Method for processing multilayer wafers, method for manufacturing processed multilayer wafers

Abstract

The stacked wafers are edge-trimmed so that the thickness at the stepped portion reaches a predetermined value. [Solution] A method for processing a laminated wafer, in which a first wafer and a second wafer are joined together, by cutting the outer edge of the laminated wafer and removing the chamfered portion, comprising: a first cutting step in which the lower end of a rotating annular cutting blade is positioned at a first height and the cutting blade is used to form a first stepped portion on a part of the outer edge of the laminated wafer; a measurement step in which the height of the bottom surface of the first stepped portion is measured; an individual difference correction value creation step in which an individual difference correction value is created based on the height of the bottom surface of the first stepped portion and the first height; and a second cutting step in which the lower end of the rotating cutting blade is positioned at a second height lower than the first height and the cutting blade is used to form a second stepped portion on the outer edge of the laminated wafer, wherein in the second cutting step, the height of the cutting blade is corrected with the individual difference correction value while the second stepped portion is formed on the laminated wafer.

Description

Technical Field

[0001] The present invention relates to a method for processing a laminated wafer, in which outer peripheral ends of two or more wafers each having chamfered outer peripheral ends on both a front surface and a back surface are joined to form a laminated wafer, and then the outer peripheral ends of the laminated wafer are cut to form a stepped portion at the outer peripheral ends of the laminated wafer, and to a manufacturing method for manufacturing the processed laminated wafer.

Background Art

[0002] In wafers made of semiconductors such as silicon, usually, the outer peripheral ends on both the front surface side and the back surface side are chamfered. That is, rounded bevel portions are formed at the outer peripheral ends on both the front surface side and the back surface side.

[0003] When such a wafer is thinned to a thickness of less than half, a so-called sharp edge (also referred to as a knife edge) is formed at the outer peripheral end, and the outer peripheral end is likely to be damaged. Therefore, in order to prevent damage to the outer peripheral end, a technique is known in which the outer peripheral end on the front surface side of the wafer is cut by a cutting blade by a predetermined depth to form an annular stepped portion, and then the back surface side is ground to thin it (see, for example, Patent Document 1). This process is called edge trimming.

[0004] A cutting apparatus for edge trimming a wafer has a chuck table for holding the wafer. The upper surface of the chuck table serves as a holding surface for holding the wafer. The cutting apparatus sucks and holds the wafer placed on the holding surface by the chuck table, and rotates the chuck table around an axis substantially perpendicular to the holding surface while cutting the cutting blade into the outer peripheral end of the wafer, thereby cutting the wafer over the entire circumference.

[0005] However, there are variations in the height of minute portions on the holding surface of the chuck table, and minute variations in the height of the holding surface may occur as the chuck table rotates. Therefore, due to the rotation of the chuck table, the cutting amount of the cutting blade into the wafer may vary, and the height of the bottom surface of the formed stepped portion may not be uniform over the entire circumference of the wafer.

[0006] Therefore, before performing edge trimming on the wafer, a test wafer (dummy wafer) is held by suction on a chuck table, edge trimming is performed on the test wafer, and the height of the bottom surface of the formed step is measured around the entire circumference. This allows the trend of variation in the cutting depth of the cutting blade to be obtained. Then, by performing edge trimming on the wafer while changing the height of the cutting blade to correspond to this trend of variation, a high-quality step can be formed on the wafer (see Patent Document 2). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2000-173961 [Patent Document 2] Japanese Patent Publication No. 2022-50762 [Overview of the project] [Problems that the invention aims to solve]

[0008] In recent years, with the increasing performance of chips manufactured by cutting wafers, stacked wafers are sometimes formed by stacking multiple wafers, and chips are formed by processing these stacked wafers. Alternatively, in order to process wafers to an extremely thin thickness, wafers may be stacked on another wafer that serves as a support substrate and thinned while becoming part of a stacked wafer. Edge trimming is also performed on stacked wafers to prevent knife-edge shapes from forming on the outer edges during grinding.

[0009] However, each wafer constituting a stacked wafer has a certain degree of individual variation in thickness. In other words, each wafer has individual differences in thickness. Therefore, due to these individual differences, the cutting depth of the cutting blade into the stacked wafer may deviate from a predetermined amount when edge trimming is performed. In other words, the thickness of the stacked wafer at the stepped portion may not be the expected value.

[0010] For example, when attempting to form a stepped portion at a predetermined height by positioning a cutting blade at a predetermined height and cutting the outer edge of a target wafer included in a stacked wafer to a predetermined depth, the target wafer may not have a predetermined thickness at the formed stepped portion.

[0011] This invention has been made in view of the aforementioned problems, and aims to provide a method for processing laminated wafers that can edge-trim laminated wafers to accommodate individual differences in the thickness of each wafer, and a method for manufacturing processed laminated wafers. [Means for solving the problem]

[0012] According to one aspect of the present invention, a method for processing a laminated wafer, wherein a first wafer and a second wafer are joined together, and the outer edge of the laminated wafer is cut to remove a chamfered portion, comprising: a laminated wafer holding step in which the laminated wafer is held in a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, with the second wafer side of the laminated wafer facing the holding surface of the chuck table; a first cutting step in which the lower end of a rotating annular cutting blade is positioned at a first height, and the chuck table is not rotated, or rotated by an amount of less than one rotation around the rotation axis, while the cutting blade is made to cut into the outer edge of the laminated wafer, thereby forming a first stepped portion on a part of the outer edge of the laminated wafer; and in the first cutting step A method for processing a laminated wafer is provided, comprising: a measurement step of measuring the height of the bottom surface of the first stepped portion formed on the laminated wafer along the outer edge; an individual difference correction value creation step of creating an individual difference correction value based on the height of the bottom surface of the first stepped portion measured in the measurement step and the first height; and a second cutting step of positioning the lower end of the rotating cutting blade at a second height lower than the first height, and rotating the chuck table around the rotation axis by an amount of rotation of one or more to form a second stepped portion on the outer edge of the laminated wafer, wherein in the second cutting step, the height of the cutting blade is corrected with the individual difference correction value to form the second stepped portion on the laminated wafer.

[0013] According to another aspect of the present invention, a method for processing a laminated wafer, wherein a first wafer and a second wafer are joined together, and the outer edge of the laminated wafer is cut to remove the chamfered portion, comprising: a test wafer holding step of placing a test wafer on the holding surface of a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, and holding the test wafer with the chuck table; and after the test wafer holding step, rotating an annular cutting blade into the outer edge of the test wafer while rotating the chuck table around the rotation axis A test cutting step in which the test wafer is rotated by an amount of rotation of one or more revolutions to form a test step having an annular bottom surface and wall surface on the outer edge of the test wafer; a test measurement step in which the height of the bottom surface of the test step formed on the test wafer along the outer edge in the test cutting step is measured over the entire circumference, and relationship data between the rotation angle of the chuck table and the height of the bottom surface of the test step is obtained; and after the test measurement step, the holding of the test wafer by the chuck table is released and the test wafer is removed. A loading step, followed by a test measurement step, a device correction data creation step, which creates device correction data based on the relationship between the rotation angle of the chuck table and the cutting feed amount of the cutting blade, based on the relevant data, a stacked wafer holding step, which holds the stacked wafer with the chuck table with the second wafer side of the stacked wafer facing the holding surface of the chuck table, and a rotating cutting blade lower end to a first height, and cutting the cutting blade into the outer edge of the stacked wafer while the cutting blade is being used A first cutting step in which a jack table is not rotated, or rotated by an amount of less than one rotation around the axis of rotation, to form a first step portion on a part of the outer edge of the stacked wafer; a measurement step in which the height of the bottom surface of the first step portion formed on the stacked wafer along the outer edge in the first cutting step is measured; an individual difference correction value creation step in which an individual difference correction value is created based on the height of the bottom surface of the first step portion measured in the measurement step and the first height; and a second height in which the lower end of the rotating cutting blade is positioned lower than the first height.A method for processing a laminated wafer is provided, comprising: a second cutting step in which the cutting blade is driven into the outer edge of the laminated wafer while the chuck table is rotated by one or more rotations around the rotation axis to form a second stepped portion on the outer edge of the laminated wafer, wherein in the second cutting step, the height of the cutting blade is corrected in accordance with the rotation of the chuck table using both the apparatus correction data and the individual difference correction value to form the second stepped portion on the laminated wafer.

[0014] Preferably, in the first cutting step, the first step portion is formed on the first wafer of the stacked wafer, and in the second cutting step, the second step portion is formed on the first wafer of the stacked wafer, and the second height is determined by the distance of the first wafer from the surface facing the second wafer.

[0015] Furthermore, according to another aspect of the present invention, a manufacturing method for producing a processed laminated wafer by cutting the outer peripheral edge of a laminated wafer in which a first wafer and a second wafer are joined, and removing the chamfered portion, comprising: a laminated wafer holding step in which the laminated wafer is held in a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, with the second wafer side of the laminated wafer facing the holding surface of the chuck table; a first cutting step in which the lower end of a rotating annular cutting blade is positioned at a first height, and the chuck table is not rotated, or rotated by an amount of less than one rotation around the rotation axis, while the cutting blade is made to cut into the outer peripheral edge of the laminated wafer, thereby forming a first stepped portion on a part of the outer peripheral edge of the laminated wafer; and in the first cutting step A method for manufacturing a processed laminated wafer is provided, comprising: a measurement step of measuring the height of the bottom surface of the first step formed on the laminated wafer along the outer edge; an individual difference correction value creation step of creating an individual difference correction value based on the height of the bottom surface of the first step measured in the measurement step and the first height; and a second cutting step of positioning the lower end of the rotating cutting blade at a second height lower than the first height, and rotating the chuck table around the rotation axis by an amount of rotation of one or more to form a second step on the outer edge of the laminated wafer and obtain a processed laminated wafer, wherein in the second cutting step, the height of the cutting blade is corrected with the individual difference correction value while forming the second step on the laminated wafer.

[0016] According to yet another aspect of the present invention, a manufacturing method for producing a processed laminated wafer by cutting the outer edge of a laminated wafer in which a first wafer and a second wafer are joined and removing the chamfered portion, comprising: a test wafer holding step of placing a test wafer on the holding surface of a chuck table having a holding surface and being rotatable about a rotation axis intersecting the holding surface, and holding the test wafer with the chuck table; and after the test wafer holding step, cutting a rotating annular cutting blade into the outer edge of the test wafer while the chuck table A test cutting step in which the chuck table is not rotated, or rotated by an amount of rotation of one or more revolutions around the axis of rotation, to form a test step having an annular bottom surface and wall surface on the outer edge of the test wafer; a test measurement step in which the height of the bottom surface of the test step formed on the test wafer along the outer edge in the test cutting step is measured over the entire circumference, and relationship data between the rotation angle of the chuck table and the height of the bottom surface of the test step is obtained; and after the test measurement step, the test wafer is held by the chuck table. A removal step in which the test wafer is unloaded and the test wafer is unloaded; a device correction data creation step in which, after the test measurement step, device correction data is created based on the relationship between the rotation angle of the chuck table and the cutting feed amount of the cutting blade; a stacked wafer holding step in which the stacked wafer is held in the chuck table with the second wafer side of the stacked wafer facing the holding surface of the chuck table; and a rotating cutting blade lower end to a first height and the cutting blade outside the stacked wafer A first cutting step in which the chuck table is rotated around the rotation axis by an amount of less than one rotation while making a cut into the peripheral edge of the stacked wafer to form a first step portion on a part of the peripheral edge of the stacked wafer; a measurement step in which the height of the bottom surface of the first step portion formed on the stacked wafer along the peripheral edge in the first cutting step is measured; an individual difference correction value creation step in which an individual difference correction value is created based on the height of the bottom surface of the first step portion measured in the measurement step and the first height; and a second height in which the lower end of the rotating cutting blade is positioned lower than the first height.A method for manufacturing a processed laminated wafer is provided, comprising: a second cutting step of rotating the chuck table around the rotation axis by an amount of rotation of one or more while cutting the cutting blade into the outer edge of the laminated wafer, thereby forming a second stepped portion on the outer edge of the laminated wafer and obtaining a processed laminated wafer; wherein in the second cutting step, the height of the cutting blade is corrected in accordance with the rotation of the chuck table using both the apparatus correction data and the individual difference correction value, while forming the second stepped portion on the laminated wafer.

[0017] Preferably, in the first cutting step, the first step portion is formed on the first wafer of the stacked wafer, and in the second cutting step, the second step portion is formed on the first wafer of the stacked wafer, and the second height is determined by the distance of the first wafer from the surface facing the second wafer. [Effects of the Invention]

[0018] In one aspect of the present invention, a method for processing a laminated wafer and a method for manufacturing a processed laminated wafer are described, in which a first step is formed on a part of the outer edge of the laminated wafer, and the height of the bottom surface of the first step is measured. Then, an individual difference correction value is created based on this bottom surface height. Subsequently, a second step is formed on the outer edge of the laminated wafer. Edge trimming is completed by forming this second step.

[0019] Here, by forming the first step on the stacked wafer before forming the second step and calculating the height of the bottom surface of this first step, it is possible to evaluate the amount of deviation in the processing position due to individual differences in the thickness of each wafer. Then, an individual difference correction value is created to eliminate the effect of individual differences in thickness, and when forming the second step, the height of the cutting blade is corrected using the individual difference correction value. As a result, the second step can be formed at a predetermined height on wafers where the formation of the second step is planned.

[0020] Therefore, the present invention provides a method for processing laminated wafers that can perform edge trimming on the laminated wafers to accommodate individual differences in the thickness of each wafer, and a method for manufacturing processed laminated wafers.

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view schematically showing a cutting device. [Figure 2] It is a partial cross-sectional side view schematically showing the inside of the cutting device. [Figure 3] FIG. 3(A) is a cross-sectional view schematically showing a chuck table at which the height position of a holding surface is measured, and FIG. 3(B) is a cross-sectional view schematically showing a test wafer sucked and held by the chuck table. [Figure 4] FIG. 4(A) is a cross-sectional view schematically showing a test wafer to be cut, and FIG. 4(B) is a perspective view schematically showing the test wafer to be cut. [Figure 5] It is a cross-sectional view schematically showing a test wafer at which the height of the bottom surface of a test step portion formed over the entire circumference of the test wafer is measured. [Figure 6] It is a graph showing an example of relational data between the rotation angle of the chuck table and the height of the bottom surface of the test step portion. [Figure 7] FIG. 7(A) is a cross-sectional view schematically showing a stacked wafer sucked and held by the chuck table, and FIG. 7(B) is a cross-sectional view schematically showing the stacked wafer cut to form a first step portion. [Figure 8] It is a cross-sectional view schematically showing a stacked wafer at which the height of the bottom surface is measured at a first step portion formed at an outer peripheral end portion. [Figure 9] It is a graph showing an example of the relationship between the rotation angle of the chuck table and the height of the bottom surface of the first step portion. [Figure 10] It is a cross-sectional view schematically showing a stacked wafer cut to form a second step portion. [Figure 11] It is a cross-sectional view schematically showing a stacked wafer in which a second step portion is formed. [Figure 12] It is a graph showing an example of the state of variation in the height position of a cutting blade when forming a second step portion in a stacked wafer. [Figure 13]This flowchart shows the flow of each step in the method for processing a stacked wafer and the method for manufacturing a processed stacked wafer according to the embodiment. [Modes for carrying out the invention]

[0022] An embodiment of one aspect of the present invention will be described with reference to the attached drawings. First, a cutting apparatus used in the method for processing a laminated wafer and the method for manufacturing a processed laminated wafer according to this embodiment will be described. Figure 1 is a schematic perspective view of the cutting apparatus 2, and Figure 2 is a schematic partial cross-sectional side view showing the inside of the cutting apparatus 2.

[0023] As shown in Figures 1 and 2, the X-axis direction (machining feed direction), Y-axis direction (indexing feed direction), and Z-axis direction (vertical direction, height direction, depth of cut feed direction) are orthogonal to each other. The cutting device 2 has a base 4 that supports or houses each component.

[0024] A cover 6 is provided on the upper part of the base 4, forming the top surface and multiple sides. A cutting unit 8 is housed inside the cover 6. The cutting unit 8 has a rectangular prism-shaped spindle housing 10.

[0025] The spindle housing 10 is positioned so that its longitudinal direction is approximately parallel to the Y-axis direction. As shown in Figure 2, a portion of the cylindrical spindle 12 is housed in the spindle housing 10 in a manner that allows it to rotate.

[0026] An annular cutting blade 16 is mounted on one end of the spindle 12. The cutting blade 16 is, for example, a hub-type blade and has an annular base made of a metal such as aluminum, and a cutting edge 16a provided in an annular shape at the outer peripheral end of the base. The cutting edge 16a is formed by dispersing and fixing abrasive grains made of diamond or the like in a binder made of resin or metal material.

[0027] The cutting edge thickness 16a of the cutting blade 16 used for edge trimming is greater than the cutting edge thickness of the cutting blade used when dividing a workpiece (wafer) into multiple chips. The cutting edge thickness 16a is, for example, 1 mm or more and 3 mm or less. A rotational drive source 14, such as a servo motor, is connected to the other end of the spindle 12.

[0028] A Z-axis movement mechanism 20 is connected to the spindle housing 10. The Z-axis movement mechanism 20 has a pair of guide rails 22. A Z-axis movement plate (not shown) is slidably mounted on the pair of guide rails 22.

[0029] A spindle housing 10 is fixed to the front surface of the Z-axis moving plate, and a nut portion (not shown) is provided on the back surface of the Z-axis moving plate. A ball screw 24, which is positioned along the Z-axis direction between a pair of guide rails 22, is rotatably connected to the nut portion.

[0030] When the ball screw 24 is rotated by a rotational drive source 26, such as a pulse motor, connected to the upper end of the ball screw 24, the cutting unit 8 moves along the Z-axis direction. The Z-axis movement mechanism 20 is located on the surface side of the Y-axis movement plate 30.

[0031] The Y-axis movable plate 30 is slidably mounted on a pair of guide rails 32 arranged along the Y-axis direction. Note that only one of the guide rails 32 is shown in Figure 2. A ball screw 34 is positioned between the pair of guide rails 32 along the Y-axis direction.

[0032] A nut (not shown) located on the back side of the Y-axis moving plate 30 is rotatably connected to the ball screw 34. A rotational drive source 36, such as a pulse motor, is connected to one end of the ball screw 34. When the ball screw 34 is rotated by the rotational drive source 36, the cutting unit 8 and the Z-axis moving mechanism 20 move along the Y-axis direction.

[0033] Below the cutting unit 8, a chuck table 38 is provided for suction-holding the workpiece. A rotating mechanism 40 is connected to the lower part of the chuck table 38, which rotates the chuck table 38 around a predetermined rotation axis 40a that is substantially parallel to the Z-axis direction.

[0034] An X-axis movement mechanism (not shown) is provided at the lower part of the rotating mechanism 40 to move the chuck table 38 and the rotating mechanism 40 along the X-axis direction. The chuck table 38 has a disc-shaped frame 42 made of metal or the like.

[0035] A disc-shaped recess is formed in the upper part of the frame 42, and a disc-shaped porous plate 44 made of porous ceramics is fixed in this recess. A flow channel (not shown) is formed in the frame 42, and one end of the flow channel is connected to the lower surface of the porous plate 44.

[0036] The other end of the flow path is connected to a suction source (not shown), such as an ejector, and when the suction source is operated, negative pressure is generated on the upper surface 44a of the porous plate 44. The upper surface 44a of the porous plate 44 is flush with the upper surface 42a of the frame 42.

[0037] The upper surfaces 42a and 44a constitute a substantially flat holding surface 38a for suction holding of the workpiece. A height measuring unit 46 is positioned above the chuck table 38. The height measuring unit 46 is either a contact-type height measuring unit equipped with a probe that contacts the workpiece, or a non-contact-type height measuring unit that measures the thickness of the workpiece and the height of its upper surface without contacting the workpiece. For example, the height measuring unit 46 has a laser displacement meter 48.

[0038] The laser displacement sensor 48 is positioned at a predetermined location above the upper surface 42a of the frame 42 (the outer edge of the chuck table 38). The laser displacement sensor 48 is also called a laser level sensor.

[0039] The laser displacement meter 48 is, for example, a spectroscopic interferometric laser displacement meter with an SLD (Super Luminescent Diode) light source, and is used to measure the distance to an object non-contact using a laser beam.

[0040] By rotating the chuck table 38 once while irradiating a single point on the upper surface 42a with a laser beam from the laser displacement meter 48, the distance from the laser displacement meter 48 to the upper surface 42a can be measured along the circumferential direction of the upper surface 42a.

[0041] Furthermore, by holding the workpiece with suction using the chuck table 38 and irradiating a laser beam onto a single point on the outer peripheral edge of the upper surface of the workpiece, the chuck table 38 can be rotated once to measure the distance from the laser displacement meter 48 to the upper surface of the workpiece along the circumferential direction of the workpiece.

[0042] For example, the thickness of the workpiece at a given point can be calculated by calculating the difference between the distance from the laser displacement meter 48 to a point on the upper surface of the workpiece and the distance from the laser displacement meter 48 to the upper surface 42a of the frame 42 at the same XY coordinates as that point. The difference in height between these two points can be calculated by calculating the difference between the distance from the laser displacement meter 48 to a point on the upper surface of the workpiece and the distance from the laser displacement meter 48 to another point on the upper surface of the workpiece.

[0043] Alternatively, for example, the height measuring unit 46 may calculate the height difference between the top and bottom surfaces of the workpiece (the thickness of the workpiece) by utilizing the interference between light reflected from the top surface of the workpiece and light that travels through the interior of the workpiece and is reflected from the bottom surface of the workpiece.

[0044] Furthermore, the non-contact height measuring unit may utilize ultrasound instead of a laser beam. In this case, the height measuring unit includes a measuring head equipped with an ultrasonic generator capable of generating ultrasound and an ultrasonic detector capable of receiving ultrasound. The ultrasound generated by the ultrasonic generator travels from the top surface of the workpiece into the interior of the workpiece, is reflected from the bottom surface of the workpiece, and travels from the top surface of the workpiece to the outside of the workpiece, where it is detected by the ultrasonic detector. The height measuring unit then calculates the thickness of the workpiece.

[0045] When a stepped portion is formed at the outer edge of a workpiece as described below, the height measuring unit may measure the height between the bottom surface of the stepped portion of the workpiece and the top surface outside the stepped portion of the workpiece, and calculate the depth of the stepped portion from the difference. Alternatively, the height measuring unit may measure the height between the bottom surface of the stepped portion of the workpiece and the bottom surface of the stepped portion of the workpiece, and calculate the thickness of the workpiece at the stepped portion from the difference. However, the method for calculating the thickness of the workpiece is not limited to these methods. Furthermore, only the height of the top surface of the workpiece may be derived, and the thickness of the workpiece may not be calculated.

[0046] Next, the method for processing a stacked wafer according to this embodiment and the stacked wafer processed in the method for manufacturing a processed stacked wafer will be described. A stacked wafer is formed by joining a plurality of wafers. Figure 7(A), etc., shows a schematic cross-sectional view of a stacked wafer 11. The stacked wafer 11 is formed, for example, by joining a first wafer 13 and a second wafer 15. However, the stacked wafer 11 may be composed of three or more wafers.

[0047] The stacked wafer 11 is composed of multiple wafers 13, 15 formed from materials such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor materials. However, the materials of wafers 13, 15 are not limited to these.

[0048] Multiple devices (not shown) are provided on one side of wafers 13 and 15 (for example, the surface sides 13a and 15a). Each device includes, for example, a semiconductor element for constituting an IC (Integrated Circuit), LSI (Large Scale Integration), etc. However, there are no restrictions on the type, number, shape, structure, size, or arrangement of the multiple devices. Furthermore, devices do not have to be provided on some or all of wafers 13 and 15.

[0049] The devices are arranged in a matrix, and the boundaries between multiple devices extend in a grid pattern. When wafers 13 and 15 are divided along these boundaries, individual device chips are obtained. These boundaries are called division lines (streets). Multiple wafers 13 and 15 are joined and stacked to form a stacked wafer 11, and when each wafer 13 and 15 is divided along the division lines, individual stacked device chips are obtained.

[0050] Furthermore, the outer edges of each wafer 13, 15 of the stacked wafer 11 are chamfered. In other words, each wafer 13, 15 has a chamfered portion (bevel portion) at its outer edge that is curved to be convex outwards. In the embodiment described below, all or part of the chamfered portion of the stacked wafer 11 (wafer 13, 15) is removed. This process is called edge trimming.

[0051] A laminated wafer 11, formed by stacking multiple wafers 13 and 15, is formed, for example, by joining two or more wafers 13 and 15 via an adhesive member. The adhesive member is, for example, an ultraviolet-curing resin, and the bond is strengthened when ultraviolet light is irradiated onto the adhesive member sandwiched between each wafer 13 and 15. However, the adhesive member used to join the wafers 13 and 15 does not have to be an ultraviolet-curing resin, and an adhesive member may not be used to join the wafers 13 and 15. For example, the joining surfaces of each wafer 13 and 15 may be plasma-treated before joining, or each wafer 13 and 15 may be joined at room temperature without plasma treatment.

[0052] Next, a test wafer used in the processing method of the stacked wafer according to this embodiment will be described. Figure 3(B), etc., shows a schematic cross-sectional view of the test wafer 21. The test wafer 21 is a so-called dummy wafer, also known as an NP (Non-Product) wafer or a QC (Quality Control) wafer. The test wafer 21 does not need to have devices such as ICs or LSIs formed on it. Alternatively, the test wafer 21 may be a wafer similar to each of the wafers 13 and 15 that constitute the stacked wafer 11.

[0053] The test wafer 21 is used to obtain a correction value for the feed rate of the cutting blade 16 during edge trimming. By using the obtained correction value, edge trimming can be performed on the stacked wafer 11 while adjusting the feed rate with high precision. In this case, high-quality stepped portions can be formed at various points on the outer edge of the stacked wafer 11.

[0054] Furthermore, both the test wafer 21 and each wafer 13, 15 constituting the stacked wafer 11 have approximately the same diameter and thickness, and the outer edges on the surface 21a and the outer edges on the back surface 21b are chamfered. Now, returning to Figure 1, the other components of the cutting apparatus 2 will be described.

[0055] As shown in Figure 1, a cassette table 50 is provided at the corner of the base 4. A cassette (not shown) containing multiple workpieces is placed on the top surface of the cassette table 50. A touch panel type display device 52, which functions as both a display and an input unit, is provided on the front surface 6a of the cover 6.

[0056] The cutting device 2 is equipped with a controller (control unit) 54 that controls the operation of the cutting unit 8, Z-axis movement mechanism 20, Y-axis movement mechanism 28, chuck table 38, suction source, rotation mechanism 40, X-axis movement mechanism, height measuring unit 46, cassette table 50, display device 52, etc.

[0057] The controller 54 is composed of a computer that includes, for example, a processor (processing unit) represented by a CPU (Central Processing Unit), main memory such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), and ROM (Read Only Memory), and auxiliary memory such as flash memory, hard disk drive, and solid state drive.

[0058] The auxiliary storage device stores software, including a predetermined program. The controller 54's functions are realized by operating the processing unit and other components according to this software.

[0059] A portion of the auxiliary storage device's resources functions as a storage unit 56 that stores relationship data between the rotation angle θ of the rotating mechanism 40 and the thickness of the stepped portion of the workpiece at the position corresponding to that rotation angle θ. Furthermore, a program stored in another portion of the auxiliary storage device's resources functions as an adjustment unit 58. When edge trimming is performed on a stacked wafer 11 as the workpiece, the adjustment unit 58 adjusts the height of the cutting blade 16 so that a high-quality stepped portion is formed on the stacked wafer 11. Details of the adjustments made by the adjustment unit 58 will be described later.

[0060] Next, the method for processing a stacked wafer according to this embodiment will be described. By performing the stacked wafer processing method described below, the stacked wafer 11 is processed and a processed stacked wafer 11 is obtained. In other words, the stacked wafer processing method described below is also a method for manufacturing a processed stacked wafer. Figure 13 is a flowchart showing the flow of each step of the stacked wafer processing method (method for manufacturing a processed stacked wafer) according to this embodiment.

[0061] In the method for processing a stacked wafer according to this embodiment, first, a test edge trimming is performed on the test wafer 21 to form a test step portion on the test wafer 21, and the height of various points on the bottom surface of this test step portion is measured. This allows for obtaining the trend regarding the height fluctuation due to the rotation of the chuck table 38. Next, a first step portion is formed as a temporary step portion at the outer edge of the stacked wafer 11, and the height of the bottom surface 17a of the first step portion 17 is measured. Then, an individual difference correction value is created based on the height of this bottom surface 17a.

[0062] Subsequently, a second step is formed on the outer edge of the stacked wafer 11. Edge trimming is completed by forming this second step. When forming the second step, the height of the cutting blade 16 is adjusted based on an individual difference correction value. At this time, the trend of height fluctuations due to the rotation of the chuck table 38 may be referenced. This makes it possible to form a step of a predetermined depth on the stacked wafer 11 with high quality, regardless of the individual differences of the individual wafers 13 and 15 of the stacked wafer 11. Each step will be described below.

[0063] In the method for processing a laminated wafer according to this embodiment (method for manufacturing a processed laminated wafer), in which the outer edge of the laminated wafer 11, formed by joining the first wafer 13 and the second wafer 15, is cut and the chamfered portion is removed, it is preferable to first perform the test wafer holding step S01. Alternatively, before performing the test wafer holding step S01, a pre-measurement step may be performed in which the height of the outer edge of the holding surface 38a of the chuck table 38 (upper surface 42a of the frame 42) is measured around the entire circumference.

[0064] Figure 3(A) is a schematic cross-sectional view of the chuck table 38 where the height of the holding surface 38a is measured. In the pre-measurement step, first, a first distance A1 is measured from the laser displacement meter 48 to the holding surface 38a of the chuck table 38 (upper surface 42a of the frame 42) using the laser displacement meter 48.

[0065] The measurement is performed by rotating the chuck table 38 once while shining a laser beam onto a single point on the upper surface 42a of the frame 42. This measures the first distance A1 from the laser displacement meter 48 to the upper surface 42a along the path of the laser beam's movement.

[0066] The upper surface 42a is substantially flat, but due to factors such as minute irregularities in the circumferential direction and minute inclinations of the rotation axis 40a, the first distance A1 varies by, for example, on the order of μm at various points on the upper surface 42a. The first distance A1 is stored in the storage unit 56 along with the rotation angle θ of the chuck table 38. The relationship between the rotation angle θ of the chuck table 38 and the first distance A1 may be referenced later when adjusting the height of the cutting blade 16. It may also be referenced when calculating the height of the bottom surface of the stepped portion formed on the stacked wafer 11 or test wafer 21, or the thickness of the stacked wafer 11, etc., at the stepped portion.

[0067] Next, the test wafer holding step S01 will be described. Figure 3(A) is a schematic cross-sectional view showing a test wafer 21 held by a chuck table 38. In the test wafer holding step S01, the test wafer 21 is placed on the holding surface 38a of the chuck table 38, which has a holding surface 38a and can rotate around a rotation axis 40a intersecting the holding surface 38a, and the test wafer 21 is held by the chuck table 38.

[0068] When placing the test wafer 21 on the chuck table 38, adjust its position so that the center of the test wafer 21 coincides with the center of the holding surface 38a of the chuck table 38. Also, orient the front surface 21a of the test wafer 21 upwards and face the back surface 21b towards the holding surface 38a. However, it is also acceptable to orient the back surface 21b of the test wafer 21 upwards and face the front surface 21a towards the holding surface 38a.

[0069] After the test wafer holding step S01, the test cutting step S02 is performed. Figure 4(A) is a schematic cross-sectional view showing the test wafer to be cut, and Figure 4(B) is a schematic perspective view showing the test wafer to be cut. In the test cutting step S02, edge trimming is performed on the test wafer 21.

[0070] More specifically, first, the cutting blade 16 is started to rotate. The rotation speed of the cutting blade 16 is set to approximately 30,000 revolutions per minute. Then, the rotating annular cutting blade 16 is made to cut into the outer edge of the test wafer 21.

[0071] At this time, the cutting blade 16a is made to cut into the outer edge of the test wafer 21 from above along the Z-axis direction so that the height of the lower end of the cutting edge 16a of the cutting blade 16 becomes the target height 23. Alternatively, the cutting edge 16a of the cutting blade 16, whose lower end height is the target height 23, is made to cut into the outer edge of the test wafer 21 from the Y-axis direction.

[0072] With the cutting edge 16a of the cutting blade 16 engaged in cutting into the outer edge of the test wafer 21, or while engaging it, the chuck table 38 is rotated at least 360° around the rotation axis 40a. In other words, the chuck table 38 is rotated by an amount of more than one revolution. As a result, a test step portion 21c having an annular bottom surface 21e and a wall surface 21f is formed on the surface 21a side of the outer edge of the test wafer 21. Figure 5 shows a schematic cross-sectional view of the test wafer 21 on which the test step portion 21c has been formed.

[0073] Next, the test measurement step S03 is performed. In the test measurement step S03, the height of the bottom surface 21e of the test step portion 21c formed on the test wafer 21 along the outer edge in the test cutting step S02 is measured around its entire circumference. Figure 5 is a schematic cross-sectional view showing the test wafer 21 on which the height position of the bottom surface 21e of the test step portion 21c formed on the test wafer 21 is measured around its entire circumference.

[0074] The height positions at various points on the bottom surface 21e of the test step 21c are measured by the height measuring unit 46. In the test measurement step S03, with the laser displacement meter 48 of the height measuring unit 46 positioned above the test step 21c, the chuck table 38 is rotated at least 360° around the rotation axis 40a. In other words, the chuck table 38 is rotated by an amount of rotation of one or more revolutions.

[0075] This allows the laser displacement meter 48 to measure the distance from the laser displacement meter 48 to the bottom surface 21e of the test step 21c along the circumferential direction of the test wafer 21. For example, in the test measurement step S03, the adjustment unit 58 may calculate the difference between this distance and the first distance A1, and calculate the thickness 21d of the test wafer 21 at the test step 21c, or the height of the bottom surface 21e.

[0076] In addition, in the test measurement step S03, the distance from the laser displacement meter 48 to the surface 21a of the test wafer 21 may be measured. The adjustment unit 58 then calculates the difference between this distance and the distance to the bottom surface 21e of the test step 21c, and the depth of the test step 21c or the height of the bottom surface 21e may be calculated.

[0077] Furthermore, an ultrasonic height measuring unit may be used in the test measurement step S03. The thickness 21d of the test wafer 21, or the height of the bottom surface 21e, may be calculated by measuring the distance from the bottom surface 21e to the back surface 21b of the test wafer 21 at the test step 21c.

[0078] In this way, in the test measurement step S03, the height of the bottom surface 21e of the test step 21c is measured directly or indirectly. In the test measurement step S03, by repeating the measurement while rotating the chuck table 38, relationship data between the rotation angle θ of the chuck table 38 and the height (thickness 21d) of the bottom surface 21e of the test step 21c is obtained.

[0079] In the wafer processing method according to this embodiment, the unloading step S04 and the equipment correction data creation step S05 are performed after the test measurement step S03. The unloading step S04 and the equipment correction data creation step S05 may be performed in either order or simultaneously.

[0080] In the unloading step S04, the chuck table 38 releases its hold on the test wafer 21, and the test wafer 21 is unloaded. In the equipment correction data creation step S05, equipment correction data is created based on the relationship between the rotation angle θ of the chuck table 38 and the height of the bottom surface 21e of the test step portion 21c. This equipment correction data is composed of the relationship between the rotation angle θ of the chuck table 38 and the correction amount of the cutting feed rate of the cutting blade 16.

[0081] Figure 6 is a graph showing an example of relationship data between the rotation angle θ of the chuck table 38 and the height of the bottom surface 21e of the test step 21c, which is obtained in the test measurement step S03. In Figure 6, the height of the bottom surface 21e of the test step 21c is shown by a solid line 31, and the target height 23 is shown by a dashed line 33. In this way, in the test measurement step S03, relationship data between the rotation angle θ of the chuck table 38 and the height of the bottom surface 21e of the test step 21c is obtained.

[0082] Furthermore, relationship data between the rotation angle θ of the chuck table 38 and the thickness of the test wafer 21 at the test step 21c may be acquired. Also, relationship data between the rotation angle θ of the chuck table 38 and the depth of the test step 21c from the surface 21a may be acquired. Both the thickness of the test wafer 21 at the test step 21c and the depth of the test step 21c from the surface 21a are values ​​that directly reflect the height of the bottom surface 21e of the test step 21c. Therefore, in either case, it is equivalent to acquiring relationship data between the rotation angle θ of the chuck table 38 and the height of the bottom surface 21e of the test step 21c.

[0083] In Figure 6, the height position of the upper surface 42a of the frame 42 is set as the reference height position (i.e., 0 μm). The target depth is, for example, 200 μm, and the thickness 21d of the test step section 21c has a variation of about 1 μm to 10 μm due to the aforementioned irregularities, inclinations, etc. In Figure 6, the value obtained by subtracting the height of the dashed line 33 from the height of the solid line 31 at each rotation angle θ is the variation amount 35 at each rotation angle θ.

[0084] Therefore, when trimming the edges of the stacked wafer 11, it is conceivable that the adjustment unit 58 calculates a correction value for the cutting feed rate of the cutting blade 16 by inverting the data of the thickness 21d of the test step portion 21c corresponding to the rotation angle θ with respect to the target height 23. The relationship between the rotation angle θ of the chuck table 38 and the correction value for the cutting feed rate of the cutting blade 16 becomes the device correction data. The derived device correction data may be stored, for example, in the storage unit 56 of the controller 54.

[0085] Then, based on the created device correction data, the height of the cutting blade 16 is adjusted to compensate for this variation as the chuck table 38 rotates, while performing edge trimming of the stacked wafer 11. This is thought to allow the formation of a stepped portion with a uniform height at the bottom of the stacked wafer 11.

[0086] However, each wafer 13 and 15 constituting the stacked wafer 11 has individual differences in thickness. Therefore, simply correcting in this way is not enough to form a stepped portion of a predetermined depth on the target wafers 13 and 15 of the stacked wafer 11. Thus, in the stacked wafer processing method according to this embodiment, information regarding the thickness of the wafers 13 and 15 constituting the stacked wafer 11 is acquired for each stacked wafer 11.

[0087] Next, in the processing method for the stacked wafer according to this embodiment, the process of acquiring information regarding the thickness of wafers 13 and 15 of the stacked wafer 11 and creating a correction value based on the acquired information will be described. In other words, the process of acquiring information regarding individual differences in the thickness of wafers 13 and 15 constituting the stacked wafer 11 and creating an individual difference correction value will be described. This information regarding individual differences is acquired by performing temporary edge trimming on the stacked wafer 11 to form a temporary step portion.

[0088] First, a stacked wafer holding step S06 is performed, in which the stacked wafer 11 is held by the chuck table 38. In the stacked wafer holding step S06, the stacked wafer 11 is held by the chuck table 38 with the second wafer 15 side of the stacked wafer 11 facing the holding surface 38a of the chuck table 38. As a result, the first wafer 13 side of the stacked wafer 11 is exposed upwards.

[0089] Figure 7(A) is a schematic cross-sectional view showing a stacked wafer 11 held by a chuck table 38. When holding the stacked wafer 11 with the chuck table 38, the position of the stacked wafer 11 is adjusted so that the center of the stacked wafer 11 aligns with the rotation axis 40a of the chuck table 38.

[0090] After the stacked wafer holding step S06, a first cutting step S07 is performed to form a first step portion on a part of the outer edge of the stacked wafer 11. Figure 7(B) is a schematic cross-sectional view showing the stacked wafer 11 after it has been cut to form the first step portion.

[0091] In the first cutting step S07, the lower end of the rotating cutting blade 16 (the lower end of the cutting edge 16a) is positioned at a first height, and the cutting blade 16 is made to cut into the outer peripheral edge of the stacked wafer 11. More specifically, the cutting blade 16 is positioned above the position where the first step portion 17 is to be formed, and the cutting blade 16 is moved downward along the Z-axis to cut the stacked wafer 11. Alternatively, the cutting blade 16 is positioned outside the position where the first step portion 17 is to be formed in the Y-axis direction, and the cutting blade 16 is moved along the Y-axis direction to cut the stacked wafer 11. This forms the first step portion 17 (see Figure 8) on a part of the outer peripheral edge of the stacked wafer 11.

[0092] In the first cutting step S07, the first height at which the lower end of the cutting blade 16 is positioned is higher than the second height at which the lower end of the cutting blade 16 is positioned in the second cutting step S10, which will be described later. In other words, a first step portion 17 (see Figure 8) is formed on the stacked wafer 11 that is shallower than the second step portion 19 (see Figure 11) that is ultimately formed on the stacked wafer 11 by edge trimming.

[0093] Here, the first height is, for example, the height relative to the holding surface 38a of the chuck table 38. Alternatively, it is the Z coordinate in the coordinate system referenced by the Z-axis movement mechanism 20 of the cutting device 2. Importantly, as will be described later, the first height is determined so that, in the individual difference correction value creation step S09, the individual difference regarding the thickness of the wafers 13 and 15 of the stacked wafer 11 can be evaluated based on the first height. As long as this objective is met, there is no restriction on the height that the first height is based on.

[0094] Furthermore, it is preferable that the amount of cut by the cutting blade 16 along the Y-axis when forming the first step portion 17 is the same as or less than the amount of cut when forming the second step portion 19 (see Figure 11), which will be described later. In other words, it is preferable that the distance from the wall surface 17b of the first step portion 17 to the outer edge of the stacked wafer 11 is the same as or less than the distance from the wall surface 19b of the second step portion 19, which will be described later, to the outer edge of the stacked wafer 11. In this case, the first step portion 17, which is formed for measurement purposes and immediately serves its purpose, will no longer remain on the stacked wafer 11 when the second step portion 19 is formed.

[0095] Furthermore, if it is planned that a second step portion 19 will be formed on the first wafer 13 of the stacked wafer 11 by edge trimming, it is preferable that the first step portion 17 be formed on the first wafer 13. Also, if it is planned that a second step portion 19 will be formed on the second wafer 15 of the stacked wafer 11 by edge trimming, it is preferable that the first step portion 17 be formed on the second wafer 15.

[0096] Here, in the first cutting step S07, the chuck table 38 may be rotated by an amount of less than 360° around the rotation axis 40a. In other words, the chuck table 38 may be rotated by an amount of less than one revolution. For example, the chuck table 38 may be rotated by an amount of 5° or more and 10° or less. Alternatively, the chuck table 38 may not be rotated at all. However, the chuck table 38 does not need to be rotated by an amount of more than one revolution. That is, the first stepped portion 17 does not need to be formed around the entire circumference of the outer edge of the stacked wafer 11.

[0097] Although there are individual differences in thickness among the multiple wafers 13 and 15, the thickness is uniform in all parts of each wafer 13 and 15, and the variation in thickness in various parts and the irregularities on the surface 13a, 15a and back surface 13b, 15b are extremely small. Therefore, information regarding the thickness of the wafers 13 and 15 constituting the stacked wafer 11 can be obtained simply by forming a first step portion 17 on a part of the outer edge. Compared to forming the first step portion 17 over the entire circumference of the outer edge of the stacked wafer 11, forming the first step portion 17 on a part of the outer edge allows the first step portion 17 to be formed in a relatively short time and with a relatively small amount of cutting.

[0098] Next, a measurement step S08 is performed to measure the height of the bottom surface of the first stepped portion 17 formed on the stacked wafer 11 along the outer edge in the first cutting step S07. Figure 8 is a schematic cross-sectional view showing the stacked wafer 11 in which the height of the bottom surface 17a of the first stepped portion 17 formed on the outer edge is measured.

[0099] The height of the bottom surface 17a of the first stepped section 17 (the thickness of the stacked wafer 11) is measured by the height measuring unit 46. In measurement step S08, with the laser displacement meter 48 of the height measuring unit 46 positioned above the first stepped section 17, the distance from the laser displacement meter 48 to the bottom surface 17a of the first stepped section 17 is measured.

[0100] In this case, to measure this distance along the circumferential direction of the stacked wafer 11, the chuck table 38 may be rotated by less than 360° around the rotation axis 40a. In other words, the chuck table 38 may be rotated by less than one full rotation. For example, the chuck table 38 may be rotated by 5° to 10°. Alternatively, the chuck table 38 may not be rotated at all.

[0101] Preferably, the amount of rotation of the chuck table 38 in the measurement step S08 is less than or equal to the amount of rotation of the chuck table 38 in the first cutting step S07. That is, in the measurement step S08, the height of the bottom surface 17a of the first stepped portion 17 may be measured over the entire area of ​​the first stepped portion 17, or this height may be measured in part of the first stepped portion 17.

[0102] In measurement step S08, the adjustment unit 58 of the controller 54 may calculate the height of the bottom surface 17a of the first step section 17 (the thickness of the stacked wafer 11 in the first step section 17) by calculating the difference between the distance from the laser displacement meter 48 to the bottom surface 17a of the first step section 17 and the first distance A1, similar to the test measurement step S03.

[0103] Alternatively, if a first step portion 17 is formed on the first wafer 13 of the stacked wafer 11, the distance in the Z-axis direction from the top surface (surface 13a) of the first wafer 13 to the bottom surface 17a of the first step portion 17 may be calculated as the height of the bottom surface 17a. In other words, the depth of the first step portion 17 may be measured. For example, the height of the bottom surface 17a of the first step portion 17 may be calculated by calculating the difference between the distance from the laser displacement meter 48 to the bottom surface 17a of the first step portion 17 and the distance from the laser displacement meter 48 to the top surface (surface 13a) of the first wafer 13, thereby calculating the depth of the first step portion 17.

[0104] Furthermore, if a first step portion 17 is formed on the first wafer 13 of the stacked wafer 11, the distance in the Z-axis direction from the bottom surface (back surface 13b) of the first wafer 13 to the bottom surface 17a of the first step portion 17 may be calculated as the height of the bottom surface 17a. That is, the height measuring unit 46 may measure the thickness of the first wafer 13 as the height of the bottom surface 17a of the first step portion 17. For example, the thickness of the first wafer 13 at the first step portion 17 may be measured by the interference of light reflected from the bottom surface 17a of the first step portion 17 and light that travels from the bottom surface 17a of the first step portion 17 into the interior of the first wafer 13 and is reflected from the back surface 13b of the first wafer 13.

[0105] In these cases as well, both the depth of the first step portion 17 and the thickness of the first wafer 13 in the first step portion 17 directly reflect the height of the bottom surface 17a of the first step portion 17. Therefore, in these cases as well, it is equivalent to measuring the height of the bottom surface 17a of the first step portion 17.

[0106] After the measurement step S08, the individual difference correction value creation step S09 is performed to create an individual difference correction value based on the height of the bottom surface 17a of the first stepped portion 17 measured in the measurement step S08 and the first height described above. Figure 9 is a graph showing an example of the relationship between the rotation angle θ of the chuck table 38 and the measured height of the bottom surface 17a of the first stepped portion 17.

[0107] In Figure 9, the first height at which the lower end of the cutting edge 16a of the cutting blade 16 is positioned in the first cutting step S07 is shown by the dashed line 37, and the height of the bottom surface 17a of the first stepped portion 17, measured in the measurement step S08, is shown by the solid line 39. The rotation angle θ of the chuck table 38 when measuring the height of the bottom surface 17a of the first stepped portion 17 is arbitrary.

[0108] The first height is determined, for example, to match the height of the bottom surface 17a of the first step portion 17 formed on the stacked wafer 11 by a cutting blade 16 positioned at a predetermined height, when the thicknesses of the wafers 13 and 15 constituting the stacked wafer 11 do not deviate from the specified value. If the thicknesses of the wafers 13 and 15 of the stacked wafer 11 deviate from the specified value, a discrepancy occurs between the first height and the height of the bottom surface 17a of the first step portion 17, depending on the amount of the discrepancy.

[0109] Therefore, the difference between the first height and the bottom surface 17a of the first stepped portion 17 is calculated as the individual difference in thickness 41. In the second cutting step S10, which will be described next, this individual difference correction value is referenced to correct the height of the cutting blade 16. This individual difference correction value may be calculated, for example, by the adjustment unit 58 of the controller 54.

[0110] For example, when forming a first step portion 17 on a first wafer 13, if the thickness of the second wafer 15 is less than the specified value, the height of the bottom surface 17a of the first step portion 17, relative to the back surface 13b of the first wafer 13, will be higher than planned. Therefore, the height of the bottom surface 17a of the first step portion 17 will be higher than the first height by the amount of individual variation 41.

[0111] In Figure 9, the magnitude of the individual difference 41 in thickness is indicated by arrows. In the individual difference correction value creation step S09, a value obtained by inverting the individual difference 41 is calculated as the individual difference correction value. By correcting the height of the cutting blade 16 with the individual difference correction value, the variation (individual difference) in the thickness of the wafers 13 and 15 can be offset. The calculated individual difference correction value is stored, for example, in the storage unit 56 of the controller 54.

[0112] In the method for processing a stacked wafer according to this embodiment, a second cutting step S10 is performed to form a second step portion 19 on the outer peripheral edge of the stacked wafer 11. In the second cutting step S10, edge trimming is performed on the stacked wafer 11. Figure 10 is a schematic cross-sectional view showing the stacked wafer 11 after it has been cut in the second cutting step S10 to form the second step portion 19. Figure 11 is a schematic cross-sectional view showing the stacked wafer 11 after the second step portion 19 has been formed by the second cutting step S10.

[0113] More specifically, first, the cutting blade 16 is started to rotate. The rotation speed of the cutting blade 16 is set to approximately 30,000 revolutions per minute. Then, the rotating annular cutting blade 16 is used to cut into the outer edge of the stacked wafer 11.

[0114] At this time, the lower end of the cutting edge 16a of the rotating cutting blade 16 is positioned at a second height lower than the first height. For example, when a second step portion 19 is formed on the first wafer 13 of a stacked wafer 11, the second height is determined such that the distance in the Z-axis direction from the lower surface (back surface 13b) of the first wafer 13 to the bottom surface 19a of the second step portion 19 is a predetermined value.

[0115] Then, the cutting blade 16a is used to cut into the outer edge of the stacked wafer 11 from above along the Z-axis direction, such that the height of the lower end of the cutting blade 16a becomes the second height. Alternatively, the cutting blade 16a of the cutting blade 16, whose lower end height is the second height, is used to cut into the outer edge of the stacked wafer 11 from the Y-axis direction. Details regarding the second height will be described later.

[0116] With the cutting edge 16a of the cutting blade 16 engaged in cutting into the outer peripheral edge of the stacked wafer 11, or while engaging in cutting, the chuck table 38 is rotated at least 360° around the rotation axis 40a. In other words, the chuck table 38 is rotated by an amount of more than one revolution. As a result, a second step portion 19 is formed on the upper surface side of the outer peripheral edge of the stacked wafer 11.

[0117] Figure 11 shows a schematic cross-sectional view of a laminated wafer 11 on which a second step portion 19 has been formed. When the second cutting step S10 is performed, a processed laminated wafer 11 with a second step portion 19 formed on the outer edge is obtained. In other words, the method for processing a laminated wafer according to this embodiment is also a method for manufacturing a processed laminated wafer.

[0118] In the second cutting step S10, the stacked wafer 11 is cut while correcting the height of the cutting blade 16 in accordance with the rotation of the chuck table 38. The correction of the height of the cutting blade 16 in accordance with the rotation of the chuck table 38 is performed, for example, by the adjustment unit 58 of the controller 54.

[0119] The height of the cutting blade 16 is corrected by both the device correction data created in the device correction data creation step S05 and the individual difference correction value created in the individual difference correction value creation step S09. For example, the adjustment unit 58 of the controller 54 reads the device correction data and the individual difference correction value stored in the storage unit 56 and corrects the height of the cutting blade 16 based on these.

[0120] Figure 12 illustrates an example of height correction for the cutting blade 16. Figure 12 is a graph showing an example of how the height position of the cutting blade 16 changes when forming the second step portion 19 on the stacked wafer 11.

[0121] In Figure 12, the height at which the cutting blade 16 is positioned is shown by a straight dashed line 47, when there is no need to adjust the height of the cutting blade 16 to correspond to the state of the device, and the thicknesses of the wafers 13 and 15 constituting the stacked wafer 11 do not deviate from the specified values.

[0122] Furthermore, in Figure 12, the dashed line 43 shows how the height of the lower end of the cutting edge 16a of the cutting blade 16 changes in accordance with the rotation of the chuck table 38 when corrected only by device correction data. In addition, in Figure 12, the solid line 45 shows how the height of the lower end of the cutting edge 16a of the cutting blade 16 changes in accordance with the rotation of the chuck table 38 when corrected by both device correction data and individual difference correction values.

[0123] The dashed line 43 in Figure 12 is the inverted version of the solid line 31 in Figure 6. This is because the variation amount 35 can be offset by varying the height of the cutting blade 16 using a correction value (device correction data) 35a, which is the inverted version of the variation amount 35 at each rotation angle θ shown in Figure 6.

[0124] Furthermore, the solid line 45 in Figure 12 is the dashed line 43 shifted vertically by the individual difference correction value 41a. The individual difference correction value 41a is the value of the individual difference 41 shown in Figure 9, but inverted vertically. In the second cutting step S10, the height of the cutting blade 16 is varied as shown by the solid line 45 in Figure 12 in conjunction with the rotation of the chuck table 38. This makes it possible to cancel out the individual difference 41 in the thickness of the wafers 13 and 15 of the stacked wafer 11.

[0125] Thus, in the second cutting step S10, the stacked wafer 11 can be appropriately formed at a predetermined height on the stacked wafer 11 by cutting the wafer with the cutting blade 16 while correcting the height of the cutting blade 16 in accordance with the rotation of the chuck table 38. By forming this second step 19, edge trimming is properly completed.

[0126] As described above, in the method for processing a stacked wafer according to this embodiment, a first step portion 17 is formed on the stacked wafer 11 before forming the second step portion 19. Then, the amount of deviation in the processing position due to individual differences in the thickness of each wafer 13, 15 is evaluated from the height of the bottom surface 17a of the first step portion 17. Then, an individual difference correction value is created to eliminate the effect of individual differences in thickness, and when forming the second step portion 19, the height position of the cutting blade 16 is corrected using the individual difference correction value. This makes it possible to edge-trim the stacked wafer 11 so that the thickness at the step portion becomes a predetermined value.

[0127] In the cutting apparatus 2, multiple stacked wafers 11 are edge-trimmed one after another. In this case, in order to obtain information on the individual differences in the thickness of each wafer 13, 15, the first cutting step S07, the measurement step S08, and the individual difference correction value creation step S09 are performed for each stacked wafer 11.

[0128] On the other hand, once the test wafer 21 is used and the equipment correction data is created only once, this equipment correction data can be repeatedly referenced when trimming the edges of multiple stacked wafers 11. In other words, even when performing edge trimming on multiple stacked wafers 11, the test wafer holding step S01, the test cutting step S02, the test measurement step S03, and the unloading step S04 only need to be performed once.

[0129] Therefore, the equipment correction data may be referenced in the edge trimming of the stacked wafer 11 performed immediately after the calculation of the equipment correction data using the test wafer 21. Furthermore, the same equipment correction data may be referenced in the edge trimming of the stacked wafer 11 performed after several stacked wafers 11 have been trimmed.

[0130] In other words, in the method for processing a stacked wafer according to this embodiment, the test wafer holding step S01, the test cutting step S02, the test measurement step S03, and the unloading step S04 do not necessarily have to be performed prior to edge trimming of the stacked wafer 11. Even in this case, the effect of performing appropriate edge trimming and forming a high-quality second stepped portion 19 is achieved.

[0131] Furthermore, in the processing method for a stacked wafer according to this embodiment, it is not necessary to refer to the equipment correction data when performing edge trimming of the stacked wafer 11. In other words, when performing edge trimming of the stacked wafer 11, if the height of the cutting blade 16 is corrected by the individual difference correction value, it may be possible to form the second step portion 19 on the stacked wafer 11 sufficiently appropriately. For example, if not much time has passed since the start of use of the cutting device 2 or the chuck table 38, and there is little need for adjustments corresponding to the condition of the equipment, equipment correction data may not be created.

[0132] In this case, the cutting apparatus 2 performs the stacked wafer holding step S06, the first cutting step S07, the measurement step S08, the individual difference correction value creation step S09, and the second cutting step S10. Then, in the second cutting step S10, the height of the cutting blade 16 is corrected with the individual difference correction value to form a second step portion 19 on the stacked wafer 11. This cancels out the effect of individual differences in the thickness of wafers 13 and 15 of the stacked wafer 11, and allows the second step portion 19 to be formed at an appropriate position on the stacked wafer 11.

[0133] It should be noted that the present invention is not limited to the embodiments described above, and the structures, methods, etc., of the embodiments described above can be modified as appropriate without departing from the scope of the object of the present invention. For example, in the embodiments described above, the case in which a cutting blade 16 cuts into the first wafer 13, which is the upper wafer of the stacked wafer 11, and a first stepped portion 17 and a second stepped portion 19 are formed in the first wafer 13 was explained using the figures as an example. However, the present invention is not limited to this.

[0134] In other words, in the first cutting step S07 and the second cutting step S10, the cutting blade 16 may cut into the second wafer 15, which is the wafer below the stacked wafer 11. In this case, at the outer peripheral edge of the stacked wafer 11, the cutting edge 16a of the cutting blade 16 cuts from the surface 13a to the back surface 13b of the first wafer 13, and then cuts into the second wafer 15 from the surface 15a side to a predetermined depth.

[0135] Even in this case, according to the method for processing a stacked wafer according to one aspect of the present invention, a second step portion 19 can be appropriately formed on the second wafer 15 of the stacked wafer 11, that is, edge trimming can be performed with high quality.

[0136] Furthermore, in the second cutting step S10, the upper wafer, the first wafer 13, is removed by cutting from the surface 13a to the back surface 13b at the outer peripheral edge of the stacked wafer 11, while the lower wafer, the second wafer 15, does not need to be cut. That is, the cutting of the first wafer 13 is performed with the lower end of the cutting edge 16a of the cutting blade 16 positioned at the height of the bonding surface of the stacked wafer 11 (the back surface 13b of the first wafer 13 and the surface surface 15a of the second wafer 15).

[0137] More precisely, in the second cutting step S10, the lower end of the cutting edge 16a of the cutting blade 16 is positioned at a height less than or equal to the height of the back surface 13b of the first wafer 13, and greater than or equal to the height of the front surface 15a of the second wafer 15. In this case, in the first cutting step S07, the first wafer 13 is cut, and the first stepped portion 17 is formed at the outer peripheral edge of the first wafer 13. Also, in the second cutting step S10, the first wafer 13 is exposed on the wall surface 19b of the second stepped portion 19, and the second wafer 15 is exposed on the bottom surface 19a of the second stepped portion 19.

[0138] When performing edge trimming to form such a second stepped portion 19 on the stacked wafer 11, the height of the cutting blade 16 must be precisely adjusted. In particular, the height of the cutting blade 16 must be adjusted to fully accommodate individual differences in the thickness of the second wafer 15.

[0139] Furthermore, according to one aspect of the present invention, a method for processing a laminated wafer, by forming a first stepped portion 17 on the first wafer 13 in advance and measuring the height of the bottom surface 17a, information regarding individual differences in the thickness of the second wafer 15 can be identified. Therefore, when performing edge trimming, the cutting blade 16 can be precisely positioned at the desired height.

[0140] In other words, even in this case, according to the method for processing a laminated wafer according to one aspect of the present invention, a second step portion 19 can be appropriately formed on the laminated wafer 11, that is, edge trimming can be performed with high quality.

[0141] Furthermore, in the above embodiment, the calculation of the height of the bottom surface 21e of the test step portion 21c formed on the test wafer 21 and the calculation of the height of the bottom surface 17a of the first step portion 17 formed on the stacked wafer 11 were described in the case where the adjustment unit 58 of the controller 54 performs these calculations. However, these height measurements may also be performed by a CPU, IC, ASIC (Application Specific Integrated Circuit), etc. mounted on the height measurement unit 46.

[0142] Furthermore, for example, the cutting device 2 and cutting method described above can be realized even if the height measuring unit 46 is equipped with a displacement meter of another type, such as an ultrasonic type, instead of the laser displacement meter 48 described above. [Explanation of Symbols]

[0143] 11. Multilayer wafer 13,15 wafers 13a,15a surface 13b,15b Back side 17, 19 Stepped section 17a,19a Bottom 17b, 19b Wall surfaces 21 Test wafers 21a surface 21b Back side 21c Test step section 21d thickness 21e Bottom 21st floor wall 23 Target height 31 Solid line 33 Dashed line 35. Variation 35a Correction Value 37 Dashed line 39 Solid line 41 Individual differences 41a Individual difference correction value 43 Dashed line 45 Solid line 47 Dashed line 2 Cutting equipment 4 bases 6 Covers 6a front 8 cutting units 10 Spindle Housing 12 spindles 14 Rotary drive source 16 cutting blades 16a Cutting blade 20 Z-axis movement mechanism 22,32 Guide rails 24,34 Ball screw 26,36 Rotary drive source 28 Y-axis movement mechanism 30 Y-axis moving plate 38 Chuck Table 38a Retaining surface 40 Rotation Mechanism 40a Rotating shaft 42 Frame 42a Top side 44 Porous plate 44a Top 46 Height measuring unit 48 Laser displacement meter 50 Cassette Table 52 Display device 54 Controllers 56 Memory section 58 Adjustment section

Claims

1. A method for processing a laminated wafer, comprising cutting the outer edge of a laminated wafer formed by joining a first wafer and a second wafer, and removing the chamfered portion, A stacked wafer holding step, comprising: holding the stacked wafer in a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, with the second wafer side of the stacked wafer facing the holding surface of the chuck table; A first cutting step involves positioning the lower end of a rotating annular cutting blade at a first height, cutting into the outer edge of the stacked wafer with the cutting blade while rotating the chuck table without rotating it, or rotating it by less than one rotation around the axis of rotation, thereby forming a first stepped portion on a part of the outer edge of the stacked wafer. A measurement step in which the height of the bottom surface of the first stepped portion formed on the laminated wafer along the outer peripheral edge in the first cutting step, An individual difference correction value creation step is performed to create an individual difference correction value based on the height of the bottom surface of the first step portion measured in the measurement step and the first height, The second cutting step includes positioning the lower end of the rotating cutting blade at a second height lower than the first height, and rotating the chuck table around the rotation axis by an amount of one or more rotations while cutting into the outer peripheral edge of the stacked wafer, thereby forming a second stepped portion on the outer peripheral edge of the stacked wafer, A method for processing laminated wafers, wherein in the second cutting step, the height of the cutting blade is corrected with the individual difference correction value while forming the second stepped portion on the laminated wafer.

2. A method for processing a laminated wafer, comprising cutting the outer edge of a laminated wafer formed by joining a first wafer and a second wafer, and removing the chamfered portion, A test wafer holding step involves placing a test wafer on the holding surface of a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, and holding the test wafer with the chuck table, A test cutting step is performed after the test wafer holding step, in which a rotating annular cutting blade is driven into the outer edge of the test wafer while the chuck table is rotated by one or more rotations around the axis of rotation to form a test stepped portion having an annular bottom surface and wall surface on the outer edge of the test wafer. A test measurement step is performed to measure the height of the bottom surface of the test step formed on the test wafer along the outer edge in the test cutting step, over the entire circumference, and to obtain relationship data between the rotation angle of the chuck table and the height of the bottom surface of the test step, Following the test measurement step, the process includes an unloading step in which the chuck table releases the test wafer and unloads the test wafer, Following the test measurement step, a device correction data creation step is performed to create device correction data based on the relationship between the rotation angle of the chuck table and the cutting feed rate of the cutting blade, A stacked wafer holding step, in which the stacked wafer is held on the chuck table with the second wafer side of the stacked wafer facing the holding surface of the chuck table, A first cutting step involves positioning the lower end of the rotating cutting blade at a first height, cutting into the outer edge of the stacked wafer while rotating the chuck table without rotating it, or rotating it by less than one rotation around the axis of rotation, to form a first stepped portion on a part of the outer edge of the stacked wafer. A measurement step in which the height of the bottom surface of the first stepped portion formed on the laminated wafer along the outer peripheral edge in the first cutting step, An individual difference correction value creation step is performed to create an individual difference correction value based on the height of the bottom surface of the first step portion measured in the measurement step and the first height, The second cutting step includes positioning the lower end of the rotating cutting blade at a second height lower than the first height, and rotating the chuck table around the rotation axis by an amount of one or more rotations while cutting into the outer peripheral edge of the stacked wafer, thereby forming a second stepped portion on the outer peripheral edge of the stacked wafer, A method for processing laminated wafers, wherein in the second cutting step, the height of the cutting blade is corrected in accordance with the rotation of the chuck table using both the apparatus correction data and the individual difference correction value, thereby forming the second stepped portion on the laminated wafer.

3. In the first cutting step, the first stepped portion is formed on the first wafer of the stacked wafer. In the second cutting step, the second step portion is formed on the first wafer of the stacked wafer. The method for processing a laminated wafer according to claim 1 or claim 2, characterized in that the second height is determined by the distance of the first wafer from the surface facing the second wafer.

4. A manufacturing method for producing a processed laminated wafer by cutting the outer edge of a laminated wafer formed by joining a first wafer and a second wafer, and removing the chamfered portion, A stacked wafer holding step, comprising: holding the stacked wafer in a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, with the second wafer side of the stacked wafer facing the holding surface of the chuck table; A first cutting step involves positioning the lower end of a rotating annular cutting blade at a first height, cutting into the outer edge of the stacked wafer with the cutting blade while rotating the chuck table without rotating it, or rotating it by less than one rotation around the axis of rotation, thereby forming a first stepped portion on a part of the outer edge of the stacked wafer. A measurement step in which the height of the bottom surface of the first stepped portion formed on the laminated wafer along the outer peripheral edge in the first cutting step, An individual difference correction value creation step is performed to create an individual difference correction value based on the height of the bottom surface of the first step portion measured in the measurement step and the first height, The process includes a second cutting step of positioning the lower end of the rotating cutting blade at a second height lower than the first height, and rotating the chuck table around the rotation axis by an amount of one or more rotations while cutting into the outer peripheral edge of the stacked wafer, thereby forming a second stepped portion on the outer peripheral edge of the stacked wafer and obtaining a processed stacked wafer. A method for manufacturing a processed laminated wafer, wherein in the second cutting step, the height of the cutting blade is corrected with the individual difference correction value while forming the second stepped portion on the laminated wafer.

5. A manufacturing method for producing a processed laminated wafer by cutting the outer edge of a laminated wafer formed by joining a first wafer and a second wafer, and removing the chamfered portion, A test wafer holding step involves placing a test wafer on the holding surface of a chuck table having a holding surface and being rotatable around a rotation axis intersecting the holding surface, and holding the test wafer with the chuck table, A test cutting step is performed after the test wafer holding step, in which a rotating annular cutting blade is driven into the outer edge of the test wafer while the chuck table is not rotated, or rotated by an amount of one or more rotations around the axis of rotation, thereby forming a test stepped portion having an annular bottom surface and wall surface on the outer edge of the test wafer. A test measurement step is performed to measure the height of the bottom surface of the test step formed on the test wafer along the outer edge in the test cutting step, over the entire circumference, and to obtain relationship data between the rotation angle of the chuck table and the height of the bottom surface of the test step, Following the test measurement step, the process includes an unloading step in which the chuck table releases the test wafer and unloads the test wafer, Following the test measurement step, a device correction data creation step is performed to create device correction data based on the relationship between the rotation angle of the chuck table and the cutting feed rate of the cutting blade, A stacked wafer holding step, in which the stacked wafer is held on the chuck table with the second wafer side of the stacked wafer facing the holding surface of the chuck table, A first cutting step involves positioning the lower end of the rotating cutting blade at a first height, and rotating the chuck table around the rotation axis by an amount of less than one rotation while cutting the cutting blade into the outer peripheral edge of the stacked wafer, thereby forming a first stepped portion on a part of the outer peripheral edge of the stacked wafer. A measurement step in which the height of the bottom surface of the first stepped portion formed on the laminated wafer along the outer peripheral edge in the first cutting step, An individual difference correction value creation step is performed to create an individual difference correction value based on the height of the bottom surface of the first step portion measured in the measurement step and the first height, The process includes a second cutting step of positioning the lower end of the rotating cutting blade at a second height lower than the first height, and rotating the chuck table around the rotation axis by an amount of one or more rotations while cutting into the outer peripheral edge of the stacked wafer, thereby forming a second stepped portion on the outer peripheral edge of the stacked wafer and obtaining a processed stacked wafer. A method for manufacturing a processed laminated wafer, wherein in the second cutting step, the height of the cutting blade is corrected in accordance with the rotation of the chuck table using both the apparatus correction data and the individual difference correction value, while forming the second stepped portion on the laminated wafer.

6. In the first cutting step, the first stepped portion is formed on the first wafer of the stacked wafer. In the second cutting step, the second step portion is formed on the first wafer of the stacked wafer. The method for manufacturing a processed laminated wafer according to claim 4 or 5, characterized in that the second height is determined by the distance of the first wafer from the surface facing the second wafer.

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