Wire saw measuring device and measuring method

Abstract

To provide a measurement device and a measurement method of a wire saw which simply and highly accurately measure a degree of parallelization of a wire row using a photographic image of a camera, and can determine its propriety.SOLUTION: A measurement device 20 of a wire saw includes: a base plate 21 which is mounted on a lifting device 7 provided above a wire row 3A for slicing a workpiece; a camera 22 which is mounted on the base plate 21 and photographs the wire row 3A; a slide mechanism 24 for slidably supporting the camera 22 in a direction parallel to the wire raw 3A; and a reference member 25 which is provided at a position reflected into the photographic image of the camera 22, and defines a reference line as a reference of a degree of parallelization of the wire raw 3A in the photographic image.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a measuring device and a measuring method used for adjusting the wire array of a wire saw. [Background technology]

[0002] Silicon wafers are produced by processing a single crystal ingot pulled from the melt using the Czochralski method into a cylindrical shape, followed by slicing, lapping, polishing, and other processes. In the single crystal ingot slicing process, a slicing table is attached to the circumferential surface of the ingot, and a work plate is attached to the top of the slicing table. The ingot is then attached to a wire saw via the work plate, and sliced ​​together with the slicing table.

[0003] The crystal orientation of a single crystal ingot varies somewhat and does not necessarily coincide with the central axis of the ingot. Therefore, if a work plate is attached to the ingot along its central axis and then attached to a wire saw to slice it, the cut surfaces of the wafers cut from the ingot do not coincide with the crystal lattice planes, resulting in variations in wafer characteristics. One common method to solve this problem is an off-site setup method in which the crystal orientation is adjusted before the single crystal ingot is attached to the wire saw (see Patent Document 1). The off-site setup method involves adjusting the crystal orientation by rotating the ingot around its central axis on the slicing table when the ingot is attached to the work plate via a slicing table, and then adjusting the crystal orientation by changing the angle at which the ingot is attached to the work plate.

[0004] Regarding a method for adjusting the position of a wire in a wire saw, for example, Patent Document 2 describes a method in which distance sensors are provided on both the left and right sides of the wire, and the distance sensors directly detect the wire spacing and the relative displacement of the entire wire relative to the workpiece, and the guide rollers are adjusted to maintain the wire spacing appropriately.

[0005] Patent Document 3 also describes a wire saw having a configuration in which a work jig can be attached and detached to a work support portion via a clamping member, in which a measuring jig is provided in place of the work jig. The measuring jig is provided with a camera for detecting the position of the wire between the main rollers of the wire saw, and the position of the work support portion is adjusted based on the wire position detected by the camera, thereby setting the clamping member at a predetermined position relative to the wire. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-24145 [Patent Document 2] Japanese Patent Application Publication No. 9-109143 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-183615 Summary of the Invention [Problem to be solved by the invention]

[0007] The conventional measuring jig described in Patent Document 3 can detect the position of the wires from images captured by a camera, but it was difficult to measure the parallelism of the wire rows simply and with high precision and determine whether it was appropriate.

[0008] Therefore, an object of the present invention is to provide a wire saw measuring device and measuring method that can easily and accurately measure the parallelism of wire rows using images captured by a camera and determine whether or not it is appropriate. [Means for solving the problem]

[0009] In order to solve the above problem, the wire saw measuring device according to the present invention includes a base plate attached to an elevator device provided above a wire array that slices a workpiece; Attached toThe system is characterized by comprising a camera that photographs the wire array, a sliding mechanism that supports the camera so that the camera can slide in a direction parallel to the wire array, and a reference member that is positioned so that it appears in the image captured by the camera and defines a reference line within the image that serves as a standard for the parallelism of the wire array.

[0010] According to the present invention, the parallelism of the wire rows can be measured easily and with high precision from the positional relationship between the reference member and the wires shown in the image captured by the camera, and the suitability of the parallelism can be determined.

[0011] In the present invention, it is preferable that the camera captures a first image including the wire array and the reference member in a first imaging area near one end of the wire array, and a second image including the wire array and the reference member in a second imaging area near the other end of the wire array, thereby making it possible to measure the parallelism of the wire array easily and with high accuracy and determine whether the parallelism is appropriate.

[0012] The wire saw measuring device according to the present invention preferably further includes an image processing device that processes images captured by the camera, and the image processing device processes the first image to calculate a first inter-wire distance from the reference line to the nearest wire, and processes the second image to calculate a second inter-wire distance from the reference line to the nearest wire. By calculating the first and second inter-wire distances, the parallelism of the wire array can be calculated easily and with high accuracy.

[0013] The image processing device preferably calculates a wire-to-wire distance difference, which is the difference between the first wire-to-wire distance and the second wire-to-wire distance, as the parallelism index of the wire saw. By calculating the wire-to-wire distance difference as the parallelism index of the wire saw, the parallelism of the wire array can be calculated easily and with high accuracy.

[0014] It is preferable that the image processing device includes a display, and the display displays the first image, the second image, the first inter-wire distance value, the second inter-wire distance value, and the inter-wire distance difference value, thereby making it possible to easily evaluate whether the parallelism of the wire array is appropriate.

[0015] The reference member is preferably made of a cemented carbide, which can improve the reliability of the reference line relative to the wire array.

[0016] In addition, a wire saw measurement method according to the present invention is characterized in that a reference member defining a reference line serving as a reference for the parallelism of the wire array and a camera for photographing the wire array together with the reference member are installed above the wire array of a wire saw that slices a workpiece, a first image in which the reference member is captured in a first photographing area near one end of the wire array, a second image in which the reference member is captured in a second photographing area near the other end of the wire array, the first image is processed to calculate a first inter-wire distance from the reference line to the nearest wire, the second image is processed to calculate a second inter-wire distance from the reference line to the nearest wire, and the inter-wire distance difference, which is the difference between the first inter-wire distance and the second inter-wire distance, is obtained as a parallelism index for the wire saw.

[0017] According to the present invention, the parallelism of the wire rows can be measured easily and with high precision from the positional relationship between the reference member and the wires shown in the image captured by the camera, and the suitability of the parallelism can be determined. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a wire saw measuring device and measuring method that can easily and accurately measure the parallelism of wire rows using images captured by a camera and determine whether the parallelism is appropriate. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic perspective view showing an example of the configuration of a wire saw according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic perspective view showing the relationship between the workpiece and the work plate. [Figure 3] 3(a) and (b) are schematic diagrams for explaining the parallelism of the wire array. [Figure 4]FIG. 4 is a schematic side view showing the configuration of a wire saw to which a measuring device is attached. [Figure 5] FIG. 5 is a schematic front view showing the configuration of a wire saw to which a measuring device is attached. [Figure 6] Figures 6(a) and (b) are diagrams for explaining the camera position when measuring the parallelism of the wire array, where Figure 6(a) shows the camera position when photographing the first shooting area, and Figure 6(b) shows the camera position when photographing the second shooting area. [Figure 7] Figures 7(a) and (b) are schematic diagrams for explaining a method for measuring the parallelism of a wire array, where Figure 7(a) shows an image captured in the first shooting area, and Figure 7(b) shows an image captured in the second shooting area. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] FIG. 1 is a schematic perspective view showing an example of the configuration of a wire saw according to an embodiment of the present invention.

[0022] As shown in Figure 1, the wire saw 1 includes two grooved guide rollers 2a, 2b, a wire 3 wound multiple times around the guide rollers 2a, 2b, nozzle units 4a, 4b that supply machining fluid (slurry) to the running wire 3, and a lifting device 7 that raises and lowers the workpiece 10, which is the object to be processed.

[0023] The workpiece 10 is, for example, single crystal silicon, and is a cylindrical silicon block obtained by dividing a silicon ingot into pieces of a predetermined length. Single crystal silicon allows for the mass production of large-diameter ingots, and a wire saw is particularly suitable for slicing large-diameter ingots. The diameter of the single crystal silicon ingot is preferably 200 mm or more, and particularly preferably 300 mm or more.

[0024] The wire saw 1 in this embodiment is a loose abrasive type, and performs cutting while supplying a machining fluid (slurry) with dispersed abrasive grains to the high-speed traveling wire 3. The wire 3 wound around one wire reel 5a passes through a payout roller 6a and is repeatedly wound around guide rollers 2a and 2b in this order, and then passes through a take-up roller 6b and is taken up around the other wire reel 5b.

[0025] The loose abrasive method uses a back-and-force method in which the wire 3 is unwound little by little while reversing its running direction (cross-propagation) along the way. Therefore, the wire 3 is run by alternately rotating the guide rollers 2a and 2b forward and backward. It is also possible to use a fixed abrasive method in which cutting is done with a diamond abrasive wire to which diamond abrasive grains are fixed.

[0026] The nozzle units 4a and 4b are arranged along the rotation axis direction of the guide rollers 2a and 2b, and have a plurality of nozzle holes so that machining fluid (slurry) is sprayed onto the wire array 3A stretched between the guide rollers 2a and 2b. The nozzle units 4a and 4b need to be arranged in front of the workpiece 10 in the direction of travel of the wire 3, but because the wire 3 travels in both directions, two nozzle units 4a and 4b are arranged on either side of the workpiece 10.

[0027] The workpiece 10 is placed above the wire array 3A stretched between the guide rollers 2a and 2b, and is fixed to the lifting device 7 via a slicing table 9 and a workpiece plate 8. By lowering the lifting device 7, the workpiece 10 is pressed against the traveling wire array 3A and cut.

[0028] To properly slice the workpiece 10, the central axis of the workpiece 10 must be kept horizontal. Furthermore, to ensure that the cut surface of the wafer has the desired crystal lattice plane, the workpiece 10 must be aligned so that its crystal orientation is perpendicular to the wire array 3A. Aligning the crystal orientation is performed by rotating the workpiece 10 by a predetermined angle in the circumferential direction to make the crystal orientation horizontal, and then by rotating the workpiece 10 by a predetermined angle in the horizontal direction to make the crystal orientation perpendicular to the wire array 3A. Crystal alignment is typically performed using an off-site setup method, in which the ingot is first rotated around its central axis on the slicing table when adhesively fixed to the workpiece plate via a slicing table to adjust the crystal orientation, and then the angle at which the ingot is attached to the workpiece plate is changed to adjust the crystal orientation.

[0029] FIG. 2 is a schematic perspective view showing the relationship between the workpiece 10 and the workpiece plate 8. As shown in FIG.

[0030] As shown in Figure 2, a slicing table 9 is attached with adhesive to the circumferential surface of the upper part of a cylindrical workpiece 10 placed so that its central axis is horizontal. The slicing table 9 is made of a material such as carbon that can be cut together with the workpiece 10. The underside of the slicing table 9 is formed with a curved surface that fits into the circumferential surface of the workpiece 10, improving adhesion to the workpiece 10. Furthermore, a work plate 8 is attached to the upper surface of the slicing table 9.

[0031] As shown in the figure, the normal to the crystal lattice plane of the workpiece 10, i.e., the crystal orientation 12, is inclined with respect to the central axis 13 of the workpiece 10. Typically, the inclination angle β of the crystal orientation 12 with respect to the central axis 13 of the workpiece 10 is at most about ±3°. Furthermore, the crystal orientation 12 of the workpiece 10 placed in an arbitrary orientation is not necessarily horizontal, but has an inclination angle γ with respect to the horizontal plane.

[0032] In the bonding method of this embodiment, the workpiece 10 is bonded with the mounting axis 8a of the workpiece plate 8 set parallel to the crystal orientation 12 of the workpiece 10. Here, the mounting axis 8a of the workpiece plate 8 refers to a virtual axis extending in the longitudinal direction of the workpiece plate 8, and the left and right side surfaces 8b, 8c of the workpiece plate 8, which are parallel to the longitudinal direction, are parallel to the mounting axis 8a. The mounting surface 8d of the workpiece plate 8 is a plane including the mounting axis 8a and is usually set horizontally. In the wire saw 1, the workpiece 10 is placed so that the mounting axis 8a is perpendicular to the wire array 3A. To make the crystal orientation 12 of the workpiece 10 parallel to the mounting axis 8a of the workpiece plate 8, the workpiece 10 must be rotated by a rotation angle α so that the crystal orientation 12 is horizontal, and then further rotated horizontally by an angle β. The rotation angle α can be calculated from the relationship sinα = sinγ / sinβ.

[0033] In this way, the workpiece 10 is adhesively fixed to the underside of the workpiece plate 8 via the slicing table 9. The workpiece plate 8 is attached to the clamp unit 7A of the lifting device 7 arranged above the wire array 3A. Therefore, the workpiece 10 is placed above the wire array 3A.

[0034] The guide rollers 2a and 2b, along with the wire 3, are consumables and are replaced as necessary. When the guide rollers 2a and 2b are replaced and the wire 3 is re-tensioned, the parallelism of the wire array 3A is measured. The wire array 3A is stretched parallel to the slicing direction (X direction) of the workpiece 10.

[0035] 3(a) and (b) are schematic diagrams for explaining the parallelism of the wire array 3A.

[0036] As shown in Figures 3(a) and 3(b), the wire array 3A is suspended between guide rollers 2a and 2b, each having a rotation axis parallel to the Y axis, and extends in the X-axis direction. Here, as shown in Figure 3(a), if the parallelism of the wire array 3A with respect to the X axis is high, the workpiece 10 can be sliced ​​accurately. However, as shown in Figure 3(b), if the parallelism of the wire array 3A with respect to the X axis is poor (the tilt angle θ is large), the workpiece 10 cannot be sliced ​​accurately, and the wafer surface orientation will be tilted. Therefore, it is necessary to accurately measure the parallelism of the wire array 3A and adjust the error. When measuring the parallelism, a measuring device is attached to the lifting device 7 instead of the workpiece 10.

[0037] 4 and 5 are schematic diagrams showing the configuration of the wire saw 1 to which the measuring device is attached, with FIG. 4 being a side view and FIG. 5 being a front view.

[0038] As shown in Figures 4 and 5, the measuring device 20 includes a base plate 21 that can be attached to the clamp unit 7A of the lifting device 7, a camera 22 attached to the base plate 21 and photographing the wire array 3A, a mirror 23 that changes the photographing direction of the camera 22, which is facing horizontally, to face downward, a slide mechanism 24 that slides the camera 22 in the running direction (X direction) of the wire array 3A, and a reference member 25 that is installed within the photographing area of ​​the camera 22 and defines an X-direction reference line within the photographed image of the camera 22 as a reference for the parallelism of the wire array 3A.

[0039] The camera 22 is connected to a computer 30 that functions as an image processing device, and an image captured by the camera 22, in which the wire array 3A and the reference member 25 are captured, is sent to the computer 30. The computer 30 is, for example, a personal computer, and has a well-known configuration including a PC main body, a display 31, a keyboard, a mouse, etc. The computer 30 may be the same as the computer that controls the operation of the wire saw 1, or may be a different computer.

[0040] The slide mechanism 24 is fixed to the base plate 21, and the camera 22 is attached to the base plate 21 via the slide mechanism 24. As shown by arrow D2 in Fig. 5, the camera 22 can be moved in the X direction by the slide mechanism 24. Therefore, it is possible to photograph the wire array 3A at any position in the X direction, and this can be applied to various types (sizes) of wire saws with different lengths of the wire array 3A (the distance between the guide rollers 2a and 2b).

[0041] The reference member 25 is a generally rectangular flat plate that is elongated in the X direction and is fixed to the lower end of an arm 26 that extends downward from the base plate 21. The long sides of the reference member 25 are parallel to the X direction, and an edge line 25e of the long sides (see FIGS. 6(a) and 6(b)) is used as a reference line for the parallelism of the wire array 3A. To prevent deformation of the reference member 25 and increase the reliability of the reference line, it is preferable that the material of the reference member 25 be a cemented carbide alloy containing tungsten or the like as a main component. This makes it possible to prevent deformation of the reference member 25 and increase the reliability of the reference line.

[0042] Figures 6(a) and (b) are diagrams for explaining the position of the camera 22 when measuring the parallelism of the wire array 3A, where Figure 6(a) shows the position of the camera 22 when photographing the first photographing area, and Figure 6(b) shows the position of the camera 22 when photographing the second photographing area.

[0043] As shown in Figures 6(a) and 6(b), when measuring the parallelism of the wire array 3A, a measuring device 20 is used to capture images of a first photographing area R1 set near one end of the wire array 3A and a second photographing area R2 set near the other end. For example, as shown in Figure 6(a), the camera 22 is moved close to one guide roller 2a, and then the first photographing area R1 is captured. Then, as shown in Figure 6(b), the camera 22 is moved close to the other guide roller 2b, and then the second photographing area R2 is captured.

[0044] Figures 7(a) and (b) are schematic diagrams for explaining a method for measuring the parallelism of the wire array 3A, where Figure 7(a) shows a captured image (first image) of the first shooting area R1, and Figure 7(b) shows a captured image (second image) of the second shooting area R2.

[0045] 7(a) and 7(b), in the evaluation of the parallelism of the wire array 3A, the inter-wire distances d1 and d2 from the reference line L defined by the reference member 25 to the nearest wire 3 are calculated in each of the first imaging region R1 and the second imaging region R2. Even if the wire array 3A has poor parallelism, when viewed enlarged, the wire array 3A is parallel to the reference line L, but the inter-wire distances d1 and d2 are different. Therefore, the difference Δd = |d1 - d2| between the first inter-wire distance d1 in the first imaging region R1 and the second inter-wire distance d2 in the second imaging region R2 is calculated, and this inter-wire distance difference Δd is used as an evaluation index for the parallelism of the wire array 3A. If the obtained inter-wire distance difference Δd is, for example, 60 μm or less (Δd≦60 μm), it is determined that readjustment is not necessary. If it is greater than 60 μm (Δd>60 μm), it is determined that readjustment is necessary.

[0046] The image captured by camera 22 is sent to computer 30. An application program for processing the image captured by camera 22 is installed in computer 30, and the application program processes the images captured in first imaging area R1 and second imaging area R2 to automatically calculate the inter-line distance difference Δd, and the calculation result is displayed on display 31 together with the captured images. That is, display 31 of computer 30 displays the values ​​of the first inter-line distance d1, the second inter-line distance d2, and the inter-line distance difference Δd together with the captured image of first imaging area R1 (first image 61) and the captured image of second imaging area R2 (second image 62).

[0047] The parallelism of the wire array 3A can be readjusted by shifting the axial position (Y direction) of either one of the guide rollers 2a or 2b. For example, as shown in FIG. 3(b), the parallelism of the wire array 3A can be improved by offsetting the guide roller 2b in the direction of arrow D1. As shown in FIG. 4, each of the guide rollers 2a and 2b is supported on a spindle shaft 40, which is fixed to the wire saw device housing 50 with a fixing nut (not shown). Therefore, to adjust the axial position of the guide roller 2a or 2b, first remove the wire saw cover, loosen the fixing nut on the spindle shaft 40, and adjust the rotation adjustment mechanism provided in front of the spindle shaft 40. Since rotating the rotation adjustment mechanism causes the spindle shaft 40 to move slightly in the axial direction, the spindle shaft 40 is adjusted based on the measurement results so that the wire-to-wire distance difference Δd is within, for example, ±60 μm. Then, the fixing nut is tightened to re-fix the spindle shaft 40.

[0048] As described above, the measuring device 20 of the wire saw 1 according to this embodiment includes the camera 22 that photographs the wire array 3A from directly above, the slide mechanism 24 that moves the camera 22 along the extension direction (X direction) of the wire array 3A, and the reference member 25 that is provided at a position that is reflected in the image photographed by the camera 22 and that defines, within the photographed image, the reference line L that serves as a reference for the parallelism of the wire array 3A. The camera 22 photographs a first image 61 including the wire array 3A and the reference member 25 in a first photographing area R1 near one end of the wire array 3A, and photographs a second image 62 including the wire array 3A and the reference member 25 in a second photographing area R2 near the other end of the wire array 3A. The first image 61 is processed to calculate a first inter-wire distance d1 from the reference line L to the nearest wire, and the second image 62 is processed to calculate a second inter-wire distance d2 from the reference line L to the nearest wire. Calculate Since the inter-wire distance difference Δd=|d1−d2| is calculated as the parallelism index of the wire array 3A, the parallelism of the wire array 3A can be measured easily and with high precision, and its suitability can be determined.

[0049] The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention, and it goes without saying that these modifications are also included in the scope of the present invention.

[0050] For example, in the above embodiment, the workpiece 10 is single crystal silicon, but the present invention is not limited to single crystal silicon and can be applied to various workpieces that are sliced ​​using a wire saw.

[0051] In the above embodiment, Two Although a two-axis type wire saw in which the wire 3 is passed over guide rollers 2a and 2b has been given as an example, the present invention is not limited to this configuration and may be a three-axis type in which the wire 3 is passed over three guide rollers, or a configuration in which the wire 3 is passed over four or more guide rollers. [Explanation of symbols]

[0052] 1 wire saw 2a, 2b Guide rollers 3 wire 3A wire string 4a, 4b Nozzle unit 5a, 5b Wire reel 6a Feed roller 6b Winding roller 7 Lifting device 7A Clamp Unit 8 Work Plate 8a Mounting axis 8b, 8c Side of work plate 8d Work plate mounting surface 9 slice table 10 Work 12 Crystal orientation 13 Center axis 20 Measuring Equipment 21 Base Plate 22 Camera 23. Mirror 24 Slide mechanism 25 Reference member 25e Edge Line 26 Arm 30 Computer 31 Display 40 Spindle axis 50 Device housing 61 First Image 62 Second image L reference line d1 Line distance (first line distance) d2 Line distance (second line distance) Δd Line distance difference α rotation angle β Tilt angle γ Tilt angle θ Tilt angle

Claims

1. A measuring device for measuring the parallelism of a wire row of a wire saw that slices a workpiece, a base plate attached to an elevator device provided above the wire array; a camera attached to the base plate for photographing the wire array; a slide mechanism that supports the camera so that the camera can slide in a direction parallel to the wire array; a reference member that is provided at a position that is reflected in an image captured by the camera and that defines a reference line within the captured image that serves as a reference for the parallelism of the wire array; A wire saw measuring device, characterized in that the reference member is fixed to a lower end of an arm extending downward from the base plate.

2. 2. The wire saw measuring device of claim 1, wherein the camera captures a first image including the wire array and the reference member in a first shooting area near one end of the wire array, and captures a second image including the wire array and the reference member in a second shooting area near the other end of the wire array.

3. further comprising an image processing device for processing the captured image of the camera; The image processing device includes: processing the first image to calculate a first distance from the reference line to a nearest wire; The wire saw measurement device according to claim 2 , wherein the second image is processed to calculate a second distance from the reference line to a nearest wire.

4. The image processing device includes: The wire saw measuring device according to claim 3 , wherein a line distance difference, which is a difference between the first line distance and the second line distance, is calculated as the parallelism index of the wire saw.

5. the image processing device includes a display; The wire saw measurement device according to claim 4 , wherein the display displays the first image, the second image, the first inter-wire distance value, the second inter-wire distance value, and the inter-wire distance difference value.

6. The wire saw measuring device according to claim 1 , wherein the reference member is made of a cemented carbide alloy.

7. A measurement method for measuring the parallelism of a wire row of a wire saw that slices a workpiece, comprising: a base plate is attached to an elevator device provided above the wire array, and a reference member defining a reference line that serves as a reference for the parallelism of the wire array and a camera that photographs the wire array together with the reference member are respectively installed above the wire array via the base plate; capturing a first image in which the reference member is captured in a first imaging area near one end of the wire array; taking a second image in which the reference member is captured in a second imaging area near the other end of the wire array; processing the first image to calculate a first distance from the reference line to a nearest wire; processing the second image to calculate a second distance from the reference line to a nearest wire; a line distance difference between the first line distance and the second line distance is calculated as a parallelism index of the wire saw; A wire saw measurement method, characterized in that the reference member is fixed to the lower end of an arm extending downward from a base plate attached to an elevator device provided above the wire row.

Images