Self aligning in-situ ellipsometer and method of using for process monitoring
First Claim
1. A measuring station for use in a production line to measure a thin film characteristic of a thin film sample, the measuring station comprising:
- a vacuum chamber having first and second windows;
a movable pallet for supporting the thin film sample and movable to a position in the vacuum chamber;
an ellipsometer havinga source of collimated light and a polarizer for producing a polarized light beam, anda photodetector for producing an output signal in response to receiving a reflected light beam;
a scanner located with respect to said polarizer and said first window for receiving said polarized light beam and aiming an incident light beam through said first window and onto the thin film sample, said scanner moving said incident light beam to different locations on a surface of said thin film sample to direct the reflected light beam from the sample through said second window and onto said photodetector;
andcontrol means responsive to the output signal and connected to said scanner and said ellipsometer forproviding control signals to cause said scanner to move the incident light beam to a location on a selected surface of the thin film sample producing a maximum intensity of the reflected light beam,operating said ellipsometer to determine ellipsometric parameters of the thin film sample, anddetermining the thin film characteristics of the thin film sample in response to the ellipsometric parameters and a stored angle of incidence determined with a different thin film sample.
2 Assignments
0 Petitions
Accused Products
Abstract
An ellipsometric measuring system is set-up in association with a vacuum chamber on a production line for thin film samples. The ellipsometer has a scanner for directing the incident light beam to different locations on a thin film sample, and the ellipsometer also has an aperture for limiting the reflected light beam received by the photodetector. The scanner implements a method of aligning the incident beam to a selected surface of the sample. The scanner and the aperture are used to provide a finer adjustment of the incident beam with respect to the selected surface. The ellipsometric measuring system further uses test thin film samples with known film thicknesses and index or refractions to calculate a value for the angle of incidence of the incident light beam.
88 Citations
21 Claims
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1. A measuring station for use in a production line to measure a thin film characteristic of a thin film sample, the measuring station comprising:
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a vacuum chamber having first and second windows; a movable pallet for supporting the thin film sample and movable to a position in the vacuum chamber; an ellipsometer having a source of collimated light and a polarizer for producing a polarized light beam, and a photodetector for producing an output signal in response to receiving a reflected light beam; a scanner located with respect to said polarizer and said first window for receiving said polarized light beam and aiming an incident light beam through said first window and onto the thin film sample, said scanner moving said incident light beam to different locations on a surface of said thin film sample to direct the reflected light beam from the sample through said second window and onto said photodetector; and control means responsive to the output signal and connected to said scanner and said ellipsometer for providing control signals to cause said scanner to move the incident light beam to a location on a selected surface of the thin film sample producing a maximum intensity of the reflected light beam, operating said ellipsometer to determine ellipsometric parameters of the thin film sample, and determining the thin film characteristics of the thin film sample in response to the ellipsometric parameters and a stored angle of incidence determined with a different thin film sample. - View Dependent Claims (2)
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3. A method for aligning an ellipsometer with a predetermined surface of a thin film sample, the ellipsometer having a source of collimated light and a photodetector, the photodetector producing an output signal as a function of an intensity of a reflected light beam from the thin film sample, the method comprising:
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operating a scanner receiving the source of collimated light to direct an incident light beam to a set position relative to the predetermined surface of the thin film sample; operating the scanner to move the incident light beam in a predetermined scanning pattern; detecting a presence of the reflected light beam to locate the predetermined surface; and operating the scanner to move the incident light beam to a location on the predetermined surface of the thin film sample producing a maximum intensity of the reflected light beam from the predetermined surface of the thin film sample. - View Dependent Claims (4, 5, 6)
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7. A method for aligning an ellipsometer with a selected surface of a thin film sample, the ellipsometer directing an incident light beam toward the thin film sample, and the ellipsometer including a photodetector producing an output signal as a function of an intensity of a reflected light beam from the thin film sample striking the photodetector, the method comprising the steps of:
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a) moving the incident light beam with a scanner to a set position relative to the thin film sample as a function of the selected surface; b) moving the incident light beam with the scanner a step in a first direction; c) monitoring the photodetector to detect a presence of the output signal; d) iterating steps and c)in response to not detecting the presence of the output signal; e) moving the incident light beam with the scanner a step in a second direction substantially perpendicular to the first direction in response to moving the incident light beam a predetermined number of steps in the first direction without detecting the presence of the output signal; f) moving the incident light beam with the scanner a step in a direction opposite the first direction; g) monitoring the photodetector to detect the presence of the output signal; h) iterating steps f) and g) in response to not detecting the presence of the output signal; i) moving the incident light beam with the scanner a step in the second direction substantially perpendicular to the first direction in response to moving the incident light beam a predetermined number of steps in the direction opposite the first direction without detecting the presence of the output signal; j) iterating steps b) through i) in response to not detecting the presence of the output signal; k) stopping motion of the incident light beam with the scanner in response to detecting the presence of the output signal in steps c) and g); and l) stopping motion of the incident light beam with the scanner in response to moving the incident light beam a predetermined number of steps in the second direction without detecting the presence of the output signal. - View Dependent Claims (8, 9, 10, 11)
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12. A method for determining an angle of incidence of an incident light beam from an ellipsometer by analyzing a reflected light beam produced by a reflection of the incident light beam from surface of a thin film sample onto a photodetector, the method comprising the steps of:
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positioning a first test thin film sample having a known film thickness and a known index of refraction with respect to the ellipsometer so that the incident light beam is directed on the test thin film sample; operating the ellipsometer to determine experimental values of ellipsometric parameters based on reflected light from the first test thin film sample; storing the experimental values of the ellipsometric parameters; and determining a first angle of incidence of the incident light beam on the first test thin film sample by a) selecting an assumed angle of incidence, b) determining calculated values of the ellipsometric parameters in response to the assumed angle of incidence, the known thin film thickness and the known index of refraction of the first test thin film sample, c) comparing the calculated values of the ellipsometric parameters for the assumed angle of incidence to the experimental values of the ellipsometric parameters to produce a difference value, d) iterating steps a), b) and c) for different values of the assumed angle of incidence to produce a plurality of difference values, e) detecting a minimum difference value, f) selecting an assumed angle of incidence associated with the minimum difference value as the first angle of incidence, and g) storing the first angle of incidence. - View Dependent Claims (13, 14)
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15. A method for determining an angle of incidence of an incident light beam from an ellipsometer by analyzing a reflected light beam produced by a reflection of the incident light beam from a surface of a thin film sample onto a photodetector, the method comprising the steps of:
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positioning a first test thin film sample having a known film thickness and a known index of refraction with respect to the ellipsometer so that the incident light beam is directed on the first test thin film sample; operating the ellipsometer to determine experimental values of ellipsometric parameters based on reflected light from the first test thin film sample; storing the experimental values of the ellipsometric parameters; and determining a first angle of incidence of the incident light beam on the first test thin film sample by a) selecting an assumed angle of incidence, b) determining calculated values of the ellipsometric parameters in response to the assumed angle of incidence, the known thin film thickness and the known index of refraction of the first test thin film sample, c) producing a difference value in accordance with the following ##EQU2## where Ψ
exp and Δ
exp are the experimental values of the ellipsometric parameters, andΨ
calc and Δ
calc are the calculated values of the ellipsometric parameters,d) iterating steps a), b) and c) for different values of the assumed angle of incidence to produce a plurality of difference values, e) detecting a minimum difference value, f) selecting an assumed angle of incidence associated with the minimum difference value as the first angle of incidence, and g) storing the first angle of incidence.
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16. A method of determining an angle of incidence of an incident light beam from an ellipsometer by analyzing a reflected light beam produced by a reflection of the incident light beam from a surface of a thin film sample onto a photodetector, the thin film sample being located on a pallet being moved from station to station on a production line, the method comprising the steps of:
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moving a first test thin film sample to a predetermined location in a vacuum chamber, the first test thin film sample having first known thin film characteristics; operating a scanner receiving polarized light from the ellipsometer to aim the incident light beam through a window in the vacuum chamber onto a predetermined surface of the first test thin film sample and to move the incident light beam in a predetermined pattern to different locations on the predetermined surface of the first test thin film sample; measuring the intensity of a reflected light beam at the different locations on the predetermined surface of the first test thin film sample; stopping the operation of the scanner in response to moving the incident light beam to a location on the predetermined surface of the first test thin film sample producing a maximum intensity of the reflected light beam from the predetermined surface of the first test thin film sample; operating the ellipsometer to determine ellipsometric parameters for the first test thin film sample; and determining a first angle of incidence of the incident light beam on the predetermined surface of the first test thin film sample using the ellipsometric parameters for the first test thin film sample and the first known thin film characteristics of the first test thin film sample. - View Dependent Claims (17, 18, 19, 20)
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21. A method Of measuring thin film characteristics of a thin film sample located on a pallet being moved from station to station on a production line comprising the steps of:
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moving a test thin film sample having known thin film characteristics to a predetermined location in a vacuum chamber; determining an angle of incidence of an incident light beam from an ellipsometer on a predetermined surface of the test thin film sample as a function of the known thin film characteristics of the test thin film sample; storing the angle of incidence of the incident light beam on the predetermined surface of the test thin film sample; moving a production thin film sample to the predetermined location in the vacuum chamber; operating a scanner to move the incident light beam in a predetermined pattern to different locations on a predetermined surface of the first production thin film sample; measuring the intensity of a reflected light beam at the different locations on the predetermined surface of the production thin film sample; stopping the operation of the scanner in response to moving the incident light beam to a location on the predetermined surface of the production thin film sample producing a maximum intensity of the reflected light beam from the predetermined surface of the production thin film sample; operating the ellipsometer to determine ellipsometric parameters for the production thin film sample; and determining the thin film characteristics of the production thin film sample using the ellipsometric parameters for the production thin film sample and the stored angle of incidence.
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Specification