Grinding device

Abstract

To provide a polishing device which polishes a wafer in a radial direction at a prescribed abrasive removal amount.SOLUTION: A spindle rotation control part controls spindle rotation speed, a chuck rotation control part controls chuck rotation speed, and an inclination control part adjusts inclination of a chuck table 31, so as to be capable of controlling relative speed between a wafer 100 and an abrasive pad 77 and load applied from the abrasive pad 77 to the wafer 100. Thereby adjusting abrasive removal amount in a radial direction of the wafer 100, the wafer 100 can be polished in the radial direction at a prescribed abrasive removal amount.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a polishing apparatus. [Background technology]

[0002] A polishing apparatus for polishing a wafer holds the wafer on a chuck table and polishes the wafer with the polishing surface of a polishing pad.

[0003] The polishing surface of the polishing pad has a diameter longer than the diameter of the wafer, and the rotation axis of the polishing surface of the polishing pad and the rotation axis of the wafer are shifted in a direction parallel to the direction of the polishing surface, and the polishing surface is pressed against the wafer to polish the wafer.

[0004] In this case, the relative rotation speed between the wafer and the polishing pad is uniform within the wafer surface, so if the load of the polishing pad pressing the wafer is uniform within the wafer surface, the amount of removal by polishing is also uniform within the wafer surface.

[0005] Therefore, when it is desired to change the amount of polishing removal in the radial direction of the wafer, the force pressing the polishing surface of the polishing pad against the polishing surface of the wafer is changed in the radial direction of the wafer by forming concentric circular irregularities in the radial direction on the polishing surface of the wafer as disclosed in Patent Documents 1 to 3. In this way, it is possible to polish the wafer to a uniform thickness, for example. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-051501 A [Patent Document 2] JP 2020-040182 A [Patent Document 3] JP 2020-142334 A [Patent Document 4] JP 2013-004726 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the pressing force of the polishing surface of the polishing pad is changed by forming concentric irregularities on the polished surface of the wafer, polishing debris and free abrasive grains become trapped between the polished surface of the wafer and the polishing surface of the polishing pad, making it difficult to obtain the expected amount of polishing removal.

[0008] It is also possible to change the inclination of the chuck table relative to the polishing surface of the polishing pad, as disclosed in Patent Document 4. However, even in this case, polishing waste and free abrasive grains are partially retained between the polishing surface and the surface to be polished of the wafer, making it difficult to obtain a predetermined amount of removal by polishing in the radial direction of the wafer.

[0009] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to polish a wafer with a predetermined amount of removal in its radial direction. [Means for solving the problem]

[0010] The polishing apparatus of the present invention (the present polishing apparatus) includes a chuck table that holds a wafer by a conical holding surface with its center at the apex, a chuck rotation mechanism that rotates the chuck table about a chuck rotation axis that passes through the center of the holding surface, a polishing unit that polishes the wafer held on the holding surface by the underside of a ring-shaped polishing pad attached to the tip of a spindle, a spindle rotation mechanism that rotates the spindle about the spindle rotation axis, a slurry supply unit that supplies slurry to the polishing pad, and a control unit, and Formed from the periphery towards the center, A circular sector-shaped polishing area, which is the area where the lower surface of the ring-shaped polishing pad comes into contact And rotatea polishing apparatus for polishing the wafer, the control unit including: a spindle rotation control unit that controls a rotation speed of the spindle; a chuck rotation control unit that controls a rotation speed of the chuck table; and an inclination control unit that controls an inclination change mechanism that changes a relative inclination between the inclination of the spindle rotation axis and the inclination of the chuck rotation axis; a spindle rotation control unit and a chuck rotation control unit controlling a relative speed between the wafer held on the holding surface and the polishing pad, and a tilt control unit controlling a load applied to the wafer from the polishing pad, the load changing in accordance with the relative tilt, The holding surface is held Applicable Wafer The polishing area It is possible to control the amount of removal by polishing. Effect of the Invention

[0011] In this polishing apparatus, the spindle rotation control unit controls the rotation speed of the spindle, the chuck rotation control unit controls the rotation speed of the chuck table, and the tilt control unit adjusts the relative tilt between the spindle rotation axis and the chuck rotation axis, thereby controlling the relative speed between the wafer and the polishing pad and the load applied to the wafer from the polishing pad. This adjusts the amount of polishing removal in the radial direction of the wafer, allowing the wafer to be polished to a predetermined amount in the radial direction. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view showing a configuration of a polishing apparatus. [Diagram 2] FIG. 2 is an explanatory diagram showing the configuration of a polishing unit and a chuck table. [Diagram 3] FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. [Figure 4] 1 is an explanatory diagram showing an example of the positions and heights of a fixed axis, an L motion axis, and an R motion axis on a plane, as well as an example of a spindle rotation speed and a chuck rotation speed. FIG. [Diagram 5] 1A to 1C are explanatory diagrams showing examples of the relative speed between a polishing pad and a wafer, and the load applied from the polishing pad to the wafer. [Figure 6] 1 is a graph showing an example of the relationship between the position in the radial direction of the wafer and the amount of removal by polishing. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a wafer after polishing. [Figure 8] FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. [Figure 9] 1 is an explanatory diagram showing an example of the positions and heights of a fixed axis, an L motion axis, and an R motion axis on a plane, as well as an example of a spindle rotation speed and a chuck rotation speed. FIG. [Figure 10] 1A to 1C are explanatory diagrams showing examples of the relative speed between a polishing pad and a wafer, and the load applied from the polishing pad to the wafer. [Figure 11] 1 is a graph showing an example of the relationship between the position in the radial direction of the wafer and the amount of removal by polishing. [Figure 12] FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. [Figure 13] 1 is an explanatory diagram showing an example of the positions and heights of a fixed axis, an L motion axis, and an R motion axis on a plane, as well as an example of a spindle rotation speed and a chuck rotation speed. FIG. [Figure 14] 1A to 1C are explanatory diagrams showing examples of the relative speed between a polishing pad and a wafer, and the load applied from the polishing pad to the wafer. [Figure 15] 1 is a graph showing an example of the relationship between the position in the radial direction of the wafer and the amount of removal by polishing. [Figure 16] FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. [Figure 17] 1 is an explanatory diagram showing an example of the positions and heights of a fixed axis, an L motion axis, and an R motion axis on a plane, as well as an example of a spindle rotation speed and a chuck rotation speed. FIG. [Figure 18] 1A to 1C are explanatory diagrams showing examples of the relative speed between a polishing pad and a wafer, and the load applied from the polishing pad to the wafer. [Figure 19] 1 is a graph showing an example of the relationship between the position in the radial direction of the wafer and the amount of removal by polishing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As shown in FIG. 1, the polishing apparatus 1 of this embodiment is an apparatus for CMP polishing a wafer 100 as a workpiece, and is equipped with a rectangular parallelepiped base 10, a column 11 extending upward, and a control unit 15 that controls each component of the polishing apparatus 1.

[0014] The wafer 100 is, for example, a circular semiconductor wafer. A front surface 101 of the wafer 100, which faces downward in Fig. 1, holds a number of devices and is protected by a protective tape 103 attached thereto. A rear surface 102 of the wafer 100 is a surface to be polished, which is subjected to polishing processing.

[0015] An opening 13 is provided on the upper surface side of the base 10. A wafer holding mechanism 30 is disposed within the opening 13. The wafer holding mechanism 30 includes a chuck table 31 having a holding surface 32 that holds the wafer 100, a support member 33 that supports the chuck table 31, a chuck motor 34 serving as a chuck rotation mechanism that rotates the chuck table 31 and the support member 33, and an L operating shaft 35, an R operating shaft 36, and a fixed shaft 37 (see FIG. 5) serving as three support columns that can adjust the inclination of the chuck table 31.

[0016] The chuck table 31 is formed in a disk shape, and has a circular holding surface 32 on its upper surface. The chuck table 31 holds the wafer 100 by means of this holding surface 32. As shown in Fig. 2, the holding surface 32 is formed as a conical surface with an apex at the center, and is made of a porous material. The holding surface 32 is connected to a suction source (not shown) to hold the wafer 100 by suction.

[0017] The chuck motor 34 rotates the chuck table 31 around a chuck rotation axis 301 that passes through the center of the holding surface 32. That is, the chuck table 31 can be rotated, for example, in the direction indicated by the arrow 401 together with the support member 33 around the chuck rotation axis 301 by the chuck motor 34 provided below, in a state in which the wafer 100 is held by the holding surface 32.

[0018] 1 support the support member 33 of the wafer holding mechanism 30 at intervals of 120 degrees from each other. When the L motion axis 35 and / or the R motion axis 36 rises or falls in the Z-axis direction, the inclination of the support member 33 and the chuck table 31 supported by the support member 33, i.e., the inclination of the chuck rotation axis 301, is changed. In other words, the L motion axis 35 and the R motion axis 36 function as an inclination changing mechanism that changes the relative inclination between the inclination of the spindle rotation axis 701 and the inclination of the chuck rotation axis 301, which will be described later.

[0019] 1, a cover plate 39 that moves along the Y-axis direction together with the chuck table 31 is provided around the periphery of the chuck table 31. A bellows cover 12 that expands and contracts in the Y-axis direction is connected to the cover plate 39. A Y-axis direction moving mechanism 40 is provided below the wafer holding mechanism 30.

[0020] The Y-axis direction moving mechanism 40 moves the wafer holding mechanism 30 and the polishing unit 70 relatively in the Y-axis direction, which is a direction parallel to the holding surface 32. In this embodiment, the Y-axis direction moving mechanism 40 is configured to move the wafer holding mechanism 30 including the chuck table 31 in the Y-axis direction relative to the polishing unit 70.

[0021] The Y-axis direction moving mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis direction, a Y-axis moving table 45 that slides on these Y-axis guide rails 42, a Y-axis ball screw 43 parallel to the Y-axis guide rails 42, a Y-axis motor 44 connected to the Y-axis ball screw 43, and a holding base 41 that holds these.

[0022] The Y-axis moving table 45 is slidably installed on the Y-axis guide rail 42. A nut portion (not shown) is fixed to the lower surface of the Y-axis moving table 45. The Y-axis ball screw 43 is screwed into the nut portion. The Y-axis motor 44 is connected to one end of the Y-axis ball screw 43.

[0023] In the Y-axis direction moving mechanism 40, the Y-axis motor 44 rotates the Y-axis ball screw 43, thereby moving the Y-axis moving table 45 in the Y-axis direction along the Y-axis guide rail 42. The support member 33 of the wafer holding mechanism 30 is placed on the Y-axis moving table 45 via the L movement shaft 35, the R movement shaft 36 and the fixed shaft 37. Therefore, as the Y-axis moving table 45 moves in the Y-axis direction, the wafer holding mechanism 30 including the chuck table 31 moves in the Y-axis direction.

[0024] In this embodiment, the wafer holding mechanism 30 is moved along the Y-axis direction by the Y-axis moving mechanism 40, roughly speaking, between a wafer placement position at the front (-Y direction side) for placing the wafer 100 on the holding surface 32 and a processing position at the rear (+Y direction side) where the wafer 100 is polished.

[0025] 1, a column 11 is provided in an upright position at the rear (+Y direction side) of the base 10. A polishing unit 70 for polishing the wafer 100 and a polishing feed mechanism 50 are provided in front of the column 11.

[0026] The polishing feed mechanism 50 relatively moves the wafer holding mechanism 30 including the chuck table 31 and the polishing unit 70 in the Z-axis direction (polishing feed direction) which is a direction perpendicular to the holding surface 32. In this embodiment, the polishing feed mechanism 50 is configured to move the polishing unit 70 in the Z-axis direction relative to the chuck table 31.

[0027] The polishing feed mechanism 50 includes a pair of Z-axis guide rails 51 parallel to the Z-axis direction, a Z-axis moving table 53 that slides on the Z-axis guide rails 51, a Z-axis ball screw 52 parallel to the Z-axis guide rails 51, a Z-axis motor 54, and a holder 56 attached to the front surface (surface) of the Z-axis moving table 53. The holder 56 holds a polishing unit 70.

[0028] The Z-axis moving table 53 is slidably installed on the Z-axis guide rail 51. A nut portion (not shown) is fixed to the rear side (back side) of the Z-axis moving table 53. A Z-axis ball screw 52 is screwed into this nut portion. The Z-axis motor 54 is connected to one end of the Z-axis ball screw 52.

[0029] In the polishing feed mechanism 50, the Z-axis motor 54 rotates the Z-axis ball screw 52, ​​thereby moving the Z-axis moving table 53 in the Z-axis direction along the Z-axis guide rail 51. As a result, the holder 56 attached to the Z-axis moving table 53 and the polishing unit 70 held by the holder 56 move in the Z-axis direction together with the Z-axis moving table 53.

[0030] As shown in FIG. 1, the polishing unit 70 includes a spindle housing 71 fixed to the holder 56, a spindle 72 rotatably held in the spindle housing 71, a spindle motor 73 as a spindle rotation mechanism that drives the spindle 72 to rotate, a mount 74 attached to the lower end of the spindle 72, and a polishing wheel 75 supported by the mount 74.

[0031] The spindle housing 71 is held by the holder 56. The spindle 72 is supported by the spindle housing 71 so as to be rotatable about a spindle rotation axis 701 (see FIG. 2) whose axial direction is parallel to the Z-axis direction.

[0032] Spindle motor 73 is connected to the upper end side of spindle 72, and rotates spindle 72 about spindle rotation axis 701 in the direction indicated by arrow 402 (see FIG. 2), for example.

[0033] 1, the mount 74 is formed in a disk shape, and is fixed to the lower end (tip) of the spindle 72. The mount 74 supports the grinding wheel 75.

[0034] The grinding wheel 75 is formed so that the outer diameter thereof is approximately the same as the outer diameter of the mount 74. The grinding wheel 75 includes a wheel base 76 connected to the lower surface of the mount 74.

[0035] A ring-shaped polishing pad 77 is provided on the lower surface of the wheel base 76. The polishing pad 77 is made of, for example, a nonwoven fabric such as felt. The ring-shaped lower surface of the polishing pad 77 serves as a polishing surface for polishing the back surface 102 of the wafer 100.

[0036] This ring-shaped polishing pad 77 is formed on the wheel base 76 so that the spindle rotation axis 701 passes through its center. Therefore, the polishing pad 77 is rotated by the spindle motor 73 via the spindle 72, the mount 74, and the wheel base 76 around the spindle rotation axis 701 (see FIG. 2) that passes through its center, and polishes the wafer 100 held on the chuck table 31 arranged at the processing position. In this manner, the polishing unit 70 polishes the wafer 100 held on the holding surface 32 with the underside of the ring-shaped polishing pad 77 attached to the tip of the spindle 72 .

[0037] 2, the polishing unit 70 has a slurry supplying section 78 that supplies slurry to the polishing pad 77. The slurry supplying section 78 supplies slurry between the back surface 102, which is the surface to be polished of the wafer 100, and the lower surface of the polishing pad 77 through a slurry supply path 79 in the spindle 72 during polishing with the polishing pad 77. The slurry supplying section may be a slurry nozzle 80 that sprays slurry onto the outer surface of the polishing pad 77 .

[0038] 1 shows a polishing area 90 as a processing area. The polishing area 90 is a radial region of the back surface 102 of the wafer 100 held on the holding surface 32 of the chuck table 31 with which the polishing pad 77 comes into contact.

[0039] The polishing area 90 is formed on the back surface 102 of the wafer 100 from the outer periphery toward the center by rotating the chuck table 31 in the direction of the arrow 401 (see FIG. 2) and rotating the polishing pad 77 in the direction of the arrow 402. The polishing area 90 has a relatively narrow circular sector shape. The width of the circular sector is 2 mm to 5 mm.

[0040] In this manner, the polishing apparatus 1 polishes the wafer 100 in a circular sector-shaped polishing area 90, which is the area in the radial portion of the wafer 100 held on the holding surface 32 where the underside of the ring-shaped polishing pad 77 comes into contact.

[0041] 1, a thickness measuring device 60 is disposed on the side of the opening 13 in the base 10. The thickness measuring device 60 can measure the height of the upper surface (the height of the back surface 102) and the thickness of the wafer 100 held on the holding surface 32 in a non-contact manner.

[0042] The thickness measuring device 60 is, for example, a laser type distance measuring device. For example, the thickness measuring device 60 can irradiate the wafer 100 with a laser beam having a wavelength that can transmit through the wafer 100, receive reflected light from the upper surface of the wafer 100 and reflected light from the lower surface of the wafer 100, and measure the thickness of the wafer from the optical path difference of the reflected light. The thickness measuring device 60 can also measure the height of the upper surface of the wafer 100 and the height of the holding surface 32, and calculate the thickness of the wafer 100 based on the difference.

[0043] Additionally, the thickness gauge 60 may use a laser beam or light of a wavelength that is not transmitted through the wafer 100 . In addition, the thickness gauge 60 may be configured as a non-contact type measuring instrument that uses a laser beam or sound waves instead of light to measure the height of the top surface of the wafer 100 and the height of the holding surface 32, and calculates the difference in height as the thickness of the wafer. Furthermore, the thickness gauge 60 may be a contact type distance gauge having two contacts. When measuring the radial thickness of the wafer 100 using the thickness gauge 60, the thickness gauge 60 may be moved in the Y-axis direction, or, as shown in FIG. 1, a radial movement mechanism 61 may be provided to move the thickness gauge 60 in the radial direction of the wafer.

[0044] 1, the polishing feed mechanism 50 has an encoder 55 disposed on the upper part of the Z-axis motor 54. The Z-axis motor 54 rotates the Z-axis ball screw 52 to rotate the encoder 55, and the encoder 55 recognizes the rotation angle of the Z-axis ball screw 52, ​​thereby making it possible to detect the position (height position) of the polishing unit 70 moved in the Z-axis direction.

[0045] The control unit 15 includes a CPU that performs calculation processing according to a control program, and a storage medium such as a memory, etc. The control unit 15 controls each of the above-mentioned members of the polishing apparatus 1 to perform polishing of the wafer 100.

[0046] As shown in FIG. 1, the control unit 15 also includes a spindle rotation control unit 16 that controls the rotation speed of the spindle 72 (spindle rotation speed), and a chuck rotation control unit 17 that controls the rotation speed of the chuck table 31 (chuck rotation speed). The chuck rotation control unit 17 may also make the rotation speed of the chuck table 31 faster than the rotation speed of the spindle 72 .

[0047] The control unit 15 further includes an inclination control unit 18. The inclination control unit 18 controls a tilt changing mechanism that changes the relative inclination between the inclination of the spindle rotation axis 701 and the inclination of the chuck rotation axis 301. In this embodiment, the inclination control unit 18 controls the heights of the L motion axis 35 and the R motion axis 36 serving as the inclination changing mechanism to change the inclination of the chuck rotation axis 301 relative to the spindle rotation axis 701.

[0048] The function of each component of the control unit 15 and the operation of the polishing process by the polishing apparatus 1 under the control of the control unit 15 will be described below.

[0049] [Holding process] In the polishing process, first, the wafer 100 is held by the holding surface 32 of the chuck table 31 of the wafer holding mechanism 30. That is, the control unit 15 or an operator holds the wafer 100 on the holding surface 32 of the chuck table 31 of the wafer holding mechanism 30 arranged in the wafer placement area, with the back surface 102 facing upward.

[0050] Thereafter, the control unit 15 controls the Y-axis direction moving mechanism 40 to move the wafer holding mechanism 30 including the chuck table 31 to a processing position on the +Y direction side.

[0051] [Polishing process] Next, the control unit 15 and the chuck rotation control unit 17 control the chuck motor 34 of the wafer holding mechanism 30 to rotate the chuck table 31 as shown by the arrow 401 around the chuck rotation axis 301 passing through the center of the holding surface 32 holding the wafer 100, as shown in FIG. 2.

[0052] Furthermore, the control unit 15 and the spindle rotation control unit 16 control the spindle motor 73 of the polishing unit 70 to rotate the spindle 72, thereby rotating the polishing pad 77 around its spindle rotation axis 701 as shown by the arrow 402.

[0053] Next, the control unit 15 controls the polishing feed mechanism 50 to move the polishing pad 77 in the Z-axis direction relative to the chuck table 31, and brings the lower surface of the polishing pad 77 into contact with the back surface 102 of the wafer 100 held on the holding surface 32. In this manner, the control unit 15 polishes the back surface 102 of the wafer 100 with the lower surface of the polishing pad 77. During polishing, the control unit 15 measures the thickness of the wafer 100 being polished using the thickness measuring device 60 shown in FIG. 1, and continues polishing until the thickness of the wafer 100 reaches a target thickness, for example.

[0054] Furthermore, in this embodiment, the control unit 15 performs the polishing removal amount control step described below, as necessary, before the polishing step.

[0055] [Polishing removal amount control process] This step is performed to adjust the amount of polishing removal in the radial direction of the wafer 100 when, for example, there is variation in the thickness of the wafer 100 before polishing.

[0056] In this step, spindle rotation control unit 16 of control unit 15 controls the spindle rotation speed, chuck rotation control unit 17 controls the chuck rotation speed, and tilt control unit 18 adjusts the tilt of chuck rotation axis 301 to control the relative speed between wafer 100 and polishing pad 77 and the load applied to wafer 100 from polishing pad 77. This adjusts the amount of polishing removal in the radial direction of wafer 100. Therefore, for example, it is possible to make the thickness of wafer 100 uniform after polishing.

[0057] An embodiment regarding adjustment of the polishing removal amount will be described below.

[0058] Example 1 In Example 1, the wafer 100 before polishing has a thickness as shown in Fig. 3. In the wafer 100 shown in Fig. 3, the thickness gradually decreases from the center 111 to the outer edge 113. In other words, the thickness of the wafer 100 before polishing is thick at the center 111 and becomes thinner toward the outer edge 113. In FIG. 3 and other figures, the wafer 100 is shown exaggerated so that its thickness appears large. In this embodiment, the wafer 100 is shown to have a diameter of 200 mm. Therefore, if the wafer 100 has a diameter of 300 mm, the outer edge 113 has a distance L of 150 mm.

[0059] In such a case, in this embodiment, the spindle rotation speed, the chuck rotation speed, and the inclination of the chuck rotation axis 301 relative to the spindle rotation axis 701 (the heights of the L motion axis 35 and R motion axis 36 shown in FIG. 1) are changed.

[0060] In Fig. 4, the positions (x, y) and heights (z) on a plane of the fixed axis 37, the L motion axis 35, and the R motion axis 36 are shown on the left side, and the spindle rotation speed (ωs) and the chuck rotation speed (ωw) are shown in revolutions per minute on the right side.

[0061] In Example 1, for example, as shown by a thick frame 500 in FIG. 4, the spindle rotation control unit 16 of the control unit 15 controls (sets) the spindle rotation speed to 300 rpm, and the chuck rotation control unit 17 controls the chuck rotation speed to also be 300 rpm.

[0062] Furthermore, the inclination control unit 18 of the control unit 15 changes the inclination of the chuck table 31, i.e., the inclination of the chuck rotation axis 301, by, for example, increasing the height of the L operating axis 35 by 0.1 mm and decreasing the height of the R operating axis 36 by 0.1 mm, as shown by a thick frame 501 in FIG. 4, compared to the fixed axis 37. It should be noted that the height of the L motion axis 35 and the height of the R motion axis 36 are set to zero when the polishing surface of the polishing pad 77 and the polishing area 90 are inclined so as to be parallel to each other.

[0063] As a result, the relative speed between the wafer 100 and the polishing pad 77 during polishing, and the load applied from the polishing pad 77 to the wafer 100 are set as shown in FIG.

[0064] That is, by setting the spindle rotation speed and the chuck rotation speed as shown in Fig. 4, the magnitude of the relative velocity V1 at the outer edge 113 of the wafer 100 and the magnitude of the relative velocity V2 at the center 111 become substantially equal to each other as shown in Fig. 5. That is, the relative velocity becomes substantially equal from the outer edge 113 to the center 111 along the polishing area 90.

[0065] In Figure 5, the rotational direction and rotational speed of the chuck table 31 (i.e., the wafer 100) are indicated by the direction and length of arrow 601, and the rotational direction and rotational speed of the spindle 72 (i.e., the polishing pad 77) are indicated by the direction and length of arrow 602.

[0066] The relative velocity V1 at the outer edge 113 of the wafer 100 is derived based on the velocity V10 of the wafer 100 at this portion and the velocity V11 of the polishing pad 77. Meanwhile, the relative velocity V2 at the center 111 of the wafer 100 is calculated in a similar manner. However, at the center 111 of the wafer 100, the velocity V10 of the wafer 100 is substantially 0. Therefore, the relative velocity V2 at the center 111 of the wafer 100 is substantially equal to the velocity V11 of the polishing pad 77 at this portion.

[0067] 5, in this embodiment, regarding the load applied from the polishing pad 77 to the wafer 100, a large load is indicated by the symbol (L), a small load is indicated by the symbol (S), and a medium load is indicated by the symbol (M) (see FIG. 14).

[0068] By setting the heights of the L motion axis 35 and the R motion axis 36 as shown in FIG. 4, the load applied by the polishing pad 77 to the wafer 100 along the polishing area 90 is small at the center 111 and the outer edge 113 of the wafer 100, but is large in the middle portion 115 of the radius of the wafer 100, as shown in FIG.

[0069] By carrying out the above-mentioned polishing process in this state, the amount of removal from back surface 102, which is the surface to be polished of wafer 100 (amount removed by polishing; polishing removal amount) and the load applied to wafer 100 are as shown in the graph of Fig. 6. In the graph shown in Fig. 6, the polishing removal amount is standardized so that the maximum value is 1, and is shown as a polishing removal amount ratio. In addition, the load is standardized so that the maximum value of the load shown in Fig. 6 is 1, and is shown as a load ratio. The amount of removal by polishing increases as the relative speed between the wafer 100 and the polishing pad 77 increases. The load applied relatively to the polishing pad 77 and the wafer 100 changes depending on the inclination between the spindle rotation axis 701 and the chuck rotation axis 301. To obtain the load shown in FIG. 6, the L movement axis 35 and the R movement axis 36 are operated so that the middle part 115 of the radius of the wafer 100 hits the polishing pad 77 strongly. As shown in the table in FIG. 4, the L movement axis 35 is lengthened and the R movement axis 36 is shortened. Therefore, in the first embodiment, as shown in FIG. 6, the amount of removal by polishing increases at the center 111 (distance L=0 mm) of the wafer 100 and gradually decreases from the center 111 to the outer edge 113 (near the distance L=100 mm). Therefore, when the wafer 100 shown in FIG. 3 is polished using the tilt relationship, spindle rotation speed, and chuck rotation speed shown in FIG. 4, it is possible to make the thickness of the polished wafer 100 substantially uniform, as shown in FIG. 7.

[0070] Example 2 In the second embodiment, as shown in FIG. 8, the thickness of the wafer 100 before polishing is thin at the center 111 and the outer edge 113, but is thick at the middle portion 115 of the radius of the wafer 100.

[0071] In such a case, for example, as shown by a thick frame 500 in Figure 9, the spindle rotation control unit 16 of the control unit 15 controls the spindle rotation speed to 30 rpm, and the chuck rotation control unit 17 controls the chuck rotation speed to 3000 rpm.

[0072] Furthermore, the inclination control unit 18 of the control unit 15 changes the inclination of the chuck rotation axis 301 by, for example, increasing the height of the L operating axis 35 by 0.1 mm and decreasing the height of the R operating axis 36 by 0.1 mm, as compared to the fixed axis 37, as shown by a thick frame 501 in FIG. 9.

[0073] As a result, the relative speed between the wafer 100 and the polishing pad 77 during polishing, and the load applied from the polishing pad 77 to the wafer 100 are set as shown in FIG. That is, as shown in FIG. 10, the magnitude of the relative velocity V1 at the outer edge 113 of the wafer 100 is different from the magnitude of the relative velocity V2 at the center 111. Also, along the polishing area 90, the load is smaller at the center 111 and outer edge 113 of the wafer 100, but is larger at the middle portion 115 of the radius of the wafer 100, as shown in FIG.

[0074] That is, by setting the spindle rotation speed and the chuck rotation speed as shown in Fig. 9, the magnitude of the relative velocity V1 at the outer edge 113 of the wafer 100 becomes greater than the relative velocity V2 at the central portion 111 as shown in Fig. 10. That is, the relative velocity gradually decreases from the outer edge 113 to the central portion 111 along the polishing area 90.

[0075] In addition, by setting the heights of the L operating axis 35 and the R operating axis 36 as shown in FIG. 9, the load applied from the polishing pad 77 to the wafer 100 is small at the center 111 and the outer edge 113 of the wafer 100 and is large at the middle portion 115 of the radius.

[0076] By carrying out the above-mentioned polishing process in this state, the amount of polishing removal of the wafer 100 and the load applied to the wafer 100 are as shown in the graph of FIG. 11. That is, as shown in FIG. 11, the amount of polishing removal increases from the center 111 (distance L=0 mm) of the wafer 100 to the middle part 115 (near distance L=50 mm) of the radius of the wafer 100, and decreases from the middle part 115 to the outer edge part 113 (near distance L=100 mm) of the wafer 100. That is, when the spindle rotation speed is significantly slower than the chuck rotation speed, the relative speed between the rotation speed of the polishing pad 77 and the rotation speed of the chuck table 31 has a very small effect on the amount of polishing removal in the radial direction of the wafer 100, and the tilt relationship between the chuck rotation axis 301 and the spindle rotation axis 701 affects the amount of polishing removal in the radial direction of the wafer 100. For example, when the ratio of the spindle rotation speed to the chuck rotation speed is set to 1:100, the effect of the relative speed on the amount of polishing removal is very small. In the graph shown in Fig. 11, the polishing removal amount is normalized so that the maximum polishing removal amount is 1, and is shown as a polishing removal amount ratio. Also, the load is normalized so that the maximum value of the load shown in Fig. 11 is 1, and is shown as a load ratio.

[0077] Therefore, also in Example 2, by polishing the wafer 100 shown in FIG. 8 using the tilt relationship, spindle rotation speed, and chuck rotation speed shown in FIG. 9, it is possible to make the thickness of the wafer 100 after polishing substantially uniform, as shown in FIG. 7.

[0078] Example 3 In the third embodiment, as shown in FIG. 12, the thickness of the wafer 100 before polishing gradually increases from the center 111 to the outer edge 113 in an approximately linear manner.

[0079] In such a case, for example, as shown by a thick frame 500 in FIG. 13, the spindle rotation control unit 16 of the control unit 15 controls the spindle rotation speed to 30 rpm, and the chuck rotation control unit 17 controls the chuck rotation speed to 3000 rpm.

[0080] Furthermore, the inclination control unit 18 of the control unit 15 changes the inclination of the chuck rotation axis 301 by, for example, lowering the height of the L operating axis 35 by 0.1 mm and lowering the height of the R operating axis 36 by 0.1 mm, as shown by a thick frame 501 in FIG. 13, compared to the fixed axis 37.

[0081] As a result, the relative speed between the wafer 100 and the polishing pad 77 during polishing, and the load applied from the polishing pad 77 to the wafer 100 are set as shown in FIG. That is, as shown in FIG. 14, the magnitude of the relative velocity V1 at the outer edge 113 of the wafer 100 is different from the magnitude of the relative velocity V2 at the center 111. As shown in FIG. 14, the load is greatest (L) at the outer edge 113 of the wafer 100 along the polishing area 90, followed by the middle portion 115 (M) and the center portion 111 (S) of the wafer 100.

[0082] That is, by setting the spindle rotation speed and the chuck rotation speed as shown in Fig. 13, the magnitude of the relative velocity V1 at the outer edge 113 of the wafer 100 differs from the magnitude of the relative velocity V2 at the central portion 111, as shown in Fig. 14. That is, the relative velocity gradually slows down from the outer edge 113 to the central portion 111 along the polishing area 90.

[0083] Furthermore, by setting the heights of the L motion axis 35 and the R motion axis 36 as shown in FIG. 13, the load applied from the polishing pad 77 to the wafer 100 is large at the outer edge 113 of the wafer 100 and becomes smaller from the outer edge 113 to the center 111 along the polishing area 90.

[0084] By carrying out the above-mentioned polishing process in this state, the amount of removal by polishing of the wafer 100 and the load applied to the wafer 100 become as shown in the graph of Fig. 15. That is, as shown in Fig. 15, the amount of removal by polishing increases gradually and almost linearly from the center 111 of the wafer 100 (distance L = 0 mm) to the outer edge 113 of the wafer 100 (near distance L = 100 mm). The amount of removal by polishing is more affected by the inclination relationship between the chuck rotation axis 301 and the spindle rotation axis 701 than by the relative speed. In the graph shown in Fig. 15, the polishing removal amount is normalized so that the maximum value is 1, and is shown as a polishing removal amount ratio. Also, the load is normalized so that the maximum value of the load shown in Fig. 15 is 1, and is shown as a load ratio.

[0085] Therefore, also in this Example 3, by polishing the wafer 100 shown in FIG. 12 using the tilt relationship, spindle rotation speed, and chuck rotation speed shown in FIG. 13, it is possible to make the thickness of the wafer 100 after polishing substantially uniform, as shown in FIG. 7.

[0086] Example 4 In the fourth embodiment, as shown in FIG. 16, the thickness of a wafer 100 before polishing is thick at a central portion 111 and gradually becomes thinner in a curved shape from the central portion 111 to an outer edge portion 113.

[0087] In such a case, for example, as shown by a thick frame 500 in Figure 17, the spindle rotation control unit 16 of the control unit 15 controls the spindle rotation speed to 1000 rpm, and the chuck rotation control unit 17 controls the chuck rotation speed to 3000 rpm.

[0088] Furthermore, the inclination control unit 18 of the control unit 15 changes the inclination of the chuck rotation axis 301 by, for example, increasing the height of the L operating axis 35 by 10 mm and decreasing the height of the R operating axis 36 by 10 mm, as compared to the fixed axis 37, as shown by a thick frame 501 in FIG. 17.

[0089] As a result, the relative speed between the wafer 100 and the polishing pad 77 during polishing, and the load applied from the polishing pad 77 to the wafer 100 are set as shown in FIG. That is, as shown in FIG. 18, the magnitude of the relative velocity V1 at the outer edge 113 of the wafer 100 and the magnitude of the relative velocity V2 at the center 111 are different. Also, along the polishing area 90, the load is smaller at the center 111 and outer edge 113 of the wafer 100, but is larger at the middle portion 115 of the radius of the wafer 100, as shown in FIG.

[0090] That is, by setting the spindle rotation speed and the chuck rotation speed as shown in Fig. 17, the magnitude of the relative speed V1 at the outer edge 113 of the wafer 100 becomes greater than the relative speed V2 at the central portion 111 as shown in Fig. 18. That is, the relative speed gradually slows down from the outer edge 113 to the central portion 111 along the polishing area 90.

[0091] Furthermore, by setting the heights of the L operating axis 35 and the R operating axis 36 as shown in FIG. 17, the load applied from the polishing pad 77 to the wafer 100 is small at the center 111 and the outer edge 113 of the wafer 100 and is large at the middle portion 115 of the radius of the wafer 100.

[0092] By carrying out the above-mentioned polishing process in this state, the amount of removal by polishing of the wafer 100 becomes as shown in the graph of Fig. 19. That is, as shown in Fig. 19, the amount of removal by polishing is approximately uniform from the center 111 (distance L = 0 mm) of the wafer 100 to the middle part 115 of the radius, and gradually decreases in a curved shape from the middle part 115 to the outer edge part 113 (near the distance L = 100 mm). In this graph, the polishing removal amount is normalized so that the maximum value is 1, and is shown as a polishing removal amount ratio. Also, the load is normalized so that the maximum value of the load shown in FIG. 19 is 1, and is shown as a load ratio.

[0093] Therefore, also in this Example 4, by polishing the wafer 100 shown in FIG. 16 using the tilt relationship, spindle rotation speed, and chuck rotation speed shown in FIG. 17, it is possible to make the thickness of the wafer 100 after polishing substantially uniform, as shown in FIG. 7.

[0094] As described above, in this embodiment, a polishing removal amount control step is performed before the polishing step, and the spindle rotation control unit 16 of the control unit 15 controls the spindle rotation speed, the chuck rotation control unit 17 controls the chuck rotation speed, and further the tilt control unit 18 changes the tilt of the chuck rotation axis 301, thereby controlling the relative speed between the wafer 100 and the polishing pad 77 and the load applied to the wafer 100 from the polishing pad 77. This adjusts the polishing removal amount in the radial direction of the wafer 100, and the wafer 100 can be polished with a predetermined polishing removal amount in the radial direction.

[0095] In this way, the polishing apparatus 1 according to this embodiment is capable of controlling the amount of polishing removal at the radial portion of the wafer 100 held on the holding surface 32. Therefore, it is possible to make the thickness of the polished wafer 100 uniform and to give the thickness of the polished wafer 100 an arbitrary distribution.

[0096] In this embodiment, in addition to adjusting the inclination of the chuck rotation axis 301 by the inclination control unit 18, the spindle rotation speed is controlled by the spindle rotation control unit 16, and the chuck rotation speed is controlled by the chuck rotation control unit 17. This makes it possible to change the amount of polishing removal at the radial portion of the wafer 100 with high precision.

[0097] 1, the control unit 15 may include a cross-sectional shape setting unit 19. The cross-sectional shape setting unit 19 sets the cross-sectional shape (target cross-sectional shape) of the polished wafer 100, for example, in response to an instruction from an operator. The target cross-sectional shape is, for example, a cross-sectional shape in which the back surface 102 of the polished wafer 100 is a flat surface, or a cross-sectional shape in which the back surface 102 of the polished wafer 100 is a predetermined inclined surface.

[0098] In this case, the control unit 15 measures the thickness of the wafer 100 at a plurality of points in the radius portion of the wafer 100 using the thickness gauge 60 in the polishing process. Then, the control unit 15 recognizes the cross-sectional shape (actual cross-sectional shape) of the actually polished wafer 100 based on the measured thickness. Furthermore, the control unit 15 controls the spindle rotation control unit 16, the chuck rotation control unit 17, and the inclination control unit 18 based on the difference between the target cross-sectional shape set by the cross-sectional shape setting unit 19 and the recognized actual cross-sectional shape, thereby performing the polishing removal amount control process. In this way, the control unit 15 can make the cross-sectional shape of the wafer 100 to be polished next closer to the target cross-sectional shape set by the cross-sectional shape setting unit 19.

[0099] In addition, in this embodiment, the tilt control unit 18 of the control unit 15 controls the height (length) of the L operating axis 35 and the R operating axis 36 serving as a tilt changing mechanism to change the tilt of the chuck rotation axis 301 relative to the spindle rotation axis 701, thereby changing the relative tilt between the spindle rotation axis 701 and the chuck rotation axis 301. 1, the polishing apparatus 1 may have a spindle inclination adjustment mechanism 58 as an inclination change mechanism for adjusting the inclination of the spindle rotation axis 701 in the holder 56 of the polishing feed mechanism 50. In this case, the inclination control unit 18 may change the relative inclination between the spindle rotation axis 701 and the chuck rotation axis 301 by changing the inclination of the spindle rotation axis 701 with respect to the chuck rotation axis 301 using the spindle inclination adjustment mechanism 58. [Explanation of symbols]

[0100] 1: polishing device, 10: base, 11: column, 12: bellows cover, 13: opening, 15: control unit, 16: spindle rotation control unit, 17: chuck rotation control unit, 18: inclination control unit, 19: cross-sectional shape setting unit, 30: wafer holding mechanism, 31: chuck table, 32: holding surface, 33: supporting member, 34: chuck motor, 301: chuck rotation shaft, 35: L-axis, 36: R-axis, 37: fixed axis, 39: cover plate, 40: Y-axis direction movement mechanism, 50: polishing feed mechanism, 51: Z-axis guide rail, 52: Z-axis ball screw, 53: Z-axis moving table, 54: Z-axis motor, 55: encoder, 56: holder, 58: Spindle tilt adjustment mechanism, 60: thickness measuring device, 61: radial movement mechanism, 70: polishing unit, 71: spindle housing, 72: spindle, 701: spindle rotation axis, 73: spindle motor, 74: mount, 75: polishing wheel, 76: wheel base, 77: polishing pad, 78: slurry supply section, 79: slurry supply passage, 90: Polishing area, 100: wafer, 101: front surface, 102: back surface, 103: protective tape, 111: center, 113: outer edge, 115: middle part

Claims

[Claim 1] a chuck table that holds a wafer by a conical holding surface having a vertex at the center; a chuck rotation mechanism that rotates the chuck table about a chuck rotation axis that passes through a center of the holding surface; a polishing unit that polishes the wafer held on the holding surface by a lower surface of a ring-shaped polishing pad attached to the tip of a spindle; a spindle rotation mechanism that rotates the spindle around a spindle rotation axis; a slurry supply unit that supplies a slurry to the polishing pad; A control unit, A polishing apparatus for polishing a rotating wafer in a circular sector-shaped polishing area, which is an area contacting a lower surface of the ring-shaped polishing pad and is formed from an outer periphery toward a center of the wafer held on the holding surface, comprising: The control unit A spindle rotation control unit that controls the rotation speed of the spindle; a chuck rotation control unit for controlling a rotation speed of the chuck table; a tilt control unit that controls a tilt change mechanism that changes a relative tilt between the tilt of the spindle rotation axis and the tilt of the chuck rotation axis, a relative speed between the wafer held on the holding surface and the polishing pad is controlled by the spindle rotation control unit and the chuck rotation control unit, and a load applied to the wafer from the polishing pad, which load changes according to the relative tilt, is controlled by the tilt control unit, thereby enabling control of the amount of removal by polishing in the polishing area of ​​the wafer held on the holding surface; Polishing equipment.

Images