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

• US 6,868,312 B2
• Filed: 08/06/2001
• Issued: 03/15/2005
• Est. Priority Date: 08/10/2000
• Status: Expired due to Fees

• Current Assignee: L'Air Liquide SA
• Original Assignee: L'Air Liquide SA
• Inventors: Rostaing, Jean-Christophe, Heitz, Thibaut, Drevillon, Bernard
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): ORTIZ RODRIGUEZ, CARLOS R
• Application Number:
  US09/921,786
• Publication Number:
  US 20020126283A1
• Time in Patent Office: 1,317 Days
• Field of Search: 700/28, 700/46, 700/121, 700/306, 356/369, 356/72, 760/296, 438/16, 427/10
• US Class Current: 700/306
• 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=tanΨ 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. A method for real-time control of the fabrication of a thin-film structure by ellipsometric measurement, said method comprising:

(a) reflecting a polarized beam of light from a surface of said structure;

(b) measuring real-time control variables representative of the reflected beam, said variables directly linked to an ellipsometric ratio ρ

=tan Ψ

exp (iΔ

);

(c) providing reference values to form a theoretical or experimental path; and

(d) comparing a path traveled by said reflected beam with the reference values, wherein the said comparison involves the length of the path traveled by said polarized beam of light at a time t in a plane of the variables with respect to an initial point at time to for each layer in the thin-film structure.

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

and Δ

.

3. Control method according to claim 2, wherein the ellipsometric measurement is one with phase modulation.

4. A method according to claim 3, wherein the measured control variables are, respectively:

I_s=(sin 2Ψ

sin Δ

) and

I_c=(sin 2Ψ

cos Δ

) or I_c=cos 2Ψ

.

5. Control method according to claim 2, wherein the ellipsometric measurement is carried out using the “

rotating polarizer”

method.

6. Control method according to claim 5, wherein the measured variables are tan Ψ

and cos Δ

.

7. Control method according to claim 2, wherein the ellipsometric measurement is a multiwavelength measurement.

8. Control method according to claim 2, wherein the reference values from a theoretically determined path.

9. Control method according to claim 2, wherein the reference values form an experimentally determined path.

10. Control method according to claim 2, wherein the reference values are discrete points corresponding to the instants of fabrication of the thin layers with respect to the time t₀.

11. Control method according to claim 2, wherein the path traveled is adjusted by a polynomial of order between 1 and 5.

12. Control method according to claim 2, wherein 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 structure to be controlled.

13. Control method according to claim 1, wherein the said variables are a combination of trigonometric functions of the parameters Ψ

and Δ

.

14. Control method according to claim 13, wherein the ellipsometric measurement is one with phase modulation.

15. A method according to claim 14, wherein the measured control variables are, respectively

I_s=(sin 2Ψ

sin Δ

) and

I_c=(sin 2Ψ

cos Δ

) or I_c=cos 2Ψ

.

16. Control method according to claim 13, wherein the ellipsometric measurement is carried out using the “

rotating polarizer”

method.

17. Control method according to claim 16, wherein the measured variables are tan Ψ

and cos Δ

.

18. Control method according to claim 13, wherein the ellipsometric measurement is a multiwavelength measurement.

19. Control method according to claim 13, wherein the reference values form a theoretically determined path.

20. Control method according to claim 13, wherein the reference values form an experimentally determined path.

21. Control method according to claim 13, wherein the reference values are discrete points corresponding to the instants of fabrication of the thin layers with respect to the time t₀.

22. Control method according to claim 13, wherein the path traveled is adjusted by a polynomial of order between 1 and 5.

23. Control method according to claim 13, wherein 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 structure to be controlled.

24. Control method according to claim 1, wherein the ellipsometric measurement is one with phase modulation.

25. A method according to claim 24, wherein the measured control variables are, respectively:

I_s=(sin 2Ψ

sin Δ

) and

I_c=(sin 2Ψ

cos Δ

) or I_c=cos 2Ψ

.

26. Control method according to claim 1, wherein the ellipsometric measurement is carried out using the “

rotating polarizer”

method.

27. Control method according to claim 26, wherein the measured variables are tan Ψ

and cos Δ

.

28. Control method according to claim 1, wherein the ellipsometric measurement is a multiwavelength measurement.

29. Control method according to claim 1, wherein the reference values form a theoretically determined path.

30. Control method according to claim 1, wherein the reference values form an experimentally determined path.

31. Control method according to claim 1, wherein the reference values are discrete points corresponding to the instants of fabrication of the thin layers with respect to the time t₀.

32. Control method according to claim 1, wherein the path traveled is adjusted by a polynomial of order between 1 and 5.

33. Control method according to claim 1, wherein 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 structure to be controlled.