JP2008290182A - Polishing equipment - Google Patents

Abstract

A polishing apparatus having a measuring means capable of measuring both a surface shape of a polishing pad and a value indicating a viscoelastic property in a state actually used in a polishing process.
A CMP apparatus for polishing a wafer by moving the wafer relative to a polishing surface 27s of a polishing pad 27 relative to the polishing surface 27 between the polishing surface 27s of the polishing pad 27 and a reference surface 62s. A pad shape measuring device having a main sensor 65 and a sub sensor 66 for measuring the distance and measuring the surface shape of the polishing surface 27s of the polishing pad 27, and a pressure load that presses against the polishing surface 27s of the polishing pad 27 and applies a pressure load A deformation amount generated on the polishing surface 27s of the polishing pad 27 by the pressure load of the pressure load device is measured using the main sensor 65 and the sub sensor 66, and whether or not the measured deformation amount is within the reference range. Configured to determine whether.
[Selection] Figure 3

Description

  The present invention relates to a polishing apparatus such as a CMP apparatus that polishes the surface of an object to be polished (for example, a semiconductor wafer) using a polishing pad.

  In a manufacturing process of a semiconductor wafer (hereinafter referred to as a wafer), a polishing tool used in a polishing apparatus (for example, a CMP apparatus; a chemical mechanical polishing apparatus) for polishing a circuit component film formed on the wafer surface, that is, As the processing time of the polishing pad increases, the polishing characteristics of the polishing pad change due to fatigue. When polishing the surface of the wafer with a polishing pad whose polishing characteristics have changed in this way, there is a risk that the surface polishing of the wafer will be non-uniform and defective products may occur, and the polishing surface of the polishing pad is periodically dressed. .

  Conventionally, after the dressing is completed, the polishing pad is removed from the polishing apparatus (polishing head), and the surface shape of the polishing pad (for example, the cone apex angle formed by the polishing pad surface or the groove depth of the polishing pad surface, etc.) Alternatively, a value indicating the viscoelastic characteristics of the polishing pad (for example, a deformation amount when a predetermined stress is applied to the polishing pad) is measured (see, for example, Patent Document 1). If this measurement result is good, the polishing pad is attached to the polishing apparatus again and used as it is for polishing. On the other hand, if the measurement result is not good, the polishing pad is attached to the polishing apparatus and dressing of the polishing pad is performed again, or the polishing pad is replaced.

  Thus, conventionally, there is no means for measuring the surface shape or viscoelastic characteristics of the polishing pad in the polishing apparatus, and once the polishing pad is removed from the polishing apparatus, the surface shape or viscoelastic characteristics of the polishing pad are measured. . However, in recent years, a surface shape measuring device capable of automatically measuring the surface shape of the polishing pad has been devised, and a polishing device equipped with this surface shape measuring device is being put into practical use (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 10-288579 International Publication No. 05/072910 Pamphlet

  By the way, conventionally, either the surface shape or the viscoelastic property of the polishing pad is measured, and the polishing pad is used for the object to be polished according to the result of whether or not the measured value falls within the standard range. It was judged whether or not the intended polishing was possible. However, since both the surface shape and the viscoelastic characteristics of the polishing pad affect the polishing result, there is a problem that this is not sufficient for accurately determining the polishing characteristics of the polishing pad. Further, when the polishing pad is once removed from the polishing apparatus and the surface shape or viscoelastic characteristics of the polishing pad is measured, there is a problem that the polishing characteristics of the polishing pad in the state actually used in the polishing process cannot be accurately determined. there were.

  The present invention has been made in view of such problems, and a polishing apparatus having a measuring means capable of measuring both the surface shape and viscoelastic characteristics of a polishing pad in a state where it is actually used in a polishing process. The purpose is to provide.

  In order to solve the above problems and achieve the object, a polishing apparatus according to the present invention is a polishing apparatus that polishes the polishing object by relatively moving both of the objects to be polished in contact with the polishing surface of the polishing pad. A surface shape measuring device for measuring a surface shape of the polishing surface of the polishing pad, a distance measuring device for measuring a distance between the polishing surface of the polishing pad and a reference surface; A pressure load device that presses against the polishing surface and applies a pressure load, and the amount of deformation generated on the polishing surface of the polishing pad due to the pressure load of the pressure load device was measured using the distance measuring device and measured. It is configured to determine whether or not the deformation amount is within a reference range.

  In the polishing apparatus, the measurement of the deformation amount generated on the polishing surface of the polishing pad is performed by measuring the deformation amount when the pressure load device is applied stepwise to the polishing surface of the polishing pad with different strength pressures. It is preferable that the measurement is performed at each stage using a distance measuring device.

  In the polishing apparatus, the amount of deformation generated on the polishing surface of the polishing pad is measured by applying a constant pressure to the polishing surface of the polishing pad by the pressure load device and then removing the constant pressure. It is preferable that measurement is performed at predetermined time intervals using the distance measuring device.

  In the polishing apparatus, the pressure load device includes a pressing member capable of contacting the polishing surface of the polishing pad, and is configured to apply a pressure load to the polishing surface of the polishing pad by moving the pressing member. When the pressure is applied to the polishing surface of the polishing pad by the pressure load device, the displacement generated on the polishing surface of the polishing pad is measured by measuring the displacement of the pressing member using the distance measuring device. It is preferred to determine the amount.

  In the polishing apparatus, the surface shape measuring device is movable along the reference surface while the distance measuring device including an optical displacement sensor, a reference member having the reference surface, and the distance measuring device are attached. And measuring the distance between the reference surface of the reference member and the polishing surface of the polishing pad using the distance measuring device while moving the movable member along the reference surface. The pressure load device is attached to the movable member constituting the surface shape measuring device together with the distance measuring device, and the movable member is attached to the reference It is preferable that the pressure is applied to a predetermined position of the polishing surface of the polishing pad by moving along the surface.

  According to the polishing apparatus of the present invention, the pressure load device is provided together with the surface shape measuring device, and the deformation amount generated on the polishing surface of the polishing pad due to the pressure load of the pressure load device is the distance constituting the surface shape measuring device. Since it can be measured using a measuring instrument, based on the measurement results of both the surface shape and viscoelastic characteristics of the polishing pad, the polishing characteristics of the polishing pad in the state actually used in the polishing process can be accurately determined. it can. For this reason, it is possible to accurately grasp the deterioration state of the polishing pad during the polishing step and prevent the wafer surface polishing from becoming uneven.

  FIG. 1 shows a part of a CMP apparatus (chemical mechanical polishing apparatus) which is a typical example of the polishing apparatus according to the present invention. The CMP apparatus C includes a cassette index unit, a wafer cleaning unit, and a polishing unit according to the polishing process. The polishing unit includes three polishing chambers and one polishing unit provided in each section of the index table divided into four parts. In this embodiment, one of the polishing chambers will be described.

  In the polishing chamber 1 into which a semiconductor wafer W (hereinafter referred to as a wafer W) is transferred from the transfer chamber, an index table 2 that is divided into four parts and rotated and fed every 90 degrees by the operation of a stepping motor, etc., and polishing An arm 3, a dressing device 4, a pad exchange base 5, and a pad shape measuring device 50 are disposed. Each section of the index table 2 is provided with a wafer holding device 10 that sucks and holds the wafer W as a polishing object from the back surface, and moves the wafer W to the polishing chamber 1 by suction. The wafer holding device 10 is rotatably supported on the index table 2 in a horizontal plane, and is rotated at high speed by driving means such as an electric motor or an air motor (not shown) disposed inside the index table 2.

  The polishing arm 3 is configured to be turnable in the horizontal direction with respect to the index table 2 and to be vertically movable in the vertical direction. A polishing head 20 is rotatably attached to the oscillating end of the polishing arm 3. The polishing head 20 is detachable from a carrier member 21 to which a pad plate 25 is attached as shown in FIG. It comes to hold. The carrier member 21 is formed in a disc shape, and is detachably attached to the lower end portion of the polishing head 20 by fitting using a pin member or the like.

  A fitting hole portion 22 that matches the shape of the pad plate 25 is formed on the lower side of the carrier member 21, and the pad plate 25 is fitted into the fitting hole portion 22 using an O-ring or the like. The plate 25 is detachably attached to the carrier member 21. Further, a plurality of suction holes 23 connected to a vacuum source (not shown) are formed inside the carrier member 21, and the carrier member 21 is fitted by applying a negative pressure to the suction holes 23 using the vacuum source. The pad plate 25 attached to the hole 22 can be sucked and held.

  The pad plate 25 includes a resin plate member 26 and a polishing pad 27 attached to the surface side (lower surface side) of the plate member 26. As described above, the pad plate 25 is fitted to the carrier member 21. The hole 22 is detachably attached. The pad plate 25 is a disposable pad plate using a resin plate member 26. By using such a disposable pad plate, the pad plate 25 can be easily attached to and detached from the carrier member 21. Yes.

  The plate member 26 is formed in a disk shape using a resin material such as PET (polyethylene-terephthalate), and a polishing pad 27 that can polish the surface of the wafer W (surface to be polished Ws) flatly is formed using a double-sided adhesive tape or the like. The plate member 26 is attached to the front surface side (lower surface side). The material of the plate member 26 is not a problem as long as it is not eroded by the abrasive (slurry), but PET is preferable because it is easily available, easy to process, and hardly causes pollution problems when discarded. .

  The polishing pad 27 is formed in a donut disk shape having a substantially same outer diameter as that of the plate member 26 using a foam resin material such as foaming polyurethane, and the vicinity of the center portion on the surface side (lower surface side) of the plate member 26 is The polishing pad 27 is exposed without being covered. On the surface (lower surface) of the polishing pad 27, a polishing surface 27 s that is in contact with the surface of the wafer W (surface to be polished Ws) and performs polishing is formed. In addition, lattice-like grooves 28 (see FIG. 4C) are formed on the surface of the polishing pad 27 at substantially equal intervals in the vertical and horizontal directions, and the diffusion of the abrasive (slurry) is promoted during the polishing process. It has come to be. The width and depth of the groove 28 are both about 1 mm.

  Such a polishing head 20 is rotationally driven by a rotation driving mechanism (not shown) disposed in the polishing arm 3 so as to be rotatable at high speed in a horizontal plane. Further, the polishing head 20 is driven to rotate in the direction opposite to the rotation direction of the wafer holding device 10 described above, and rotates the wafer W by rotating the polishing pad 27 (pad plate 25) relative to the wafer W at high speed. The surface (surface to be polished Ws) is polished flat. Further, as shown in FIG. 1, the polishing head 20 can be moved above the wafer holding device 10, the dressing device 4, the pad changer 5, and the pad shape measuring device 50 by swinging the polishing arm 3. It can be done.

  The dressing device 4 shown in FIG. 1 is a device that corrects clogging or unevenness of the polishing pad 27 caused by polishing the wafer W (dressing, sharpening), and detailed illustration is omitted. In addition, a disk having diamond abrasive grains or the like fixed on its surface and a rotatable disk, and a cleaning nozzle for cleaning the polishing pad 27 with pure water by spraying pure water onto the surface of the dressed polishing pad 27 are provided. The pad exchange table 5 is a device for exchanging the used pad plate 25 with a new one.

  As shown in FIGS. 2 and 3, the pad shape measuring device 50 for measuring the surface shape and viscoelastic property of the polishing pad 27 (the amount of deformation when a predetermined pressure is applied) has a waterproof cover attached thereto. Each component is accommodated in the housing portion 51. A front block 55 and a rear block 56 are attached to a mounting base 53 provided inside the housing portion 51, and a guide holding plate 57 is attached between the front block 55 and the rear block 56. A guide member 58 is attached to the lower side of the guide holding plate 57. A slide table 58 a is slidably fitted to the guide member 58, and the guide member 58 and the slide table 58 a constitute a guide mechanism 52. A ball screw 60 is attached to the lower side of the guide holding plate 57 (lower side of the guide member 58) so as to be parallel to the guide holding plate 57 (guide member 58). A screw nut (not shown) is fitted into the slide table 58a, and a ball screw 60 is screwed into the screw nut. The movable member 59 is fastened to the slide table 58a, and slides along the guide member 58 together with the slide table 58a by the rotation of the ball screw 60.

  A motor 61 is attached to the rear block 56 via a motor holding member 61a, and the ball screw 60 is rotated by receiving the rotational driving force of the motor 61. A reference block 62 having a predetermined reference surface 62s is held by the front block 55 and the rear block 56 via the first holding member 63 and the second holding member 64, respectively.

  The motor 61 may be an AC motor, a DC motor, or a stepping motor. The motor 61 has a built-in rotary encoder (not shown), and can detect the position of the movable member 59 driven by the motor 61 via the ball screw 60 or the like based on a motor encoder signal output from the motor 61. It is like that. Regarding the origin position, an origin sensor (not shown) is attached to a predetermined location of the guide member 58, and the origin reset operation is performed when the movable member 59 passes this position. The rotational driving torque of the motor 61 is transmitted from a motor shaft (not shown) to the ball screw 60 via a gear mechanism and a belt mechanism. Note that when the rotary encoder in which the motor 61 is built is an absolute value type and the accuracy of the mechanical system including the ball screw 60 is sufficient, the origin sensor is unnecessary. Also, a combination of a linear motor and a linear encoder may be used.

  A main sensor 65 composed of an optical (non-contact) displacement sensor is provided on the upper portion of the movable member 59 so as to measure the distance from the surface of the polishing pad 27. Further, a sub sensor 66 composed of an eddy current type displacement sensor is provided below the movable member 59 so as to measure the distance from the reference surface 62 s of the reference block 62. Note that a window (not shown) is provided in a portion of the housing portion 51 that faces the polishing pad 27 and is opened only when measurement is performed.

  As the main sensor 65, an optical (non-contact) displacement sensor is used. The surface to be measured is the surface of the polishing pad 27 (the polishing surface 27s), which is the surface of the foam resin. Since the pore diameter of the foam is 20 to 30 μm, the optical sensor spot is preferably larger than the pore area. Further, since the width of the groove 28 of the polishing pad 27 is about 1 mm, the spot diameter is preferably smaller than the groove width. In the case of a contact-type pick sensor, since the diameter of the probe tip is 1 mm or more, the depth of the groove 28 cannot be detected. Further, in the case of the eddy current type or the ultrasonic type, the depth of the groove 28 cannot be similarly detected because the measurement range is about 5 mm.

  As the sub sensor 66, an eddy current displacement sensor is used. In order to increase the measurement sensitivity and reduce the influence of noise, the reference block 62 uses iron-based material or martensite-based stainless steel. When accuracy is not particularly required, various metals such as aluminum and copper-based materials may be used. Although the reference surface 62s of the reference block 62 is precisely machined flat, it is preferable to use an eddy current type displacement sensor capable of calculating an average distance in the range of several millimeters in diameter.

  The measurement point of the main sensor 65, the measurement point of the sub sensor 66, and the drive point of the movable member 59 are arranged on the same axis, and each measurement point and drive with respect to the drive direction of the movable member 59, that is, the rotation axis of the ball screw 60. The axes connecting the three points are orthogonal.

  Further, a pressure load device 70 is provided on the upper portion of the movable member 59 so as to press the surface of the polishing pad 27 and apply a pressure load. The pressure load device 70 includes a pressing member 71 that can come into contact with the polishing surface 27s of the polishing pad 27, and a pressing member drive mechanism 72 that moves the pressing member 71 in a direction in which the pressing member 71 comes into contact with the polishing surface 27s.

  The pressing member 71 is formed in a substantially bar shape, and comes into contact with the polishing surface 27 s of the polishing pad 27 at the tip portion. A measured portion 71 a that protrudes so as to intersect with the optical axis of the main sensor 65 is formed at an intermediate portion of the pressing member 71. In addition, a rotary actuator 73 is provided at an intermediate portion of the pressing member 71 (below the position where the measured portion 71 a is formed), and the pressing member 71 (measured portion 71 a) above the rotary actuator 73 is rotated. Then, the portion to be measured 71a is moved to a position where it intersects or does not intersect with the optical axis of the main sensor 65 (for example, it is located at either the solid line position or the broken line position shown in FIG. 2). The shape of the tip of the pressing member 71 is determined according to the material, hardness, thickness, etc. of the polishing pad 27, such as a substantially hemispherical shape, a substantially cone shape, or a substantially planar shape.

  The pressing member driving mechanism 72 includes an actuator (not shown) inside, and moves the pressing member 71 in the up and down direction in FIG. 2 (for example, a direction substantially perpendicular to the polishing surface 27s of the polishing pad 27). A part of the polishing pad 27 is deformed by pressing the polishing pad 27 through the member 71 and applying a pressure load. The pressing member drive mechanism 72 can apply pressures of different strengths to the polishing pad 27 in stages or a constant pressure, and thereafter, the constant pressure can be instantaneously reduced to zero. Yes.

  By the way, what is actually measured using the pad shape measuring device 50 is that the polishing pad 27 is pressed by the surface shape such as the cone apex angle, groove depth, and pad thickness of the polishing pad 27 and the pressure load device 70. This is the amount of deformation. As shown in FIG. 2, the main sensor 65 measures the distance L1 to the surface of the polishing pad 27 or the distance L2 to the surface (lower surface) of the measured portion 71a of the pressing member 71, and the sub sensor 66 measures the reference block 62. The distance Ls to the reference surface 62s is measured. In the polarity where L1 and L2 decrease and Ls increases when the movable member 59 approaches the polishing pad 27, the value actually measured is the value of (L1 + Ls) or (L2 + Ls). That is, the reference block 62 is used to provide a reference position for measuring the surface position of the polishing pad 27 or the surface position of the measured portion 71a, and thereby, for example, the guide holding plate 57 and the guide member 58 Even if the position of the movable member 59 fluctuates due to deformation, correct measurement is performed.

  When the polishing head 20 is located at a predetermined reference relative position (measurement position) (indicated by a broken line in FIG. 1), the vicinity of the center of rotation of the polishing pad 27 (that is, the polishing head 20) is along the measurement direction of the main sensor 65. The movable member 59 linearly moves in the left-right direction in FIG. 2 along the guide member 58 so that the surface of the polishing pad 27 is near the center of rotation of the polishing pad 27. It is possible to measure the surface shape of the polishing pad 27 along the straight line passing through. Further, by rotating the polishing head 20 by a predetermined angle, the surface shape of the polishing pad 27 along the plurality of straight lines passing through the vicinity of the rotation center of the polishing pad 27 (surface shape in almost the entire area of the polishing pad 27) is measured. Can do.

  Further, since the pressure load device 70 is configured to be mounted on the movable member 59 together with the main sensor 65, the polishing pad is located at a position along a straight line passing through the vicinity of the center of rotation of the polishing pad 27 on the surface of the polishing pad 27. The amount of deformation when 27 is pressed can be measured. The amount of deformation when the polishing pad 27 is pressed can be measured over almost the entire area of the polishing pad 27 by rotating the polishing head 20 by a predetermined angle in the same manner as the measurement of the surface shape. However, since this deformation amount shows almost the same value over the entire surface of the polishing pad 27 (especially on the same circumference), it is sufficient to measure one predetermined location. In this embodiment, the amount of deformation when the polishing pad 27 is pressed is measured at one location near the rotation center of the polishing pad 27 (for example, point A in FIG. 4C).

  In this embodiment, the movable member 59 is configured to linearly move along the guide member 58. However, the present invention is not limited to this. For example, the movable member is rotated using an arm member or the like. You may do it. In this case, the measurement position by the main sensor is a position along an arc passing through the vicinity of the center of rotation of the polishing pad on the surface of the polishing pad.

  As described above, the measurement control unit 80 is provided to measure the surface shape (conical apex angle, groove depth, pad thickness) of the polishing pad 27 and the amount of deformation when the polishing pad 27 is pressed. Accordingly, the measurement control unit 80 moves the main sensor 65 and performs the distance measurement (measurement of (L1 + Ls) or (L2 + Ls)). The result measured by the pad shape measuring apparatus 50 in this way is sent to the measurement control unit 80, and determination is made as to whether or not the polishing pad 27 can be continuously used based on the measurement result.

  Next, in the CMP apparatus C configured as described above, the contents of determination as to whether or not the polishing pad 27 can be continuously used in the measurement control unit 80 will be described with reference to a flowchart. The determination content of whether or not the polishing pad 27 according to the first embodiment can be continuously used is shown in the flowchart of FIG.

  In the polishing process of the wafer W using the CMP apparatus C, the polishing surface 27 s of the polishing pad 27 is rotated and held by the wafer holding apparatus 10 while rotating the polishing pad 27 (pad plate 25) together with the polishing head 20. This is performed in contact with the surface to be polished Ws. At this time, the polishing pad 27 rotates and reciprocates (oscillates) in the horizontal direction (that is, the direction in the surface to be polished Ws) while rotating, so that the entire surface of the wafer W is polished flat. The At this time, an abrasive (slurry) is supplied between the polishing pad 27 and the wafer W.

  When polishing of the wafer W is completed, the polishing head 3 is moved from above the wafer holding device 10 to above the dressing device 4 by the operation of the polishing arm 3, and dressing of the polishing pad 27 is performed there (step S1).

  After the dressing is completed, the polishing head 3 is moved from above the dressing device 4 to the reference relative position above the pad shape measuring device 50 by the operation of the polishing arm 3, where the surface shape of the polishing pad 27 (conical apex angle, groove depth). , Pad thickness) and the amount of deformation when the polishing pad 27 is pressed (value indicating the viscoelastic characteristics of the polishing pad 27) are measured (step S2).

  Specifically, the surface shape of the polishing pad 27 is measured by rotating the pressing member 71 of the pressure load device 70 by the operation of the rotary actuator 73 by the measurement control unit 80 and moving the measured portion 71 a of the pressing member 71 to the main sensor 65. In a state where the motor 61 is moved to a position that does not intersect the optical axis (for example, the position of the broken line shown in FIG. 2), the movable member 59 is moved in a direction substantially parallel to the reference surface 62s of the reference block 62. . Then, from the X axis (left and right direction axis in FIG. 2) position information obtained by a rotary encoder (not shown), the Z axis (in FIG. 2) of the main sensor 65 and the sub sensor 66 with respect to the surface of the polishing pad 27 at a predetermined sample pitch. Take the vertical axis) direction distance measurement. Then, the polishing head 20 is rotated by a predetermined angle, and the rotation of the polishing head 20 and the surface measurement of the polishing pad 27 are repeated until the entire surface of the polishing pad 27 is scanned. For example, if the polishing head 20 rotates by 10 degrees, the entire surface of the polishing pad 27 can be measured by 18 reciprocating scanning operations.

  In addition, the deformation amount when the polishing pad 27 is pressed is measured by first rotating the pressing member 71 of the pressure load device 70 by the operation of the rotary actuator 73 by the measurement control unit 80 to measure the measured portion 71a of the pressing member 71. Is moved to a position that intersects the optical axis of the main sensor 65 (for example, a position indicated by a solid line in FIG. 2). Next, the X axis (left and right direction axis in FIG. 2) position information obtained by a rotary encoder (not shown) is pressed to a position near the rotation center of the polishing pad 27 (for example, point A in FIG. 4C). The motor 61 is operated so as to move the movable member 59 in a direction substantially parallel to the reference surface 62 s of the reference block 62 so that the tip of the member 71 is located at the opposite position. Then, the pressing member driving mechanism 72 moves the pressing member 71 in the vertical direction in FIG. 2 to apply stepwise different pressures to positions in the vicinity of the rotation center of the polishing pad 27, and when each pressure is applied. The Z-axis (vertical direction axis in FIG. 2) direction distance measurement values of the main sensor 65 and the sub sensor 66 with respect to the measured portion 71a of the pressing member 71 are captured. The amount of deformation when the polishing pad 27 is pressed may be measured during the surface shape measurement of the polishing pad 27 or may be measured after the surface shape measurement.

  Since the reference surface 62s of the reference block 62 is used as a reference surface, the output of the main sensor 65 with respect to the polishing pad 27 is L1, the output of the main sensor 65 with respect to the measured portion 71a of the pressing member 71 is L2, and the output of the sub sensor 66 is Ls. When the movable member 59 approaches the polishing pad 27, assuming that L1 and L2 decrease and Ls increases, the relative distance L from the reference surface 62s of the reference block 62 to the surface of the polishing pad 27 is L = The relative distance L ′ from the reference surface 62s to the surface of the measured portion 71a of the pressing member 71 is obtained by L ′ = (L2 + Ls).

  In step S2, the cone apex angle, groove depth, pad thickness, and the like are detected based on the relative distance L measured at each measurement point along the X-axis direction. These calculation methods are described in, for example, International Publication No. 05/072910 pamphlet and the like, and detailed description thereof is omitted. 4A or 4B, the cone apex angle is an angle indicated by α, and the dressing position is the relative position β of the dressing device 4. In FIG. 4B, the groove depth is a value represented by γ, and the pad thickness is a value represented by δ. The amount of deformation when pressing the polishing pad 27 (value indicating the viscoelastic characteristics of the polishing pad 27) is calculated based on the relative distance L ′ to the surface of the measured portion 71a when each pressure is applied. That is, it is a value showing the relationship between the displacement amount (relative distance L ′) of the measured portion 71a and the pressure applied at that time.

  When the measurement of the shape of the polishing pad 27 in step S2 is completed, the process proceeds to step S3, where it is determined whether or not the measured groove depth γ and pad thickness δ of the polishing pad 27 are equal to or greater than a reference value. If there is, the process proceeds to step S4, and if the reference value is not satisfied, the process proceeds to step S8.

  First, when it is determined that the groove depth γ and the pad thickness δ of the polishing pad 27 are equal to or larger than the reference value, whether or not the cone apex angle α of the polishing pad 27 measured in step S2 is within the range of the reference value. If it is within the reference range, the process proceeds to step S5. If it is out of the reference range, the process proceeds to step S6.

  When it is determined that the cone apex angle α of the polishing pad 27 is out of the reference range, the process proceeds to step S6, where the polishing pad 27 is defective (the dressing of the polishing pad 27 is not properly performed). Is determined. If it is determined that the cone apex angle α of the polishing pad 27 is correctable, the process proceeds to step S7, the polishing head 20 is returned to the upper side of the dressing device 4, and the dressing conditions (such as the relative position β) are changed. Then, the dressing of the polishing pad 27 is performed again, and then the process of measuring the surface shape of the polishing pad 27 is repeated again.

  When it is determined that the cone apex angle α of the polishing pad 27 is within the reference range, the process proceeds to step 5, and whether the deformation amount when the polishing pad 27 measured in step 2 is pressed is within the reference range. If it is within the reference range, the polishing pad 27 is continuously used (polishing of the new wafer W ′ is started by returning the polishing head 20 to the upper side of the wafer holding device 10) and it is out of the reference range. Sometimes go to step S8.

  On the other hand, when it is determined in step S3 that the groove depth γ and the pad thickness δ of the polishing pad 27 do not satisfy the reference values, or when the polishing pad 27 is pressed in step S5, the deformation amount is outside the reference range. If it is determined that the polishing pad 27 is present, the polishing pad 27 is worn out due to fatigue or the like and cannot be used. Therefore, the process advances to step S8 to replace the pad. Specifically, the polishing head 20 is moved above the pad changer 5 to replace the polishing pad 27 (that is, the pad plate 25), and the polishing head 20 is moved above the wafer holding device 10 to obtain a new one. The wafer W ′ is polished.

  Next, the contents of determination as to whether or not the polishing pad 27 according to the second embodiment can be continuously used will be described with reference to the flowchart of FIG.

  When polishing of the wafer W is completed, the polishing arm 3 is moved from above the wafer holding device 10 to above the dressing device 4 by the operation of the polishing arm 3, and dressing of the polishing pad 27 is performed there (step S11).

  After the dressing is completed, the polishing head 3 is moved from above the dressing device 4 to the reference relative position above the pad shape measuring device 50 by the operation of the polishing arm 3, where the surface shape of the polishing pad 27 (conical apex angle, groove depth). , Pad thickness) and the amount of deformation when the polishing pad 27 is pressed are measured (step S12).

  Specifically, the deformation amount when the polishing pad 27 is pressed is measured by first rotating the pressing member 71 of the pressure load device 70 by the operation of the rotary actuator 73 by the measurement control unit 80 to measure the pressing member 71. The part 71a is moved to a position that intersects the optical axis of the main sensor 65 (for example, a solid line position shown in FIG. 2). Next, the X axis (left and right direction axis in FIG. 2) position information obtained by a rotary encoder (not shown) is pressed to a position near the rotation center of the polishing pad 27 (for example, point A in FIG. 4C). The motor 61 is operated so as to move the movable member 59 in a direction substantially parallel to the reference surface 62 s of the reference block 62 so that the tip of the member 71 is located at the opposite position. Then, the pressing member 71 is moved in the vertical direction in FIG. 2 by the pressing member driving mechanism 72 to apply a constant pressure to a position near the rotation center of the polishing pad 27, and the pressing when the constant pressure is instantaneously made zero. The Z-axis (vertical direction axis in FIG. 2) direction distance measurement values of the main sensor 65 and the sub sensor 66 with respect to the measured portion 71a of the member 71 are captured at predetermined time intervals. The measurement of the surface shape of the polishing pad 27 is performed in the same manner as in the first embodiment. Further, the amount of deformation when the polishing pad 27 is pressed may be measured during the surface shape measurement of the polishing pad 27 or may be measured after the surface shape measurement.

  Similarly to the first embodiment, since the reference surface 62s of the reference block 62 is used as the reference surface, the output of the main sensor 65 to the polishing pad 27 is L1, and the output of the main sensor 65 to the measured portion 71a of the pressing member 71 is L2. Assuming that the output of the sub sensor 66 is Ls, and the movable member 59 approaches the polishing pad 27, L1 and L2 decrease and Ls increases. From the reference surface 62s of the reference block 62 to the surface of the polishing pad 27. The relative distance L ′ is obtained by L = (L1 + Ls), and the relative distance L ′ from the reference surface 62s to the surface of the measured portion 71a of the pressing member 71 is obtained by L ′ = (L2 + Ls).

  In step S12, the cone apex angle, groove depth, pad thickness, and the like are detected based on the relative distance L measured at each measurement point along the X-axis direction. These calculation methods are the same as those in the first embodiment. Further, when the polishing pad 27 is pressed, a deformation amount (a value indicating the viscoelastic characteristics of the polishing pad 27) is applied to the surface of the measured portion 71a when a constant pressure is applied and the constant pressure is instantaneously reduced to zero. Is calculated based on the relative distance L ′ acquired at a predetermined time interval, that is, a value indicating the relationship between the return amount (relative distance L ′) and the time when the deformation of the polishing pad 27 returns. is there.

  When the measurement of the shape of the polishing pad 27 in step S12 is completed, the process proceeds to step S13, and it is determined whether or not the deformation amount when the measured polishing pad 27 is pressed is within the reference range, and is within the reference range. Sometimes the process proceeds to step S14, and when it is out of the reference range, the process proceeds to step S18.

  First, when it is determined that the deformation amount when the polishing pad 27 is pressed is within the reference range, whether the groove depth γ and the pad thickness δ of the polishing pad 27 measured in step S12 are greater than or equal to the reference value. If the reference value is equal to or greater than the reference value, the process proceeds to step S15. If the reference value is not satisfied, the process proceeds to step S18.

  When it is determined that the groove depth γ and the pad thickness δ of the polishing pad 27 are equal to or larger than the reference value, whether or not the cone apex angle α of the polishing pad 27 measured in step S12 is within the reference range. If the polishing pad 27 is within the reference range, the polishing pad 27 is continuously used (the polishing head 20 is returned to the upper side of the wafer holding apparatus 10 to start polishing a new wafer W ′). Proceed to S16.

  When it is determined that the cone apex angle α of the polishing pad 27 is out of the reference range, the process proceeds to step S16, where it is determined that the polishing pad 27 is defective (the dressing of the polishing pad 27 is not properly performed). To do. If it is determined that the cone apex angle α of the polishing pad 27 is correctable, the process proceeds to step S17 where the polishing head 20 is returned to the upper side of the dressing device 4 and the dressing conditions (such as the relative position β) are changed. Then, the dressing of the polishing pad 27 is performed again, and then the process of measuring the surface shape of the polishing pad 27 is repeated again.

  On the other hand, when it is determined in step S13 that the deformation amount when the polishing pad 27 is pressed is out of the reference range, or in step S14, the groove depth γ and the pad thickness δ of the polishing pad 27 satisfy the reference value. If it is determined that the polishing pad 27 is not present, the polishing pad 27 is worn out due to fatigue and cannot be used. Specifically, the polishing head 20 is moved above the pad changer 5 to replace the polishing pad 27 (that is, the pad plate 25), and the polishing head 20 is moved above the wafer holding device 10 to obtain a new one. The wafer W ′ is polished.

  As described above, in the CMP apparatus C, after the dressing of the polishing pad 27 is finished, the surface shape of the polishing pad 27 and the deformation amount when the polishing pad 27 is pressed are measured by the pad shape measuring apparatus 50, and this surface shape is measured. In addition, based on the measurement results of both the amount of deformation and the amount of deformation (value indicating the viscoelastic characteristics), it is possible to accurately determine the polishing characteristics of the polishing pad 27 in a state actually used in the polishing process. For this reason, it is possible to accurately grasp the deterioration state of the polishing pad during the polishing process and prevent the wafer surface polishing from becoming uneven.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist. For example, the pressure load device 70 is not necessarily provided on the movable member 59 together with the main sensor 65. In this case, the pressure load device 70 is provided on a movable member movable along the surface of the polishing pad 27, and the polishing pad 27 is attached. Any configuration may be used as long as the displacement of the pressing member 71 can be measured by the main sensor 65 when pressed.

It is a top view which shows the outline | summary of the grinding | polishing chamber which comprises some CMP apparatuses based on this invention. It is a front view which shows the principal part of the pad shape measuring apparatus which comprises the said polishing chamber. FIG. 3 is a cross-sectional view taken along arrow III-III in FIG. 2. It is a schematic diagram of the pad plate with which the polishing head of the polishing arm constituting the CMP apparatus is mounted. It is a flowchart which shows the judgment content of whether the continuous use of the polishing pad which concerns on 1st Example in the said CMP apparatus is possible. It is a flowchart which shows the judgment content of whether the continuous use of the polishing pad which concerns on 2nd Example in the said CMP apparatus is possible.

Explanation of symbols

C CMP equipment (polishing equipment)
W wafer (object to be polished)
27 Polishing pad (polishing pad)
27s Polished surface (Polished surface)
50 Pad shape measuring device (surface shape measuring device)
59 Movable member (movable member)
62 Reference block (reference member)
62s Reference surface (reference surface)
65 Main sensor (distance measuring instrument)
66 Sub sensor (distance measuring device)
70 Pressure load device (pressure load device)
71 Pressing member (pressing member)

Claims (5)

A polishing apparatus for polishing the polishing object by relatively moving both objects in a state where the polishing object is in contact with the polishing surface of the polishing pad,
A surface shape measuring device having a distance measuring device for measuring a distance between a polishing surface of the polishing pad and a reference surface, and measuring a surface shape of the polishing surface of the polishing pad;
A pressure load device that applies pressure load by pressing against the polishing surface of the polishing pad;
Measuring a deformation amount generated on the polishing surface of the polishing pad by the pressure load of the pressure load device using the distance measuring device, and determining whether the measured deformation amount is within a reference range. A characteristic polishing apparatus.   The measurement of the amount of deformation generated on the polishing surface of the polishing pad is performed by using the distance measuring device to determine the amount of deformation when the pressure load device is applied stepwise to the polishing surface of the polishing pad with different strength pressures. The polishing apparatus according to claim 1, wherein measurement is performed at each stage.   The amount of deformation generated on the polishing surface of the polishing pad is measured by applying a constant pressure to the polishing surface of the polishing pad by the pressure load device, and then measuring the amount of deformation when the constant pressure is removed using the distance measuring device. The polishing apparatus according to claim 1, wherein the polishing apparatus is used by measuring at predetermined time intervals. The pressure load device has a pressing member that can contact the polishing surface of the polishing pad, and is configured to apply a pressure load to the polishing surface of the polishing pad by moving the pressing member,
The amount of deformation generated on the polishing surface of the polishing pad by measuring the amount of displacement of the pressing member using the distance measuring device when pressure is applied to the polishing surface of the polishing pad by the pressure load device. The polishing apparatus according to claim 1, wherein the polishing apparatus is configured so as to obtain The surface shape measuring device includes the distance measuring device including an optical displacement sensor, a reference member having the reference surface, and a movable member to which the distance measuring device is attached and movable along the reference surface. Have
By measuring the distance between the reference surface of the reference member and the polishing surface of the polishing pad using the distance measuring device while moving the movable member along the reference surface, Configured to measure surface shape,
The pressure load device is attached to the movable member constituting the surface shape measuring device together with the distance measuring device, and moves the movable member along the reference surface to apply pressure to a predetermined position on the polishing surface of the polishing pad. The polishing apparatus according to any one of claims 1 to 4, wherein the polishing apparatus is configured to load a load.

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