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US 12,760,202 B2Granted
Polishing composition
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsNaoki Yarita, Daijitsu Harada, Harunobu Matsui, Masaki Takeuchi
Life of this patent
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Abstract
A polishing composition including a colloidal silica containing colloidal silica particles, a pH adjusting agent, and a chelating agent provides a substrate that has a surface having a high flatness, low defects and a low surface roughness with low cost and high productivity, and a substrate having high surface quality suitable as a substrate for mask blanks such as a glass substrate containing SiO2 as a main component, particularly, as a substrate for mask blanks used in EUVL.
Claims10
A polishing composition comprising
- a colloidal silica comprising colloidal silica particles, a pH adjusting agent, and a chelating agent,
- wherein
- the colloidal silica particles contain secondary particles formed by association of primary particles,
- the primary particles have an average primary particle size DA1 of not less than 5 nm and not more than 50 nm that is calculated from a specific surface area measured by a gas absorption method,
- the colloidal silica particles have a degree of association P32 DA2/DA1 of not more than 1.8 calculated by dividing a secondary particle size DA2 by the average primary particle size DA1, DA2 being measured by a dynamic light scattering method, and
- a maximum of an auto-correlation function G2(f) is not less than 1.40 in a region of frequency f of not less than 0.001 MHz and not more than 1 MHz, G2(f) being obtained by variable transformation of G2 (t) with “frequency f=1/τ”, wherein G2(τ) is calculated, from I(t) representing time dependency of intensity of scattered light that is obtained by measuring translational motion of the colloidal silica particles existing in the polishing composition measured by a dynamic light scattering method using laser, by the following expression (1):
- G
- 2
- (
- τ
- )
- =
- 〈
- I
-
- (
- t
- )
- ·
- I
-
- (
- t
- +
- τ
- )
- 〉
- 〈
- I
-
- (
- t
- )
- 〉
- 2
- =
- (
- ∫
- 0
- T
- I
-
- (
- t
- )
- ·
- I
-
- (
- t
- +
- τ
- )
-
- dt
- T
- )
- (
- ∫
- 0
- T
- I
-
- (
- t
- )
-
- dt
- T
- )
- 2
- =
- T
-
- ∫
- 0
- T
- I
-
- (
- t
- )
- ·
- I
-
- (
- t
- +
- τ
- )
-
- dt
- (
- ∫
- 0
- T
- I
-
- (
- t
- )
-
- dt
- )
- 2
- (
- 1
- )
- wherein T is a measuring time of an intensity of scattered light, I(t) is an intensity of scattered light at an arbitrary time t, and I(t+τ) is an intensity of scattered light after a predetermined time τ has elapsed from the arbitrary time t.
106 more elements
Dependencies are inferred from the claim text.