JP5473818B2 - Polishing apparatus and polishing method - Google Patents

Description

  The present invention relates to a polishing apparatus and a polishing method, for example, a polishing apparatus and a polishing method for polishing a substrate surface having a film to be processed such as an active layer formed on an SOI (silicon on insulator) wafer.

  SOI wafers can obtain characteristics such as high durability and low power consumption, and are widely used in power devices, MEMS (micro electro mechanical systems), and the like. As shown in FIG. 5, in the SOI wafer 50, an insulating film 52 is formed on a support wafer 51 made of single crystal silicon, and a thin film active layer (SOI layer) 53 made of single crystal silicon is formed thereon. It has a formed structure.

Conventionally, in manufacturing the SOI wafer 50, for example, as shown in FIG. 6A, first, the support wafer 51 is activated through a silicon oxide film (insulating film 52) formed by, for example, thermal oxidation. The layer wafer 53 is bonded and bonded.
Then, the active layer wafer 53 can be ground and polished to form a thin film, which can be obtained as the active layer 53 as shown in FIG.

By the way, in polishing of this SOI wafer, when continuously polishing a plurality of wafers that are substrates to be processed, if the conditions such as the surface condition of the polishing cloth (clogging, etc.) and the composition of the polishing liquid change, There has been a problem that the polishing rate (polishing amount per predetermined time) fluctuates greatly, resulting in large variations in the polishing amount to be polished.
For such a problem, after polishing the semiconductor wafer, the polishing time in the polishing, the target film thickness value, the measured film thickness value before polishing of the semiconductor wafer, and the measured film thickness value after polishing, the optimal polishing time is polished. There is known a polishing method in which the optimum polishing time calculated for each polishing is applied to the subsequent polishing of the semiconductor wafer and continued until the total number of semiconductor wafers in one lot is completed (for example, Patent Document 1).

JP-A-10-106984

However, in the polishing method disclosed in Patent Document 1, when there is a difference in the film thickness before polishing between the wafers to be polished continuously (difference in the polishing amount of the film thickness to be polished), Since the polishing time between the wafers to be polished differs, the polishing rate may vary from wafer to wafer, and there is a problem that the amount of deviation from the target value of the film thickness after polishing becomes large.
On the other hand, in order to improve the polishing accuracy, it is preferable to carry out polishing and measurement operations a plurality of times for each wafer, but in that case, the processing time in lot units becomes long, and the productivity is lowered. was there.

  The present invention has been made under the circumstances as described above, and in a polishing apparatus and a polishing method for continuously polishing a plurality of substrates to be processed, a film after polishing without reducing productivity. It is an object of the present invention to provide a polishing apparatus and a polishing method capable of reducing the amount of deviation from the target value of thickness and performing highly accurate polishing.

In order to solve the above-described problems, a polishing apparatus according to the present invention is a polishing apparatus that continuously polishes a target film formed on the surface of each substrate with respect to a plurality of target substrates. An initial film thickness measuring means for measuring an initial film thickness of the film to be processed on the substrate, and an initial film thickness difference of the film to be processed between the substrates to be continuously polished based on the measurement result of the initial film thickness is a predetermined value Sorting means for rearranging the plurality of substrates in the order of thickness of the initial film thickness so that the initial film thicknesses of the rearranged films of the plurality of substrates are determined according to a predetermined polishing time. A first polishing means for performing primary polishing in the order of the thickness, a post-polishing film thickness measuring means for measuring a film thickness of the processed film after the primary polishing, and the measured initial film thickness and post-polishing In the primary polishing based on the film thickness of the film to be processed and the polishing time at that time. A polishing rate is calculated, and further, a polishing time is calculated based on the calculated polishing rate, the measured initial film thickness of the substrate to be first polished next, and a target value of the film thickness of the processed film after polishing, And control means for sequentially performing control for feeding back the polishing time as the polishing time of the substrate to be subjected to primary polishing next in order of the thickness of the initial film thickness.
The sorting means rearranges the plurality of substrates in the order of the thickness of the initial film thickness so that the initial film thickness difference of the film to be processed between the substrates polished continuously is 0.2 μm or less. Is desirable.

  According to such a configuration, since the deviation amount of the initial film thickness of the film to be processed is small between the substrates that are continuously polished, the deviation amount from the target value of the film thickness after polishing can be reduced. . Therefore, polishing accuracy can be improved without reducing productivity.

In order to solve the above-described problems, a polishing method according to the present invention is a polishing method for continuously polishing a film to be processed formed on the surface of each substrate with respect to a plurality of substrates to be processed. Based on the first step of measuring the initial film thickness of the processed film on each substrate and the measurement result of the initial film thickness, the initial film thickness difference of the processed film between the substrates to be continuously polished is a predetermined value A second step of rearranging the plurality of substrates in the order of the thickness of the initial film thickness so as to satisfy the following: the initial film on the processed films of the plurality of the rearranged substrates according to a predetermined polishing time; A third step of primary polishing in order of thickness; a fourth step of measuring the film thickness of the processed film after the primary polishing; and the measured initial film thickness and the processed film after polishing. In the primary polishing based on the film thickness and the polishing time at that time A polishing rate is calculated, and further, a polishing time is calculated based on the calculated polishing rate, the measured initial film thickness of the substrate to be first polished next, and a target value of the film thickness of the processed film after polishing, And a fifth step of sequentially performing control for feeding back the polishing time as the polishing time of the substrate to be subjected to primary polishing next in order of the thickness of the initial film thickness.
In the second step, the plurality of substrates are rearranged in the order of the thickness of the initial film thickness so that the initial film thickness difference of the film to be processed between the substrates polished continuously is 0.2 μm or less. It is desirable.

  According to such a method, since the deviation amount of the initial film thickness of the film to be processed is small between the substrates to be polished continuously, the deviation amount from the target value of the film thickness after polishing can be reduced. . Therefore, polishing accuracy can be improved without reducing productivity.

  According to the present invention, in a polishing apparatus and a polishing method for continuously polishing a plurality of substrates to be processed, the amount of deviation from the target value of the film thickness after polishing can be reduced without reducing productivity. Thus, a polishing apparatus and a polishing method capable of performing high-precision polishing can be obtained.

FIG. 1 is a block diagram schematically showing the configuration of the polishing apparatus of the present invention. FIG. 2 is a flowchart showing the flow of polishing processing for the active layer of each wafer as a substrate to be processed in the polishing apparatus of FIG. FIG. 3 is a graph showing the results of the example of the present invention. FIG. 4 is a graph showing the results of the comparative example. FIG. 5 is a cross-sectional view for explaining the structure of the SOI wafer. FIG. 6 is a cross-sectional view for explaining an SOI wafer manufacturing process. FIG. 7 is a plan view showing an example of measurement points (9 points) of the active layer of the SOI wafer.

Hereinafter, embodiments according to a polishing apparatus and a polishing method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of the polishing apparatus of the present invention.
The illustrated polishing apparatus 1 is an apparatus for polishing a substrate to be processed using, for example, a plurality of SOI wafers W (hereinafter simply referred to as wafers W) processed in lot units. More specifically, it is an apparatus for continuously polishing an active layer (SOI layer), which is a film to be processed, formed on the surface of each wafer W to obtain a predetermined film thickness.

  The polishing apparatus 1 sequentially polishes, for example, a sorter unit 2 that rearranges a plurality of wafers W accommodated in a cassette along a predetermined reference, and an active layer of the plurality of wafers W rearranged in the sorter unit 2. And a polishing unit 3.

The sorter unit 2 measures the initial film thickness (film thickness before polishing) of the active layer for each of the wafers 5 accommodated in the cassette 5 and the wafers 5 accommodated in the cassette 5. A film thickness measuring unit 6 (initial film thickness measuring means). Further, the sorter unit 2 has, for example, two cassettes 7 and 8 for storing the wafers W whose film thickness has been measured in units of lots.
Note that all the wafers W whose film thickness has been measured by the film thickness measuring unit 6 are once returned to the cassette 5. After all the wafers W have been measured, the transfer robot 10 is driven under the control of the control unit 20 (control means) comprising a computer, and the wafers W are accommodated in the cassette 7 or the cassette 8 in a predetermined arrangement order. It is made so that. In this way, the control unit 20 and the transfer robot 10 constitute a sorting unit.
The sorter unit 2 includes a transfer robot 12 for transferring the cassettes 7 and 8 containing the wafers W to the polishing unit 3.

Further, the polishing unit 3 performs primary processing on the loading unit cassette 13 in which the cassette 7 or the cassette 8 transferred from the sorter unit 2 by the transfer robot 12 is installed, and the wafer W sequentially taken out from the loading unit cassette 13. It has the 1st grinding | polishing part 14 (1st grinding | polishing means) which grind | polishes. Further, a film thickness measuring unit 15 (film thickness measuring means after polishing) for measuring the film thickness of the active layer polished by the first polishing unit 14 and a second polishing unit 16 (first film) for performing final polishing on each wafer W. 2 polishing means) and a carry-out section cassette 17 for storing the wafer W polished by the second polishing section 16.
Similar to the sorter unit 2, the polishing unit 3 is configured such that its operation is controlled by the control unit 20.

Next, each part (each means) described above will be described in more detail.
The film thickness measurement unit 6 in the sorter unit 2 uses, for example, a reflection spectral film thickness meter (near infrared light (wavelength 900 nm to 1600 nm)) for each wafer W accommodated in the cassette 5 to start the active layer. The film thickness (film thickness before polishing) is measured.
Since the thickness of the active layer varies slightly within the wafer surface, for example, nine measurement points (for example, wafer center, R / 2 (radius), outer periphery (3 mm from the outer periphery): FIG. Reference) is set to measure the film thickness at each point, and the measurement result is output to the control unit 20.
In the control unit 20, an average value of these measured values or a value obtained by (maximum value + minimum value) / 2 at nine measured points is set as an initial film thickness value of the active layer. In addition, the wafer W that has been measured is once returned to the cassette 5.

  Further, when the measurement of the initial film thickness is completed for all the wafers W in the cassette 5, the transfer robot 10 is driven by the control of the control unit 20 based on the measurement result and takes out the wafers W in the cassette 5. The cassettes 7 or 8 are accommodated in a new arrangement order (polishing order). This arrangement order is accommodated by arranging the plurality of wafers W in the order of the thickness of the initial film thickness so that the initial film thickness difference of the film to be processed between the wafers to be polished continuously becomes a predetermined value or less. The

In the polishing unit 3, the first polishing unit 14 includes a surface plate 14 a that can rotate at a predetermined number of revolutions and a polishing head 14 b that can hold the wafer W at the lower end.
A polishing pad is provided on the surface plate 14a, and a polishing head 14b is rotatably disposed facing the surface plate 14a.
When the first polishing unit 14 polishes the wafer W, the surface plate 14a and the polishing head 14b are rotated at a predetermined number of revolutions by the control unit 20 for a predetermined polishing time. An agent (not shown) is supplied. Then, the polishing head 14b holding the wafer W is pressed with a predetermined pressure against the polishing cloth of the surface plate 14a, and the processed films of the plurality of wafers W rearranged are in the order of the thickness of the initial film thickness. Primary polishing is performed.

Further, the film thickness measuring unit 15 uses the reflection spectral film thickness meter using near infrared light (wavelength 900 nm to 1600 nm) to perform the first polished polishing wafer W in a predetermined atmosphere or underwater environment. The thickness of the active layer is measured.
In the wafer plane, since the thickness of the active layer varies slightly, for example, the same nine measurement points (for example, see FIG. 7) as the film thickness measurement unit 6 of the sorter unit 2 are set and each is set. The film thickness of the point is measured, and the measurement result is output to the control unit 20.
In the control unit 20, an average value of these measured values or a value obtained by (maximum value + minimum value) / 2 at nine measured points is set as the thickness of the active layer after the primary polishing.
Further, the film thickness measuring unit 15 is movable along a transfer path 18 provided on the polishing unit 3 and can transfer the wafer W after film thickness measurement to the second polishing unit 16 at the subsequent stage. It is configured.

Similarly to the first polishing unit 14, the second polishing unit 16 that performs finish polishing includes a surface plate 16 a that can rotate at a predetermined number of revolutions, and a polishing head 16 b that can hold the wafer W at the lower end.
When polishing the wafer W in the second polishing unit 16, the surface plate 16a and the polishing head 16b are rotated at a predetermined number of rotations based on the polishing time set in advance by the control unit 20, respectively. Abrasive (not shown) is supplied. Then, the polishing head 16b holding the wafer W is pressed against the surface plate 16a with a predetermined pressure, and finish polishing is performed.

  The control unit 20 performs the primary polishing in the first polishing unit 14 based on the initial film thickness measured by the film thickness measurement unit 6, the film thickness after polishing measured by the film thickness measurement unit 15, and the polishing time at that time. The polishing rate at is calculated. Furthermore, based on the calculated polishing rate, the initial film thickness of the wafer W to be subjected to primary polishing next measured by the film thickness measuring unit 6, and the target value of the film thickness of the film to be processed, a new polishing time is obtained. Is calculated. The control for feeding back the calculated polishing time as the polishing time of the wafer W to be subjected to the next primary polishing is sequentially performed in the order of the thickness of the initial film thickness.

Next, the flow of polishing of the active layer of each wafer W in the polishing apparatus 1 configured as described above will be described more specifically with reference to FIG.
First, in the sorter unit 2, for each wafer W accommodated in the cassette 5, the initial film thickness (film thickness before polishing) of the active layer is, for example, nine measurement points in the wafer surface (see FIG. 7). As shown in FIG. Then, an average value of measurement data (film thickness) at each effective measurement point or a value obtained by (maximum value + minimum value) / 2 at 9 measured points is calculated and set as the initial film thickness of the active layer. (Step S1 in FIG. 2). The wafer W that has been measured is returned to the same accommodation position in the cassette 5 again.

The measurement result by the film thickness measuring unit 6 is acquired by the control unit 20. In the control unit 20, a new processing order (arrangement order) is determined according to the measured thickness of the active layer of the wafer W.
The control unit 20 drives the transfer robot 10 to transfer each wafer W in the cassette 5 to the cassette 7 or 8 so that the determined processing order is obtained, and a film to be processed between the wafers to be continuously polished. A plurality of measured wafers W are rearranged and accommodated in the order of the thickness of the initial film thickness so that the initial film thickness difference becomes equal to or less than a predetermined value (step S2 in FIG. 2).
The cassette 7 or the cassette 8 that accommodates the rearranged wafers W is transferred to the polishing unit 3 by the transfer robot 12 and installed as a loading unit cassette 13.

Next, the control unit 20 sets a polishing time in advance for the wafer W to be subjected to primary polishing (step S3 in FIG. 2). As described above, the polishing time is basically set based on the polishing rate of the wafer W that has been subjected to the primary polishing one time before.
However, for the first wafer W taken out from the carry-in cassette 13, the target polishing amount is calculated from the difference between the measured initial film thickness and the target value of the film thickness of the processed film after polishing, and the known polishing amount is calculated. The primary polishing is performed by setting the polishing time by dividing by the rate.
The wafers W sequentially taken out from the cassette 13 are subjected to primary polishing of the active layer in the first polishing unit 14 based on the polishing time set for each (step S4 in FIG. 2).

  The film thickness of the active layer is measured in the film thickness measuring unit 15 on the wafer W subjected to the primary polishing. In this film thickness measurement, for example, nine points in the wafer surface are used as measurement points (see FIG. 7), as in the measurement of the initial film thickness. And the active layer film thickness of each measurement point is measured, and the measurement result is output to the control part 20 (step S5 of FIG. 2).

  When the measurement of the thickness of the active layer after polishing is completed, the control unit 20 calculates the average value of effective measurement data (film thickness) at each measurement point or (maximum value + minimum value) / 2 at nine measured points. The obtained value is calculated as the thickness of the active layer after polishing (step S6 in FIG. 2).

Next, the control unit 20 divides the difference (removal allowance) between the initial film thickness obtained in Step 1 and the thickness of the active layer after polishing obtained in Step S6 by the polishing time performed in Step 3. Thus, a new polishing rate is calculated (step S7 in FIG. 2).
It is checked whether or not the calculated polishing rate is within an effective range (is not an abnormal value) (step S8 in FIG. 2).

Here, if the calculated polishing rate is valid (Yes), the polishing rate is updated (step S9 in FIG. 2), and the initial film thickness measured in step 1 of the wafer W to be subjected to primary polishing next is determined. The primary polishing time of the next wafer W is calculated by dividing the difference (polishing allowance) of the target value of the film thickness after polishing by the updated polishing rate, and is fed back to step S3. (Step S10).
On the other hand, if the calculated polishing rate is not within the effective range and is invalid (No), the polishing rate is not updated, and the same polishing rate is also obtained in step 3 for the wafer W to be subjected to primary polishing next. Quoted (step S11).

The term “effective polishing rate” means that the value falls within a range of polishing rates effective for polishing a film to be processed that has been set in advance. The range of this effective polishing rate is set as appropriate depending on the polishing apparatus, polishing conditions, polishing cloth used, polishing agent, and the like.
In addition, the case where the polishing rate is invalid corresponds to a case where there is a mistake in the data acquired in the wafer W and the control unit 20 due to human error, or a change in the surface condition of the polishing cloth.

In the check of the calculated polishing rate (step S8 in FIG. 2), the polishing rate difference between adjacent wafers is compared. If the polishing rate difference is within 0.1 μm / min, the calculated polishing rate is calculated. Is effective (Yes), the polishing rate is updated (step S9 in FIG. 2), and when the difference between the polishing rates exceeds 0.1 μm / min, the polishing rate is not updated, and then the primary For the wafer W to be polished, the same polishing rate is preferably cited in step 3 (step S11).
With such a configuration, more accurate polishing can be performed.

Furthermore, in the embodiment according to the present invention, finish polishing is performed for the purpose of smoothing the active layer surface and removing particles from the primary polishing surface (step S12 in FIG. 2).
In this final polishing, first, the wafer W after the measurement of the thickness of the active layer in the post-polishing measuring unit 15 is transferred to the second polishing unit 16 via the transfer path 18.
The polishing time in the finish polishing by the second polishing unit 16 is set to a certain time (for example, 2 minutes to 15 minutes).
When the finish polishing is completed, the wafers W are sequentially accommodated in the unloading unit cassette 17.

As described above, in the polishing apparatus and the polishing method according to the present invention, the plurality of wafers W are arranged so that the initial film thickness difference of the active layer between the wafers to be continuously polished is not more than a predetermined value. Rearranging in order of thickness of the initial film thickness, and measuring the film thickness of the active layer after the primary polishing for each wafer W, and based on the polishing amount and polishing time, the polishing rate of the primary polished wafer W is determined. After the calculation, the polishing time of the wafer W to be subjected to the next primary polishing is calculated and fed back as the polishing time of the primary polishing.
That is, since the deviation amount of the initial film thickness of the active layer is small between the wafers that are continuously polished, the fluctuation of the polishing time and the polishing rate between the wafers that are continuously polished can be reduced. . Furthermore, the fluctuation of the polishing time set by feedback of the measurement result can be reduced.
Therefore, the amount of deviation from the target value of the film thickness after polishing can be reduced without reducing productivity, and highly accurate polishing can be performed.

In the polishing apparatus and the polishing method, the plurality of wafers W are preferably rearranged so that the initial film thickness difference of the film to be processed between the wafers to be continuously polished is 0.2 μm or less. .
With such a configuration, it is possible to reliably reduce the deviation from the target value of the film thickness after polishing, and to perform highly accurate polishing. Further, the initial film thickness difference is 0.2 μm. In the case of rearranging so as to be the following, when there is a wafer W in which the initial film thickness difference of the film to be processed between the wafers polished continuously exceeds 0.2 μm, the initial film thickness is the next closest It is preferable to rearrange in order.

  Moreover, in the said embodiment, although it was rearranged after the film thickness measurement by the sorter part 2, and the cassette accommodated for every lot was set as the structure of two sets (cassettes 7 and 8), it has more cassettes than it. May be. That is, by preparing a large number of wafers W in which the processing order is rearranged in advance for each lot before processing in the polishing processing unit 3, the processing in the polishing unit 3 can be performed more efficiently.

  The polishing apparatus and the polishing method according to the present invention will be further described based on examples. In this example, the effect of the present invention was verified by polishing the active layer of the SOI wafer according to the above embodiment.

〔Example〕
In the example, based on the flowchart shown in FIG. 2, the active layer of 10 SOI wafers was continuously polished as a sample, and the amount of polishing rate variation and the amount of film thickness deviation from the target value were measured.
FIG. 3 shows a plot of the amount of deviation of the initial film thickness between successive wafers, the amount of fluctuation of the polishing rate, and the amount of film thickness deviation from the target value in the example.

In the graph of FIG. 3, the horizontal axis is the SOI wafer sample number (processing order), the left vertical axis is the polishing rate variation (μm / min), and the right vertical axis is the deviation of the active layer thickness from the target value. The amount (μm) and the deviation amount (μm) of the initial film thickness between successive wafers.
As shown in FIG. 3, the difference (shift amount) in the initial film thickness (film thickness before polishing) of the active layer is set to 0.2 μm or less between continuously polished wafers.
In this case, the polishing rate was substantially constant, and the deviation amount from the target value of the active layer thickness was found to be in a range of less than ± 0.1 μm for all wafers.

[Comparative example]
In the comparative example, the wafer arrangement order of the nine samples was set so that the difference in the thickness of the active layer before polishing between the wafers polished continuously in the same configuration as in Example 1 was increased.
Then, active layer polishing was continuously performed on nine samples (SOI wafers), and the amount of fluctuation in the polishing rate and the amount of film thickness deviation from the target value were measured.
FIG. 4 is a graph plotting the amount of deviation of the initial film thickness between successive wafers, the amount of fluctuation of the polishing rate, and the amount of film thickness deviation from the target value in the comparative example.

In the graph of FIG. 4, as in FIG. 3, the horizontal axis is the SOI wafer sample number (processing order), the left vertical axis is the polishing rate variation (μm / min), and the right vertical axis is from the target value. These are the film thickness shift amount (μm) of the active layer and the initial film thickness shift amount (μm) between successive wafers.
As shown in FIG. 4, when the difference (deviation amount) in the initial film thickness (film thickness before polishing) of the active layer between the wafers polished continuously is large, the fluctuation of the polishing rate also increases. It was recognized that when the polishing rate fluctuates greatly, the amount of deviation between the post-polishing film thickness and the target value also increases.

DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Sorter part 3 Polishing part 5 Cassette 6 Film thickness measuring part (initial film thickness measuring means)
7 Cassette 8 Cassette 10 Transport robot (sorting means)
13 Carry-in section cassette 14 First polishing section (first polishing means)
15 Film thickness measuring part (film thickness measuring means after polishing)
16 2nd grinding | polishing part (2nd grinding | polishing means)
17 Unloading part cassette 20 Control part (control means, sorting means)
W SOI wafer (substrate to be processed)

Claims (4)

A polishing apparatus for continuously polishing a target film formed on the surface of each substrate for a plurality of target substrates,
An initial film thickness measuring means for measuring an initial film thickness of the film to be processed on each substrate;
Based on the measurement result of the initial film thickness, the plurality of substrates are arranged in the order of the thickness of the initial film so that the initial film thickness difference of the processed film between the substrates to be polished continuously becomes a predetermined value or less. Sorting means to change;
First polishing means for first polishing the rearranged films of the plurality of substrates in order of thickness of the initial film thickness according to a predetermined polishing time;
A post-polishing film thickness measuring means for measuring the film thickness of the film to be processed after the primary polishing;
Based on the measured initial film thickness, the film thickness of the film to be processed after polishing, and the polishing time at that time, a polishing rate in the primary polishing is calculated. Further, the calculated polishing rate and the measured primary polishing Control of calculating the polishing time based on the initial film thickness of the substrate to be processed and the target value of the film thickness of the processed film after polishing, and feeding back the polishing time as the polishing time of the substrate to be subjected to primary polishing next Control means for sequentially performing in order of thickness,
A polishing apparatus comprising:   The sorting means rearranges the plurality of substrates in order of the thickness of the initial film thickness so that an initial film thickness difference of a film to be processed between the substrates polished continuously is 0.2 μm or less. The polishing apparatus according to claim 1. A polishing method for continuously polishing a film to be processed formed on the surface of each substrate for a plurality of substrates to be processed,
A first step of measuring an initial film thickness of a film to be processed on each of the substrates;
Based on the measurement result of the initial film thickness, the plurality of substrates are arranged in the order of the thickness of the initial film so that the initial film thickness difference of the processed film between the substrates to be polished continuously becomes a predetermined value or less. A second step to replace;
A third step of performing primary polishing of the rearranged films of the plurality of substrates in order of thickness of the initial film thickness according to a predetermined polishing time;
A fourth step of measuring a film thickness of the processed film after the primary polishing;
Based on the measured initial film thickness, the film thickness of the film to be processed after polishing, and the polishing time at that time, a polishing rate in the primary polishing is calculated, and the calculated polishing rate and the measured next polishing are then primary polishing. Control of calculating the polishing time based on the initial film thickness of the substrate to be processed and the target value of the film thickness of the processed film after polishing, and feeding back the polishing time as the polishing time of the substrate to be subjected to primary polishing next A fifth step sequentially performed in order of thickness;
A polishing method comprising:   In the second step, the plurality of substrates are rearranged in the order of the thickness of the initial film thickness so that an initial film thickness difference of a film to be processed between each substrate polished continuously is 0.2 μm or less. The polishing method according to claim 3, wherein:

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