EP3864690A1 - Appareil et procédé de serrage sous vide - Google Patents

Appareil et procédé de serrage sous vide

Info

Publication number
EP3864690A1
EP3864690A1 EP19802329.3A EP19802329A EP3864690A1 EP 3864690 A1 EP3864690 A1 EP 3864690A1 EP 19802329 A EP19802329 A EP 19802329A EP 3864690 A1 EP3864690 A1 EP 3864690A1
Authority
EP
European Patent Office
Prior art keywords
wafer
chuck
chuck surface
justifier
lip seal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19802329.3A
Other languages
German (de)
English (en)
Inventor
David T. LILLEY
Martin Bugg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nordson Corp
Original Assignee
Nordson Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nordson Corp filed Critical Nordson Corp
Publication of EP3864690A1 publication Critical patent/EP3864690A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/683—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping
    • H01L21/6838—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping with gripping and holding devices using a vacuum; Bernoulli devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67242—Apparatus for monitoring, sorting or marking
    • H01L21/67288—Monitoring of warpage, curvature, damage, defects or the like

Definitions

  • the present invention relates to a vacuum clamping apparatus for supporting a warped semiconductor wafer, and to a method of clamping a warped semiconductor wafer.
  • the invention relates to an apparatus for clamping a warped semiconductor wafer during bond testing.
  • Further aspects of the invention relate to a vacuum chuck and a justifier for a vacuum clamping apparatus, a bond testing apparatus, and a method of testing a bond on a semiconductor wafer.
  • Semiconductor devices are very small, typically from 5mm x 5mm square to 50mm x 50mm square, and typically comprise numerous sites for the bonding of electrical conductors to a semiconductor substrate. Each bond consists of a solder or gold ball deposit, known as a “bump”, a copper pillar, or a wire adhered to the substrate.
  • a solder or gold ball deposit known as a “bump”, a copper pillar, or a wire adhered to the substrate.
  • “Wafer” is a generic term for silicon, ceramic or compound materials which contain the desired semiconductor circuit.
  • a wafer typically consists of a thin layer of semiconductor material, with an upper surface onto which bonds may be attached. Wafers may typically be provided as round, circular, wafers, or as square or rectangular wafers that are sometimes referred to as“panels”. In the present document, the term“wafer” should be taken to include both round wafers and square or rectangular panels.
  • Semiconductor wafers may be provided in a variety of sizes.
  • standard round wafers used in the semiconductor industry can range in diameter from 50 mm to 300 mm, typically in 50 mm (2 inch) increments.
  • warping of wafers is a common problem experienced in wafer handling. Instead of being perfectly flat, warping may cause a wafer to flex into a non-flat shape that creates difficulties for further processing, particularly where wafer handling systems are automated.
  • the vacuum chuck has a flat chuck surface on which the wafer is positioned (either manually or by an automated wafer handling system), before a“justifier” with a flat contact surface is lowered onto the upper surface of the wafer to press the perimeter of the wafer downwards against the chuck surface.
  • the justifier presses the wafer onto the chuck surface to ensure good contact between the underside of the wafer and the chuck surface, and vacuum suction is applied through holes in the chuck surface to“suck” the wafer down onto the chuck surface.
  • the wafer is then“clamped” onto the chuck by the vacuum suction.
  • the justifier can then be lifted off the wafer, while the wafer is held still on the chuck by the vacuum during bond testing, and released after the test by releasing the vacuum pressure.
  • the invention may provide a vacuum clamping apparatus for supporting a warped semiconductor wafer, the apparatus comprising:
  • a vacuum chuck having a chuck surface for supporting the wafer
  • a justifier which is configured to press the wafer onto the chuck surface, so that the lip seal contacts the underside of the wafer and forms a seal between the underside of the wafer and the first portion of the chuck surface;
  • a vacuum source in fluid communication with the first portion of the chuck surface, for applying vacuum suction to attract the wafer onto the chuck surface.
  • the vacuum clamping apparatus may be operated similarly to the prior art vacuum chuck and justifier described in the background of the invention, above.
  • a wafer is positioned (either manually or by an automated wafer handling system) on the chuck, so that the wafer sits on top of and covers the first portion of the chuck surface and the lip seal.
  • the justifier is lowered onto the upper surface of the wafer to flatten the warped wafer, and press the wafer downwards against the chuck surface and the lip seal, so that the lip seal contacts the underside of the wafer and forms a seal between the underside of the wafer and the first portion of the chuck surface.
  • Vacuum suction is then applied through the first portion of the chuck surface so that any air between the underside of the wafer and the first portion of the chuck surface is evacuated.
  • the wafer is then“sucked” down onto the chuck surface, and held (or“clamped”) onto the chuck by the vacuum suction.
  • the justifier can then be lifted off the wafer, while the wafer remains held in place on the chuck by the vacuum suction. Bond tests, or further processing steps, may be carried out on the upper side of the semiconductor wafer (the side not facing the chuck surface) if desired.
  • the wafer may be released from the chuck surface by releasing the vacuum pressure.
  • the lip seal of this vacuum clamping apparatus advantageously provides an improved contact with the underside of a semiconductor wafer when it is positioned on the chuck surface.
  • the lip seal may advantageously improve the“vacuum clamping” effect on the underside of the wafer, and reduce the likelihood of warped edges of the wafer lifting off the chuck surface and break the vacuum seal.
  • the lip seal helps to prevent the warped wafer from “springing” away from the chuck surface.
  • the lip seal may thus advantageously allow a warped semiconductor wafer to be reliably clamped to the vacuum chuck.
  • the lip seal also performs the important task of assisting with the creation of the initial seal between the wafer and the chuck, and therefore allowing the propagation of the secure vacuum clamping pressure.
  • the underside of that wafer is still in the non-flat state, although it is flatter than if the wafer was simply resting on the chuck surface naturally.
  • the lip seal is somewhat compliant, then as portions of the warped wafer begin to contact the seal the wafer continues to flatten, and at the same time the compliant lip seal will deform slightly to contact the wafer as it deforms.
  • the combined effect of the wafer continually flattening and the lip seal deforming is that the vacuum seal initiates more easily than if the warped wafer were pressed simply onto a hard (aluminium) chuck surface.
  • the lip seal may form a ring, or a loop, around the first portion of the chuck surface.
  • the lip seal may encircle, or completely surround, the first portion of the chuck surface.
  • the lip seal may contact the underside of the wafer around the perimeter of the lip seal to form a seal between the chuck and the wafer.
  • the lip seal, the underside of the wafer, and the chuck surface may define an enclosed volume that is evacuated on application of the vacuum suction. This may improve the clamping effect of the vacuum suction (which may be termed“vacuum pressure”) on the wafer without requiring an increase in the vacuum pressure applied to the wafer.
  • the lip seal may be a flexible or resilient lip seal. This may allow the lip seal to maintain contact with the underside of the wafer even if a wafer edge flexes upwards by a short distance, for example when the justifier is lifted off the wafer.
  • the vacuum suction may be provided through holes or apertures in the chuck surface.
  • the chuck surface may comprise a plurality of grooves through which air may flow to the vacuum source.
  • the semiconductor wafer may preferably be a silicon wafer.
  • the justifier may comprise a justifier contact surface configured to contact an edge portion of the semiconductor wafer when the justifier presses the wafer onto the chuck surface.
  • the justifier may be configured to press an edge portion of the wafer against the lip seal, or to press the perimeter of the wafer against the lip seal or the chuck surface.
  • the justifier is preferably movable to be raised and lowered relative to the chuck surface. Wafers may be pressed against the chuck surface by lowering the justifier until the wafer contacts the lip seal, for example.
  • the justifier may comprise a plurality of guide pins configured to project towards the chuck surface, the guide pins having a tapered edge for contacting an edge of the wafer and guiding the wafer into alignment with the lip seal.
  • the tapered surface exerts a lateral force on the wafer edge as the justifier is lowered, so that the wafer is moved into its correct alignment with the justifier and the chuck surface. In its correct alignment, the wafer covers the lip seal and the first portion of the chuck surface.
  • the guide pins may project beyond the justifier contact surface, so that as the justifier is lowered towards the wafer and the chuck surface, the guide pins contact the wafer and guide it into alignment before the contact surface presses the wafer against the chuck surface.
  • the guide pins are preferably positioned so that the centres of the pins lie outside the intended perimeter of a correctly aligned wafer on the chuck surface.
  • the guide pins may be spring loaded. This may advantageously reduce the likelihood of damage to the wafer, for example if the wafer is severely misaligned and the guide pin contacts the upper surface of the wafer, rather than its edge, when the justifier is lowered.
  • the guide pins are preferably positioned on the justifier so that the plurality of pins are arranged around the periphery of the wafer’s intended position on the chuck surface. This may mean that, in whichever direction the wafer is misaligned, one or more of the guide pins will contact the wafer and guide it into alignment as the justifier is lowered towards the chuck surface.
  • the justifier preferably comprises three guide pins configured to contact the wafer at a plurality of positions around the wafer edge.
  • the justifier may comprise three, or four, or five, or more guide pins configured to contact the wafer edge when the justifier is lowered towards the chuck surface.
  • the justifier preferably comprises three or more guide pins positioned around a virtual circle with a diameter slightly larger than the diameter of the circular lip seal.
  • the guide pins may be on a virtual circle with a diameter at least 4 mm, or 6 mm, or 8 mm larger than the diameter of the lip seal.
  • the justifier may comprise four or more guide pins positioned on different edges of a virtual square with dimensions slightly larger than the dimensions of the square lip seal.
  • the guide pins may be on a virtual square with a length and width at least 4 mm, or 6 mm, or 8 mm larger than the length and width of the lip seal.
  • the chuck may comprise a plurality of holes configured to receive the guide pins when the justifier presses the wafer onto the chuck surface.
  • the shape of the lip seal is preferably configured to correspond to the shape of the wafers to be clamped to the wafer chuck.
  • the lip seal is preferably provided as a ring, encircling the first portion of the chuck surface.
  • the lip seal is preferably provided as a square, the sides of the square extending around and enclosing the first portion of the chuck surface.
  • the lip seal is circular, and the chuck is configured to support a circular semiconductor wafer.
  • the semiconductor wafer may have a variety of sizes, as mentioned above, but the chuck and the lip seal must be an appropriate size for use with the chosen wafer dimensions.
  • it is desirable that the lip seal is positioned close to the edge of the semiconductor wafer, so that the first portion of the chuck surface is in contact with a large area of the wafer’s underside. As the vacuum suction is applied through the first portion of the chuck surface, placing the lip seal close to the wafer edge maximises the area of the wafer on which the vacuum suction can act.
  • the clamping force is applied as close to the wafer edges as possible, as the warping of the wafers particularly affects wafer edges, and in order to allow bond tests to be carried out near wafer edges it is important that the wafer edges are securely clamped.
  • the chuck is configured to receive a circular semiconductor wafer with a predetermined diameter
  • the lip seal is circular and has an outer diameter that is 4 mm less than the wafer diameter, so that the lip seal contacts the underside of the wafer within 2 mm of the wafer periphery. Having the lip seal contacting the wafer within 2mm of the wafer periphery may advantageously mean that a good clamping force is applied up to the edges of the wafer.
  • the chuck is configured to receive a circular semiconductor wafer with a diameter of 300 mm, and the lip seal is circular and has an outer diameter of 296 mm.
  • the lip seal comprises a resilient lip configured to project above the chuck surface in a non-use configuration, the lip being configured to flatten relative to the chuck surface when the wafer is pressed onto the chuck surface by the justifier.
  • the resilient lip may stick up above the chuck surface when no wafer is positioned on the chuck, but when the wafer is in place and the justifier is applying a downwards force to press the wafer onto the chuck surface, the resilient lip preferably flattens to allow the underside of the wafer to come into contact with the chuck surface.
  • the resilience of the lip may advantageously mean that even if the edge of the wafer flexes upwards, for example during a bond test or when the justifier is removed after the vacuum is applied, the lip may maintain contact with the wafer to maintain the vacuum seal and the clamping effect.
  • the resilient lip may project above the chuck surface at an acute angle relative to the chuck surface.
  • the resilient lip projects 1.5 mm above the chuck surface in its non-use configuration.
  • the chuck comprises a groove configured to receive a portion of the lip seal.
  • the groove may receive a base portion of the lip seal from which the resilient lip projects upwards.
  • the chuck may comprise a plurality of lift pins which are retractable into the chuck when a wafer is supported on the chuck surface, and extendable out of the first portion of the chuck surface to lift the wafer off the chuck surface.
  • the lip seal is square, and the chuck is configured to support a square semiconductor wafer or panel.
  • a plurality of alignment members may be provided on the chuck surface, with at least one alignment member being positioned adjacent to each side of the square lip seal.
  • the alignment members are preferably positioned outside the perimeter of the lip seal and configured to guide the wafer into alignment with the lip seal. This may be particularly advantageous for an apparatus using square wafers, as the rotational position of the wafer may be more important than it is for a circular wafer.
  • Each alignment member may comprise a tapered surface sloping towards the lip seal.
  • the tapered edges may act similarly to the tapered surfaces of the guide pins described above, as a misaligned wafer edge may be urged towards its correct position as it makes contact and travels down the tapered surface.
  • the size of the chuck and the chuck surface is preferably selected to correspond to a predetermined wafer size
  • the lip seal preferably has the same shape as the wafer and is configured to contact the underside of the wafer around its periphery.
  • the lip seal has the same shape as the wafer and is configured to contact the underside of the wafer around its periphery no more than 5 mm, or 4 mm, or 3 mm, or 2 mm from the outer edge of the wafer.
  • the vacuum chuck may comprise two or more lip seals, each surrounding a portion of the chuck surface.
  • the two or more lip seals may have different dimensions. This may advantageously allow wafers of different sizes to be vacuum clamped on the same chuck surface.
  • the two or more lip seals may be arranged one within another on the chuck surface, to make efficient use of the space on the chuck. Particularly preferably, the two or more lip seals are arranged concentrically within one another on the chuck surface.
  • the chuck surface comprises a first lip seal surrounding a first portion of the chuck surface, and a second lip seal arranged outside the perimeter of the first lip seal, which encloses a second portion of the chuck surface.
  • the first and second lip seals may both be circular, for example.
  • the first lip seal may have a first diameter smaller than the second diameter of the second lip seal, and the first lip seal may be positioned concentrically within the perimeter of the second lip seal.
  • vacuum suction may be applied through the first portion of the chuck surface, so that the wafer is clamped on the chuck surface.
  • vacuum suction may be applied through both the first portion and the second portion of the chuck surface, so that the wafer is clamped on the chuck surface.
  • the justifier is preferably configured for the same requirement.
  • the justifier may comprise two or more contact surfaces, configured to contact wafers of different sizes and to press them against the chuck surface.
  • Each contact surface may be specifically sized to match the diameters of the wafers intended to be loaded onto the apparatus. This may advantageously mean that the apparatus can accommodate semiconductor wafers of different sizes.
  • the contact surfaces may be provided in the form of justifier clamp rings configured to contact semiconductor wafers around their periphery.
  • the justifier may comprise an inner justifier ring corresponding to the size and shape of the first lip seal discussed above, and an outer justifier ring corresponding to the size and shape of the second lip seal.
  • the apparatus may
  • the apparatus may be configured so that, if the larger of the two possible wafer sizes is loaded, then the larger (outer) of the two contact surfaces (for example the outer justifier ring) will lower to flatten that wafer against the chuck surface. If the smaller of the two possible wafer sizes is loaded, then the smaller (inner) of the two contact surfaces (for example the inner justifier ring) will lower to flatten that wafer.
  • the justifier-lowering mechanism controlling the downward travel of the justifier may be configured to lower only the“correct” contact surface to match the wafer size loaded onto the chuck.
  • the warped semiconductor wafer may comprise bonds on its upper surface.
  • the chuck may be configured to vacuum clamp the wafer onto the chuck surface during bond testing, such as during mechanical pull tests or shear tests.
  • the chuck is configured to be mounted on a bond test apparatus.
  • the bond test apparatus is preferably configured so that the position of the chuck may be controlled in x, y and z axes during bond testing.
  • the invention may provide a bond testing apparatus comprising a vacuum clamping apparatus according to the first aspect of the invention.
  • the features of the vacuum clamping apparatus, including the vacuum chuck and the justifier, may be as described above in relation to the first aspect of the invention.
  • the invention may provide a vacuum chuck comprising:
  • a vacuum source in fluid communication with the first portion of the chuck surface, for applying vacuum suction to attract the wafer onto the chuck surface;
  • the lip seal is configured to contact the underside of the wafer and to form a seal between the underside of the wafer and the first portion of the chuck surface.
  • the vacuum chuck may be a vacuum chuck for a vacuum clamping apparatus, or a vacuum chuck for a bond testing apparatus.
  • the lip seal improves the seal between the vacuum suction and the underside of the wafer, so that wafers are more reliably vacuum clamped on the chuck surface.
  • the chuck is particularly beneficial for vacuum clamping of semiconductor wafers that are warped out of their normal flat shape.
  • Such warped wafers must be flattened against the chuck surface and the lip seal so that the lip seal contacts the underside of the wafer and forms a seal between the underside of the wafer and the chuck. This allows the vacuum suction to suck the wafer down onto the chuck surface.
  • Warped wafers may be flattened manually, or by a separate apparatus configured to flatten and press the wafer against the chuck surface.
  • the vacuum chuck is advantageously usable with a justifier configured to press the wafer onto the chuck surface. Where the wafer is warped out of its intended flat shape, this may advantageously flatten the wafer and allow the lip seal to contact the underside of the wafer.
  • the vacuum chuck may form part of a vacuum clamping apparatus and/or a bond test apparatus.
  • the invention may provide a justifier for a vacuum clamping apparatus, the justifier comprising:
  • a plurality of guide pins configured to project towards the chuck surface, the guide pins having a tapered edge for contacting an edge of the wafer and guiding the wafer into alignment with the chuck surface.
  • the justifier may advantageously be usable with the vacuum chuck according to the third aspect described above.
  • the justifier may be usable with alternative vacuum chucks.
  • the justifier may be lowerable towards the chuck surface to press the wafer onto the chuck surface, and raisable away from the chuck surface.
  • the justifier and its guide pins may advantageously allow wafers to be automatically aligned with a predetermined position on the vacuum chuck, as the tapered surfaces of the guide pins move the wafer automatically as the justifier is lowered towards the chuck surface. This may be particularly advantageous where relatively large wafers must be positioned precisely on the chuck surface, or for example, where a wafer has warped out of shape, making it difficult to position accurately.
  • the justifier may comprise two or more contact surfaces, configured to contact wafers of different sizes and to press them against the chuck surface. Each contact surface may be specifically sized to match the diameters of the wafers intended to be loaded onto the apparatus. This may advantageously mean that the apparatus can accommodate semiconductor wafers of different sizes.
  • the justifier may be used in combination with a vacuum chuck comprising one or more lip seals, as described above, or it may be used with a prior art vacuum chuck without a lip seal.
  • the multiple contact surfaces may advantageously allow the justifier to press wafers of different sizes against the chuck surface, whether or not there is a lip seal on the chuck surface.
  • the contact surfaces may be provided in the form of justifier clamp rings configured to contact semiconductor wafers around their periphery.
  • the justifier may comprise an inner justifier ring corresponding to the size and shape of a first wafer, and an outer justifier ring corresponding to the size and shape of a second, larger, wafer.
  • the apparatus may accommodate
  • the justifier is preferably lowerable and raisable by a justifier-lowering mechanism.
  • the justifier-lowering mechanism may be configured to independently lower only the“correct” portion of the justifier with the contact surface matching the wafer size loaded onto the chuck.
  • the invention may provide a method of clamping a semiconductor wafer to a vacuum chuck, comprising the steps of:
  • the method is preferably a method of clamping a warped semiconductor wafer to a vacuum chuck.
  • the wafer is preferably pressed onto the chuck surface by a justifier.
  • the step of pressing the wafer onto the chuck surface preferably includes guiding the wafer into alignment with the first portion of the chuck surface and the lip seal with a plurality of guide pins with tapered edges, so that the tapered edges contact an edge of the wafer and guide the wafer into alignment.
  • the guide pins preferably project from the justifier towards the chuck surface.
  • the step of pressing the wafer onto the chuck surface preferably includes lowering the justifier towards the wafer and the chuck surface until the wafer is flattened against the chuck surface and the lip seal is in contact with the wafer.
  • the method of clamping is preferably a method of use of the vacuum clamping apparatus according to the first aspect. Further features of the method are described in relation to the other aspects of the invention.
  • the invention may provide a method of testing a bond on a semiconductor wafer, comprising the steps of:
  • vacuum suction may be ceased to release the wafer from the chuck.
  • the wafer may then be lifted off the chuck surface by a plurality of lift pins.
  • the method of clamping is preferably a method of use of the bond testing apparatus of the second aspect, and/or of the vacuum clamping apparatus, vacuum chuck, and justifier according to the other aspects of the invention. Further features of the method are described in relation to the other aspects of the invention.
  • Figure 1 A is a simplified front view of a bond test apparatus that may be used with the present invention
  • Figure 1 B is a cross-sectional view showing the test tool supported by the tool mounting bracket of the test tool cartridge of the bond test apparatus;
  • Figure 1 C is a perspective view showing the test tool clamped to the tool mounting bracket
  • Figure 1 D is a perspective view of a test tool mount and drive portions of the bond test apparatus, including an anti-backlash cylinder;
  • Figure 1 E is a perspective view of the test tool cartridge of the bond test apparatus
  • Figure 1 F is a perspective view of the bond test apparatus
  • Figure 2A is a perspective view photograph showing a warped silicon wafer
  • Figure 2B is a close-up view of the warped wafer shown in Figure 2A;
  • Figure 3A is a plan view of a vacuum chuck according to an aspect of the present invention.
  • Figure 3B is a schematic illustration of the lip seal and wafer arrangement in the vacuum chuck of Figure 3B;
  • Figure 3C is a schematic cross-section of a lip seal usable in a preferred embodiment of the vacuum chuck of Figures 3A and 3B;
  • Figure 4A is a perspective view of a vacuum chuck according to an aspect of the present invention.
  • Figure 4B is a plan view of the vacuum chuck of Figure 4A;
  • Figure 4C is a perspective view of the vacuum chuck with a wafer and a justifier according to an aspect of the present invention
  • Figure 4D is a perspective view of the vacuum clamping apparatus of Figure 4C, with a wafer handling unit;
  • Figure 4E is a side view of the vacuum clamping apparatus of Figure 4C, with the wafer raised off the chuck surface by lift pins;
  • Figure 4F is a view of a portion of the justifier and vacuum chuck of Figures 4A to 4E, with the justifier pressing the wafer onto the chuck surface;
  • Figure 4G is an enlarged view of the guide pin shown in Figure 4F;
  • Figure 5A shows a bond test apparatus comprising a vacuum clamping apparatus according to an aspect of the present invention
  • Figure 5B is an enlarged view of the vacuum chuck and justifier of the bond test apparatus of Figure 5A.
  • FIGS 6A to 10C illustrate preferred embodiments of the invention.
  • Figure 1A is an illustration of a bond testing apparatus usable with the present invention.
  • the apparatus comprises a test tool 10 mounted to a test tool cartridge 1 1 , which is itself mounted to the main body of the bond test apparatus 12.
  • the bond test apparatus Beneath the test tool, the bond test apparatus includes a motorized stage table 13, on which samples or substrates 100 to be tested can be mounted.
  • the motorized stage table 13 may include a vacuum chuck on which substrates 100 such as silicon wafers may be supported and held during bond testing.
  • the test tool 10, mounted to cartridge 1 1 can be a shear tool, push tool or a pull tool and can be switched in order to perform different tests.
  • Shear tools are used, for example, for applying a force horizontally across the board to shear a bond off the substrate, and push tools are used, for example, to apply a vertical compression force on a component on the substrate. The force applied by these tools is measured.
  • a pull tool may, for example, have a hook at the bottom of the tool that is used to hook an electrical lead, which is attached between a component and a sample circuit board, with a vertical force being applied to the tool to pull the lead off the board and measure the force required to pull the lead off the board.
  • An example of a suitable shear tool is described in US 6,078,387, the contents of which are incorporated herein by reference.
  • An example of a suitable pull tool is described in US 6,310,971 , the contents of which are incorporated herein by reference.
  • the test tool 10 is typically attached to the cartridge 1 1 by a tool mount bracket 70 having cantilever arms 72, 74 fixed at one end to the cartridge 1 1 by screws 73, with the free ends of the arms 72, 74 supporting a clamp 76.
  • the tool 10 is clamped in clamp 76 by means of clamp screw 78.
  • any suitable means for attaching a test tool to the cartridge mount plate may be used in a system in accordance with the present invention.
  • Figure 1 D shows the retaining channel 71 on the cartridge mount plate 21 into which the test tool cartridge 11 is slid and then secured using one or more screws 22.
  • the cartridge mount plate 21 includes a data port 23 that couples with an electrical connector on the test tool cartridge 1 1 for transferring data from the transducers of cartridge 11 to a PC, such as data representing the force required to shear a solder ball off a substrate or pull a lead off a substrate.
  • An interchangeable test tool cartridge design for a bond test apparatus is well known in the prior art. See for example the Dage 4000 multipurpose bond tester available from Dage Holdings Limited, 25 Faraday Road, Rabans Lane Industrial Area, Aylesbury, Buckinghamshire, United Kingdom.
  • the cartridge 1 1 is moveable in a z direction normal to the surface of the substrate 100 on the stage table 13. This allows the test tool 10 to be positioned vertically relative to the substrate 100 under test so that it can contact a particular bond during a test. Relative x-y movement between the test tool 10 and the table 13 in a direction parallel to the plane of the substrate 100 is typically achieved by moving the table 13. Movement of the table 13 in x and y is achieved using suitable servo motors or stepper motors, coupled to the table 13 via a lead screw and nut, ball screw and nut, or suitable belt-drive mechanism (not shown), as is also well known in the prior art, such as the Dage 4000 Multipurpose Bond Tester referenced above.
  • control devices comprising two joystick controls 14,
  • a display 17, a light 18 for illuminating the substrate 100 under test, and a microscope, aiding accurate positioning of the test tool 10, are also shown.
  • Figure 1 D shows that the mounting plate 21 and its connection to the main body 25.
  • the test tool (not shown in Figure 1 D) must be moveable towards and away from a substrate under test. This is achieved by moving the cartridge mount plate 21 , to which the test tool 10 is attached, relative to the main body 25 of the device in a direction towards and away from the substrate, herein referred to as the z-axis direction or axial direction.
  • the cartridge mount plate 21 is rigidly coupled to a moving block 24, using screws 75.
  • the moving block 24 is coupled to the main body 25 via a ball screw (or lead screw) and nut and nut block (not shown) that are driven by a servo motor or stepper motor 26.
  • an anti-backlash mechanism as described in US 9,170,189 may be included.
  • This mechanism is shown in Figure 1 D, and preferably comprises a pneumatic piston 27 and cylinder 28.
  • FIGs 2A shows an example of a vacuum chuck 200 with a warped silicon wafer 1000 on the chuck surface 210.
  • a flat wafer should sit flat against the chuck surface, allowing vacuum suction applied through holes in the chuck surface to suck down the wafer and hold it in place.
  • the wafer shown in Figure 2A is warped out of shape, so that opposite edges of the wafer are lifted upwards off the chuck surface.
  • Figure 2B shows a close-up of the wafer edge, which is warped so that the wafer edge is lifted 20 mm above the chuck surface 210. This means that the vacuum suction of a conventional prior art vacuum chuck is unable to“clamp” the warped wafer on the chuck surface using vacuum suction alone.
  • the present invention provides a solution to this problem by providing a vacuum chuck with a lip seal that forms a seal with the underside of the semiconductor wafer, as shown in Figures 3A to 3C.
  • Figure 3A shows a plan view of a vacuum chuck 300 with a chuck surface 310.
  • the chuck 300 is adapted to support a circular semiconductor wafer with a diameter of 300 mm.
  • a circular lip seal 320 is provided on the chuck surface 310.
  • the lip seal surrounds a circular first portion 330 in which a series of concentric circular and radial grooves are formed in the chuck surface.
  • a plurality of holes are also formed in the first portion 330 of the chuck surface, through which a vacuum source (not shown) in the chuck can draw air into the chuck.
  • the lip seal 320 has an outer diameter of 296 mm, so that when a 300 mm wafer (wafer outline 340 is shown on Figure 3B) is positioned on the chuck, the wafer is aligned to cover the lip seal and the first portion 330 of the chuck surface.
  • the lip seal therefore contacts the underside of the wafer around its perimeter, a distance of 2 mm from the wafer edge.
  • the vacuum source applies vacuum suction, air enclosed between the first portion 330 of the chuck surface, the lip seal 320 and the underside of the wafer 340 is evacuated, and the wafer is attracted down onto the chuck surface.
  • Figure 3C shows the cross-section of a preferred lip seal 320 usable in the vacuum chuck 300.
  • a base portion 350 of the lip seal 320 has a roughly rectangular cross-section, which may be received in a groove in the chuck surface 310.
  • a lip 360 of the lip seal projects upwards from the base portion 350 at an acute angle.
  • the lip seal 320 is formed from resilient material, for example rubber or synthetic rubber, so that the lip 360 is resiliently deformable.
  • the angle at which the lip 360 projects from the base portion allows the lip to deform downwards and flatten onto the base portion when a wafer (not shown) is pressed down onto the lip. When the wafer is removed, the resilient lip 360 returns to the uncompressed non-use configuration shown in Figure 3C.
  • Figure 4A to 4F show a vacuum clamping apparatus comprising a vacuum chuck 400 and a justifier 500.
  • the vacuum chuck 400 is similar to the chuck 300 of Figure 3A.
  • a circular lip seal 420 encircles a first portion 430 of the chuck surface 410.
  • the diameter of the lip seal and the dimensions of the chuck are selected depending on the size of semiconductor wafer to be clamped using the chuck.
  • the lip seal is shaped to correspond to the shape of the wafers for testing, and sized to contact the underside of the wafer approximately 2 mm from the wafer edge.
  • the chuck 400 contains a vacuum source (not shown) which is configured to draw in air from inlets (not shown) in the first portion 430 of the chuck surface 410.
  • the chuck comprises four retractable lift pins 450 which are movable between a retracted state (shown in Figures 4A and 4B) in which the lift pins do not protrude out of the chuck surface, and an extended state (shown in Figure 4E) in which the lift pins extend upwards out of the chuck surface 410 to lift a wafer 440 off the chuck.
  • Figure 4C illustrates the vacuum chuck 400 with a semiconductor wafer 440 placed on the chuck surface 410.
  • the wafer is positioned so that it sits over and entirely covers the first portion 430 of the chuck surface 410 and the lip seal 420.
  • a justifier 500 is positioned above the chuck surface 410.
  • the justifier can be lowered onto the chuck surface to press the wafer 440 onto the chuck surface 410, and raised off the chuck surface, by a lowering mechanism (not shown).
  • the justifier flattens the wafer onto the chuck surface as it is lowered onto the chuck surface 410.
  • the justifier 500 comprises a justifier clamp ring 510, the lower surface of which is a contact surface 520 configured to contact the edge of the wafer 440 and to press the edge of the wafer downwards when the justifier is lowered towards the chuck surface 410.
  • the inner diameter of the clamp ring is slightly less than the diameter of the wafer 440, so that the contact surface 520 contacts the wafer around its edge without contacting
  • Three spring-loaded guide pins 530 are mounted on the justifier and positioned approximately 120 degrees apart around the perimeter of the justifier 500.
  • the guide pins 530 project downwards from the justifier and extend below the level of the contact surface 520.
  • Each guide pin is tapered in shape so that a tapered surface 540 extends between its narrowed bottom end (facing the chuck surface) and its wider upper end.
  • the guide pins 530 are positioned so that they are slightly outside the intended circumference of a wafer in its correct position on the chuck surface 410.
  • Three holes 460 in the chuck surface 410 are positioned to receive the guide pins 530 as shown in Figures 4F and 4G when the justifier 500 is lowered against the chuck surface to flatten the wafer 440.
  • the justifier 500 also comprises an inner clamp ring 515 with a smaller diameter than the other“outer” justifier clamp ring 510.
  • the inner clamp ring 515 also comprises sprung guide pins, and is lowerable separately from the outer ring, so that either one of the justifier clamp rings may be lowered to press against a wafer on the chuck surface.
  • the two clamp rings of different sizes make the justifier usable with two different sizes of wafer.
  • This double-clamp-ring justifier design is particularly suitable for use with a chuck comprising two concentric lip seals corresponding to the two justifier clamp rings (not shown in the drawings).
  • a chuck comprising two concentric lip seals corresponding to the two justifier clamp rings (not shown in the drawings).
  • smaller wafers may be clamped between the inner clamp ring 515 and the smaller-diameter lip seal, and larger wafers may be clamped between the outer clamp ring 510 and the outer lip seal.
  • a semiconductor wafer 440 is placed on the chuck surface 410 by a wafer handler 470.
  • the wafer handler deposits the wafer as closely as possible to its intended position on the chuck surface, so that the wafer covers the first portion 430 of the chuck surface and the lip seal 420. If the wafer 440 is severely warped, however, the wafer handler may be unable to position the wafer with enough accuracy to correctly overlap the lip seal.
  • the justifier 500 is lowered towards the wafer and the chuck surface.
  • the contact surface 520 of the justifier clamp ring 510 contacts the edge of the wafer and pushes it downwards towards the lip seal 420 and the chuck surface 410.
  • the wafer 440 is warped and slightly misaligned with its intended position on the chuck, instead of contacting the contact surface 520 of the justifier, the wafer is first contacted by the tapered surfaces 540 of one or two of the justifier guide pins 530. As the justifier 500 is lowered further towards the chuck surface, the tapered surfaces 540 of the guide pins bias the wafer sideways towards its intended position. By the time the justifier is completely lowered, the wafer 440 is in its intended position aligned concentrically with the lip seal 420 and the justifier 500. In its final lowered position, the guide pins 530 are received in holes 460 in the chuck surface, and the contact surface 520 of the justifier is pressing the wafer 440 downwards against the lip seal and the chuck surface.
  • the vacuum source With the wafer 440 held against the chuck surface 410 by the justifier 500, the vacuum source is turned on and vacuum suction is applied through openings in the first portion 430 of the chuck surface. Any air trapped between the underside of the wafer 440, the lip seal 520 and the first portion 430 of the chuck surface is then evacuated, and the wafer is attracted down onto the chuck by the vacuum suction.
  • the justifier 500 may then be raised, while the wafer remains held down on the chuck surface 410 by the“vacuum clamping” effect of the vacuum suction. Further processing or bond testing may then be carried out on the upper side of the clamped wafer, as desired.
  • the wafer 440 may be released from the chuck 400 when desired, by stopping the vacuum suction, and extending the lift pins 450 out of the chuck surface to lift the wafer. The wafer may then be removed using the wafer handler.
  • Figures 3A to 4F illustrate the invention with a circular wafer and a circular lip seal
  • the apparatus may alternatively be adapted for use with a square or rectangular wafer or semiconductor panel by altering the shape of the lip seal and the justifier.
  • a version suitable for square wafers is shown in Figures 5A and 5B.
  • the apparatus may be adapted for use with wafers of different sizes by altering the dimensions of the chuck, lip seal and justifier.
  • a particularly preferred embodiment of the invention is illustrated in Figures 5A and 5B, where the vacuum clamping apparatus is part of a bond test apparatus 600.
  • the bond test apparatus 600 is similar to the apparatus described above in relation to Figures 1A to 1 F, with the vacuum chuck forming part of the motorized stage table 13.
  • the illustrated bond test apparatus 600 includes a square vacuum chuck 610 with a square lip seal 620 and a square justifier 630 connected to a justifier lowering mechanism 640 capable of lowering and raising the justifier relative to the vacuum chuck.
  • the vacuum chuck 610 comprises four alignment members 650 protruding upwards from the chuck surface.
  • the alignment members are positioned just outside the perimeter of the lip seal 620, with one alignment member 650 positioned adjacent to each side of the square lip seal.
  • Each alignment member comprises a tapered surface sloping towards the lip seal.
  • the operation of the vacuum chuck 610 and the justifier 620 is as described above in relation to Figures 4A to 4F.
  • the chuck is movable along x- and y- axes relative to the test tool in order to position the test tool relative to the wafer for bond testing.

Abstract

Un appareil de serrage sous vide pour supporter une tranche de semi-conducteur gauchie comprend un plateau de maintien à vide qui a une surface de plateau pour supporter la tranche et un joint à lèvre qui entoure une première partie de la surface de plateau. Un dispositif de justification est configuré pour presser la tranche sur la surface de plateau, de telle sorte que le joint à lèvre entre en contact avec la face inférieure de la tranche et forme un joint d'étanchéité entre la face inférieure de la tranche et la première partie de la surface de plateau. Une source de vide est en communication fluidique avec la première partie de la surface de plateau, pour appliquer une aspiration sous vide pour attirer la tranche sur la surface de plateau. L'appareil de serrage sous vide peut faire partie d'un appareil de test de liaison. L'invention concerne également un plateau de maintien à vide, un dispositif de justification, un procédé de serrage d'une tranche de semi-conducteur gauchie, et un procédé de test d'une liaison sur une tranche de semi-conducteur.
EP19802329.3A 2018-10-10 2019-10-09 Appareil et procédé de serrage sous vide Withdrawn EP3864690A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201862743936P 2018-10-10 2018-10-10
PCT/US2019/055395 WO2020076949A1 (fr) 2018-10-10 2019-10-09 Appareil et procédé de serrage sous vide

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EP3864690A1 true EP3864690A1 (fr) 2021-08-18

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Family Cites Families (10)

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Publication number Priority date Publication date Assignee Title
JP3689455B2 (ja) 1995-07-03 2005-08-31 キヤノン株式会社 情報処理方法及び装置
GB9724457D0 (en) 1997-11-20 1998-01-14 Dage Precision Ind Limited Test apparatus
US6521292B1 (en) * 2000-08-04 2003-02-18 Applied Materials, Inc. Substrate support including purge ring having inner edge aligned to wafer edge
KR101296157B1 (ko) * 2006-09-11 2013-08-19 주성엔지니어링(주) 기판 가장자리의 증착을 방지하는 기판처리장치 및 이를이용한 기판처리방법
EP2363702B1 (fr) 2010-03-05 2016-09-28 Nordson Corporation Testeur de résistance d'adhésion avec contrôle de jeu commutable
US8695990B2 (en) * 2010-04-01 2014-04-15 Nidec-Read Corporation Wafer flattening apparatus and method
US10014228B2 (en) * 2014-11-24 2018-07-03 Rudolph Technologies, Inc. Method and apparatus to assist the processing of deformed substrates
WO2016092700A1 (fr) * 2014-12-12 2016-06-16 キヤノン株式会社 Appareil de maintien de substrat, appareil de lithographie et procédé de fabrication d'articles
US20170053822A1 (en) * 2015-08-23 2017-02-23 Camtek Ltd. Warped wafers vacuum chuck
US10468288B2 (en) * 2016-10-19 2019-11-05 Kla-Tencor Corporation Methods and systems for chucking a warped wafer

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