CN115335684A

CN115335684A - Reflectometer, spectrophotometer, ellipsometer and polarimeter system comprising a wavelength modifier

Info

Publication number: CN115335684A
Application number: CN202180022393.4A
Authority: CN
Inventors: 贺平; M·M·理帕特; J·A·范德斯利斯; C·M·赫兹恩格; B·D·古恩瑟尔; D·E·梅耶; S·斯科驰; J·D·威尔驰; J·S·海乐
Original assignee: JA Woollam Co Inc
Current assignee: JA Woollam Co Inc
Priority date: 2021-01-29
Filing date: 2021-12-27
Publication date: 2022-11-11
Also published as: EP4285100A1; KR20230133961A; JP2024516053A; WO2022164417A8; WO2022164417A1

Abstract

Ellipsometer, polarimeter, reflectometer and spectrophotometer systems include one or more wavelength modifiers that convert wavelengths provided by an electromagnetic radiation source to different wavelengths for use in investigating a sample, and/or wavelengths that can be detected by its detector.

Description

Reflectometer, spectrophotometer, ellipsometer and polarimeter system comprising a wavelength modifier

This application claims the benefit of provisional application 63/143,187, filed on 29/1/2021 and 63/259,830, filed on 17/8/2021.

Technical Field

Ellipsometer, polarimeter, reflectometer and spectrophotometer systems include one or more wavelength modifiers that convert the wavelength provided by an electromagnetic radiation source to a different wavelength for investigating a sample and/or to a wavelength that its detector can detect.

Background

The use of electromagnetic radiation to investigate a sample is well known. For example, reflectometer, spectrophotometer, ellipsometer, and polarimeter systems direct a beam of electromagnetic radiation to interact with a sample (in reflection and/or transmission), which then enters a detector. The detected changes in intensity (in reflectometer and spectrophotometer systems) and changes in polarization state (in ellipsometer and polarimeter systems) provide insight into properties of the sample as a result of said interaction. Attributes such as absorption constants, ellipsometric parameters Psi and Delta are typically evaluated by performing a mathematical regression of the accumulated data on a mathematical model of the sample.

It is conventional practice to provide a source of electromagnetic radiation comprising the desired wavelength and to direct its beam so that it interacts with the sample and then enters a detector. However, detecting provided wavelengths, for example, in the IR or THZ range requires a special detector system (e.g., a golay box or bolometer, etc.). Detectors of IR and THZ wavelengths are far more difficult to use than, for example, solid state detectors suitable for detecting wavelengths in the visible range. The present invention recognizes this and provides a wavelength modifier that receives, for example, IR or THZ wavelengths and provides, for example, visible range wavelengths derived from IR and THZ wavelengths. Further, investigators who might use systems that provide, say, IR or THZ wavelengths, may wish to easily extend the investigation to include, say, visible wavelengths. In this case, a wavelength modifier may be applied before the sample. An example of a currently available wavelength modifier, which converts MIR range wavelengths to near visible wavelengths, is produced by danish NLIR. Thus, a data table is provided in the Information Disclosure (Information Disclosure).

The present invention focuses on the use of wavelength modifiers in ellipsometer, polarimeter, reflectometer and spectrophotometer systems for patenting, while also having as subject matter additional concerns such as electromagnetic radiation sources and their detectors. With regard to upconversion, the wavelength modifier apparently works by exploiting the properties of the surface state in the semiconductor. In recent press releases, mona jarahi report by the computer and electrical engineering community of los angeles University (UCLA) at the university of california that electrons in a semiconductor lattice experience an increase in energy when hit by incident light, allowing them to jump in the lattice. The electric field boosts the energy even further. When electrons release their energy by photon emission, their wavelengths are different.

Continuing, it is always beneficial to investigate the sample with multiple angles of incidence of the light beam to the sample surface and as many wavelengths as possible. Although preferred sources are not identified herein (except for identifying sources compatible with the use of a wavelength modifier), the latter point can be addressed by using a source of a beam of electromagnetic radiation known as a supercontinuum laser. For more insight into supercontinuum sources, see Van Derslice, U.S. Pat. No. 11/035,729. Although the formation of supercontinuum laser spectra is the result of many complex nonlinear effects, we do not need to be concerned with this in the sense of the present invention, which does not depend on how the supercontinuum is generated, only on how it is supercontinuum and can be applied in for example reflectometers, spectrophotometers, ellipsometers or polarimeters. Furthermore, the present invention concerns the use of a wavelength modifier in such a sample investigation system.

No findings were found from a search of patents that apply wavelength modifiers in ellipsometer, polarimeter, reflectometer and spectrophotometer systems. However, the inventors previously discovered and known patents in the patent work of closely related fields and are therefore disclosed herein. For example, disclosed are:

knight et al, U.S. Pat. Nos. 8,422,519;

clowes et al, U.S. Pat. No.8,718,104;

application No.2014/0233091 published by Clowes et al;

liphordt et al, patent No.7,345,762;

LeVan, U.S. Pat. No.6,104,488.

Additional patent references identified in computer searches are:

the search for "Supercontinuum Laser and Ellipsometer" provides five patents with patent numbers 9,080,971, 8,873,054, 8,441,639, 8,031,337 and 7,570,358, and six published applications with application numbers 2015/0323316, 2015/0036142, 2013/0222795, 2011/0069312, 2009/0262366 and 2008/0239265; and

the search "Supercontininum & Laser and Ellipsometer and Speckle" does not provide a patent and has four published applications with application numbers 2015/0058813, 2015/0046121, 2015/0046118 and 2015/0330770.

Also, known patents and published applications relating to speckle reduction are: 6,895,149 to Jacob et al; 7,522,331 to Lapchuk et al; US 2013/0027673 to Moussa; US 2006/0238743 to Lizotte et al and US 2013/0010365 to Curtis.

Further, in the examination of patent application 14/757,280, the examiner identified:

US2012/0057158 to Hilfiker et al;

U.S. Pat. No.6,983,0026368 to Herzinger;

U.S. Pat. No. 4,2013/0304408 to Pandev;

US2013/0268336 by Ostermeyer;

US2015/0219497 to John;

US2009/0267003 to Moriva et al;

U.S. Pat. No. 5,2014/0304963 to Grejeda;

US2013/0063700 to Yamaguchi et al.

A paper entitled "A New Spectrometry Using Multiple Gratings With A Two-Dimensional Charge-Coupled Diode Array Detector" published 6.6.2003 by Han et al, volume 74 of the Scientific Instruments, no.6, is also known and describes a grating consisting of three laterally stacked sub-Gratings to produce a particular grating of three wavelength ranges.

It will be appreciated that a wavelength modifier may be applied after the stage of the sample investigation system to change the wavelength provided by its source to a wavelength detectable by the detector after interaction with the sample. It should also be understood that a wavelength modifier may be placed in front of the stage of the sample investigation system to shift the wavelengths used in the sample investigation. The latter effect can be used to extend the range of, for example, IR and THZ systems to the visible range.

Even in view of the known prior art, there is still a need for the benefits provided by using wavelength modifiers in ellipsometer, polarimeter, reflectometer and spectrophotometer sample investigation systems (either on the detector side of the system stage or on the source side thereof).

Disclosure of Invention

First, it must be understood that the sample investigation system and method of use of the present invention, as in co-pending application Ser. No.16/602,088, may be comprised of and derived from various combinations in at least three different sub-areas of invention, these being:

a combined application of the detector system that can be optimized for various wavelength ranges of electromagnetic radiation;

the use of a supercontinuum laser for providing a beam of coherent electromagnetic radiation in a wavelength range of at least 400-4400nm, possibly in combination with other sources of electromagnetic radiation in an extended wavelength range; and

the use of a speckle reducer in conjunction with a supercontinuum laser source to effectively provide a more consistent intensity versus position relationship in an electromagnetic radiation beam derived from the supercontinuum laser output in an ellipsometer, reflectometer, spectrophotometer, or the like.

However, the presently disclosed invention further includes from the additional sub-areas of invention, namely:

most importantly, the use of a wavelength modifier that receives, for example, relatively longer wavelengths of electromagnetic radiation (e.g., in the Infrared (IR) and Terahertz (THZ) ranges) that cannot be detected by, for example, a solid-state detector element, and provides, for example, relatively shorter wavelengths of electromagnetic radiation that can be detected by a solid-state (or other type) detector element;

use of a wavelength modifier that receives relatively shorter wavelength electromagnetic radiation that is undetectable by detectors such as Gaylei cells, bolometers, microbolometers, thermocouples, photoconductive materials, deuterated triglycidyl sulfate (DTGS), hgCdTe (MCT), liTaO3, pbSe, pbS, and InSb, and provides relatively longer wavelength electromagnetic radiation that they can detect.

Additional sub-areas of invention are:

providing the use of a supercontinuum laser source having a wavelength of up to about 18000 nm;

the use of additional types of electromagnetic radiation sources in combination with or in place of a supercontinuum laser to extend the wavelength range over which the sample investigation system of the present invention can be used (e.g., nernst and C-Si rods and other sources, up to wavelengths of 14000nm and 50000nm, respectively, may be provided, or other possible sources including DTHS; laser stabilized arc lamps, hg arc lamps, fixed or tunable quantum cascade lasers, QTH and Xe lamps, laser stabilized arc lamps, other laser drive sources);

by combining a supercontinuum laser with a michelson interferometer, applying the supercontinuum laser in a fourier transform infrared source, in combination with other distinguishing factors, it is believed that no previous disclosure has been made in the context of the application of systems such as ellipsometers, reflectometers, spectrophotometers, etc.;

it is believed that the inventive sub-categories described in various combinations provide new, novel and nonobvious sample investigation systems and enable new, nonobvious and useful methods of use thereof.

In this application, the invention as claimed focuses on a sample investigation system selected from the group consisting of:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for supporting a sample; and

a detector (PA) comprising detector elements (DE's).

In an important embodiment, the system source (LS) provides long wavelength electromagnetic radiation in the IR and THZ ranges, and the detector comprises solid state elements (DE's) incapable of detecting the IR and THZ wavelengths. However, the system is characterized in that before the detector (PA) there is at least one Wavelength Modifier (WM) for accepting electromagnetic radiation of a wavelength outside the range detectable by the detector elements (DE's) of the detector (PA) and providing an output electromagnetic radiation of a wavelength detectable by the detector elements (DE's) on the basis thereof.

The system may further comprise a Polarization State Generator (PSG) and a Polarization State Analyzer (PSA) before and after the stage, respectively, and the system is an ellipsometer.

The system may provide that the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the IR and THZ ranges and outputs electromagnetic radiation having a wavelength in the visible wavelength range.

The system may provide that the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the far IR range and outputs electromagnetic radiation having wavelengths in the visible wavelength range.

The system may provide that the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the mid IR range and outputs electromagnetic radiation having wavelengths in the visible wavelength range.

The system may provide that the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the near IR range and outputs electromagnetic radiation having wavelengths in the visible wavelength range.

The system may further comprise Dispersive Optics (DO) between the stage and the detector for spatially separating different wavelengths for presentation to a multi-element (DE's) detector (PA).

The wavelength modifier may be placed in one of:

between the source (LS) and the object Stage (STG);

between the Stage (STG) and the Dispersive Optics (DO);

between said Dispersive Optics (DO) and said detector (PA).

The present invention is also a sample investigation system selected from the group consisting of:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for supporting a sample; and

a detector (PA).

A source (LS) of said system providing electromagnetic radiation in a wavelength range which is longer or shorter than what said detector elements (DE's) can detect; and said system being characterized in that, before said detector (PA), there is at least one Wavelength Modifier (WM) for accepting electromagnetic radiation of a wavelength outside the range detectable by said solid state element (DE's) of said detector (PA) and providing, on the basis thereof, an output electromagnetic radiation of a wavelength detectable by said solid state element (DE's). The system may provide that the source (LS) provides electromagnetic radiation having a wavelength in a range selected from:

ultraviolet rays;

visible light;

a far infrared ray;

middle infrared rays;

terahertz waves;

and the detector detects wavelengths in a range selected from:

ultraviolet rays;

visible light;

a far infrared ray;

middle infrared rays;

terahertz waves;

wherein the selected detected wavelength range is different from that provided by the source (LS).

The system may provide that the source provides wavelengths in a range selected from:

a far infrared ray;

middle infrared rays;

near infrared rays; and

terahertz waves;

and the wavelength modifier provides wavelengths in a range selected from the group consisting of:

ultraviolet rays; and

visible light.

The invention is also a method of investigating a sample comprising the steps of:

a) Providing:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for holding a sample; and

a detector (PA) comprising detector elements (DE's);

wherein a source (LS) of said system provides electromagnetic radiation in a wavelength range which is longer or shorter than what can be detected by said detector elements (DE's); and in that, before the detector (PA), there is at least one Wavelength Modifier (WM) for accepting electromagnetic radiation of a wavelength outside the range detectable by the solid-state element (DE's) of the detector (PA) and providing, on the basis thereof, an output electromagnetic radiation of a wavelength detectable by the solid-state element (DE's).

The method continues with:

b) -placing a sample to be investigated on said Stage (STG);

c) Causing said source (LS) to provide electromagnetic radiation comprising wavelengths that cannot be detected by said detector elements (DE's) and to direct its beam to said sample;

d) -causing said wavelength modifier to receive the wavelengths of electromagnetic radiation from said sample provided by said source (LS) and modify them to wavelengths detectable by said detector elements (DE's);

e) Causing the detector element to detect the modified electromagnetic radiation and provide output data;

f) Analyzing the output data to determine a sample characteristic.

The method may provide that the system further comprises Dispersive Optics (DO) spatially separating the different electromagnetic wavelengths.

The Wavelength Modifier (WM) may be positioned between the source (LS) and the stage, or between the Stage (STG) and the Dispersive Optics (DO), or between the Dispersive Optics (DO) and the detector (PA).

Another method for investigating a sample with electromagnetic radiation of different wavelengths provided by a source of electromagnetic radiation comprises the steps of:

a) Providing:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for holding a sample; and

a detector (PA) comprising detector elements (DE's);

a source (LS) of said system providing electromagnetic radiation in a wavelength range which is longer or shorter than what said detector elements (DE's) can detect;

the system is characterized in that before the Stage (STG) there is a Wavelength Modifier (WM).

The method continues with:

b) -placing a sample to be investigated on said Stage (STG);

c) Causing the source (LS) to provide electromagnetic radiation and to direct its beam to the sample;

d) -causing said Wavelength Modifier (WM) to receive wavelengths of electromagnetic radiation within a first range provided by said source (LS) thereof and to emit wavelengths within a modified range;

e) Causing the detector elements (DE's) to detect the modified wavelength of electromagnetic radiation after the modified wavelength of electromagnetic radiation has interacted with the sample (MS); and

f) Analyzing the output data to determine a sample characteristic.

The method may further comprise, between steps c) and d), a step (c'): -placing a second Wavelength Modifier (WM) between the Stage (STG) and the detector (PA) to place the wavelength from the sample (MS) within a range detectable by detector elements (DE's) in the detector (PA).

In view of the main invention claimed herein, which uses a Wavelength Modifier (WM) to vary the wavelength of electromagnetic radiation at various points within the sample investigation system, it should be understood that any source of electromagnetic radiation may be used with the present invention to provide electromagnetic radiation of a desired wavelength. For example, continuum sources (such as Ar, xe, and He discharge lamps in the UV region; and tungsten filament lamps in the visible; and black body radiators in the infrared range, nernst, and carbon silicon rod sources) can be applied. Linear sources (such as Hg and Na lamps in the UV and visible range), as well as lasers in the visible and IR range, may also be applied. However, the benefits may stem from the fact that: the intensity of the beam of electromagnetic radiation from a supercontinuum laser is generally much higher over a larger wavelength range than from other sources of electromagnetic radiation conventionally used in ellipsometry and similar applications. Since the detector system of the present invention can provide optimized detection of electromagnetic radiation within a particular wavelength range (including the modified wavelengths produced by the wavelength modifier-typically from longer to shorter, but may be from shorter to longer wavelengths), the present invention provides utility in a form that allows its user to conveniently investigate a sample over a large range of wavelengths without having to reconfigure the system with a different source of electromagnetic radiation and electromagnetic radiation detector. However, other known sources provide longer wavelengths than can currently be produced by supercontinuum lasers (but certainly will be produced in the future by improved supercontinuum lasers), and so the invention also includes its use to enable sample investigation at longer/shorter wavelengths, if necessary, until improved supercontinuum lasers become available. It is noted that, approximately five years ago, the wavelength range increased from about 400-2500nm, and currently available supercontinuum lasers provided wavelengths as high as at least 4400 nm. For example, an IR supercontinuum laser in NP Photonics Spectrachrome 1000. It is also noted that supercontinuum lasers providing wavelengths up to about 18000nm are useful, although at the longest wavelength the intensity of the wavelength drops. For example, sources from the IPG photovoltaics (CLPF-2500-SC IDFG series) show patterns up to 18 microns. However, many of these sources can only extend up to about 5000nm. The present invention is considered to encompass the wavelength range of any such possible supercontinuum laser.

Sample investigation system

In view of the above, the present invention may be first described as a sample investigation system selected from the group consisting of:

reflectometer

Spectrophotometer

An ellipsometer; and

a polarimeter;

the sample investigation system comprises:

a) A spectroscopic beam (spectroscopic beam) source of electromagnetic radiation;

b) A stage for holding a sample; and

c) A detector system for monitoring electromagnetic radiation provided from a single sample.

The system is distinguished in that:

the source of the split beam of electromagnetic radiation is a supercontinuum laser that provides a high intensity, highly directional coherent spectrum of electromagnetic radiation wavelengths in a range including 400 to at least 4400nm, resulting from the interaction of a pulsed laser and a nonlinear process that leads to extensive spectral broadening; and in that the sample investigation system is characterized by at least one selection of a primary selection group, the primary selection group being:

first selection group

In use, the source of the split beam of electromagnetic radiation directs the beam provided thereby at an angle to a sample placed on the stage for holding a sample, but does not involve the beam passing sequentially through a combined beam splitter and objective lens;

in use, fluorescence arising from the illumination beam of electromagnetic radiation is not detected by the detector for spatially resolving the radiation emitted by the object to be examined, and neither the illumination beam path between the illumination means and the object to be examined, nor the detection beam path between said object to be examined and the detector, includes such illumination optics: the illumination optics are designed to produce an illuminating radiation light sheet (light sheet) extending transversely to an illumination beam path, and wherein an axis of a detection beam path is oriented substantially perpendicular to a cross-sectional plane of the light sheet and the object to be examined, and the illumination beam path between the illumination device and the object to be examined, and the detection beam path between the object to be examined and the detector do not comprise such illumination optics: the illumination optics are designed to produce a sheet of illuminating radiation light extending transversely to the axis of the illumination beam path, and the detection beam path is not oriented at an angle of θ degrees deviation from the plane of the cross-section of the light sheet and the object to be examined; and

in use, the system does not use a supercontinuum source consisting of a pulsed laser suitable for pumping into a photonic crystal fiber made of chalcogenide glass as the basic element; or from a pumped (pumping) CO2 laser adapted to launch into a photonic crystal fiber formed in part from at least one selected from the group consisting of: alClxBr (1-x), naCl and ZnSe; or the system includes a titanium sapphire laser adapted to emit femtosecond pulses through a nonlinear optical element disposed in an inert gas within a gas-sealed chamber to generate second harmonic pulses and generate supercontinuum terahertz wave radiation.

Note that two or all three selections may be made.

The sample investigation system may further comprise a speckle reducer; the speckle reducer serves to reduce the drastic fluctuations in electromagnetic radiation intensity over time and position in the beam, caused by interference effects between different coherent wavelengths in the widely broadened spectrum.

The sample investigation system may further comprise a polarisation state generator between the source of the beam of electromagnetic radiation and the stage for holding a sample, and a polarisation state analyser between the stage for holding a sample and the detector, and the system is an ellipsometer or polarimeter, and optionally further comprises a compensator in the polarisation state generator and/or the polarisation state detector.

The sample investigation system may comprise a speckle reducer in the form of a multimode optical fibre.

The sample investigation system may comprise a speckle reducer in the form of a beam diffuser.

The sample investigation system may include a speckle reducer in the form of a fly's eye beam homogenizer.

The sample investigation system may comprise a speckle reducer in the form of a rotating beam diffuser.

The sample investigation system may include a speckle reducer in the form of a piezoelectric transistor driven beam diffuser.

The sample investigation system may comprise a speckle reducer in the form of an electronic device for reducing the temporal coherence length.

The sample investigation system may further comprise at least one selected from the group consisting of:

the system further comprises a michelson interferometer and the supercontinuum laser source of electromagnetic radiation is functionally combined therewith, the source being an FTIR source;

the system further comprises a wavelength modifier for accepting relatively long (short) wavelength electromagnetic radiation and providing an output of shorter (longer) wavelengths that can be detected by the detector element(s);

the detector system comprises a single element;

the detector system comprises a plurality of detector elements that can detect wavelengths exiting from the wavelength modifier when relatively longer (shorter) wavelengths enter the wavelength modifier, and wherein the detectable wavelengths are directed into the detector elements by selection from at least one of the group consisting of:

at least one beam splitter;

at least one combined dichroic mirror and prism; and

at least one grating; and

the system also includes a second source that provides a wavelength in a range that is longer or shorter than that provided by the supercontinuum laser.

The method of investigating a sample of the present invention may comprise:

a) Providing a sample investigation system selected from the group consisting of:

a reflectometer;

a spectrophotometer;

an ellipsometer; and

a polarimeter;

the method comprises the following steps:

a') a beam source of a split beam of electromagnetic radiation;

b') a stage for holding a sample; and

c') a detector system for monitoring electromagnetic radiation provided from a single sample. The system is distinguished in that the high intensity, high directivity source of the beam of split electromagnetic radiation is a supercontinuum laser providing a coherent spectrum of wavelengths of electromagnetic radiation in a range including 400 to at least 4400nm, caused by the interaction of pulsed laser light and nonlinear processes resulting in extensive spectral broadening, the system further including a second source providing wavelengths in a range longer or shorter than that provided by the supercontinuum laser, the system being configured such that both sources provide electromagnetic radiation to substantially the same location on the sample as the supercontinuum source.

The system further includes a speckle canceller in a form selected from the group consisting of:

a multimode optical fiber;

a beam diffuser;

a fly's eye beam homogenizer;

a rotating beam diffuser;

a beam diffuser driven by a piezoelectric transistor;

electronic means for reducing the temporal coherence length;

the speckle reducer serves to reduce the drastic fluctuations in electromagnetic radiation intensity as a function of position in the beam, caused by interference effects between different coherent wavelengths in the widely broadened spectrum.

The sample investigation system is characterized by at least one selected from the group consisting of:

first selection group

The method continues with:

b) Causing the split beam of speckle-reduced electromagnetic radiation provided by the supercontinuum laser and speckle reducer to interact with a sample on the stage before entering the detector system, and/or causing electromagnetic radiation provided by the second source to interact with a sample on the stage and enter the detector;

c) Analyzing data provided by the detector to characterize a characteristic of the sample.

The detector may comprise a system having at least two detectors and means for assigning a portion of the split beam to each detector on a wavelength basis.

Another description of a sample investigation system selected from the group consisting of:

a reflectometer;

a spectrophotometer;

an ellipsometer; and

a polarimeter;

the sample investigation system comprises:

a) An electromagnetic radiation beam source;

b) A stage for holding a sample; and

c) A detector system for monitoring electromagnetic radiation;

the system is distinguished by:

the source of the split beam of electromagnetic radiation is a supercontinuum laser providing a high intensity, highly directional coherent spectrum of wavelengths of electromagnetic radiation in a range including 400 to at least 4400nm, caused by the interaction of pulsed laser light and nonlinear processes resulting in broad spectral broadening, the system further comprising a second source providing wavelengths in a range longer or shorter than the wavelengths provided by the supercontinuum laser, the system being configured such that both sources provide electromagnetic radiation to substantially the same location on the sample as the supercontinuum source;

and in that the sample investigation system is characterized by:

first selection group

The system further comprises a speckle reducer in a form selected from the group consisting of:

a multimode optical fiber;

a beam diffuser;

a fly's eye beam homogenizer;

a rotating beam diffuser;

a beam diffuser driven by a piezoelectric transistor;

electronic means for reducing the temporal coherence length;

the speckle reducer serves to reduce the drastic fluctuations in electromagnetic radiation intensity over time and position in the beam, caused by interference effects between different coherent wavelengths in the widely broadened spectrum.

The system may further comprise a polarization state generator between the source of the beam of electromagnetic radiation and the stage for holding the sample, and a polarization state analyzer between the stage for holding the sample and the detector, and the system is an ellipsometer or polarimeter, the system optionally further comprising a compensator in the polarization state generator and/or the polarization state detector.

The sample investigation system may include a speckle reducer in the form of a multimode optical fiber, a beam diffuser, a fly's eye beam homogenizer, a rotating beam diffuser, a piezoelectric transistor driven beam diffuser, or an electronic device for reducing the temporal coherence length.

Where applicable, the detector system in any embodiment may consist of a selection from the group of:

a Gaolai box;

a bolometer;

a thermocouple;

is composed of a photoconductive material;

is composed of a photovoltaic material;

consisting of deuterated triglycidyl sulfate (DTGS);

consists of HgCdTe (MCT);

consists of LiTaO3;

is composed of PbSe;

consists of PbS; and

consists of InSb;

the group further comprises:

the detector system comprises a plurality of detector elements that can detect wavelengths that are directed into their elements by at least one of the following group:

at least one beam splitter;

at least one combined dichroic mirror and prism; and

at least one grating;

another description of a sample investigation system for investigating a sample in a wavelength range comprised between 400nm and at least 50000nm, said sample investigation system being selected from the group consisting of:

a reflectometer;

a spectrophotometer;

an ellipsometer; and

a polarimeter;

and comprises:

a) An electromagnetic radiation beam source;

b) A stage for holding a sample; and

c) At least one detector system for monitoring electromagnetic radiation.

The source of the beam of electromagnetic radiation is selected from the group consisting of:

a supercontinuum laser;

a Nernst light emitter;

a carbon silicon rod;

a laser stabilized arc lamp;

HG arc lamps; and

a fixed or tunable quantum cascade laser; and is provided with

Which provide wavelengths in the infrared and/or terahertz wave range.

The at least one detector system may comprise detector element(s) that are not capable of detecting long wavelengths of electromagnetic radiation in at least part of the infrared and terahertz wave ranges. In this case, the sample investigation system further comprises at least one wavelength modifier which, in use, accepts relatively long (short) wavelengths of electromagnetic radiation that are not detectable by the element(s) in the at least one detector system and provides as output shorter (longer) wavelengths that are detectable by the detector element(s) and passes the detectable wavelengths into the at least one detector system consisting of the element(s) that can detect the shorter (longer) wavelengths of electromagnetic radiation.

Another description of a method of investigating a sample includes the steps of:

a) Providing a sample investigation system for investigating a sample in a wavelength range comprised between 400nm and at least 50000nm, the sample investigation system being selected from the group consisting of:

a reflectometer;

a spectrophotometer;

an ellipsometer; and

a polarimeter;

and comprises:

a') a source of a split beam of electromagnetic radiation;

b') a stage for holding a sample; and

c') at least one detector system for monitoring electromagnetic radiation;

wherein the source of the beam of electromagnetic radiation is selected from the group consisting of:

a supercontinuum laser;

a Nernst light emitter;

a carbon silicon rod;

a laser stabilized arc lamp;

HG arc lamps; and

a fixed or tunable quantum cascade laser;

which provide wavelengths in the infrared and/or terahertz wave range.

The at least one detector system may comprise detector element(s) incapable of detecting long wavelengths of electromagnetic radiation in at least part of the infrared and terahertz ranges, and the sample investigation system further comprises at least one wavelength modifier which, in use, accepts relatively long (short) wavelengths of electromagnetic radiation that are not detectable by element(s) in the at least one detector system element(s) and provides as output shorter (longer) wavelengths detectable by the detector element(s) and passes the detectable wavelengths into the at least one detector system consisting of detector element(s) capable of detecting the shorter (longer) wavelengths of electromagnetic radiation.

The method continues with:

b) Selecting a supercontinuum laser source and further providing a speckle reduction system selected from the group consisting of:

a multimode optical fiber;

a beam diffuser;

a fly's eye beam homogenizer;

a rotating beam diffuser;

a beam diffuser driven by a piezoelectric transistor; and

electronic means for reducing the temporal coherence length;

c) Placing a sample to be investigated on the stage for holding a sample;

d) Causing a beam of electromagnetic radiation to be generated by the supercontinuum laser source and interact with the sample before entering the at least one detector system for monitoring electromagnetic radiation; causing the beam of electromagnetic radiation to further interact with the speckle reduction system and the wavelength modifier between the supercontinuum laser source and the at least one detector system comprising element(s) incapable of detecting long (short) wavelengths of electromagnetic radiation in at least part of the infrared and terahertz ranges; causing electromagnetic radiation of wavelength(s) detectable by element(s) in the at least one detector to enter the at least one detector system; and

e) Analyzing output from the at least one detector to provide insight into the sample characteristic.

Another method of investigating a sample comprises the steps of:

a reflectometer;

a spectrophotometer;

an ellipsometer; and

a polarimeter;

and comprises:

a') a source of a split beam of electromagnetic radiation;

b') a stage for holding a sample; and

c') at least one detector system for monitoring electromagnetic radiation.

The source of the beam of electromagnetic radiation may be selected from the group consisting of:

a supercontinuum laser;

a Nernst light emitter;

a carbon silicon rod;

a laser stabilized arc lamp;

HG arc lamps; and

a fixed or tunable quantum cascade laser;

which provide wavelengths in the infrared and/or terahertz wave range.

The at least one detector system may comprise detector element(s) incapable of detecting wavelengths of electromagnetic radiation in at least part of the infrared and terahertz ranges;

the sample investigation system may further comprise at least one wavelength modifier which, in use, accepts relatively long (short) wavelengths of electromagnetic radiation that are not detectable by the detector element(s) in the at least one detector system and provides as output shorter (longer) wavelengths that are detectable by the detector element(s) and passes the detectable wavelengths into the at least one detector system consisting of element(s) that can detect the shorter wavelengths of electromagnetic radiation.

The method continues with:

b) Selecting a source of electromagnetic radiation other than a supercontinuum laser;

c) Placing a sample to be investigated on the stage for holding a sample;

d) Causing a beam of electromagnetic radiation to be generated by the source and interact with the sample before entering the at least one detector system for monitoring electromagnetic radiation;

causing the beam of electromagnetic radiation to also interact with the wavelength modifier between the source and the at least one detector system comprising detector element(s) that are not capable of detecting long (short) wavelengths of electromagnetic radiation in at least part of the infrared and terahertz ranges;

causing electromagnetic radiation of wavelength(s) detectable by detector element(s) in the at least one detector to enter the at least one detector system; and

e) Analyzing output from the at least one detector to provide insight into a characteristic of the sample.

In any of the foregoing examples, where appropriate, the sample investigation system may provide that a supercontinuum laser source of electromagnetic radiation is functionally combined with a michelson interferometer; and the detector is selected from the group consisting of:

a Gaolai box;

a bolometer;

a thermocouple;

characterized by a detector comprising a material selected from the group consisting of:

deuterated triglycidyl sulfate (DTGS);

HgCdTe(MCT)；

LiTaO3；

PbSe；

PbS；

InSb; and

InGaAs。

another inventive sample investigation system for investigating a sample in a wavelength range provides that the sample investigation system is selected from the group consisting of:

a reflectometer;

a spectrophotometer;

an ellipsometer; and

a polarimeter;

the sample investigation system comprises:

a) A beam source of a split beam of electromagnetic radiation selected from the group consisting of:

a supercontinuum laser; and

a source for providing a longer or shorter wavelength than that provided by the supercontinuum laser;

b) A stage for holding a sample; and

The at least one detector system may comprise detector element(s) that are not capable of detecting long (short) wavelengths of electromagnetic radiation within at least part of the wavelength range provided by the source.

The system may further require that there is at least one selected from the group consisting of:

at least one wavelength modifier which, in use, accepts relatively long (short) wavelengths of electromagnetic radiation not detectable by the element(s) in the at least one detector system and provides as an output shorter (longer) wavelengths detectable by the detector element(s), the output of the wavelength modifier entering as a detectable wavelength into the detector element(s) of the detector system; and

a speckle reducer for reducing severe fluctuations in the intensity of electromagnetic radiation over time and position in the beam caused by interference effects between different coherent wavelengths in the widely broadened spectrum;

the invention was then found in the use of the following combinations:

use of a system of detectors;

the use of a supercontinuum laser;

the application of a speckle reducer;

the use of additional sources of electromagnetic radiation;

the application of a supercontinuum laser in a Fourier transform infrared source;

use of a wavelength modifier.

Detector system

The present invention includes the use of both single element and multi-element detectors. When the beam (whether a monochromatic or a split beam) is to be analyzed as a whole, a single element detector may be used, such as:

a Gaolai box;

a bolometer;

a thermocouple;

alternatively, the following detectors may be used:

a photoconductive material;

a photovoltaic material;

including deuterated triglycidyl sulfate (DTGS);

including HgCdTe (MCT);

including LiTaO3;

comprises PbSe;

comprises PbS; or

Comprises InSb;

this is often the case, for example, when the electromagnetic radiation source is functionally combined with a michelson interferometer.

The inventive detector system may alternatively comprise means for generating a plurality of separate wavelength ranges from the split beam incident thereon, said system comprising a series of at least two elements, wherein each element is selected from the group consisting of:

a grating that, when supplied with an incident split beam of electromagnetic radiation, produces a spectrum of diffraction-dispersed wavelengths and, at the same time, produces an electromagnetic radiation reflected beam of varying spectral content;

a combined dichroic beamsplitter-prism that, when supplied with a split beam of electromagnetic radiation, produces a spectrum of dispersed wavelengths that is transmitted through and exits from the prism while producing a reflected beam of electromagnetic radiation of altered spectral content.

In use, a split beam of electromagnetic radiation from a source of electromagnetic radiation is caused to interact with a sample placed on the stage and then impinge on a first selective element, thereby generating and directing a spectrum of dispersed wavelengths to a first detector, while a reflected beam of electromagnetic radiation of altered spectral content is generated which is directed to impinge on a second selective element which likewise generates a spectrum of dispersed wavelengths which is directed to a second detector.

The reflected beam of electromagnetic radiation having the altered spectral content may be directed to impinge upon a beam splitter which directs at least some of the beam to a third selective element which produces a spectrum of dispersed wavelengths which is directed to a third detector while continuing to direct at least some of the beam having the altered spectral content to the second selective element which continues to direct a limited range of the spectrum of dispersed wavelengths produced thereby to the second detector.

The detector system may comprise functionally enabling at least one selection from the group consisting of:

at least one of the first and second selection elements is designed to optimally configure the wavelength range exiting therefrom;

at least one of the first and second detectors is designed to optimally detect the wavelength range input thereto by the first and second selection elements, respectively.

The detector system may further comprise more than two selection elements and wherein the reflected electromagnetic beam generated by the second selection element is directed to at least one selection from the group consisting of:

a dichroic beamsplitter and then impinging a third selection element therefrom;

directly striking a third selection element;

at least one reflector, then a dichroic beamsplitter, and then from there to impinge a third selective element; and

at least one reflector and then strikes the third selection element.

The detector system may provide that the third selective element, upon receiving the electromagnetic radiation reflected beam, produces a spectrum of dispersed wavelengths directed to a third detector.

The detector system may provide that at least one selection from the group consisting of:

the third selection element is designed to optimally configure the wavelength range exiting therefrom;

said third detector being designed to optimally detect the wavelength ranges input thereto by said first and second selection elements, respectively;

the detector system may provide for selecting a fourth element, and wherein the reflected electromagnetic beam generated by the third selected element or the reflected electromagnetic beam exiting the existing dichroic beamsplitter associated with the second selected element is directed to at least one selected from the group consisting of:

a dichroic beamsplitter and then impinging therefrom onto a fourth selection element;

directly onto the fourth selection element;

at least one reflector, then a dichroic beamsplitter, and then impinging upon a fourth selective element therefrom; and

at least one reflector and then impinges on the fourth selection element.

The detector system may provide that the fourth selective element, upon receiving the electromagnetic radiation reflected beam, produces a spectrum of dispersed wavelengths that is directed to a fourth detector.

the fourth selection element is designed to optimally configure the wavelength range exiting therefrom;

the fourth detector is designed to optimally detect the wavelength ranges input thereto by the first and second selection elements, respectively.

The detector system may specifically involve a beam of split electromagnetic radiation from the sample that impinges on a grating or a combined dichroic beamsplitter-prism that produces a spectrum of the diffractively dispersed wavelengths that is directed into a detector; and simultaneously producing said altered spectral content reflected electromagnetic radiation beam that is directed to interact with a dichroic beam splitter to split said altered spectral content reflected electromagnetic radiation beam into two beams that are both directed to an independent selection from the group consisting of:

a combined dichroic beamsplitter-prism which, when supplied with a split beam of electromagnetic radiation, produces a spectrum of wavelengths which are transmitted through said prism and out of said prism while producing a reflected beam of electromagnetic radiation of altered spectral content;

this allows the spectra of the dispersed wavelengths exiting from the existing grating or combined dichroic beamsplitter-prism to each enter a separate detector.

The detector system may provide that the split beam of electromagnetic radiation from the sample is caused to impinge on a first selective element, thereby generating a spectrum of dispersed wavelengths and directing it to a first detector, while a reflected beam of electromagnetic radiation of altered spectral content is generated which is directed to impinge on a second selective element, which likewise generates a spectrum of dispersed wavelengths directed to a second detector, which is the output beam of the ellipsometer or polarimeter leaving its analyzer.

The detector system may in particular relate to a beam of split electromagnetic radiation from the sample which interacts with a series of elements including:

a first grating and a first detector, wherein a reflected beam exiting the first grating is a zero order (zero order) beam and is directed to a second grating and a second detector.

The detector system may specifically relate to a beam of split electromagnetic radiation from the sample, which interacts with a series of elements, including:

a first grating and a first detector, wherein a reflected beam exiting the first grating is a zeroth order beam and is directed to a first combined dichroic beamsplitter-prism and a second detector.

The detector system may in particular involve a beam of split electromagnetic radiation from the sample which interacts with a series of elements including:

a dichroic beamsplitter that transmits first and second ranges of dispersed wavelengths that are substantially above and below a particular wavelength, respectively, each selected from the group consisting of:

a first grating and a first detector, wherein a reflected beam exiting the first grating is a zero order beam and is directed to a second grating and a second detector; and

a first grating and a first detector, wherein a reflected beam exiting the first grating is a zero order beam and is directed to a first dichroic beamsplitter-prism combination and a second detector.

a first combined dichroic beamsplitter-prism and a first detector, and wherein a reflected beam reflected from the first combined dichroic beamsplitter-prism is directed to a first grating and a second detector.

a first grating and a first detector, wherein a reflected beam produced by the first grating is a zero-order beam and is directed to a second grating and a second detector, and wherein a reflected beam produced by the second grating is a zero-order beam and is directed to a third grating and a third detector.

a first grating and a first detector, wherein a reflected beam produced by the first grating is a zeroth order beam and is directed to a first combined dichroic beamsplitter-prism and a second detector, and wherein a reflected beam reflected off the first combined dichroic beamsplitter-prism is directed by a dichroic beamsplitter to a third grating and a third detector.

a first grating and a first detector, wherein the reflected beam produced by the first grating is a zero-order beam and is directed to a second grating and a second detector, and wherein the reflected beam produced by the second grating is a zero-order beam and is directed to a first dichroic beam splitter-prism combination and a third detector.

a first grating and a first detector, wherein a reflected beam produced by the first grating is a zeroth order beam and is directed to a first combined dichroic beamsplitter-prism and a second detector, and wherein a reflected beam reflected from the first combined dichroic beamsplitter-prism is directed by the beamsplitter to a second dichroic beamsplitter-prism combination and a third detector.

The detector system may specifically involve a beam of split electromagnetic radiation from the sample, which is caused to interact with a series of elements including:

a first combined dichroic beamsplitter-prism and a first detector, wherein a reflected beam reflected by the first combined dichroic beamsplitter-prism is directed to a second grating and a second detector, and wherein a reflected beam produced by the second grating is a zeroth order beam and is directed to a third grating and a third detector.

a first combined dichroic beamsplitter-prism and a first detector, wherein a reflected light beam reflected from the first combined dichroic beamsplitter-prism is directed to a second dichroic beamsplitter-prism combination and a second detector, and wherein a reflected light beam reflected from the second combined dichroic beamsplitter-prism is directed through a dichroic beamsplitter to a third grating and a third detector.

a first combined dichroic beamsplitter-prism and a first detector, wherein a reflected beam reflected from the first combined dichroic beamsplitter-prism is directed to a first grating and a second detector, and wherein a reflected beam produced by the second grating is a zeroth order beam and is directed to a second combined dichroic beamsplitter-prism and a third detector.

a first combined dichroic beamsplitter-prism and a first detector, wherein a reflected beam reflected from the first combined dichroic beamsplitter-prism is directed to a second combined dichroic beamsplitter-prism and a second detector, and wherein a reflected beam reflected from the second combined dichroic beamsplitter-prism is directed by the beamsplitter to a third combined dichroic beamsplitter-prism and a third detector.

The detector system may relate to a spectrum of dispersed diffraction wavelengths produced by the grating, which is a + or-order spectrum.

It will be appreciated that relatively shorter wavelengths may be modified to longer wavelengths which are to be detected by, for example, a golay cell, bolometer or microbolometer or the like. However, since the source in the present invention provides a relatively long wavelength, the present invention is more likely to include a wavelength modifier for changing relatively longer wavelength electromagnetic radiation to shorter wavelength electromagnetic radiation, in functional combination with, for example, a solid state detector element that is unable to monitor longer wavelengths, but can monitor shorter wavelength, higher energy wavelengths.

A typical configuration in the context of the present invention is that the source provides wavelengths in the infrared and/or terahertz range and the detector element is solid-state, which can only detect higher-energy, shorter wavelengths. However, this does not exclude a situation in which the wavelength modifier inputs a relatively shorter wavelength and outputs a longer wavelength and the detector element is a golay cell, a bolometer or a microbolometer or the like. Where solid state detector elements are used, the invention provides utility in the form of reduced initial and operational costs, (e.g., cooling when detecting longer wavelengths).

In the claims, where one or more elements are recited, a distinction between detector types is indicated. That is, the claims should be interpreted as applying to the case where the detector comprises a single element and monitors a monochromatic wavelength of the split light beam or all wavelengths together, or to the case where the wavelengths are separately and individually monitored.

The invention will be better understood by reference to the detailed description of the specification in conjunction with the accompanying drawings.

Drawings

Fig. 1 illustrates a number of wavelength ranges over which various multi-channel detectors (DET 1) (DET 2) (DET 3) are designed to perform optimal processing.

Fig. 2 shows, as an example, some inventive combinations of a plurality of gratings (G) and/or dichroic beam splitter-prism combinations (DBSPs) (generally denoted (G/P)), respectively producing at least one + or-order spectrum of wavelengths and a reflected beam of relatively higher energy, e.g. Zero Order (ZO) in the case of a grating, an example of a beam of electromagnetic radiation being directed to a subsequent grating (G).

Fig. 3a shows a grating (G) which reflects an electromagnetic Incident Beam (IB) and provides a spectrum of wavelengths (λ) in its order (e.g. first + order) together with a Zero Order (ZO).

Fig. 3a' shows the case where the Reflected (RB) light beam is reflected from a dichroic beamsplitter-prism (DBS-PR) combination at the surface on which the coating is present to give it dichroic properties. Note that the spectrum of at least the + or-order spectrum leaves the prism (P).

FIG. 4 shows an ellipsometer system in which the present invention finds a very relevant application.

Fig. 5 shows the use of successive subsequent gratings, which successively encounter electromagnetic radiation.

Fig. 6 shows the use of a beam splitter to direct portions of the beam to different detectors that may be optimized to respond to different wavelength ranges.

FIGS. 7a and 7b show typical intensity versus position of a beam of electromagnetic radiation in the beam provided by a supercontinuum laser source in the range of about 400-2500nm, respectively, and the same results when applying a speckle reducer to the graph of FIG. 7 a.

FIGS. 8a-8 a' "illustrate a fly-eye method for reducing speckle.

Fig. 8b-8f show various speckle reducers.

Fig. 9a and 9b are included to show a basic reflectometer or spectrophotometer system, and a basic ellipsometer or polarimeter system, respectively, including one or more Wavelength Modifiers (WM).

Fig. 9c shows a basic FTIR system comprising an electromagnetic radiation source therein.

Fig. 9d and 9e show fig. 9a and 9b with dispersive optics and Wavelength Modifier (WM).

Fig. 9f shows a basic reflectometer or spectrophotometer system, which presents two Wavelength Modifiers (WM).

FIGS. 9g-9i show further examples of ellipsometer systems in which the Wavelength Modifier (WM) is present.

FIG. 10a is included to show the intensity versus wavelength relationship resulting from a typical inventors generated supercontinuum laser compared to the intensity versus wavelength relationship of a typical conventional electromagnetic radiation source.

Fig. 10b is included to show that recent advances have extended the range of supercontinuum lasers to at least 4400nm, even up to 18000nm.

Detailed Description

First, it should be understood that the invention claimed herein is best shown in fig. 9F-9J, which pertains to the Wavelength Modifier (WM) applied in the context of reflectometer, spectrophotometer, ellipsometer and polarimeter sample investigation systems. The Wavelength Modifier (WM) changes the wavelength of the incoming electromagnetic radiation, which may occur before or after the Sample (SAM) support Stage (STG). However, the presently claimed invention is also not separably related to the source (LS) and the detector (PA) of the electromagnetic radiation. The figures herein are adapted from co-pending application 17/300,091 (related to source (LS) and Detector (DET)) and discussed in the order presented therein.

Turning now to fig. 1, a number of wavelength ranges are shown in which various multi-channel detectors (DET 1) (DET 2) (DET 3) are designed to perform optimal processing. Many additional wavelength ranges may be similarly shown, such as (4) shown in fig. 2.

Fig. 2 shows illustrative use of a source of electromagnetic wavelengths (EM) in the infrared or terahertz wave range, a commonly present aperture and a Wavelength Modifier (WM) for accepting the infrared or terahertz wave wavelengths and generally providing output wavelengths in the wavelength range detectable by solid state Detector (DET) elements (DE's) (see fig. 4). Fig. 2 also shows a combination in fig. 2 of a plurality of gratings (G) (see fig. 3 a) and/OR dichroic beam splitter-prism combinations (DBS-RP) (see fig. 3 a'), each of which produces at least one + OR-order spectrum (Δ λ) of wavelength, and a reflected beam of electromagnetic radiation (RB/OR) of altered spectral content, (e.g., a zeroth Order (OR) beam in the case of a grating (G) OR a functionally similar Reflected Beam (RB) in the case of a dichroic beam splitter-prism combination (DBS-PR)) (both possibilities are indicated in fig. 2 as G/P-). See Reflected Beam (RB) in fig. 3a' with respect to combined dichroic beamsplitter-prism (DBS-PR) and zero Order (OR) beam in fig. 3 a. (note that the term Zeroth Order (ZO) is incorrect in the very strict sense of applying a dichroic beam splitter-prism combination (DBSP) instead of a grating (G), even if the results provided are functionally similar). FIG. 2 is an example of a detector system associated with the system of the present invention in which a source (EM) of a beam of electromagnetic radiation (IB) is shown providing electromagnetic radiation through an Aperture (AP) and impinging (G/P1). Leaving (G/P1) is a first range of + or-, typically a first order spectrum of wavelength (λ), which continues to reflect into detector (DET 1) through mirror (M) as shown. Also shown is a Reflected Beam (RB) reflected from another mirror (M) and encountering the Dichroic Beam Splitter (DBS) which directs a first amount of the incoming light beam to (G/P3) which disperses the light beam into a series of wavelengths () which are directed to a detector (DET 3). A second amount of the optical beam entering (DBS) exits toward (G/P2), which (G/P2) provides a dispersed series of wavelengths (λ) that are directed to the detector (DET 2), and also directs the reflected optical beam (RB "/OR") to (G/P4), which (G/P4) provides a dispersed series of wavelengths (λ) to the detector (DET 4). It should be understood that fig. 2 is included to show that the invention may comprise a plurality of detectors (DET's), each detector comprising a plurality of solid state detector elements (DE's) (see fig. 4) which can detect wavelengths exiting from said Wavelength Modifier (WM) when relatively longer wavelengths (e.g. in the IR or THZ range) enter said Wavelength Modifier (WM), and wherein said wavelengths from said Wavelength Modifier (WM) which are detectable by solid state detector elements (DE's) are directed to said solid state detector elements (DE's) by means of a beam splitter (DBS) and/or a prism/dichroic beam splitter combination (DBS-PR) (see fig. 3a ') and/or a grating (G) (see fig. 3 a).

FIG. 3a shows a grating (G) upon which an Input Beam (IB) of electromagnetic radiation impinges, resulting in at least one +/-order spectrum of wavelengths along with a zero-order (ZO) beam.

Fig. 3a' shows the case where the Reflected (RB) beam is reflected from a dichroic beamsplitter-prism (DBS-PR) combination at the surface on which the coating is present to give it dichroic properties. Note that at least the spectrum of the + or-order spectrum leaves the prism (P). The coating (C) is indicated to be present on the surface on which the input light beam impinges and is used to form a Dichroic Beam Splitter (DBS). To gain insight, dichroic refers to different properties based on wavelength, such as reflection/transmission of electromagnetic radiation.

It should be understood that the designation in FIG. 2 (G/P _) will be interpreted as possible for either of the systems in FIGS. 3a and 3 a'.

FIG. 4, which is FIG. 2 taken from Liphardt et al, patent No.7,345,762, is included to show an ellipsometer system in which the present invention finds very relevant application with ellipsometers and polarimeters, and similar systems. When so applied, the beam exiting the ellipsometer polarization analyzer (i.e., (EPCLB) in said FIG. 4) is advantageously considered to be the beam (IB) shown in FIG. 2. Roughly, the grating (G1) in fig. 2 corresponds to the dispersive element (i.e., grating) (DO) in said fig. 4. Note that fig. 4 shows an ellipsometer source (LS) that provides an ellipsometer beam (PPCLB) that has been polarized by interaction with the shown polarizer (P). The beam (PPCLB) is then caused to interact with the sample (MS), indicating that at this point it may be a focused beam. The beam reflected from the sample (MS) may be re-collimated, then passed through an analyzer (a) and emerges as a beam (EPCLB) before being Focused (FE) to a dispersive element (e.g. a grating) (DO) which is used to disperse the wavelength into a multi-element detector (PA). One or two compensators (C) may also be present, as shown in the polarization state generator or analyzer or the system associated with the polarizer and analyzer, respectively. Further, for the sake of correspondence, the dispersive element (DO) roughly corresponds to the grating (G1) in fig. 2. An indication that the position of the focusing (SSC) and re-collimating (SSC') lenses can be controlled to optimize the desired effect is also shown.

Figure 5 (from figure 9 of patent 7,345,762) is included to illustrate the use of successive subsequent gratings (e.g., G1 and G1') to achieve the desired wavelength in the spectrometer system.

Fig. 6 (taken from fig. 1a of patent 8,169,611) is included to show the use of beam splitters (B1 and B2) to direct portions of the beam to different detectors (D1 and D2) that can be optimized to respond to different wavelength ranges. See, for further explanation, U.S. Pat. Nos. 7,345,762 and 8,169,611. However, the patent does not suggest that the present invention directs the reflected beam with altered spectral content to a subsequent beam-dispersing element. FIG. 6 also shows the use of a beam splitter to direct portions of the beam to different detectors that may be optimized to respond to different wavelength ranges.

The +/-order shown in the figures may be generally described as a range of wavelengths produced when the grating is provided with an incident split beam of electromagnetic radiation and in response produces a spectrum of diffraction dispersed wavelengths, while producing a reflected beam of electromagnetic radiation (typically a zero order beam) with varying spectral content.

Continuing, FIG. 7a shows a typical intensity versus position of a beam of electromagnetic radiation provided by a supercontinuum laser source in the range of about 400 to at least 4400nm in a beam cross-section. Of particular note, the effects of interactions between their coherent components can result in very inconsistent intensity profiles. It is noted that speckle can lead to wavelength instability. A supercontinuum laser may be applied to the presently claimed invention to change the wavelength provided thereby to a wavelength that a solid state detector (possibly used in conjunction with a filter) can detect.

Fig. 7b shows the application of a "speckle reducer" to the beam intensity profile in fig. 6, allowing a much more stable beam intensity versus position relationship in the beam profile to be obtained. This much more stable intensity distribution curve is well suited for application in metrology systems such as ellipsometers, polarimeters, reflectometers, and reflectometers. The use of the supercontinuum laser source and speckle reducer described in this specification is believed to be new and novel, particularly in conjunction with the detector system also described. As previously described in this specification, where a coherent source causes interference effects, the system includes a speckle canceller in a form selected from the group consisting of:

a multimode optical fiber;

a beam diffuser;

a fly's eye beam homogenizer;

a rotating beam diffuser;

a beam diffuser driven by a piezoelectric transistor;

electronic means for reducing the temporal coherence length;

to effectively eliminate wide variations in the wavelength range where the intensity is very small, (i.e., speckle).

Fig. 8a-8 a' "illustrate a beam homogenization method that reduces speckle. Note that in fig. 8a it is shown that the input electromagnetic radiation is shown as (EMI), which is very uneven in intensity, but can be converted into output electromagnetic radiation, shown as (EMO), which is very flat in intensity. The system consists of a Beam Expander (BE), a beam collimator (BC 1), two fly's eye lenses (MF 1) (MF 2), a second beam collimator (BC 2) applied to focus the collimated beam leaving (MF 2), and a second beam collimator (BC 2) to re-collimate the beam supplied to it. The energy content of (EM 1) has been uniformly distributed by the action of fly-eye lenses (MF 1) and (MF 2), as indicated by (EMO). FIGS. 8a' and 8a "illustrate a typical fly-eye lens configuration. Fig. 8a' "is included to indicate how the system (BH) of fig. 8a may be applied to an ellipsometer system. The incoming beam from the source (LS) at "a" is shown as (EMI) and the distribution of the beam energy at "B" is shown as (EMO), and a polarizing element (DE) may be applied before the beam interacts with the sample, and a position (D) where a detector is positioned to monitor the reflected beam from position (D) on the sample.

Fig. 8b-8f show various other speckle reducers. Fig. 8b shows a beam diffuser plate into which the input Beam (BI) enters and exits as a Diffused Beam (DBO) component. FIG. 8c is a simple fly-eye lens (FE) that causes a similar effect to the beam diffuser of FIG. 8b when the light beam passes therethrough. Fig. 8d shows the Beam Diffuser (BD) of fig. 8b attached to a motor (M) that causes it to rotate in use. The input beam (B) passes through it again as shown and emerges as a Diffused Beam (DBO). Fig. 8e shows a Beam Diffuser (BD) plate as in fig. 8b attached to a piezoelectric actuator (PZ) applied to vibrate the Beam Diffuser (BD) vertically and/or horizontally in use. Fly Eye (FE) lenses can also be used in the configurations of fig. 8d and 8 e. FIG. 8f shows an end view of a multimode optical fiber. Note that core region 1 and outer region 2. In a multimode fiber, region 1 is a significant portion of region 2. The zone 1 core does not protrude as much in a single mode fiber.

Fig. 9a is included to illustrate a basic reflectometer or spectrophotometer system, including:

a) A source (S) of a beam of electromagnetic radiation;

b) A Stage (STG) for supporting a Sample (SAM);

c) An electromagnetic detector system (DET);

in the present invention, the system is distinguished in that the source (S) of the split beam of electromagnetic radiation is a supercontinuum laser providing an output spectrum as shown in fig. 7a and preferably 7 b. That is, a main distinguishing aspect of the present invention is the use of a high intensity, high directivity supercontinuum laser to provide the electromagnetic radiation. As described previously with respect to fig. 2, another aspect of the invention involves the use of a detector system that provides various ranges of wavelengths to a detector well suited to detecting such wavelengths.

Fig. 9b shows the elements of fig. 9a with the addition of a Polarization State Generator (PSG) and a Polarization State Analyzer (PSA) to implement an ellipsometer or polarimeter system. (note that if more than one source (S) is mentioned in this specification and claims, the indication of (S) in any relevant figure should be interpreted as representing which source is being used.)

It will be appreciated that the aforementioned detector system may provide for the presence of multiple multi-element arrays as presented in fig. 2, or for the presence of a single array as in fig. 4 or a single detector as indicated in fig. 9a and 9b. Fig. 9d and 9e show the detector side of the system shown in fig. 9a and 9b modified to include Detector (DET) array elements (DE's). Note that the Wavelength Modifier (WM) in fig. 9e has moved from before the Dispersive Optics (DO) to after it. In any configuration, the functional element(s) providing a measurable electrical signal may be a solid state (e.g., a CCD array) or a signal element, such as a golay cell or a bolometer. The latter detector can be applied to monitor electromagnetic radiation at infrared and terahertz frequencies. The golay box converts electromagnetic radiation induced temperature changes into an electrically monitorable signal. For example, there may be a deformable membrane/film that reflects electromagnetic radiation into one or the other photovoltaic cell. Deformation of the diaphragm/film shape in the chambers of the golay cell causes electromagnetic radiation to be directed into the monitoring photocell. Bolometers operate by converting the change in resistance caused by electromagnetic radiation impinging on a blackened material. Further, the detector may, where applicable, comprise a wavelength modifier for changing the far infrared frequencies/wavelengths to near infrared frequencies/wavelengths, so that cheaper and more easily used silicon based elements may be used. Fig. 9a, 9b, 9d and 9e identify the Wavelength Modifier (WM). An example of a wavelength modifier that converts longer wavelengths to shorter wavelengths is an NLIR nonlinear infrared sensor that changes the mid-infrared wavelength to a near-visible wavelength. Fig. 9c is included to indicate that the electromagnetic radiation source (S) may be part of a Fourier Transform Interferometer (FTIR) system. Shown is a source (S), a Beam Splitter (BS) and two mirrors (M1) and (M2). In use, mirror M1 is moved up and down as shown. This increases and decreases the path length of the light beam from the Beam Splitter (BS) thereto. Due to interference at the beam splitter, interference between the Beam Splitter (BS) and the mirror (M1) and between the Beam Splitter (BS) and the mirror (M2), the various wavelengths are transmitted and blocked at different positions of the mirror (M1).

Fig. 9f shows a basic reflectometer or spectrophotometer system with two Wavelength Modifiers (WM). There is typically only one, and so the two shown should not be construed as limiting, but it is noted that when there is only one, it may be located on either side of the Stage (STG). When the wavelength modifier is present before the Stage (STG), the sample investigation system is converted into a system for investigating the sample (MS) in a different wavelength range than that provided by the electromagnetic radiation source (LS). This may be useful if it is desired to investigate a sample with a very wide wavelength range using the same sample investigation system without changing the electromagnetic radiation source (LS).

Fig. 9g-9i show further examples of ellipsometer systems with Wavelength Modifiers (WM) in various positions behind the object Stage (STG). The system shown comprises a source of spectroscopic electromagnetic radiation (LS), a polarizer (P), a compensator (C) (note that (P) and (C) in combination constitute (PSG)), a sample (MS) on a Stage (STG), a second compensator (C ') and an analyzer (a') (note that (C ') and (a) constitute (PSA)), a Focusing Element (FE), dispersive Optics (DO) and a detector (PA) comprising a plurality of detector elements (DE's). In fig. 9g, a Wavelength Modifier (WM) is present between the Stage (STG) and the Dispersive Optics (DO). Fig. 9h further comprises a Beam Splitter (BS) and a mirror (M) to provide two detector arrangements, both with a Wavelength Modifier (WM) present between the Stage (STG) and the Dispersive Optics (DO). Fig. 9i differs from fig. 9g in that a Wavelength Modifier (WM) is present between the Dispersive Optics (DO) and the detector (PA). Any such arrangement is considered to be within the scope of the present invention. Fig. 9g-9i show the position of the Wavelength Modifier (WM) in an illustrative inventive system. Note also that the configuration of fig. 9g may exist in fig. 9h-9 i. That is, whether the system is a reflectometer, spectrophotometer, ellipsometer or polarimeter, the Wavelength Modifier (WM) may be present between the source (LS) and the Stage (STG).

Note that the polarizer (P), analyzer (a) or compensator(s) (C), incorporated into the Polarization State Generator (PSG) or Polarization State Analyzer (PSA), as shown in fig. 6 or in fig. 9b, may be stationary in use, or some or all may be rotated.

FIG. 10a is included to show the typical supercontinuum laser induced intensity versus wavelength relationship generated by the inventors of the present invention when there is a 0.0325% neutral density filter in the path of the supercontinuum laser beam, compared to the intensity versus wavelength relationship of a conventional electromagnetic radiation source. Note that the supercontinuum laser intensity is much greater than that of the conventional source spectrum (shown as about 30 times greater) and in order to compare their wavelength spectral characteristics it is necessary to attenuate it greatly by a 0.0325 neutral density filter.

FIG. 10b is included to illustrate the progress that has been made with supercontinuum laser sources since the filing of the patent application. Note the greatly enlarged wavelength range in fig. 10b compared to fig. 10 a. It is expected that further expansion of the wavelength range will continue and the present invention should be considered from this perspective. That is, the supercontinuum laser source wavelength ranges shown in FIGS. 10a and 10b are exemplary, and not limiting. For example, supercontinuum laser sources providing wavelengths up to 18000nm are available, although at longer wavelengths the intensity may decrease.

Having disclosed the subject matter of the invention herein, it should be apparent that many modifications, substitutions, and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described and that it should be limited only by the claims as broadly as the scope.

Claims

1. A sample investigation system selected from the group consisting of:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for supporting a sample; and

a detector (PA) comprising detector elements (DE's);

a source (LS) of the system provides long wavelength electromagnetic radiation in the IR and THZ ranges, and the detector comprises solid state elements (DE's) unable to detect the IR and THZ wavelengths;

the system is characterized in that before the detector (PA) there is at least one Wavelength Modifier (WM) for accepting electromagnetic radiation of a wavelength outside the range detectable by the detector elements (DE's) of the detector (PA) and providing output electromagnetic radiation of a wavelength detectable by the detector elements (DE's) on the basis thereof.

2. The sample investigation system according to claim 1, further comprising a Polarization State Generator (PSG) and a Polarization State Analyzer (PSA) assembly before and after the Stage (STG), respectively, and the system is an ellipsometer.

3. A sample investigation system according to claim 1, wherein the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the IR and THZ ranges and outputs electromagnetic radiation having a wavelength in the visible wavelength range.

4. A sample investigation system according to claim 1, wherein the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the far IR range and outputs electromagnetic radiation having wavelengths in the visible wavelength range.

5. The sample investigation system according to claim 1, wherein the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the mid IR range and outputs electromagnetic radiation having wavelengths in the visible wavelength range.

6. The sample investigation system according to claim 1, wherein the at least one Wavelength Modifier (WM) accepts electromagnetic radiation comprising wavelengths in the near IR range and outputs electromagnetic radiation having wavelengths in the visible wavelength range.

7. The sample investigation system according to claim 1, further comprising Dispersive Optics (DO) present after the Stage (STG) for spatially separating different wavelengths, and wherein the wavelength modifier is placed in one of the following options:

between the source (LS) and the Stage (STG);

between the Stage (STG) and the Dispersive Optics (DO);

between said Dispersive Optics (DO) and said detector (PA).

8. A sample investigation system selected from the group consisting of:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for supporting a sample; and

a detector (PA);

a source (LS) of said system providing electromagnetic radiation in a wavelength range which is longer or shorter than what said detector elements (DE's) are capable of detecting;

the system is characterized in that before the detector (PA) there is at least one Wavelength Modifier (WM) for accepting electromagnetic radiation of a wavelength outside the range detectable by the solid state element (DE's) of the detector (PA) and providing output electromagnetic radiation of a wavelength detectable by the solid state element (DE's) on the basis thereof.

9. A sample investigation system as claimed in claim 8, wherein the source (LS) provides electromagnetic radiation having a wavelength in a range selected from the group consisting of:

ultraviolet rays;

visible light;

a far infrared ray;

middle infrared rays;

terahertz waves.

10. The sample investigation system according to claim 9, wherein the detector detects wavelengths in a range selected from:

ultraviolet rays;

visible light;

a far infrared ray;

middle infrared rays;

terahertz waves;

the selected range is different from the range provided by the source (LS).

11. The sample investigation system according to claim 10, wherein the source provides a wavelength in a range selected from:

a far infrared ray;

middle infrared rays;

near infrared rays; and

terahertz waves;

and the wavelength modifier provides a wavelength in a range selected from the group consisting of:

ultraviolet rays; and

visible light.

12. The sample investigation system of claim 8, wherein the electromagnetic radiation source is selected from the group consisting of:

ar, xe and He discharge lamps in the UV region;

a tungsten lamp in the visible light region;

a black body radiator, an nernst light emitter and a carbon silicon rod in the infrared range;

hg and Na linear production lamps in the UV and visible range;

lasers in the visible and IR ranges; and

a supercontinuum laser with a wavelength range of 400nm to 18000 nm; and the detector is characterized by being selected from the group consisting of:

a Gaolai box;

a bolometer;

a micro bolometer;

a thermocouple;

a photoconductive material;

deuterated triglycidyl sulfate (DTGS);

HgCdTe(MCT)；

LiTaO3；

PbSe；

PbS；

InSb; and

silicon, germanium, and gallium arsenide solid state devices.

13. A method of investigating a sample comprising the steps of:

a) Providing:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for supporting a sample; and

a detector (PA) comprising detector elements (DE's);

said system being characterized in that, before said detector (PA), there is at least one Wavelength Modifier (WM) for accepting electromagnetic radiation of a wavelength outside the range detectable by said solid state element (DE's) of said detector (PA) and providing, on the basis thereof, output electromagnetic radiation of a wavelength detectable by said solid state element (DE's);

b) -placing a sample to be investigated on said Stage (STG);

d) -causing said wavelength modifier to receive electromagnetic radiation wavelengths different from the wavelengths provided by said source (LS) and modify them to wavelengths detectable by said detector elements (DE's);

e) Causing the detector elements (DE's) to detect the modified electromagnetic radiation and provide output data;

f) Analyzing the output data to determine a sample characteristic.

14. A method as claimed in claim 13, wherein said system further comprises Dispersive Optics (DO) spatially separating different electromagnetic wavelengths, said Wavelength Modifier (WM) being positioned between said source (LS) and said detector (PA).

15. The method of claim 14, wherein the at least one wavelength modifier is placed between the source (LS) and the Stage (STG).

16. The method of claim 14, wherein the at least one wavelength modifier is placed between the Stage (STG) and the Dispersive Optics (DO).

17. The method of claim 14, wherein said at least one Wavelength Modifier (WM) is positioned between said Dispersive Optics (DO) and said detector (PA).

18. A system as claimed in claim 1, comprising at least two wavelength modifiers between the source (LS) or electromagnetic radiation and the detector (PA).

19. The system of claim 8, comprising at least two wavelength modifiers between the source (LS) or electromagnetic radiation and the detector (PA).

20. A method as claimed in claim 13, wherein the system comprises at least two wavelength modifiers between the source (LS) or electromagnetic radiation and the detector (PA).

21. A method of investigating a sample with electromagnetic radiation of different wavelengths provided by a source of electromagnetic radiation, comprising the steps of:

(a) Providing:

an ellipsometer;

a polarimeter;

a reflectometer; and

a spectrophotometer;

for investigating a sample with electromagnetic radiation;

the system comprises:

an electromagnetic source (LS);

a Stage (STG) for supporting a sample; and

a detector (PA) comprising detector elements (DE's);

-said system source (LS) provides electromagnetic radiation in a wavelength range which is longer or shorter than what said detector elements (DE's) are capable of detecting;

the system is characterized in that, before the Stage (STG), there is a Wavelength Modifier (WM);

a) -placing a sample to be investigated on said Stage (STG);

b) Causing the source (LS) to provide electromagnetic radiation and to direct its beam to the sample;

c) -causing said Wavelength Modifier (WM) to receive wavelengths of electromagnetic radiation within a first range provided by said source (LS) and to emit wavelengths within a modified range;

d) Causing the detector elements (DE's) to detect the modified wavelength of electromagnetic radiation after interaction with the sample (MS); and

e) Analyzing the output data to determine a sample characteristic.

22. The method of claim 21, further comprising step (c') between steps c) and d): placing a second Wavelength Modifier (WM) between the Stage (STG) and the detector (PA) to place wavelengths from the sample (MS) within a range detectable by detector elements (DE's) in the detector (PA).