Polishing agent, polishing method and additive liquid for polishing

1. A polishing agent, comprising a particle of a metal oxide, a water-soluble polyamide having a tertiary amino group and/or an oxyalkylene chain in a molecule thereof, an organic acid and water, and having a pH of 7 or less.

2. The polishing agent according to claim 1 , wherein the water-soluble polyamide has the tertiary amino group in a main chain thereof and/or a side chain thereof.

3. The polishing agent according to claim 1 , wherein the water-soluble polyamide has the oxyalkylene chain in a main chain thereof.

4. The polishing agent according to claim 1 , wherein the water-soluble polyamide is a copolymer obtained from: aminoethylpiperazine and/or a modified polyalkylene glycol; and a lactam.

5. The polishing agent according to claim 1 , wherein the metal oxide is a cerium oxide.

6. The polishing agent according to claim 1 , wherein the organic acid is at least one selected from the group consisting of tetrahydrofuran-2-carboxylic acid, pyrrolidone carboxylic acid, 2-hydroxyisobutyric acid, N-acetylglycine, 2-furancarboxylic acid, iminodiacetic acid and levulinic acid.

7. The polishing agent according to claim 1 , wherein a content of the water-soluble polyamide is 0.0001 mass % or more and 1 mass % or less.

8. The polishing agent according to claim 1 , wherein a content of the organic acid is 0.005 mass % or more and 2.0 mass % or less.

9. The polishing agent according to claim 1 , wherein the pH is 3 or more and 6 or less.

10. The polishing agent according to claim 1 , wherein an average particle diameter of the particle of the metal oxide is 0.01 μm or more and 0.5 μm or less.

11. The polishing agent according to claim 1 , wherein a content of the particle of the metal oxide is 0.05 mass % or more and 2 mass % or less.

12. A polishing method, comprising bringing a surface to be polished and a polishing pad into contact with each other while supplying the polishing agent according to claim 1 , thereby performing polishing by relative movement between the surface to be polished and the polishing pad, wherein the surface to be polished which includes a face comprising silicon oxide of a semiconductor substrate is polished.

13. An additive liquid for polishing, which is to be added to a dispersion liquid of a particle of a metal oxide to prepare a polishing agent, the additive liquid comprising a water-soluble polyamide having a tertiary amino group and/or an oxyalkylene chain in a molecule thereof, an organic acid and water, and having a pH of 7 or less.

14. The additive liquid for polishing according to claim 13 , wherein the water-soluble polyamide has at least one of the tertiary amino group bonded to a main chain thereof or side chain thereof and the oxyalkylene chain bonded to the main chain.

15. The additive liquid for polishing according to claim 13 , wherein the water-soluble polyamide is a copolymer obtained from: aminoethylpiperazine and/or a modified polyalkylene glycol; and a lactam.