WO2004021391A1 - Dispositif a correcteur de feuille pour aberrations optoelectroniques a faible energie - Google Patents

Dispositif a correcteur de feuille pour aberrations optoelectroniques a faible energie Download PDF

Info

Publication number
WO2004021391A1
WO2004021391A1 PCT/NL2003/000612 NL0300612W WO2004021391A1 WO 2004021391 A1 WO2004021391 A1 WO 2004021391A1 NL 0300612 W NL0300612 W NL 0300612W WO 2004021391 A1 WO2004021391 A1 WO 2004021391A1
Authority
WO
WIPO (PCT)
Prior art keywords
electron
foil
optical device
aperture
electrons
Prior art date
Application number
PCT/NL2003/000612
Other languages
English (en)
Inventor
Pieter Kruit
Rogier Herman Van Aken
Original Assignee
Technische Universiteit Delft
Stichting Fundementeel Onderzoek Der Materie (Fom)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Technische Universiteit Delft, Stichting Fundementeel Onderzoek Der Materie (Fom) filed Critical Technische Universiteit Delft
Priority to AU2003261023A priority Critical patent/AU2003261023A1/en
Priority to EP03791500A priority patent/EP1547119A1/fr
Publication of WO2004021391A1 publication Critical patent/WO2004021391A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/10—Lenses
    • H01J37/12—Lenses electrostatic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/05—Electron or ion-optical arrangements for separating electrons or ions according to their energy or mass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/153—Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators

Definitions

  • the present invention relates to an electron optical device. Also, the present invention relates to an electron lens system comprising such an electron optical device. Further, 5 the present invention relates an electron microscope comprising such electron optical device. Finally, the present invention relates an electron lithography system comprising such electron optical device.
  • these correctors are operated at a beam energy at the foil of 100 keV and larger.
  • the pressure in an electron microscope is usually 10 " mbar at best and mobile adsorbants will be present on the foils surface. Electrons impinging on the surface with an energy larger than ⁇ 5 eV will crack these adsorbants and create a carbon species that locally sticks to the surface. As the adsorbants move over the surface, new adsorbants move into the beam and are cracked continuously. So the electron beam will cause a carbon build up on the foils surface. This contamination and its associated scattering and charging is a major problem for the use of phase plates in electron microscopes (see for example: R. Danev, K.
  • an electron optical device for, in use, creating negative spherical and chromatic aberration and reducing the energy spread in an electron beam travelling on an optical axis, comprising:
  • the very low voltage operation advantageously makes the electron optical device according to the present invention, or foil corrector, more attractive for low voltage SEM and it greatly reduces the contamination problem.
  • the foil of the device may act as a high-pass energy filter: electrons with insufficient forward energy are reflected at the foil.
  • the present invention relates to an electron lens system, using an electron optical device as described above for a compensation, in use, of a positive spherical aberration of other lenses in the electron lens system.
  • the present invention relates to an electron lens system, using an electron optical device as described above for a compensation, in use, of a positive chromatic aberration of other lenses in the electron lens system.
  • the present invention relates to an electron microscope, using an electron optical device as described above. Also, the present invention relates to an electron microscope, using an electron lens system as described above.
  • the present invention relates to an electron lithography system, using an electron optical device as described above. Moreover, the present invention relates to an electron lithography system, using an electron lens system as described above.
  • Figure 1 shows schematically a basic design of a foil corrector according to the present invention (not to scale) wherein D denotes a diameter of an aperture and s denotes a gap between a foil and the aperture;
  • Figure 2 shows schematically positive spherical aberration for a positive and a negative lens, by means of two rays entering the lens at different radii, r / and r 2 . In both cases, the intercept with the z-axis shifts in the negative z direction for increasing radius of incidence;
  • Figure 3 shows a schematic sketch of electric field lines in the foil corrector according to the present invention
  • Figure 5 shows schematically a foil corrector according to the present invention with equi-potentials as calculated by Elens;
  • Figure 8 shows a plot of coefficient of 2 n order chromatic aberration C c2 , normalized to the aperture diameter! ) , versus the corrector gap, for a voltage on aperture
  • Figure 10 shows schematically an electron microscope column with the foil corrector according to the present invention.
  • FIG. 1 shows schematically a basic design of a foil corrector according to the present invention (not to scale) wherein D denotes a diameter of an aperture and 5 denotes a gap between a foil and the aperture. It consists of a flat free-standing foil of nanometer size thickness with apertures on both sides.
  • the foil is put on a retarding potential, such that the electrons (e-) have almost 0 eV kinetic energy when they enter the foil (and also when they have just left the foil at the other side).
  • Figure 2 shows schematically positive spherical aberration for a positive (left) and a negative (right) lens, by means of two rays entering the lens at different radii, r; and r 2 .
  • positive spherical aberration is the effect that the focussing power of the lens increases for increasing radius of incidence.
  • a negative lens with positive spherical aberration the defocusing power of the lens decreases for increasing radius of incidence. This is illustrated in figure 2.
  • a spherical aberration corrector the opposite effect is desired.
  • an approximative description of its properties will be obtained by a simple analysis of the radial momentum the electron obtains in the electric field.
  • the calculation can be limited to one half part of the corrector: a flat surface (representing the foil) with an aperture in front of it. First, the calculation will be done for a conventional foil corrector operating at high beam energy. Thereafter the calculation for the low voltage foil corrector will be done according to the same reasoning and the difference between both correctors will be pointed out.
  • E r (z,r) is the radial component of the electric field
  • v z (z,r) is the electron's axial velocity component.
  • a cylindrical coordinate system is adopted here in which the positive z-direction is perpendicular to the foil and directed towards the aperture, and the radial coordinate r is perpendicular to the z-axis. Close to the axis the potential ⁇ (z,r) can be expanded as
  • Vz (6) p z is the axial momentum of the electron leaving the corrector. If the velocity of the electron is assumed to be constant and the radial velocity component is negligible, the following substitution is allowed:
  • the first term l nd term proportional to r is the 3 r order focal strength and is a measure for the 3 r order spherical aberration.
  • the deflection angle can be expressed in terms of the z-field at the foil (neglecting the 0(r") term):
  • Figure 3 shows a schematic sketch of electric field lines in the foil corrector according to the present invention.
  • the side at the aperture with the lower potential has a positive spherical aberration. Because the electron velocity is lower at this side, its contribution is larger than the side with the negative spherical aberration and the net result is always positive.
  • E t is the kinetic energy and m is the electron mass.
  • m is the electron mass.
  • a new expression for the radial momentum change is obtained.
  • the l/v z term in the integral can be expanded into a series of r using equation 2.
  • the deflection angle is ⁇ p0p z (equation 6).
  • » z is the axial momentum of the electron when leaving the corrector, it is (under the same approximation for v z as above)
  • a positive electrostatic lens will, in general, have a positive chromatic aberration: electrons with a larger velocity will spend less time in the lens field and are less deflected. So the focussing power is weaker for higher energies. In a negative lens, the higher energy electrons are less deflected as well and the defocusing power is weaker. This results in a negative chromatic aberration for negative electrostatic lenses. Therefore a foil corrector with the foil on a retarding potential is expected to have a negative chromatic aberration.
  • any optical element can also be determined, when the electron trajectories in the exit plane are known as function of their radius and angle of incidence. Therefore, the spherical and chromatic aberration can be determined from ray tracing results. This will be discussed below.
  • the symmetry around the foil is used. The electrons start just in front of the foil, perpendicular to its surface with almost zero kinetic energy.
  • Coefficient C s is obtained from ray tracing results in two steps (see figure 2 for visual illustration): 1. Evaluate the deflection angle as function of the radius of incidence:
  • this angle is equal to the deflection angle due to the 1 st order lens effect:
  • E start is the starting energy of the electron
  • U en d the potential in the exit plane
  • C c i and C c2 the coefficients of 1 st and 2 nd order chromatic aberration.
  • Figure 5 shows schematically a foil corrector according to the present invention with equi-potentials as calculated by Elens.
  • Elens divides this geometry into a fine mesh of maximum 100,000 points. The potential on every mesh point is determined such that the total energy is minimized.
  • the electron trajectories are calculated with Trasys (B. Lencova, G.Wisselink, "Electron Optical Design Program Package Trasys 3.7", 2002).
  • Trasys uses a high accuracy interpolation in z and r to determine the potential in between the mesh points, as described by J. Chmelik and J.E. Barth, "An interpolation method for ray tracing in electrostatic fields calculated by the finite element method", SPIE Charged-Part. Opt. 2014 (1993) 133. With this information, it can calculate the electric force on the electron at any point and thus trace its trajectory.
  • the corrector has 3 independent parameters: the gap s between foil and aperture, the diameter D of the aperture (both as shown in Figure 1) and the voltage V applied to the aperture.
  • An important result of the calculations is that the magnitude of the voltage on the aperture has little influence on the trajectories.
  • The/ C S 3, C s s and C c j are hardly affected by the voltage, as is illustrated in figure 6, only the C c2 is.
  • the results scale linearly with the size of the corrector. Therefore the corrector properties as function of the gap are normalized to the diameter of the aperture, see figure 7.
  • Figures 8 and 9 show that the coefficient of second order chromatic aberration is independent of the gap and increases for increasing voltage respectively.
  • Figure 10 shows schematically an electron microscope column with an electron optical device or foil corrector according to the present invention.
  • the corrector can be used in an electron lithography system for the reduction of the spherical or chromatic aberration.
  • the foil will act as a high pass energy filter because the electrons in the lower part of the energy distribution do not have sufficient energy to pass the foil.
  • a quantum mechanical effect due to the wave character of the electrons has to be taken into account.
  • the electrons enter the foil their kinetic energy is increased with around 10 eV, being the difference between the vacuum level and the bottom of the conduction band. As a consequence the wavelength is decreased. Opposed to its high voltage counterpart, this effect is not negligible for the low energy foil corrector.
  • the electrons form a standing wave in the foil and a quantum mechanical reflection at the foils surfaces can occur. Calculations of the transmission as function of the electron kinetic energy show an oscillating behaviour, causing a high cut-off as well.
  • a corrector geometry is assumed of identical apertures on both sides of the foil, gap sizes 30 ⁇ m, aperture diameters 200 ⁇ m and a voltage between foil and apertures of 300 V, which is based on the practical limit of 10 kV/mm. It has been taken into account that in this case the field on the optical axis is considerably lower, see fig. 4. Then for an electron beam with a reduced brightness of 10 Am " sr " V " , a diameter of 40 ⁇ m at the foil (20% of the aperture diameter) and current 1 nA (assuming no current loss in the foil), the illumination angle is 5.8x10 " rad and the Coulomb interactions angular deflection is 2.2x10 " rad. This causes an increase of the spot size of about 7%.
  • the fifth order C s and the second order C c can limit the spot size.
  • the calculations show that the C s s of the corrector can be zero, giving no extra contribution to the spot size due to aberrations. Preliminary calculations indicate that the spot size due to the second order chromatic aberration can be kept sufficiently small.
  • the transmission should be measured for sub 10 nm foils and with a sub 0.1 eV energy resolution because of the quantum mechanical reflection.
  • the principal scattering mechanism at the energy of interest is electron-electron scattering. See: P. Wolff, "Theory of secondary electron cascade in Metals", Physical Review 95 (1954) 56. Therefore, a semiconductor foil may be favourable over a metal foil. Because of its lower density of conduction electrons, scattering is expected to be much less and the transmission will be better or such a foil needs to be less thin.
  • Another option to improve the transmission is the use of a gauze or perforated foil. The gauze mazes or perforations should be sufficiently small, that they do not significantly disturb the electric field.
  • a low voltage spherical and chromatic aberration corrector is proposed based on a thin transparent foil sandwiched between two apertures.
  • the electrons are retarded to almost zero energy at the foil, at which energies the electrons may travel ballistically through the foil.
  • From an approximate analytical model the feasibility to correct spherical and chromatic aberrations was shown.
  • the third and fifth order spherical aberration coefficients as well as the first and second order chromatic aberration coefficients were obtained from electric field simulations and ray tracing.
  • a schematic design of a corrector for potential use in a low- voltage scanning electron microscope or in the gun-section of a scanning transmission electron microscope has been described.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Beam Exposure (AREA)

Abstract

L'invention concerne un dispositif optoélectronique destiné, en cours d'utilisation, à la création d'aberration sphérique et chromatique négative, et à la réduction de l'énergie répandue dans un faisceau électronique se déplaçant sur un axe optique, caractérisé en ce qu'il comprend : au moins une plaque conductrice sensiblement perpendiculaire à l'axe optique, présentant une première ouverture ayant un premier rayon autour dudit axe optique, une feuille mince en un matériau conducteur, disposée parallèlement à / et à une première distance / d'au moins une plaque conductrice. En cours d'utilisation, la feuille mince est à un potentiel électrique qui génère un champ électrique pour la réduction de l'énergie cinétique des électrons dans le faisceau d'électrons, à une valeur sensiblement voisine de zéro à la surface de la feuille, tout en laissant l'énergie cinétique des électrons dans la première ouverture à une valeur relativement élevée.
PCT/NL2003/000612 2002-08-30 2003-09-01 Dispositif a correcteur de feuille pour aberrations optoelectroniques a faible energie WO2004021391A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2003261023A AU2003261023A1 (en) 2002-08-30 2003-09-01 Device with foil corrector for electron optical aberrations at low energy
EP03791500A EP1547119A1 (fr) 2002-08-30 2003-09-01 Dispositif a correcteur de feuille pour aberrations optoelectroniques a faible energie

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US40701202P 2002-08-30 2002-08-30
US60/407,012 2002-08-30

Publications (1)

Publication Number Publication Date
WO2004021391A1 true WO2004021391A1 (fr) 2004-03-11

Family

ID=31978407

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NL2003/000612 WO2004021391A1 (fr) 2002-08-30 2003-09-01 Dispositif a correcteur de feuille pour aberrations optoelectroniques a faible energie

Country Status (3)

Country Link
EP (1) EP1547119A1 (fr)
AU (1) AU2003261023A1 (fr)
WO (1) WO2004021391A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2051278A1 (fr) * 2007-10-17 2009-04-22 ICT Integrated Circuit Testing Gesellschaft für Halbleiterprüftechnik mbH Filtre d'énergie pour appareil de faisceau d'électron à émission à champ froid
WO2014191370A1 (fr) * 2013-05-31 2014-12-04 Commissariat A L'energie Atomique Et Aux Energies Alternatives Lentille electrostatique a membrane semiconductrice dielectrique
US20160189916A1 (en) * 2014-12-17 2016-06-30 Applied Materials Israel Ltd. Scanning charged particle beam device having an aberration correction aperture and method of operating thereof

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5587586A (en) * 1994-10-03 1996-12-24 U.S. Philips Corporation Particle-optical apparatus comprising an electron source with a needle and a membrane-like extraction electrode

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5587586A (en) * 1994-10-03 1996-12-24 U.S. Philips Corporation Particle-optical apparatus comprising an electron source with a needle and a membrane-like extraction electrode

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
HANAI T ET AL: "CHARACTERISTICS AND EFFECTIVENESS OF FOIL LENS FOR CORRECTION SPHERICAL ABERRATION IN SCANNING TRANSMISSION ELECTRON MICROSCOPY", JOURNAL OF ELECTRON MICROSCOPY, JAPANESE SOCIETY FOR ELECTRON MICROSCOPY. TOKYO, JP, vol. 47, no. 3, 1998, pages 185 - 192, XP000801950, ISSN: 0022-0744 *
STEPANOV I S ET AL: "Fabrication of ultra-thin free-standing chromium foils supported by a Si3N4 membrane-structure with search pattern", MICROELECTRONIC ENGINEERING, ELSEVIER PUBLISHERS BV., AMSTERDAM, NL, vol. 46, no. 1-4, May 1999 (1999-05-01), pages 435 - 438, XP004170757, ISSN: 0167-9317 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2051278A1 (fr) * 2007-10-17 2009-04-22 ICT Integrated Circuit Testing Gesellschaft für Halbleiterprüftechnik mbH Filtre d'énergie pour appareil de faisceau d'électron à émission à champ froid
US7919749B2 (en) 2007-10-17 2011-04-05 ICT Integrated Circuit Testing Gesellschaft für Halbleiterprüftechnik mbH Energy filter for cold field emission electron beam apparatus
WO2014191370A1 (fr) * 2013-05-31 2014-12-04 Commissariat A L'energie Atomique Et Aux Energies Alternatives Lentille electrostatique a membrane semiconductrice dielectrique
FR3006499A1 (fr) * 2013-05-31 2014-12-05 Commissariat Energie Atomique Lentille electrostatique a membrane isolante ou semiconductrice
JP2016522973A (ja) * 2013-05-31 2016-08-04 コミサリヤ・ア・レネルジ・アトミク・エ・オ・エネルジ・アルテルナテイブ 誘電半導体膜を有する静電レンズ
US9934934B2 (en) 2013-05-31 2018-04-03 Commissariat A L'energie Atomique Et Aux Energies Alternatives Electrostatic lens having a dielectric semiconducting membrane
US20160189916A1 (en) * 2014-12-17 2016-06-30 Applied Materials Israel Ltd. Scanning charged particle beam device having an aberration correction aperture and method of operating thereof

Also Published As

Publication number Publication date
AU2003261023A1 (en) 2004-03-19
EP1547119A1 (fr) 2005-06-29
AU2003261023A8 (en) 2004-03-19

Similar Documents

Publication Publication Date Title
Spence High-resolution electron microscopy
US7786454B2 (en) Optics for generation of high current density patterned charged particle beams
KR20210016064A (ko) 복수의 하전 입자 빔들의 장치
US8178850B2 (en) Chromatic aberration corrector for charged-particle beam system and correction method therefor
JP4176149B2 (ja) 粒子光学機器の色収差を補正する補正装置
JP5849108B2 (ja) 電子ビーム装置
JP5794990B2 (ja) 分散イオン源加速カラム
TW200402602A (en) Electron beam exposure apparatus, exposure method of using electron beam, control method of electron beam, and manufacturing method of semiconductor device
Steele et al. High-brightness Cs focused ion beam from a cold-atomic-beam ion source
JP3986792B2 (ja) 荷電粒子投射リソグラフィ・システムにおける空間電荷に起因する収差を抑制する装置
Mankos et al. Multisource optimization of a column for electron lithography
Steinwand et al. Fabrication and characterization of low aberration micrometer-sized electron lenses
WO2004021391A1 (fr) Dispositif a correcteur de feuille pour aberrations optoelectroniques a faible energie
Van Aken et al. Low-energy foil aberration corrector
Munro et al. Simulation software for designing electron and ion beam equipment
Munro Electron and ion optical design software for integrated circuit manufacturing equipment
JP7406009B2 (ja) 電子銃および電子線応用装置
Van Aken et al. Design of an aberration corrected low-voltage SEM
Khursheed et al. On-axis electrode aberration correctors for scanning electron/ion microscopes
US20190096629A1 (en) A corrector structure and a method for correcting aberration of an annular focused charged-particle beam
Mankos et al. Basic constraints for a multibeam lithography column
Lutsch et al. Initial resolution measurements of miniaturized electrostatic lenses for LVSEM
Mankos et al. Electron–electron interactions in cathode objective lenses
Mankos et al. 1 Principles of Dual-Beam Low-Energy Electron Microscopy
Rosi Controllo e misura sperimentale del momento angolare orbitale di elettroni in un microscopio elettronico a trasmissione (TEM)

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LU MC NL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
WWE Wipo information: entry into national phase

Ref document number: 2003791500

Country of ref document: EP

WWP Wipo information: published in national office

Ref document number: 2003791500

Country of ref document: EP

NENP Non-entry into the national phase

Ref country code: JP

WWW Wipo information: withdrawn in national office

Country of ref document: JP

WWW Wipo information: withdrawn in national office

Ref document number: 2003791500

Country of ref document: EP