JP2011224758A - Polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To polish a thickness of a workpiece to a target finishing thickness with high accuracy.SOLUTION: The thickness of the workpiece is measured from the exposed surface to be polished of the workpiece (step S1), the surface to be polished of the workpiece is polished for a predetermined time by pressing a polishing pad to the whole surface of the surface to be polished of the workpiece (step S2), the thickness of the workpiece is measured from the exposed surface to be polished of the workpiece while a part of the surface to be polished is exposed (step S3), a polishing amount is calculated by the thickness of the workpiece obtained from the processing of the step S1 and the thickness of the workpiece obtained from the processing of the step S3 and the thickness variation of the workpiece to an elapsed time of polishing is obtained based on a polishing time in the processing of the step S1 (step S4), and the polishing time is set based on the thickness variation of the workpiece to the elapsed time of polishing obtained from the processing of the step S4 and the target finishing thickness and the surface to be polished of the workpiece is polished by pressing the polishing pad to the whole surface of the surface to be polished of the workpiece at pressure equal to that of the step S1 (step S5).

Description

  The present invention relates to a polishing method in which a polishing pad is pressed against the entire surface of a workpiece to be polished until the target finish thickness is reached.

  In the manufacturing process of a semiconductor device, in order to process the thickness of the semiconductor device to a target thickness, the semiconductor wafer is obtained by performing a grinding process of grinding the back surface side of the semiconductor wafer in which a large number of semiconductor devices are formed on the front surface side. Thinly processed. In addition, with the recent thinning of semiconductor devices, semiconductor wafers are processed thinner in the grinding process. For this reason, in the grinding process, it is required to manage the thickness of the semiconductor wafer with high accuracy.

  Generally, the grinding process is performed while measuring the thickness of a semiconductor wafer. As a method of measuring the thickness of the semiconductor wafer during the grinding process, there is a contact-type thickness measurement method using a measurement probe brought into contact with the back side of the semiconductor wafer (see Patent Document 1). In this measurement method, the difference in height measured by applying a pair of contacts of a two-point in-process gauge to the back surface of the semiconductor wafer attracted by the chuck and the attracting surface of the chuck is measured as the thickness of the semiconductor wafer. To do.

  However, according to this measuring method, there is a problem in that the semiconductor probe is scratched by contact with the measuring probe, and the scratch causes a reduction in the bending strength of the semiconductor wafer. This problem is particularly noticeable when the thickness of the semiconductor wafer is relatively thin because the influence of the depth of the flaw becomes greater. Further, according to this measuring method, the difference in height between the back surface of the semiconductor wafer and the chucking surface of the chuck is measured as the thickness of the semiconductor wafer. For this reason, it is impossible to directly measure the thickness of the semiconductor wafer itself excluding the thickness of the protective tape attached to the surface side of the semiconductor wafer.

  Therefore, the patent applicant of the present invention has proposed a non-contact type thickness measuring method for measuring the thickness of a semiconductor wafer without bringing a measuring element such as a measuring probe into contact with the semiconductor wafer (see Patent Document 2). . In this measurement method, a semiconductor wafer is irradiated with laser light, and the thickness of the semiconductor wafer is measured based on a waveform of an interference wave between reflected light from the back surface of the semiconductor wafer and reflected light from the surface of the semiconductor wafer. According to this measurement method, since the thickness of the semiconductor wafer is measured in a non-contact manner, the semiconductor wafer is not damaged. Further, according to this measurement method, the thickness of the semiconductor wafer is measured by using the reflected light from the back surface and the front surface of the semiconductor wafer, so the thickness of the semiconductor wafer itself is directly measured excluding the thickness of the protective tape. be able to.

Japanese Patent Laid-Open No. 2001-9716 JP 2009-50944 A

  However, when the polishing pad is pressed against the entire back surface of the semiconductor wafer to polish the back surface of the semiconductor wafer, the contact-type or non-contact-type thickness measurement method described above is used because the back surface of the semiconductor wafer is not exposed by the polishing pad. It is not possible to measure the thickness of the semiconductor wafer during polishing. For this reason, when the polishing pad is pressed against the entire back surface of the semiconductor wafer and the back surface of the semiconductor wafer is polished, the thickness of the semiconductor wafer is accurately polished to the target finish thickness by setting the polishing time with high accuracy. It was difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a polishing method capable of highly accurately polishing a workpiece to a target finish thickness.

  In order to solve the above-described problems and achieve the object, the polishing method according to the present invention applies a workpiece to the workpiece until the polishing pad is pressed against the entire surface to be polished of the workpiece held on the holding surface until the target finish thickness is reached. A polishing method for polishing a polishing surface, wherein at least a part of the surface to be polished is exposed, and the thickness of the workpiece is measured by a measuring unit from the exposed surface to be polished of the workpiece held on the holding surface. One measuring step, and after the first measuring step, a first polishing step of pressing the polishing pad against the entire surface of the workpiece to be polished to polish the workpiece to be polished for a predetermined time, A second measuring step of measuring the thickness of the workpiece from the exposed surface to be polished of the workpiece held on the holding surface in a state where a part of the surface to be polished is exposed again after the one polishing step; And the thickness of the workpiece obtained in the first measuring step and the A calculation step for calculating a polishing amount according to the thickness of the workpiece obtained in step 2 and calculating a change in the thickness of the workpiece with respect to the elapsed time of polishing based on the polishing time in the first polishing step; The polishing pad is set on the entire surface of the workpiece to be polished with the same pressure as in the first polishing step by setting the polishing time based on the change in the thickness of the workpiece with respect to the polishing elapsed time determined in the process and the target finish thickness And a final polishing step of polishing the surface to be polished of the workpiece by pressing.

  According to the polishing method of the present invention, the polishing time is set based on the change in the thickness of the workpiece with respect to the elapsed time of polishing and the target finish thickness, and the same pressure as in the first polishing step is applied to the entire surface to be polished of the workpiece. Since the surface to be polished of the workpiece is polished by pressing the polishing pad, the thickness of the workpiece can be accurately polished to the target finish thickness.

FIG. 1 is a perspective view showing a configuration of a surface side of a workpiece to be polished by a polishing method according to an embodiment of the present invention. FIG. 2 is a perspective view showing the configuration of a polishing apparatus used in the polishing method according to one embodiment of the present invention. FIG. 3 is a side view showing a configuration of a polishing tool and a chuck table constituting the polishing apparatus shown in FIG. FIG. 4 is an enlarged perspective view showing a part of the polishing apparatus shown in FIG. FIG. 5 is a cross-sectional view showing a configuration of a thickness measuring device constituting the polishing apparatus shown in FIG. FIG. 6 is a flowchart showing a flow of a polishing method according to an embodiment of the present invention. FIG. 7 is a diagram for explaining the first and second measurement steps shown in FIG. FIG. 8 is a diagram for explaining the first polishing step and the final polishing step shown in FIG. FIG. 9 is a diagram for explaining the calculation step shown in FIG.

  Hereinafter, a polishing method according to an embodiment of the present invention will be described with reference to the drawings.

[Work structure]
First, with reference to FIG. 1, the structure of the workpiece | work used as the grinding | polishing object of the grinding | polishing method which is one Embodiment of this invention is demonstrated.

  FIG. 1 is a perspective view showing a configuration of a surface side of a workpiece to be polished by a polishing method according to an embodiment of the present invention. As shown in FIG. 1, the workpiece 1 has a substantially disk shape, and a plurality of devices 2 are formed in a lattice shape on the surface thereof. Further, the work 1 has a notch 3 indicating a crystal orientation. In the polishing method according to an embodiment of the present invention, polishing is performed with the back side as the surface to be polished while the surface side of the work 1 is held as the surface to be held. Although not shown, it is desirable to attach a protective tape for protecting the surface of the work 1 on the surface side of the work 1 serving as a held surface.

The material for forming the workpiece 1 is not particularly limited, but a silicon wafer, a semiconductor wafer such as GaAs, ceramic, glass, a sapphire (Al ₂ O ₃ ) inorganic material substrate, a ductile material such as a plate metal or a resin, Furthermore, the flatness (TTV: Total Thickness Variation: the difference between the maximum value and the minimum value of the entire surface to be polished measured in the thickness direction with the surface to be polished as the reference surface) Various required processing materials can be exemplified.

[Configuration of polishing equipment]
Next, the configuration of a polishing apparatus used in the polishing method according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 2 is a perspective view showing the configuration of a polishing apparatus used in the polishing method according to one embodiment of the present invention. FIG. 3 is a side view showing a configuration of a polishing tool and a chuck table constituting the polishing apparatus shown in FIG. FIG. 4 is an enlarged perspective view showing a part of the polishing apparatus shown in FIG. FIG. 5 is a cross-sectional view showing a configuration of a thickness measuring device constituting the polishing apparatus shown in FIG. In the following, in the horizontal plane, the extending direction of the main portion 21 is the X direction, the direction in the horizontal plane perpendicular to the X axis direction is the Y axis direction, and the normal direction of the XY plane (horizontal plane) (Vertical direction) is defined as the Z-axis direction.

  As shown in FIG. 2, the polishing apparatus 10 used in the polishing method according to one embodiment of the present invention polishes the surface to be polished of the workpiece 1 using a polishing tool 43 and includes an apparatus housing 20. . The device housing 20 includes a rectangular parallelepiped main portion 21 that extends in the X-axis direction and an upright wall 22 that is provided at the rear end of the main portion 21 and extends substantially in the Z-axis direction. A chuck table mechanism 30 is disposed on the upper surface of the main portion 21. The chuck table mechanism 30 includes a support base 31 and a disk-shaped chuck table 32 disposed on the support base 31.

  The support base 31 supports the chuck table 32 so as to be horizontally movable in the X-axis direction by a table horizontal movement mechanism 211 extending in the X-axis direction. Thereby, the chuck table 32 includes a work loading / unloading area E1 on the table horizontal movement mechanism 211 indicated by a one-dot chain line in FIG. 2 and a polishing tool 43 below the polishing unit 40 as indicated by a two-dot chain line in FIG. And the workpiece polishing processing area E2 which is a position on the table horizontal movement mechanism 211 facing each other.

  In the present embodiment, the chuck table 32 is horizontally moved by the table horizontal movement mechanism 211. However, the polishing surface of the polishing tool 43 and the chuck table 32 (specifically, a holding surface formed by a suction holding unit 321 described later). ) Are relatively moved in a plane parallel to each other, another configuration may be used. For example, the polishing tool 43 side may be moved horizontally without moving the chuck table 32, or both the chuck table 32 and the polishing tool 43 may be moved in the opposite directions in the horizontal plane to change the polishing surface of the polishing tool 43. The chuck table 32 may be moved relative to the holding surface.

  The support base 31 rotatably supports the chuck table 32 about a rotation center axis extending substantially in the Z-axis direction with respect to the support base 31 by a table rotation mechanism (not shown). As shown in FIG. 3, the chuck table 32 includes a suction holding portion 321 whose upper surface forms a holding surface, and the workpiece 1 is placed on the suction holding portion 321 so that the surface to be polished is exposed with the surface to be polished facing up. Placed on. The suction holding unit 321 is made of a porous material such as porous ceramics, for example, and sucks the workpiece 1 (specifically, the surface of the workpiece 1 that is a held surface) placed on the upper surface by a suction mechanism (not shown). Hold.

  As shown in FIG. 2, a pair of guide rails 221 and 221 extending in the Z-axis direction are provided on the front surface of the upright wall 22, and a polishing unit 40 is mounted on the pair of guide rails 221 and 221 so as to be movable up and down. ing. The polishing unit 40 includes a moving base 41 and a spindle unit 42 attached to the moving base 41. A pair of engaging portions (not shown) are provided on the rear surface of the movable base 41 along the Z-axis direction, and the pair of engaging portions (not shown) are slidably engaged with the pair of guide rails 221 and 221. Thus, the polishing unit 40 can be moved up and down. The up-and-down movement of the polishing unit 40 is realized by the processing unit feed mechanism 50.

  The machining unit feed mechanism 50 includes a male screw rod 51 disposed on the front side of the upright wall 22 and extending substantially in the Z-axis direction. The male screw rod 51 has a bearing member 52 having an upper end portion and a lower end portion attached to the upright wall 22. , 53 are rotatably supported. The upper bearing member 52 is provided with a pulse motor 54 as a drive source for rotationally driving the male screw rod 51, and an output shaft of the pulse motor 54 is connected to the male screw rod 51 by transmission. A through female screw hole (not shown) extending rearward from the center in the width direction is formed on the rear surface of the movable base 41, and a male screw rod 51 is screwed into the through female screw hole (not shown). Thereby, when the pulse motor 54 rotates forward, the moving base 41, that is, the polishing unit 40 moves down (advances) along the guide rails 221 and 221. On the other hand, when the pulse motor 54 rotates in the reverse direction, the moving base 41, that is, the polishing unit 40 moves up (retracts) along the guide rails 221 and 221.

  In the present embodiment, the polishing unit 40 is moved up and down in the Z-axis direction by the processing unit feed mechanism 50. However, the processing unit feed mechanism 50 (specifically, the processing unit feed mechanism 50 is attached to the lower end portion). As long as the polishing surface of the polishing tool 43) and the holding surface of the chuck table 32 are relatively moved in the direction orthogonal to the holding surface of the chuck table 32, another configuration may be used. For example, the chuck table 32 may be moved up and down without moving the machining unit feed mechanism 50, or both the machining unit feed mechanism 50 and the chuck table 32 may be moved up and down in the reverse direction along the Z-axis direction. Thus, the polishing surface of the polishing tool 43 and the holding surface of the chuck table 32 may be moved relative to each other.

  A support portion 413 protruding forward is provided on the front surface of the movable base 41, and a spindle unit 42 is attached to the support portion 413. The spindle unit 42 includes a spindle housing 421 mounted on the support portion 413, a rotating spindle 422 as a spindle rotatably disposed on the spindle housing 421, and a servo as a drive source for rotationally driving the rotating spindle 422. A motor 423. The lower end of the rotary spindle 422 protrudes downward beyond the lower end of the spindle housing 421, and a tool mounting member 424 having a disk shape in plan view is provided at the lower end. The polishing tool 43 is mounted on the lower surface of the tool mounting member 424 with the polishing surface side facing down. Thereby, the polishing surface of the polishing tool 43 is rotated in the XY plane by the rotation of the servo motor 423.

  The polishing tool 43 includes a disk-shaped wheel base 431 and a polishing pad 432 that is attached to the wheel base 431 to form a polishing surface. As shown in FIG. 3, a slurry supply port 433 that communicates with the slurry supply source 60 through the slurry supply path 61 is formed in the center of the surface of the polishing pad 432. On the surface of the polishing pad 432, grooves (not shown) communicating with the slurry supply port 433 are formed in a lattice shape so as to spread over the entire area. With this configuration, a polishing liquid (slurry) containing free abrasive grains supplied from the slurry supply source 60 is guided to the slurry supply port 433 and supplied to the entire surface of the polishing surface along a groove (not shown). The polishing surface formed by the polishing pad 432 has a size equal to or larger than the diameter of the workpiece 1 to be polished.

As shown in FIG. 2, the polishing apparatus 10 includes a slurry supply source 60 disposed at an appropriate position in the apparatus, and is connected to the upper end portion of the polishing unit 40 via a slurry supply path 61. The slurry supply source 60 stores the slurry. For example, the slurry may be an alkaline chemical solution such as potassium hydroxide (KOH), sodium hydroxide (NaOH), ammonia (NH ₃ OH), silicon oxide (SiO ₂ ), cerium oxide (CeO ₂ ), alumina (Al ₂ O). ₃ ) Abrasive grains such as those suspended as an abrasive.

  A thickness measuring device 70 is disposed adjacent to the position of the table horizontal movement mechanism 211 in the vicinity of the workpiece polishing area E2. As shown in FIG. 4, the thickness measuring device 70 includes an inverted L-shaped frame 71. The frame 71 has a hollow cylindrical shape, and a cylindrical stand portion 711 whose axis extends in the Z-axis direction, and an arm portion 712 that extends from the upper end of the stand portion 711 toward the workpiece polishing area E2 of the table horizontal movement mechanism 211. With. A cylindrical laser head portion 72 whose axis extends in the Z-axis direction is formed integrally with the frame 71 at the tip of the arm portion 712. The laser head portion 72 has a hollow cylindrical shape, and the inside thereof communicates with the inside of the frame 71.

  The frame 71 is attached so as to be movable up and down along a guide 212 provided in the main portion 21 via a thin plate-like bracket 73. The bracket 73 is driven up and down along the guide 212 by a lift drive mechanism (not shown). A motor 74 is fixed between the stand portion 711 on the bracket 73 and the attachment portion to the guide 212. The stand portion 711 is supported on the tip end of the bracket 73 via a bearing member 75 so as to be rotatable about its axis. A gear (not shown) is formed on the outer periphery of the stand portion 711, and a belt 76 is wound around a gear (not shown) and a drive shaft of the motor 74. When the motor 74 is driven, the power is transmitted to the stand portion 711 via the belt 76 and a gear (not shown). Thereby, the laser head part 72 turns in the XY plane. The laser head unit 72 reciprocally turns between two positions, a measurement position directly above the workpiece 1 in the workpiece polishing area E2 of the table horizontal movement mechanism 211 and a retracted position outside the chuck table 32. The laser head portion 72 moves up and down integrally with the bracket 73.

  As shown in FIG. 5, a laser beam irradiation end 721 is supported by the support plate 722 inside the laser head unit 72 while penetrating the support plate 722. The laser beam irradiation end 721 irradiates the laser beam LB downward. Below the support plate 722, a glass plate 723 that closes the tip opening of the laser head portion 72 is mounted in a liquid-tight manner. The lower end surface of the laser light irradiation end portion 721 is held in a state of being in contact with the inner surface of the glass plate 723. An internal space 725 is formed below the glass plate 723 that forms the tip of the laser head portion 72 by a cylindrical cover 724 that extends downward integrally with the laser head portion 72.

  A laser unit 213 having a laser light source is accommodated in the main portion 21. The laser beam LB oscillated in the laser unit 213 is guided to the optical fiber 214 and irradiated downward from the laser beam irradiation end 721. The laser unit 213 is also equipped with a photodiode that receives the interference wave that is reflected from the laser light irradiation end 721 and the optical fiber 214 by reflecting the laser light LB emitted from the laser light irradiation end 721 to the workpiece 1. Has been. As the laser light source, an SLD (super luminescent diode) having a wavelength of about 0.8 to 1.3 μm can be used.

  A water supply pipe 726 that supplies water (liquid) W to the internal space 725 of the cover 724 is provided inside the laser head portion 72. The water supply pipe 726 passes through the support plate 722 and the glass plate 723, and is supported by the support plate 722 and the glass plate 723. A water supply hose 727 passed through the frame 71 is connected to the upper end of the water supply pipe 726. The water supply hose 727 is guided into the main portion 21 and connected to a water supply source 215 such as a water supply pump.

  The thickness measuring instrument 70 having such a configuration measures the thickness of the workpiece 1 as follows. First, the vertical position of the bracket 73 is adjusted so that the laser head unit 72 is positioned higher than the workpiece 1, and then the motor 74 is driven to rotate the arm unit 712 so that the laser head unit 72 is moved to the workpiece 1. Place on top. Next, the bracket 73 is lowered to bring the lower end surface of the laser head portion 72 close to the upper surface of the work 1 to ensure a gap 728 for draining. From the viewpoint of reducing the amount of water supplied from the water supply pipe 726, the gap 728 is preferably as small as possible.

  Next, water W is discharged from the water supply source 215 through the water supply hose 727 and from the water supply pipe 726, and the internal space 725 of the cover 724 is kept in a state where the water W is filled and the air is not mixed and sealed with the water W. To do. The water W supplied to the internal space 725 is discharged from a gap 728 that is vacant between the laser head portion 72 and the workpiece 1. The internal space 725 can be filled with water by discharging the amount of water exceeding the amount of drainage from the gap 728 from the water supply pipe 726. In addition, the timing which takes out water W from the water supply pipe 726 is not limited to the above, What is necessary is just to select an appropriate timing.

  Next, the laser beam LB is oscillated by the laser light source in the laser unit 213, and the laser beam LB is irradiated from the laser beam irradiation end 721. The laser beam LB passes through the glass plate 723 and further passes through the water W filling the internal space 725 and reaches the workpiece 1. The thickness of the workpiece 1 is measured by using an interference wave between the first reflected light reflected by the back surface 1b of the workpiece 1 and the second reflected light transmitted through the workpiece 1 and reflected by the surface 1a of the workpiece 1. Is done. These reflected lights are reflected by the back surface 1b and the front surface 1a of the workpiece 1 and then interfere with each other to generate an interference wave. The interference wave passes through the laser beam irradiation end 721 and the optical fiber 214 and is received by the photodiode in the laser unit 213. A waveform of the interference wave between the first reflected light and the second reflected light received by the photodiode is analyzed by a control means (not shown) having a detection circuit and the like, and is converted into an electric signal or the like according to the waveform. . The numerical value corresponds to the thickness of the workpiece 1, and thereby the thickness of the wafer 1 is measured.

  In the present embodiment, the internal space 725 is filled with water W and is held in a state where air is not mixed and is sealed with water W. However, the internal space 725 is not necessarily sealed with water W. There is no. However, depending on the position at which the thickness of the workpiece 1 is measured, there may be a measurement error due to the influence of water and contamination (for example, slurry and polishing scraps) used in the polishing process. For this reason, in order to stabilize the measurement environment and reduce the measurement error, it is desirable that the internal space 725 be sealed with the water W.

  As shown in FIG. 2, a polishing surface cleaning mechanism 82 and a polished surface cleaning mechanism 83 are disposed adjacent to each other in the vicinity of the workpiece polishing area E <b> 2 of the table horizontal movement mechanism 211. As shown in FIG. 4, the polishing surface cleaning mechanism 82 includes a support shaft 821 that freely moves up and down in the Z-axis direction and rotates around a vertical line passing through the base end portion of the polishing surface cleaning mechanism 82 and the support shaft 821. A cleaning arm 822 having one end connected to the upper end, and a polishing surface cleaning nozzle 823 configured by, for example, a two-fluid cleaning nozzle provided on the other end side of the cleaning arm 822 with an injection port facing upward, In addition, a cleaning liquid supply source, an air supply source, a cleaning liquid from the cleaning liquid supply source, and a pipe for guiding the air from the air supply source to the polishing surface cleaning nozzle 823, respectively.

  In the polishing surface cleaning mechanism 82, when the polishing surface is cleaned, the cleaning arm 822 is rotated by the rotation of the support shaft 821, and the polishing surface cleaning nozzle 823 moves below the polishing surface of the polishing tool 43 located at the polishing surface cleaning position. It is supposed to be. Thereby, the cleaning liquid from the polishing surface cleaning nozzle 823 can be supplied toward the polishing surface of the polishing tool 43 at the polishing surface cleaning position. The cleaning arm 822 is positioned at a position where it does not interfere with the horizontal movement of the chuck table 32 and the vertical movement of the polishing unit 40 except when the polishing surface is cleaned.

  Similarly, the polished surface cleaning mechanism 83 also has a support shaft 831 that freely moves up and down in the Z-axis direction and rotates around a vertical line passing through its base end, and one end at the upper end of the support shaft 831. The cleaning arm 832 is connected to the other end of the cleaning arm 832, and the polished surface cleaning nozzle 833, for example, a two-fluid cleaning nozzle, is provided with the spray port facing downward. , A cleaning liquid supply source, an air supply source, a cleaning liquid from the cleaning liquid supply source, and a pipe for guiding air from the air supply source to the polished surface cleaning nozzle 833, respectively.

  In the polished surface cleaning mechanism 83, the cleaning arm 832 is rotated by the rotation of the support shaft 831 during the cleaning of the polished surface, and the polished surface cleaning position 83 is located between the workpiece loading / unloading area E1 and the workpiece polishing processing area E2. The polished surface cleaning nozzle 833 is moved above the chuck table 32 positioned. As a result, the cleaning liquid from the polishing surface cleaning nozzle 833 is supplied onto the chuck table 32 at the polishing surface cleaning position. The cleaning arm 832 is positioned at a position where it does not interfere with the horizontal movement of the chuck table 32 except when the surface to be polished is cleaned.

  As shown in FIG. 2, the polishing apparatus 10 includes carry-in means 91, carry-out means 92, cassettes 101 and 102, carry-in / out means 110, positioning means 120, cleaning means 130, and control means 140. .

  The carry-in means 91 includes a transfer arm 911 that freely moves up and down in the Z-axis direction and rotates around a vertical line passing through its base end as a central axis, and holds the work 1 on the transfer arm 911. A pad 912 is attached and configured. The carry-in means 91 sucks and holds the surface to be polished of the workpiece 1 before the polishing process positioned by the positioning means 120 and carries it onto the chuck table 32 positioned in the work carry-in / out area E1.

  The carry-out means 92 includes a transfer arm 921 that freely moves up and down in the Z-axis direction and rotates about a vertical line passing through its base end as a central axis, and holds the work 1 on the transfer arm 921 by suction. A pad 922 is attached and configured. The carry-out means 92 sucks and holds the workpiece 1 after polishing on the chuck table 32 located at the carry-in / out position, and carries it out to the cleaning means 130.

  The cassettes 101 and 102 are containers for the work 1 having a plurality of slots. The cassette 101 accommodates the workpiece 1 before polishing and the cassette 102 accommodates the workpiece 1 after polishing. The carry-in / out means 110 includes a robot arm 111 having, for example, a U-shaped hand. The robot arm 111 sucks and holds the surface to be polished of the workpiece 1 and carries it. Specifically, the carry-in / out means 110 carries the workpiece 1 before the polishing process from the cassette 101 to the positioning means 120, and carries the workpiece 1 after the polishing process into the cassette 102 from the cleaning means 130.

  The positioning means 120 is a table for temporarily placing the work 1 taken out from the cassette 101 and positioning the center position thereof. The cleaning unit 130 cleans the workpiece 1 after polishing and removes contamination such as polishing dust adhering to the surface of the workpiece 1. The control means 140 is composed of a microcomputer or the like with a built-in memory for holding various data necessary for the operation of the polishing apparatus 10, and controls the polishing apparatus 10 by controlling the operation of each part constituting the polishing apparatus 10. To do.

[Polishing method]
Next, a polishing method according to an embodiment of the present invention will be described with reference to FIG.

  FIG. 6 is a flowchart showing a flow of a polishing method according to an embodiment of the present invention. As shown in FIG. 6, in the polishing method according to an embodiment of the present invention, first, the control unit 140 brings the laser head unit 72 close to the surface to be polished of the workpiece 1 and uses the thickness measuring instrument 70. Then, the thickness TH1 of the workpiece 1 on the surface to be polished is measured (first measurement step, step S1). Specifically, first, the loading means 91 loads the workpiece 1 onto the chuck table 32 with the surface to be polished facing up. Next, the control unit 140 drives the suction mechanism of the chuck table mechanism 30 to suck and hold the held surface of the workpiece 1 on the chuck table 32. Next, the control means 140 drives the table horizontal movement mechanism 211 to horizontally move the chuck table 32 from the work carry-in / out area E1 to the work polishing area E2. In detail, as shown in FIG. 7, the control means 140 controls the workpiece 1 on the chuck table 32 to a position where a part of the polished surface of the workpiece 1 overlaps the polishing pad 432, in other words, on the chuck table 32. The chuck table 32 is moved until at least a part of the surface to be polished of the workpiece 1 is exposed. Then, the control means 140 brings the laser head portion 72 close to the exposed surface to be polished, and measures the thickness TH1 of the workpiece 1 on the exposed surface to be polished using the thickness measuring device 70.

  Next, the controller 140 presses the polishing pad 432 against the entire surface of the workpiece 1 to polish the surface of the workpiece 1 for a predetermined time (first polishing step, step S2). Specifically, as shown in FIG. 8, first, the control unit 140 drives the table horizontal movement mechanism 211 so that the entire surface to be polished of the workpiece 1 on the chuck table 32 overlaps with the polishing pad 432. The chuck table 32 is moved to the position. Next, the control unit 140 drives the servo motor 423 to rotate the rotary spindle 422 to rotate the polishing surface of the polishing tool 43 in a horizontal plane, and to drive the pulse motor 54 of the processing unit feed mechanism 50. The polishing unit 40 is moved downward. Due to the downward movement of the polishing unit 40, the entire surface of the workpiece 1 to be polished comes into contact with the polishing pad 432. In addition, the control unit 140 drives a table rotation mechanism (not shown) to rotate the chuck table 32 to rotate the surface to be polished of the workpiece 1 in a horizontal plane. Further, the control unit 140 drives the slurry supply source 60 to supply the slurry from the slurry supply port 433 to the surface to be polished of the workpiece 1.

  Next, the control means 140 moves the chuck table 32 to a position where a part of the surface to be polished of the workpiece 1 on the chuck table 32 overlaps with the polishing pad 432 in the same manner as in the first measurement step. The thickness TH2 of the workpiece 1 on the exposed surface to be polished is measured using the height measuring device 70 (second measurement step, step S3). Next, the control means 140 uses the difference value (TH1−TH2) between the thickness TH1 of the work 1 obtained in the first measurement process and the thickness TH2 of the work 1 obtained in the second measurement process as a polishing amount. While calculating, the thickness change (polishing rate) of the workpiece 1 with respect to the polishing time is obtained by dividing the calculated polishing amount by the polishing time (predetermined time) in the first polishing step (calculation step, step S4). Specifically, as shown in FIG. 9, the control means 140 uses the thickness TH1 of the workpiece 1 obtained in the first measurement step and the thickness TH2 of the workpiece 1 obtained in the second measurement step to polish the workpiece. A straight line L indicating the relationship between the time T and the thickness TH of the workpiece 1 is calculated.

  Next, the control means 140 sets the polishing time ΔT based on the polishing rate and the target finish thickness obtained in the calculation process, and polishes the entire surface to be polished of the workpiece 1 with the same pressure as in the first polishing process. The pad 432 is pressed to polish the surface to be polished of the workpiece 1 for the polishing time ΔT (finish polishing step, step S5). Specifically, as shown in FIG. 9, the control unit 140 calculates the polishing time ΔT required until the thickness of the workpiece 1 changes from the thickness TH2 to the target finish thickness TH3 using the straight line L calculated in the calculation step. . More specifically, the thickness TH1 of the workpiece 1 measured in the first measurement step is 100 μm, the polishing time in the first measurement step is 30 seconds, and the thickness TH2 of the workpiece 1 calculated in the second measurement step is When 97 μm and the target finish thickness TH3 are 90 μm, the control means 140 sets the polishing time ΔT to 70 seconds (= (97−90) / {(100−97) / 30}). Next, as shown in FIG. 8, the controller 140 drives the table horizontal movement mechanism 211 to chuck the entire surface of the workpiece 1 to be polished on the chuck table 32 to a position where it overlaps the polishing pad 432. The table 32 is moved. Then, the control unit 140 presses the polishing pad 432 against the entire surface to be polished of the workpiece 1 with the same pressure as in the first polishing step, and polishes the surface to be polished of the workpiece 1 for the polishing time ΔT.

  Thereafter, the polishing apparatus 10 performs a polishing surface cleaning process and a polished surface cleaning process as cleaning processes. Note that the polishing surface cleaning step and the polished surface cleaning step may be performed after the first polishing step shown in FIG. When performing the polishing surface cleaning process and the polishing target surface cleaning process, first, the control unit 140 drives the pulse motor 54 of the processing unit feeding mechanism 50 to move the polishing processing unit 40 upward. Then, the polishing surface of the polishing tool 43 is moved to a preset polishing surface cleaning position by the upward movement of the polishing unit 40. Thereafter, as a polishing surface cleaning step, the control unit 140 drives the polishing surface cleaning mechanism 82 in a state where the polishing surface of the polishing tool 43 is rotated in a horizontal plane by the rotation of the rotary spindle 422. Then, the control unit 140 ejects the cleaning liquid from the polishing surface cleaning nozzle 823 toward the central polishing surface while rotating the cleaning arm 822 by rotating the support shaft 821. In this polishing surface cleaning process, each part operates as described above to supply the cleaning liquid to the polishing surface of the polishing tool 43 that rotates at the polishing surface cleaning position. Thereby, contamination such as slurry and polishing debris adhering to the polishing surface is removed.

  Further, as the surface to be polished cleaning step, the control means 140 drives the table horizontal movement mechanism 211 to move the chuck table 32 horizontally from the workpiece polishing processing area E2 to the workpiece loading / unloading area E1 side, thereby moving the workpiece loading / unloading area E1. The chuck table 32 is moved to a polishing surface cleaning position that is preset as a position between the workpiece polishing area E2 and the workpiece polishing area E2. Here, the polishing surface cleaning position is set as a position where the entire surface of the workpiece 1 on the chuck table 32 does not overlap the entire polishing surface of the polishing tool 43. In parallel with this, the control means 140 drives a table rotation mechanism (not shown), rotates the chuck table 32 to rotate the surface to be polished of the workpiece 1 in the horizontal plane, and also cleans the surface to be polished cleaning mechanism 83. As shown in FIG. 8, the cleaning liquid is sprayed from the polishing surface cleaning nozzle 833 of the workpiece 1 onto the surface to be polished while rotating the cleaning arm 832 by rotating the support shaft 831. In this polishing surface cleaning process, each part operates as described above, so that it moves toward the polishing surface of the workpiece 1 on the chuck table 32 moving from the workpiece polishing area E2 to the polishing surface cleaning position. Supply cleaning solution. Thereby, contamination such as slurry and polishing debris adhering to the surface to be polished of the workpiece 1 is removed.

  When the polishing surface cleaning process and the polished surface cleaning process are completed, the chuck table 32 moves to the work carry-in / out area E1 under the control of the control means 140 and is sucked and held by the suction pad 922 of the carry-out means 92. Then, it is carried out to the cleaning means 130. After the surface to be polished is cleaned by the cleaning unit 130, the workpiece 1 transported to the cleaning unit 130 is gripped by the robot arm 111 of the loading / unloading unit 110, transported to the cassette 102, and stored in the cassette 102. . Further, after unloading the workpiece 1 after polishing, the next workpiece 1 is loaded and held on the chuck table 32 by the loading means 91.

  As is apparent from the above description, in the polishing method according to an embodiment of the present invention, first, the control means 140 has the workpiece 1 that is held with the workpiece 1 held with a part of the surface to be polished exposed. The thickness of the workpiece 1 is measured from the surface (first measurement step). Next, the control means 140 presses the polishing pad 432 against the entire surface to be polished of the workpiece 1 and polishes the workpiece 1 for a predetermined time (first polishing step). Next, the control means 140 measures the thickness of the workpiece 1 from the exposed surface to be polished of the workpiece 1 with a part of the surface to be polished exposed (second measuring step). Next, the control unit 140 calculates the polishing amount based on the thickness of the work 1 obtained in the first measurement process and the thickness of the work 1 obtained in the second measurement process, and in the first polishing process. Based on the polishing time, the change in the thickness of the workpiece 1 with respect to the elapsed time of polishing is calculated (calculation step). And the control means 140 sets polishing time based on the thickness change of the workpiece | work 1 with respect to the elapsed time of grinding | polishing calculated | required at the calculation process, and target finishing thickness, and makes the 1st grinding | polishing process on the whole surface of the workpiece | work 1 to be polished. Polishing is performed by pressing the polishing pad 432 with a pressure equivalent to (finish polishing step). Accordingly, even when the polishing pad 432 is pressed against the entire back surface of the workpiece 1 to polish the workpiece 1, the thickness of the workpiece 1 is accurately polished to the target finish thickness by setting the polishing time with high accuracy. can do.

  In this embodiment, the polishing time ΔT is set based on the thickness change (polishing rate) of the workpiece 1 with respect to the elapsed time of polishing calculated based on the first and second measurement steps and the first polishing step. However, a plurality of sets of the first and second measurement steps and the first polishing step are performed as one set, and the polishing time ΔT is set using the average value of the polishing rates calculated in each set. May be. Thereby, since the reliability of the polishing rate is increased, the thickness of the workpiece 1 can be polished with the target finish thickness with high accuracy by setting the polishing time with higher accuracy.

  The embodiment to which the invention made by the present inventors has been described has been described above, but the present invention is not limited by the description and drawings that form part of the disclosure of the present invention according to the above embodiment. That is, other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above-described embodiments are all included in the scope of the present invention.

1 Work 1a Front 1b Back (Polished surface)
10 Polishing device 32 Chuck table 70 Thickness measuring device (measuring means)
72 Laser Head Unit 321 Suction Holding Unit 432 Polishing Pad

Claims (1)

A polishing method in which a polishing pad is pressed against the entire surface of a workpiece to be polished held by a holding surface to polish the workpiece to be polished until a target finish thickness is achieved,
A first measuring step of measuring the thickness of the workpiece from the exposed polished surface of the workpiece held on the holding surface in a state where at least a part of the polished surface is exposed; and
After the first measuring step, a first polishing step of pressing the polishing pad against the entire surface of the workpiece to be polished to polish the workpiece to be polished for a predetermined time;
After the first polishing step, the thickness of the workpiece is measured by the measuring means from the exposed surface to be polished of the workpiece held on the holding surface with a part of the surface to be polished exposed again. Measuring process;
The polishing amount is calculated based on the workpiece thickness obtained in the first measurement step and the workpiece thickness obtained in the second measurement step, and the polishing is performed based on the polishing time in the first polishing step. A calculation step for obtaining a change in the thickness of the workpiece with respect to the elapsed time of
The polishing time is set based on the change in the thickness of the workpiece with respect to the elapsed time of polishing and the target finish thickness obtained in the calculation step, and the entire surface of the workpiece to be polished is subjected to the same pressure as in the first polishing step. A final polishing process in which a polishing pad is pressed to polish the work surface of the workpiece;
A polishing method comprising:

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