How to check wafers

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

[Technical Field]

[0001] The present invention relates to a wafer verification method. [Background technology]

[0002] As methods for dividing a semiconductor wafer having devices formed on its surface into chips, there have been proposed a method in which a laser beam is irradiated along a planned dividing line formed on the wafer to ablate the wafer and divide it (see Patent Document 1), and a method in which a modified layer is formed inside the wafer as a dividing starting point and an external force is applied to divide it (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-320466 [Patent Document 2] Patent No. 3408805 Summary of the Invention [Problem to be solved by the invention]

[0004] However, for example, a wafer manufactured in a front-end process and then sent to a back-end process may be a defective wafer due to the presence of structures, films, dust, or the like that should not be present on the dividing line. In this case, the wafer cannot be divided reliably by irradiating it with a laser beam, resulting in a processing defect. After a processing defect occurs, it becomes difficult to determine whether the processing defect is caused by the laser processing device or by a processing defect caused by a front-end process. This investigation takes time, resulting in a problem of reduced productivity.

[0005] The present invention has been made in consideration of the above problems, and its object is to provide a wafer checking method that can reduce the time required for determining which process is causing a wafer processing defect. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a wafer checking method of the present invention is a method for checking a wafer having a plurality of planned dividing lines set on its surface, and includes a holding step of holding the wafer with the front surface side of the wafer exposed, a positioning step of positioning an imaging area on the planned dividing lines set on the surface of the wafer, an imaging step of imaging the imaging area including the planned dividing lines while relatively moving the imaging area and the wafer in a direction parallel to a direction along the planned dividing lines, and a storage step of storing a position on the wafer of the image taken in the imaging step, In the same direction as the relative movement direction between the imaging area and the wafer in the imaging step While relatively moving a processing point located at a predetermined distance from the wafer in a direction parallel to the direction along the planned dividing line, The processing point is positioned a certain distance behind the imaging area in the relative movement direction, The method further includes a processing step of processing the wafer at the processing points along the planned dividing lines.

[0007] In the wafer checking method of the present invention, the processing step may process the wafer by irradiating the processing point with a laser beam along the intended dividing line.

[0008] Furthermore, in the wafer confirmation method of the present invention, the processing step may involve irradiating the processing point along the intended dividing line with a laser beam of a wavelength that is transparent to the wafer, thereby forming a modified layer inside the wafer along the intended dividing line. [Effects of the Invention]

[0009] The present invention can reduce the time required for determining which process caused the wafer processing defect. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a perspective view showing an example of the configuration of a processing device for carrying out a wafer checking method according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing an example of a wafer to be checked by the wafer checking method according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing the flow of the wafer checking method according to the embodiment. [Figure 4] FIG. 4 is a side view showing a state where the imaging area is positioned in the first imaging area in the positioning step shown in FIG. [Figure 5] FIG. 5 is a diagram showing an example of an image captured in the first imaging region shown in FIG. [Figure 6] FIG. 6 is a side view showing a state in which the second imaging region is imaged in the imaging step shown in FIG. 3 and the first imaging region is processed in the processing step. [Figure 7] FIG. 7 is a diagram showing an example of an image captured in the second imaging region shown in FIG. [Figure 8] FIG. 8 is a side view showing a state in which the third imaging region is processed in the processing step shown in FIG. [Figure 9] FIG. 9 is a diagram showing an example of an image captured in the third imaging region shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0012] [Embodiment] A method for checking a wafer 10 according to an embodiment of the present invention will be described with reference to the drawings. First, a configuration example of a processing device 100 for implementing the method for checking a wafer 10 according to the embodiment and an example of a wafer 10 to be checked will be described. FIG. 1 is a perspective view showing an example of the configuration of a processing device 100 for implementing the method for checking a wafer 10 according to the embodiment. FIG. 2 is a perspective view showing an example of a wafer 10 to be checked by the method for checking a wafer 10 according to the embodiment.

[0013] In the following description, the X-axis direction is one direction on a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on a horizontal plane. The Z-axis direction is a direction perpendicular 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.

[0014] As shown in FIG. 1 , the processing apparatus 100 is a laser processing apparatus 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 indexing feed unit 150, a focal point position adjustment unit 160, a display unit 170, and a control unit 180. The processing apparatus 100 according to the embodiment processes the wafer 10 by irradiating the wafer 10 held on the holding table 110 with a laser beam 121 using the laser beam irradiation unit 120. The processing of the wafer 10 by the processing apparatus 100 includes, for example, a modified layer forming process for forming a modified layer 17 inside the wafer 10 by stealth dicing, a groove forming process for forming grooves in the front surface 12 of the wafer 10, or a cutting process for cutting the wafer 10 along planned division lines 13.

[0015] 2 is a wafer such as a disk-shaped semiconductor device wafer or optical device wafer, having a substrate 11 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), lithium tantalate (LiTa3), or the like. The wafer 10 has a plurality of dividing lines 13 set in a grid pattern on a surface 12 of the substrate 11, and devices 14 formed in areas defined by the dividing lines 13.

[0016] The device 14 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), or an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The surface of the wafer 10 opposite to the front surface 12 on which the device 14 is formed is referred to as the back surface 15.

[0017] The wafer 10 is divided into individual devices 14 along the planned division lines 13 and singulated into chips. Note that the wafer 10 is not limited to the embodiment, and does not have to be disk-shaped in the present invention. The wafer 10 is supported within an opening of the frame 20, for example, with an annular frame 20 attached and a tape 21 having a diameter larger than the outer diameter of the wafer 10 attached to the back surface 15 of the wafer 10.

[0018] The holding table 110 shown in FIG. 1 holds the wafer 10 on a holding surface 111. The holding surface 111 has a disk shape made of porous ceramic or the like. In this embodiment, the holding surface 111 is a plane parallel to the horizontal direction. The holding surface 111 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 110 holds the wafer 10 placed on the holding surface 111 by suction. A plurality of clamps 112 are arranged around the holding table 110 to clamp a frame 20 that supports the wafer 10.

[0019] The holding table 110 is rotated about an axis parallel to the Z-axis direction by a rotation unit 113. The rotation unit 113 is supported by an X-axis direction moving plate 114. The rotation unit 113 and the holding table 110 are moved in the X-axis direction by a 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 an indexing feed unit 150 via the X-axis direction moving plate 114, the processing feed unit 140, and the Y-axis direction moving plate 115.

[0020] 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 the laser beam 121, a condenser, and various optical components that are provided on the optical path of the laser beam 121 between the laser oscillator and the condenser. The condenser condenses the laser beam 121 that is emitted from the laser oscillator and propagated through the various optical components onto the wafer 10 held on the holding surface 111 of the holding table 110, and irradiates the wafer 10 with the laser beam.

[0021] The imaging unit 130 captures an image of 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 captures an image of the wafer 10 held on the holding table 110. The imaging unit 130 is fixed, for example, at a position a predetermined distance from the condenser of the laser beam irradiation unit 120 so as to be adjacent to the condenser in the processing feed direction. An imaging region 30 (see, for example, FIGS. 4 to 9) captured by the imaging unit 130 is located forward in the processing feed direction from the processing point by the laser beam 121 irradiated by the laser beam irradiation unit 120. The imaging unit 130 captures an image of the wafer 10 in the imaging region and outputs the obtained image 131 (see, for example, FIGS. 5, 7, and 9) to the control unit 180.

[0022] The processing feed unit 140 is a unit that moves the holding table 110 and the laser beam irradiation unit 120 relatively in the X-axis direction, which is the processing feed direction. In the embodiment, the processing feed unit 140 moves the holding table 110 in the X-axis direction. In the embodiment, the processing feed unit 140 is installed on the device body 101 of the processing device 100. The processing feed unit 140 supports the X-axis moving plate 114 so that it can move freely in the X-axis direction.

[0023] The indexing feed unit 150 is a unit that moves the holding table 110 and the laser beam irradiation unit 120 relatively in the Y-axis direction, which is the indexing feed direction. In this embodiment, the indexing feed unit 150 moves the holding table 110 in the Y-axis direction. In this embodiment, the indexing feed unit 150 is installed on the apparatus body 101 of the processing apparatus 100. The indexing feed unit 150 supports a Y-axis moving plate 115 so that it can move freely in the Y-axis direction.

[0024] The focal point position adjustment unit 160 is a unit that moves the focal point (processing point) of the laser beam 121 focused 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, thereby adjusting the height position of the focal point. More specifically, the focal point position adjustment unit 160 moves the holding table 110 and the laser beam irradiation unit 120 relatively in the Z-axis direction, which is the focal point position adjustment direction. In the embodiment, the focal point position adjustment unit 160 moves at least the condenser of the laser beam irradiation unit 120 in the Z-axis direction. In the embodiment, the focal point position adjustment unit 160 is installed on the upright wall portion 102 that stands upright from the apparatus body 101 of the processing apparatus 100. The focal point position adjustment unit 160 supports at least the condenser of the laser beam irradiation unit 120 so that it can be moved in the Z-axis direction.

[0025] The processing feed unit 140, the indexing feed unit 150, and the focal point position adjustment unit 160 each include, for example, a well-known ball screw, a well-known pulse motor, and a well-known guide rail. The ball screw is rotatable about its axis. The pulse motor rotates the ball screw about its axis. The guide rail of the processing feed unit 140 supports the X-axis moving plate 114 so that it can move in the X-axis direction. The guide rail of the processing feed unit 140 is fixed to the Y-axis moving plate 115. The guide rail of the indexing feed unit 150 supports the Y-axis moving plate 115 so that it can move in the Y-axis direction. The guide rail of the indexing feed unit 150 is fixed to the device body 101. The guide rail of the focal point position adjustment unit 160 supports at least the condenser of the laser beam irradiation unit 120 so that it can move in the Z-axis direction. The guide rails of the light-converging point position adjusting unit 160 are fixed to the vertical wall portion 102 .

[0026] The display unit 170 is a display unit configured with 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, etc. on the display surface. If the display surface of the display unit 170 includes a touch panel, the display unit 170 may also include an input unit. The input unit can accept various operations, such as an operator registering processing content information. The input unit may be an external input device such as a keyboard. The information and images displayed on the display surface of the display unit 170 can be switched by operations from the input unit or the like. The display unit 170 may also include an alarm device. The alarm device emits at least one of sound and light to notify the operator of the processing apparatus 100 of predetermined alarm information. The alarm device may be an external alarm device such as a speaker or a light-emitting device.

[0027] The control unit 180 controls each of the above-mentioned components of the processing apparatus 100, causing 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 indexing feed unit 150, the focal point position adjustment unit 160, and the display unit 170.

[0028] The control unit 180 is a computer including an arithmetic processing device as a calculation means, a storage device as a storage means, and an input / output interface device as a communication means. The arithmetic processing device includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The arithmetic processing device performs various calculations based on predetermined programs stored in the storage device. In accordance with the calculation results, the arithmetic processing device outputs various control signals to the above-mentioned components via the input / output interface device, thereby controlling the processing apparatus 100.

[0029] The control unit 180 includes a storage unit 181. The storage unit 181 stores an image 131 captured by the imaging unit 130 (for example, image 131-1 in FIG. 5, image 131-2 in FIG. 7, or 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 was captured. The position on the wafer 10 is stored based on, for example, an XY coordinate system based on a marker or the like set on the surface 12 of the wafer 10.

[0030] Next, a method for checking the wafer 10 according to the embodiment will be described. Fig. 3 is a flowchart showing the flow of the method for checking the wafer 10 according to the embodiment. The method for checking the wafer 10 according to the embodiment includes a holding step 1, a positioning step 2, an imaging step 3, a storage step 4, and a processing step 5.

[0031] The holding step 1 is a step of holding the wafer 10 with the front surface 12 side of the wafer 10 exposed. In the holding step 1 of the embodiment, as shown in Fig. 4 described later, the back surface 15 side of the wafer 10 is suction-held via tape 21 on a holding surface 111 of a holding table 110 of a processing apparatus 100. At this time, the frame 20 is pressed down below the front surface 12 of the wafer 10 and fixed by a clamp portion 112, whereby the front surface 12 of the wafer 10 is fixed to the holding surface 111 of the holding table 110.

[0032] In this embodiment, the wafer 10 held in the holding step 1 has a surface 12 in an area where the devices 14 are to be formed covered with a film 16. The area of the film 16 corresponding to the planned dividing lines 13 is removed in advance before the holding step 1, or after the holding step 1 and before the positioning step 2.

[0033] Positioning step 2 is a step of positioning the imaging area 30 on the planned dividing line 13 set on the wafer 10. Fig. 4 is a side view showing the state where the imaging area 30 is positioned on the first imaging area 30-1 in positioning step 2 shown in Fig. 3. The first imaging area 30-1 is, for example, the field of view of the camera of the imaging unit 130 that includes the position of the processing point on the planned dividing line 13 of the wafer 10 where the laser beam 121 is first irradiated.

[0034] In positioning step 2, the holding table 110 holding the wafer 10 is moved to an imaging position located below the imaging unit 130 by the processing feed unit 140 and the indexing feed unit 150. Next, the wafer 10 is imaged by the imaging unit 130 to detect the planned dividing lines 13. Once the planned dividing lines 13 have been detected, alignment is performed to align the imaging unit 130 with a first imaging region 30-1, which includes the position of the processing point on the planned dividing lines 13 of the wafer 10 where the laser beam 121 is first irradiated.

[0035] The imaging step 3 is a step of imaging an imaging region 30 including the planned dividing lines 13 set on the front surface 12 of the wafer 10. Fig. 5 is a diagram showing an example of an image 131-1 captured in the first imaging region 30-1 shown in Fig. 4. In the imaging step 3, the imaging region 30 and the wafer 10 are moved relatively by the imaging unit 130 in a direction parallel to the direction along the planned dividing lines 13, and images of the imaging region 30 that change with the movement are periodically captured. Note that the direction along the planned dividing lines 13 is the X-axis direction, which is the processing feed direction, in this embodiment.

[0036] The storage step 4 is a step of storing the position on the wafer 10 of the image 131 captured in the imaging step 3. More specifically, in the storage step 4, the image 131 captured in the imaging step 3 is stored, and coordinate information of the position on the wafer 10 where the image 131 was captured is stored in association with the image 131.

[0037] Processing step 5 is a step of processing the wafer 10 at a processing point along the planned dividing line 13. Fig. 6 is a side view showing the state in which the second imaging region 30-2 is imaged in imaging step 3 shown in Fig. 3 and the first imaging region 30-1 is processed in processing step 5. In processing step 5 of the embodiment, a laser beam 121 having a wavelength that is transparent to the wafer 10 is irradiated onto the processing point along the planned dividing line 13, thereby performing modified layer formation processing to form a modified layer 17 inside the wafer 10 along the planned dividing line 13.

[0038] In 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 front surface 12 side of the wafer 10. At this time, in processing step 5, the holding table 110 is moved relatively to the laser beam irradiation unit 120, so that the processing point of the laser beam 121 and the wafer 10 are moved in a direction parallel to the direction along the planned dividing lines 13, while the laser beam 121 is irradiated.

[0039] The processing point irradiated with the laser beam 121 is located on the planned division line 13 after being imaged in the imaging step 3. Furthermore, at a certain point in time, the processing point is located at a certain distance from the imaged region 30 captured by the imaging unit 130. That is, as shown in Fig. 6, when the imaging unit 130 captures an image of the second imaging region 30-2, the laser beam irradiation unit 120 irradiates the laser beam 121 onto the planned division line 13 of the first imaging region 30-1, which was imaged before the second imaging region 30-2.

[0040] The image 131-2 of the captured second region 30-2 is stored in the storage unit 181 together with information about its position on the wafer 10. After processing the planned dividing line 13 in the first imaging region 30-1, the laser beam irradiation unit 120 processes the planned dividing line 13 in the second imaging region 30-2. At this time, the imaging unit 130 captures an image of the imaging region 30 including the planned dividing line 13 in front of the second imaging region 30-2.

[0041] In this way, the imaging step 3, the storage step 4, and the processing step 5 are repeatedly performed from the start of the relative movement between the imaging region 30 and the wafer 10 until the movement is completed when the modified layers 17 are formed along all of the planned dividing lines 13. The processing step 5 is performed at a point on the planned dividing lines 13, delayed from the imaging step 3 and the storage step 4 by the distance between the processing point of the laser beam 121 and the imaging region 30.

[0042] Fig. 7 is a diagram showing an example of an image 131-2 captured in the second imaging region 30-2 shown in Fig. 6. As shown in Fig. 7, the planned division line 13 captured in the second imaging region 30-2 has a protruding portion 16-1 of the film 16 covering the device 14. If a foreign object such as the film 16 exists on the planned division line 13 in this way, problems may occur when the laser beam 121 is irradiated.

[0043] In the embodiment, the image 131-2 captured from the second imaging region 30-2 is stored in the storage unit 181, so that after the processing is completed, it is possible to check the planned division line 13 immediately before processing. For example, in the example shown in Fig. 7, it is possible to check that there is a protruding portion 16-1 of the film 16 on the planned division line 13 immediately before processing, so that it can be determined that the processing defect is not due to the processing device 100 but is due to the previous process.

[0044] 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. 3. Fig. 9 is a diagram showing an example of an image captured in the third imaging region 30-3 shown in Fig. 6. As shown in Fig. 9, dust 13-1 is attached to the planned division line 13 captured in the third imaging region 30-3. If foreign matter such as dust 13-1 is present on the planned division line 13 in this way, problems may occur when the laser beam 121 is irradiated.

[0045] In the embodiment, the storage unit 181 stores the image 131-3 captured from the third imaging region 30-3, and therefore, after the processing is completed, it is possible to check the planned division line 13 immediately before processing. For example, in the example shown in Fig. 9, it can be confirmed that dust 13-1 is attached to the planned division line 13 immediately before processing, and therefore it can be determined that the processing defect is not due to the processing device 100 but due to a previous process.

[0046] As described above, the method for checking the wafer 10 according to the embodiment involves imaging the planned dividing lines 13 before they are processed, and processing the planned dividing lines 13 immediately after the image is captured. Specifically, the position of the processing point is kept constant at a predetermined distance in the processing feed direction from the imaging area 30 that images the planned dividing lines 13. The captured image 131 is stored together with information about the position on the wafer 10 where the image was captured.

[0047] This makes it possible to check the state of the planned dividing line 13 before processing at the location where the defect occurred when a processing defect occurs on the wafer 10, thereby achieving the effect of reducing the time required to isolate the cause of the defect. For example, the control unit 180 may have a function of calling up the corresponding image 131 from the storage unit 181 and displaying it on the display unit of the display unit 170 when the coordinate position, the number of lines, etc. of the location where the defect occurred are input to the input unit of the processing apparatus 100.

[0048] The present invention is not limited to the above-described embodiment. That is, various modifications can be made without departing from the gist of the present invention. For example, in the embodiment, modified layer formation processing is performed by stealth dicing in processing step 5, but in the present invention, groove formation processing by ablation or the like may also be performed. Furthermore, the processing apparatus 100 is not limited to the laser processing apparatus of the embodiment, and in the present invention, it may be, for example, a cutting apparatus.

[0049] Furthermore, the imaging area 30 imaged in imaging step 3 does not have to be imaged so as to include all of the planned dividing lines 13 of the wafer 10 and connect one line, but may be imaged by thinning out at predetermined intervals. [Explanation of symbols]

[0050] 10 wafers 12 Surface 13 Planned division line 17 Modified layer 30, 30-1, 30-2, 30-3 Imaging area 121 Laser Beam 131, 131-1, 131-2, 131-3 Images

Claims

1. A method for checking a wafer having a plurality of planned dividing lines set on its surface, comprising: a holding step of holding the wafer with the front surface side of the wafer exposed; a positioning step of positioning an imaging area on the planned dividing line set on the surface of the wafer; an imaging step of imaging the imaging area including the planned dividing line while relatively moving the imaging area and the wafer in a direction parallel to a direction along the planned dividing line; a storing step of storing the position on the wafer of the image captured in the imaging step; Including, The method further includes a processing step of relatively moving the wafer and a processing point located on the planned dividing line after being imaged in the imaging step and at a fixed distance from the imaging area in the same direction as the relative movement direction between the imaging area and the wafer in the imaging step in a direction parallel to the direction along the planned dividing line, positioning the processing point at a fixed distance behind the imaging area in the relative movement direction, and processing the wafer at the processing point along the planned dividing line. How to check wafers.

2. In the processing step, a laser beam is irradiated to the processing point along the planned dividing line to process the wafer. The wafer checking method according to claim 1 .

3. In the processing step, a laser beam having a wavelength that is transparent to the wafer is irradiated to the processing point along the intended dividing line, thereby forming a modified layer along the intended dividing line inside the wafer. The wafer checking method according to claim 2.

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