CN1142280A - Chromatically compensated particle-beam column - Google Patents
Chromatically compensated particle-beam column Download PDFInfo
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- CN1142280A CN1142280A CN 94194857 CN94194857A CN1142280A CN 1142280 A CN1142280 A CN 1142280A CN 94194857 CN94194857 CN 94194857 CN 94194857 A CN94194857 A CN 94194857A CN 1142280 A CN1142280 A CN 1142280A
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- lens
- particle
- staggered
- aberration
- ion
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Abstract
A particle-beam column comprises needle type ion source(1)such as liquid metal ion source, one or more cylindrial lens(2), and many interlaced quadrupole lens (14,16). In addition, ion-beam column comprises liquid alloy ion source(1), interlaced quadrupole lens (14,16)and Wien velocity colander(22). The column generates more fine and focused beam than the column on the base of electrostatic lens, and increases lens pore and allows more beam flux.
Description
There is a paid-up special permission in U.S. government to the right under this invention and the certain occasion, requires the patent owner to permit other people under the reasonable terms of the clause regulation of the grant number ISI8521280 that is authorized by National Science Foundation.
The present invention relates to the ion optics field, such as the device that is used for being used for forming the ion beam of fine focus, be generally used for the field of micro-manufacturing and microscopic analysis, such as micromachining, ion beam lithography art and the assisting ion microtechnic of the injection of the ion in the semiconductor, material.
In the prior art, the device that is used to produce pencil generally comprises a pin type particle source, this particle source can emitting electrons or is made the ambient gas ionization, comprises the surface ionization under the low temperature, the pin that perhaps the most common liquid metal that is contained desired ion or alloy are got wet.In some cases, form the image of very little emitter region, source with single lens.Utilize collector lens or a plurality of collector lens can obtain bigger density near the source.When adopting several lens, can produce the intermediate imagery in source; And if this intermediate imagery is when being positioned at the center of the ion optics assembly such as acceleration gap or Wien filter, the aberration of being given birth to by assembly has reduced widely.Yet all adopt the focusing power of the system of electrostatic lens to be subjected to the aberration of these lens and by the restriction of the inevitable energy dissipation of the ion of ion source emission.The whole width of final focus is provided by following formula:
d＝CadE/E
Wherein dE is the energy dissipation degree around the ion central energy E, and a is the whole convergent angle in final focusing place, and C is a chromatic aberration coefficient.A is depended on first rank of aberration, and these are different with other aberrations.Such as, the spherical aberration of circle lens is with a
3Variation and change.Therefore, the first rank aberration is important at place, lenslet hole, and spherical aberration has become very little there, and at a place of some higher value, the 3rd rank spherical aberration will account for major part.
The past focusing power that can not win of electrostatic system is restricted ion optics, and this is a long-standing difficult problem in prior art.In the application such as micromachining, jet density is most important.Jet from a liquid metal ion source is provided by following formula:
I＝Ba
sb
sr
2
Wherein typical numeral is: brightness B=10
6A/sr-cm
2, angle of departure a
s, b
s=400 milliradians, effectively the source radius is less than the r=100 dust.Because effectively the source is so little, the size of bundle is provided by d rather than is provided by how much images in source.Therefore jet density J is provided by following formula:
J＝I/d
2＝B(ab/ab)(rE/CdE)
2
Because therefore value E/C substantially constant in electrostatic lens it is said " to be about 1A/cm
2Maximum jet density do not have big increase in the near future.All produce 10A/cm even comprise the complicated electrostatic lens of four electrodes
2Maximum.For overcoming this long-standing difficulty, an object of the present invention is to utilize the achromatic lens of C=0 to increase jet density.
When hope hides bigger sample area, cover ion such as the nothing of the integrated circuit that is used for making special purpose and inject, be that jet rather than jet are conspired and become important.Under the jet of 1 nA, in a simple lens system with 10
13Ion/cm
2Dosage write required time of cake formula sample of one 4 inches and be about one hour.In this device, low jet has become a difficulty.Perhaps can obtain bigger jet in having the system of a plurality of lens, this makes and allows a and b with higher value to operate.Yet the angle of this increase has caused aberration, can make focused beam greater than desirable characteristic size.For the angle at the right angle that equates with other aberrations less than aberration, color difference eliminating can produce bigger operating angle and bigger jet to any given aggregation bunch chi.Therefore, an object of the present invention is, produce higher jet and allow and carry out micro-manufacturing with higher writing speed by adopting the complete achromatic system of C=0.
The ion beam column that comprises liquid metal ion source and a plurality of electrostatic lens can not produce the pencil of the same little point of the ionogenic image of focal imaging.On the contrary, the energy of ions diffusion of launching from the source makes focusing length that variation take place, and this makes image fog and amplifies.This class aberration is a characteristic of all electrostatic lens and independent magnetic lens.The grain a fluid stream of eliminating this problem is combined by a pin type ion source, a plurality of electrostatic lens and a plurality of staggered quadrupole lens (they are 8 utmost point lens with utmost point of alternately electric and magnetic), to form the staggered electricity and the quadrupole lens of magnetic.By regulating the electromagnetism ratio, staggered lens can become achromatic, thereby the aberration of post reduces greatly, perhaps can have negative aberration, thereby eliminate the aberration of post fully.
The separating substances ion beam column that one usefulness of using in field ion implantation removes the unwanted ion that is produced by the liquid alloy ion source comprises such post: a Wien speed filter is positioned at after the ion source.Such post can be short and non-bending, but also produces the ion with monatomic number in final focusing.
Color difference eliminating allows to adopt bigger hole simultaneously in lens, can produce bigger line like this under given focused beam focal spot size.Therefore hole dimension is limited by the aberration of higher-order, rather than is limited by the aberration on first rank.
Fig. 1 represents the sectional drawing of an achromatism ion beam column.Fig. 2 represents the sectional drawing of a staggered quadrupole lens.Fig. 3 to Fig. 7 is the schematic diagram of achromatism post, has wherein shown the typical ray in two major parts of optical system.Fig. 3 represents to contain an optically inactive condenser lens a plurality of significantly posts of achromatic staggered lens.In Fig. 4 to Fig. 7, the negative aberration of employing in staggered lens corrects the aberration of other lenses in the post.In Fig. 4, condenser lens becomes parallel beam with ion convergent.In Fig. 5, condenser lens becomes to intersect to form with ion convergent.Fig. 6 has shown the achromatism ion beam column 15 of a separate substance, and Fig. 7 has shown the achromatic system of a separate substance, is used for forming under the feasible energy in being higher than the post of lens the bundle of fine focus.
The liquid metal ion source 1 of ion beam column places under the negative voltage of many kilovolts with respect to separate mesh electrode 8 on every side usually, and separate mesh electrode 8 typically is a plane surface, is drilled with a hole on it, to allow ion beam therefrom pass through.As knowing in ion optics and electron optics, this has constituted " the aperture lens " with lensing of dispersing.There is a pump that is connected to outlet 7 to be used near ion source, producing 10
-8The vacuum of torr.
One focus lens system 2 is outside separate mesh electrode, if suitably regulate, it can become parallel beam with ion convergent.Can adopt a single condenser lens, but since only in very narrow voltage range the separation of ion just carry out finely, and the focussing force in single space also needs the voltage fixed, therefore the energy of output is fixed basically.Therefore, the double lens focusing system can be as the means that transformable ion energy is provided.Electrode 6,7,8 has constituted such focus lens system, and wherein the space between three electrodes 5,6 has constituted the electrostatic lens of two circles.Ion source and electrode are remained under the required electromotive force by high voltage source according to the mode of knowing in the prior art.
The ion that leaves condenser lens 2 enters a staggered quadrupole lens system 4 through a drift space 3.Multipole deflector 11,13 is positioned at drift space, they can be with the ion deflecting in the axial any orientation of jet in a plane, in drift space, also have an assembly that constitutes aperture 12 of forming by four independently hands-off grid sheets, for clarity sake, only show one among the figure.
As shown in Figure 2, staggered quadrupole lens includes eight utmost points, and their center separates in the azimuth equal intervals in the direction around bundle.These utmost points are magnetic pole 17 and electrodes 18 alternately, thereby have constituted the electric quadrupole lens and the quadrupole lens of magnetic.45 degree of the utmost point make the quadrupole force field of two lens have superimposed principal plane at interval, and make lens have superimposed primary flat in the center on single plane.
In preferred embodiment, make with ferrimagnet and on it utmost point 17 round coil 19 be bonded to ceramic locating rack 20 rigidly, locating rack 20 itself is used for supporting diamagnetic electrode 18.Therefore this structure has formed four utmost points of laying of two mutually noninterferes, and they can both have realizes being close to the required wide pole tip radius of perfect quadrupole field.Cage-shaped structure has narrower pole tip, and must introduce unwanted multipole fields composition when they are encouraged by four pole tensions.
Staggered lens can be used to form the single quadrupole force field with adjustable electric power and ratio of magnetic force.According to the means of knowing in the prior art,, and, determined force rate R by magnetic field intensity and the electric field strength relational expression of measured value therewith by measurement electrode voltage and coil current.
Thereby when electric adjustment to having half magnetic force amplitude and rightabout when making R=-0.5, be achromatic the first time that staggered lens become E.This means that it is a point with a some object image-forming, this some the width form in a principal plane be:
d＝C
1adE/e＋C
2a(dE/E)
2
C wherein
1=0.
If electric power further increases, but be not increased to amplitude greater than magnetic force, staggered lens have become and have had negative value C
1Chromatically compensated lens (V.M.Ke1man and S.Ya.Yavor, Zuhmal Tekhnicheskoi Fiziki33 (1963) 368).For other force rate, it plays has on the occasion of C
1The effect of normal lens.The simplest lens arrangement that can both focus in two principal planes is the doublet system.The staggered lens 14 of upstream and the staggered lens in downstream 16 constitute this doublet.Locating rack 15 is used for regulating the separation of lens.The system that is made up of two lens always has the single axis that is made of two lens centres, and only need regulate the angle of doublet with respect to input bundle as a whole, to play correct effect.Doublet has different multiplication factors at two principal plane, therefore is used for producing the focused beam with two different in width, and the both is very little.
As shown in Figure 3,, will not have focusing effect, therefore not produce aberration if all electrodes of condenser lens are set to same voltage.Function element is made up of ion source 1 and separate mesh electrode 8, and doublet system 4 is made up of staggered quadrupole lens.When staggered lens settings during in achromatic working point, the aberration of introducing by the final condenser lens of optical column not.When therefore working under identical beam width, focus is less than the similar system of the size of being made up of ion source, separate mesh electrode and electrostatic lens, and this width is set by adjustable hole 12.This width can increase, and when focal spot size was identical, the post that contains staggered lens had produced than the more jet of the post that contains electrostatic lens like this.
As shown in Figure 4, when the electrode of condenser lens was switched to appropriate voltage, more ions from the source can be imported into staggered lens 4.Most of jets from LMIS betide in the half-angle of about 14 degree.When from the source when the distance in the first lens space is 9 millimeters, will form the parallel beams of about 5 millimeters full width, as long as first lens have enough big diameter.
The angle a that might increase
sAnd b
sIn condenser lens, increase aberration.In order to eliminate positive aberration, the doublet of regulating staggered lens to be producing the negative aberration of accurate compensation, as being determined by the insensitivity of focal spot size to the ion energy E at aperture 12 places of the predetermined angle turned down.This adjusting has compensated the first positive rank aberration, is included in accelerating electrode and the interior formed aperture lens in hole of accelerating field in the space between source and the separator.So aperture can reach certain point, the higher order aberratons remaining at this some place makes focused beam reach specific focus diameter.Increase with respect to system thereby enter the jet that focuses on focus, this system does not comprise the staggered quadrupole lens system of color difference eliminating of being used for.
Not just can see at once having the aberration that the staggered lens of independent principal plane on two can be adjusted to the compensation circle lens.And single staggered lens can not because it has introduced the aberration of opposite in sign in two principal planes.Yet two staggered lens import two variablees, provide the size of system, can answer the simultaneous linear equations that is used for the aberration in two principal planes.For the parallel beam geometry among Fig. 4, the coefficient C of two staggered lens
x, C
yMust satisfy
C
x/f
x 2＝C
y/f
y 2＝-C/h
2
F wherein
x, f
yBe the focal length of doublet 4, h, c are the focal length and the chromatic aberration coefficients of circle lens 2.In the approximate equation of thin lens, the coefficient C in the principal plane of the convergence of the single upstream and downstream lens of doublet
Yu, C
XdProvide by following formula:
C
yu/f
u＝-(1＋2s/v)vC/2h
2，
C
xd/f
d＝-vC/2h
2，
Wherein v is the image distance of downstream lens, and the coefficient in the face of dispersing is provided by following formula:
C
xu＝-C
yu，C
yd＝-C
xd
And s is the spacing of lens.When bundle is not parallel, adopt different expression formulas.The form of thin lens coefficient own is:
C
yu/f
u＝(2R
u＋1)/(2R
u＋2)
C
xd/f
d＝(2R
d＋1)/(2R
d＋2)
Like this, electromagnetic force compares R
u, R
dWhen given staggered lens sizes s, v and condenser lens parameters C, h, can calculate.In best mode of operation, adopt in the prior art that class energy to supply with, the wherein electricity of staggered lens and magnetic variations that partly be directly proportional, thus when fixing R, make the f variation.R
uAnd R
dBe set in the value place that C, h calculated for the lens that will compensate.Then according to the f of the step of knowing in the prior art by two lens of change quadrupole-doublet lens
u, f
dAnd obtain to focus on.
The measurement of submicron bundle size can adopt a deflector in deflector 11,13 or lens 4 downstreams to realize.Width can be from deciding the required deflection in the inswept knife-edge of focused beam edge.When grid stroke during less than beam width, a kind of to have avoided because of ion beam sputtering causes the method for edge damage be to measure the required electric charge of micromachining outside the inswept zone of grating of thin sample.The third method that does not need the submicron test sample in the prior art is the d that measures as a function.When making that aperture 12 is less to produce single ray, deflector 11 and 13 identical and relative layout make ray enter away from the aperture of the staggered lens of its axis and therefore have a of higher value.When staggered lens during, produced the aberration d that big tool is measured easily by inappropriate adjusting.Then the magnetoelectricity ratio that calculates in staggered lens can be adjusted, with minimum aberration rather than the minimum focal spot size that produces ray.
The multiplication factor that the system that is made up of a plurality of staggered lens can be designed in two principal planes equates.The simplest this system is triplet (J.Vac.Sci.Tech.B8 (1990) 1706 for L.R.Harriott, W.L.Brown and D.L.Barr).The shortcoming of triplet is complicated operation and needs suitable high accuracy mechanical manufacturing, and this is necessary, with being positioned on the straight line of the center that guarantees three lens.
Do not need to come operation post with parallel beam.Condenser lens has generally speaking formed ionogenic intermediate imagery, and it can be positioned at any position along the axis of post, comprises the downstream on ionogenic upstream and final picture plane.This has constituted so-called variable focal length lens major gene, and wherein as minimum dimension (from taking no account of the multiplication factor decision of aberration) changes when the position change of intermediate imagery.As shown in Figure 5, intermediate imagery can be between condenser lens and next lens, and in this case, owing to cross the axis of system from the ray of periphery, bundle intersects.The ion source of liquid alloy type once produces several ions, and needs species analysis, so that produce the focused beam of single kind ion.Place Wien speed filter 22 between condenser lens and the next downstream lens to make the axis of unwanted ion deflection bundle as shown in Figure 6, the ion that only allows to have given electric charge and the ratio of quality moves on and does not depart from.Although all this deflection can take place in any position to middle image, produce bundle that disperse, parallel or that assemble from condenser lens, intersecting 21 when occurring in Wien filter 22 central, work the best of post, thus eliminated the aberration that produces by filter.
Enough deflection and can not disappearing from the image of its formation fully through the ion of staggered lens aperture.Although this system can not separate leaning on of certain point element very near isotope, such as gallium (quality is 69,71), they can be used to separate the very wide various ions in interval that produced by the alloy-based ion source.Such as alloy Ni
4B
6Produce Ni
+ 2(electric charge and mass ratio are 30, produce 32%) and commercially important B
+ 1(electric charge and mass ratio are 10 or 11, are produced as 33%).This system comprises an electrostatic focusing lens and a staggered quadrupole-doublet lens, therefore can be used to form final image 23 from single atomicity, to realize such as purposes such as micro-manufacturing and ion injections.
Species analysis generally must carry out under low E value, because big mass ion need be than the bigger magnetic field, magnetic field that is produced by air cooled electromagnet with high-octane the combination.If carry out the high energy capacity material analysis, need two extremely crooked magnets, it will be restrainted with larger radius of curvature and carry out bending (United States Patent (USP) 4,555,666 of Martin).Yet the ion in semiconductor injects needs 300KV or higher energy, to inject one micron dark zone of less than.As shown in Figure 7, high voltage source 24, control electronic instrument 25 and acceleration gap 26 play the effect that increases beam energy, and object lens 27 become high-octane final image 28 with ion focusing.
When second intermediate imagery 23 places the acceleration gap place as shown in Figure 7, the aberration minimum that the space is produced.Object lens 27 can be the lens of any kind of, electricity, magnetic or staggered quadrapole.The electromagnetism ratio of the lens combination 4 of staggered quadrapole 14,16 is conditioned, to produce minimum focal spot size, thereby to utilize its negative aberration to compensate the positive aberration of every other ion optics assembly at minimum angles a, b place in a plurality of lens.When making aberration hour like this, can open the aperture of setting up angle, up to higher order aberratons focal spot size is increased.Comprise ion source 1, condenser lens 2, staggered quadrupole system 4, acceleration gap 26 and object lens 27 major gene this in the final focus of intended size, produces the ion flow of increase.
The most useful structure comprises low-energy staggered quadrupole lens system 4, and is opposite because electric power in this lens and magnetic force are directions, thereby need reach same focusing power in the field higher than simple lens.If staggered lens carry out work with the particle of the low energy, perhaps it has an aperture, then can alleviate this difficulty.Close lens if object lens 27 are four utmost points two of a magnetic, and second lens 4 is the staggered lens that produce negative aberration, then can obtain useful system.In this system, can use object lens 27 to offset the multiplication factor that does not wait that causes by second lens 4, thereby the multiplication factor of system is equated in two principal plane.If second lens 4 is big electrostatic lens, and object lens 27 are to have the interleaving systems of aperture and short focal length to produce negative aberration, then can obtain another useful system.
The substantive characteristics of these particle speed posts is to have a plurality of staggered quadrupole lenss, and they have negative aberration together, and can compensate the positive aberration of miscellaneous part in the post.
Claims (7)
1, a kind of particle-optical column, comprise a pin type particle source, one separate mesh electrode, one collector lens, one is used for forming the staggered quadrupole lens system of the particle beams of fine focus, and wherein staggered lens carry out work at the critical ratio place in electric field and magnetic field, like this, the negative aberration of staggered lens has been offset the positive aberration of every other particle optics parts, and focus diameter basically with particle energy in little variation irrelevant.
2, particle-optical column as claimed in claim 1 is characterized in that, also comprises the Wien speed filter between ion source and staggered quadrupole lens, and it is used for producing single particle beams of planting the fine focus of material.
3, the particle-optical column of the separate substance described in claim 2 is characterized in that, also comprises a bundle that intersects in the Wien filter, thereby has reduced aberration with respect to the bundle of wherein broad through the sort of post of Wien filter.
4, a kind of particle-optical column, comprise a pin type particle source, a separate mesh electrode, a plurality of staggered quadrupole lenss that are used for forming the fine focus particle beams, wherein staggered lens carry out work at the critical ratio place in electric field and magnetic field, and like this, they do not increase aberration to the positive aberration that is produced by pin type particle source and separate mesh electrode, and compare with the post that only adopts electrostatic lens to form pencil, reduced the degree of dependence of focus diameter to energy.
5, particle-optical column as claimed in claim 4 is characterized in that, also comprises the Wien speed filter between ion source and staggered quadrupole lens, and its produces single particle beams of planting the fine focus of material.
6, the particle-optical column of separate substance as claimed in claim 5 is characterized in that, also comprises a bundle that intersects in the Wien filter, thereby has reduced the aberration of wide beam wherein through the post of Wien filter.
7, a kind of particle-optical column, be used for forming the particle beams of fine focus, comprise a pin type source and a plurality of lens, also comprise a staggered quadrupole lens system, it carries out work at the critical ratio place in electric field and magnetic field, like this, the negative aberration of staggered lens has been offset the positive aberration of every other particle-optical component exactly, and focus diameter is irrelevant with the little variation in particle energy basically.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN94194857A CN1084041C (en) | 1994-11-18 | 1994-11-18 | Chromatically compensated particle-beam column |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN94194857A CN1084041C (en) | 1994-11-18 | 1994-11-18 | Chromatically compensated particle-beam column |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1142280A true CN1142280A (en) | 1997-02-05 |
| CN1084041C CN1084041C (en) | 2002-05-01 |
Family
ID=5039584
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN94194857A Expired - Fee Related CN1084041C (en) | 1994-11-18 | 1994-11-18 | Chromatically compensated particle-beam column |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1084041C (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4555666A (en) * | 1979-03-29 | 1985-11-26 | Martin Frederick W | Energy-stable accelerator with needle-like source and focused particle beam |
| US4590379A (en) * | 1980-09-16 | 1986-05-20 | Martin Frederick W | Achromatic deflector and quadrupole lens |
-
1994
- 1994-11-18 CN CN94194857A patent/CN1084041C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CN1084041C (en) | 2002-05-01 |
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Granted publication date: 20020501 Termination date: 20121118 |