Thin Film Interference Filter and Bootstrap Method for Interference Filter Thin Film Deposition Process Control
AssigneeUniversity of South Carolina
InventorMichael L. Myrick
Life of this patent
Estimating the term…
Abstract
A thin film interference filter system includes a plurality of stacked films having a determined reflectance; a model monitor curve; and a topmost layer configured to exhibit a wavelength corresponding to one of the determined reflectance or the modeled monitor curve. The topmost layer is placed on the plurality of stacked films and can he a low-index film such as silica or a high index film such as niobia.
Claims21
(canceled)
The method as in claim 23, wherein the topmost layer is a niobia layer.
(canceled)
The method as in claim 23, further comprising determining the maxima in the reflectance of each of the plurality of monitor curves, wherein the topmost layer exhibits a wavelength that is determined according to the characteristics of the modeled monitor curve when there is no maxima in the reflectance of each of the plurality of monitor curves.
The method as in claim 23, further comprising the step of computing a value of δ for all monitor wavelengths based on a value calculated for the modeled monitor wavelength.
The method according to claim 23, the method further comprising
- determining phase angle φκ at the modeled monitor wavelength from |rk′| and Rk using a first equation expressed as:
- cos
-
- (
- ±
- φ
- k
- )
- =
-
- r
- k
- ′
-
- 2
-
- (
- 1
- +
- R
- k
-
-
- r
- 2
-
- 2
- )
- -
-
- r
- 2
-
- 2
- -
- R
- k
- 2
-
-
- r
- 2
-
-
- R
- k
-
- (
- 1
- -
-
- r
- k
- ′
-
- 2
- )
- ;
- and
- estimating rk′ using a second equation and
- r
- k
- ′
- =
- r
- k
- -
- r
- 2
- 1
- -
- r
- 2
-
- r
- k
- ;
The method according to claim 23, wherein the step of measuring the reflectance of the stack of the plurality of films comprises measuring the intensity reflectance of the stack, the method further comprising
- determining from the measurement of intensity reflectance at the topmost interface a phase angle φ at an interface k according to an equation expressed as:
- cos
-
- (
- φ
- k
- )
- =
- (
- A
-
- (
- 1
- +
- r
- 2
- 2
- )
-
- sin
-
- (
- δ
- )
- ±
- B
-
-
- cos
-
- (
- δ
- )
- C
- )
- A
- =
- R
- f
- +
- r
- 2
- 4
-
- (
- R
- f
- -
- R
- k
- )
- -
- R
- k
- +
- 2
-
- r
- 2
- 2
-
- (
- (
- 1
- -
- R
- f
- )
-
- (
- 1
- +
- R
- k
- )
-
- cos
-
- (
- 2
-
- δ
- )
- -
- (
- 1
- -
- R
- f
-
- R
- k
- )
- )
- B
- =
- D
-
- (
- 1
- +
- r
- 2
- 12
- )
- +
- F
-
- (
- r
- 2
- 2
- +
- r
- 2
- 10
- )
- +
- G
-
- (
- r
- 2
- 4
- +
- r
- 2
- 8
- )
- +
- H
-
-
- r
- 2
- 6
- C
- =
- sin
-
- (
- δ
- )
-
- (
- 4
-
- r
- 2
-
- (
- 1
- -
- R
- f
- )
-
- R
- k
- 1
- /
- 2
-
- (
- 2
-
- r
- 2
- 2
-
- cos
-
- (
- 2
-
- δ
- )
- -
- 1
- -
- r
- 2
- 4
- )
- )
- D
- =
- -
- (
- R
- f
- -
- R
- k
- )
- 2
- F
- =
- 2
-
- (
- R
- k
-
- (
- 2
- +
- R
- k
- )
- +
- R
- f
- 2
-
- (
- 1
- +
- 2
-
- R
- k
- )
- +
- 2
-
- R
- f
-
- (
- 1
- -
- 5
-
- R
- k
- +
- R
- k
- 2
- )
- -
- 2
-
- (
- 1
- -
- R
- f
- )
-
- (
- 1
- -
- R
- k
- )
-
- (
- R
- f
- +
- R
- k
- )
-
- cos
-
- (
- 2
-
- δ
- )
- )
- G
- =
- -
- 6
- -
- 4
-
- R
- f
- -
- 5
-
- R
- f
- 2
- -
- 4
-
- R
- k
- +
- 38
-
- R
- f
-
- R
- k
- -
- 4
-
- R
- f
- 2
-
- R
- k
- -
- 5
-
- R
- k
- 2
- -
- 4
-
- R
- f
-
- R
- k
- 2
- -
- 6
-
- R
- f
- 2
-
- R
- k
- 2
- +
- 8
-
- (
- 1
- -
- R
- f
- 2
- )
-
- (
- 1
- -
- R
- k
- 2
- )
-
- cos
-
- (
- 2
-
- δ
- )
- -
- 2
-
- (
- 1
- -
- R
- f
- )
- 2
-
- (
- 1
- -
- R
- k
- )
- 2
-
- cos
-
- (
- 4
-
- δ
- )
- H
- =
- 4
-
- (
- 3
- +
- 2
-
- R
- f
- 2
- -
- 10
-
- R
- f
-
- R
- k
- +
- 2
-
- R
- k
- 2
- +
- 3
-
- R
- f
- 2
-
- R
- k
- 2
- -
- 2
-
- (
- 1
- -
- R
- f
- )
-
- (
- 1
- -
- R
- k
- )
-
- (
- 2
- +
- R
- f
- +
- R
- k
- +
- 2
-
- R
- f
-
- R
- k
- )
-
- cos
-
- (
- 2
-
- δ
- )
- +
- (
- 1
- -
- R
- f
- )
- 2
-
- (
- 1
- -
- R
- k
- )
- 2
-
- cos
-
- (
- 4
-
- δ
- )
- )
(canceled)
20-22. (canceled)
A method for forming a thin film interference filter comprising:
- measuring the reflectance of a stack of a plurality of films;
- modeling a monitor curve at a modeled monitor wavelength for a topmost layer to be deposited on the stack of the plurality of films;
- depositing the topmost layer on the stack of the plurality of films;
- and
- recording a plurality of monitor curves during the deposition, each monitor curve being recorded for a different monitor wavelength of the topmost layer;
- wherein the topmost layer exhibits a wavelength that is determined according to the characteristics of either the modeled monitor curve or one of the recorded monitor curves.
Dependencies are inferred from the claim text.