Focused beam spectroscopic ellipsometry method and system

A method for performing spectroscopic ellipsometry measurements on a sample, including the steps of:

• (a) polarizing the broadband radiation, thereby producing a sample beam;
• (b) reflectively focusing the sample beam to a small spot on the sample using all-reflective optics in such a manner that the sample beam reflects with an angle from each component of the all-reflective optics of not more than 30 degrees from a normal direction to each such component;
• (c) analyzing radiation of the sample beam that has reflected from the sample, thereby producing an output beam, said output beam having a polarization state;
• and
• (d) detecting the output beam to determine amplitude and phase changes of the output beam polarization state caused by reflection by the sample.

An optical instrument, including a spectrophotometer and an ellipsometer integrated together as a single instrument with the spectrophotometer, said instrument including:

• radiation source means which emits radiation;
• and
• means for directing a first portion of the radiation to the spectrophotometer and a second portion of the radiation to the ellipsometer, wherein the spectrophotometer and the ellipsometer simultaneously focus the radiation received thereby to a single spot on a sample, and
• wherein the ellipsometer includes:
• a polarizer for polarizing the radiation, thereby producing a sample beam;
• an analyzer positioned for receiving radiation of the sample beam that has reflected from the sample, wherein the analyzer produces an output beam in response to said radiation, said output beam having a polarization state;
• detector means for detecting the output beam to determine amplitude and phase changes of the output beam polarization state caused by reflection by the sample;
• all-reflective optics between the polarizer and the analyzer, wherein the sample beam reflects with an angle from each component of the all-reflective optics of not more than 30 degrees from a normal direction to each such component, and wherein the all-reflective optics reflectively focuses the sample beam to the spot on the sample.

An optical instrument, including a spectrophotometer and an ellipsometer integrated together as a single instrument with the spectrophotometer, said instrument including:

• radiation source means which emits radiation;
• and
• beam diverting means for directing the radiation to a selected one of the spectrophotometer and the ellipsometer, to enable only said selected one of the spectrophotometer and the ellipsometer to focus said radiation received from the beam diverting means to a spot on a sample,
• wherein the ellipsometer includes:
• a polarizer for polarizing the radiation, thereby producing a sample beam;
• an analyzer positioned for receiving radiation of the sample beam that has reflected from the sample, wherein the analyzer produces an output beam in response to said radiation, said output beam having a polarization state;
• detector means for detecting the output beam to determine amplitude and phase changes of the output beam polarization state caused by reflection by the sample;
• all-reflective optics between the polarizer and the analyzer, wherein the sample beam reflects with an angle from each component of the all-reflective optics of not more than 30 degrees from a normal direction to each such component, and wherein the all-reflective optics reflectively focuses the sample beam to the spot on the sample at a substantial range of high incidence angles.

A spectroscopic ellipsometer for measuring a sample, including:

• a source which emits broadband radiation;
• a polarizer for polarizing the broadband radiation, thereby producing a sample beam;
• an analyzer positioned for receiving radiation of the sample beam that has reflected from the sample, wherein the analyzer produces an output beam in response to said radiation, said output beam having a polarization state;
• detector means for detecting the output beam to determine amplitude and phase changes of the output beam polarization state caused by reflection by the sample;
• all-reflective optics between the polarizer and the analyzer, wherein the sample beam reflects with an angle from each component of the all-reflective optics of not more than 30 degrees from a normal direction to each such component, and wherein the all-reflective optics reflectively focuses the sample beam to a spot on the sample;
• sample stage means for supporting the sample and moving the sample relative to the all-reflective optics;
• and
• an autofocus assembly for measuring a focus signal indicative of radiation reflected from the spot on the sample during movement of the sample stage means with the sample supported thereon, whereby a best focus position of the all-reflective optics relative to the sample can be determined from the focus signal, wherein the autofocus assembly consists of:
• a dual photodiode detector, which receives a substantially focused image of the spot, wherein the dual photodiode detector includes a first photodiode which outputs a first intensity signal and a second photodiode which outputs a second intensity signal;
• and
• a processor which receives the first intensity signal and the second intensity signal, wherein the processor is programmed to process the first intensity signal and the second intensity signal to generate a focus signal indicative of said best focus position.

A spectroscopic ellipsometer for measuring a sample, including:

• a source which emits broadband radiation;
• a polarizer for polarizing the broadband radiation, thereby producing a sample beam;
• an analyzer positioned for receiving radiation of the sample beam that has reflected from the sample, wherein the analyzer produces an output beam in response to said radiation, said output beam having a polarization state;
• detector means for detecting the output beam to determine amplitude and phase changes of the output beam polarization state caused by reflection by the sample;
• all-reflective optics between the polarizer and the analyzer, wherein the sample beam reflects with an angle from each component of the all-reflective optics of not more than 30 degrees from a normal direction to each such component, and wherein the all-reflective optics reflectively focuses the sample beam to a spot on the sample at a substantial range of high incidence angles;
• and
• an incidence angle selection element for selecting, for measurement by the detector means, only radiation reflected from the sample at a subrange of said substantial range of high incidence angles, wherein the incidence angle selection element determines a slit-shaped region and all radiation selected by the incidence angle selection element for measurement by the detector means propagates away from the slit-shaped region after incidence at the incidence angle selection element.

A method of performing spectroscopic ellipsometry measurements on a sample, including the steps of:

• (a) polarizing broadband radiation, thereby producing a sample beam;
• (b) reflectively focusing the sample beam to a spot on the sample using all-reflective optics at a substantial range of high incidence angles so that the sample beam reflects from each component of the all-reflective optics with an angle of not more than 30 degrees from the normal direction of each such component;
• (c) selecting, for detection, only radiation reflected from the sample at a subrange of the substantial range of high incidence angles, by positioning an incidence angle selection element in the path of radiation of radiation of the sample beam that has reflected from the sample, where the incidence angle selection element determines a slit-shaped region and all radiation selected by the incidence angle selection element for detection propagates away from the slit-shaped region following incidence at the incidence angle selection element;
• (d) analyzing radiation of the sample beam that has reflected from the sample, thereby producing an output beam;
• and
• (e) detecting radiation of the output beam that has been analyzed in step (d) and has been selected by the incidence angle selection element during step (c).