JP2023002418A - Confirmation method for wafer - Google Patents

Abstract

To provide a confirmation method for a wafer which can reduce the time required for the work to classify the steps causing a processing failure in the wafer.SOLUTION: A confirmation method for a wafer comprises: a holding step 1 for holding a wafer in such a state that the front surface side of the wafer is exposed; a positioning step 2 of positioning an imaging region on a division schedule line set on the front surface of the wafer; an imaging step 3 of imaging the imaging region including the division schedule line while relatively moving the imaging region and the wafer in a direction parallel to a direction along the division schedule line; a storing step 4 of storing a position in the wafer in the image captured in the imaging step 3; and a processing step 5 of processing the wafer at a processing point along the division schedule line while relatively moving the processing point and the wafer at positions with a fixed distance to the imaging region and on the division schedule line after imaging in the imaging step 3 in the direction parallel to the direction along the division schedule line.SELECTED DRAWING: Figure 5

Description

The present invention relates to a wafer checking method.

As a method of dividing a semiconductor wafer having devices formed on its surface into chips, a laser beam is irradiated along dividing lines formed on the wafer to ablate the wafer, thereby dividing the wafer (see Patent Document 1). ), and a method of dividing the wafer by forming a modified layer serving as a division starting point inside the wafer and applying an external force (see Patent Document 2).

Japanese Patent Application Laid-Open No. 2003-320466 Japanese Patent No. 3408805

By the way, there is a possibility that, for example, a wafer manufactured in a pre-process and transferred to a post-process is a defective wafer in which structures, films, dust, etc. that should not exist originally exist on the dividing line. In this case, the wafer cannot be reliably divided by laser beam irradiation, resulting in defective processing. After a processing defect occurs, it becomes difficult to determine the cause of the processing defect, whether it is caused by the laser processing equipment or by a previous process rather than the processing process, and it takes time to investigate. There is a problem that productivity decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and its object is to provide a wafer checking method capable of reducing the time required for sorting out which process causes defective processing of a wafer. to provide.

In order to solve the above-described problems and achieve the object, a method of checking a wafer according to the present invention is a method of checking a wafer having a plurality of dividing lines set on the surface thereof, wherein the surface side of the wafer is exposed. a holding step of holding the wafer in a state of being held; a positioning step of positioning the imaging region on the line to divide set on the surface of the wafer; and a direction parallel to the direction along the line to divide the imaging region and the wafer. and a storage step of storing the position of the image captured in the imaging step on the wafer, wherein the imaging step comprises: The division is performed while relatively moving the wafer and the processing point located on the line to be divided after being imaged and at a certain distance from the imaging area in a direction parallel to the direction along the line to be divided. The method further includes a processing step of processing the wafer at the processing point along the scheduled line.

Further, in the wafer checking method of the present invention, in the processing step, the wafer may be processed by irradiating the processing point with a laser beam along the dividing lines.

Further, in the method for checking a wafer of the present invention, in the processing step, a laser beam having a wavelength that is transparent to the wafer is irradiated to the processing point along the line to divide, so that the inside of the wafer is , a modified layer may be formed along the planned dividing line.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to reduce the time required for sorting out which process causes defective processing of a wafer.

FIG. 1 is a perspective view showing a configuration example of a processing apparatus that implements a wafer confirmation method according to an embodiment. FIG. 2 is a perspective view showing an example of a wafer to be checked by the wafer checking method according to the embodiment. FIG. 3 is a flow chart showing the flow of the wafer confirmation method according to the embodiment. FIG. 4 is a side view showing a state of positioning in the first imaging area in the positioning step shown in FIG. 5 is a diagram showing an example of an image captured in the first imaging area shown in FIG. 4. FIG. FIG. 6 is a side view showing a state in which the second imaging area is imaged in the imaging step shown in FIG. 3 and the first imaging area is processed in the processing step. 7 is a diagram showing an example of an image captured in the second imaging area shown in FIG. 6. FIG. FIG. 8 is a side view showing a state of processing the third imaging area in the processing step shown in FIG. 9 is a diagram showing an example of an image captured in the third imaging area shown in FIG. 6. FIG.

A form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or changes in configuration can be made without departing from the gist of the present invention.

[Embodiment]
A method for checking the wafer 10 according to the embodiment of the present invention will be described with reference to the drawings. First, a configuration example of the processing apparatus 100 that implements the confirmation method of the wafer 10 according to the embodiment and an example of the wafer 10 to be confirmed will be described. FIG. 1 is a perspective view showing a configuration example of a processing apparatus 100 that implements a method for checking a wafer 10 according to an embodiment. FIG. 2 is a perspective view showing an example of the wafer 10 to be checked by the wafer 10 checking method according to the embodiment.

In the following description, the X-axis direction is one direction in the horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on the horizontal plane. The Z-axis direction is a direction orthogonal to the X-axis direction and the Y-axis direction. In the processing apparatus 100 of the embodiment, the processing feed direction is the X-axis direction, and the indexing feed direction is the Y-axis direction.

As shown in FIG. 1, processing device 100 is a laser processing device in the embodiment. The processing apparatus 100 includes a holding table 110, a laser beam irradiation unit 120, an imaging unit 130, a processing feed unit 140, an index feed unit 150, a focusing point position adjustment unit 160, a display unit 170, and a control unit. 180 and. The processing apparatus 100 according to the embodiment is an apparatus that processes the wafer 10 by irradiating the wafer 10 held on the holding table 110 with the laser beam 121 from the laser beam irradiation unit 120 . The processing of the wafer 10 by the processing apparatus 100 includes, for example, modified layer forming processing for forming the modified layer 17 inside the wafer 10 by stealth dicing, groove processing for forming grooves on the surface 12 of the wafer 10, or a dividing line. A cutting process for cutting the wafer 10 along the line 13, or the like.

A _{wafer 10} shown in _FIG . wafers such as disk-shaped semiconductor device wafers and optical device wafers. The wafer 10 has a plurality of division lines 13 set in a lattice pattern on the surface 12 of the substrate 11 and devices 14 formed in regions partitioned by the division lines 13 .

The device 14 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), a CCD (Charge Coupled Device), or an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor). A back surface 15 is the surface of the wafer 10 opposite to the surface 12 on which the devices 14 are formed.

The wafer 10 is divided into individual devices 14 along dividing lines 13 to be singulated into chips. It should be noted that the wafer 10 is not limited to the embodiment, and does not have to be disc-shaped in the present invention. The wafer 10 is supported in the opening of the frame 20 by, for example, attaching an annular frame 20 and attaching a tape 21 having a larger diameter than the outer diameter of the wafer 10 to the rear surface 15 of the wafer 10 .

The holding table 110 shown in FIG. 1 holds the wafer 10 on the holding surface 111 . The holding surface 111 is disk-shaped and is made of porous ceramic or the like. The holding surface 111 is a plane parallel to the horizontal direction in the embodiment. The holding surface 111 is connected to a vacuum suction source via, for example, a vacuum suction path. The holding table 110 sucks and holds the wafer 10 placed on the holding surface 111 . A plurality of clamping units 112 are arranged around the holding table 110 to clamp the frame 20 that supports the wafer 10 .

The holding table 110 is rotated around an axis parallel to the Z-axis direction by a rotating unit 113 . The rotating unit 113 is supported by the X-axis direction moving plate 114 . The rotation unit 113 and the holding table 110 are moved in the X-axis direction by the processing feed unit 140 via the X-axis direction moving plate 114 . The rotation unit 113 and the holding table 110 are moved in the Y-axis direction by the indexing feed unit 150 via the X-axis direction movement plate 114 , the machining feed unit 140 and the Y-axis direction movement plate 115 .

The laser beam irradiation unit 120 is a unit that irradiates the wafer 10 held on the holding table 110 with a pulsed laser beam 121 having a predetermined wavelength for processing the wafer 10 . The laser beam irradiation unit 120 includes, for example, a laser oscillator that emits a laser beam 121, a condenser, and various optical components provided on the optical path of the laser beam 121 between the laser oscillator and the condenser. include. The condenser converges the laser beam 121 emitted from the laser oscillator and propagated through various optical components onto the wafer 10 held on the holding surface 111 of the holding table 110 to irradiate the wafer 10 with the laser beam 121 .

The imaging unit 130 images the wafer 10 held on the holding table 110 . The imaging unit 130 includes a CCD (Charge Coupled Device) camera or an infrared camera that images the wafer 10 held on the holding table 110 . The imaging unit 130 is, for example, fixed at a position a predetermined distance from the collector of the laser beam irradiation unit 120 so as to be adjacent to it in the feed direction. An imaging area 30 (see, for example, FIGS. 4 to 9) by the imaging unit 130 is positioned ahead of the processing point by the laser beam 121 irradiated by the laser beam irradiation unit 120 in the processing feed direction. The imaging unit 130 images the wafer 10 in the imaging area and outputs the obtained image 131 (eg, see FIGS. 5, 7 and 9) to the control unit 180 .

The processing feed unit 140 is a unit that relatively moves the holding table 110 and the laser beam irradiation unit 120 in the X-axis direction, which is the processing feed direction. The processing feed unit 140 moves the holding table 110 in the X-axis direction in this embodiment. The processing feed unit 140 is installed on the device main body 101 of the processing device 100 in the embodiment. The processing feed unit 140 supports the X-axis direction moving plate 114 so as to be movable in the X-axis direction.

The indexing feed unit 150 is a unit that relatively moves the holding table 110 and the laser beam irradiation unit 120 in the Y-axis direction, which is the indexing feed direction. The indexing unit 150 moves the holding table 110 in the Y-axis direction in the embodiment. The indexing and feeding unit 150 is installed on the device main body 101 of the processing device 100 in the embodiment. The indexing unit 150 supports the Y-axis moving plate 115 so as to be movable in the Y-axis direction.

The condensing point position adjusting unit 160 moves the condensing point (processing point) of the laser beam 121 condensed by the condenser of the laser beam irradiation unit 120 in the optical axis direction perpendicular to the holding surface 111 of the holding table 110. It is a unit that moves and adjusts the height position of the focal point. More specifically, the focal point position adjusting unit 160 relatively moves the holding table 110 and the laser beam irradiation unit 120 in the Z-axis direction, which is the focal point position adjusting direction. In the embodiment, the focal point position adjusting unit 160 moves at least the concentrator of the laser beam irradiation unit 120 in the Z-axis direction. In the embodiment, the condensing point position adjusting unit 160 is installed on an upright wall portion 102 erected from the device main body 101 of the processing device 100 . The condensing point position adjusting unit 160 supports at least the concentrator of the laser beam irradiation unit 120 so as to be movable in the Z-axis direction.

The processing feed unit 140, the index feed unit 150, and the focal point position adjustment unit 160 each include, for example, a known ball screw, a known pulse motor, and a known guide rail. A ball screw is rotatably provided around an axis. The pulse motor rotates the ball screw around its axis. A guide rail of the processing feed unit 140 supports the X-axis direction moving plate 114 so as to be movable in the X-axis direction. A guide rail of the processing feed unit 140 is fixed to the Y-axis direction moving plate 115 . The guide rails of the indexing unit 150 support the Y-axis moving plate 115 so as to be movable in the Y-axis direction. A guide rail of the indexing feed unit 150 is fixed to the apparatus main body 101 . The guide rail of the focal point position adjusting unit 160 supports at least the concentrator of the laser beam irradiation unit 120 so as to be movable in the Z-axis direction. A guide rail of the condensing point position adjusting unit 160 is fixed to the standing wall portion 102 .

The display unit 170 is a display section configured by a liquid crystal display device or the like. The display unit 170 displays, for example, a processing condition setting screen, the state of the wafer 10 imaged by the imaging unit 130, the state of the processing operation, and the like on the display surface. When the display surface of display unit 170 includes a touch panel, display unit 170 may include an input section. The input unit can receive various operations such as registration of processing content information by the operator. The input unit may be an external input device such as a keyboard. Information and images displayed on the display surface of the display unit 170 are switched by an operation from an input unit or the like. The display unit 170 may include an alerting device. The notification device emits at least one of sound and light to notify the operator of the processing device 100 of predetermined notification information. The notification device may be an external notification device such as a speaker or light emitting device.

The control unit 180 controls each component of the processing apparatus 100 described above to cause the processing apparatus 100 to perform processing operations on the wafer 10 . The control unit 180 controls the laser beam irradiation unit 120 , the imaging unit 130 , the processing feed unit 140 , the index feed unit 150 , the focal point position adjustment unit 160 and the display unit 170 .

The control unit 180 is a computer including an arithmetic processing device as arithmetic means, a storage device as storage means, and an input/output interface device as communication means. The arithmetic processing unit includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has memory such as ROM (Read Only Memory) or RAM (Random Access Memory). The arithmetic processing unit performs various arithmetic operations based on a predetermined program stored in the storage device. The arithmetic processing unit outputs various control signals to the components described above via the input/output interface device according to the calculation results, thereby controlling the processing apparatus 100 .

Control unit 180 includes storage section 181 . The storage unit 181 stores an image 131 captured by the imaging unit 130 (for example, the image 131-1 in FIG. 5, the image 131-2 in FIG. 7, or the image 131-3 in FIG. 9). The storage unit 181 stores the position on the wafer 10 of the imaging region 30 (for example, see FIGS. 4 to 9) where the image 131 is captured. The position on the wafer 10 is stored, for example, based on an XY coordinate system based on markers or the like set on the surface 12 of the wafer 10 .

Next, a method for checking the wafer 10 according to the embodiment will be described. FIG. 3 is a flow chart diagram showing the flow of the confirmation method for the wafer 10 according to the embodiment. The confirmation method of the wafer 10 of the embodiment includes a holding step 1, a positioning step 2, an imaging step 3, a storing step 4, and a processing step 5.

The holding step 1 is a step of holding the wafer 10 with the surface 12 side of the wafer 10 exposed. In the holding step 1 of the embodiment, the rear surface 15 side of the wafer 10 is suction-held via the tape 21 on the holding surface 111 of the holding table 110 of the processing apparatus 100, as shown in FIG. At this time, the surface 12 of the wafer 10 is fixed to the holding surface 111 of the holding table 110 by clamping the frame 20 downward from the surface 12 of the wafer 10 and fixing it with the clamping portion 112 .

Note that, in the embodiment, the wafer 10 held in the holding step 1 has the surface 12 of the region where the devices 14 are formed covered with the film 16 . It is assumed that the region corresponding to the dividing line 13 of the film 16 has been previously removed before the holding step 1 or after the holding step 1 and before the positioning step 2 .

The positioning step 2 is a step of positioning the imaging region 30 on the dividing line 13 set on the wafer 10 . FIG. 4 is a side view showing the state of being positioned in the first imaging region 30-1 in the positioning step 2 shown in FIG. The first imaging area 30-1 is, for example, the camera field of view of the imaging unit 130 including the position of the processing point to be irradiated with the laser beam 121 first among the division lines 13 of the wafer 10. FIG.

In the positioning step 2, the holding table 110 holding the wafer 10 is moved to the imaging position located below the imaging unit 130 by the processing feed unit 140 and the index feed unit 150 . Next, by imaging the wafer 10 with the imaging unit 130 , the planned division lines 13 are detected. When the division line 13 is detected, the imaging unit 130 is aligned with the first imaging area 30-1 including the position of the processing point to be irradiated with the laser beam 121 first among the division lines 13 of the wafer 10. perform the alignment to be performed.

The imaging step 3 is a step of imaging the imaging region 30 including the dividing line 13 set on the surface 12 of the wafer 10 . FIG. 5 is a diagram showing an example of an image 131-1 captured in the first imaging area 30-1 shown in FIG. In the imaging step 3, while moving the imaging area 30 and the wafer 10 by the imaging unit 130 relatively in a direction parallel to the direction along the line 13 to be divided, the imaging area 30 that changes along with the movement is periodically imaged. do. Note that the direction along the planned division line 13 is the X-axis direction, which is the processing feed direction, in the embodiment.

The storing step 4 is a step of storing the position of the image 131 captured in the imaging step 3 on the wafer 10 . More specifically, in the storing step 4, the image 131 captured in the imaging step 3 is stored, and the coordinate information of the position on the wafer 10 where the image 131 is captured is linked to the image 131 and stored.

The processing step 5 is a step of processing the wafer 10 at a processing point along the dividing line 13 . FIG. 6 is a side view showing a state in which the second imaging region 30-2 is imaged in the imaging step 3 shown in FIG. 3 and the first imaging region 30-1 is processed in the processing step 5. FIG. In the processing step 5 of the embodiment, a laser beam 121 having a wavelength that is transparent to the wafer 10 is irradiated along the dividing line 13 to the processing point, so that the inside of the wafer 10 is reformed along the dividing line 13 . A modified layer forming process for forming a modified layer 17 is performed.

In the processing step 5 of the embodiment, the focal point (processing point) of the pulsed laser beam 121 is positioned inside the wafer 10 and the laser beam 121 is irradiated from the surface 12 side of the wafer 10 . At this time, in the processing step 5, by moving the holding table 110 relative to the laser beam irradiation unit 120, the processing point of the laser beam 121 and the wafer 10 are aligned in a direction parallel to the direction along the dividing line 13. , the laser beam 121 is irradiated.

The processing point irradiated with the laser beam 121 is positioned on the planned dividing line 13 after being imaged in the imaging step 3 . Also, at a certain point in time, the processing point is located at a constant distance from the imaging area 30 by the imaging unit 130 . That is, as shown in FIG. 6, when the imaging unit 130 images the second imaging region 30-2, the laser beam irradiation unit 120 detects the first imaged before the second imaging region 30-2. A laser beam 121 is applied to the planned division line 13 of the imaging area 30-1 of .

The captured image 131-2 of the second region 30-2 is stored by the storage unit 181 together with the positional information on the wafer 10. FIG. After processing the planned division lines 13 of the first imaging region 30-1, the laser beam irradiation unit 120 processes the planned division lines 13 of the second imaging region 30-2. At this time, the image capturing unit 130 captures the image of the image capturing area 30 including the planned division line 13 ahead of the second image capturing area 30-2.

In this manner, in the imaging step 3, the storing step 4, and the processing step 5, after the relative movement between the imaging region 30 and the wafer 10 is started, the modified layer 17 is formed along all the dividing lines 13. It is executed repeatedly until it is formed and the move ends. The processing step 5 is performed later than the imaging step 3 and the storing step 4 by the distance between the processing point of the laser beam 121 and the imaging region 30 at a certain point on the planned division line 13 .

FIG. 7 is a diagram showing an example of an image 131-2 captured in the second imaging area 30-2 shown in FIG. As shown in FIG. 7, the dividing line 13 imaged in the second imaging region 30-2 has a portion 16-1 where the film 16 covering the device 14 protrudes. If a foreign substance such as the film 16 exists on the dividing line 13 as described above, there is a possibility that a problem may occur when the laser beam 121 is irradiated.

In the embodiment, since the storage unit 181 stores the image 131-2 obtained by imaging the second imaging region 30-2, it is possible to check the planned division line 13 immediately before the processing after the processing is completed. For example, in the case of the example shown in FIG. 7, it can be confirmed that there is a portion 16-1 where the film 16 protrudes from the scheduled division line 13 immediately before processing. can be determined to be defective.

FIG. 8 is a side view showing a state in which the third imaging region 30-3 is processed in processing step 5 shown in FIG. FIG. 9 is a diagram showing an example of an image picked up in the third imaging area 30-3 shown in FIG. As shown in FIG. 9, dust 13-1 is attached to the planned dividing line 13 captured in the third imaging region 30-3. If a foreign object such as dust 13-1 is present on the line 13 to be divided in this way, there is a possibility that a problem will occur when the laser beam 121 is irradiated.

In the embodiment, since the storage unit 181 stores the image 131-3 obtained by imaging the third imaging region 30-3, it is possible to check the planned dividing line 13 immediately before the processing after the processing is completed. For example, in the case of the example shown in FIG. 9, since it can be confirmed that the dust 13-1 is attached to the planned dividing line 13 immediately before processing, it is not the processing defect caused by the processing apparatus 100, but the processing defect caused by the previous process. can be determined to exist.

As described above, the method for checking the wafer 10 according to the embodiment captures an image of the line to be divided 13 before being processed, and processes the line to be divided 13 immediately after the image is captured. Specifically, the position of the processing point is maintained constant at a predetermined distance in the processing feed direction with respect to the imaging area 30 that captures the dividing line 13 . The captured image 131 is stored together with the positional information on the wafer 10 where the image was captured.

As a result, when a processing defect occurs in the wafer 10, it is possible to check the state of the planned division line 13 before the processing of the defective portion, thereby reducing the time required to isolate the cause of the defect. It has the effect of being able to For example, the control unit 180, when the coordinate position and the number of lines of the location where the defect occurs is input to the input unit of the processing apparatus 100, calls the corresponding image 131 from the storage unit 181 and displays it on the display unit of the display unit 170. may have functions.

It should be noted that the present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the gist of the present invention. For example, in the embodiment, in the processing step 5, modified layer formation processing is performed by stealth dicing, but in the present invention, groove formation processing or the like by ablation may be performed. Moreover, the processing device 100 is not limited to the laser processing device of the embodiment, and may be, for example, a cutting device in the present invention.

Further, the imaging area 30 imaged in the imaging step 3 does not have to be imaged so as to include all the division lines 13 of the wafer 10 and one line is connected, and may be imaged by thinning out at predetermined intervals.

REFERENCE SIGNS LIST 10 Wafer 12 Surface 13 Scheduled Division Line 17 Modified Layer 30, 30-1, 30-2, 30-3 Imaging Area 121 Laser Beam 131, 131-1, 131-2, 131-3 Image

Claims (3)

A method for checking a wafer having a plurality of planned division lines set on its surface, comprising:
a holding step of holding the wafer with the surface side of the wafer exposed;
a positioning step of positioning the imaging area on the line to be divided set on the surface of the wafer;
an imaging step of imaging the imaging region including the planned division line while relatively moving the imaging region and the wafer in a direction parallel to the direction along the planned division line;
a storage step of storing the position in the wafer of the image captured in the imaging step;
including
After being imaged in the imaging step, the processing point located on the line to be divided and at a certain distance from the imaging area and the wafer are relatively moved in a direction parallel to the direction along the line to be divided. while further comprising a processing step of processing the wafer at the processing point along the planned division line,
Wafer confirmation method. In the processing step, the wafer is processed by irradiating the processing point with a laser beam along the dividing line,
The method for checking a wafer according to claim 1. In the processing step, a modified layer is formed inside the wafer along the line to divide by irradiating the processing point along the line to divide the wafer with a laser beam having a wavelength that is transparent to the wafer. characterized by forming
3. The wafer checking method according to claim 2.

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