemplary embodiments shown in FIGS. 1 and 2, the magnetic shielding casing 105 includes a cylindrical shape that is concentrically located within a cylindrical inspection zone casing.

[0038] The magnetic shielding casing can include any number of magnetic shielding materials, i.e., materials that can change the direction of a magnetic field or attenuate a magnetic field and protect the area enclosed by the material from external magnetic flux. Magnetic shielding materials include, for example, ferromagnetic materials including ferroalloys, nickel-iron alloys, and nickel-iron-molybdenum alloys. Exemplary materials include ASTM A753 alloy type 4, ASTM A753 alloy 2, MIL-N-14411 composition 1, supermalloy, supermumetal, nilomag, sanbold, and molybdenum. Commercially available materials include, for example, MUMETALS™ (Holland Shielding Systems, Dordrecht, Netherlands) or CRYOPERM™ (MuShield, Londonderry New Hampshire, USA) and ALLOY49™. The wall thickness of the magnetic shielding casing can be any thickness suitable for effective magnetic shielding of the internal space enclosed thereby, for example, in the range of 0.2 to 4.0 mm.

[0039] The bottom opening of the inspection zone casing and the bottom opening of the magnetic shielding casing are generally approximately the same size and shape (e.g., diameter). In some embodiments, there is a size mismatch, in which case, as described below, the smaller of the two bottom openings defines the lateral extent of the column.

[0040] It is located within the inspection zone casing and is thermally connected thereto, so the magnetic shielding casing is maintained at the cryogenic state of the inspection zone casing. Thus, the magnetic shielding casing defines a magnetically isolated and thermally defined chamber or inspection zone. The inspection of electronic components is performed within this chamber where high-quality measurements can be advantageously achieved.

[0041] In an alternative embodiment, the wafer inspection apparatus of the present invention does not require substantial magnetic isolation of the inspection zone. In this alternative embodiment, the magnetic shielding casing is completely omitted from the device, and the inspection zone is defined only by the boundary of the inspection zone casing.

[0042] Probe card One or more probes or probe cards are located within the inspection zone. A probe card is an array of probe elements (such as terminals or needles) that contact a device or other device under test on a wafer for measurements of conductivity, performance, etc. The probe card can be electrically connected to and thereby actuated by one or more external devices including a computerized controller. When actuated, the terminals of the probe card contact the inspection substrate at the target contact points, the probe card sends an electrical input signal to the inspection substrate, and the probe card receives an electrical output signal from the inspection substrate. The probe card is wire-connected to external components such as a control system, a power supply, a regulator, and a signal processing / memory device that enables electrical stimulation of the terminals and / or measurement of the output signal, and the wires pass through any intervening casings by way of openings or conduits.

[0043] The probe card can be suspended within the inspection zone by being connected, for example, to a point on the inner surface of the inspection zone casing by one or more structural elements such as beams, pillars or other elements. Such a support structure is thermally conductive and is connected to the inspection zone casing. In one embodiment, the structural element includes a support element or bridge 107 whose ends are each fixed by a vertical element that passes through the magnetic shielding casing (if any) and is connected to the inner surface of the bottom face of the inspection zone casing, as shown, for example, in FIGS. 1 and 2.

[0044] Wafer holding element The electronic component to be inspected can be any electronic component, for example, a component including a device or a plurality of devices. To start the inspection, the electronic component is introduced into the inspection zone. In a main embodiment, the electronic component is a wafer, for example, a wafer including a plurality of devices arranged in a grid pattern.

[0045] The inspection zone includes a receiving element for the electronic component. When a wafer is inspected, the receiving element can include a chuck. The chuck includes a platform having a substantially planar body with a flat upper surface where the wafer to be inspected is located and held in a predetermined position. The material of the platform is ideally a pure metal or alloy having high rigidity, high thermal conductivity and non-magnetism. Examples include copper, aluminum, molybdenum and their alloys. In one embodiment, the electronic component to be inspected includes a circular wafer and the chuck includes a substantially circular face for receiving the wafer.

[0046] The chuck includes one or more clamping elements that hold the wafer 127 at its edge. The operation of the clamping elements is achieved by one or more rods, such as push bars, or other elements, such as an actuator and a push bar inside the central column described below. The electric actuator can be connected to an external power source and control components via wires. For example, in one aspect, the chuck includes clamping elements, such as two, three, four, five, or more spring-type clamps, which can create a receiving space for the wafer when lifted by a central operating rod and, when released after the introduction of the wafer, retract downward due to the spring tension and clamp the wafer to the chuck surface.

[0047] In a particular aspect of the present invention, the chuck 102 includes one or more operable clamping elements 126 that hold the wafer 127 or other inspection piece in a predetermined position during an inspection process, as shown in the exemplary aspects seen in FIGS. 5A, 5B, 6A, 6B, 7, 8A, 8B, 8C. The clamping element 126 includes a clamp 300 attached to a cross member 306, and the cross member is disposed below the platform 305. A spring 302 forms contact between the cross member and the platform. Referring to FIG. 6B, a plurality of vertical supports 301 are connected to the cross member 306 and pass through an opening 303 located on the platform 305.

[0048] Referring to FIGS. 5A, 6A, 8A and 8B, when the push bar 304 attached to the cross member 306 is lifted upward with respect to the platform 305, the spring 302 is compressed, and a space for supplying the wafer 127 is opened between the clamp 300 and the platform 305. The wafer can be introduced, for example, by a wafer supply arm 307 of an externally located wafer supply system. The support 301 is generally oriented in the vertical direction and is connected to the cross member 306. When the push bar is lifted upward, the vertical support is exposed above the surface of the platform 305. For example, as shown in the exemplary FIG. 8A, when loading the wafer 127 onto the chuck, the vertical support 301 supports the wafer and provides a space between the wafer 127 and the platform 305. In a particular aspect of the present invention, an electric actuator is disposed, for example, at the bottom of the central column, below the chuck, within the central column, and is connected to the clamp element of the chuck via a push bar passing through the column to move the clamp element. The actuator can be connected to and thereby actuated by a control system outside the outer housing.

[0049] Referring to FIGS. 5B, 6B and 8C, when the push bar 304 is released, the spring 302 located between the platform and the cross member applies a force to the cross member 306. As a result, the cross member, and thus the clamp element attached to the cross member, descends, causing the clamp 300 to provide a downward force on the wafer 127 disposed on the platform 305. At the same time, the vertical support 301 is lowered, thereby lowering the wafer onto the surface of the platform 305. In this way, the wafer 127 is clamped between the clamp 300 and the platform 305.

[0050] Advantageously, the wafer clamping element and chuck of the present invention are located within a controlled cryogenic environment of the inspection zone. Thus, during wafer introduction and inspection processes, the shrinkage of the metal constituting the chuck element is minimized, minimizing or eliminating substantial compressive stress on the wafer. In contrast, in prior art wafer cooling systems, the wafer must be introduced into the cryogenic working zone after being clamped or fixed to the holding element while outside the device. This creates a contradiction between excessive clamping force that causes compressive stress and wafer breakage, and insufficient clamping force that causes inadequate thermal equilibration of the wafer. Thus, while prior art processes are not free of substantial time and risk, the process of the present invention, in which the wafer is rapidly cooled on a pre-cooled holding device, results in significantly increased throughput and safety. The introduced clamped wafer shrinks when rapidly cooled in the inspection zone, creating tensile stress, but the inventors of the present disclosure have found that silicon wafers can generally withstand this stress without cracking or breaking.

[0051] Precise Movement of the Wafer In order to successfully inspect a circuit or other electronic component, the target contact point of the component must be accurately positioned under the terminals of the probe card. In the case of a wafer, after the circuit has been inspected, the wafer must be repositioned under the probe card while accurately positioning the target contact point under the terminals again so that another circuit is presented to the probe card. Thus, the wafer must be positioned under the probe card with very high accuracy, for example, with a tolerance in the range of 1 to several tens of microns. The wafer probe station of the present invention enables high-precision alignment of the probe card and the inspection substrate.

[0052] To control the position of the wafer with respect to the probe card, it is convenient to enable visualization of the wafer and the probe card in the inspection zone from outside the probe station. Visualization of the working zone by equipment located outside the housing can be enabled by a series of aligned openings or windows, including transparent materials, in various casings. The window can include glass, sapphire, or other transparent materials. For example, in the exemplary embodiments shown in FIGS. 1 and 2, the probe station includes an outer housing 124, a thermal buffer casing 125, an inspection zone casing 104, and a magnetic shielding casing 105, and the wafer and the probe card are visualized by an optical element 118 outside the outer housing through a series of aligned optical openings or windows 117a - d. Such a visual monitoring system can include, for example, a CCD or CMOS camera connected to a computerized control element to guide the operation of the wafer to a selected position under the probe card.

[0053] While being guided by the control system, the wafer must be moved with high precision to a selected point under the probe card. This is achieved in the system of the present invention by the novel use of a motion stage system. The motion stage is located inside the outer housing 124 and outside the severe thermal environment of the inspection zone and is connected by a vertical column to a chuck within the inspection zone. The lower end of the column is connected to the motion stage 103. The motion stage includes an electric system that causes fine movement of the column with an accuracy in the range of, for example, 1 to 100 microns. In a particular embodiment, the motion stage is configured to move the column in the lateral, vertical, and rotational directions with high precision. An exemplary motion stage system includes a commercially available precision vacuum-compatible motion stage. Examples of commercially available products of such motion stages include those provided by NEWPORT CORPORATION (trademark) and PI MICOS (trademark).

[0054] The arrangement of the transfer system outside the magnetically isolated cryogenic working zone requires that the working zone be accessible from the column. Further, it is advantageous for the column to have a substantial lateral movement range so that the entire working surface of the wafer or other parts can be moved under the probe card. The bottom opening of the inspection zone casing (and, if any, the bottom opening of the magnetic casing) enables this lateral movement range. The width of the bottom opening of the inspection zone casing and / or the width of the bottom opening of the magnetic shielding casing are selected such that the entire working surface of the wafer (including the device being inspected) is accessible from the probe card, which is achieved by the lateral movement of the column. For example, in the case of a circular wafer and a round bottom opening in the inspection zone casing, the distance between the outer surface of the column and the edge of the bottom opening of the inspection zone casing (or, if present and smaller, the magnetic shielding casing) will generally be approximately the diameter of the working area of the wafer + the diameter of the column. For example, for a 200 mm wafer with a 2 mm exclusion zone on the outer periphery and a column with a 40 mm diameter, the bottom opening of the first casing will have a diameter of at least 236 mm.

[0055] Floating shield To achieve a larger lateral column movement range, a relatively large opening is required at the bottom of the inspection zone casing (and, if any, the magnetic shielding casing). This presents potential problems when maintaining the integrity of magnetic shielding and the thermal isolation of the working zone. To address this issue, the scope of the present invention includes the use of a novel shielding element that thermally shields the bottom opening of the casing defining the inspection zone while allowing a wide lateral movement of the central column. In a main aspect, the shielding element includes a "floating shield". The floating shield of the present invention includes a planar structure disposed around the central column that is parallel to the bottom surface of the casing and provides coverage of the bottom opening of such casing during the lateral operation of the column. The floating shield of the present invention is sized such that the bottom opening of the associated casing is completely covered by the floating shield over the entire lateral movement range of the column. These floating shields serve to block thermal radiation from outside the casing.

[0056] Also, by the vertical operation of the column, the floating shield can be lifted so that the gap between the bottom surface of the associated casing and the upper surface of the floating shield is minimized, sealing or substantially sealing the interior of the casing. In some embodiments, the upper surface of the floating shield contacts the bottom surface of the associated casing. In other embodiments, by lifting the column, the gap between the upper surface of the floating shield and the bottom surface of the associated casing can be reduced to about 1 mm or less, for example 0.1 mm or 0.5 mm.

[0057] The floating shield includes a planar aspect, such as a disk-shaped body. The floating shield is attached to the column in a state substantially perpendicular to the longitudinal axis of the column. In certain embodiments of the present invention, the floating shield is supported by a support element, such as struts 110 as shown in FIGS. 1 and 2, or by spurs, ties or angle elements that assist in supporting the floating shield by the column. The main function of the floating shield is to maintain thermal isolation of the upper chamber, and the shield includes materials that can insulate the upper chamber, such as metals such as aluminum, steel, copper, their alloys, and generally materials having high thermal conductivity. For example, the shield may include a layer of aluminum having a thickness of 0.25 to 5.0 mm. In some embodiments, the planar structure of the floating shield includes the same material as the casing it seals.

[0058] In certain embodiments of the present invention, the probe station apparatus includes more than one floating shield, for example, a first floating shield for surrounding an inspection zone, such as an inspection zone chamber, and a second floating shield for surrounding a second thermal buffer chamber, such as a 50K chamber, as described below.

[0059] The topmost floating shield covers the bottom opening of the inspection zone chamber. In these embodiments where a magnetic shielding casing is present within the inspection zone chamber and magnetic shielding of the working zone is desired, the top surface of the floating shield includes a magnetic shielding material to achieve optimal magnetic isolation of the inspection zone.

[0060] Referring to FIGS. 1, 2, 4, 9A, and 9B, in one embodiment, the floating shield includes, for example, a first layer 109 including a thermally conductive material and a second layer 111 including a magnetic shielding material. In some embodiments, the upper surface of the first floating shield includes a magnetic shielding layer. Examples of materials for magnetic shielding include, for example, ferromagnetic materials such as iron alloys and metals having a high magnetic permeability such as nickel-iron alloys. In certain aspects of the present invention, the thickness of the magnetic shielding layer is any thickness suitable for effective magnetic shielding, for example, a thickness in the range of 0.5 to 5.0 mm. In certain aspects of the present invention, the magnetic shielding layer 111 is located directly on the upper surface of the planar thermal shield 109. The first and second layers of the floating shield can be joined thereto by fasteners such as screws, bolts or other fastening elements. In certain aspects, the thermal shielding layer of the floating shield and the magnetic shielding layer of the floating shield have different coefficients of thermal expansion. In such embodiments, the physical connection between the layers is configured to accommodate different rates of contraction and expansion by the thermal shielding layer and the magnetic shielding layer of the floating shield, for example, by bends or slots that prevent warping of the assembly or applying excessive stress during expansion and contraction.

[0061] Compliant bellows In an alternative embodiment, the shielding element that shields the bottom opening of the casing includes a compliant bellows, such as a compliant bellows that surrounds the bottom opening of the inspection zone casing and / or the thermal buffer casing. An exemplary bellows is shown in FIG. 25. The bellows is a compliant structure that can expand and contract, for example, a device having a concertinaed, accordion, or pleated side surface that allows its upper and lower edges to be laterally displaced by expansion and contraction. The bellows will cover the bottom opening of the casing and have sufficient flexibility and size to allow the column to move over its lateral movement range. The bellows can be substantially tubular, with the diameter or width of the upper part being substantially equal to the diameter or width of its bottom. Alternatively, the bellows may be pyramidal in shape with one opening being larger than the other. The bellows includes an upper opening defined by an upper edge 310 and a lower opening defined by a lower edge 311. The upper edge of the bellows is attached to the bottom of the casing (e.g., the inspection zone casing or the thermal buffer casing) so as to surround the bottom opening of the casing, and its lower edge can be attached to the lower structure. Attachment of the bellows to other structures can be achieved by brazing, welding, screws, bolts, or other attachment means. In one aspect, the structure to which the lower edge is attached is a floating shield. In one aspect, the floating shield includes a small flange having a diameter smaller than the bottom opening of the casing, and the lower edge is attached to this flange. In one aspect, for example, as shown in FIG. 10, the lower edge is attached directly to the central column and there is no floating shield.

[0062] The function of the bellows is to be configured to enable lateral and / or vertical (longitudinal) movement of the column while maintaining thermal and / or magnetic shielding of the bottom opening of the casing. In some embodiments, the bellows supplements the floating shield by providing an additional vertical dimension of shielding. In some embodiments, the bellows replaces part or all of the floating shield. The bellows can include, for example, a metal foil (or laminate of foils) including copper, aluminum, steel, or an alloy thereof. The thickness of the foil can be any thickness that allows for a sufficient range of movement, such as 0.25 to 2 mm. In one embodiment, the bellows includes one or more springs coated with a foil. In other embodiments, the bellows can include a textile material that maintains compliance under cryogenic conditions. Exemplary fiber materials include woven and non-woven fabrics, such as glass fiber fabrics, polyester fabrics, glass-polyester composite fabrics, glass-epoxy composite fabrics, polytetrafluoroethylene, poly(p-phenylene terephthalamide), and other cryogenic textiles known in the art. In one embodiment, the textile includes a fabric coated, impregnated, or metallized with a thermal shielding material and / or a magnetic shielding material, such as a particle or film including a thermal or magnetic shielding material, such as a copper, nickel, or cobalt composition. One or more material layers can be deposited on the textile material.

[0063] During operation, the bellows is compliant and deforms as the column 101 moves, for example, within the movement radii 114, 122 of the floating shield as seen in FIG. 9B. In certain embodiments of the present invention, two or more bellows are radially oriented around the bottom opening of the casing. Referring to FIGS. 9A and 9B, the bellows 308 is positioned within the vertical gap 112. In a particular embodiment, the bellows 308 is connected between the bottom of the inspection zone casing 104, for example near the opening of the inspection zone casing, and the floating shield, such as the magnetic shielding layer 111. In a particular embodiment, the bellows 309 is positioned within the vertical gap 120 and connects the thermal buffer casing 125 and the second floating shield 119.

[0064] In certain embodiments, bellows 308, 309 are connected between the column and the upper casing. Referring to FIG. 10, in one embodiment, bellows 308 is connected to column 101 and the upper casing, such as inspection zone casing 104. In one embodiment, a second bellows 309 connects column 101 to the upper casing (such as thermal buffer casing 125).

[0065] Thermal buffer zone In one embodiment of the present invention, the probe station includes only a single thermally isolated zone defined by an inspection zone casing housed within an outer housing. However, in the main embodiments of the present invention, the thermal isolation of the inspection zone is improved by the use of one or more thermal buffer zones. As used herein, a "thermal buffer zone" includes a thermally isolated chamber within which the inspection zone casing is enclosed. For example, in the exemplary embodiments shown in FIGS. 1 and 2, inspection zone casing 104 is surrounded by the thermally defined environment of a second thermal buffer zone 121 within thermal buffer casing 125.

[0066] Each thermal buffer casing includes a bottom opening and associated shielding elements (such as a floating shield and / or bellows). The configuration of one or more thermal buffer casings and the enclosed inspection zone casing can be in any number of arrangements, for example, the casings can be concentrically nested cylinders as shown in FIGS. 1 and 2.

[0067] The thermal buffer zone created by one or more thermal buffer casings can be maintained at a temperature lower than the temperature of the volume surrounding the housing and higher than the temperature of the inspection zone. For example, in an exemplary aspect of the present invention, the components of the inspection zone are maintained at a temperature of about 4 K while being surrounded by a second thermally isolated zone maintained at about 40 - 60 K, for example about 50 K.

[0068] In a main embodiment, two thermal casings, for example, the inspection zone 104 and the thermal buffer casing 125 shown in FIGS. 1 and 2 are utilized, resulting in two thermally defined zones, namely the inspection zone and the thermal buffer zone. It will be understood that additional thermal casings each having its own bottom opening and its own bottom opening shielding element (e.g., a floating shield and / or a compliant bellows) can be utilized to define, for example, third, fourth or higher order thermally isolated buffer zones, and that a series of casings can be concentrically configured within one another. Such a configuration allows the innermost casing, i.e., the inspection zone casing, to be set at a very low temperature and isolated within a plurality of thermal shielding and buffer layers.

[0069] Configuration within the housing One or more structural members may support the inspection zone casing, the thermal buffer zone casing, the magnetic shielding casing (if any), and other parts of the system. In certain embodiments, structural members 129, 130 provide support, for example, by connecting the outer wall of inspection zone casing 104 to the inner wall of thermal buffer casing 125 and connecting the outer wall of thermal buffer casing 125 to outer housing 124. Generally, the structural members should have a low thermal conductivity and be sized, numbered, and positioned to provide sufficient support to hold the nested casings in place. In certain embodiments, one or more structural members include a flexible material or a flexible shape or design to accommodate differences in thermal expansion rates and expansion differences due to different temperatures of the elements.

[0070] Cooling element The probe station of the present invention includes a plurality of cooling elements. Each cooling element includes a device or system that removes heat from the structure in which the cooling element is present. For example, in a main embodiment, one or more cooling elements are present within or on the surface of each casing. The cooling elements are sized and configured to maintain each zone at selected temperature conditions. The cooling elements may be located on the surface / inside of the central column, within the casing, or attached to the casing.

[0071] In one embodiment, one or more cooling elements include a heat exchanger, e.g., a coil or other structure through which a liquid cryogen such as liquid helium, liquid nitrogen, or other liquefied gas known in the art flows. In certain aspects, the liquid cryogen is connected from an external source through an outer casing (described below) and supplied by pumping or otherwise through a hose or conduit housed within the column. In an exemplary aspect of the present invention, referring to FIG. 4, a plurality of cooling elements 123 are present within the apparatus 100, i.e., the probe station. Within the apparatus 100, the liquid cryogen flows through tubes to the cooling elements. The tubes may be seen within a particular feature of the apparatus, e.g., within the column 101, or may be seen through the casing, housing, and shielding material. In certain aspects, an inlet port 203 provides an opening for introducing the liquid cryogen into the system and an outlet port 204 provides an opening for removing the liquid cryogen from the system. The flow of liquid cryogen into the system cools the plurality of cooling elements 123 located within the apparatus 100. Still referring to FIG. 4, the heat exchanger 123 may be located within the inspection zone 113 and between the inspection zone casing 104 and the thermal buffer casing 125. For example, in the thermally defined environment of a second thermal buffer zone 121, one or more additional cooling elements may be utilized. In a particular aspect of the present invention, the cooling system further includes a service line 201. Additionally, in a particular aspect of the present invention, the column 101 includes insulation 202.

[0072] Dry probe system In an alternative embodiment, one or more cooling elements can be a physical structure including a heat sink that is thermally conductive with a cooling device and is made of a conductive material such as copper (heat is recovered from a thermally defined zone by such a conductive element). Conventional probe stations struggle to maintain a temperature of about 4K and require large amounts of prohibitively expensive liquid helium or numerous commercially available large two-stage pulse tubes or Gifford-McMahon cryocoolers. One solution to the problems of using liquid helium is the use of a closed-cycle cryocooler in what is called a "dry" wafer inspection system.

[0073] What is provided herein is an improved dry system. The first aspect of novelty in the improved dry system of the present invention is to divide the cooling function between two separate cryocooler elements. Cooling of the elements in the dry system of the present invention is achieved by dividing the cooling of the inspection zone and the thermal buffer zone into separate cryocoolers. In a first embodiment, the improved system of the present invention includes the use of two separate cooling elements, such as liquid helium cryocoolers or similar units, and the cryogenic stage of the cryocooler is located above or within the static portion of the wafer probing station (with appropriate connections to cryocooler components outside the device, such as pumps, compressors, and refrigerant reservoirs). The first cooling element cools the static components of the thermal buffer zone to an intermediate temperature, such as 10 - 30 K, for example about 15 - 20 K. The cryogenic stage of the second cooling element may be located within the intermediate buffer zone (with appropriate connections to components outside the outer housing, such as pumps, compressors, and refrigerant reservoirs) and achieves cooling of the moving inspection components enclosed within the inspection zone casing to a low temperature (such as 1 - 6 K) by means of a thermal conduction connection including a series of elements including flexible straps. The novel configurations of the present invention all enable the use of large cryocooler units operating on static stages, which reduces the complexity of cooling the internal inspection environment. In a main embodiment, the cryocooler is a closed-cycle cryocooler, such as a liquid helium cryocooler, or may include coolers such as Gifford-McMahon cooling systems, adiabatic demagnetization systems, Stirling engines, and pulse tube refrigerators. In a given system, the cryogenic stage may be cooled by a first cooling element optimized for low-temperature inspection conditions, such as a system like Cryomech PT420 (trademark) (Cryomech Systems, Syracuse NY), which cools to, for example, 1 - 6 K. On the other hand, the shield stage may be cooled by a second dedicated cooler optimized to cool to 10 - 35 K, such as about 15 - 25 K, for example a system like Cryomech AL 630 (trademark) (Cryomech Systems, Syracuse NY).

[0074] The second aspect of the novelty in the dry system of the present invention is the improved flexible strap design. Designing an effective flexible and thermally conductive strap is very difficult because it imposes conflicting requirements on the strap. For it to be conductive, it should be thick, short, and made of a highly conductive material such as pure copper or pure aluminum. For it to be flexible, it should be long, thin, and made of a stronger material. This design paradox is very difficult, and the strap is prone to subtle failure modes such as work hardening of the strap, which leads to a decrease in thermal conductivity.

[0075] The scope of the present invention includes a novel flexible and thermally conductive strap that includes materials selected such that heat conduction increases in a temperature range of about 15 - 25K. For example, materials with very high thermal conductivity, such as pure alloys of copper and aluminum, significantly increase the thermal conductivity in this temperature range and greatly reduce the amount of strap material required. In addition, the allowable temperature difference between the mobile shielding stage and the static shielding stage increases, allowing the use of less strap material and increasing flexibility. Finally, if correctly implemented, the reduction in the temperature of the static shielding stage reduces the thermal load on the mobile stage, also reducing the amount of strap material required here. When the requirements for the strap material are cut to a very low level, the desired balance between conductivity and flexibility in the strap is much more easily achieved.

[0076] FIG. 22 shows an exemplary dry cryogenic probe station of the present invention. In this embodiment, the wafer is inserted into the probe station by standard wafer handling equipment known in the art. The wafer enters the system through door 606. The wafer is held on chuck 605 by a mechanical clamp. This interface brings the wafer to cryogenic temperatures. Motion stage 602 moves the chuck and mobile elements so that various regions of the wafer can be imaged through window 611 and interrogated by electrical, optical, or other means depending on the nature of the probe station. A common example would be electrical probing where a series of probes disposed within static shielding element 610 make electrical contact with various parts of the wafer. The cryogenic mobile and static elements are cooled by a commercially available two-stage cryocooler 612. The first stage 613a of this cryocooler need not be thermally connected to anything but can be used to provide auxiliary cooling to other parts of the system (not shown). The second stage 613b of the cryocooler is connected to the cryogenic static stage 615 via one or more first thermal links 614. The cryogenic mobile stage 604 and chuck are thermally fixed to the cryogenic static stage via one or more thermally conductive straps 616 having one or more first compliances.

[0077] The intermediate static and mobile elements (608 and 603 respectively) are cooled in a similar manner. Intermediate cryocooler 617 is optimized for cooling in the temperature regime of 10 - 30K. The cryogenic interface of cryocooler 618 is attached to thermal equilibration block 620 via one or more second thermal links 619. The mobile intermediate stage element 603 is cooled via one or more second flexible thermally conductive straps 621.

[0078] One element of the system is what is referred to herein as a "thermal equilibration block". These elements serve as thermal bulkhead connections or joints between flexible thermal straps and their respective cryocoolers. The thermal equilibration blocks can be composed of any metal, such as high-purity copper or high-purity aluminum, and can be manufactured by any means, such as machining. Exemplary shapes are cubes or rectangular parallelepipeds. Exemplary dimensions are, for example, in the range of 2 to 10 cm in length and width and 1 to 5 cm in height, such as 5 cm in width, 5 cm in length, and 1.5 cm in height. Each thermal block can be connected to an inner floating shield, such as thermal blocks 615 and 620, as shown in FIG. 22.

[0079] Another element of the dry probe system is the "thermal link". These structures draw heat away from the element to be cooled. In some embodiments, the thermal link is substantially rigid or minimally flexible. In a preferred embodiment, the thermal link structure is slightly flexible to allow for some thermal contraction or vibration isolation, for example having a movement range of 2 to 10 mm. The thermal link can be configured, for example, as a strap or band including a plurality of metal foil layers, such as a structure including laminated foils including 2 to 10 layers of foils with a thickness of 2 to 5 mm. In other embodiments, the thermal link can include a cable, a rod, a structure including one or more joints, or other configurations that allow for a small range of movement. The thermal link material can include any thermally conductive material, such as high-purity copper, high-purity aluminum, or a carbon composition. One end of the thermal link is joined to a cryocooler, such as the second stage of a cryocooler. The other end of the thermal link is joined to a thermal equilibration block. The ends of the thermal link can be connected to the structure by screws, bolts, welding, brazing, or soldering.

[0080] Flexible thermal strap These elements must be conductive and flexible and have a range of motion, for example, from 20 to 200 mm, for example, from 50 to 100 mm. In the main embodiment, the strap includes a material having a high thermal conductivity. The strap may be planar or may include a cable. In one embodiment, the strap is substantially planar and is composed of a laminate of a plurality of layers, for example, two or more layers of foil, for example, from 5 to 30 layers, for example, from 10 to 20 layers, for example, eight layers. For example, the strap may include a stack of foils having a thickness of 0.25 to 2 mm, a width of 25 to 75 mm, and a length, for example, about three times the maximum horizontal range of motion. The foil layers may be connected together over the entire length of the strap, intermittently over the length of the strap, or, in the main embodiment, only at the ends of the strap, to form a plate for joining to other structures. The foil layers may be joined together by mechanical connections such as welding (e.g., TIG or diffusion welding), brazing, soldering, or screws. One end of each strap is connected to a thermal equilibration block and the other end is connected to a structure selected from a floating shield, a casing, a motion stage, or a chuck. For example, as shown in FIG. 22, strap 622 is connected to a lower floating shield (e.g., a 50K shield) and strap 616 is connected to an upper inner floating shield (e.g., a 4K floating shield). The strap may have its ends connected to the elements by mechanical connections such as welding (e.g., TIG or diffusion welding), brazing, soldering, or screws or bolts.

[0081] In the main embodiment, the material has a high or maximum thermal conductivity in the range of 15 to 35 K. Exemplary materials include copper, aluminum, alloys containing copper or aluminum, and other metals. For example, the strap may include copper or aluminum, for example, substantially pure copper or aluminum (e.g., 4N, 5N, or 6N purity). Exemplary materials include, for example, 101 copper, 1000 series aluminum, 5N pure aluminum or copper, or conductive crystals in filament or laminate form, such as silicon, sapphire, silicon carbide, and aluminum nitride.

[0082] Figures 23A and 23B are graphical representations of the range of motion achieved by the thermally conductive strap. The thermal equilibration block 700 has a flexible strap 701 attached thereto. A suitable mobile stage element 702 is attached to the other end of the thermal strap. In Figure 23A, the stage element 702 is shown in a first position. In Figure 23B, the stage element 702 is shown in a second position, and the range of motion is enabled by the flexible strap.

[0083] Figure 24A shows the flexible thermal strap. The strap 800 is composed of three foils 801, 802, and 803, and end plates 804 and 805 that include short sections where the layers of foil are joined together, for example, by welding, brazing, or soldering. The end plates are joined at one end to the thermal equilibration block and at the opposite end to the element of the mobile stage.

[0084] Wafer access door The wafer or other electronic component to be inspected is introduced from outside the outer housing to the chuck through a series of aligned gated slots, traversing any intervening casings. The gated slots can include a door that is lifted by an actuator under the control of a computerized control system.

[0085] Certain aspects of the present invention include a door assembly 150 positioned on a gate slot for providing continuous thermal casing while a wafer is being transferred into or out of the system. As seen in FIG. 1, access through gated slots 116a, 116b, 116c, and 116d is achieved by opening and closing the door assembly 150 connected to an actuator 154 via a support rod 153. It will be understood that the actuator 154 includes, for example, a motor that moves the support rod 153 in a vertical direction. The actuator is connected to control and power lines outside the outer housing, for example, by holes in the outer casing or conduits passing through the outer casing.

[0086] Referring to FIGS. 3A, 3B, and 3C, in certain aspects of the present invention, the door assembly 150 is positioned between the inspection zone casing 104 and the thermal buffer casing 125. Referring to FIG. 3C, in certain aspects of the present invention, the door assembly 150 includes a first door 151 disposed toward the inspection zone 113 and positioned adjacent to the inspection zone casing 104. Further referring to FIG. 3C, the door assembly 150 includes a second door 152 positioned adjacent to the thermal buffer casing 125. Generally, the first door 151 and the second door 152 have an area larger than that of the gated slots 116a, 116b, 116c, and 116d positioned on the casing. An enlarged side cross-sectional view of the door assembly positioned relative to the inspection zone casing 104, the magnetic shielding casing 105, the thermal buffer casing 125, the outer housing 124, and the gated slots 116a, 116b, 116c, and 116d is shown in FIG. 3B.

[0087] In certain embodiments, it is understood that the first door 151 insulates the cryogenic conditions of the inspection zone 113, which is set, for example, to 4K. The first door 151 may be referred to as the "inspection zone door" in certain embodiments. Also, as seen in FIGS. 1 and 3C, it is understood that the second door 152 insulates the thermally defined environment of the second thermal buffer zone 121. The second door 152 may be referred to as the "thermal buffer door" in certain embodiments. As seen in FIGS. 3A, 3B, and 3C, the first door 151 and the second door 152 are oriented in a coplanar orientation and are attached together with one or more insulating elements 155. The insulating elements 155 prevent thermal radiation and heat transfer from one door to another. Still referring to FIGS. 3B and 3C, a spring 157 provides the extension force for the first door 151 and the second door 152. Further, each door includes one or more thermally conductive strips of a material (such as a metal such as copper, aluminum, or an alloy thereof), herein referred to as a "thermal strip", that connects the door of the door assembly 150 to the casing to cool the door and assist in maintaining the cryogenic conditions in each of the thermally isolated zones. As seen in FIGS. 3A, 3B, and 3C, a thermal strip 156a connects the inspection zone door 151 to the inspection zone casing 104, and another thermal strip 156b connects the thermal buffer door 152 to the thermal buffer casing 125. The thermal strip has a sufficient thermal conductivity to effectively recover heat from the door and sufficient flexibility to move with the door as the door operates between the open and closed positions.

[0088] The inspection zone door 151 and the thermal buffer door 152 are attached to the actuator 154 by one or more support rods 153. In a particular aspect of the present invention, as seen in FIG. 3A, a plurality of support rods 153 are attached to the doors 151, 152 and further attached to the actuator 154. Referring to FIGS. 3A and 3C, a heat insulating element 159 can be seen at the connection between the actuator 154 and the doors 151, 152 to prevent heat radiation or heat transfer.

[0089] Wafer inspection system In one aspect, the scope of the present invention includes a system for inspecting a wafer under thermally defined and optionally magnetically isolated conditions by use of the probe station of the present invention. In the wafer inspection system of the present invention, a wafer supply system is located outside the probe station device of the present invention. The wafer supply system includes an apparatus for introducing and retrieving a wafer or other electronic component to be inspected to and from a chuck within a work zone for inspection. When the inspection is completed, the wafer supply system transports the wafer or other electronic component out of the device. In a particular embodiment, the wafer supply system includes a cassette or magazine where a plurality of wafers are held. The wafer supply system includes a retractable arm, such as a telescopic arm, the end of which may include elements for moving the wafer into and out of the probe station. The telescopic arm may include a gripper, clip or other actuating structure for gripping and releasing the wafer, generally in an exclusion zone of the wafer. The arm may be motorized or manual. In a main embodiment, the end of the wafer supply arm includes a paddle or other flat structure, on which the wafer is scooped up or lifted, and then the paddle or other flat structure moves into and out of the probe station. By the arm, the wafer is introduced to the chuck for inspection and retrieved therefrom after inspection. The wafer supply system holds the wafer in a vacuum and is separated from the outer housing of chamber 124 by a commercially available slot valve for opening and closing the boundary between two vacuum spaces, shown as 116d in FIG. 1.

[0090] In a particular embodiment of the present invention, the system includes a wafer handling robot. An exemplary wafer supply system is provided by Brooks Automation®.

[0091] In the wafer inspection system of the present invention, outside the probe station device, there is one or more computer control systems for the operation of the device. The one or more computer control systems include processor elements and software for the following: the association of the introduction and recovery of the wafer to the chuck; the operation of the clamp elements on the chuck for fixing and releasing the wafer; the movement of the column to facilitate the sealing of the inspection zone and any thermal buffer zone by the floating shield; the placement of the wafer and the contact between the wafer and the probe card; the operation of the probe card and the data collection therefrom; and the operation of the aligned doors of the gated slots and the control of the cryogenic environment. It will be understood that motors, actuators, signal and control wires, and other elements necessary for the achievement of the processes recited are included in the system of the present invention.

[0092] Vacuum chamber surface for equipment The scope of the present invention further encompasses a novel vacuum chamber design for use with precision equipment such as the probe station of the present invention. In many cases, measurements or other operations must be performed in a vacuum environment. In addition, in many cases, such vacuum operations require the movement of components with very high precision. For example, in the case of cryogenic wafer inspection, the placement of the wafer under the probe card requires the precise movement of the wafer with a tolerance in the range of about 1 to 15 microns.

[0093] High-precision operation of components can be achieved by many types of equipment. However, in order to maintain the tolerance in the micron range, it is essential that the surface on which the equipment is placed has extreme flatness. Flatness can be expressed as the deviation of the surface from a perfectly flat surface.

[0094] Metals can be easily machined and polished to a very high flatness and can serve as the base surface of precision instruments. General vacuum chamber bases are made of thick metals such as steel or aluminum alloys. However, metals have an inherent flexibility that poses a problem with respect to vacuum chambers, as the outer surface defining the vacuum chamber is subjected to enormous pressures when a vacuum condition is established inside. For example, a one-square-meter area with a vacuum on one side and standard atmospheric pressure on the other experiences an atmospheric pressure of approximately 23,000 lbf. These huge forces act on the metal base and can result in bending of the base and loss of flatness. Additionally, metals have high thermal conductivity and a significant coefficient of thermal expansion, so the temperature difference between the outer and inner surfaces of an ultra-low temperature vacuum chamber can result in substantial collapse of the metal's bending and flatness. On the other hand, metals are an ideal surface for achieving a high level of vacuum.

[0095] Accordingly, there is a need in the art for a new vacuum chamber design that provides an extremely flat bottom surface for the placement of precision instruments and maintains that flatness when operated under vacuum. The scope of the present invention encompasses a novel vacuum chamber base that includes a highly rigid slab including a substantially planar body on which a metal plate having a highly flat upper surface is mounted. In the novel assembly of the present invention, the slab has a very high flatness, a very high rigidity, and a high thermal inertia. Accordingly, the slab is highly resistant to the atmospheric and thermal forces that act to deform the metal vacuum chamber base. In various embodiments, the flatness of the working surface can range from less than 1 micron, less than 2 microns, less than 3 microns, less than 4 microns, less than 5 microns, less than 6 microns, less than 7 microns, less than 8 microns, less than 9 microns, or less than 10 microns.

[0096] The slab includes a high-rigidity material. In materials science, rigidity can be measured as the resistance of a material to deformation. Rigidity can be evaluated by the elastic modulus (also known as Young's modulus) E, and the larger the value of E, the greater the stress required to achieve deformation of the material. In one aspect, the slab includes a material with high rigidity, for example, with an elastic modulus exceeding 50 GPa, exceeding 60 GPa, exceeding 70 GPa, exceeding 80 GPa, exceeding 90 GPa, or exceeding 100 GPa in various aspects.

[0097] The high-rigidity material can include any high-rigidity material, such as organic materials, inorganic materials, synthetic materials, polymer materials, composites of various materials, and natural materials such as rocks. In one aspect, the base is made of rock. In one aspect, the slab is made of a high-rigidity rock, such as granite, diabase, gneiss, basalt, diorite, and other rocks known in the art. High-rigidity rocks include those with minimal pores and joints, and these properties can vary among rocks of the same type depending on the origin, composition, and rock formation process. Also, the anisotropy of the mineral structure affects rigidity, and higher anisotropy gives higher rigidity. Preferably, the material of the slab includes homogeneous isotropic granite. In one aspect, the rock is granite.

[0098] A working surface including a highly flat metal plate is attached to the slab to form the bottom inner surface of the vacuum chamber. The plate is attached to the slab by a plurality of fastening elements spaced at a density sufficient to maintain the flatness of the metal. By combining the metal plate with the slab, the properties unique to each material can be utilized. The metal plate is airtight and serves to seal the container. The metal plate can also be polished to a very high flatness. When joined to the slab, for example, a granite slab, by a sufficient number of fasteners, the high rigidity of the slab is imparted to the metal plate, enabling it to maintain a high flatness under severe vacuum and thermal forces.

[0099] The metal plate can include any number of high-strength metals, including steel, aluminum and aluminum alloys, such as ATP5, 6061, or others known in the art. The metal plate can have a thickness of, for example, 5 to 50 mm, for example, about 10 to 50 mm, for example, 15 to 25 mm. The metal plate can be a rectangular slab or prism, or can be disk-shaped, or can have an irregular shape, and the lateral dimensions (e.g., width and length or diameter) of the metal plate are selected to fit the size of the vacuum chamber.

[0100] The plate can include on its bottom surface several holes, such as threaded holes, produced, for example, by machining, which allow the plate to be screwed, bolted, or otherwise fastened to the slab. In a main aspect, the holes are blind holes that do not pass through the entire thickness of the plate, as shown, for example, in FIG. 14.

[0101] The holes are in a sufficient number to hold the plate firmly to the slab. The holes can be arranged in a grid or other pattern, such as a 3×3 cm grid, 5×5 cm grid, 7.5×7.5 cm grid, 10×10 cm grid, etc., as shown, for example, in FIG. 13.

[0102] The vacuum vessel plate can be fastened to the slab by any number of fasteners including bolts, screws, studs or tie rods. The use of studs, tie rods or similar structures is advantageous in that such fasteners can hold the vacuum vessel plate to the slab by tensile force.

[0103] In an alternative embodiment, the vacuum vessel plate is omitted and the vacuum vessel jacket or body is directly fastened to the slab, for example, by bolts, tie rods or other fasteners. In this embodiment, the upper surface of the slab becomes the base working surface and the upper surface has to be machined, for example, by grinding, lapping or other means to provide a flatness of a desired level, for example, less than 10 microns, for example, 5 - 7 microns. In this embodiment, if a porous material such as rock is used for the slab, there is a risk of compromising the airtight seal of the vacuum chamber. This effect can be reduced or substantially eliminated by the use of a sealant, in which case the upper surface of the slab is treated with a polymeric resin or similar material that can penetrate into the gaps of the uppermost layer of the rock and then cure or crosslink to create a substantially airtight upper surface. Exemplary resin materials include glycidyl-based resins, bisphenol A resins, BADGE or DGEBA-based resins, linear polyethers having glycidyl end groups, novolac epoxy resins, aliphatic epoxy resins, halogenated epoxy resins, epoxy resin diluents, glycidylamine epoxy resins. The resin can be cured by reaction with a curing agent to form a three-dimensional crosslinked thermoset structure. The curing can also be self-reactive or by the use of a curing agent or curing composition, for example, an anionic catalyst, polyfunctional primary amines, aliphatic amines, cycloaliphatic and aromatic amines, cyclic anhydrides, polyphenols, mercaptans and other agents known in the art. Exemplary commercial products include STYCAST (trademark) resins such as STYCAST 1266 (trademark).

[0104] The following is an explanation of an exemplary embodiment of the vacuum chamber base of the present invention. Referring to FIGS. 11 and 12, the vacuum chamber is attached to a vacuum vessel plate 401, and the vacuum vessel plate is further attached to a slab 400. The slab 400 is disposed on one or more adjustable legs 402. Referring to FIGS. 13 and 18, which show a bottom view of the probe station device, a plurality of adjustable legs 402 are disposed at the bottom of the slab 400. In a preferred embodiment, three adjustable legs 402 are utilized. The adjustable legs enable the horizontal adjustment of the device. It will be understood that the vacuum chamber may also be referred to as an outer housing 124. The outer housing 124 includes the vacuum vessel plate 401. The outer housing 124 is attached to the vacuum vessel plate 401, for example, by bolts 414, but it will be understood that the attachment may also be achieved by welding. Also contemplated is the outer housing 124 and the vacuum vessel plate 401 being a single piece. Referring to FIG. 12, a plurality of fasteners secure the base 400 to the vacuum vessel plate 401.

[0105] Referring to FIG. 14, which shows a side cross-sectional view in a particular aspect of the present invention, a plurality of fasteners 403 secure the vacuum vessel plate 401 to the slab 400. In a particular aspect of the present invention, referring to FIG. 15, the first end 415 of the fastener is located on the first side 416 of the slab and is attached to the vacuum vessel plate 401. The second end 417 of the fastener is located on the second side 418 of the slab and is fastened, thereby attaching the vacuum vessel plate 401 to the slab 400. The attachment creates an airtight joint sufficient to maintain a vacuum within the chamber with sufficient airtightness by use of bolts or other fasteners of appropriate size and spacing. Referring to FIGS. 14, 15, and 16, in a particular aspect, the fastener includes a stud 405 having a first end 406 and a second end 407. The stud first end 406 attaches to a fastening hole 413 located in the second surface 411 of the vacuum vessel plate 401. The stud passes through a through-hole 412 from the first side to the second side of the slab, and the second end 407 is fastened with a nut 409 located on the lower surface of the slab. In a particular aspect, a washer 408 is disposed adjacent to the nut 409. In a particular aspect of the present invention, one or more fasteners are fastened to the vacuum vessel plate 401 via a load distribution plate 404. The load distribution plate includes a flattened side surface that functions to distribute the compressive force of the fastener on the slab. As seen in FIG. 18, which shows a bottom perspective view of the probe station device, the load distribution plate 404 extends onto the surface of the slab 400 and is attached to one or more fasteners 403.

[0106] In certain embodiments of the present invention, referring to FIGS. 15 and 16, the vacuum vessel plate 401 includes a first surface 410 located at the upper part and a second surface 411 located at the lower part. Some or all regions of the first surface 410 have flatness within a specific flatness tolerance range. Equipment or devices that require such a specific flatness tolerance range are placed on such regions. In certain embodiments of the present invention, the second surface 411 of the vacuum vessel plate 401 further includes a plurality of fastening holes 413. In certain embodiments, the fastening holes 413 are connected to the second surface 411. In certain other embodiments, the fastening holes 413 are connected to both the second surface 411 and the first surface 410. The plurality of fastening holes 413 are aligned with the plurality of through holes 412 of the slab 400. A plurality of fasteners 403 fix the vacuum vessel plate 401 to the slab 400. In certain embodiments of the present invention, the distribution of the fastening holes 413 and the through holes 412 reduces possible perturbations on the first surface 410 of the vacuum vessel plate 401.

[0107] It will be appreciated that the combination of the vacuum vessel plate 401 and the slab 400 enables the vacuum vessel plate to maintain its shape under vacuum. It is important that the vacuum vessel plate 401, particularly the first surface 410 as seen in FIG. 17, maintains its flatness under vacuum conditions.

[0108] In certain embodiments of the present invention, the vacuum vessel plate 401 includes a material that is airtight so as to be able to maintain a vacuum. The vacuum vessel plate 401 includes, for example, a metal. Preferred materials include aluminum, stainless steel, copper, and their alloys. The material of the vacuum vessel plate 401 (e.g., aluminum) is airtight and suitable for interfacing with a vacuum, but it may also bend or deform under vacuum conditions. When the vacuum vessel plate 401 is attached to the slab 400 via a plurality of fasteners, it helps to reduce the bending that may occur under vacuum conditions and maintain the flatness of the vacuum vessel plate.

[0109] Vacuum surface preparation In certain aspects of the present invention, steps are taken to ensure the flatness of the first surface 410 of the vacuum vessel plate 401 (as seen, for example, in FIG. 17). It is particularly important to ensure that the area on the first surface where the equipment is placed has a high degree of flatness. Such an area of the first surface includes, for example, referring to FIG. 21, the first surface 410 of the vacuum vessel plate 401 that holds the motion stage 103. From FIG. 21, it can be seen that during the introduction of vacuum and cryogenic conditions into the apparatus 100, for example, the alignment of the probe card 108 in contact with the wafer 127 must be maintained.

[0110] Referring to FIG. 19, the steps taken to create the flatness of the vacuum vessel plate 401 include the following steps: (1) step 510 of identifying the area for creating the flat surface; (2) step 511 of marking a grid on the area; (3) step 512 of measuring and marking the relative distance from the reference surface; (4) step 513 of identifying the areas with the minimum and maximum relative distances; (5) step 514 of removing the surface material from the appropriate area; and (6) step 515 of repeating steps 1 to 5 until the flatness is achieved. In a particular embodiment, these steps are performed after the slab 400 is assembled with the vacuum vessel plate 401.

[0111] In the first step (1) step 510 of identifying the area for creating the flat surface, the area in the vacuum vessel plate 401 that requires flatness is identified and marked. Referring to FIG. 20A here, for example, the area 500 that requires flatness is located on the first surface 410 of the vacuum vessel plate 401. It can be understood that equipment, for example including a motion stage, is placed in this area.

[0112] In the second step, (2) step 511 of marking a grid on the area is performed. Referring to FIG. 20B, a grid 501 is marked on, inside, or near the area 500 located on the first surface 410 of the vacuum vessel plate 401. An exemplary embodiment of the grid 501 is shown, for example, in FIG. 20C.

[0113] In a third step, step 512 of measuring the relative distance from the (3) reference plane and marking is performed. Referring to FIG. 20B, the reference plane 502 can include a flat surface having a known flatness located on the reference block 505. The reference plane 502 of the reference block 505 is oriented parallel to the first surface 410 of the vacuum vessel plate 401. The reference block 505 may further be supported on the support block 504. The reference block and the support block can be moved along the slab 400, and the dial indicator 503 can be slid on the reference plane 502. The relative distance from the reference plane 502 to the vacuum vessel plate 401 is measured using the dial indicator and marked on the grid 501.

[0114] In a fourth step, step 513 of identifying the regions having the (4) minimum and maximum relative distances is performed. Referring to FIG. 20C, for example, a plurality of relative distances 506 between the reference plane and the vacuum vessel plate 401, measured using the dial indicator, are marked along the grid 501. The maximum and minimum relative distances can be marked along the grid. The relative distance measurements are used to identify the surface areas that require material removal to achieve a flatness within the flatness tolerance of the motion stage.

[0115] In a fifth step, step 514 of removing the surface material from the appropriate regions is performed. The material on the first surface of the vacuum vessel plate is removed, for example, by polishing, grinding, or other means of removing material from the surface.

[0116] In a sixth step, step 515 of repeating steps 1 - 5 until the flatness is achieved is performed. Further relative distance measurements are taken to confirm whether sufficient material has been removed. Further removal of the surface material is repeated until the appropriate flatness is achieved.

[0117] Exemplary embodiments Next, to illustrate certain concepts of the present invention, an exemplary embodiment of the present invention will be described. Refer to FIGS. 1 and 2 showing this exemplary probe station.

[0118] Referring to FIG. 1, a temperature-controlled inspection zone casing 104 surrounds an inspection zone area 113. The inspection zone casing surrounds an internal magnetic shielding casing 105. The inspection zone casing 104 and the magnetic shielding casing 105 surround the inspection zone 113.

[0119] A probe card 108 for the inspection device is located within the inspection zone 113. A bridge 107 provides a structure for supporting the probe card above the inspection substrate, and the terminals of the probe card are directed downward toward the inspection surface.

[0120] Still referring to FIG. 1, a chuck 102 including a planar inspection surface for receiving a semiconductor wafer 127. The chuck 102 includes a tensioned operable clamp element 126 that provides a force for holding the wafer 127 on the chuck surface. One or more cooling elements, such as a cryogenic heat exchanger 123, are present on the column 101 to create a cryogenic environment for the inspection zone 113. The inspection surface is maintained within a selected cryogenic temperature by cooling the casing 104 surrounding the inspection zone. Loading a bare wafer directly onto the chuck 102 set to cryogenic temperature results in the wafer being directly cooled. The inspection device includes inlet openings 116a - d located on a plurality of casings that provide access for loading an inspection substrate onto a receiving surface located within the inspection zone 113.

[0121] In certain embodiments, the thermal buffer casing 125 defines a second thermally defined environment of the thermal buffer zone 121 that is set to a temperature different from, for example, the first thermally defined environment of the inspection zone. In a typical embodiment, the first thermally defined environment of the inspection zone 113 is set to a lower temperature than the thermally defined environment of the second thermal buffer zone 121. In other embodiments, the first thermally defined environment and the second thermally defined environment are at the same temperature. The thermal buffer zone surrounds the thermally defined inspection zone environment and aids in its insulation against heat intrusion from the external environment. Still referring to FIG. 1, the probe station includes a central vertical column 101. The chuck 102 and its inspection surface are located at the first upper end of the column, and the inspection surface is located within the inspection zone chamber and is configured to receive an electronic component. A motion stage 103 is connected to the second lower end of the column, and the motion stage is configured to operate the column at least in the horizontal and vertical axes. In certain embodiments of the present invention, the motion stage moves the inspection surface in the horizontal directions (x and y axes), the vertical direction (z axis), and the rotational directions (φ, θ, ψ angles). The adjustment and alignment of the inspection substrate and the probe card are achieved by moving the column and its attached inspection surface and wafer laterally. The inspection substrate is raised and lowered to bring the circuit elements of the wafer into contact with the terminals of the probe card. The rotation of the inspection substrate further enables the alignment of the terminals of the probe card with the target sites on the wafer.

[0122] Referring to FIG. 1, column 101 extends through the bottom openings of the inspection zone casing, the magnetic shielding casing, and the thermal buffer casing and connects to the motion stage. A first floating shield 109 is oriented substantially perpendicular to the central axis of the column and covers the bottom openings of the inspection zone casing and the magnetic shielding casing. In certain embodiments, the first floating shield includes a magnetic shielding layer 111. The first floating shield covers the bottom of the inspection zone 113 to assist in magnetic isolation in the inspection zone chamber and maintenance of defined thermal conditions. The first floating shield has a diameter larger than the bottom openings of the first casing and the magnetic shielding casing, and lateral movement of the first floating shield maintains coverage of these openings. The first floating shield can be moved vertically. When raised, the vertical gap 112 between the bottom of the inspection zone casing and the upper portion of the floating shield is removed or reduced to a distance of less than 1 mm to effectively seal the inspection zone chamber and maintain the temperature conditions and magnetically shielded environment of the inspection zone. In certain embodiments of the present invention, gap 112 includes a distance of less than 1 mm, although distances greater than 1 mm are contemplated.

[0123] In the exemplary probe station of FIGS. 1 and 2, the inspection zone casing is surrounded by a thermal buffer casing. The thermal buffer casing includes a bottom surface further having a bottom opening. A second floating shield 119 covers the bottom opening of the thermal buffer casing to assist in surrounding the thermal buffer zone 121. The second floating shield 119 has a diameter larger than the bottom opening of the thermal buffer casing, and lateral movement of the second floating shield maintains coverage of the bottom opening during lateral actuation of the column. The second floating shield 119 can be moved vertically. When raised, the vertical gap 120 between the bottom of the thermal buffer casing and the upper portion of the second floating shield is removed or reduced to a distance of less than 1 mm to assist in maintaining the temperature conditions of the thermal buffer zone.

[0124] The outermost chamber defined by the outer housing 124 further includes a motion stage 103.

[0125] The foregoing description has been made with reference to exemplary orientations of the device, such as the upper, lower, lateral, and vertical aspects. This description is merely exemplary, and the device may be configured in any number of orientations, e.g., a device having a vertical orientation of the wafer, e.g., a device described herein where the vertical and horizontal axes are rotationally angled from the depictions of FIGS. 1 and 2. Similarly, in alternative embodiments, the floating shield of the present invention is configured to be located above the bottom opening of the casing.

[0126] Method of Use The scope of the present invention further includes a method of inspecting a circuit on a wafer or other electronic component using the device described herein. In a general method of the present invention, the inspection process includes a series of steps as follows: Lifting a wafer in a wafer supply system by an arm of the wafer supply system; Actuating a door that covers the aligned gated slots of some of the casings of the device to provide an opening for introducing the wafer into the inspection device; Extending the arm of the wafer supply system and the wafer thereon through a series of gated slots to introduce the wafer onto the planar inspection surface of a chuck located in a magnetically isolated and thermally defined inspection zone surrounded by a first casing and, if any, a magnetic shielding casing; Actuating a chuck mechanism by a lift pin that raises the wafer above the arm of the wafer supply system; Retracting the arm of the wafer supply system; Closing the door and the slot valve; Actuating a clamping element of the chuck to fix the wafer to the inspection surface of the chuck; Rapidly cooling the wafer to cryogenic temperatures within an inspection zone defined by an inspection zone casing; Actuating a motion stage to position the wafer in a selected alignment under a probe card; Moving a column vertically by the motion stage to bring the wafer into contact with pins of the probe card and simultaneously sealing an inspection zone chamber and any thermal buffer zones with a floating shield; Activating the probe card to inspect one or more circuits on the wafer and outputting an output signal to a data storage device or processing element outside the inspection device; Lowering the column to a position where the terminals of the probe card are not in contact with the wafer; Repeating the four steps one or more times to inspect multiple circuits or devices on the wafer; Actuating a series of aligned gates to provide an opening for an arm of a wafer supply system; Actuating a clamp element of the chuck to release the wafer; and Extending an arm of the wafer supply system into the inspection device, lifting and removing the wafer by the arm are included.

[0127] The cryogenic conditions of the inspection zone and the thermal buffer chamber can be selected based on desired inspection conditions. In a main aspect of the present invention, the inspection substrate is directly cooled to a temperature of 0K to 6K, such as 1K, 2K, 3K, 4K or 5K. In other aspects, it will be understood that the inspection substrate may be cooled to a temperature above 6K. In certain aspects, a thermal buffer casing surrounds the inspection zone casing and has a temperature of 0K to 150K. In a particular aspect of the present invention, the thermal buffer chamber has a temperature of 40 to 60K, such as about 50K.

[0128] The novel system of the present invention enables direct cooling of the bare wafer on the chuck, significantly reducing the time required for cooling. During the rapid cooling process, substantial thermal shrinkage is experienced by the wafer, but the inventors of the present disclosure have advantageously determined that silicon wafers resist tensile stress forces and do not break even during the rapid cooling process when clamped to the chuck at their edges. After inspection, while returning to ambient conditions, the wafer experiences substantial thermal expansion, but without any carrier body or chuck clamping mechanism and thus generally without being subject to forces that would cause wafer breakage.

[0129] All behaviors of electronic devices can be inspected by the apparatus and method of the present invention. In a main aspect, wafers, such as 150 mm, 200 mm or 300 mm wafers as known in the art, including, for example, cryogenic elements, i.e., devices configured to operate at ultra-low temperatures, such as superconductors, quantum computing circuits or other cryogenic devices, are inspected.

[0130] The dimensions of the part to be inspected influence the size of the parts of the wafer inspection system. For example, the housing, outer casing, inner casing, chuck, floating shield and other parts are sized to accommodate the wafer or other part to be inspected and the range of movement necessary to position all devices on the wafer or other part under the probe station. Exemplary systems can include, for example, an outer housing with a diameter of 500 cm to 2 meters, an inspection zone casing with a diameter of 25 to 100 cm, a 50K thermal buffer housing with a diameter of 400 cm to 1.5 meters, an outer housing height of 300 cm to 1 meter and a floating shield diameter of 300 cm to 1 meter.

[0131] With the system and method of the present invention, multiple wafers can be inspected very quickly while avoiding wafer breakage problems and avoiding the use of adhesives or greases that must be removed from the wafers. For example, in some embodiments, a processing speed of several hours per wafer can be achieved, whereas much longer times are required when using prior art wafer inspection systems.

[0132] Exemplary aspects The following sections describe various configurations and aspects of the wafer inspection system of the present invention.

[0133] Principal aspects In a principal aspect, a device for inspecting electronic components under controlled conditions, such as cryogenic conditions, includes an inspection zone housed by a thermally shielded housing including a bottom opening, the bottom opening being connected at a lower end to a motion stage and at an upper end to a vertical column connected to a chuck configured to receive an electronic component such as a wafer. A probe station is mounted above the chuck. The bottom opening enables the column to be moved laterally so that the entire working surface of the component clamped to the chuck can be accessed by the probe station. To maintain thermal shielding and controlled conditions in the inspection zone, the bottom opening of the inspection zone casing is shielded by a shielding element, the shielding element being a floating shield; a flexible bellows; or a combination of a floating shield and a flexible bellows including.

[0134] In one aspect, the device is configured as follows: a device for inspecting the device under defined thermal conditions, including an outer housing 124, within a chamber defined by the outer housing, A chuck 102 including a surface for receiving a device and one or more clamp elements 126 configured to operate to hold the device against the surface of the chuck, the chuck being connected to a motion stage 103 via a column 101, the motion stage being configured to operate the column in at least a lateral and a vertical direction, the chuck 102; A probe card 108 configured to contact a device with one or more terminals; An inspection zone 113 defined by an inspection zone casing 104 being located; the inspection zone casing surrounding the chuck and the probe card, the inspection zone casing and the outer housing including aligned slots in the same plane through which a wafer can be introduced to the chuck, the inspection zone casing including a thermal shielding material, the inspection zone casing including a bottom surface having an opening through which a thermally isolated inspection zone is accessed by the column, the thermally isolated inspection zone including one or more cooling elements 123, the probe card 108 being attached to the inspection zone casing by one or more support elements 107 and disposed on the inspection surface of the chuck; the bottom opening of the inspection zone casing being thermally shielded by a shielding element circumscribing the column; the shielding element being a floating shield; a flexible bellows; or a combination of a floating shield and a flexible bellows including, the apparatus.

[0135] In one embodiment of a main aspect, the shielding element includes a floating shield 109; the floating shield including a thermal shielding material; The floating shield has a horizontal upper surface that is wider than the bottom opening of the inspection zone casing and is configured to allow the column to be actuated laterally while maintaining coverage of the bottom opening of the inspection zone casing by the floating shield.

[0136] In one embodiment of the main aspect, the shielding element includes a flexible bellows. The flexible bellows can include foil, a spring wrapped in foil, or a fabric coated or impregnated with a heat shielding material. The bellows includes a tube, ring, skirt, or funnel having an upper edge and a lower edge. In various aspects, the bellows is concertinaed, pleated, corrugated, or folded so that it is compliant and can move over a range of motion. The upper edge of the bellows is connected to the inspection zone casing around its bottom opening. The lower edge is connected to the floating shield or the central column. In the case of the combination of the flexible bellows and the floating shield, the floating shield may be smaller than, equal to, or larger than the size of the bottom opening.

[0137] One or more cooling elements in the inspection zone include any structure or device that recovers heat from components enclosed within the inspection zone. One or more cooling elements can be located within the column. One or more cooling elements can be located on the outer or inner surface of the inspection zone casing.

[0138] In one aspect, the inspection zone includes one or more heat exchangers, for example, heat exchangers that include coils or other structures through which a liquid cryogen such as liquid helium, liquid nitrogen, or other liquefied gas flows. The heat exchanger can be provided with cryogen from lines within an outer housing that are connected to a pump and a cryogen reservoir outside the outer housing.

[0139] In one aspect, the cooling element includes one or more flexible straps. The flexible straps have sufficient thermal conductivity to cool the elements of the inspection zone to a desired temperature and have sufficient flexibility to move with the column as the column operates over its entire range of motion (defined by the inspection zone casing and the openings of any casing surrounding the same). In one aspect, the flexible straps include a plurality of foil layers, in one aspect 5 to 10 foil layers, and in one aspect each layer is 0.25 to 2 mm thick. In various aspects, the foil includes a metal such as copper, aluminum, or an alloy thereof. The flexible straps are connected to a cryocooler, such as a closed-cycle cryocooler, and the connection is by means of a thermal link structure.

[0140] In various aspects of the main embodiment, the device is configured to maintain the inspection zone at 1K, 2K, 3K, 4K, 5K, 6K or a higher temperature.

[0141] Magnetically shielded inspection zone In a second embodiment of the main aspect, the inspection zone is magnetically shielded by a combination of a magnetic shielding casing located within the inspection zone casing and having a bottom opening; and a floating shield and / or bellows. In one aspect, there is a floating shield, and the upper surface of the floating shield includes a layer of magnetic shielding material. In one aspect, there is a flexible bellows, and the flexible bellows includes a magnetic shielding material.

[0142] In one aspect, the second embodiment of the main aspect is an apparatus for inspecting electronic components under defined thermal conditions as in the main aspect, further including elements for magnetically isolating the inspection zone; including a magnetic shielding casing; the magnetic shielding casing including a magnetic shielding material; the magnetic shielding casing surrounding the chuck and the probe card; the magnetic shielding casing being surrounded by the inspection zone casing; The magnetic shielding casing includes a bottom surface having an opening through which a column is connected to the chuck; The magnetic shielding casing includes a slot covered by a door that can be actuated to open and close the slot, such slot being aligned with the aligned slots of the outer housing and the inspection zone casing; The floating shield and / or the flexible bellows include a magnetic shielding material, and may include a device.

[0143] Thermal buffer In various aspects of the main aspect, the inspection zone casing is enclosed within one or more concentric thermal buffer casings. In one aspect, a single thermal buffer casing surrounds the inspection zone casing. The one or more thermal buffer casings include a bottom opening through which a column connecting the chuck to the motion stage passes. The bottom opening has a width sufficient to allow lateral movement and positioning of the chuck so that the entire working surface of the electronic component can be accessed by the probe station, and the bottom opening of the inspection zone casing is thermally shielded by a shielding element circumscribing the column; The shielding element is a floating shield; a flexible bellows; or a combination of a floating shield and a flexible bellows and includes.

[0144] In one embodiment of the main aspect, the thermal buffer casing bottom opening shielding element includes a floating shield 119; The floating shield includes a thermal shielding material; The floating shield has a horizontal upper surface wider than the bottom opening of the thermal buffer casing, and is configured such that the column can operate laterally while maintaining coverage of the bottom opening of the inspection zone casing by the floating shield.

[0145] In one embodiment of the main aspect, the thermal buffer casing bottom opening shielding element includes a flexible bellows. The flexible bellows may include foil, a spring wrapped with foil, or a fabric coated or impregnated with a heat shielding material. The bellows includes a tube, ring, skirt, or funnel having an upper edge and a lower edge. The upper edge is connected around the bottom opening to the inspection zone casing. The lower edge is connected to a floating shield or a central column. In the case of the combination of the flexible bellows and the floating shield, the floating shield may be smaller than, equal to, or larger than the size of the bottom opening.

[0146] One embodiment of the main aspect is an apparatus for inspecting electronic components under defined thermal conditions as in the main aspect, including one or more thermal buffer zones; each of the one or more thermal buffer zones being defined by a thermal buffer casing; each of the one or more thermal buffer casings including a heat shielding material; one or more cooling elements being present in or on each of the one or more thermal buffer casings; each of the one or more thermal buffer casings surrounding the inspection zone casing; each of the one or more thermal buffer casings including a slot covered by a door operable to open and close the slot, such slot being aligned with the aligned slots of the outer housing and the inspection zone casing; each of the one or more thermal buffer casings including a bottom opening through which a central column passes; for each of the one or more thermal buffer casings, a thermal buffer floating shield disposed below the bottom surface of the associated thermal buffer casing circumscribing the central column; each thermal buffer floating shield including a heat shielding material; An apparatus in which each thermal buffer floating shield has a horizontal upper surface wider than the bottom opening of its associated thermal buffer casing, such that the column can operate horizontally while maintaining coverage of the bottom opening by the thermal buffer floating shield.

[0147] Each thermal buffer casing includes or surrounds one or more cooling elements. The one or more cooling elements can be located within the column. The one or more cooling elements can be located on the outer or inner surface of the thermal buffer casing. In one aspect, the thermal buffer casing includes or houses one or more heat exchangers, for example, heat exchangers including coils or other structures through which a liquid cryogen such as liquid helium, liquid nitrogen, or other liquefied gas flows. The heat exchanger can be provided with cryogen from lines within an outer housing connected to a pump and a cryogen reservoir outside the outer housing.

[0148] In one aspect, the cooling element includes one or more flexible straps. The flexible straps have sufficient thermal conductivity to cool elements of the inspection zone to a desired temperature and have sufficient flexibility to move with the column as the column operates over its entire range of motion (defined by the openings of the inspection zone casing and any casing surrounding the like). In one aspect, the flexible straps include a plurality of foil layers, in one aspect 5 to 10 foil layers, and in one aspect each layer is 0.25 to 2 mm thick. In various aspects, the foil includes a metal such as copper, aluminum, or an alloy thereof. The flexible straps are connected to a cryocooler, for example a closed cycle cryocooler, and the connection is by means of a thermal link.

[0149] In one aspect, the apparatus includes an inspection zone casing configured to be maintained at a temperature of 1 to 6 K and a thermal buffer casing configured to be maintained at a temperature of 35 to 80 K, in one aspect about 50 K.

[0150] Wafer chuck The scope of the present invention includes a novel chuck for receiving wafers and other devices. The chuck includes a receiving surface and surrounding clamping elements that hold the wafer 127 at its edge. The operation of the clamping elements is achieved by a rod, such as a push bar, connected to one or more electric actuators. In various embodiments, when the chuck is lifted by a central operating rod, it can create a receiving space for the wafer, and when released after the introduction of the wafer, it can retract downward due to the spring tension and clamp the wafer to the chuck surface, including two, three, four, five, or more spring-loaded clamps.

[0151] In a particular embodiment, the chuck 102 includes one or more operable clamping elements 126, which include clamps 300 attached to a cross member 306, the cross member being disposed below the receiving surface platform 305 of the chuck; A spring 302 forms a contact between the cross member and the platform; A plurality of vertical supports 301 are connected to the cross member 306 and pass through openings 303 located on the platform 305; A push bar 304 attached to the cross member 306 is configured such that when it is lifted upward relative to the platform 305, the spring 302 is compressed and a space is opened between the clamp 300 and the platform 305 for the delivery of the wafer 127 or other components introduced, in one embodiment, by a wafer supply arm 307; When the push bar 304 is released, the chuck is configured such that the spring 302 located between the platform and the cross member applies a force to the cross member 306, thereby lowering the cross member and, in turn, the clamping elements attached to the cross member, and the clamp 300 provides a downward force on the wafer 127 disposed on the platform 305; The chuck is configured such that the vertical support 301 is lowered simultaneously with the push bar being released so that the wafer can be lowered onto the surface of the platform 305.

[0152] The chuck of the present invention can be used in any situation where an electronic component or other test piece is fixed to a surface, for example, a surface connected to a motion stage. In one embodiment, the chuck of the present invention is utilized in an apparatus for inspecting an electronic component configured as in the main aspect.

[0153] Door with gate In one embodiment, the scope of the present invention includes a novel gated door assembly for transferring components such as wafers between chambers including two separate casings. The door assembly is located in the space between adjacent housing walls and there are slots in the adjacent casings that are aligned and coplanar. The door assembly includes a first door that is a planar body sized and shaped to cover a first slot in a first casing and an opposing second door that is a planar body sized and shaped to cover a second slot in a second casing, with the first slot and the second slot being aligned, i.e., coplanar. The doors include a thermal shielding material, in one aspect a metal such as aluminum, copper, steel or an alloy thereof. In one aspect, the door further includes an outer surface including a layer of magnetic shielding material. One or more spring elements between the doors bias the door elements in opposite directions and press them against the casings, and the one or more springs are separated from the doors by intervening thermal insulating elements that are in various aspects ceramic, polymeric or other thermal insulating materials that prevent heat transfer from the door to the one or more springs. The one or more springs are attached to a vertical push bar that is mechanically connected to an actuator so that the push bar can be moved up and down. During operation, the doors are positioned in a first position such that they cover the slots that are coplanar in the adjacent casings. By actuating the push bar, the door assembly can be moved up and down so that it slides above or below the slots and creates an open path for components, such as wafers, to pass through the aligned slots.

[0154] In some embodiments, the door assembly of the present invention is utilized in any system including two adjacent casing walls having slots that are coplanar. In one embodiment, the door assembly of the present invention is utilized in the main embodiment of the present invention, and in one aspect, the door assembly is present between an inspection zone casing and an adjacent thermal buffer casing and / or between a thermal buffer casing and an outer housing.

[0155] Vacuum chamber base In one embodiment, the scope of the present invention is a slab including a high-rigidity material; a vacuum vessel plate attached to the upper part of the slab by a plurality of fasteners and includes a base for use in a vacuum chamber, wherein the upper surface of the vacuum vessel plate has a high flatness.

[0156] In one aspect, the slab includes rock; in one aspect, the slab includes granite; in one aspect, the vacuum vessel plate includes metal; in one aspect, the vacuum vessel plate includes a metal selected from the group consisting of steel, aluminum, copper, and aluminum alloys; in one aspect, the flatness of the upper surface of the vacuum vessel plate is 1 to 15 microns. In one aspect, the vacuum vessel plate is attached to the slab by a plurality of studs or tie rods.

[0157] In one aspect, the present invention includes a slab including a high-rigidity material and having a high flatness upper surface; and includes a base for use in a vacuum chamber, wherein the upper surface of the slab is treated with resin to create an airtight material layer.

[0158] In one aspect, the present invention is an apparatus for inspecting a device under specified thermal conditions, an outer housing 124 including a vacuum vessel plate 401; the vacuum vessel plate includes a first surface 410 with a high flatness and a second surface; a slab 400 including a through hole 412; a fastener including a first end disposed on a first side of the slab and connected to the second surface of the vacuum vessel plate, and a second end disposed on a second side of the slab and fastened An apparatus is included that includes a fastener disposed within a through-hole of a slab. In one aspect, one or more adjustable legs 402 are attached to a second side of the slab. In one aspect, the slab includes granite. In one aspect, the second surface of the vacuum vessel plate further includes fastening holes; the fastener includes a nut and a stud having a first end and a second end, the stud is disposed within the through-hole of the slab, the first end of the stud is connected to the fastening hole of the vacuum vessel plate on a first side of the slab, and the second end is fastened to the nut on a second side of the slab.

[0159] In one aspect, the flatness tolerance is less than 6 microns.

[0160] The vacuum chamber base of the present invention can be utilized in any vacuum chamber. In one aspect, the vacuum chamber base is utilized as the base of the outer housing in the main embodiment of the present invention.

[0161] Wafer inspection system In one embodiment, the scope of the present invention includes an apparatus for inspecting a device as in the main embodiment, and further includes a wafer supply system located outside the outer housing of the apparatus for inspecting electronic components, the wafer supply system including a plurality of wafers and an arm operable to introduce a wafer into and remove a wafer from an inspection zone of the apparatus for inspecting electronic components, including a wafer inspection system.

[0162] Configuration The device of the present invention can be configured in any number of configurations. For example, the device of the main embodiment can be configured such that the bottom opening of the inspection zone casing is thermally shielded by a floating shield and / or a flexible bellows, with the following features: cooling by a liquid cryogen heat exchanger and / or cooling by a flexible thermally conductive strap; a magnetic shielding casing; one or more thermal buffer casings (the bottom opening of the one or more thermal buffer casings can be shielded by a floating shield and / or a flexible bellows); the chuck of the present invention; the door assembly of the present invention; and the vacuum chamber base of the present invention, all or a subset thereof can be combined.

[0163] Method of use The scope of the present invention further includes a method of using the devices and systems described herein. In one aspect, it is a method of inspecting an electronic component under defined thermal conditions, introducing, by an arm of an external component supply system, the electronic component through a series of aligned slots in an outer casing, any intervening thermal buffer casing, an inspection zone casing, and, if any, a magnetic shielding casing, into a chuck in a thermally isolated inspection zone of the device of the present invention; engaging a clamping element with the chuck to hold the electronic component on the chuck surface; moving, by a motion stage, a central column, the connected chuck, and the held electronic component horizontally to a selected position under a probe card; moving, by a motion stage, the central column, the connected chuck, and the held electronic component vertically such that the electronic component contacts one or more terminals of the probe card; and engaging the probe card to generate an input to the electronic component and record an output from the electronic component, A method is provided that includes these steps.

[0164] In one aspect, the electronic component is a wafer. In various aspects, the wafer includes a 50mm, 150mm, 200mm or 300mm wafer. In various aspects, the wafer includes a plurality of cryogenic elements, and in various aspects, the cryogenic elements include superconductors and / or quantum computing circuits.

[0165] In one aspect, the inspection process is performed while the wafer is maintained at a temperature of 1 - 6K.

Example

[0166] Example 1 A wafer probe station including a floating shield was constructed substantially as shown in FIGS. 1 and 2. The inspection zone was continuously maintained at approximately 4K. The thermal buffer zone was continuously maintained at approximately 50K. A 200mm wafer containing cryogenic elements was introduced into the system by a wafer supply system. The wafer was rapidly cooled, evaluated by the probe station, and removed at a throughput of several wafers per hour without breaking the wafer.

[0167] All patents, patent applications, and publications cited herein are incorporated herein by reference to the same extent as if each individual patent application or publication was specifically and individually indicated to be incorporated by reference. The disclosed aspects are presented for purposes of illustration and not limitation. The invention has been described with reference to its described aspects, but it will be understood by those skilled in the art that changes can be made to the structure and elements of the invention without departing from the spirit and scope of the invention as a whole.

Claims

1. An apparatus for inspecting a device under specified thermal conditions, comprising an outer housing defining a chamber, within the chamber defined by the outer housing, a chuck including a surface for receiving the device and one or more clamping elements configured to receive the device and operate to hold it against the surface of the chuck, the chuck being connected to a motion stage via a column, the motion stage being configured to operate the column at least in lateral and vertical directions, the chuck; a probe card configured to bring the device into contact with one or more terminals; an inspection zone surrounded by an inspection zone casing being located; the inspection zone casing surrounding the chuck and the probe card; the probe card being attached to the inspection zone casing by one or more support elements and disposed above the surface of the chuck; the inspection zone casing and the outer housing including aligned slots in the same plane through which a wafer can be introduced to the chuck, the inspection zone casing including a thermal shielding material, the inspection zone casing including a bottom surface having an opening through which the inspection zone is accessed by the column; the inspection zone including one or more cooling elements located within the inspection zone casing, on the inspection zone casing, or in the column, the opening in the bottom surface of the inspection zone casing being thermally shielded by a shielding element circumscribing the column; the shielding element being a floating shield; a flexible bellows; or a combination of a floating shield and a flexible bellows including, The inspection zone is (i) a magnetic shielding casing that includes a magnetic shielding material, is located within the inspection zone casing, surrounds the chuck, and has a bottom opening; and (ii) a floating shield or the flexible bellows that includes a magnetic shielding material magnetically shielded by a combination of the device. **Claim 2** The shielding element includes a floating shield; the floating shield includes a heat shielding material; the floating shield has a horizontal upper surface that is wider than the opening in the bottom surface of the inspection zone casing, and the column is operable laterally while maintaining coverage of the opening in the bottom surface of the inspection zone casing by the floating shield. The device according to claim 1. **Claim 3** The device according to claim 1, wherein the shielding element includes a flexible bellows. **Claim 4** The flexible bellows includes a concertina-shaped or pleated tube, ring, skirt, or funnel having an upper edge and a lower edge; the upper edge is connected to the inspection zone casing around the opening in the bottom surface, and the lower edge is connected to a floating shield or the column. The device according to claim 3. **Claim 5** The one or more cooling elements of the inspection zone include a heat exchanger through which a liquid cryogen flows, the device according to claim 1. **Claim 6** The device according to claim 5, wherein the liquid cryogen includes liquid helium. **Claim 7** The one or more cooling elements of the inspection zone include one or more flexible straps connected to a cooling stage of a cryocooler by a heat conducting element, the device according to claim 1. **Claim 8** The apparatus according to claim 7, wherein the one or more flexible straps comprise a plurality of layers of metal foil.

9. The apparatus according to claim 8, wherein the metal foil comprises copper, aluminum, or an alloy thereof.

10. The apparatus according to claim 1, configured to maintain the device in the inspection zone at a temperature of 1 to 6K.

11. The magnetic shielding casing surrounds the chuck and the probe card; The magnetic shielding casing is surrounded by the inspection zone casing; The magnetic shielding casing includes a bottom surface having an opening through which the column is connected to the chuck; The magnetic shielding casing includes a slot covered by a door operable to open and close the slot, the slot being aligned with aligned slots in the same plane of the outer housing and the inspection zone casing. The apparatus according to claim 1.

12. The inspection zone casing is surrounded within one or more thermal buffer casings; Each of the thermal buffer casings contacts or houses one or more cooling elements; Each of the one or more thermal buffer casings includes a bottom opening through which the column connecting the chuck to the motion stage passes; Each of the one or more thermal buffer casings includes a thermal shielding material; The bottom opening of each of the one or more thermal buffer casings is thermally shielded by a corresponding shielding element circumscribing the column; The corresponding shielding element is A corresponding floating shield; A corresponding flexible bellows; or The corresponding combination of a floating shield and a flexible bellows The apparatus according to claim 1, comprising

13. The apparatus includes one or more thermal buffer zones; Each of the one or more thermal buffer zones is defined by a corresponding thermal buffer casing of the one or more thermal buffer casings; Each of the one or more thermal buffer casings includes a thermal shielding material; One or more cooling elements are in contact with or present inside each of the one or more thermal buffer casings; Each of the one or more thermal buffer casings surrounds the inspection zone casing; Each of the one or more thermal buffer casings includes a slot covered by a door operable to open and close the slot, the slot being aligned with aligned slots on the same plane of the outer housing, inspection zone casing, and magnetic shielding casing; Each of the one or more thermal buffer casings includes a bottom opening through which the column passes; For each of the one or more thermal buffer casings, a thermal buffer floating shield disposed below the bottom surface of its corresponding thermal buffer casing of the one or more thermal buffer casings circumscribes the column; Each thermal buffer floating shield includes a thermal shielding material; Each thermal buffer floating shield has a horizontal upper surface wider than the bottom opening of its corresponding thermal buffer casing of the one or more thermal buffer casings, and the column is operable horizontally while maintaining the covering of the bottom opening by the thermal buffer floating shield. The apparatus according to claim 12.

14. The apparatus according to claim 12, comprising a single thermal buffer casing.

15. The apparatus according to claim 14, comprising an inspection zone casing configured to be maintained at a temperature of 1 to 6K and a thermal buffer casing configured to be maintained at a temperature of 35 to 80K.

16. The apparatus according to claim 15, wherein the thermal buffer casing is configured to be maintained at a temperature of about 50K.

17. The apparatus according to claim 12, wherein the one or more cooling elements of the inspection zone include a heat exchanger through which a liquid cryogen flows.

18. The apparatus according to claim 17, wherein the liquid cryogen includes liquid helium.

19. The apparatus according to claim 12, wherein the one or more cooling elements of the inspection zone include one or more flexible straps connected to a cooling stage of a cryocooler via a heat conduction element.

20. The chuck includes a receiving surface and one or more spring-type clamping elements surrounding the receiving surface of the chuck, and the one or more spring-type clamping elements are configured to hold the wafer at its edge to the chuck; The chuck is configured such that the operation of the one or more spring-type clamping elements is achieved by connection to a push bar in the column connected to one or more electric actuators; the operation of the push bar on the one or more spring-type clamping elements lifts the one or more spring-type clamps above the receiving surface of the chuck to create a receiving space for the wafer, and the release of the push bar pulls the one or more spring-type clamping elements downward to clamp the wafer to the receiving surface. The apparatus according to claim 1.

21. The apparatus includes a thermal buffer casing, and a door assembly is located between the adjacent thermal buffer casing and the inspection zone casing, The door assembly includes a first door including a planar body sized and shaped to cover a slot of the thermal buffer casing, and an opposing second door including a planar body sized and shaped to cover a slot of the inspection zone casing; The first door and the opposing second door include a thermal shielding material; One or more spring elements between the first door and the opposing second door bias the one or more spring elements in opposite directions to press against the thermal buffer casing and the inspection zone casing, and ends of the one or more spring elements are separated from the first door and the opposing second door by intervening heat insulating elements; The one or more spring elements connect to an element connected to a push bar, and the push bar is mechanically connected to an actuator so that the push bar can be moved to move the door assembly; The door assembly is configured such that actuation of the push bar slides the first door and the opposing second door to expose the aligned slots in the same plane of the outer housing and the inspection zone casing. The apparatus according to claim 1.

22. The apparatus includes a magnetic shielding casing within the inspection zone casing, The opposing second door includes a layer of magnetic shielding material. The apparatus according to claim 21.

23. The outer housing is attached to a base, The base includes a slab including a high-rigidity material; a vacuum vessel plate attached to an upper portion of the slab by a plurality of fasteners and; The upper surface of the vacuum vessel plate has a high flatness. The device according to claim 1.

24. The device according to claim 23, wherein the slab contains rock.

25. The device according to claim 24, wherein the slab contains granite.

26. The device according to claim 24, wherein the high flatness of the upper surface of the vacuum vessel plate is 1 to 15 microns.

27. The device according to claim 26, wherein the flatness tolerance of the upper surface of the vacuum vessel plate is less than 6 microns.

28. A method for inspecting an electronic component under specified thermal conditions, comprising: introducing the electronic component by an arm of an external component supply system into a chuck in a thermally isolated inspection zone of the device according to any one of claims 1 to 27; a step in which the electronic component is introduced through aligned slots on the same plane as the outer housing, and if any, any intervening thermal buffer casing, the inspection zone casing, and the magnetic shielding casing; engaging a clamping element with the chuck to hold the electronic component on the chuck surface; moving the column, the connected chuck, and the held electronic component horizontally to a selected position under the probe card by a motion stage; moving the column, the connected chuck, and the held electronic component vertically by the motion stage so that the electronic component contacts one or more terminals of the probe card; engaging the probe card to generate an input to the electronic component and record an output from the electronic component. A method comprising the above steps.

29. The method according to claim 28, wherein the electronic component is a wafer.

30. The method according to claim 29, wherein the wafer includes a plurality of cryogenic elements.

31. The method according to claim 29, wherein the inspecting method is performed while the wafer is maintained at a temperature of 1 to 6K.

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