JP7815519B2 - Vacuum chuck and inspection device equipped with same - Google Patents

Description

The present invention relates to a vacuum chuck for suctioning semiconductor wafers and an inspection device equipped with the same, and in particular to a vacuum chuck suitable for suctioning warped semiconductor wafers and an inspection device equipped with the same.

As semiconductor devices become faster and more highly integrated, wafer-level packaging (WLP) is becoming increasingly popular. This technology not only reduces the mounting area but also reduces the effective inductance of interconnects. WLP packages chips on a wafer, enabling greater bandwidth, speed, and reliability with less power consumption. These advantages enable a wider range of form factors for multi-chip packages used in mobile consumer devices, high-end supercomputing, gaming, artificial intelligence, and Internet-related products.
High Band-width Memory (HBM), a type of WLP, connects multiple stacked memories to a single processor, and is fabricated by forming multiple ultra-wideband memory chips, generally having a rectangular planar shape, on a substrate made of a semiconductor wafer, and then dividing the semiconductor wafer into multiple ultra-wideband memories, each measuring approximately 100 to 200 ^mm2 . In the ultra-wideband memory, the processor and a memory section, in which multiple memories (DRAMs) are stacked vertically, are connected via a silicon interposer, and the connection between the processor and the memory section is connected to and mounted on the substrate via the silicon interposer.

When conducting functional testing of ultra-wideband memories formed in this manner, it is clear that testing efficiency is improved by testing each ultra-wideband memory chip on the wafer immediately before it is divided, rather than testing each individual ultra-wideband memory chip formed after it has been divided from the semiconductor wafer. In order to test ultra-wideband memories collectively on an undivided semiconductor wafer, the semiconductor wafer must be flat so that the test probes can be easily positioned at their designated locations while protecting them. However, as described below, wafers on which ultra-wideband memories are formed may be warped, and so the current method involves testing each ultra-wideband memory chip individually after it has been divided from the semiconductor wafer.

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

However, if the peripheral portion of a large-diameter wafer is significantly warped and deformed compared to the center, even if the peripheral portion is vacuum-sucked when the wafer is placed on the chuck, the conventional suction diameter will result in the ambient air being sucked out, and the peripheral portion of the wafer will not be sucked into the chuck, and the warped state will remain. If inspection is performed while the wafer is still in a warped state, the inspection probe will abut at an angle against the wafer surface, and in the worst case scenario, there is a risk of damaging the wafer or the expensive probe. To eliminate problems caused by this type of wafer warpage, various methods have been proposed to cancel out wafer warpage during wafer inspection.

Patent Document 1 describes a method for maintaining good flatness of a substrate, such as a wafer, even when it is held by suction with significant warpage. Specifically, an annular recess is formed in a position surrounding the opening of the communication path on the top surface of the base, 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 top surface of the base. The upper element is provided with a first portion that extends upward while facing inward in the annular shape, and a second portion that extends upward while facing outward in the annular shape.

Patent Document 2 also describes a work stage that vacuum-sucks a warped workpiece, comprising a base with a recess that supplies 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.

Patent Document 3 describes a wafer processing machine with a suction cup structure that can suction and hold a wafer without being affected by 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, spreading out like a skirt and extending 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 response to warping, undulations, or steps on the wafer surface, adhering to the wafer surface and forming an enclosure. As a result, the gap can be sealed, preventing air and grinding fluid from being sucked in through the suction groove.

Japanese Patent Application Laid-Open No. 2019-4017 JP 2010-153419 A Japanese Patent Application Publication No. 7-308856

The vacuum chuck described in Patent Document 1 has an annular recess formed around the periphery of a substantially circular ceramic base, and a sealing 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 or bellows-shaped elastic material expands and contracts, adsorbing 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.

However, with the vacuum chuck described in Patent Document 1, when the bellows-shaped elastic body is compressed, a large groove must be formed in the ceramic base to accommodate the elastic body. Furthermore, because the bellows-shaped body is not a simple shape, there is a risk that part of the elastic body will deviate from smooth deformation when compressed and protrude in the in-plane direction between the top surface of the ceramic base and the back surface of the wafer. 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 wafer may be damaged by the suction force when the wafer is sucked. Furthermore, it becomes impossible to position the wafer in the appropriate position for inspection, and the height of the wafer in the suction direction changes, making it impossible to ensure flatness, and there is a risk of a collision with the probe. If the functionality of the ultra-wideband memory 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.

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

However, because this work stage is intended for use in exposure applications, if a workpiece with significant peripheral warping is placed on the work stage with a downward convex shape, before vacuum suction, the workpiece's center will abut against the suction plate, rather than the sealant, making it difficult to eliminate the warp and suction. In order to make such a workpiece abut against the sealant before vacuum suction, the height of the sealant can be increased, but even if the height of the sealant is increased, the center of the sealant, which is closer to the suction plate, will immediately abut against the suction plate during vacuum suction, and the workpiece will tend to maintain its warp or be slightly reduced when adsorbed. On the other hand, if the workpiece is placed on the work stage with an upward convex shape, it is possible for the workpiece to abut against 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 warp will remain.

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 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, a gap is eliminated between the chuck and the wafer, preventing grinding water and other substances from penetrating the backside of the wafer. However, since the processing machine described in this publication is only concerned with preventing the intrusion of grinding water, no consideration is given to correcting the warpage of the wafer itself. In other words, no problems arise even if peripheral grinding and other processing are continued while the wafer remains warped.

The present invention was developed in consideration of the above-mentioned shortcomings of the conventional technology, and its purpose 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 significant warping around the periphery. Preferably, it also aims to enable functional testing of semiconductor chips in the wafer state all at once. Furthermore, functional testing includes testing in a temperature environment, and it also aims to achieve a uniform temperature environment for all semiconductor chips formed on the wafer. The present invention aims to achieve at least one of these multiple purposes.

The present invention, which achieves the above-mentioned objective, is characterized by a vacuum chuck having a disk-shaped chuck body for vacuum-suctioning a semiconductor wafer, comprising: 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; first communication passages 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 in the upper surface of the chuck body at concentric positions in the chuck body. The chuck body has a plurality of second holes spaced apart in the radial direction, second communication passages extending radially of the chuck body and connecting the second holes in the radial direction of the chuck body, a second circumferential groove formed on the top 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 being a dovetail groove whose radial width on the top surface of the chuck body is narrower than its radial width on the bottom surface.

Another feature of the present invention that achieves the above object is a vacuum chuck having a disk-shaped chuck body that vacuum-sucks a semiconductor wafer, the vacuum chuck comprising: 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; first communication passages 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. The chuck body has a plurality of second holes formed at circumferentially spaced positions, a second communication passage extending radially of the chuck body and connecting the second holes radially 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 that fits into the second circumferential groove, the elastic body being formed as a ring-shaped tube or a solid O-ring made of a foam material.

In these features, the chuck body may further include a plurality of concentric third circumferential grooves formed on the upper surface thereof, a plurality of third holes extending in the vertical direction of the chuck body and spaced apart circumferentially at the positions of each of the third circumferential grooves, and third communication passages extending in the radial direction of the chuck body and radially communicating with the third holes, and the third holes may preferably include holes located radially inward of the first holes and the second holes. The first communication passage may also serve as the third communication passage.

In the above feature, the diameter of the plurality of second holes is preferably larger than the diameter of the first holes, and the vacuum chuck may be provided with 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, below the portion where the first and second communication passages 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.

Another feature of the present invention that achieves the above objective is that a wafer inspection device is equipped with a vacuum chuck having any of the above features and a probe card that can simultaneously measure multiple semiconductor chips formed on the top surface of the wafer.

According to this invention, a vacuum suction chuck for suctioning a wafer and used for wafer functional testing has an annular groove formed near the outer periphery of the vacuum suction chuck. An elastic body is disposed in the vacuum suction chuck and fitted into the groove, protruding from the groove higher than the amount of warpage of the wafer before vacuum suction. A vacuum suction passage is formed that opens near the groove. This enables functional testing of semiconductor chips in wafer form before they are separated into individual chips. It also enables a uniform temperature environment to be achieved for all semiconductor chips formed on the wafer.

1 is a front view of an embodiment of an inspection device according to the present invention; FIG. 2 is a diagram illustrating an example of a semiconductor wafer inspected by an inspection device. 1 is a perspective view of an embodiment of a vacuum chuck according to the present invention; FIG. 4 is a top view of the vacuum chuck shown in FIG. 3 . FIG. 2 is a schematic cross-sectional view of a vacuum chuck. FIG. 5 is a cross-sectional view showing a detailed shape of a suction portion of the vacuum chuck shown in FIG. 4 . FIG. 10 is a cross-sectional view illustrating vacuum suction of a wafer. FIG. 1 is a block diagram of a system for heating and cooling a vacuum chuck.

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 on 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, a means for heating and cooling the wafer W is generally provided.

As shown in FIG. 1, the wafer inspection device 200 comprises a base 236, a moving 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. A wafer W is placed on the vacuum chuck 100 and vacuum-sucks the wafer W. As will be described in detail below, 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. Furthermore, a vacuum exhaust device 270, such as a vacuum pump, is connected to the vacuum chuck 100 to ensure reliable vacuum suction of the wafer W.

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

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, to which a card holder 262 is attached. A probe card 266 corresponding to the semiconductor chip 450 (see Figure 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 multiple probes 264 that come into contact with the semiconductor chip 450. The probes 264 have a delicate structure to specifically contact the microscopic terminals on the order of μm formed on the chip 450, and are designed to prevent excessive loads from being applied. Therefore, the probes 264 are set to approach the wafer W in a predetermined posture and at a predetermined speed during inspection.

A test head 220 is rotatably mounted on the upper end of the support 218. When the test head 220 rotates, a contact cylinder 268 is provided on the surface of the test head 220 that faces the probe card 266, and information detected by the probes 264 is transmitted to the control device 210 via the test head 220.

The XYZ-Θ table 240 can move left and right in the figure via the 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. After placing and suctioning the wafer W onto the vacuum chuck 100, the XYZ-Θ table 240 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 the probe 264. Here, "all at once" means that while the wafer W remains suctioned onto the vacuum chuck 100, the XYZ-Θ table 240 is driven to continuously inspect multiple chips 450, preferably all chips 450 created on the surface of the wafer W.

Figure 2 shows an example of a semiconductor wafer W that can be placed on and attracted by the vacuum chuck 100 of 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 that shown in Figure 2; 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 warped semiconductor wafers W.

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 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 approximately 13.3 mm wide and 10.9 mm long, are formed on a surface on which an orientation flat is formed.

The semiconductor chip 450 shown in Figure 2(b) is called an ultra-high bandwidth memory (HBM: High Bandwidth Memory), and includes a processor 410 and multiple layers (four layers in the figure) of stacked memory (DRAM) 420. An interface (I/F) 426 is located below the memory 420 in the stacked structure. The processor 410 and memory 420 are connected via a silicon 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 semiconductor wafer substrate 400, and the silicon interposer 430 and interface 426 are connected using terminals 412, 402, 422, etc. formed on the respective parts, and the memories 420 are connected via lead wires 424. The semiconductor chip 450 formed in this manner can become distorted due to the difference in weight between the processor 410 and the stacked memory 420, as well as the processing method used to form the chip 450, and is formed to a thickness of several hundred microns.

An embodiment of the vacuum chuck 100 according to the present invention, which is provided in the inspection apparatus 200 shown in FIG. 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 vertical cross-sectional view of the chuck body 190 provided in the vacuum chuck 100, showing various examples equipped with means for heating and/or cooling the wafer W. Figure 5(a) shows an example in which only a heating means is provided, Figure 5(b) shows the most standard example in which both heating and cooling means are provided, and Figure 5(c) shows an example in which both a vacuum suction unit and a cooling unit are integrated and equipped with means for heating and cooling. In Figure 5, the left half is a cross-section taken at position B in Figure 4, and the right half is a cross-section taken at position A or C in Figure 4. Figure 6 is a diagram illustrating the details of the suction holes and vacuum seals formed in the chuck body 190. Figure 6(a) is a vertical 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.

The following explanation will use the standard vacuum chuck 100 shown in Figure 5(b) as an example, but the other vacuum chucks 100 shown in Figures 5(a) and (c) are similar. As shown in Figure 5(b), the vacuum chuck 100 comprises 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 or the like (not shown) 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. Furthermore, a heater 182 is disposed in the heating block 180 and is wound in a spiral pattern.

The vacuum suction block 190 that forms the top of the vacuum chuck 100 has traditionally been formed with numerous holes and grooves to stably suction and hold 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 to accommodate warped wafers W.

As shown in Figures 3 and 4, the chuck body 190 is circular and has a larger diameter than the wafer W. The portion of the chuck where the wafer W is placed has a plurality of first suction holes 154 formed in the radial direction to suck and hold the flat wafer W. These suction holes 154 are provided at multiple 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 approximately 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.

The number of first suction holes 154 may be reduced on the central side (smaller diameter side) of the chuck body 190. Each of the first suction holes 154 at the same circumferential position is connected by a first communication passage 158 extending radially from the outer periphery. Vacuum suction pipe connections 120, to which vacuum suction fittings are attached according to the position of each of the first communication passages 158, are provided on the outer periphery of the chuck body 190 (see Figure 3), and are connected to a vacuum exhaust device 270 via piping (see Figure 1). This allows the entire top surface of the chuck body 190 to be vacuum suctioned.

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 circumferential intervals in the vacuum chuck. As described above, various processes, including those for arranging a temperature sensor (described later), are concentrated in the center of the chuck body 190. To avoid excessive processing, the first suction hole 154 is omitted near the center. Instead, a third suction hole 156, which primarily serves to vacuum the center of the chuck body 190, is formed at a different circumferential position from the first suction hole 154 (position A in the figure). As with the first suction hole 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 hole 154 and the third suction hole 156 are set to be the same. By using these first and third suction holes 154, 156 to vacuum-suck the backside of the wafer W, in the case of a flat wafer W, the wafer W can be fixed and held on 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 communication path 160 are located separately from the first suction hole 154 and the first communication path 158, but one of the multiple first communication paths 158 and its corresponding first suction hole 154 can also be used as both the third communication path 160 and the third suction hole 156.

However, in the case of large-diameter wafers W in which the semiconductor wafer substrate 400 of the wafer W is very thin relative to its outer diameter, particularly wafers W on which semiconductor chips 450 such as HBMs are formed, the amount of warping becomes large at the periphery, and even if suction is performed using only the first and third suction holes 154, 156, a gap may form between the wafer W and the vacuum chuck 100 at the periphery. 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 could cause damage to the expensive probe 264.

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 substantially 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.

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 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 a foam material. Silicon resin is preferred as the foam material.

When the elastic body 110 is a tetrafluoroethylene resin tube, 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.

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 there is a risk that empty suction will occur even if vacuum suction is performed to flatten the wafer W. 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.

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 or 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, the second suction hole 132, which is larger in diameter than the first suction hole 154 or the third suction hole 156, is positioned centrally 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: location 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 radial locations. Second suction holes 132 at the same circumferential position are connected to each other by a second communication passage 136 formed from the outer periphery toward the center.

6(a) shows the positional relationship of 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.

The plurality of second suction holes 132, which are primarily used to correct 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 located radially 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. In other words, 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. At the radial positions of the chuck body 190 where the first suction holes 154 and the third suction holes 156 are formed, a full-circumferential groove 152 having a depth of 1 mm or less is formed to reduce suction unevenness. 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 only about 5 second suction holes 132. Therefore, if the 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.

The dovetail groove 140, which has a trapezoidal cross section, is located radially outward of the first to third suction holes 154, 132, and 156. In other words, the dovetail groove 140 is located radially outward of the outermost circumferential groove 152 or the first suction hole 154, and serves as a seal groove that prevents the first to third suction holes 154, 132, and 156 from sucking in air radially outward of the dovetail groove 140.

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 .

From this state, as shown in Figure 7(b), the center of the wafer W, which is relatively flat and has minimal warping, is vacuum-sucked first using the third suction hole 156. This prevents the wafer W from moving within the horizontal plane during vacuum suction. By fixing the wafer W to the chuck body 190, the wafer W is prevented from shifting position due to the airflow generated when the peripheral edge is vacuum-sucked as shown in Figure 7(c).

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 larger than that of the first suction hole 154, so it has a strong suction force and can flatten the wafer W despite its rigidity. In this way, suction from the second suction hole 132 generates a large force, which is likely to cause a force to move the wafer W in a horizontal plane. For this reason, suction from the third suction hole 156 and the first suction hole 154 is also used in combination.

Once the wafer W is sucked into the chuck body 190, the sealing action of the elastic body 110 ensures that there is almost no leakage between the wafer W and the suction surface 102 of the chuck body 190. Therefore, vacuum suction 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.

7(d) to 7(f) are enlarged schematic views showing the state of the elastic body 110 in the dovetail groove 140 in each state shown in FIGS. 7(a) to 7(c). When the backside of the wafer W is brought into contact with the elastic body 110 without vacuum suction, the height of the elastic body 110 from the chucking surface 102 of the chuck body 190 is approximately the natural height _h0 . On the other hand, when only the center side of the wafer W is suctioned, the height of the elastic body 110 is slightly reduced, and the height from the chucking surface 102 is _h1 (< _h0 ). Next, when the wafer W is flattened by vacuum suction through the second suction hole 132, the elastic body 110 is substantially entirely contained within the dovetail groove 140 without protruding from the dovetail groove 140. This completely flattens the wafer W, preventing tilting of the wafer W and erroneous contact with the probe 264.

Figure 8 shows a block diagram of wafer W temperature control using the heating and cooling block shown in Figure 5. Here, heating and control of wafer W will be explained using the standard vacuum chuck 100 shown in Figure 5(b) as an example, but the same applies to other vacuum chucks (Figures 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.

The coolant flow path is connected by coolant piping 316 to a cooling unit (cooling device) 314 provided in a chiller unit 310 located remotely from the inspection device 200. The coolant piping 316 has a supply pipe 316a that supplies the coolant generated in the chiller unit 310 to the vacuum chuck 100, and a return pipe 316b that returns the coolant warmed by the vacuum chuck 100 to the chiller unit 310. The cooling unit 314 is controlled via signal line 308 by a chiller control unit 312 provided in the chiller unit 310. The heater 182 built into the vacuum chuck 100 is connected by a power line 338 to a heater controller 324 provided in the temperature control device 320, and is supplied with power from the heater controller 324.

In order 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 in this manner, 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, converted into a digital signal, and input via signal line 336 to a main control device 322 provided in the temperature control device 320. The main control device 322 is connected to a heater controller 324 via signal line 326 and to a chiller control unit 312 via signal line 318. Therefore, the temperature of the chucking surface 102 of the vacuum chuck 100 detected by the temperature sensor 334, in other words, the temperature of the wafer W, is fed back to control the temperature of the heater 182 and the temperature of the coolant. At the same time, the detection results of a prober (CPU) 222, an inspection means disposed opposite the wafer W, are also fed back to the temperature control device 320.

As explained above, the vacuum chuck of this embodiment can sufficiently flatten even large diameter 300 mm wafers with peripheral warpage up to about 2 mm, making it possible to perform functional inspections on the wafers all at once. Furthermore, it was confirmed that wafers with downward convex warpage can be reliably flattened to the above warpage range, and that even if the warpage is downward convex, it can be reliably flattened up to about 2 mm.

In tests and inspections in which the temperature of a wafer W was controlled using this vacuum chuck 100, warpage tended to increase at high temperatures compared to room temperature. Therefore, a warpage of 2 mm at room temperature increases to 4 mm at 100°C, and even if vacuum suction was attempted at that temperature, a gap exceeding the allowable warpage would be 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/inspection temperature while 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 temperature.

In the above example, the elastic body was a tube. However, by using a solid foam resin for the elastic body, air is sucked from the internal bubbles when vacuum suction is applied, causing the entire elastic body to shrink and deform so that it fits into the dovetail groove. Therefore, as with 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 vacuum suction or preventing the wafer from being sucked at an angle, thereby straightening the wafer flat. When a foam material is used, the solid material allows it to almost completely return to its pre-vacuum state and regain its rigidity even after vacuum suction is released. Therefore, when a new wafer is placed, the same state as the previous wafer can be reproduced. In other words, wafers with the same amount of warpage can be tested. This prevents damage to the probe card probes caused by improper contact between the probe and the wafer.

100... vacuum chuck, 102... suction surface, 110... elastic body (tube or foam material 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 Lock, 182... heater, 190... suction block (chuck 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 section, 314... cooling unit (cooling device), 316... cooling liquid piping, 316a... forward 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 (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 surface), _W2 ...dovetail groove width (top surface)

Claims (7)

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. 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. The vacuum chuck described in claim 2, wherein when the semiconductor wafer is placed so that its outer periphery abuts against the elastic body, the fourth suction hole sucks the central portion of the semiconductor wafer, and the second suction hole sucks the outer periphery. The vacuum chuck of claim 3, wherein the plurality of third suction holes begin suctioning the semiconductor wafer together with the second suction holes. The vacuum chuck of claim 4, wherein when the semiconductor wafer is suctioned, the semiconductor wafer is sucked by the third suction hole and the fourth suction hole. The vacuum chuck of claim 4, wherein the suction by the second suction hole is weakened when the semiconductor wafer is suctioned. A wafer inspection device comprising the vacuum chuck described in any one of claims 1 to 6 and a probe card capable of simultaneously measuring multiple semiconductor chips formed on the upper surface of a semiconductor wafer.