US3197635A - Regulating device for the correction of image defects of an electron-optical system - Google Patents

Regulating device for the correction of image defects of an electron-optical system Download PDF

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Publication number
US3197635A
US3197635A US204912A US20491262A US3197635A US 3197635 A US3197635 A US 3197635A US 204912 A US204912 A US 204912A US 20491262 A US20491262 A US 20491262A US 3197635 A US3197635 A US 3197635A
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terminals
resistance
electron
voltage
correcting
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US204912A
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English (en)
Inventor
Adrianus Cornelis Van Dorsten
Franken Adrianus Jacobus Jozef
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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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
    • H01J37/153—Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators

Definitions

  • the systems most commonly used comprise eight correcting elements of which opposite elements have equal polarity while elements disposed at angles of 90 relative to one another have opposite polarity.
  • the value of the astigmatism added to the electron lens by the system is controlled by variation of all pole strengths in the same sense While the direction of the astigmatism is adjusted by varying the pole strengths of adjacent poles in opposite senses.
  • a suitable regulating device hence preferably has an adjusting knob for the value and an adjusting knob for the direction of the correcting field which are separately operated.
  • an electrostatic stigmator the voltages set up at adjacent electrodes are varied in 0pposite senses (so that the astigmatism caused by the stigmator rotates) until the residual astigmatism is a minimum.
  • the directions of the added astigmatism and of the astigmatism caused by the image defect are the same.
  • a known regulating device for this purpose comprises fixed resistors and variable resistors constituting bridge circuits to which an adjustable direct voltage is applied.
  • the values of the resistors are chosen so that by simultaneous variation of the adjustment of the variable resistors the voltages set up between the regulating members and the ends of the said resistors are varied in a predetermined manner.
  • Such a variation has also been produced by converting the rotary motion of an adjusting knob into translatory motion of the control members of two potentiometers. In this case, only two variable voltages are produced, while for a system of eight correcting elements at least four voltages are requ'ed. This means that for controlling the direction of the correcting astigmatism two coupled regulating members are required.
  • Another known regulating device comprises a rotary switch the number of moving parts of which is equal to the number of electrode pairs of the stigmator to which they are connected.
  • the switch contacts are connected to tappings on a resistor.
  • a controllable direct voltage is applied to the resistor.
  • the voltage steps should not be excessive and hence a large number of contacts are required in the switch. This gives rise to difl'iculty in mounting the re- 3 (Ilaims.
  • the invention relates to a device for controlling the voltages for the elements of an electrostatic correcting system enabling any desired voltage distribution and a continuously variable adjustment of the stigmator to be obtained.
  • the device includes a regulating resistor comprising a number of equal resistance elements connected to an adjustable direct voltage, each element comprising a layer of resistance material provided on an insulating support, the cross-sectional area of the resistance material gradually decreasing to a minimum between the terminals so that the resistance measured between one of the terminals and a point moving from one terminal to the other varies according to a nonlinear function from the beginning.
  • Sliding contacts are provided between adjacent terminals. They are mutually shifted through one half of the length of a resistance element and adapted to be moved simultaneously over contact areas of the resistance elements. Each sliding contact is separately connected to at least one electrode of the correcting system.
  • the resistance elements form' a single continuous member. In each section the potential gradient is opposite to that in the adjacent section.
  • the combined elements may be united to form a rectilinear structure.
  • the contact area it is in better agreement with the purpose of the voltage regulation, which is to change the direction of rotation of the added astigmatism, to use a rotary control member than to use a translatory member, and therefore it is of advantage for the contact area to be circular and for the resistance layer to extend along this area as a circularly curved strip of varying width.
  • This strip may be bounded at the inner or outer side by a circle concentric with the contact area or it may vary in width on both sides of the contact area.
  • the pattern of the resistance elements may without dilrlculty be chosen so that the voltages taken from the contact area and applied to the stigma or poles vary sinusoidally on displacement of the slide contacts. However, the voltage values obtained when the adjusting knob is positioned between zero and the positive and negative maximum values are too high. By removing a small amount of the resistance material the values of the voltages derived at the intermediate positions may be varied and given the correct value for each position of the adjusting knob.
  • FIGURE 1 shows a linear embodiment
  • FIGURE 2 shows a rotary controller
  • FIGURE 3 is a longitudinal sectional view of an electron microscope.
  • FIGURE 4 shows a rotary controller to be used in combination therewith.
  • the circuit arrangement for the production of the control voltage is provided with terminals 1 and 2 adapted to be connected to a direct-voltage source.
  • the terminals are shunted by a resistor 3 the center 4 of which is connected to earth.
  • the positive and negative terminals of the current supply source consequently are symmetrical with respect to earth.
  • the stigmator is shown schematically by eight electrodes 9 and 16. Opposite electrodes 9-13, lit-14, 11-15 and 12-16 are electrically connected to one another. The electrode pairs 9-13 and 11-15 form a four-terminal network and the electrode pairs 19-14 and 12-16 form another four-terminal network.
  • the regulating member for the electrode voltages com prises resistance elements 17, 18 and 19. Although said elements are shown separately they form a continuous surface of resistance material applied to an insulating support. In the figure lines dividing the elements indicate terminals 29, 21, 22 and 23 to which the voltage is applied. The voltage may be applied to metal strips extending throughout the height of the resistance layer. The voltage required is taken from the sliders 7 and 8 of the potentiometers 5 and 6 of which the slider 7 is electrically connected to the terminals 29 and 22 and the slider 8 is elecrically connected to the terminals 21 and 23 so that when the resistance layer is scanned from one end to the other alternately a positive and a negative potential exists. Four contacts 24, 25, 26 and 27 are adapted to be moved over a contact area 2.8.
  • Each contact is spaced from the nearest contact by one half of the length of the resistance element.
  • This arrangement supplies the voltages required for a correcting system comprising eight electrodes. Any other even number of electrodes involves a modification of the arrangement.
  • the resistance elements are bounded on one side by a straight edge 29 and on the opposite side by a curved edge 30 of suitably chosen curvature, the thicknes of the layer of resistance material being assumed to be constant.
  • the resistance material may substantially consist of carbon to which substances may be added to provide the required coherence of the carbon particles. Compositions suitable for manufacturing resistance layers are commonly known.
  • the voltages derived by the contacts and supplied to the electrodes of the correcting system produce the electric correcting field for the stigmator but the strength of this field does not remain constant on movement of the contacts.
  • the curved shape of the boundary of the resistance elements has to be slightly altered, for example to the form indicated by a broken line 31. This operation is simply obtainable by removal of a small amount of resistance material, the correct shape being most readily found empirically.
  • the entire resistance layer comprises a number of equal portions enabling the voltage of each pair of electrodes to be varied between positive and negative values.
  • three elements are require-d for this purpose.
  • the two resistance elements 32 and 33 are curved into the form of semi-circles and engage one another at the ends. Terminals 34 and 35 are provided at the junctions.
  • the arrangement for adjusting the voltage is the same as that shown in FIGURE 1.
  • the resistance layer is provided on an insulating plate 36 which also supports a vertical pin 37 provided with a knob 38.
  • the pin 37 is made of insulating material and has four contact springs 3?, 4t), 41 and 42. attached to it and which consequently are insulated from one another. The free ends of these springs slide over the resistance layer and are connected each to a current conductor 43, 44, 45 and 4-6 respectively connected to electrodes 9 to 16 respectively of the correcting system.
  • each conductor is connected to a pair of opposite electrodes.
  • the four-terminal network comprising the electrodes 9, 13 and 11, 15 has no voltage applied to it with the adjustment shown while the full voltage is applied to the electrodes 10, 14 and 11, 16 of the second tour-terminal network.
  • FIGURE 3 is a longitudinal sectional view of an electron microscope provided with a device in accordance with the invention.
  • the outer wall of this microscope is a steel tube 47 the upper end of which encloses an electrode system 48 serving for the production of the electron beam which extends along the axis of the tube 47 through the entire microscope.
  • the microscope has three magnetic lenses: a condenser 49, an objective 56 and a projection lens 51. The design and operation of these lenses are assumed to be known.
  • the tube is provided with a glass window coated with a layer 66 of fluorescent material.
  • a system of correcting electrodes 52 serving to eliminate the astigmatism of the objective as far as possible is interposed between the objective 5i ⁇ and the projection lens 51.
  • the arrangement as shown in FIG. 4 for regulating the electrode voltages is more elaborate than in the preceding examples.
  • the controller comprises four resistance elements 53, 54, 55 and 56 and the spindle corresponding to that of FIGURE 2 has eight sliding contacts. Each sliding contact is connected to an electrode of the correcting system, opposite electrodes being connected to alined contacts which in principle have equal potentials. In the embodiment shown, however, one may depart from this principle in order to provide a correcting system also enabling symmetry deviations to be eliminated. If the stigmator electrodes are not accurately centered about the optical axis the entire image is laterally displaced and on variation of the adjustment of the stigmator the image on the fluorescent screen is shifted.
  • FIG. 4 has four voltage supply terminals 57, 58, 59 and 60 which are displaced with respect to each other along the circumference. Between the two opposed terminals 57 and 59 the resistance element of a potentiometer 61 and between two other terminals 58 and 60 the resistance element of a potentiometer 62 is connected.
  • the potentials of opposite terminals may be mutually varied so that voltage diiierences result which produce a transverse field between opposite stigmator electrodes which solely deflects the electron beam.
  • Adjustment is eifected with the aid of potentiometer 61 and 62 by displacement of the sliders 63 and 64 which are connected to the sliders 7 and S of the potentiometers 5 and 6.
  • the value of the applied voltage is adjustable in the manner described hereinbefore with the aid of potentiometers 5 and 6.
  • the tapping 4 on the resistor 3 may also be adapted to be displaced for correction purposes.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Adjustable Resistors (AREA)
US204912A 1961-07-10 1962-06-25 Regulating device for the correction of image defects of an electron-optical system Expired - Lifetime US3197635A (en)

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Application Number Priority Date Filing Date Title
NL266898 1961-07-10

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US3197635A true US3197635A (en) 1965-07-27

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US (1) US3197635A (enrdf_load_html_response)
DE (1) DE1464282A1 (enrdf_load_html_response)
GB (1) GB961089A (enrdf_load_html_response)
NL (1) NL266898A (enrdf_load_html_response)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4962309A (en) * 1989-08-21 1990-10-09 Rockwell International Corporation Magnetic optics adaptive technique
US5041731A (en) * 1989-01-20 1991-08-20 Fujitsu Limited Deflection compensating device for converging lens
US5719402A (en) * 1994-01-28 1998-02-17 Fujitsu Limited Method of and system for charged particle beam exposure

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3901980C2 (de) * 1989-01-24 2001-06-28 Ceos Gmbh Multipolelement und Verfahren zur Herstellung eines Multipolelements

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1826673A (en) * 1925-10-03 1931-10-06 Mcilvaine Patent Corp Resistance apparatus
US2432029A (en) * 1945-10-05 1947-12-02 Howe & Fant Inc Correction of selsyn transmitter errors
US2547994A (en) * 1947-03-13 1951-04-10 Csf Electronic microscope
US2580675A (en) * 1947-06-26 1952-01-01 Csf Correction device for microscopes of the reflection mirror type
US2919381A (en) * 1956-07-25 1959-12-29 Farrand Optical Co Inc Electron lens

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1826673A (en) * 1925-10-03 1931-10-06 Mcilvaine Patent Corp Resistance apparatus
US2432029A (en) * 1945-10-05 1947-12-02 Howe & Fant Inc Correction of selsyn transmitter errors
US2547994A (en) * 1947-03-13 1951-04-10 Csf Electronic microscope
US2580675A (en) * 1947-06-26 1952-01-01 Csf Correction device for microscopes of the reflection mirror type
US2919381A (en) * 1956-07-25 1959-12-29 Farrand Optical Co Inc Electron lens

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5041731A (en) * 1989-01-20 1991-08-20 Fujitsu Limited Deflection compensating device for converging lens
US4962309A (en) * 1989-08-21 1990-10-09 Rockwell International Corporation Magnetic optics adaptive technique
US5719402A (en) * 1994-01-28 1998-02-17 Fujitsu Limited Method of and system for charged particle beam exposure
US5965895A (en) * 1994-01-28 1999-10-12 Fujitsu Limited Method of providing changed particle beam exposure in which representative aligning marks on an object are detected to calculate an actual position to perform exposure

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GB961089A (en) 1964-06-17
NL266898A (enrdf_load_html_response)
DE1464282A1 (de) 1968-12-12

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