Vacuum chuck and inspection device equipped with same

Abstract

To enable an inspection of a function of a semiconductor chip in a state of a wafer before it is divided into a chip even if a warping of the wafer is large.SOLUTION: A vacuum chuck comprises: a plurality of concentric circular first circumferential grooves that is formed on an upper side front surface of a vacuum chuck main body; a plurality of first holes that is extended to a vertical direction and is formed with an interval to a peripheral direction at each position of a plurality of first grooves; a first communication hole that is extended to a radial direction and communicates each first hole to the radial direction; a plurality of second holes that is formed to the peripheral direction with the interval at the plurality of concentric circular positions on the upper side front surface of a chuck main body; a second communication hole that is extended to the radial direction, and communicates each second hole to the radial direction; a second circumferential groove that is formed to an outside of the radial direction from the position that is the upper surface side of the chuck main body, and in which each first hole and each second hole are provided; and a ring-like elastic body that is fitted to the second circumferential groove. The second circumferential groove is a dovetail groove of which the upper surface part is narrower than a bottom part.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vacuum chuck for suctioning a semiconductor wafer and an inspection device equipped with the same, and more particularly to a vacuum chuck suitable for suctioning a warped semiconductor wafer and an inspection device equipped with the same. [Background technology]

[0002] As semiconductor devices become faster and more highly integrated, wafer-level packaging (WLP) is becoming more common, offering the advantages of reducing the mounting area and the effective inductance of wiring. WLP packages chips on a wafer, achieving greater bandwidth, speed, and reliability with less power consumption. These advantages enable a wider range of form factors to be offered for multi-chip packages used in mobile consumer devices, high-end supercomputing, games, artificial intelligence, and Internet-related products. High Bandwidth Memory (HBM), a type of WLP, connects multiple stacked memories to a single processor. Its fabrication involves forming a large number of ultra-wideband memory chips, generally rectangular in plan view, on a semiconductor wafer substrate, and then cutting the chips approximately 100 to 200 mm apart. 2 The semiconductor wafer is divided into a large number of ultra-wideband memories, each about the size of a single chip. In the ultra-wideband memory, the processor and the memory section, which consists of multiple memories (DRAMs) stacked vertically, are connected via a silicon interposer, and the connection between the processor and the memory section is connected to and mounted on a substrate via the silicon interposer.

[0003] When testing the functionality of ultra-wideband memories formed in this way, it is clear that testing each ultra-wideband memory in the wafer state immediately before separation is more efficient than testing each individual ultra-wideband memory chip formed by separating the semiconductor wafer. To test the ultra-wideband memories collectively in an unseparated semiconductor wafer, the semiconductor wafer must be flat so that the test probes can be easily positioned at predetermined positions while protecting them. However, as described below, wafers on which ultra-wideband memories are formed may be warped, and so currently, a method of individually testing the ultra-wideband memories separated from the semiconductor wafer is used.

[0004] On the other hand, there are also attempts to inspect general semiconductor chips, not just ultra-wideband memory chips, formed on warped semiconductor wafers while they are still in the semiconductor wafer state. A 12-inch wafer with a diameter of 300 mm and ultra-wideband memory chips formed on it can have, for example, more than 400 such chips. Even with the larger diameter, such wafers are only a few hundred microns thick, meaning the overall rigidity of the wafer is low. External forces applied during wafer processing, particularly during packaging, can easily cause warpage or undulation (deformation) in the wafer. Wafer warpage is measured by the difference in height between the periphery and center, and this value can be as much as several millimeters.

[0005] However, if a large-diameter wafer has a peripheral portion that is significantly warped compared to the center portion, even if the peripheral portion is vacuum-suctioned when the wafer is placed on the chuck, the conventional suction diameter results in the vacuum being drawn in from the surrounding air, and the peripheral portion of the wafer is not sucked into the chuck, and the warped state of the wafer remains. If an inspection is performed while the wafer is still in the warped state, the inspection probe may contact the wafer surface at an angle, and in the worst case, the wafer or the expensive probe may be damaged. To eliminate such defects caused by wafer warpage, various methods have been proposed to cancel the wafer warpage during wafer inspection.

[0006] Patent Document 1 describes a method for maintaining good flatness of a substrate, such as a wafer, even when the substrate is held by suction with significant warpage. Specifically, an annular recess is formed in the upper surface of the base at a position surrounding the opening of the communication path, and a lower element of a sealing member made of an annular elastic material is placed in the annular recess. Meanwhile, an upper element of the sealing member protrudes from the upper surface of the base. The upper element has a first portion extending upward while facing inward in the annular shape, and a second portion extending upward while facing outward in the annular shape.

[0007] Patent Document 2 also describes a work stage that vacuum-sucks a warped workpiece, comprising a base with a recess for supplying vacuum and a suction plate with multiple through holes that is attached to the recess. It also describes providing a sealing elastic body around the periphery of the suction plate that sucks and holds the warped workpiece.

[0008] Patent Document 3 describes a wafer processing machine with a suction cup structure that can suction-hold a wafer regardless of the wafer's flatness. Specifically, a cylindrical body made of an elastic material, such as a rubber plate, is provided around the periphery of the suction cup, expanding into a skirt shape and extending a predetermined length from the suction surface of the suction cup. This allows the cylindrical body to elastically deform in response to warping, undulations, or unevenness of the wafer surface, adhering closely to the wafer surface and forming an enclosure, even if a gap occurs between the wafer surface and the suction surface. As a result, the gap can be sealed, preventing air and grinding fluid from being sucked in through the suction groove. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2019-4017 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-153419 [Patent Document 3] Japanese Patent Application Publication No. 7-308856 Summary of the Invention [Problem to be solved by the invention]

[0010] The vacuum chuck described in Patent Document 1 has an annular recess formed on the periphery of a substantially circular ceramic base, and a seal member made of an elastic material is placed in the annular recess. The elastic material is bellows-shaped and contacts the wafer at its upper end surface. When vacuum-sucked, the bellows-shaped elastic material expands and contracts to suction the wafer to the base without changing the contact position between the wafer and the elastic material. This flattens the wafer and holds it in a predetermined position.

[0011] However, the vacuum chuck described in Patent Document 1 requires a large groove in the ceramic base to accommodate the bellows-shaped elastic body when it is compressed. Furthermore, because the bellows-shaped body is not a simple shape, there is a risk that a portion of the elastic body will deviate from smooth deformation and protrude in the in-plane direction between the top surface of the ceramic base and the backside of the wafer when it is compressed. If the elastic body protrudes from the groove, foreign matter may adhere to the backside of the wafer, and if foreign matter adheres, the wafer may be damaged by the suction force when the wafer is sucked. Furthermore, it may not be possible to position the wafer properly for inspection, and the wafer's height in the suction direction may change, making it impossible to ensure flatness, which may result in a collision with the probe. If the ultra-wideband memory's functionality is tested in a temperature-controlled environment, such as a low-temperature or high-temperature functional test, an improper wafer position may cause the set temperature to be off.

[0012] In the work stage described in Patent Document 2, a sealant is placed near the periphery of a rectangular base, and a workpiece is placed on top of it, while a rectangular perforated suction plate is placed in the space inside the base partitioned by the sealant. Vacuum suction is applied from the backside of the rectangular suction plate, causing the sealant to shrink and for the workpiece to conform to the flat suction plate.

[0013] However, because this work stage is intended for use in exposure applications, if a workpiece with significant peripheral warpage is placed on the work stage with a downward convex shape, before vacuum suction, the workpiece will not contact the sealant but will instead contact the suction plate at its center, making it difficult to eliminate the warpage and suction. To ensure that such a workpiece contacts the sealant before vacuum suction, the height of the sealant can be increased. However, even if the sealant height is increased, the center of the sealant, which is closer to the suction plate, will immediately contact the suction plate during vacuum suction, resulting in the workpiece being adsorbed with its warpage maintained or slightly reduced. On the other hand, if the workpiece is placed on the work stage with an upward convex shape, the workpiece can contact the sealant before vacuum suction. However, the center of the area partitioned by the sealant is too far from the suction plate, making it difficult to achieve sufficient vacuum suction, and the warpage will remain.

[0014] In the wafer processing machine described in Patent Document 3, a chuck holds a warped wafer by vacuum suction during processing such as peripheral grinding of the wafer. The chuck has an elastic body on the periphery, and after the backside of the wafer is abutted against the elastic body, the wafer is held in the chuck by vacuum suction. At the same time, by abutting the wafer against the elastic body, a gap is eliminated between the chuck and the wafer, preventing grinding water and other substances from penetrating the backside of the wafer. However, the processing machine described in this publication is only concerned with preventing the intrusion of grinding water, and does not take into consideration correcting the warpage of the wafer itself. In other words, no problems arise even if peripheral grinding and other processing are continued on the wafer while it is still in a warped state.

[0015] The present invention has been made in consideration of the above-mentioned drawbacks of the conventional technology, and its object is to enable functional testing of semiconductor chips in the wafer state before they are separated into individual chips, even for wafers with large diameters and therefore large warpage at the periphery. Preferably, it also has the object of enabling functional testing of semiconductor chips in the wafer state all at once. The functional testing includes testing in a temperature environment, and it is also an object of the present invention to achieve a uniform temperature environment for all semiconductor chips formed on the wafer. The present invention has the object of achieving at least one of these multiple objects. [Means for solving the problem]

[0016] The present invention, which achieves the above object, is characterized in that the vacuum chuck has a disk-shaped chuck body for vacuum-suctioning a semiconductor wafer, and includes a plurality of concentric first circumferential grooves formed on the upper surface of the chuck body, a plurality of first holes extending in the vertical direction of the chuck body and spaced apart in the circumferential direction at the positions of each of the plurality of first circumferential grooves, a first communication passage extending in the radial direction of the chuck body and communicating the first holes in the radial direction, and a plurality of circumferential holes formed at concentric positions on the upper surface of the chuck body. a second communication passage extending in the radial direction of the chuck body and communicating the second holes in the radial direction of the chuck body; a second circumferential groove formed on the upper surface of the chuck body radially outward from the positions where the first holes and the second holes are arranged; and a ring-shaped elastic body fitted into the second circumferential groove, wherein the second circumferential groove is a dovetail groove formed so that the radial width at the upper surface of the chuck body is narrower than the radial width at the bottom surface.

[0017] Another feature of the present invention for achieving the above object is a vacuum chuck having a disk-shaped chuck body for vacuum-chucking a semiconductor wafer, the vacuum chuck including a plurality of concentric first circumferential grooves formed on the upper surface of the chuck body, a plurality of first holes extending in the vertical direction of the chuck body and spaced apart in the circumferential direction at the positions of each of the plurality of first circumferential grooves, a first communication passage extending in the radial direction of the chuck body and communicating the first holes in the radial direction, and a plurality of concentric first circumferential grooves formed on the upper surface of the chuck body. a second communication passage extending in the radial direction of the chuck body and communicating the second holes in the radial direction of the chuck body; a second circumferential groove formed on the upper surface of the chuck body radially outward from the positions where the first holes and the second holes are arranged; and a ring-shaped elastic body fitted into the second circumferential groove, the elastic body being formed in the form of a ring-shaped tube or a solid O-ring made of a foam material.

[0018] In these features, it is preferable that the chuck further comprises a plurality of concentric third circumferential grooves formed on the upper surface of the chuck body, a plurality of third holes extending in the up-down direction of the chuck body and spaced apart in the circumferential direction at the positions of each of the plurality of third circumferential grooves, and third communication passages extending in the radial direction of the chuck body and communicating the third holes in the radial direction, wherein the plurality of third holes include holes located radially inward of the plurality of first holes and the plurality of second holes. Note that the first communication passage and the third communication passage may be combined.

[0019] In the above-mentioned features, it is preferable that the hole diameter of the plurality of second holes is larger than the hole diameter of the first hole, and in the vacuum chuck, a heater for heating the vacuum chuck, or a coolant passage through which a coolant capable of cooling the heater and the vacuum chuck flows, may be arranged below the portion where the first communicating passage and the second communicating passage are formed, and the sum of the radially arranged numbers of the first holes and the third holes may be greater than the radially arranged number of the second holes.

[0020] Yet another feature of the present invention that achieves the above object is that a wafer inspection device is provided with a vacuum chuck having any of the above features and a probe card that can simultaneously measure multiple semiconductor chips formed on the upper surface of the wafer. [Effects of the Invention]

[0021] According to the present invention, a vacuum chuck for suctioning a wafer and used for functional testing of a wafer has an annular groove formed near the outer periphery of the vacuum chuck, an elastic body is disposed in the vacuum chuck and fitted into the groove so as to protrude from the groove to a height greater than the amount of warpage of the wafer before vacuum suction, and a vacuum suction passage is formed near the groove, which enables functional testing of semiconductor chips in the wafer state before they are separated into individual chips.In addition, a uniform temperature environment can be achieved for all semiconductor chips formed on the wafer. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a front view of an embodiment of an inspection device according to the present invention; [Figure 2] FIG. 2 is a diagram illustrating an example of a semiconductor wafer inspected by an inspection device. [Figure 3] 1 is a perspective view of an embodiment of a vacuum chuck according to the present invention; [Figure 4] FIG. 4 is a top view of the vacuum chuck shown in FIG. 3. [Figure 5] FIG. 2 is a schematic cross-sectional view of a vacuum chuck. [Figure 6] FIG. 5 is a cross-sectional view showing a detailed shape of a suction part of the vacuum chuck shown in FIG. 4. [Figure 7] FIG. 10 is a cross-sectional view illustrating vacuum suction of a wafer. [Figure 8] FIG. 1 is a block diagram of a system for heating and cooling a vacuum chuck. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a vacuum chuck suitable for wafer inspection according to the present invention and an inspection apparatus equipped with the same will now be described with reference to the drawings. FIG. 1 is a front view of an embodiment of a wafer inspection apparatus 200 equipped with a vacuum chuck 100 according to the present invention. In this wafer inspection apparatus 200, electrical inspection is performed by simultaneously contacting multiple probes 264 of a probe card 266 with pads of semiconductor chips formed on a semiconductor wafer (hereinafter also referred to as a wafer) W. The electrical inspection also checks the operating state under various temperature conditions. For this reason, a means for heating and cooling the wafer W is generally provided.

[0024] 1, the wafer inspection apparatus 200 includes a base 236, a movable base 242 mounted on the base 236, and an XYZ-Θ table 240. A vacuum chuck (hereinafter also referred to as a chuck) 100 according to the present invention is disposed on the upper surface of the XYZ-Θ table 240. The vacuum chuck 100 holds a wafer W thereon and vacuum-sucks the wafer W. As will be described in detail later, the vacuum chuck 100 is connected to a temperature control system 300 provided in the control device 210, which enables control of the temperature of the wafer W placed on the vacuum chuck 100. In addition, a vacuum exhaust device 270 such as a vacuum pump is connected to the vacuum chuck 100 to ensure vacuum suction of the wafer W.

[0025] The XYZ-Θ table 240 includes an X-axis table 244 that moves the wafer W in the X direction (left and right in the figure), a Y-axis table 246 that moves the wafer W in the Y direction (depth direction in the figure), and a Z-axis table 248 that moves the wafer W in the Z direction (up and down in the figure). The XYZ-Θ table 240 further includes a Θ table 252 that rotates the wafer W around an axis in the vertical direction.

[0026] Support columns 218 are provided on the sides surrounding the XYZ-Θ table 240, and a head stage 234 is provided above it. An opening is provided in part of the head stage 234, and a card holder 262 is attached to this opening. A probe card 266 corresponding to the semiconductor chip 450 (see FIG. 2(a)) to be inspected formed on the wafer W is attached to the card holder 262. Furthermore, the probe card 266 is provided with a plurality of probes 264 that come into contact with the semiconductor chip 450. The probes 264 have a delicate structure in order to specifically contact minute terminals on the order of μm formed on the chip 450, and are designed not to apply excessive load. Therefore, the probes 264 are set to approach the wafer W in a predetermined posture and at a predetermined speed during inspection.

[0027] A test head 220 is rotatably provided on the upper end of the support column 218. A contact cylinder 268 is provided on the surface of the test head 220 that faces the probe card 266 when the test head 220 rotates, and transmits information detected by the probes 264 to the control device 210 via the test head 220.

[0028] The XYZ-Θ table 240 can move left and right in the figure via a moving base 242. When the wafer W is transported by the transport unit 230, the XYZ-Θ table 240 moves to the wafer information acquisition and setting position 204 on the right side of the figure, where the wafer W is placed on the vacuum chuck 100 and attracted thereto, and then acquires position information and chip 450 information using a camera 232 fixed to the head stage 234. After acquiring the wafer information, the XYZ-Θ table 240 moves to the inspection position 202 on the left side of the figure, where inspection is performed all at once using a probe 264. Here, "all at once" means that the XYZ-Θ table 240 is driven while the wafer W is still attracted to the vacuum chuck 100 to continuously inspect multiple chips 450, preferably all chips 450 formed on the surface of the wafer W.

[0029] 2 shows an example of a semiconductor wafer W that can be placed on and attracted by the vacuum chuck 100 according to the present invention. Note that the semiconductor wafer W that can be placed on and attracted by the vacuum chuck 100 is not limited to the one shown in FIG. 2, and any semiconductor wafer W can be placed on and attracted by the vacuum chuck 100. In particular, the vacuum chuck 100 has the special feature of being able to attract even a warped semiconductor wafer W.

[0030] 2(a) is a top view of a semiconductor wafer W, and FIG. 2(b) is a schematic side view showing an example of a large number of semiconductor chips 450 formed on the semiconductor wafer W. The semiconductor wafer W is a so-called 12-inch wafer with a diameter of φ300 mm, and more than 400 chips 450, each about 13.3 mm wide and about 10.9 mm long, are formed on a surface on which an orientation flat is formed.

[0031] The semiconductor chip 450 shown in FIG. 2(b) is called an ultra-high bandwidth memory (HBM) and includes a processor 410 and multiple layers (four layers in the figure) of stacked memory (DRAM) 420, with an interface (I / F) 426 disposed below the memory 420 in the stacked structure. The processor 410 and memory 420 are connected via a silicon interposer (interposer) 430, and the integrated processor 410 and memory 420 is connected to a semiconductor wafer substrate (silicon substrate) 400 via the silicon interposer 430. The processor 410 and silicon interposer 430, the silicon interposer 430 and the semiconductor wafer substrate 400, and the silicon interposer 430 and the interface 426 are connected using terminals 412, 402, 422, etc. formed on the respective parts, and the memories 420 are connected to each other by lead wires 424. The semiconductor chip 450 formed in this manner can cause distortion of the semiconductor chip 450, which is formed to a thickness of several hundred μm, due to the difference in weight between the processor 410 and the stacked memory 420, and the processing method used to form the chip 450.

[0032] An embodiment of the vacuum chuck 100 according to the present invention, which is included in the inspection apparatus 200 shown in FIG. 1, will be described with reference to FIGS. 3 to 6. FIG. 3 is a perspective view of the vacuum chuck 100, and FIG. 4 is a top view thereof. FIG. 5 is a schematic vertical cross-sectional view of the chuck body 190 included in the vacuum chuck 100, showing various examples of a chuck including a heating and / or cooling means for the wafer W. FIG. 5(a) shows an example of a chuck including only a heating means, FIG. 5(b) shows the most typical example of a chuck including both a heating and a cooling means, and FIG. 5(c) shows an example of a chuck including both a heating and a cooling means in which the vacuum suction unit and the cooling unit are integrated. In FIG. 5, the left half is a cross-section taken at position B in FIG. 4, and the right half is a cross-section taken at position A or C in FIG. 4. Figure 6 is a diagram for explaining the details of the suction holes and vacuum seals formed in the chuck body 190, where Figure 6(a) is a vertical cross-sectional view of the chuck body 190 for explaining the positional relationship of the suction holes, and Figure 6(b) is a cross-sectional view for explaining the fitting state of the elastic body.

[0033] The following description will be given using the standard vacuum chuck 100 shown in FIG. 5(b) as an example, but the other vacuum chucks 100 shown in FIGS. 5(a) and 5(c) are similar. As shown in FIG. 5(b), the vacuum chuck 100 includes a chuck body 190, which is a disk-shaped vacuum suction block located at the top, a disk-shaped cooling block 170 located below the chuck body 190, and a disk-shaped heating block 180 located below the cooling block 170. These blocks 190, 170, and 180 are integrated using bolts (not shown) or the like to form the cylindrical vacuum chuck 100. The cooling block 170 has multiple coolant passages 172 formed therein, through which a coolant, such as cooling water cooled by a chiller, flows. The heating block 180 is provided with a heater 182, which is wound in a spiral pattern.

[0034] A vacuum suction block 190 forming the top of the vacuum chuck 100 has conventionally been formed with a large number of holes and grooves for stably suctioning and holding the wafer W. In the present invention, in addition to these conventional holes and grooves, the vacuum chuck 100 is provided with new holes and grooves and elastic bodies 110 that fit into the grooves so that it can accommodate a warped wafer W.

[0035] 3 and 4, the chuck body 190 is formed in a circular shape with a diameter larger than that of the wafer W, and a plurality of first suction holes 154 are formed in the radial direction in the portion on which the wafer W is placed in order to suck and fix the flat wafer W. These suction holes 154 are provided at a plurality of locations in the circumferential direction (four locations, positions C in the figure), and are formed in a number of shallow grooves 152 formed concentrically. When the wafer W to be sucked has a diameter of about 300 mm, the number of grooves 152 is preferably 10 or more, more preferably 20 or more, and the number of suction holes 154 in the circumferential direction is preferably 4 or more.

[0036] The number of first suction holes 154 may be reduced on the central side (smaller diameter side) of the chuck body 190. The first suction holes 154 at the same circumferential position are connected by first communication passages 158 extending radially from the outer periphery. Vacuum suction pipe connections 120, to which vacuum suction fittings are attached, are provided on the outer periphery of the chuck body 190 in accordance with the positions of the first communication passages 158 (see FIG. 3), and are connected to a vacuum exhaust device 270 via pipes (see FIG. 1). As a result, the entire upper surface of the chuck body 190 is vacuum-suctioned.

[0037] In this embodiment, a push pin is provided in the center of the chuck body 190 to facilitate the removal of the wafer W from the vacuum chuck after the vacuum is released. Therefore, push pin holes 124 are formed at intervals around the circumferential direction of the vacuum chuck. As described above, various processes, including processes for disposing a temperature sensor (described later), are concentrated in the center of the chuck body 190. To avoid excessive processing, the first suction holes 154 are omitted near the center. Instead, third suction holes 156, which are primarily used to vacuum the center of the chuck body 190, are formed at a different circumferential position from the first suction holes 154 (position A in the figure). Similar to the first suction holes 154, a third communication passage 160 is also formed for the third suction hole 156, extending from the outer periphery toward the center of the chuck body 190. The diameters of the first suction holes 154 and the third suction holes 156 are set to be the same. By vacuum-suctioning the backside of the wafer W using these first and third suction holes 154, 156, in the case of a flat wafer W, the wafer W can be fixed and held on the vacuum chuck 100 without any hindrance, and various inspections can be performed according to the program in the inspection device 200. In this embodiment, the third suction hole 156 and the third communication path 160 are provided in positions separate from the first suction hole 154 and the first communication path 158, but one of the multiple first communication paths 158 and the corresponding first suction hole 154 can also be used as the third communication path 160 and the third suction hole 156.

[0038] However, in the case of a large-diameter wafer W in which the semiconductor wafer substrate 400 of the wafer W is very thin relative to its outer diameter, particularly in the case of a wafer W on which semiconductor chips 450 such as HBM are formed, the amount of warping becomes large at the peripheral portion, and even if suction is performed using only the first and third suction holes 154, 156, a gap may be formed between the wafer W and the vacuum chuck 100 at the peripheral portion. In this case, as described above, when inspecting the wafer W, there is a risk that the probe 264 may come into contact with the surface of the wafer W in a position different from the normal position. The probe 264 used for inspecting the wafer W is a delicate instrument, and if it comes into contact with the wafer W in a position different from the normal or predetermined position, this may cause damage to the expensive probe 264.

[0039] To prevent such problems from occurring, the present invention provides a circumferential groove 140 and second suction holes 132 that hold the wafer W, particularly its peripheral edge, flat. That is, a circumferential groove 140 is formed near the outer periphery of the wafer W where the φ300 mm wafer is placed, into which the sealing elastic body 110 can fit. Referring to FIG. 6(b), the cross section of the groove 140 is approximately trapezoidal with rounded corners, forming a dovetail groove in which the width W2 on the top surface of the chuck body 190 is narrower than the width W1 on the bottom surface.

[0040] The elastic body 110 that fits into the groove 140 is easily deformable, and the portion that protrudes from the groove 140 before vacuum suction remains within the width of the groove 140 during and after vacuum suction, preventing misalignment and getting caught between the wafer W and the chuck body 190, and ultimately being completely housed within the groove 140. The elastic body 110 is a tube made of silicone resin or tetrafluoroethylene resin, or a solid O-ring made of a foam material. Silicon resin is preferred as the foam material.

[0041] When the elastic body 110 is a tube made of tetrafluoroethylene resin, the tube 110 is cut to a predetermined length, formed into a ring shape, and held in the dovetail groove 140 while being deformed. When the tube 110 is held in the dovetail groove 140, the maximum diameter d1 portion of the tube 110 remains within the dovetail groove 140, maintaining almost the original outer diameter (corresponding to the nominal diameter) of the tube 110. In this state, the tube 110 has a natural height h0. This natural height h0 corresponds to the outer periphery of the wafer W to be inspected, or more precisely, the maximum allowable amount of warpage of the wafer W at the position where the elastic body 110 abuts.

[0042] That is, when the amount of warpage of the wafer W at the position where it contacts the elastic body 110 is h0 or less, the outer periphery of the wafer W is partitioned by the elastic body 110 when the wafer W is placed on the chuck body 190, and an airtight space can be formed between the chuck body 190 and the wafer W. This enables vacuum suction, as described below. On the other hand, when the warpage of the wafer W exceeds h0, a gap is formed at the periphery between the chuck body 190 and the wafer W, and even if vacuum suction is performed to flatten the wafer W, there is a risk of empty suction. Since the amount of warpage of most wafers W is 2 mm or less, in this embodiment as well, the size of the dovetail groove 140 and the size (diameter and thickness, or rigidity) of the tube 110 are set so that h0 is 2 mm or more.

[0043] Forming the dovetail groove 140 as described above creates a sealed space between the chuck body 190 and the wafer W. However, this sealed space is larger than the gap created when vacuum suction is performed using the first suction hole 154 and the third suction hole 156. Furthermore, a force must be generated to flatten the wafer W by suction, resisting the rigidity of the semiconductor wafer substrate 400 of the wafer W. Therefore, in this embodiment, second suction holes 132, which are larger in diameter than the first suction hole 154 and the third suction hole 156, are disposed centered on the outer diameter side of the chuck body 190. As shown in FIG. 4 , the second suction holes 132 are provided at multiple locations (four locations in this embodiment: locations B) circumferentially different from the first and third suction holes 154 and 156, and are located at multiple locations on the inner diameter side of the outer diameter location where the circumferential dovetail groove 140 is formed. In this embodiment, the second suction holes 132 are provided at five locations radially. The second suction holes 132 at the same circumferential position are communicated with each other by a second communication passage 136 formed from the outer periphery toward the center.

[0044] 6(a) shows the positional relationship between the first to third suction holes 154, 132, 156, the first to third communication passages 158, 136, 160, and the dovetail groove 140, superimposed in the circumferential direction. The diameters φD1 and φD3 of the first and third suction holes 154, 156 are approximately 1 mm, and they are formed at intervals in the radial direction of the chuck body 190. The first communication passage 158, which connects the multiple first suction holes 154, stops at a position radially outward of the third communication passage 160, which connects the multiple third suction holes 156.

[0045] The plurality of second suction holes 132, primarily for correcting warpage on the outer periphery of the wafer W, have a diameter φD2 of approximately 2 to 3 mm, which is several times larger than φD1 and φD3. The second suction holes 132 are radially spaced between the first suction holes 154 and are formed at multiple locations around the large-diameter side of the chuck body 190. Second communication paths 136, which connect the second suction holes 132, extend from the outer periphery toward the center of the chuck body 190, and their lengths are generally shorter than those of the first communication paths 158. The arrangement of the second suction holes 132 indicates that the second suction holes 132 contribute to correcting warpage on the outer periphery of the wafer W. A full-circumferential groove 152 having a depth of 1 mm or less is formed at the radial positions of the chuck body 190 where the first suction holes 154 and the third suction holes 156 are formed, thereby reducing uneven suction. Furthermore, the number of first suction holes 154 and second suction holes 132 in the circumferential direction is approximately the same, but in the radial direction there are approximately 10 to 25 first suction holes 154, while there are approximately 5 second suction holes 132. Therefore, if third suction hole 156 is also included, the total number of first and third suction holes 154, 156 is greater than the number of second suction holes 132.

[0046] The dovetail groove 140 having a trapezoidal cross section is disposed on the outer diameter side of the first to third suction holes 154, 132, and 156. In other words, the dovetail groove 140 is located on the outer diameter side of the circumferential groove 152 on the outermost peripheral side or the first suction hole 154, and is a seal groove that prevents the first to third suction holes 154, 132, and 156 from sucking air on the outer diameter side of the dovetail groove 140.

[0047] FIG. 7 shows a schematic diagram of an example of suctioning a large-diameter wafer W using the vacuum chuck 100 of the present invention configured as described above. The vacuum suction method is not limited to this method, and suction may be performed simultaneously through all suction holes or through different types of suction holes. FIG. 7(a) shows a state in which a wafer W is placed on the chuck body 190. Vacuum suction is not being performed, and the convexly warped outer periphery of the wafer abuts against the bottom of the elastic body 110, forming a sealed space between the wafer W and the elastic body 110. Only the weight of the wafer itself acts on the elastic body 110. At this time, the elastic body 110 is statically settled at approximately its natural height or a slightly deformed height h0.

[0048] From this state, as shown in Fig. 7(b), the center of the wafer W, which is substantially flat and has little warpage, is first vacuum-sucked using the third suction holes 156. This prevents the wafer W from moving within a horizontal plane during vacuum suction. By fixing the wafer W to the chuck body 190, it is possible to prevent the wafer W from shifting position due to airflow generated when the peripheral edge is vacuum-sucked as shown in Fig. 7(c).

[0049] Next, vacuum suction is performed from the second suction hole 132 together with the first suction hole 154. Note that vacuum suction from the first suction hole 154 may be started after the wafer W has been flattened by vacuum suction from the second suction hole 132. The second suction hole 132 has a diameter several times larger than that of the first suction hole 154, and therefore has a large suction force, making it possible to flatten the wafer W despite the rigidity of the wafer W. As described above, suction from the second suction hole 132 generates a large force, and therefore a force that moves the wafer W in a horizontal plane is likely to be generated. For this reason, suction from the third suction hole 156 and the first suction hole 154 is used in combination.

[0050] Once the wafer W is sucked into the chuck body 190, the sealing action of the elastic body 110 prevents leakage from between the wafer W and the chucking surface 102 of the chuck body 190, so vacuum chucking can be achieved by using only suction from the first and third suction holes 154, 156, or by using a small amount of suction from the second suction hole 132 in combination.

[0051] Figs. 7(d) to (f) are diagrams schematically showing an enlarged state of the elastic body 110 in the ant groove 140 in each state shown in Figs. 7(a) to (c). When the back surface of the wafer W is brought into contact with the elastic body 110 in a state where vacuum suction is not performed, the height of the elastic body 110 from the suction surface 102 of the chuck body 190 becomes about the natural height h0. On the other hand, when only the central side of the wafer W is sucked, the elastic body 110 slightly reduces its height, and the height from the suction surface 102 becomes h1 (<h0). Next, when the wafer W is flattened by vacuum suction from the second suction hole 132, the entire elastic body 110 is substantially accommodated in the ant groove 140 without protruding from the ant groove 140. As a result, the wafer W is completely flattened, and it is possible to prevent the wafer W from tilting and coming into accidental contact with the probe 264.

[0052] Fig. 8 shows a temperature control block diagram of the wafer W using the heating / cooling block shown in Fig. 5. Here, the heating / control of the wafer W will be described by taking the case of the standard vacuum chuck 100 shown in Fig. 5(b) as an example, but the same applies to other vacuum chucks (Figs. 5(a) and (c)). The vacuum chuck 100 on which the wafer W is placed has a built-in heater 182, and although not shown, a coolant flow path is also formed inside.

[0053] The coolant flow path is connected to a cooling unit (cooling device) 314 provided in a chiller unit 310 disposed remotely from the inspection device 200 by a coolant pipe 316. The coolant pipe 316 has a forward pipe 316a for feeding the coolant generated in the chiller unit 310 to the vacuum chuck 100 and a return pipe 316b for returning the coolant heated in the vacuum chuck 100 to the chiller unit 310. The cooling unit 314 is controlled via a signal line 308 by a chiller control unit 312 provided in the chiller unit 310. The heater 182 built in the vacuum chuck 100 is connected to a heater controller 324 provided in a temperature control device 320 by a power line 338, and power is supplied from the heater controller 324.

[0054] To uniformly control the surface temperature of the vacuum chuck 100 to a predetermined temperature, for example, between −10°C and +100°C, using the heating and cooling mechanism configured as described above, temperature sensors 334 are embedded at five different points on the vacuum chuck 100. The output of the temperature sensor 334 is input to a 5-channel conversion board (A / D converter) 332, where it is converted into a digital signal, and input to a main control device 322 included in the temperature control device 320 via a signal line 336. The main control device 322 is connected to a heater controller 324 via a signal line 326 and also to a chiller control unit 312 via a signal line 318. Therefore, the temperature of the chucking surface 102 of the vacuum chuck 100, in other words, the temperature of the wafer W, detected by the temperature sensor 334 is fed back to control the temperatures of the heater 182 and the coolant. At this time, the detection result of a prober (CPU) 222, which is an inspection means disposed opposite the wafer W, is also fed back to the temperature control device 320.

[0055] As described above, with the vacuum chuck of this embodiment, even a large diameter wafer of 300 mm with a warped edge can be sufficiently flattened as long as the warpage is up to about 2 mm, making it possible to perform functional tests on the wafer in one go. Furthermore, it was confirmed that if the wafer warpage is downward convex, it can be reliably flattened to the above-mentioned warpage range, and even if the warpage is downward convex, it can be reliably flattened up to about 2 mm.

[0056] In addition, in tests and inspections in which wafers W were temperature-controlled using this vacuum chuck 100, warpage tended to increase at high temperatures compared to room temperature. As a result, a warpage of 2 mm at room temperature increased to 4 mm at 100°C, and even if vacuum suction was attempted at that temperature, a gap exceeding the allowable warpage was formed, making vacuum suction impossible. This problem could be addressed by timing the vacuum suction to room temperature and raising the temperature of the wafer from room temperature to the test and inspection temperature while it was still under vacuum suction. This demonstrated that even at high temperatures, wafers W with a warpage of only about 2 mm at that temperature could be successfully tested and inspected regardless of the temperature.

[0057] While the elastic body is a tube in the above-described embodiment, a solid foam resin can be used. When vacuum suction is applied, air is sucked from the internal bubbles, causing the entire elastic body to shrink and deform so that it fits into the dovetail groove. Therefore, similar to a tube-type elastic body, the elastic body can be prevented from protruding radially inward or outward from the dovetail groove during vacuum suction, preventing the wafer from being sucked at an angle, thereby flattening the wafer. When a foam material is used, the solid material allows the wafer to almost completely return to its pre-vacuum state and regain its rigidity even after the vacuum suction is released. Therefore, when a new wafer is placed, the same condition as the previous wafer can be reproduced. This means that wafers with the same degree of warpage can be tested. This prevents damage to the probes on the probe card due to improper contact between the probes and the wafer. [Explanation of symbols]

[0058] 100...vacuum chuck, 102...suction surface, 110...elastic body (tube or foam O-ring), 120...vacuum suction pipe connection part, 124...push pin hole, 132...second (suction) hole, 136...second communication passage, 140...(circumferential) groove or dovetail groove, 152...(circumferential) groove, 154...first (suction) hole, 156...third (suction) hole, 158...first communication passage, 160...third communication passage, 170...cooling block, 172...coolant passage, 180...heating block, 182...heater, 190...suction block (char main body), 200...(wafer) inspection device, 202...inspection position, 204...wafer information acquisition and setting position, 210...control device, 218...support, 220...test head, 222...prober (CPU), 230...(wafer) transport unit, 232...camera, 234...head stage, 236...base, 240...XYZ-Θ table, 242...moving base, 244...X-axis table, 246...Y-axis table, 248...Z-axis table, 252...Θ table, 262...card holder, 264...probe, 266... Probe card, 268...contact cylinder, 270...vacuum exhaust device, 300...temperature control system, 310...chiller unit, 312...chiller control unit, 314...cooling unit (cooling device), 316...coolant piping, 316a...supply piping, 316b...return piping, 318...signal line, 320...temperature control device, 322...main control device, 324...heater controller, 326...signal line, 332...5ch conversion board (A / D converter), 336...signal line, 338...power line, 334...temperature sensor, 400...semiconductor wafer substrate Plate (silicon substrate), 402... terminal, 410... processor, 412... terminal, 420... memory (DRAM), 422... terminal, 424... lead wire, 426... interface (I / F), 430... silicon inclusion (interposer), 450... (semiconductor) chip, d1... maximum diameter of elastic body, D1... first suction hole diameter, D2... second suction hole diameter, D3... third suction hole diameter, h0... natural height of elastic body, h1... height of elastic body (intermediate position), W... (semiconductor) wafer, W1... dovetail groove width (bottom), W2... dovetail groove width (top)

Claims

1. In a vacuum chuck that vacuum-sucks a semiconductor wafer, a groove formed concentrically on the upper surface of the vacuum chuck; a first suction hole formed in the groove; a plurality of second suction holes formed at circumferentially spaced intervals on the outer side of the upper surface; a dovetail groove formed on the upper surface at an outer periphery of the first suction hole and the second suction hole; a sealing elastic body that fits into the dovetail groove, A vacuum chuck, characterized in that the hole diameter of the second suction hole is formed to be larger than the hole diameter of the first suction hole.

2. the first suction hole has a plurality of third suction holes and a fourth suction hole; the second suction hole is formed on the dovetail groove side in an inner region of the dovetail groove, the fourth suction hole is formed in the center of the vacuum chuck; 2. The vacuum chuck according to claim 1, wherein the third suction holes are formed outside the fourth suction holes and spaced apart in the circumferential direction.

3. 3. The vacuum chuck according to claim 2, wherein, when the semiconductor wafer is placed so that the outer peripheral portion of the semiconductor wafer abuts against the elastic body, the central portion of the semiconductor wafer is sucked by the fourth suction hole, and the outer peripheral portion is sucked by the second suction hole.

4. The vacuum chuck of claim 3 , wherein the plurality of third suction holes start suctioning the semiconductor wafer together with the second suction holes.

5. 5. The vacuum chuck according to claim 4, wherein when the semiconductor wafer is suctioned, the semiconductor wafer is sucked by the third suction hole and the fourth suction hole.

6. 5. The vacuum chuck according to claim 4, wherein the suction by the second suction holes is weakened when the semiconductor wafer is suctioned.

7. 7. A wafer inspection device comprising: the vacuum chuck according to claim 1; and a probe card capable of simultaneously measuring a plurality of semiconductor chips formed on the upper surface of a semiconductor wafer.

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