NL2027333A

NL2027333A - Wafer machining system and wafer machining method

Info

Publication number: NL2027333A
Application number: NL2027333A
Authority: NL
Inventors: Fuke Tomoki
Original assignee: Tokyo Seimitsu Co Ltd
Priority date: 2020-01-17
Filing date: 2021-01-18
Publication date: 2021-09-01
Also published as: NL2027333B1; JP7478945B2; JP2021114528A; JP2024091765A

Abstract

OF THE DISCLOSURE The invention provides a wafer machining system and a wafer machining method for performing appropriate blade machining on a laser-machined groove. The laser machining device machines a groove along a scribe line formed on a surface of a wafer with a laser beam, and acquires misalignment information indicating misalignment of the groove with respect to the scribe line by capturing an image of a surface of the wafer, and stores the misalignment information in a storage unit in association with wafer-specific information. The blade dicing device acquires misalignment information associated with the wafer- specific information of the wafer on which the groove has been formed from the storage unit, and cuts the wafer on which the groove has been formed, along the groove with the blade based on the acquired misalignment information.

Description

WAFER MACHINING SYSTEM AND WAFER MACHINING METHOD

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The present invention relates to a wafer machining system and a wafer machining method, particularly to technology for forming grooves on a wafer with laser machining and then dicing the wafer with a blade. Description of the Related Art

[0002] With improvement in performance of semiconductor devices, more and more wafers are provided with films having low mechanical strength (for example, Low-k films and Hi-k films) on their device surfaces. When such a wafer is diced with a blade, the film may be damaged or delaminated due to the mechanical load during dicing. If the delamination reaches the device on the wafer, it will result in a defective chip, which will lead to a yield loss. To reduce such a yield loss, it has been a common practice to perform before the blade dicing, a process of removing the film with low strength from a blade dicing line by a laser machining whose mechanical load is low (see Japanese Patent Application Laid-Open No. 2005-064231). In a case where the process is performed, dicing is performed using two machines: a preceding laser machining device and a subsequent blade dicing device.

[0003] In recent years, the machining line is becoming narrower due to reduction in chip size associated with improvement in chip performance and increase in the number of chips per water. Therefore, the width of grooves to be machined is reduced for both laser machining and blade machining, and machining with higher precision has been required. Cited Documents

[0004] Patent Literature 1: Japanese Patent Application Laid-Open No. 2005-064231

SUMMARY OF THE INVENTION

[0005] In the process described above, the blade dicing needs to machine the center of the laser-machined groove. This is because if the cutting edge of the blade does not fall within the laser-machined grooves, a mechanical load may cause the delamination of the film. Accordingly, in the blade dicing in this process, it is necessary to recognize the pattern of the chip and the previously formed laser-machined grooves.

[0006] In a case where the device adjusts the machining position in preceding laser machining process, the relative position between the chip and the laser-machined groove is shifted to the correct position since the current machining line, compared to the previous machining line. However, because this adjusted position cannot be understood in the subsequent blade dicing, the laser-machined groove and the blade machining position are relatively displaced from each other on and after the current machining line. To prevent this, it is necessary to recognize the positions of the laser-machined grooves in the entire machining lines during blade dicing, but this takes time and is not practical.

[0007] The present invention has been made in view of these circumstances, and aims to provide a wafer machining system and a wafer machining method which can perform blade machining appropriately on a laser-machined groove.

[0008] One aspect of a wafer machining system to achieve the object described above is a wafer machining system including wafer machining system including a laser machining device, a blade dicing device and a storage unit, wherein the laser machining device includes: a first stage configured to hold a wafer that has a scribe line formed on a surface; a laser irradiation unit configured to irradiate the surface of the wafer with a laser beam; a grooving control unit configured to machine a groove with the laser beam along the scribe line of the wafer by moving the first stage and the laser irradiation unit relatively to each other; an acquisition unit configured to acquire misalignment information indicating misalignment of the groove with respect to the scribe line by capturing an image of the surface of the wafer by an image-capturing unit; and a storage control unit configured to store the misalignment information in the storage unit in association with wafer-specific information, and wherein the blade dicing device is a device configured to machine the wafer on which the groove is formed by the laser machining device, as an object to be machined, and the blade dicing device includes: a positional information acquisition unit configured to acquire the misalignment information corresponding to the water from the storage unit; a second stage configured to hold the wafer; a blade configured to cut the wafer; and a cutting control unit configured to perform cutting on the wafer with the blade along the groove by moving the second stage and the blade relative to each other based on the acquired misalignment information.

[0009] According to the present aspect, it is possible to appropriately perform blade machining on the laser-machined groove.

[0010] The image-capturing unit is preferably disposed downstream of the laser irradiation unit with respect to a relative movement direction of the first stage and the laser irradiation unit. This allows the image-capturing unit to capture the image of the surface of the wafer immediately after the groove is machined.

[0011] Itis preferable that the laser irradiation unit includes an objective lens configured to condense the laser beam, and the image-capturing unit captures the image of the surface of the wafer via the objective lens. Accordingly, the focus of the laser irradiation unit and the image-capturing unit can be adjusted with a common objective lens so that machining of the groove and image capturing of the surface of the wafer can be achieved with the common objective lens.

[0012] Itis preferable that the focus of the laser irradiation unit and the focus of the image- capturing unit can be adjusted independently of each other. Accordingly, it is possible to machine the groove and capture the image of the surface of the wafer by the laser irradiation unit and the image-capturing unit whose focuses are individually adjusted.

[0013] Itis preferable that the acquisition unit acquires misalignment information simultaneously with the machining of the groove. Accordingly, it is possible to shorten time required to acquire misalignment information.

[0014] One aspect of a wafer machining method to achieve the object described above is a wafer machining method including: a grooving control step of moving a first stage that configured to hold a wafer that has a scribe line formed on a surface of the wafer and a laser irradiation unit configured to irradiate the surface of the wafer with a laser beam, relative to each other, and machining a groove along the scribe line of the wafer with the laser beam; an acquiring step of acquiring misalignment information indicating misalignment of the groove with respect to the scribe line by capturing an image of the surface of the wafer; a storage control step of storing the misalignment information in a storage unit in association with wafer-specific information; a positional information acquisition step of acquiring from the storage unit, the misalignment information associated with wafer-specific information of the wafer on which the groove has been formed; and a cutting control step of moving a second stage configured to hold a wafer on which the groove has been formed and a blade configured to cut the wafer on which the groove has been formed, relatively to each other, based on the acquired misalignment information, and cutting the wafer on which the groove has been formed, along the groove with the blade.

[0015] According to the present aspect, it is possible to appropriately perform blade machining on the laser-machined groove.

[0016] According to the invention, it is possible to appropriately perform blade machining on the laser-machined groove.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 11s an overview diagram of a wafer machining system;

Fig. 2 is a plan view of a wafer; Fig. 3 is a schematic diagram of a laser machining device according to a first embodiment; Fig. 4 is a schematic diagram of a blade dicing device; Fig. 5 is a flowchart illustrating an example of process in a wafer machining method, Fig. 6 illustrates an example of a barcode marked on the wafer; Fig. 7 illustrates an example of data stored in a database server; and Fig. 8 is a schematic diagram of a laser machining device according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the embodiments, the X, Y, and Z directions are perpendicular to each other. The X and Y directions are horizontal, and the Z direction is vertical.

[0019] <First Embodiment> [General Configuration of Wafer Machining System] Fig. 1 is an overview diagram of the wafer machining system 10. The wafer machining system 10 is provided with a laser machining device 20, a blade dicing device 50, and a database server 60.

[0020] The laser machining device 20 is a device configured to perform laser machining on a workpiece on which a laminated film including a metallic film, is formed. Here, a wafer W as the workpiece, has streets L, which are scribe lines, on its front surface, and the laser machining device 20 irradiates the wafer W with a laser beam, which is a processing light, along the streets L, to form grooves C which are machined grooves (kerf). The blade dicing device 50 is a device for cutting the wafer with a blade. Here, the blade dicing device 50 cuts the wafer W on which the grooves C have been formed.

[0021] The database server 60 corresponds to a storage unit which stores misalignment information described below. The database server 60 is provided with a server function and large capacity storage. Between the laser machining device 20 and the database server 60, and between the blade dicing device 50 and the database server 60, are respectively connected so as to communicate with each other via a network such as a peer-to-peer (P2P) connection. The database server 60 may be provided in the laser machining device 20 or the blade dicing device 50.

[0022] [General Configuration of Laser Machining Device] Fig. 2 is a plan view of the wafer W. The wafer W is a laminated body formed by laminating a Low-k film and a functional film which forms circuits, on a front surface of a substrate made of silicon or the like. The wafer W is partitioned into a plurality of regions 5 by the plurality of streets L arrayed along directions which intersect with each other so as to form a grid pattern. In Fig. 2, streets parallel to the X direction are designated as LX, and streets parallel to the Y direction are designated as LY. In each chip C, which is a region divided by the streets LX and LY, a device such as an IC (integrated circuit) and a LSI (large scale integration) is formed.

[0023] Fig. 3 is a schematic diagram of the laser machining device 20 according to the first embodiment. As illustrated in Fig. 3, the laser machining device 20 is provided with a stage 22, a laser beam source 24, a laser irradiation unit 26, a Z-base 28 for laser irradiation unit, a camera 30, a Z-base 32 for camera, a common base 34, a moving mechanism 36, and a control device 38.

[0024] The stage 22 (an example of "first stage") holds the wafer W on its upper surface, in a state where the front surface of the wafer W faces upward in the Z direction. The stage 22 is provided with a motor (not illustrated). The stage 22 is configured to be movable in the X and Y directions, and rotatable in the XY plane by the moving mechanism 36.

[0025] The laser beam source 24 is provided with a laser oscillator (not illustrated) and generates a laser beam which is a processing light. The laser irradiation unit 26 is configured to irradiate the front surface of the water W with the laser beam. The laser irradiation unit 26 is provided with an irradiation optical system (not illustrated) including an objective lens 26A. The laser beam generated by the laser beam source 24 is converged and emitted by the irradiation optical system. The Z-base 28 for laser irradiation unit holds the laser irradiation unit 26 in a state where the objective lens 26A of the laser irradiation unit 26 faces downward in the Z direction.

[0026] The camera 30 (an example of "image-capturing unit") is provided with an observation optical system (not illustrated) including a light source (not illustrated), an imaging element (not illustrated) and an objective lens 30A. The camera 30 is configured to capture an image (observes) of the front surface of the wafer W. The camera 30 is provided with the light source (not illustrated) equivalent to a 250 W metal halide light source, and can capture an image with an exposure time of less than 1 [us]. The objective lens 30A has a performance of: a numerical aperture NA of about 0.4; and a resolution of about 0.8 [um], with the observation light having a wavelength of 550 [nm].

[0027] The Z-base 32 for camera holds the camera 30 in a state where the objective lens 30A of the camera 30 faces downward in the Z direction. The common base 34 holds the Z-base 28 for laser irradiation unit and the Z-base 32 for camera.

[0028] In this manner, the laser irradiation unit 26 and the camera 30 are held so that the laser irradiation unit 26 and the camera 30 can individually adjust their focus. In addition, the common base 34 holds the camera 30 downstream of the laser irradiation unit 26 with respect to a direction of relative movement between the common base 34 and the stage 22 along the X direction, during laser machining as described below.

[0029] The control device 38 integrally controls the laser machining device 20. The laser machining device 20 performs grooving along the streets LX and LY of the wafer W, according to the control of the control device 38.

[0030] In other words, the control device 38 causes the laser beam source 24 to generate a laser beam. Further, the control device 38 controls a motor (not illustrated) and moves the Z-base 28 for laser irradiation unit in the Z direction so that the focus of the objective lens 206A of the laser irradiation unit 26 is aligned with a desired Z-direction position of the wafer W.

[0031] The control device 38 controls the motor (not illustrated) to move the Z-base 32 for camera in the Z direction so that the focus of the objective lens 30A of the camera 30 is aligned with the desired Z-direction position of the wafer W.

[0032] The control device 38 (an example of "grooving control unit") controls the motor (not illustrated) and moves (scans) the common base 34 in the X direction relative to the stage 22 in order to remove the Low-k film along the street LX of the wafer W by a laser beam and perform grooving. In the example illustrated in Fig. 3, the stage 22 is scanned in the X direction leftward with respect to the common base 34. When the laser machining of one street LX is completed, the control device 38 controls the motor (not illustrated) to move the stage 22 in the Y direction with respect to the common base 34, and then performs the laser machining of the adjacent street LX in the same manner.

[0033] In the present embodiment, the stage 22 is configured to be movable in the X and Y directions, and the laser irradiation unit 26 is configured to be movable in the Z direction.

However, it is sufficient as long as the stage 22 and the laser irradiation unit 26 can be moved relative to each other in the X, Y, and Z directions. For example, the stage 22 may be configured to be movable in the X direction and the laser irradiation unit 26 may be configured to be movable in the Y and Z directions.

[0034] When laser machining for all the streets LX is completed, the control device 38 controls the motor (not illustrated) to rotate the wafer W by 90° by rotating the stage 22 by

90°. Then, as in the case of the streets LX, the stage 22 is scanned in the X direction leftward with respect to the common base 34, and the grooves C are machined along the streets LY of the wafer W by the laser beam.

[0035] The control device 38 (an example of "acquisition unit") observes the streets LX and LY and the grooves C during the machining of the grooves C with the laser beam by capturing the image of the front surface of the wafer W with the camera 30 in order to acquire misalignment information indicating misalignment (displacement) of the grooves C with respect to the streets LX and LY. Further, the control device 38 (an example of "storage control unit") stores the acquired misalignment information in the database server 60 in association with unique information of the wafer W on which the grooves C have been formed.

[0036] [General configuration of Blade Dicing Device] The blade dicing device 50 is a device for machining the wafer W, as a workpiece to be machined, on which the grooves C have been formed by the laser machining device 20. Fig 4 is a schematic diagram of the blade dicing device 50. As illustrated in Fig. 4, the blade dicing device 50 is provided with a stage 52, a blade 54, a moving mechanism 56, and a control device 58.

[0037] The stage 52 (an example of "second stage") holds the wafer W on its upper surface in a state where the front surface of the wafer W faces upward in the Z direction. The stage 521s provided with a motor (not illustrated). The stage 52 is configured to be movable in the X direction and rotatable in the XY plane (movement in the 8Z direction) by the moving mechanism 56. The blade 54 is a disk-shaped member parallel to an XZ plane, and has an annular-shaped cutting edge (not illustrated) on its periphery. The center of the disk- shaped blade 54 is supported by a spindle (not illustrated) which is parallel to the Y direction. The spindle is provided with a motor (not illustrated) and is configured to be movable in the Y and Z directions by the moving mechanism 56. The blade 54 is provided with a motor (not illustrated) connected to the spindle, and is supported so as to be rotatable in the XZ plane.

[0038] The control device 58 integrally controls the blade dicing device 50. The blade dicing device 50 cuts the wafer W according to the control of the control device 58.

[0039] In other words, the control device 58 (an example of "positional information acquisition unit") acquires misalignment information corresponding to the wafer W to be machined from the database server 60. The control device 58 controls the motor (not illustrated) to rotate the blade 54. The control device 58 (an example of "cutting control unit") controls the motor (not illustrated) to move the stage 52 in the X direction while adjusting the machining position based on the acquired misalignment information, and cuts the center of the groove which is along the street LX of the wafer W, with the blade 54. When completing cutting the center of the groove which is along one street LX, the control device 58 controls the motor (not illustrated) to move the blade 54 in the Y direction and then cuts the center of the groove which is along an adjacent street LX in the same manner.

[0040] Further, when completing cutting along all the streets LX, the control device 58 controls the motor (not illustrated) to rotate the wafer W by 90° by rotating the stage 52 by 90°. Then, as in the case of the grooves along streets LX, the stage 52 is moved in the X direction while adjusting the machining position based on the acquired misalignment information, and then, the blade 54 cuts the center of each of the grooves which are along the streets LY of wafer W.

[0041] In the present embodiment, the stage 52 is configured to be movable in the X and 0Z directions, and the blade 54 is configured to be movable in the Y and Z directions. However, it is sufficient as long as the stage 52 and the blade 54 can move relative to each otherin the X,Y, Z, and 6Z directions. For example, the stage 52 may be configured to be movable in the X, Y, and 6Z directions, and the blade 54 may be configured to be movable in the Z direction.

[0042] [Wafer Machining Method] Fig. 5 is a flowchart showing an example of process in the wafer machining method. Here, the positions of all streets L and grooves C of wafer W are inspected in advance, and blade dicing is performed based on the inspected information. Another inspection device can be used for this inspection. In this case, however, in the laser machining process with the preceding laser machining device 20, the amount of misalignment between the street L and groove C is ascertained simultaneously with laser machining, and the information on the amount of misalignment of groove C with respect to each street L is associated with the wafer W, thereby handing over the information to the subsequent blade dicing device 50. Based on the misalignment information, the blade dicing device 50 machines the centers of the grooves C using only the pattern recognition of the chip.

[0043] In Step S1 (an example of "grooving control step", an example of "acquisition step"), grooving is performed on the wafer W with the laser machining device 20. Simultaneously, the positions of the grooves C with respect to the street L is observed, and the amount of misalignment of the grooves C with respect to the street L is inspected. Upon determining that the amount of misalignment between street L and grooves C is large,

the laser machining device 20 corrects the position of the grooving with respect to the neighboring street L by the next scan.

[0044] In this manner, the laser machining device 20 performs inspections during laser machining. As used herein the term "simultaneously" does not necessarily mean exactly the same timing but rather means executing in parallel in a single scan.

[0045] The processing time increases when machining with the laser beam is stopped. For this reason, in the present embodiment, a method of capturing images of the street L and the groove C during laser machining (while the laser beam and the wafer W are moving relative to each other) and inspecting the amount of misalignment is employed. This method is called a scan kerf check. This scan kerf check requires a light source with a high light intensity and a processing unit that continuously performs image processing so that street L and groove C can be recognized even with a short exposure time to capture the image of the wafer W during scanning.

[0046] Here, the scanning speed of the grooving process is 600 [mm/sec]. According to the camera 30, the misalignment in the Y direction can be reduced to about 3 [um].

[0047] The inspection of the amount of misalignment of groove C may be done on all streets L or some streets L. If there is a street L that has not been inspected for the amount of misalignment of groove C, the misalignment amount of the position of groove C with respect to the corresponding street L is generated by interpolation from the amount of misalignment of the position of groove C with respect to neighboring streets L.

[0048] In Step S2 (an example of "storage control step"), in order to hand over the misalignment information from the laser machining device 20 to the blade dicing device 50, the misalignment information recorded in Step SI is associated with the wafer W on which the grooves C are formed and stored in the database server 60.

[0049] The wafer W on which the grooves C are formed is associated with the misalignment information obtained from the wafer W by using the wafer ID stamped on the wafer W (an example of "wafer-specific information") and the barcode attached on the frame of the wafer W (an example of "wafer-specific information") as keys. Fig. 6 illustrates an example of a barcode marked on the wafer W. In Fig. 6, a wafer W with wafer ID #1 and a wafer W with wafer ID #2 are illustrated. As illustrated in Fig. 6, each wafer W is given a specific barcode B on the back surface.

[0050] The laser machining device 20 acquires the wafer ID of the wafer W on which the grooves C are formed and stores wafer ID in the database server 60 in association with the misalignment information.

[0051] Fig. 7 illustrates an example of the misalignment information stored in the database server 60. In the example illustrated in Fig. 7, the amounts of misalignment of groove C with respect to streets L with street numbers 1, 2, 3, 4, … on the wafer W with wafer ID #1 are -0.5 um, +1.0 um, +0.1 um, +0.1 um, … respectively. The amounts of misalignment of grooves C with respect to the streets L with street number 1, 2, … on the wafer W with wafer ID #2 are -2.0 um, -3.0 um, ..., respectively.

[0052] As described above, the amounts of misalignment of the grooves C with respect to the streets L can be associated with the wafer ID of the wafer W on which the grooves C are formed and stored in the database server 60. Here, the example of managing wafer IDs with barcode B is explained, but wafer-specific information can be managed in the order of "the number of wafers machined".

[0053] In Step S3 (an example of "positional information acquisition step"), the blade dicing device 50 acquires the wafer ID of the wafer W to be machined and acquires the misalignment information of the wafer ID from the database server 60.

[0054] In Step S4 (an example of "cutting control step"), the blade dicing device 50 adjusts the cutting position based on the acquired misalignment information for the street L to be cut on the wafer W. This allows the blade dicing device 50 to cut the centers of the grooves C of the wafer W without inspecting the position of the grooves C of the wafer W to be machined.

[0055] Here, association of the streets L recognized by the laser machining device 20 with the streets L recognized by the blade dicing device 50 is achieved by pattern matching using unique patterns such as chip ends and notches of the wafer W.

[0056] For example, when registering information about wafer W first in the laser machining device 20 and the blade dicing device 50, the first street L can be aligned between the laser machining device 20 and the blade dicing device 50 by registering information on the distance from the unique pattern to the position of the first street L. For example, the wafer W illustrated in Fig. 2 has a unique pattern P with no similar pattern in the proximity region. In this case, when the distance from the pattern P to the first street L is specified, the first street L can be commonly recognized by the laser machining device 20 and the blade dicing device 50. As a unique pattern, features of the outline of the wafer W, such as a notch and an orientation flat, may be used.

[0057] The position of the first street L can be aligned by setting the distance from the center of the wafer W to the first street L in advance, and obtaining the center of the wafer W by using an outline measurement function.

[0058] In this manner, according to the wafer machining method of the present embodiment, the positions of the grooves C measured by the laser machining device 20 can be handed over to the blade dicing device 50, and the cutting can be performed without inspecting the positions of the grooves C again on the blade dicing device 50 side. Asa result, processing with high quality, high accuracy, and shorter time can be achieved throughout the process.

[0059] Itis also theoretically possible to observe the grooves C in the blade dicing device 50 to acquire the misalignment information before cutting. However, the blade dicing device 50 is not a desirable imaging environment because cutting water for cooling the blades or the like 1s used in the blade dicing device 50 and much external disturbance is caused therefrom. The laser machining device 20 is more preferable than the blade dicing device 50 because the position of the grooves C can be observed in a stable environment,

[0060] In the present embodiment, the objective lens 26A of the laser irradiation unit 26 and the objective lens 30A of the camera 30 are independent of each other. Further, the laser irradiation unit 26 and the camera 30 are configured to be individually movable with the Z-base 28 for laser irradiation unit and the Z-base 32 for camera respectively, in the Z- direction. Therefore, there are no restrictions on the wavelength of the processing light, depth of focus, pupil diameter, emission during machining, focus position during machining or the like. Even when an optical system with a shallow depth of field is used, because the laser irradiation unit 26 and the camera 30 can adjust the focus independently of each other, each of their focus positions can be adjusted at an appropriate height. Therefore, both of them can perform machining and image-capturing under optimal conditions, respectively.

[0001] On the other hand, since the position of irradiation by the laser irradiation unit 26 is separated from the position of image-capturing of the camera 30, the scanning distance in the X direction is extended by the distance therebetween and the processing time becomes longer. For this reason, the inspection is not required to be performed for grooves C for all the streets L. The inspection may be performed for grooves C at an interval of an arbitrary number of streets L, or at an arbitrary timing such as before or after correction in laser machining. In addition, the wafer machining system 10 may be configured such that a user can set the timing of performing the inspection. Moreover, as to grooves C which are not subject to inspection, the amounts of misalignment may or may not be interpolated linearly or any using higher-order curve.

[0062] The Z-bases for the laser irradiation unit 26 and the camera 30 may be a common one base so that the laser irradiation unit 26 and the camera 30 may be movable simultaneously in the Z direction.

[0063] Furthermore, instead of the database server 60, a portable storage medium such as a USB (Universal Serial Bus) memory may be employed. In this case, the laser machining device 20 and the blade dicing device 50 are respectively configured to be accessible to data in the portable storage medium.

[0064] <Second Embodiment> Fig. 8 is a schematic diagram of the laser machining device 70 according to a second embodiment. The same reference numerals designate parts common to the laser machining device 20, and a detailed description of these common parts will be omitted. As illustrated in Fig. 8, the laser machining device 20 is provided with a laser irradiation unit 72, a dichroic mirror 74, and a common Z-base 76.

[0065] The laser irradiation unit 72 is provided with an objective lens 72A. The dichroic mirror 74 is disposed on an optical path of the laser beam from the laser beam source 24 to the objective lens 72A. The common Z-base 76 holds the laser irradiation unit 72 in a state where the objective lens 72A of the laser irradiation unit 72 faces downward in the Z direction.

[0066] The laser beam emitted from the laser beam source 24 passes through the dichroic mirror 74 and enters the objective lens 72A of the laser irradiation unit 72. The objective lens 72A condenses the incident laser beam on a focus point on the wafer W.

[0067] The common Z-base 76 also holds the camera 30. The camera 30 is provided with an observation light source 30B, a half-mirror 30C, and an imaging element 30D. The observation light emitted from the observation light source 30B is reflected by the half- mirror 30C and the dichroic mirror 74 and enters the objective lens 72A. The objective lens 72A allows the incident observation light to enter the focus point on the wafer W.

[0068] Of the observation light incident on the wafer W, a portion of the reflected light reflected on the wafer W enters the objective lens 72A as a subject light. The subject light incident on the objective lens 72A is reflected by the dichroic mirror 74 and enters the camera 30 and passes through the half-mirror 30C to enter the imaging element 30D. The imaging element 30D receives the incident subject light and captures the subject image.

[0069] Thus, the camera 30 captures an image of the front surface of the wafer W on which the grooves C are formed, through the objective lens 72A of the laser irradiation unit 72. Because the laser machining device 70 has a single objective lens 72A, the entire optical system can be made compact. In addition, the common Z-base 76 can simultaneously adjust the focus of the processing light and the focus of the observation light. In addition, the scanning distance during machining can be shortened. Here, it is possible to add an additional optical system so that the focus of the processing light and the focus of the observation light may be adjustable independently.

[0070] The single objective lens 72A has lower contrast and lower resolution compared to the dedicated objective lens 30A for the camera 30 (see Fig. 3). Specifically, assuming that the wavelength of the observation light is 430 [nm], the objective lens 72A has a performance of: a numerical aperture NA of about 0.15; and a resolution of about 1.7 [um].

[0071] <Others> According to the laser machining device 20 and the laser machining device 70, the amounts of misalignment of the grooves C can also be used for feedback, such as adjusting the position in the Y direction during machining in real-time (active Y) or adjusting the angle (active 0), toward the direction to cancel the amounts of misalignment of the grooves C illustrated in Fig. 7.

[0072] In a case where the amount of misalignment in a certain coordinate in the Y direction at a certain speed in X the direction is reproducible, once the amount of misalignment is observed and stored under that condition, there is no need to inspect a wafer real-time when the wafer is machined under the same condition afterward. However, ina case where there are disturbances such as changes in water temperature or air temperature, the method of measuring and compensating in real-time is more effective. Non-real-time inspection can achieve following advantages. Fine sampling can be performed because the inspection interval does not affect the machining speed. There are no problems even in a case where an equipment having low processing capacity is used because the processing time does not affect the machining speed so as to provide a margin in processing capacity.

[0073] The camera 30 may also be used to observe the amount of debris generated and inspect the soundness of the nozzle based on the amount of debris generated.

[0074] In a case where the grooves C for all the streets L of the wafer W can be observed all over the wafer, it means that grooves C for all the chips are visually inspected in the laser machining device 20 (70). Therefore, it is possible to identify in advance, defective chips with machining defects or process omission. Moreover, by measuring change in distortion, it is possible to predict failure in the laser machining device 20 (70) and measure timing of maintenance for the laser machining device 20 (70).

[0075] The technical scope of the present invention is not limited to the scope described in the embodiments described above. The configuration and the like in each embodiment may be combined among the embodiments as appropriate to the extent that the purpose of the invention is not departed from the invention.

Reference Signs List

[0076] 10: wafer machining system 20: laser machining device 22: stage 24: laser beam source

26: laser irradiation unit 26A: objective lens 28: laser irradiation unit-dedicated Z-base 30: camera

30A: objective lens 32: camera-dedicated Z-base 34: common base 36: moving mechanism 38: control device

50: blade dicing device 52: stage 54: blade 56: moving mechanism 58 control device

60: database server 70: laser machining device 72: laser irradiation unit 72A: objective lens 74: dichroic mirror

76: common Z-base B: barcode C: groove L, LX, LY: street P: pattern

W: wafer S1 to S4: respective steps of wafer machining method

Claims

Conclusions

A wafer processing system comprising a laser processing device, a sheet cutting device and a storage unit, the laser processing device comprising: a first stage configured to hold a wafer having a surface having a scribe line formed therein; a laser irradiation unit configured to irradiate the surface of the wafer with a laser beam; a groove control unit configured to process a groove along the scribe line of the wafer with the laser beam by moving the first stage and the laser irradiation unit relative to each other; an acquisition unit configured to acquire misalignment information indicating misalignment of the groove with respect to the scribe line by capturing an image of the surface of the wafer by an image pickup unit; and a storage controller configured to store the misalignment information in the storage unit in combination with wafer-specific information, the blade cutter being a device configured to process the wafer having the groove formed therein by the laser processing device as a die. processing object, and wherein the blade cutter comprises: a position information acquisition unit configured to acquire the misalignment information corresponding to the wafer from the storage unit; a second platform configured to hold the wafer;

a blade configured to cut the wafer; and a cutting control unit configured to perform cutting with the blade along the groove on the wafer by moving the second stage and the blade relative to each other based on the obtained misalignment information.

The wafer processing system according to claim 1, wherein the image pickup unit is arranged downstream of the laser irradiation unit in accordance with the relative direction of movement of the first stage and the laser irradiation unit.

The wafer processing system according to claim 1 or 2, wherein the laser irradiation unit comprises an objective lens configured to densify the laser beam, and the image pickup unit captures the image of the surface of the wafer through the objective lens.

The wafer processing system according to any one of claims 1 to 3, wherein focuses of the laser irradiation unit and the image pickup unit are adjustable independently of each other.

The wafer processing system according to any one of claims 1 to 4, wherein the acquisition unit obtains the misalignment information during processing of the groove.

A wafer processing method comprising: a groove control step of moving a first stage and a laser irradiation unit relative to each other, the first stage configured to hold a wafer having a surface having a scribe line formed therein, and wherein the laser irradiation unit configured to irradiate the surface of the wafer with a laser beam, and to machine a groove along the scribe line of the wafer with the laser beam; an acquiring step of acquiring misalignment information indicating misalignment of the groove with respect to the scribe line by capturing an image of the surface of the wafer; a storage control step of storing the erroneous rooting information in a storage unit in conjunction with wafer-specific information; a step of acquiring position information from the storage unit from the misalignment information associated with wafer-specific information of the wafer having the groove formed therein; and a cutting control step of moving a second stage and a blade relative to each other based on the obtained misalignment information, the second stage being configured to hold a wafer having the groove formed therein and the blade being configured to cut the wafer with the groove formed therein, and to cut the wafer with the blade along the groove.