Chamfering device for wafer, and chamfering method

Abstract

Disclosed is a chamfering device for a wafer, which is provided with a crystal orientation measurement instrument 24 for measuring the crystal orientation of a wafer, and which repeats grinding of a peripheral edge of the wafer until the consistency between an alignment mark of the wafer and the crystal orientation satisfies a predetermined criterion. Consequently, this chamfering device can eliminate mismatching between the alignment mark and the crystal orientation.

Description

Wafer chamfering device and method

[0001] The present disclosure relates to a chamfering device and a chamfering method.

[0002] Marks are provided on the periphery of a wafer for positioning purposes during processing and other processes. Marks include orientation flats and notches. In this specification, these are collectively referred to as alignment marks. In single crystal wafers, alignment marks also function as marks that indicate the reference for crystal orientation.

[0003] A single crystal wafer is a wafer whose entire surface should be composed of a single crystal. However, the crystalline structure at the wafer's periphery (also called the "edge") can be imperfect due to differences in cooling rates during the crystal growth process and mechanical processing history. For the primary uses of single crystal wafers, even partial irregularities in the crystalline structure are undesirable. Crystal structure irregularities increase the risk of dielectric breakdown. For this reason, the manufacturing process for general wafers, including single crystal wafers, includes a chamfering process in which the entire periphery, including the area with the alignment mark, is ground. Chamfering is also expected to have other effects, such as preventing chipping and cracking.

[0004] Japanese Patent Application Laid-Open No. 2018-170312

[0005] The chamfering conditions are set taking into consideration the grinding of the portion with the alignment mark. Therefore, information about the wafer shape, such as the position of the alignment mark, is acquired by a photoelectric sensor or the like and used to set the conditions (see Patent Document 1). Chamfering is generally performed by bringing a grinding wheel into contact with the wafer held on a grinding table. In this case, the grinding conditions include, for example, the approach angle of the grinding wheel relative to the wafer, the movement speed of the grinding table, the rotation speed of the grinding wheel and grinding table, and the relative positions of the grinding wheel and grinding table.

[0006] Alignment marks are required to function as marks corresponding to any crystal orientation in a single crystal wafer. Alignment marks are usually provided before chamfering. Essentially, alignment marks are required to coincide with a predetermined crystal orientation or to form a predetermined angle with the predetermined crystal orientation. In this specification, this is also referred to as "ensuring alignment between the alignment mark and the crystal orientation." Also, the alignment between the alignment mark and the crystal orientation is sometimes simply referred to as "alignment."

[0007] However, in many cases, wafers before chamfering do not have a proper alignment. Therefore, chamfering requires not only grinding the edge of the wafer but also adjusting the relationship between the alignment mark and the crystal orientation. In other words, chamfering requires adjusting the shape and position of the alignment mark, taking into account the relationship with the crystal orientation. In this specification, the state in which alignment is not properly achieved is sometimes referred to as "misalignment."

[0008] However, the present inventors have found that misalignment may occur or remain in the wafer W even after chamfering using the conventional method.

[0009] In recent years, wafers other than silicon (Si) have become increasingly popular for applications such as optical applications, high-speed electronic devices, and power devices, including sapphire, gallium arsenide (GaAs), indium phosphide (InP), and silicon carbide (SiC). Because single crystal wafers made of these materials are more expensive than ever before, there is an increasing demand for improved yields. Therefore, even a single test wafer should not be wasted. This is also one of the challenges of the conventional method.

[0010] The present inventors have been investigating the possibility that there may be other factors causing misalignment after chamfering than the misalignment before chamfering. As explained above, it has been common knowledge that wafers of sufficient quality can be obtained by setting grinding conditions that can eliminate the misalignment before chamfering within the same lot as a systematic error, making it difficult to investigate this issue. However, as a result of intensive investigation, the inventors have identified a new factor causing misalignment after chamfering.

[0011] The cause is random errors (errors) related to wafer positioning that occur when the test wafer is placed on different tables during crystal orientation measurement, shape information acquisition, and grinding. These errors can include errors in wafer transfer between the measurement table and the transfer mechanism, errors in transfer within the transfer mechanism, and errors in wafer transfer between the transfer mechanism and the grinding table. Furthermore, we have identified the presence of random errors in measurements using crystal orientation measurement instruments, and their causes. Previously, the existence of these random errors and their correction were not taken into consideration, resulting in unpredictable inconsistencies even within the same lot, which could not be resolved.

[0012] The present disclosure solves at least some of the problems of the prior art. The present disclosure may provide a chamfering device that can eliminate misalignment between an alignment mark and a crystal orientation. The present disclosure may also provide a chamfering method that can eliminate misalignment between an alignment mark and a crystal orientation.

[0013] The first chamfering device of the present disclosure is a wafer chamfering device that is equipped with a crystal orientation measuring device that measures the crystal orientation of the wafer, and that repeatedly grinds the peripheral edge of the wafer until the alignment between the wafer's alignment mark and the crystal orientation satisfies a predetermined standard.

[0014] The second chamfering apparatus of the present disclosure is the first chamfering apparatus, but is equipped with a sensor that measures the position of the alignment mark, and the crystal orientation and the position of the alignment mark are each measured for the wafer held on the same measurement table.

[0015] A third chamfering device of the present disclosure is a chamfering device that is the second chamfering device and is equipped with a transport mechanism that moves the measurement table in a translational manner, and the transport mechanism moves the measurement table to a first position for measuring the position of the alignment mark and to a second position for measuring the crystal orientation.

[0016] A fourth chamfering device of the present disclosure is the third chamfering device, wherein the measurement table rotates to face the alignment mark toward the crystal orientation measuring device at the second position based on the measurement results of the position of the alignment mark.

[0017] A fifth chamfering apparatus of the present disclosure is the third chamfering apparatus, wherein the sensor measures the size of the wafer, and the transport mechanism adjusts the amount of translational movement from the first position to the second position based on the size.

[0018] A sixth chamfering apparatus of the present disclosure is the third chamfering apparatus, wherein the transport mechanism moves the measurement table to a third position for grinding the wafer.

[0019] A first chamfering method of the present disclosure is a method for chamfering a wafer using a chamfering device equipped with a crystal orientation measuring device that measures the crystal orientation of the wafer, and includes repeatedly grinding the peripheral edge of the wafer until the alignment between the alignment mark of the wafer and the crystal orientation satisfies a predetermined standard.

[0020] The second chamfering method of the present disclosure is the first chamfering method, wherein the chamfering device is equipped with a sensor that measures the position of the alignment mark, and includes measuring the crystal orientation and the alignment mark for the wafer held on the same measurement table.

[0021] The present disclosure solves at least some of the problems of the conventional techniques. The present disclosure may provide a chamfering device that can eliminate misalignment between an alignment mark and a crystal orientation. The present disclosure may also provide a chamfering method that can eliminate misalignment between an alignment mark and a crystal orientation.

[0022] FIG. 1 is a hardware configuration diagram of a chamfering device of Example 1. FIG. 2 is a schematic plan view of the main parts of the chamfering device of Example 1. FIG. 3 is a front view of a crystal orientation measuring unit and a measurement unit of the chamfering device of Example 1. FIG. 4 is a side view of a grinding unit of the chamfering device of Example 1. FIG. 5 is a flow diagram of a chamfering method using the chamfering device of Example 1. FIG. 6 is an explanatory diagram of a method for adjusting the rotation angle of a measuring table. FIG. 7 is an explanatory diagram of a method for adjusting the rotation angle of a measuring table. FIG. 8 is an explanatory diagram of a method for adjusting the rotation angle of a measuring table. FIG. 9 is an explanatory diagram of information regarding the consistency between an alignment mark and a crystal orientation. FIG. 10 is a hardware configuration diagram of a chamfering device of Example 2. FIG. 11 is a schematic plan view of the main parts of the chamfering device of Example 2.

[0023] FIG. 1 is a hardware configuration diagram of a chamfering apparatus 10 according to a first embodiment. FIG. 2 is a schematic plan view of the main components of the chamfering apparatus 10. FIG. 3 is a front view of a crystal orientation measurement unit 10-3 and a measurement unit 10-2 of the chamfering apparatus 10. FIG. 4 is a side view of a grinding unit 10-1 of the chamfering apparatus 10.

[0024] The chamfering apparatus 10 includes a controller 12, a grinding unit 10-1, a measurement unit 10-2, a crystal orientation measurement unit 10-3, a first transport mechanism 10-5, a second transport mechanism 10-4, a storage unit 10-6, and a measurement table 20. In addition to the above, the chamfering apparatus 10 may further include a cleaning / drying unit that cleans and dries the wafer W.

[0025] The controller 12 controls each part of the chamfering device 10. The controller 12 is a computer including a processor and a memory as hardware. A program (instruction set) for controlling each part is stored in the memory in advance. The processor executes instructions included in the program to control each part of the chamfering device 10. The controller 12 may also include a touch-sensitive display or the like as an input / output interface.

[0026] The grinding unit 10-1 includes a grinding wheel 51 and a grinding wheel 52. The grinding unit 10-1 chamfers the wafer W held on the grinding table 50 using the grinding wheels 51 and 52. Specifically, the grinding wheels 51 and 52 and the wafer W are brought into contact with each other while being rotated. The number of grinding wheels included in the grinding unit 10-1 does not need to be two, and may be one, or three or more. The number of grinding wheels can be selected appropriately depending on the chamfering method, etc.

[0027] The grinding table 50 is disk-shaped and has a diameter smaller than that of the wafer W. The grinding table 50 holds the wafer W by vacuum suction. The grinding table 50 is rotatably supported by a spindle motor 53. Under the control of the controller 12, the grinding table 50 can rotate in accordance with predetermined grinding conditions. The held wafer W can also rotate together with the grinding table 50.

[0028] A position adjustment mechanism (not shown) is connected to the grinding table 50. The position adjustment mechanism can translate the grinding table 50 in accordance with the grinding conditions. Such position adjustment mechanisms are well known, and examples thereof include those described in paragraphs 0013 to 0019 and FIGS. 1 to 3 of European Patent Application Publication No. 962282 (EP0962282(A1)). The disclosures in the above-mentioned application specification are incorporated herein by reference. Note that the third position Pos-3 for grinding is the initial position for grinding. During chamfering, the position of the grinding table 50 can be adjusted appropriately by the position adjustment mechanism.

[0029] The grinding wheels 51 and 52 are rotatably supported by spindle motors 54 and 55, respectively (FIG. 4). Furthermore, the spindle motors 54 and 55 are fixed to a support base (not shown) so as to be vertically movable. Such support bases are well known, and examples thereof include those described in paragraphs 0020 to 0021 and FIG. 1 of European Patent Application Publication No. 962282 (EP0962282(A1)). The present specification incorporates the disclosure of the above-mentioned application by reference.

[0030] The grinding wheels 51 and 52 are both disk-shaped. The outer peripheries of the grinding wheels 51 and 52 are provided with grinding grooves. These grooves are brought into contact with the periphery (edge) of the wafer W to chamfer it. The grinding wheel 51 is used for rough grinding (primary grinding) of the wafer W. The type of grinding wheel is not particularly limited, but a metal-bonded grinding wheel in which abrasive grains made of metal and / or inorganic compounds are held in a metal-based binder may be used. Meanwhile, the grinding wheel 52 may have a smaller diameter than the wafer W. The grinding wheel 52 is used for precision grinding (finish grinding) of the wafer W. Again, the type of grinding wheel is not particularly limited, but a resin-bonded grinding wheel in which the binder is resin may be used. The rotation axis of the grinding wheel 52 may be tilted by approximately 3 to 10 degrees relative to the rotation axis of the wafer W. The technique of grinding with a tilted rotation axis is sometimes called "helical grinding." Helical grinding may improve the shape accuracy and surface condition of the finished wafer W.

[0031] The measurement unit 10-2 includes a sensor unit 40. The sensor unit 40 is composed of a laser sensor, a capacitance sensor, an air microsensor, an image sensor, a photoelectric sensor, and the like. The sensor unit 40 can acquire information about the shape of the wafer W held on the measurement table 20, such as the size, thickness, eccentricity, and position of the alignment mark AM. In particular, the photoelectric sensor can be a reflective type that irradiates light onto the wafer W and receives reflected light, or a transmissive type that irradiates light onto the wafer W and detects blockage of the optical path by the wafer W, making it possible to acquire information about the shape of the wafer W more precisely.

[0032] When the measuring table 20 is located at the first position Pos-1, the measuring unit 10-2 measures the wafer W. While the measuring table 20 is located at the first position Pos-1, the timing of the measurement can be selected as appropriate. Examples of the timing of the measurement include after the first transport mechanism 10-5 delivers the wafer W to the measuring table 20, before the second transport mechanism 10-4 moves the measuring table 20 from the first position Pos-1, and before the first transport mechanism 10-5 receives the wafer W from the measuring table 20. It is particularly preferable that the measurement be performed at least after the first transport mechanism 10-5 delivers the wafer W to the measuring table 20 and before the measuring table 20 moves from the first position Pos-1. The sequence of movement of the measuring table 20 will be described later.

[0033] The crystal orientation measurement unit 10-3 includes a crystal orientation measurement device 24 based on the principle of X-ray diffraction. The crystal orientation measurement device 24 includes an X-ray generation unit 28 and an X-ray detection unit 29. When the measurement table 20 is located at the second position Pos-2, the crystal orientation measurement device 24 irradiates X-rays near the alignment mark of the wafer W and detects diffracted X-rays. The attitudes of the X-ray generation unit 28 and the X-ray detection unit 29 may be adjustable by an attitude adjustment mechanism (not shown). Alternatively, they may be fixed depending on the material of the target wafer W and the relationship between the alignment mark AM and the crystal orientation. For example, if an orientation flat is provided parallel to the (011) plane of a gallium arsenide wafer, the diffraction angle is 2θ = 45°. The incident angle and detection position can be adjusted accordingly.

[0034] The crystal orientation measuring unit 10-3 may further include a sensor unit 27. The sensor unit 27 may include a sensor group similar to that of the sensor unit 40. In particular, it is preferable that the sensor unit 27 includes a reflective photoelectric sensor. The sensor unit 27 can acquire information about the shape of the wafer on the measuring table 20 that has moved to the second position Pos-2. In particular, it is preferable that the sensor unit 27 detects the position of the alignment mark AM.

[0035] It should be noted that the crystal orientation measuring unit 10-3 does not necessarily have to include the sensor unit 27. As will be described in detail later, after measurement by the measuring unit 10-2, the rotation angle of the measuring table 20 can be controlled so that the alignment mark AM is oriented in a predetermined direction. This allows the crystal orientation to be measured without having to remeasure the orientation of the alignment mark AM of the transported wafer W. Detecting the alignment mark AM requires, for example, one rotation of the wafer W. Therefore, if the remeasurement of the alignment mark AM in the crystal orientation measuring unit 10-3 can be avoided, the entire process can be shortened accordingly.

[0036] The second transport mechanism 10-4 moves the measurement table 20 between a first position Pos-1 and a second position Pos-2. The first position Pos-1 is the measurement position of the measurement unit 10-2. The second position Pos-2 is the measurement position of the crystal orientation measurement unit 10-3. In other words, the second transport mechanism 10-4 is a hardware group having the function of allowing the measurement table 20 to be shared between the measurement unit 10-2 and the crystal orientation measurement unit 10-3.

[0037] The measurement table 20 is a disk-shaped support base with a diameter smaller than that of the wafer W. The measurement table 20 holds the wafer W. There are no particular limitations on the holding method, but one example is a method of holding the wafer W by vacuum suction. The measurement table 20 can be rotated by a spindle motor 21 around a rotation axis parallel to the Z axis.

[0038] The second transport mechanism 10-4 and its relationship to other components will be described with reference to Figure 3. The second transport mechanism 10-4 includes a guide rail 23A fixed to a main body base 26, a ball screw 23B, a stepping motor 23C, and a linear guide 22. While the combination of the ball screw 23B and stepping motor 23C is shown as the actuator for the second transport mechanism 10-4, this configuration is not limiting and actuators such as servo motors and linear motors can also be used as appropriate.

[0039] The ball screw 23B is driven to rotate by a stepping motor 23C. The rotation of the ball screw 23B causes the linear guide 22 to translate along the guide rail 23A (in the direction of arrow Ar-1). The measuring table 20 is fixed to the linear guide 22 via a spindle motor 21. Therefore, the measuring table 20 also translates along the guide rail 23A. The measuring table 20 is driven by the spindle motor 21 and rotates around a rotation axis parallel to the Z-axis direction. These mechanisms cause the measuring table 20 to translate and rotate. The translation and rotation of the measuring table 20 are controlled by the controller 12.

[0040] The crystal orientation measuring instrument 24 is fixed on a pedestal 25. The pedestal 25 is connected to a main body base 26. The second transport mechanism 10-4 can move the wafer W received from the first transport mechanism 10-5 at the first position Pos-1 to the second position Pos-2. Furthermore, the second transport mechanism 10-4 can move the wafer W after measurement at the second position Pos-2 to the first position Pos-1, making it available for reception by the first transport mechanism 10-5. Separate measurement positions for the measurement unit 10-2 and the crystal orientation measuring unit 10-3 provide greater flexibility in the layout of the apparatus. In particular, because the crystal orientation measuring instrument 24 is based on the X-ray diffraction method, a shielding mechanism such as a shield may be provided. Positioning the crystal orientation measuring unit 10-3 away from the measurement unit 10-2 also facilitates the placement of the shielding mechanism. Furthermore, upgrading conventional chamfering apparatuses becomes easier. Conventional chamfering devices do not include a crystal orientation measuring unit 10-3. However, by adding a second transport mechanism 10-4, the crystal orientation measuring unit 10-3 can be easily retrofitted. This is also one of the advantages of providing separate measurement positions for the measuring unit 10-2 and the crystal orientation measuring unit 10-3. As will be described later, this is also advantageous in terms of measuring the crystal orientations of wafers of various sizes.

[0041] In this example, the sensor unit 40 is fixed to the measurement unit 10-2, independent of the measurement table 20. However, the sensor unit 40 may be configured to be fixed to the linear guide 22 and move to the crystal orientation measurement unit 10-3 together with the measurement unit 10-2.

[0042] The first transport mechanism 10-5 includes an arm 71 that can move rotationally and translationally. The arm 71 can take out a wafer W from a wafer cassette 70 in the storage unit 10-6, transfer the wafer W to and from the measurement table 20, and transfer the wafer W to and from the grinding table 50.

[0043] The arm 71 may be, for example, a three-axis rotating arm. The arm 71 may further include a suction pad for fixing the wafer W. In this case, the suction pad can be brought into contact with the backside of the wafer W to adsorb it under reduced pressure. The arm 71 can move back and forth, up and down, and rotate while holding the wafer W. By combining these operations, the wafer W can be taken out of the wafer cassette 70, stored therein, and the wafer W can be transferred between each table. The first transport mechanism 10-5 is controlled by the controller 12.

[0044] Next, a description will be given of a chamfering method using the chamfering device 10. Fig. 5 is a flow chart of the chamfering method.

[0045] First, in step S10, the measuring unit 10-2 measures information about the shape of the wafer W placed on the measuring table 20. Specifically, this information may include the size and thickness of the wafer W, the amount of eccentricity from the center of the measuring table 20, and the position of the alignment mark. The information about the shape of the wafer W includes at least the position of the alignment mark. Note that the wafer W may have been removed from the wafer cassette 70 in the storage unit 10-6 by the first transport mechanism 10-5 before the start of this step. The first transport mechanism 10-5 delivers the removed wafer W to the measuring table 20.

[0046] Next, in step S11, the second transport mechanism 10-4 transports the measurement table 20 (and the wafer W) to the crystal orientation measurement unit 10-3. At this time, the wafer W is adjusted so that it faces a predetermined direction on the measurement table 20. Specifically, based on the information about the shape, the rotation angle of the measurement table 20 is adjusted so that the alignment mark faces the crystal orientation measurement device 24.

[0047] 6A to 6D are explanatory diagrams of a method for adjusting the rotation angle of the measuring table 20, using a plan view of the second transport mechanism 10-4. FIG. 6A is a diagram showing the state after the measurement unit 10-2 has finished acquiring information about the shape. At this time, the measuring table 20 is at the first position Pos-1. A wafer W is fixed on the measuring table 20. The alignment mark AM faces a certain direction. More specifically, the first position Pos-1 can be defined as the center position of the measuring table 20 when acquiring information about the shape.

[0048] Next, the measurement table 20 is rotated so that the alignment mark AM faces the measurement position Pos-X of the crystal orientation measuring instrument 24. The amount of rotation (rotation angle) of the measurement table 20 is controlled based on the amount of eccentricity of the wafer W, the position of the alignment mark AM, and the direction of the measurement position Pos-X. In FIG. 6A, the measurement table 20 rotates in the direction of arrow Ar-3. After the rotation, for example, the alignment mark AM (X1 axis) is adjusted to be parallel to the X2 axis. FIG. 6B is a diagram showing the state of the wafer after rotation. Note that the X1 axis and the X2 axis do not necessarily need to be adjusted to be parallel. It is preferable to adjust the angle between these axes to be approximately constant. The reason for this will be explained later.

[0049] The X2 axis is perpendicular to the Y1 axis, which is the movement axis of the measuring table 20, and the intersection thereof is the measurement position Pos-X. The second position Pos-2 is the position of the measuring table 20 during measurement by the crystal orientation measuring instrument 24. The second position Pos-2 is defined as the center position of the measuring table 20. The second position Pos-2 is determined based on the measurement position Pos-X, the size of the wafer W, and the amount of eccentricity.

[0050] Next, the measurement table 20 moves in the direction of arrow Ar-4 along the Y1 axis. The amount of movement is the amount by which the X1 axis and the X2 axis coincide. In other words, it is the position at which the alignment mark AM reaches the measurement position Pos-X. This may eliminate the need to align the wafer W before measuring the crystal orientation. This is because the rotation angle of the measurement table 20 is set in advance to an angle suitable for crystal orientation measurement based on the information acquired by the measurement unit 10-2.

[0051] 6C is a diagram showing the state in which the measurement table 20 is at the second position Pos-2. Since the alignment mark AM was adjusted in the previous step so that it faces the direction of the crystal orientation measuring instrument 24 (measurement position Pos-X), it is only necessary to move the measurement table 20 a predetermined amount along the Y1 axis. This causes the X1 axis and the X2 axis to coincide. In other words, the alignment mark AM is at the measurement position Pos-X of the crystal orientation measuring instrument 24. The position of the measurement table 20 (second position Pos-2) is adjusted depending on the size of the wafer W and the amount of eccentricity of the wafer.

[0052] 6D is a diagram showing the state in which the measurement table 20, with the larger-diameter wafer W2 placed thereon, is at the second position Pos-2. As in FIG. 6C, the alignment mark AM is at the measurement position Pos-X of the crystal orientation measuring instrument 24. At this time, the center of the measurement table 20 is on the Y1 axis, just as in FIG. 6C, but its position is different. Specifically, it has moved to the right of the Y1 axis by the difference in the radius of the wafer W. While the drawing shows a case in which there is no eccentricity, the amount of eccentricity is also taken into consideration.

[0053] By configuring the chamfering device 10, particularly the second transport mechanism 10-4, and the measurement table 20 supported thereby, as described above, it is possible to easily measure the crystal orientation of wafers W of various sizes. In other words, because the chamfering device 10 is equipped with the second transport mechanism 10-4, it is possible to measure the crystal orientation of wafers W of any size.

[0054] Furthermore, because the alignment mark AM is positioned at the measurement position Pos-X simply by rotating the measurement table 20 using the shape information obtained by the measurement unit 10-2, the relationship between the alignment mark AM and the measurement position Pos-X is less likely to shift. While a jig can be used for positioning, this is also one of the causes of random errors in crystal orientation measurement. The chamfering device 10 positions the alignment mark AM at the measurement position Pos-X in a non-contact manner, which reduces the occurrence of random errors.

[0055] It is also important that the measurement table 20 can be shared for both acquiring information about the shape and measuring the crystal orientation. Sharing the measurement table 20 eliminates the influence of errors in transferring the wafer W and installation of different devices. By sharing the measurement table 20 for acquiring information about the shape and measuring the crystal orientation, the relationship between the alignment mark AM and the crystal orientation can be acquired with higher accuracy.

[0056] Note that the above is just an example, and it is not necessary to start the crystal orientation measurement with the X1 axis and the X2 axis aligned. As will be described in the next step, the wafer W is rotated during the measurement. Therefore, taking into account the rotation angle, the crystal orientation measurement may be started with the X1 axis and the X2 axis forming a certain angle. Generally, the misalignment is often an angle of 10° or less. Therefore, the angle between the X1 axis and the X2 axis at the start of the crystal orientation measurement may also be set taking this into consideration.

[0057] Returning to the flow chart of Figure 5, when the wafer W is transferred to the crystal orientation measurement unit 10-3, the crystal orientation is measured in step S12. This allows information regarding the consistency between the alignment mark AM and the crystal orientation to be obtained. The crystal orientation is measured while the wafer W is rotated. The wafer W is rotated to detect changes in the intensity of diffracted X-rays.

[0058] FIG. 7 is an explanatory diagram of information regarding the alignment between the alignment mark AM and the crystal orientation. FIG. 7 is an explanatory diagram using a plan view of the wafer W. The following describes a case in which the alignment mark AM and a certain crystal plane MP are originally aligned. If the alignment mark AM and the crystal plane MP are aligned, when X-rays are incident on the alignment mark AM from the X-ray generator 28 at a predetermined angle, stronger diffracted X-rays are detected due to Bragg reflection. In the case of FIG. 7, the crystal plane MP is offset from the alignment mark AM by an angle θC. The angle θC can be determined from the rotation angle of the wafer W and the change in intensity of the diffracted X-rays. This angle θC can be information indicating the alignment between the alignment mark AM and the crystal orientation. Note that the alignment mark AM and the crystal plane MP do not necessarily have to be aligned. For example, there are cases in which the alignment mark AM and the crystal plane MP form a predetermined angle. In this case, the information indicating the alignment between the alignment mark AM and the crystal orientation can be the deviation (angle) of the crystal plane MP based on the angle.

[0059] Next, in step S13, the wafer W is transported to the grinding unit 10-1. Specifically, first, the first transport mechanism 10-5 receives the wafer W from the measuring table 20. Then, the arm 71 rotates and translates to move the wafer in the direction of arrow Ar-2 (FIG. 2). Thereafter, the grinding table 50 receives the wafer W from the first transport mechanism 10-5.

[0060] Information about the shape of the wafer W measured in step S10 (particularly, the position of the alignment mark AM in the rotation direction of the measuring table 20) is maintained even after the wafer W is moved to the grinding table 50. In other words, based on the position information of the alignment mark AM, the wafer W is moved to the measuring table 20, the first transport mechanism 10-5, and the grinding table 50. In other words, the position information of the alignment mark AM, etc. is maintained during the movement from the measuring table 20 to the grinding table 50.

[0061] Next, in step S14, the peripheral edge (edge ​​portion) of the wafer W on the grinding table 50 is ground (chamfered). The grinding conditions are set based on the relationship between the alignment mark AM and the crystal orientation. That is, the shape of the alignment mark AM is modified to correct the misalignment between the alignment mark AM and the crystal orientation. The grinding method for the edge portion including the alignment mark AM is not particularly limited, and known methods can be applied. For example, see paragraphs 0029 to 0039, 0044 to 0057, and Figures 4(a) to 4(f), and 5(a) to 5(e) of European Patent Application Publication No. 962282 (EP0962282(A1)). The present specification incorporates the above-mentioned application specifications by reference.

[0062] Next, in step S15, the chamfered wafer W is transported to the measurement unit. Specifically, first, the first transport mechanism 10-5 receives the wafer W from the grinding table 50. Then, the arm 71 rotates and translates to move the wafer in the direction of arrow Ar-2 ( FIG. 2 ). The measurement table 20 then receives the wafer W from the first transport mechanism 10-5. During this movement, the position information of the alignment mark AM does not need to be maintained. The actual shape of the alignment mark AM may have changed due to chamfering. However, the position information of the alignment mark AM may be maintained. In practice, the deviation between the alignment mark AM and the predetermined crystal orientation is often about 10° or less. Therefore, the shape of the chamfered wafer is rarely significantly changed. In other words, the new alignment mark AM after chamfering is often located at approximately the same position as the (old) alignment mark AM before chamfering.

[0063] In such a case, the efficiency of the subsequent process may be improved by maintaining the position information of the original alignment mark AM even when the chamfered alignment mark AM is transported to the measurement table 20. In other words, when detecting the alignment mark AM in the subsequent process, the approximate position of the new alignment mark AM can be identified based on the position information of the original alignment mark AM, and the alignment mark AM can be measured efficiently.

[0064] Next, in step S16, the measuring unit 10-2 measures information about the shape of the wafer W placed on the measuring table 20. The measurement method may be the same as in step S10. However, in this step, as long as at least the eccentricity of the wafer W relative to the center of the measuring table 20 and the position of the alignment mark AM are measured, other measurements may be omitted. Specifically, measurements of the size and thickness of the wafer W may be omitted. Omitting these measurements may speed up the process. Information about the shape of the wafer W is stored in the memory of the controller 12. At this time, among the information about the shape of the wafer W already stored in the memory, at least the eccentricity relative to the center of the measuring table 20 and the position of the alignment mark may be updated. The information before the update may be the information stored in step S10 or the information stored in step S16 from the second time onwards. The information before the update may also be separately stored in the memory.

[0065] Next, in step S17, the second transport mechanism 10-4 transports the measurement table 20 (and the wafer W) to the crystal orientation measurement unit 10-3. At this time, the wafer W is adjusted so that it faces a predetermined direction on the measurement table 20. Specifically, based on the information about the updated shape, the rotation angle of the measurement table 20 is adjusted so that the alignment mark AM faces the crystal orientation measurement device 24. The transport method may be the same as in step S11.

[0066] Next, in step S18, the crystal orientation is measured. This obtains information about the consistency between the alignment mark AM and the crystal orientation. This information is stored in the memory of the controller 12. At this time, the information about the consistency stored in the memory may be updated. The information before the update may be the information stored in step S12, or the information stored in step S18 from the second time onwards. The information before the update may also be separately stored in the memory.

[0067] Next, in step S19, it is determined whether the consistency between the alignment mark AM and the crystal orientation satisfies a predetermined criterion. The processor executes a program stored in memory to make the determination. The criterion may be, for example, the allowable range for the angle θC between the alignment mark AM and an arbitrary crystal plane (or a line forming a predetermined angle with the crystal plane) in FIG. 7. One example is a numerical range in which the angle θC is greater than or equal to -0.05° and less than or equal to +0.05°. The allowable range is determined appropriately depending on the required quality, etc.

[0068] If the result of the determination is that the alignment between the alignment mark AM and the crystal orientation does not satisfy the criteria (step S19: NO), steps S13 to S19 are repeated. At this time, there is no need to discard or replace the wafer W. In conventional chamfering methods, the test wafer was replaced (i.e., discarded). However, this is not necessary in this method. As already explained, the conventional method aimed to eliminate misalignment between the alignment mark AM and the crystal orientation within the same lot as a systematic error. For this reason, multiple test wafers were sometimes used to determine the grinding conditions.

[0069] This method is based on the discovery that random errors caused by the placement of the wafer W on each table, etc., cause unpredictable misalignment in the chamfered wafer. By identifying an error factor that was not even considered in the past, it is now possible to efficiently chamfer even expensive wafers.

[0070] On the other hand, if the result of the determination is that the alignment between the alignment mark AM and the crystal orientation satisfies the predetermined criteria (step S19: YES), the chamfering is completed. After the chamfering is completed, in the subsequent step S20, the first transport mechanism 10-5 stores the wafer W in the storage unit 10-6.

[0071] Next, another embodiment of the chamfering device will be described. Fig. 8 is a hardware configuration diagram of the chamfering device 11 of the second embodiment. Fig. 9 is a schematic plan view of the main part of the chamfering device 11.

[0072] The grinding section 11-1 of the chamfering device 11 does not include a grinding table 50. The second transport mechanism 10-4 of the chamfering device 11 includes a guide rail 23A that extends to a third position Pos-3 for grinding. One of the features of the chamfering device 11 is that the table is shared for acquiring information about the shape of the wafer W, measuring the crystal orientation, and grinding (chamfering). By sharing the table, the occurrence of installation errors when transferring the wafer W is further suppressed. Therefore, misalignment can be corrected with higher precision, or the occurrence of misalignment can be further suppressed.

[0073] The chamfering method in the chamfering device 11 can be performed according to a flow similar to that of Fig. 5. The first difference from the flow of Fig. 5 is that the transfer of the wafer W in step S13 can be performed by the movement of the second transfer mechanism 10-4 in the direction of arrow Ar-3. Furthermore, in the subsequent step S14, the wafer on the measuring table 20 is ground by grinding wheels 51 and 52.

[0074] The same applies to the subsequent steps, and the transfer of the wafer W between the grinding table 50 and the first transport mechanism 10-5 is omitted. In other words, instead of this transfer, the measuring table 20 moves between the first position Pos-1, the second position Pos-2, and the third position Pos-3. By using the chamfering device 11, the occurrence of errors due to the transfer of the wafer W is further suppressed, and as a result, misalignment can be corrected with higher precision, or the occurrence of misalignment in the wafer W after chamfering can be further suppressed.

[0075] Both Example 1 (chamfering device 10) and Example 2 (chamfering device 11) are equipped with the second transport mechanism 10-4. However, even a chamfering device that does not have the second transport mechanism 10-4 can correct misalignment. For example, the crystal orientation measuring device 24 may be disposed near the measurement unit 10-2. In this case, the wafer at the second position Pos-2 may be rotated appropriately to move the alignment mark AM to the measurement position of the crystal orientation measuring device 24. In other words, the alignment mark AM may be directed toward the crystal orientation measuring device 24 mainly by rotating the wafer W. This makes the entire chamfering device more compact.

[0076] 10, 11 Chamfering device 10-1 Grinding section 10-2 Measuring section 10-3 Crystal orientation measuring section 10-4 Second conveying mechanism 10-5 First conveying mechanism 10-6 Storage section 12 Controller 20 Measuring table 24 Crystal orientation measuring device 50 Grinding table

Claims

1. A wafer chamfering device comprising a crystal orientation measuring device for measuring the crystal orientation of the wafer, and which repeatedly grinds the peripheral edge of the wafer until the alignment between the wafer's alignment mark and the crystal orientation satisfies a predetermined standard.

2. The chamfering device according to claim 1, further comprising a sensor for measuring the position of the alignment mark, wherein the crystal orientation and the position of the alignment mark are each measured for the wafer held on the same measurement table.

3. The chamfering device according to claim 2, further comprising a transport mechanism that translates the measurement table, the transport mechanism moving the measurement table to a first position for measuring the position of the alignment mark and to a second position for measuring the crystal orientation.

4. The chamfering device according to claim 3, wherein the measurement table rotates to orient the alignment mark toward the crystal orientation measuring device at the second position based on the measurement result of the position of the alignment mark.

5. The chamfering device according to claim 3, wherein the sensor measures the size of the wafer, and the transport mechanism adjusts the amount of translational movement from the first position to the second position based on the size.

6. The chamfering apparatus according to claim 3, wherein the transport mechanism moves the measurement table to a third position for grinding the wafer.

7. A method for chamfering a wafer using a chamfering device equipped with a crystal orientation measuring device that measures the crystal orientation of the wafer, the method comprising repeatedly grinding the peripheral edge of the wafer until the alignment between the alignment mark of the wafer and the crystal orientation satisfies a predetermined standard.

8. The chamfering method according to claim 7, wherein the chamfering device is provided with a sensor that measures the position of the alignment mark, and the method includes measuring the crystal orientation and the alignment mark for the wafer held on the same measurement table.

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