JP2005243996A - Device and method for detecting holding hole of semiconductor wafer carrier and polishing method of semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for securely inserting a semiconductor wafer into a holding hole and safely performing polishing at the time of automatically polishing the wafer. <P>SOLUTION: A method detects a position of the holding hole 5 of a carrier 4 holding the wafer used when a double face polishing device polishes the semiconductor wafer. A picture processing means picture-processes data obtained by two picture detecting means 20a and 20b installed to form a prescribed center angle θ with respect to the holding hole. Two points on a boundary of the holding hole and polishing cloth 37b are detected, and the center position of the holding hole is calculated based on the detected two points and the center angle. Thus, the position of the holding hole is detected. A conveyance means sets the semiconductor wafer in the holding hole based on the detected position of the holding hole, and the wafer is polished. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a detection device and a detection method for detecting a position of a carrier holding hole for holding a wafer when a semiconductor wafer such as a silicon wafer is polished on both sides, and a method for polishing a semiconductor wafer.

  Conventionally, a single-side polishing apparatus and a double-side polishing apparatus have been used as apparatuses for polishing a semiconductor wafer such as a silicon wafer. As a general double-side polishing apparatus, a so-called 4-way type apparatus 50 using a planetary gear mechanism as shown in FIGS. 9 and 10 is known.

  When the silicon wafer W is polished by such a double-side polishing apparatus 50, the wafer W is inserted and held in a plurality of wafer holding holes 58 formed in the carrier 51. Then, the wafer W in the holding hole is sandwiched between the upper surface plate 56a and the lower surface plate 56b to which the polishing cloths 57a and 57b are respectively attached, the polishing slurry is supplied through the slurry supply hole 53, and the carrier 51 is connected to the sun gear 54 and the internal gear. Rotate and revolve with the gear 55. Thereby, both surfaces of the wafer W in each holding hole can be polished simultaneously.

  As another type of double-side polishing apparatus, for example, as shown in FIGS. 11 and 12, the carrier 31 sandwiched between upper and lower surface plates 36a and 36b (polishing cloths 37a and 37b) is not rotated. There is known a device 30 that swings so as to draw a small circle (see Patent Document 1 and Patent Document 2). A carrier 31 having a holding hole 34 is held by a carrier holder 38, and an eccentric arm 40 is rotatably attached to a bearing portion 39 of the holder 38. For example, 24 through holes (fixed holes) 44 are provided in the periphery of the carrier 31 as shown in FIG. 13, and pins 43 attached to the holder 38 as shown in FIG. The carrier 31 is fixed to the holder 38 by being inserted into the fixing hole 44.

  At the time of polishing, all the eccentric arms 40 are rotated in synchronization with the rotation shaft 41 via the timing chain 42, so that the carrier 31 held by the carrier holder 38 does not rotate and is a small circle in the horizontal plane. You can do a circular motion like drawing. Since the swing-type double-side polishing apparatus 30 can be downsized, the polishing operation can be performed in a relatively narrow space. With the recent increase in diameter of wafers, a oscillating double-side polishing apparatus 30 is often used.

  More specifically, the polishing procedure by the double-side polishing apparatus 30 will be described. For example, a box (generally called FOSB, FOUP, etc.) containing 25 wafers is an automatic transfer apparatus (AGV or the like). ) To a predetermined position and placed in a loading station (loader unit) of the double-side polishing apparatus 30. Next, after the wafer in the box is set in each holding hole 34 of the carrier 31, both surfaces of the wafer W are sandwiched between upper and lower surface plates 36a and 36b (polishing cloths 37a and 37b). The upper and lower surface plates 36 a and 36 b are rotated and the carrier 31 is swung to supply the polishing slurry from the slurry supply hole 33. The slurry reaches the lower polishing cloth 37b through the slurry passage hole 35 of the carrier 31, and both surfaces of the wafer W are simultaneously polished. After polishing for a predetermined time, the movement of the surface plates 36a and 36b and the carrier 31 is stopped. And the wafer W in the holding hole 34 is carried out to an unloading station (unloader part), maintaining a wet state, and is collect | recovered in the container (water tank) for collection | recovery.

Conventionally, the wafer is set in the carrier holding hole, and the polished wafer is manually collected from the carrier. However, in recent years, automation has progressed, and the loading of wafers in a box and unloading of wafers after polishing have been automatically performed by a transfer robot.
For example, in a double-side polishing machine with a planetary gear structure, the wafer holding surface of the carrier is recognized by a visual sensor, the position of the wafer holding hole is calculated from the recognized image data, and the position of the wafer transfer robot is controlled based on the calculation result An automatic transfer device has been proposed (see Patent Document 3).

  Further, in the swing type double-side polishing apparatus, for example, a carrier holder having a mechanical positioning function (index function) is used. If the carrier 31 has five holding holes 34 as shown in FIG. By positioning in such a manner, it is possible to set the wafers one by one at a fixed position with respect to each holding hole 34 by the transport robot. In addition, after grinding | polishing, a carrier can be similarly rotated, and a wafer can be carried out one sheet at a time by a conveyance robot.

However, even if the carrier 31 is mechanically positioned by the index, the carrier 31 may be slightly shifted from a predetermined position. There is no problem even if it is slightly deviated during unloading after polishing. For example, in the case of a carrier for a silicon wafer having a diameter of 300 mm, the holding hole is a circle having a diameter of about 301 mm. If the position of the hole is shifted by ± 1 mm or more, the wafer cannot be mechanically inserted into the holding hole. If polishing is performed in a state where the wafer is not completely in the holding hole, the wafer may be broken at the start of polishing, and the polishing cloth and even the surface plate may be damaged.
Thus, if the wafer is not set at the proper position due to the deviation of the carrier, it will cause troubles and hinder automation.

JP-A-10-202511 JP 2000-42912 A JP-A-11-207611

  In view of the problems as described above, an object of the present invention is to provide a technique capable of securely polishing a wafer by reliably inserting the wafer into a holding hole when the semiconductor wafer is automatically polished. .

  According to the present invention, there is provided a device for detecting the position of a carrier holding hole for holding the wafer used when polishing a semiconductor wafer by a double-side polishing apparatus, and at least a predetermined central angle with respect to the holding hole. Two image detecting means installed so as to form an image, and an image processing means for processing image data obtained by the image detecting means. The two image detecting means Two points on the boundary are detected and data is sent to the image processing means, and the center position of the holding hole is calculated based on the two points detected by the image detection means and the central angle. A holding hole detecting device is provided that detects the position of the holding hole (claim 1).

  With such a holding hole detection device, two image detection means detect two points at the boundary between the carrier holding hole and the polishing pad, and hold based on the two detected points and the central angle with respect to the holding hole. The position of the center of the hole can be calculated, whereby the position of the holding hole can be detected simply and accurately. Therefore, even if the position of the holding hole is slightly shifted, the wafer can be surely inserted into the holding hole by the transport robot based on the detected position of the holding hole, and automation can be made more stable.

In this case, the image detection means is preferably a CCD camera.
In the case of a CCD camera, the boundary between the carrier holding hole and the polishing pad can be detected easily and reliably, and the detection accuracy can be made higher.

It is preferable that the two image detection means are installed so as to form a central angle of 90 degrees with respect to the holding hole.
If the central angle of the two image detection units with respect to the holding hole is 90 degrees, the calculation of the center coordinates of the holding hole based on the two detected points and the central angle becomes extremely easy.

It is preferable that the holding hole detection device includes an illumination unit that illuminates a boundary between the holding hole and a polishing pad.
By illuminating the boundary between the holding hole and the polishing pad with such an illuminating means, the contrast between the carrier and the polishing pad becomes clear, and the detection of the boundary between the holding hole and the polishing pad becomes easier.

It is preferable that the holding hole detecting device has an injection unit that injects gas onto the polishing cloth in the holding hole.
If moisture at the boundary between the holding hole and the polishing pad is removed by such a jetting means, the detection error can be suppressed and the accuracy can be further improved.

In the holding hole detecting device, it is preferable that at least the image detecting means can be moved by a moving means.
If the image detecting means is movable by the moving means, the apparatus becomes more compact and the inspection can be easily performed.

  Furthermore, according to the present invention, there is provided a method for detecting the position of a carrier holding hole for holding a wafer used when polishing a semiconductor wafer by a double-side polishing apparatus, wherein a predetermined central angle is set with respect to the holding hole. The image data obtained by the two image detecting means installed so as to be formed is subjected to image processing by the image processing means to detect two points at the boundary between the holding hole and the polishing cloth, and the two detected points and the A holding hole detecting method is provided, wherein the position of the holding hole is detected by calculating the position of the center of the holding hole based on a center angle.

  By using such a method, it is possible to calculate the position of the center of the holding hole based on the two points of the boundary between the holding hole of the carrier and the polishing cloth detected by the two image detecting means and the central angle with respect to the holding hole. This makes it possible to accurately detect the position of the holding hole. Therefore, even if the holding hole is slightly deviated, the wafer can be reliably inserted into the holding hole by the transport robot based on the detected position of the holding hole.

Before performing the detection by the image detection means, the liquid existing at the boundary between the holding hole of the carrier and the polishing cloth is scattered by performing gas injection and / or rotation of the polishing cloth in the holding hole. (Claim 8).
Thus, if excess liquid is scattered before detection, detection error can be reduced and detection accuracy can be further improved.

In the method of polishing by holding the semiconductor wafer in the holding hole of the carrier by the double-side polishing apparatus, the position of the holding hole is detected by the detection method, and the semiconductor wafer is removed by the conveying means based on the detected position of the holding hole. It is preferable that the wafer is polished after being set in the holding hole.
As described above, if the wafer is set in the holding hole by the conveying means based on the position of the holding hole detected by the detection method according to the present invention, the wafer can be surely set in the holding hole, and the subsequent polishing is safe. And contributes to the complete automation of the double-side polishing process.

According to the invention, after the semiconductor wafer is set in the holding hole by the transport means, the wafer is polished after the image detecting means confirms that the wafer is set in the holding hole. (Claim 10)
After the wafer is set in this way, the safety can be further improved by confirming that the wafer is set in the holding hole with a CCD camera or the like.

  According to the present invention, the position of the wafer holding hole of the carrier can be measured easily and accurately, and even if the position of the wafer holding hole is shifted, the wafer is securely set in the holding hole and polished safely. be able to. Therefore, it can greatly contribute to automation of wafer polishing.

Hereinafter, as a preferred embodiment of the present invention, the case of double-side polishing a silicon wafer will be specifically described with reference to the accompanying drawings.
1 and 2 schematically show an example of a holding hole detection device according to the present invention, and FIG. 3 shows an example of a double-side polishing device provided with the holding hole detection device.

As shown in FIG. 3, the double-side polishing apparatus 1 includes a swinging polishing apparatus main body (polishing section) 2, a loading station (loader section) 10, an unloading station (unloader section) 16, and a wafer W. A transfer robot 13 for transferring is provided. Although not shown in FIG. 3, upper and lower surface plates, polishing cloths, slurry supply means and the like necessary for a double-side polishing apparatus are also provided.
Further, the double-side polishing apparatus 1 is provided with a holding hole detecting device 12 for detecting the position of the wafer holding hole 5 in the carrier 4 of the polishing apparatus main body 2.

  In order to polish a silicon wafer with such a polishing apparatus 1, first, the box 11 containing the wafer W to be polished is carried by the box automatic transfer device 14 and placed on the loader unit 10. The method of transporting the box 11 to the loader unit 10 is not particularly limited. In addition to a method of transporting by a self-propelled transport vehicle (AGV) that travels on the floor surface, a rail is laid on the ceiling of the room. A method of transporting the box 11 along the rail (OHT) may be employed.

  The box 11 arranged in the loader unit 10 is opened with a lid by an opener or the like. Then, the wafer W in the box 11 is set in the holding hole 5 of the carrier 4 by the transfer robot 13. At this time, as seen in FIG. 15, there is a gap G between the fixing hole 44 and the fixing pin 43, and if the carrier 4 is mechanically positioned by an index, the carrier 4 may not be positioned accurately. In particular, if the fixing hole 44 of the carrier 4 is worn with use and the gap G becomes large, the wafer is not set at a proper position, which may lead to a machine trouble.

  Therefore, in the present invention, after the positioning by the index and before the wafer W is set in the holding hole 5, the position of the holding hole 5 is accurately detected by the holding hole detecting device 12, and the detected position of the holding hole 5 is detected. Based on the above, the wafer W can be reliably inserted into the holding hole 5 by the transfer robot 13.

  Here, the holding hole detection device 12 will be described in detail. As shown in FIGS. 1 and 2, the holding hole detecting device 12 includes two image detecting means (CCD camera) installed so as to form a central angle θ of 90 ° with respect to the wafer holding hole 5 of the carrier 4. ) 20a, 20b and image processing means (monitor) 21 for processing image data obtained by the CCD cameras 20a, 20b. Further, an illumination unit 22 and a gas injection unit 23 for the detection area are provided so as to accompany the camera 20.

  The holding hole detection device 12 is provided with a moving means for positioning the cameras 20a, 20b and the like on the carrier 4 at the time of detection. For example, as shown in FIG. 4, a horizontal X-axis slider 24a and a vertical Z-axis slider 24b are provided on the upper frame 19 of the polishing apparatus, and the holding hole detecting device 12 is attached to the Z-axis slider 24b. By providing such moving means 24, the holding hole detecting device 12 (camera 20) can be moved between the surface plates, that is, on the carrier 4, as shown in FIG. Sometimes, as shown in FIG. 5 (B), it can be retracted to a position away from the surface plates 36a, 36b. Further, a Y-axis slider perpendicular to the X-axis and Z-axis sliders 24a and 24b may be provided.

  Although the upper surface plate 36a is provided with a swing mechanism and the upper surface plate 36a can be moved laterally when the holding hole is detected, the surface plate has become larger as the diameter of the wafer has increased in recent years. If a swing mechanism for the surface plate is provided, it takes a place and there is a possibility that the polishing accuracy is lowered. Therefore, as shown in FIGS. 5 (A) and 5 (B), it is preferable to provide a moving means for moving the upper surface plate 36a upward at the time of detection so that the cameras 20a and 20b can enter between the surface plates. As a result, it is sufficient that the upper surface plate can only move up and down, and a large-diameter wafer can be polished easily and with high accuracy.

Next, a procedure for detecting the position of the holding hole 5 of the carrier 4 by the holding hole detection device 12 will be described.
After the upper surface plate 36a is moved upward, the carrier 4 is positioned by the index. Next, the two CCD cameras 20a and 20b are moved between the surface plates by the X-axis and Z-axis sliders 24a and 24b to scan the vicinity of the holding hole 5 of the carrier 4 at a predetermined position with respect to the holding hole 5. Stop. At this time, if a liquid (water droplet) such as polishing slurry is present at the boundary between the holding hole 5 and the polishing pad 37b, a detection error may occur.

  Therefore, it is preferable that air or nitrogen gas is jetted from the gas jet nozzle immediately before detection to scatter the excess liquid existing at the boundary between the holding hole 5 of the carrier 4 and the polishing pad 37b. Thereby, it is possible to remove only excess water without drying the boundary between the holding hole 5 and the polishing cloth 37b and the polishing cloth in the holding hole.

  Next, the boundary between the holding hole 5 and the polishing pad 37b is detected by the cameras 20a and 20b. Specifically, image data obtained by the two cameras 20a and 20b is sent to the monitor 21 for image processing. When the boundary of the holding hole 5 is in the field of view of the camera 20, as shown in FIG. 6, the carrier 4 and the polishing cloth 37b appear on the monitor screen 21 as a difference between light and dark, so that the holding hole 5 and the polishing cloth 37b Can be detected. At this time, it becomes easy to detect the boundary (the edge of the holding hole) between the holding hole 5 and the polishing cloth 37b by illuminating the vicinity of the boundary between the holding hole 5 and the polishing pad 37b with the illumination means 22 and making the contrast clearer. For example, it is possible to detect with an accuracy of 50 μm.

When the boundary between the holding hole 5 and the polishing pad 37b is detected by the two cameras 20a and 20b, the coordinates of two points of the edge of the holding hole 5 can be specified. In addition, the two cameras 20a and 20b are fixed at predetermined positions with respect to the holding holes 5, and the angle formed with respect to the center C of each holding hole 5 is set at 90 °. The position (coordinates) of the center C of the holding hole 5 can be easily calculated based on the two points and the center angle θ (90 °).
Note that the center angle θ of the two cameras 20a and 20b with respect to the holding hole 5 is not limited to 90 °, and the center angle θ with respect to the holding hole 5 is specified in advance, and the coordinates of two points on the edge of the holding hole 5 can be detected. The center position of the holding hole 5 can be calculated based on the two detected points and the center angle θ.

Thus, by calculating the center position of the holding hole based on the center angle θ of the two CCD cameras 20a and 20b with respect to the holding hole 5 and the detected two points of the edge of the holding hole 5, the position of the holding hole is accurately determined. Can be detected.
Then, if the detected position of the holding hole 5 is fed back to a controller that controls the transfer means (transfer robot) 13, the transfer robot 13 takes out the wafer W from the box 11 of the loader unit 10, and detects the detected holding hole 5. Based on the position data, the carrier 4 can be reliably inserted into the holding hole 5.

  After the wafer W is inserted into the holding hole 5 as described above, the carrier 4 is rotated at intervals of 72 ° with respect to other holding holes as well, and the position of the holding hole 5 is similarly detected by the holding hole detection device 12. Then, the wafer W is set by the transfer robot 13. In the detection of the second and subsequent holding holes, if the carrier is rotated at a constant angle (72 °) according to the index, the holding hole detecting device 12 does not need to be moved. The wafers can be set sequentially.

  The transfer robot 13 can move up and down, right and left, and can rotate. In particular, as shown in FIG. 8, the transfer robot 13 is suspended from the upper frame 19 in the polishing apparatus and has the joint portion 8. The polishing apparatus 1 can be further downsized, and is also suitable for preventing interference with the unloader unit 16 and the like installed at the lower part. Then, for example, as shown in FIG. 8, a plate-like holding means 9 is provided at the tip of the transfer robot 13, and the lower surface side of the wafer horizontally accommodated in the box of the loader unit 10 is scooped up. And can be held horizontally.

  Further, when the wafer W is transferred to the carrier 4 by the transfer robot 13 and set in the holding hole 5, as shown in FIG. 3, the table for changing the wafer W before setting in the holding hole. (Centering stage 15) or the like may be provided. After the wafer W holding the lower surface side is once placed on the centering stage 15, the wafer W can be held more reliably by holding the upper surface side central portion of the wafer by holding means by suction, for example. Insertion into the holding hole 5 is also facilitated. If the transfer robot 13 is provided with a holding means by suction in addition to the plate-like holding means 9, the wafer W can be changed by one unit, the polishing apparatus 1 can be made smaller and the cost can be reduced. It can be further suppressed.

  After the wafer W is set in the holding hole 5 by the transport robot 13, it may be confirmed that the wafer W is securely set in the holding hole 5 by the CCD cameras 20 a and 20 b of the holding hole detection device 12. Alternatively, a confirmation CCD camera may be provided separately.

  After the wafers W are set in all the holding holes 5, the holding hole detecting device 12 is retracted. Then, the upper surface plate 36a is lowered, the wafer in the holding hole 5 is sandwiched between the upper and lower polishing cloths 37a and 37b, the polishing slurry is supplied, and the upper and lower surface plates 36a and 36b (polishing cloths 37a and 37b) are supplied. Wafer polishing is started by rotation and swing of the carrier 4.

  After polishing for a predetermined time, the operations of the surface plates 36a and 36b and the carrier 4 are stopped, and the wafer is recovered. The wafers are taken out from the holding holes 5 by holding means by suction and are sequentially carried out to a collection container (water tank) 17 of the unloader section 16. The wafer W is preferably collected by the transfer robot 13 having the holding means by suction as described above, but a collection transfer robot may be provided separately.

  After polishing, a separate CCD camera is provided near the collection container 17 by the CCD cameras 20a and 20b of the holding hole detection device 12 or as a wafer crack detection area, and before the wafer is accommodated in the collection container 17, You may make it confirm the presence or absence of generation | occurrence | production of a crack. For example, as shown in FIG. 7, a double line 25 inside the outer periphery of the wafer W can be read, and cracks can be detected based on the brightness of the wafer W and the background.

  After all the wafers in the box are polished and accommodated in the collection container 17, they are carried to the next process (cleaning) by the automatic transfer device (AGV) 18.

  As described above, in the double-side polishing apparatus, the holding hole detecting device of the present invention is provided, and the position of the holding hole of the carrier wafer can be accurately detected, so that the wafer can be reliably set in the holding hole. As a result, it is possible to prevent the occurrence of a mechanical trouble and perform the polishing safely. As a result, it greatly contributes to the full automation of the polishing process.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

For example, a robot having an articulated function such as the transfer robot shown in FIG. 8 may be used as the moving means of the holding hole detection device.
Further, the arrangement in the polishing apparatus is not limited to that shown in FIG. 3, and may be set as appropriate. Furthermore, the holding hole detection device of the present invention is not limited to the swing type double-side polishing device, and may be applied to a four-way type double-side polishing device.

It is the schematic which shows an example of the holding hole detection apparatus which concerns on this invention. It is a figure which shows an example of arrangement | positioning of two image detection means (CCD camera) of a holding hole detection apparatus. It is the schematic which shows an example of the double-side polish apparatus provided with the holding hole detection apparatus. It is the schematic which shows an example of the moving means of a holding hole detection apparatus. It is the schematic which shows the position (A) at the time of holding hole detection of a holding hole detection apparatus, and the position (B) at the time of wafer grinding | polishing. It is a figure which shows the image of the carrier and polishing cloth which were reflected on the monitor screen. It is a figure which shows the image of the wafer reflected on the monitor screen. It is the schematic which shows an example of a conveyance robot. It is a schematic diagram showing an example of a 4-way double-side polishing apparatus. It is a schematic plan view which shows a planetary gear structure. It is the schematic of a rocking | swiveling type double-side polish apparatus. It is a schematic plan view of the carrier holder in the swing type double-side polishing apparatus. It is a top view which shows an example of a carrier. It is a schematic sectional drawing which shows the pin and hole which fix a carrier to a holder. It is a schematic plan view which shows the pin and hole which fix a carrier to a holder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Double-side polish apparatus, 2 ... Polishing apparatus main body, 3 ... Carrier holder, 4 ... Carrier,
5 ... Holding hole, 6 ... Slurry passage hole, 7 ... Eccentric arm, 8 ... Joint part,
9 ... Wafer holding means, 10 ... Loader, 11 ... Wafer storage box,
12 ... Holding hole detection device, 13 ... Transfer robot, 14 ... Box automatic transfer device,
15 ... Centering stage, 16 ... Unloader section, 17 ... Recovery container (water tank),
18 ... automatic transfer device, 19 ... frame, 20 ... image detection means (CCD camera),
21 ... Image processing means (monitor), 22 ... Illumination means, 23 ... Gas injection means,
24a, 24b ... moving means (slider), W ... wafer.

Claims (10)

  A device for detecting the position of a carrier holding hole for holding the wafer used when polishing a semiconductor wafer by a double-side polishing apparatus, and is installed so as to form at least a predetermined central angle with respect to the holding hole. Two image detection means and image processing means for processing the image data obtained by the image detection means, and the two image detection means detect two points at the boundary between the holding hole and the polishing pad. The data is sent to the image processing means, and the position of the holding hole is detected by calculating the position of the center of the holding hole based on the two points detected by the image detecting means and the central angle. A holding hole detecting device characterized by that.   The holding hole detecting device according to claim 1, wherein the image detecting means is a CCD camera.   The holding hole detecting device according to claim 1 or 2, wherein the two image detecting means are installed so as to form a central angle of 90 degrees with respect to the holding hole.   The holding hole detection device according to any one of claims 1 to 3, wherein the holding hole detection device includes an illumination unit that illuminates a boundary between the holding hole and a polishing pad.   The holding hole detecting device according to any one of claims 1 to 4, wherein the holding hole detecting device includes an injection unit that injects a gas onto a polishing cloth in the holding hole.   The holding hole detecting device according to any one of claims 1 to 5, wherein at least the image detecting means is movable by a moving means.   A method of detecting a position of a holding hole of a carrier for holding the wafer used when polishing a semiconductor wafer by a double-side polishing apparatus, and installed at a predetermined center angle with respect to the holding hole. Image data obtained by two image detection means is subjected to image processing by an image processing means to detect two points at the boundary between the holding hole and the polishing pad, and the holding is performed based on the detected two points and the central angle. A holding hole detecting method, wherein the position of the holding hole is detected by calculating a position of a center of the hole.   Before performing the detection by the image detection means, the liquid existing at the boundary between the holding hole of the carrier and the polishing cloth is scattered by performing gas injection and / or rotation of the polishing cloth in the holding hole. The holding hole detecting method according to claim 7, wherein:   In the method of polishing by holding a semiconductor wafer in a holding hole of a carrier by a double-side polishing apparatus, the position of the holding hole is detected by the method according to claim 7 or 8, and the position of the detected holding hole is detected. A method for polishing a semiconductor wafer, comprising: setting a semiconductor wafer in a holding hole by a conveying means based on the above; and polishing the wafer.   2. The semiconductor wafer is polished in the holding hole after the semiconductor wafer is set in the holding hole by the conveying means and then the image detecting means confirms that the wafer is set in the holding hole. 10. The method for polishing a semiconductor wafer according to 9.

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