JP6665827B2 - Wafer double-side polishing method - Google Patents

Description

  The present invention relates to a method for polishing a wafer on both sides using a plurality of double-side polishing carriers and a double-side polishing apparatus.

  2. Description of the Related Art In a double-side polishing apparatus for flattening a wafer such as a silicon wafer, a disk-shaped double-side polishing carrier provided with a work hole for holding a wafer is generally used.

  The double-side polishing apparatus usually includes an upper surface plate and a lower surface plate to which a polishing cloth (polishing pad) made of a nonwoven fabric or the like is stuck, and a sun gear is disposed at a central portion and an internal gear is disposed at an outer peripheral portion. A so-called 4-way type having a planetary gear structure is used. In such a double-side polishing apparatus, a wafer is inserted into and held by a single or plural work holes formed in a carrier for double-side polishing (hereinafter, also simply referred to as a carrier).

  Then, the slurry is supplied to the wafer from the upper platen side, the polishing cloth is pressed against the front and back surfaces of the wafer while rotating the upper and lower platens, and the carrier is rotated around the sun gear and the internal gear to revolve around each wafer. Both sides are polished simultaneously.

  By the way, it has been known that the thickness of a carrier holding the flatness of a wafer polished on both sides is important. For this reason, attempts have been made to reduce the variation in the thickness of the carrier to thereby reduce the variation in the flatness of the wafer polished on both sides (see Patent Document 1).

JP 2015-174168 A

  However, even if the thickness of the carrier is uniform, there may be a difference in the edge flatness between the double-side polished wafers obtained by holding each of the carriers during double-side polishing.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a method for double-side polishing a wafer capable of suppressing a difference (variation) in flatness between wafers obtained by double-side polishing using a plurality of double-side polishing carriers. And a double-side polishing apparatus.

  In order to achieve the above object, the present invention provides a double-side polishing apparatus, wherein a plurality of double-side polishing carriers are disposed between an upper and lower platen to which a polishing cloth is attached, and each of the plurality of double-side polishing carriers is provided. A double-sided polishing method for a wafer in which a wafer is held in a formed work hole and sandwiched between the upper and lower platens to perform double-side polishing, wherein a plurality of double-side polishing carriers disposed between the upper and lower platens are provided. When preparing a carrier set, the swell amount calculated from the data obtained by measuring the shape of the double-sided polishing carrier using a shape measuring device is obtained in all of the plurality of double-sided polishing carriers of the carrier set, and the carrier set A carrier set in which the difference between the maximum value and the minimum value of the undulation between the plurality of double-side polishing carriers in the plurality of carriers is equal to or smaller than a predetermined value is selected and prepared. It provides a double-side polishing method for a wafer, characterized in that by arranging a plurality of double-side polishing carrier assets to the double-side polishing apparatus for double-sided polishing the wafer.

  The present inventors have found through research that the undulation (warpage) of the double-sided polishing carrier affects the flatness of the double-sided polished wafer. And, in the case of the double-side polishing method as described above, a carrier set in which the difference between the maximum value and the minimum value of the amount of undulation between a plurality of double-side polishing carriers in the carrier set is equal to or less than a certain value is selected and used. The difference in flatness between the double-side polished wafers obtained by the double-side polishing can be suppressed. For this reason, it is possible to prevent a difference in flatness between the double-sided polished wafers as in the conventional case, thereby preventing an increase in the ratio of the double-sided polished wafers whose flatness deviates from the specified value, thereby improving the yield. can do.

  At this time, in the calculation of the undulation amount, a three-dimensional coordinate measuring machine having a laser sensor can be used as the shape measuring device, and the undulation amount can be calculated from the point cloud data obtained by measuring the entire carrier for double-side polishing. .

  With this configuration, the shape of the carrier for double-side polishing can be measured with higher accuracy, and a more accurate undulation amount can be calculated. As a result, a carrier set can be selected more appropriately, and a difference in flatness can be prevented between the obtained double-side polished wafers.

  In the calculation of the undulation amount, the leveling is performed on all the measured point group data, and the undulation amount of the double-side polishing carrier is calculated from the converted point group data obtained by removing a noise component having a wavelength of 20 mm or less. be able to.

  By doing so, the undulation amount of the double-side polishing carrier can be calculated more appropriately.

  Further, the wafer to be polished on both sides is 300 mm in diameter, and in the calculation of the waviness amount, data within 175 mm from the center of the work hole is extracted from the conversion point group data, and the arithmetic mean calculated from the extracted data is used. In the selection of the carrier set, a carrier set in which the difference between the maximum value and the minimum value of Sk between the plurality of double-side polishing carriers is 10 μm or less can be selected.

  In this way, it is possible to calculate the amount of undulation using data around the work hole, which tends to affect the flatness of the double-sided polished wafer, and to obtain a double-sided polished wafer with a commonly used size of 300 mm in diameter. This is preferable because it can be obtained in a state where the difference in flatness is suppressed.

  Also, the present invention provides an upper and lower platen to which a polishing cloth is attached, a slurry supply mechanism for supplying slurry between the upper and lower platens, and a slurry supply mechanism disposed between the upper and lower platens, and A double-side polishing apparatus comprising a carrier set including a plurality of double-side polishing carriers each having a work hole for holding a wafer sandwiched between boards, wherein the plurality of double-side polishing in the carrier set is performed. A double-side polishing apparatus characterized in that the difference between the maximum value and the minimum value of the arithmetic average roughness Sk, which is the amount of undulation, between carriers is 10 μm or less.

  With such a double-side polishing apparatus, it is possible to suppress the difference in flatness between the double-side polished wafers obtained by double-side polishing using the apparatus, to suppress the flatness variation, and to improve the yield. can do.

  As described above, the double-side polishing method and the double-side polishing apparatus for a wafer according to the present invention can suppress the difference in flatness between wafers obtained by performing double-side polishing using a plurality of double-side polishing carriers. Thereby, the yield based on flatness can be improved.

It is a longitudinal section showing an example of the double-sided polishing device of the present invention which can be used for the double-sided polishing method of the wafer of the present invention. It is an internal structure figure showing an example of the double-side polish device of the present invention by plane view. It is a process figure showing an example of a process of a double-side polish method of a wafer of the present invention. FIG. 4 is a measurement diagram showing an example of measurement data in carrier shape measurement.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that a large difference in the amount of undulation in the carrier set for double-side polishing affects flatness.
Then, the present inventors measure the carrier with a shape measuring machine such as a laser type three-dimensional coordinate measuring machine in a carrier set including a plurality of double-side polishing carriers, and calculate the undulation amount of the carrier from the measurement data. Then, by selecting a carrier set in which the difference between the maximum value and the minimum value of the undulation amount of the carriers in the carrier set is equal to or less than a certain value and using the selected carrier set for double-side polishing of the wafer, a plurality of obtained double-side polished wafers The present inventors have found that the difference in flatness can be suppressed, and completed the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a longitudinal sectional view of an example of a double-side polishing apparatus of the present invention which can be used for the double-side polishing method of a wafer of the present invention. FIG. 2 is a plan view showing the internal structure of the double-side polishing apparatus of the present invention. .

As shown in FIGS. 1 and 2, a double-side polishing apparatus 2 including a plurality of double-side polishing carriers 1 includes a lower surface plate 3 and an upper surface plate 4 provided to face each other up and down. A polishing cloth 5 is attached to each of the facing surfaces 3 and 4. For example, a foamed polyurethane pad can be used as the polishing cloth 5.
A slurry supply mechanism 6 (a nozzle 7 and a through hole 8 of the upper surface plate 4) for supplying slurry between the upper surface plate 4 and the lower surface plate 3 is provided above the upper surface plate 4. As the slurry, an inorganic alkali aqueous solution containing colloidal silica can be used.

  As shown in FIGS. 1 and 2, a sun gear 9 is provided at the center between the upper surface plate 4 and the lower surface plate 3, and an internal gear 10 is provided at the peripheral portion. is there.

Each carrier 1 can be made of metal. In the carrier 1, a work hole 11 for holding a wafer W such as a semiconductor silicon wafer is formed in addition to a polishing liquid hole 12 through which a slurry passes. In order to protect the peripheral portion of the wafer W from damage caused by the metal carrier 1, for example, a resin insert material is attached along the inner peripheral portion of the work hole 11 of the carrier 1.
The number of the work holes 11 in each carrier 1 is not particularly limited, and can be appropriately determined according to the size of the work hole 11 itself (the size of the wafer W to be held) and the like. Here, a case where one work hole is formed per carrier is taken as an example.
Further, the number of carriers 1 provided between the upper and lower stools is not particularly limited as long as it is plural. FIG. 2 shows an example of five sheets. The combination of the plurality of carriers 1 is defined as one carrier set.

Further, as will be described later, each of the plurality of carriers 1 actually disposed between the upper and lower stools is previously measured in shape, and the undulation amount is calculated from the measured data. The difference (Range) between the maximum value and the minimum value of the undulation amount between the carriers 1 is equal to or less than a fixed value (hereinafter, also referred to as a management value).
By providing such a management value and managing the amount of undulation between the carriers 1 in the carrier set, it is possible to suppress a difference in flatness between a plurality of double-side polished wafers to be obtained. The specific value of the control value is not particularly limited, and can be appropriately determined according to a required standard value of the flatness of the double-sided polished wafer, and the like. The management value of the arithmetic average roughness Sk) can be 10 μm. That is, the range is 10 μm or less.

  As shown in FIGS. 1 and 2, the outer teeth of the carrier 1 are meshed with the respective teeth of the sun gear 9 and the internal gear 10, and the upper stool 4 and the lower stool 3 are rotated by a drive source (not shown). Accordingly, the plurality of carriers 1 revolve around the sun gear 9 while rotating. At this time, the wafer W is held in the work hole 11 of the carrier 1 and both surfaces are simultaneously polished by the upper and lower polishing cloths 5. At the time of polishing, slurry is supplied from the nozzle 7 through the through hole 8.

Next, a method for polishing both sides of a wafer of the present invention using the above-described double-side polishing apparatus 1 will be described. FIG. 3 is a process chart showing an example of the process of the double-side polishing method.
As shown in FIG. 3, a carrier set including steps 1 and 2 is prepared, and in step 3, double-side polishing of a wafer is performed using a plurality of carriers of the prepared carrier set. Hereinafter, each step will be described in detail.

(Step 1: Measurement of shape of carrier for double-side polishing and calculation of undulation amount)
In preparing a carrier set used for double-side polishing, first, the shapes of all of the plurality of carriers constituting the carrier set are measured. Then, the amount of undulation in each carrier is calculated from the measurement data.
Note that the number of carrier sets for calculating the swell amount is not particularly limited. It is possible to calculate in advance for a plurality of carrier sets frequently used in the manufacture of a double-sided polished wafer.

Here, the shape measuring machine used for the shape measurement is not particularly limited as long as it can obtain measurement data capable of appropriately calculating the undulation amount of the carrier.
For example, a three-dimensional coordinate measuring machine XYZAX-SVA equipped with a line laser sensor manufactured by Tokyo Seimitsu Co., Ltd. can be used. When using such a measuring device, the sensor can be scanned so that the point cloud data on the entire carrier is 2,000,000 points or more. However, the number of data point groups is not limited to this, and can be determined as appropriate according to the required shape accuracy and the like.

If the measurement is performed using such a measuring device, the carrier shape can be measured with higher accuracy, a more accurate undulation amount can be calculated, and furthermore, from the Range based on the accurate undulation amount, an appropriate The two-side polishing can be performed by selecting a carrier. Therefore, it is possible to more reliably obtain a plurality of double-side polished wafers in which the difference in flatness is suppressed.
Note that, in the above example, a measuring device in which the sensor scans while the work (carrier) is stopped is used, but other examples include Nano Metro FR manufactured by Kuroda Seiko Co., Ltd.

Next, after leveling the entire point cloud data on the carrier obtained above, the carrier undulation is obtained from the converted point cloud data obtained by removing noise components having a wavelength of 20 mm or less.
By performing such leveling and removing noise components, it is possible to more appropriately calculate the undulation amount of the carrier.

Regarding the amount of undulation, for example, when the diameter of a wafer to be polished on both sides is 300 mm, the arithmetic mean roughness Sk obtained from the data within 175 mm from the center of the work hole in the above-mentioned conversion point group data is used as the undulation of the carrier. Quantity.
The undulation amount can be calculated by using the data around the work hole which easily affects the flatness of the double-side polished wafer.

In addition, here, an example in which a wafer having a commonly used size of 300 mm is polished on both sides has been described. However, the data extraction range can be appropriately set according to the wafer size.
Further, the specific undulation amount is not limited to the arithmetic average roughness Sk, but may be, for example, another parameter that provides a good correlation with the flatness of the obtained double-side polished wafer. Is also possible.

(Step 2: Selection of carrier set)
Next, a carrier set to be actually used for double-side polishing is selected from the plurality of carrier sets for which the swell amount has been calculated.
More specifically, a carrier set in which the difference (Range) between the maximum value and the minimum value of the undulation between a plurality of carriers in the carrier set is equal to or less than a fixed value (management value) is selected. The specific value of the management value is not particularly limited. For example, the correlation between the control value and the difference in flatness between actually double-side polished wafers, or the ratio of double-side polished wafers that satisfy the standard value for flatness should be checked in advance and determined from the results. Can be.

  As an example, when the swell amount (Sk) is obtained by the above-described measurement data extraction method and calculation method for a wafer having a diameter of 300 mm, the management value can be set to 10 μm. That is, a carrier set in which the difference between the maximum value and the minimum value of Sk between carriers in the carrier set is 10 μm or less can be selected. By doing so, the difference in flatness between the plurality of obtained double-sided polished wafers is small, the flatness variation is suppressed, and a desired double-sided polished wafer can be obtained with high yield.

(Step 3: Arrangement of carrier for double-side polishing and double-side polishing of wafer)
Next, a plurality of carriers of the selected carrier set are provided in a double-side polishing apparatus, and the wafer held in the work hole of each carrier is double-side polished.
A plurality of carriers are rotated and revolved as the upper and lower platens are rotated while supplying the slurry from the nozzles, and both surfaces of the plurality of wafers are simultaneously polished with the upper and lower polishing cloths.

  According to the method for polishing a wafer on both sides of the present invention as described above, the difference in flatness between the wafers on both sides can be suppressed. For this reason, it is possible to prevent an increase in the ratio of double-sided polished wafers whose flatness deviates from the specified value, thereby improving the yield. As described above, it is possible to solve a problem that cannot be solved only by the conventional method of managing the thickness of the carrier.

Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
(Example 1)
A plurality of carrier sets each comprising five double-side polishing carriers manufactured to have a uniform thickness as in the related art were prepared. It is a carrier for polishing both sides of a wafer having a diameter of 300 mm.

Then, as in step 1 of FIG. 3, the shape measurement and the amount of undulation were performed on the carriers in each carrier set. The measurement and calculation conditions are as follows.
For the shape measurement, a three-dimensional coordinate measuring machine XYZAX-SVA equipped with a line laser sensor manufactured by Tokyo Seimitsu Co., Ltd. was used.
The laser width of the line laser was set to 24 mm (Fh mode), and the entire area of a 540 mm square area including the carrier was measured at a scanning speed of 20 mm / sec.
From the above measured data, 3.31 million data on the carrier were extracted.
After leveling the entire point group, noise components having a wavelength of 20 mm or less were removed, and further, arithmetic mean roughness Sk was obtained from data obtained by extracting data within 175 mm from the center of the work hole.
FIG. 4 shows an example of data according to these series of procedures.

After the swell amount (Sk) of the five carriers in each carrier set is obtained as described above, the maximum swell amount of the five carriers in each carrier set is determined as in step 2 in FIG. The difference (Range) between the value and the minimum value was calculated and compared with a preset management value (10 μm) to select a carrier set that was equal to or less than the management value.
Specifically, a carrier set (Set C) having a Range of 8.5 μm was selected.

Then, as in step 3 in FIG. 3, five carriers of the selected carrier set were arranged in a double-side polishing apparatus to perform double-side polishing of the wafer. Various conditions for double-side polishing are as follows.
As the wafer, a P-type silicon single crystal wafer having a diameter of 300 mm was used.
The polishing apparatus used was DSP-20B manufactured by Fujikoshi Machinery.
As the polishing pad, a foamed polyurethane pad having a Shore A hardness of 90 was used.
The carrier was a titanium substrate, and FRP in which glass fiber was impregnated with an epoxy resin was used as an insert.
The slurry used was a slurry containing silica abrasive grains, an average particle diameter of 35 nm, an abrasive grain concentration of 1.0 wt%, a pH of 10.5, and a KOH base.

The processing load was set to 150 gf / cm ² .
The processing time was set so that an optimum gap was obtained for each carrier set.
The edge shape of the double-side polished wafer is determined by a value (gap) obtained by subtracting the carrier thickness from the finished thickness of the wafer. According to the present invention, it has been found that a carrier having a large undulation shows a good edge flatness when the gap is large. Therefore, the processing time in Example 1 and Example 2 and Comparative Examples 1 and 2, which will be described later, was set to be the optimum gap for each carrier set.

The rotation speed of each drive unit was set to -13.4 rpm for the upper stool, 35 rpm for the lower stool, 25 rpm for the sun gear, and 7 rpm for the internal gear.
The dressing of the polishing pad was performed by sliding a dress plate on which diamond abrasive grains were electrodeposited with upper and lower polishing pads while flowing pure water at a predetermined pressure.
Condition SC-1 cleaning _{NH 4 OH: H 2 O 2} : H 2 O = 1: 1: was performed in 15.
Five batches of five batches, that is, a total of 25 wafers were polished on both sides and cleaned.

  The double-sided polished wafer thus obtained was measured by WaferSight (manufactured by KLA Tencor). ESFQRmax was calculated from the measured data, and the yield relative to the specified value was determined. At the time of ESFQRmax calculation, the zone (also called Polar Sites) was set to 30 mm Length (2 mm EE) of 72 Sector in M49 mode.

(Example 2)
When selecting from a plurality of carrier sets initially prepared in Example 1, a carrier set (Set D) having a range of 3.0 μm was selected, and the processing time in the double-side polishing described above was not used. The wafer was polished on both sides in the same manner as in Example 1. Thereafter, ESFQRmax was calculated, and the yield with respect to the specified value was obtained.

(Comparative Examples 1 and 2)
From the plurality of carrier sets initially prepared in the first embodiment, the carrier sets are randomly selected (that is, unlike the first and second embodiments, without considering the relationship between the Range and the management value (10 μm)). (Set A) and a carrier set (Set B) were selected, and both sides of the wafer were polished. The processing time in the double-side polishing was set so as to be an optimum gap. Other conditions for double-side polishing are the same as those in the first embodiment.
Thereafter, ESFQRmax was calculated, and the yield with respect to the specified value was obtained.
For comparison, the Range of the carrier set (Set A) and the range of the carrier set (Set B) were calculated to be 19.1 μm and 12.3 μm, respectively, from the control values (10 μm) in Examples 1 and 2. Was also big.

  Table 1 summarizes the amount of undulation, Range, average gap, yield, and the like in Examples 1 and 2 and Comparative Examples 1 and 2.

As shown in Table 1, in Examples 1 and 2 in which the present invention was carried out, the yields were 92% and 96%, respectively, which were much higher than those of Comparative Examples 1 and 2 of 72% and 84%. As described above, when the wafer was processed using the carrier set (Examples 1 and 2) in which the swell was also controlled and the conventional carrier set (Comparative Examples 1 and 2) in which only the thickness was controlled, the yield of ESFQRmax was obtained. Has improved.
In Examples 1 and 2, by managing the range of the undulation amount between a plurality of carriers in the carrier set and suppressing the value, it was possible to suppress the variation in flatness between the obtained plurality of double-side polished wafers. . As a result, the rate at which the flatness deviated from the specified value was reduced, and the yield was improved.

  Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

1: Carrier for double-side polishing, 2: Double-side polishing machine, 3: Lower platen, 4: Upper platen,
5: polishing cloth, 6: slurry supply mechanism, 7: nozzle, 8: through hole,
9 ... Sun gear, 10 ... Internal gear, 11 ... Work hole,
12: Polishing liquid hole, W: Wafer.

Claims (4)

In the double-side polishing apparatus, a plurality of double-side polishing carriers are disposed between the upper and lower platens to which the polishing cloth is attached, and a wafer is held in a work hole formed in each of the plurality of double-side polishing carriers, A double-sided polishing method for a wafer sandwiched between the upper and lower platens and polished on both sides,
When preparing a carrier set consisting of a plurality of double-side polishing carriers disposed between the upper and lower platens,
The swell amount calculated from the data obtained by measuring the shape of the double-sided polishing carrier using a shape measuring instrument is obtained in all of the plurality of double-sided polishing carriers of the carrier set, and the plurality of double-sided polishing carriers in the carrier set are obtained. Select and prepare a carrier set in which the difference between the maximum value and the minimum value of the undulation amount between carriers is equal to or less than a certain value,
A double-side polishing method for a wafer, wherein the plurality of double-side polishing carriers of the prepared carrier set are arranged in the double-side polishing apparatus and the wafer is double-side polished. In calculating the swell amount,
A three-dimensional coordinate measuring machine having a laser sensor is used as the shape measuring device, and the amount of undulation is calculated from point cloud data obtained by measuring the entirety of the double-side polishing carrier, according to claim 1, wherein Double-side polishing method. In calculating the swell amount,
The leveling is performed on all the measured point cloud data, and the undulation amount of the double-side polishing carrier is calculated from the converted point cloud data obtained by removing a noise component having a wavelength of 20 mm or less. The double-side polishing method for a wafer according to the above. The wafer to be polished on both sides has a diameter of 300 mm,
In calculating the swell amount,
From the conversion point group data, data within 175 mm from the center of the work hole is extracted, and the arithmetic average roughness Sk calculated from the extracted data is defined as the undulation amount,
In selecting the carrier set,
4. The method for polishing both sides of a wafer according to claim 3, wherein a carrier set in which a difference between a maximum value and a minimum value of Sk of the plurality of double-side polishing carriers is 10 μm or less is selected.

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