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 or ion-optical arrangement
  • H01J37/09—Diaphragms; Shields associated with electron or ion-optical arrangements; Compensation of disturbing fields
• • 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
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/3002—Details
  • H01J37/3007—Electron or ion-optical systems

Definitions

• This invention is directed to an electron beam system where the system is capable of selectively producing either a small round electron beam spot on a target or a larger square electron beam spot on the target.
• the small spot is used for exposing fine pattern structures and the larger square electron spot is for exposing larger areas.
• a small beam size is capable of writing fine structures, but takes a long time to fill-in large areas.
• a previously known method provides a completely variable square or rectangular spot size. However, this requires an extremely complex electron-optical system as well as complex computer software.
• An aperture is positioned at the focal point of the lens when it is operating in the focus mode, and this aperture is flooded when the lens is operating in the flood mode.
• Downstream optics demagnify the image at the aperture plane and direct the image onto a target. It is thus an object of this invention to provide an electron beam system which is capable of operation with a small spot on the target or a larger area on the target. It is another object to provide an electron beam system capable of operating in a small spot mode or a larger area exposure mode with the change of operating parameters of only one lens in the electron optical system. It is a further object to provide an electron beam system which is capable of being easily programed for selectively producing a small round electron exposure beam for exposing fine patterned details, or a larger square electron beam on the target for exposing larger areas.
• FIG. 1 is a longitudinal sectional view of a preferred embodiment of the electron beam system of this invention.
• FIG. 2 is a schematic beam trace of electron beams in the system of this invention.
• FIG. 3 is a side elevational view of an adjustable aperture for use in the system of FIG. 1.
• FIG. 4 is a plan view of the aperture structure.
• FIG. 1 illustrates a practical embodiment of the system while FIG. 2 illustrates a schematic construction with a simplified ray trace of. the electron beam paths.
• housing 12 is vacuum tight to permit the electron source and beam to operate in a vacuum.
• Electron source 14 emits electrons.
• Grid 16 is provided a control beam intensity and anode 18 has a positive potential applied thereto to accelerate the beam.
• Beam 20 is the beam accelerated by the anode.
• First electronoptical lens 22 has an iron core 24 which has central passageway 26 and magnetic gap 28 along the- central passageway.
• Electromagnet core 30 is enerized to provide a magnetic field in gap 28. The magnetic field serves as a magnetic focussing lens for beam 20.
• Aperture 32 is located at the focal point of lens 22 when the lens is operated in a first, or small spot mode.
• first mode the image of electron source 14 as focussed as a small spot at the image plane at the level of aperture 32.
• aperture 32 is positioned at the point where the first lens 22 focusses the image of electron source 14 when operated in the first mode. This mode is shown in solid lines in FIGS. 1 and 2.
• second mode aperture 32 is flooded.
• Second electron optical lens 34 is the same as first lens 22. It has iron core 36, electromagnetic coil 38 and magnetic field gap 40 around central passage 42.
• second electron optical lens 34 The purpose of second electron optical lens 34 is to focus and demagnify the image at the image plane of aperture 32. This image is focussed at focal plane 44
• Third electron optical lens 46 is positioned in the column in housing 12 below second electron optical lens 34. Third lens 46 is constructed similarly to the lenses 22 and 34. It has electro magnetic coil 48 located with respect to iron core 50 which has magnetic field gap 52. Central passage 54 is open through lens 46 to allow passage of the beam 20. Lens 46 also demagnefies the beam.
• Target chamber 56 is at the bottom of column 12 and is for containing target 58 which has its top surface at the final focal plane 60 of beam 20. Target chamber 56 preferably contains beam scanning equipment, such as electrostatic deflection plates for deflecting the beam in accordance with a desired path to expose the desired pattern.
• the approximately 20 micron diameter electron source 14 is imaged at image plane 32 to a 4 micron diameter by lens 22 when the lens is operated in its fine focussing mode.
• the 4 micron diameter image seen at image plane 32 by second lens 34 is demagnified to focal plane 44 to a 0.2 micron diameter. That image is demagnified by lens 46 to form a 0.1 micron round electron beam on the target.
• the 20 micron source is defocussed to flood the 40 micron square aperture 32.
• the beam at target 58 becomes a 1 micron square beam.
• the electron current automatically increases by a factor of 50 to 100 thus allowing the 1 micron square beam to expose large pattern areas much more rapidly than the small beam.
• Changing the demagni fication of lens 34 will allow both the small round beam and the large square to be each porportionally changed in size as required.
• the principle use of the electron beam system of this invention will be for the exposing of masks used in semiconductor processing. These masks have electron sensitive material thereon, and with patterned exposure followed by development, serve as masks for the exposure of resist on semiconductor wafers.
• the present electron beam system accurate and finely detailed lithography is achieved.
• the system can be used for the direct exposure of a resist on a wafer for experimental semiconductor wafer production or for other one of a kind wafer production.
• the advantages of electron beam litho graphy over light optical techniques include better resolution, fast cycling, improved alignment capability, large pattern capability and control over defects through computer drive of the pattern.
• FIGS. 3 and 4 illustrate that aperture 32 is defined by two upper blades 62 and 64 and two lower blades 66 and 68. These blades are mounted together and each is beveled, wi th the bevels of blades 66 and 68 best illustrated in FIG. 3. The sharp edges of the blades, that is the beveled edges, face aperture 32 so that a minimum thickness of the blades is present at the aperature. The blades are preferably mounted so that they can be adjusted to the desired aperture size, and then clamped in place.
• first electron optical lens 22 Since the first electron optical lens 22 is to be rapidly changed from its first focus mode to its second flood mode rapidly under computer control, it may be desirable to employ an electrostatic lens rather than an electromagnetic lens at that location. Since lenses 34 and 46 are not changed in magnification during the processing, electromagnetic lenses are preferred at those locations, as illustrated although electrostatic lenses could be employed instead.

Landscapes

• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Electron Beam Exposure (AREA)
• Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=22125151

Family Applications (1)

Country Status (5)

Cited By (2)

Families Citing this family (8)

Citations (4)

Family Cites Families (4)

• 1979
  • 1979-09-13 US US06/075,354 patent/US4263514A/en not_active Expired - Lifetime
• 1980
  • 1980-09-11 WO PCT/US1980/001173 patent/WO1981000784A1/en not_active Ceased
  • 1980-09-11 DE DE8080901880T patent/DE3067625D1/de not_active Expired
  • 1980-09-11 JP JP50219380A patent/JPS56501228A/ja active Pending
• 1981
  • 1981-03-23 EP EP80901880A patent/EP0035556B1/en not_active Expired

Patent Citations (4)

Non-Patent Citations (1)

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