JP2003138247A - Fixed abrasive grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixed abrasive grain which can polish an object to leave it almost free from metal contamination. SOLUTION: The fixed abrasive grain comprises a metal or a metal compound at a content of 100 ppm or less so that the object can be polished to have an even and mirror-like surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed abrasive grain for polishing, and more particularly to a fixed abrasive grain for polishing a polishing object such as a semiconductor wafer into a flat and mirror surface.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has increased, the wiring of circuits has become finer and the dimensions of integrated devices have also become finer. Therefore, it may be necessary to remove the coating film formed on the surface of the semiconductor wafer by polishing to flatten the surface. As a means of this planarization method, a chemical mechanical polishing (CMP) apparatus is used. Is being done. This type of chemical mechanical polishing (CMP) device has a turntable to which a polishing cloth (pad) is attached and a top ring, and a polishing target object is interposed between the turntable and the top ring to provide a top ring. Both rotate while applying a constant pressure to the evening table, and supply the polishing liquid (slurry) to the polishing cloth to polish the surface of the polishing object flat and mirror-like.

In chemical mechanical polishing (CMP) using such an abrasive liquid (slurry), polishing is performed while supplying a relatively soft polishing cloth with an abrasive liquid (slurry) containing a large amount of abrasive grains. There is a problem with pattern dependence. The pattern dependency means that the uneven pattern existing on the semiconductor wafer before polishing forms gentle unevenness due to the unevenness even after polishing, and it is difficult to obtain perfect flatness. That is, the polishing rate is high for the fine pitch irregularities, and the polishing rate is low for the large pitch irregularities, whereby gentle irregularities are formed between the high polishing rate portion and the low polishing rate portion. Is a problem.

On the other hand, polishing of semiconductor wafers using so-called fixed abrasives (grinding stones) in which abrasives such as cerium oxide (CeO ₂ ) is fixed by using a binder such as phenol resin has been studied. In polishing with such fixed abrasives, the abrasive material is hard unlike conventional chemical mechanical polishing, so convex and concave convex portions are preferentially polished, and concave portions are difficult to polish, so absolute flatness is obtained. It has the advantage of being easy.
Further, depending on the composition of the fixed abrasive grains, when the polishing of the convex portion is completed and the surface becomes flat, the polishing rate is remarkably reduced, and a so-called self-stop function in which polishing practically does not proceed appears.
Further, polishing with fixed abrasive grains does not use a suspending liquid (slurry) containing a large amount of abrasive grains, so that there is an advantage that the load of environmental problems is reduced.

However, the use of fixed abrasive grains has the following problems. Abrasive grain material used for fixed abrasive grains,
Binder materials and additives contain a large amount of impurities other than the raw materials, such as metals or metal compounds, and wafers polished with fixed abrasive grains are particularly heavily contaminated with metals. Therefore, while devising a method for cleaning the wafer after polishing with fixed abrasives, it is compatible with the semiconductor device manufacturing process, but it was difficult to clean the wafer once contaminated to a sufficient level with high yield. .

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fixed abrasive having less metal contamination of an object to be polished after polishing.

[0007]

According to a first aspect of the present invention, there is provided a fixed abrasive for polishing a polishing object in a flat and mirror-like manner, wherein the content of the metal or metal compound contained in the fixed abrasive is 100 ppm. It is a fixed abrasive characterized by the following. Thus, by using a material containing no metal or metal compound for the fixed abrasive grains, it is possible to perform clean polishing without causing metal contamination on the polishing target during polishing.

The invention according to claim 2 is the fixed abrasive characterized in that the content of the metal or the metal compound contained in the binder used for the fixed abrasive is 100 ppm or less. Thus, by using a binder containing no metal or metal compound as the binder that is one of the fixed abrasive grain raw materials, it is possible to perform clean polishing without metal contamination.

The third aspect of the present invention is the fixed abrasive grain characterized in that the content of the metal or metal compound contained in water used in the step of producing the binder is 100 ppm or less. As a result, by using pure water or ultrapure water that does not have metal contamination as the water used in the resin manufacturing stage, it is possible to manufacture a binder that does not have metal contamination, and use the binder to polish with fixed abrasives. Can perform clean polishing without metal contamination.

A fourth aspect of the present invention is a fixed abrasive grain characterized in that the content of the metal or the metal compound contained in the solvent or the chemical agent used in the binder manufacturing process is 100 ppm or less. As a result, by using a solvent and chemicals that do not have metal contamination as the solvent and chemicals used in the resin manufacturing stage, it is possible to produce a binder that does not have metal contamination, and with fixed abrasives using the binder. In the polishing, the clean polishing without metal contamination can be performed.

The invention as set forth in claim 5 is characterized in that, in the abrasive raw material used for the fixed abrasive, the content of the metal or metal compound in the abrasive raw material containing the slurry abrasive is 100 ppm or less. It is a fixed abrasive grain. One of the fixed abrasive raw materials, the abrasive raw material directly involved in the polishing action,
By using a raw material containing no metal or metal compound other than the abrasive grains, clean polishing without metal contamination can be performed.

The invention as set forth in claim 6 is characterized in that, in the additive used for producing the fixed abrasive, the content of the metal or the metal compound contained in the additive is 100 ppm or less. Is. Generally, in the fixed abrasive grain manufacturing process, processing accelerators (such as amines) containing microcapsule chemicals, processing performance stabilizers (buffers), specularity improving agents (water-soluble polymers), abrasive grain aggregation inhibitors (organic polymers) ) Or the like, a polishing aid self-developing amount adjusting agent (a binder dissolving agent), and a fixed abrasive forming aid are added in advance to form the fixed abrasive. At this time, by using a metal or metal compound contained in the fixed abrasive grain additive contained in the fixed abrasive grains, clean polishing without metal contamination can be performed.

According to a seventh aspect of the present invention, the metal or metal compound is Na, K, Ca, Al, Fe, Ni, C.
It is a fixed abrasive characterized by being r, Mn, Cu, Ti, Zn or a compound thereof.

According to an eighth aspect of the present invention, in a method for producing fixed abrasive grains for polishing a polishing object in a flat and mirror-like manner, raw material adjustment, molding, attachment to a device mounting jig or adhesion is performed in a clean room or This is a method for producing fixed abrasive grains, which is characterized in that it is performed in a clean booth. Not only can the metal contaminants of the raw material be completely removed, but also metal contamination can be prevented during manufacturing and assembly, so that a clean polishing target without metal contamination can be polished by performing in a clean environment.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a method for producing fixed abrasive grains according to the present invention. First, fine abrasive grains, an abrasive grain dispersant such as a binder and a surfactant, a processing stabilizer such as a buffer, K
A fixed abrasive raw material is prepared by mixing a fixed abrasive additive including a processing accelerator typified by a pH adjusting agent such as OH and a specularity improving agent such as a polymer. Each raw material may be either powder or liquid. Mix these ingredients and, if necessary,
Pure water is added to produce a mixed solution. At this time, a dispersion process such as a stirrer and an ultrasonic disperser is performed to sufficiently disperse each raw material.

Next, dry granulation is performed using a method typified by a spray dryer to produce granulated powder having an average particle diameter of about 50 μm in which various raw materials are uniformly mixed. Then, this granulated powder is molded by a compression molding technique typified by hot pressing to obtain fixed abrasive grains. The fixed abrasive grains obtained as described above are bonded and fixed to a reinforcing plate (support) to complete a product.

The abrasive raw material which is the raw material of the fixed abrasive may be either powder abrasive raw material or slurry abrasive raw material, but the composition ratio of the granulated powder which is an intermediate product is made uniform and further fixed. Since it is possible to improve the homogeneity of the abrasive grains, it is desirable to use a slurry-like abrasive grain raw material that stably exists as fine abrasive grains. Further, in order to realize wafer polishing with less metal contamination, which is the object of the present invention, it is desirable to reduce the amount of metal mixed in the abrasive grain raw material as much as possible. 100 ppm, depending on the raw material form and raw material composition ratio
Or less, preferably 10 ppm or less, more preferably 1
It is desirable to set it to ppm or less.

Further, the binder material which is another fixed abrasive grain raw material may be either a powder raw material or a slurry raw material, but the composition ratio of the granulated powder which is an intermediate product is made uniform, and further the fixed abrasive grain is made uniform. The use of a latex suspension that is homogeneously dispersed in the liquid is desirable to improve performance. Further, in order to realize polishing of an object to be polished with less metal contamination, which is an object of the present invention, it is desirable to reduce the amount of metal contained in the binder raw material as much as possible.
Depending on the raw material form and raw material composition ratio, 100 ppm or less,
Desirably 10 ppm or less, more desirably 1 ppm
The following is desirable.

Further, it is desirable to select a synthetic resin, that is, a synthetic polymer compound (polymer) as the binder. A synthetic high molecular compound (polymer) is produced by polymerizing a large number of low molecular compounds (monomers). At the production stage, it is manufactured by operations such as addition polymerization, copolymerization, condensation polymerization, and addition condensation.At that time, a polymerization catalyst represented by an organometallic compound or an inorganic metal compound, a polymerization inhibitor, a dispersant, an activity is used. Various agents such as agents, solvents, catalyst deactivators, stabilizers, emulsifiers, antioxidants, and water are used, and a product is obtained through complicated steps. In order to reduce the mixing of metal elements in the binder used for this fixed abrasive, it is desirable to reduce the chemicals used in the various polymerization steps and the metal compounds of water. Although it depends on the residual amount and the like, it is desirable to use pure water or ultrapure water in water at 100 ppm or less, preferably 10 ppm or less, more preferably 1 ppm or less.

Further, a processing accelerator (such as amine) containing a microcapsule drug, which is one of the fixed abrasive grain raw materials, a processing performance stabilizer (buffer), a specularity improving agent (water-soluble polymer), and prevention of abrasive grain aggregation. The amount of metal mixed is reduced as much as possible even for polishing aids such as agents (organic polymers), abrasive grain autogenous amount adjusters (binder dissolving agents), fixed abrasive additive such as fixed abrasive molding aids, etc. It is desirable to do. Depending on the additive form and addition ratio, etc., similarly, 100 ppm or less,
Desirably 10 ppm or less, more desirably 1 ppm
In the following, it is desirable to use pure water or ultrapure water as water.

Further, it is necessary to devise not only to reduce the metal contamination from the fixed abrasive raw material but also to reduce the metal contaminant mixed in the manufacturing process. It is desirable to carry out operations such as a granulating step, a molding step, and a step of attaching / adhering to a device mounting jig in a clean room or a clean booth in an environment in which clean air is supplied through a filter. Moreover,
In order to prevent contamination from the jigs and equipment used, it is effective to protect the metal contact surface with jigs and coatings that do not use metal.

By selecting these materials and manufacturing methods, Na, K, Ca, Al, Fe, N contained in the fixed abrasive grains can be obtained.
The amount of metal contaminants such as i, Cr, Mn, Cu, Ti, Zn, etc., or their compounds is sufficiently reduced, and even for the metal contaminants remaining in a part, normal cleaning of an object to be polished after polishing. It can be removed sufficiently in the process.

FIG. 2 shows an ultrasonic dispersion treatment apparatus for a slurry or a mixed liquid of abrasive grains and a resin. In the manufacturing process of the fixed abrasive grains of the present invention, a suspension (slurry) containing the abrasive grains or a mixed liquid of the abrasive grain raw material and the binder resin (hereinafter referred to as a treatment liquid) is subjected to ultrasonic dispersion treatment to completely remove the abrasive grains. Dispersing in a different liquid, and dry granulation in the next step, for example.

In the ultrasonic dispersion treatment, in order to prevent contamination from the ultrasonic vibrator (vibration tip), cooling water is vibrated by the vibration tip, and the treatment liquid in the flask is dispersed by the vibration of the cooling water. It is adopted. This equipment uses resin tubes for piping and uses Teflon (registered trademark)
I am using a valve made by. In addition, pure water is used as cooling water for the parts that require processing instead of oil or city water. The working space is in a clean environment such as a clean room.

Next, an outline of this device will be described. The tank 11 stores the processing liquid before the dispersion processing, and the pump 1
2 is sent to the flask 13 where the ultrasonic dispersion treatment is performed. The flask 13 is a container 1 containing pure water as cooling water.
An ultrasonic generator 16 provided with a vibrating tip is provided below the flask 13 in the container 15 of the ultrasonic generator 16.
The ultrasonic generator 16 receives electric power from the power supply unit 17 and oscillates ultrasonic waves to generate pure water in the container 15 and the flask 13.
Ultrasonic vibration is applied to the treatment liquid in the flask 13 via.

As a result, in the treatment liquid of the abrasive grains and the binder resin, the abrasive grains are uniformly dispersed in the treatment liquid. Further, in the suspension containing abrasive grains, the abrasive grains are uniformly dispersed in the liquid. The treatment liquid after the ultrasonic dispersion treatment is sent by the pump 18 to the tank 19 which stores the mixed liquid after the dispersion treatment. In addition, this apparatus may be provided with a three-way valve 20 to perform the ultrasonic dispersion treatment while circulating the treatment liquid through the pipe 21. Also, these processes may be used together.

Here, the ultrasonic wave generator 16 has a titanium chip as a vibrator at the tip. However, when the titanium chips are directly put into the processing liquid, there are problems that the abrasive grains collide with the titanium chips, holes are formed in the chips, and metal contamination occurs from the holes. Therefore, by applying ultrasonic vibration from the outside of the flask 13 via the cooling water in the container 15, metal contamination due to such titanium chips can be prevented.

The pumps 12 and 18 are preferably tube pumps using Teflon tubes or the like, which can prevent metal contamination. The three-way valve 20 is preferably made of Teflon. Also, the tanks 11 and 1
9 is equipped with stirrers 22 and 23. These stirrers are coated with Teflon to prevent the metal from flowing out of the stirrer into the processing liquid, thereby preventing metal contamination of the processing liquid. There is.

Although the dispersion processing apparatus is provided with the two pumps 12 and 18, only one pump may be provided, and the tank 19 may be omitted if necessary. Further, the treatment liquid after the ultrasonic dispersion treatment is completed is in the tank 1.
It is also possible to directly lead to the line for the next process without storing in No. 9. In the next step, for example, dry granulation with a spray dryer is performed to produce granulated powder.

Next, regarding the metal content and the level of pollution
consider. As an example, 500-1000 ppm Na
Fixed abrasive grains with a binder having a content of
Consider the case of polishing the roof. Polished semiconductor
The amount of Na contamination on the wafer surface was measured.
After the treatment including the cleaning process, the wafer surface is turned into Na and Na
10 per unit area of compound¹⁰/ Cm^TwoTo a degree
is there. Therefore, the Na content inside the binder is
If it is 10/100, the Na content is 10-100.
ppm, and the amount of Na contamination on the surface of the semiconductor wafer after polishing
10⁸-10 ⁹/ Cm^TwoCan be Obey
In the manufacturing process of the fixed abrasive grains and the materials that make up the fixed abrasive grains,
The impurity content of the metal or metal compound of the material used
Polishing with fixed abrasives by setting it to 10 to 100 ppm or less
To reduce metal contamination of semiconductor wafers
it can.

As a method for investigating the content of metal contaminants in the fixed abrasive grains, dressing (dressing treatment) is performed before polishing.
The metal content in the drainage and the amount of wear (wear) of the fixed abrasive grains due to the dressing are measured, and the metal concentration can be calculated from this. It is also possible to scrape a part of the fixed abrasive grains, dissolve the fixed abrasive grains in a liquid, measure the metal amount, and calculate the metal content from the mass of the scraped portion.

FIG. 3 shows a polishing tool provided with the fixed abrasive grains of the present invention. The above-mentioned fixed abrasive 25 is adhered and fixed to a pedestal 26 made of metal or the like, and is attached to and detached from a CMP device as a polishing tool 27. Adhesion is performed with, for example, an epoxy resin adhesive. Fixed abrasive grains 25 on such a pedestal 26
The adhering work is also carried out in a clean room or in an environment cleaner than a cleanness class of about 100,000.

It should be noted that the above-mentioned embodiment merely describes one mode of the preferred embodiment of the present invention, and various modifications can be taken without departing from the gist of the present invention. Is.

[0035]

As described above, according to the present invention, by using fixed abrasives for polishing, which use a raw material having a very low content of metal or metal compound, a clean polishing target with almost no metal contamination is obtained. Allows polishing of objects.

[Brief description of drawings]

FIG. 1 is a flow chart showing a manufacturing process of fixed abrasive grains according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of an ultrasonic dispersion treatment apparatus suitable for the manufacturing process.

FIG. 3 is a perspective view of a fixed-abrasive polishing tool according to an embodiment of the present invention.

[Explanation of symbols]

11,19 tanks 12,18 pump 13 flasks 15 containers 16 Ultrasonic generator 17 power supply 20 three-way valve 21 piping 22,23 stirrer

Claims (8)

[Claims] 1. A fixed abrasive for polishing a polishing object flat and mirror-like, wherein the content of the metal or metal compound contained in the fixed abrasive is 100 ppm or less. 2. The fixed abrasive according to claim 1, wherein the content of the metal or the metal compound contained in the binder used for the fixed abrasive is 100 ppm or less. 3. The content of the metal or metal compound contained in water used in the binder manufacturing process is 100 ppm.
The fixed abrasive according to claim 2, characterized in that: 4. The content of the metal or metal compound contained in the solvent or chemical used in the binder manufacturing process is set to 100 ppm or less.
The fixed abrasive described. 5. The fixed abrasive according to claim 1, wherein, in the abrasive raw material used for the fixed abrasive, the content of the metal or metal compound in the abrasive raw material containing slurry-like abrasive is 100 ppm or less. Abrasive grain. 6. The additive used for producing the fixed abrasive grains, wherein the content of the metal or metal compound contained in the additive is 100 ppm or less.
The fixed abrasive described. 7. The metal or metal compound is Na,
K, Ca, Al, Fe, Ni, Cr, Mn, Cu, T
The fixed abrasive grain according to any one of claims 1 to 6, which is i, Zn, or a compound thereof. 8. In a method for producing fixed abrasive grains for polishing a polishing object into a flat and mirror-like state, adjustment of raw materials, molding, attachment to a device mounting jig or adhesion is performed in a clean room or a clean booth. A method for producing a fixed abrasive grain characterized.