JP2003071712A - Original position setting mechanism for grinding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an original position setting mechanism for grinding apparatus which does not employ an operation mechanism in a sensor and may set the original position with respect to a chuck table of a grinding tool with a high precision. SOLUTION: The original position setting mechanism for grinding apparatus comprises a load detection means for detecting a load applied to a chuck table, a grinding unit position detection means for detecting a movement position of a grinding unit moved by a grinding unit feeding mechanism, and a control means for setting the original position according to detected signals from the load detection means and the grinding unit position detection means. The control means sets the movement position of the grinding unit as the original position, the movement position being detected by the grinding unit position detection means when the load detection means detects the load applied to the chuck table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an origin position setting mechanism of a grinding device for setting an origin position of a grinding tool for grinding a workpiece held on a chuck table with respect to the chuck table.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a large number of rectangular areas are divided by cutting lines called streets arranged in a lattice pattern on a surface of a semiconductor wafer having a substantially disk shape, and a semiconductor is formed in each of the rectangular areas. Form a circuit. Individual semiconductor chips are formed by separating the semiconductor wafer on which a large number of semiconductor circuits are formed in this way along the streets. In order to reduce the size and weight of a semiconductor chip, usually, the back surface of the semiconductor wafer is ground to a predetermined thickness before the semiconductor wafer is cut along the streets to separate the individual rectangular areas. Is forming. Further, in a semiconductor chip separation method called a front dicing method, a groove having a predetermined depth is formed by cutting along a street from a surface of the semiconductor wafer, and then a back surface of the semiconductor wafer is ground to the groove. As a result, the semiconductor wafer is formed to have a predetermined thickness and individual rectangular regions are separated. A grinding device for grinding the back surface of such a semiconductor wafer is
A chuck table having a mounting surface for mounting a workpiece, a grinding unit having a grinding tool for grinding the workpiece mounted on the mounting surface of the chuck table, and the grinding unit. And a grinding unit feeding mechanism for moving the unit in a direction perpendicular to the mounting surface of the chuck table.

In recent years, electric equipment using semiconductor chips has been reduced in size and weight, and a semiconductor wafer has a thickness of 1 or less.
It is desired to process it to be not more than 00 μm, more preferably not more than 50 μm. However, in order to grind the back surface of the semiconductor wafer to a predetermined thickness of 100 to 50 μm or less, the relative distance from the mounting surface of the chuck table to the processed surface of the grinding tool needs to be grasped with high accuracy. .

Conventionally, as a method of ascertaining the relative distance from the mounting surface of the chuck table to the machined surface of the grinding tool, a contact sensor preset at a predetermined height position from the mounting surface of the chuck table is installed below the grinding tool. Then, the position of the grinding unit was detected when the grinding tool was moved down to and the grinding tool touched the contact sensor.

[0005]

In the above-mentioned conventional method, however, the contact sensor needs to be moved below the grinding tool each time the setup is performed, which complicates the operation mechanism. When the grinding tool is soft, such as a buff, the tip shape of the contact sensor is thin and needle-shaped, so when the contact sensor contacts the grinding tool, the cutting tool bites into the grinding tool or the grinding tool dents. Therefore, the contact position may be erroneously recognized.

The present invention has been made in view of the above-mentioned facts, and its main technical problem is to grind the origin position of a grinding tool with respect to a chuck table with high accuracy without using an operating mechanism for a sensor. It is to provide an origin position setting mechanism of the device.

[0007]

In order to solve the above-mentioned main technical problems, according to the present invention, a chuck table having a mounting surface on which a workpiece is mounted and a mounting surface of the chuck table are provided. Grinding provided with a grinding unit having a grinding tool for grinding a mounted workpiece, and a grinding unit feeding mechanism for moving the grinding unit in a direction perpendicular to the mounting surface of the chuck table. In the device,
An origin position setting mechanism for setting an origin position of the grinding tool with respect to the chuck table, the load detecting means detecting a load acting on the chuck table, and the grinding unit moved by the grinding unit feeding mechanism. Grinding unit position detecting means for detecting the moving position of the, and control means for setting the origin position based on the detection signals from the load detecting means and the grinding unit position detecting means, the control means comprising: An origin position setting of a grinding apparatus, wherein a moving position of the grinding unit detected by the grinding unit position detecting means at a time point when the load detecting means detects a load acting on the chuck table is set as an origin position. A mechanism is provided.

The load detecting means comprises a Kistler dynamometer, and the grinding unit position detecting means comprises a linear scale and a detector for detecting a detected line of the linear scale. Further, the grinding tool is made of a felt grindstone in which abrasive grains are dispersed in a felt and fixed with an appropriate bonding agent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of an origin position setting mechanism of a grinding machine constructed according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a perspective view of a grinding apparatus having an origin position setting mechanism according to the present invention. Grinding equipment
It comprises a device housing generally designated by the number 2. The device housing 2 has a rectangular parallelepiped main portion 2 that extends in a slender shape.
1 and an upright wall 22 provided at a rear end portion (upper right end in FIG. 1) of the main portion 21 and extending substantially vertically upward. On the front surface of the upright wall 22, a pair of vertically extending guide rails 221 and 221 are provided. The grinding unit 3 is mounted on the pair of guide rails 221 and 221 so as to be vertically movable.

The grinding unit 3 includes a moving base 31 and a spindle unit 32 mounted on the moving base 31. The moving base 31 is provided with a pair of leg portions 311 and 311 extending in the vertical direction on both sides of the rear surface. The pair of leg portions 311 and 311 are provided with the pair of guide rails 221.
Guided grooves 312 and 312 that slidably engage with 221 are formed. In this way, the front surface of the movable base 31 slidably mounted on the pair of guide rails 221 and 221 provided on the upright wall 22 is provided with the support portion 313 projecting forward. The spindle unit 32 is attached to the support portion 313.

The spindle unit 32 has a support portion 313.
A spindle housing 321 mounted on the spindle housing 321, a rotary spindle 322 rotatably disposed on the spindle housing 321, and a servomotor 323 (M1) as a drive source for rotationally driving the rotary spindle 322. The output shaft of the servo motor 323 (M1) is transmission-coupled to the rotary spindle 322 via a reduction mechanism (not shown). The lower end of the rotary spindle 322 is projected downward beyond the lower end of the spindle housing 321, and a grinding tool 325 is attached to the lower end of the rotary spindle 322. More specifically, a disc-shaped mounting member 324 is fixed to the lower end of the rotary spindle 322, and a plurality of through holes (not shown) are formed in the mounting member 324 at intervals in the circumferential direction. Has been done. As shown in FIGS. 3 and 4, the grinding tool 325 includes a disc-shaped support member 326 and a disc-shaped grinding member 3.
And 27. The support member 326 is formed with a plurality of blind screw holes 326a that extend downward from the upper surface of the support member 326 at intervals in the circumferential direction. The lower surface of the support member 326 forms a circular support surface, and the grinding member 327 is used as the support member 3 with an appropriate adhesive such as an epoxy resin adhesive.
It is joined to 26 circular bearing surfaces. Grinding member 327
In the illustrated embodiment, a felt grindstone in which abrasive grains are dispersed in the felt and fixed with an appropriate bonding agent is used. Since the detailed description of the structure of the grinding member 327 itself made of the felt grindstone is described in detail in the specification and drawings of Japanese Patent Application No. 2001-93397 already proposed by the applicant, the description is left to the present specification. The description is omitted in the book. The grinding tool 32 is attached to the lower surface of the mounting member 324 fixed to the lower end of the rotary spindle 322.
5 is positioned and the fastening bolt 327 is screwed into the blind screw hole 326a formed in the support member 326 of the grinding tool 325 through the through hole formed in the mounting member 324, whereby the grinding tool 325 is attached to the mounting member 324. It is installed.

Returning to FIG. 1, the description will be continued. In the grinding apparatus in the illustrated embodiment, the grinding unit 3 is moved along the pair of guide rails 31 and 31 in the vertical direction (a mounting surface of a chuck table, which will be described later). A grinding unit feed mechanism 4 for moving the grinding unit in a vertical direction is provided. The grinding unit feeding mechanism 4 includes a male screw rod 41 that is disposed on the front side of the upright wall 22 and extends substantially vertically. The male screw rod 41 has an upper end portion and a lower end portion which are upright walls 2.
It is rotatably supported by bearing members 42 and 43 attached to the unit 2. The upper bearing member 42 is provided with a pulse motor 44 (M2) as a drive source for rotationally driving the male screw rod 41, and the output shaft of the pulse motor 44 (M2) is transmission-coupled to the male screw rod 41. Has been done. A connecting portion (not shown) is formed on the rear surface of the movable base 31 so as to project rearward from the center portion in the width direction, and a through female screw hole extending in the vertical direction is formed in this connecting portion. The male screw rod 41 is screwed into the female screw hole. Therefore, when the pulse motor 44 (M2) rotates in the normal direction, the moving base 31 or the grinding unit 3 is lowered, and when the pulse motor 44 (M2) rotates in the reverse direction, the moving base 31 or the grinding unit 3 is raised.

The grinding device in the illustrated embodiment is shown in FIG.
As shown in FIG. 3, the grinding unit position detecting means 5 for detecting the moving position of the grinding unit 3 is provided. The grinding unit position detecting means 5 includes a linear scale 51 arranged in the upright wall 22 in parallel with the male screw rod 41.
And the linear scale 5 attached to the moving base 31.
And a detector 52 (LIS) for detecting one detected line. The detector 52 (LIS) may be a photoelectric detector known per se, and generates a pulse signal in response to detection of a detected line (formed at intervals of 1 μm, for example) of the linear scale 51, and outputs the pulse signal. The signal is sent to the control means described later. The vertical wall 22 has a detector 52 (L
An elongated hole is formed to allow the movement of IS).

Continuing the description with reference to FIGS. 1 and 2, a substantially rectangular recess 211 is formed on the rear half of the main portion 21 of the housing 2, and the chuck table is provided in the recess 211. A mechanism 6 is provided. The chuck table mechanism 6 includes a support base 61 and a disk-shaped chuck table 62 rotatably arranged on the support base 61 about a rotation center axis line extending substantially vertically. The support base 61 has a pair of guide rails 23 extending on the recessed portion 211 in the front-rear direction (direction perpendicular to the front surface of the upright wall 22) indicated by arrows 23a and 23b.
It is slidably mounted on (only one guide rail is shown in FIG. 2).

The chuck table 62 has a mounting surface 621 for mounting a workpiece on the upper surface thereof, and the support base 61 is provided.
It is rotatably supported by the supporting means 63 on the upper side.
A rotation shaft 622 is attached to the lower surface of the chuck table 62 at the center thereof. The chuck table 62
Is made of an appropriate porous material such as porous ceramics and is connected to suction means (not shown). Therefore, the workpiece placed on the placement surface 621 is suction-held by selectively communicating the chuck table 62 with a suction unit (not shown).

The support means 63 constituting the chuck table mechanism 6 are three support columns 631 (only two are shown in FIG. 2) provided on the support base 61, and the support columns 631. And a disc-shaped support plate 632 disposed above the support plate 632.
The chuck table 62 is rotatably supported via the shaft 3. A hole 632a through which the rotary shaft 622 is inserted is provided at the center of the support plate 632. A servo motor 65 (M3) as a drive source for rotationally driving the chuck table 62 is disposed on the support base 61 below the support plate 632. The output shaft of the servo motor 65 (M3) is transmission-coupled to the rotary shaft 622 of the chuck table 62. In addition, in the illustrated embodiment, the three support columns 631 and the support plate 632 are provided.
And a load detecting means 64 (LOS) for detecting the load acting on the chuck table 62, respectively. As the load detecting means 64 (LOS), a Kistler dynamometer is used in the illustrated embodiment and outputs a voltage signal corresponding to the load acting on the chuck table 62. The voltage signal output from the load detection means 64 (LOS) is converted into a digital signal by an A / D converter (not shown) and sent to the control means described later.

The grinding device in the illustrated embodiment is shown in FIG.
3, a chuck table moving mechanism 66 for moving the chuck table mechanism 6 along the pair of guide rails 23 in the directions indicated by arrows 23a and 23b is provided. The chuck table moving mechanism 66 includes a male screw rod 661 arranged between the pair of guide rails 23 and extending parallel to the guide rails 23. Both ends of the male screw rod 661 are rotatably supported by bearing members 662 and 663 attached by connecting the pair of guide rails 23. The front bearing member 662 is provided with a servo motor 664 (M4) as a drive source for rotationally driving the male screw rod 661, and the output shaft of this servo motor 664 (M4) is the male screw rod 6.
It is transmission-coupled to 61. The front end of the support base 61 (see FIG. 2
The female screw block 665 having a penetrating female screw hole is attached to the left end in FIG.
The male screw rod 661 is screwed into the penetrating female screw hole 65. Therefore, the servo motor 664 (M4)
When the normal rotation occurs, the support base 61, that is, the chuck table mechanism 6
Moves in the direction indicated by the arrow 23a, and the servo motor 664
When (M4) is reversed, the support base 61, that is, the chuck table mechanism 6 is moved in the direction indicated by the arrow 23b.
The chuck table mechanism 6, which is moved in the directions indicated by the arrows 23a and 23b, selectively operates in the workpiece loading / unloading area 24 and the grinding area 25, which are positioned at intervals in the directions indicated by the arrows 23a and 23b. Positioned. In addition, the chuck table mechanism 6 has a grinding area 25.
In the case of arrow arrows 23a and 23
It can be reciprocated in the direction indicated by b.

As shown in FIG. 1, bellows means 71 and 72 having a reverse channel shape in cross section and covering the male screw rod 661 are attached to both sides of the chuck table moving mechanism 66 in the moving direction. ing. The bellows means 71 and 72 can be formed from any suitable material such as campus cloth. The front end of the bellows means 71 is the immersive section 2.
It is fixed to the front wall of 11, and the rear end is fixed to the front end surface of the support base 61 of the chuck table moving mechanism 65. The front end of the bellows means 72 is fixed to the rear end surface of the support base 61 of the chuck table moving mechanism 65, and the rear end is fixed to the front surface of the upright wall 22 of the apparatus housing 2. When the chuck table moving mechanism 65 is moved in the direction shown by the arrow 23a, the bellows means 71 is expanded and the bellows means 72 is contracted, and the chuck table moving mechanism 65 is moved by the arrow 23b.
When it is moved in the direction indicated by, the bellows means 71 is contracted and the bellows means 72 is expanded.

Continuing the description with reference to FIG. 1, the first cassette 11, the second cassette 12, and the workpiece temporary placing means 13 are provided on the front half of the main portion 21 of the apparatus housing 2. A cleaning means 14, a workpiece conveying means 15,
Workpiece carry-in means 16 and workpiece carry-out means 17 are provided. The first cassette 11 accommodates a workpiece to be ground and is placed in the cassette loading area in the main portion 21 of the apparatus housing 2. The second cassette 12 is placed in the cassette unloading area in the main portion 21 of the apparatus housing 2 and stores the workpiece after grinding. The workpiece temporary placing means 13 is disposed between the first cassette 11 and the workpiece loading / unloading area 24, and temporarily places the workpiece before grinding. The cleaning means 14 is disposed between the workpiece loading / unloading area 24 and the second cassette 12 and cleans the workpiece after grinding. Workpiece conveying means 15 is arranged between the first cassette 11 and the second cassette 12, and the workpiece stored in the first cassette 11 is carried out to the workpiece temporary placing means 13. At the same time, the workpiece cleaned by the cleaning means 14 is conveyed to the second cassette 12. The workpiece loading means 16 is disposed between the workpiece temporary placing means 13 and the workpiece loading / unloading area 24, and is placed on the workpiece temporary placing means 13 before grinding. The workpiece is conveyed onto the chuck table 62 of the chuck table mechanism 6 positioned in the workpiece loading / unloading area 24. Workpiece unloading means 1
7 is disposed between the workpiece loading / unloading area 24 and the cleaning means 14, and is placed on the chuck table 62 positioned in the workpiece loading / unloading area 24 after grinding. The workpiece is conveyed to the cleaning means 14.

The workpiece accommodated in the first cassette 11 is a semiconductor wafer whose front side is attached to an annular frame via a protective tape (hence, the back side of the semiconductor wafer is located on the upper side) or a support. It may be a semiconductor wafer whose front surface side is mounted on a substrate (therefore, the back surface of the semiconductor wafer is located on the upper side).
The first cassette 11 accommodating the semiconductor wafer that is such a workpiece is placed in a predetermined cassette loading area in the main portion 21 of the apparatus housing 2. Then, when all the semiconductor wafers before grinding which have been housed in the first cassette 11 placed in the cassette carry-in area are carried out, a new cassette containing a plurality of semiconductor wafers instead of the empty cassette 11 is carried out. 11 is manually placed in the cassette loading area. On the other hand, when a predetermined number of ground semiconductor wafers are carried into the second cassette 12 placed in a predetermined cassette unloading area in the main portion 21 of the apparatus housing 2, the second cassette 12 is manually operated. It is carried out and a new empty second cassette 12 is placed.

The grinding device in the illustrated embodiment is shown in FIG.
The control means 10 is provided as shown in FIG. Control means 1
0 is composed of a microcomputer, and a central processing unit (CP) that performs arithmetic processing according to a control program.
U) 101, a read only memory (ROM) 102 for storing control programs and the like, and a readable / writable random access memory (RAM) 103 for storing calculation results and the like.
, Timer (T) 104, and input interface 1
05 and an output interface 106. The grinding unit position detection means 5 is connected to the input interface 105 of the control means 10 thus configured.
Of the linear scale 51 constituting the detector 52 (LI
S), load detection means 64 (LOS), setup switch 110 (SW1), and other signals are input. Further, from the output interface 106, the servo motor 323 (M1), the pulse motor 44 (M2), the servo motor 65 (M3), the servo motor 664 (M4) and the cleaning means 14, the workpiece conveying means 15, the workpiece. A control signal is output to the article carry-in means 16, the workpiece carry-out means 17, and the like.

Next, the processing operation of the above-mentioned grinding apparatus will be briefly described with reference to FIG. A semiconductor wafer as a workpiece to be ground, which has been stored in the first cassette 11, is transported by the vertical movement and forward / backward movement of the workpiece transport means 15, and is placed on the workpiece temporary placement means 13. . The semiconductor wafer placed on the workpiece temporary placement means 13 is subjected to centering here, and then the workpiece loading / unloading area 24 is operated by the turning operation of the workpiece loading means 16.
The chuck table 62 is placed on the chuck table 62 of the chuck table mechanism 6. Chuck table 6
The semiconductor wafer placed on 2 is suction-held on the chuck table 62 by suction means (not shown).
After that, the chuck table mechanism 6 is moved in the direction indicated by the arrow 23a and positioned in the grinding area 25. Then, in the grinding area 25, the chuck table 62 holding the semiconductor wafer is rotated and the grinding member 327 of the grinding tool 325 is driven to rotate.
Is pressed against the back surface of the semiconductor wafer on the chuck table 62, and the chuck table mechanism 6 also causes the arrow 23 to move.
The semiconductor wafer is reciprocated over a predetermined range in the directions indicated by a and 23b, and thus the back surface of the semiconductor wafer is dry-ground by the action of the grinding member 327 to remove the residual processing strain.

When the grinding is completed, the grinding tool 325 is separated upward from the back surface of the semiconductor wafer, and the chuck table mechanism 6 is moved to the workpiece loading / unloading area 24 in the direction indicated by the arrow 23b. After that, suction holding of the ground semiconductor wafer on the chuck table 62 is released, and the semiconductor wafer whose suction holding is released is carried out by the workpiece carrying-out means 17 and conveyed to the cleaning means 14. The semiconductor wafer transferred to the cleaning means 14 is cleaned here and then stored in a predetermined position of the second cassette 12 by the workpiece transfer means 15.

In order to accurately process a semiconductor wafer, which is a workpiece, to a predetermined thickness by the above-described grinding operation, the origin position of the grinding tool with respect to the chuck table, that is, the grinding forming the grinding tool 325, is performed prior to the grinding operation. Member 327
It is necessary to set up a position where the ground surface of 1 contacts the mounting surface 621 of the chuck table 62. The setup will be described below. First, when the setup switch 110 (SW1) is turned on, the control means 10 drives the servo motor 664 (M4) of the chuck table moving mechanism 66 in the normal direction to move the chuck table mechanism 6 in the direction indicated by the arrow 23a, When the chuck table mechanism 6 reaches the grinding area 25, the servo motor 66
4 (M4) is stopped. Next, the control means 10 drives the pulse motor 44 (M2) of the grinding unit feeding mechanism 4 in the normal direction to lower the grinding unit 3. Then, when the grinding surface of the grinding member 327 constituting the grinding tool 325 comes into contact with the mounting surface 621 of the chuck table 62, the load detecting means 64 (LS) which has been outputting a predetermined voltage value until now.
The output voltage value of changes rapidly. On the other hand, the detector 5 of the linear scale 51 that constitutes the grinding unit position detection means 5
2 (LIS) outputs a pulse signal for each detected line of the linear scale 51 as the grinding unit 3 descends,
The control means 10 detects the movement of the grinding unit 3 from the detector 52 (LIS) moving along the linear scale 51 from the predetermined reference position to the time when the output voltage value of the load detection means 64 (LS) suddenly changes. The number of pulses is detected, the number of pulses is stored in the origin position storage area of the random access memory 103 (RAM) as the number of pulses corresponding to the origin position, and is set as the origin position. In the illustrated embodiment, three load detection means 64 (LS) are provided, so the origin position is set at the time when the signal with the fastest change in the output voltage value is output.

As described above, in the origin position setting mechanism of the grinding apparatus in the illustrated embodiment, the grinding unit 3 is moved down and the grinding surface of the grinding member 327 forming the grinding tool 325 is placed on the mounting surface 621 of the chuck table 62. Since the position of the grinding unit 3 detected by the grinding unit position detection unit 5 is set as the origin position when the load detection unit 64 (LS) that contacts and detects the load acting on the chuck table 62 detects the load, the grinding unit 3 detects the load. Whether the tool has a high hardness like a fixed grindstone or has a low hardness like a felt grindstone, it is possible to accurately detect the contact with the mounting surface 621 of the chuck table 62. An accurate origin position can be set. Further, the origin position setting mechanism of the grinding device in the illustrated embodiment is a load detection unit 64 (LS) that detects contact between the grinding surface of the grinding member 327 that constitutes the grinding tool 325 and the mounting surface 621 of the chuck table 62. Does not use an actuating mechanism like the conventional contact sensor, the configuration is extremely simple.

Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to the embodiment. For example, in the embodiment, an example is shown in which a felt grindstone in which abrasive grains are dispersed in a felt and fixed with an appropriate bonding agent is used as a grinding tool, but a grinding device using a fixed whetstone in which the abrasive grains are fixed with an appropriate bonding agent is used. Can also be applied to.

[0028]

In the origin position setting mechanism of the grinding apparatus according to the present invention, the origin position of the grinding tool with respect to the chuck table can be accurately set. Further, the load detecting means for detecting the contact between the grinding tool and the mounting surface of the chuck table does not use an actuating mechanism unlike the conventional contact sensor, so that the configuration is extremely simple.

[Brief description of drawings]

FIG. 1 is a perspective view of a grinding apparatus having an origin position setting mechanism according to the present invention.

FIG. 2 is a schematic configuration diagram of an origin position setting mechanism according to the present invention.

3 is a perspective view showing a grinding tool used in the grinding device shown in FIG. 1. FIG.

FIG. 4 is a perspective view showing a state of the grinding tool shown in FIG. 3 viewed from a lower surface side thereof.

[Explanation of symbols]

2: Device housing 3: Grinding unit 31: Moving base 32: Spindle unit 321: Spindle housing 322: rotating spindle 323: Servo motor (M1) 325: Grinding tool 4: Grinding unit feed mechanism 41: Male thread rod 44: Pulse motor (M2) 5: Grinding unit position detection means 51: Linear scale 52: Detector (LIS) 6: Chuck table mechanism 61: Support base 62: Chuck table 64: Load detection means (LOS) 65: Servo motor (M3) 66: Chuck table moving mechanism 661: Male thread rod 664: Servo motor (M4) 71, 72: bellows means 10: Control means 11: First cassette 12: Second cassette 13: Workpiece temporary placement means 14: Cleaning means 15: Workpiece conveying means 16: Workpiece loading means 17: Workpiece unloading means

Claims (4)

[Claims] 1. A chuck table having a mounting surface on which a workpiece is mounted, and a grinding tool provided with a grinding tool for grinding the workpiece mounted on the mounting surface of the chuck table. In a grinding device including a unit and a grinding unit feed mechanism that moves the grinding unit in a direction perpendicular to the mounting surface of the chuck table, an origin for setting an origin position of the grinding tool with respect to the chuck table. A position setting mechanism, load detecting means for detecting a load acting on the chuck table, grinding unit position detecting means for detecting a moving position of the grinding unit moved by the grinding unit feeding mechanism, and the load detecting means. Means and control means for setting the origin position based on a detection signal from the grinding unit position detection means, the control means The origin position setting of the grinding device is characterized in that the moving position of the grinding unit detected by the grinding unit position detecting means at the time when the load detecting means detects the load acting on the chuck table is set as an origin position. mechanism. 2. The origin position setting mechanism of the grinding apparatus according to claim 1, wherein the load detecting means is a Kistler dynamometer. 3. The origin position setting mechanism of a grinding apparatus according to claim 1, wherein said grinding unit position detecting means comprises a linear scale and a detector for detecting a detected line of said linear scale. 4. The origin position setting mechanism of a grinding apparatus according to claim 1, wherein the grinding tool is made of a felt grindstone in which abrasive grains are dispersed in a felt and fixed with an appropriate bonding agent.