Polishing slurry and polished substrate

Abstract

A polishing slurry comprising an abrasive comprising as a basic ingredient rare earth oxides containing cerium oxide, which polishing slurry further comprises an anionic surfactant and a nonionic surfactant and has a pH value of at least 11. The polishing slurry is especially suitable for polishing a glass substrate for magnetic disc, and other substrates used in electronic field.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is an application filed under 35 U.S.C. § 111(a) claiming benefit pursuant to 35 U.S.C. § 119(e)(1) of the filing date of Provisional Application 60 / 423,376 filed Nov. 4, 2003, pursuant to 35 U.S.C. § 111(b).TECHNICAL FIELD [0002] This invention relates to a polishing slurry used for precision polishing of substrates with optical and electronic applications, such as glass substrates for optical lens, optical disc, magnetic disc, plasma display, liquid crystal display, and LSI photomask. This polishing slurry exhibits excellent polishing properties, namely, has a high rate of polishing and gives a polished surface with a reduced surface roughness and not having surface defects such as scratches to any appreciable extent. [0003] The invention further relates to a process for polishing a substrate with the above-mentioned polishing slurry, a process for producing a polished substrate, and a polished substrate. BACKGROUND AR...

AI Technical Summary

Benefits of technology

The present invention provides a polishing slurry that can achieve high-precision surface polishing with a high flatness and minimal surface roughness and scratches. The slurry comprises rare earth oxides containing cerium oxide as the abrasive, an anionic surfactant, a nonionic surfactant, and a pH value of at least 11. The abrasive particles have a specific size and surface area, and the slurry further contains a liquid medium and other ingredients such as phosphoric acid esters, cellulose ethers, and water-soluble high-molecular-weight compounds. The substrate, such as glass, can be polished with this slurry for various applications such as optical lens, optical disc, plasma display, and magnetic disc.

Problems solved by technology

These glass substrates have very poor processability, and are difficult to polish with conventional abrasive composition at a high polishing rate and with good productivity.

However, the addition of different kind of sol causes an increase of scratches or pits on a polished surface and hence high surface precision cannot be attained.

The alkaline ceric oxide sol containing an organic acid with at least two carboxyl groups in the abrasive composition has a small average particle diameter in the range of 2 nm to 200 nm, and hence, the rate of polishing is low, the polishing cost is high, and it is difficult to stably produce a polished substrate with high quality.

The above-mentioned CMP polishing liquid inevitably has a low pH value because it contains ceric oxide abrasive grains, and the rate of polishing is low and the surface roughness is large.

Thus, it is impossible to satisfy both of high-precision surface polishing performance and high rate of polishing with any of the hitherto proposed polishing techniques.