JP2003071715A - Grinding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing apparatus which may not cause surface burn on a polishing surface and may polish a workpiece to have even thickness. SOLUTION: A polishing apparatus includes a chuck table for holding the workpiece, the polishing unit having the polishing tool for polishing the workpiece held on the chuck table, a polishing unit feeding mechanism for moving the polishing unit back and forth, and a chuck table mechanism for moving the chuck table to a polishing area and moving the chuck table back and forth in the polishing area. The apparatus comprises a load detection means for detecting a load applied to the chuck table, and a control means for controlling the polishing unit feeding mechanism and the chuck table mechanism according to a detected signal from the load detection means. The control means reduces a moving speed of the chuck table mechanism by a predetermined amount when the detected load detected by the load detection means is higher than a predetermined upper limit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer held on a 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 semiconductor chips, the back surface of the semiconductor wafer is usually ground to a predetermined thickness before cutting the semiconductor wafer along the streets to separate the individual rectangular areas. Is forming. A polishing apparatus for polishing the back surface of such a semiconductor wafer polishes a chuck table having a mounting surface on which a workpiece is mounted and a workpiece mounted on the mounting surface of the chuck table. And a polishing unit feed mechanism for moving the polishing unit in a direction perpendicular to the mounting surface of the chuck table. In such a polishing apparatus, a polishing unit is pressed against the back surface of a semiconductor wafer, which is a workpiece, at a predetermined feed rate to perform polishing.
The surface to be machined may be burnt or damaged due to the relationship between the polishing capacity and the feed rate of the polishing unit.

To solve the above-mentioned problems, the present applicant has a polishing resistance value detecting means for detecting a polishing resistance value generated when polishing a workpiece, and the polishing resistance value detecting means detects the polishing resistance value. Japanese Patent Application Laid-Open No. 2001-138219 proposes a polishing apparatus in which the feed of the polishing unit is controlled based on the resistance value to maintain the polishing resistance value within a predetermined range.

[0004]

Therefore, in particular, in a polishing apparatus for performing dry polishing using a felt grindstone in which abrasive grains are dispersed in felt and fixed with an appropriate bonding agent as a polishing tool, In order to release the frictional heat between the workpiece and the polishing tool, the chuck table holding the workpiece is reciprocated with respect to the polishing tool, and polishing is performed so that the polishing resistance value, that is, the polishing load falls within a predetermined range. Controlling the feed of the unit causes the following problems. That is, the above polishing apparatus uses a chuck table that holds a workpiece to
The workpiece is reciprocated at a moving speed of about 50 mm / minute from the outer peripheral portion of the workpiece to a region slightly beyond the center of rotation with respect to the polishing tool rotating at about 5000 rpm while rotating at about pm. Grind. However, when the thickness of the work piece is uneven and the polishing surface has irregularities, the polishing load increases when the polishing tool hits the protrusions, so the polishing unit moves backwards in order to keep the polishing load within the specified range. As a result, the polishing tool moves up and down along the unevenness of the work piece, so that the work piece cannot be ground to a uniform thickness. If the polishing work is performed without retracting the polishing unit even if the polishing load becomes large in order to solve such a problem, frictional heat between the workpiece and the polishing tool rises, causing surface burn on the polishing surface. The problem arises.

The present invention has been made in view of the above facts, and its main technical problem is to provide a polishing apparatus capable of polishing a workpiece to a uniform thickness without causing surface burn on the polishing surface. To provide.

[0006]

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. A polishing unit equipped with a polishing tool for polishing a workpiece to be mounted, a polishing unit feeding mechanism for moving the polishing unit forward and backward in a direction perpendicular to the mounting surface of the chuck table, and the chuck table. A chuck table mechanism for moving the chuck table to the polishing zone and reciprocating the chuck table in the polishing zone, and a load detecting means for detecting a load acting on the chuck table; Control means for controlling the polishing unit feeding mechanism and the chuck table mechanism based on the detection signal of the load. Polishing apparatus load detected by the detection means allowed to a predetermined amount decelerating the moving speed of the chuck table mechanism is higher than a predetermined upper limit value, characterized in that.

The control means retracts the polishing unit feed mechanism by a predetermined amount when the load is higher than the upper limit value even after a predetermined time elapses after decelerating the moving speed of the chuck table mechanism by a predetermined amount. . When the load detected by the load detection unit is lower than a predetermined lower limit value that is lower than the upper limit value, the control unit preferably advances the polishing unit feeding mechanism by a predetermined amount.

Further, according to the present invention, the above-mentioned polishing tool is made of a felt grindstone in which abrasive grains are dispersed in a felt and fixed with an appropriate bonding agent, and a polishing apparatus for polishing a workpiece by a dry method is provided. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of a polishing apparatus constructed according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a perspective view of a polishing apparatus according to the present invention. The polishing machine comprises a machine housing, generally designated by the number 2. The device housing 2 has an elongated rectangular parallelepiped main portion 21 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. There is. On the front surface of the upright wall 22, a pair of vertically extending guide rails 221 and 221 are provided.
Is provided. This pair of guide rails 221, 22
A polishing unit 3 is attached to the first unit so as to be movable in the vertical direction.

The polishing unit 3 has 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 polishing 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 polishing tool 325 includes a disc-shaped support member 326 and a disc-shaped polishing 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 supporting member 326 forms a circular supporting surface, and the polishing member 327 is used as the supporting member 3 by an appropriate adhesive such as an epoxy resin adhesive.
It is joined to 26 circular bearing surfaces. Polishing 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 polishing 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 description. The description is omitted in the book. The polishing 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 328 is screwed into the blind screw hole 326a formed in the support member 326 of the polishing tool 325 through the through hole formed in the mounting member 324, whereby the polishing tool 325 is attached to the mounting member 324. It is installed.

Returning to FIG. 1 and continuing the description, in the polishing apparatus in the illustrated embodiment, the polishing unit 3 is moved in the vertical direction along the pair of guide rails 221 and 221 (to be described below as a mounting surface of a chuck table). A polishing unit feed mechanism 4 for moving the polishing unit in the vertical direction is provided. The polishing 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 is rotatably supported at its upper end and lower end by bearing members 42 and 43 attached to the upright wall 22. 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 forward direction, the moving base 31 or the polishing unit 3 is lowered or advanced, and the pulse motor 44
When (M2) reverses, the moving base 31 or the polishing unit 3
Is raised or retracted.

The polishing apparatus in the illustrated embodiment is shown in FIG.
As shown in FIG. 3, the polishing unit position detecting means 5 for detecting the moving position of the polishing unit 3 is provided. The polishing 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 three load detecting means 64 (LOS), a Kistler dynamometer is used in the illustrated embodiment,
A voltage signal corresponding to the load acting on the chuck table 62 is output. The voltage signals output from the three load detection means 64 (LOS) are converted into digital signals by an A / D converter (not shown) and sent to the control means described later.

The polishing apparatus 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 polishing 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 polishing 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 mechanism 6. The front end of the bellows means 72 is fixed to the rear end surface of the support base 61 of the chuck table mechanism 6, and the rear end thereof is the upright wall 2 of the apparatus housing 2.
It is fixed to the front of 2. When the chuck table mechanism 6 is moved in the direction indicated by the arrow 23a, the bellows means 71 is expanded and the bellows means 72 is contracted, and when the chuck table mechanism 6 is moved in the direction indicated by arrow 23b, the bellows means is formed. 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 an object to be processed before polishing 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 of the main portion 21 of the apparatus housing 2 and stores the workpiece after polishing. 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 polishing. The cleaning means 14 is arranged between the workpiece loading / unloading area 24 and the second cassette 12 and cleans the workpiece after polishing. 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 polishing. 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
Reference numeral 7 denotes a workpiece to be processed after polishing, which 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. The object 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 polishing which were accommodated in the first cassette 11 placed in the cassette carry-in area are unloaded, 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 polished semiconductor wafers are loaded 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 polishing apparatus 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 polishing 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), signals from the load detection means 64 (LOS), etc. are input. From the output interface 106, the servo motor 323 (M1) and the pulse motor 44 (M
2), servo motor 65 (M3), servo motor 664
(M4) and cleaning means 14, workpiece conveying means 15,
The control signal is output to the workpiece carry-in means 16, the workpiece carry-out means 17, and the like.

Next, the processing operation of the above-mentioned polishing apparatus will be briefly described with reference to FIGS. 5 and 6. The semiconductor wafer as the workpiece before polishing, which is accommodated in the first cassette 11, is transported by the vertical movement and the 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 placing means 13 is positioned in the workpiece loading / unloading area 24 by the turning operation of the workpiece loading means 16 after centering is performed here. It is placed on the chuck table 62 of the chuck table mechanism 6. The semiconductor wafer W placed on the chuck table 62 is suction-held on the chuck table 62 by suction means (not shown).

When the semiconductor wafer W is suction-held on the chuck table 62, the servo motor 664 (M4) of the chuck table moving mechanism 66 is driven to rotate normally, and the chuck table mechanism 6 is moved in the direction indicated by the arrow 23a to be polished. It is positioned at the polishing start position P1 (see FIGS. 5 and 6) in the zone 25. Polishing start position P1 in the polishing area 25
In addition, the servo motor 65 (M3) is driven to rotate the chuck table 62 holding the semiconductor wafer W, the servo motor 323 (M1) is driven to rotate the polishing tool 325, and the polishing unit is also used. The pulse motor 44 (M2) of the feed mechanism 4 is normally driven to move the polishing unit 3 downward or forward. And the polishing tool 3
25 polishing members 327 press the back surface of the semiconductor wafer on the chuck table 62, and the three load detecting means 6
The total value of the loads detected by the 4 (LOS) is a predetermined upper limit value (for example, 10 kg) and a predetermined lower limit value (for example, 10 kg).
The polishing unit 3 is lowered until it reaches the range of 5 kg).
Next, the servo motor 664 (M4) of the chuck table moving mechanism 66 is normally driven to drive the chuck table mechanism 6 in the direction indicated by the arrow 23a to hold the polishing member 327 of the polishing tool 325 on the chuck table 62. It moves to the polishing end position P2 which slightly exceeds the center position O of W. At this time, the initial speed (V5) of the chuck table mechanism 6 is set to, for example, 50 mm / min.
When the chuck table 62 has moved to the polishing end position P2, the servo motor 664 (M4) is reversely driven to move the chuck table mechanism 6 in the direction indicated by the arrow 23b to return it to the polishing start position P1, and the above operation is repeated. Run. By performing this grinding operation for a preset time or reciprocating the chuck table mechanism 6 a set number of times, the back surface of the semiconductor wafer is dry-polished by a predetermined amount by the action of the polishing member 327.

When the polishing is completed, the polishing 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 polished 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. Cleaning means 14. The transported semiconductor wafer is cleaned here and then stored in a predetermined position of the second cassette 12 by the workpiece transfer means 15.

In the illustrated embodiment, the control shown in the flow chart of FIG. 5 is executed in order to polish the semiconductor wafer, which is the workpiece, to a uniform thickness without causing surface burning in the above-mentioned polishing work. . The routine shown in FIG. 7 is performed by the read only memory (ROM) 10 of the control means 10.
2 is stored in advance in the central processing unit (CPU) 10
1 is repeated every predetermined time.

The control of the polishing unit feed mechanism 4 and the chuck table moving mechanism 66 during the polishing operation will be described below with reference to the flowchart of FIG. In addition,
The flowchart of FIG. 7 shows control of the polishing unit feed mechanism 4 and the chuck table moving mechanism 66 while the chuck table 62 moves from the polishing start position to the polishing end position described above. The control means 10 first determines that the total value P0 of the loads detected by the three load detection means 64 (LOS) in step S1 is a predetermined upper limit value P2.
(For example, 10 kg) Check whether it is below. When the total value P0 of the loads is less than or equal to the upper limit value P2, the control means 10 proceeds to step S2 and the three load detection means 6 described above.
4 (LOS), it is checked whether the total value P0 of the loads detected is equal to or less than a predetermined lower limit value P1 (for example, 5 kg). If the total value P0 of the loads is less than or equal to the lower limit value P1, the control means 10 determines that the polishing load is within the predetermined range, and the moving speed V of the chuck table moving mechanism 66 is set to the initial speed V5 (for example, 50 mm / minute). ) And continue the polishing operation.

When the total value P0 of the loads detected by the three load detecting means 64 (LOS) in the step S1 is higher than a predetermined upper limit P2 (eg 10 kg) (eg, as shown in FIG. 5). In the case where the semiconductor wafer W is formed in a convex shape toward the center, P
3 position is polished), the control means 10 determines that the surface burn may occur if the polishing operation is continued in this state, and the process proceeds to step S3, where the servo motor 664 ( M4) moving speed V is V4
(For example, 40 mm / min) The speed is reduced. Then, the control means 10 sets the timer (T) 104 to the predetermined time T.
Set to 1 (eg 5 seconds). Next, the control means 1
0 proceeds to step S4 and the above three load detection means 64
It is checked whether the total value P0 of the loads detected by (LOS) has become equal to or less than a predetermined upper limit value P2. When the total value P0 of the loads becomes equal to or less than the predetermined upper limit value P2, the control means 10 determines that the polishing load is within the predetermined range, and the moving speed V of the chuck table moving mechanism 66 is set to the current V4 ( For example, 40 mm / min) is maintained and the polishing operation is continued. The total value P0 of the loads is a predetermined upper limit value P2
If not, the control means 10 proceeds to step S5 to set the moving speed V of the chuck table moving mechanism 66 to V4.
It is checked whether or not the elapsed time TS after has passed the predetermined time T1. If the elapsed time TS has not passed the predetermined time T1, the process returns to step S3 and step S3.
The step S5 is repeatedly executed. In this way, the total value P0 of the loads detected by the three load detecting means 64 (LOS) is the predetermined upper limit value P2 (for example, 10).
If it is higher than kg), the moving speed of the chuck table 62 is decelerated, so that the polishing time becomes longer and the polishing load is reduced. It can be ground to a thickness.

Although the total value P0 of the loads detected by the three load detecting means 64 (LOS) in the step S4 has not yet become the predetermined upper limit value P2 or less, the elapsed time TS is the predetermined time T1 in the step S4. When, for example, the semiconductor wafer W is formed in a convex shape toward the center as shown in FIG. 5 and the position P4 is polished, the control means 10
Advances to step S6 and the chuck table moving mechanism 66
The servo motor 664 (M4) of No. 1 to reduce the moving speed V to V3 (for example, 30 mm / min),
The control means 10 sets the timer (T) 104 to a predetermined time T1.
(For example, 5 seconds). And the control means 1
0 proceeds to step S7 and the above-mentioned three load detecting means 64
It is checked whether the total value P0 of the loads detected by (LOS) has become equal to or less than a predetermined upper limit value P2. If the total value P0 of the loads becomes equal to or less than the predetermined upper limit value P2, the control means 10 determines that the polishing load is within the predetermined range, and the moving speed V of the chuck table moving mechanism 66 is set to the current V3 ( For example, 30 mm / min) is maintained and the polishing operation is continued. The total value P0 of the loads is a predetermined upper limit value P2
If not, the control means 10 proceeds to step S8 to set the moving speed V of the chuck table moving mechanism 66 to V3.
It is checked whether or not the elapsed time TS after has passed the predetermined time T1. If the elapsed time TS has not passed the predetermined time T1, the process returns to step S6 and step S6.
The steps S8 to S8 are repeated. When the total value P0 of the loads does not become equal to or less than the predetermined upper limit value P2 in step S7 and the elapsed time TS exceeds the predetermined time T1 in step S8, the control means 10
Advances to step S9 to reverse drive the pulse motor 44 (M2) of the polishing unit feed mechanism 4 by a predetermined number of pulses.
As a result, the polishing unit 3 is raised or retracted by a predetermined amount, and the pressing force of the polishing tool 325 on the semiconductor wafer is reduced, so that polishing can be performed without causing surface burning.

Next, a case where the total value P0 of the loads detected by the three load detecting means 64 (LOS) in step S2 is lower than a predetermined lower limit value P1 (for example, 5 kg) will be described. When the total value P0 of the loads is lower than a predetermined lower limit value P1 (for example, 5 kg) (for example, when the semiconductor wafer W is formed in a concave shape toward the center as shown in FIG. 6, the position of P5 is Is polished), the control means 10 controls step S10.
To the pulse motor 44 of the polishing unit feed mechanism 4.
(M2) is driven forward by a predetermined number of pulses. As a result, the polishing unit 3 is lowered or advanced by a predetermined amount, and the pressing force of the polishing tool 325 on the semiconductor wafer is increased.
Polishing efficiency is improved.

[0031]

In the polishing apparatus according to the present invention, the load acting on the chuck table holding the workpiece is detected, and when the load is higher than the predetermined upper limit value, the moving speed of the chuck table is reduced by a predetermined amount. Since the polishing time is lengthened and the polishing load is reduced, even if there is a convex portion on the ground surface of the workpiece, polishing can be performed to a uniform thickness without causing surface burning.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a polishing apparatus configured according to the present invention.

FIG. 2 is a schematic configuration diagram showing a main part of the polishing apparatus shown in FIG.

FIG. 3 is a perspective view showing a polishing tool used in the polishing apparatus shown in FIG.

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

5 is an explanatory view showing a relationship with a polishing tool when a workpiece placed on a chuck table equipped in the polishing apparatus shown in FIG. 1 is formed in a convex shape toward a central portion.

6 is an explanatory view showing a relationship with a polishing tool when a workpiece placed on a chuck table provided in the polishing apparatus shown in FIG. 1 is formed in a concave shape toward a central portion.

FIG. 7 is a flowchart showing an operation procedure of control means provided in the polishing apparatus shown in FIG.

[Explanation of symbols]

2: Device housing 3: Polishing unit 31: Moving base 32: Spindle unit 321: Spindle housing 322: rotating spindle 323: Servo motor (M1) 325: Polishing tool 4: Polishing unit feeding mechanism 44: Pulse motor (M2) 5: Polishing 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 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

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Claims (4)

[Claims] 1. A polishing apparatus including a chuck table having a mounting surface on which a workpiece is mounted, and a polishing tool for polishing the workpiece mounted on the mounting surface of the chuck table. A unit, a polishing unit feed mechanism for moving the polishing unit forward and backward in a direction perpendicular to the mounting surface of the chuck table, and a chuck for moving the chuck table to the polishing area and reciprocating the chuck table in the polishing area. In a polishing apparatus including a table mechanism, load detecting means for detecting a load acting on the chuck table, and controlling the polishing unit feeding mechanism and the chuck table mechanism based on a detection signal from the load detecting means. And a control means for controlling the load when the load detected by the load detection means is higher than a predetermined upper limit value. A polishing apparatus, wherein the moving speed of the chuck table mechanism is reduced by a predetermined amount. 2. The control means controls the polishing unit feed mechanism by a predetermined amount when the load is higher than the upper limit value even after a predetermined time elapses after decelerating the moving speed of the chuck table mechanism by a predetermined amount. The polishing apparatus according to claim 1, which is retracted. 3. The control unit advances the polishing unit feed mechanism by a predetermined amount when the load detected by the load detection unit is lower than a predetermined lower limit value lower than the upper limit value. 2. The polishing apparatus according to 2. 4. The polishing apparatus according to claim 1, wherein the polishing tool comprises a felt grindstone in which abrasive grains are dispersed in a felt and fixed with an appropriate bonding agent.