EDGE TRIMMING METHOD AND EDGE TRIMMING APPARATUS

Abstract

An edge trimming method for removing a chamfered portion on an outer periphery of a grinding-object wafer in a bonded wafer is provided. The method includes a holding process to hold the bonded wafer on a chuck table, a finishing-grindstone mark forming process to form a finishing-grindstone mark in the grinding-object wafer with the finishing grindstone, a finishing-grindstone mark height measuring process to measure a height of a bottom of the finishing-grindstone mark with a height measurer, a finishing-grindstone height calculating process to calculate a height of the finishing grindstone based on the measured height of the bottom, a rough-grinding process to lower the rough grindstone and rotate the bonded wafer to roughly grind the grinding-object wafer with the rough grindstone, and a finish-grinding process to lower the finishing grindstone to the calculated height and rotate the bonded wafer to finely grind the grinding-object wafer with the finishing grindstone.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2023-172450, filed on Oct. 4, 2023; the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to an edge trimming method and an edge trimming apparatus for trimming an outer peripheral portion of a bonded wafer.

BACKGROUND

When a wafer is ground and thinned with a grindstone, a sharp edge may be formed in a chamfered portion of an outer periphery of the wafer, and the sharp edge may cause cracks or chips on the outer periphery of the wafer. In order to prevent such cracks or chips, a method to trim the chamfered portion on the outer periphery of the wafer before grinding (edge trimming) has been suggested (see, for example, Japanese Patent Laid-Open Publications No. 2013-149822 and No. 2020-040181).

Moreover, Japanese Patent Laid-Open Publication No. 2017-004989 suggests a method for trimming edges of a grinding-object wafer, which is a wafer to be ground among two wafers forming a bonded wafer, including the grinding-object wafer and a base wafer bonded together. According to this edge trimming method, an outer peripheral portion of the grinding-object wafer may be ground in a shape of a ring, and the ground outer peripheral portion may be removed by etching. Thereby, the chamfered portion of the grinding-object wafer may be removed completely, and the grinding-object wafer may prevent a sharp edge from being formed therein in a later process.

SUMMARY

When the outer peripheral portion is removed by etching in the above method, if an amount to be removed from the outer peripheral portion is small, a height of the remaining outer peripheral portion may become large. Accordingly, there may rise a problem that etching the outer peripheral portion of the grinding-object wafer takes longer time.

When the outer peripheral portion is removed by etching in the above method, if an amount to be removed from the outer peripheral portion is small, a height of the remaining outer peripheral portion may become large. Accordingly, there may rise a problem that etching the outer peripheral portion of the grinding-object wafer takes longer time.

In view of these problems, the present disclosure is directed to providing an edge trimming method and an edge trimming apparatus, by which a grinding accuracy in trimming an edge of an outer peripheral portion of a grinding-object wafer bonded to a base wafer may be improved.

An edge trimming method according to an aspect of the present disclosure is a method for removing a chamfered portion on an outer periphery of a grinding-object wafer in a bonded wafer, which includes the grinding-object wafer with the chamfered portion and a base wafer bonded together, by grinding with a rough grindstone and thereafter grinding with a finishing grindstone. The method includes a holding process including operating a chuck table to hold the bonded wafer by the base wafer, a finishing-grindstone mark forming process including lowering the finishing grindstone from a position above an outer peripheral portion of the grinding-object wafer in the bonded wafer to a predetermined height and forming a finishing-grindstone mark in the grinding-object wafer with the finishing grindstone, a finishing-grindstone mark height measuring process including measuring a height of a bottom surface of the finishing-grindstone mark formed in the finishing-grindstone mark forming process with a height measurer, a finishing-grindstone height calculating process including calculating a height of the finishing grindstone to be located when grinding the grinding-object wafer based on the height of the bottom surface of the finishing-grindstone mark measured in the finishing-grindstone mark height measuring process, a rough-grinding process including lowering the rough grindstone from a position above the outer peripheral portion of the grinding-object wafer in the bonded wafer and rotating the bonded wafer to roughly grind the grinding-object wafer with the rough grindstone, and a finish-grinding process including lowering the finishing grindstone from a position above a ground surface of the grinding-object wafer having been ground with the rough grindstone to the height calculated in the finishing-grindstone height calculating process and rotating the bonded wafer to finely grind the grinding-object wafer with the finishing grindstone.

An edge trimming apparatus according to an aspect of the present disclosure includes a chuck table including a holding surface configured to hold a bonded wafer, which includes a grinding-object wafer with a chamfered portion on an outer periphery thereof and a base wafer bonded together, a rotating device configured to rotate the chuck table about an axis at a center of the holding surface, a rough-grinding device configured to roughly grind an outer peripheral portion of the grinding-object wafer in the bonded wafer held by the chuck table in a ring shape with a rough grindstone, a finish-grinding device configured to finely grind the outer peripheral portion of the grinding-object wafer with a finishing grindstone, of which grain diameter is smaller than a grain diameter of the rough grindstone, a height measurer configured to measure a height of a surface of the grinding-object wafer having been ground with the finishing grindstone, and a controller. The controller is configured to control the finishing grindstone to form a process mark on the outer peripheral portion of the grinding-object wafer, measure a height of the process mark with the height measurer and calculate a height of the finishing grindstone to be located when grinding the grinding-object wafer, control the rough grindstone to contact and roughly grind the outer peripheral portion of the grinding-object wafer; and control the finishing grindstone to be located at the calculated height and to finely grind a ground surface of the grinding-object wafer having been ground roughly with the rough grindstone.

According to the present invention, for edge trimming of a grinding-object wafer by grinding with a rough grindstone and a finishing grindstone, a finishing-grindstone mark is formed, a height of the finishing-grindstone mark is measured and calculated, and the grinding-object wafer is ground by the finishing grindstone lowered to the calculated finishing-grindstone height. Thereby, the grinding accuracy of the edge trimming to the grinding-object wafer in a direction of height may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an edge trimming apparatus according to an embodiment of the present disclosure.

FIG. 2A is an illustrative view of a holding process.

FIG. 2B is another illustrative view of the holding process.

FIG. 3 is an illustrative view of a finishing-grindstone mark forming process in a first adjusting process.

FIG. 4A is an illustrative view of a finishing-grindstone mark height measuring process in the first adjusting process.

FIG. 4B is another illustrative view of the finishing-grindstone mark height measuring process in the first adjusting process.

FIG. 5 is an illustrative view of a finishing-grindstone height calculating process in the first adjusting process.

FIG. 6 is an illustrative view of a rough-grindstone mark forming process in a second adjusting process.

FIG. 7A is an illustrative view of a rough-grindstone mark height measuring process in the second adjusting process.

FIG. 7B is another illustrative view of the rough-grindstone mark height measuring process in the second adjusting process.

FIG. 8 is an illustrative view of a rough-grindstone height calculating process in the second adjusting process.

FIG. 9A is an illustrative view of a rough-grinding process.

FIG. 9B is another illustrative view of the rough-grinding process.

FIG. 10A is an illustrative view of a finish-grinding process.

FIG. 10B is another illustrative view of the finish-grinding process.

FIG. 11 is a schematic plan view after completing the finish-grinding process.

FIG. 12 is an illustrative view of a third adjusting process.

FIG. 13 is a block diagram to illustrate a controlling system in the edge trimming apparatus.

FIG. 14 is an illustrative view of the first adjusting process in a modified example.

DESCRIPTION OF EMBODIMENTS

Hereinafter, with reference to the accompanying drawings, an edge trimming apparatus 1 according to the embodiment of the present disclosure will be described. It may be noted that a configuration of the edge trimming apparatus 1 according to the embodiment of the present disclosure is not necessarily be limited to that described below but may be modified optionally or preferably. In FIG. 1, some of members that may be included in the edge trimming apparatus 1 are omitted for easier explanation.

First, with reference to FIG. 1, an overall configuration of the edge trimming apparatus 1 will be described. FIG. 1 is a perspective view of the edge trimming apparatus 1 according to the embodiment of the present disclosure. An X-axis direction, a Y-axis direction, and a Z-axis direction shown in FIG. 1 are orthogonal to one another. The X-axis direction and the Y-axis direction are each substantially horizontal direction, and the Z-axis direction is an up-down direction (vertical direction).

As shown in FIG. 1, the edge trimming apparatus 1 is configured to trim an edge of an outer periphery of a grinding-object wafer W1, which is a wafer to be ground in a bonded wafer W held by a chuck table 21, with a rough-grinding device 51 and a finish-grinding device 52.

The grinding-object wafer W1 shown in FIG. 1 is, for example, a semiconductor wafer formed of silicon as a base material having a circular outer shape. A front surface W11 of the grinding-object wafer W1 is sectioned into a plurality of areas in grid, and in each area, a device such as an IC, which is not shown, is formed. The grinding-object wafer W1 has a chamfered portion W13 (see FIG. 2B), of which edges toward the front surface W11 and a back surface W12 are chamfered in a substantially semi-circular ark or a substantially quarter arc in a cross-sectional view, on an outer periphery thereof. With the chamfered portion W13, the grinding-object wafer W1 may prevent cracking or generating dust that may otherwise be caused during fabrication processes. The grinding-object wafer W1 may not necessarily be composed of silicon alone but may optionally be composed of gallium arsenide, sapphire, gallium nitride, ceramics, resin, or silicon carbide. Moreover, the grinding-object wafer W1 may not necessarily have the devices formed thereon.

The bonded wafer W is composed of the grinding-object wafer W1 and a base wafer W2 bonded together. The base wafer W2 is formed in a disc-shape having a substantially same diameter as the grinding-object wafer W1, and materials thereof may not necessarily be limited. For example, the base wafer W2 may be formed of a substrate made of an inorganic material such as glass or ceramics, a substrate made of semiconductor such as silicon, or a substate made of a metal such as stainless steel. In the bonded wafer W, the front surface W11 of the grinding-object wafer W1 is bonded to an entire upper surface of the base wafer W2 in FIG. 2B through an adhesive layer. As such, the grinding-object wafer W1 is handled as a part of the bonded wafer W, and thereby the grinding-object wafer W1 may be processed more preferably, and the grinding-object wafer W1 may be prevented from warping or from being damaged while being through a fabrication process.

On a base 11 of the edge trimming apparatus 1, an X-axis movable device 15 for moving the chuck table 21 in the X-axis direction is arranged. The X-axis movable device 15 includes a pair of guide rails 16, which extend in parallel to the X-axis direction on the base 11, and an X-axis table 17, which is arranged on the base 11 and is slidable on the pair of guide rails 16. On a back side of the X-axis table 17, a nut (not shown) is formed, and a feed screw 18 is engaged with the nut. The feed screw 18 is coupled with a driving motor 19 on one end thereof, and by activating the driving motor 19 to rotate, the chuck table 21 is moved in the X-axis direction along the pair of guide rails 16.

On the X-axis table 17, the chuck table 21 for holding the bonded wafer W and a rotating device 22 are arranged. The chuck table 21 has a holding surface 211 formed of a porous ceramic material, and the bonded wafer W may be suctioned to be held on the holding surface 211 by a negative pressure produced in the holding surface 211. The rotating device 22 includes a motor located below the chuck table 21 and a rotation shaft, of which axial direction coincides with the Z-axis direction (vertical direction), and the chuck table 21 is rotated about an axis at a center of the holding surface 211. On an upper surface of the base 11, an upright wall 12 in a form of a gate erecting to straddle a movable path of the chuck table 21 is arranged.

On the upright wall 12, a Y-axis movable device 31 for moving the rough-grinding device 51 and the finish-grinding device 52 in the Y-axis direction is arranged. Further, on the upright wall 12, a first Z-axis movable device 41 for moving the rough-grinding device 51 in the Z-axis direction and a second Z-axis movable device for moving the finish-grinding device 52 in the Z-axis direction are arranged.

The Y-axis movable device 31 includes a pair of guide rails 34, which extend in parallel to the Y-axis direction, and a pair of Y-axis tables 35, which are arranged on a front surface of the upright wall 12 and are slidable on the pair of guide rails 34. On a back side of each Y-axis table 35, a nut (not shown) is formed, and a feed screw 36 is engaged with the nut. The feed screws 36 are each coupled with a driving motor 37 on one end thereof, and by activating the driving motor 37 to rotate, the first or second Z-axis movable device 41, 42, and the rough-grinding device 51 or the finish-grinding device 52 may be moved in the Y-axis direction along the pair of guide rails 34.

The first and second Z-axis movable devices 41, 42 each include a pair of guide rails 44, which extend in the Z-axis direction on the Y-axis table 35, and a Z-axis table 45, which is slidable on the pair of guide rails 4. On a back side of each Z-axis table 45, a nut (not shown) is formed, and a feed screw 46 is engaged with the nut. The feed screws 46 are each coupled with a driving motor 47 on one end thereof, and by activating the driving motor 47 to rotate, the rough-grinding device 51 or the finish-grinding device 52 may be moved in the Z-axis direction (vertically) along the pair of guide rails 44.

The rough-grinding device 51 includes a spindle 53 supported rotatably and a rough grindstone 54 attached to a tip of the spindle 53 (see FIGS. 2A and 2B). The rough grindstone 54 may consist of, for example, a resin blade, in which abrasive grains such as diamond are hardened with resin bond in a form of a round blade. The rough-grinding device 51 may drive the spindle 53 to rotate in a trimming process and thereby drive the rough grindstone 54 to rotate while grinding water is emitted from a jet nozzle (not shown) at a processing spot where the rough grindstone 54 works.

The finish-grinding device 52 includes a spindle 55 supported rotatably and a finishing grindstone 56 attached to a tip of the spindle 55 (see FIGS. 2A and 2B). The finishing grindstone 56 may consist of, likewise, for example, a resin blade, in which abrasive grains such as diamond are hardened with resin bond in a form of a round blade. The finishing grindstone 56 is provided with abrasive grains, of which grain diameter is smaller than that of the rough grindstone 54. The finish-grinding device 52 may drive the spindle 55 to rotate in a trimming process and thereby drive the finishing grindstone 56 to rotate while grinding water is emitted from a jet nozzle (not shown) at a processing spot where the rough grindstone 54 works.

On the upper surface of the base 11, at a position frontward with respect to the upright wall 12 in the form of gate, a support frame 58 straddling the movable path of the chuck table 21 is arranged, and a height measurer 59 is arranged at a central area of the support frame 58 in the Y-axis direction. The height measurer 59 may exemplarily consist of a laser displacement meter equipped with a light emitter and a light receiver (not shown) using a spot laser beam. The height measurer 59 measures a height of an upper surface (a position in the Z-axis direction) of the grinding-object wafer W1 in the bonded wafer W held by the chuck table 21 without contacting.

The edge trimming apparatus 1 is provided with a controller 70 that may generally control the components in the edge trimming apparatus 1 (see FIGS. 1 and 13). The controller 70 may consist of a processor to execute various types of processes, a memory, and the like. The controller 70 may control various type of operations such as forming a finishing-grindstone mark W15 and a rough-grindstone mark W16 (see FIGS. 3 and 6), grinding roughly with the rough-grinding device 51, grinding finely with the finish-grinding device 52, and measuring the height of the upper surface of the grinding-object wafer W1 according to controlling programs stored in the memory.

In the description below, if a subject to perform operations in the edge trimming apparatus 1 is not explicitly described, it may be recognized that the operations are controlled by controlling signals transmitted from the controller 70.

In the edge trimming apparatus 1 configured as above, edge trimming to remove a chamfered portion W13 of the grinding-object wafer W1 in the bonded wafer W by grinding with the rough grindstone 54 and thereafter with the finishing grindstone 56 is performed. In paragraphs below, with reference to FIGS. 2A through 12, an edge trimming method according to the embodiment of the present disclosure will be described. The edge trimming method according to the embodiment of the present disclosure includes a holding process, a first adjusting process, a second adjusting process, a rough-grinding process, a finish-grinding process, and a third adjusting process, which are performed in this given order.

[Holding Process]

In the edge trimming method according to the embodiment of the present disclosure, first, as shown in FIGS. 2A and 2B, the holding process is performed. FIGS. 2A and 2B are illustrative views of the holding process; FIG. 2A is a schematic plan view, and FIG. 2B is a schematic front view. In the holding process, the bonded wafer W is held by the chuck table 21 in an arrangement such that a center of the bonded wafer W coincides with a rotation axis of the chuck table 21. In particular, a lower surface of the base wafer W2 is suctioned by a negative pressure generated on a holding surface 211 of the chuck table 21, and thereby the bonded wafer W is held by the chuck table 21.

[First Adjusting Process]

After the holding process, as shown in FIGS. 3 through 5, the first adjusting process is performed. The first adjusting process includes a finishing-grindstone mark forming process, a finishing-grindstone mark height measuring process, and a finishing-grindstone height calculating process, which are performed in this given order.

[First Adjusting Process: Finishing-Grindstone Mark Forming Process]

FIG. 3 is a schematic front view of the edge trimming apparatus 1 to illustrate the finishing-grindstone mark forming process. As shown in FIG. 3, in the finishing-grindstone mark forming process, by the X-axis movable device 15 (see FIG. 1) being driven, the bonded wafer W held by the chuck table 21 is located at a position below the finishing grindstone 56 of the finish-grinding device 52. Moreover, by the Y-axis movable device 31 (see FIG. 1) being driven, the finishing grindstone 56 is located at a position shifted inward from the chamfered portion W13 of the grinding-object wafer W1 by a predetermined distance in a radial direction.

Next, the finishing grindstone 56 is rotated at a high speed by the spindle 55 in the finish-grinding device 52 spinning at a high speed. Moreover, by the second Z-axis movable device 42 being driven, the finishing grindstone 56 in the finish-grinding device 52 is lowered from the position above the outer peripheral portion of the grinding-object wafer W1 of the bonded wafer W to a predetermined height. The descending movement of the finishing grindstone 56 is controlled based on a preset height h1 (see FIG. 5), where a lower end surface of the finishing grindstone 56 should be located in the Z-axis direction, and the preset height h1 is stored in advance in the controller 70 (see FIG. 1). The preset height h1 may be, for example, a position higher than a rough-grindstone height h6 (see FIG. 8) of the rough grindstone 54 in the grinding process, which will be described further below.

By the finishing grindstone 56 rotating and descending against the back surface W12 of the grinding-object wafer W1, the outer peripheral portion of the grinding-object wafer W1 is narrowly ground downward. The finishing grindstone 56 is controlled to descend to a position corresponding to the preset height h1 and thereafter to ascend to separate from the grinding-object wafer W1. In the outer peripheral portion (chamfered portion W13) of the grinding-object wafer W1, a finishing-grindstone mark W15 being a processed mark is formed by the rotating finishing grindstone 56. In the meantime, rotation of the chuck table 21 in the Z-axis direction is regulated, and the finishing-grindstone mark W15 is formed in a narrow range in the peripheral portion of the grinding-object wafer W1.

According to the edge trimming apparatus 1 in the embodiment of the present disclosure, the rough-grinding device 51 and the finish-grinding device 52 are aligned in the Y-axis direction (crosswise direction in FIG. 3). Therefore, in the finishing-grindstone mark forming process, when the bonded wafer W is located at the position below the finishing grindstone 56 of the finish-grinding device 52, the bonded wafer W is located at the same time at a position below the rough grindstone 54 of the rough-grinding device 51. However, during the first adjusting process including the finishing-grindstone mark forming process, the rough grindstone 54 is maintained to standby at a position above the grinding-object wafer W1.

[First Adjusting Process: Finishing-Grindstone Mark Height Measuring Process]

FIGS. 4A and 4B are illustrative views of the finishing-grindstone mark height measuring process in the first adjusting process; FIG. 4A is a schematic plan view, and FIG. 4B is a schematic front view. After the finishing-grindstone mark forming process, the finishing-grindstone mark height measuring process as shown in FIGS. 4A and 4B is performed. In the finishing-grindstone mark height measuring process, after the finishing-grindstone mark W15 as described above is formed, the chuck table 21 is rotated clockwise in FIG. 4A by 90 degrees by the rotating device 22 (see FIG. 1) being driven. Thereby, the grinding-object wafer W1 is placed such that the finishing-grindstone mark W15 is at a position below the height measurer 59. In this placement, a height h2 of a bottom surface of the finishing-grindstone mark W15 formed in the finishing-grindstone mark forming process is measured by the height measurer 59, and a measured result is output to the controller 70.

[First Adjusting Process: Finishing-Grindstone Hight Calculating Process]

FIG. 5 is a schematic front view of the edge trimming apparatus 1 to illustrate the finishing-grindstone height calculating process in the first adjusting process. After the finishing-grindstone mark height measuring process, the finishing-grindstone height calculating process as shown in FIG. 5 is performed. In the finishing-grindstone height calculating process, a height of a lower end surface of the finishing grindstone 56 for grinding the grinding-object wafer W1 (for performing the finish-grinding process) is calculated based on the height h2 of the bottom surface of the finishing-grindstone mark W15 measured as above. In the present embodiment, the height of the lower end surface of the finishing grindstone 56 is referred to as a finishing-grindstone height h3. The finishing-grindstone height h3 is stored in advance in the controller 70 as past data or an initial value.

For calculating the finishing-grindstone height h3, a difference d1 between the height h2 of the bottom surface of the finishing-grindstone mark W15 and the preset height h1 stored in the controller 70 is calculated. Moreover, a position of a height lowered from the finishing-grindstone height h3 stored in the controller 70 by the difference d1 is calculated, and the calculated results overwrites the finishing-grindstone height h3 as an updated finishing-grindstone height h3. The updated (calculated) finishing-grindstone height h3 is stored in the controller 70. Completing the finishing-grindstone height calculating process completes the first adjusting process.

[Second Adjusting Process]

After the first adjusting process, as shown in FIGS. 6 through 8, the second adjusting process is performed. The second adjusting process includes a rough-grindstone mark forming process, a rough-grindstone mark height measuring process, and a rough-grindstone height calculating process, which are performed in this given order. During the second adjusting process, the finishing grindstone 56 is maintained to standby at a position above the grinding-object wafer W1.

[Second Adjusting Process: Rough-Grindstone Mark Forming Process]

FIG. 6 is a schematic front view of the edge trimming apparatus 1 to illustrate the rough-grindstone mark forming process in the second adjusting process. Before the rough-grindstone mark forming process starts, in the first adjusting process, the bonded wafer W held by the chuck table 21 is located below the rough grindstone 54 of the rough-grinding device 51 as shown in FIG. 4B. In this arrangement, as shown in FIG. 6, by the Y-axis movable device 31 (see FIG. 1) being driven, the rough grindstone 54 is located at a position shifted inward from the chamfered portion W13 of the grinding-object wafer W1 by a predetermined distance in the radial direction.

Next, the rough grindstone 54 is rotated at a high speed by the spindle 53 in the rough-grinding device 51 spinning at a high speed. Moreover, by the first Z-axis movable device 41 being driven, the rough grindstone 54 in the rough-grinding device 51 is lowered from the position above the outer peripheral portion of the grinding-object wafer W1 of the bonded wafer W to a predetermined height. The descending movement of the rough grindstone 54 is controlled based on a preset height h4 (see FIG. 8), where a lower end surface of the rough grindstone 54 should be located in the Z-axis direction, and the preset height h4 is stored in advance in the controller 70 (see FIG. 1). The preset height h4 may be, for example, a position equal to or substantially equal to the preset height h1.

By the rough grindstone 54 rotating and descending against the back surface W12 of the grinding-object wafer W1, the outer peripheral portion of the grinding-object wafer W1 is narrowly ground downward. The rough grindstone 54 is controlled to descend to a position corresponding to the preset height h4 and thereafter to ascend to separate from the grinding-object wafer W1. In the outer peripheral portion of the grinding-object wafer W1, a rough-grindstone mark W16 being a processed mark is formed by the rotating rough grindstone 54. In the meantime, rotation of the chuck table 21 in the Z-axis direction is regulated, and the rough-grindstone mark W16 is formed in a narrow range in the outer peripheral portion of the grinding-object wafer W1.

[Second Adjusting Process: Rough-Grindstone Mark Height Measuring Process]

FIGS. 7A and 7B are illustrative views of the rough-grindstone mark height measuring process in the second adjusting process; FIG. 7A is a schematic plan view, and FIG. 7B is a schematic front view. After the rough-grindstone mark forming process, the rough-grindstone mark height measuring process as shown in FIGS. 7A and 7B is performed. In the rough-grindstone mark height measuring process, after the rough-grindstone mark W16 as described above is formed, the chuck table 21 is rotated counterclockwise in FIG. 7A by 90 degrees by the rotating device 22 (see FIG. 1) being driven. Thereby, the grinding-object wafer W1 is placed such that the rough-grindstone mark W16 is at the position below the height measurer 59. In this placement, a height h5 of a bottom surface of the rough-grindstone mark W16 formed in the rough-grindstone mark forming process is measured by the height measurer 59, and a measured result is output to the controller 70.

[Second Adjusting Process: Rough-Grindstone Hight Calculating Process]

FIG. 8 is a schematic front view to illustrate the rough-grindstone height calculating process in the second adjusting process. After the rough-grindstone mark height measuring process, the rough grindstone height calculating process as shown in FIG. 8 is performed. In the rough grindstone height calculating process, a height of the lower end surface of the rough grindstone 54 for grinding the grinding-object wafer W1 (for performing the rough-grinding process) is calculated based on the height h5 of the bottom surface of the rough-grindstone mark W16 measured as above. In the present embodiment, the height of the lower end surface of the rough grindstone 54 is referred to as a rough-grindstone height h6. The rough-grindstone height h6 is stored in advance in the controller 70 as past data or an initial value.

For calculating the rough-grindstone height h6, a difference d2 between the height h5 of the bottom surface of the rough-grindstone mark W16 and the preset height h4 stored in the controller 70 is calculated. Moreover, a position of a height lowered from the rough-grindstone height h6 stored in the controller 70 by the difference d2 is calculated, and the calculated result overwrites the rough-grindstone height h6 as an updated rough-grindstone height h6. The updated (calculated) rough-grindstone height h6 is stored in the controller 70. Completing the rough-grindstone height calculating process completes the second adjusting process.

[Rough-Grinding Process]

FIGS. 9A and 9B are illustrative views of the rough-grinding process; FIG. 9A is a schematic plan view, and FIG. 9B is a schematic front view. After the second adjusting process, the rough-grinding process as shown in FIGS. 9A and 9B is performed.

Before the rough-grinding process starts, in the second adjusting process, the bonded wafer W held by the chuck table 21 is located below the rough grindstone 54 of the rough-grinding device 51, and the rough grindstone 54 is located at a position shifted inward from the chamfered portion W13 of the grinding-object wafer W1 by a predetermined distance in the radial direction. For example, the rough grindstone 54 may be placed such that approximately ⅔ of the lower end surface of the rough grindstone 54 contacts the chamfered portion W13 of the grinding-object wafer W1.

With the rough grindstone 54 being set in this position, the rough grindstone 54 is rotated at a high speed by the spindle 53 in the rough-grinding device 51 spinning at a high speed. Moreover, by the first Z-axis movable device 41 being driven, the rough grindstone 54 in the rough-grinding device 51 is lowered from the position above the outer peripheral portion of the grinding-object wafer W1 of the bonded wafer W to the rough-grindstone height h6 (see FIG. 8) calculated and updated in the rough-grindstone height calculating process.

With the rough grindstone 54 being lowered to the height described above and maintained at the height position, the rotation of the rough grindstone 54 is continued, and the chuck table 21 is rotated clockwise in a view from above. Thereby, as the chuck table 21 and the bonded wafer W held by the chuck table 21 are rotated, grinding roughly by the rough grindstone 54 progresses along the outer periphery of the grinding-object wafer W1, and a rough-ground surface (ground surface) W17 is formed. The chuck table 21 is rotated by approximately 180 degrees, and thereafter, while the rough-grinding process continues further, the finish-grinding process is started. Accordingly, the rough-grinding process and the finish-grinding process are performed simultaneously.

[Finish-Grinding Process]

FIGS. 10A and 10B are illustrative views of the finish-grinding process; FIG. 10A is a schematic plan view, and FIG. 10B is a schematic front view. FIG. 11 is a plan view to schematically illustrate the edge trimming apparatus 1 after the finish-grinding process is completed. While the rough-grinding process is being performed, the finish-grinding process as shown in FIGS. 10A and 10B is performed.

Before the finish-grinding process starts, the bonded wafer W held by the chuck table 21 is located below the finishing grindstone 56 of the finish-grinding device 52. In this arrangement, the finishing grindstone 56 is located at a position shifted inward from the chamfered portion W13 of the grinding-object wafer W1 by a predetermined distance in the radial direction. For example, the finishing grindstone 56 may be placed such that approximately ⅔ of the lower end surface of the finishing grindstone 56 contacts the chamfered portion W13 of the grinding-object wafer W1.

With the finishing grindstone 56 being set in this position, the finishing grindstone 56 is rotated at a high speed by the spindle 55 spinning in the finish-grinding device 52 at a high speed. As the rotation of the chuck table 21 in the rough-grinding process progresses by approximately 180 degrees, and when the rough-ground surface W17 reaches the position below the finishing grindstone 56, the second Z-axis movable device 42 is driven. By the second Z-axis movable device 42 being driven, the finishing grindstone 56 in the finish-grinding device 52 is lowered from the position above the rough-ground surface W17 of the grinding-object wafer W1 to the finishing-grindstone height h3 (see FIG. 5) calculated and updated in the finishing-grindstone height calculating process.

With the finishing grindstone 56 being lowered to the height described above and maintained at the height position, the rotations of the rough grindstone 54 and the finishing grindstone 56 are continued, and the chuck table 21 is rotated clockwise continuously. Thereby, as shown in FIG. 10A, while the chuck table 21 and the bonded wafer W held by the chuck table 21 are rotated, grinding roughly by the rough grindstone 54 and grinding finely by the finishing grindstone 56 are performed simultaneously along the outer periphery of the grinding-object wafer W1. In this embodiment, the ground surface to which both rough-grinding and finish-grinding are applied is referred to as a finish-ground surface (ground surface) W18. In FIG. 10A, the finish-ground surface W18 is indicated by hatching finer than hatching that indicates the rough-ground surface W17.

During the finish-grinding process, after the chuck table 210 is rotated by approximately 360 degrees since the start of grinding in the rough-grinding process, by the first Z-axis movable device 41 being driven, the rough grindstone 54 ascends and separates from the grinding-object wafer W1. Thereby, the chamfered portion W13 (outer peripheral portion) of the grinding-object wafer W1 is entirely ground by the rough grindstone 54 in a ring shape, and the rough-grinding process is completed. While the rough grindstone 54 ascends, the finishing grindstone 56 continues grinding.

Further, after the chuck table 210 is rotated by approximately 360 degrees since the start of grinding in the finish-grinding process, by the second Z-axis movable device 42 being driven, the finishing grindstone 56 ascends and separates from the grinding-object wafer W1. Thereby, the chamfered portion W13 of the grinding-object wafer W1 is entirely ground by the finishing grindstone 56 in the ring shape, and the finish-ground surface W18 is formed entirely in the outer peripheral portion of the grinding-object wafer W1 as shown in FIG. 11, and the finish-grinding process is completed.

[Third Adjusting Process]

After the second adjusting process, the third adjusting process as shown in FIG. 12 is performed. FIG. 12 is a schematic front view to illustrate the third adjusting process. The third adjusting process includes a finish-ground surface height measuring process, a calculating process, and a correcting process, which are performed in this given order.

[Third Adjusting Process: Finish-Ground Surface Height Measuring Process]

In the finish-ground surface height measuring process, a height h7 of the finish-ground surface W18 being the surface ground in the finish-grinding process described above is measured by the height measurer 59, and a measured result is output to the controller 70.

[Third Adjusting Process: Calculating Process]

In the third adjusting process, after the finish-ground surface height measuring process, the calculating process is performed. In the calculating process, a difference d3 between the height h7 of the finish-ground surface W18 measured as above and an upper surface height h8 of the base wafer W2 is calculated. The upper surface height h8 of the base wafer W2 is stored in advance in the controller 70 as past data or an initial value.

[Third Adjusting Process: Correcting Process]

In the third adjusting process, after the calculating process, the correcting process is performed. In the correcting process, the finishing-grindstone height h3 (see FIG. 5) calculated in the finishing-grindstone height calculating process in the first adjusting process described above is corrected to be lowered by the difference d3 calculated in the calculating process. The corrected finishing-grindstone height h3 is stored in the controller 70. Completing the correcting process completes the third adjusting process.

By performing each of the above steps, a series of edge trimming processes on the grinding-object wafer W1 in the edge trimming apparatus 1 is completed. After the edge trimming processes are completed, the finish-ground surface W18 (see FIG. 11) of the grinding-object wafer W1 is etched. In the process of etching, the bonded wafer W is held by a spinner table, which is not shown, and is rotated via the spinner table while an etching solution is ejected at the finish-ground surface W18 from a nozzle, which is not shown, located at a position above the grinding-object wafer W1. Thereby, the thicker portion forming the finish-ground surface W18 is removed entirely by a chemical action of the etching solution, and the grinding-object wafer W1 may prevent a sharp edge from being formed in subsequent processes.

FIG. 13 is a diagram to illustrate exemplary functional blocks of the controller 70 in the edge trimming apparatus 1. As shown in FIG. 13, the controller in the edge trimming apparatus functions as a process mark forming controlling unit 71, a calculating unit 72, a rough-grinding controlling unit 73, and a finish-grinding controlling unit 74. These functional blocks are realized by the controller 70 executing programs stored in a memory of the controller 70, and it may not mean that the functional blocks exist as individual hardware devices. Moreover, the controller 70 shown in FIG. 13 may optionally include other functional blocks than the functional blocks recited above.

The process mark forming controlling unit 71 controls operations of the devices including the X-axis movable device 15, the Y-axis movable device 31, the first Z-axis movable device 41, the second Z-axis movable device 42, the rough-grinding device 51, and the finish-grinding device 52 in the first and second adjusting processes described above. In particular, the process mark forming controlling unit 71 may control forming the finishing-grindstone mark W15 in the outer peripheral portion of the grinding-object wafer W1 with the finishing grindstone 56 and forming the rough-grindstone mark W16 in the outer peripheral portion of the grinding-object wafer W1 with the rough grindstone 54.

The calculating unit 72 controls measuring the height h2 of the bottom surface of the finishing-grindstone mark W15, the height h5 of the bottom surface of the rough-grindstone mark W16, and the height h7 of the finish-ground surface W18 with the height measurer 59 in the first and third adjusting processes described above. Moreover, the calculating unit 72 calculates, updates, and corrects the finishing-grindstone height h3 and the rough-grindstone height h6 and outputs the finishing-grindstone height h3 and the rough-grindstone height h6 having been calculated, updated, and corrected to the finish-grinding controlling unit 74 and the rough-grinding controlling unit 73.

The rough-grinding controlling unit 73 controls operations of devices including the X-axis movable device 15, the Y-axis movable device 31, the first Z-axis movable device 41, and the rough-grinding device 51 in the rough-grinding process described above. The rough-grinding controlling unit 73 controls locating the rough grindstone 54 at the rough-grindstone height h6 calculated by the calculating unit 72 and causing the rough grindstone 54 to contact the outer peripheral portion of the grinding-object wafer W1 to grind roughly to form the rough-ground surface W17.

The finish-grinding controlling unit 74 controls operations of devices including the X-axis movable device 15, the Y-axis movable device 31, the second Z-axis movable device 42, and the finish-grinding device 52 in the finish-grinding process described above. The finish-grinding controlling unit 74 controls locating the finishing grindstone 56 at the finish-grindstone height h3 calculated by the calculating unit 72 and causing the finishing grindstone 56 to contact the rough-ground surface W17 of the grinding-object wafer W1 to grind finely to form the finish-ground surface W18.

As described above, in the embodiment of the present disclosure, before the finish-grinding process is performed, the finishing-grindstone mark W15 is formed on the grinding-object wafer W1 and the height h2 of the finishing-grindstone mark W15 having been formed is measured, and the finishing-grindstone height h3 (the height of the lower end surface of the finishing grindstone 56 when grinding with the finishing grindstone 56) is calculated. Thereby, positional accuracy of the finish-ground surface W18 formed in the finish-grinding process in the height direction may be improved.

As such, by improving the grinding accuracy of the finish-ground surface W18, the time required for etching to remove the thicker portion of the finish-ground surface W18 entirely may be prevented from increasing. Moreover, when the finishing grindstone 56 grinds the grinding-object wafer W1, the base wafer W2 may be prevented from being ground by the finishing grindstone 56 that may otherwise grind through the thicker portion of the grinding-object wafer W1. Accordingly, the base wafer W2 may be prevented from being damaged, and the processing efficiency may be prevented from being lowered by the interruption of the grinding process due to the damage.

Moreover, in the embodiment of the present disclosure described above, the edge trimming is performed with use of the two types of grindstones having different grinding grain sizes, which are the rough grindstone 54 and the finishing grindstone 56. Therefore, the finishing grindstone 56 may be prevented from being worn unevenly, and the edge trimming may be completed in shorter time.

Moreover, in the embodiment of the present disclosure described above, in the third adjusting process after the finish-grinding process, the height of the finish-ground surface W18 is measured, and the finishing-grindstone height h3 being the height of the finishing grindstone 56 to grind the grinding-object wafer W1 in the next edge trimming is corrected. Thereby, the finish-grindstone height h3 in the finish-grinding process for the next edge trimming is corrected in consideration of an amount of the finishing grindstone 56 being worn in the finish-grinding process, and the positional accuracy of the finish-ground surface W18 in the direction of height may be improved.

Moreover, in the embodiment of the present disclosure described above, before the rough-grinding process is performed, the rough-grindstone mark W16 is formed on the grinding-object wafer W1 and the height 5 of the rough-grindstone mark W16 having been formed is measured, and the rough-grindstone height h6 (the height of the lower end surface of the rough grindstone 54 when grinding with the rough grindstone 54) is calculated. Thereby, positional accuracy of the rough-ground surface W17 formed in the rough-grinding process in the height direction may be improved, and an amount of the finishing grindstone 56 to be worn in the finish-grinding process may be maintained within a certain range.

In the embodiment of the present disclosure described above, in the first adjusting process, the finishing-grindstone mark forming process and the finishing-grindstone mark height measuring process are each performed once. However, optionally, the finishing-grindstone mark forming process and the finishing-grindstone mark height measuring process may each performed twice. In this arrangement, the finishing-grindstone mark forming process and the finishing-grindstone mark height measuring process may each be performed once in the same manner as those in the embodiment described above, and thereafter, the finishing-grindstone mark forming process may be performed for the second round. In the finishing-grindstone mark forming process in the second round, at the position to overlap the finishing-grindstone mark W15 formed in the finishing-grindstone mark forming process in the first round, a finishing-grindstone mark W152 as shown in FIG. 14 may be formed in the second round. The finishing-grindstone mark W15 formed in the first round is formed under the control such that the height of the finishing grindstone 56 is based on the preset height h1, and the finishing-grindstone mark W152 formed in the second round is formed under the control such that the height of the finishing grindstone 56 is based on a preset height h12. The preset height h12 is set to be lower than the preset height h1, and the bottom surface of the finishing-grindstone mark W152 formed in the second round is lower than the bottom surface of the finishing-grindstone mark W15 formed in the first round.

After the finishing-grindstone mark forming process in the second round, the finishing-grindstone mark height measuring process in the second round is performed. In the finishing-grindstone mark height measuring process in the second round, a height h22 of the bottom surface of the finishing-grindstone mark W152 formed in the second round is measured. After the finishing-grindstone mark height measuring process in the second round, the finishing-grindstone height calculating process is performed.

In the finishing-grindstone height calculating process, a difference d5 between the preset height h1 and the preset height h12 described above is calculated. Moreover, a difference d6 between the height h2 of the bottom surface of the finishing-grindstone mark W15 in the first round and the height h22 of the bottom surface of the finishing-grindstone mark W152 in the second round is calculated, and a difference d7 between the difference d5 and the difference d6 is calculated. Thereafter, a position of a height lowered from the finishing-grindstone height h3 being the height of the finishing grindstone 56 when the finish-grinding process was actually performed by the difference d7 is calculated, and the finishing-grindstone height 3 is updated with the calculated result.

In the meantime, in the edge trimming method according to the embodiment of the present disclosure, optionally, at least one of the second adjusting process and the third adjusting process may be omitted. Moreover, for edge trimming with a plurality of bonded wafers W, all of the above-described processes may be applied to each of the bonded wafers W, or for once in every predetermined number in the plurality of bonded wafers W (for example, once in every five bonded wafers W), at least one of the second adjusting process and the third adjusting process may be omitted.

Moreover, in the above-described embodiment of the present disclosure, for edge trimming with a plurality of bonded wafers W, the first adjusting process may be applied to each of the bonded wafers W or may be applied to once in every predetermined number in the plurality of bonded wafers W (for example, once in every five bonded wafers W).

Moreover, in the third adjusting process, the height h7 of the finish-ground surface W18 may be measured continuously in the circumferential direction of the grinding-object wafer W1 by rotating the chuck table 21 while the height measurer 59 is measuring. According to this measuring method, for example, the height h7 of the finish-ground surface W18, which may vary depending on the amount of the finishing grindstone 56 to be worn during the finish-grinding process, may be measured continuously, and the finishing-grindstone height h3 in the finish-grinding process in the next round may be changed according to the varied amount of the finishing grindstone 56 being worn. Thereby, the height h7 of the finish-ground surface W18 in the ring shape may be evened out in the circumferential direction, and the positional accuracy of the finish-ground surface W18 in the direction of height may be improved.

Moreover, the embodiment of the present invention may not necessarily be limited to the configuration described above or the modified examples but may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention may be realized in a different way due to technological progress or other derived technology, it may be implemented with use of the method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of the present invention.

As described above, the present invention has an effect of improving the grinding accuracy by trimming an edge of the outer peripheral portion of the grinding-object wafer before etching.

Claims

1. An edge trimming method for removing a chamfered portion on an outer periphery of a grinding-object wafer in a bonded wafer, the bonded wafer including the grinding-object wafer with the chamfered portion and a base wafer bonded together, by grinding with a rough grindstone and thereafter grinding with a finishing grindstone, the method comprising:

a holding process including operating a chuck table to hold the bonded wafer by the base wafer;

a finishing-grindstone mark forming process including lowering the finishing grindstone from a position above an outer peripheral portion of the grinding-object wafer in the bonded wafer to a predetermined height and forming a finishing-grindstone mark in the grinding-object wafer with the finishing grindstone;

a finishing-grindstone mark height measuring process including measuring a height of a bottom surface of the finishing-grindstone mark formed in the finishing-grindstone mark forming process with a height measurer;

a finishing-grindstone height calculating process including calculating a height of the finishing grindstone to be located when grinding the grinding-object wafer based on the height of the bottom surface of the finishing-grindstone mark measured in the finishing-grindstone mark height measuring process;

a rough-grinding process including lowering the rough grindstone from a position above the outer peripheral portion of the grinding-object wafer in the bonded wafer and rotating the bonded wafer to roughly grind the grinding-object wafer with the rough grindstone; and

a finish-grinding process including lowering the finishing grindstone from a position above a ground surface of the grinding-object wafer having been ground with the rough grindstone to the height calculated in the finishing-grindstone height calculating process and rotating the bonded wafer to finely grind the grinding-object wafer with the finishing grindstone.

2. The edge trimming method according to claim 1, further comprising:

a finish-ground surface height measuring process including measuring a height of the ground surface having been ground with the finishing grindstone in the finish-grinding process with the height measurer;

a calculating process including calculating a difference between the height of the ground surface and a height of an upper surface of the base wafer; and

a correcting process including correcting the height of the finishing grindstone calculated in the finishing-grindstone height calculating process by shifting the height in a lowering direction by the difference calculated in the calculating process.

3. The edge griming method according to claim 1, further comprising:

a rough-grindstone mark forming process including lowering the rough grindstone from a position above the outer peripheral portion of the grinding-object wafer in the bonded wafer to a predetermined height and forming a rough-grindstone mark in the grinding-object wafer with the rough grindstone;

a rough-grindstone mark height measuring process including measuring a height of a bottom surface of the rough-grindstone mark formed in the rough-grindstone mark forming process with the height measurer; and

a rough-grindstone height calculating process including calculating a height of the rough grindstone to be located when grinding the grinding-object wafer based on the height of the bottom surface of the rough-grindstone mark measured in the rough-grindstone mark height measuring process,

wherein, in the rough-grinding process, the rough grindstone is lowered to the height calculated in the rough-grindstone height calculating process.

4. An edge trimming apparatus, comprising:

a chuck table including a holding surface configured to hold a bonded wafer, the bonded wafer including a grinding-object wafer with a chamfered portion on an outer periphery thereof and a base wafer bonded together;

a rotating device configured to rotate the chuck table about an axis at a center of the holding surface;

a rough-grinding device configured to roughly grind an outer peripheral portion of the grinding-object wafer in the bonded wafer held by the chuck table in a ring shape with a rough grindstone;

a finish-grinding device configured to finely grind the outer peripheral portion of the grinding-object wafer with a finishing grindstone, of which grain diameter is smaller than a grain diameter of the rough grindstone;

a height measurer configured to measure a height of a surface of the grinding-object wafer having been ground with the finishing grindstone; and

a controller configured to: control the finishing grindstone to form a process mark on the outer peripheral portion of the grinding-object wafer; measure a height of the process mark with the height measurer and calculate a height of the finishing grindstone to be located when grinding the grinding-object wafer; control the rough grindstone to contact and roughly grind the outer peripheral portion of the grinding-object wafer, and control the finishing grindstone to be located at the calculated height and to finely grind a ground surface of the grinding-object wafer having been ground roughly with the rough grindstone.