US3596090A - Particle beam apparatus having an imaging lens which is provided with an associated phase-displacing foil - Google Patents

Particle beam apparatus having an imaging lens which is provided with an associated phase-displacing foil Download PDF

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Publication number
US3596090A
US3596090A US813629A US3596090DA US3596090A US 3596090 A US3596090 A US 3596090A US 813629 A US813629 A US 813629A US 3596090D A US3596090D A US 3596090DA US 3596090 A US3596090 A US 3596090A
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foil
combination
phase
specimen
particle beam
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US813629A
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Walter Hoppe
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    • 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 or ion-optical arrangement

Definitions

  • a particle beam device has a longitudinal axis and a beam-generating portion for issuing particle beams along the axis.
  • a holder is provided for accommodating a specimen in the path of the beams and a particle beam imaging lens is disposed beyond the specimen locality coaxial with the axis.
  • a foil is disposed in the lens in the path of the particle beams for shifting the respective phases of the latter and scatlering the incident particles of the beams in bunches in distinct directions. The beam particles scattered in at least one of these directions are blocked by a diaphragm disposed beyond the foil.
  • My invention relates to particle beam apparatus having a radiation portion normally incorporating beam-generating and condenser systems.
  • the apparatus is also equipped with at least one imaging lens arranged in the beam path beyond the '0 specimen, and associated with the lens is a foil for displacing or shifting the phases of the imaging particle beams.
  • the foil can be commonly assigned to several lenses. However, as a rule, it is preferable to eliminate any disturbance in the particle beam caused by errors in the first image lens by arranging a foil directly behind the lens. This arrangement is preferred because image lenses in beam direction magnify the influences caused by errors of the first lens, these errors being especially pronounced relative to the quality of the image.
  • phase-displacing devices which for particle beam apparatus are phase displacing foils.
  • phase-displacing foils are phase displacing foils.
  • phase-displacing foils produced from the materials customarily used for this purpose not only provide the desired phase displacement, but, also diffusely scatter the particles such that the scattered particles are superimposed upon the particles which contain the actual information at the image locality thereby reducing the quality of the image.
  • the beams diffracted in the specimen of at least a positive and negative first order must have a phase displacement relative to the primary beam of n'180 if the phase specimen is to provide an amplitude image, the quantity :1 being a whole number including zero.
  • the diffracted beams in any case have a phase displacement of 90 with respect to the primary beam. Therefore, in order to fulfill the aforementioned condition, the diffracted beams must be phase-displaced by an additional 90, either positively or negatively. With a large aperture for individual lens zones, such phase displacements can be produced merely by wave aberrations of the lens which are caused by apertural errors and any defocusing which may be present.
  • the word unidirectional relates to the phases of those waves whose associated space frequencies are imaged or reproduced either with positive or with negative contrasts only.
  • this diaphragm arrangement known as a zone diaphragm, the waves which do not meet the phase conditions required for forming an image can therefore not arrive at the image plane.
  • zone diaphragm A certain disadvantage of the zone diaphragm becomes evident when the principles of imaging which utilize the phase-contrast effect, discovered during the past few years, are considered. It was found convenient in theoretical investigation to treat the specimen according to Fourier as being combined of sinusoidal phase lattices of various space frequencies. The total of all space frequencies represents the total of all specimen points. In the present case, it is of special importance that different zones of the image lens plane are responsible for transmitting various space frequencies into the image plane. With respect the known zone diaphragm, this fact indicates that the masking of specific waves can sometimes result in certain losses of information.
  • I provide a foil made of a material which scatters the impinging particles, in bunches, in distinct directions.
  • l arrange beyond the foil in the beam path diaphragms which block the scattered particles.
  • the foil materials used produced diffuse scattering of the beam particles
  • the present invention employs a foil with a preferential structure so that although there is inevitably some scatter, this is in discrete spatial directions and is also accompanied by bunching of the beam particles.
  • the correcting foil will be of crystal so that the bunching and scattering of the corpuscles is depen dent upon the crystal structure.
  • a monocrystal foil has been found to be particularly suitable, especially since foils of this kind can be produced with a particularly flat surface.
  • a crystalline foil this may be of graphite or silicon, for example.
  • the correcting foil can be arranged in the rear focal plane of the lens in just the same way as the known zone diaphragm. Alternatively, it can be located in the plane of an aperture diaphragm associated with the lens, this even if the diaphragm is not located in the focal plane, so that the provi sion of an additional mounting for the foil is rendered unnecessary.
  • the aperture diaphragm can be constructed to contain the foil.
  • the Zernike condition has already been referred to hereinbefore, in accordance with which the beams diffracted in the specimen should have a phase of H with respect to the primary beam, and it was also explained that fundamentally there is only a phase difference of 90. It is possible, as those skilled in the art will appreciate, to make the thickness of the correcting foil used in accordance with the invention constant, and therefore to achieve a constant phase-shifting effect in all zones of the foil, with the exception of the central zone through which the primary ray passes without undergoing any phase shift. in accordance with the condition just referred to the foil thickness will be so chosen that the phase shift of 90 is positive or negative.
  • This kind of dimensioning of the foil generally only approximately satisfies the phase condition because the beams have already undergone phase shift as a consequence of the wave aberration of the particular lens involved, which phase shift will be dependent upon the distance from the lens axis.
  • the thickness of the foil and therefore the phaseshifting efi'ect which it produces must be chosen differently in different areas of the foil in order that the phases (determined by the wave aberration of the lens and the phase-shifting effect of the foil) of all the particle beams have approximately the same value relative to the primary beam.
  • zone diaphragm may be modified in such a way that the zones thereof which are impermeable or opaque to the beam particles are replaced by zones which produce a phase-shifting effect relative to the beams passing through the permeable or transmissive zones, the modification being provided by having the foil of the invention contain a pattern corresponding to that of the zone diaphragm.
  • the phase shift in these zones must, to accord with the laws governing exclusively positive or negative contrast in reproduction, be l80 or multiple thereof. Outside these zones, the foil will be so dimensioned that on transition to the neighboring impermeable zones, no changes of phase occur.
  • zone diaphragm As is well known, in the conventional form of zone diaphragm, penneable and impermeable annular zones alternate with one another provided that the associated lens has no axial astigmatism; failing this, there are departures from the circular form, to configurations which are roughly elliptical in a first approximation.
  • a zone diaphragm correcting foil In order to produce a zone diaphragm correcting foil first of all a negative in the form ofa metal foil can be produced and then, by using ion etching through said negative, a monocrystalline foil can be etched away at those areas to which the negative allows the ion beam to pass. This process can be applied in a corresponding manner to the manufacture of a variable thickness foil.
  • the diaphragms provided to block the scattered beam particles can be located anywhere behind the foil, considered in the direction of the radiation, provided they are intended simply to block the scattered particles without disturbing the main image, i.e. the image of zero order.
  • a field-of-view diaphragm which blocks these intermediate images but passes the main image.
  • the beam-generating section of the apparatus should be arranged to direct onto the specimen a particle beam of such a slight cross section (fine zone illumination), that the different images are located in separate areas of the intermediate image plane in which the diaphragm is located.
  • FIG. 1 schematically illustrates those pans of the particle beam apparatus which are essential to the invention.
  • FIG. 2 is a broken-out view of a microscope column in which is illustrated, in section, an imaging lens provided with an associated phase-displacing foil according to my invention.
  • an object 1 is irradiated by a fine electron beam.
  • the beam passes through an objective lens 2, illustrated in purely schematic fashion, which may be an electrostatic or electromagnetic lens, and which may be followed by other lenses, not shown.
  • an objective lens 2 illustrated in purely schematic fashion, which may be an electrostatic or electromagnetic lens, and which may be followed by other lenses, not shown.
  • a phase-shifting correcting foil 3 is located, and in this particular example this is a monocrystalline foil.
  • the intermediate image plane there is a main image 4 produced by the central beam, and also secondary images 5 and 6 produced by electrons scattered in the foil 3. Due to the structure of the particular material used for the foil 3, the electrons are scattered in a bunched way in discrete spatial directions.
  • the secondary images 5 and 6, and any other secondary images which may occur, but which have not been shown in the figure, can be blocked and in this embodi ment this is achieved by a ficld-of-view diaphragm 7 arranged in the intermediate image plane, which passes the central beam, said diaphragm 7 having individual zones which, under the influence of the phase-shifting effect of the foil 3, present the requisite phase values for image production, and being employed to obtain the electron microscopic image of the specimen.
  • PK]. 2 illustrates the relevant part of an exemplary electron microscope embodiment.
  • the microscope has a column ll in which there is located an objective lens 12, for the magnified reproduction of an object held in vacuum-sealed fashion in an object cartridge 13.
  • the essential components of the objective lens 12 are an upper pole piece 14 and a lower pole piece 15 between which the lens gap is located.
  • an elec tromagnetic lens is utilized having winding 16 which develops a flux that passes through an iron circuit l7, the two pole pieces 14 and I5 and the lens gap.
  • a nonmagnetic perforated plate 18 is provided for the passage of a diaphragm drive system 19 carrying an aperture diaphragm 110.
  • the aperture diaphragm is so constructed that it also functions as the mounting for a phase-shifting foil 111, for example a monocrystalline foil, which foil may be designed as a zone diaphragm.
  • a drive 112 provides for the transverse displace ment of the diaphragm 110.
  • a further nonmagnetic ring 113 for example of brass, which locates a mounting "4 for a field-of-view diaphragm 115, which in this embodiment blocks the electrons scattered in the foil "1.
  • This mounting 114 is provided with a drive arrangement "6 which extends in vacuum-tight fashion through the wall ofthe column 11.
  • the diaphragms serving to block the beam particles scattered in the foil can comprise parts of the corpuscular beam apparatus which are already present, such as suitable flanges or projections.
  • a particle beam device which has a longitudinal axis, beam-generating means for issuing a particle beam along said axis, means for accommodating a specimen in the path of said beam, an electrooptical imaging lens disposed beyond the specimen locality coaxial with said axis, foil means having a crystalline structure and being disposed beyond the specimen locality in the path of said particle beam for shifting the phases of the resulting diffracted beams and for scattering the incident particles of said diffracted beams in bunches in distinct directions, and blocking means disposed beyond said foil means for blocking the beam particles scattered in at least one of said distinct directions.
  • said foil means is a foil consisting of crystalline silicon.
  • said imaging lens has two focal planes, one of said focal planes being spaced from said beam-generating means a larger distance than the other of said focal planes, said foil means being disposed in said one focal plane.
  • said particle beam issuing from said beam-generating means has beyond the specimen locality a primary central portion on said axis and portions diffracted by a specimen placeable at said specimen locality, said diffracted portions surrounding said central portion and having different phases resulting from wave aberration in said lens and phase shifting in said foil, and wherein said foil means is a foil having a thickness varying along directions radial of said axis, so that said different phases have approximately the same value relative to said central portion.
  • phase value is substantially nl where n is a whole number or zero.
  • foil means is a diaphragm having mutually separate beamtransmissive and beam'opaque zones.
  • foil means is a diaphragm having mutually separate beam-transmissive and beam-phaseshifting zones.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Electron Sources, Ion Sources (AREA)
US813629A 1968-04-16 1969-04-04 Particle beam apparatus having an imaging lens which is provided with an associated phase-displacing foil Expired - Lifetime US3596090A (en)

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CH558668 1968-04-16

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US3596090A true US3596090A (en) 1971-07-27

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US (1) US3596090A (enrdf_load_stackoverflow)
DE (1) DE1810818A1 (enrdf_load_stackoverflow)
GB (1) GB1259352A (enrdf_load_stackoverflow)
NL (1) NL170900C (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5814815A (en) * 1995-12-27 1998-09-29 Hitachi, Ltd. Phase-contrast electron microscope and phase plate therefor
US20020148962A1 (en) * 2001-02-09 2002-10-17 Jeol Ltd. Lens system for phase plate for transmission electron microscope and transmission electron microscope
US20070284528A1 (en) * 2006-03-14 2007-12-13 Gerd Benner Phase contrast electron microscope
US20110174971A1 (en) * 2010-01-19 2011-07-21 Marek Malac Phase contrast imaging and preparing a tem therefor
CN106104744A (zh) * 2014-01-21 2016-11-09 拉莫特特拉维夫大学有限公司 用于调节粒子波束的方法与装置

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5814815A (en) * 1995-12-27 1998-09-29 Hitachi, Ltd. Phase-contrast electron microscope and phase plate therefor
US20020148962A1 (en) * 2001-02-09 2002-10-17 Jeol Ltd. Lens system for phase plate for transmission electron microscope and transmission electron microscope
US6744048B2 (en) * 2001-02-09 2004-06-01 Jeol Ltd. Lens system for phase plate for transmission electron microscope and transmission electron microscope
US8330105B2 (en) 2006-03-14 2012-12-11 Carl Zeiss Nts Gmbh Phase contrast electron microscope
US20070284528A1 (en) * 2006-03-14 2007-12-13 Gerd Benner Phase contrast electron microscope
US7741602B2 (en) * 2006-03-14 2010-06-22 Carl Zeiss Nts Gmbh Phase contrast electron microscope
US20100181481A1 (en) * 2006-03-14 2010-07-22 Carl Zeiss Nts Gmbh Phase contrast electron microscope
US8039796B2 (en) 2006-03-14 2011-10-18 Carl Zeizz NTS GmbH Phase contrast electron microscope
US20110174971A1 (en) * 2010-01-19 2011-07-21 Marek Malac Phase contrast imaging and preparing a tem therefor
US8785850B2 (en) 2010-01-19 2014-07-22 National Research Counsel Of Canada Charging of a hole-free thin film phase plate
CN106104744A (zh) * 2014-01-21 2016-11-09 拉莫特特拉维夫大学有限公司 用于调节粒子波束的方法与装置
EP3097577A4 (en) * 2014-01-21 2017-09-20 Ramot at Tel-Aviv University Ltd. Method and device for manipulating particle beam
US9953802B2 (en) 2014-01-21 2018-04-24 Ramot At Tel-Aviv University Ltd. Method and device for manipulating particle beam
US10497537B2 (en) 2014-01-21 2019-12-03 Ramot At Tel-Aviv University Ltd. Method and device for manipulating particle beam

Also Published As

Publication number Publication date
DE1810818B2 (enrdf_load_stackoverflow) 1970-12-17
DE1810818A1 (de) 1969-10-23
NL170900B (nl) 1982-08-02
GB1259352A (enrdf_load_stackoverflow) 1972-01-05
NL170900C (nl) 1983-01-03
NL6902406A (enrdf_load_stackoverflow) 1969-10-20

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