JP2018176393A - Both surface polishing method and both surface polishing device for wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a both surface polishing method and a both surface polishing method for a wafer that can suppress a difference (variations) in flatness between wafers which are obtained through both surface polishing using a plurality of both surface polishing carriers.SOLUTION: In a both surface polishing method for a wafer in which a plurality of both surface polishing carriers are arranged in a both surface polishing device, when preparing a carrier set constituted of the plurality of both surface polishing carriers to be arranged between upper and lower surface plates, wavinesses calculated from data determined by measuring shapes of both surface polishing carriers using a shape measuring machine are obtained in all of the plurality of both surface polishing carriers of the carrier set, the carrier set, in which a difference between the maximum value and the minimum value of the wavinesses between the plurality of both surface polishing carriers in the carrier set is below a certain value, is selectively prepared, and the set is arranged in both surface polishing device to polish both surfaces of the wafer.SELECTED DRAWING: Figure 3

Description

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

  In a double-side polishing apparatus for planarizing a wafer such as a silicon wafer, a disk-shaped double-sided polishing carrier provided with a work hole for holding a wafer is generally used.

  The double-side polishing apparatus usually comprises an upper surface plate and a lower surface plate to which an abrasive cloth (abrasive pad) made of non-woven fabric or the like is attached, a sun gear at the center and an internal gear at the outer periphery. A so-called four-way system having a planetary gear structure is used. In such a double-sided polishing apparatus, a wafer is inserted and held in a work hole formed in a single or a plurality of double-sided polishing carriers (hereinafter, also simply referred to as carriers).

  Then, the slurry is supplied to the wafer from the upper surface plate side, and while the upper and lower surface plates are rotated, the polishing cloth is pressed against both the front and back sides of the wafer, and the carrier is rotated and revolved between the sun gear and the internal gear. Both sides are polished simultaneously.

  By the way, it has been known that the thickness of the carrier holding the wafer is important for the flatness of a double-sided polished wafer. From this, an attempt has been made to reduce the flatness variation of a double-sided polished wafer by reducing the carrier thickness variation (see Patent Document 1).

JP, 2015-174168, A

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

  The present invention has been made in view of the above problems, and a method for double-sided polishing of wafers capable of suppressing a difference (variation) in flatness between wafers obtained by double-sided polishing using a plurality of carriers for double-sided polishing. And it aims at providing a double-sided polisher.

  In order to achieve the above object, according to the present invention, in a double-sided polishing apparatus, a plurality of double-sided polishing carriers are disposed between upper and lower platens to which a polishing pad is attached, and each of the plurality of double-sided polishing carriers is A method for holding a wafer in a formed work hole, and holding the wafer between the upper and lower surface plates for double-sided polishing of the wafer, comprising a plurality of double-sided polishing carriers disposed between the upper and lower surfaces. When preparing a carrier set as described above, the amount of waviness calculated from data obtained by measuring the shape of the carrier for double-sided polishing using a shape measuring machine is acquired for all of the plurality of carriers for double-sided polishing of the carrier set, The carrier set is selected and prepared such that the difference between the maximum value and the minimum value of the waviness amount of the plurality of double-side polishing carriers in the inside is smaller than a predetermined value, 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 inventors of the present invention have found that the waviness (warpage) of the double-sided polishing carrier influences the flatness of the double-sided polished wafer. Then, 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 waviness amounts of a plurality of double-side polishing carriers in the carrier set is equal to or less than a predetermined value is selected The difference in flatness between double-sided polished wafers obtained by double-sided polishing can be suppressed. For this reason, as in the conventional case, a difference in flatness occurs between double-sided polished wafers, which can prevent an increase in the ratio of 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 amount of waviness, it is possible to calculate the amount of waviness from the point cloud data obtained by measuring the entire double-side polishing carrier using a three-dimensional coordinate measuring machine having a laser sensor as the shape measuring machine. .

  In this way, the shape of the double-side polishing carrier can be measured with higher accuracy, and it is possible to calculate a more accurate amount of waviness. As a result, the carrier set can be selected more appropriately, and it is possible to prevent the occurrence of a difference in flatness between the double-sided polished wafers obtained.

  Further, in the calculation of the amount of waviness, leveling is performed on all the measured point cloud data, and the amount of waviness of the carrier for double-side polishing is calculated from conversion point cloud data obtained by removing noise components of wavelength 20 mm or less. be able to.

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

  The wafer to be double-sided polished is 300 mm in diameter, and in the calculation of the amount of undulation, 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 extraction data The carrier set may be selected such that the difference between the maximum value and the minimum value of Sk of the plurality of double-sided polishing carriers is 10 μm or less, where the roughness Sk is the waviness amount, and the carrier set is selected.

  In this way, the amount of waviness can be calculated using data around the work hole that easily affects the flatness of the double-sided polishing wafer, and a double-sided polishing wafer with a commonly used size of 300 mm is used. This is preferable because the difference in flatness can be obtained in a mutually suppressed state.

  Further, according to the present invention, there is provided an upper and lower surface plate to which a polishing pad is attached, a slurry supply mechanism for supplying a slurry between the upper and lower surface plates, and the upper and lower surface plate. A double-sided polishing apparatus comprising a carrier set comprising a plurality of double-sided polishing carriers each having a work hole for holding a wafer sandwiched between discs, the plurality of double-sided polishing in the carrier set Provided is 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 corrugation, between carriers for use is 10 μm or less.

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

  As described above, with the double-sided polishing method and double-sided polishing apparatus of wafers according to the present invention, it is possible to suppress the difference in flatness between wafers obtained by double-sided polishing using a plurality of double-sided polishing carriers. This can improve the yield based on flatness.

It is a longitudinal cross-sectional view which shows an example of the double-sided grinding | polishing apparatus of this invention which can be used for the double-sided grinding | polishing method of the wafer of this invention. It is an internal structure figure which shows an example of the double-sided grinding | polishing apparatus of this invention by planar view. It is process drawing which shows an example of the process of the double-sided grinding method of the wafer of this invention. It is a measurement figure which shows an example of the measurement data in shape measurement of a carrier.

The inventors of the present invention conducted intensive studies to solve the problems described above, and it was found that if the difference in the amount of corrugation in the double-side polishing carrier set is large, the flatness is affected.
Then, the present inventors measure the carrier by a shape measuring machine such as a laser type three-dimensional coordinate measuring machine in a carrier set consisting of a plurality of carriers for double-side polishing, and calculate the amount of wave of the carrier from the measurement data Between a plurality of double-sided polished wafers obtained by selecting a carrier set in which the difference between the maximum value and the minimum value of the amount of undulations of carriers in the carrier set is a fixed value or less and using it for double-sided polishing of the wafers. The present invention has been completed by finding that the difference in flatness can be suppressed.

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 the double-side polishing apparatus of the present invention which can be used for the double-sided polishing method of a wafer of the present invention, and FIG. 2 is an internal structural view of the double-side polishing apparatus of the present invention .

As shown in FIGS. 1 and 2, the double-side polishing apparatus 2 equipped with a plurality of double-sided polishing carriers 1 includes a lower surface plate 3 and an upper surface plate 4 provided opposite to each other in the vertical direction. Abrasive cloths 5 are attached to the facing surfaces 3 and 4 respectively. As the polishing pad 5, for example, a foam polyurethane pad can be used.
Further, a slurry supply mechanism 6 (a nozzle 7 and a through hole 8 of the upper surface plate 4) for supplying a slurry between the upper surface plate 4 and the lower surface plate 3 is provided in the upper portion of the upper surface plate 4. As a slurry, an inorganic alkaline 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 edge. is there.

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

Further, as will be described later, the plurality of carriers 1 actually disposed between the upper and lower surface plates are each measured in advance in shape, and the amount of corrugation is calculated from the measurement data. Then, the difference (Range) between the maximum value and the minimum value of the amount of waves of 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 undulations of the carriers 1 in the carrier set, it is possible to suppress the difference in flatness of the plurality of double-sided polished wafers obtained. The specific value of this control value is not particularly limited, and can be appropriately determined according to the required standard value of flatness of double-sided polished wafer etc., but in the double-sided polishing apparatus of the present invention, the amount of waviness (described later The control value of the arithmetic mean 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 in mesh with the teeth of the sun gear 9 and the internal gear 10, and the upper surface plate 4 and the lower surface plate 3 are rotated by a drive source (not shown). Along with the rotation, 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 pads 5. At the time of polishing, the slurry is supplied from the nozzle 7 through the through hole 8.

Next, the double-sided polishing method of the wafer of the present invention using the double-sided polishing apparatus 1 as described above will be described. FIG. 3 is a process chart showing an example of the process of this double-sided polishing method.
As shown in FIG. 3, the carrier set consisting of step 1 and step 2 is prepared, and in step 3, double-side polishing of the wafer is performed using a plurality of carriers of the prepared carrier set. Each step will be described in detail below.

(Step 1: Measurement of shape of carrier for double-side polishing and calculation of waviness)
In preparing the carrier set used for double-sided polishing, first, the shapes of all of the plurality of carriers constituting the carrier set are measured. Then, from the measurement data, the amount of waves in each carrier is calculated.
The number of carrier sets for calculating the amount of undulations is not particularly limited. It is possible to calculate in advance for a plurality of carrier sets often used in the production of double-sided polished wafers.

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

If measurement is performed using such a measuring machine, the carrier shape can be measured with higher accuracy, more accurate amount of undulation can be calculated, and further, from Range based on the accurate amount of undulation, appropriate It is possible to carry out double-sided polishing by selecting the yardstick. Therefore, it is possible to more reliably obtain a plurality of double-sided polished wafers in which the difference in flatness is suppressed.
In the above-mentioned example, although the measuring machine which a sensor scans in the state where work (carrier) stopped is used, for example, Nano Metro FR by Kuroda Seiko Co., Ltd. etc. are mentioned, for example.

Next, leveling is performed on the entire point cloud data relating to the carrier obtained above, and then the carrier's undulation is determined from conversion point cloud data obtained by removing noise components of 20 mm or less in wavelength.
By performing such leveling and removing the noise component, it is possible to more appropriately calculate the carrier waviness amount.

With regard to the amount of corrugation, for example, if the diameter of the wafer to be double-sided polished is 300 mm, the arithmetic mean roughness Sk determined from the data within 175 mm from the center of the work hole of the above conversion point group data It can be a quantity.
The amount of waviness can be calculated using data around the work hole that is likely to affect the flatness of the double-sided polished wafer.

In addition, although an example in the case of double-sided polishing of a wafer having a commonly used size of 300 mm is described here, an extraction range of data can be appropriately set depending on the wafer size.
Furthermore, the specific waviness amount is not limited to the arithmetic mean roughness Sk, and for example, another parameter may be used to obtain a good correlation with the flatness of the double-sided polished wafer to be obtained. Is also possible.

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

  As one example, in the case of obtaining the waviness amount (Sk) by the measurement data extraction method and the calculation method as described above with a wafer having a diameter of 300 mm, the control value can be 10 μm. That is, it is possible to select 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. In this way, the difference in flatness between the plurality of double-sided polished wafers obtained is small, and the variation in flatness is suppressed, and it is possible to obtain a desired double-sided polished wafer with a high yield.

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

  According to the double-side polishing method of a wafer of the present invention as described above, the difference in flatness between double-sided polished wafers can be suppressed. For this reason, it is possible to prevent an increase in the ratio of the double-side polished wafer in which the flatness deviates from the specified value, and it is possible to improve the yield. Thus, it is possible to solve the problem which could not be solved only by the conventional method of managing the thickness of the carrier.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.
Example 1
A plurality of carrier sets comprising five double-sided polishing carriers manufactured so as to have a uniform thickness as in the prior art were prepared. In addition, it is a carrier for carrying out double-sided grinding of a wafer 300 mm in diameter.

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

After determining the waviness (Sk) of the five carriers in each carrier set as described above, as in step 2 of FIG. 3, the maximum amount of waviness between the five carriers in each carrier set is obtained. The difference (Range) between the value and the minimum value was calculated, compared with a control value (10 μm) set in advance, and a carrier set equal to or less than the control value was selected.
Specifically, a carrier set (Set C) having a range of 8.5 μm was selected.

Then, as shown in step 3 of FIG. 3, five carriers of the selected carrier set were disposed in the double-side polishing apparatus to perform double-side polishing of the wafer. The various conditions of double-sided polishing are as follows.
As a wafer, a P-type silicon single crystal wafer with a diameter of 300 mm was used.
As a polishing apparatus, DSP-20B manufactured by Fuji Machine Industry Co., Ltd. was used.
The polishing pad used was a foamed polyurethane pad of Shore A hardness 90.
The carrier was a titanium substrate, and an FRP in which glass fiber was impregnated with epoxy resin was used as an insert.
The slurry used contained silica abrasive, an average particle diameter of 35 nm, an abrasive 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 to be an optimal gap for each carrier set.
The edge shape of the double-sided polished wafer is determined by the value (gap) obtained by subtracting the carrier thickness from the finished thickness of the wafer. According to the present invention, carriers with large undulations were found to exhibit better edge flatness with larger gaps. Therefore, the processing time in Example 1 and Example 2 and Comparative Examples 1 and 2 described later was set to be an optimal gap for each carrier set.

The rotational speed of each drive unit was set to −13.4 rpm for the upper platen, 35 rpm for the lower platen, 25 rpm for the sun gear, and 7 rpm for the internal gear.
Dressing of the polishing pad was carried out by bringing a dressing plate electrodeposited with diamond abrasive grains into sliding contact with the upper and lower polishing pads while flowing pure water at a predetermined pressure.
The SC-1 wash was performed under the conditions NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 15.
A total of 25 wafers were subjected to double-side polishing processing and cleaning, with 5 batches per 5 batches, that is, 25 wafers in total.

  The double-sided polished wafer thus obtained was measured by WaferSight (manufactured by KLA Tencor). From the measured data, ESFQRmax was calculated, and the yield relative to the specified value was determined. In addition, at the time of ESFQRmax calculation, the zone (another name: Polar Sites) was set to M49 mode at 30 mm Length (2 mm E.E.) of 72 Sector.

(Example 2)
When selecting from the plurality of carrier sets prepared first in Example 1, the carrier set having a range of 3.0 μm (Set D) was selected, and other than the processing time in double-side polishing described above, an example. The double-side polishing of the wafer was performed in the same manner as in 1. Then, ESFQRmax was calculated and the yield relative to the specified value was determined.

(Comparative Examples 1 and 2)
From the plurality of carrier sets prepared first in the first embodiment, at random (that is, unlike in the first and second embodiments, the relationship between the Range and the management value (10 μm) is not considered), respectively, the carrier set (Set A) and carrier set (Set B) were selected, and double-sided polishing of the wafer was performed. The processing time in double-side polishing was set to be an optimal gap. The other conditions for double-side polishing are the same as in Example 1.
After that, ESFQRmax was calculated, and the yield relative to the specified value was determined.
When the ranges of the carrier set (Set A) and the carrier set (Set B) were calculated for comparison, they were 19.1 μm and 12.3 μm, respectively, from the control values (10 μm) in Examples 1 and 2. It was big too.

  Table 1 shows the undulation amount, 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 greatly exceeded 72% and 84% of Comparative Examples 1 and 2. Thus, when the wafer was processed by the carrier set (Examples 1 and 2) which also managed the waviness and the carrier set (Comparative Examples 1 and 2) which managed the conventional thickness only, the yield of ESFQRmax was obtained. Improved.
In Examples 1 and 2, by managing the range of the amount of undulations of the plurality of carriers in the carrier set and suppressing the value thereof, it was possible to suppress the variation in flatness of the plurality of double-sided polished wafers obtained. . As a result, the yield could be improved by reducing the rate at which the flatness deviates from the specified value.

  The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and it has substantially the same configuration as the technical idea described in the claims of the present invention, and any one having the same function and effect can be used. It is included in the technical scope of the invention.

1 Carrier for double-sided polishing 2 Double-sided polishing device 3 Lower surface plate 4 Upper surface plate
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 (5)

In the double-sided polishing apparatus, a plurality of double-sided polishing carriers are disposed between upper and lower platens to which a polishing pad is attached, and a wafer is held in a work hole formed in each of the plurality of double-sided polishing carriers. It is a double-sided polishing method of a wafer which is sandwiched between the upper and lower plates and is double-sided polished,
When preparing a carrier set comprising a plurality of double-sided polishing carriers disposed between the upper and lower surface plates,
The amount of waviness calculated from the data obtained by measuring the shape of the double-sided polishing carrier using a shape measuring machine is obtained for all of the plurality of double-sided polishing carriers of the carrier set, and the plurality of double-sided polishing in the carrier set Select and prepare a carrier set in which the difference between the maximum value and the minimum value of the waviness between carriers is equal to or less than a fixed value,
A method for double-sided polishing of a wafer comprising disposing the plurality of double-sided polishing carriers of the prepared carrier set in the double-sided polishing apparatus and double-sided polishing the wafer. In the calculation of the amount of undulation,
The wafer according to claim 1, wherein the three-dimensional coordinate measuring machine having a laser sensor is used as the shape measuring machine, and the amount of waviness is calculated from point cloud data obtained by measuring the entire double-side polishing carrier. Double-sided polishing method. In the calculation of the amount of undulation,
The leveling of the double-side polishing carrier is calculated from conversion point cloud data obtained by leveling all the measured point cloud data and removing noise components of a wavelength of 20 mm or less. The double-sided polishing method of the described wafer. The wafer to be double-sided polished is 300 mm in diameter,
In the calculation of the amount of undulation,
Data within 175 mm from the center of the work hole is extracted from the conversion point group data, and the arithmetic average roughness Sk calculated from the extracted data is taken as the amount of waviness.
In selecting the carrier set,
4. The method according to claim 3, wherein a carrier set having a difference between a maximum value and a minimum value of Sk between the plurality of double-side polishing carriers is 10 [mu] m or less. An upper and lower surface plate to which an abrasive cloth is attached, a slurry supply mechanism for supplying a slurry between the upper and lower surface plates, and the upper and lower surface plate are disposed and sandwiched between the upper and lower surface plates during polishing. A double-sided polishing apparatus comprising a carrier set comprising a plurality of double-sided polishing carriers each having a work hole for holding a fixed wafer,
The double-side polishing apparatus, wherein the difference between the maximum value and the minimum value of the arithmetic average roughness Sk, which is the amount of corrugation, between the plurality of double-side polishing carriers in the carrier set is 10 μm or less.

Images