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US 6,552,803 B1Granted
Detection of film thickness through induced acoustic pulse-echos
AssigneeKLA-Tencor Corporation
InventorsHaiming Wang, Shing Lee, Mehrdad Nikoonahad
Life of this patent
Estimating the term…
Abstract
Thickness of a film in a sample may be detected by directing pump laser pulses to the surface of a sample to generate an acoustic pulse in a sample. The acoustic pulse propagates downwards until it reaches an interface between the bottom of the film and a substrate and is reflected back to the top surface of the film as a first echo. A reflection of the first echo propagates downwards and is again reflected back towards the surface as a second echo. Heterodyne interferometry is used to measure the lapse of time between the first and second echos from which the thickness of the film may be determined.
Claims64
A system for non-destructively measuring properties of a sample, comprising:
- a first optical source supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- an interferometer providing an output, said interferometer including:
- a second optical source providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- a detector;
- optics directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample, so that the modified pulses interfere at the detector and so that the probe pulse together with the modified probe pulse substantially share a common optical path with the reference pulse together with the modified reference pulse between the second optical source and the detector;
- and
- a first modulator in the common optical path modulating phase or frequency of at least one of the pair of pulses before or after modification by the sample.
5 more elements
A system for non-destructively measuring properties of a sample, comprising:
- means for supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- an interferometer providing an output, said interferometer including:
- means for providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- a detector;
- means for directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample, so that the modified pulses interfere at the detector and so that the probe pulse together with the modified probe pulse substantially share a common optical path with the reference pulse together with the modified reference pulse between the second optical source and the detector;
- and
- means in the common optical path for modulating phase or frequency of one of the pair of pulses before or after modification by the sample.
5 more elements
A method for non-destructively measuring properties of a sample, comprising:
- supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample, so that the modified pulses interfere at a detector to provide an output, and so that the probe pulse together with the modified probe pulse substantially share a common optical path with the reference pulse together with the modified reference pulse between the second optical source and the detector;
- and
- modulating phase or frequency of one of the pair of pulses before or after modification by the sample.
3 more elements
A method for non-destructively measuring properties of a sample, comprising:
- forming a layer of material on a substrate to make a sample;
- supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample, so that the modified pulses interfere at a detector to provide an output, and so that the probe pulse together with the modified probe pulse substantially share a common optical path with the reference pulse together with the modified reference pulse between the second optical source and the detector;
- and
- modulating phase or frequency of one of the pair of pulses before or after modification by the sample.
4 more elements
A system for non-destructively measuring properties of a sample, comprising:
- a first optical source supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- an interferometer providing an output, said interferometer including:
- a second optical source providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- a detector;
- optics directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample, and so that the modified pulses interfere at the detector;
- and
- a modulator in the common optical path modulating phase or frequency of at least one of the pair of pulses before or after modification by the sample.
5 more elements
A method for non-destructively measuring properties of a sample, comprising:
- supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample and so that the modified pulses interfere at a detector to provide an output;
- and
- modulating phase or frequency of one of the pair of pulses before or after modification by the sample.
3 more elements
A method for non-destructively measuring properties of a sample, comprising:
- forming a layer of material on a substrate to make a sample;
- supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse influencing said first surface area;
- and
- providing a pair of a probe pulse and a reference pulse of radiation that are substantially in phase with each other;
- directing the probe pulse to said first surface area when it is influenced by the elastic pulse and the reference pulse to a second surface area of the sample so that the pair of pulses are modified by the sample and so that the modified pulses interfere at a detector to provide an output;
- and
- modulating phase or frequency of one of the pair of pulses before or after modification by the sample.
4 more elements
A system for non-destructively measuring properties of a sample, comprising:
- a first source supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse causing said surface area to move;
- and
- an interferometer providing an output, said interferometer including:
- a detector;
- a second source providing a pair of a probe pulse and a reference pulse of radiation and for directing the probe pulse to said first surface area when it is moved by the elastic pulse and the reference pulse to a second surface area so that the pair is modified by the sample, wherein said pair of pulses have durations of less than about 10 picoseconds;
- and
- optics directing the modified pair of pulses to the detector so that the modified pair interferes at the detector to cause the detector to provide said output.
4 more elements
A method for non-destructively measuring properties of a sample, comprising:
- supplying a pump pulse of radiation to a first surface area of the sample to non-destructively generate an elastic pulse in the sample, said elastic pulse causing said surface area to move;
- providing a pair of a probe pulse and a reference pulse of radiation, wherein said pair of pulses have durations of less than about 10 picoseconds;
- directing the probe pulse to said first surface area when it is moved by the elastic pulse and the reference pulse to a second surface area so that the pair of pulses are modified by the sample;
- and
- interfering the pair of modified pulses to provide an output.
2 more elements
Dependencies are inferred from the claim text.