JP2001064630A - Composite abrasive grain for polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain subject abrasive grains enabling polishing to stably be carried out at a sufficient speed without causing scratches by supporting abrasive grains for polishing with the surfaces of elastic bodies. SOLUTION: Abrasive grains for polishing are made to attach or adhere to, or are fixed on or supported with the peripheral surfaces of elastic bodies. These composite abrasive grains 11 are prepared by fixing an abrasive grain layer 13 on soft elastic bodies 12 made of e.g. rubber or polystyrene latex. The abrasive grain layer 13 is prepared by including e.g. minute cerium oxide powder having a size of around 0.1 μm as abrasive grains for polishing in ethylene cellulose as a binder material and then covering the surfaces of ball-shaped elastic bodies 12 with the resultant mixture. A magnetic material (e.g. samarium cobalt magnetic material) is preferably enclosed in each of the elastic bodies 12 of the composite abrasive grains 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus for polishing a surface of a substrate such as a semiconductor wafer into a flat and mirror-like surface, and more particularly to a structure of abrasive grains used for a polishing stone or a polishing liquid.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become more highly integrated, circuit wiring has become finer, and the dimensions of integrated devices have become finer. Therefore, a step of planarizing the surface by removing the film formed on the surface of the semiconductor wafer by polishing may be required. As a means of this planarization method, polishing is performed by a chemical mechanical polishing (CMP) apparatus. That is being done. This type of chemical mechanical polishing (CMP) apparatus has a turntable on which a polishing cloth (pad) is stuck and a top ring for holding a substrate to be polished, and a substrate to be polished is interposed between the turntable and the top ring. Then, while the top ring applies a constant pressure to the polishing target substrate to the polishing cloth (pad) attached to the turntable, the two rotate while supplying the abrasive liquid (slurry) to the sliding surfaces of both. The surface of the substrate to be polished is polished flat and mirror-like.

In chemical mechanical polishing (CMP) using such an abrasive liquid (slurry), polishing is performed while supplying an abrasive liquid (slurry) containing a large amount of abrasive grains to a relatively soft polishing cloth (pad). Therefore, there is a problem in pattern dependency.
The pattern dependency means that, due to the uneven pattern on the semiconductor wafer before polishing, gentle unevenness due to the unevenness is formed even after polishing, and it is difficult to obtain perfect flatness. That is, the polishing rate is high in the uneven portion with a fine pitch, and the polishing speed is low in the uneven portion with a large pitch, so that gentle unevenness is formed between a portion having a high polishing speed and a portion having a low polishing speed. That is the problem.
In addition, in chemical mechanical polishing (CMP) using a polishing cloth (pad), not only the convex portions but also the concave portions are polished.
It has been difficult to realize a so-called self-stop function in which the progress of polishing is stopped in a state where only the convex portions are polished and completely flattened.

On the other hand, polishing of semiconductor wafers and the like using so-called fixed abrasive grains (grinding stones) in which abrasive grains such as cerium oxide (CeO ₂ ) are fixed using a binder such as phenol resin is studied. . In polishing with such a grindstone, the abrasive is hard, unlike conventional chemical mechanical polishing, so that the convex portions of the irregularities are preferentially polished, and the concave portions are difficult to be polished, so that absolute flatness is easily obtained. There are advantages.
Further, depending on the composition of the grindstone, when the polishing of the convex portion is completed and the surface becomes flat, the polishing rate is significantly reduced, and a so-called self-stop function in which polishing does not actually proceed appears. In addition, in the case of polishing using a whetstone, a slurry containing a large amount of abrasive grains (slurry)
There is also an advantage that the load of environmental problems is reduced because no is used.

However, in the case of polishing a semiconductor wafer using a grindstone, the polishing rate is high immediately after the dressing, but gradually decreases, so that the polishing rate is not stable. In addition, when a hard grindstone is used, there is also a problem that the polishing rate is low, the throughput is reduced practically, and the productivity is reduced. Furthermore, in polishing using a grindstone, since the grindstone is generally hard, there is also a problem that a scratch or the like is easily generated on a substrate to be polished.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has a sufficient polishing rate and is capable of performing stable polishing without generating scratches and the like. It is intended to provide abrasive grains.

Another object of the present invention is to provide abrasive grains for polishing capable of easily recovering abrasive grains from a waste liquid due to environmental problems.

[0008]

According to the first aspect of the present invention, there is provided a composite abrasive grain for polishing, characterized in that abrasive grains are adhered, adhered, fixed, or carried around an elastic body. .

According to the above-described composite abrasive grains, the abrasive grains are carried around the elastic body by means of adhesion or the like, so that the elastic body is deformed during polishing, thereby scratching the surface of the substrate to be polished. Can be prevented.
In addition, a large amount of fine abrasive grains can be supplied to the polished surface because the fine abrasive grains attached to the periphery of the elastic body are released and self-generated during polishing of the substrate to be polished, thereby improving the polishing rate and stabilizing the polishing rate. Can be achieved.

The invention according to claim 2 is the polishing compound abrasive grain according to claim 1, wherein a magnetic material is enclosed in the elastic body. A third aspect of the present invention is a composite abrasive grain for polishing, characterized in that abrasive grains for polishing are adhered, adhered, fixed, or carried around a magnetic material.
By forming a magnetic field in the waste liquid after polishing with a magnet or the like, an elastic body enclosing the magnetic material or the magnetic material itself can be adsorbed. This makes it possible to easily recover the elastic body, the magnetic material, and the fine abrasive particles attached to these from the waste liquid used for polishing.

According to a fourth aspect of the present invention, there is provided a grinding wheel for polishing a substrate, wherein the composite abrasive grains are combined with a binder material. Thereby, the free abrasive grains can be sufficiently generated, a stable polishing rate can be obtained, and a whetstone that does not easily cause scratches on the surface of the substrate to be polished can be provided.

A fifth aspect of the present invention is a polishing liquid for polishing a substrate, wherein the composite abrasive is mixed in a solution for chemical mechanical polishing. Thereby, especially by using the composite abrasive grains enclosing the magnetic material, unused abrasive grains can be easily collected by adsorbing from the waste liquid of the polishing slurry using a magnetic field. Accordingly, the burden on the polishing liquid waste liquid treatment apparatus can be reduced, and the polishing liquid can be used for recycling abrasive grains.

According to a sixth aspect of the present invention, a magnetic field is formed in a container for performing solid-liquid separation, and abrasive grains containing a magnetic material are adsorbed and recovered from the waste liquid after polishing by the magnetic field. It is an apparatus for collecting abrasive grains for polishing. This makes it possible to easily and reliably recover the abrasive grains containing the magnetic material from the waste liquid.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a composite abrasive grain according to a first embodiment of the present invention. The composite abrasive grains 11 are applied to a soft elastic body such as rubber or polystyrene latex, and the abrasive layer 1
3 is fixed. The abrasive layer 13 is, for example, a cerium oxide-containing ethylene cellulose layer. That is, the abrasive layer 13 is made of abrasive grains, for example, 0.1 μm.
A fine cerium oxide (CeO ₂ ) powder of about m is bound with ethylene cellulose as a binder material to cover the surface of a spherical elastic body 11 such as polystyrene latex. Alumina (Al ₂ O ₃ ) or the like may be used as a material for the fine abrasive grains, and a phenol resin or a water-soluble sweet potato or starch may be used as a binder material.

In any case, by covering the elastic body 12 with the abrasive grain layer 13 in which abrasive grains are bonded with a binder material, the abrasive grains are adhered, adhered, fixed or held around the elastic body 12. At the time of polishing, the abrasive layer 13 is formed so that loose abrasive particles are easily separated from the binder material. Therefore, at the time of polishing, self-generated abrasive grains can be easily supplied to the sliding surface, and the elastic body 12 has elasticity.
Soft polishing can be performed, thereby preventing generation of scratches and the like.

FIG. 2 shows a composite abrasive grain according to a second embodiment of the present invention. In this composite abrasive grain 11A, a magnetic material 14 is enclosed inside a spherical elastic body 12 made of rubber or polystyrene latex. As the magnetic material 14, a samarium-cobalt magnetic material is preferable, but any material that receives a force by a magnetic field may be used. For example, a magnetic material such as iron powder or ferrite powder may be used. The abrasive layer 13 covering the elastic body 12 has, for example, the same configuration as described above. The elastic body 12 may be made of the magnetic material itself, or the magnetic material may be dispersed and arranged in the elastic body 12.

Next, an example of a method for producing the composite abrasive grains 11 or 11A will be described. First, a large number of polystyrene latex spheres having a uniform particle size are prepared as the elastic body 12. Cerium oxide (CeO ₂ ) is sufficiently dispersed in an ethanol solution of ethyl cellulose dissolved in powdered cellulose by stirring while applying, for example, ultrasonic vibration, and then dried to obtain cerium oxide coated and coated with ethyl cellulose ( CeO ₂ ) abrasive grains are obtained. Furthermore, the cerium oxide (CeO ₂ ) abrasive grains are coated on the surface of a polystyrene latex sphere, the surface is slightly dissolved in an ethanol atmosphere, and then dried to obtain the composite abrasive grains 11 or 11A.

In the case where fine abrasive grains having a high activity of several nm to several hundred nm are used as the abrasive grains, the entire surface of the polystyrene latex sphere 12 is coated with the fine abrasive grains using an encapsulation technique, and then the whole is coated. Enclose in a capsule (jacket). In this case, the capsule (sheath) is broken at the time of polishing, and a large amount of fine abrasive grains are released to the polished surface.

FIG. 3 shows an example of the configuration of a grindstone constructed using the composite abrasive grains. The grindstone 16 is obtained by combining composite abrasive grains 11 each having an elastic body 12 covered with an abrasive layer 13 using a binder material 17 such as a phenol resin. Although not shown, the binder material 17 contains an appropriate amount of pores. The abrasive layer 13 is formed by bonding fine abrasive grains such as cerium oxide (CeO ₂ ) or alumina (Al ₂ O ₃ ) with a sweet potato, starch, or the like, which is a water-soluble binder material having a relatively weak bonding force. It is configured. Also, the elastic body 12
As described above, an elastic member such as rubber or latex is used.

A grindstone 16 using such composite abrasive grains 11
When polishing a semiconductor wafer or the like, pure water is supplied to the polished surface, so that the water-soluble binder material of the abrasive layer 13 is dissolved, and a large amount of fine abrasive grains are spontaneously generated. Stabilization can be achieved. And this composite abrasive grain 11
Since the elastic body 12 is provided in the inside, the elastic body 12 has elasticity, thereby enabling polishing with a soft touch, and preventing generation of a scratch or the like on the substrate to be polished.

The above-mentioned ethyl cell is used as the composite abrasive.
Loose coated cerium oxide (CeO ₂) May be used
In addition, a microcapsule containing fine abrasive grains
Of course, it may be used. In addition, as a component of this whetstone,
Composite abrasive grains 11A containing a conductive material may be used.
No. As a result, the magnetic force is applied to the used abrasive grains as described later.
And it is possible to separate the elastic body 12.
It will be easier.

The composite abrasive grains 11A may be mixed into, for example, an alkaline solution as a polishing liquid for chemical mechanical polishing to form a polishing slurry. FIG. 4 shows a configuration example of a polishing apparatus using a polishing slurry using such composite abrasive grains. The polishing apparatus 20 supplies a turntable 22 having a polishing cloth (pad) 21 attached to the surface thereof, a top ring 23 for holding a semiconductor substrate to be polished, and a polishing slurry Q to the surface of the polishing cloth (pad) 21. And the main nozzle 25.

The turntable 22 is fixed to a main shaft 24 and is driven to rotate by a motor 27 via a belt 26. Similarly, the top ring 23 holding the substrate to be polished is rotated by its main shaft 28, and the substrate 29 to be polished is pressed against the surface of the polishing cloth (pad) 21 by the piston 29. Therefore, the surface of the substrate to be polished is a polishing cloth (pad).
While being pressed by the polishing surface 21, the two slide due to the rotational movement. Then, the polishing slurry Q containing the composite abrasive grains supplied from the nozzle 25 is supplied to the sliding surface between the polishing target substrate and the polishing cloth (pad), whereby chemical mechanical polishing (CMP) proceeds.

In this chemical mechanical polishing, the composite abrasive 1
1 (11A) includes a soft elastic body 12 inside and an abrasive layer 13 containing hard fine abrasive grains is fixed around the soft elastic body 12, so that a large amount of fine abrasive grains is transferred to the substrate to be polished with the progress of polishing. The polishing liquid is supplied to the sliding surface, whereby the polishing proceeds at a stable polishing rate, and the polishing proceeds while being pressed by the soft elastic body, so that the generation of scratches or the like on the surface of the substrate to be polished is prevented.

Of the polishing slurry Q supplied from the nozzle 25, the amount of slurry actually supplied to the sliding surface of the substrate to be polished and the polishing cloth (pad) and used for polishing is relatively small, and most of the slurry is used for polishing. It enters the recovery tank 31 as it is not used, and is guided to the waste liquid pool 33 through the abrasive recovery device 32 by solid-liquid separation, where the waste liquid is treated.

FIG. 5 shows an example of the configuration of an abrasive grain collecting apparatus.
This abrasive grain collecting device includes a permanent magnet or an electromagnet 36 at a lower portion of a container 35 and a thin film filter 37 on a magnetic pole surface thereof. Solid-liquid separation is performed inside the container 35 by gravity and a magnetic field.
It is separated into abrasive grains and supernatant. In the case of the composite abrasive grains 11A enclosing the magnetic material 14 described above, the waste slurry entering the apparatus through the inflow pipe 38 is caused by the magnetic field formed by the composite abrasive grains 11A from the magnetic pole surface of the permanent magnet or the electromagnet 37. It is adsorbed and deposited on the thin film filter 37.

As a result, solid-liquid separation is promoted, and the waste liquid becomes a processable supernatant liquid having no solid content, and is discharged from the outflow pipe 39. Then, the abrasive particles and the elastic body are prevented from flowing downstream from the outflow pipe 39, whereby the burden on the waste liquid for processing the environment is significantly reduced as compared with a conventional waste liquid treatment apparatus. Further, when the abrasive grains and the elastic body are also accumulated to some extent, the door 40 can be opened and collected. Then, by reattaching the abrasive layer around the elastic body, semi-permanent use of the composite abrasive by recycling is possible.

In the above-described embodiment, an example has been described in which a member such as rubber or polystyrene latex is used as the elastic body serving as the core of the composite abrasive grains. It goes without saying that the above member may be used.
Further, the shape is not limited to a spherical shape, but may be a shape like a spheroid. In addition, although examples of cerium oxide (CeO ₂ ) or alumina (Al ₂ O ₃ ), which is a non-magnetic material, have been described as abrasive grains, by using magnetic material abrasive grains, it is possible to perform adsorption using a magnetic field. More complete recovery of abrasive grains from the waste liquid becomes possible. Thus, various modifications can be made without departing from the spirit of the present invention.

[0030]

As described above, according to the present invention, polishing abrasive grains are adhered to the periphery of the elastic body, so that a large amount of fine abrasive grains can be spontaneously generated by using the abrasive grains for, for example, a grindstone. At the same time, it is possible to perform soft polishing in which scratches and the like hardly occur on the surface of the substrate to be polished.

Further, by enclosing the magnetic material in the elastic body, it becomes possible to adsorb these abrasive grains by the magnetic field in the abrasive grain collecting device, whereby abrasive grains for polishing, which can easily treat waste liquid, are obtained. Can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing a composite abrasive grain according to a first embodiment of the present invention.

FIG. 2 is a view showing a composite abrasive grain according to a second embodiment of the present invention.

FIG. 3 is a view showing a configuration example of a grindstone using the composite abrasive grains shown in FIG. 1 or FIG. 2;

FIG. 4 is a diagram showing a configuration example of a polishing apparatus using a polishing abrasive liquid configured using the composite abrasive grains shown in FIG. 1 or FIG.

FIG. 5 is an enlarged view of the abrasive grain collecting device in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Composite abrasive grain 12 Elastic body 13 Abrasive grain layer 14 Magnetic material 16 Whetstone 17 Binder material Q Slurry

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/304 622 H01L 21/304 622F (72) Inventor Yutaka Wada 4-chome Motofujisawa, Fujisawa City, Kanagawa Prefecture No. 1 Inside Ebara Research Institute, Inc. (72) Inventor Naoki Matsuo 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa F-term inside Ebara Research Institute, Ltd. 3C047 GG14 GG17 3C058 AA07 AA16 AB06 AC04 CB01 CB03 DA02 DA17 3C063 BB15

Claims (6)

[Claims] 1. A composite abrasive grain for polishing, wherein abrasive grains for polishing are attached, adhered, fixed, or carried around an elastic body. 2. The polishing compound abrasive grain according to claim 1, wherein a magnetic material is enclosed in the elastic body. 3. A composite abrasive grain for polishing, wherein abrasive grains for polishing are adhered, adhered, fixed, or carried around the magnetic material. 4. A polishing wheel for polishing a substrate, comprising: the polishing compound abrasive grains according to claim 1 combined with a binder material. 5. A polishing liquid for polishing a substrate, comprising: mixing the polishing compound abrasive grains according to claim 1 in a solution for chemical mechanical polishing. 6. A magnetic field is formed in a container for performing solid-liquid separation,
An apparatus for collecting abrasive grains for polishing, characterized in that abrasive grains containing a magnetic material are adsorbed and collected by the magnetic field from waste liquid after polishing.