JP5120696B2 - Polishing equipment - Google Patents

Description

  The present invention includes a substrate rotation mechanism that rotates a substrate, a pad rotation mechanism that rotates a polishing pad having a smaller diameter than the substrate, and a rocking mechanism that swings the polishing pad relative to the substrate while the substrate and the polishing pad are in contact with each other. The present invention relates to a polishing apparatus including a moving mechanism, and a control device that controls the rotation of the substrate, the rotation of the polishing pad, and the relative swing of the polishing pad with respect to the substrate to control the polishing process of the substrate.

  A CMP apparatus is exemplified as a polishing apparatus for polishing the substrate surface. A CMP apparatus is widely used for polishing a substrate such as a silicon substrate, a glass substrate, or a semiconductor wafer as a technique for polishing a substrate surface with high precision by chemical mechanical polishing (CMP). In such a polishing apparatus, the substrate held by the chuck and the polishing pad mounted on the polishing head are relatively rotated and pressed, and a slurry (Slurry) corresponding to the polishing content is brought into contact with the substrate and the polishing pad. Is supplied to cause a chemical and mechanical polishing action to polish the substrate surface flatly.

  Such polishing apparatuses are roughly classified into two types, a type in which the diameter of the polishing pad is larger than the diameter of the substrate, and a type in which the diameter of the polishing pad is smaller than the diameter of the substrate, based on the size relationship between the substrate and the polishing pad. The In a polishing apparatus of a type in which the diameter of the polishing pad is smaller than the diameter of the substrate, a swinging mechanism for swinging the polishing pad relative to the substrate is generally provided to uniformly polish the entire surface of the substrate. (For example, see Patent Document 1).

JP 2006-319249 A

  As described above, in the polishing apparatus in which the diameter of the polishing pad is smaller than the diameter of the substrate and the base and the polishing pad are moved relative to each other by the swing mechanism, the polishing pad is in contact with the polishing pad during the polishing process. The region where the polishing pad is separated and not subjected to the polishing action changes instantaneously and instantaneously (depending on the rotation angle position of the substrate and the position of the polishing pad with respect to the substrate). Therefore, the polishing of the substrate surface depends on a combination of processing conditions such as the rotation speed of the substrate, the rotation speed of the polishing pad, and the relative rocking speed of the polishing pad with respect to the substrate (referred to as a polishing recipe). The rate varies from region to region and asymmetry occurs in the polishing amount distribution, so that the desired flatness cannot be obtained.

  In such a case, conventionally, it has been difficult to determine how much of the polishing recipe should be changed. For this reason, when asymmetry of the polishing amount distribution occurs, it is necessary to repeatedly perform test processing using a monitor wafer while changing each condition value of the polishing recipe little by little. There was a problem that it became a factor that hinders productivity in terms of cost. In particular, when similar polishing equipment has been used to obtain good polishing results in the past, or when the substrate content is different, but the processing details are similar, this is a time-consuming and costly test. In order to avoid the occurrence of new problems associated with processing and changes in the polishing recipe, there has been a strong demand for polishing without changing the proven polishing recipe as much as possible.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a polishing apparatus capable of eliminating troublesome work related to a polishing recipe and improving productivity.

  To achieve the above object, a polishing apparatus according to a first aspect of the present invention rotates a substrate rotating mechanism that holds and rotates a substrate, and a polishing pad that is formed in a smaller diameter than the substrate and is disposed in a posture opposite to the substrate. A pad rotating mechanism and a swinging mechanism that swings the polishing pad relative to the substrate in a state where the surface to be polished of the substrate and the polishing surface of the polishing pad that are relatively rotated are in contact with each other (for example, arm swinging in the embodiment). And a controller for controlling the polishing process of the substrate by controlling the rotation of the substrate, the rotation of the polishing pad, and the relative oscillation of the polishing pad with respect to the substrate. In addition, when a polishing processing condition is input, the control device in the polishing apparatus is configured such that the rotation speed of the substrate, the rotation speed of the polishing pad, the relative swing range of the polishing pad with respect to the substrate, and the relative Based on a predetermined acceleration / deceleration pattern set in advance as a swing speed and a swing mechanism control condition, the travel locus of each part of the polishing surface on the surface to be polished is integrated to distribute the travel locus on the surface to be polished. When the density is calculated, and it is determined that the variation in the circumferential direction of the calculated distribution density exceeds a predetermined reference value, a predetermined acceleration / deceleration pattern is changed on the surface to be polished. It is configured to calculate the distribution density of the running trajectory and change the default acceleration / deceleration pattern to an acceleration / deceleration pattern in which the variation in the circumferential direction of the distribution density is below the reference value

  A polishing apparatus according to a second aspect of the present invention is the polishing stop time in which the relative swing speed becomes zero when the control device reverses the relative movement direction of the polishing pad with respect to the substrate in the predetermined acceleration / deceleration pattern. Is configured to change.

  In the polishing apparatus according to a third aspect of the present invention, the control device is set in processing conditions from a state in which the relative movement direction of the polishing pad with respect to the substrate is reversed and the relative rocking speed is zero in the predetermined acceleration / deceleration pattern. The acceleration time until the relative rocking speed is reached is changed. The polishing apparatus according to a fourth aspect of the present invention is the polishing apparatus according to the fourth aspect of the present invention, wherein the control device is configured to move from a state of relative rocking speed set in a processing condition for reversing a relative movement direction of the polishing pad with respect to the substrate in the predetermined acceleration / deceleration pattern. The deceleration time until the relative rocking speed becomes zero is changed.

  According to the polishing apparatus of the present invention, based on the polishing recipe, the travel locus of each part of the polishing surface is integrated to calculate the distribution density of the travel locus on the surface to be polished, and the distribution density varies in the circumferential direction. Is automatically changed to an acceleration / deceleration pattern in which the variation in the circumferential direction is less than or equal to the reference value, so that asymmetry problems do not occur without changing the polishing recipe. Be controlled. For this reason, it is not necessary to search for processing conditions that do not cause asymmetry by repeating test processing that consumes a large number of expensive monitor wafers, and it is possible to reduce time and cost and perform polishing processing with a desired polishing recipe. it can.

  Therefore, according to this invention, the grinding | polishing apparatus which can eliminate the complicated operation | work regarding a grinding | polishing recipe and can improve productivity can be provided.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. A schematic configuration of a polishing apparatus 1 to which the present invention is applied is shown in FIG. The polishing apparatus 1 includes a substrate rotating mechanism 10 that holds and rotates a substrate W such as a silicon wafer, a pad rotating mechanism 20 that rotates a polishing head 21 on which a polishing pad 23 is mounted, and a polishing pad 23 that moves up and down relative to the substrate W. Further, although not shown in detail, the head moving mechanism 30 that relatively swings, the slurry supply mechanism 40 that supplies the slurry to the center of the polishing pad 23, the rotation of the substrate W and the polishing pad 23, the raising and lowering of the polishing pad 23 relative to the substrate W And a control device 50 for controlling the polishing process of the substrate W by controlling the operation of the polishing apparatus such as swinging and supplying the slurry to the polishing processing unit.

  The substrate rotating mechanism 10 includes a disk-shaped chuck 11, a spindle 14 extending vertically downward from the lower portion of the chuck 11, a chuck driving motor 15 that transmits a rotational driving force to the spindle 14, and rotates the chuck 11 in a horizontal plane. Composed. The chuck 11 includes a chuck plate 12 formed in a disk shape with high flatness using a high-rigidity material such as ceramic, and a suction pad 13 attached to the upper surface of the chuck plate 12. The chuck plate 11 is provided with a vacuum chuck structure that vacuum-sucks the lower surface of the substrate W so that the substrate W can be attached and detached, and an upper portion of the chuck is exposed from the processing table T. A surface to be polished (surface to be polished) of the substrate W attracted and held by 11 is disposed in an upward horizontal posture.

  The operation of the chuck drive motor 15 is controlled by the control device 50, and the control device 50 controls the rotation / stop, rotation direction, rotation speed, etc. of the substrate W attracted and held by the chuck 11 according to the processing program. A head moving mechanism 30 is provided adjacent to the substrate rotating mechanism 10, and a pad rotating mechanism 20 is provided at the tip of the polishing arm 32 of the head driving mechanism 30.

  The pad rotating mechanism 20 includes a disk-shaped polishing head 21, a spindle 24 extending vertically upward from the upper portion of the polishing head 21, and a pad driving motor 25 that transmits a rotational driving force to the spindle 24 to rotate the polishing head 21 in a horizontal plane. Etc.

  The polishing head 21 includes a polishing plate 22 formed in a disk shape with high flatness using a high-rigidity material similar to that of the chuck 11, and a polishing pad 23 attached to the lower surface of the polishing plate 22. The The polishing pad 23 is formed in an annular shape whose outer diameter is somewhat smaller (about 80 to 95%) than the diameter of the substrate W to be polished. For example, a hard polyurethane sheet having an independent foam structure is used. The polishing surface is affixed to the lower surface of the polishing plate 22 and the polishing surface is disposed in a downward horizontal posture.

  A slurry supply structure for supplying the slurry supplied by the slurry supply mechanism 40 to the center of the polishing pad 23 is provided in the center of the polishing head 21 so as to penetrate the center of the polishing plate 22 vertically. Further, a so-called airbag-type pad pressurizing mechanism is provided in which air is supplied to a pressurization chamber formed inside the polishing head 21 to pressurize the polishing plate 22 downward, and the polishing pad 23 is attached to the substrate. By controlling the pressure in the pressurizing chamber while being in contact with W, the contact pressure between the substrate W and the polishing pad 23, that is, the polishing pressure can be controlled.

The operation of the pad drive motor 25 and the pressure in the pressurizing chamber are controlled by the control device 50, and the rotation / stop, rotation direction, rotation speed, polishing pressure, etc. of the polishing pad 23 mounted on the polishing head 21 are based on the machining program. Are controlled by the control device 50.

  The head moving mechanism 30 horizontally swings the polishing arm 32 around a base 31 protruding upward from the processing table T, a polishing arm 32 extending horizontally from the base 31, and a swinging shaft extending vertically through the base 31. An arm swinging mechanism 35 for moving the polishing arm, an arm lifting mechanism (not shown) for vertically moving the entire polishing arm, and the like. The pad rotating mechanism 20 described above is provided at the tip of the polishing arm 32. The head moving mechanism 30 is configured such that the substrate rotating mechanism 10 is positioned on the swing locus of the polishing head 21 when the polishing arm 32 is horizontally swinged by the arm swing mechanism 35. The entire polishing arm is moved up and down while facing the chuck 11, and the polishing pad 23 can be horizontally swung with respect to the substrate W while the polishing surface of the polishing pad 23 is in contact with the surface to be polished of the substrate W. Is done.

  The operations of the arm swing mechanism 35 and the arm lifting mechanism are controlled by the control device 50, and the swing start point (the swing start angle position of the polishing arm 32) of the polishing pad 23 with respect to the substrate W held by the chuck 11 is swung. The movement stroke (the rocking angle range of the polishing arm 32), the rocking speed, and the like are controlled by the control device 50 based on the machining program.

  The control device 50 reads a polishing recipe (a polishing processing condition) from the input processing program. In the processing program, as a polishing recipe, the rotation speed of the polishing pad 23, the rotation speed of the substrate W, the swing start point and swing stroke of the polishing pad 23 relative to the substrate W, the swing speed of the polishing pad 23, the polishing pressure, and the slurry Condition values such as type and slurry supply flow rate are included.

From the polishing recipe, the control device 50 determines the rotation speed of the polishing pad 23, the rotation speed of the substrate W, the rotation start point of the polishing pad 23 relative to the substrate W, the swing stroke, The rocking speed of the pad 23 is acquired, and the traveling locus of each part of the polishing pad 23 on the surface to be polished of the substrate W is calculated based on these condition values. Specifically, the rotational speed V _p = 110 [rpm] of the polishing pad 23 set in the processing program, the rotational speed V _w = −60 [rpm] of the substrate W, and the swing start point of the polishing pad 23 relative to the substrate W are set. The traveling locus of the polishing pad is calculated for 30 [mm] from the center of the substrate, a swing stroke of 90 [mm], and a swing speed V _s = 60 [mm / sec]. Here, the reciprocating swing of the polishing pad 23 with respect to the substrate W is repeated from a clockwise swing to a stop to a counterclockwise swing in a plan view, and the swing control of the polishing arm 32 is basically performed. Is executed based on a predetermined acceleration / deceleration pattern P _V (see FIG. 4) preset and stored in the memory in the control device 50. Therefore, when calculating the first traveling locus, the calculation is performed for the case where the polishing arm 32 is reciprocally swung with a predetermined acceleration / deceleration pattern. The length of the arm of the polishing arm 32 is constant, and the acceleration / deceleration pattern of oscillation of the polishing arm 32 is synonymous with the acceleration / deceleration pattern of relative oscillation of the polishing pad 23 with respect to the substrate W.

  FIG. 3 shows the temporal change of the running locus L under the above conditions at an arbitrary point P of the polishing pad 23. FIGS. 3 (a), (b), and (c) are shown in FIG. Start: t = 0 [sec], (b) 3 seconds after polishing starts: t = 3 [sec], (c) 9 seconds after polishing starts: t = 9 [sec] Yes.

  As can be understood from this figure, the traveling locus L of the arbitrary point P is extremely complex, and on the surface to be polished of the substrate W, a region where the density of the traveling locus L is high and a region where the density is low are seen. There are also some trajectories that run in the outer peripheral area outside the surface to be polished. Since the traveling locus L formed on the surface to be polished of the substrate W is a polishing locus that is polished by an arbitrary point P of the polishing pad 23, the higher the density of the traveling locus L, the higher the polishing rate (Removal Rate). The lower the density of the running locus L, the lower the polishing rate.

The control device 50 integrates the traveling locus for each part of the polishing surface of the polishing pad 23 and calculates the density distribution of the traveling locus formed on the surface to be polished of the substrate W. For example, the arbitrary point P, the circumferential direction in 5 degree pitch, set in the radial direction as a number of travel point P ₁ to P _n of 5mm pitch, running locus L ₁ ~L of the points of P ₁ to P _{n n} is integrated over the polishing time, and the density of the running locus of the polished surface on the surface to be polished is calculated. It has been confirmed by experiments by the inventors that the density distribution of the running trajectory thus obtained has a high correlation with the measurement data of the surface distribution of the polishing rate obtained by measuring the shape of the substrate actually polished. Multiplying the calculated travel locus density by a predetermined coefficient k simulates the surface distribution of the polishing rate.

  Then, from the surface distribution of the polishing rate, the one developed as the distribution of the polishing rate at an angle of 0 to 360 degrees located on the circumference of the same radius is the polar removal rate. The polar axis (Polar Range = (Max-Min) / Average) representing the non-uniformity of the polishing amount distribution is not flat in the graph of the polar polishing rate with an angle on the horizontal axis. This means that the polishing rate distribution is not axially symmetric, that is, a problem of asymmetry occurs.

  The present invention is based on the high correlation between the density distribution of the running locus and the surface distribution of the polishing rate as described above, and the relationship between the polar range and the asymmetry of the surface to be polished. The device 50 calculates the distribution density of the travel locus for a plurality of radial positions, and in other words, simulates whether or not the variation in the circumferential direction of the calculated distribution density exceeds a predetermined reference value set in advance. It is determined whether or not the maximum value of the polar range (Max Polar Range) exceeds a predetermined reference value. When it is determined that the distribution density of the traveling locus exceeds a predetermined reference value set in advance, the traveling locus of the traveling locus is changed when the default acceleration / deceleration pattern of the polishing arm 32 set in the memory in the control device 50 is changed. Calculate the density distribution. Then, the predetermined acceleration / deceleration pattern is changed to an acceleration / deceleration pattern in which the variation in the circumferential direction of the density of the travel locus is equal to or less than the reference value.

FIG. 4 shows the acceleration / deceleration pattern P _V of the polishing arm. In FIG. 4, the horizontal axis represents time t, and the vertical axis represents the absolute value | V | of the swing speed of the polishing arm 32 (the swing speed of the polishing pad 23 relative to the substrate W). Since the polishing arm 32 alternately repeats the clockwise swing and the counterclockwise swing in plan view, the acceleration / deceleration pattern repeats acceleration to a set swing speed V _s (V _Oscillation ) to deceleration. In order to prevent the moment acting on the arm swing mechanism 35 from becoming infinite between the deceleration region and the acceleration region where the swing direction is reversed, there is a stop region where the swing speed is zero. Provided.

Here, even in each of the acceleration / deceleration / stop regions, the substrate W and the polishing pad 23 are relatively rotated in a pressing state under the supply of slurry, and a traveling locus is formed on the surface to be polished. Therefore, by changing the pattern of the acceleration-deceleration and stopping area, without changing the rocking speed V _s designated in the polishing recipe, it is possible to change the density distribution of the traveling locus, it Polar Range An acceleration / deceleration pattern that is equal to or less than a predetermined reference value can be extracted.

Specifically, the acceleration time until the set speed V _s is reached from the state where the swing speed is zero is t _up , the time in the constant speed region where the constant speed swing is performed at the set speed V _s is t _v , and the swing speed There set speed V _s t a deceleration time until zero the _down, the swing stop time to pause when inverting the swing direction when the t _stop, each time the acceleration-deceleration and stopping region t _At least one of _up , t _down , and t _stop is changed to change the time t _offset (oscillation delay time: referred to as Oscillation offset Time) of a region that does not satisfy the set speed V _s other than the constant velocity region. Here, t _offset = t _up + t _down + t _stop .

If the absolute value of acceleration in the acceleration / deceleration region is the same value a,
t _up = t _down = V _s / a
t _offset = t _up + t _down + t _stop = (2V _s / a) + t _stop

From this equation, by changing the acceleration magnitude a in the acceleration / deceleration region to change the acceleration time t _up and the deceleration time t _down , or by changing the swing stop time t _stop for swing back, The value of the polar range can be changed by changing the density distribution.

When the acceleration a is obtained from the above equation,
a = 2V _s / (t _offset −t _stop )
When the oscillation stop time t _stop is obtained,
t _stop = (2V _s / a) + t _offset

The control device 50 changes the acceleration a (acceleration time t _up , deceleration time t _down ) set as a parameter in the control program of the polishing device within a predetermined acceleration range, or similarly swings that are parameter-set. For the acceleration / deceleration pattern in which the oscillation delay time t _offset is changed by changing the stop time t _stop or both of them, the density distribution of the running trajectory is calculated and the polishing rate simulated based on this is calculated. The maximum polar range for each condition is calculated from the surface distribution.

FIG. 1 is a graph showing changes in the maximum polar range calculated as described above. In FIG. 1, the horizontal axis is the oscillation offset time t _offset , the vertical axis is the maximum polar range, and the oscillation delay time t _offset is 0 to 0.1 [sec]. It shows the change of the maximum polar range when changing between.

As is apparent from FIG. 1, the maximum polar range can be changed by changing the oscillation delay time t _offset . For example, when the oscillation delay time t _offset is 0.02 [sec] in the predetermined acceleration / deceleration pattern and the maximum polar range calculated at this time is 17%, the oscillation delay time t _{offset is set} to 0. If it is changed to .04 [sec] or more, the maximum polar range can be suppressed to 7% or less, and if the oscillation delay time t _offset is changed to 0.05 [sec], the maximum polar range is 2%. It can be as follows.

Based on the simulation results as described above, the control device 50 changes the acceleration / deceleration pattern so that the variation in the density of the travel locus in the circumferential direction is not more than the reference value. For example, an acceleration / deceleration pattern in which the value when converted to the polar range is 7% or less is changed to an acceleration / deceleration pattern of the oscillation delay time t _offset = 0.05 [sec], which is the minimum value. In this case, the specific parameter to be changed may be either the absolute value of acceleration a (or acceleration time t _up , deceleration time t _down ) or swing stop time t _stop .

  The control device 50 starts the polishing process according to the execution operation of the polishing process, and controls the operations of the substrate rotation mechanism 10, the pad rotation mechanism 20, the head moving mechanism 30, the arm swing mechanism 35, the slurry supply device 40, and the like. Then, the polishing process is executed under the processing conditions based on the polishing recipe. The parameter of the changed acceleration / deceleration pattern is stored in the RAM in the control device, and when executing the same machining program, the polishing process is executed by replacing the parameter of the default acceleration / deceleration pattern.

In some cases, the processing range set in the polishing recipe remains the same, and the density distribution of the running locus is not biased and the polar range is relatively small. FIG. 5 shows a case where the rotation speed V _w of the substrate W = −65 [rpm], the swing speed V _s of the polishing pad 23 relative to the substrate W = 62 [mm / sec], and other processing conditions are the same. FIG. 3 is a graph displayed by superimposing the change of the maximum polar range when the dynamic delay time t _offset is changed by plotting with triangle marks and overlapping the data of FIG. 1 plotted with circle marks.

As can be understood from FIG. 5, even when the maximum polar range is relatively small with the processing conditions set in the polishing recipe, the maximum polar range is changed by changing the oscillation delay time t _offset. Can be minimized. For example, when the oscillation delay time t _offset is 0.02 [sec] in the predetermined acceleration / deceleration pattern, the calculated maximum polar range is a little less than 4%, which is a sufficiently small value, but the oscillation delay time t _{If the offset} is changed to 0.07 [sec], the maximum polar range can be further reduced to 2% or less. In other words, even when the variation in the circumferential direction of the density distribution of the running trajectory is relatively small, the asymmetry can be minimized without changing the polishing recipe by performing the same process as described above and changing the acceleration / deceleration pattern. Polishing processing can be executed under such conditions.

Also, among the processing conditions set in the polishing recipe, the substrate rotation speed V _w and the polishing pad swing speed V _s with respect to the substrate are changed within a certain range, and these processing conditions are changed as described above. Alternatively, the density distribution of the travel locus may be calculated and the conditions may be optimized including the polishing recipe. According to such a configuration, for example, the characteristic plotted with a circle in FIG. 5 can be changed to the characteristic plotted with a triangle, thereby changing the maximum polar range with respect to the change in the oscillation delay time t _offset. It can be made smaller (the influence on the symmetry when the oscillation delay time varies) can be reduced.

  As described above, in the polishing apparatus of the present invention, test processing that consumes a large number of expensive monitor wafers is repeated to find processing conditions that do not cause asymmetry, and the polishing recipe is changed and set based on this. There is no need, and high-quality polishing can be performed with the polishing recipe initially set in the processing program. Therefore, according to this invention, the grinding | polishing apparatus which can eliminate the complicated operation | work regarding a grinding | polishing recipe and can improve productivity can be provided.

It is a graph which shows the change of the maximum polar range with respect to rocking | fluctuation delay time. It is explanatory drawing which shows schematically the structure of the grinding | polishing apparatus to which this invention is applied. It is explanatory drawing which shows the driving | running locus | trajectory of the arbitrary points of the polishing pad with respect to a board | substrate. It is a graph which shows the acceleration / deceleration pattern in rocking | fluctuation control of a grinding | polishing arm. It is a graph which shows the change of the maximum polar range with respect to rocking | fluctuation delay time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing apparatus 10 Substrate rotating mechanism 20 Pad rotating mechanism 23 Polishing pad 30 Head moving mechanism 35 Arm swing mechanism (swing mechanism)
50 Control device L Traveling track P _V Acceleration / deceleration pattern W Substrate t _up acceleration time t _down deceleration time t _stop oscillation stop time t _offset oscillation delay time

Claims (4)

A substrate rotating mechanism for holding and rotating the substrate, a pad rotating mechanism for rotating a polishing pad formed in a posture opposite to the substrate and having a smaller diameter than the substrate, and a surface to be polished of the substrate that is relatively rotated A swinging mechanism for swinging the polishing pad relative to the substrate in a state where the polishing pad is in contact with a polishing surface of the polishing pad, rotation of the substrate, rotation of the polishing pad, and the polishing pad with respect to the substrate In a polishing apparatus comprising a control device that controls the relative polishing of the substrate to control the polishing of the substrate,
When a processing condition for polishing is input, the control device is configured to input the rotation speed of the substrate, the rotation speed of the polishing pad, the relative swing range of the polishing pad with respect to the substrate, and the relative Based on a rocking speed and a predetermined acceleration / deceleration pattern set in advance as a control condition of the rocking mechanism, the traveling locus of each part of the polishing surface on the surface to be polished is integrated and the surface on the surface to be polished is integrated. When the distribution density of the travel locus is calculated, and it is determined that the variation in the circumferential direction of the calculated distribution density exceeds a predetermined reference value set in advance, the default acceleration / deceleration pattern is changed The distribution density of the travel locus on the surface to be polished is calculated for the predetermined acceleration / deceleration pattern, and the variation in the circumferential direction of the distribution density is equal to or less than the reference value. Polishing apparatus characterized by being configured to change the acceleration and deceleration patterns.   The control device is configured to change, in the predetermined acceleration / deceleration pattern, a swing stop time in which a relative swing speed becomes zero when a relative movement direction of the polishing pad with respect to the substrate is reversed. The polishing apparatus according to claim 1, wherein the polishing apparatus is characterized.   The control device reaches a relative rocking speed set in the processing conditions from a state in which the relative movement direction of the polishing pad with respect to the substrate is reversed and the relative rocking speed is zero in the predetermined acceleration / deceleration pattern. The polishing apparatus according to claim 1, wherein the acceleration time is changed. In the predetermined acceleration / deceleration pattern, the control device reverses the relative movement direction of the polishing pad with respect to the substrate, and the relative rocking speed becomes zero from the state of the relative rocking speed set in the processing conditions. The polishing apparatus according to any one of claims 1 to 3, wherein the deceleration time is changed.

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