JP2006351928A - Polishing method and polishing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method and a polishing apparatus which has small reduction in polishing rate and uniform polishing performance. <P>SOLUTION: The polishing apparatus comprises a rotary platen 11, having a polishing pad 13 bonded on its surface, and a wafer holding mechanism 14 for rotatably holding a wafer 10, while being pushed against the polishing pad 13. The apparatus also comprises a silicon member holding means for pushing a silicon member 30, having a silicon material 32 formed on its surface, against the rotating polishing pad 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing method and a polishing apparatus for performing chemical mechanical polishing (CMP) on a surface of a layer formed on a wafer in a semiconductor manufacturing process.

  In recent years, in a semiconductor manufacturing process, the surface of a wafer in the middle of a process is subjected to chemical mechanical polishing (CMP) using a polishing apparatus (CMP apparatus), which is described in Patent Documents 1 and 2 and the like. Yes. First, a schematic configuration of a conventional CMP apparatus will be briefly described.

  In the CMP apparatus, polishing is performed by rotating the platen to which the polishing pad is attached and supplying the polishing agent (slurry) to the polishing pad while pressing the wafer held by the wafer holding mechanism against the polishing pad. In CMP, an oxide film or a metal film layer formed on the surface of a wafer is polished.

  FIG. 1 is a schematic configuration diagram of a CMP apparatus. As shown in FIG. 1, the platen 11 with the polishing pad 13 attached is rotated around the rotation shaft 12, and the slurry holding device 14 is supplied onto the polishing pad 13 while supplying the slurry 17 from the slurry supplier 16. The wafer 10 held on the substrate is pressed while rotating. The wafer holding mechanism 14 rotates around the rotation shaft 15.

  Since the polishing pad 13 becomes thinner as it is polished, the polishing pad 13 is replaced with a new polishing pad 13 when it reaches a certain thickness. Since the new polishing pad 13 has insufficient surface unevenness holding the slurry and familiarity with the slurry, it cannot perform stable and high-quality polishing as it is. Therefore, when the new polishing pad 13 is replaced, the surface of the polishing pad 13 is dressed by the dressing apparatus 20 shown in FIG. The dressing device 20 includes a disk 21 that rotates around a rotation shaft 22, and the surface 23 of the disk 21 is made of a metal containing diamond abrasive grains, and irregularities that are partially protruded by diamond abrasive grains. Have The rotating dressing device 20 is pressed against the entire surface of the polishing pad 13 by pressing the surface 23 to dress the surface of the polishing pad 13. After dressing, a plurality of preliminary wafers are polished so that the surface of the polishing pad is adapted to the slurry, and then a normal polishing operation can be performed. In addition, the surface of the polishing pad may become clogged according to use, and in such a case, a dressing process is performed.

JP 2001-221754 A JP 2004-63482 A

  As described above, the surface of the polishing pad is clogged according to use, and sufficient polishing cannot be performed, but how long the period until polishing can be performed, that is, how long the polishing period can be extended, This is an important problem in terms of cost reduction and throughput improvement.

  In the state where sufficient polishing cannot be performed, the thickness removed per unit time decreases, and the uniformity of polishing with respect to the position on the wafer decreases. The thickness removed per unit time by polishing is called the polishing rate (nm / min). When the polishing rate decreases, the time required for polishing becomes longer, resulting in a problem that the throughput decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is also to realize a polishing method and a polishing apparatus in which a decrease in polishing rate and polishing uniformity is small.

  In order to achieve the above object, the polishing method and polishing apparatus of the present invention are characterized in that when polishing a wafer having an oxide film material on the surface, a silicon member having a surface made of silicon is brought into contact with a rotating polishing pad. And

  The surface state of the polishing pad is an important factor that greatly affects the polishing rate (polishing rate) and polishing uniformity, but the polishing mechanism has not been fully elucidated.

  When polishing a wafer having an oxide film material on the surface, the inventor of the present application recovers the surface state of the polishing pad by bringing a silicon member having a surface made of silicon into contact with the rotating polishing pad, thereby reducing the polishing rate. I found that I can make it smaller.

FIG. 2 shows a state in which the polishing pad is raised, dressing is turned off, a wafer having a silicon oxide film (SiO ₂ film) on the surface is polished for 30 minutes, and the polishing rate is measured every 5 minutes. It is a figure which shows the change of a polishing rate when a silicon wafer is made to contact a polishing pad and the polishing rate is measured by polishing a wafer having a silicon oxide film every 5 minutes. As shown in FIG. 2, while polishing a wafer having a silicon oxide film from state A to C, the polishing rate decreases. This is considered that the polishing pad is clogged during this period. From the state C where the polishing pad is clogged, when the contact of the silicon wafer to the polishing pad is started, it can be seen that the polishing rate increases even though dressing is not performed. This is presumably because the surface of the polishing pad was chemically affected by bringing the silicon wafer into contact with the polishing pad. In other words, it can be said that the surface state of the polishing pad is changed not only by a mechanical action but also by a chemical action.

FIG. 3 shows the results of measuring the surface of the polishing pad as indicated by A to D in FIG. 2 by FT-IR (Fourier Infrared Spectroscopy). In the clogging process of the polishing pad from the state A to state C, C = O (carbonyl) -NH peak of bending vibration of the stretching vibration peak and around 1540 cm ^-1 in 1710 cm ^-1 is reduced, 1250 cm ^{- 1} -COC (= O) - (ester) bond, a peak of Si-O bonds of 1080 cm ^-1 is increased. After polishing the silicon wafer, the qualitative spectrum does not change greatly, but it can be confirmed that the C = O stretching peak and the NiH deflection peak are partially recovered.

  From the above experimental results, it is considered as follows.

  In general, a silica-based slurry is used when polishing a silicon oxide-based material such as a silicon oxide film formed on a silicon (Si) substrate. On the other hand, the polishing pad is made of polyurethane. Polyurethane generally exists in a state of minute phase separation. One is called a hard segment and the other is called a soft segment. It is known that the hard segment has a structure in which polar molecules are present and the polar molecules are aggregated and aligned. Examples of the polar molecule include a urethane group and a urea group. These polar molecules are easy to hydrogen bond, and usually polar molecules are aggregated with each other.

  On the other hand, the water in the slurry used for polishing is a typical polar molecule. Since water also has a large polarity, it has the property of adsorbing with other polar molecules by hydrogen bonds. By polishing while performing dressing, the state in which the polishing rate increases and stabilizes is such that when the polar molecules of this polishing pad are bonded to each other, water enters between the polar molecules, Hydrogen bonding occurs between the polishing pad polar molecules, and other water molecules are attracted to the water molecules, resulting in a familiar state. In other words, the presence of polar molecules in the polishing pad and the presence of water in the slurry are indispensable in order for the polishing pad to stand up and become a state in which the so-called polishing pad becomes familiar. It is not necessarily water that adsorbs to the polar molecules of this polishing pad. It can be said that it was confirmed that a highly reactive functional group called silanol contained in the aforementioned silica-based slurry was adsorbed by the polar molecules of the polishing pad and consumed the polar molecules of the polishing pad.

  In general, a silica-based slurry may contain a large amount of silanol (SiOH). However, when a new silicon oxide is polished, the silanol is a factor that suppresses the polishing. The chemical reaction that occurs in the polishing of silicon oxide is expressed by the following equation.

  Silicon oxide penetrates water under tensile stress and hydrates siloxane bonds under compressive stress, resulting in the formation of silanol. When there is a lot of silanol, the reaction in the right direction of the above chemical formula is limited. Therefore, when polishing a silicon oxide film, in a slurry containing a large amount of silanol, silanol not only obstructs the progress of polishing, but also surplus silanol binds to the polar molecules of the polishing pad, which reduces the familiarity of the slurry of the polishing pad. As a result, the polishing rate decreases dramatically.

  On the other hand, the case of bringing a silicon (Si) wafer into contact with the polishing pad is as follows.

  When a silicon (Si) wafer is brought into contact with the polishing pad, a reaction opposite to the above occurs. Silicon has a hydroxyl group on its surface in water, particularly in an alkaline solution. The silicon surface having a hydroxyl group reacts with silanol to form a siloxane bond and is removed. This reaction formula is as follows.

  Thus, silanol is efficiently removed by combining with Si atoms when silicon is brought into contact with the polishing pad to form a siloxane bond. In contact of silicon with the polishing pad, silanol is a factor that promotes polishing. Further, when silicon is brought into contact with the oxide film during polishing, polishing proceeds while reacting with surplus silanol present in the vicinity, so that the silanol as a polishing inhibiting factor can be effectively removed.

  In silicon oxide film polishing, when a silica slurry containing silanol is used, the polishing rate is lowered not only by normal physical clogging but also by the chemical polishing pad surface modification. As a result, if the dressing process for preventing clogging is neglected in the silicon oxide film polishing, the polishing rate is drastically lowered. In particular, when a silicon oxide film is polished, the polishing rate is drastically lowered even during polishing, and therefore, an in-situ dressing technique for dressing a polishing pad during polishing is common. However, there is no guarantee that the dressing of the polishing pad will always be performed stably. When the dressing is intermittent, the dressing may sometimes be insufficient and the polishing rate may suddenly drop. In addition, the dresser's abrasive grains may fall off during dressing, causing problems such as scratches on the wafer, or polishing scraps that are one of the causes of clogging and dressing scraps on the polishing pad generated by dressing. It is desirable to avoid dressing as much as possible because it will cause defects.

  As for the distribution of the polishing amount, when a silicon oxide film is polished, if a slurry containing a large amount of silanol is used, the distribution at the center of the wafer is low and the distribution called a center throw tends to occur. The reason is considered as follows.

  In the case of the conventional rotary polishing machine as shown in FIG. 1, at each radial position of the polishing pad, a portion where the distance across the wafer per circumference of the polishing pad is long is a radial portion passing near the center of the wafer. Corresponds to the middle part of the pad center and outer periphery. The longer the distance across the wafer in the polishing pad, the more efficiently the silanol and polar molecules of the polishing pad are bonded by polishing. Therefore, the polishing efficiency contributed by the portion of the polishing pad is greatly reduced as compared with other portions.

  According to the principle as described above, since it is considered that the silanol and the polar molecule of the polishing pad are bonded most at the intermediate position between the polishing pad center and the outer peripheral part (radius part of the radius of the polishing pad). The efficiency becomes the lowest, and the polar molecules of the polishing pad are not bonded to the silanol as it goes to the outer periphery or the center of the polishing pad. When the silicon oxide film is polished in this state, the center of the wafer has a center throw distribution with a lower polishing rate than other portions. If the distribution of the center throw becomes remarkable and the difference between the center and other portions becomes large, the uniformity of polishing is greatly deteriorated, and the allowable range of polishing performance is exceeded.

  Such a phenomenon that the polishing rate rapidly decreases and the difference in the distribution of the polishing amount that becomes center slow can be reduced if dressing can be performed stably, thereby reducing the surface of the polishing pad. The state is also stable. However, since the dressing physically removes the surface of the polishing pad, the dressing cannot be performed frequently because the thickness of the polishing pad is drastically reduced. As described above, since the surface modification on the polishing pad side proceeds very rapidly, dressing that cannot be performed frequently cannot be dealt with.

  In the present invention, by bringing silicon into contact with the polishing pad, the phenomenon that the polishing rate rapidly decreases and the difference in the distribution of the polishing amount becomes large, and the behavior that becomes the center throw is suppressed.

  As explained so far, by bringing silicon into contact with the polishing pad, clogging of the surface of the polishing pad is eliminated, so polishing the silicon as in the present invention reduces the polishing rate and reduces the polishing amount. An increase in the difference in distribution can be suppressed.

  There can be various configurations for bringing silicon into contact with the polishing pad.

  The first configuration is a configuration in which a silicon member having a surface made of silicon is brought into contact with a rotating polishing pad during polishing of a wafer having an oxide film material on the surface. In this configuration, the surface of the polishing pad is polished with the oxide film, and at the same time, the silicon is in contact with the surface. When the oxide film material is being polished, the surface condition of the polishing pad is deteriorated, but the silicon is in contact with the surface. The surface state of the polishing pad is recovered at the portion where the polishing pad is present.

  As shown in FIG. 1, the portion that contacts the wafer to be polished is a part of the polishing pad, and the silicon member can be in contact with the other portion of the polishing pad. It is also possible to dispose a ring-shaped silicon member around.

  When the silicon member is provided at a position different from the wafer to be polished, a silicon wafer having the same surface shape as the wafer to be polished can be used. In this case, it is desirable that the distance from the center of rotation of the polishing pad to the center of the silicon wafer is the same as the distance from the center of rotation of the polishing pad to the center of the wafer to be polished. As a result, the portion of the polishing pad that is deteriorated by polishing the wafer to be polished matches the portion of the polishing pad that is improved by bringing the silicon wafer into contact with the polishing pad.

  In the CMP apparatus, a ring-shaped retainer ring is provided around the wafer to be polished. When the silicon member is provided in a ring shape around the wafer to be polished, the silicon member is formed on the surface of the retainer ring.

  In the second configuration, every time a number of polishing target wafers having an oxide film material on the surface are polished, a silicon wafer having a surface made of silicon is brought into contact with the polishing pad. In this case, a conventional CMP apparatus can be used as it is. In this case, the thickness distribution before and after polishing of the wafer to be polished is measured using a film thickness meter, the distribution of the polishing amount is calculated from the measured thickness distribution before and after polishing, and the calculated polishing amount distribution is calculated. When the difference exceeds a predetermined amount, the silicon wafer is brought into contact with the polishing pad. An alarm may be generated when the calculated difference in polishing amount distribution exceeds a predetermined amount.

  According to the present invention, in the polishing method and the polishing apparatus, it is possible to suppress a decrease in the polishing rate and the uniformity of polishing, and not only the throughput is improved, but also the frequency of dressing the polishing pad is decreased, so that the polishing pad is worn out. The running cost can be reduced.

  4A and 4B are diagrams showing a schematic configuration of the CMP apparatus according to the first embodiment of the present invention, in which FIG. 4A is a top view and FIG. 4B is a side view. The CMP apparatus of the first embodiment is a conventional CMP apparatus as shown in FIG. 1 in which a silicon member 31 is provided in contact with the polishing pad 13. Since the conventional CMP apparatus is widely known as described in Patent Documents 1 and 2, the description thereof is omitted here.

  As shown in FIG. 4, the platen 11 and the polishing pad 13 rotate around the rotation shaft 12 at a rotation speed of 50 rpm. The wafer 10 is a wafer in which a silicon oxide film is formed on a silicon substrate having a diameter of about 200 mm, is held by the wafer holding member 14, is pressed against the polishing pad with a pressure of 27.6 kPa (4 psi), and rotates at a rotation speed of 50 rpm. To do. Polishing of one wafer 10 is completed in 2 minutes.

  As shown in the figure, the wafer holding member 14 is disposed on the right portion of the rotating polishing pad 13, and the silicon member 30 is pressed against the polishing pad 13 with the same pressure as the wafer 10 on the left portion of the polishing pad 13. The silicon member 30 is obtained by attaching a silicon material 32 to the surface of a base 31 made of iron, and can be formed by forming a silicon layer on the surface of the base 31. The silicon member 30 has a bar-shaped surface in contact with the polishing pad 13 and is disposed radially from the center of the polishing pad. The position where the silicon member 30 is provided is not limited to the position shown in the figure, and may be any position as long as it is arranged in the radial direction from the center of the polishing pad. Further, the wafer 10 is removed by moving the wafer holding member 14. At that time, the silicon member 30 is also retracted from the polishing pad 13. The dressing apparatus 20 shown in FIG. 1 dresses the polishing pad 13 with the silicon member 30 retracted.

  In the CMP apparatus of the first embodiment, when the wafer 10 to be polished is being polished, the silicon member 30 is always in contact with the surface of the polishing pad, so that the polishing pad deteriorated by polishing the wafer 10 to be polished. The surface state is recovered when the polishing pad rotates to the silicon member 30 and contacts the silicon material 32.

  FIG. 5 is a diagram showing a schematic configuration of a CMP apparatus according to the second embodiment of the present invention. The CMP apparatus of the second embodiment is a conventional CMP apparatus. In addition to the wafer holding member 14 that holds and rotates the wafer 10 to be polished, the CMP apparatus is provided with a member having the same configuration as the wafer holding member, and the polishing pad 13 has silicon. The wafer 33 is configured to contact.

  As shown in FIG. 5, the distance from the rotation center of the polishing pad 13 to the rotation center of the silicon wafer 33 is arranged to be equal to the distance from the rotation center of the polishing pad 13 to the rotation center of the wafer 10 to be polished. The The length of contact with the wafer 10 to be polished while the surface of the polishing pad 13 makes one rotation is the longest in the radial portion where the center of the wafer 10 to be polished is located, and becomes shorter as it is further away from both sides. In the CMP apparatus of the second embodiment, since the silicon wafer 33 is arranged at the same radial position as the wafer 10 to be polished, each part of the surface of the polishing pad 13 contacts the wafer 10 to be polished during one rotation. It contacts the silicon wafer 33 by the same length as the length. Therefore, the portion of the polishing pad that is in contact with the wafer 10 to be polished is worse in surface condition than the portion that is in contact with the short length, but the portion that is in contact with the wafer 10 is longer in contact with the silicon wafer 33. So it will recover more than that. Thereby, the variation in the modification of the polishing pad surface can be reduced.

  6A and 6B are diagrams showing a schematic configuration of a CMP apparatus according to a third embodiment of the present invention, in which FIG. 6A is a side sectional view and FIG. 6B is a view of a state where a wafer 10 is held as viewed from below. It is. In the CMP apparatus, the portion of the polishing pad against which the wafer is pressed sinks slightly relative to the surroundings. For this reason, when the polishing pad rotates and enters the lower side from the edge of the wafer, there arises a problem that the wafer is vibrated to deteriorate the polishing, particularly the uniformity of polishing. Therefore, as described in Patent Documents 1 and 2, etc., a retainer ring 41 is provided so as to surround the held wafer 10, and the surface of the polishing pad is pushed by the retainer ring 41, thereby polishing pads around the wafer 10. Is set to the same height as the lower surface of the wafer 10.

  In the CMP apparatus of the third embodiment, a silicon layer 42 is formed on the surface of the iron retainer ring 41 that contacts the polishing pad 13. Thereby, when polishing the wafer 10 to be polished, since the polishing pad always contacts the silicon layer 42 of the retainer ring 41, the surface state of the polishing pad deteriorated by polishing the wafer 10 to be polished is The polishing pad is recovered by contacting the silicon layer 42.

  FIG. 7 is a diagram showing a schematic configuration of a CMP apparatus 50 according to the fourth embodiment of the present invention. The CMP apparatus of the fourth embodiment includes two CMP units 51A and 51B, a wafer transfer mechanism 52 for transferring wafers, and a wafer loading / unloading unit that supplies the wafer 10 to be polished and collects the polished wafer. A load unit 53, a silicon wafer load / unload unit 54 that supplies and recovers the silicon wafer 60, and a film thickness measurement unit 55 that measures the film thickness of the silicon oxide film of the wafer 10 to be polished. Each CMP unit has the same configuration as a conventional CMP apparatus, the CMP unit 51A is for primary polishing or rough polishing, and the CMP unit 51B is for finishing (or secondary) polishing or precision polishing. The wafer transfer mechanism 52 transfers the wafer 10 to be polished between the wafer load / unload unit 53, the film thickness measurement unit 55, and the CMP units 51A and 51B, and also the silicon wafer load / unload unit 54 and the CMP. The silicon wafer 60 is transferred between the parts 51A and 51B. An apparatus for measuring the film thickness of the silicon oxide film provided in the film thickness measuring unit 55 is widely used as described in Patent Document 2, and any apparatus may be used. The wafer loading / unloading unit 53 and the silicon wafer loading / unloading unit 54 have cassettes that accommodate a plurality of wafers. Although not shown, a control unit for controlling the CMP apparatus 50 is provided.

  FIG. 8 is a flowchart showing the polishing operation in the CMP apparatus 50 of the fourth embodiment. In step 101, the wafer transfer mechanism 52 takes out the oxide film wafer 10 to be polished from the wafer load / unload unit 53 and transfers it to the film thickness measurement unit 55. In step 102, the thickness of the silicon oxide film on the wafer 10 is measured. The film thickness is measured at a plurality of locations on the wafer, and the film thickness distribution is measured. In step 103, the wafer transfer mechanism 52 transfers the wafer to be polished from the film thickness measuring unit 55 to the primary polishing CMP unit 51A. After the primary polishing is performed, the wafer transfer mechanism 52 transfers the wafer to be polished from the primary polishing CMP unit 51A to the final polishing CMP unit 51B to perform the final polishing.

  After the final polishing is performed, in step 104, the wafer transfer mechanism 52 transfers the polished target wafer from the final polishing CMP unit 51B to the film thickness measuring unit 55, and the silicon oxide film of the polished wafer 10 is transferred. Measure the film thickness. Again, the film thickness distribution is measured. In step 105, the wafer transfer mechanism 52 transfers the wafer to be polished from the film thickness measuring unit 55 to the wafer loading / unloading unit 53.

  In step 106, the distribution of the polishing amount is calculated from the change in the thickness of the silicon oxide film before and after polishing the wafer to be polished measured in steps 102 and 104. In step 107, it is determined whether the polishing amount distribution calculated in step 106 is within an allowable range. Here, it is determined whether the polishing amount of each part of the wafer to be polished is within an allowable range. Therefore, it is determined whether the absolute value of the polishing amount is within the allowable range, and it is determined whether the difference in polishing amount depending on the position is within the allowable range.

  If it is determined in step 107 that the polishing amount distribution is within the allowable range, the process returns to step 101.

  If it is determined in step 107 that the polishing amount distribution is outside the allowable range, the process proceeds to step 109. In step 109, the wafer transfer mechanism 52 takes out the silicon wafer 60 from the silicon wafer load / unload unit 54, and transfers the silicon wafer 60 to both the primary polishing CMP unit 51A and the final polishing CMP unit 51B. Therefore, the wafer transport mechanism 52 transports two silicon wafers 60. In step 110, the silicon wafer 60 is polished for a predetermined time by both the primary polishing CMP unit 51A and the final polishing CMP unit 51B. In step 111, the wafer transport mechanism 52 transports the silicon wafer 60 that has finished contact with the silicon wafer loading / unloading unit 54 from the primary polishing CMP unit 51A and the final polishing CMP unit 51B. The silicon wafer 60 can be used any number of times until the thickness reaches a predetermined thickness. After step 111, the process returns to step 101.

  FIG. 9 is a flowchart showing a modification of the polishing operation of the fourth embodiment. In the flowchart of FIG. 8, when it is determined in step 107 that the distribution of the polishing amount is out of the allowable range, the process proceeds to step 109. However, after step 107, the process proceeds to step 121 and an alarm is output to the operator. Depending on, the process may proceed to step 109. This informs the operator that it is necessary to bring the silicon wafer into contact with the polishing pad and can call attention. If alarms occur frequently, the operator can recognize that a situation that cannot be dealt with simply by bringing the silicon wafer into contact with the polishing pad, for example, a situation requiring dressing, has occurred.

  As described above, the present invention is mainly intended to be applied to a semiconductor manufacturing process for forming a semiconductor device. However, if a wafer having an oxide film formed on the surface is to be polished, any wafer can be used. Is also applicable.

It is a figure which shows schematic structure of the conventional CMP apparatus. It is a figure which shows the experimental result explaining the principle of this invention. It is a figure which shows the experimental result explaining the principle of this invention. It is a figure which shows schematic structure of the CMP apparatus of 1st Example of this invention. It is a figure which shows schematic structure of the CMP apparatus of 2nd Example of this invention. It is a figure which shows schematic structure of the CMP apparatus of 3rd Example of this invention. It is a figure which shows schematic structure of the CMP apparatus of 4th Example of this invention. It is a flowchart which shows operation | movement of the CMP apparatus of 4th Example. It is a flowchart which shows the modification of operation | movement of the CMP apparatus of 4th Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wafer 11 Platen 13 Polishing pad 14 Wafer holding member 17 Slurry 30 Silicon member 32 Silicon material 33 Silicon wafer

Claims (11)

In a polishing method for polishing by bringing a wafer having an oxide film material into contact with a polishing pad attached to the surface of a rotating platen,
A polishing method, wherein a silicon member having a surface made of silicon is brought into contact with the rotating polishing pad during polishing.   The polishing method according to claim 1, wherein the silicon member is brought into contact with the polishing pad at a position different from a position at which the wafer is brought into contact.   The polishing apparatus according to claim 2, wherein the silicon member has the same surface shape as the wafer.   The polishing method according to claim 1, wherein the silicon member has a ring shape surrounding the periphery of the wafer, and is in contact with the polishing pad around a position where the wafer is brought into contact. In a polishing method for polishing by bringing a wafer to be polished having an oxide film material on its surface into contact with a polishing pad attached to the surface of a rotating platen,
A polishing method comprising contacting a silicon wafer having a surface made of silicon with the polishing pad after polishing of the wafer to be polished and before polishing the next wafer to be polished. Measure the film thickness distribution before and after polishing of the wafer to be polished,
Calculate the polishing amount distribution from the measured film thickness distribution before and after polishing,
The polishing method according to claim 5, wherein the silicon wafer is brought into contact with the polishing pad when the difference in the calculated distribution of polishing amounts exceeds a predetermined amount.   The polishing method according to claim 6, wherein an alarm is generated when the calculated difference in polishing amount distribution exceeds a predetermined amount. A rotatable platen with a polishing pad affixed to the surface;
In a polishing apparatus comprising a wafer holding mechanism that rotatably holds a wafer so as to press the wafer against the polishing pad,
A polishing apparatus comprising: a silicon member holding unit that presses a silicon member having a surface formed of silicon against the rotating polishing pad.   The polishing apparatus according to claim 8, wherein the silicon member has the same surface shape as the wafer. A rotatable platen with a polishing pad affixed to the surface;
In a polishing apparatus comprising a wafer holding mechanism that rotatably holds a wafer so as to press the wafer against the polishing pad,
The wafer holding mechanism is provided around the wafer, and includes a retainer ring whose surface presses the polishing pad,
A polishing apparatus, wherein a surface of the retainer ring is made of silicon. At least one polishing apparatus comprising: a rotatable platen with a polishing pad affixed to a surface; and a wafer holding mechanism that rotatably holds the wafer against the polishing pad;
A polishing target wafer load / unload unit for supplying and discharging the polishing target wafer having an oxide film material on the surface;
A polishing wafer load / unload unit for supplying and discharging a silicon wafer having a surface formed of silicon, and
A film thickness meter for detecting the film thickness of the oxide film material on the surface of the wafer to be polished;
The distribution of film thickness before and after polishing of the wafer to be polished is measured with the film thickness meter to calculate the distribution of polishing amount, and when the calculated difference in polishing amount distribution exceeds a predetermined amount, the polishing pad A polishing apparatus for contacting a silicon wafer.

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