JPH03277683A - Precision polishing composition - Google Patents

Abstract

PURPOSE:To obtain an aqueous polishing composition containing alumina, which gives a polished surface having low surface roughness and freed from surface defects at high polishing efficiency by incorporating an alumina powder having specified physical properties into an aqueous medium. CONSTITUTION:Alumina (preferably one obtained by calcining a hydrated alumina produced through the hydrolysis of an organoaluminum compound) having a mean primary particle diameter of 0.35mum or smaller, an alpha-phase content of 95% or higher and a rectangular shape is incorporated into an aqueous medium to give a precision polishing composition. This composition can realize the precision polishing of a magnetic disc base plate, a semiconductor substrate, metal, and ceramic material with low surface roughness and very few surface defects by merely using it between a work piece and a polishing pad in sliding contact with the surface thereof as in the conventional polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polishing composition. More specifically, the present invention relates to a polishing composition used for precision polishing of magnetic disk substrates, semiconductor substrates such as St and GaAs, thin M magnetic head substrates, single crystal materials, metals, ceramic glasses, synthetic resin materials, and the like.

<Conventional technology> Currently, the materials that are subjected to precision polishing and mirror polishing have become extremely diverse due to the progress of industries such as optics, electronics, and optoelectronics, and include semiconductor substrates, oxide single crystals, glass, metals, and synthetic resins. There are a wide variety of types.

Requirements for processing accuracy have also become stricter, requiring nanometer-order surface roughness and distortion-free mirror surfaces, while also requiring improvements in processing efficiency and productivity, that is, polishing speed.

Lapping and boring using free abrasive grains have been used for a long time as a processing method that provides precision, and alumina, silica, cerium oxide, zirconium oxide, iron oxide, chromium oxide, silicon carbide, diamond, etc. are used as abrasive grains. has been used.

Among them, alumina has high hardness and excellent polishing ability.
Also, since it is an easily available material, fused alumina,
Both calcined alumina and alumina have been widely used as abrasive grains for abrasive materials.

Conventionally, alumina powder with an average primary particle diameter of about 111 m or less has been used for polishing for precision finishing.

However, these alumina powders are disadvantageous in that they contain a mixture of agglomerated grains and coarse grains that are substantially larger than desired, resulting in surface defects such as pits and deep scratches on the polished surface.

In order to improve this inconvenience, it may be possible to perform polishing using alumina powder with a small average primary particle size (generally 0.5 μm or less), but normally, as the alumina particle size becomes smaller, the polishing power decreases and the polishing becomes more difficult. It takes a long time.

Furthermore, two-stage polishing in which rough polishing is followed by final polishing using alumina having a fine particle size is also known, but this method has the disadvantage of reducing work efficiency in the process.

From the viewpoint of improving the finish of the polished surface and improving the polishing efficiency, an invention has been proposed in which a polishing accelerator is added depending on the object to be processed.

For example, Japanese Patent Publication No. 53-3518 discloses a composition for polishing plastic products using an oxidizing polishing accelerator such as aluminum nitrate, and Japanese Patent Publication No. 64-436 discloses a polishing composition using nickel sulfate as a polishing accelerator. JP-A-62-236669 discloses a neutral to weakly acidic polishing composition for plastic products, memory hard disks, and disks, and a polishing composition for magnetic disks to which acids or acid salts such as sulfuric acid, nitric acid, and phosphoric acid are added. Polishing agent for substrates, JP-A-1-121163
The publication discloses a weakly alkaline aluminum magnetic disk polishing composition comprising a triethanolamine carboxylate salt and a triethanolamine hydrochloride polishing accelerator.

However, these polishing accelerators only work effectively on a limited number of objects to be polished, and because they are acidic or alkaline accelerators, they can harm polishing machines, jigs, and workers' hands. Moreover, it also has some disadvantages in terms of wastewater treatment, and it has been desired to improve the polishing surface finish and polishing efficiency by improving the abrasive powder itself.

(Problems to be Solved by the Invention) In view of the above circumstances, the present inventors have obtained an alumina-containing aqueous polishing composition that has high polishing efficiency, has low surface roughness, and can provide a polished surface free of surface defects. As a result of extensive research, the inventors have discovered that a polishing composition that satisfies all of the above objectives can be obtained when alumina powder having specific physical properties is used, leading to the completion of the present invention.

In other words, the present invention contains alumina having an average primary particle diameter of 0.35 μm or less, an α phase content of 95% or more, and an angular shape in an aqueous medium. We are currently developing a precision polishing composition.

The present invention will be explained in more detail below.

The alumina used in the present invention has an average primary particle diameter of about 0.35 μm or less, an α phase content of about 95% or more, and is angular in shape.

The average primary particle diameter of the alumina powder is essentially about 0.35 μm or less, preferably about 0.05 μm to about 0.30 μm.
It is μm.

If the average primary particle diameter is larger than about 0.35 μm, microscratches are likely to occur on the polished surface and the surface roughness increases.

Furthermore, if the particle size is too small, dispersion in an aqueous medium is difficult and insufficient, and microscratches and orange peels are likely to occur due to aggregated particles.

Further, it is essential that the α phase content of the alumina powder used in the present invention is about 95% or more.

In the crystal form of alumina, in addition to the α phase, which has high hardness, there are generally so-called intermediate alumina phases such as σ, δ, θ, and p1χ phases, which are fine particles with a large surface area.

If the content of α-alumina, which has high hardness, is less than about 95%, the polishing speed will be low, and intermediate alumina, which is a fine particle, has poor dispersion in an aqueous medium, so it tends to agglomerate, making it difficult to drink orange beer. This causes the inconvenience of making it more likely to occur.

It is essential that the alumina powder used in the present invention has an angular shape.

The definition of angular is not fixed, but the transmission electron WA
This refers to a state in which when the particle shape is observed using a mirror or the like, the edge portion of the particle is clearly observed to be angular.

Due to the angular shape, the average primary particle diameter is 0.3
It becomes possible to have high polishing power even though the particle size is 5 μm or less.

Such alumina can be obtained by known methods such as calcination of alumina hydrate or intermediate alumina, thermal decomposition of aluminum-containing compounds, or hydrothermal synthesis, but in particular alumina obtained by hydrolysis of organic aluminum A hydrate calcined under uniform temperature conditions of about 150°C to about 1300°C is preferably used.

The polishing composition according to the present invention is prepared by adding water, preferably pure water, to
It is a slurry in which about 2 to about 30% by weight of such alumina is dispersed and suspended, and is a neutral or weakly alkaline slurry with a pH of 7 to 10.

Depending on the object to be polished, a polishing accelerator for accelerating mechanochemical polishing or a pH adjuster may be added as necessary.

<Effects of the Invention> The polishing composition of the present invention described in detail above is similar to the case where conventional polishing compositions are used. It is possible to perform precision polishing of magnetic disk substrates, semiconductor substrates, metal ceramic materials, etc. with low surface roughness and extremely few surface defects simply by using a chemical composition, and its industrial value is extremely high. .

<Examples> The present invention will be described in more detail below using Examples, but the present invention is not limited to these Examples.

Incidentally, in the present invention, the analysis was performed according to the following method.

Average primary particle size: scanning electron of alumina powder! Read the particle size (major axis α phase content, shape, surface roughness, surface observation, and average of short axis) from the J microphotograph, create the diagram on the right for the cumulative frequency, calculate the central particle size from this, and calculate the average primary particle size and did.

: α-A l * Ox alumina Powder X&? ! By diffraction measurement ( 116) Integral strength of surface diffraction line α-Aluminum Specified θ of Na content /α-Diffraction of mixed alumina By the integrated intensity of the line, the standard It was calculated by .

: Transmission electron of alumina powder Micrograph (40,000x, 10 Observation was made with a magnification of 10,000 times.

:Surfco made by Koita Research Institute By ET-30HK Non-contact stylus HIPO Measured using SS.

: Polished surface, differential interference microscope Due to micro scratches, orange peel, pinto, Observe the presence or absence of the module ( 100 times, 400 times).

Polishing rate: The thickness of the workpiece before and after polishing was measured using a micrometer, and the polishing rate was determined by dividing the amount of polishing by the polishing time.

Visual observation: The polished surface was visually observed and it was determined whether a mirror surface was formed or not.

Example 1 The workpiece has an outer diameter of 3.5 inches and an N1-P layer thickness of 1.
7μm, surface roughness before polishing RaO, 01#m, RII
An aluminum magnetic disk substrate plated with electroless Ni-P with an AI of 0.08 pm was polished using a 4-way type double-sided boring machine (surface plate diameter 640φ), and a suede-type polishing pad ( Polytex), lower surface plate rotation speed 4Qrpm, processing pressure 80g/cm
Polishing was performed for 10 minutes at a slurry supply rate of 80 ml/min.

The abrasive slurry is an alumina abrasive obtained by firing aluminum hydroxide obtained by a hydrolysis method of organic aluminum, with an average primary particle diameter of 0°25 μm and an α phase content of 10.
A suspension of 5 parts by weight of 0% angular alumina in 95 parts by weight of pure water was used.

After polishing, the polishing speed, long surface roughness of the polished surface, microscratches, and the presence or absence of orange beer were examined.

The results are shown in Table 1.

Example 2, Comparative Examples 1-3 Same as Example 1 except that the alumina powder was replaced with alumina powder having the physical properties shown in Table 1 in the method of Example 1.
An aluminum disk substrate with electroless N1-P plating was polished.

The results are shown in Table 1.

Example 3 A suede type polishing pad was attached to a single-sided polishing machine, and a silicon wafer was polished.

The processing pressure was 100 g/csl, the relative speed between the wafer and the polishing band was 60 m/min, and 2 parts by weight of angular alumina with an average primary particle diameter of 0.17 μm and 100% α phase content was added as an abrasive slurry to 98 parts by weight of pure water. 100 parts
Polishing was performed for 10 minutes by supplying at a rate of m1/min.

The results are shown in Table 2.

Visual observation of the polished surface revealed a highly mirror-like finish.

Examples 4-6 In the method of Example 3, polishing was performed using a gallium arsenide compound semiconductor substrate, an aluminum nitride substrate, a titanium substrate, etc. shown in Table 2 as the workpiece.

The results are shown in Table 2.

Claims (2)

[Claims] (1) A precision polishing composition comprising alumina having an average primary particle diameter of 0.35 μm or less, an α phase content of 95% or more, and a square shape in an aqueous medium. (2) The precision polishing composition according to claim 1, wherein the alumina is alumina obtained by calcining an alumina hydrate obtained by hydrolyzing an organoaluminum compound. .