TW201839836A - Double-sided wafer polishing method and double-sided polishing apparatus - Google Patents

Abstract

The present invention provides a double-sided wafer polishing method for placing multiple double-sided polishing carriers in a double-sided polishing apparatus and performing double-sided polishing of wafers, wherein, when readying a carrier set comprising multiple double-sided polishing carriers to be disposed between upper and lower surface plates: the amount of waviness, calculated from data measuring the shape of the double-sided polishing carrier using a shape measuring machine, is acquired for all of the multiple double-sided polishing carriers of the carrier set; a carrier set for which the difference between the maximum value and minimum value for the amounts of waviness among the multiple double-sided polishing carriers in the carrier set is not more than a fixed value is selected and readied; and the carrier set is placed in the double-sided polishing apparatus and double-sided polishing of wafers is performed.

Description

Double-side polishing method of wafer and double-side polishing device

The invention relates to a method and a double-side polishing device for double-side polishing of a wafer by using a plurality of carriers for surface polishing.

In a double-side polishing apparatus for planarizing a wafer such as a silicon wafer, a disc-shaped double-side polishing carrier provided with a workpiece hole for supporting a wafer is generally used.

As the double-side polishing device, an upper plate and a lower plate generally provided with an abrasive cloth (polishing pad) made of a non-woven fabric or the like are attached, and a sun gear is disposed at a central portion and an internal gear is disposed at an outer peripheral portion. The planetary gear structure is a so-called 4way thing. In such a double-side polishing apparatus, a wafer is inserted and supported inside a work hole formed in a singular or plural number in a carrier for double-side polishing (hereinafter also simply referred to as a carrier).

In addition, while supplying mud to the wafer from the upper platen side, while rotating the upper and lower platens and pushing the polishing cloth to both sides of the wafer, the carrier rotates between the sun gear and the internal gear to revolve at the same time. Polish both sides of each wafer.

In addition, it is known that, for the flatness of a wafer polished on both sides, the thickness of a carrier supporting the wafer is important. For this reason, attempts have been made to reduce the variation in the thickness of the carrier so that the variation in the flatness of the wafer polished on both sides is reduced (see Patent Document 1). [Previous Technical Literature]

Patent Document 1: Japanese Patent Application Laid-Open No. 2015-174168

[Problems to be Solved by the Invention] However, even if the thicknesses of the carriers are uniform, the flatness of the edges of the double-sided polished wafers supported by the two sides during the double-sided polishing varies between the carriers.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a double-side polishing method and a double-side polishing device capable of suppressing wafers having flatness (staggered) between wafers obtained by performing double-side polishing using a plurality of double-side polishing carriers. [Technical means to solve the problem]

In order to achieve the above object, the present invention provides a method for double-side polishing of a wafer, which is arranged in a double-side polishing device, and a plurality of double-side polishing is arranged between an upper platen and a lower platen to which a polishing cloth is attached. The carrier is used to support the wafer in the workpiece holes formed by the plurality of double-sided polishing carriers, and is sandwiched between the upper platen and the lower platen for double-side polishing. In the case of a carrier set composed of a plurality of double-side polishing carriers between the pan and the lower plate, from the plurality of the double-side polishing carriers of the carrier set, the carrier measured from the shape measuring machine is used. The ripple amount calculated from the data of the shape of the double-sided polishing carrier, and the difference between the maximum value and the minimum value of the ripple amount in the plurality of double-sided polishing carriers in the carrier set is a carrier set with a fixed value or less It is selected and prepared, and the plurality of carriers for the double-side polishing prepared in the prepared carrier set are arranged in the double-side polishing apparatus to double-side polish the wafer.

The inventors of the present case have found through research that the corrugation (warpage) of the carrier for double-sided polishing affects the flatness of the double-sided polished wafer. In addition, according to the double-side polishing method described above, a carrier set having a difference between a maximum value and a minimum value of a plurality of double-side polishing carriers in the carrier set is selected to be used, so it can be used. Differences in flatness between the double-sided polished wafers obtained from the double-side polishing are suppressed. Therefore, it is possible to prevent the flatness of the conventional double-sided polished wafers from being different from each other, so that the proportion of double-sided polished wafers having flatness exceeding a predetermined value can be increased, and the yield can be improved.

At this time, in the calculation of the amount of waviness, a three-dimensional coordinate measuring machine having a laser sensor was used as the shape measuring machine, and the amount of waviness was calculated from the point group data of the entire double-sided polishing carrier.

According to this, the shape of the carrier for double-side polishing can be measured more accurately, and the amount of corrugation can be calculated more accurately. As a result, a more appropriate carrier set can be selected, and a difference in flatness between the obtained double-sided polished wafers can be prevented.

In the calculation of the amount of corrugation, the ripple of the double-sided polishing carrier is calculated from the level point data obtained by leveling all the measured point group data, and the converted point group data obtained by removing noise components having a wavelength of 20 mm or less. the amount.

This makes it possible to more appropriately calculate the amount of waviness of the carrier for double-side polishing.

The diameter of the wafer polished on both sides can be set to 300 mm. In the calculation of the amount of corrugation, from the transformation point group data, data within 175 mm from the center of the workpiece hole can be extracted, and the data extracted from the The calculated arithmetic average rough Sk is determined as the amount of corrugation. In the selection of the carrier set, a carrier set having a difference between the maximum value and the minimum value of Sk in the plurality of double-side polishing supports of 10 μm or less is selected. .

Based on this, it is possible to calculate the amount of corrugation by using the data around the workpiece hole that is likely to affect the flatness of the double-side polished wafer. Since the flatness between them can be suppressed, the commonly used double-side polishing with a diameter of 300 mm can be obtained. Wafer is appropriate.

The present invention also provides a double-side grinding device, comprising: an upper platen and a lower platen, attached with a polishing cloth; a mud supply device, supplying mud between the upper platen and the lower platen; and a carrier sleeve A group disposed between the upper platen and the lower platen, including a plurality of double-sided polishing carriers, each of the plurality of double-sided polishing carriers is formed to be sandwiched between the upper platen and the support plate during grinding The workpiece hole of the wafer between the lower plates, wherein the difference between the maximum and minimum values of the arithmetic average roughness Sk of the plurality of double-sided polishing carriers in the carrier set is 10 μm or less, and the arithmetic average roughness Sk is the amount of ripple.

With such a double-side polishing device, it is possible to suppress the difference in flatness between the double-sided polished wafers obtained by double-side polishing using the device, suppress the variation in flatness, and improve the yield. [Contrast with the effect of the prior art]

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

In order to solve the above-mentioned problems, the inventors of the present invention conducted careful research and learned that if the difference in the amount of corrugations in the carrier set for double-side polishing is large, the flatness will be affected. In addition, the inventors of the present invention have found that from a carrier set composed of a plurality of double-sided polishing carriers, the carrier is measured by a shape measuring machine such as a laser-type three-dimensional coordinate measuring machine, and the amount of corrugation of the carrier is calculated from the measurement data. A carrier set having a difference between the maximum value and the minimum value of the ripples of the carriers in the carrier set is selected to be used for double-sided polishing of the wafer, thereby suppressing the obtained multiple double-sided polished wafers. The flatness of each other is different, and the present invention has been completed.

Although the embodiments of the present invention are described below with reference to the drawings, the present invention is not limited thereto. FIG. 1 is a vertical cross-sectional view showing an example of the double-side polishing apparatus of the present invention that can be used in the double-side polishing method of the wafer of the present invention, and FIG. 2 is a view showing the inside of an example of the double-side polishing apparatus of the present invention in a plane structure map.

As shown in FIG. 1 and FIG. 2, a double-side polishing device 2 including a plurality of double-side polishing carriers 1 is provided, and a lower plate 3 and an upper plate 4 are provided facing each other up and down. To the surface side, a polishing cloth 5 is attached. As the polishing cloth 5, for example, a foamed urethane pad can be used. A mud supply mechanism 6 (a nozzle 7 and a through hole 8 for the upper plate 4) is provided at an upper portion of the upper plate 4 to supply mud between the upper plate 4 and the lower plate 3. As the slurry, an inorganic alkaline aqueous solution containing colloidal silica can be used.

In addition, as shown in FIGS. 1 and 2, a sun gear 9 is provided at a center portion between the upper platen 4 and a lower platen 3, and an internal gear 10 is provided at a peripheral portion thereof, which is a 4-way type double-side polishing device.

Each carrier 1 can be made of metal. In the carrier 1, in addition to the polishing liquid holes 12 through which the slurry flows, a work hole 11 for supporting a wafer W such as a semiconductor silicon wafer is also formed. In order to protect the peripheral edge portion of the wafer W from damage caused by the metal carrier 1, an insertion member made of, for example, resin is mounted along the inner peripheral portion of the work hole 11 of the carrier 1. The number of the work holes 11 of each carrier 1 is not particularly limited, and can be appropriately determined by the size of the work hole 11 itself (the size of the work W to be supported) and the like. As an example, a case where one workpiece hole is formed in each carrier 1 is described here. The number of the carriers 1 arranged between the upper and lower fixed plates is not particularly limited as long as it is plural. An example of 5 pieces is shown in FIG. 2. The combination of the plurality of carriers 1 is regarded as a carrier set.

As described later, the plurality of carriers 1 arranged between the upper and lower plates are actually measured in advance, and the amount of corrugation is calculated from the measurement data. The difference (Range) between the maximum value and the minimum value of the ripple amount between the carriers 1 is equal to or less than a fixed value (hereinafter also referred to as a management value). By setting such a management value, the amount of waviness between the carriers 1 in the carrier set can be managed, and the difference in flatness between the obtained plurality of double-sided polished wafers can be suppressed. The specific value of this management value is not particularly limited, and can be appropriately determined in accordance with the specification value of the flatness of the required double-side polished wafer, etc. However, in the double-side polishing apparatus of the present invention, this ripple amount (described later) The management value of the arithmetic average roughness Sk) was 10 μm. That is, the Range is 10 μm or less (0 μm or more).

In addition, as shown in FIGS. 1 and 2, each tooth portion of the sun gear 9 and the internal gear 10 meshes with the outer peripheral teeth of the carrier 1, and is rotated along with the upper platen 4 and the lower platen 3 by driving sources not shown in the figure. The plurality of carriers 1 revolve around the sun gear 9 while rotating. At this time, the wafer W is supported by the work hole 11 of the carrier 1, and both sides are simultaneously polished by the upper and lower polishing cloths 5. In addition, the slurry is supplied from the nozzle 7 through the through hole 8 during polishing.

Next, a double-side polishing method of a wafer according to the present invention using the double-side polishing apparatus 1 described above will be described. FIG. 3 is a step diagram showing an example of a step of a double-side polishing method for a wafer of the present invention. As shown in FIG. 3, the carrier set prepared in step 1 and step 2 is prepared. In step 3, a plurality of carriers of the prepared carrier set are used to perform double-side polishing of the wafer. Each step is described in detail below.

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

Here, the shape measuring machine used for the shape measurement is not particularly limited, as long as a measurement data capable of calculating the amount of corrugation of the carrier can be appropriately obtained. For example, a three-dimensional coordinate measuring machine XYZAX-SVA equipped with a line laser sensor manufactured by Tokyo Precision Co., Ltd. can be used. When such a measuring machine is used, the sensor can be scanned so that the point cluster data on the entire carrier becomes 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 required shape accuracy and the like.

With such a measuring machine, the carrier shape can be measured with higher accuracy, and the amount of corrugation can be calculated more accurately. Furthermore, an appropriate carrier set can be selected from the range based on the accurate amount of corrugation for double-side polishing. Therefore, it is possible to more surely obtain a plurality of double-side polished wafers in which variations in flatness are suppressed. In addition, in the above-mentioned example, although the measuring machine which uses a sensor to scan a workpiece (carrier) in a stopped state is used, other examples include Nanometro FR manufactured by Kuroda Seiko Co., Ltd. and the like.

Next, the ripple of the carrier is obtained from the transformed point group data obtained by leveling the entire point group data of the carrier obtained above and removing noise components having a wavelength of 20 mm or less (0 mm or more). By performing such leveling and removal of noise components, it is possible to more appropriately calculate the amount of waviness of the carrier.

Regarding the amount of corrugation, for example, if the wafer diameter of double-side polishing is 300 mm, the arithmetic average roughness Sk obtained from the data within 175 mm from the center of the workpiece hole of the point group data can be used as the amount of corrugation of the carrier. It is possible to calculate the amount of corrugation by using data on the periphery of the workpiece hole which is likely to affect the flatness of the double-side polished wafer.

Here, although an example of a case where a 300-mm wafer having a common size is double-sided polished will be described here, the data extraction range can be appropriately set according to the wafer size. Furthermore, the specific amount of corrugation is not limited to the arithmetic average roughness Sk, and may be other parameters that can obtain a good correlation between the flatness of the obtained double-side polished wafer, for example.

(Step 2: Selection of a carrier set) Next, a carrier set which is actually used for double-side polishing is selected from a plurality of carrier sets having a corrugation amount calculated. More specifically, the difference (Range) between the maximum value and the minimum value of the ripple amounts of a plurality of carriers in the selected carrier set is a fixed value (managed value) or less. The specific value of this management value is not particularly limited. For example, the correlation between the management value and the flatness difference between the actual double-sided polished wafers, or the ratio of double-sided polished wafers that satisfy the flatness specification value can be investigated in advance. Decide.

As an example, when a wafer diameter of 300 mm is obtained by using the extraction method and calculation method of the measurement data as described above, the amount of corrugation can be adjusted to 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 of the carriers in the carrier set is 10 μm or less (0 μm or more). Accordingly, the flatness difference between the obtained double-sided polished wafers is small, and the flatness variation can be suppressed, and the desired double-sided polished wafer can be obtained at a high yield.

(Step 3: Arrangement of the carrier for double-side polishing and double-side polishing of the wafer) Next, a plurality of carriers of the selected carrier set are arranged in a double-side polishing apparatus, and the workpiece holes supported by each carrier are supported. Wafer grinding on both sides. As the slurry is supplied from the nozzle, the upper and lower platens are rotated to rotate and revolve the plurality of carriers, and the upper and lower polishing cloths simultaneously polish both sides of the plurality of wafers.

According to the double-sided polishing method of the wafer element of the present invention as described above, it is possible to suppress a difference in flatness between the double-sided polished wafers. Therefore, it is possible to prevent an increase in the ratio of the double-sided polished wafer whose flatness exceeds a predetermined value, and to improve the yield. In this way, it is possible to solve a problem that cannot be solved by only the conventional method of managing the thickness of the carrier. [Example]

Hereinafter, the present invention will be specifically described by showing examples and comparative examples, but the present invention is not limited to these. (Example 1) A plurality of carrier sets consisting of five carriers for double-side polishing, which were conventionally manufactured to have a uniform thickness, were prepared. In addition, it is a carrier for double-sided polishing of a wafer having a diameter of 300 mm.

In addition, as shown in step 1 of FIG. 3, the shape measurement and the calculation of the corrugation amount are 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 manufactured by Tokyo Precision Co., Ltd. and equipped with a line laser sensor was used. The laser width of the line laser was set to 24 mm (Fh mode), and a square area including a carrier with a side length of 540 mm was measured as a whole at a scanning speed of 20 mm / sec. 3.31 million points of carrier-related data were extracted from the above-mentioned measurement data. The whole point group is leveled and noise components with a wavelength of 20 mm or less are removed, and the arithmetic average rough Sk is further obtained from the extracted data within 175 mm from the center of the workpiece hole. An example of the data obtained by these successive procedures is shown in FIG. 4.

After the corrugation amount (Sk) of the five carriers in each carrier set is obtained as described above, as shown in step 2 of FIG. 3, the maximum and minimum corrugation amounts of the five carriers in each carrier set are calculated. The difference in value (Range) is compared with a preset management value (10 μm), and a carrier set below this management value is selected. Specifically, a carrier set (Set C) having a Range of 8.5 μm was selected.

In addition, as shown in step 3 of FIG. 3, five carriers of the selected carrier set are arranged in a double-side polishing apparatus to perform double-side polishing of the wafer. Various conditions for double-side polishing are as follows. The wafer uses a P-type single crystal silicon wafer with a diameter of 300 mm. For the polishing device, DSP-20B manufactured by Fuji-Etsu Machinery Co., Ltd. was used. As the polishing pad, a foamed polyurethane pad having a Shore A hardness of 90 was used. The carrier is a titanium substrate and glass fiber-impregnated FRP is used as an insert. As the slurry, a substance containing silica dioxide abrasive grains, an average particle diameter of 35 nm, an abrasive grain concentration of 1.0 wt%, a pH of 10.5, and KOH as a matrix was used.

The processing load was set to 150 gf / cm ² . The processing time is set so that the composition of each carrier sleeve becomes the most appropriate gap. The edge shape of the double-side polished wafer is determined by subtracting the carrier thickness from the completed thickness of the wafer (gap). According to the present invention, it is known that a carrier with a large amount of ripples exhibits good edge flatness when the gap is large. Therefore, the processing time in Example 1 and Example 2 and Comparative Examples 1 and 2 to be described later is set so that the composition of each carrier sleeve becomes the most appropriate gap.

The rotation speed of each drive unit is 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 is performed by causing a dressing disc with electrodeposited diamond abrasive particles to discharge pure water at a specified pressure while slidingly contacting the upper and lower polishing pads. SC-1 washing was performed under the conditions of NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 15. In a batch of 5 wafers, a total of 25 wafers in five batches are double-sided polished and cleaned.

The thus-obtained double-sided polished wafer was measured with WaferSight (manufactured by KLA Tencor). ESFQRmax was calculated from the measured data, and the yield to a prescribed value was obtained. In addition, when calculating ESFQRmax, set the area (also known as Polar Sites) in M49 mode to 30mm Length (2mm E.E.) of 72Sector.

(Example 2) Except when selecting a plurality of carrier sets initially prepared in Example 1, a carrier set (Set D) with a Range of 3.0 μm was selected, and the above-mentioned double-side polishing processing time was selected and implemented. Example 1 Double-sided polishing of the wafer was performed in the same manner, and then ESFQRmax was calculated to obtain a yield to a predetermined value.

(Comparative Examples 1, 2) From the plurality of carrier sets initially prepared in Example 1, randomly selected carriers (that is, different from those in Examples 1 and 2 without considering the relationship between Range and the management value (10 μm)), The set (Set A) and the carrier set (Set B) perform double-sided polishing of the wafer. The processing time for the double-side polishing is set so that the gap becomes the most appropriate for each. The other conditions of double-side polishing are the same as in Example 1. Then, ESFQRmax was calculated, and the yield to a predetermined value was calculated | required. In addition, when the ranges of the carrier set (Set A) and the carrier set (Set B) are calculated for comparison, they are 19.1 μm and 12.3 μm, respectively, which are larger than the management values (10 μm) in Examples 1 and 2.

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

【Table 1】

As shown in Table 1, in Examples 1 and 2 in which the present invention was implemented, the yields were 92% and 96%, respectively, significantly exceeding 72% and 84% of Comparative Examples 1 and 2. In this way, when a wafer is processed with a carrier set (Examples 1 and 2) that also manages corrugations and a conventional carrier set (Comparative Examples 1 and 2) that manages only the thickness, the yield of ESFQRmax is improved. . In Examples 1 and 2, by managing the range of the ripple amounts of the plurality of carriers in the carrier set and suppressing the value thereof, it is possible to suppress variations in the flatness of the obtained plurality of double-sided polished wafers. As a result, the ratio of the flatness exceeding a predetermined value can be reduced, and the yield can be improved.

In addition, the present invention is not limited by the foregoing embodiments. The foregoing embodiments are examples, and those having substantially the same configuration as the technical idea described in the patent application scope of the present invention and achieving the same effects are all included in the technical scope of the present invention.

1‧‧‧ Double-sided Carrier

2‧‧‧ Double-side grinding device

3‧‧‧ lower order

4‧‧‧ Upper Order

5‧‧‧ abrasive cloth

6‧‧‧ Mud supply mechanism

7‧‧‧ Nozzle

8‧‧‧through hole

9‧‧‧ sun gear

10‧‧‧ Internal gear

11‧‧‧Workpiece hole

12‧‧‧ Grinding liquid hole

W‧‧‧ Wafer

FIG. 1 is a vertical cross-sectional view showing an example of the double-side polishing apparatus of the present invention that can be used in the double-side polishing method of the wafer of the present invention. FIG. 2 is a diagram showing an internal structure of an example of a double-side polishing apparatus according to the present invention when viewed in a plane. FIG. 3 is a step diagram showing an example of a step of a double-side polishing method for a wafer of the present invention. FIG. 4 is a measurement diagram showing an example of measurement data in the shape measurement of a carrier.

Claims (5)

A method for double-side polishing of a wafer is provided in a double-side polishing device. A plurality of double-side polishing carriers are arranged between an upper platen and a lower platen to which a polishing cloth is attached, and the wafer is supported on the plate. A plurality of workpiece holes each formed by the double-sided polishing carrier are sandwiched between the upper and lower platens for double-sided grinding. Among them, a plurality of workpiece holes are prepared to be arranged between the upper and lower platen. In the case of a carrier set composed of two double-sided polishing carriers, the shape of the double-sided polishing carrier measured from a shape measuring machine is obtained from all the plurality of double-sided polishing carriers of the carrier set. The amount of corrugation calculated from the data is prepared by selecting a carrier set with a difference between the maximum value and the minimum value of the corrugation amount of the plurality of double-sided grinding carriers in the carrier set below a fixed value, and preparing the prepared The plurality of double-side polishing carriers are arranged in the double-side polishing device to grind the wafer on both sides. The method for double-sided polishing of a wafer according to claim 1, wherein in the calculation of the amount of corrugation, a three-dimensional coordinate measuring machine with a laser sensor is used as the shape measuring machine, and the double-sided grinding is measured from the measurement Calculate the amount of ripple using the entire point group data of the carrier. The double-side polishing method for a wafer according to claim 2, wherein in the calculation of the amount of corrugation, all the measured point group data are leveled, and noise components having a wavelength of 20 mm or less are removed. The obtained converted point group data was used to calculate the amount of waviness of the double-sided polishing carrier. The double-side polishing method for a wafer according to claim 3, wherein the diameter of the double-side polished wafer is set to 300 mm, and in the calculation of the amount of corrugation, the transformation point group data is extracted from the workpiece hole. The data within 175mm from the center of the lens, and the arithmetic average roughness Sk calculated from the extracted data is determined as the ripple amount. In the selection of the carrier set, the maximum value of Sk in the plurality of double-sided polishing carriers is determined. A carrier kit having a difference from the minimum value of 10 μm or less was selected. A double-side grinding device includes: an upper platen and a lower platen, attached with a polishing cloth; a mud supply device, which supplies mud between the upper platen and the lower platen; and a carrier set, which is provided with Between the upper platen and the lower platen, a plurality of double-sided grinding carriers are included, and each of the plurality of double-side grinding carriers is formed to support and be sandwiched between the upper platen and the lower platen during grinding. The difference between the maximum and minimum values of the arithmetic average roughness Sk of the plurality of double-sided polishing carriers in the carrier set is 10 μm or less, and the arithmetic average roughness Sk is corrugated. the amount.