Apparatus for analyzing multi-layer thin film stacks on semiconductors
AssigneeTherma-Wave, Inc.
InventorsAllan Rosencwaig, Jon Opsal
Life of this patent
Estimating the term…
Abstract
An optical measurement system is disclosed for evaluating samples with multi-layer thin film stacks. The optical measurement system includes a reference ellipsometer and one or more non-contact optical measurement devices. The reference ellipsometer is used to calibrate the other optical measurement devices. Once calibration is completed, the system can be used to analyze multi-layer thin film stacks. In particular, the reference ellipsometer provides a measurement which can be used to determine the total optical thickness of the stack. Using that information coupled with the measurements made by the other optical measurement devices, more accurate information about individual layers can be obtained.
Claims37
A method of analyzing a sample having a multiple layer thin film stack thereon comprising the steps of:
- measuring the sample using an off-axis ellipsometer which includes a stable narrow band wavelength source and generating first output signals;
- measuring the response of the sample to reflected light from a broad band wavelength source and generating a plurality of second output signals corresponding to different wavelengths;
- and
- determining the characteristics of the individual layers on the sample based on the first and second output signals using an algorithm wherein the first output signals are used to provide an accurate measure of the overall optical thickness of the stack in order to improve the accuracy of the analysis of the individual layers.
A method of determining the characteristics of individual layers in a thin film stack formed on a sample comprising the steps of:
- generating a first probe beam defined by quasi-monochromatic light of a known wavelength;
- directing the first probe beam to reflect off the surface of the sample at a non-normal angle of incidence;
- analyzing the change in polarization state of the first probe beam induced by the interaction with the sample and generating first output signals in response thereto;
- generating a second probe beam from a broad band wavelength source;
- directing said second probe beam to reflect off the surface of the sample;
- monitoring the second probe beam after reflection from the sample and determining either a phase or magnitude thereof at a plurality of wavelengths and generating a plurality of second output signals corresponding thereto;
- and
- determining the characteristics of the individual layers on the sample based on the first and second output signals using an algorithm wherein the first output signals are used to provide an accurate measure of the overall optical thickness of the stack in order to improve the accuracy of the analysis of the individual layers.
An apparatus for characterizing thin film layers in a stack formed on a sample comprising:
- an off-axis ellipsometer, said ellipsometer having a quasi-monochromatic source for generating a first probe beam of a known wavelength, said ellipsometer for measuring the change in polarization state of the first probe beam after reflection from the sample and generating first output signals corresponding thereto;
- a broad band light source for generating a second probe beam;
- a detector system for monitoring either the phase or magnitude changes of the second probe beam after interacting with the sample and generating a plurality of second output signals corresponding to a plurality of different wavelengths;
- and
- processor for determining the characteristics of the individual layers on the sample based on the first and second output signals, said processor using an algorithm wherein the first output signals are used to provide an accurate measure of the overall optical thickness of the stack in order to improve the accuracy of the analysis of the individual layers.
Dependencies are inferred from the claim text.