JP2013094873A - Polishing cloth dressing method of double-sided polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing cloth dressing method of a double-sided polishing device capable of improving a degree of parallelism between the operating surface of an upper polishing cloth and that of a lower polishing cloth so that a high degree of the flatness of wafer after double-sided polishing can be achieved.SOLUTION: When dressing, by using a first dressing tool in a shape of a ring of a first dress plate, for instance, a portion out of the operating surface of the upper polishing cloth, that is, the outer periphery thereof that is raised from the central section thereof is mainly dressed. Simultaneously, by using a second dressing tool in a rectangular shape of a second dress plate, for example, a part out of the operating surface of the lower polishing cloth, that is, the central section thereof that is raised from the outer periphery thereof is mainly dressed. This improves the degree of parallelism between the operating surface of the upper polishing cloth and that of the lower polishing cloth as compared with the case that the conventional method of equivalent dressing has been applied so that the degree of the flatness of wafer after double-sided polishing can be enhanced.

Description

  The present invention relates to a polishing cloth dressing method for a double-side polishing apparatus, and more particularly, to a polishing cloth dressing method for a double-side polishing apparatus for dressing (sharpening) the surface of a polishing cloth whose polishing performance of the double-side polishing apparatus has deteriorated and enhancing the wafer polishing performance. .

  Conventionally, double-side polishing by a double-side polishing apparatus has been performed on a silicon wafer after etching in order to flatten the silicon wafer. As a general double-side polishing apparatus, a plurality of carrier plates holding a silicon wafer in a wafer holding hole are sandwiched between an upper surface plate and a lower surface plate in which a pair of upper and lower polishing cloths are attached to opposite surfaces, While supplying a polishing liquid containing loose abrasive grains to each silicon wafer in this state, the carrier plate rotates and revolves between the sun gear and the internal gear, and the upper surface plate and the lower surface plate are rotated. A sun gear type that simultaneously polishes both the front and back sides of a wafer is known.

By the way, if both sides of the silicon wafer are polished for a long time, the polishing surface of the upper polishing cloth (upper polishing cloth) attached to the upper surface plate and the lower polishing cloth (lower surface) attached to the lower surface plate Side polishing cloth) and the polishing action surface of each side wear unevenly. This is because the relative rotation trajectory (trajectory) of the silicon wafer with respect to the upper and lower surface plate surfaces varies depending on the polishing conditions, even if the polishing pressure acting on the upper and lower polishing cloths from the upper and lower surface plates is equal during double-side polishing of the wafer. This is because the change in the (thickness) shape of the polishing cloth is generally not uniform. As a result, the silicon wafer that was polished on both sides by the upper and lower polishing cloths that had been used many times was easily deformed.
Therefore, in order to solve this problem, dressing for repairing the shape (surface shape) of the polishing surface is periodically performed on the upper polishing cloth and the lower polishing cloth in a state of being adhered to the upper and lower surface plates.
For example, Patent Document 1 is known as a conventional technique for dressing a polishing cloth of a double-side polishing apparatus. In Patent Document 1, double-side polishing is performed so that a dressing member having the same shape on the front and back surfaces is accommodated in a wafer holding hole of a carrier plate, and then the dressing reflects the deformation of the upper and lower surface plates that occurs during double-side polishing of the wafer. In this method, the upper and lower polishing cloths are dressed by applying a thermal load or stress load substantially equal to the thermal load or stress load acting on the upper and lower surface plates. As a result, the temperature distribution of the upper and lower surface plates during dressing can be made closer to the temperature distribution during double-side polishing, and as a result, the upper and lower polishing cloths are put into a state suitable for performing double-side polishing of wafers with high flatness. It can be dressed at the same time.

Japanese Patent Laid-Open No. 2002-46058

In the conventional dressing method, as in Patent Document 1, the upper and lower polishing cloths are simultaneously dressed by sandwiching the above-mentioned dressing members having the same shape between the upper and lower polishing cloths attached to the upper and lower surface plates. It was. Therefore, the dressing amount (removal allowance distribution) for the polishing action surfaces of the upper and lower polishing cloths is substantially the same, and even if such an equal amount dressing is applied to the upper polishing cloth and the lower polishing cloth whose polishing action faces are greatly worn, It has been clarified by experiments of the present inventors that the flatness (global shape) of the wafer is not improved so much.
In other words, double-side polishing differs from final polishing (single-sided mirror polishing) that adjusts the fine surface roughness of the wafer surface, and requires a larger amount of polishing to increase the flatness of the entire wafer. The polishing pressure and the polishing amount on the wafer are large. In general, since the upper and lower surface plates are rotated in opposite directions in double-side polishing, the upper and lower polishing cloths are rotated in the same direction as the rotation direction of the carrier plate (rotation direction of the wafer) and in a different direction. A rotating force is acting. Therefore, as the number of times of double-side polishing increases, the wear amount distribution on the polishing surface of the upper and lower polishing cloths tends to differ. Specifically, the amount of wear at the outer periphery of the polishing surface of the upper polishing cloth is small, and the amount of wear at the center of the polishing surface of the upper polishing cloth tends to be concave. The amount of wear at the center of the surface tends to be convex as compared to the amount of polishing at the center of the polishing surface of the upper polishing cloth. Therefore, even if a general equal amount of dressing is applied to the polishing surfaces of the upper and lower polishing cloths, the flatness of the subsequent polishing surfaces is not so high.

  Therefore, as a result of intensive studies, the inventors focused on the shape of the dressing tool fixed to each dressing working surface of the dressing member for the upper polishing cloth and the dressing member for the lower polishing cloth. That is, the polishing action surfaces of the upper and lower polishing cloths affixed to the upper and lower surface plates do not necessarily need to be flattened. If both polishing action surfaces have parallelism (matching properties), We found that flatness increases. That is, even if the polishing surface of the upper polishing cloth has a curved shape with a recessed central portion, the shape of the polishing action surface of the lower polishing cloth is convex to match the shape of the polishing surface of the upper polishing cloth. The present inventors have found that the global flatness of the wafer after double-side polishing is increased if the curved shape is improved, and the present invention has been completed.

  The present invention provides a polishing cloth dressing method for a double-side polishing apparatus capable of increasing the parallelism between the polishing action surface of the upper polishing cloth and the polishing action surface of the lower polishing cloth, thereby increasing the flatness of the wafer after double-side polishing. The purpose is to do.

  According to the first aspect of the present invention, either the upper polishing cloth or the lower polishing cloth is dressed between the upper polishing cloth fixed to the upper surface plate and the lower polishing cloth fixed to the lower surface plate. A disc-shaped first dress plate and a disc-shaped second dress plate for dressing the remaining one of the upper polishing cloth and the lower polishing cloth are sandwiched, and in this state, the upper surface plate and A polishing cloth dressing method of a double-side polishing apparatus for simultaneously dressing the polishing action surface of the upper polishing cloth and the polishing action surface of the lower polishing cloth by rotating the lower surface plate in a predetermined direction, respectively, A ring-shaped first dressing tool is provided on the dressing working surface side of the first dress plate so that the dressing amount of the outer peripheral portion is larger than the dressing amount of the central portion of The dressing surface of the second dress plate has a rectangular shape extending in the diameter direction through the center point of the dressing surface so that the dressing amount at the center is larger than the dressing amount at the outer periphery of the polishing cloth. A polishing cloth dressing method of a double-side polishing apparatus, wherein a second dressing tool is provided, and the upper and lower polishing cloths are simultaneously dressed by the first dressing tool and the second dressing tool.

  According to a second aspect of the present invention, any one of the upper polishing cloth and the lower polishing cloth has a curved polishing action surface having a recessed central portion compared to the outer peripheral portion, and the upper polishing cloth The remaining other of the lower polishing cloths has a curved polishing action surface with a convex central portion compared to the outer peripheral portion, and a curved polished surface with a concave central portion compared to the outer peripheral portion. The working surface is dressed by the first dressing tool of the first dress plate so that the dressing amount of the outer peripheral portion is larger than that of the central portion, and the central portion is convex compared to the outer peripheral portion. The curved polishing action surface thus formed is dressed by the second dressing tool of the second dress plate so that the dressing amount at the center thereof is larger than that at the outer periphery thereof, whereby the upper polishing cloth Abrasive working surface of the The shape of the polishing working surface of the fabric, these abrasive action surface is abrasive cloth dressing method for double-side polishing apparatus according to claim 1, adjusted to be parallel.

  According to a third aspect of the present invention, the uneven wear of the double-side polishing apparatus causes the carrier plate holding the semiconductor wafer in the wafer holding hole to rotate and revolve between the sun gear and the internal gear, thereby providing a front and back surface of the semiconductor wafer. It is of a sun gear type that polishes both surfaces simultaneously, and the first dress plate and the second dress plate have the same diameter as the carrier plate, and external teeth that mesh with the sun gear and the internal gear are circumferential. The polishing cloth dressing method of the double-side polishing apparatus according to claim 1 or 2, wherein the polishing cloth dressing method is provided.

  According to a fourth aspect of the present invention, the dressing of the upper polishing cloth and the lower polishing cloth has the same diameter as that of the carrier plate, and a dress assist in which a dummy wafer having the same size as the semiconductor wafer is held in a wafer holding hole. 4. The polishing cloth dressing method for a double-side polishing apparatus according to claim 3, wherein the carrier plate is carried out in a state where external teeth provided on the outer periphery of the carrier plate are engaged with the sun gear and the internal gear.

  According to a fifth aspect of the present invention, a first opening penetrating the upper surface and the lower surface of the first dress plate is formed at a central portion of the first dress plate, and the second dress plate 2. The second opening that penetrates the upper and lower surfaces of the second dress plate is formed in a portion of the central portion excluding the formation portion of the second dressing tool. 4. A polishing cloth dressing method for a double-side polishing apparatus according to claim 1.

A double-side polishing device is a device that polishes both the front and back surfaces of a semiconductor wafer such as a silicon wafer at the same time. It uses a sun gear (planetary gear) type or a circular motion that does not rotate on the carrier plate, so that the front and back surfaces of the semiconductor wafer can be removed. A non-sun gear system that grinds at the same time can be employed. In particular, since the sun gear type double-side polishing apparatus tends to cause uneven wear of the upper and lower polishing cloths, it is effective to apply the dressing method according to the present invention.
The sun gear type double-side polishing apparatus polishes both the front and back surfaces of a semiconductor wafer simultaneously by rotating and revolving a carrier plate holding a semiconductor wafer in a wafer holding hole between a sun gear and an internal gear. The number of wafer holding holes formed in the carrier plate of the sun gear type double-side polishing apparatus is arbitrary. For example, one, two to five, or more may be used. The same applies to the carrier plate of the double-side polishing apparatus of the sun gear type.

As a non-sun gear type double-side polishing apparatus, for example, a lower surface plate in which a lower polishing cloth for polishing one surface of a semiconductor wafer is attached to an upper surface (surface plate surface), and a lower surface (fixed surface) are disposed directly above the lower surface plate. A carrier in which a plurality of wafer holding holes for a semiconductor wafer are formed between an upper surface plate having an upper polishing cloth adhered to the other surface of the semiconductor wafer and a lower surface plate and an upper surface plate. The front and back surfaces of a plurality of semiconductor wafers held in the wafer holding holes are moved between the upper polishing cloth and the lower plate by causing the carrier plate to perform a circular motion without rotation between the lower platen and the upper platen. A thing provided with the carrier circular motion mechanism grind | polished simultaneously with a polishing cloth can be employ | adopted.
Here, the circular motion without rotation refers to a circular motion in which the carrier plate always turns and swings (oscillates and rotates) while maintaining a state where the carrier plate is decentered by a predetermined distance from the axis of the upper and lower surface plates. By this circular motion without rotation, all points on the carrier plate draw a small circular locus having the same size (radius r). Since the sun gear does not exist like the planetary gear type double-side polishing apparatus of the sun gear type, it is suitable for a large diameter wafer having a diameter of 300 mm or more, for example.

The first dress plate and the second dress plate are made of a dressing tool made of pellets, flocks, scrapers, etc. on a dressing working surface of a circular substrate made of a metal such as stainless steel or a synthetic resin such as polyvinyl chloride. The dressing tool or the second dressing tool) is fixed. The first dressing tool and the second dressing tool may be made of the same material or different materials.
The direction of rotation of the upper and lower surface plates during dressing is not limited. Further, during dressing, the first dress plate and the second dress plate may or may not rotate.
For example, pure water can be used as the dressing liquid.

Here, the “ring shape” is an annular shape extending over the entire circumference of the outer peripheral portion of the polishing surface.
When the ring-shaped first dressing tool is used to dress the polishing surface of the polishing cloth (including a curved polishing surface with a concave center compared to the outer periphery), the center of the polishing surface is ground. However, the outer peripheral portion is more actively ground than the central portion.
As used herein, “extending in the diameter direction through the center point of the dressing action surface” means that the circular dressing action surface is moved along the one or more virtual straight lines passing through the center point of the dressing action surface. 2 means that the dressing tool is extended. In the case of one imaginary straight line, the circular dressing surface is divided into two (two divisions). The shape of the second dressing tool when there are two or more virtual straight lines includes a radial shape (for example, a cross shape) centered on the center point of the dressing working surface.
Here, the “rectangular shape” means a strip shape or a band shape having a uniform width over the entire length.
When using a rectangular second dressing tool and dressing the polishing surface of the polishing cloth (including a curved polishing surface with a convex center compared to the outer periphery), the outer periphery of the polishing surface However, the central part is more actively ground than the outer peripheral part.

  In particular, according to the present invention, any one of the upper polishing cloth and the lower polishing cloth has a curved polishing action surface with a recessed central portion as compared with the outer peripheral portion. The other has a curved polishing surface that is convex at the center compared to the outer periphery, and the curved polishing surface that is recessed at the center compared to the outer periphery. The curved polishing surface that is dressed by the first dressing tool of the first dress plate so that the dressing amount is larger than the central portion, and the central portion is convex compared to the outer peripheral portion, The dressing surface of the upper polishing cloth and the polishing action surface of the lower polishing cloth are dressed by the second dressing tool of the second dress plate so that the dressing amount at the center is larger than the outer peripheral part. And the shape of these polishing surfaces It is preferable adjusted to be parallel.

  “Adjusting the shape of these polishing surfaces so that these polishing surfaces are parallel” means that the polishing surface of the upper polishing cloth and the polishing surface of the lower polishing cloth are the same as in the past. By changing the dressing amount (rolling allowance distribution) of the polishing surface of the upper polishing cloth and the polishing surface of the lower polishing cloth (the global shape of the site) instead of applying the amount of dressing, both polishing surfaces Is to adjust the shape of both polishing surfaces so that they are parallel. Specifically, the polishing surface of the upper polishing cloth has a curved shape with a concave central portion (the outer peripheral portion is convex), and the polishing surface of the lower polishing cloth has a convex central portion. If it has a curved shape (the outer periphery is recessed), the polishing surface of the upper polishing cloth will eventually match the shape of the polishing surface of the lower polishing cloth with the shape of the polishing surface of the upper polishing cloth. Actively dressing so that the center part of the lower polishing cloth has a larger dressing amount than its outer peripheral part, while actively dressing so that the outer peripheral part has a larger dressing amount than its central part. Say.

  The present invention provides a dressing auxiliary carrier plate in which a dummy wafer having the same diameter as the carrier plate and the same size as the semiconductor wafer is held in the wafer holding hole when dressing each polishing working surface of the upper polishing cloth and the lower polishing cloth. It is desirable to engage with the sun gear and the internal gear. In this way, the first and second dresses are used during dressing by sandwiching not only the first dress plate and the second dress plate but also the dressing assisting carrier plate between the upper surface plate and the lower surface plate. Compared to the case where dressing is performed using only the plate, the pressure receiving area of the dressing pressure acting on the upper surface plate via the rotating shaft is expanded. Thereby, the inclination of the upper surface plate at the time of dressing caused by the small pressure receiving area can be prevented.

The dummy wafer may be made of the same material as the semiconductor wafer to be polished on both sides or may be made of a different material. The dummy wafer having the same thickness as that of the semiconductor wafer subjected to double-side polishing can better prevent the inclination of the upper surface plate during dressing described above.
The dressing assisting carrier plate may be made of the same material as the carrier plate used during polishing or may be made of a different material.

  In the present invention, a first opening penetrating the upper surface and the lower surface of the first dress plate is formed in the central portion of the first dress plate, and the second of the central portions of the second dress plate. It is desirable to form a second opening penetrating the upper and lower surfaces of the second dress plate in a portion other than the dressing tool forming portion. With this configuration, dress waste generated during dressing is discharged out of the first dress plate through the first opening, or discharged out of the second dress plate through the second opening. The Thereby, the dress scraps of the upper and lower polishing cloths can be smoothly discharged out of the double-side polishing apparatus, and the dressing liquid can be supplied to the first and second dress plates without any trouble.

Examples of the dressing scraps of the upper polishing cloth and the lower polishing cloth include grinding scraps generated when the upper and lower polishing cloths are dressed by the corresponding dressing tools, and dressing materials dropped from the dressing tools.
The shapes of the first opening and the second opening are not limited. For example, in addition to a semicircular shape, a circular shape, and an elliptical shape, a triangular shape or a polygonal shape that is equal to or more than a quadrangle can be employed. Moreover, the magnitude | size and formation number of a 1st opening part and a 2nd opening part are not limited.
For example, pure water can be used as the dressing liquid.
The dressing amount on both polishing surfaces of the upper and lower polishing cloths at the time of dressing is 5 to 50 μm on one side (10 to 100 μm on both sides). A particularly preferred dressing amount is 10 to 30 μm on one side (20 to 60 μm on both sides).
The surface pressure with respect to the first dress plate and the second dress plate at the time of dressing is, for example, 10 to 150 g / cm ² . If the surface pressure is less than 10 g / cm ² , the surface pressure may be too low to dress the polishing cloth itself. Conversely, if the surface pressure is too high (over 150 g / cm ² ), such as scratches caused by dress debris, etc. There is a risk of occurrence. A particularly preferable surface pressure is 20 to 100 g / cm ² .

According to the first to fifth aspects of the present invention, when both the upper and lower polishing cloths are simultaneously dressed using the double-side polishing apparatus, either the upper polishing cloth or the lower polishing cloth is included. For example, the first dressing tool formed on the dressing working surface is dressed by the first dressing tool on the curved polishing working surface having a concave central portion compared to the outer peripheral portion. At that time, since the first dressing tool has a ring shape, the outer peripheral portion of the polishing surface is positively ground, and the dressing amount of the outer peripheral portion becomes larger than the dressing amount of the central portion.
Further, a curved polishing action surface having a convex central portion compared to the outer peripheral portion of either the upper polishing cloth or the lower polishing cloth, for example, the second dressing tool is a dressing action surface. Dressing with a second dressing plate formed in At this time, since the second dressing tool has a rectangular shape extending in the diameter direction of the dressing operation surface, the center portion of the polishing operation surface is actively ground, and the dressing amount of this center portion is the outer periphery. It becomes larger than the dressing amount of the part.

  Even if the polishing action surfaces of the upper and lower polishing cloths are not flattened, the flatness of the wafer after double-side polishing can be improved if both polishing action surfaces have parallelism (matching properties). Therefore, by using the ring-shaped first dressing tool and the rectangular second dressing tool, as described above, by applying dressing to the corresponding polishing action surface, the polishing action surface of the upper polishing cloth and The parallelism with the polishing action surface of the lower polishing cloth is increased, and as a result, the flatness of the wafer after double-side polishing can be increased.

  According to the invention described in claim 3, since the sun gear type is adopted as the double-side polishing apparatus, uneven wear of the upper and lower polishing cloths is likely to occur, and the application of the dressing method according to the present invention is effective.

  Furthermore, according to the invention of claim 4, for dressing, not only the first dress plate and the second dress plate but also a dummy wafer is held between the upper surface plate and the lower surface plate. Insert the carrier plate. Thereby, compared with the case where it dresses only by the 1st and 2nd dress plate, the pressure receiving area of the dressing pressure which acts on an upper surface plate via a rotating shaft increases. As a result, it is possible to prevent the upper surface plate from tilting during dressing due to the small pressure receiving area.

Furthermore, according to the invention described in claim 5, the first opening is formed in the central portion of the first dress plate, and the second dressing tool of the second dress plate is out of the central portion of the second dress plate. Since the second opening is formed in the portion excluding the formation portion, dressing waste generated during dressing is discharged out of the first dress plate through the first opening and through the second opening. It is discharged out of the second dress plate. Thereby, the dress waste of the upper and lower polishing cloths can be smoothly discharged out of the double-side polishing apparatus, and the supply of the dressing liquid to the dressing working surfaces of the first and second dress plates can be performed without any trouble. be able to.
In particular, when a pair of second openings are formed on both sides of one second dressing tool, compared to a case where a plurality of second dressing tools are formed, the opening is made with respect to the second dressing plate. The second opening having a large area can be secured, the penetration of the dressing liquid into the second dress plate is enhanced, and the generation of scratches on the second dress plate due to dress waste can be reduced.

It is a top view which shows the whole structure of the double-side polish apparatus used with the polishing cloth dressing method of the double-side polish apparatus which concerns on Example 1 of this invention. It is a longitudinal cross-sectional view which shows the polishing cloth dressing method of the double-side polish apparatus which concerns on Example 1 of this invention. It is a top view of the 1st dress plate used with the polishing cloth dressing method of the double-side polish apparatus concerning Example 1 of this invention. It is a bottom view of the 2nd dress plate used with the polishing cloth dressing method of the double-side polish apparatus concerning Example 1 of this invention. 3 is a graph showing the thickness distribution of the upper polishing cloth before dressing in Example 1. FIG. 3 is a graph showing the thickness distribution of the upper polishing cloth after dressing in Example 1. FIG. 3 is a graph showing the thickness distribution of the lower polishing cloth before dressing in Example 1. FIG. 3 is a graph showing a thickness distribution of a lower polishing cloth after dressing in Example 1. FIG. It is a top view which shows the whole structure of the double-side polish apparatus used by the conventional method. It is a graph which shows the thickness distribution of the upper and lower polishing cloth before dressing in the conventional method. It is a graph which shows the thickness distribution of the upper and lower polishing cloth after dressing in the conventional method. It is a graph which shows the flatness of the silicon wafer which carried out double-side polishing using the upper and lower polishing cloth before dressing in Example 1. FIG. 4 is a graph showing the flatness of a silicon wafer that has been double-side polished using upper and lower polishing cloths after dressing in Example 1. FIG. It is a graph which shows the flatness of the silicon wafer which carried out double-side polishing using the upper and lower polishing cloth before the dressing in the conventional method. It is a graph which shows the flatness of the silicon wafer which carried out double-side polishing using the upper and lower polishing cloth after the dressing in the conventional method.

  Examples of the present invention will be specifically described below.

1 and 2, reference numeral 10 denotes a double-side polishing apparatus (hereinafter referred to as double-side polishing apparatus) to which the polishing cloth dressing method of the double-side polishing apparatus according to the first embodiment is applied. First, the double-side polishing apparatus will be described in detail.
The double-side polishing apparatus 10 is of a sun gear (planetary gear) type that can simultaneously polish the front and back surfaces of five silicon wafers (semiconductor wafers) W. Specifically, the double-side polishing apparatus 10 includes an upper surface plate 11 and a lower surface plate 12 provided in parallel, an upper polishing cloth 13 attached to the lower surface of the upper surface plate 11, and an upper surface of the lower surface plate 12. The attached lower polishing cloth 14, the small-diameter sun gear 15 provided at the center of the lower surface plate 12, the large-diameter internal gear 16 provided rotatably around the sun gear 15, and five circles A plate-shaped carrier plate 17 is provided.

Each carrier plate 17 has a diameter of 510 mm, a thickness of 0.75 μm, and is made of epoxy glass. Each carrier plate 17 is formed with one wafer holding hole 17a for holding a silicon wafer W having a diameter of 300 mm and a thickness of 0.8 μm in the central portion. A sun gear 15 and an internal gear are formed on the outer peripheral portion of the carrier plate 17. The external teeth 17 b that mesh with the external gear 16 are formed. Further, as the upper polishing cloth 13 and the lower polishing cloth 14, MHS15A (Asker hardness 85 °, density 0.53 g / cm ³ , compression ratio 3.0%, diameter 1340 mm, thickness 1000 μm, manufactured by Nitta Haas, Inc. Foamed urethane foam) is used.

In the double-side polishing of the wafer by the double-side polishing apparatus 10, the five carrier plates 17 holding the silicon wafer W in the wafer holding holes 17a are sandwiched between the upper surface plate 11 and the lower surface plate 12, and a polishing liquid containing free abrasive grains is supplied. However, these carrier plates 17 are rotated and revolved between the sun gear 15 and the internal gear 16, and the front and back surfaces of the silicon wafers W are simultaneously polished. At this time, the sun gear 15 and the internal gear 16 are rotating in directions opposite to each other.
By performing double-side polishing for a long time, uneven wear occurs on each polishing working surface of the upper polishing cloth 13 and the lower polishing cloth 14, and the silicon wafer W after double-side polishing is deformed. Here, like the knitting wear that occurs during general double-side polishing, the polishing surface of the upper polishing cloth 13 has a curved shape with a recessed central portion compared to the outer periphery, and the polishing surface of the lower polishing cloth 14 has an outer periphery. It has a curved shape with a convex center part compared to the part. Note that the curvature of the polishing surface of the lower polishing cloth 14 is larger than the curvature of the polishing surface of the upper polishing cloth 13.
Therefore, for the purpose of reducing wafer deformation due to uneven wear, the double-side polishing apparatus 10 is used to periodically polish the first dress plate 18 for dressing the polishing surface of the upper polishing cloth 13 and the polishing action of the lower polishing cloth 14. Dressing for repairing the shape (surface shape) of each polishing action surface of the upper and lower polishing cloths 13 and 14 by the second dress plate 19 for dressing the surface is performed.

The first dress plate 18 used here has a ring-shaped first dressing tool 20 fixed to the entire periphery of the plate outer peripheral portion on the dressing working surface (upper surface) of the outer peripheral portion, and at the center of the plate. A circular first opening 21 penetrating the upper surface and the lower surface is formed (FIG. 3).
In addition, the second dress plate 19 has a dressing action surface (lower surface) fixed with one second dress tool 23 having a rectangular shape (strip shape) extending in the diameter direction of the second dress plate 19. Yes (Fig. 4). A second opening having a substantially semicircular shape penetrating the upper surface and the lower surface of the second dress plate 19 is formed in the central portion of the second dress plate 19 except for the formation portion of the second dress tool 23. A pair of portions 24 are formed.

The first dress plate 18 and the second dress plate 19 have a circular substrate 25 made of stainless steel (SUS) as a main body. As a result, the rigidity of the dress plates 18 and 19 can be ensured and the electrodeposition of the dress material made of alumina, diamond or the like used for the first dress tool 20 and the second dress tool 23 to the substrate 25 is possible. It becomes. The outer diameter of the substrate 25 is the same as that of the carrier plate 17, and outer teeth 25 a that mesh with the sun gear 15 and the internal gear 16 are formed on the outer periphery of the substrate 25.
In particular, the second dress plate 19 has a lower surface (dressing) of the rectangular region of the substrate 25 in which the annular portion and the rectangular portion are integrated so that the weather symbol has a clear shape (a crest shape drawn in a circle). A diamond having an average particle diameter of 20 to 80 μm is electrodeposited on the working surface. Also in the case of the first dress plate 18, the average particle diameter of diamond electrodeposited on the upper surface (dressing action surface) of the outer peripheral portion of the substrate 25 is 20 to 80 μm.

  Further, at the time of dressing, not only the two carrier plates 17 of the double-side polishing apparatus 10 are replaced with the first dress plate 18 and the second dress plate 19, but also the remaining three carrier plates 17 are replaced with dress assisting carriers. Instead of the plate 26. The dressing auxiliary carrier plate 26 is a thin plate made of epoxy glass having the same size and shape as the carrier plate 17, and the dummy wafer W <b> 1 is held in one wafer holding hole 26 a formed in the center portion, External teeth 26b are formed in the portion. The dummy wafer W1 is a pseudo wafer having the same diameter and the same thickness as the silicon wafer W.

Next, with reference to FIGS. 1-8, the polishing cloth dressing method of the double-side polish apparatus based on Example 1 of this invention using this double-side polish apparatus 10 is demonstrated.
As shown in FIGS. 1 and 2, when simultaneously dressing the upper polishing cloth 13 and the lower polishing cloth 14, first, of the five carrier plates 17 arranged in the double-side polishing apparatus 10, the upper carrier cloth 17 is arranged on the upper side in FIG. 1. 3 is replaced with the first dressing plate 18 with the dressing working surface shown in FIG. 3 facing upward, and the dressing working surface shown in FIG. The remaining three carrier plates 17 are replaced with the dress assisting carrier plate 26 in which the dummy wafer W1 shown in FIG. 1 is held in the wafer holding hole 26a.

  Thereafter, the upper surface plate 11 is gradually lowered in this state, and the first and second dresses between the upper polishing cloth 13 fixed to the upper surface plate 11 and the lower polishing cloth 14 fixed to the lower surface plate 12. The plates 18 and 19 and the three dress assisting carrier plates 26 are sandwiched (FIGS. 1 and 2). Next, the upper surface plate 11 and the lower surface plate 12 are rotated in opposite directions while supplying a dressing solution made of pure water at 5 to 10 liters / minute, and between the sun gear 15 and the internal gear 16. The first and second dress plates 18 and 19 and the dress assisting carrier plates 26 are rotated and revolved at a predetermined speed, respectively, so that both polishing working surfaces of the upper polishing cloth 13 and the lower polishing cloth 14 are changed to the first and second polishing cloth surfaces. Dressing is simultaneously performed by the second dress plates 18 and 19 (FIGS. 1 and 2).

  At this time, the ring-shaped first dressing tool 20 formed on the dressing working surface of the outer peripheral portion of the first dress plate 18 is compared with the polishing working surface of the upper polishing cloth 13, particularly the central portion of the polishing working surface. The raised outer periphery is actively ground (dressed) (region A in FIG. 6). On the other hand, the rectangular second dressing tool 23 formed on the dressing working surface of the second dress plate 19 causes the polishing working surface of the lower polishing cloth 14, in particular, the central portion that is raised compared to the outer peripheral portion of the polishing working surface. It is actively ground (region B in FIG. 8). Accordingly, the parallelism between the polishing action surface of the upper polishing cloth 13 and the polishing action surface of the lower polishing cloth 14 is estimated from the comparison of the graphs of FIG. 5 and FIG. It is raised to a state estimated by comparison with the graph of 8. 5 to 8, the vertical axis represents the thickness of the polishing cloth, and the horizontal axis of the graph represents the position in the diameter direction of the polishing cloth, and the position closer to the outer periphery of the polishing cloth as it goes to the right. Indicates.

  By the way, if the polishing action surface of the upper polishing cloth 13 and the polishing action face of the lower polishing cloth 14 are not flattened, the flatness of the wafer after double-side polishing can be obtained if both polishing action surfaces have parallelism (matching). Will rise. Therefore, as described above, the ring-shaped first dressing tool 20 and the rectangular second dressing tool 23 are used, and dressing is performed on both polishing working surfaces of the upper and lower polishing cloths 13 and 14, and the upper polishing cloth is used. By increasing the parallelism between the polishing surface 13 and the polishing surface 14 of the lower polishing cloth 14, the flatness of the silicon wafer W after double-side polishing can be increased.

Further, at the time of dressing, not only the first and second dress plates 18 and 19 but also the dress assisting carrier plate 26 holding the dummy wafer W1 between the upper surface plate 11 and the lower surface plate 12 as described above. It is sandwiched. Therefore, as compared with the case where dressing is performed only by the first and second dress plates 18 and 19, the pressure receiving area of the dressing pressure acting on the upper surface plate 11 from the rotating shaft increases. Thereby, the inclination of the upper surface plate 11 at the time of dressing which arises because the pressure receiving area is small can be prevented.
Furthermore, the dress waste of the upper polishing cloth 13 generated during dressing can be discharged out of the first dress plate 18 through the first opening 21 formed at the center of the first dress plate 18. it can. Further, the dressing scraps of the lower polishing cloth 14 generated during dressing pass outside the second dress plate 19 through a pair of second openings 24 formed on both side portions of the center portion of the second dress plate 19. Can be discharged. Thereby, the dress waste of the upper and lower polishing cloths 13 and 14 can be smoothly discharged out of the double-side polishing apparatus without damaging the silicon wafer W by the dress waste during polishing. In addition, the dressing liquid can be supplied to the first and second dress plates 18 and 19 without any trouble. In particular, since the second opening 24 having a substantially half-moon shape is formed on both sides of the second dressing tool 23 having a rectangular shape, the dressing liquid can enter the dressing working surface more effectively and the dress waste can be discharged more effectively. Rise.

Here, referring to FIG. 9 to FIG. 15, the upper and lower polishing cloths dressed by the polishing cloth dressing method of the double side polishing apparatus according to the present invention method and the conventional method are used, and the front and back surfaces are simultaneously polished. We will report the results of wafer flatness comparison.
In the method of the present invention, the double-side polishing apparatus 10 of Example 1 was used, and upper and lower polishing cloths were simultaneously dressed under the same conditions as in Example 1. Further, in the conventional method, as shown in FIG. 9, the double-side polishing apparatus 10 was used in the same manner as in Example 1, and the upper and lower polishing cloths were simultaneously dressed according to the dressing conditions in accordance with Example 1. However, instead of the second dress plate 19, another second dress plate 19A was adopted. Another second dress plate 19A is one in which a ring-shaped first dressing tool 20 is formed on the dressing working surface (lower surface) and a circular first opening 21 is formed in the center of the plate. However, it is the same as the first dress plate 18 whose upper and lower surfaces are inverted.

  The results of dressing the upper and lower polishing cloths 13 and 14 in accordance with the conventional method are shown in FIGS. The thickness distribution of the lower polishing cloth 14 is a distribution in the diameter direction when the thickness of the outer peripheral portion of the lower polishing cloth 14 is 0, and the thickness distribution of the upper polishing cloth 13 is the outer peripheral portion of the upper polishing cloth 13. This shows the distribution in the diameter direction when the thickness is 20 μm. As is clear from the comparison between the graph of FIG. 10 and the graph of FIG. 11, the parallelism between the polishing surface of the upper polishing cloth 13 and the polishing surface of the lower polishing cloth 14 did not improve much before and after dressing. . This is considered to be because the first and second dress plates 18 and 19 having the ring-shaped first dress tool 20 formed on the dressing operation surface are adopted. That is, in the dressing using the dressing tool having the same shape, the dressing amount (removal allowance distribution) with respect to the polishing action surfaces of the upper and lower polishing cloths 13 and 14 is substantially equal. Even if such an equal amount of dressing is applied to the polishing surfaces of the upper and lower polishing cloths 13 and 14 whose uneven wear has increased by long-time polishing, the polishing surface and the lower polishing cloth of the upper polishing cloth 13 after dressing. The parallelism with the 14 polishing surface is not significantly improved.

Next, when the upper and lower polishing cloths 13 and 14 dressed according to the method of the present invention are used, the silicon wafer W is polished on both sides, and when the upper and lower polishing cloths 13 and 14 dressed according to the conventional method are used. The wafer flatness was compared with the case where the silicon wafer W was polished on both sides (the graph of FIG. 14 and the graph of FIG. 15).
In the method of the present invention, the flatness of the silicon wafer W when double-side polishing was performed under the conditions of Example 1 using the polishing cloths 13 and 14 before dressing was GBIR; 0.36 μm (concave), SFQD P Ave; It was 37 nm (graph in FIG. 12). The flatness of the silicon wafer W when the double-side polishing was performed with the polishing cloths 13 and 14 after dressing under the conditions of Example 1 was GBIR; 0.20 μm (convex), and SFQD P Ave; −25 nm. (Graph of FIG. 13), the wafer flatness was clearly improved.

  On the other hand, in the conventional method, the flatness of the silicon wafer W when double-side polishing was performed using the polishing cloths 13 and 14 before dressing under the conditions of Example 1 was GBIR: 0.56 μm (concave), SFQD P Ave; It was -45 nm (graph of FIG. 14). Further, the flatness of the silicon wafer W when double-side polishing was performed with the polishing cloths 13 and 14 after dressing under the conditions of Example 1 was GBIR; 0.53 μm (concave), SFQD P Ave; −53 nm. (Graph of FIG. 15) The wafer flatness was not improved so much.

  The present invention is useful as a technique for dressing the surface of a polishing cloth in which the polishing performance of the double-side polishing apparatus has deteriorated and enhancing the wafer polishing performance.

10 Double-side polishing equipment,
11 Upper surface plate,
12 Lower surface plate,
13 Top polishing cloth,
14 Lower polishing cloth,
15 Sungear,
16 Internal gear,
17 carrier plate,
18 First dress plate,
19 Second dress plate,
20 first dressing tool,
21 first opening,
23 Second dress tool,
24 second opening,
26 Dressing support carrier plate,
26a Wafer holding hole,
W Silicon wafer (semiconductor wafer),
W1 Dummy wafer.

Claims (5)

A disk-shaped first dress plate for dressing either the upper polishing cloth or the lower polishing cloth between an upper polishing cloth fixed to the upper surface plate and a lower polishing cloth fixed to the lower surface plate And a disk-shaped second dress plate for dressing the remaining one of the upper polishing cloth and the lower polishing cloth, and in this state, the upper surface plate and the lower surface plate are respectively rotated in predetermined directions. A polishing cloth dressing method of a double-side polishing apparatus for simultaneously dressing the polishing action surface of the upper polishing cloth and the polishing action surface of the lower polishing cloth,
A ring-shaped first dressing tool is provided on the dressing working surface side of the first dress plate so that the dressing amount of the outer peripheral portion is larger than the dressing amount of the center portion of the polishing cloth.
A rectangular shape extending in the diametrical direction through the center point of the dressing working surface on the dressing working surface side of the second dress plate so that the dressing amount of the central portion is larger than the dressing amount of the outer peripheral portion of the polishing cloth. A second dressing tool is provided,
A polishing cloth dressing method of a double-side polishing apparatus for simultaneously dressing the upper and lower polishing cloths with the first dress tool and the second dress tool. Either one of the upper polishing cloth and the lower polishing cloth has a curved polishing action surface with a central portion recessed relative to the outer peripheral portion, and the remaining of the upper polishing cloth and the lower polishing cloth The other has a curved polishing surface with a convex central portion compared to the outer peripheral portion,
The curved polishing surface having a concave central portion compared to the outer peripheral portion is formed by the first dressing tool of the first dress plate so that the dressing amount of the outer peripheral portion is larger than the central portion. The curved polishing action surface that is dressed and has a convex central portion as compared with the outer peripheral portion has the second dress plate so that the dressing amount in the central portion is larger than that in the outer peripheral portion. By dressing with a second dressing tool, the shape of the polishing action surface of the upper polishing cloth and the polishing action surface of the lower polishing cloth are adjusted so that these polishing action surfaces are parallel to each other. The polishing cloth dressing method of the double-side polishing apparatus as described. The double-side polishing apparatus is a sun gear type that simultaneously polishes both the front and back surfaces of the semiconductor wafer by rotating and revolving the carrier plate holding the semiconductor wafer in the wafer holding hole between the sun gear and the internal gear.
The first dress plate and the second dress plate have the same diameter as the carrier plate, and are provided with external teeth that mesh with the sun gear and the internal gear. Item 3. A polishing cloth dressing method for a double-side polishing apparatus according to Item 2.   The dressing of the upper polishing cloth and the lower polishing cloth includes a dressing auxiliary carrier plate having the same diameter as the carrier plate and a dummy wafer having the same size as the semiconductor wafer held in a wafer holding hole on the outer periphery thereof. 4. The polishing cloth dressing method for a double-side polishing apparatus according to claim 3, wherein the outer peripheral teeth are engaged with the sun gear and the internal gear. A first opening penetrating the upper and lower surfaces of the first dress plate is formed at the center of the first dress plate,
A second opening penetrating the upper and lower surfaces of the second dress plate is formed in a portion of the central portion of the second dress plate except for a portion where the second dress tool is formed. The polishing cloth dressing method of the double-side polishing apparatus according to any one of claims 1 to 4.

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