Method for real-time control of the fabrication of a thin-film structure by ellipsometric measurement

• US 20020126283A1
• Filed: 08/06/2001
• Published: 09/12/2002
• Est. Priority Date: 08/10/2000
• Status: Active Grant

• Current Assignee: L'Air Liquide SA
• Original Assignee: L'Air Liquide SA
• Inventors: Heitz, Thibaut, Rostaing, Jean-Christophe, Drevillon, Bernard
• Granted Patent: US 6,868,312 B2
• Time in Patent Office: Days
• US Class Current: 356/369
• CPC Class Codes: G01B 11/0641 with measurement of polarization
• CPC Class Codes: G01N 2021/213 Spectrometric ellipsometry
• CPC Class Codes: G01N 21/211 Ellipsometry optical thickness measurement G01B11/06

Abstract

Method for real-time control of the fabrication of a thin-film structure comprising a substrate by ellipsometric measurement in which:

variables directly linked to the ellipsometric

ratio ρ=tan Ψ exp(iΔ) are measured; and

the said variables are compared with reference values.

The comparison relates to the length of the path traveled at a time t in the plane of the variables with respect to an initial point at time t₀, for each layer participating in the thin-film structure.

Claims

1. Method for real-time control of the fabrication of a thin-film structure comprising a substrate by ellipsometric measurement in which:

variables directly linked to the ellipsometric ratio ρ

=tan Ψ

exp(iΔ

) are measured; and

the said variables are compared with reference values,

characterized in that the comparison relates to the length of the path traveled at a time t in the plane of the variables with respect to an initial point at time t₀, for each layer participating in the thin-film structre.

2. Control method according to claim 1, characterized in that the said variables are a combination of the parameters Ψ

and Δ

.

3. Control method according to claim 1, characterized in that the said variables are a combination of trigonometric functions of the parameters Ψ

and Δ

.

4. Control method according to one of claims 1 to 3, characterized in that the ellipsometric measurement is one with phase modulation.

5. Control method according to claim 4, characterized in that the measured variables are, respectively:

I_s=(sin 2Ψ

sin Δ

) andI_c=(sin 2Ψ

cos Δ

) or I_c=cos 2Ψ

.

6. Control method according to one of claims 1 to 3, characterized in that the ellipsometric measurement is carried out using the method called “

rotating polarizer”

method.

7. Control method according to claim 6, characterized in that the measured variables are tan Ψ

and cos Δ

.

8. Control method according to any one of claims 1 to 7, characterized in that the ellipsometric measurement is a multiwavelength measurement.

9. Control method according to any one of claims 1 to 8, characterized in that the reference values form a theoretically determined path.

10. Control method according to any one of claims 1 to 8, characterized in that the reference values form an experimentally determined path.

11. Control method according to any one of claims 1 to 10, characterized in that the reference values are discrete points corresponding to the instants of fabrication of the thin layers with respect to the time t₀.

12. Control method according to any one of claims 1 to 11, characterized in that the path traveled is adjusted by a polynomial of order between 1 and 5.

13. Control method according to any one of claims 1 to 12, characterized in that the reference values are determined by measurement, using the succession of the following steps:

measurement of a known layer on a simple substrate;

measurement of the same known layer on an industrial substrate;

measurement of the thin-film structre to be controlled.