JP2009262239A - Grinder for plate form object and plate thickness calculating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinder that senses, on the grinder, the thickness of a wafer immediately after it is ground. <P>SOLUTION: The grinder is equipped with a chuck table having a holding surface for a plate form object, a grinding means to grind the plate held by the chuck table, and a plate transporting means fitted with a transporting pad to suck fast the work ground on the chuck table and having a suction surface with a smaller diameter than the work, characterized by that the arrangement further includes a first non-contact distance measuring means installed over the pad on the transport path for the pad holding the work and measuring the distance to the plate oversurface, a second non-contact distance measuring means installed under the pad on the transport path for the pad in such a manner as confronting the first measuring means and measuring the distance to the plate undersurface, and a memory means to store the distance to the plate oversurface obtained by the first measuring means and the distance to the plate undersurface obtained by the second measuring means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a grinding apparatus for grinding a plate-like object such as a semiconductor wafer and a method for calculating the thickness of the plate-like object using the grinding apparatus.

  A plate-like object such as a semiconductor wafer, a glass substrate, or a sapphire substrate on which a plurality of devices such as IC and LSI are formed is ground to the desired thickness and then the individual device is cut by a cutting device such as a dicing device. And is widely used in various electronic devices such as personal computers and mobile phones.

  For grinding a plate-like object, the plate-like object is sucked and adsorbed to the chuck table and rotated, and the grinding wheel facing the chuck table is rotated and fed to the grinding surface of the rotating plate-like object. A grinding apparatus of a pressing type is used. In such a grinding apparatus, the plate-like object is ground to a desired thickness by constantly detecting the thickness of the plate-like object being processed with a contact-type thickness measuring gauge.

  On the other hand, at the end of grinding, the thickness gauge is retracted from the plate to remove contact marks and scratches on the plate due to the contact thickness gauge contacting the plate during grinding. In this state, grinding feed of the grinding wheel is stopped, and so-called “spark out” is performed in which the rotation of the grinding wheel is continued for a predetermined time at the stop position.

The grinding wheel is retracted from the plate-like object after the spark-out is performed. Such a spark-out is required to flatten the surface to be ground by rotating the plate-like material at least once and to remove grinding distortion of the plate-like material.
JP 2006-21264 A

  In the conventional grinding method, test grinding is performed for each application, and how much is ground by spark-out is calculated, and then the spark-out timing is set by taking into account the grinding amount and finish thickness at spark-out. Therefore, the exact thickness of the plate-like object after the spark-out is not detected.

  Thus, since the grinding amount during spark-out is not detected, it is necessary to measure the thickness of a separately ground wafer when the wafer thickness after processing is required in the subsequent steps.

  In particular, in a wafer manufacturing process in which a semiconductor wafer is manufactured by cutting a semiconductor wafer from a silicon ingot, grinding and then etching, it is necessary to measure each wafer thickness after grinding in order to manage the etching rate.

  The present invention has been made in view of such points, and the object of the present invention is to use a grinding apparatus capable of detecting the thickness of a plate-like object immediately after grinding on the grinding apparatus and the grinding apparatus. It is to provide a plate-like thickness measuring method.

  According to the first aspect of the present invention, a chuck table having a holding surface for holding a plate-like object, a grinding means for grinding the plate-like object held on the chuck table, and a workpiece ground on the chuck table In a grinding apparatus comprising a plate-like object conveying means having a conveyance pad having a suction pad having a suction surface smaller in diameter than the workpiece, the workpiece is sucked and held on the conveyance path of the conveyance pad holding the plate-like object A first non-contact distance measuring means disposed on the upper side of the transport pad for measuring the distance to the upper surface of the plate-like object, and on the transport path of the transport pad facing the first non-contact distance measuring means; A second non-contact type distance measuring means that is disposed on the lower side of the transport pad and measures the distance to the lower surface of the plate-like object, and the upper surface of the plate-like object measured by the first non-contact type distance measuring means. Measured by the second non-contact distance measuring means. Grinding apparatus is provided which is characterized by comprising storage means for storing the distance to the plate-like workpiece lower surface, the.

  According to invention of Claim 2, it is the thickness calculation method of the plate-shaped object using the grinding apparatus of Claim 1, Comprising: Said 1st non-contact-type distance measurement means and said 2nd non-contact-type distance measurement means, Is set to a predetermined distance L, the distance A to the upper surface of the plate-like object is measured by the first non-contact distance measuring means, and the lower surface of the plate-like object is measured by the second non-contact type distance measuring means. Thickness calculation of the plate-like object characterized by measuring the distance B and calculating the thickness h of the plate-like substance by h = L− (A + B) based on the predetermined distance L, the distance A and the distance B A method is provided.

  According to a third aspect of the present invention, at least one of the first non-contact type distance measuring means and the second non-contact type distance measuring means is composed of a movable non-contact type distance measuring means that is movable in the horizontal direction. A method for calculating the thickness of a plate-like object using the grinding apparatus according to claim 1, wherein a horizontal movement distance Z of the movable non-contact distance measuring means is measured, and the movement of the movable non-contact distance measuring means is measured. A difference Y in distance to the plate-like object measured before and after is calculated, and an angle θ formed by the distance measuring direction of the movable non-contact distance measuring means and the thickness direction of the plate-like object is calculated, The distance between the contact type distance measuring means and the second non-contact type distance measuring means is set to a predetermined distance L, and the first non-contact type distance measuring means measures the distance A to the upper surface of the plate-like object, The second non-contact type distance measuring means measures the distance B to the lower surface of the plate-like object, and the predetermined distance Based on the measured distances A and B and the angle θ, the thickness h of the plate-like object is calculated as h = {L− (A + B)} cos θ. The

  According to the present invention, since the thickness of a ground plate-like object can be measured on a grinding device, it is not necessary to measure the thickness of the plate-like object in a subsequent process, which is efficient. Further, since the thickness of the plate-like object is detected during conveyance, it takes no time for measurement, and productivity is not reduced for thickness detection.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a grinding apparatus 2 according to an embodiment of the present invention. Reference numeral 4 denotes a housing of the grinding device 2, and two columns 6a and 6b are provided upright on the rear side of the housing. A pair of guide rails (only one is shown) 8 extending in the vertical direction is fixed to the column 6a.

  A rough grinding unit 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. The rough grinding unit 10 is attached to a moving base 12 whose housing 20 moves up and down along a pair of guide rails 8.

  The rough grinding unit 10 includes a housing 20, a spindle (not shown) rotatably accommodated in the housing 20, a servo motor 22 that rotationally drives the spindle, and a plurality of rough grinding grinding wheels fixed to the tip of the spindle. A grinding wheel 24 having 26 is included.

  The rough grinding unit 10 includes a rough grinding unit moving mechanism 18 including a ball screw 14 and a pulse motor 16 that move the rough grinding unit 10 up and down along a pair of guide rails 8. When the pulse motor 16 is pulse-driven, the ball screw 14 rotates and the moving base 12 is moved in the vertical direction.

  A pair of guide rails 19 (only one is shown) 19 extending in the vertical direction are also fixed to the other column 6b. A finish grinding unit 28 is mounted along the pair of guide rails 19 so as to be movable in the vertical direction.

  The finish grinding unit 28 is attached to a moving base (not shown) in which the housing 36 moves in the vertical direction along the pair of guide rails 19. The finish grinding unit 28 includes a housing 36, a spindle (not shown) rotatably accommodated in the housing 36, a servo motor 38 that rotationally drives the spindle, and a grinding wheel 42 for finish grinding fixed to the tip of the spindle. A grinding wheel 40 is included.

  The finish grinding unit 28 includes a finish grinding unit moving mechanism 34 including a ball screw 30 and a pulse motor 32 that move the finish grinding unit 28 in the vertical direction along the pair of guide rails 19. When the pulse motor 32 is driven, the ball screw 30 rotates and the finish grinding unit 28 is moved in the vertical direction.

  The grinding device 2 includes a turntable 44 disposed so as to be substantially flush with the upper surface of the housing 4 on the front side of the columns 6a and 6b. The turntable 44 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 45 by a rotation drive mechanism (not shown).

  On the turntable 44, three chuck tables 46 are arranged so as to be rotatable in a horizontal plane, spaced from each other by 120 ° in the circumferential direction. The chuck table 46 has a suction chuck formed in a disk shape by a porous ceramic material, and sucks and holds the wafer placed on the holding surface of the suction chuck by operating a vacuum suction means.

  The three chuck tables 46 arranged on the turntable 44 are rotated in accordance with the turntable 44, 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 front portion of the housing 4 includes a first wafer cassette 50, a second wafer cassette 52, a wafer transfer robot 54, a positioning table 56 having a plurality of positioning pins 58, and a wafer carry-in mechanism (loading arm) 60. A wafer unloading mechanism (unloading arm) 62 and a spinner unit 63 are disposed.

  The wafer carry-out mechanism (unloading arm) 62 is composed of an arm 62a capable of turning and a transport pad 62b attached to the tip of the arm 62a. A first non-contact type distance measuring means 66 for measuring the distance to the upper surface of the wafer after finish grinding that is attracted and transported by the transport pad 62b is provided above the transport path 64 of the transport pad 62b of the wafer carry-out mechanism 62. Is provided.

  A second non-contact type distance measuring unit 68 for measuring the distance to the lower surface of the wafer after finish grinding is provided below the transfer path 64 of the transfer pad 62b in opposition to the first non-contact type distance measuring unit 66. Is provided.

  The first and second non-contact type distance measuring means 66 and 68 are each composed of a distance sensor based on, for example, a triangulation method as shown in FIG. The first non-contact distance measuring unit 66 shown in FIG. 2 includes a laser beam irradiation unit 72 and a light receiving unit 74.

  The irradiating means 72 includes, for example, a semiconductor laser and an objective lens for condensing the emitted beam of the semiconductor laser on the wafer 70, and the light receiving means 74 collects an optical position detector having a photodetector and reflected light at the optical position detector. And a light receiving lens.

  When the laser beam is irradiated from the laser beam irradiation means 72 to the wafer 70 in a substantially vertical direction, the laser beam is diffused and reflected in various directions. When the diffuse reflected light is collected by the light receiving lens, the diffuse reflected light that has passed through the light receiving lens is collected at one point of the optical position detector. Since the distance from the laser beam irradiation position to the light receiving lens is known in advance, the distance from the irradiation means 72 to the wafer 70 can be obtained from the similarity of triangles.

  The grinding operation of the grinding device 2 configured as described above will be described below. The semiconductor wafer accommodated in the first wafer cassette 50 is transported by the vertical motion and the forward / backward motion of the wafer transport robot 54 and is placed on the wafer positioning table 56.

  The wafer placed on the wafer positioning table 56 is centered by a plurality of positioning pins 58 and then moved to the chuck table 46 positioned in the wafer loading / unloading area A by the turning operation of the loading arm 60. It is placed and sucked and held by the chuck table 46.

  Next, the turntable 44 is rotated 120 °, and the chuck table 46 holding the wafer is positioned in the rough grinding region B. While rotating the chuck table 46 with respect to the wafer positioned in this manner at, for example, 300 rpm, the grinding wheel 24 is rotated in the same direction as the chuck table 46 at, for example, 6000 rpm, and the rough grinding unit moving mechanism 18 is operated to perform roughing. A grinding wheel 26 for grinding is brought into contact with the back surface of the wafer.

  Then, the grinding wheel 24 is ground and fed by a predetermined amount at a predetermined grinding feed speed to perform rough grinding of the wafer. The wafer is finished to a desired thickness while measuring the thickness of the wafer with a contact-type thickness measurement gauge (not shown).

  The chuck table 46 holding the wafer after the rough grinding is positioned in the finish grinding region C by rotating the turntable 44 by 120 °, and finish grinding by the finish grinding unit 28 having the grinding wheel 42 for finish grinding. Is implemented.

  The chuck table 46 holding the wafer for which finish grinding has been completed is positioned in the wafer loading / unloading area A by rotating the turntable 46 by 120 °.

  After the suction and holding of the wafer held on the chuck table 46 is released, the wafer is adsorbed by the transfer pad 62b of the wafer unloading mechanism (unloading arm) 62, and the unloading arm 62 turns to rotate the spinner unit 63. It is conveyed to.

  The wafer carry-out mechanism 62 has a conveyance pad 62b having a smaller diameter than the wafer to be adsorbed. Therefore, while the wafer is being carried out by the wafer carry-out mechanism 62, the wafer 70 passes between the first non-contact distance measuring means 66 and the second non-contact distance measuring means 68 as shown in FIG.

  Since the distance between the first non-contact type distance measuring unit 66 and the second non-contact type distance measuring unit 68 is set in advance to a predetermined distance L, the first non-contact type distance measuring unit 66 reaches the upper surface of the wafer 70. The distance A to the lower surface of the wafer 70 is measured by the second non-contact type distance measuring means 68. When the thickness of the wafer 70 is h, the thickness h of the wafer 70 can be calculated by h = L− (A + B) based on the predetermined distance L and the measured distances A and B.

  Since the distance L between the first non-contact type distance measuring means 66 and the second non-contact type distance measuring means 68 fluctuates due to a temperature change or the like, in order to pursue the accuracy of thickness measurement, the thickness is known in advance. It is preferable to measure the distances A and B using the calibration piece, calculate the distance L, and correct it.

  The wafer conveyed to the spinner unit 63 by the unloading arm 62 is cleaned and spin-dried here. Next, the wafer is stored in a predetermined position of the second wafer cassette 52 by the wafer transfer robot 54.

  Next, with reference to FIG. 4, a method for calculating the thickness of the wafer 70A when the ground wafer is thin and the wafer 70A adsorbed by the transport pad 62b is bent will be described.

  In this case, at least one of the first and second non-contact distance measuring means 66 and 68 needs to be movable in the horizontal direction. In FIG. 4, the first non-contact type distance measuring means 66A will be described as being movable in the horizontal direction.

  (Step 1) The distance A is measured by the first non-contact distance measuring means 66A, and the distance B is measured by the second non-contact distance measuring means 68. Since the distance L is known, X is calculated from X = L− (A + B).

  (Step 2) The distance Y can be calculated by moving the first non-contact distance measuring means 66A in the horizontal direction by the distance Z and measuring the distance A ′ to the upper surface of the wafer 70A. The movement of the distance Z can be accurately detected by the control means of the grinding device 2.

  (Step 3) Since θ can be calculated from Z and Y with tan θ = Y / Z, the thickness h of the wafer 70A can be calculated from h = X cos θ.

  According to the grinding apparatus 2 of the present embodiment described above, the thickness of the ground wafer 70 can be measured on the grinding apparatus 2, and it is not necessary to measure the wafer thickness in a subsequent process, which is efficient. Further, since the thickness of the wafer is measured during the wafer conveyance by the wafer unloading mechanism (unloading arm) 62, the measurement does not take time, and the productivity is not reduced for the thickness measurement.

1 is an external perspective view of a grinding apparatus according to an embodiment of the present invention. It is explanatory drawing of the non-contact-type distance sensor which uses a laser beam. It is explanatory drawing of the thickness measurement of a wafer. It is explanatory drawing of the thickness measurement of a wafer in case the wafer is bent.

Explanation of symbols

2 Grinding device 10 Rough grinding unit 28 Finish grinding unit 44 Turntable 46 Chuck table 60 Wafer loading mechanism (loading arm)
62 Wafer unloading mechanism (unloading arm)
62b Transport pad 66 First non-contact distance measuring means 68 Second non-contact distance measuring means 70 Wafer

Claims (3)

A chuck table having a holding surface for holding a plate-like object, a grinding means for grinding the plate-like object held on the chuck table, and a workpiece ground on the chuck table by suction and holding, In a grinding apparatus comprising a plate-like object conveying means provided with a conveying pad having a suction surface with a small diameter compared to
A first non-contact distance measuring means that is disposed above the transport pad on the transport path of the transport pad that holds the plate-shaped object and measures the distance to the upper surface of the plate-shaped object;
A second non-contact type distance measuring means which is disposed on the lower side of the transport pad on the transport path of the transport pad and measures the distance to the lower surface of the plate-like object, facing the first non-contact type distance measuring means; ,
Storage means for storing the distance to the upper surface of the plate-like object measured by the first non-contact type distance measuring means, and the distance to the lower surface of the plate-like object measured by the second non-contact type distance measuring means;
A grinding apparatus comprising: A method for calculating the thickness of a plate-like object using the grinding device according to claim 1,
A distance between the first non-contact distance measuring means and the second non-contact distance measuring means is set to a predetermined distance L;
Measure the distance A to the upper surface of the plate-like object with the first non-contact distance measuring means,
Measure the distance B to the lower surface of the plate-like object with the second non-contact distance measuring means,
Based on the predetermined distance L, the distance A, and the distance B, the thickness h of the plate is calculated by h = L− (A + B). The grinding apparatus according to claim 1, wherein at least one of the first non-contact type distance measuring unit and the second non-contact type distance measuring unit includes a movable non-contact type distance measuring unit that is movable in a horizontal direction. A method for calculating the thickness of the plate-like material used,
Measure the horizontal movement distance Z of the movable non-contact distance measuring means,
Calculating a difference Y in the distance to the plate-like object measured before and after the movement of the movable non-contact distance measuring means;
Calculating the angle θ formed by the distance measuring direction of the movable non-contact distance measuring means and the thickness direction of the plate-like object;
The distance between the first non-contact distance measuring means and the second non-contact distance measuring means is set to a predetermined distance L;
Measure the distance A to the upper surface of the plate with the first non-contact type distance measuring means,
Measure the distance B to the lower surface of the plate-like object with the second non-contact distance measuring means,
Based on the predetermined distance L, the measured distances A and B, and the angle θ, the thickness h of the plate-like object is calculated by h = {L− (A + B)} cos θ. Method.

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