REFERENCE TO RELATED APPLICATIONS

Reference is hereby made to U.S. Provisional Patent Application Serial No. 61/655,567, filed June 5, 2012 and entitled METHOD FOR IMPROVING LATERAL RESOLUTION, the disclosure of which is incorporated by reference in its entirety and priority of which is hereby claimed pursuant to 37 CFR 1.78(a) (4) and (5)(i).

Reference is also made to the following U.S. Patents, patent publications and pending patent applications, the contents of which are hereby incorporated by reference herein:

U.S. Patent Nos. 8,164,057 and 8,334,510;

Published PCT Patent Application No. WO 2012/007941, entitled "A Vacuumed Device and A Scanning Electron Microscope" and filed September 24, 2009; and

Chinese Patent Application No. 201210299149.5, entitled "Electron Microscope Imaging System and Method" and filed August 21, 2012.

FIELD OF THE INVENTION

The present invention relates generally to scanning electron microscopes.

BACKGROUND OF THE INVENTION

Various different types of scanning electron microscopes are known. SUMMARY OF THE INVENTION

The present invention seeks to provide an improved scanning electron microscope.

There is thus provided in accordance with a preferred embodiment of the present invention a method for performing analysis of materials when present in a non- vacuum environment using an electron microscope, the method including generating a first characteristic spectrum for a material by: directing an electron beam from the electron microscope onto the material in a first non-vacuum environment, in which a first amount of scattering of the electron beam takes place, collecting first X-rays emitted from the material and performing spectral analysis on the first X-rays, thereafter, generating a second characteristic spectrum for the material by: directing an electron beam from the electron microscope onto the material in a second non-vacuum environment, in which a second amount of scattering of the electron beam takes place, collecting second X-rays emitted from the material and performing spectral analysis on the second X-rays, comparing the first and second characteristic spectra and noting peaks whose intensity increases with increased scattering, generating a scattering- compensated characteristic spectrum for the material from at least one of the first and second characteristic spectra by eliminating at least one peak whose intensity increases with increased scattering.

In accordance with a preferred embodiment of the present invention the scattering compensated characteristic spectrum includes at least one peak whose intensity decreases with increased scattering.

Preferably, the first non-vacuum environment includes a first gas and the second non-vacuum environment includes a second gas, having electron beam scattering characteristics different from those of the first gas. Alternatively or additionally, the first non-vacuum environment has a first electron beam travel distance to the material associated therewith and the second non-vacuum environment has a second electron beam travel distance to the material associated therewith, the second electron beam travel distance producing a different amount of electron beam scattering than the first electron beam travel distance. There is also provided in accordance with another preferred embodiment of the present invention a system for performing analysis of materials when present in a non-vacuum environment using an electron microscope, the system including a characteristic spectrum generator, generating first and second characteristic spectra for a material by: directing an electron beam from the electron microscope onto the material in respective first and second non-vacuum environments, in which respective first and second amounts of scattering of the electron beam takes place, collecting X-rays emitted from the material in the first and second non-vacuum environments and performing spectral analysis on the X-rays from the material in the first and second non-vacuum environments and a scattering-compensated characteristic spectrum generator operative by: comparing the first and second characteristic spectra and noting peaks whose intensity increases with increased scattering and generating a scattering-compensated characteristic spectrum for the material from at least one of the first and second characteristic spectra by eliminating at least one peak whose intensity increases with increased scattering.

Preferably, the scattering compensated characteristic spectrum includes least one peak whose intensity decreases with increased scattering.

In accordance with a preferred embodiment of the present invention the system for performing analysis of materials when present in a non-vacuum environment using an electron microscope also includes a gas supply controller operative to supply a first gas to the first non-vacuum environment and a second gas to the second non- vacuum environment, the second gas having electron beam scattering characteristics different from those of the first gas. Additionally or alternatively, the system for performing analysis of materials when present in a non-vacuum environment using an electron microscope also includes a movable sample mount operative to be positioned at a first electron beam travel distance to the material in the first non- vacuum environment and to be positioned at a second electron beam travel distance to the material in the second non-vacuum environment, the second electron beam travel distance producing a different amount of electron beam scattering than the first electron beam travel distance.

There is further provided in accordance with yet another preferred embodiment of the present invention, for use with an electron microscope-based material analysis system operative for directing an electron beam from the electron microscope onto a material in a non-vacuum environment, collecting X-rays emitted from the material and performing spectral analysis on the X-rays, a computerized method for performing analysis of materials when present in a non-vacuum environment using the electron microscope-based system, the method including operating the microscope -based material analysis system for: generating a first characteristic spectrum for a material by: directing an electron beam onto a material in a first non-vacuum environment, in which a first amount of scattering of the electron beam takes place, collecting first X-rays emitted from the material and performing spectral analysis on the first X-rays, thereafter, generating a second characteristic spectrum for the material by: directing an electron beam onto a material in a second non- vacuum environment, in which a second amount of scattering of the electron beam takes place; collecting second X-rays emitted from the material and performing spectral analysis on the second X-rays, comparing the first and second characteristic spectra and noting peaks whose intensity increases with increased scattering, generating a scattering-compensated characteristic spectrum for the material from at least one of the first and second characteristic spectra by eliminating at least one peak whose intensity increases with increased scattering.

In accordance with a preferred embodiment of the present invention the scattering compensated characteristic spectrum includes at least one peak whose intensity decreases with increased scattering.

Preferably, the first non-vacuum environment includes a first gas and the second non-vacuum environment includes a second gas, having electron beam scattering characteristics different from those of the first gas. Additionally or alternatively, the first non-vacuum environment has a first electron beam travel distance to the material associated therewith and the second non-vacuum environment has a second electron beam travel distance to the material associated therewith, the second electron beam travel distance producing a different amount of electron beam scattering than the first electron beam travel distance.

There is even further provided in accordance with still another preferred embodiment of the present invention computer software for use in controlling the operation of an electron microscope-based material analysis system operative for directing an electron beam from the electron microscope onto a material in a non- vacuum environment, collecting X-rays emitted from the material and performing spectral analysis on the X-rays, a computerized method for performing analysis of materials when present in a non-vacuum environment using the electron microscope- based system, the computer software including instructions for operating the microscope -based material analysis system for: generating a first characteristic spectrum for a material by: directing an electron beam onto a material in a first non-vacuum environment, in which a first amount of scattering of the electron beam takes place, collecting first X-rays emitted from the material and performing spectral analysis on the first X-rays, thereafter, generating a second characteristic spectrum for the material by: directing an electron beam onto a material in a second non-vacuum environment, in which a second amount of scattering of the electron beam takes place; collecting second X-rays emitted from the material and performing spectral analysis on the second X-rays, comparing the first and second characteristic spectra and noting peaks whose intensity increases with increased scattering and generating a scattering-compensated characteristic spectrum for the material from at least one of the first and second characteristic spectra by eliminating at least one peak whose intensity increases with increased scattering.

In accordance with a preferred embodiment of the present invention the scattering compensated characteristic spectrum includes at least one peak whose intensity decreases with increased scattering.

Preferably, the first non-vacuum environment includes a first gas and the second non-vacuum environment includes a second gas, having electron beam scattering characteristics different from those of the first gas. Additionally or alternatively, the first non-vacuum environment has a first electron beam travel distance to the material associated therewith and the second non-vacuum environment has a second electron beam travel distance to the material associated therewith, the second electron beam travel distance producing a different amount of electron beam scattering than the first electron beam travel distance. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description with reference to the drawings in which:

Fig. 1 is a simplified illustration of a system for performing analysis of materials when present in a non-vacuum environment constructed and operative in accordance with a preferred embodiment of the present invention;

Figs. 2A and 2B are, respectively, simplified X-ray spectra obtained by directing an electron beam onto the same spot on the same sample in first and second different non-vacuum environments in which different gases are present, producing different amounts of scattering of the electron beam;

Fig. 2C is a scattering-compensated simplified X-ray spectrum derived from the spectra of Figs. 2A & 2B by eliminating at least one peak whose intensity increases with increased scattering;

Figs. 3A and 3B are respectively simplified X-ray spectra obtained by directing an electron beam onto the same spot on the same sample in first and second different non-vacuum environments in which different electron beam path lengths are present, producing different amounts of scattering of the electron beam; and

Fig. 3C is a scattering-compensated simplified X-ray spectrum derived from the spectra of Figs. 3 A & 3B by eliminating at least one peak whose intensity increases with increased scattering.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to Fig. 1, which illustrates a scanning electron microscope 100 constructed and operative in accordance with a preferred embodiment of the present invention. In accordance with a preferred embodiment of the present invention, the scanning electron microscope 100 includes a conventional SEM column 102, an example of which is a SEM column which forms part of a Gemini® column based SEM, commercially available from Carl Zeiss SMT GmbH, Oberkochen, Germany, having a beam aperture 104 arranged along an optical axis 106 of the SEM column 102. The SEM column 102 is typically maintained under vacuum.

A vacuum interface 108, typically in the form of a vacuum enclosure coupled to a vacuum pump (not shown) via a conduit 109, interfaces between the interior of the SEM column 102 at the beam aperture 104 and the ambient and is formed with a vacuum retaining, beam permeable membrane 110, which is aligned with the beam aperture 104 along optical axis 106.

Membrane 110 is preferably a model 4104SN-BA membrane, commercially available from SPI Supplies, West Chester, PA, USA. In accordance with a preferred embodiment of the invention, the membrane 110 is not electrically grounded. It is noted that the thickness of the membrane 110 is in the nanometer range and is not shown to scale.

Membrane 110 is typically supported onto the vacuum interface 108 by means of a membrane holder 112, typically in the form of an apertured disc formed of an electrical conductor, such as stainless steel. The membrane holder 112 sealingly underlies an electrical insulator 114, also typically in the form of an apertured disc. The electrical insulator 114 is sealingly mounted onto an inner facing bottom flange portion 116 of vacuum interface 108.

A sample, here designated by reference numeral 120, is located below and spaced from membrane 110, typically by a distance of up to 500 microns and is positioned such that an electron beam directed along optical axis 106 impinges thereon. Sample 120 is preferably supported by a sample holder 122. Sample holder 122 is preferably formed of an electrical conductor, such as stainless steel or aluminum, and may or may not be grounded, depending on the application. In accordance with a preferred embodiment of the present invention, sample holder 122 is supported on a movable sample mount 126, which provides movement of the sample holder in an upward-downward direction relative to SEM column 102, as shown by arrow 128. It is appreciated that movable sample mount 126 provides for multiple positioning of sample 120 relative to SEM column 102 and provides for multiple electron beam travel distances to sample 120 within the non-vacuum environment producing different amounts of electron beam scattering.

Preferably, a gas, such as helium or nitrogen, is injected into the space between membrane 110 and sample 120, typically by means of a supply conduit 130 connected to a gas supply controller 132. Gas supply controller 132 is preferably operative to select a gas for injecting from one or more of multiple gas input conduits 134, each coupled to a different gas supply (not shown). It is appreciated that different gases may provide different electron beam scattering characteristics.

An X-ray spectrometer 150 is operative to collect X-ray photons 152 emitted from sample 120 and generate an X-ray spectrum therefrom, which is preferably used for material analysis such as qualitative or quantitative analysis of the elements which are present in the sample 120.

In accordance with a preferred embodiment of the present invention, scanning electron microscope 100 is used to generate a scattering-compensated characteristic spectrum for a material in sample 120 by comparing at least two X-ray spectra to eliminate at least one peak whose intensity increases with increased scattering.

Thus, a first characteristic spectrum for a material is generated by directing an electron beam from scanning electron microscope 100 along axis 106 onto a material in a first non-vacuum environment, in which a first amount of scattering of the electron beam about axis 106 takes place, collecting X-rays emitted from the material and performing spectral analysis on the X-rays. A second characteristic spectrum for a material is generated by directing an electron beam from scanning electron microscope 100 along axis 106 onto a material in a second non-vacuum environment, in which a second amount of scattering of the electron beam about axis 106 takes place, collecting X-rays emitted from the material and performing spectral analysis on the X-rays. The first and second spectra are then compared, noting peaks whose intensity increases with increased scattering and a scattering-compensated characteristic spectrum for the material is generated by eliminating at least one peak whose intensity increases with increased scattering.

It is appreciated that the generated scattering-compensated characteristic spectrum may include at least one peak whose intensity decreases with increased scattering.

In a preferred embodiment of the present invention, the first and second non-vacuum environments having different scattering characteristics include using gas supply controller 132 to introduce different gases using into the non- vacuum environment, where the different gases have different scattering characteristics.

In another preferred embodiment of the present invention, the first and second non-vacuum environments having different scattering characteristics include using movable sample mount 126 to change the electron beam travel distance to the material, where the different travel distances produce different amounts of electron beam scattering.

In yet another preferred embodiment of the present invention, the first and second non-vacuum environments having different scattering characteristics include using gas supply controller 132 to introduce different gases using into the non- vacuum environment and using movable sample mount 126 to change the electron beam travel distance to the material.

Figs. 2A and 2B illustrate simplified X-ray spectra obtained by directing an electron beam onto the same spot on the same sample in first and second different non-vacuum environments in which different gases are present, producing different amounts of scattering of the electron beam. Fig. 2C shows a scattering-compensated simplified X-ray spectrum derived from the spectra of Figs. 2A & 2B by eliminating the peak centered at about 1.5 kEv whose intensity increases with increased scattering. As seen from a comparison of Figs. 2A and 2B, the X-ray spectra also includes a peak centered at about 1.75 kEv whose intensity decreases with increased scattering, which is not eliminated in the scattering-compensated simplified X-ray spectrum shown in Fig. 2C.

Figs. 3A and 3B illustrate simplified X-ray spectra obtained by directing an electron beam onto the same spot on the same sample in first and second different non-vacuum environments in which different electron beam path lengths are present, producing different amounts of scattering of the electron beam. Fig. 3C shows a scattering-compensated simplified X-ray spectrum derived from the spectra of Figs. 3A & 3B by eliminating a peak centered at about 1.5 kEv whose intensity increases with increased scattering. As seen from a comparison of Figs. 3 A and 3B, the X-ray spectra also includes a peak centered at about 1.75 kEv whose intensity decreases with increased scattering, which is not eliminated in the scattering-compensated simplified X-ray spectrum shown in Fig. 3C.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the invention includes both combinations and subcombinations of the various features described hereinabove as well as modifications and variations thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not in the prior art.