JPH10277923A - Polishing device and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong a life of a polishing layer and thereby enhance throughput of polishing treatment. SOLUTION: A wafer, a body to be polished, is kept into contact with polishing cloth, a polishing layer. The wafer and the polishing cloth are rotated to polish the wafer. In the polishing cloth, for example, mechanical polishing particles 31 are dispersed into a binder resin. The binder resin is foamed and is cut to a given shape for formation. The formed surface is used as a polishing surface. The polishing cloth is formed of the mechanical polishing particles 31-containing foamed resin 32. Polishing the wafer, using the polishing cloth reduces the degree of a reduction in a polishing rate even if polishing treatment is promoted. The result reduces frequency for polishing the surface of the polishing cloth by means of diamond, etc., in the polishing treatment, resulting in the prolonged life of the polishing cloth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polishing apparatus and a polishing method.

[0002]

2. Description of the Related Art Semiconductor wafers (hereinafter referred to as "wafers")
CMP (Chemical M)
There is a polishing process called mechanical polishing. In the CMP process, a polishing liquid containing mechanical polishing particles and chemical polishing particles is dropped on the surface of a polishing cloth, the surface of the polishing cloth is pressed against a wafer, and a part of the surface of the wafer is removed by polishing. This method is applied to, for example, a process called etch back in a multilayer wiring forming process.

In a conventional CMP process, for example, in a CMP apparatus shown in FIG.
The wafer holding mechanism 1 is attached to the rotating table 12 on which the wafer 1 is formed.
The rotating table 12 is rotated while the polishing liquid is supplied from the nozzle 14 to the surface of the polishing cloth 11 while the wafer 10 held by the wafer 3 is brought into pressure contact with a predetermined pressure. The surface of the wafer 10 is polished by rotating the wafer 10 on the rotating table 12 and relatively revolving.

As the polishing cloth 11, for example, 1.2 m
m, a foamed resin such as a urethane foam resin having a thickness of about m is used. As a polishing liquid, silica (S
A slurry in which iO ₂ ) and chemical abrasive particles are dispersed in a solution is used. In such a CMP process, mechanical abrasive particles enter into concave portions formed on the surface of the foamed resin, and a mechanical polishing action of friction by the mechanical abrasive particles captured in the concave portions is obtained. It is considered that the combined effect of the mechanical polishing action and the chemical polishing action is greatly related to the polishing mechanism.

[0005]

However, the above C
In the MP process, when one wafer 10 is polished, for example, the polishing rate becomes smaller. The reason is considered as follows. That is, when the wafer 10 is polished, the mechanical polishing particles in the polishing liquid enter, but the shavings of the wafer 10 also enter the concave portions on the surface of the polishing cloth 11. Then, as the polishing proceeds and the amount of shavings of the wafer 10 entering the concave portion increases, the mechanical shaping particles already entering the concave portion are expelled by the shavings.

[0006] As the polishing process proceeds, the amount of mechanical abrasive particles trapped in the concave portion decreases,
If the mechanical abrasive particles are not trapped in the recesses, the polishing cloth 1
Since the sliding occurs between the wafer 1 and the wafer 10 and a large frictional force cannot be obtained, the polishing rate is reduced.

At this time, the shavings that have entered the recesses on the surface of the polishing cloth 11 cannot be removed with a brush or the like.
For example, every time one wafer 10 is processed, the surface of the polishing cloth 11 is shaved with diamond or the like, and a new polishing cloth surface is exposed. However, if you do this,
Since the foamed resin (polishing cloth 11) itself is also shaved, the life cycle of the polishing cloth 11 is shortened.
1 must be replaced when 500 wafers 10 have been processed. Therefore, a troublesome replacement operation must be performed many times, and the CMP process is hindered each time. As a result, the throughput of the CMP process is reduced.

The present invention has been made under such circumstances, and an object thereof is to provide an improved polishing apparatus and an improved polishing method.

[0009]

According to the present invention, there is provided a polishing apparatus for polishing an object to be polished while relatively sliding the object to be polished and the polishing layer, wherein the polishing layer comprises a plurality of concave portions. Are formed, and mechanical polishing particles having a mechanical polishing action embedded in the polishing layer so as to be exposed from the polishing surface. Still another invention provides a polishing liquid containing a chemical abrasive having a chemical polishing action to the polishing layer while relatively sliding the object to be polished and the polishing layer, In the polishing apparatus for polishing, the polishing layer has a polishing surface in which a large number of concave portions are formed, and mechanical polishing particles having a mechanical polishing action embedded in the polishing layer so as to be exposed from the polishing surface. And characterized in that:

It is preferable that the polishing liquid contains only a chemical abrasive among, for example, mechanical abrasive particles and a chemical abrasive. Further, the polishing layer, while dispersing the mechanical abrasive particles in a binder resin, foaming the binder resin to obtain a foam, is processed by cutting into a predetermined shape, the cut surface and the polishing surface. Can be used.
Still another invention is a polishing method for polishing the object to be polished while relatively sliding the object to be polished and the polishing layer, wherein a polishing surface in which a large number of concave portions are formed and a polishing surface exposed from the polishing surface. Embedded in the polishing layer as described above, using a polishing layer containing mechanical polishing particles having a mechanical polishing action,
The object to be polished is polished while supplying a polishing liquid containing a chemical polishing material having a chemical polishing action to the polishing layer.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention described below uses a polishing layer formed of a foamed resin containing mechanical polishing particles having a mechanical polishing action (hereinafter referred to as mechanical polishing particles). By performing a polishing process (CMP process) on an object to be polished, for example, a wafer, the life of the polishing layer is lengthened, and as a result, the throughput of the polishing process is improved.

Next, an example of an embodiment of the polishing apparatus of the present invention will be described. First, the overall configuration of a polishing apparatus according to the present invention will be described with reference to FIGS. 1 and 2. This polishing apparatus includes a rotating table 2 which is horizontally rotated by a motor 21 via a vertical rotating shaft 22. A polishing pad 3 as a polishing layer attached to the surface of the rotary table 2; and a wafer holder 4 for holding a wafer 10 as an object to be polished and contacting the polishing pad 3 with a predetermined pressure. And a polishing liquid supply nozzle 5 for supplying a polishing liquid to the surface of the polishing cloth 3.

The wafer holding unit 4 is provided with, for example, a vacuum chuck mechanism, and sucks and holds the wafer 10 at a position displaced from the center of the rotary table 2 so that the surface to be polished faces down.
The surface to be polished is brought into contact with the polishing pad 3 and is rotated horizontally by a motor 41 via a vertical rotating shaft 42. The motor 41 has an elevating shaft 45 by an elevating unit 44 attached to a fixed plate 43.
It is attached to an elevating body 46 that can be raised and lowered via the.
The polishing liquid supply nozzle 5 is provided with a polishing liquid containing a chemical compound (hereinafter, referred to as a chemical polishing compound), such as a fluorine compound, having a chemical polishing action from the polishing liquid supply source 51, for example, the rotation center of the polishing pad 3. It is configured to supply to the vicinity. When the surface to be polished is made of metal, ferric nitrate (mainly for tungsten), hydrogen peroxide, oxalic acid, or the like is used as the chemical polishing material.
_{In the} case where the surface is polished, potassium hydroxide, potassium fluoride, ammonia or the like is used. When the surface to be polished is made of an organic material, ferric nitrate or the like is used.
The chemical abrasive is not limited to the above, and various abrasives such as chelate compounds can be applied according to the properties of the surface to be polished.

The polishing cloth 3 is made of, for example, a foamed resin 32 containing mechanical abrasive particles 31, as shown in FIG. The foam resin 32 is
It is made of a urethane foam resin having a thickness of about 1.2 mm, and has, for example, a void 33 having an average diameter of about 200 nm to 2000 nm, preferably an average diameter of about 200 nm to 500 nm. In the foamed resin 32, for example, a particle diameter of 200
nm mechanical polishing particles 31 such as silica (Si
O ₂ ) has entered, and a polishing surface 34 is formed on the surface of the foamed resin 32. The mechanical polishing particles 31 are exposed on the polishing surface 34, and a concave portion 35 which is a part of the void 33 is formed. The mechanical abrasive particles 31 exposed on the polishing surface 34 are formed in a concave portion 35 which is a part of the void 33.
And the polishing surface 34 except for the recess 35
Some are partially embedded in Examples of mechanical abrasive particles, silica abrasive, such as SiO ₂ is for polishing the silicon wafer, abrasive silica of for polishing the SiO ₂ film including SiO _2, alumina Abrasives or ceria-based abrasives are used, for example, an alumina-based abrasive or ceria-based abrasive is used for polishing a metal film, and a ceria-based abrasive is used for polishing optical glass. You. The silica-based mechanical polishing particles preferably have an average particle size of 30 to 100 nm, and the alumina-based or Celica-based mechanical polishing particles have an average particle size of 50 to 3 nm.
00 nm is preferred.

Such a polishing cloth 3 can be formed, for example, by dispersing mechanical abrasive particles in a binder resin and foaming the binder resin. In this method, the above-mentioned polishing cloth 3 is formed by adding SiO ₂ particles having a particle diameter of about 30 nm to several percent to several tens wt% in, for example, urethane resin as a binder resin, and stirring the urethane resin. It is manufactured by dispersing _two particles in a urethane resin and heating in this state to foam the urethane resin. In this case SiO ₂ particles becomes about particle size 200nm agglomerated with a binder resin, a urethane resin is foamed while incorporating SiO ₂ particles, and a state that has entered SiO ₂ particles in the voids or other areas caused by foaming Become. The abrasive cloth 3 is formed by cutting and processing the foam thus obtained into a predetermined shape. In this case, the foam density (volume of voids with respect to the apparent volume of the whole foam) is preferably 15 to 30%. That is, the foam density is increased by increasing the hardness of the foamed resin and reducing the amount of deformation of the portion of the polishing layer in contact with the object to be polished following the undulation of the surface to be polished of the object to be polished. Small enough to efficiently flatten the undulations,
Further, it is desirable that the polishing rate is large enough to increase the polishing rate by increasing the amount of the concave portion and increasing the amount of the abrasive particles trapped in the concave portion.

In the above-mentioned polishing apparatus, the wafer is polished as follows. First, the wafer 10 is placed at the ascending position by the elevating unit 44, and the wafer 10 is vacuum-adsorbed to the wafer holding unit 4 with the surface to be polished facing downward. And the wafer holding unit 4
The wafer holding unit 4 is lowered while rotating the rotary table 2 to bring the wafer 10 into contact with the polishing pad 3 at a predetermined pressure, and the polishing liquid containing a chemical polishing material is polished from the polishing liquid supply nozzle 5. It is supplied dropwise to the center of the surface of the cloth 3. The polishing liquid supplied to the center of the polishing cloth 3 is supplied to the rotating table 2.
Due to the centrifugal force caused by the rotation of the polishing pad, it spreads around the polishing cloth 3 and enters between the polishing cloth 3 and the wafer 10. At this time, for example, if the surface of the polishing pad 3 is smooth, the polishing liquid is unlikely to enter between the polishing pad 3 and the wafer 10, but in this embodiment, the polishing pad 3 is formed of a foam. In addition, irregularities are formed over the entire surface, that is, the surface is not smooth, and therefore, the polishing liquid flows between the polishing pad 3 and the wafer 10 through a gap formed by the irregularities. Easy to enter. Therefore, waste of the polishing liquid is small, and the polishing time is shortened. Further, since the unevenness is formed over the entire polished surface, even if the object to be polished is in close contact with the polished surface, the polishing liquid easily enters between them, so that polishing unevenness does not occur.

In this manner, the wafer 10 rotates and rotates
The polished surface is polished while revolving relatively to the bull 12. Although the mechanism of this polishing is not clear, the mechanical polishing effect of friction between the surface to be polished of the wafer 10 and the mechanical polishing particles 31 and the chemical polishing effect of the chemical reaction between the surface to be polished and the chemical polishing particles are considered. It is considered that the polishing proceeds due to the synergistic effect of the above, and the heat generated by the friction of the mechanical polishing particles 31 also promotes the chemical polishing action.

At the time of this polishing, since the mechanical abrasive particles 31 are contained in the foamed resin 32 itself, the mechanical abrasive particles 31
Are in a state of being captured by the foamed resin 32. Therefore, the mechanical polishing particles 31 do not slip between the polishing surface of the polishing cloth 3 and the surface to be polished of the wafer 10 and a predetermined frictional force cannot be obtained. As a result, the surface to be polished of the wafer 10 is polished with a large frictional force.

Here, regarding the polishing rate of the wafer 10,
Compared with the case where the polishing processing is performed using the conventional polishing apparatus shown in FIG. 6, the polishing rate of the polishing apparatus of the present embodiment decreases when the polishing processing of one wafer 10 is performed. Smaller than before. The reason is considered as follows. As described above, the polishing of the mechanical abrasive particles 31 by friction is performed by the mechanical abrasive particles 31 captured by the foamed resin 32.
It is considered that the decrease in the polishing rate is caused by the swarf of the wafer 10 generated by the polishing weakening the force of capturing the mechanical abrasive particles 31.

In the conventional polishing cloth 11, as shown in FIG. 4 (a), nothing is originally contained in the concave portion 11a of the polishing surface. The mechanical abrasive particles 31 and the shavings 10a enter. That is, the mechanical abrasive particles 31 enter the concave portion 11a earlier than the shavings, the shavings enter first, or both enter the recesses 11a together. For this reason, it is considered that the probability that the mechanical abrasive particles 31 enter the concave portion 11a in a stable state is low, and thus the capturing force of the mechanical abrasive particles 31 is relatively weak.

Therefore, when the amount of shavings increases due to the progress of the polishing process, the shavings 10a can easily enter the vicinity of the bottom of the concave portion 11a, thereby further weakening the trapping force of the mechanical abrasive particles 31, and Abrasive particles 31 into recesses 11
You will be kicked out of a. Thus, the conventional polishing cloth 11
In this case, as the polishing process proceeds, the number of the mechanical abrasive particles 31 trapped in the concave portion 11a decreases at a high rate, so it is assumed that the polishing force by the mechanical abrasive particles 31 is greatly reduced.

On the other hand, in the polishing cloth 3 of the present embodiment, the mechanical abrasive particles 31 are contained in the foamed resin 32, and FIG.
As shown in (b), the mechanical polishing particles 31
Are trapped in the concave portion 35 from the beginning of the polishing process in a stable state, that is, with a large trapping force. Since the mechanical abrasive particles 31 are present at the resin foaming stage, the concave portions 35 are formed in a shape relatively compatible with the mechanical abrasive particles 31.

Therefore, even if the swarf is generated due to the progress of the polishing process, the swarf is originally difficult to enter the concave portion 35, and even if it enters, it is difficult to enter the bottom of the concave portion 35. It is unlikely that the particles 31 will be expelled from the recess 35. Furthermore, since the concave portion 35 is not formed around the mechanical polishing particles 31 entering the region other than the gap 33, the mechanical polishing particles 31 always exist on the polishing surface. As described above, in the polishing cloth 3, even if the polishing process proceeds, the reduction rate of the number of the mechanical abrasive particles 31 captured by the foamed resin 32 is small, so that the polishing force by the mechanical abrasive particles 31 is extended for a long time. It is thought that it can be maintained.

As described above, in the polishing cloth 3 of the present embodiment, since the degree of reduction in the polishing rate when one wafer 10 is polished is small, the polishing cloth 3 is made of diamond or the like which is used to recover the polishing force. The polishing of the polishing pad 3 does not need to be performed frequently, and may be performed after, for example, 25 wafers 10 are polished. Therefore, since the total number of times of polishing with diamond or the like during the polishing process is reduced, the shaving of the foamed resin 32 due to the polishing is suppressed to some extent, and the life of the foamed resin 32 is prolonged.

As a result, the replacement of the polishing cloth 3 may be performed, for example, when 3,000 wafers 10 have been processed, and the number of times of replacement of the polishing cloth 3 during the polishing process is reduced.
As a result, the throughput of the polishing process can be improved.

In the above-described embodiment, the polishing liquid does not need to contain the mechanical polishing particles 31, so that the polishing liquid can be easily adjusted. Further, by performing the polishing process while supplying the polishing liquid containing the chemical polishing particles, the chemical polishing particles are supplied in a liquid state, so that the chemical polishing particles are uniformly dispersed on the polishing surface, and thereby the uniform polishing is performed. Processing can be performed. However, in the present embodiment, the foamed resin 32 of the polishing pad 3 itself is impregnated with the chemical polishing particles in advance, so that the supply of the polishing liquid containing the chemical polishing material from the nozzle is not performed. Also, it may be used together with the supply from this nozzle. The polishing liquid supplied from the nozzle may contain mechanical polishing particles, and may be used in combination with the mechanical polishing particles contained in the polishing cloth.

In the present invention, since at least the surface portion of the polishing cloth 3 on the polishing surface side may be formed of the foamed resin 32 containing the mechanical abrasive particles 31, for example, as shown in FIG. On the first foamed resin 61 not containing the abrasive particles 31, a second foamed resin 62 forming a polishing layer containing the mechanical abrasive particles 31 is laminated, and the second foamed resin 62 is formed.
The polishing cloth 6 may be formed using the surface of the polishing pad as a polishing surface.

Such a polishing cloth 6 is formed, for example, on the surface of the first foamed resin 61 by adding mechanical abrasive particles 31 to a binder resin.
Is formed by a method of applying a liquid in which is dispersed by spin coating, a method of attaching a thin second foamed resin 62 containing mechanical abrasive particles 31 to the surface of the first foamed resin 61 in advance, or the like. You. Even with such a polishing cloth 6, since the degree of reduction in the polishing rate is small, the life of the polishing cloth 6 is prolonged, and as a result, the throughput of the polishing process can be improved.

As described above, in the present invention, as the foamed resin forming the polishing layer, other foamed resins can be used in addition to the urethane foamed resin. A material having a non-smooth surface, that is, a material having irregularities and a certain elasticity, such as a nonwoven fabric, can be used. However, the polishing layer in the present invention is not limited to such an elastic body, and may be formed of, for example, a material having no elastic force such as a hard synthetic resin. The object to be polished is not limited to a semiconductor wafer, but may be, for example, a liquid crystal panel display substrate.

In the polishing apparatus of the above-described embodiment, one polishing object is polished by using one wafer holding portion (polishing object holding portion). A plurality of objects to be polished may be polished simultaneously by arranging them on a horizontal surface so as to face the polishing layer. Although the polishing apparatus has been described as an example in the embodiment, another type of polishing apparatus, for example, an apparatus in which a polishing cloth is attached on an endless belt may be used.

[0031]

According to the present invention, an improved polishing apparatus and an improved polishing method can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a polishing apparatus according to one embodiment of the present invention.

FIG. 3 is a sectional view showing a part of a polishing cloth used in the polishing apparatus of the present invention.

FIG. 4 is an explanatory diagram for explaining an operation of the polishing cloth.

FIG. 5 is a sectional view showing another example of a polishing cloth used in the polishing apparatus of the present invention.

FIG. 6 is a sectional view showing a conventional polishing apparatus.

[Explanation of symbols]

 2 rotating table 3 polishing cloth 31 mechanical abrasive particles 32 foam resin 33 void 34 polishing surface 35 recess 4 polishing liquid supply nozzle

Claims (5)

[Claims] 1. A polishing apparatus for polishing an object to be polished while relatively sliding the object to be polished and a polishing layer, wherein the polishing layer comprises: a polishing surface having a large number of concave portions; Embedded in the polishing layer so as to be exposed from the surface,
A mechanical polishing particle having a mechanical polishing action. 2. A polishing liquid containing a chemical polishing agent having a chemical polishing action is supplied to the polishing layer while relatively sliding the object to be polished and the polishing layer, thereby polishing the object to be polished. In a polishing apparatus for polishing, the polishing layer, a polishing surface in which a number of recesses are formed, and embedded in the polishing layer so as to be exposed from the polishing surface,
A mechanical polishing particle having a mechanical polishing action. 3. The polishing apparatus according to claim 2, wherein the polishing liquid contains only the chemical abrasive among the mechanical abrasive particles and the chemical abrasive. 4. The polishing layer according to claim 1, wherein the mechanical polishing particles are dispersed in a binder resin, and the binder resin is foamed to obtain a foam, and then processed into a predetermined shape. The polishing apparatus according to claim 1, wherein the polishing apparatus is a polishing apparatus. 5. A polishing method for polishing an object to be polished while relatively sliding the object to be polished and a polishing layer, wherein a polishing surface having a large number of recesses formed therein and a polishing surface exposed from the polishing surface. Using a polishing layer embedded in the polishing layer and containing mechanical polishing particles having a mechanical polishing action, and supplying a polishing liquid containing a chemical abrasive having a chemical polishing action to the polishing layer. A polishing method, wherein the object to be polished is polished.