JP2006128271A - Work holding plate, method of manufacturing semiconductor wafer and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a work holding plate by which a work such as semiconductor wafer or the like can be polished at high flatness and of which the service life is long. <P>SOLUTION: The work holding plate 1 is used to hold a work W when the work W is polished, and provided at least with a holding plate body 2 and a backing pad 4 adhered to the holding plate body. A groove 7 is formed on the side of the holding plate body to which the backing pad is adhered, and the backing pad is formed with a through hole 8 aligned with the position of the groove in the holding plate body. The face of the work opposite to a face to be polished is adhered to the backing pad, so that the work is held and polished. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to a workpiece holding plate, and more particularly to a workpiece holding plate that can be suitably used for polishing a semiconductor wafer that requires high flatness, and a semiconductor wafer manufacturing method and polishing method.

When manufacturing a semiconductor wafer such as a silicon wafer, an important process is a polishing process for improving the surface roughness of the wafer and increasing the flatness.
With the recent increase in device accuracy, semiconductor wafers used for device fabrication are required to be planarized with very high accuracy. In response to such demands, chemical mechanical polishing (CMP) is used as a technique for planarizing the surface of a semiconductor wafer.

In the case of performing chemical mechanical polishing, there is conventionally a method in which a surface opposite to a surface to be polished (surface to be polished) is attached to a glass plate or the like via an adhesive such as wax.
On the other hand, as one of the so-called wax-free polishing (also called waxless polishing) methods for holding and polishing a wafer without using an adhesive such as wax, a backing pad made of a soft resin foam sheet is provided. There is a method using a holding plate.

  For example, in the polishing apparatus 38 shown in FIG. 5, the holding plate 31 in which a backing pad 34 and a template 35 having a circular hole surrounding the wafer W are attached to a circular holding plate main body 32 made of ceramics or the like. Used, one side of the wafer W is held in close contact with the backing pad 34 through water. Then, the polishing slurry 33 is supplied to the polishing cloth 36 affixed to the rotating surface plate 37, and the surface to be polished of the wafer W is pressed against the polishing cloth 36 while rotating the surface plate 37 and the holding plate 31, respectively, and slidably contacted. Let Thereby, the to-be-polished surface of the wafer W can be finished into a mirror surface.

In such a wax-free polishing method, after the polishing, an operation of peeling the wafer W from a glass plate or the like is unnecessary, and there is no possibility that the wafer W is contaminated by an adhesive such as wax.
However, when the wafer W is polished using the backing pad, the central portion of the wafer W may become thin and the flatness may deteriorate.

6A to 6D schematically show the shape of the wafer when the wafer is polished by holding the wafer with a holding plate having a general backing pad.
In this holding plate 41, a backing pad 44 is attached to a ceramic plate 42 constituting the main body via a double-sided adhesive tape 43. A template 45 having a circular hole for accommodating and positioning the wafer W is provided on the side of the backing pad 44 that holds the wafer W.
The backing pad 44 has a foam structure, and bubbles (air) 47, water, and the like exist inside the pad 44 and between the wafer W and the pad 44 (FIG. 6A).

  When the wafer W is held by such a holding plate 41 and polishing is performed while supplying the polishing slurry 40 onto the polishing cloth 46, the temperature of the surface to be polished rises due to friction with the polishing cloth 46, and the polishing target is The shape of the wafer W changes due to the expansion on the surface side. As a result, air 47, water, and the like are confined in the vicinity of the center of the wafer between the backing pad 44 (FIG. 6B).

  Further, heat is transferred from the polished surface side to the held surface side, and the backing pad 44 functions as a heat insulating material to store heat. Then, the air 47a accumulated between the wafer W and the backing pad 44 expands due to heat, so that polishing is performed in a state where the vicinity of the center of the wafer W is further pushed down toward the polishing cloth (FIG. 6C )).

As a result, at the end of polishing, the wafer W is finished in a state where the central portion is thin, that is, in a concave shape (FIG. 6D).
Thus, when it grind | polishes using the conventional general backing pad, there exists a problem that the center part of a wafer becomes concave shape and flatness deteriorates.

  In order to prevent such deterioration of the flatness of the wafer, a backing pad 54 in which a large number of grooves 59 as shown in FIG. 7A are formed in a lattice shape has been proposed (see Patent Document 1). Then, as shown in FIG. 7B, if the holding plate 51 having the backing pad 54 as described above is used, the air 57 and water accumulated between the backing pad 54 and the wafer W are removed from the groove 59. The wafer W can be polished while escaping.

However, the backing pad 54 provided with a large number of grooves 59 has a problem that the groove 59 is likely to be deteriorated and has a short life, and when the groove 59 is deteriorated, it is difficult to discharge air and water. .
Further, when the wafer is polished using the holding plate 51 provided with the grooved backing pad 54, there is a problem that the groove pattern of the backing pad 54 is transferred to the wafer W and high flatness cannot be achieved.
Such a problem of flatness is the same when the interlayer insulating film such as a silicon oxide film formed on the surface of the semiconductor wafer is flattened by polishing in the device manufacturing process.

JP-A-9-201765

  In view of the above problems, it is a main object of the present invention to provide a workpiece holding plate that can polish a workpiece such as a semiconductor wafer with high flatness and has a long life.

  According to the present invention, a holding plate for holding the workpiece when polishing the workpiece, comprising at least the holding plate main body and a backing pad bonded to the holding plate main body, the holding plate main body A groove is provided on the side where the backing pad is bonded, and a through hole is provided in the backing pad in accordance with the position of the groove of the holding plate body. Provides a workpiece holding plate characterized in that polishing is performed by holding the workpiece by bringing the opposite surface into close contact with each other (Claim 1).

With such a workpiece holding plate, in addition to the air accumulated between the workpiece and the backing pad, water and polishing slurry are discharged to the outside of the holding plate through the through hole of the backing pad and the groove of the holding plate body. Will be able to. If the workpiece is held and polished by such a holding plate, the unevenness on the workpiece can be prevented from being transferred and finished to a high flatness workpiece.
Further, since the backing pad has only through-holes and no complicated irregularities such as grooves, it does not easily deteriorate and has a long life.

In this case, it is preferable that a template for positioning the workpiece is provided on the side of the backing pad that is in close contact with the workpiece.
If such a template is provided, it is possible to reliably prevent the workpiece from being displaced or lost during polishing and to perform stable polishing.

It is preferable that the through-holes are provided in the backing pad at intervals in the range of 10 to 15 mm (Claim 3), and the diameter of the through-holes of the backing pad is 0.5 to 1. It is preferable to be within a range of 5 mm.
If the backing pad is provided with the through-holes as described above, air and water etc. are surely discharged, and the unevenness based on the through-holes of the backing pad is reliably prevented from being transferred to the wafer during polishing. Will be able to. Moreover, if it is the above through-holes, deterioration of a backing pad can be prevented or suppressed reliably.

The groove width of the holding plate body is preferably in the range of 0.5 to 1.5 mm (Claim 5), and the groove depth of the holding plate body is 0.5 mm or more. (Claim 6).
If the groove as described above is provided in the holding plate main body, air and water can be reliably discharged, and the groove pattern can be reliably prevented from being transferred to the wafer during polishing. .

Furthermore, according to the present invention, there is provided a method for manufacturing a semiconductor wafer, wherein at least one of the workpiece holding plates is used, one side of the semiconductor wafer is held in close contact with the backing pad, and an abrasive is supplied to the polishing cloth. However, there is provided a method for manufacturing a semiconductor wafer, comprising a step of polishing the surface of the wafer to be polished by sliding it on the polishing cloth.
By polishing a semiconductor wafer using the work holding plate according to the present invention, it is possible to achieve the extremely high flatness by preventing the transfer of the concave shape and groove pattern in the central portion of the wafer, leading to an improvement in device yield. Semiconductor wafers can be manufactured.

Further, the present invention is a method for polishing a semiconductor wafer on which an interlayer insulating film is formed, using the work holding plate, holding one surface of the semiconductor wafer in close contact with the backing pad, and polishing it on a polishing cloth. There is also provided a method for polishing a semiconductor wafer, wherein an interlayer insulating film formed on the wafer is slidably contacted with the polishing cloth while supplying an agent.
That is, after an interlayer insulating film is formed on the surface of a wafer in a semiconductor device manufacturing process, CMP may be performed to planarize the surface. The present invention is also applicable to polishing a wafer in such a device process. An extremely high flatness can be achieved by using the workpiece holding plate.

In the work holding plate according to the present invention, a groove is provided in the holding plate main body, and a through hole is provided in the backing pad according to the position of the groove of the holding plate main body. If a workpiece such as a semiconductor wafer is held and polished by such a workpiece holding plate, air and water accumulated between the workpiece and the backing pad during polishing are removed from the through-holes of the backing pad and the holding plate body. In addition to being discharged to the outside of the holding plate through the groove, it is possible to finish the workpiece with high flatness without transferring the unevenness of the backing pad to the wafer.
Further, since the backing pad is not formed with complicated and large irregularities such as grooves, it is difficult to deteriorate and has a long life.

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings, but the present invention is not limited thereto.
Prior to the completion of the present invention, the present inventors investigated the flatness of the wafer when a silicon wafer was polished using a backing pad. As a result, when polishing a silicon wafer using a holding plate provided with a backing pad in which grooves are formed in a lattice shape, than when using a holding plate with a general backing pad in which no grooves are formed, The flatness of the wafer after polishing was improved.

  However, when the polished wafer was observed with a magic mirror (magic mirror image), it was found that the groove pattern was transferred as shown in FIG. As a cause thereof, it is considered that when air or the like between the backing pad and the wafer is eliminated, the wafer is polished in a state of being in close contact with the backing pad, and the unevenness of the groove pattern is transferred to the wafer.

  Therefore, the present inventors have conducted extensive research to effectively prevent the unevenness of the backing pad from being transferred, and as a result, provided a groove in the holding plate body, and the backing pad has a groove in the holding plate body. If polishing is performed by holding the wafer with a holding plate with through holes that match the position, air can be discharged through the through holes of the backing pad and the grooves of the holding plate body, and the unevenness of the backing pad can be transferred. The present invention was completed by finding that a silicon wafer having a very high flatness can be finished.

FIG. 1 shows an example of a work holding plate according to the present invention. The holding plate 1 includes a holding plate body 2 and a backing pad 4, and the backing pad 4 is bonded to the holding plate body 2 via a double-sided adhesive tape (PET) 3.
The holding plate main body 2 can be formed of a hard plate having high processing accuracy, such as ceramics and glass, and having high flatness. A groove 7 that is opened on the side surface of the main body 2 is formed on the side of the holding plate main body 2 on which the backing pad 4 is bonded so that air 9 and water can be removed outside the holding plate 1. ing.

The groove pattern is not particularly limited. For example, if the grooves are formed in a lattice shape so as to communicate with the outermost peripheral portion of the holding plate body, air and polishing slurry can be reliably discharged from the entire holding plate. However, a radial, spiral or random groove pattern may be used.
Although the cross-sectional shape of the groove 7 is not particularly limited, for example, if it is U-shaped, it is possible to effectively prevent clogging of the abrasive grains and the like into the groove 7.

The width of the groove 7 is preferably in the range of 0.5 to 1.5 mm, and particularly preferably about 1 mm. If the groove width is within the above range, it is possible to prevent clogging of the abrasive grains and polishing debris in the polishing slurry into the groove 7 and to reliably discharge air and polishing slurry. Transfer to the wafer W can be reliably prevented.
Moreover, although the depth of the groove | channel 7 is based on the cross-sectional shape and width | variety of a groove | channel, if it exists in the range of about 0.5 mm or more and about 5 mm, the air 9 and water etc. can be discharged | emitted reliably, and it is preferable.

On the other hand, the backing pad 4 can be made of a sheet-like elastic foam made of, for example, polyurethane foam. A through hole 8 is formed in the backing pad 4 in accordance with the corresponding position of the groove 7 of the holding plate body 2.
Since the through-hole 8 of the backing pad 4 is provided at a position corresponding to the groove 7 of the holding plate main body 2, the size and interval depends on the width and interval of the groove 7 of the holding plate main body 2. If a large through hole is formed, irregularities due to the through hole and other parts may be transferred to the wafer. On the other hand, if the through hole is too small, there is a possibility that the air 9 and water will not pass quickly. Therefore, the diameter of the through hole 8 is preferably in the range of 0.5 to 1.5 mm, particularly about 0.8 mm.

If the through-hole 8 as described above is formed in the backing pad 4, the contact area with the wafer W is much larger than when the groove is formed in the backing pad 4 itself. Therefore, even if polishing is performed with the wafer W in close contact with the backing pad 4, the influence on the wafer W due to the unevenness of the backing pad 4 can be effectively suppressed.
However, if the backing pad 4 has more through holes 8 than necessary, the unevenness of the backing pad 4 may be transferred to the wafer W. Further, when a large number of through holes 8 are formed, the interval between the grooves 7 of the holding plate main body 2 needs to be narrowed, but in that case, it is difficult to align the grooves of the main body and the through holes of the backing pad. is there. Therefore, it is preferable that the through-holes 8 are provided in the backing pad 4 at intervals in the range of 10 to 15 mm. The through holes 8 do not necessarily have to be provided along all the grooves of the holding plate main body 2 and may be appropriately provided in accordance with the grooves as long as bubbles and water can be effectively discharged. Since air, water, etc. are likely to accumulate in the center of the wafer, the through holes 8 of the pad 4 are, for example, relatively short intervals in the vicinity of the center of the wafer (for example, a region having a radius of 1/2), It may be provided as follows.

The method for producing the holding plate 1 according to the present invention is not particularly limited, but for example, it can be suitably produced by the following procedure.
First, a ceramic circular plate serving as a holding plate main body is prepared, and U-shaped, concave, etc. grooves are formed in a lattice shape on the side of the plate holding the wafer using a tool such as a diamond wheel.
Next, a backing pad is attached to the side where the grooves are formed via a double-sided pressure-sensitive adhesive tape, a double-sided pressure-sensitive adhesive sheet, an adhesive, or the like. Thereafter, as shown in FIG. 2, through holes are formed in the backing pad 4 at predetermined intervals using the pins 12 in accordance with the positions of the grooves 7 of the holding plate body 2.

Further, as shown in FIG. 1, a template 5 for positioning the wafer W can be provided on the holding plate 1 according to the present invention. The template 5 having the circular holes 11 corresponding to the size of the wafer W to be polished may be attached to a predetermined position via a double-sided adhesive tape or the like.
When the template is provided, the backing pad contacts the wafer only in the circular hole of the template. Therefore, after attaching the template to the backing pad, a through hole is formed in the portion located inside the circular hole. May be.
Further, the number of circular holes in the template is not limited to one, and a template having a plurality of circular holes can be provided according to the size of the holding plate main body, the size of the wafer to be polished, and the like.

When the semiconductor wafer is polished using the holding plate according to the present invention, the holding plate 1 is attached to a polishing apparatus 38 as shown in FIG.
As shown in FIG. 1, the surface opposite to the surface to be polished of the semiconductor wafer W is held in close contact with the backing pad 4, the holding plate 1 and the surface plate are rotated, and the polishing cloth 6 is coated with the abrasive 10. The surface to be polished of the wafer W is brought into sliding contact with the polishing pad 6 while supplying. During polishing, even if air or the like is present or generated between the backing pad 4 and the wafer W, it is quickly discharged to the outside of the holding plate 1 through the through hole 8 of the backing pad 4 and the groove 7 of the holding plate body 2. It will be.

Accordingly, when a silicon wafer is manufactured through the polishing process using the holding plate according to the present invention as described above, the central portion of the wafer is thinned by air and water accumulated between the backing pad and the wafer during polishing. It is possible to prevent finishing. Moreover, since the unevenness of the backing pad can be effectively suppressed, a semiconductor wafer with extremely high flatness can be manufactured.
Furthermore, since only the through-hole is formed in the soft backing pad, it does not easily deteriorate and has a long life. Further, in the conventional polishing apparatus, if only the holding plate is replaced with the holding plate of the present invention, it can be used continuously, which is advantageous in terms of cost.

Examples of the present invention and comparative examples will be described below.
A silicon single crystal having a diameter of 200 mm and an orientation <100> was pulled by the Czochralski method, and this was sliced to prepare five etching wafers of the same production lot.

U-shaped grooves having an opening width of 1 mm and a depth of 1 mm were formed in a lattice shape at intervals of 10 mm on a ceramic plate serving as a holding plate body.
In addition, a commercially available backing pad (1000 DM manufactured by Fujibow) was attached to the ceramic plate via a double-sided adhesive tape (material PET).
Further, a template having five circular holes was prepared so that five wafers could be held, and the template was attached to the side of the backing pad that holds the wafer.
As shown in FIG. 3, the main body is configured with respect to the backing pad inside the three circular holes 21, 23, 25 among the five circular holes 21, 22, 23, 24, 25 of the template 26. A through-hole (diameter 0.8 mm) 27 was formed by being stabbed with a pin so as to coincide with the position of the groove of the ceramic plate, and the intervals were 10 mm, 15 mm, and 20 mm, respectively.

  The five silicon wafers were held in each circular hole of the template by using the holding plate 20 produced in this way and polished. Polishing was performed in steps of primary, secondary, and finishing. In each step, an alkaline solution abrasive containing colloidal silica was used. As the polishing cloth, a hard polishing cloth was used in the primary and secondary polishing, a suede type polishing cloth was used in the final polishing, and the polishing allowance was about 10 μm in total.

After finishing polishing, the flatness of each wafer was measured. Wafer flatness is measured by GBIR (Global Back-Side Ideal Range), SFQR (Site Flatness Front Squares Range) (cell size 25 × 25 mm) of ADE flatness measuring device UltraGage9800 (excluding 3 mm from the wafer periphery). 12.5 × 12.5 mm).
The results are shown in FIG.

As shown in FIG. 4, wafers held by circular holes 21 and 23 having through holes formed in the backing pad at intervals of 10 mm or 15 mm are held by circular holes 22 and 24 having no through holes formed in the backing pad. Both GBIR and SFQR were as good as about one-half as compared to the wafer.
In addition, the wafer held by the circular holes 25 in which the through holes are formed in the backing pad at intervals of 20 mm is not as good as the cases of the intervals of 10 mm and 15 mm, but the SFQR is clearly improved as compared with the case without the through holes. The flatness was improved.

The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
For example, although the case where the semiconductor wafer is polished has been described in the above embodiment, the holding plate of the present invention can also be applied to polishing other workpieces that require high flatness, such as a quartz substrate. The holding plate of the present invention can also be applied to a case where an interlayer insulating film is formed on the surface of a semiconductor wafer in a device process and then the interlayer insulating film is polished to make the film thickness uniform.

It is the schematic which shows an example of the workpiece holding plate which concerns on this invention. It is explanatory drawing which shows an example of the method of making the through-hole of a backing pad. It is the schematic which shows the holding plate used in the Example. It is a figure which shows the measurement result of the flatness of the wafer after grinding | polishing in an Example. It is the schematic which shows an example of the single-side polish apparatus using a backing pad. It is explanatory drawing which showed typically the semiconductor wafer under grinding | polishing using the conventional holding plate. It is the schematic which shows the holding plate which formed the groove | channel in the backing pad. It is a figure of a magic mirror image which shows the groove pattern of the backing pad transcribe | transferred to the wafer after grinding | polishing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Holding plate, 2 ... Holding plate main body, 3 ... Double-sided adhesive tape, 4 ... Backing pad,
5 ... Template, 6 ... Polishing cloth, 7 ... Groove, 8 ... Through-hole, 9 ... Bubble (air),
10: Slurry.

Claims (8)

  A holding plate for holding the workpiece when polishing the workpiece, having at least a holding plate main body and a backing pad bonded to the holding plate main body, and the backing pad in the holding plate main body being bonded A groove is provided on the back side, and a through-hole is provided in the backing pad in accordance with the position of the groove of the holding plate body. A workpiece holding plate for polishing by holding the workpiece by bringing it into close contact.   2. The work holding plate according to claim 1, wherein a template for positioning the work is provided on a side of the backing pad that is in close contact with the work.   3. The work holding plate according to claim 1, wherein the through holes are provided in the backing pad at intervals within a range of 10 to 15 mm.   The diameter of the through-hole of the said backing pad exists in the range of 0.5-1.5 mm, The workpiece holding plate of any one of Claim 1 thru | or 3 characterized by the above-mentioned.   The work holding plate according to any one of claims 1 to 4, wherein a width of the groove of the holding plate main body is in a range of 0.5 to 1.5 mm.   The work holding plate according to any one of claims 1 to 5, wherein a depth of the groove of the holding plate main body is 0.5 mm or more.   A method of manufacturing a semiconductor wafer, wherein at least one workpiece holding plate according to any one of claims 1 to 6 is used, and one surface of the semiconductor wafer is held in close contact with the backing pad and polished. A method of manufacturing a semiconductor wafer, comprising a step of polishing a surface of the wafer to be brought into sliding contact with the polishing cloth while supplying an abrasive to the cloth.   A method for polishing a semiconductor wafer on which an interlayer insulating film is formed, wherein the work holding plate according to any one of claims 1 to 6 is used, and one surface of the semiconductor wafer is brought into close contact with the backing pad. A method for polishing a semiconductor wafer, comprising: polishing and holding the interlayer insulating film formed on the wafer in sliding contact with the polishing cloth while supplying the polishing agent to the polishing cloth.

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