JP7175644B2 - Polishing pad for substrate polishing apparatus and substrate polishing apparatus provided with the polishing pad - Google Patents

Description

The present invention relates to a polishing pad for a substrate polishing apparatus and a substrate polishing apparatus having the polishing pad.

2. Description of the Related Art Conventionally, there has been known an apparatus for polishing a substrate with a polishing pad attached to a polishing table. For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2003-197587) discloses a substrate polishing apparatus having a rotatable surface plate and a polishing pad (“abrasive” in Patent Document 1) attached to the surface plate. (Fig. 1).

Japanese Patent Application Laid-Open No. 2003-197587

In a typical substrate polishing apparatus, polishing pads are consumables. In conventional substrate polishing apparatuses, the maximum number of uses or the maximum usage time of the polishing pad is set based on the amount of wear measured or calculated in advance. That is, in the conventional substrate polishing apparatus, when the polishing pad has been used a predetermined number of times or for a predetermined period of time (hereinafter simply referred to as "predetermined number of times"), it is determined that the polishing pad has reached the end of its life. However, the life of the polishing pad is not exactly exhausted when the polishing pad has been used a predetermined number of times. If the polishing pad has reached the end of its life before the predetermined number of uses, the substrate is polished with a post-life polishing pad. Therefore, there is a possibility that the substrate polishing apparatus cannot exhibit the predetermined polishing performance. On the other hand, if the life of the polishing pad has not expired even after being used a predetermined number of times, the polishing pad that is still usable is replaced. Replacing a polishing pad that can still be used shortens the replacement cycle of the polishing pad and increases the cost required for replacement.

Therefore, the object of the present application is to solve at least a part of the above problems.

The present application provides, as an embodiment, a polishing table for attaching a polishing pad having a transparent window, and an indicator provided on the polishing table for checking deterioration of the transparent window, which is visible through the transparent window. A substrate polishing apparatus is disclosed, comprising: an indicator provided at a desired position.

1 is a front cross-sectional view of a substrate polishing apparatus; FIG. FIG. 4 is a top view of a polishing table with a polishing pad attached; It is a top view of a polishing table. 4 is an enlarged view of an alignment mark; FIG. FIG. 5 is a top view of a portion of the polishing table with the polishing pad attached. FIG. 5A is an illustration of the case where the polishing pad 150 is misaligned. FIG. 5 is a top view of a portion of the polishing table with the polishing pad attached. FIG. 5B is a diagram of when the polishing pad 150 is properly aligned. FIG. 4 is a top view of a polishing table with indicators; FIG. 7 is a diagram showing how the indicator located on the left side of FIG. 6 is observed through the transparent window. FIG. 7A is a diagram when the transparent window has not deteriorated. FIG. 7 is a diagram showing how the indicator located on the left side of FIG. 6 is observed through the transparent window. FIG. 7B is a diagram when the transparent window is deteriorated. FIG. 8 is a diagram showing how the indicator located on the right side of FIG. 6 is observed through the transparent window. FIG. 8A is a diagram when the transparent window has not deteriorated. FIG. 8 is a diagram showing how the indicator located on the right side of FIG. 6 is observed through the transparent window. FIG. 8B is a diagram when the transparent window is deteriorated. 1 is a front cross-sectional view of a substrate polishing apparatus having an imaging mechanism; FIG. 1 is a front cross-sectional view of a substrate polishing apparatus equipped with a light source; FIG.

<<First Embodiment>>
<Background technology and problems of the first embodiment>
The substrate polishing apparatus disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-197587) can measure the progress of polishing by a liquid-sealed sensor provided below a polishing table (also referred to as a surface plate). is configured to The surface plate of Patent Document 1 is provided with a liquid supply hole so that the irradiation light emitted from the sensor and the sealing liquid can pass through the inside of the surface plate. Like the liquid supply holes, the polishing pad of Patent Document 1 is provided with through holes.

In the device of Patent Document 1, if the positions of the liquid supply hole and the through hole are misaligned, the flow of the sealing liquid near the substrate may be disturbed. If the flow of the sealing liquid is disturbed, it is considered that the performance of the sensor section may deteriorate. Therefore, in Patent Document 1, it is preferable that the polishing pad is accurately aligned with the surface plate.

Polishing pads are generally made of a non-transparent material. When the non-transparent polishing pad is attached to the platen, most of the platen is covered by the polishing pad except for the portion exposed through the through holes. Therefore, it was difficult to align the polishing pad while visually checking the positions of the liquid supply holes. Furthermore, in recent years, substrates are becoming larger. As the size of the substrate increases, the surface plate and polishing pad also tend to increase in size. Attaching a large polishing pad to a large platen and aligning the large polishing pad are difficult. Further, Patent Document 1 assumes a configuration in which only one sensor unit is provided. However, some polishing apparatuses have a plurality of sensor units. When there are a plurality of sensor units, a great deal of labor is required to align the polishing pads. Therefore, there is a demand for facilitating alignment of the polishing pad.

<Overview of substrate polishing apparatus 100>
FIG. 1 is a front cross-sectional view of a substrate polishing apparatus 100 according to the first embodiment. FIG. 2 is a top view of the polishing table 110 with the polishing pad 150 attached. However, the drawings used in the present application are schematic diagrams. The dimensions, shapes, positions, etc. of the elements shown in each drawing do not necessarily match the dimensions, shapes, positions, etc. of the actual device. The characters “PAD” and “TABLE” shown in some drawings are characters for distinguishing the upper surface of the polishing pad 150 and the upper surface of the polishing table 110 . That is, the letters “PAD” and “TABLE” in the drawings are not elements of the substrate polishing apparatus 100 . In addition, in the drawings attached to this specification, there may be differences between the configuration shown by the top view and the configuration shown by the cross-sectional view. For example, in FIG. 2, the sealing liquid supply path 111 and the sealing liquid discharge path 112 are arranged in the circumferential direction of the polishing table 110 (the circumferential direction of the polishing pad 150). The liquid discharge paths 112 are arranged in the radial direction of the polishing table 110 . This difference is merely a difference caused by convenience of illustration. When embodying the idea disclosed by this specification, the sealing liquid supply path 111 and the sealing liquid discharge path 112 may be aligned in the circumferential direction of the polishing table 110 or may be aligned in the radial direction. Note that the positional relationship between the sealing liquid supply path 111 and the sealing liquid discharge path 112 is not limited to the illustrated positional relationship.

A substrate polishing apparatus 100 according to this embodiment is a CMP (Chemical Mechanical Polishing) apparatus. The substrate polishing apparatus 100 may be an apparatus other than the CMP apparatus as long as it is an apparatus that measures the progress of polishing using a detector from the lower surface of the polishing table. The substrate polishing apparatus 100 includes a polishing table 110 , a liquid-sealed optical sensor 120 , a polishing head 130 and a polishing liquid supply mechanism 140 . A polishing pad 150 is detachably attached to the upper surface of the polishing table 110 . A substrate 131 is detachably attached to the lower surface of the polishing head 130 .

<Regarding the polishing table 110>
The polishing table 110 is rotatable in at least one direction by a motor (not shown) or the like. Depending on the type of substrate polishing apparatus 100, the polishing table 110 may not be rotatable. The polishing table 110 is provided with a sealing liquid supply path 111 and a sealing liquid discharge path 112 . The sealing liquid supply path 111 is provided to supply the sealing liquid to the through holes 151 of the polishing pad 150 arranged on the upper surface of the polishing table 110 (the through holes 151 will be described later). The sealing liquid discharge path 112 is provided for discharging the sealing liquid from the through hole 151 .

The sealing liquid supply path 111 is connected to a sealing liquid source 113 . The number of sealing liquid sources 113 is not limited. Sealing liquid source 113 may be a component of substrate polishing apparatus 100 . A separate sealing liquid source 113 from the substrate polishing apparatus 100 may be used. The sealing liquid is pure water, for example. However, the sealing liquid may be another liquid. Sensing light from the optical sensor 120 travels through the sealing liquid. Therefore, the sealing liquid is preferably substantially transparent at least in the wavelength region of the sensing light. The “sensing light” refers to “irradiation light traveling from the optical sensor 120 toward the substrate 131” and “reflected light traveling from the substrate 131 toward the optical sensor 120”.

After being supplied to the optical path of the sensing light, the sealing liquid is discharged to the outside of the polishing table 110 through the sealing liquid discharge path 112 . The sealing liquid discharged to the outside of the polishing table 110 may be returned to the sealing liquid source 113 as shown in FIG. The sealing liquid may be discarded without being returned to the sealing liquid source 113 . The sealing liquid supply path 111 and the sealing liquid discharge path 112 and the sealing liquid source 113 may be connected by a rotary joint 114 .

As will be described later, two optical sensors 120 are provided in this embodiment. Therefore, the sealing liquid supply path 111 in FIG. 1 is configured to branch into two paths to supply the sealing liquid to each of the optical sensors 120 . Similarly, the sealing liquid discharge path 112 of FIG. 1 is configured such that two paths merge. However, it is also possible to employ a configuration other than the illustrated configuration. For example, two independent sealing liquid supply channels 111 and two independent sealing liquid drain channels 112 may be provided for each of the two optical sensors 120 .

<Regarding the optical sensor 120>
The optical sensor 120 is a sensor that measures the progress of polishing of the substrate 131 . Specifically, the optical sensor 120 irradiates the polished surface of the substrate 131 with light and measures the optical characteristics of the reflected light. Since the optical properties of the reflected light can change depending on the state of the polished surface of the substrate 131, the progress of polishing can be measured by measuring the optical properties of the reflected light. The optical sensor 120 may be a sensor that measures the polishing amount of the substrate 131 . The optical sensor 120 may be a sensor that detects the polishing end point of the substrate 131 .

The substrate polishing apparatus 100 according to this embodiment has two optical sensors 120 . More specifically, one optical sensor 120 is provided near the center of the polishing table 110 and the other optical sensor 120 is provided near the edge of the polishing table 110 . The distance between the optical sensor 120 and the axis of rotation of the polishing table 110 determines which area of the substrate 131 is measured. In other words, the measured area of the substrate 131 depends on the distance between the optical sensor 120 and the rotation axis of the polishing table 110 . The number and arrangement of optical sensors 120 are exemplary, and other configurations may be employed. For example, by providing a plurality of optical sensors 120 on concentric circles, it is possible to increase the frequency of measurements of the substrate 131 in a specific area.

The optical sensor 120 includes a sensor main body 121 , an optical fiber 122 for irradiation light, and an optical fiber 123 for reflected light. For convenience of illustration, the optical fiber for irradiation light 122 and the optical fiber for reflected light 123 are blacked out in FIG. In this embodiment, a sensor main body 121 is provided under the polishing table 110 . The sensor main body 121 includes a light source (not shown) for irradiating light toward the optical fiber 122 for irradiation light and a photodetector (not shown) for measuring reflected light passing through the optical fiber 123 for reflected light. Prepare.

The optical fiber 122 for irradiated light and the optical fiber 123 for reflected light extend from the sensor main body 121 . The optical fiber 122 for irradiation light and the optical fiber 123 for reflected light extend from the lower part of the polishing table 110 toward the upper part of the polishing table 110 and reach the inside of the sealing liquid supply path 111 . The sealing liquid supply path 111 can also be expressed as an opening through which the optical fibers (irradiating light optical fiber 122 and reflected light optical fiber 123) extending from the sensor main body 121 are passed. As long as the optical fiber 122 for irradiation light and the optical fiber 123 for reflected light do not protrude from the upper surface of the polishing pad 150, and as long as the measurement by the optical sensor 120 is possible, the optical fiber 122 for irradiation light and the optical fiber 123 for reflected light are used. The position of the upper end of may be arbitrary. Typically, the positions of the upper ends of the optical fiber 122 for irradiation light and the optical fiber 123 for reflected light are slightly lower than the upper surface of the polishing table 110 .

Wiring (not shown) may be provided to power the sensor body 121 and to transmit signals from the sensor body 121 . The wiring may be connected to the sensor main body 121 via a rotary joint (which may be the rotary joint 114 or another rotary joint). Signals from the sensor body 121 may be received by a controller (not shown). Wiring can be omitted by adopting wireless transmission technology or the like. Upon receiving a signal from the sensor main body 121 that "the substrate 131 has been polished by a predetermined amount" or "the polishing of the substrate 131 has reached the end point", the control unit performs at least one of the following steps (1) to (4). Polishing of the substrate 131 may be stopped by controlling the substrate polishing apparatus 100 to run. (1) raise the polishing head 130, (2) stop the rotation of the polishing head 130, (3) stop the rotation of the polishing table 110, and (4) stop the supply of the polishing liquid from the polishing liquid supply mechanism 140. Stop.

<Regarding the polishing head 130>
The polishing head 130 is provided above the polishing table 110 so as to face the polishing table 110 . A substrate 131 is detachably attached to the lower surface of the polishing head 130 . The polishing head 130 is rotatable in at least one direction, preferably in the same direction as the polishing table 110, by a motor (not shown) or the like. The polishing head 130 is configured to be vertically movable by a vertical movement mechanism (not shown) or the like. When the polishing head 130 is lowered by the vertical movement mechanism, the substrate 131 is pressed against the polishing pad 150 . The substrate 131 is polished by rotating either the polishing head 130 or the polishing table 110, preferably both, while the substrate 131 is pressed against the polishing pad 150. FIG.

<Regarding the Polishing Liquid Supply Mechanism 140>
A polishing liquid supply mechanism 140 is provided above the polishing table 110 . The tip of the polishing liquid supply mechanism 140 has a nozzle shape, and can supply polishing liquid (slurry) or the like toward the polishing pad 150 . The polishing liquid supply mechanism 140 may be capable of supplying not only polishing liquid but also cleaning liquid and/or chemical liquid. Different from the configuration of this embodiment, a configuration in which the polishing liquid is supplied from the lower surface of the polishing table 110 or a configuration in which the polishing liquid is supplied from the inside of the polishing head 130 may be employed.

<Regarding the polishing pad 150>
The polishing pad 150 is a plate-like member attached to the upper surface of the polishing table 110 . Incidentally, depending on the material and thickness of the polishing pad 150, the polishing pad 150 may be expressed as a "cloth-like member". Polishing pad 150 is generally made of an opaque material (eg, foamed polyurethane).

Through-holes 151 are required in the polishing pad 150 to allow the sensing light and sealing liquid to pass through. If the polishing pad 150 is provided with openings, it is necessary to position the polishing pad 150 so that the openings are positioned above the sealing liquid supply path 111 and the like. However, since the polishing pad 150 is generally non-transparent, it is difficult to align the polishing pad 150 while visually checking the positions of the sealing liquid supply path 111 and the sealing liquid discharge path 112 . Note that "aligning the polishing pad 150" may be read as "adjusting the mounting position and/or mounting angle of the polishing pad 150".

Therefore, a transparent window 152 is provided in the polishing pad 150 according to this embodiment. Preferably, the transparent window 152 is substantially transparent at least in the wavelength region of visible light. Materials for transparent window 152 include, for example, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyurethane resin, and polyester resin. A through hole 151 is provided in the center of the transparent window 152 . It can also be expressed as "an annular transparent window 152 is provided around the through hole 151". However, the term "annular" here means not only a circular ring but also an angular ring. As shown in FIG. 2, the shape of through-hole 151 is elliptical. However, the through hole 151 may be circular or rectangular. The through hole 151 communicates with the sealing liquid supply path 111 and the sealing liquid discharge path 112 when the polishing pad 150 is properly attached to the polishing table 110 . As described above, the substrate polishing apparatus 100 of this embodiment has two optical sensors 120 . In this embodiment, the number of sets of sealing liquid supply paths 111 and sealing liquid discharge paths 112 is two so as to correspond to the number of optical sensors 120 . Further, two through-holes 151 are provided in the polishing pad 150 of this embodiment so as to correspond to the number of sealing liquid supply paths 111 and sealing liquid discharge paths 112 . More specifically, one through-hole 151 is provided near the center of the polishing pad 150 and the other through-hole 151 is provided near the edge of the polishing pad 150 . The distance between through hole 151 and the center of polishing pad 150 determines which area of substrate 131 is measured. In other words, the measured area of substrate 131 depends on the distance between through-hole 151 and the center of polishing pad 150 .

When the polishing pad 150 according to the present embodiment is attached to the polishing table 110, not only the portion of the polishing table 110 exposed through the through hole 151 but also the portion of the polishing table 110 located below the transparent window 152 is exposed. You can also see the parts. Therefore, when attaching the polishing pad 150 according to the present embodiment to the polishing table 110 , it is easy to align the polishing pad 150 while visually checking the positions of the sealing liquid supply path 111 and the sealing liquid discharge path 112 .

Note that the configuration of the substrate polishing apparatus 100 is merely an example. In particular, for the configuration of the polishing table 110 and the optical sensor 120, any conventionally known configuration (for example, the configuration disclosed in Patent Document 1) may be adopted. For example, a plurality of optical fibers 122 for irradiation light and optical fibers 123 for reflected light may be connected to one sensor main body 121 .

<<Second Embodiment>>
<Overview of Second Embodiment>
In the second embodiment, a substrate polishing apparatus 100 having alignment marks 300 on a polishing table 110 for facilitating alignment of the polishing pad 150 will be described. FIG. 3 is a top view of the polishing table 110 according to this embodiment. FIG. 4 is an enlarged view of the alignment mark 300. FIG. FIG. 5 is a top view of a portion of the polishing table 110 to which the polishing pad 150 is attached, showing how the polishing pad 150 is aligned using the alignment marks 300. FIG. FIG. 5A is an illustration of the case where the polishing pad 150 is misaligned. FIG. 5B is a diagram of when the polishing pad 150 is properly aligned.

<Regarding the alignment mark 300>
Alignment marks 300 are marks provided on the upper surface of the polishing table 110 . Specifically, the alignment mark 300 is provided near the sealing liquid supply path 111 and the sealing liquid discharge path 112 . More specifically, at least a portion of alignment mark 300 is configured to be located directly below transparent window 152 when polishing pad 150 is properly attached to polishing table 110 . Alignment mark 300 is used when aligning polishing pad 150 with respect to polishing table 110 . Alignment mark 300 is configured to be visible to a user of substrate polishing apparatus 100 . However, when some imaging device or the like observes the alignment mark 300 instead of the user, the alignment mark 300 may be invisible to the user as long as it is visible to the imaging device or the like. Alignment marks 300 may be formed by any technique such as laser marking, painting, printing and scribing. In order to distinguish between the alignment marks 300 and the through holes 151 and the like, the alignment marks 300 are drawn with dotted lines in FIGS. However, the alignment marks 300 in an actual device need not be dotted lines.

Preferably, alignment mark 300 has a first mark 310 corresponding to the outer edge of transparent window 152 . Specifically, first mark 310 coincides with the outer edge of transparent window 152 when polishing pad 150 is properly attached to polishing table 110 . Preferably, alignment mark 300 further has a second mark 320 corresponding to the outer edge of through-hole 151 . Specifically, the second mark 320 coincides with the outer edge of the through-hole 151 when the polishing pad 150 is properly attached to the polishing table 110 . For example, the first mark 310 is circular and the second mark 320 is elliptical. More preferably, alignment mark 300 has a cross-shaped third mark 330 . If through-hole 151 is elliptical, cross-shaped third mark 330 is preferably configured to correspond to the major and minor axes of through-hole 151 . Specifically, the cross-shaped third mark 330 coincides with the major and minor axes of the through-hole 151 when the polishing pad 150 is properly attached to the polishing table 110 . Note that a part of the third mark 330 is cut off in FIG. The sealing liquid supply path 111 and the sealing liquid discharge path 112 are positioned at the portion where the third mark 330 is interrupted. Alignment mark 300 may comprise a fourth mark 340 , for example circular, between first mark 310 and second mark 320 .

As shown in FIG. 5A, first mark 310 and second mark 320 are visible through transparent window 152 or through-hole 151 if polishing pad 150 is not properly aligned. By comparing the outer edge of the transparent window 152 and the first mark 310, the displacement amount of the polishing pad 150 can be grasped. The displacement amount of the polishing pad 150 can also be grasped by comparing the outer edge of the through-hole 151 and the second mark 320 . Also, the amount of rotation of the polishing pad 150 can be grasped from the degree of inclination of the second mark 320 and/or the third mark 330 . By adjusting the mounting position and/or mounting angle of polishing pad 150 based on the grasped amount of misalignment and/or amount of rotation, polishing pad 150 can be correctly aligned.

As shown in FIG. 5B, when the polishing pad 150 is properly aligned, the outer edge of the transparent window 152 overlaps the first mark 310, making the first mark 310 nearly invisible. Similarly, when the polishing pad 150 is properly aligned, the outer edge of the through-hole 151 overlaps the second mark 320, making the second mark 320 almost invisible.

By providing the alignment mark 300, the polishing pad 150 can be easily aligned with the polishing table 110 with high accuracy. Note that the shape of the alignment mark 300 is merely an example. In the simplest case, alignment mark 300 may be just a point. Any other mark that can be used for alignment can be used. When some imaging device observes the alignment mark 300 , a control device such as a computer may calculate the amount of displacement and/or the amount of rotation of the polishing pad 150 .

<<Third Embodiment>>
<Overview of Third Embodiment>
In a typical substrate polishing apparatus, polishing pads are consumables. In conventional substrate polishing apparatuses, the maximum number of uses or the maximum usage time of the polishing pad is set based on the amount of wear measured or calculated in advance. That is, in the conventional substrate polishing apparatus, when the polishing pad has been used a predetermined number of times or for a predetermined period of time (hereinafter simply referred to as "predetermined number of times"), it is determined that the polishing pad has reached the end of its life. However, the life of the polishing pad is not exactly exhausted when the polishing pad has been used a predetermined number of times. If the polishing pad has reached the end of its life before the predetermined number of uses, the substrate is polished with a post-life polishing pad. Therefore, there is a possibility that the substrate polishing apparatus cannot exhibit the predetermined polishing performance. On the other hand, if the life of the polishing pad has not expired even after being used a predetermined number of times, the polishing pad that is still usable is replaced. Replacing a polishing pad that can still be used shortens the replacement cycle of the polishing pad and increases the cost required for replacement.

In order to solve the above problems, a substrate polishing apparatus 100 having an indicator on the polishing table 110 will be described in the third embodiment. FIG. 6 is a top view of polishing table 110 having indicator 600 .

<Regarding the indicator 600>
At least part of the indicator 600 is provided in a region of the polishing table 110 that is directly below the transparent window 152 of the polishing pad 150 when the polishing pad 150 is properly attached. In other words, indicator 600 is provided at a position that is visible through transparent window 152 when polishing pad 150 is properly attached to polishing table 110 . In other words, the indicator 600 is provided on the surface of the polishing table 110 to which the polishing pad 150 is attached, and the indicator 600 allows the optical fibers (irradiating light optical fiber 122 and reflected light optical fiber 123) to pass therethrough. (sealing liquid supply path 111 or opening 610: details of opening 610 will be described later). Note that unlike the previous embodiments, the optical sensor 120 may or may not be of a liquid-sealed type. In the example of FIG. 6, the sealing liquid supply path 111 and the reflected light optical fiber 123 located on the right side of the drawing are connected to the liquid-sealed optical sensor 120 . Since the liquid-sealed optical sensor 120 has been described in the previous embodiments, detailed description thereof will be omitted. On the other hand, in the example of FIG. 6, the optical fiber 122 for irradiated light and the optical fiber 123 for reflected light located on the left side of the drawing are connected to the optical sensor 120 which is not liquid-sealed. Therefore, the sealing liquid supply path 111 and the sealing liquid discharge path 112 are not provided in the left portion of the polishing table 110 in the figure. As an alternative to the sealing liquid supply path 111 and the sealing liquid discharge path 112, the polishing table 110 is provided with an opening 610 for passing the optical fiber and sensing light in the left part of the drawing. However, the configuration of the optical sensor 120 and other accompanying elements is an example, and configurations other than the configuration illustrated in FIG. 6 can be employed.

In FIG. 6, four types of patterns (close-spaced stripes, wide-spaced stripes, close-spaced checkerboard, and wide-spaced checkerboard) form a set of indicators 600 . However, the specific configuration of the indicator 600 is not limited to the configuration shown in FIG. 6 as long as deterioration of the transparent window 152, which will be described later, can be confirmed. For example, indicator 600 may comprise any number of markings. In the simplest case, indicator 600 may be just a dot. Indicator 600 is configured to be visible to a user of substrate polishing apparatus 100 . However, if some imaging mechanism (for example, the imaging mechanism 900 in FIG. 9) or the like images the indicator 600 on behalf of the user, the indicator 600 may be invisible to the user as long as it is visible to the imaging mechanism or the like. Indicator 600 may be formed by any technique such as laser marking, painting, printing and scribing.

If a new polishing pad 150 is used, the transparent window 152 is also new. Therefore, the optical properties of the transparent window 152, such as transmittance, refractive index, reflectance and degree of scattering, are unchanged. However, when the substrate polishing apparatus 100 is driven, not only the substrate 131 is polished but also the transparent window 152 is worn. Wear of the transparent window 152 is particularly noticeable during dressing of the polishing pad 150 . It is believed that when the transparent window 152 wears, the optical properties of the transparent window 152 change. Hereinafter, the change in the optical properties of the transparent window due to abrasion is referred to as "deterioration of the transparent window". It is considered that what kind of optical characteristics change due to deterioration depends on the specific process, the type of polishing liquid used, the material of the substrate 131, the material of the transparent window 152, the material of the dresser, and the like. Here, it is assumed that the transmittance of the transparent window 152 is lowered. FIG. 7 is a diagram showing how the indicator 600 located on the left side of FIG. 6 is observed through the transparent window 152 of the polishing pad 150. As shown in FIG. FIG. 7A is a diagram when the transparent window 152 has not deteriorated. FIG. 7B is a diagram when the transparent window 152 is deteriorated. FIG. 8 is a diagram showing how the indicator 600 located on the right side of FIG. 6 is observed through the transparent window 152 of the polishing pad 150. As shown in FIG. FIG. 8A is a diagram when the transparent window 152 has not deteriorated. FIG. 8B is a diagram when the transparent window 152 is deteriorated. 7 and 8, the thickness of the hatching of the transparent window 152 indicates the transmittance of the transparent window 152. In FIG. Specifically, the thicker the hatching, the lower the transmittance of the transparent window 152 .

As the transparent window 152 deteriorates, the appearance of the indicator 600 when observed through the transparent window 152 also changes. For example, in FIGS. 7B and 8B, the transmittance of the transparent window 152 is reduced so that the indicator 600 is less visible. It is possible to grasp the deterioration of the transparent window 152 from the change in the appearance of the indicator 600 . Since the deterioration of the transparent window 152 occurs simultaneously with the abrasion of the polishing pad 150, it is possible to indirectly grasp the amount of abrasion of the polishing pad 150 by grasping the deterioration of the transparent window 152. FIG. By grasping the wear amount of the polishing pad 150, it becomes possible to replace the polishing pad 150 at an appropriate timing.

The timing for replacement of polishing pad 150 may be determined, for example, based on at least one of the following parameters. When the indicator 600 is observed through the transparent window 152, (1) the brightness of the indicator 600, (2) the sharpness of the edge portion of the indicator 600, and (3) a predetermined point of the indicator 600 and another point (the indicator 600 and (4) the color of indicator 600; If the indicator 600 has a pattern (such as a striped pattern or a checkered pattern) consisting of repetitions of a predetermined shape, the timing for replacing the polishing pad 150 is (5) when the indicator 600 is observed through the transparent window 152. It may be determined by whether or not the shape and the shape next to it can be distinguished, that is, whether or not the pattern of the indicator 600 can be determined. Note that the above (1) to (5) are merely examples. The threshold value may be appropriately set when the determination is made based on the above (1) to (5). For example, the user may not be able to distinguish between one pattern (for example, a closely spaced grid pattern) of the indicator 600 and the point of being unable to distinguish all the patterns of the indicator 600. The polishing pad 150 may be replaced at any timing. The user may determine when to replace the polishing pad 150 by visually observing the indicator 600 . On the other hand, if the substrate polishing apparatus 100 has some imaging mechanism (for example, an imaging mechanism 900 in FIG. 9 described later), the indicator 600 may be observed by the imaging mechanism. When the indicator 600 is observed by the imaging mechanism, the replacement timing of the polishing pad 150 may be determined by any conventionally known image processing technique.

According to the configuration described above, the polishing pad 150 can be replaced at an appropriate timing. In addition, once the indicator 600 is visually observed, it is possible to grasp the amount of wear of the polishing pad 150 almost in real time. Note that the polishing pad 150 is not necessarily worn uniformly over its entire surface. Therefore, by providing a plurality of indicators 600 as shown in FIG. 6, it is possible to grasp the position dependence of the wear amount of the polishing pad 150 .

Alignment mark 300 may also serve as indicator 600 . Conversely, the indicator 600 may also serve as the alignment mark 300 . Both alignment marks 300 and indicators 600 may be provided. It is also possible to have an alignment mark 300 under one transparent window 152 and an indicator 600 under another transparent window 152 .

In order to observe the transparent window 152 and/or the indicator 600, the substrate polishing apparatus 100 may include an imaging mechanism 900. FIG. FIG. 9 is a front cross-sectional view of a substrate polishing apparatus 100 having an imaging mechanism 900. As shown in FIG. At least a portion of indicator 600 is described as being located where an arrow extending from "600" points. However, since the height (thickness) of indicator 600 in FIG. 9 is substantially zero, the cross section of indicator 600 is not shown in FIG. Note that this description is not intended to exclude indicators 600 having a height. For example, if indicator 600 were formed by some member embedded in polishing table 110, indicator 600 would have a height.

Imaging mechanism 900 is configured to be able to capture an image and/or video of indicator 600 through transparent window 152 . That is, the imaging mechanism 900 observes the indicator 600 . Hereinafter, "image and/or video" is simply referred to as "image". Also, hereinafter, "acquisition of an image" is simply referred to as "imaging". Underneath the transparent window 152 is an indicator 600 when the components are properly attached. Accordingly, imaging mechanism 900 can image at least a portion of indicator 600 through transparent window 152 . Preferably, imaging mechanism 900 is configured to allow the entire area of transparent window 152 to be in its field of view. In other examples, imaging mechanism 900 can bring at least a portion of transparent window 152 into its field of view. In the example of FIG. 9, an imaging mechanism 900 such as a CCD camera is arranged so as to face the polishing table 110 . Optical elements such as mirrors and lenses may be arranged on the optical path between the imaging mechanism 900 and the polishing table 110 . When the polishing table 110 is surrounded by a housing, the amount of light for imaging may be insufficient. The substrate polishing apparatus 100 may have a light source for assisting imaging. A light source 1000 to be described later may assist imaging by the imaging mechanism 900 . Preferably, the imaging mechanism 900 can detect light of the same wavelength as the sensing light. A light source for assisting imaging may be capable of emitting light having the same wavelength as the sensing light.

The imaging mechanism 900 may be controlled by the controller 910 . The connection method between the imaging mechanism 900 and the control unit 910 is not limited to wired connection, and may be wireless connection (wired connection in the example of FIG. 9). The control unit 910 may be provided inside the imaging mechanism 900 or may be a component separate from the imaging mechanism 900 . Controller 910 may comprise storage device 911 , processor 912 and display 913 . Control unit 910 may further include other elements. The controller 910 may be connected not only to the imaging mechanism 900 but also to other components of the substrate polishing apparatus 100 .

The imaging mechanism 900 transfers the captured image to the control unit 910 . After acquiring the image of transparent window 152 and/or indicator 600 from imaging mechanism 900 , controller 910 calculates the degree of deterioration of transparent window 152 from the image of transparent window 152 and/or indicator 600 . Controller 910 (more specifically, processor 912) may determine the degree of deterioration of transparent window 152 based on, for example, (1) to (5) (brightness of indicator 600, etc.) described above. As another example, the degree of deterioration may be calculated based on the number or area of scratches on the transparent window 152, for example.

Specifically, the degree of deterioration of transparent window 152 may be calculated according to the following method:
imaging transparent window 152 and/or indicator 600 with imaging mechanism 900;
comparing the image captured by the imaging mechanism 900 with the ideal image and/or the feature amount calculated from the image captured with the imaging mechanism 900 with the ideal feature amount;
calculating the degree of deterioration of the transparent window 152 based on the comparison result obtained in the comparing step;
How to prepare. However, the "ideal image and/or ideal feature amount" refers to "an image and/or feature amount obtained or would be obtained if the transparent window 152 had not deteriorated".

The step of storing the ideal image and/or features in the storage device 911 may be performed prior to the step of imaging. The ideal image and/or features stored in storage device 911 may be used in the comparing step.

The comparing may be controlled by processor 912 . Any conventionally known image processing technique may be used in the comparing step. Here, the “feature amount” refers to a parameter (or parameter value) that can be used to determine the degree of deterioration of the transparent window 152 . For example, the aforementioned (1) to (5) (brightness of indicator 600, etc.) can be feature amounts. As another example, the number or area of scratches on the transparent window 152 can also be a feature amount. The number of feature values used in each stage may be one or plural. The ideal image and/or features recorded in the storage device 911 may be the images and/or features actually obtained when using the transparent window 152 that is not degraded at all. The ideal image and/or feature amount recorded in the storage device 911 may be an image and/or feature amount calculated by simulation or the like.

The following steps may be performed prior to the imaging step:
cleaning the surface of the polishing pad 150; The term “cleaning” as used herein refers to cleaning the surface of the polishing pad 150 so as to remove foreign matter on the transparent window 152 . Therefore, the term "cleaning" here has a meaning different from the technical term "dressing" in the industry to which this technology belongs. However, if the dressing allows removal of foreign matter on top of the transparent window 152, such dressing may be included in the cleaning. Also, the term “foreign matter on the transparent window” used herein refers to an object that obstructs imaging of the transparent window 152 , such as slurry adhering to the transparent window 152 . Once the foreign matter is removed by cleaning, transparent window 152 and/or indicator 600 can be properly imaged. The cleaning may be performed by washing with pure water, by jetting gas from a blower, by wiping with a wiper, or by other methods. The cleaning step may be performed by a user or automatically under the control of processor 912 .

The following steps may be performed prior to the imaging step:
A step of bringing at least part or all of the transparent window 152 into the field of view of the imaging mechanism 900 (hereinafter referred to as a “field of view adjustment step”). The field of view adjustment step may be performed by rotating the polishing table 110 and moving the transparent window 152 into position. Here, the "predetermined position" refers to a "position that can be imaged by the imaging mechanism 900". If the imaging mechanism 900 is configured to be movable, the field of view adjustment step may be performed by moving the imaging mechanism 900 . If an optical element is placed in the optical path between the imaging mechanism 900 and the transparent window 152, the field adjustment step may be performed by moving, moving or adjusting the optical element. Additionally, if the polishing head 130 is within the field of view of the imaging mechanism 900 during imaging, moving the polishing head 130 out of the field of view of the imaging mechanism 900 may be performed. The moving of each component, etc. may be controlled by processor 912 .

Prior to the comparing step, the following steps may be performed:
A step of calculating a feature amount from the image acquired by the imaging mechanism 900 . Feature calculation may be controlled by processor 912 .
After calculating the degradation of the transparent window 152, the following steps may be performed:
executing error processing if the degree of deterioration of the transparent window 152 exceeds a predetermined value; The error handling may be displaying a message prompting replacement of the polishing pad 150 on the display 913 . A determination of whether the degree of degradation of transparent window 152 exceeds a predetermined value may be made by processor 912 . The display of messages may be controlled by processor 912 . The error handling may be processor 912 stopping polishing of substrate 131 by substrate polishing apparatus 100 . If the substrate polishing apparatus 100 is equipped with a warning device, such as a red light or buzzer, the error handling may be to activate the warning device.

After the comparing step, the following steps may be performed:
Predicting the remaining life of the transparent window 152 based on the comparison result. Remaining life prediction may be performed by processor 912 . The "remaining life of the transparent window" refers to the polishing time or the number of times of polishing from the time when the step of prediction is performed to the time when the degree of deterioration of the transparent window will exceed a predetermined value. The remaining life of the transparent window 152 may be predicted by a formula recorded in the storage device 911 in advance. The remaining life of the transparent window 152 may be predicted using the images acquired by the imaging mechanism 900 and/or the feature values obtained from the images acquired by the imaging mechanism 900 so far as learning data. Learning data may be recorded in the storage device 911 . A message may be displayed on display 913 indicating the predicted remaining life. If the predicted remaining life falls below a predetermined value, a message may be displayed on display 913 warning that the end of life is approaching. Message display is processor 9
12 may be controlled.

After calculating the degree of deterioration of the transparent window 152 , the controller 910 may calculate the amount of wear of the polishing pad 150 based on the calculated degree of deterioration of the transparent window 152 .

The result of calculating the degree of deterioration of the transparent window 152 or the result of predicting the remaining life of the transparent window 152 is compared with the degree of deterioration or the remaining life actually confirmed visually by the user, and the comparison result is sent to the calculation or prediction process. By feeding back, it is possible to improve the accuracy of the calculation of the degree of deterioration or the prediction of the remaining life, or to compensate for the deviation of the prediction.

Although the transparent window 152 having the through hole 151 is used in FIG. 9, the transparent window 152 (see FIG. 7) without the through hole 151 may be used.

When the sensing light passes through the transparent window 152 , it is also possible to check the degree of deterioration of the transparent window 152 without using the indicator 600 . FIG. 10 is a front cross-sectional view of substrate polishing apparatus 100 having light source 1000 . The substrate polishing apparatus 100 of FIG. 10 is not provided with the indicator 600 . Accordingly, the imaging mechanism 900 of FIG. 10 is configured to image at least a portion of the transparent window 152 instead of the indicator 600 . In FIG. 10, the transparent window 152 shown in FIG. 7, ie the transparent window 152 without the through hole 151 is used. Accordingly, the configurations of the polishing table 110 and the optical sensor 120 are also changed from those in FIG. 9 (see the description of FIG. 7). A substrate polishing apparatus 100 in FIG. 10 includes a light source 1000 . The light source 1000 can emit light toward at least the transparent window 152 . Specifically, the light source 1000 is configured to allow light to enter the reflected light optical fiber 123 through the transparent window 152 . Preferably, the light source 1000 can irradiate light having at least the same wavelength as the sensing light. Light source 1000 may be, for example, a light bulb, a laser device, or the like. Optical elements such as lenses and mirrors may be arranged in the optical path between the light source 1000 and the transparent window 152 .

In the following description, it is assumed that the transmittance of the transparent window 152 decreases when the transparent window 152 deteriorates. Also, for convenience of explanation, the following description assumes that the transmittance of the transparent window 152 is the only factor that affects the amount of light detected by the optical sensor 120 . When the light source 1000 emits light toward the transparent window 152 , the light reaches the optical fiber 123 for reflected light. The light reaching the reflected light optical fiber 123 is detected by a photodetector inside the sensor main body 121 . If the transparent window 152 has not degraded at all, the transmittance of the transparent window 152 is maximum. Therefore, when the transparent window 152 has not deteriorated at all, the amount of light detected by the optical sensor 120 is the maximum value. If the transparent window 152 has deteriorated and the transmittance of the transparent window 152 has decreased, the amount of light detected by the optical sensor 120 also decreases. Therefore, by measuring the amount of light detected by the optical sensor 120, the degree of deterioration of the transparent window 152 can be calculated. The degree of deterioration of transparent window 152 may be calculated from the absolute value of the amount of light detected by optical sensor 120 . The degree of deterioration of the transparent window 152 may be calculated by comparing the maximum amount of light and the current amount of light. The "maximum amount of light" means the amount of light detected when the transparent window 152 is not deteriorated at all, that is, the ideal amount of light. If there are other factors that affect how much light the optical sensor 120 senses, those factors may be taken into account.

Even if optical characteristics other than the transmittance of the transparent window 152 change when the transparent window 152 deteriorates, the degree of deterioration of the transparent window 152 can be calculated by a similar method. If an optical characteristic other than the amount of light detected by the optical sensor 120 changes as the optical characteristic of the transparent window 152 changes, it is preferable that the optical sensor 120 can measure the change. For example, the optical sensor 120 may measure the degree of polarization, wavelength, incident angle, etc. of light in addition to the amount of light.

Next, a second method of calculating deterioration of the transparent window 152 without using the indicator 600 when sensing light passes through the transparent window 152 will be described. In the method described below, irradiation light emitted from the optical fiber 122 for irradiation light is used. When the transparent window 152 is covered with the substrate 131 (see the transparent window 152 located on the left side of FIG. 10), the illumination light from the illumination optical fiber 122 is reflected by the substrate 131 . The reflected light travels toward the optical fiber 123 for reflected light. At this time, the irradiation light and reflected light (sensing light) pass through the transparent window 152 . Therefore, the sensing light is affected by changes in the optical properties of the transparent window 152 . For example, when the transmittance of the transparent window 152 decreases due to deterioration of the transparent window 152, the transparent window 152 deteriorates and the amount of reflected light detected by the photodetector of the sensor main body 121 decreases. Therefore, by measuring the amount of sensing light detected by the optical sensor 120, the degree of deterioration of the transparent window 152 can be calculated. If an optical characteristic other than the amount of light detected by the optical sensor 120 changes as the optical characteristic of the transparent window 152 changes, it is preferable that the optical sensor 120 can measure the change. For example, the optical sensor 120 may measure the degree of polarization, wavelength, incident angle, etc. of light in addition to the amount of light. The substrate 131 used when measuring the amount of sensing light may be the substrate 131 that will/is being polished by the substrate polishing apparatus 100 . A dummy substrate may be used as the substrate 131 in order to reduce the effects of individual differences between substrates and the progress of substrate polishing.

Next, a third method of calculating deterioration of transparent window 152 without using indicator 600 when sensing light passes through transparent window 152 will be described. In the method described below, irradiation light emitted from the optical fiber 122 for irradiation light is used. When the transparent window 152 is not covered with the substrate 131 , the substrate 131 does not block the irradiation light from the irradiation light optical fiber 122 . If the imaging mechanism 900 is properly positioned, the illumination light passes through the transparent window 152 and reaches the imaging mechanism 900 . The illuminating light is affected by changes in the optical properties of the transparent window 152 . For example, when the transmittance of the transparent window 152 is reduced due to deterioration of the transparent window 152, the transparent window 152 is deteriorated and the amount of irradiation light detected by the imaging mechanism 900 is reduced. Therefore, the degree of deterioration of the transparent window 152 can be calculated by measuring the amount of irradiation light detected by the imaging mechanism 900 . If the optical characteristics other than the amount of light detected by the optical sensor 120 change as the optical characteristics of the transparent window 152 change, the imaging mechanism 900 is preferably capable of measuring the change. For example, the imaging mechanism 900 may measure the degree of polarization, wavelength, incident angle, etc. of light in addition to the amount of light. A change in the optical properties of the transparent window 152 may be calculated from the image acquired by the imaging mechanism 900 .

A number of embodiments of the present invention have been described above. The embodiments of the invention described above are intended to facilitate understanding of the invention, and are not intended to limit the invention. The present invention may be modified and improved without departing from its spirit, and the present invention includes equivalents thereof. In addition, any combination or omission of each component described in the claims and the specification is possible within the range that at least part of the above problems can be solved or at least part of the effect is achieved. is.

It should be noted that the directional terminology is used herein for convenience. In this specification, up, down, left, right, front and back directions are defined with reference to FIG. 1, but the upward direction in FIG. 1 does not always coincide with the vertically upward direction.

The present application provides, as an embodiment, a polishing table for attaching a polishing pad having a transparent window, and an indicator provided on the polishing table for checking deterioration of the transparent window, which is visible through the transparent window. A substrate polishing apparatus is disclosed, comprising: an indicator provided at a desired position.

Further, the present application provides, as an embodiment, a substrate polishing method comprising a polishing table for attaching a polishing pad having a transparent window, and an optical sensor attached to the polishing table for measuring the progress of polishing of the substrate. In the apparatus, the polishing table has an opening for passing the optical fiber extending from the optical sensor and an indicator for checking deterioration of the transparent window, the indicator being on the surface of the polishing table to which the polishing pad is attached. an indicator, wherein the indicator is provided around the opening.

As an example, these substrate polishing apparatuses have the effect that it is possible to determine the degree of deterioration of the transparent window by visually observing the indicator. Further, these substrate polishing apparatuses have the effect that it is possible to determine the amount of wear of the polishing pad by determining the degree of deterioration of the transparent window from the appearance of the indicator, and to determine the replacement timing of the polishing pad. Play as an example.

Furthermore, the present application discloses, as an embodiment, a substrate polishing apparatus further comprising an imaging mechanism configured to be capable of imaging an indicator through a transparent window.

This substrate polishing apparatus has, as an example, the effect that the imaging mechanism can image the indicator, that is, the indicator can be observed without the user's visual observation.

Further, the present application provides, as an embodiment, a substrate polishing apparatus, the substrate polishing apparatus further comprising a controller, wherein the controller calculates from the image acquired by the imaging mechanism and/or the image acquired by the imaging mechanism. Disclosed is a substrate polishing apparatus that calculates the degree of deterioration of a transparent window from a feature amount obtained by using the substrate polishing apparatus.

Further, the present application provides, as an embodiment, a substrate polishing apparatus, wherein the control unit compares an ideal image and/or feature amount with an indicator image and/or feature amount acquired by an imaging mechanism. Disclosed is a substrate polishing apparatus that calculates the degree of deterioration of a transparent window by

These disclosures clarify the details of the deterioration degree calculation process.

Further, the present application discloses, as an embodiment, a substrate polishing apparatus in which the controller executes error processing when the calculated degree of deterioration of the transparent window exceeds a predetermined value. .

This substrate polishing apparatus has, as an example, the effect that the use of a deteriorated transparent window can be stopped.

Further, the present application discloses, as an embodiment, a substrate polishing apparatus in which the controller calculates the wear amount of the polishing pad based on the calculated degree of deterioration of the transparent window.

This disclosure makes it clear that the wear amount of the polishing pad can be calculated from the degree of deterioration of the transparent window.

Further, the present application provides, as one embodiment, a method for calculating the degree of deterioration of a transparent window provided on a polishing pad attached to a polishing table of a substrate polishing apparatus, wherein a step of capturing an image of an indicator on the polishing table provided at a suitable position using an imaging mechanism; comparing the feature quantity with the ideal feature quantity;
and calculating a degree of deterioration of the transparent window based on the comparison result obtained in the comparing step.

Furthermore, the present application discloses, as one embodiment, a method of calculating the wear amount of the polishing pad based on the degree of deterioration of the transparent window calculated by the method of calculating the degree of deterioration of the transparent window.

These disclosed contents clarify a method for calculating the degree of deterioration of the transparent window and a method for calculating the amount of wear of the polishing pad.

DESCRIPTION OF SYMBOLS 100... Substrate polishing apparatus 110... Polishing table 111... Sealing liquid supply path 112... Sealing liquid discharge path 113... Sealing liquid source 114... Rotary joint 120... Optical sensor 121... Sensor body 122... Optical fiber for irradiation light 123... Optical fiber for reflected light 130 Polishing head 131 Substrate 140 Polishing liquid supply mechanism 150 Polishing pad 151 Through hole 152 Transparent window 300 Alignment mark 310 First mark 320 Second mark 330 Third Mark 340... Fourth mark 600... Indicator 610... Opening 900... Imaging mechanism 910... Control section 911... Storage device 912... Processor 913... Display 1000... Light source

Claims (9)

a polishing table for mounting a polishing pad having a transparent window;
an indicator provided on the polishing table for checking deterioration of the transparent window, the indicator provided at a position visible through the transparent window;
A substrate polishing apparatus comprising: a polishing table for mounting a polishing pad having a transparent window;
an optical sensor mounted on the polishing table for measuring the progress of polishing of the substrate;
A substrate polishing apparatus comprising
The polishing table is
an aperture for passing an optical fiber extending from the body of the optical sensor;
An indicator for confirming deterioration of the transparent window, the indicator being provided at a position visible through the transparent window on a surface of the polishing table on which the polishing pad is attached, the indicator being an indicator provided around the opening;
comprising
Substrate polishing equipment. 3. The substrate polishing apparatus according to claim 1, further comprising an imaging mechanism capable of imaging said indicator through said transparent window. The substrate polishing apparatus according to claim 3,
The substrate polishing apparatus further comprises a controller,
The control unit calculates the degree of deterioration of the transparent window from the image acquired by the imaging mechanism and/or the feature amount calculated from the image acquired by the imaging mechanism.
Substrate polishing equipment. The substrate polishing apparatus according to claim 4,
The control unit calculates the degree of deterioration of the transparent window based on a result of comparison between an ideal image and/or feature amount and the image and/or feature amount of the indicator acquired by the imaging mechanism, substrate polishing. Device. The substrate polishing apparatus according to claim 4 or 5,
The control unit executes error processing when the calculated degree of deterioration of the transparent window exceeds a predetermined value.
Substrate polishing equipment. The substrate polishing apparatus according to any one of claims 4 to 6,
The control unit calculates the amount of wear of the polishing pad based on the calculated degree of deterioration of the transparent window.
Substrate polishing equipment. A method for calculating the degree of deterioration of a transparent window provided in a polishing pad attached to a polishing table of a substrate polishing apparatus, comprising:
using an imaging mechanism to image the transparent window and/or an indicator on the polishing table provided at a position visible through the transparent window;
comparing the image captured by the imaging mechanism with an ideal image and/or the feature amount calculated from the image captured by the imaging mechanism with the ideal feature amount;
calculating the degree of deterioration of the transparent window based on the comparison result obtained in the comparing step;
A method. A method of calculating the wear amount of the polishing pad based on the degree of deterioration of the transparent window calculated by the method of claim 8 .

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