Apparatus and methods for inspecting wafers and masks using multiple charged-particle beams

A system for inspecting for defects in a pattern on a sample, comprising:

• (a) a source of multiple electron beams directed toward the sample, each electron beam having a respective initial propagation axis;
• (b) a first lens for focusing each electron beam on a separate respective locus in an irradiation region on a surface of the sample so as to produce secondary electrons upon impingement of the respective electron beam on the locus;
• (c) a deflector for simultaneously scanning each electron beam over its respective locus in the irradiation region;
• (d) for each electron beam, a detector of secondary electrons released from the respective locus;
• and
• (e) the source of electron beams comprising a plate that defines multiple apertures, each aperture having an optical axis that is shifted relative to the respective initial propagation axis so as to provide each charged-particle beam from the plate to the sample with a propagation path of substantially identical length.

A system for inspecting for defects in a pattern defined in a sample, comprising:

• (a) a source of multiple electron beams directed toward the sample;
• (b) a first lens for focusing each electron beam on a separate respective locus in an irradiation region on a surface of the sample so as to produce secondary electrons upon impingement of the electron beam on the locus;
• (c) a deflector for scanning each electron beam over its respective locus in the irradiation region;
• (d) a positively biased electrode plate, defining multiple apertures, situated so as to attract the secondary electrons as the secondary electrons are released from the irradiated region, each aperture of the electrode plate being situated so as to receive secondary electrons attracted from a corresponding locus in the irradiated region;
• and
• (e) for each electron beam, a detector of secondary electrons released from the respective locus, each detector being situated downstream of the respective aperture in the electrode plate, the detectors being more positively biased than the electrode plate.

A system for inspecting for defects in a pattern defined in a sample, comprising:

• (a) multiple electron-beam sources, each source being operable to generate multiple electron beams directed toward the sample, each electron-beam source irradiating a respective irradiation region on a surface of the sample;
• (b) a lens serving to focus each electron beam on a respective locus in the respective irradiation region so as to produce secondary electrons upon impingement of the electron beam on the locus;
• (c) a deflector serving to scan each electron beam over its respective locus;
• (d) an electrode plate situated and biased so as to attract secondary electrons as the secondary electrons are released from the loci in the respective irradiation region, each electrode plate defining multiple apertures, wherein the secondary electrons released from the respective locus in the respective irradiation region pass through a respective aperture;
• and
• (e) a secondary-electron detector situated downstream of each respective aperture to detect the secondary electrons released from the respective locus.

A system for inspecting for defects in a pattern defined in a sample, comprising:

• (a) a source of an electron-beam flux directed toward the sample;
• (b) an aperture plate located downstream of the source, the aperture plate defining multiple apertures each for passing a portion of the electron-beam flux so as to produce multiple electron beams;
• (c) a lens, located downstream of the aperture plate, for focusing the electron beams on respective loci in an irradiation region of a surface of the sample;
• (d) a deflector, located downstream of the lens, for simultaneously scanning each electron beam over a limited area in the irradiation region corresponding to the respective locus;
• (e) a scintillator plate, situated downstream of the sample and comprising multiple detection areas each corresponding to a respective locus, each detection area producing photons in response to secondary electrons from the respective locus impinging upon the detection area, the scintillator plate having a positive bias so as to attract the secondary electrons as the secondary electrons are released from the respective loci;
• (f) a photoguide situated downstream of each detection area for routing the respective photons to a terminus of the photoguide;
• and
• (g) a respective detector situated at the terminus of each photoguide for receiving and detecting the respective photons routed through the respective photoguide and for producing electrical signals in response to detecting the photons.

An apparatus for detecting defects in a pattern on a sample, comprising:

• (a) an irradiation system operable to irradiate each of multiple loci in an irradiation region on a surface of the sample with a separate charged-particle beam so as to cause each locus to produce secondary electrons;
• (b) an electrode having a concave surface oriented toward the irradiation region, the electrode being operable to collect the secondary electrons or reflected charged particles from the sample, the electrode defining multiple apertures each corresponding to and operable to collect secondary electrons produced by a respective locus;
• and
• (c) an electron detector situated downstream of each aperture in the electrode for detecting the secondary electrons or reflected charged particles passing through the aperture.

An apparatus for detecting defects in a pattern on a sample, the sample comprising multiple subfields each defining pattern areas and non-pattern areas, the apparatus comprising:

• (a) a source operable to produce multiple charged-particle beams each directed toward a respective locus in a respective subfield on a surface of the sample;
• (b) a scanner operable to scan each charged-particle beam about the respective locus within the respective subfield;
• (c) a beam accelerator situated and configured to apply an accelerating voltage to the beams for providing the beams with sufficient energy to pass through the non-pattern areas and to pass through the pattern areas more easily than through the non-pattern areas of the respective subfields;
• and
• (d) multiple charged-particle detectors each operable to detect the respective charged-particle beam passing through the respective subfield of the sample.

A method for inspecting a sample defining a pattern, the method comprising:

• (a) irradiating each of multiple loci in a region of the sample with a separate charged-particle beam so as to cause the irradiated loci to selectively release secondary charged particles in response to the irradiation;
• (b) attracting and collecting the secondary charged particles as they are released from the irradiated loci;
• (c) detecting the collected charged particles so as to produce data concerning a characteristic of the pattern at each locus;
• and
• (d) processing the data relative to reference data to detect loci in which the pattern has a defect.

An apparatus for detecting defects in a pattern on a sample, comprising:

• (a) a charged-particle-beam optical system for irradiating multiple charged-particle beams on respective loci in an irradiation region of a surface of the sample;
• (b) a charged-particle detector situated so as to detect secondary electrons propagating, during irradiation, from the loci in the irradiated region of the sample as a result of the charged-particle beams impinging on the loci, the detector being operable to produce data on whether or not the pattern in the irradiated region has any defects;
• and
• (c) an electrode plate, configured to have a spherical profile and defining multiple apertures, situated so as to capture the secondary electrons propagating from the irradiated region, each aperture of the electrode plate being situated so as to receive secondary electrons released from a corresponding locus in the irradiated region, wherein the charged-particle detector comprises a separate detector situated downstream of each aperture of the electrode plate.

A system for inspecting for defects in a pattern defined in a sample, comprising:

• (a) a source of multiple electron beams directed toward the sample;
• (b) a first lens for focusing each electron beam on a separate respective locus in an irradiation region on a surface of the sample so as to produce secondary electrons upon impingement of the electron beam on the locus;
• (c) a deflector for simultaneously scanning each electron beam over its respective locus in the irradiation region;
• (d) an electrode plate, having a profile that is a portion of a sphere, the electrode plate defining multiple apertures and being situated so as to attract the secondary electrons propagating from the irradiated region, each aperture of the electrode plate being situated so as to receive secondary electrons released from a corresponding locus in the irradiated region;
• and
• (e) for each electron beam, a detector of secondary electrons released from the respective locus, each detector being situated downstream of the respective aperture in the electrode plate.

A multiple-channel SEM, comprising:

• (a) a source of multiple charged-particle beams each directed toward a respective locus in an irradiation region on a surface of a sample, the particle-beam source comprises a source plate defining multiple apertures;
• (b) a charged-particle-beam deflector for scanning each charged-particle beam over a scanning region around the respective locus;
• (c) a detector associated with each scanning region for detecting secondary electrons generated in the scanning region from impingement of the respective charged-particle beam on the scanning region;
• and
• (d) a retention base oriented at a slant relative to the irradiation region, the retention base thus holding the source plate relative to the irradiation surface such that each incidence trajectory has a similar length from the source plate to the irradiation region.