Vacuum chuck and inspection apparatus equipped therewith

Abstract

Even with wafers that have significant warping, it is possible to perform functional testing of semiconductor chips in the wafer state before dividing them into individual chips. [Solution] The vacuum chuck comprises a plurality of concentric first circumferential grooves formed on the upper surface of the vacuum chuck body, a plurality of first holes formed at each position of the plurality of first grooves, extending vertically and spaced apart in the circumferential direction, a first communication hole extending radially and connecting the first holes radially, a plurality of second holes formed at multiple concentric positions on the upper surface of the chuck body, spaced apart in the circumferential direction, a second communication hole extending radially and connecting the second holes radially, a second circumferential groove formed on the upper surface of the chuck body radially outward from the positions where the first and second holes are arranged, and a ring-shaped elastic body that fits into the second circumferential groove. The second circumferential groove is a dovetail groove, with its upper portion narrower than its bottom portion.

Description

Technical Field

[0001] The present invention relates to a vacuum chuck for adsorbing a semiconductor wafer and an inspection apparatus including the same, and more particularly to a vacuum chuck suitable for adsorbing a warped semiconductor wafer and an inspection apparatus including the same.

Background Art

[0002] With the progress of high-speed and high-integration of semiconductor devices, wafer level packages (WLPs) having the advantages of being able to reduce the mounting area and also reduce the effective inductance of wiring are widely used. A WLP packages chips on a wafer and can obtain lower power consumption, a larger bandwidth, speed, and reliability. Taking advantage of these, a wider form factor can be provided for multi-chip packages used in mobile consumer devices, high-end supercomputing, games, artificial intelligence, and Internet-related products. In a high bandwidth memory (HBM), which is a type of WLP, a plurality of memories stacked on one processor are connected. In the production thereof, generally, a large number of high bandwidth memory chips having a rectangular planar shape are formed on a substrate made of a semiconductor wafer, and then the semiconductor wafer is divided into a large number of high bandwidth memories having a size of about 100 to 200 mm. 2 In a high bandwidth memory, a processor and a memory section in which a plurality of memories (DRAMs) are stacked in the vertical direction are connected via a silicon interposer, and the connection of the processor and the memory section is connected and placed on the substrate via the silicon interposer.

[0003] When performing functional testing of ultra-broadband memory formed in this manner, it is clear that testing each ultra-broadband memory in its wafer state immediately before splitting is more efficient than testing each ultra-broadband memory chip individually after it has been split from the semiconductor wafer. In order to test ultra-broadband memory all at once in the unsplit semiconductor wafer state, the semiconductor wafer needs to be flat so that the test probe can be easily positioned in the predetermined location while protecting the test probe. However, as described below, wafers on which ultra-broadband memory is formed may be warped, and currently, a method is used in which ultra-broadband memory separated from the semiconductor wafer is tested individually.

[0004] On the other hand, there are attempts to inspect general semiconductor chips, not ultra-wideband memory, that are formed on semiconductor wafers, even if they are warped. In a 12-inch wafer with a diameter of φ300 mm on which ultra-wideband memory is formed, the number of ultra-wideband memory chips can be as many as 400 or more. In such wafers, even with a large diameter, the thickness is only a few hundred μm, so the overall rigidity of the wafer is low, and external forces applied during wafer processing, especially during packaging, can easily cause warping or undulation (deformation). Wafer warping is indicated by the difference in height between the periphery and the center, and this value can be as low as a few millimeters.

[0005] Incidentally, if a large-diameter wafer is significantly warped and deformed at the edges compared to the center, even if the edges are vacuum-suctioned when the wafer is placed in a chuck, conventional suction diameters will result in the surrounding air being drawn in, and the edges of the wafer will not be sucked into the chuck, maintaining their warped state. If inspection is performed while the wafer is still warped, the inspection probe may contact the wafer surface at an angle, and in the worst case, there is a risk of damaging the wafer or the expensive probe. To resolve such problems caused by wafer warping, various methods have been proposed to cancel the wafer warping during inspection.

[0006] Patent Document 1 describes how to maintain good flatness of a substrate, even when adsorbing and holding a substrate such as a wafer that has a large warp. Specifically, an annular recess is formed at a position surrounding the opening of the communication path on the upper surface of the base body, and the lower element of a sealing member made of an annular elastic material is placed in the annular recess. On the other hand, the upper element of the sealing member protrudes from the upper surface of the base body. The upper element is provided with a first portion that extends upward while facing inward in the annular direction, and a second portion that extends upward while facing outward in the annular direction.

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

[0008] Patent Document 3 describes a wafer processing machine having a suction cup structure that can adsorb and hold wafers regardless of the flatness of the wafer. Specifically, a cylindrical body is provided on the outer circumference of the suction cup, which is made of an elastic material such as a rubber plate, expands in a skirt-like shape, and extends a predetermined length from the suction surface of the suction cup. As a result, even if a gap occurs between the wafer surface and the suction surface, the cylindrical body elastically deforms in accordance with the warping, undulation, or steps of the wafer surface, and adheres closely to the wafer surface, forming an enclosure. As a result, the gap can be sealed, and air or grinding fluid is prevented from being sucked in from the suction groove. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2019-4017 [Patent Document 2] Japanese Patent Publication No. 2010-153419 [Patent Document 3] Japanese Patent Application Publication No. 7-308856 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] In the vacuum chuck described in Patent Document 1 above, an annular recess is formed on the periphery of a substantially circular ceramic substrate, and a sealing member made of an elastic material is placed in the annular recess. The elastic material is bellows-shaped or corrugated, and its upper end surface contacts the wafer. When vacuum adsorption occurs, the bellows-shaped or corrugated elastic material expands and contracts without changing the contact position between the wafer and the elastic material, thereby adsorbing the wafer to the substrate. As a result, the wafer is flattened and held in a predetermined position.

[0011] However, in the vacuum chuck described in Patent Document 1, when compressing the bellows-shaped elastic body, it is necessary to provide a large groove in the ceramic substrate to house the elastic body. Furthermore, because it is bellows-shaped and not a simple shape, when compressed, a part of the elastic body may deviate from smooth deformation and protrude between the upper surface of the ceramic substrate and the back surface of the wafer in the in-plane direction. If the elastic body protrudes from the groove, there is a risk that foreign matter will adhere to the back surface of the wafer, and if foreign matter adheres, the suction force when the wafer is sucked may cause the wafer to be damaged. In addition, it becomes impossible to position the wafer in the correct position for inspection, the height in the suction direction of the wafer changes, making it impossible to guarantee flatness, and there is a risk of collision with the probe. If the functional inspection of the ultra-wideband memory is performed in a temperature-controlled environment, for example, low-temperature functional inspection or high-temperature functional inspection, there is a risk that the set temperature will be shifted if the wafer position is not correct.

[0012] In the work stage described in Patent Document 2, a sealing material is placed near the periphery of a rectangular base, and a workpiece is placed on top of it. On the other hand, a rectangular perforated suction plate is placed in the space inside the base partitioned by the sealing material. Then, by vacuum suction from the back surface of the rectangular suction plate, the sealing material is contracted, and the workpiece conforms to the shape of the flat suction plate.

[0013] However, since this work stage is used for exposure and the like, if a workpiece with a large curvature at its periphery is placed on the work stage with a convex shape facing downwards, before vacuum suction, the workpiece will not come into contact with the sealing material, but only with the suction plate in the center, making it difficult to eliminate the curvature and suction the workpiece. In order to make such a workpiece come into contact with the sealing material before vacuum suction, the height of the sealing material can be increased, but even if the height of the sealing material is increased, the center of the sealing material, which is at a short distance from the suction plate, will immediately come into contact with the suction plate during vacuum suction, and the workpiece tends to be adsorbed while maintaining its curvature or with only a slight reduction in curvature. On the other hand, if the workpiece is placed on the work stage with a convex shape facing upwards, it is possible for the workpiece to come into contact with the sealing material before vacuum suction. However, in the central part of the area partitioned by the sealing material, the distance from the suction plate becomes too long, making it difficult to obtain a sufficient vacuum suction effect, and the curvature is maintained.

[0014] In the wafer processing machine described in Patent Document 3, when processing such as outer edge grinding of a wafer, the chuck holds the warped wafer by vacuum suction. The chuck has an elastic body on its outer circumference, and after the back surface of the wafer is brought into contact with the elastic body, the wafer is held in the chuck by vacuum suction. At the same time, by bringing the wafer into contact with the elastic body, the gap between the chuck and the wafer is eliminated, preventing grinding fluid from entering the back surface of the wafer. However, the processing machine described in this publication only needs to prevent the intrusion of grinding fluid, so it does not take into consideration correcting the warp of the wafer itself. In other words, even if outer edge grinding or other processes are continued with the wafer in a warped shape, no problems occur.

[0015] This invention has been made in view of the shortcomings of the prior art described above, and its purpose is to enable functional testing of semiconductor chips in the wafer state before dividing it into individual chips, even for wafers that have a large diameter and therefore have significant warping at their edges. Preferably, it also aims to enable functional testing of semiconductor chips in the wafer state as a whole. Functional testing includes testing under temperature conditions, and it also aims to achieve a uniform temperature environment for all semiconductor chips formed on the wafer. This invention aims to achieve at least one of these multiple objectives. [Means for solving the problem]

[0016] The present invention, which achieves the above objective, is characterized by a vacuum chuck having a disc-shaped chuck body for vacuum adsorption of semiconductor wafers, wherein the chuck body has a plurality of concentric first circumferential grooves formed on the upper surface of the chuck body, a plurality of first holes formed at the positions of each of the plurality of first circumferential grooves, extending vertically on the chuck body and spaced apart in the circumferential direction, a first communication passage extending radially on the chuck body and communicating the first holes in the radial direction, and circumferentially at the plurality of concentric positions on the upper surface of the chuck body. The chuck comprises a plurality of second holes formed at intervals in the direction, a second communication passage extending radially from the chuck body and connecting the second holes in the radial direction, a second circumferential groove formed on the upper surface of the chuck body radially outward from the positions where the first and second holes are arranged, and a ring-shaped elastic body that fits into the second circumferential groove, wherein the second circumferential groove is a dovetail groove formed such that its radial width on the upper surface of the chuck body is narrower than its radial width on the bottom surface.

[0017] Another feature of the present invention that achieves the above objective is a vacuum chuck having a disc-shaped chuck body for vacuum adsorption of semiconductor wafers, wherein the chuck body has a plurality of concentric first circumferential grooves formed on the upper surface of the chuck body, a plurality of first holes formed at the position of each of the plurality of first circumferential grooves, extending vertically on the chuck body and spaced apart in the circumferential direction, a first communication passage extending radially on the chuck body and communicating radially with the first holes, and a plurality of concentric circles on the upper surface of the chuck body The chuck comprises a plurality of second holes formed at circumferential intervals, a second communication passage extending radially through the chuck body and connecting the second holes radially through the chuck body, a second circumferential groove formed on the upper surface of the chuck body radially outward from the positions where the first and second holes are located, and a ring-shaped elastic body that fits into the second circumferential groove, wherein the elastic body is formed as a ring-shaped tube or as a solid O-ring made of foamed material.

[0018] Furthermore, in these features, the chuck body is preferably further comprising a plurality of concentric third circumferential grooves formed on the upper surface of the chuck body, a plurality of third holes formed at the position of each of the plurality of third circumferential grooves, extending vertically from the chuck body and spaced apart in the circumferential direction, and a third communication passage extending radially from the chuck body and communicating the third holes in the radial direction, wherein the plurality of third holes preferably include holes located radially inward from the plurality of first holes and the plurality of second holes. The first communication passage and the third communication passage may be used interchangeably.

[0019] In the above-described features, it is preferable that the diameters of the plurality of second holes are larger than the 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 provided below the portion where the first and second communication passages are formed, and the sum of the radially arranged number of the first hole and the third hole may be greater than the radially arranged number of the second hole.

[0020] Still another feature of the present invention for achieving the above object is that a wafer inspection apparatus includes a vacuum chuck having any of the above features and a probe card capable of collectively measuring a plurality of semiconductor chips formed on the upper surface of the wafer.

Advantages of the Invention

[0021] According to the present invention, in a vacuum suction chuck for sucking a wafer used for functional inspection of the wafer, an annular groove is formed near the outer peripheral edge of the vacuum suction chuck, and an elastic body that protrudes from the groove higher than the amount of warpage of the wafer before vacuum suction in a state of being fitted in the groove is disposed on the vacuum suction chuck, and a vacuum suction passage that opens near the groove is formed. Therefore, the functional inspection of the semiconductor chips can be performed in the state of the wafer before being divided into individual chips. In addition, a uniform temperature environment can be realized for all the semiconductor chips formed on the wafer.

Brief Description of the Drawings

[0022] [Figure 1] It is a front view of an embodiment of an inspection apparatus according to the present invention. [Figure 2] It is a view showing an example of a semiconductor wafer inspected by the inspection apparatus. [Figure 3] It is a perspective view of an embodiment of a vacuum chuck according to the present invention. [Figure 4] It is a top view of the vacuum chuck shown in FIG. 3. [Figure 5] It is a schematic cross-sectional view of the vacuum chuck. [Figure 6] It is a cross-sectional view showing the detailed shape of the suction portion of the vacuum chuck shown in FIG. 4. [Figure 7] It is a cross-sectional view for explaining vacuum suction of the wafer. [Figure 8] It is a block diagram of a system for heating and cooling the vacuum chuck.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, an embodiment of a vacuum chuck suitable for wafer inspection according to the present invention and an inspection apparatus equipped therewith will be described with reference to the drawings. Figure 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, an electrical inspection is performed by simultaneously contacting a plurality of probes 264 of a probe card 266 with the pads of a semiconductor chip 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, means for heating and cooling the wafer W are generally provided.

[0024] As shown in Figure 1, the wafer inspection apparatus 200 comprises a base 236, a movable base 242 and an XYZ-Θ table 240 provided on the base 236. A vacuum chuck (hereinafter also referred to as a chuck) 100 according to the present invention is provided on the upper surface of the XYZ-Θ table 240, on which a wafer W is placed and which is vacuum-adsorbed by 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, and the temperature of the wafer W placed on the vacuum chuck 100 can be controlled. In addition, to ensure vacuum adsorption of the wafer W, a vacuum exhaust device 270 such as a vacuum pump is connected to the vacuum chuck 100.

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

[0026] The XYZ-Θ table 240 is surrounded by support columns 218 on its sides, and a head stage 234 is provided above it. The head stage 234 has an opening in part of it, and a card holder 262 is attached to this opening. A probe card 266 corresponding to the semiconductor chip 450 to be inspected (see Figure 2(a)) formed on the wafer W is attached to the card holder 262. Furthermore, multiple probes 264 that contact the semiconductor chip 450 are arranged on the probe card 266. The probes 264 have a delicate structure to identify and contact minute terminals on the order of μm formed on the chip 450, and are designed so as not to be subjected to unnecessary load. Therefore, the probes 264 are set to approach the wafer W at a predetermined posture and speed during inspection.

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

[0028] The XYZ-Θ table 240 is movable in the left-right direction in the diagram via the moving base 242. When the wafer W is being transported to the transport unit 230, the XYZ-Θ table 240 moves to the wafer information acquisition / setting position 204 on the right side in the diagram, places and holds the wafer W on the vacuum chuck 100, 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 in the diagram and performs a batch inspection using the probe 264. Here, "batch" means driving the XYZ-Θ table 240 while the wafer W is held on the vacuum chuck 100 to continuously inspect multiple chips 450, preferably all chips 450 created on the surface of the wafer W.

[0029] Figure 2 shows an example of a semiconductor wafer W on which the vacuum chuck 100 according to the present invention can be placed and adsorbed. However, the semiconductor wafer W on which the vacuum chuck 100 can be placed and adsorbed is not limited to that shown in Figure 2; any semiconductor wafer W can be placed and adsorbed, and the vacuum chuck 100 has the special feature of being able to adsorb even semiconductor wafers W that are warped.

[0030] Figure 2(a) is a top view of a semiconductor wafer W, and Figure 2(b) is a schematic side view showing an example of numerous 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 approximately 13.3 mm wide and 10.9 mm long, are formed on the surface where the orientation flat is formed.

[0031] The semiconductor chip 450 shown in Figure 2(b) is called a high-bandwidth memory (HBM) and has a processor 410 and a memory (DRAM) 420 with multiple layers (four layers in the figure) stacked on top of it, with an interface (I / F) 426 located below the stacked memory 420. The processor 410 and the memory 420 are connected via a silicon interposer 430, and the integrated processor 410 and memory 420 are connected to a semiconductor wafer substrate (silicon substrate) 400 via the silicon interposer 430. The connections between the processor 410 and the silicon interposer 430, between the silicon interposer 430 and the semiconductor wafer substrate 400, and between the silicon interposer 430 and the interface 426 are made using terminals 412, 402, 422, etc. formed on each, and the individual memory 420s are connected by lead wires 424. The semiconductor chip 450 formed in this manner is subject to distortion due to the difference in weight between the processor 410 and the stacked memory 420, as well as the processing method used when forming the chip 450, which results in a thickness of several hundred micrometers.

[0032] An embodiment of the vacuum chuck 100 according to the present invention, which is provided in the inspection apparatus 200 shown in Figure 1, will be described using Figures 3 to 6. Figure 3 is a perspective view of the vacuum chuck 100, and Figure 4 is a top view thereof. Figure 5 is a schematic longitudinal cross-sectional view of the chuck body 190 provided in the vacuum chuck 100, and shows various examples of having heating and / or cooling means for the wafer W. Figure 5(a) is an example where only the heating means is provided, Figure 5(b) is the most standard example where both heating and cooling means are provided, and Figure 5(c) is an example where both heating and cooling means are provided in which the vacuum adsorption part and the cooling part are integrated. In Figure 5, the left half is shown as a cross-section at position B in Figure 4, and the right half is shown as a cross-section at position A or C in Figure 4. Figure 6 is a diagram illustrating the details of the suction holes and vacuum seal formed in the chuck body 190. Figure 6(a) is a longitudinal cross-sectional view of the chuck body 190 illustrating the positional relationship of the suction holes, and Figure 6(b) is a cross-sectional view illustrating the fitting state of the elastic body.

[0033] The following explanation will use the standard vacuum chuck 100 shown in Figure 5(b) as an example, but the same applies to the other vacuum chucks 100 shown in Figures 5(a) and (c). As shown in Figure 5(b), the vacuum chuck 100 comprises a chuck body 190, which is a disc-shaped vacuum suction block located at the top, a disc-shaped cooling block 170 positioned below the chuck body 190, and a disc-shaped heating block 180 positioned below the cooling block 170. These blocks 190, 170, and 180 are integrated using bolts (not shown) to form a cylindrical vacuum chuck 100. Multiple coolant passages 172 are formed in the cooling block 170, through which a coolant such as cooling water cooled by a chiller flows. A heater 182 is provided in the heating block 180, which is wound in multiple spirals.

[0034] The vacuum suction block 190, which forms the uppermost part of the vacuum chuck 100, has conventionally had numerous holes and grooves formed in it to stably adsorb and hold the wafer W. In the present invention, in addition to these conventional holes and grooves, new holes and grooves, as well as elastic bodies 110 that fit into the grooves, are provided on the vacuum chuck 100 to accommodate warped wafers W.

[0035] As shown in Figures 3 and 4, the chuck body 190 is formed in a circular shape with a diameter larger than that of the wafer W. Multiple first suction holes 154 are formed radially in the portion on which the wafer W is placed, in order to attract and securely hold the flat wafer W. These suction holes 154 are provided at multiple locations in the circumferential direction (four locations in the figure, position C) and are formed within numerous shallow grooves 152 formed concentrically. The number of grooves 152 is preferably 10 or more, more preferably 20 or more, when the wafer W to be adsorbed is about φ300 mm, and the number of suction holes 154 in the circumferential direction is preferably 4 or more.

[0036] Note that the number of first suction holes 154 may be reduced on the center side (small diameter side) of the chuck body 190. Each of the first suction holes 154 located at the same position in the circumferential direction is connected by a first communication passage 158 that extends radially from the outer circumference. The outer circumference of the chuck body 190 is provided with a vacuum suction piping connection section 120, to which vacuum suction fittings are attached according to the position of each of the first communication passages 158 (see Figure 3), and is connected to a vacuum exhaust device 270 via piping (see Figure 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 so that the wafer W can be easily separated from the vacuum chuck after the vacuum is released. For this reason, push pin holes 124 are formed in the vacuum chuck at intervals in the circumferential direction. As such, various processing is performed in the center of the chuck body 190, including processing for the temperature sensor to be installed later, so the processing is concentrated there. To avoid excessive processing, the first suction hole 154 is omitted near the center, and a third suction hole 156, mainly for vacuum suction of the center of the chuck body 190, is formed at a different circumferential position (position A in the figure) from the first suction hole 154. Similar to the case of the first suction hole 154, a third communication passage 160 is formed from the outer circumference of the chuck body 190 toward the center for the third suction hole 156. The diameters of the first suction hole 154 and the third suction hole 156 are set to be the same. By using these first and third suction holes 154 and 156 to vacuum-suction the back surface of the wafer W, a flat wafer W can be fixed and held in the vacuum chuck 100 without any problems, and various inspections in the inspection device 200 can be performed according to the program. In this embodiment, the third suction hole 156 and the third connecting passage 160 are provided in different positions from the first suction hole 154 and the first connecting passage 158, but one of the multiple first connecting passages 158 and its corresponding first suction hole 154 can also be used interchangeably as the third connecting passage 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, especially in the case of a wafer W on which a semiconductor chip 450 such as HBM is formed, the amount of warping at the periphery becomes large, and even if suction is performed using only the first and third suction holes 154 and 156, a gap may occur between the wafer W and the vacuum chuck 100 at the periphery. In that case, as described above, when attempting to inspect the wafer W, there is a risk that the probe 264 will come into contact with the surface of the wafer W in a position different from the normal position. The probe 264 for inspecting 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, it can be a cause of damage to the expensive probe 264.

[0039] To prevent such malfunctions, the present invention provides a circumferential groove 140 and a second suction hole 132 that hold the wafer W flat, particularly the peripheral edge. Specifically, a circumferential groove 140 into which a sealing elastic body 110 can be fitted is formed near the outer circumference at the position where the φ300 mm wafer is placed. Referring to Figure 6(b), the cross-section of the groove 140 is approximately trapezoidal with rounded corners, and the width W2 on the upper side of the chuck body 190 is narrower than the width W1 on the lower side, forming a dovetail groove.

[0040] The elastic body 110 that fits into the groove 140 is designed to be 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 jamming between the wafer W and the chuck body 190, and ultimately being entirely contained 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 foam material. Silicone resin is preferred as the foam material.

[0041] If the elastic body 110 is a tube made of tetrafluoroethylene resin, the tube 110 is cut to a predetermined length, then 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 part of the tube 110 with the maximum diameter d1 remains within the dovetail groove 140 while maintaining almost the original outer diameter (corresponding to the nominal diameter) of the tube 110. In this state, the tube 110 is at its natural height h0. This natural height h0 corresponds to the maximum allowable warpage of the wafer W at the outer circumference of the wafer W to be inspected, or more precisely, at the position where the elastic body 110 contacts the wafer W.

[0042] In other words, if the amount of warpage of the wafer W at the position where it contacts the elastic body 110 is h0 or less, when the wafer W is placed on the chuck body 190, the outer periphery of the wafer W is separated by the elastic body 110, and a sealed space can be formed between the chuck body 190 and the wafer W. This makes vacuum suction, as described below, possible. On the other hand, if 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 there is a risk that vacuum suction to flatten the wafer W will result in no suction. For most wafers W, the amount of warpage is 2 mm or less, so 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] As described above, forming the dovetail groove 140 creates a sealed space between the chuck body 190 and the wafer W. However, this sealed space is larger than the gap created when using vacuum suction with the first suction hole 154 or the third suction hole 156. Furthermore, suction requires generating a force to flatten the wafer W against the rigidity of the semiconductor wafer substrate 400. Therefore, in this embodiment, a second suction hole 132, which is larger in diameter than the first suction hole 154 or the third suction hole 156, is positioned mainly on the outer diameter side of the chuck body 190. As shown in Figure 4, the second suction holes 132 are provided at multiple locations (four locations in this embodiment: position B) that are different in the circumferential direction from the first and third suction holes 154 and 156, and at multiple locations on the inner diameter side of the outer diameter position where the circumferential dovetail groove 140 is formed. In this embodiment, there are five locations in the radial direction. The second suction holes 132 located at the same circumferential position are connected by a second communication passage 136 formed from the outer circumference toward the center.

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

[0045] Multiple second suction holes 132, primarily for correcting warping on the outer periphery of the wafer W, are formed with a diameter φD2 of approximately 2-3 mm, which is several times larger than φD1 and φD3. They are formed radially between the first suction holes 154, at multiple locations centered on the larger diameter side of the chuck body 190. A second communication passage 136 connecting the second suction holes 132 extends from the outer periphery of the chuck body 190 toward the center, and its length is generally shorter than the first communication passage 158. In other words, the arrangement of the second suction holes 132 indicates that they contribute to correcting warping of the outer edge of the wafer W. Furthermore, a full-circumferential groove 152 with a depth of 1 mm or less is formed at the radial position of the chuck body 190 where the first suction holes 154 and the third suction holes 156 are formed, reducing uneven suction. Furthermore, while the number of suction holes 154 and 132 in the circumferential direction is almost the same, the number of suction holes 154 in the radial direction is approximately 10 to 25, compared to approximately 5 for the second suction holes 132. Therefore, including the third suction hole 156, the total number of suction holes 154 and 156 is greater than the number of suction holes 132.

[0046] Outer diameter than the first to third suction holes 154, 132, and 156, the aforementioned dovetail groove 140, which has a trapezoidal cross-section, is positioned. In other words, the dovetail groove 140 is located outer diameter than the outermost circumferential groove 152 or the first suction hole 154, and is a sealing groove that prevents the first to third suction holes 154, 132, and 156 from drawing in air from the outer diameter side of the dovetail groove 140.

[0047] Figure 7 schematically shows an example of using the vacuum chuck 100 of the present invention, configured as described above, to suck up a large-diameter wafer W. The vacuum suction method is not limited to this method; suction may be performed simultaneously from all suction holes or simultaneously from different types of suction holes. Figure 7(a) shows the wafer W placed on the chuck body 190. Vacuum suction is not being performed, and the outer periphery of the wafer, which has a convex curvature, is in contact with the elastic body 110, forming a sealed space between the wafer W and the elastic body 110, while only the weight of the wafer acts on the elastic body 110. At this time, the elastic body 110 is statically fixed at approximately its natural height or a slightly deformed height h0.

[0048] From this state, as shown in Figure 7(b), the central part of the wafer W, which has little warping and is nearly flat, is vacuum-adsorbed first using the third suction hole 156. This prevents the wafer W from moving in the horizontal plane during vacuum suction. By fixing the wafer W to the chuck body 190, displacement of the wafer W due to the generation of airflow during vacuum suction at the periphery, as shown in Figure 7(c), is prevented.

[0049] Next, vacuum suction is applied from the second suction hole 132 along 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 that of the first suction hole 154, so it has a large suction force and can flatten the wafer W against its rigidity. As such, suction from the second suction hole 132 generates a large force, which can easily create a force that moves the wafer W in the horizontal plane. For this reason, suction from the third suction hole 156 and the first suction hole 154 are used in combination.

[0050] Once the wafer W is attracted to the chuck body 190, the sealing action of the elastic body 110 prevents almost any leakage between the wafer W and the suction surface 102 of the chuck body 190. Therefore, vacuum suction can be handled by using only the suction from the first and third suction holes 154 and 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 in an enlarged manner the states 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 elastic body 110 is substantially entirely accommodated within 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 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), (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 by a coolant pipe 316 to a cooling unit (cooling device) 314 provided in a chiller unit 310 disposed remotely from the inspection device 200. 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 warmed 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 by a power line 338 to a heater controller 324 provided in a temperature control device 320, 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, one or more points within the range of -10°C to +100°C, using the heating and cooling mechanism configured in this way, temperature sensors 334 are embedded at five different points on the vacuum chuck 100. The output of the temperature sensors 334 is input to a 5-channel conversion board (A / D converter) 332, converted into a digital signal, and input to the main control unit 322 of the temperature control device 320 via a signal line 336. The main control unit 322 is connected to the heater controller 324 via the signal line 326 and also to the chiller control unit 312 via a signal line 318. Therefore, the temperature of the suction surface 102 of the vacuum chuck 100, in other words, the temperature of the wafer W, detected by the temperature sensors 334, is fed back to control the temperature of the heater 182 and the temperature of the coolant. At the same time, the detection result of the prober (CPU) 222, which is an inspection means positioned opposite the wafer W, is also fed back to the temperature control device 320.

[0055] As explained above, with the vacuum chuck of this embodiment, even large-diameter wafers of 300 mm with warped edges can be sufficiently flattened if the warp is up to about 2 mm, making it possible to perform functional testing on the wafer all at once. Furthermore, it was confirmed that if the wafer is convex downwards, it can be reliably flattened up to the above-mentioned warp range, and even if it is convex downwards, it can be reliably flattened up to about 2 mm.

[0056] Furthermore, in temperature-controlled testing and inspection of wafer W using this vacuum chuck 100, the warp tended to increase and expand at high temperatures compared to room temperature. Therefore, a warp of 2 mm at room temperature increased to 4 mm at 100°C, and attempting to vacuum-suction at that temperature resulted in a gap exceeding the allowable warp, preventing vacuum suction. This problem could be addressed by performing vacuum suction at room temperature and then raising the wafer temperature from room temperature to the test / inspection temperature while maintaining vacuum suction. From this, it was found that even at high temperatures, if wafer W has a warp of only about 2 mm at that temperature, good testing and inspection can be performed regardless of the temperature.

[0057] In the above embodiment, the elastic body was a tube, but by using a solid foamed resin as the elastic body, when vacuum suction is applied, air is sucked in from the internal air bubbles, causing the entire elastic body to contract and deform so that it fits within the dovetail groove. Therefore, similar to the tube-type elastic body, it is possible to prevent the elastic body from protruding radially inward or outward from the dovetail groove during vacuum suction, thereby preventing it from obstructing vacuum suction or tilting the wafer during suction, and allowing the wafer to be straightened to a flat position. When using a foamed material, even when vacuum suction is released, it is solid and therefore almost completely returns to its state before vacuum suction, restoring its rigidity. Therefore, even when a new wafer is placed, the same state as the previous wafer can be reproduced. In other words, wafers with a similar degree of warping can be inspected. This prevents damage to the probe caused by the probe on the probe card contacting the wafer in an inappropriate position. [Explanation of Symbols]

[0058] 100... Vacuum chuck, 102... Suction surface, 110... Elastic body (tube or foam O-ring), 120... Vacuum suction pipe connection, 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 (chuck) (Main unit), 200…(wafer) inspection device, 202…inspection position, 204…wafer information acquisition / setting position, 210…control device, 218…support column, 220…test head, 222…probe (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 base 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...Diameter of first suction hole, D2...Diameter of second suction hole, D3...Diameter of third suction hole, h0...Natural height of elastic body, h1...Height of elastic body (intermediate position), W...(Semiconductor) wafer, W1...Dovetail groove width (bottom surface), W2...Dovetail groove width (top surface)

Claims

1. In a vacuum chuck for vacuum adsorption of semiconductor wafers, A first suction hole formed on the upper surface of the vacuum chuck, A plurality of second suction holes are formed on the outer surface of the upper surface at intervals in the circumferential direction, On the upper surface, a dovetail groove is formed on the outer circumference beyond the first suction hole and the second suction hole, It comprises an elastic body for sealing that fits into the dovetail groove, A vacuum chuck characterized in that the diameter of the second suction hole is formed to be larger than the 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 side in the region inside the dovetail groove, The fourth suction hole is formed in the center of the vacuum chuck, The vacuum chuck according to claim 1, wherein the plurality of third suction holes are formed outside the fourth suction hole and spaced apart in the circumferential direction.

3. The vacuum chuck according to claim 2, wherein when the semiconductor wafer is placed such that the outer peripheral portion of the semiconductor wafer is in contact with 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 according to claim 3, wherein the plurality of third suction holes, together with the second suction hole, begin to suck up the semiconductor wafer.

5. The vacuum chuck according to claim 4, wherein when the semiconductor wafer is adsorbed, the third suction hole and the fourth suction hole are used to suck the semiconductor wafer.

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

7. A wafer inspection apparatus comprising a vacuum chuck according to any one of claims 1 to 6, 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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