The present invention relates to compositions for polish› ing (hereinafter polishing compositions) and methods for polishing. The present invention particularly relates to a method for polishing a layer containing elemental silicon, by which a silicon compound other than the elemental silicon is selectively polished while limiting the polishing rate of the elemental silicon. 

Manufacturing process of semiconductor devices include a step of polishing an object made of elemental silicon ( e.g., polysilicon, single crystalline silicon, or amorphous silicon), silicon compounds, metals or the like. In this step, when a semiconductor to be manufactured includes a gate electrode made of polysilicon and a silicon-based material other than polysilicon surrounding the gate electrode, such a silicon› base material other than polysilicon, which may be silicon nitride or silicon dioxide, is required to be polished prefer› entially. For instance, Patent Literature 1 proposes a polish- ing liquid capable of polishing a layer containing a silicon material other than polysilicon quickly and limiting the polishing of polysilicon. The polishing liquid proposed contains colloidal particles, organic acid, and at least one nonionic additive selected from nonionic surfactant and nonionic hydrophilic resin. Such a polishing liquid, how› ever, does not have good washing efficiency because it contains nonionic additive and the nonionic additive remains after the polishing. Therefore this polishing liquid does not satisfy user’s demand fully. 

The present invention aims to provide a polishing com› position and a method for polishing to solve the problems of the conventional techniques as stated above. According to the present invention, when a polishing object including elemental silicon, a silicon compound, metals and the like is polished, the polishing rate of the elemental silicon, such as polysilicon, single crystalline silicon, or amorphous silicon, especially the polishing rate of polysilicon, can be limited, and the silicon compound other than the elemental silicon, such as a silicon nitride or silicon dioxide, can be selectively polished. 

To solve the above problems, a polishing composition according to one embodiment of the present invention includes: abrasives, an organic acid and a conjugate base of this organic acid. 

A polishing composition according to one embodiment may include abrasives, an organic acid and a conjugate base of the organic acid. 

## POLISHING COMPOSITION AND POLISHING METHOD 

## BACKGROUND ART 

PTL 1: JP 2009-289886 A 

## SUMMARY OF INVENTION 

## TECHNICAL FIELD 

## CITATION LIST 

## Patent Literature 

## Technical Problem 

## Solution to Problem 

In the polishing compos1t10n in this embodiment, the organic acid may have a value of pKa that is 0.3 or more and 6.0 or less, and the polishing composition may have a value of pH that is equal to or higher than a value smaller than the value of pKa of the organic acid by 1.0 unit and that is equal to or lower than a value larger than the value of pKa by 1.5 units. 

In the polishing composition in this embodiment, the conjugate base of the organic acid may be at least one type selected from ammonium salt, sodium salt and potassium salt. 

In the polishing composition in this embodiment, the abrasives may be silica with an organic acid immobilized to a surface of the silica. 

In the polishing composition in this embodiment, content of the abrasives may be 0.1 % by mass or more and 20.0% by mass or less. 

In the polishing composition in this embodiment, content of the conjugate base of the organic acid may be 0.01 % by mass or more and 10.0% by mass or less. 

This polishing composition can be used for polishing a substrate including elemental silicon, especially polysilicon. 

A method for polishing according to another aspect of the present invention includes polishing a polishing object using the polishing composition according to the above embodi› ment. In this method for polishing, the polishing object may be a substrate including polysilicon. 

A polishing composition and a method for polishing of the present invention are capable of, when a polishing object includes elemental silicon, limiting the polishing rate of the elemental silicon, especially polysilicon. According to the polishing composition and the method for polishing, while limiting the polishing rate of elemental silicon, especially polysilicon, a silicon compound other than the elemental silicon, such as a silicon nitride or silicon dioxide, can be polished at a high polishing rate. 

The following describes embodiments of the present invention in details. A polishing composition of the present embodiment can be prepared by mixing abrasives, organic acid, and a conjugate base of the organic acid. 

This polishing composition is suitably used for polishing of an object such as elemental silicon, silicon compounds or metals, e.g., for polishing the surface of a wiring substrate made of silicon, containing elemental silicon, a silicon compound, or metals, during the manufacturing process of a semiconductor device. The polishing composition is particu› larly suitably used for polishing of a substrate containing polysilicon. Elemental silicon includes polysilicon, single crystalline silicon, and amorphous silicon. Polysilicon includes typical polysilicon and modified polysilicon. Modi- fled polysilicon includes silicon doped with impurities such as B or P in polysilicon. Silicon compounds include silicon nitride, silicon oxide and silicon carbide. A silicon com› pound film includes a low-permittivity coat having specific permittivity of 3 or less. This polishing composition enables limiting of a polishing rate of the elemental silicon and polishing of the silicon compounds other than the elemental silicon at a high polishing rate. 

## Advantageous Effects of Invention 

## DESCRIPTION OF EMBODIMENTS 

