WO2001035440A9 - Method and apparatus for electron beam column assembly with precise alignment using displaced semi-transparent membranes - Google Patents
Method and apparatus for electron beam column assembly with precise alignment using displaced semi-transparent membranesInfo
- Publication number
- WO2001035440A9 WO2001035440A9 PCT/US2000/023500 US0023500W WO0135440A9 WO 2001035440 A9 WO2001035440 A9 WO 2001035440A9 US 0023500 W US0023500 W US 0023500W WO 0135440 A9 WO0135440 A9 WO 0135440A9
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- membrane
- target
- electron beam
- aperture
- base
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/18—Assembling together the component parts of electrode systems
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/15—Means for deflecting or directing discharge
- H01J2237/1501—Beam alignment means or procedures
Definitions
- This invention relates to electron guns (sources) for use, e.g., in electron beam lithography and specifically to the fabrication of such electron guns.
- Electron beam columns are well known for use, for instance, in electron beam lithography for imaging a pattern onto a substrate typically coated with a resist sensitive to electron beams. Subsequent development of the exposed resist defines a pattern in the resist which later can be used as a pattern for etching or other processes. Electron beam columns are also used in electron microscopy for imaging surfaces and thin samples. Conventional electron beam columns for electron microscopy and lithography are well known and typically include an electron gun, including an electron emitter, that produces an electron beam. The beam from the gun may be used to produce a scanning probe, or may be used to illuminate a sample or an aperture using a series of electron beam lenses, which are magnetic or electrostatic lenses.
- a variant is called a microcolumn which is a very short and small diameter electron beam column typically used in an array of such columns; See “Electron beam microcolumns for lithography and related applications” by T.H.P. Chang, et al.. Journal of Vacuum Science Technology Bulletin, 14(6), pp. 3774-3781, Nov/Dec 1996. See also U.S. Patent 5,122,663 to T.H.P. Chang, et al., issued June 16, 1992, also describing microcolumns. These documents are incorporated herein by reference. Both conventional electron beam columns and microcolumns include a source of electrons.
- this source is a conventional Schottky emission gun (emitter) or a field emission gun (both are generally referred to as electron guns) which typically includes an emitter (cathode) and the triode region surrounding the emitter downstream of which, with respect to the direction of the electron beam, is an electrostatic pre-accelerator lens that focuses and accelerates the electron beam to its final energy.
- this gun "optics” is followed by a series of "lenses” which refocuses and images the source aperture or sample onto the target. (These are electrostatic or electromagnetic elements, not light optics.)
- An important requirement for microcolumn operation is the accurate alignment of the emitter tip to the center of the aperture, e.g., an extractor aperture.
- Such apertures can have a diameter of 5 ⁇ m or less, thus making precision alignments very difficult.
- Another difficulty in emitter to aperture alignment arises from the microcolumn geometry which prohibits the simultaneous viewing of the emitter tip and aperture.
- a current method conventionally known in the art for aligning the emitter tip to the aperture center during electron gun assembly involves recording a digitized image of the aperture with a conventional digital camera and electronically placing cross hairs at an alignment target at some point on the image. Another point on the backside of the emitter assembly (typically the center point of the filament posts) is then aligned to the cross hairs on the digitized aperture image.
- an off-axis alignment assembly for aligning an electron beam emitter tip to an aperture is described and a method for aligning the two is also described for use during electron beam column assembly.
- One embodiment in an electron beam column of the alignment assembly is made of an electrically conductive material which is formed integrally with a microcolumn assembly.
- This alignment assembly is, e.g., a wafer of silicon, having several areas etched down to thin membranes ranging in thickness from about 2 ⁇ m to 10 ⁇ m.
- Conventional electron beam or optical lithography defines an aperture in the alignment assembly and targeting positions (holes) in each of the membranes during the same operation so that precise distances between each of the targeting positions and between each targeting position and aperture are maintained.
- the alignment assembly may be integrally formed with a microcolumn assembly within the electron source assembly or possibly with the Einzel lens but it is formed so that the aperture on the assembly is aligned with a targeted aperture within the microcolumn and the targeting membranes are off-axis of the aperture and outside the source assembly and Einzel lens columns.
- An electron beam emitter is then positioned over one of the membranes and viewed with a conventional (light) imaging camera from beneath the membrane and the microcolumn base through a viewing hole in the base.
- a method of alignment involves first directing the light beneath the membrane onto the membrane surface so that the targeting position can be located on the membrane surface. The second light above the membrane is then used to illuminate its opposite surface, thereby making it largely transparent (transmissive) when viewed from beneath.
- the tip of the emitter can be seen through the transmissive membrane and moved so it becomes aligned with the targeting position on the membrane.
- An alternative method of alignment involves simultaneously providing a light beneath the membrane and a second light above the membrane; this allows simultaneous super- imposed viewing of both the targeting position on the membrane and the emitter tip seen through the transmissive membrane.
- the emitter tip can then be aligned with the target and the tip position recorded. Once this is done, the electron beam emitter is moved to another targeting position on a second membrane and the same procedure is repeated. This is performed for three separate targeting positions. Once completed, the exact position of the emitting tip relative to the targeting positions and aperture is known and can then be aligned with great accuracy.
- Another embodiment has the membranes and targeting positions formed directly into the uppermost layer of the source assembly. This requires having viewing holes extending beneath each of the membranes through the source stack and the microcolumn base so emitting tip alignment can be done prior to assembling the microcolumn assembly with the attachment of the Einzel lens.
- a second method involves providing the viewing holes through the source stack, microcolumn base, and also the Einzel lens.
- Figure 1 is a perspective view of the present alignment assembly formed on top of a microcolumn assembly at the extractor aperture.
- Figure 2 A is a bottom view of Detail A taken from Figure 1.
- the bottom surface is illuminated with a light and appears opaque; also shown is the targeting position on the membrane surface.
- Figure 2B is the same view as in Figure 2A, but with the opposite surface of the membrane illuminated. The membrane appears transparent and reveals the electron beam emitter and emitting tip on the opposite side.
- Figure 2C is the same view as in Figures 2A and 2B, but with both surfaces of the membrane illuminated.
- the membrane appears semi-transparent and reveals both the emitting tip and the targeting position.
- Figure 3 is a perspective view of the alignment assembly formed between the source stack and microcolumn base with alignment to the limiting aperture.
- Figure 4 is a perspective view of the chip scale alignment targets formed integrally with the source stack and the Einzel assembly.
- Figure 5A is a cross-sectional view A-A taken from Figure 4. The cross- section shows the membranes formed on the top layer of the source stack and the viewing holes within the source stack and microcolumn base.
- Figure 5B is the same view as in Figure 5A, but with additional viewing holes formed within the Einzel lens assembly.
- FIG. 1 shows a perspective view of an embodiment of alignment assembly 12 integrated with otherwise conventional microcolumn assembly 100.
- alignment assembly 12 is used with a microcolumn, but this is illustrative and is not meant to preclude other uses. Described below is an apparatus and a process used for an intermediate alignment procedure in aligning electron beam emitter 2 to a microcolumn assembly.
- Alignment assembly 12 is of an electrically conductive material, e.g., heavily doped silicon, with a thickness dependent on the microcolumn application and geometry. Additionally, materials such as silicon nitride, Si 3 N , may also be used to fabricate alignment assembly 12 for applications that do not require conductive membranes. Having alignment assembly 12 made of such materials enables it to be formed as an integral part of microcolumn assembly 100.
- Alignment assembly 12 has several regions which have been etched into the material by conventional electron beam or optical lithographic methods at predetermined locations. This etching reduces portions of alignment assembly 12 to thin membrane layers ranging in thickness from about 2 ⁇ m to 10 ⁇ m as seen in first, second, third, and fourth membranes Ml, M2, M3, M4, respectively. Although membrane thickness may vary over the range, in one embodiment the membranes are 3 ⁇ m thick, and alignment assembly 12 has three membranes located on its surface for purposes of alignment, as explained in greater detail below.
- a targeting location e.g., a circle
- first target TP1 on first membrane Ml is etched through each membrane by electron beam or optical lithographic methods to define first target TP1 on first membrane Ml, second target TP2 on second membrane M2, third target TP3 on third membrane M3.
- an aperture e.g., extractor aperture 14, having a diameter of about 5 ⁇ m is also etched through alignment assembly 12.
- Targets TP1 to TP4 and extractor aperture 14 are fabricated by conventional lithography methods during a single operation to maintain accurate spacing between each of targets TP1 to TP4 and extractor aperture 14.
- a single membrane Ml may be etched and a single target TP1 formed rather than a plurality of membranes and targets. Such a process is able to locate the center of extractor aperture 14 relative to each of targets TP1 to TP4 to within an accuracy of about 2.5 nm.
- targets TP1 to TP4 are locations having a thicker cross section than the surrounding portion of the respective membrane.
- Alignment assembly 12 may be placed in various locations within microcolumn assembly 100, but in one embodiment it is located on top of and integrally with source assembly (stack) 6, as seen in Figure 1 , to form extractor aperture alignment assembly 102. Alignment assembly 12 thereby becomes a permanent part of the microcolumn structure.
- Microcolumn assembly 100 includes, as is well known in the art, source stack.6, Einzel lens 8, microcolumn base 4, and electron beam emitter 2, which is a Schottky emitter in one embodiment.
- Correctly aligning emitting tip 2T, the tip at which electrons exit the emitter, of electron beam emitter 2 to aperture 14 involves visually aligning them. This is accomplished by providing viewing holes 10 drilled (or formed by any other conventional method) into microcolumn base 4 at locations directly beneath each membrane Ml to M4.
- the actual alignment involves moving either electron beam emitter 2 or microcolumn assembly 100 with, e.g., conventional precision stages, to first align the body of electron beam emitter 2 with first membrane Ml .
- a conventional video camera (camera is not shown) mounted below microcolumn base 4 is then used to view the bottom side of first membrane Ml through viewing hole 10.
- first light source 16 which can be any white light source such as, e.g., a light pipe.
- First light source 16 illuminates the bottom surface of first membrane Ml giving the surface an opaque appearance, as seen in Figure 2 A, which is a bottom view of Detail A taken from Figure 1. The opaque appearance allows first target TPl to become visible to the camera.
- second light source 18, which can also be any white light source such as, e.g., a ring lamp, is used to illuminate the top surface of first membrane Ml.
- First light source 16 is then turned off.
- First membrane Ml appears transparent when viewed from below through viewing hole 10 in Figure 2B, which is the same view as Figure 2 A but with first membrane Ml illuminated from its top surface.
- the transparent first membrane Ml also reveals emitting tip 2T and the bottom side of electron beam emitter 2.
- An alternative aligning method involves directing light from first light source 16 onto the bottom surface of first membrane Ml and directing light from second light source 18 simultaneously onto the top surface of first membrane M 1.
- Figure 2C which is the same view as Figures 2A and 2B, using both first and second light sources 16,18, respectively, makes first membrane Ml appear semi-transparent and allows the simultaneous viewing of both first target TPl and emitting tip 2T on the bottom side of electron beam emitter 2.
- electron beam emitter 2 or extractor aperture alignment assembly 102 is positioned to superimpose first target TPl with emitting tip 2T. Once the two are aligned, the position is conventionally recorded and then electron beam emitter 2 is positioned over second membrane M2 and the above described procedure of illuminating opposite membrane surfaces and then superimposing targets with emitting tip 2T is repeated.
- An alternative embodiment uses only a single target TPl disposed on a single membrane Ml to align emitting tip 2T to extractor aperture 14 by the above procedure, with perhaps some loss of accuracy.
- Alignment assembly 12 may have N number of membrane surfaces, and this procedure is repeated for at least three different membranes Ml to M4 and targets TPl to TP4.
- the precise position of emitting tip 2T and electron beam emitter 2 is known relative to the position of extractor aperture 14.
- Emitting tip 2T may then be positioned directly over extractor aperture 14 without the need for digitizing any images or directly viewing emitting tip 2T relative to extractor aperture 14.
- electron beam emitter 2 is properly aligned, it is fastened in place by conventional methods used in fabricating microcolumns. This method of off-axis aligning greatly increases tip 2T to aperture 14 alignment by allowing direct visual alignment as well as limiting electron beam emitter 2 motion to the X- Y plane, which is defined as the plane coplanar with microcolumn base 4.
- Electron beam emitters 2 are often tested under varying thermal conditions prior to installation. Also, operating such emitters 2 often causes large temperature swings and this may cause emitting tip 2T to become displaced slightly relative to the position of emitter 2 because of the thermal expansion of materials within emitter 2. Once the displacement of emitting tip 2T is obtained, electron beam emitter 2 can be offset by this value after emitting tip 2T has been aligned with extractor aperture 14. Thus, once microcolumn assembly 100 begins operations, emitting tip 2T will displace accordingly and move into alignment with extractor aperture 14.
- limiting aperture alignment assembly 104 is shown in Figure 3.
- Figure 3 is similar in most respects to assembly 102 of Figure 1 (in a similar view) with similar elements identically labeled with the exception of alignment assembly 12 which is located between source stack 6 and microcolumn base 4.
- viewing holes 10 are hidden by alignment assembly 12 but are present to give a view of the bottom surfaces of membranes Ml to M4.
- This embodiment is more structurally stable than assembly 102 because alignment assembly 12 is adjacent to microcolumn base 4.
- the alignment procedure is the same as for assembly 102, except that emitting tip 2T can now be more easily aligned with the limiting aperture (not shown) within microcolumn assembly 100.
- alignment assembly 12 is formed integral to Einzel lens 8 (this particular embodiment is not shown).
- This embodiment is similar in most respects to assembly 104, except that alignment assembly 12 is formed atop Einzel lens 8 and placed in between the top of Einzel lens 8 and the bottom surface of microcolumn base 4. The alignment procedure would remain similar to that of assemblies 102 and 104.
- Figure 4 shows yet another embodiment with chip scale alignment assembly 106. In this embodiment, rather than utilizing alignment assembly 12, the membranes and their corresponding targets are etched directly into the top layer of source stack 6.
- the membranes are seen in Figure 4 as first, second, third, and fourth chip membranes CM1, CM2, CM3, CM4, respectively, and the targets located on .each corresponding chip membrane are seen as first, second, third, and fourth chip targets CT1, CT2, CT3, CT4, respectively.
- chip targets CT1 to CT4 two methods can be utilized.
- the first method involves forming the individual layers of source stack 6 with vias extending through its length beneath each of chip membranes CM1 to CM4.
- Cross-sectional view A-A in Figure 5A, taken from Figure 4, shows source stack vias 20 beneath first and fourth chip membranes CM1, CM4, respectively.
- Viewing holes 10 have also been formed beneath each of their respective chip membranes CM1 to CM4. This allows the alignment of electron beam emitter 2 to chip targets CT1 to CT4 in much the same manner as described for extractor aperture assembly 102.
- Einzel lens 8 can then be attached to complete microcolumn assembly 100.
- the second method is similar to the first, but it involves forming additional vias within Einzel lens 8.
- Cross-sectional view A-A in Figure 5B is similar to Figure 5A but includes Einzel lens vias 22.
- Vias 22 are formed collinear to and beneath source stack vias 20 and can be formed during the fabrication of Einzel lens 8.
- Source stack and Einzel lens vias 20, 22, respectively, allow the alignment of emitting tip 2T to the chip aperture after the fabrication of microcolumn assembly 100.
- Chip scale alignment assembly 106 may conserve the most surface area of microcolumn assembly 100 foot print.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020017008706A KR20010092776A (en) | 1999-11-10 | 2000-08-25 | Method and apparatus for electron beam column assembly with precise alignment using displaced semi-transparent membranes |
EP00959465A EP1153411A1 (en) | 1999-11-10 | 2000-08-25 | Method and apparatus for electron beam column assembly with precise alignment using displaced semi-transparent membranes |
JP2001537087A JP2003514348A (en) | 1999-11-10 | 2000-08-25 | Method and apparatus for an electron beam column assembly using precisely aligned and displaced translucent films |
AU70786/00A AU7078600A (en) | 1999-11-10 | 2000-08-25 | Method and apparatus for electron beam column assembly with precise alignment using displaced semi-transparent membranes |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US43780899A | 1999-11-10 | 1999-11-10 | |
US09/437,808 | 1999-11-10 |
Publications (3)
Publication Number | Publication Date |
---|---|
WO2001035440A1 WO2001035440A1 (en) | 2001-05-17 |
WO2001035440A9 true WO2001035440A9 (en) | 2002-09-12 |
WO2001035440A8 WO2001035440A8 (en) | 2003-11-13 |
Family
ID=23737976
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2000/023500 WO2001035440A1 (en) | 1999-11-10 | 2000-08-25 | Method and apparatus for electron beam column assembly with precise alignment using displaced semi-transparent membranes |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1153411A1 (en) |
JP (1) | JP2003514348A (en) |
KR (1) | KR20010092776A (en) |
AU (1) | AU7078600A (en) |
WO (1) | WO2001035440A1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US6458564B1 (en) | 1999-08-31 | 2002-10-01 | Ortho-Mcneil Pharmaceutical, Inc. | DNA encoding the human serine protease T |
US10388489B2 (en) | 2017-02-07 | 2019-08-20 | Kla-Tencor Corporation | Electron source architecture for a scanning electron microscopy system |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6281508B1 (en) * | 1999-02-08 | 2001-08-28 | Etec Systems, Inc. | Precision alignment and assembly of microlenses and microcolumns |
-
2000
- 2000-08-25 AU AU70786/00A patent/AU7078600A/en not_active Abandoned
- 2000-08-25 WO PCT/US2000/023500 patent/WO2001035440A1/en not_active Application Discontinuation
- 2000-08-25 KR KR1020017008706A patent/KR20010092776A/en not_active Application Discontinuation
- 2000-08-25 EP EP00959465A patent/EP1153411A1/en not_active Withdrawn
- 2000-08-25 JP JP2001537087A patent/JP2003514348A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
JP2003514348A (en) | 2003-04-15 |
WO2001035440A8 (en) | 2003-11-13 |
WO2001035440A1 (en) | 2001-05-17 |
KR20010092776A (en) | 2001-10-26 |
AU7078600A (en) | 2001-06-06 |
EP1153411A1 (en) | 2001-11-14 |
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