JP7670517B2 - Polishing Equipment - Google Patents

Description

The present invention relates to a polishing device.

A polishing device that polishes wafers holds the wafer on a chuck table and polishes it using the polishing surface of a polishing pad.

The polishing surface of the polishing pad has a diameter longer than the diameter of the wafer, and the axis of rotation of the polishing surface of the polishing pad and the axis of rotation 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.

In this case, the relative speed between the rotational speed of the wafer and the rotational speed of the polishing pad is uniform across the wafer surface. Therefore, if the load of the polishing pad pressing against the wafer is uniform across the wafer surface, the amount of polishing removal across the wafer surface will also be uniform.

Therefore, if it is desired to change the amount of polishing removal in the radial direction of the wafer, as disclosed in Patent Documents 1 to 3, concentric irregularities are formed in the radial direction on the polished surface of the wafer, and the force pressing the polishing surface of the polishing pad against the polished surface of the wafer is changed in the radial direction of the wafer. In this way, it is possible, for example, to polish the wafer to a uniform thickness.

JP 2015-051501 A JP 2020-040182 A JP 2020-142334 A JP 2013-004726 A

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 removal by polishing.

As disclosed in Patent Document 4, it is also possible to change the inclination of the chuck table relative to the polishing surface of the polishing pad. However, even in this case, polishing debris 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 polishing removal in the radial direction of the wafer.

Therefore, the object of the present invention is to polish a wafer in its radial direction with a predetermined amount of polishing removal.

The polishing apparatus of the present invention (present polishing apparatus) comprises a chuck table which holds a wafer by a conical holding surface having an apex at the center, a chuck rotation mechanism which rotates the chuck table about a chuck rotation axis which passes through the center of the holding surface, a polishing unit which 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 which rotates the spindle about the spindle rotation axis, a slurry supply unit which supplies slurry to the polishing pad, and a control unit, and rotates in a circular sector-shaped polishing area which is formed from the outer periphery toward the center of the wafer held on the holding surface and is the area with which the underside of the ring-shaped polishing pad comes into contact. The polishing apparatus polishes the wafer, and the control unit includes a spindle rotation control unit that controls the rotation speed of the spindle, a chuck rotation control unit that controls the rotation speed of the chuck table, and a tilt control unit that controls a tilt change mechanism that changes the relative tilt between the tilt of the spindle rotation axis and the tilt of the chuck rotation axis.The spindle rotation control unit and the chuck rotation control unit control the relative speed between the wafer held on the holding surface and the polishing pad, and the tilt control unit controls the load applied to the wafer from the polishing pad, which changes in accordance with the relative tilt, thereby making it possible to control the amount of polishing removal in the polishing area of the wafer held on the holding surface.

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 with a predetermined amount of polishing removal in that radial direction.

FIG. 2 is a perspective view showing a configuration of a polishing apparatus. FIG. 2 is an explanatory diagram showing the configuration of a polishing unit and a chuck table. FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. 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. 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. 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. FIG. 2 is a cross-sectional view showing an example of a wafer after polishing. FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. 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. 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. 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. FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. 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. 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. 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. FIG. 2 is a cross-sectional view showing an example of a wafer before polishing. 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. 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. 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.

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

Wafer 100 is, for example, a circular semiconductor wafer. In FIG. 1, the front surface 101 of wafer 100, which faces downward, holds multiple devices and is protected by a protective tape 103 attached thereto. The back surface 102 of wafer 100 is the polishing surface on which polishing is performed.

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 as a chuck rotation mechanism that rotates the chuck table 31 and the support member 33, and an L operating axis 35, an R operating axis 36, and a fixed axis 37 (see FIG. 5) as three support columns that can adjust the inclination of the chuck table 31.

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.

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

The L motion axis 35, R motion axis 36, and fixed axis 37 shown in FIG. 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 change mechanism that changes the relative inclination between the inclination of the spindle rotation axis 701 (described later) and the inclination of the chuck rotation axis 301.

As shown in FIG. 1, a cover plate 39 that moves along the Y-axis direction together with the chuck table 31 is provided around 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 movement mechanism 40 is provided below the wafer holding mechanism 30.

The Y-axis direction moving mechanism 40 moves the wafer holding mechanism 30 and the polishing unit 70 relative to each other 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.

The Y-axis movement mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis direction, a Y-axis movement table 45 that slides on the 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 holder 41 that holds these.

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 underside of the Y-axis moving table 45. The Y-axis ball screw 43 is screwed into this nut portion. The Y-axis motor 44 is connected to one end of the Y-axis ball screw 43.

In the Y-axis direction moving mechanism 40, the Y-axis motor 44 rotates the Y-axis ball screw 43, causing the Y-axis moving table 45 to move 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 operating axis 35, the R operating axis 36, and the fixed axis 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.

In this embodiment, the wafer holding mechanism 30 is moved along the Y-axis direction by the Y-axis movement mechanism 40 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.

As shown in FIG. 1, a column 11 is erected on 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 on the front side of the column 11.

The polishing feed mechanism 50 moves the wafer holding mechanism 30 including the chuck table 31 and the polishing unit 70 relative to each other 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.

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) of the Z-axis moving table 53. The holder 56 holds the polishing unit 70.

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. The 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.

In the polishing feed mechanism 50, the Z-axis motor 54 rotates the Z-axis ball screw 52, causing the Z-axis moving table 53 to move 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.

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.

The spindle housing 71 is held by the holder 56. The spindle 72 is supported by the spindle housing 71 so that it can rotate around a spindle rotation axis 701 (see FIG. 2) whose axial direction is parallel to the Z-axis direction.

The spindle motor 73 is connected to the upper end of the spindle 72 and rotates the spindle 72 around the spindle rotation axis 701 in the direction indicated by the arrow 402 (see FIG. 2 ).

As shown in FIG. 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.

The grinding wheel 75 is formed so that its outer diameter is approximately the same as the outer diameter of the mount 74. The grinding wheel 75 includes a wheel base 76 that is connected to the underside of the mount 74.

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

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, mount 74, and 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 .

2, the polishing unit 70 has a slurry supplying section 78 that supplies a slurry to the polishing pad 77. During polishing with the polishing pad 77, the slurry supplying section 78 supplies a 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 via a slurry supply path 79 in the spindle 72.
The slurry supplying section may be a slurry nozzle 80 that sprays slurry onto the outer surface of the polishing pad 77 .

In addition, FIG. 1 shows a polishing area 90 as a processing area. This 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, where the polishing pad 77 comes into contact.

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.

In this way, the polishing apparatus 1 polishes the wafer 100 in the annular sector-shaped polishing area 90, which is the area in the radius of the wafer 100 held on the holding surface 32 where the underside of the ring-shaped polishing pad 77 comes into contact.

As shown in FIG. 1, a thickness gauge 60 is disposed on the side of the opening 13 in the base 10. The thickness gauge 60 can measure the top surface height (height of the back surface 102) and thickness of the wafer 100 held on the holding surface 32 in a non-contact manner.

The thickness gauge 60 is, for example, a laser distance measuring instrument. For example, the thickness gauge 60 irradiates the wafer 100 with a laser beam having a wavelength that can pass through the wafer 100, receives reflected light from the upper surface of the wafer 100 and reflected light from the lower surface of the wafer 100, and can measure the thickness of the wafer from the optical path difference of the reflected light. The thickness gauge 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.

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 height difference 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.

As shown in FIG. 1, the polishing feed mechanism 50 has an encoder 55 disposed on top of the Z-axis motor 54. The Z-axis motor 54 rotates the Z-axis ball screw 52, which rotates the encoder 55, and the encoder 55 recognizes the rotation angle of the Z-axis ball screw 52, thereby detecting the position (height position) of the polishing unit 70 being moved in the Z-axis direction.

The control unit 15 includes a CPU that performs calculations according to a control program, and a storage medium such as a memory. The control unit 15 controls the above-mentioned components of the polishing apparatus 1 to perform polishing processing on the wafer 100.

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 set the rotation speed of the chuck table 31 to be faster than the rotation speed of the spindle 72 .

The control unit 15 further includes a tilt control unit 18. The tilt control unit 18 controls a tilt change mechanism that changes the relative tilt between the tilt of the spindle rotation axis 701 and the tilt of the chuck rotation axis 301. In this embodiment, the tilt control unit 18 controls the height of the L operation axis 35 and the R operation axis 36 as the tilt change mechanism to change the tilt of the chuck rotation axis 301 relative to the spindle rotation axis 701.

The following describes the functions of each component of the control unit 15, as well as the operation of the polishing process performed by the polishing device 1 under the control of the control unit 15.

[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.

Then, 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 the processing position on the +Y direction side.

[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 that holds the wafer 100, as shown in FIG. 2.

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 the spindle rotation axis 701 as shown by the arrow 402.

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 gauge 60 shown in FIG. 1, and continues polishing until the thickness of the wafer 100 reaches a target thickness, for example.

In addition, in this embodiment, the control unit 15 performs the polishing removal amount control process described below as necessary before the polishing process.

[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.

In this process, 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 the tilt control unit 18 adjusts the tilt of the chuck rotation axis 301 to control 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 amount of polishing removal in the radial direction of the wafer 100. Therefore, for example, it is possible to make the thickness of the wafer 100 uniform after polishing.

Below is an example of how to adjust the amount of polishing removal.

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 has 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.

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 height of the L motion axis 35 and the R motion axis 36 shown in Figure 1) are changed.

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

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 the same 300 rpm.

Furthermore, the tilt control unit 18 of the control unit 15 changes the tilt of the chuck table 31, i.e., the tilt 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.

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 Figure 5.

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

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

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 zero. 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.

In this embodiment, as shown in FIG. 5, a heavy load is indicated by the symbol (L) with respect to the load applied from the polishing pad 77 to the wafer 100, while a light load is indicated by the symbol (S). A medium load is indicated by the symbol (M) (see FIG. 14).

By setting the heights of the L motion axis 35 and the R motion axis 36 as shown in FIG. 4, the load applied from the polishing pad 77 to the wafer 100 is small along the polishing area 90 at the center 111 and the outer edge 113 of the wafer 100, but is large in the middle part 115 of the radius of the wafer 100, as shown in FIG. 5.

By carrying out the above-described polishing process in this state, the amount of removal (amount removed by polishing; polishing removal amount) from the back surface 102, which is the surface to be polished of the wafer 100, and the load applied to the 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 shown in Fig. 6 is standardized so that the maximum value of the load is 1, and is shown as a load ratio.
For example, 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 motion axis 35 and the R motion 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 motion axis 35 is lengthened and the R motion 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 wafer 100 after polishing substantially uniform, as shown in FIG. 7.

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.

In such a case, for example, as shown by a thick frame 500 in FIG. 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.

Furthermore, the tilt control unit 18 of the control unit 15 changes the tilt 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 compared to the fixed axis 37, as shown by the thick frame 501 in Figure 9.

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.

That is, by setting the spindle rotation speed and the chuck rotation speed as shown in FIG. 9, 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 center 111, as shown in FIG. 10. That is, the relative speed gradually slows down from the outer edge 113 to the center 111 along the polishing area 90.

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 outer edge 113 of the wafer 100 and large at the middle radius 115.

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, if 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, if 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 amount of polishing removal is standardized so that the maximum amount of polishing removal is 1, and is shown as the polishing removal amount ratio. Also, the load shown in FIG. 11 is standardized so that the maximum value of the load is 1, and is shown as the load ratio.

Therefore, 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.

Example 3
In the third embodiment, as shown in FIG. 12, the thickness of the wafer 100 before polishing is gradually increased in a substantially linear manner from the central portion 111 to the outer edge portion 113.

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 3,000 rpm.

Furthermore, the tilt control unit 18 of the control unit 15 changes the tilt 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 compared to the fixed axis 37, as shown by the thick frame 501 in Figure 13.

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 intermediate portion 115 (M) and the central portion 111 (S) of the wafer 100.

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

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

By carrying out the above-mentioned polishing process in this state, the amount of the wafer 100 removed by polishing and the load applied to the wafer 100 are as shown in the graph of Fig. 15. That is, as shown in Fig. 15, the amount of the wafer 100 removed 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.

Therefore, in this Example 3 as well, 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.

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

In such a case, for example, as shown by a thick frame 500 in FIG. 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.

Furthermore, the tilt control unit 18 of the control unit 15 changes the tilt 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 compared to the fixed axis 37, as shown by the thick frame 501 in Figure 17.

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 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.

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 center 111, as shown in FIG. 18. That is, the relative speed gradually slows down from the outer edge 113 to the center 111 along the polishing area 90.

In addition, by setting the heights of the L motion axis 35 and the R motion 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 part 115 of the radius of the wafer 100.

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 manner from the middle part 115 to the outer edge part 113 (distance L = approximately 100 mm).
In this graph, the polishing removal amount is also 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.

Therefore, in this Example 4 as well, 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.

As described above, in this embodiment, a polishing removal amount control process is performed before the polishing process, 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 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.

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 wafer 100 after polishing uniform, and to make the thickness of the wafer 100 after polishing have any desired distribution.

In addition to adjusting the inclination of the chuck rotation axis 301 by the inclination control unit 18, the spindle rotation control unit 16 controls the spindle rotation speed, and the chuck rotation control unit 17 controls the chuck rotation speed. This allows the polishing removal amount in the radial portion of the wafer 100 to be changed with high precision.

The control unit 15 may include a cross-sectional shape setting unit 19 as shown in FIG. 1. The cross-sectional shape setting unit 19 sets the cross-sectional shape (target cross-sectional shape) of the wafer 100 after polishing, for example, in response to instructions from an operator. The target cross-sectional shape is, for example, a cross-sectional shape in which the back surface 102 of the wafer 100 after polishing is a flat surface, or a cross-sectional shape in which the back surface 102 of the wafer 100 after polishing is a predetermined inclined surface.

In this case, in the polishing process, the control unit 15 uses the thickness gauge 60 to measure the thickness of the wafer 100 at multiple points in the radius portion of the wafer 100. 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 tilt 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, to perform the polishing removal amount control process. In this way, the control unit 15 can bring 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.

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 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.

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: Support member, 34: Chuck motor, 301: Chuck rotation shaft,
35: L operating shaft, 36: R operating shaft, 37: fixed shaft, 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 shaft,
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: central portion, 113: outer edge portion, 115: middle portion

Claims (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