JP2000354945A - Chemical and mechanical polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical and mechanical polishing method capable of mirror finishing a glass substrate to a degree where no abnormal protrusions can be seen on a surface. SOLUTION: A chemical and mechanical polishing method is constituted of a process to travel a tape T having voids on its surface by pushhing it on a surface of a glass substrate D while supplying a coolant L to which a solution having a hydroxyl group is added to the surface of the glass substrate D. A plastic fiber made woven or unwoven fabric tape, a tape on a plastic film surface of which a foaming body layer is fixed or a tape on the plastic film surface of which a foaming body layer on the surface of which abrasive grains are fixed is used for this tape T. The coolant L added with a solution having a hydroxyl group of a potassium hydroxide solution, sodium hydroxide solution, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical mechanical polishing method for mirror-polishing a glass substrate for a magnetic disk.

[0002]

2. Description of the Related Art A glass substrate for a magnetic disk is mirror-finished on its surface and then textured so as to have a predetermined surface roughness. A magnetic layer is formed on the magnetic recording medium, and it is commercialized as a magnetic recording medium. For such mirror finishing, C
MP method (Chemical Mechanical P
A chemical mechanical polishing method called "olishing" is applied.

In this chemical mechanical polishing method, a solid phase reaction is caused at a contact interface between a solid and a workpiece, a foreign substance is generated at the contact interface, and processing is performed while removing the contact interface. This is a processing method in which the processing unit is extremely small, so that a high degree of flattening is performed, and the use of a chemical reaction has an advantage that processing deterioration is extremely small.

[0004] In the chemical mechanical polishing process, generally, an abrasive grain suspension obtained by dispersing powder of silicon carbide, chromium oxide, alumina, or the like having an average particle size of about 5 μm or less in an acidic or alkaline liquid is used. Excellent in chemical resistance, artificial leather with moderate hardness, etc., between the buff and the glass substrate surface,
The two are relatively moved, and are performed using a single-side polishing machine (not shown in FIG. 2A) or a double-side polishing machine (not shown in FIG. 2B).

In the single-side polishing machine, as shown in FIG. 2 (a), a glass substrate D attached to the lower surface of a pressure head H or vacuum-adsorbed is pressed onto a buff C attached to a surface plate J1. (In the direction of arrow V), the glass substrate D is rotated (in the direction of arrow X1) together with the pressure head H while the abrasive suspension S is supplied to the buff C on the surface plate J1 through the nozzle N, By rotating the board J1 (in the direction of the arrow W1), one side of the glass substrate D is subjected to chemical mechanical polishing.

Further, as shown in FIG. 2 (b), the double-side polishing machine has a donut-shaped lower surface plate for mounting a plurality of glass substrates D disposed in a plurality of openings K of the planetary gear G3. It has a surface plate composed of J2 and a donut-shaped upper surface plate (not shown) having the same shape as the lower surface plate J2. The glass substrate D on the lower platen J2 is pressed from above by the upper platen. A sun gear (external gear) G1 connected to an external drive motor is located at the center of the surface plate, and an internal gear (internal gear) G2 is fixed around the surface plate. The upper platen is provided with a plurality of abrasive grain suspension supply holes (not shown), and the above-mentioned abrasive suspension is supplied between the upper and lower platens through these holes. In the illustrated double-side polishing machine, the sun gear G is supplied between the upper and lower platens while the abrasive suspension is supplied between the upper and lower plates through a hole for supplying the abrasive suspension provided on the upper platen.
1 is rotated in the direction of arrow W2, and the planetary gear G3 meshed with the sun gear G1 and the internal gear G2 and located between the upper and lower stool is rotated in the direction of arrow X2 between the upper and lower stool. In this direction, the two sides of the plurality of glass substrates D arranged in the respective openings K of the planetary gear G3 are chemically and mechanically polished in a batch manner. Generally, such a double-side polishing processing method is called a “two-way method”.

[0007] As described above, conventionally, the above-mentioned chemical mechanical polishing is performed using an abrasive suspension. Therefore, after the chemical mechanical polishing is completed, the abrasive suspension remaining on the surface of the glass substrate is removed. In order to remove suspended liquids and polishing debris, the polishing machine was stopped, the glass substrate was taken out of the polishing machine, and the glass substrate was washed with various cleaning liquids.

However, since the surface of the glass substrate is kept in contact with the abrasive suspension between the time when the polishing machine is stopped and the time when the glass substrate is taken out of the polishing machine and washed, the abrasive suspension is used. An extraneous substance is generated at the contact interface between the abrasive grains (solid) in the suspension and the contact interface between the glass substrate (workpiece) and this unnecessary interface that cannot be removed by washing on the glass substrate surface. There is a problem that abnormal projections are formed and the surface of the glass substrate cannot be highly flattened, ie, cannot be mirror-finished.

Accordingly, an object of the present invention is to provide a chemical mechanical polishing method capable of mirror-polishing a glass substrate to the extent that abnormal projections are not seen on the surface.

[0010]

According to a chemical mechanical polishing method of the present invention for solving the above-mentioned problems, a coolant containing a solution having a hydroxyl group is supplied to the surface of a glass substrate for a magnetic disk while a gap is formed on the surface. Pressing the tape having the above to the glass substrate surface and running the tape.

The tape having voids on the surface is made of a woven or non-woven fabric tape made of plastic fiber such as polyester, nylon, rayon, or the like, or a foam layer such as foamed polyurethane, made of a plastic material such as polyester or polyethylene terephthalate. A tape fixed to the surface of the film or a tape fixed to the surface of the plastic film with a foam layer having abrasive particles fixed to the surface is used.

The coolant supplied to the surface of the glass substrate is obtained by adding a solution having a hydroxyl group, such as a potassium hydroxide solution or a sodium hydroxide solution. This coolant not only absorbs the frictional heat generated by the mechanical polishing between the tape and the glass substrate, but also allows the solution containing hydroxyl groups added to the coolant to contact the tape (solid) with the glass substrate (workpiece). It promotes chemical polishing by solid phase reaction occurring at the interface. When the tape is pressed against the surface of the glass substrate to which the coolant has been supplied and run, the plastic fibers constituting the tape, a foam layer, or abrasive grains fixed to the foam layer are pressed against the glass substrate surface,
A solid phase reaction occurs at these contact interfaces, the protrusions on the glass substrate surface are scraped off by tape, and the scraped off foreign matter is
It is taken into the voids on the tape surface (ie, voids between the plastic fibers, or numerous voids formed on the foam layer surface during foaming).

In the chemical mechanical polishing method of the present invention,
When the tape running while being pressed against the surface of the glass substrate is separated from the surface of the glass substrate, no further solid phase reaction occurs at the contact interface between the tape and the glass substrate, and the chemical mechanical polishing is completed. Immediately after the completion of the chemical mechanical polishing, the surface of the glass substrate is washed, and the coolant remaining on the surface of the glass substrate can be easily and quickly washed away.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the chemical mechanical polishing according to the present invention, while supplying a coolant containing a solution having a hydroxyl group to the surface of a glass substrate for a magnetic disk, a tape having a void on the surface is made of glass. This is performed by pressing the substrate against the substrate surface and running.

The tape having voids on its surface is made of a woven fabric of 5 to 3000 μm thick made of 0.05 to 5 denier plastic fiber having excellent heat resistance such as polyester, nylon and rayon and having high tensile strength. Or a tape in which a foamed material having a thickness of 0.1 mm to 1 mm and a hardness of 10 to 90 formed by foaming and molding a foamed material such as a nonwoven fabric tape or polyurethane is fixed to the surface of a plastic film such as polyester or polyethylene terephthalate. (For example,
JP-A-11-151651), or a tape in which a layer of a foam having abrasive grains fixed on the surface thereof is fixed to the surface of a plastic film (for example, see JP-A-10-337795) can be used.

Here, for example, a foam layer made of polyurethane (foamed polyurethane layer) is mixed well with water at the time of reacting isocyanates with polyester having a functional hydroxyl group, and the mixture is finely mixed with carbon dioxide gas. Disperse air bubbles,
It is cured and foamed and molded in a mold. A large number of voids formed by carbon dioxide gas bubbles are dispersed on the surface of the foam layer. Abrasive grains, on the surface of the foam layer, a mixed solution of abrasive grains and a water-soluble adhesive such as polyurethane resin,
It can be fixed to the surface of the foam layer by applying it so that the voids on the surface of the foam layer are not closed and drying it.

The abrasive has an average particle size of 0.01 μm to 10 μm.
m silicon carbide, chromium oxide, alumina, cerium oxide,
Fine powder such as magnesium oxide is used. The plastic film has chemical resistance and high tensile strength with a thickness of 5μ.
A plastic film such as polyester, polyethylene terephthalate or the like having a thickness of 10 to 10 μm is used.

The coolant is obtained by adding a solution having a hydroxyl group to water. Examples of the solution having a hydroxyl group include potassium hydroxide, sodium hydroxide, and cesium hydroxide.

The chemical mechanical polishing according to the present invention comprises:
This is performed using a single-side polishing machine (FIG. 1A) or a double-side polishing machine (FIG. 1B).

In the single-side polishing machine shown in FIG. 1A, a coolant L to which a solution having a hydroxyl group is added is supplied to the surface of the glass substrate D through a nozzle N,
Is rotated in the direction of arrow R, and a tape T having a gap on the surface is pressed against the surface of the glass substrate D via a rubber roller P, and the tape T is rotated in the direction opposite to the rotation direction R of the glass substrate D (direction of arrow M). To perform a chemical mechanical polishing process.

In the double-side polishing machine shown in FIG. 1B, a coolant L to which a solution having a hydroxyl group is added is supplied to both surfaces of a glass substrate D rotating in the direction of arrow R in a substantially vertical plane through left and right nozzles N. While pressing, the tape T is pressed against both sides of the glass substrate D via rubber rollers P from both left and right sides of the glass substrate D, and the tape T is caused to run in a direction opposite to the rotation direction R of the glass substrate D (the direction of arrow M). A chemical mechanical polishing process is performed.

In these single-side and double-side polishing machines,
When the rubber roller P is moved away from the surface of the glass substrate D together with the tape T, and the tape T is separated from the surface of the glass substrate D, the chemical mechanical polishing is completed. After the completion of the chemical mechanical polishing, the coolant L remaining on the surface of the glass substrate D is easily and quickly washed away by spraying water on the surface of the glass substrate D while the glass substrate D is mounted on the polishing machine. Can be.

[0023]

EXAMPLE After a glass substrate for a magnetic disk was mirror-polished by a conventional chemical mechanical polishing method, one surface of the glass substrate was further mirror-finished according to the chemical mechanical polishing method of the present invention. .

FIG. 2 shows a conventional chemical mechanical polishing process.
This was performed using a double-side polishing machine shown in (b). For the buffs respectively attached to the upper and lower platens, a wet polishing pad made of foamed polyurethane (Rodel, DG (product name)) was used. The composition of the abrasive suspension used and the polishing conditions are as shown in Tables 1 and 2, respectively.

[0025]

[Table 1]

[0026]

[Table 2]

After the conventional chemical mechanical polishing, the glass substrate is taken out of the double-side polishing machine and washed with water, and an arbitrary area of 30 μm × 30 μm on the surface of the polished glass substrate is scanned with a scanning probe microscope. Scanning was performed using a digital instrument (Nanoscope Dimension 3100 series) (256 points), and the average surface roughness (Ra) and the maximum surface roughness (Ry) in this scanning range were measured. The average surface roughness after conventional chemical mechanical polishing is 4.50 ° and the maximum surface roughness is 177.0.
(These measured values are shown in Table 5 below (before processing)
Shown).

Next, according to the present invention, the glass substrate (average surface roughness 4.50 °, average surface roughness 4.50 ° C.) after the conventional chemical mechanical polishing was performed using the single-side polishing machine shown in FIG.
Mirror finishing on one side having a maximum surface roughness of 177.03 °) was further performed (Examples 1 to 4). The average surface roughness was measured using the scanning probe microscope described above. Example 1
Polishing conditions in No. 4 are as shown in Table 3.
Examples 1 to 4 were performed using different tapes, and the polishing conditions and the composition of the coolant used were the same in each example, except for the type of tape.

[0029]

[Table 3]

<Example 1> In Example 1, a thickness of 0.0
300 μm thick made of 6 denier polyester fiber
Woven cloth tape was used.

<Example 2> In Example 2, a nonwoven fabric tape having a thickness of 1000 µm and made of polyester fiber having a thickness of 2 deniers was used.

Example 3 Hardness 60, thickness 500 μm
Was used in which a foamed polyurethane layer was bonded and fixed to the surface of a polyester film having a thickness of 25 μm.

Example 4 A solution of a cerium oxide fine powder having an average particle size of 1.0 μm and a polyester resin was prepared with a hardness of 6
0, applied to the surface of the foamed polyurethane layer having a thickness of 0.5 mm, and dried to fix fine cerium oxide powder on the surface of the foamed polyurethane layer.
m, a tape adhered and fixed to the surface of a polyester film was used.

The composition of the coolant used in Examples 1 to 4 is as shown in Table 4.

[0035]

[Table 4]

After the chemical-mechanical polishing according to the present invention described in Examples 1 to 4, the glass substrate is washed with water while being attached to the single-side polishing machine, and the glass substrate is polished and the glass substrate is polished. The area of 30 μm × 30 μm is scanned (256 points) using the above scanning probe microscope,
The average surface roughness (Ra) and the maximum surface roughness (Ry) in this scanning range were measured. Table 5 below shows the average surface roughness and the maximum surface roughness after the chemical mechanical polishing in Examples 1 to 4 according to the present invention.

[0037]

[Table 5]

As shown in Table 5, according to the present invention, the mirror surface was flattened more than the surface of the glass substrate obtained by the conventional chemical mechanical polishing. In addition, the state of the glass substrate surface after the conventional polishing process and after the polishing process according to the present invention was observed with the above-mentioned scanning probe microscope. Were scattered, but no abnormal protrusions visible with a microscope could be observed on the surface of the glass substrate after polishing according to the present invention.

[0039]

According to the chemical mechanical polishing method of the present invention, when a tape having a void on the surface is separated from the surface of the glass substrate, a further solid phase reaction occurs at the contact interface between the tape and the glass substrate. As a result, there is an effect that a highly flat surface without abnormal projections can be obtained.

According to the chemical mechanical polishing method of the present invention, the surface of the glass substrate can be washed immediately after the completion of the chemical mechanical polishing, so that the polishing machine is stopped for cleaning the surface of the glass substrate. In addition, the time and labor required to take out the glass substrate from the polishing machine can be saved, and the time required to shift to the next processing step can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic view of a single-side polishing machine (FIG. 1 (a)) and a double-side polishing machine (FIG. 1 (b)) used in the present invention.

FIG. 2 is a schematic view of the vicinity of a lower surface plate of a single-side polishing machine (FIG. 2A) and a batch-type double-side polishing machine (FIG. 2B).

[Explanation of symbols]

 C: Buff D: Glass substrate G1: Sun gear G2: Internal gear G3: Planetary gear H: Pressurizing head J1: Platen J2: Lower platen K ··· Opening of planetary gears L ··· Coolant N ··· Nozzle P ··· Rubber roller S · ··· Abrasive suspension T · · · Tape with voids on the surface M · · · Polishing tape running direction R · ··· Glass substrate rotation direction V ··· Pressing head pressing direction W1 ··· Plate surface rotation direction W2 ··· Sun gear rotation direction X1 ··· Pressing head rotation direction X2 ··· Planetary gear rotation direction Y · ..Planetary gear revolution direction

Continued on the front page F term (reference) 3C049 AA05 AA07 AA09 AA12 AA18 AC04 CA01 CB02 3C058 AA05 AA07 AA09 AA12 AA18 AC04 CA01 CB02 DA12

Claims (8)

[Claims] 1. A chemical mechanical polishing method comprising: a step of supplying a coolant containing a solution having a hydroxyl group to a surface of a glass substrate while pressing a tape having a void on the surface against the surface of the glass substrate to run the tape. 2. A tape made of a woven or non-woven fabric made of plastic fibers, a tape having a foam layer fixed on the surface of a plastic film, or a tape having a foam layer having abrasive particles fixed on the surface thereof, fixed on the surface of the plastic film. The chemical mechanical polishing method according to claim 1, wherein is used. 3. The chemical mechanical finishing method according to claim 1, wherein a potassium hydroxide solution is used as the solution having a hydroxyl group. 4. A method for chemically and mechanically polishing a glass substrate for a magnetic disk, comprising: (1) a step of rotating the glass substrate; and (2) a step of adding a coolant containing a solution having a hydroxyl group to the glass substrate. A chemical mechanical polishing method comprising: a step of supplying the tape to the surface; and (3) a step of pressing a tape having voids on the surface against the surface of the glass substrate and running the tape. 5. The chemical mechanical polishing method according to claim 4, further comprising the step of separating the tape from the surface of the glass substrate, whereby the chemical mechanical polishing is completed. 6. The chemical mechanical polishing method according to claim 5, further comprising a step of spraying a cleaning liquid onto the surface of the glass substrate after separating the tape from the surface of the glass substrate. 7. As the tape, a woven or nonwoven fabric tape made of plastic fiber, a tape having a foam layer fixed on the surface of a plastic film, or a tape having a foam layer having abrasive particles fixed on the surface of the plastic film The chemical mechanical polishing method according to any one of claims 4 to 6, wherein 8. The chemical mechanical polishing method according to claim 4, wherein a potassium hydroxide solution is used as the solution having a hydroxyl group.