JP2003311613A - Polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing device having a detecting means capable of accurately detecting a load charged to a workpiece placed on a chuck table even when mechanical vibration occurs. <P>SOLUTION: The polishing device comprises the chuck table having a placing surface for supporting a workpiece, a polishing unit having a polishing tool for polishing the workpiece placed on the placing surface of the chuck table, a polishing unit feeding mechanism for moving the polishing unit back and forth in the vertical direction to the placing surface of the chuck table, a load sensor for detecting a load charged to the chuck table, and a controlling means for controlling the polishing unit feeding mechanism based on an output signal from the load sensor. The polishing device has a low pass filter for passing a predetermined frequency or lower of the output signal from the load sensor, and inputs the signal having passed through the low pass filter into the controlling means. <P>COPYRIGHT: (C)2004,JPO

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, the chuck table is rotated, the polishing tool is rotated and the polishing unit is lowered to press the workpiece placed on the chuck table with a predetermined load while the chuck table is being rotated. The workpiece is polished by polishing and feeding in a horizontal plane. Therefore, the polishing apparatus includes a load sensor that detects a load that presses the workpiece by the polishing tool, and a control unit that controls the polishing unit feeding mechanism based on the detection signal from the load sensor.

[0003]

Therefore, a high-sensitivity sensor such as a Kistler dynamometer is used as the load sensor. Therefore, vibration due to rotation of the spindle equipped with the polishing tool, chuck table It is greatly affected by vibrations generated during polishing feed and vibrations caused by rotation of the chuck table. FIG. 7 shows the output signal of the Kistler dynamometer arranged between the chuck table and the supporting member of the polishing apparatus. The operating conditions of the polishing apparatus at this time are that the spindle rotation speed is 6000 rpm, the polishing feed speed is 200 mm / min, and the chuck table rotation speed is 300 rpm. In FIG. 7, the horizontal axis represents time and the vertical axis represents output voltage. The output voltage fluctuates by about 1.6 V due to the influence of each vibration described above, and this fluctuation value corresponds to a pressure of about 3.2 kgf. In such a situation, even if a load is applied to the workpiece placed on the chuck table, it is not possible to accurately determine the load.

The present invention has been made in view of the above facts, and its main technical problem is to apply a load acting on a workpiece placed on the chuck table even in a situation where mechanical vibration occurs. An object of the present invention is to provide a polishing apparatus provided with a detecting means capable of accurately detecting

[0005]

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. In a polishing apparatus including a load sensor that detects a load acting on a load and a control unit that controls the polishing unit feeding mechanism based on an output signal from the load sensor, a predetermined value of the output signal from the load sensor A polishing apparatus comprising a low-pass filter that passes the following frequencies, and a signal passed through the low-pass filter is input to the control means as a load signal. It is provided.

The specification of the low-pass filter is preferably set to 10 Hz.

[0007]

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 comprises 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 supporting portion 313.
A spindle housing 321 mounted on the spindle housing 321, a rotary spindle 322 rotatably arranged 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 servomotor 323 (M1) is transmission-coupled to the rotary spindle 322. The lower end of the rotary spindle 322 has a spindle housing 321.
Of the rotary spindle 322, 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 32.
6 and a disk-shaped polishing member 327.
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 constitutes a circular support surface, and the polishing member 327 is joined to the circular support surface of the support member 326 by an appropriate adhesive such as an epoxy resin adhesive. As the polishing member 327, in the illustrated embodiment, a felt grindstone in which abrasive grains are dispersed in a felt and fixed with an appropriate bonding agent is used. For a detailed description of the structure of the polishing member 327 itself made of the felt grindstone, Japanese Patent Application No. 2001-93397 already proposed by the present applicant.
Since the detailed description is given in the specification and drawings, the description will be omitted and the description will be omitted in the present specification. The polishing tool 325 is positioned on the lower surface of the mounting member 324 fixed to the lower end of the rotary spindle 322, and the mounting member 3
By attaching a fastening bolt 328 to a blind screw hole 326a formed in the support member 326 of the polishing tool 325 through a through hole formed in the mounting member 324, the mounting member 32
The polishing tool 325 is attached to the No. 4 unit.

Returning to FIG. 1 and continuing the description, in the polishing apparatus in the illustrated embodiment, the polishing unit 3 is moved vertically along the pair of guide rails 221 and 221 (to a mounting surface of a chuck table to be described later). 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 FIG. 1 and FIG. 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 supporting base 61.
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 supporting means 63 constituting the chuck table mechanism 6 are three supporting columns 631 (only two are shown in FIG. 2) arranged on the supporting base 61, and the supporting 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 64 (M3) as a drive source for rotationally driving the chuck table 62 is arranged on the support base 61 below the support plate 632. The output shaft of the servo motor 64 (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.
A load sensor 65 (LOS) for detecting the load acting on the chuck table 62 is provided between and. As the three load sensors 65 (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 (P1, P2, P3) output from the three load sensors 65 (LOS) pass through the low-pass filters 8 that pass frequencies of 10 Hz or less, and are converted into digital signals by the A / D converters 9. And sent to the control means described later. FIG. 6 shows a load signal detected by the load sensor 65 and output through the low-pass filter 8. The operating condition of the polishing apparatus at this time is that the rotation speed of the spindle is 6000.
rpm, polishing feed speed is 200 mm / min, and chuck table rotation speed is 300 rpm. Load sensor 6
Since the frequency signal higher than 10 Hz is cut by the low-pass filter 8 from the voltage signal output from 5, the load fluctuation component due to the vibration due to the rotation of the motors is removed. As a result, the voltage signal output through the low pass filter 8 has an output voltage fluctuation of about 0.
2V, which corresponds to a pressure of about 0.4 kgf. In this way, the fluctuation of the voltage signal output through the low-pass filter 8 is 1/8 of the fluctuation of the voltage signal output from the load sensor shown in FIG. 7 described above. It should be noted that the low-pass filter 8 has a specification that if the frequency to be passed is high, it is easily affected by vibration, and if the frequency to be passed is low, the reaction when a load acts on the chuck table 62 is lowered, so about 10 Hz is suitable. is there.

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 above, the reciprocating movement, that is, the grinding feed, is performed in a direction indicated by arrows 23a and 23b over a predetermined range.

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, a first cassette 11, a second cassette 12, and a 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 contained 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 sensor 65 (LOS), etc. are input. From the output interface 106, the servo motor 323 (M1) and the pulse motor 44 (M
2), servo motor 64 (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. 1 and 2. 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 for polishing. It is located at the polishing start position in zone 25. At the polishing start position in the polishing area 25, the servo motor 64
(M3) is driven to rotate the chuck table 62 holding the semiconductor wafer W, and the servo motor 323 (M
1) is driven to rotate the polishing tool 325, and the pulse motor 44 (M2) of the polishing unit feed mechanism 4 is driven.
To drive the polishing unit 3 downward or forward. Then, the polishing member 327 of the polishing tool 325 presses the back surface of the semiconductor wafer on the chuck table 62, and the total value of the loads detected by the three load sensors 65 (LOS) is a predetermined upper limit value (for example, 10 kg. ) And a predetermined lower limit value (for example, 5 kg), the polishing unit 3 is lowered. Next, the servo motor 664 (M4) of the chuck table moving mechanism 66 is normally driven to move the chuck table mechanism 6 in the direction indicated by the arrow 23a so that the polishing member 327 of the polishing tool 325 causes the chuck table 632 to move.
The semiconductor wafer W held by is moved to a polishing end position slightly beyond the center position. At this time, the moving speed of the chuck table mechanism 6 is set to, for example, 200 mm / min. When the chuck table 62 moves to the polishing end position, 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 to the polishing start position, and the above polishing operation is repeatedly performed. To do. By performing this polishing operation for a preset time or by 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 three load sensors 65 (LOS) are used to polish the semiconductor wafer, which is the workpiece, to a uniform thickness without surface burning in the above-described polishing operation. Based on the detected detection signal, the control shown in the flowchart of FIG. 5 is executed. The routine of FIG. 5 is stored in advance in the read-only memory (ROM) 102 of the control means 10, and is repeatedly executed by the central processing unit (CPU) 101 at predetermined time intervals.

The control of the polishing unit feeding mechanism 4 during the polishing operation will be described below with reference to the flowchart of FIG. The flowchart of FIG. 5 shows the control of the polishing unit feed mechanism 4 while the chuck table 62 moves from the polishing start position to the polishing end position described above. The control means 10 first sets the above-mentioned 3 in step S1.
The total value (P0 = P1 + P) of the load signals (P1, P2, P3) detected by the individual load sensors 65 (LOS).
2 + P3) is calculated. When the total value (P0) of the load signals detected by the three load sensors 65 (LOS) is obtained in step S1, the control means 10 proceeds to step S2 and the total value (P0) of the load signals is predetermined. It is checked whether the upper limit value (PS2: for example, 15 kg) or less. The total value (P0) of the load signals is the upper limit value (PS
2) In the case of the following, the control means 10 proceeds to step S3 and the total value (P0) of the load signals is a predetermined lower limit value (PS1:
For example, check whether it is 14 kg or more. If the total value (P0) of the load signals is equal to or higher than the lower limit value (PS1), the control means 10 causes the polishing load to fall within a predetermined range (14 to 1).
5 kg), the process proceeds to step S4, the operation of the pulse motor 44 (M2) of the polishing unit feeding mechanism 4 is stopped, and the polishing operation is continued.

When the total value (P0) of the load signals is higher than the predetermined upper limit value (PS2) in step S2, the control means 10 may cause surface burn if the polishing operation is continued in this state. If it is determined, the process proceeds to step S5, and the pulse motor 44 (M2) of the polishing unit feed mechanism 4 is reversely driven 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, when the total value (P0) of the load signals is lower than the predetermined lower limit value (PS1) in step S3, the control means 10 proceeds to step S6 to pulse the polishing unit feed mechanism 4. The motor 44 (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, so that the polishing efficiency is improved.

As described above, during the polishing operation, the polishing tool 325 is based on the load signals (P1, P2, P3) detected by the three load sensors 65 (LOS).
Pulse motor 44 (M of the polishing unit feeding mechanism 4 so that the pressing force of the semiconductor unit on the semiconductor wafer is maintained within a predetermined range.
2) is controlled. At this time, load signals (P1, P2, P
3) is the three load sensors 65 (LO
The frequency signals higher than 10 Hz are cut by the low-pass filter 8 from the voltage signals output from S), and the load fluctuation component based on the mechanical vibration is removed. Therefore, the fluctuation is as described above, the load sensor 65 (LOS). It is as small as ⅛ with respect to the fluctuation of the voltage signal output from. Therefore, the pressing force of the polishing tool 325 on the semiconductor wafer can be accurately controlled within a predetermined range.

[0029]

In the polishing apparatus according to the present invention, the output signal from the load sensor for detecting the load acting on the chuck table holding the workpiece is passed through a low pass filter which passes a frequency below a predetermined value. Since the signal passed through the low pass filter is used as the weight signal,
The fluctuation of the load due to mechanical vibration is removed, and the fluctuation of the load signal becomes extremely small. Therefore, the pressing force of the polishing tool acting on the workpiece held on the chuck table can be accurately determined.

[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 a flowchart showing an operation procedure of a control means equipped in the polishing apparatus shown in FIG.

FIG. 6 is a diagram showing an output voltage obtained by passing an output voltage from a load sensor through a low pass filter.

FIG. 7 is a diagram showing an output voltage from a load sensor.

[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: Servo motor (M3) 65: Load detection means (LOS) 66: Chuck table moving mechanism 664: Servo motor (M4) 71, 72: bellows means 8: Low pass filter 9: A / D converter 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 (2)

[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, a load sensor for detecting a load acting on the chuck table, and an output signal from the load sensor. A polishing apparatus having a control means for controlling the polishing unit feeding mechanism based on the above, comprising a low-pass filter for passing a frequency of a predetermined value or less among output signals from the load sensor, and outputting a signal passed through the low-pass filter. The polishing apparatus is characterized in that it is inputted to the control means as a load signal. 2. The polishing apparatus according to claim 1, wherein the low-pass filter has a specification of 10 Hz.