CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase of International Patent Application No. PCT/JP2017/011527, filed Mar. 22, 2017, which claims priority to Japanese Patent Application No. 2016-071478, filed Mar. 31, 2016. The contents of these applications are herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a polishing composition. In particular, it relates to a polishing composition used in polishing a material to be polished (a polishing object).

The present International Application claims priority to Japanese Patent Application No. 2016-071478 filed on Mar. 31, 2016; and the entire content thereof is incorporated herein by reference.

BACKGROUND ART

With respect to materials such as diamond, sapphire (aluminum oxide), silicon carbide, boron carbide, tungsten carbide, silicon nitride and titanium nitride, surfaces are typically processed by polishing (lapping) processes in which diamond abrasives are supplied to polishing platens. However, in lapping processes that use diamond abrasives, scratching is likely to occur on surface of lapped objects. In addition, diamond abrasive particles are left on surfaces of lapped objects. Thus, the surfaces of lapped objects are likely to suffer defects and deformation. Accordingly, studies are underway for a polishing process that is carried out after diamond lapping, using a polishing pad and polishing slurry supplied to the interface between the polishing pad and a polishing object. Alternatively, substituting polishing for the lapping has been examined. Publications disclosing this type of conventional art include Patent Document 1.

CITATION LIST

Patent Literature

[Patent Document 1] Japanese Patent Application Publication No. 2011-211178

SUMMARY OF INVENTION

Technical Problem

Lately, higher-quality surfaces are required of polished articles of silicon carbide and the like (e.g. semiconductor substrates and other substrates). Thus, there is a demand for a polishing composition that can satisfy a level of polishing removal rate required for practical use while achieving a polished surface with fewer scratches (scars caused by polishing). Here, the polishing removal rate means the amount (thickness) of surface of polishing object removed per unit time.

The present invention has been made under these circumstances with a primary objective to provide a polishing composition capable of effectively reducing the number of scratches present on a polished surface while maintaining a high polishing removal rate. Another related objective is to provide a method for producing a polished object using the polishing composition.

Solution to Problem

The present invention provides a polishing composition for polishing a material having a Vickers hardness of 1500 Hv or higher. The polishing composition comprises an alumina abrasive and water. The alumina abrasive has an isoelectric point that is below 8.0 and is lower than the pH of the polishing composition.

The use of the alumina abrasive having an isoelectric point that is 8.0 and lower than the pH of the polishing composition can effectively reduce the number of scratches present on the polished surface while maintaining a high polishing removal rate.

The present invention also provides a method for producing a polished object. The production method comprises polishing an object having a Vickers hardness of 1500 Hv or higher, supplying a polishing composition disclosed herein to the object. The production method can efficiently provide a polished object having a high-quality surface with greatly reduced scratches.

