Chuck table, processing device, and method for processing object wafer

Abstract

To provide a holding table capable of reducing processing defects when processing a wafer having a step.SOLUTION: A chuck table is configured to hold the surface of an object having a device region on its surface, in which devices having convex portions are formed in multiple regions partitioned by multiple intersecting planned division lines, and a peripheral surplus region surrounding the device region, the chuck table includes a holding surface that faces the convex portions and holds the device region, and a peripheral surplus region support portion that surrounds the holding surface, protrudes from the holding surface, and supports the peripheral surplus region of the object, the peripheral surplus region support portion includes an elastic member that can elastically deform in accordance with the height of the convex portions, and a non-elastic member that is arranged between the elastic member and the peripheral surplus region of the object.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a chuck table and a method for machining a workpiece. [Background technology]

[0002] In the manufacturing process of semiconductor devices, a mounting technique called flip-chip bonding has recently been put into practical use. In this technique, multiple metal protrusions called bumps are formed on the surface of the device and these bumps are then bonded to electrodes formed on a wiring substrate.

[0003] Typically, devices are formed in the central region of the wafer and not in the peripheral region, so in such a bumped wafer, a step occurs between the device region where the bumps are formed and the peripheral excess region that surrounds this device region and where no bumps are formed.

[0004] When processing a wafer with such a step, if the surface of the wafer is held by suction on a chuck table, a negative pressure leak occurs, making it impossible to hold the wafer by suction, which poses a problem.

[0005] Therefore, a method has been devised in which an elastic member protruding from the holding surface is provided on the outer periphery of the chuck table to prevent leakage and hold the wafer by suction (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-50461 Summary of the Invention [Problem to be solved by the invention]

[0007] However, as disclosed in Patent Document 1, in a configuration in which the peripheral excess region of the wafer is held by an elastic member, a new problem has become apparent in that the peripheral excess region is supported only by the elastic member, causing it to sag relative to the device region.

[0008] For example, if a laser beam is irradiated from the back side of the wafer in this state to form a modified layer inside the wafer, the focusing position of the laser beam will change between the peripheral excess region and the device region, which may prevent the modified layer from being formed in the desired position and result in poor division.

[0009] The present invention has been made in view of the above circumstances, and has as its object to provide a holding table that can reduce processing defects when processing a wafer having a step. [Means for solving the problem]

[0010] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0011] According to one aspect of the present invention, there is provided a chuck table for holding the surface of an object having a device region on its surface, in which devices having convex portions are formed in multiple regions partitioned by multiple intersecting planned division lines, and a peripheral surplus region surrounding the device region, the chuck table comprising: a holding surface facing the convex portion and holding the device region; and a peripheral surplus region support portion surrounding the holding surface, protruding from the holding surface and supporting the peripheral surplus region of the object, the peripheral surplus region support portion including an elastic member that can elastically deform in accordance with the height of the convex portion, and a non-elastic member arranged between the elastic member and the peripheral surplus region of the object.

[0012] According to another aspect of the present invention, the non-elastic member is made of any one of SUS, aluminum, and glass, or a combination of a plurality of these materials.

[0013] According to one aspect of the present invention, the processing apparatus comprises the chuck table, a processing unit for processing the object held on the chuck table, and a control unit, wherein the control unit is capable of controlling the amount of contraction of the elastic member by changing the negative pressure value acting on the chuck table from a suction source.

[0014] According to one aspect of the present invention, the processing unit is a laser beam irradiation unit that processes the object by irradiating the object with a focused laser beam.

[0015] According to one aspect of the present invention, there is provided a method for processing an object having, on its surface, a device region in which devices having convex portions are formed in multiple regions partitioned by multiple intersecting planned division lines, and a peripheral excess region surrounding the device region, the method comprising: a holding step of placing the object with the front side facing the chuck table and applying negative pressure from a suction source to the chuck table to hold the object; and a processing step of performing a predetermined process on the object from the back side of the object after the holding step.

[0016] Furthermore, according to one aspect of the present invention, the method further includes a correlation acquisition step of acquiring in advance the correlation between the negative pressure value applied to the chuck table from the suction source and the amount of contraction of the elastic member at that negative pressure value, and in the holding step, the negative pressure value applied to the chuck table from the suction source is determined based on the correlation acquired in the acquisition step and the height of the convex portion formed on the object so that the back side of the object is approximately flat with the holding surface of the chuck table. [Effects of the Invention]

[0017] The present invention provides the following effects. In other words, according to one aspect of the present invention, the sagging of the peripheral surplus region of the target object relative to the device region is suppressed, thereby preventing the focusing position of the laser beam from changing between the peripheral surplus region and the device region, allowing a modified layer to be formed in the desired position and avoiding poor division.

[0018] Furthermore, according to one aspect of the present invention, when processing an object with a laser beam, the elastic member can be protected by the non-elastic member from being hit by the laser beam. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a laser processing device. [Figure 2] FIG. 1 is a perspective view of the front surface side of a wafer as an example of an object. [Figure 3] FIG. 1 is a side view of a wafer as an example of an object. [Figure 4] FIG. 2 is a diagram illustrating the configuration of a frame unit. [Figure 5] FIG. 2 is a diagram illustrating the configuration of a chuck table. [Figure 6] 1A to 1C are diagrams showing steps constituting a processing method. [Figure 7] FIG. 10 is a diagram showing the correlation between negative pressure value and contraction amount. [Figure 8] (A) is a diagram showing the state when the negative pressure value is 0, (B) is a diagram showing the state when the negative pressure value is P1, and (C) is a diagram showing the state when the negative pressure value is P2. [Figure 9] FIG. [Figure 10] 10A and 10B are diagrams illustrating a state in which a wafer is held by suction. [Figure 11] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 shows a schematic configuration diagram of a laser processing apparatus 2 equipped with a chuck table according to an embodiment of the present invention. The laser processing apparatus 2 includes a pair of guide rails 6 mounted on a stationary base 4 and extending in the Y-axis direction.

[0021] The Y-axis moving block 8 is moved in the indexing feed direction, i.e., in the Y-axis direction, by a Y-axis feed mechanism (Y-axis feed means) 14 consisting of a ball screw 10 and a pulse motor 12. A pair of guide rails 16 extending in the X-axis direction are fixed on the Y-axis moving block 8.

[0022] The X-axis moving block 18 is guided by the guide rail 16 and moved in the processing feed direction, that is, in the X-axis direction, by an X-axis feed mechanism (X-axis feed means) 28 composed of a ball screw 20 and a pulse motor 22 .

[0023] A chuck table 50 is mounted on the X-axis moving block 18. The chuck table 50 is provided with a plurality of clamps 51 (four in this embodiment) for clamping the annular frame F shown in FIG.

[0024] A column 32 is erected behind the stationary base 4. A casing 36 of a laser beam irradiation unit 34, which is a processing unit, is fixed to a Z-axis moving block 33 that is movable up and down on the column 32. A laser beam oscillation means including a YAG laser oscillator and the like is housed inside the casing 36, and a condenser (laser head) 38 that focuses the laser beam on the wafer to be processed is attached to the tip of the casing 36.

[0025] An imaging unit 40 is attached to the tip of the casing 36 of the laser beam irradiation unit 34, and captures an image of the wafer 11 held on the chuck table 50. The imaging unit is equipped with an imaging element compatible with infrared light. The condenser 38 and imaging unit 40 are aligned in the X-axis direction.

[0026] The laser processing device 2 is provided with a touch panel 9 that enables an operator to perform various setting operations and displays various operating conditions of the device.

[0027] The laser processing device 2 is provided with a control unit 80 for automatically controlling the laser processing device 2 in accordance with the operation of various operating parts and the touch panel 9.

[0028] FIG. 2 is a perspective view of the front surface side of a wafer 11 as an example of an object to be suction-held by the chuck table 50, and FIG. 3 is a side view of the same.

[0029] A plurality of dividing lines (streets) 13 are formed in a grid pattern on the surface 11a of the wafer 11, and devices 15 such as ICs and LSIs are formed in each area partitioned by the orthogonal dividing lines 13. The wafer 11 may be made of, for example, silicon, as well as lithium tantalate (LT), lithium niobate (LN), sapphire, GaN, GaAs, etc., but is not limited to these.

[0030] The wafer 11, in which each device 15 has a plurality of bumps 17 (electrode bumps), has on its surface a device region 19 in which a plurality of devices 15, each having a plurality of bumps 17, are formed, and a peripheral excess region 21 surrounding the device region 19. The height of the bumps 17 is, for example, 50 μm to 200 μm.

[0031] 4, the back surface 11b of the wafer 11 is attached to tape T having an adhesive layer, and the outer periphery of the tape T is attached to an annular frame F. As a result, the wafer 11 is handled in the form of a frame unit 23 in which the wafer 11 is fixed to the opening of the annular frame F via the tape T. In the form of this frame unit 23, the front surface 11a of the wafer 11 on which the devices 15 and bumps 17 are formed is exposed. The tape T is formed by applying an adhesive layer to a base material made of a resin such as polyolefin.

[0032] Next, the configuration of the chuck table 50 shown in FIG. 5 will be described. The chuck table 50 holds the surface 11a of the wafer 11, which is the object, and is configured to include a holding surface 53a that faces the bumps 17, which are the convex portions of the surface 11a of the wafer 11, and holds the device region 19, and a peripheral surplus region support portion 54 that surrounds the holding surface 53a, protrudes from the holding surface 53a, and supports the peripheral surplus region 21 of the wafer 11.

[0033] A porous sheet 53 having breathability and elasticity is laid on the upper surface of the disk-shaped porous member 52, and a holding surface 53a for holding the wafer 11 is formed by the exposed surface of the porous sheet 53. The porous member 52 is made of, for example, porous ceramic, and the porous sheet 53 is made of, for example, synthetic resin.

[0034] The underside of the porous member 52 is connected to a suction source 66 via suction paths 61, 62 and a control valve 64. When the control valve 64 is opened, suction from the suction source 66 generates negative pressure on the holding surface 53a through the porous member 52 and the porous sheet 53, and the wafer 11 is held by suction. The elasticity of the holding surface 53a prevents damage to the bumps 17.

[0035] A regulator 65 for adjusting the negative pressure value generated on the holding surface 53a is provided in the suction path 62. The regulator 65 is connected to a control unit 80, which monitors the pressure of the regulator 65 and adjusts the pressure by controlling the operation of the regulator 65.

[0036] With the above-described configuration, by changing the negative pressure value acting on the chuck table 50 from the suction source 66, it becomes possible to control the amount of contraction of the elastic member 54c, as will be described later.

[0037] The outer peripheral excess area support portion 54 is formed in a ring shape so as to surround the holding surface 53a, and in this embodiment, is composed of an inner ring 54a, an outer ring 54b that is provided to cover the inner ring 54a, an elastic member 54c attached to the upper part of the outer ring 54b, and a non-elastic member 54d attached to the upper part of the elastic member 54c.

[0038] The inner ring 54a is configured, for example, as a ring-shaped member made of metal, and is disposed on the upper surface 50c of the outer circumferential portion 50b of the table body 50a of the chuck table 50. The inner ring 54a is a member for fixing the porous sheet 53 laid on the upper surface of the bolus member 52, and is not particularly limited to a ring-shaped member.

[0039] The outer ring 54b is, for example, a metal ring-shaped member, and is positioned at a specified position by being attached so as to cover the inner ring 54a. Furthermore, suction holes 50d that communicate with the suction source 66 via suction paths 71 and 72 are formed in the upper surface 50c of the outer periphery 50b of the table main body 50a, and the outer ring 54b is held to the outer periphery 50b of the table main body 50a by suction. Note that instead of being held by suction, the outer ring 54b may also be fixed by, for example, screws.

[0040] The outer ring 54b is detachable from the table body 50a, and multiple types with different thicknesses in the Z-axis direction are available, making it possible to select the outer ring 54b to be used appropriately depending on the object, such as the height of the protrusions, as will be described in detail later.

[0041] The elastic member 54c is an elastic member that can be elastically deformed, and can be configured, for example, as a ring-shaped member made of synthetic resin. The elastic member 54c is disposed between the outer ring 54b and the non-elastic member 54d, and functions to allow movement of the non-elastic member 54d in the Z-axis direction within the range of elastic deformation.

[0042] The ring-shaped elastic member 54c functions to prevent leakage of negative pressure (vacuum) between the non-elastic member 54d and the outer peripheral excess area 21.

[0043] The cross section of the elastic member 54c can be, for example, a rectangle having an upper surface and a lower surface. The lower surface of the elastic member 54c is bonded to the upper surface of the outer ring 54b, and the two are fixed so as not to shift relative to each other. The upper surface of the elastic member 54c is bonded to the lower surface of the non-elastic member 54d, and the two are fixed so as not to shift relative to each other.

[0044] The thickness of the elastic member 54c in the Z-axis direction is, for example, 1 mm to 4 mm.

[0045] The non-elastic member 54d can be configured, for example, by a ring-shaped member made of stainless steel (SUS), aluminum, glass, etc. Note that the non-elastic member 54d may be configured by combining materials or by using a plurality of members.

[0046] The cross section of the inelastic member 54d may be, for example, a rectangle having an upper surface and a lower surface. The upper surface of the inelastic member 54d is configured to abut against the peripheral excess region 21 of the wafer 11. The lower surface of the inelastic member 54d is bonded to the elastic member 54c, and the two are fixed so as not to shift relative to each other.

[0047] The thickness of the non-elastic member 54d in the Z-axis direction is, for example, 0.3 mm to 1.5 mm when the material is SUS.

[0048] Next, an example of a method for processing an object using the above configuration will be described. FIG. 6 is a diagram showing steps constituting the processing method.

[0049] <Correlation acquisition step> As shown in FIG. 7, this is a step in which the correlation between the negative pressure value P applied to the chuck table from the suction source and the contraction amount H of the elastic member 54c at the negative pressure value P is obtained in advance.

[0050] Specifically, as shown in FIG. 8A, for example, a test wafer 11 (frame unit 23 (FIG. 3)) is prepared so that the front surface 11a of the wafer 11 can be held by the holding surface 53a of the chuck table 50. The contraction amount H of the elastic member 54c in a state where there is no suction (negative pressure value = 0) is set to 0 (zero). Next, as shown in FIG. 8B, the contraction amount H1 of the elastic member 54c is measured when a negative pressure value P1 is set. Furthermore, as shown in FIG. 8C, the negative pressure value is increased, and the contraction amount H2 of the elastic member 54c at a negative pressure value P2 is measured. Similarly, as shown in FIG. 7, the contraction amounts H3 and H4 are also measured when the negative pressure values ​​are set to P3 and P4. FIG. 7 shows that as the negative pressure value increases, the degree of vacuum increases, and the wafer 11 is more strongly attracted to the holding surface 53a, resulting in a larger contraction amount.

[0051] The shrinkage amount H1 is measured by, for example, measuring the shrinkage amount of the thickness of the elastic member 54c using a measuring device (not shown). Note that, as shown in Fig. 8(A), a change in the height position 11h of the back surface 11b of the wafer 11 may be measured, and the amount of change may be used as the shrinkage amount of the thickness of the elastic member 54c.

[0052] As described above, by measuring the contraction amount of the elastic member corresponding to each negative pressure value, the correlation between the two is obtained in advance. This correlation is stored in the control unit 80 (FIG. 1) and is referred to as appropriate in subsequent holding steps, etc.

[0053] <Holding step> As shown in FIG. 9, this is a step in which a negative pressure is applied to the chuck table 50 from a suction source 66 to hold the wafer 11 as the object.

[0054] In addition, in the holding step, the negative pressure value acting on the chuck table from the suction source is determined based on the correlation obtained in the acquisition step and the height of the convex portion formed on the object so that the back surface 11b side of the object, i.e., the wafer 11, is approximately flat with the holding surface 53a of the chuck table 50.

[0055] Specifically, as shown in FIG. 9, the frame unit 23 is placed on the chuck table 50 with the front surface 11a of the wafer 11 facing downward, and the frame F is clamped by the clamps 51.

[0056] Then, for example, when the operator operates the touch panel 9 (FIG. 1) to input the height D (protrusion height) of the bump 17, which is the convex portion of the wafer 11, the control unit 80 refers to the correlation and sets the negative pressure value P that generates the contraction amount H of the elastic member 54c according to this height D.

[0057] For example, when the bump height is high, a small negative pressure value P1 is set so as to result in a small contraction amount H1, as shown in Fig. 7. Even when the negative pressure value P1 is small, the elastic member 54c is reliably contracted so that the back surface 11b of the wafer 11 becomes substantially flat with the holding surface 53a of the chuck table 50. Here, a small negative pressure value means a low degree of vacuum, e.g., -30 kPa.

[0058] On the other hand, when the height of the bump is low, a large negative pressure value P4 is set so as to result in a large amount of shrinkage H4, as shown in Fig. 7. Here, a large negative pressure value means a high degree of vacuum, for example -60 kPa.

[0059] Next, as shown in FIG. 10, the control unit 80 controls the regulator 65 to achieve the specified negative pressure value P, and opens the control valve 64 to start suction.

[0060] When suction begins, the wafer 11 is sucked as a whole to be attracted to the holding surface 53a, and the wafer 11 is supported by the bumps 17 in the device region 19, while the outer periphery of the outer periphery surplus region 21 is supported by the outer periphery surplus region support portion 54.

[0061] At this time, the elastic member 54c of the peripheral surplus region support portion 54 contracts, so that the portion of the peripheral surplus region 21 supported by the peripheral surplus region support portion 54 does not rise up, and the wafer 11 can be held flat as a whole.

[0062] <Processing steps> As shown in FIG. 11, this is a step in which a predetermined process is performed on the wafer 11, which is the object, from the back side thereof after the holding step.

[0063] Specifically, in the laser beam irradiation unit 34, which is a processing unit, the focusing position is adjusted to a predetermined height position on the wafer 11, and the chuck table 50 is processed and moved while irradiating the laser beam, thereby forming a modified layer 55 at the desired location.

[0064] In this case, the change in the focusing position of the laser beam between the peripheral surplus region 21 (Figure 10) and the device region 19 is prevented, so that the modified layer 55 can be formed at the desired position, and defective division can be avoided.

[0065] Furthermore, in this embodiment, which involves laser processing, a non-elastic member 54d is disposed at the top of the outer circumferential excess area support portion 54, as shown in the enlarged portion of Figure 11, and this non-elastic member 54d can protect the elastic member 54c from being hit by the laser beam LB. For example, by using SUS as the material for the non-elastic member 54d, the laser beam LB can be blocked, preventing damage and deterioration of the elastic member 54c. In particular, since the elastic member 54c is prone to deterioration, the use of the non-elastic member 54d is highly effective in preventing negative pressure (vacuum) leaks due to damage.

[0066] Furthermore, the upper surface of the inelastic member 54d may be formed with irregularities to diffusely reflect the laser beam.

[0067] Furthermore, as shown in FIG. 1, in this embodiment, the processing unit is a laser beam irradiation unit 34 that processes the target object, wafer 11, by concentrating and irradiating a laser beam on it. However, the embodiment of the present invention is not limited to this, and may be, for example, a cutting unit that cuts the wafer with a cutting blade, a grinding unit that thins the wafer with a grinding wheel, or a polishing unit that polishes the wafer with a polishing pad.

[0068] Furthermore, the object may be a workpiece such as a wafer to be processed, or may be an object to be inspected. For example, even when an object to be inspected having a convex portion is inspected by being held by suction on a chuck table, the object can be held so that the back side of the object to be inspected is substantially flat with the holding surface, and sagging of the peripheral excess area toward the device area is suppressed, thereby improving the measurement accuracy in various inspections. [Explanation of symbols]

[0069] 2. Laser processing equipment 4 Stationary base 9 Touch Panel 11 wafers 11a surface 11b Back side 11h position 13 Planned division line 15 devices 17 Bump 19 Device Area 21 Surplus outer area 23 Frame Unit 34 Laser beam irradiation unit 40 Imaging unit 50 Chuck Table 50a Table body 50b outer periphery 50c top surface 50d suction hole 51 Clamp 52 Porous material 53 Porous Sheet 53a Holding surface 54 Outer periphery excess area support part 54a Inner ring 54b Outer ring 54c Elastic member 54d Inelastic members 62 Suction path 64 Control Valve 65 Regulator 66 Suction source 80 Control Unit Front annular frame H shrinkage amount H1 shrinkage amount P negative pressure value P1 negative pressure value T-tape LB laser beam

Claims

1. a device region in which devices having convex portions are formed in a plurality of regions partitioned by a plurality of intersecting planned division lines; a chuck table for holding a surface of an object having a peripheral excess area surrounding the device area on its surface, a holding surface that faces the protrusion and holds the device region; a peripheral excess area support portion that surrounds the holding surface and protrudes from the holding surface to support the peripheral excess area of ​​the object, The outer circumferential excess area support portion is an elastic member that is elastically deformable in accordance with the height of the protrusion; a non-elastic member disposed between the elastic member and the outer peripheral excess region of the object; A chuck table comprising:

2. 2. The chuck table according to claim 1, wherein the non-elastic member is made of any one of SUS, aluminum, and glass, or a combination of a plurality of these.

3. The chuck table according to claim 1 or 2; a processing unit for processing the object held on the chuck table; a control unit, The control unit A processing apparatus capable of controlling the amount of contraction of the elastic member by changing the negative pressure value acting on the chuck table from a suction source.

4. The processing unit 4. The processing apparatus according to claim 3, wherein the processing apparatus is a laser beam irradiation unit that processes the object by irradiating the object with a focused laser beam.

5. a device region in which devices having convex portions are formed in a plurality of regions partitioned by a plurality of intersecting planned division lines; a peripheral excess region surrounding the device region on a surface thereof, The object is placed on the chuck table according to claim 1 or 2 with the front surface facing the chuck table, a holding step of applying negative pressure from a suction source to the chuck table to hold the object; A method for processing an object, comprising: after the holding step, a processing step of performing a predetermined process on the object from the back side of the object.

6. a correlation obtaining step of obtaining in advance a correlation between a negative pressure value applied to the chuck table from a suction source and an amount of contraction of the elastic member at the negative pressure value, In the holding step, According to the correlation obtained in the obtaining step and the height of the convex portion formed on the object, 6. The method for machining an object according to claim 5, wherein a negative pressure value acting on the chuck table from the suction source is determined so that the back side of the object is substantially flat with the holding surface of the chuck table.

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