WO2013001719A1 - Polishing head and polishing apparatus - Google Patents

Abstract

The present invention is a polishing head which is provided with at least: an annular rigid ring; a rubber film that is bonded to the rigid ring at a uniform tension; a back plate that is joined to the rigid ring so as to form a space together with the rubber film and the rigid ring; and an annular template that is arranged concentrically with the rigid ring in the periphery of the lower surface portion of the rubber film and holds an edge portion of a workpiece. The polishing head polishes the front surface of the workpiece by holding the back surface of the workpiece in the lower surface portion of the rubber film and bringing the front surface of the workpiece in slide contact with a polishing cloth that is bonded to a polishing plate. The polishing head is characterized by additionally comprising a non-compressible fluid that is sealed in the above-described space. Consequently, final polishing of a workpiece can be performed and the entire of the workpiece can be uniformly polished regardless of the thickness of a template by a polishing head that holds the back surface of the workpiece at a rubber film, while holding the edge portion of the workpiece with the template. The present invention also provides a polishing apparatus.

Description

Polishing head and polishing apparatus

The present invention relates to a polishing head for holding a workpiece when polishing the surface of the workpiece, and a polishing apparatus including the same, and more particularly, to a polishing head for holding a workpiece on a rubber film and a polishing apparatus including the polishing head. .

With the recent high integration of semiconductor devices, the demand for flatness of semiconductor wafers used therein has become increasingly severe. In addition, flatness up to a region near the edge of the wafer is required to increase the yield of semiconductor chips.
The shape of the semiconductor wafer is determined by the final mirror polishing process. In particular, for silicon wafers with a diameter of 300 mm, primary polishing is performed by double-sided polishing in order to satisfy strict flatness specifications, and then surface secondary and final polishing on one side is performed to improve surface scratches and surface roughness. Is going.

In the single-surface secondary and finish polishing, it is required to maintain or improve the flatness created by the double-side primary polishing and finish the surface to a perfect mirror surface free from defects such as scratches.
For example, as shown in FIG. 10, a general single-side polishing apparatus includes a surface plate 103 to which a polishing cloth 102 is attached, an abrasive supply mechanism 104, a polishing head 101, and the like. In such a polishing apparatus 110, the workpiece W is held by the polishing head 101, the polishing agent 105 is supplied from the polishing agent supply mechanism 104 onto the polishing cloth 102, and the surface plate 103 and the polishing head 101 are rotated to rotate the workpiece. Polishing is performed by bringing the surface of W into sliding contact with the polishing pad 102.

As a method of holding the work on the polishing head, there is a method of attaching the work to a flat work holding board via an adhesive such as wax. Further, as shown in FIG. 11, a template assembly 113 that is commercially available with a template 113b for preventing workpiece popping out adhered to an elastic film called a backing film 113a is attached to a workpiece holding board 112 to hold the workpiece W. There is a waxless type polishing head 121 or the like.

As another waxless type polishing head, as shown in FIG. 12, a backing film 113a is pasted on the surface of the work holding plate 112 instead of a commercially available template, and an annular guide for preventing the workpiece from jumping out on the side of the work holding plate. A polishing head 131 provided with a ring 113b is also used.
The work holding plate 112 is generally made of a highly flat ceramic plate. However, due to uneven thickness of the backing film 113a, etc., a minute pressure distribution is generated, and the surface of the work after processing is swelled. There is a problem that worsens the degree.

Therefore, instead of the work holding plate, the work holding part is made of a rubber film, a pressurized fluid such as air is poured into the back surface of the rubber film, and the rubber film is expanded with a uniform pressure to press the work against the polishing cloth. A chuck-type polishing head has also been proposed (see, for example, Patent Document 1).

An example of the structure of a rubber chuck type polishing head is schematically shown in FIG. The main part of the polishing head 141 includes an annular rigid ring 144 made of SUS, a rubber film 143 bonded to the rigid ring 144, and a back plate 145 coupled to the rigid ring 144. A sealed space 146 is formed by the rigid ring 144, the rubber film 143, and the back plate 145. A backing film 148 is attached to the lower surface portion of the rubber film 143, and an annular template 147 is provided concentrically with the rigid ring 144. Further, the pressure of the space 146 is adjusted by supplying a pressurized fluid to the center of the back plate 145 by the pressure adjusting mechanism 150. Further, the polishing head upper part 149 connected to the back plate 145 has a pressing means (not shown) for pressing the back plate 145 in the polishing cloth direction.

JP 2008-110407 A

By using such a rubber chuck type polishing head, a minute pressure distribution due to uneven thickness of the backing film does not occur, so that the surface of the workpiece after processing does not waviness. However, since the inner diameter of the template is larger than the outer diameter of the workpiece, there is a slight gap between the template and the workpiece. As described above, the pressure adjustment mechanism supplies the pressurized fluid to the inside of the space portion to adjust the pressure. In this case, the swelling of the rubber film in the gap portion between the template and the workpiece increases, the pressure on the outer periphery of the workpiece increases, and the outer periphery of the workpiece is excessively polished, so that the outer peripheral sag is likely to occur.

By adjusting the thickness of the template, it is possible to adjust the pressure on the outer periphery of the work to some extent, but the polishing margin of the work outer periphery changes due to variations in the thickness of the template, and stable flatness cannot be obtained. Occurs.
In finish polishing of a workpiece, if the template is brought into contact with the final polishing cloth, defects such as scratches may be generated on the surface of the workpiece due to detachment of foreign matter from the template. It is desirable not to contact.

However, when the thickness of the template is made thinner than the thickness of the workpiece so as not to contact the polishing cloth, the pressure on the outer periphery of the workpiece becomes high, and the outer periphery of the workpiece is overpolished, resulting in peripheral sagging. Since the flatness is deteriorated, there is a problem that it cannot be applied to the finish polishing of the workpiece.

The present invention has been made in view of the above-described problems, and causes a surface defect such as a scratch on the work surface in a polishing head that holds a back surface of a work on a rubber film and holds an edge portion of the work with a template. Even if the thickness of the template is made thinner than the thickness of the workpiece so that the template is not brought into contact with the polishing cloth without polishing, the workpiece can be uniformly polished to the outer periphery of the workpiece, that is, finish polishing of the workpiece is possible, and An object of the present invention is to provide a polishing head and a polishing apparatus that can uniformly polish the entire workpiece regardless of the thickness of the template.

In order to achieve the above object, according to the present invention, at least an annular rigid ring, a rubber film bonded to the rigid ring with a uniform tension, and a rubber film coupled to the rigid ring, the rubber film and the rigid A back plate that forms a space together with the ring, and an annular template that is provided concentrically with the rigid ring on the periphery of the lower surface portion of the rubber film and holds the edge portion of the workpiece, and the lower surface of the rubber film An incompressible fluid sealed in the space part is further provided in a polishing head that holds the back surface of the work in a portion and polishes the work surface by sliding the surface of the work in contact with a polishing cloth affixed on a surface plate. There is provided a polishing head characterized by comprising:

With such a polishing head, it becomes possible to appropriately adjust the surface shape of the rubber film holding the workpiece by the enclosed incompressible fluid, and the surface shape of the rubber film is locally localized during polishing of the workpiece. Deformation can be suppressed. As a result, the entire workpiece can be uniformly polished regardless of the thickness of the template. Moreover, even if the thickness of the template is made thinner than the thickness of the workpiece, the entire workpiece can be polished uniformly, so that it can also be applied to finish polishing of the workpiece.

At this time, the incompressible fluid can be water or an incompressible fluid whose main component is water.
If it is such, it can comprise at low cost, and even if an incompressible fluid leaks from a space part, there is no possibility of contaminating the inside of a workpiece | work and a grinding | polishing apparatus.

Further, at this time, the incompressible fluid can be an aqueous solution having at least one component of a polishing agent used when polishing the workpiece or a component contained in the polishing agent.
If it is such, even if an incompressible fluid leaks from a space part, the influence on the grinding | polishing characteristic of a workpiece | work can be suppressed.

At this time, it is preferable that the bulging shape of the lower surface portion of the rubber film is adjusted according to the difference in thickness between the template and the workpiece.
If it is such, the grinding | polishing allowance of a workpiece | work outer peripheral part can be adjusted, and the whole workpiece | work can be grind | polished uniformly more reliably.

At this time, it is preferable that the incompressible fluid is sealed at a pressure higher than a polishing pressure at the time of polishing the workpiece.
With such a configuration, it is possible to suppress an increase in pressure on the outer periphery of the workpiece, and the workpiece can be polished with a more uniform polishing load with respect to the workpiece.

At this time, it is preferable that the rubber film is bonded to the rigid ring while being stretched with a tension of 30 N or more.
With such a configuration, the surface shape of the rubber film after filling the incompressible fluid can be reliably maintained during the polishing of the workpiece, and the entire workpiece can be polished more reliably and uniformly.

Further, at this time, the rubber film is made of any one material of isoprene rubber, styrene butadiene rubber, chloroprene rubber, NBR rubber, urethane rubber, fluorine rubber, silicon rubber, ethylene propylene rubber, polyester elastomer, polysulfone resin, and grill amide resin. It is preferable that it consists of.
In this way, if a material that is tough and does not tear easily even when pulled with high tension, the surface shape of the rubber film after filling incompressible fluid can be maintained over a long period of time, and the entire workpiece can be further improved. The polishing can be performed uniformly and the cost can be reduced.

Further, according to the present invention, there is provided a polishing apparatus for use in polishing the surface of a workpiece, and at least for supplying a polishing cloth affixed on a surface plate and a polishing agent on the polishing cloth. As a polishing head for holding an abrasive supply mechanism and the workpiece, a polishing apparatus comprising the polishing head of the present invention is provided.
With such a polishing apparatus, it is possible to appropriately adjust the surface shape of the rubber film holding the workpiece by the incompressible fluid sealed in the polishing head of the present invention, and during polishing of the workpiece. Local deformation of the surface shape can be suppressed, and as a result, the entire workpiece can be uniformly polished regardless of the thickness of the template. Further, even if the thickness of the template is made thinner than the thickness of the workpiece, the entire workpiece can be polished uniformly, so that it can also be applied to finish polishing of the workpiece.

In the present invention, since the polishing head has the incompressible fluid sealed in the space portion, the surface shape of the rubber film holding the workpiece is appropriately adjusted by the sealed incompressible fluid. In addition, it is possible to suppress local deformation of the surface shape during polishing of the workpiece. As a result, the entire workpiece can be uniformly polished regardless of the thickness of the template. Moreover, even if the thickness of the template is made thinner than the thickness of the workpiece, the entire workpiece can be polished uniformly, so that it can also be applied to finish polishing of the workpiece.

It is the schematic which shows an example of the grinding | polishing head of this invention. It is explanatory drawing explaining the sealing method of an incompressible fluid. (A) When the template thickness is thinner than the workpiece thickness. (B) When the template thickness is thicker than the workpiece thickness. It is the schematic which shows another example of the grinding | polishing head of this invention. It is the schematic which shows an example of the grinding | polishing apparatus of this invention. It is a figure which shows the result of Example 1-3. It is a figure which shows the result of Comparative Example 1-3. It is a figure which shows the result of Example 4-7. (A) Polishing allowance distribution of workpiece. (B) Polishing allowance distribution ranging from 120 mm to 148 mm from the workpiece center. It is the figure which showed the result of the relationship between the tension | tensile_strength at the time of rubber film adhesion | attachment in Example 4-7, and outer periphery part grinding | polishing margin variation. It is a figure which shows the result of Example 8-9. It is the schematic which shows an example of the conventional grinding | polishing apparatus. It is the schematic which shows an example of the conventional grinding | polishing head using a backing film. It is the schematic which shows another example of the conventional grinding | polishing head using a backing film. It is a schematic diagram showing an example of a conventional rubber chuck type polishing head.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
Conventionally, there is a problem that the polishing margin of the outer periphery of the workpiece varies depending on the thickness of the template, and stable flatness cannot be obtained. In addition, the thickness of the template must be the same as or thicker than that of the workpiece in order to suppress peripheral sagging. In this case, the template contacts the polishing cloth during polishing, and foreign matter is generated. However, there arises a problem that defects such as scratches are generated on the surface of the workpiece.

Therefore, the present inventor has intensively studied to solve such problems. As a result, the rubber film is bonded to the annular rigid ring with a uniform tension, and the rubber chuck part that holds the workpiece by sealing the incompressible fluid in advance in the sealed space formed by providing the back plate on the top. As a result, it was found that a flat workpiece can be polished regardless of the thickness of the template, and the present invention was completed.

FIG. 1 is a view showing an example of the polishing head of the present invention.
As shown in FIG. 1, the polishing head 1 includes an annular rigid ring 4 made of a rigid material such as SUS (stainless steel), a rubber film 3 bonded to the lower surface side of the rigid ring 4 with a uniform tension, and a rigidity. And a back plate 5 provided on the upper surface of the ring 4.
The rigid ring 4, the rubber film 3, and the back plate 5 form a sealed space 6.

Here, the material and shape of the back plate 5 are not particularly limited as long as the space 6 can be formed together with the rigid ring 4 and the rubber film 3.
An annular template 7 having an inner diameter slightly larger than the outer diameter of the workpiece W is disposed concentrically with the rigid ring 4 at the periphery of the lower surface portion of the rubber film 3. The template 7 is for holding the edge portion of the workpiece W, and is disposed so as to protrude downward along the outer peripheral portion of the lower surface portion of the rubber film 3.

Here, the template 7 can have an outer diameter that is at least larger than an inner diameter of the rigid ring 4 and an inner diameter that is smaller than the inner diameter of the rigid ring 4. In this way, the pressing force applied to the entire work surface can be made more uniform.
Here, the material of the template 7 is softer than the work W so as not to contaminate the work W and not to be scratched or indented, and wears even if it comes into sliding contact with the polishing cloth of the polishing apparatus during polishing. It is preferable that the material is difficult and has high wear resistance.
In the example of the polishing head shown in FIG. 1, the thickness of the template 7 is thinner than the thickness of the workpiece W. However, the thickness of the template 7 is not limited to this, as shown in FIG. May be thicker than the thickness of the workpiece W, or may be the same.

Further, the backing film 8 can be attached to at least a portion of the lower surface portion of the rubber film 3 that holds the workpiece W. The backing film 8 includes water and affixes the work W, and holds the work W on the work holding surface of the rubber film 3. Here, the backing film 8 can be made of polyurethane, for example. By providing such a backing film 8 and containing water, the workpiece W can be reliably held by the surface tension of the water contained in the backing film 8.

Here, a commercially available template assembly may be used by attaching a template to the surface of the backing film.
In such a rubber chuck portion composed of the rubber film 3, the rigid ring 4, the back plate 5, and the like, the incompressible fluid 2 is sealed in the space portion 6 in advance before the workpiece W is polished. When the incompressible fluid 2 is sealed, the surface shape of the workpiece holding portion of the rubber film 3 holding the workpiece W is adjusted to be optimally formed. Thereafter, the polishing head upper part 9 provided with a pressing means (not shown) is mounted on the upper surface of the back plate 5. Here, the incompressible fluid referred to in the present invention is, for example, a fluid that is not a fluid that is compressed and greatly reduced in volume when pressurized, such as a gas.

Further, in order to enclose the fluid 2 in the space portion 6, as shown in FIG. 3, the back plate 5 is provided with through holes 11a and 11b and couplers 10a and 10b. The apparatus can be configured to be connectable.

When such a polishing head of the present invention is used, the volume of the incompressible fluid 2 enclosed in the space 6 is hardly changed during the polishing of the workpiece, so that the optimally formed rubber film 3 is formed. The deformation of the surface shape, particularly the local swelling of the rubber film 3 in the gap portion between the workpiece W and the template 7 can be suppressed, and the workpiece W can be polished by applying a uniform load to the entire workpiece. As a result, the entire workpiece can be uniformly polished regardless of the thickness of the template 7. Further, in order to polish without causing surface defects such as scratches on the surface of the work W, the thickness of the template 7 may be made thinner than the thickness of the work W so that the template 7 does not come into contact with the polishing cloth of the polishing apparatus. Since the outer periphery of the workpiece W can be uniformly polished, the workpiece W can be used for final polishing.

At this time, the incompressible fluid can be water or an incompressible fluid whose main component is water.
If it is such, it can comprise at low cost. Further, even if the incompressible fluid leaks from the space portion, for example, when the rubber film is torn during polishing, there is no possibility of contaminating the inside of the workpiece or the polishing apparatus.
In particular, when the workpiece is a semiconductor material, pure water containing no metal ions or the like is suitable as an incompressible fluid for the purpose of preventing metal contamination and the like.

At this time, the incompressible fluid can also be an aqueous solution having at least one component of an abrasive used for polishing a workpiece or a component contained in the abrasive.
If it is such, even if an incompressible fluid leaks from a space part, the influence on the grinding | polishing characteristic of a workpiece | work can be suppressed to the minimum.

Here, a method for enclosing an incompressible fluid in the space will be described.
FIG. 2A is a diagram illustrating an example of a fluid sealing method when a template thinner than the thickness of the workpiece is used.
As shown in FIG. 2A, the polishing head 21 has two through holes on the upper surface of the back plate 5 for introducing and discharging the incompressible fluid 2 into the space 6. 11a and 11b are provided in order to enclose the incompressible fluid 2 in the space 6 while maintaining the pressure of the incompressible fluid 2 (hereinafter sometimes abbreviated as the enclosing pressure). The couplers 10a and 10b are mounted in the through holes 11a and 11b. When the incompressible fluid 2 is sealed in the space 6 before the workpiece is polished, first, for example, the fluid sealing device is connected to the polishing head as described below.

As shown in FIG. 2 (A), the fluid sealing device 30 has a circuit in which a pressure gauge 33 and a valve 32a are connected to introduce the incompressible fluid 2, and a nipple 31a is provided at the end of the circuit. Connected. The nipple 31 a is connected to a coupler 10 a provided on the back plate 5. Further, the fluid sealing device 30 has a circuit in which a terminal is connected to the drain and a valve 32b is connected in the middle for discharging the incompressible fluid 2. A nipple 31b is connected to the front end of the circuit, and this nipple 31b is connected to a coupler 10b provided on the back plate 5.

Next, a work W or an adjustment plate 36 having the same thickness as the work W is placed on the flat base 35, and an adjustment spacer 34 equal to the difference in thickness between the work W and the template 7 is placed on the lower surface of the template 7. Put. Further, a polishing head member composed of the backing film 8, the template 7, the rubber film 3, the rigid ring 4, and the back plate 5 is placed on the base 35 so that the workpiece W or the adjustment plate 36 is accommodated in the hole of the template 7. . Further, the base 35 and the back plate 5 are fixed by the clamp jig 37 so that the height of the back plate 5 does not change when the incompressible fluid 2 is sealed.

Next, the valves 32 a and 32 b are opened, the incompressible fluid 2 is introduced into the space 6, and the air in the space 6 is vented. This venting can be performed, for example, by closing the valve 32a and opening the valve 32b and connecting a decompression circuit to the drain side.
Next, the valves 32a and 32b are closed, and the pressure gauge 33 is adjusted to a predetermined pressure by a pressure adjusting mechanism for the non-compressible fluid 2 (not shown), and the valve 32a is opened so that the pressure in the space 6 is not increased. A compressible fluid 2 is introduced. After confirming that the pressure gauge 33 is at a predetermined pressure, the valve 32 a is closed, and the incompressible fluid 2 is sealed in the space 6. After the sealing, the nipples 31a and 31b are removed from the couplers 10a and 10b mounted on the upper part of the back plate 5.

At this time, when the fluid 2 is sealed using the adjustment spacer 34 having a thickness smaller than the thickness difference between the workpiece and the template, the surface shape of the rubber film 3 is formed so that the bulge in the central portion is reduced. . By using the polishing head adjusted in this way, the pressure applied to the outer peripheral part of the workpiece during polishing is increased, and the polishing margin of the outer peripheral part is increased. Conversely, when the fluid 2 is sealed using the adjustment spacer 34 having a thickness larger than the thickness difference between the workpiece and the template, the surface shape of the rubber film 3 is formed so that the bulge of the central portion is increased. . By using the polishing head adjusted in this way, the pressure applied to the outer periphery of the workpiece during polishing is reduced, and the polishing allowance of the outer periphery is reduced. In this way, by adjusting the thickness of the adjusting spacer 34 used when the fluid is sealed, it is also possible to adjust the polishing allowance of the outer periphery of the workpiece.

FIG. 2B is a diagram showing an example of a fluid sealing method when a template thicker than the thickness of the workpiece is used. In this case, as shown in FIG. 2B, the adjustment spacer 34 is inserted into the lower surface of the workpiece W, and the incompressible fluid 2 can be sealed in the same manner as described above. Also in this case, it is possible to adjust the polishing allowance of the work outer peripheral portion by adjusting the thickness of the adjusting spacer 34.

Further, when the thickness of the workpiece is equal to the thickness of the template, the incompressible fluid 2 may be enclosed without using the adjustment spacer.
As described above, it is preferable that the bulge shape of the lower surface portion of the rubber film is adjusted according to the difference in thickness between the template and the workpiece. The entire workpiece can be polished more reliably and uniformly.

The incompressible fluid is preferably sealed at a pressure higher than the polishing pressure at the time of polishing the workpiece. The adjustment of the sealing pressure can be performed using, for example, the pressure adjusting mechanism of the fluid sealing device as described above.
If it is such, the increase in the pressure to the outer peripheral part of a workpiece | work can be suppressed, and a workpiece | work can be grind | polished with a more uniform grinding | polishing load with respect to a workpiece | work.

The rubber film bonded to the rigid ring is desirably stretched with high tension in order to maintain the surface shape formed as described above by enclosing an incompressible fluid. , And preferably adhered to a rigid ring in a state of being stretched with a tension of 30 N or more.
With such a configuration, the surface shape of the rubber film after the incompressible fluid is sealed can be reliably maintained during the polishing of the workpiece, and the entire workpiece can be polished more reliably and uniformly.

In addition, the material of the rubber film is tough and resistant to tearing even when pulled at high tension, and keeps the surface shape of the rubber film formed as described above by enclosing an incompressible fluid for a long time. A material with less deformation is preferred.
Therefore, the rubber film is made of any one material of isoprene rubber, styrene butadiene rubber, chloroprene rubber, NBR rubber, urethane rubber, fluorine rubber, silicon rubber, ethylene propylene rubber, polyester elastomer, polysulfone resin, and grill amide resin. Preferably there is.
If it is such, it can polish the whole workpiece | work more reliably and uniformly, can extend the lifetime of a rubber film, and can reduce cost.

Next, the polishing apparatus of the present invention will be described.
FIG. 4 is a schematic view showing an example of the polishing apparatus of the present invention.
As shown in FIG. 4, the polishing apparatus 20 of the present invention includes an abrasive cloth 22 attached on a surface plate 23, an abrasive supply mechanism 24 for supplying an abrasive 25 onto the abrasive cloth 22, As a polishing head for holding the workpiece W, the polishing head 21 of the present invention described above is provided. The polishing head 21 has a structure in which a work W can be pressed against a polishing cloth 22 affixed to a surface plate 23 by a pressure mechanism (not shown).

Then, while supplying the abrasive 25 onto the polishing cloth 22 by the abrasive supply mechanism 24, the surface of the workpiece W is slidably brought into contact with the rotation of the polishing head 21 connected to the rotation shaft and the rotation of the surface plate 23. Polish.
With such a polishing apparatus, deformation of the surface shape of the rubber film during workpiece polishing, especially local swelling of the rubber film in the gap between the workpiece and the template can be suppressed, and a uniform load can be applied to the entire workpiece. The workpiece can be polished by applying As a result, the entire workpiece can be uniformly polished regardless of the thickness of the polishing head template. Further, even if the thickness of the template is made thinner than the thickness of the workpiece, the entire workpiece can be polished uniformly, so that it can also be applied to finish polishing of the workpiece.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these.

(Example 1-3)
The workpiece was polished using the polishing apparatus of the present invention equipped with the polishing head of the present invention as shown in FIG. 3, and the variation in the polishing allowance within the workpiece surface after polishing was evaluated. As the workpiece W, a silicon single crystal wafer having a diameter of 300 mm and a thickness of 775 μm was used. Here, with respect to the polishing allowance, the thickness of the wafer before and after polishing was measured with a flatness measuring device in the area excluding the outermost 2 mm width as the flatness guarantee area, and before and after polishing in the cross section in the wafer diameter direction. It was calculated by taking the difference in thickness. As the flatness measuring device, a flatness measuring device (WaferSight) manufactured by KLA-Tencor was used.

First, the following polishing head was prepared. A rigid ring made of SUS having an outer diameter of 360 mm and an inner diameter of 320 mm was used, and a rubber rubber having a tension of 7.5 N and silicon rubber having a rubber hardness of 90 degrees was bonded to the lower surface of the rigid ring. On the surface of the rubber film, a template having an outer diameter of 355 mm, an inner diameter of 302 mm, a thickness of 700 μm (Example 1), a thickness of 780 μm (Example 2), and a thickness of 800 μm (Example 3) was attached to the surface of the backing film. A commercially available template assembly was glued.

Then, as shown in FIG. 2A, an incompressible fluid was sealed using a fluid sealing device. At this time, when the thickness of the template is 700 μm, a 75 μm adjustment spacer is inserted into the lower surface of the template. When the thickness is 780 μm, the adjustment spacer is not used. When the thickness is 800 μm, the adjustment spacer is 25 μm on the lower surface of the wafer. Were inserted to seal the fluid, pure water was used as an incompressible fluid, and the space was sealed at a pressure of 20 kPa.
The prepared polishing head was mounted on the polishing apparatus of the present invention as shown in FIG. 4 to polish the wafer. Note that the used wafer is preliminarily polished on both surfaces thereof and the edge portion is also polished. In addition, a surface plate having a diameter of 800 mm was used, and a commonly used surface was used for the polishing cloth.

In polishing, an alkaline solution containing colloidal silica was used as an abrasive, and the polishing head and the surface plate were each rotated at 30 rpm. The polishing load (pressing force) of the wafer was set to 20 kPa in terms of surface pressure on the wafer surface by a not-shown pressurizing means, and the wafer was polished. The polishing time was adjusted so that the average polishing amount of the wafer was 1 μm.
The polishing allowance distribution of the wafer polished in Example 1-3 is shown in FIG. As shown in FIG. 5, it can be seen that the polishing allowance distribution of the wafer hardly depends on the thickness of the template, unlike Comparative Example 1-3 described later, and a substantially uniform polishing allowance distribution is obtained. The range of the cross section polishing allowance was 0.042 μm in Example 1, 0.027 μm in Example 2, and 0.048 μm in Example 3, which was improved compared to Comparative Example 1-3 described later.

Thus, it was confirmed that by using the polishing head and the polishing apparatus of the present invention, the entire wafer can be uniformly polished regardless of the thickness of the template.

(Comparative Example 1-3)
Using a polishing apparatus as shown in FIG. 10 equipped with a conventional polishing head having no incompressible fluid of the present invention as shown in FIG. 13, under the same conditions as in Example 1-3, a silicon single crystal The wafer was polished. Here, the rigid ring and template of the polishing head are the same as those in Example 1-3, silicon rubber having a rubber hardness of 70 degrees is used as the rubber film, and the rubber ring is bonded to the lower surface of the rigid ring with a tension of 5 N. It was.

For each of the templates having a thickness of 700 μm (Comparative Example 1), 780 μm (Comparative Example 2), and 800 μm (Comparative Example 3), the variation in the polishing allowance in the wafer surface after polishing was evaluated.
The polishing allowance distribution of the wafer polished in Comparative Example 1-3 is shown in FIG. As shown in FIG. 6, the polishing allowance distribution of the wafer strongly depends on the thickness of the template. When the thickness of the template is thinner than the thickness of the wafer (Comparative Example 1), the wafer outer peripheral portion is excessive. On the contrary, when the thickness of the template is thicker than the thickness of the wafer (Comparative Example 3), it can be seen that the polishing margin of the outer peripheral portion of the wafer is reduced. The range of the cross section polishing allowance was 0.181 μm in Comparative Example 1, 0.061 μm in Comparative Example 2, and 0.104 μm in Comparative Example 3, which were worse than those in Example 1-3.

(Example 4-7)
Silicon single crystal under the same conditions as in Example 1 except that silicon rubber was bonded under the conditions of tension 5N (Example 4), 20N (Example 5), 35N (Example 6), and 48N (Example 7). The wafer was polished, and in the same manner as in Example 1, the variation in the polishing allowance in the polished wafer surface was evaluated.
FIG. 7A shows the polishing allowance distribution of the wafer polished in Example 4-7. Further, as a polishing allowance distribution on the outer peripheral portion of the wafer, a polishing allowance distribution in a range from 120 mm to 148 mm from the wafer center is shown in FIG. As shown in FIGS. 7A and 7B, it can be seen that in any of Examples 4-7, the wafer was uniformly polished to the outer periphery.

Further, as an index representing the polishing margin distribution of the wafer outer peripheral portion, the difference between the maximum value and the minimum value of the polishing margin from 135 mm to 148 mm from the wafer center was obtained, and this was used as the wafer outer peripheral portion polishing margin variation. The variation in the polishing margin of the outer peripheral portion of the wafer was 0.043 μm in Example 4, 0.027 μm in Example 5, 0.016 μm in Example 6, and 0.011 μm in Example 7.
FIG. 8 shows the relationship between the tension of silicon rubber and the variation in the polishing margin of the outer periphery of the wafer. As shown in FIG. 8, it can be seen that the larger the rubber tension is, the smaller the peripheral portion polishing margin variation of the wafer is. In addition, when the tension is 30 N or more, the outer peripheral portion polishing margin variation of the wafer is 0.020 μm or less, which indicates that the outer peripheral portion of the wafer can be polished more uniformly.

(Examples 8 and 9)
In order to investigate the influence of the sealing pressure of the incompressible fluid, a polishing head in which pure water was sealed with the pressure at the time of sealing set to 10 kPa (Example 8) and 40 kPa (Example 9) was used. Except for the above, the silicon single crystal wafer was polished under the same conditions as in Example 7, and as in Example 7, the variation in the polishing allowance within the wafer surface after polishing was evaluated.
FIG. 9 shows a polishing margin distribution of the outer peripheral portion of the wafer polished in Examples 8 and 9. As described above, the variation in polishing margin at the outer peripheral portion of the wafer in Example 7 is 0.011 μm, whereas that in Example 8 in which the sealing pressure is 10 kPa lower than the pure water sealing pressure in Example 7 is 20 kPa. The variation in polishing margin on the outer periphery of the wafer was as large as 0.033 μm, and the variation in polishing margin on the outer periphery of the wafer in Example 9 which was 40 kPa higher than that in Example 7 was reduced to 0.005 μm. .

From this result, it was found that by setting the sealing pressure of the incompressible fluid high, the variation in polishing allowance on the outer periphery of the wafer becomes small. By setting the sealing pressure of at least the incompressible fluid higher than the polishing load of the wafer, the outer peripheral portion of the wafer can be polished more uniformly.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.
For example, the polishing head according to the present invention is not limited to the embodiment shown in FIGS. 1 and 3. For example, the shape and the like of the polishing head may be appropriately designed except for the requirements described in the claims. Further, the configuration of the polishing apparatus is not limited to that shown in FIG. 4, and for example, a polishing apparatus including a plurality of polishing heads according to the present invention may be used.

Claims (8)

At least an annular rigid ring, a rubber film bonded to the rigid ring with a uniform tension, a back plate coupled to the rigid ring and forming a space with the rubber film and the rigid ring, and the rubber film An annular template provided concentrically with the rigid ring on the periphery of the lower surface portion of the rubber film, and holding an edge portion of the workpiece, and holding the back surface of the workpiece on the lower surface portion of the rubber film, A polishing head that performs polishing by sliding in contact with a polishing cloth affixed on a surface plate, further comprising an incompressible fluid sealed in the space. The polishing head according to claim 1, wherein the incompressible fluid is water or an incompressible fluid whose main component is water. 2. The polishing head according to claim 1, wherein the incompressible fluid is an aqueous solution having at least one component of a polishing agent used when polishing the workpiece or a component contained in the polishing agent. . 4. The bulge shape of the lower surface portion of the rubber film is adjusted according to a difference in thickness between the template and the workpiece. 5. Polishing head. The polishing head according to any one of claims 1 to 4, wherein the incompressible fluid is sealed at a pressure higher than a polishing pressure at the time of polishing the workpiece. The polishing head according to any one of claims 1 to 5, wherein the rubber film is bonded to the rigid ring while being stretched with a tension of 30 N or more. The rubber film is made of any one material of isoprene rubber, styrene butadiene rubber, chloroprene rubber, NBR rubber, urethane rubber, fluorine rubber, silicon rubber, ethylene propylene rubber, polyester elastomer, polysulfone resin, and grill amide resin. The polishing head according to any one of claims 1 to 6, wherein: A polishing apparatus for use in polishing the surface of a workpiece, comprising at least an abrasive cloth affixed on a surface plate, an abrasive supply mechanism for supplying an abrasive onto the abrasive cloth, and the workpiece A polishing apparatus comprising the polishing head according to any one of claims 1 to 7 as a polishing head for holding the surface.

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