Machining tools and polishing pads

Abstract

We propose a novel technology for a processing tool for polishing workpieces such as disc-shaped wafers, and for a polishing pad used with that processing tool. [Solution] A machining tool used for polishing a workpiece, comprising a disc-shaped base and a plurality of polishing layers fixed to one surface of the base and arranged in the circumferential direction of the base, wherein the circumferential width of each polishing layer expands from the center of the base toward the outer edge to a predetermined position and then narrows from that predetermined position toward the outer edge, and at least one groove is formed on the polishing surface of each polishing layer, extending from the center of the base toward the outer edge.

Description

Technical Field

[0001] The present invention relates to a processing tool for polishing a workpiece such as a wafer having a disc shape, and a polishing pad used for the processing tool.

Background Art

[0002] Conventionally, as disclosed in, for example, Patent Document 1, the back surface of a wafer in the semiconductor manufacturing field is ground using a known grinding apparatus, and a polishing wheel is attached to the spindle of the grinding apparatus to be processed to a predetermined thickness through rough grinding and finish grinding. It is known.

[0003] And, as disclosed in, for example, Patent Document 2, when the back surface of a wafer is ground, grinding marks (saw marks) remain on the ground surface. Therefore, after the grinding process, the back surface of the wafer is polished with a polishing pad by CMP (Chemical Mechanical Polishing) to remove the saw marks. It is known.

[0004] In this CMP, polishing is performed while supplying a polishing liquid (slurry) containing abrasive grains between the polishing pad and the wafer. However, since chemicals are used in the polishing liquid in CMP, there is a problem that its handling and waste liquid treatment of the polishing liquid after polishing are required. In this regard, for example, as in Patent Document 3, a polishing wheel (also referred to as a dry polishing wheel) that performs polishing without using a polishing liquid is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0006] However, it has been confirmed that surface abnormalities (surface burning) can occur in the wafer, particularly in the central region, during polishing using the polishing wheel configuration disclosed in Patent Document 3. Upon investigating the cause, it was found that this is due to the continuous accumulation of polishing debris (contamination) generated during the polishing process because the central region of the wafer is constantly in contact with the polishing wheel.

[0007] Furthermore, it was confirmed that the accumulation of polishing debris can sometimes cause a depression in the center of the wafer.

[0008] In view of the above problems, the present invention proposes a novel technology relating to a processing tool for polishing workpieces such as disc-shaped wafers, and a polishing pad used in the processing tool. [Means for solving the problem]

[0009] The problems that this invention aims to solve are as described above, and the means for solving these problems will now be explained.

[0010] That is, according to one aspect of the present invention, a machining tool used for polishing a workpiece comprises a disc-shaped base and a plurality of polishing layers fixed to one surface of the base and arranged in the circumferential direction of the base, wherein the circumferential width of each polishing layer expands from the center side of the base toward the outer edge side up to a predetermined position and then narrows from that predetermined position toward the outer edge, and at least one groove is formed on the polishing surface of each polishing layer extending from the center side of the base toward the outer edge side.

[0011] Furthermore, according to one aspect of the present invention, the width of the groove narrows from the center of each base toward the outer edge.

[0012] Furthermore, according to one aspect of the present invention, the polishing layer is configured as a polishing pad that is molded separately from the base and is integrated with the base by adhesion.

[0013] Furthermore, according to one aspect of the present invention, there is a polishing pad used in a machining tool used for polishing a workpiece, wherein a plurality of polishing pads are arranged circumferentially on one side surface of a disc-shaped base of the machining tool to form a polishing layer, the circumferential width of each polishing pad is such that, when placed on the base, it expands from the center of the base toward the outer edge to a predetermined position and then narrows from that predetermined position toward the outer edge, and at least one groove is formed on the polishing surface of each polishing pad, extending from the center of the base toward the outer edge when placed on the base. [Effects of the Invention]

[0014] The present invention provides the following effects: In other words, according to one aspect of the present invention, even in situations where the contact time with the polishing layer is long in the central region of the wafer, polishing debris (contaminants) generated during the polishing process can be taken into the grooves and prevented from accumulating, thereby preventing indentation in the center of the wafer and variations in wafer thickness caused by this accumulation. [Brief explanation of the drawing]

[0015] [Figure 1] An external perspective view showing one embodiment of a polishing apparatus. [Figure 2] A diagram illustrating polishing wheels, etc. [Figure 3] A diagram illustrating the rotation direction of the polishing wheel and wafer. [Figure 4] A diagram showing the arrangement of the polishing pads. [Figure 5] (A) is a schematic diagram illustrating the polishing process. (B) is a diagram showing an example of the back surface of a polished wafer. [Figure 6] A diagram illustrating the movement of polishing debris through the polishing groove.

Best Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an external perspective view of a polishing apparatus 2 equipped with a polishing wheel which is a processing tool of the present invention. A column 6 is erected behind a base 4 of the polishing apparatus 2. A pair of guide rails 8 extending in the vertical direction are fixed to the column 6.

[0017] A polishing unit 10 is mounted movably in the vertical direction along the pair of guide rails 8. The polishing unit 10 has a spindle housing 12 and a support portion 14 for holding the spindle housing 12, and the support portion 14 is attached to a moving base 16 that moves in the vertical direction along the pair of guide rails 8.

[0018] The polishing unit 10 includes a spindle (not shown) rotatably accommodated in the spindle housing 12, a wheel mount 20 fixed to the tip of the spindle, a polishing wheel 22 fixed to the wheel mount 20, and an electric motor 19 for rotationally driving the spindle.

[0019] The polishing apparatus 2 includes a polishing unit moving mechanism 32. The polishing unit moving mechanism 32 includes a ball screw 31 that moves the polishing unit 10 in the vertical direction along the pair of guide rails 8, and a pulse motor 30. When the pulse motor 30 is driven, the ball screw 31 rotates and the moving base 16 moves in the vertical direction.

[0020] A recess 4a is formed on the upper surface of the base 4, and a chuck table mechanism 34 is disposed in the recess 4a. The chuck table mechanism 34 has a chuck table 36 and is moved in the Y-axis direction between a wafer loading / unloading position A and a polishing position B facing the polishing unit 10 by a moving mechanism (not shown). In the chuck table 36, a disk-shaped wafer W as a workpiece is sucked and held, and the back surface of the wafer W is polished.

[0021] The space above the base 4 is surrounded by a panel 7, forming a processing chamber 9 that encloses the polishing unit 10 and the chuck table mechanism 34. The processing chamber 9 is connected to a vacuum device (not shown) and configured as a negative pressure chamber, which keeps the processing chamber 9 clean by sucking up floating processing debris. Furthermore, by reducing the pressure in the processing chamber 9 with this vacuum device (not shown), polishing debris in the grooves 27 of the polishing pad 26, which will be described in more detail later, is expected to be drawn out of the grooves 27, thereby preventing clogging of the grooves 27.

[0022] The exterior surface of the polishing device 2 is equipped with an operation panel 42, which consists of a touch panel or the like. The control unit 40 automatically controls each operating part according to the settings of the polishing conditions, etc., made by the operator.

[0023] Figure 2 shows the polishing wheel 22 and other components mounted on the polishing unit 10. A disc-shaped wheel mount 20 is provided at the lower end of the spindle 11 of the polishing unit 10. A polishing wheel 22 is detachably fixed to the wheel mount 20 by bolts 21, 21.

[0024] The polishing wheel 22, as a processing tool, comprises a disc-shaped metal base 24 and multiple polishing pads 26 fixed to one side of the base 24 (the bottom surface in Figure 2), arranged in the circumferential direction of the base, each forming a polishing layer.

[0025] Each polishing pad 26 is molded separately from the base 24 and then attached to the base 24 for fixation. It is designed to be removable from the base 24 and replaced, or it may be integrally molded with the base 24 as a polishing layer. The polishing pad 26 is also called a segmented polishing pad.

[0026] As shown in Figure 2, the wafer W is held on the chuck table 36 via tape T, and as shown in Figure 3, the wafer W is rotated in the direction of arrow B and the polishing wheel 22 is rotated in the direction of arrow A, while the polishing pad 26 of the polishing wheel 22 is pressed against the wafer W with a constant load to perform the polishing process.

[0027] Specifically, for example, the polishing wheel 22 is rotated at 1600 rpm, and the wafer W is rotated at 100 rpm while the polishing unit moving mechanism 32 (Figure 1) is driven to apply a load of approximately 300 N to the wafer W with the polishing pad 26, thereby polishing the back surface of the wafer W. Grinding distortion remaining on the back surface of the wafer W can be removed in a polishing time of about 100 seconds, and the back surface of the wafer W can be finished to a mirror finish.

[0028] Each polishing pad 26 is formed by embedding and fixing fine abrasive grains together with a binder such as varnish in an abrasive cloth such as a nonwoven fabric, and the abrasive grains consist of silica, cerium oxide, etc., with a particle size of 0.01 μm to 10.0 μm. Alternatively, the polishing pad may be formed by fixing silica or cerium oxide with foamed urethane.

[0029] Figure 4 shows the arrangement of the multiple polishing pads 26 provided on the polishing wheel 22. In this embodiment, a central hole 25 into which polishing fluid is supplied is formed in the center 24c of the base 24, and five polishing pads 26 are evenly arranged around this central hole 25, with their angles changing in the circumferential direction. The circumferential width of each polishing pad 26 is set to expand from the center 24c of the base 24 to the outer edge 24g, up to a point approximately 2 / 3 of the way from there, and then to contract until it reaches the outer edge 24g. This setting gives each polishing pad 26 a shape resembling a cherry blossom petal.

[0030] The shape of each polishing pad 26 allows for a reduction in the amount of polishing at the outer periphery and the center of rotation of the wafer W, while maximizing the amount of polishing at the radial center. This enables the back surface of the wafer W to be polished to a uniform thickness, and allows each polishing pad 26 to wear down almost uniformly, enabling stable polishing of the wafer W over a long period of time.

[0031] Furthermore, as shown in Figure 4, each polishing pad 26 has at least one groove 27 formed on the polishing surface 26a for polishing the wafer W, which extends continuously from the center 24c side of the base 24 to the outer edge 24g side.

[0032] In this embodiment, the width of the groove 27 (width in the circumferential direction) is configured to narrow from the center 24c side of the base 24 toward the outer edge 24g side. As a result, the opening 27k formed by the groove 27 is wider on the center 24c side of the base 24, making it easier to collect polishing debris through this opening 27k, as will be described later.

[0033] In this embodiment, each polishing pad 26 has three grooves 27 formed in it, and the grooves 27 are arranged radially overall. As a result, polishing debris can be efficiently collected by the multiple grooves 27, as will be described later.

[0034] The depth and width of the groove 27 can be suitably set according to the size (diameter) and material of the wafer W, the material of the polishing pad, etc. The depth and width of the groove 27 are not particularly limited, but for example, the depth can be about 1 / 8 to 3 / 8 of the thickest part of the polishing pad 26, and the width can be about 0.5 cm to 1.0 cm.

[0035] Figure 5(A) is a schematic diagram showing how a wafer W is polished by a polishing pad 26, illustrating how polishing debris K is generated as the back surface Wb of the wafer W is polished. This polishing debris K is taken into the groove 27 on the polishing pad 26 side, preventing it from accumulating on the back surface Wb of the wafer W. Furthermore, even if the polishing debris K enters the segmented groove Wm formed in the wafer W, as polishing progresses, the polishing debris K is taken into the groove 27, preventing it from accumulating on the back surface Wb of the wafer W.

[0036] As shown in the left-hand diagram of Figure 5(B), if polishing debris K accumulates on the back surface Wb of the wafer W, surface abnormalities Wz (surface burning) will occur on the back surface Wb of the wafer W. However, according to the present invention, as shown in the right-hand diagram of Figure 5(B), the occurrence of such surface abnormalities (surface burning) can be effectively prevented.

[0037] Figure 6 illustrates how polishing debris K is taken into the opening 27k on the center 24c (center of the base 24 (polishing wheel 22)) side of the groove 27, moves to the outer edge 24g, and is discharged from the other opening 27g. In this way, the accumulation of polishing debris K near the center 24c is suppressed, and in particular, surface abnormalities Wz (surface burning) in the central region Wd of the wafer shown in Figure 3 (see Figure 5(B)) can be effectively prevented.

[0038] As described above, according to the embodiment of the present invention, even in situations where the contact time with the polishing layer (polishing pad) is long in the central region Wd (Figure 3) of the wafer, polishing debris (contaminants) generated during polishing can be taken into the grooves and prevented from accumulating, thereby preventing indentation in the center of the wafer and variations in wafer thickness caused by this accumulation. [Explanation of Symbols]

[0039] 2 Polishing equipment 7 Panels 9 Processing room 10 polishing units 20 Wheel Mount 22 Polishing Wheels 24 base 24c center 24g outer edge 26 polishing pads 26a Polished surface 27 Groove 27g opening 27k aperture K Polishing waste T Tape W wafer Wb back side Wd center area Wm dividing groove Wz surface abnormality

Claims

1. A machining tool used for polishing a workpiece, The machining tool is, It comprises a disc-shaped base and a plurality of polishing layers fixed to one surface of the base and arranged in the circumferential direction of the base, The circumferential width of each polishing layer expands from the center of the base toward the outer edge up to a predetermined position, and then narrows from that predetermined position toward the outer edge. A machining tool having at least one groove formed on the polishing surface of each polishing layer, extending from the center of the base towards the outer edge.

2. The width of the groove narrows from the center of each base towards the outer edge. The machining tool described in feature 1.

3. The polishing layer is configured as a polishing pad that is molded separately from the base and is integrated with the base by adhesion. A machining tool according to claim 1 or 2.

4. A polishing pad used in a machining tool used for polishing a workpiece, The polishing pad is, These are arranged in multiple circumferential directions on one side of the disc-shaped base of the processing tool, forming a polishing layer. The circumferential width of each polishing pad, when placed on the base, expands from the center of the base toward the outer edge up to a predetermined position, and then narrows from that predetermined position toward the outer edge. Each polishing pad has at least one groove formed on its polishing surface, extending from the center of the base to the outer edge when it is mounted on the base. Polishing pad.

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