Therma-wave, Inc.

Kla Tencor Corporation

Other

Lanhua Wei

Jon Opsal

Allan Rosencwaig

Shankar Krishnan

Hanyou Chu

Leonid Poslavsky

Hidong Kwak

Mikhail M Sushchik

John F Lesoine

Malik Sadiq

Walter Dean Mieher

Jeffrey Thomas Fanton

Martin Ebert

Guorong Vera Zhuang

Haiming Wang

Paul Aoyagi

Methods and systems for matching measurement spectra across one or more optical metrology systems are presented. The values of one or more system parameters used to determine the spectral response of a specimen to a measurement performed by a target metrology system are optimized. The system parameter values are optimized such that differences between measurement spectra generated by a reference system and the target system are minimized for measurements of the same metrology targets. Methods and systems for matching spectral errors across one or more optical metrology systems are also presented. A trusted metrology system measures the value of at least one specimen parameter to minimize model errors introduced by differing measurement conditions present at the time of measurement by the reference and target metrology systems. Methods and systems for parameter optimization based on low-order response surfaces are presented to reduce the compute time required to refine system calibration parameters.

Metrology system calibration refinement

Methods and systems for performing broadband spectroscopic metrology with reduced sensitivity to grating anomalies are presented herein. A reduction in sensitivity to grating anomalies is achieved by selecting a subset of available system parameter values for measurement analysis. The reduction in sensitivity to grating anomalies enables an optimization of any combination of precision, sensitivity, accuracy, system matching, and computational effort. These benefits are particularly evident in optical metrology systems having large ranges of available azimuth angle, angle of incidence, illumination wavelength, and illumination polarization. Predictions of grating anomalies are determined based on a measurement model that accurately represents the interaction between the measurement system and the periodic metrology target under measurement. A subset of available system parameter values is selected to reduce the impact of grating anomalies on measurement results. The selected subset of available system parameters is implemented on a configurable spectroscopic metrology system performing measurements.

Optical metrology with reduced sensitivity to grating anomalies

A normalization procedure for an ellipsometric system having a rotating optical element such as a polarizer or compensator is disclosed. In operation, a first DC component is extracted from the measured output signals obtained during the first 180 degrees of rotation of the optical element and a second DC component is extracted from the output signals obtained during the second 180 degrees of rotation of the optical element. The first DC component is used to normalize the output signals obtained during the first 180 degrees of rotation of the optical element and the second DC component is used to normalize the output signals obtained during the second 180 degrees of rotation of the optical element.

Method for noise improvement in ellipsometers

A method for improving the measurement of semiconductor wafers is disclosed. In the past, the repeatability of measurements was adversely affected due to the unpredictable growth of a layer of contamination over the intentionally deposited dielectric layers. Repeatability can be enhanced by removing this contamination layer prior to measurement. This contamination layer can be effectively removed in a non-destructive fashion by subjecting the wafer to a cleaning step. In one embodiment, the cleaning is performed by exposing the wafer to microwave radiation. Alternatively, the wafer can be cleaned with a radiant heat source. These two cleaning modalities can be used alone or in combination with each other or in combination with other cleaning modalities. The cleaning step may be carried out in air, an inert atmosphere or a vacuum. Once the cleaning has been performed, the wafer can be measured using any number of known optical measurement systems.

Optical inspection equipment for semiconductor wafers with precleaning

A real-time calibration method for beam profile ellipsometry systems includes projecting an electromagnetic probe beam having a known polarization state though an objective lens onto the surface of a subject and collecting the reflected probe beam using the same objective. The reflected probe beam is then passed through a rotating compensator and analyzer before being received by a detector. A processor performs a harmonic analysis on the detector output to determine normalized Fourier coefficients. The processor uses Fourier coefficients to measure the retardation &#x3b4;and the azimuth angle Qof the objective lens; and uses the retardation &#x3b4;and the azimuth angle Qto identify the ellipsometric effects of the objective lens.

Self-calibrating beam profile ellipsometer

A method and apparatus are disclosed for accurately and repeatably determining the thickness of a thin film on a substrate. A rotating compensator ellipsometer is used which generates both 2&#x3c9; and 4&#x3c9; output signals. The 4&#x3c9; omega signal is used to provide an indication of the temperature of the sample. This information is used to correct the analysis of the thin film based on the 2&#x3c9; signal. These two different signals generated by a single device provide independent measurements of temperature and thickness and can be used to accurately analyze a sample whose temperature is unknown.

Monitoring temperature and sample characteristics using a rotating compensator ellipsometer

An ellipsometer capable of generating a small beam spot is disclosed. The ellipsometer includes a light source for generating a narrow bandwidth probe beam. An analyzer is provided for determining the change in polarization state of the probe beam after interaction with the sample. A lens is provided having a numerical aperture and focal length sufficient to focus the beam to a diameter of less than 20 microns on the sample surface. The lens is formed from a graded index glass wherein the index of refraction varies along its optical axis. The lens is held in a relatively stress free mount to reduce stress birefringence created in the lens due to changes in ambient temperature. The ellipsometer is capable of measuring features on semiconductors having a dimensions as small as 50&#xd7;50 microns.

Small spot ellipsometer

This invention relates to optical metrology tools that are used to evaluate small measurement areas on a semiconductor wafer, where the measurement area is surrounded by a material different from the measurement area. In one embodiment, a probe beam is scanned over the measurement area and the surrounding material as data is taken at multiple locations. A processor determines the characteristics of the measurement area by identifying an extremum value of the measurements which represents the center of the measurement area. In another embodiment, the processor determines the characteristics of the sample using a combination of light measured from within and without the measurement area. The measured data is treated as a combination of light from both regions and mathematically modeled to account for both the contribution of the light reflected from the measurement area and the light reflected from the surrounding material.

Spatial averaging technique for ellipsometry and reflectometry

An ellipsometer capable of generating a small beam spot is disclosed. The ellipsometer includes a light source for generating a narrow bandwidth probe beam. An analyzer is provided for determining the change in polarization state of the probe beam after interaction with the sample. A lens is provided having a numerical aperture and focal length sufficient to focus the beam to a diameter of less than 20 microns on the sample surface. The lens is formed from a graded index glass wherein the index of refraction varies along its optical axis. The lens is held in a relatively stress free mount to reduce stress birefringence created in the lens due to changes in ambient temperature. The ellipsometer is capable of measuring features on semiconductors having a dimensions as small as 50&times;50 microns.

A composite metrology tool, measures basic optical parameters of thin films (e.g., thickness, index of refraction, and birefringence) and stress (e.g., wafer displacements, such as bow and warp). These measurements are combined (e.g. in a processor) using optimization techniques to yield accurate overall information of the wafer parameters.

Combination thin-film stress and thickness measurement device

An method and apparatus are disclosed for accurately and repeatably determining the thickness of a thin film on a substrate. A rotating compensator ellipsometer is used which generates both 2&ohgr; and 4&ohgr; output signals. The. 4&ohgr; omega signal is used to provide an indication of the temperature of the sample. This information is used to correct the analysis of the thin film based on the 2&ohgr; signal. These two different signals generated by a single device provide independent measurements of temperature and thickness and can be used to accurately analyze a sample whose temperature is unknown.

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Fremont, CA, United States of America

Lanhua Wei