JP2011210827A - Adjusting method of wafer carrying mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for adjusting a wafer carrying mechanism by easily measuring the displacement of the center position of a wafer carried on a chuck table by means of the wafer carrying mechanism.SOLUTION: In the adjusting method of a wafer carrying mechanism, an annular scribe line is formed on a wafer for test which is carried on a chuck table by means of the wafer carrying mechanism while rotating the chuck table. The coordinate (X1, Y1) of the center of rotation of the chuck table is indexed from three arbitrary points of the annular scribe line, and the coordinate (X2, Y2) of the center of the wafer for test is indexed from three arbitrary points on the outer peripheral edge of the wafer for test. Displacement of the coordinate (X1, Y1) of the center of rotation of the chuck table and the coordinate (X2, Y2) of the center of the wafer for test is then determined, and if the displacement exceeds a predetermined value, the length of a supporting arm of the wafer carrying mechanism on which a suction pad is attached and/or the moving distance of the suction pad is corrected.

Description

  The present invention relates to a method for adjusting a wafer transport mechanism that transports a wafer from a temporary placement table on which a wafer is placed with a center position of the wafer to a predetermined position.

  In the manufacture of semiconductor devices and the like, automation is performed using machines in almost all processes, and a wafer transport mechanism for transporting a wafer from one process to the next is operating in many situations.

  For example, even in a grinding apparatus that grinds a wafer to a predetermined thickness, a wafer transport mechanism that transports the wafer between processes in the apparatus is operating. For example, a wafer transport mechanism is used when a wafer is taken out from a cassette in which a plurality of unprocessed wafers are stored, or when a ground wafer is transported to a spinner cleaning device.

  What is very important in such a wafer transport mechanism is the positional accuracy of placing the wafer transported by the wafer transport mechanism. If the position accuracy is out of order, the processing in the next process will be adversely affected.

  For example, a wafer transported to a chuck table from a wafer center alignment device such as a temporary table (see, for example, Japanese Patent Application Laid-Open Nos. 7-2111766 and 2007-317982) has a chucked center position. In order to perform the grinding process, which is the next process, it is preferable to place the table so as to match the rotational center position of the table.

  In particular, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-19461, the back surface corresponding to the device region of the wafer is ground to form a circular recess, and the outer peripheral region of the wafer is left to form an annular reinforcing portion. In the processing method to be performed, the center alignment is important in order to form the annular reinforcing portion with a constant width over the entire outer periphery of the wafer.

Japanese Patent Laid-Open No. 7-211766 JP 2007-317982 A JP 2007-19461 A

  However, in order to adjust the wafer transport mechanism in order to place the wafer on the chuck table so that the center position of the wafer indexed by the temporary table matches the center position of the chuck table, It is necessary to detect the center position of each.

  Conventionally, the back surface corresponding to the device area of the test wafer was actually ground to form an annular reinforcing portion on the outer periphery, and the width of the annular reinforcing portion was measured at many points to adjust the wafer transport mechanism. . However, there is a problem that the inspection is impossible unless the apparatus is assembled until grinding is actually possible.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer transport mechanism that can measure a deviation amount of the center position of a wafer placed on a chuck table by a simple method. It is to provide an adjustment method.

  According to the present invention, a wafer transfer mechanism for holding a wafer with a suction pad attached to the tip of a support arm and transferring the wafer from a temporarily placed table on which the wafer is temporarily placed to a rotatable chuck table for processing the wafer. An adjustment method, a test wafer preparation step for preparing a test wafer having the same shape as a wafer to be transported, a temporary placement step for setting the test wafer on the temporary placement table, and the wafer transport A wafer is transported from the temporary placement table to the chuck table by a mechanism, and the test wafer is sucked and held by the chuck table; and the upper surface of the test wafer held by the chuck table is The chuck table is rotated in a state where the scoring means that comes into contact is in contact with the upper surface of the test wafer. An annular crease line forming step for forming a crease line, and a center position coordinate (X1, Y1) of the annular crease line from any three points of the annular crease line, thereby calculating the rotation center of the chuck table A rotation center position determining step for determining a position, a test wafer center position determining step for determining the center position coordinates (X2, Y2) of the test wafer from arbitrary three points on the outer peripheral edge of the test wafer, and the rotation center The amount of deviation between the rotation center position coordinates (X1, Y1) of the chuck table obtained in the position indexing process and the center position coordinates (X2, Y2) of the test wafer centered in the test wafer center position indexing process. A correction step of correcting the length of the support arm on which the suction pad is mounted and / or the movement distance of the suction pad when the amount of deviation is equal to or greater than a predetermined value. Adjustment method for a wafer transport mechanism, characterized in that it has are provided.

  According to the present invention, the amount of deviation between the center of the test wafer transported on the chuck table and the center of rotation of the chuck table can be easily formed by forming the annular scribe line on the test wafer transported on the chuck table. Measurement can be performed, and the wafer transport mechanism can be adjusted based on the amount of deviation.

It is an external appearance perspective view of a grinding device. It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer by which the protective tape was stuck on the surface. It is a schematic diagram which shows the positional relationship of the center of a wafer, the center of a holding arm, and the center of a temporary placement table. It is a schematic diagram when the wafer is positioned below the imaging means by the holding arm and the outer peripheral edge of the wafer is imaged. It is explanatory drawing which detects the center of a wafer based on a captured image. FIG. 7A is an explanatory diagram showing a wafer center position deviation amount detecting step, and FIG. 7B is an explanatory diagram of placing the wafer on the temporary placement table with the center of the wafer aligned with the center of the temporary placement table. It is. It is explanatory drawing which shows the positional relationship of a wafer conveyance mechanism, a temporary placement table, and a chuck table. It is a perspective view of a test wafer. It is a perspective view which shows the cyclic | annular ruled line formation process implemented with the chuck table of a grinding device. It is explanatory drawing which shows the rotation center position determination process of a chuck table, and the center position determination process of the test wafer conveyed on the chuck table.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a perspective view of a grinding apparatus to which the method for adjusting a wafer transport mechanism of the present invention can be applied. The grinding apparatus includes a device housing 2 having a substantially rectangular parallelepiped shape. A vertical support plate 4 is disposed at the upper right end of the device housing 2.

  Two pairs of guide rails 6 and 8 extending in the vertical direction are provided on the inner surface of the vertical support plate 4. A rough grinding unit 10 is mounted on one guide rail 6 so as to be movable in the vertical direction, and a finish grinding unit 12 is mounted on the other guide rail 8 so as to be movable in the vertical direction.

  The rough grinding unit 10 includes a unit housing 14, a grinding wheel 18 attached to a wheel mount 16 rotatably attached to the lower end of the unit housing 14, and a wheel mount 16 attached to the lower end of the unit housing 14 counterclockwise. An electric motor 20 that rotates in the rotating direction and a moving base 22 on which the unit housing 14 is mounted are configured.

  The grinding wheel 18 includes an annular grinding wheel base 18a and a grinding wheel 18b for rough grinding mounted on the lower surface of the grinding wheel base 18a. A pair of guided rails 24 are formed on the moving base 22, and these guided rails 24 are movably fitted to guide rails 6 provided on the vertical support plate 4, so that the rough grinding unit 10 can be moved. Is supported so as to be movable in the vertical direction.

  A grinding feed mechanism 26 moves the moving base 22 of the rough grinding unit 10 along the guide rail 6 and feeds the grinding wheel 18 by grinding. The grinding feed mechanism 26 is arranged on the vertical support plate 4 in a vertical direction parallel to the guide rail 6 and rotatably supported, a pulse motor 30 that rotationally drives the ball screw 28, and a moving base 22. It comprises a nut (not shown) that is mounted and screwed onto the ball screw 28.

  By rotating the ball screw 28 forward or backward by the pulse motor 30, the rough grinding unit 10 is moved in the vertical direction (perpendicular to the holding surface of the chuck table described later).

  The finish grinding unit 12 is configured in the same manner as the rough grinding unit 10, and includes a unit housing 32, a grinding wheel 36 attached to a wheel mount 34 rotatably attached to the lower end of the unit housing 32, and a unit housing 32. An electric motor 38 that is mounted on the upper end and drives the wheel mount 34 in a counterclockwise direction, and a moving base 40 on which the unit housing 32 is mounted. The grinding wheel 36 includes an annular grindstone base 36a and a grinding wheel 36b for finish grinding mounted on the lower surface of the grindstone base 36a.

  A pair of guided rails 42 is formed on the movable base 40, and these guided rails 42 are movably fitted to guide rails 8 provided on the vertical support plate 4, so that the finish grinding unit 12 can be moved. Is supported so as to be movable in the vertical direction.

  Reference numeral 44 denotes a grinding feed mechanism that moves the moving base 40 of the finish grinding unit 12 along the guide rail 8 and feeds the grinding wheel 36 by grinding. The grinding feed mechanism 44 includes a ball screw 46 that is vertically supported on the vertical support plate 4 in parallel with the guide rail 8, a pulse motor 48 that rotationally drives the ball screw 46, and a moving base 40. And a nut (not shown) that engages with the ball screw 46.

  By driving the ball screw 46 forward or backward by the pulse motor 48, the finish grinding unit 12 is moved in the vertical direction (perpendicular to the holding surface of the chuck table described later).

  The grinding apparatus includes a turntable 50 disposed so as to be substantially flush with the upper surface of the apparatus housing 2 on the front side of the vertical support plate 4. The turntable 50 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 51 by a rotation driving mechanism (not shown).

  On the turntable 50, three chuck tables 52 are arranged so as to be rotatable in a horizontal plane, spaced from each other by 120 degrees in the circumferential direction. The chuck table 52 includes a disk-shaped base 54 and a suction chuck 56 formed in a disk shape from a porous ceramic material. The chuck table 52 includes suction means (not shown) for a wafer placed on the holding surface of the suction chuck 56. Holds by suction when activated.

  The chuck table 52 configured as described above is rotated in a direction indicated by an arrow 53 by a rotation driving mechanism (not shown). The three chuck tables 52 arranged on the turntable 50 are rotated in accordance with the rotation of the turntable 50, so that the wafer loading / unloading area A, rough grinding area B, finish grinding area C, and wafer loading / unloading are performed. The region A is sequentially moved.

  The grinding device is disposed on one side with respect to the wafer carry-in / out region A, and is disposed on the other side with respect to the first cassette 58 for stocking the wafer before grinding, and the wafer carry-in / out region A, A second cassette 60 for stocking the wafer after grinding is provided.

  Between the first cassette 58 and the wafer loading / unloading area A, a temporary placing table 62 for placing the wafer carried out from the first cassette 58 is disposed, and above the temporary placing table 62. An image pickup means 64 for picking up an image of the wafer carried out from the first cassette 58 by the wafer transfer robot 70 is arranged. The imaging means 64 is attached to the support member 66.

  A spinner cleaning device 68 is disposed between the wafer loading / unloading area A and the second cassette 60. The wafer transfer robot 70 includes a holding arm 72 and a multi-joint link mechanism 74 that moves the holding arm 72. The wafer transport robot 70 carries the wafer stored in the first cassette 58 to the temporary placement table 60, and spinner cleaning apparatus. The wafer cleaned at 68 is transported to the second cassette 60.

  The wafer carry-in means (wafer carrying mechanism) 76 carries the wafer before grinding, which is placed on the temporary placement table 62, onto the chuck table 52 positioned in the wafer carry-in / out area A. The wafer carry-out means 78 carries the wafer after grinding mounted on the chuck table 52 positioned in the wafer carry-in / out area A to the spinner cleaning device 68.

  A semiconductor wafer 11 shown in FIG. 2 is accommodated in the first cassette 58. The semiconductor wafer 11 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and an IC, a plurality of areas partitioned by the plurality of streets 13, A device 15 such as an LSI is formed.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. In addition, the width | variety of the outer periphery surplus area | region 19 is set to about 2-3 mm. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  A protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and as shown in FIG. 3, the back surface 11b is exposed, and the plurality of semiconductor wafers 11 are placed in the first cassette 58 with the back surface 11b facing upward. It is stored.

  Next, referring to FIG. 4, the relationship among the center 80 of the wafer 11, the center 82 of the holding arm 72, and the center 84 of the temporary table 62 is schematically shown. The temporary placement table 62 has a holding surface 62a, and the holding surface 62a is sucked by a suction means (not shown). The center 82 of the holding arm 72 and the center 84 of the temporary placement table 62 are registered in advance in the controller 104 (see FIG. 8).

  In the embodiment of the present invention, the wafer 11 is held from the lower side by the holding arm 72, and the wafer 11 is placed on the temporary placement table 62 with the center 80 of the wafer 11 aligned with the center 84 of the temporary placement table 62.

  Referring to FIG. 5, there is shown a schematic diagram in which the wafer 11 is positioned below the imaging means 64 by the holding arm 72 and the outer periphery of the wafer 11 is photographed. Reference numeral 86 denotes a photographing field.

  Next, a method for detecting the center position of the wafer 11 based on the image picked up by the image pickup means 64 will be described with reference to FIG. Reference numeral 87 denotes a picked-up image picked up by the image pickup means 64, and three points A, B, and C are extracted by scanning the picked-up image 87. By this scanning operation, the X and Y coordinates of the three points A, B, and C can be obtained.

  When a perpendicular bisector 90 of a line segment 88 connecting points A and B is drawn, and further a perpendicular bisector 94 of a line segment 92 connecting points B and C is drawn, a vertical bisector 90 is drawn. 94 is obtained as the center position 80 of the wafer 11.

  If one point is added in addition to the above three points A to C, four combinations of three points are obtained. Therefore, when the intersection of the perpendicular bisectors is obtained for each combination of three points, and the center of the wafer 11 is obtained from the average value of these intersections, the center 80 of the wafer 11 can be obtained more accurately.

  After obtaining the center 80 of the wafer 11 in this way, as shown in FIG. 7A, a deviation amount 106 between the center 82 of the holding arm 72 and the center 80 of the wafer 11 is detected by a deviation amount detecting means.

  Next, as shown in FIG. 7B, the holding arm 72 is moved by driving the multi-joint link 74 of the wafer transfer robot 70 so that the center 80 of the wafer 11 matches the center 84 of the temporary placement table 62. The wafer 11 is placed on the temporary placement table 62.

  Next, with reference to FIG. 8, the relationship between the wafer carry-in means (wafer transport mechanism) 76, the temporary placement table 62, and the chuck table 52 will be described. The operating arm (support arm) 98 of the wafer carry-in means 76 rotates around the axis of the connecting shaft 103 that connects the pulse motor 102 to the operating arm 98.

  A suction pad 100 is attached to the tip of the operating arm 98. When the pulse motor 102 is driven, the operation arm 98 rotates so that the center of the suction pad 100 draws an arcuate locus 105 passing through the center 84 of the temporary table 62 and the center of the chuck table 52.

  As a result, the wafer 11 placed on the temporary placement table 62 with its center 80 aligned with the center 84 of the temporary placement table is sucked by the suction pad 100 of the wafer carry-in means 76, and the pulse motor 102 is driven by a predetermined pulse. Thus, the wafer 11 can be moved onto the chuck table 52 with its center 80 aligned with the center of the suction chuck 56 of the chuck table 52.

  Next, the suction chuck 56 is driven to suck and the suction of the suction pad 100 is released, whereby the wafer 11 is sucked and held on the chuck table 52 with its center 80 aligned with the center of the suction chuck 56.

  The controller 104 controls the imaging means 64 and the multi-node link 74 of the wafer transfer robot 70, and controls many other units such as the rough grinding unit 10, the finish grinding unit 12, and the chuck table 52.

  In the embodiment described above, the wafer 11 is placed on the temporary placement table 62 with the center 80 of the wafer 11 aligned with the center 84 of the temporary placement table 62. This centering step is performed on the chuck table 52. You may make it perform.

  In this case, the wafer 11 placed on the temporary placement table 62 is imaged by the imaging means 64, and the center position coordinates of the wafer 11 are detected by the method shown in FIG. No control is performed so that the center 80 of 11 is aligned with the center 84 of the temporary table 62. Therefore, the wafer 11 is usually placed with its center 80 slightly shifted from the center 84 of the temporary table 62.

  Therefore, the temporary placement table 62 is slightly rotated so that the center 80 of the wafer 11 is on the arcuate locus 105. Next, when the wafer 11 is sucked by the suction pad 100 of the wafer carry-in means 76 and transported and placed on the chuck table 52, the center 80 of the wafer 11 is placed in alignment with the center of the chuck table 52. For this purpose, the number of drive pulses of the pulse motor 102 required to rotate the operating arm 98 of the wafer carry-in means 76 is obtained by calculation.

  Next, the wafer 11 is sucked by the suction pad 100 of the wafer carry-in means 76, and the pulse motor 102 is driven at the number of drive pulses obtained by calculation, so that the center of the suction pad 100 moves along an arcuate locus 100. The wafer 11 can be placed on the chuck table 52 by aligning the center 80 of the wafer 11 with the center of the chuck table 52.

  By accurately controlling the length and / or rotation angle of the support arm 98 of the wafer carry-in means (wafer transport mechanism) 76, that is, the moving distance of the suction pad 100, the wafer 11 has its center 80 at the chuck chuck of the chuck table 52. It should be placed on the chuck table 52 in accordance with the center of 56.

  However, there has conventionally been a problem that there is no method for easily detecting this. Therefore, as described in the column of the problem to be solved by the invention, the back surface of the region corresponding to the device region of the test wafer is actually ground to form a circular recess, and the excess peripheral region of the wafer is left. The wafer conveyance mechanism 76 is adjusted by forming an annular reinforcing portion and measuring the width of the annular reinforcing portion at a number of points.

  In the present invention, in order to solve this problem, a test wafer 25 as shown in FIG. 9 is prepared. The test wafer 25 is formed, for example, from a wafer obtained by grinding or polishing both the front and back surfaces of a silicon wafer that does not have a semiconductor device cut out from a silicon ingot and processed to 700 μm.

  The test wafer 25 has the same shape as the wafer 11 shown in FIG. Such a test wafer 25 is taken out from the first cassette 58 by the wafer transfer robot 74, centered as described above, and placed on the temporary placement table 62.

  Then, the test wafer 25 centered and placed on the temporary placement table 62 is sucked by the suction pad 100 of the wafer transport mechanism 76 as shown in FIG. 8, and the pulse motor 102 is driven by a predetermined pulse. By rotating the support arm 98 by a predetermined angle, the test wafer 25 is conveyed onto the chuck table 52 and sucked and held.

  Next, as shown in FIG. 10, the test table 25 is rotated by rotating the chuck table 52 in a state where the scoring means 110 that contacts the upper surface of the test wafer 25 sucked and held by the chuck table 52 is in contact. An annular ruled line 112 is formed on the upper surface of the substrate.

  The test wafer 25 sucked and held on the chuck table 52 is imaged by an imaging device (not shown) arranged adjacent to the rough grinding unit 10. As shown in FIG. 11, arbitrary three points A, B, and C are extracted from the circular ruled line 112, and the coordinates of the center 55A of the circular ruled line 112 are obtained by the same method as described with reference to FIG. (X1, Y1) is calculated. The coordinates (X1, Y1) of the center 55A of the circular ruled line 112 coincide with the rotation center coordinates of the chuck table 52.

  Further, arbitrary three points D, E, and F on the outer periphery of the test wafer 25 are extracted, and the coordinates (X2, Y2) of the center 27 of the test wafer 25 are calculated from these three points. Then, a deviation amount S between the rotation center position coordinates (X1, Y1) of the chuck table 52 and the center position coordinates (X2, Y2) of the test wafer 25 is obtained.

  When the deviation amount S is equal to or larger than a predetermined allowable value, the length of the support arm 98 of the wafer transport mechanism 76 to which the suction pad 100 is mounted and / or the rotation angle of the support arm 98, that is, the suction pad 100 Is adjusted so that the center of the test wafer 25 transported onto the chuck table 52 by the wafer transport mechanism 76 coincides with the center of rotation of the chuck table 52.

  When the imaging device is not provided adjacent to the rough grinding unit 10, marks in the X-axis direction and the Y-axis direction are formed on the test wafer 25 on which the annular scribe line 112 is formed as shown in FIG. , The test wafer 25 is removed from the chuck table 52, and the test wafer 25 and the annular scribe line 112 are imaged by a separate imaging device, and the center position 55A of the annular scribe line 112, that is, the rotation of the chuck table 52 is rotated. The deviation amount S may be calculated by detecting the center position and the center position 27 of the test wafer 25.

  As the ruler 110, a contact-type thickness measuring gauge that measures the thickness of the wafer 11 being ground, which is usually installed in a grinding apparatus, can be used. In this case, a thin film is formed on the entire surface of the test wafer 25 with magic ink or the like, and the annular ruled line 112 is formed by rotating the chuck table 52 while contacting the contact-type thickness measuring gauge with the film. Preferably formed.

  According to the above-described embodiment of the present invention, the annular scoring line 112 is formed on the test wafer 25 held on the chuck table 52 by the scoring means 110 that makes point contact with the test wafer 25, and is formed on the chuck table 52. The amount of deviation between the center of the test wafer 25 conveyed and the center of rotation of the chuck table 52 can be easily measured, and the wafer conveyance mechanism 76 can be adjusted based on this amount of deviation.

DESCRIPTION OF SYMBOLS 10 Rough grinding unit 12 Finish grinding unit 25 Test wafer 50 Turntable 52 Chuck table 62 Temporary placing table 64 Imaging means 70 Wafer transfer robot 76 Wafer carrying means (wafer transfer mechanism)
98 Support arm (working arm)
100 suction pad 110 crease means 112 annular crease line

Claims (1)

An adjustment method of a wafer transfer mechanism that holds a wafer with a suction pad attached to the tip of a support arm and transfers the wafer from a temporary table on which the wafer is temporarily placed to a rotatable chuck table that processes the wafer. ,
A test wafer preparation step of preparing a test wafer having the same shape as the wafer to be transported;
A temporary placing step of setting the test wafer on the temporary placing table;
A wafer transfer step of transferring a wafer from the temporary table to the chuck table by the wafer transfer mechanism and sucking and holding the test wafer by the chuck table;
An annular ruled line that forms an annular scored line on the upper surface of the test wafer by rotating the chuck table in a state where the scored means contacting the point with the upper surface of the test wafer held on the chuck table is in contact. Writing line forming process;
A rotation center position indexing step for determining the rotation center position of the chuck table by determining the center position coordinates (X1, Y1) of the annular score line from any three points of the annular score line;
A test wafer center position determining step of determining the center position coordinates (X2, Y2) of the test wafer from arbitrary three points on the outer peripheral edge of the test wafer;
The rotation center position coordinates (X1, Y1) of the chuck table obtained in the rotation center position indexing step and the center position coordinates (X2, Y2) of the test wafer obtained in the test wafer center position indexing step. A correction step for obtaining a shift amount and, if the shift amount is equal to or greater than a predetermined value, correcting the length of the support arm on which the suction pad is mounted and / or the movement distance of the suction pad;
A method for adjusting a wafer transport mechanism.

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