CN101484965B - Apparatus for accelerating an ion beam - Google Patents

Abstract

An apparatus for accelerating an ion beam comprising: a) a first electrode having a proximal side and a distal side and having at least one aperture therethrough, the wall of the aperture being shaped such that the radius of the aperture on the distal side of the first electrode is greater than that on the proximal side of the electrode; b) a second electrode located such that it is adjacent to but spaced from the distal side of the first electrode and having at least one aperture therethrough; and c) a third electrode located such that it is adjacent to and spaced from the second electrode and having at least one aperture therethrough, said at least one apertures in each electrode being aligned with corresponding apertures in the other electrodes; wherein the electrodes are arranged such that there is a potential difference between the first and second electrodes and a potential difference between the second and third electrodes.

Description

The equipment that is used for accelerated ion beam

Technical field

The present invention relates to be used for the equipment that ion beam quickens.More specifically, the equipment that relates to the low beam voltage ion acceleration of in ion beam technology, using such as sputter.In addition, the present invention relates to be used to produce the equipment of charged particle beam.

Background technology

In the production of the magnetic thin film device in element in microelectronic industry and the storage medium industry, ion beam has used for many years.Usually, ion beam (such as ar-ion beam) need have large tracts of land, high electric current and the energy between 100eV to 2keV.

Can use beam to change the surface of substrate in many ways, for example, by sputtering sedimentation, sputter etching, milling or smooth surface.

In general ion beam source (or ion gun), produce plasma by allowing gas or steam enter arc chamber, wherein in arc chamber, ion forms by electron impact ionization and moves indoor by result of random thermal motion.This can realize by the dc device of use heater type cathode or by the high-frequency device that uses the rf antenna.

Modern ion sources uses high-frequency discharge to excite more at large, but not excites by electric arc.Although the radio frequency of use in from about 500kHz to about 60MHz scope is the radio frequency in can using from about 13.56MHz to about 60MHz scope more at large.Also there is the device that utilizes microwave-excitation.

Be suitable on the target or the ion beam that clashes on the substrate axial direction that ion need be accelerated to single energy (monochromatic energy) and limit in order to produce.This is normally by using one group of accelerating electrode that is called as grid (grid) to realize.

Plasma cognition shows positive plasma potential, and it is higher than the current potential on any surface that contacts with plasma.Can use the grid that has carried out various layouts, its current potential is Be Controlled individually.In multigrid system, the common positive bias of first grid that ion collision is arrived, and second the grid negative bias that collides.In addition, other electrode can be used to collimate ion beam.For ion sputtering, target is placed on can be by ion beam usually in the target chamber with angular impingement, and will be placed on the position that sputter material can strike by the substrate that material is splashed on it.When implementing sputter etching, milling or smooth surface, substrate is placed on the path of ion beam.

Therefore, in general ion gun, the ion that arrives porous extraction grid assembly (multi-aperture extraction grid assembly) at first runs into positively biased grid.Relevant with grid is plasma sheath.Potential difference between plasma and the grid is passed this sheath and is descended.This accelerating potential is attracted to first grid with the ion in the sheath zone.Move through the hole in this first grid and enter first, each ion in the space between the positive bias grid and second, negative bias grid, all in highfield, quickened strongly.When ion passed the hole in the second grid and flies to the conductive target of ground connection, it passed decelerating field.Then, ion with equal first, the current potential of positive grid adds that the energy of sheath current potential arrives the ground connection target.

Therefore, the conventional ion rifle comprises charged particle source, applies electric field by the outside that produces and quicken these charged particles between a pair of grid.Traditionally, in order to produce low energy ion beam, use three grids (although can use more a plurality of), first remains on positive potential, second remains on and is adjusted to the negative potential that best diversity is provided, and if have the 3rd, then it remains on earth potential, that is, wherein produce the current potential of the chamber of beam.

The beam of this specific character has been described in the open source literature in more than 70 year in the past well.

In semiconductor, it is a kind of technique known that the ion of film and material industry injects, and it is used for ion is embedded into the lattice of material, to revise the electrical characteristics of material.Usually use beam voltage to carry out the ion injection, though they also can be up to 500kV greater than 25kV.The meticulous characteristic that the manufacturing of many microdevices and nano-device all depends on film interface improves valid function.Therefore the ability that produces the atom level smooth surface has important function in device and thin film fabrication technology.For example, the quality of bed boundary is very important in the manufacturing of thin-film magnetic field sensor and extreme ultraviolet (EUV) and X ray mirror image mask (mirror mask).

When ion beam is used for thin-film technique and nonionic when injecting, beam energy has the upper limit of 2kV usually, but for specific ion beam sputtering process, this value can be low to moderate 500V, and the efficient of technology depends on beam energy, and wherein, the energy increase causes efficient to reduce and heat radiation increases.In some applications, expectation is with such as the low value of 100V or even be low to moderate 50V and propagate beam.The extraction of known high energy ion bundle and propagation are easier than the extraction and the propagation of low energy ion beam.This is because the following fact: beam current and beam energy power 3/2 times is proportional, and this is described by the Child-Langmuir formula, and beam shows significant diversity, and the diversity of beam reduces along with the increase of beam energy.Therefore when high energy charged beams is passed accelerator, have higher speed, compare with the ion that moves relative to low speed under low-voltage, reduced space charge effect.Owing to pass through polymerization (coalescence) from a plurality of narrow beams (beamlet) in a plurality of holes, ion beam tends to become broad-beam condition, and the sole mode that obtains high current density (the comprehensive output greater than 1A is provided usually) is to use the aperture of dense arrangement, so space charge effect makes that producing the low-energy ion beam of high density becomes difficult.

In order to produce thin film magnetic device such as transducer, the process constraint condition by diffraction limit, this makes and is difficult to realize required ion beam size.Along with thin film magnetic device becomes littler, it is more harsh that the constraints of technology becomes, and the low energy ion beam that therefore realizes having the good quality of required high current density is difficult to handle film.The constraints of technology comprises from substrate and removes the inhomogeneities of thickness of speed, etching-film of material and the angle of divergence of ion beam.In addition, these constraintss must realize in the beam energy scope of 100V to 700V.In fact, for highstrung nano-device,, need to be lower than the beam energy of 100V (such as about 50V) sometimes owing to the material complex effect of worrying at the interface (material mixing effect).In some cases, owing to need to produce the heavy ion beam diameter to handle the substrate of 200m and 300m, these constraintss also can further increase.

In the manufacturing such as the gadget of the Magnetic Sensor that is used for hard disk drive, the shape of device must symmetry, and each part of device substrate formed thereon is all identical.When with ion beam milling or milling, the diversity of beam can have significant impact to this characteristic.

The beam axis of circular beam is aimed at the center of circular substrate, and the effect at center is a symmetry.For not in the position of center, the effect of dispersing is bring brightness asymmetric.Unless beam is much larger than substrate, otherwise more near the edge of substrate, the brightness at center will be better than the brightness at edge more.This has caused two kinds of not desired effects.At first, the interior whole inhomogeneities of substrate will be shown as the profile of bell (bell shaped).Secondly, the shape symmetry of pattern characteristics is towards the edge direction deterioration.Compared with outward flange, inward flange can be shown as the profile of steeper (steep).

More than two kinds of defectives all can overcome by the divergence characterization that reduces beam.Can obtain two advantages.At first, the interior whole inhomogeneities of substrate will be shown as the profile of the carnival hat shape of expectation.Secondly, the shape symmetry of pattern characteristics will make the characteristic on the inside and outside surface layer feature (facing feature) of whole base plate be consistent.

Beam divergence on extremely low-yield depends on two factors, the influence of the influence of beam emittance and remaining non-neutral beam space charge.The minimum divergence that is caused by emittance is that the effective ion temperature is divided by the beam energy square root of (the two is all represented with electron-volt).Ion temperature is the summation that the true ion temperature (being generally 0.3 electron-volt (eV)) in the plasma adds the effective temperature that out of order (disorder) that caused by spherical aberration produced, and spherical aberration causes by using simple non-shaping (unshaped) hole again.Usually the influence of back one factor is far longer than the influence of last factor.As will be discussed in more detail, in reducing aberration, the concrete shape of ion accelerator electrodes is crucial.

Because device production requirements has been specified inhomogeneities and low beam divergence in the substrate, so use the method for super large beam to be not enough to satisfy the demand that improves beam quality and keep enough power outputs.So, need to produce much smaller ion beam source, to satisfy the process requirements of modern semiconductors and thin-film device.

Above-mentioned application need uses low energy ion beam, promptly is lower than 500 volts, and therefore being starved of design can be with the ion accelerator of desired energy work.At first, accelerator must produce required ion beam current in reliable mode, and secondly, the ion beam of formation also must collimate.Known accelerator by two or more the polylith metal sheet form, each metallic plate all has array of circular apertures, makes that the hole in each plate in the accelerator is aimed at the respective aperture on other plate or the electrode.These holes normally parallel sidewalls in the simple bore of hole axle.Spacing between the hole is usually less than 1mm.

Fig. 1 shows the ideal diagram of general accelerator 10, and wherein, the accelerating electrode that illustrates forms the part of sphere.From forming the plasma generator 100 of electrode 102 (hereinafter referred to as beam forms electrode or G1), first plate of adjacent accelerator or beam extract ion.This plasma generator 100 produces the plasma of being made up of the positive charged ions and the electronegative electronics of equal number densities.

By the ion accelerating field, ion is drawn out plasma 100.Electronics with negative electrical charge is repelled by identical electric field.This is to be formed by the potential difference that the beam in the accelerator forms between electrode 102 (G1) and second electrode 104 (hereinafter referred to as extracting electrode or G2).Therefore the current potential of G2 must be lower than the current potential of G1, to extract the ion of positively charged from plasma generator.

When ion arrived extraction electrode 104 (G2), they had sizable energy, and the potential difference that this energy equals between G1 and the G2 adds that plasma sheath gives their small amount of thermal energy.Yet also have other requirement for accelerator 10: prevent to pass through accelerator 10 by reverse extraction from the electronics of plasma, described plasma self forms by the beam (beam downstream of accelerator) in accelerator downstream.If this thing happens, then can cause badly damaged to equipment.Can make this risk reduce to very little in the ion retardation field by after extracting electrode, arranging.This realizes by increasing than the high but not high third electrode (not shown in figure 1) that forms the current potential of electrode to beam of the current potential that extracts electrode.With respect to the beam plasma that is present between G3 and the target (not shown), the electrode G3 of back bears, and magnitude reaches 30 volts.Because beam plasma is current potential (but positive) very closely usually, thus G3 current potential earth potential normally itself, but also can be different from earth potential.

Therefore, final beam energy is to be set by G1 and the potential difference between the dirty beam plasma of accelerator.Beam plasma is generally earth potential, so G3 also is in earth potential.Therefore, G3 usually is known as grounding electrode.Therefore, G1 must be in the positive potential that has improved, realizing essential accelerating field.

Beam-focusing is mainly by the Interface Control between plasma generator and the accelerator electrode 102.Pull out from plasma and electronics when being subjected to repelling when ion, form sheath or meniscus, its position is limiting with 60.6% of the decline of exponential factor (0.5) or the electron density value in the main body of plasma by electron density.Ion vertically passes meniscus with half the value that equals the electron temperature in the plasma, is accelerated to the energy by the accelerator potential setting then.Outside meniscus, electron amount density drops to zero fast, and ion is along trajectory (ballistic trajectory) operation by electrostatic field control, and this electrostatic field is set up by the hole in a plurality of electrodes and these electrodes.

In above-mentioned triode accelerator arangement, formed two electrostatic lens, one at the G2 place, and one at the G3 place.The former is a divergent lens unchangeably almost, and the latter normally can condenser lens.Meniscus and this two lens form optical system, and the function of this optical system is to extract ion beam and ion beam is collimated to desired beam spot size (spot size).

The electric current of ion beam depends on a plurality of factors.These factors are associated by the Child-Langmuir formula.For radius is the single round hole of a, and the complete form of this formula is:

$I=\frac{\mathrm{\&pi;}{a}^2}{4\mathrm{\&pi;}{\mathrm{<figure-callout\; id="2"\; label="R\; c"\; filenames="H2007800250414E00031.png,H2007800250414E00051.png"\; state="\{\{state\}\}">R</figure-callout>}}_c^{}}\&times;\frac{2.934\&times;{10}^{-5}}{{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="H2007800250414E00031.png,H2007800250414E00071.png"\; state="\{\{state\}\}">A</figure-callout>}}^{1/2}\&times;{\mathrm{\&alpha;}}^2}\&times;{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="H2007800250414E00031.png,H2007800250414E00081.png"\; state="\{\{state\}\}">V</figure-callout>}}^{3/2}$ Formula 1

A is a mass number, and for the general plasma gas such as argon, A is 40.R _cBe the radius of curvature of the plasma meniscus of contiguous G1, R _aBe the radius of curvature of extracting the ion trajectory at electrode G2 place, V is the voltage between these two electrodes, and α is the infinite series of natural logrithm, and its first three items is:

$\mathrm{\&alpha;}=\ln \left(\frac{R_a}{R_c}\right)-0.3{\left[\ln \left(\frac{R_a}{R_c}\right)\right]}^2+0.075{\left[\ln \left(\frac{R_a}{R_c}\right)\right]}^3-......$ Formula 2

In fact, can use the standard mathematical method that formula 1 is reduced to:

$I=1.72\&times;{10}^{-7}\frac{a^2{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="H2007800250414E00031.png,H2007800250414E00081.png"\; state="\{\{state\}\}">V</figure-callout>}}^{3/2}}{{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="H2007800250414E00031.png,H2007800250414E00071.png"\; state="\{\{state\}\}">A</figure-callout>}}^{1/2}{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="H2007800250414E00031.png,H2007800250414E00051.png"\; state="\{\{state\}\}">d</figure-callout>}}^2}\&times;{(1-0.8\frac{d}{R_c})}^2$ Formula 3

Formula 3 shows in the extremely low difficulty of working under the energy of extracting.If define mass of ion, beam energy and V, then big if desired ionic current just must reduce to extract gap d.Yet experiment shows, has only as pore radius a to remain a half that is not more than gap d always, and this is only possible.Simultaneously, it is four times of clearance distance that beam collimation requires the recessed meniscus curvature of regulation, thereby last of formula 3 becomes 0.64.Therefore in order to make the beam current maximum, the conventional low accelerator has very short gap and even littler pore radius.

As a result, extracting electrode must be extremely thin, becomes shorter to avoid short air gap.In this, should be noted that because thickness of electrode forms the part of effective electrostatic gap, so the gap generally includes thickness of electrode.Use extremely thin extraction electrode to mean that grid is mechanically fragile relatively.This is a problem, because it makes that foundation is reliable, large-scale, low voltage accelerator becomes difficulty.

Being used to increase beam current and keeping a scheme of high quality optical system is to use very large current potential between G1 and G2, uses almost equal subsequently between G2 and G3 but opposite polarity current potential.Final beam energy is the poor of these two big current potentials, but the beam that extracts from plasma is controlled by big G1-G2 current potential (V in the formula 3).This mode of operation is called " acceleration-deceleration ".

Although proposed the acceleration-deceleration system, its not successfully commercialization is so because big current potential can cause aberration usually.Everybody thinks that all accelerators all comprise " deceleration " characteristic, and therefore is considered to " acceleration-deceleration ".Yet in these were arranged, ratio only was 0.1 usually, and therefore in the context of the present invention, they are not real " acceleration-deceleration " system.This is V _{Slow down}With V _BeamRatio, wherein, V _{Slow down}Be second gap voltage, be expressed as positive number.

It is the unlimited thin sheet that forms the part of complete sphere that formula 3 is simplified with hypothesis beam electrode.Yet this can not realize physically, so the result has intrinsic problem.J.R.Pierce in Applied Physics in 1940 (Applied Physics) the 11st are rolled up the 548th page, the J suggestion, electrode should be (shaped) that is shaped.Particularly, suggestion makes the G1 electrode with limited thickness adjacent with plasma meniscus have specific bevel angle, so that the remainder of accelerator experience (see) and the middle identical electric field of electric field that exists of accelerator (being complete sphere).

If this scheme can finally be carried out, then beam will not have any spherical aberration fully.Yet this needs to have very big spacing between the adjacent holes, and this is unpractical.Therefore this scheme does not have commercialization yet.

Summary of the invention

The objective of the invention is to overcome the problem relevant with prior art, and provide a kind of be used for producing have low emission and reduced spherical aberration and the system of the ion beam propagated with enough power densities (literary composition is also referred to as current density).

Therefore, according to the present invention, provide a kind of equipment that is used for accelerated ion beam, this equipment comprises:

First electrode has nearside and distally, and has at least one hole of passing first electrode, and the shape of the wall in hole forms and makes the radius in the hole on the distally be positioned at first electrode greater than the radius in the hole on the nearside that is positioned at this electrode;

Second electrode is arranged so that adjacently with the distally of first electrode but spaced apart, and has at least one hole of passing second electrode; And

Third electrode is arranged so that adjacently with second electrode but spaced apart, and has at least one hole of passing third electrode,

At least one hole in each electrode is aimed at the corresponding hole in other electrode;

Wherein, arrange that so these electrodes make, exist potential difference, and have potential difference between second electrode and third electrode between first electrode and second electrode.

Should be appreciated that the direction of propagation that " first ", " second " and " the 3rd " electrode and its distally of mentioning and nearside relate to beam.

Advantageously, because so the shaped hole of arranging in first electrode compared with prior art, has been eliminated spherical aberration substantially, and has been used whole extraction hole, thereby can use bigger hole from the ion beam that quickens.This unified bundle spot uniformity on given cross section provides obvious improvement.

Though only there is shaped hole (or a plurality of hole) usually in invention of the present invention in first electrode, they also may be present in second electrode and/or the third electrode.

Preferably, first electrode is that beam forms electrode, and second electrode is to extract electrode, and third electrode is a grounding electrode.Additionally or alternatively, second electrode is to disperse electrostatic lens, and third electrode is a focus electrostatic lens.In this preferred arrangements, provide and dispersed electrostatic lens and focus electrostatic lens, this produces the highly beam of collimation.

Different potentials between shaped hole of first electrode (can be the shape with oblique angle) and the electrode means the ion beam that the invention provides a kind of low emission, reduced spherical aberration together, and it is propagated with enough power densities.In addition, this layout provides a kind of firmer ion accelerator, and it is not easy to the influence of subject plasma source heat load.Other advantage is because this equipment does not need radius tip electrode is carried out complicated layout, thereby manufacturing cost descends.

The hole of any desired configuration can be provided.In one arrangement, the hole can have the profile at oblique angle.This oblique angle profile can have the shape of any appropriate, but In one arrangement, at least a portion thickness of electrode can be flat, and it is outward-dipping to arrive about 60 ° angle with about 20 ° then.About 45 ° angle may be particularly useful.This angle is the angle that comes from perpendicular to the plane of ion beam axis.

This hole in the electrode or each Kong Junke think the shape of any appropriate, yet they are normally circular.

The pore radius that is positioned at the hole on the nearside of first electrode can be less than the pore radius in the hole on the distally that is positioned at first electrode.The ratio that is positioned at pore radius on pore radius on the nearside of first electrode porch of hole (promptly) and the distally that is positioned at first electrode exit of hole (promptly) can be about 1.2 to about 1.4, and more preferably, approximately 1.3.1.5 also is suitable.

Can be about 0.5 to about 1 from the adjacent side of first electrode to the thickness in the distally of first electrode and the ratio of pore radius.Representative value is about 0.7.

Can select proper voltage to a plurality of electrodes.In one arrangement, potential difference between first electrode and second electrode and the potential difference between second electrode and the third electrode on magnitude (in magnitude) can approximately equals but are opposite.

In preferred arrangements of the present invention, cross over the potential difference of first electrode and second gaps between electrodes and the ratio of final beam energy and be at least 2:1.More preferably, be 3:1, though 2:5 also is suitable.Yet, can be up to 100:1, the ratio in the scope of about 40:1 has certain advantage.

Final beam energy will be limited by the potential difference between first electrode and the third electrode, and beam current will be limited by the potential difference between first electrode and second electrode.Required beam energy will change according to the application target of beam, therefore, supposes that third electrode is in earth potential, and then the current potential of first electrode also will be determined.Yet the current potential that can select second electrode is to provide the beam collimation of expectation.

Accelerator of the present invention can use at the equipment that is used for producing low-yield charged particle beam, therefore, according to a second aspect of the invention, a kind of equipment that is used to produce low-yield charged particle beam is provided, this equipment comprises: plasma chamber, be used for producing at plasma chamber the device of plasma, plasma comprises the particle of second polarity of the particle of first polarity and oppositely charged; Be used for the particle of first polarity is limited in the device of plasma chamber, and according to the accelerator of above-mentioned first aspect, wherein, the nearly face of first electrode (proximal face) contact plasma.

Description of drawings

Hereinafter, only the mode by example further describes the present invention with reference to the accompanying drawings, in the accompanying drawings:

Fig. 1 shows the prior art layout that the sphere diode quickens layout;

Fig. 2 shows according to of the present invention the hole at oblique angle and a sectional view of arrangement of electrodes;

Fig. 3 shows the Axcel figure that has non-shaped hole in the layout of Fig. 2;

Fig. 4 shows the Axcel emittance figure according to Fig. 3;

Fig. 5 shows the Axcel figure of the shaped electrode of 5mm under 600V;

Fig. 6 shows the Axcel emittance figure of the layout among Fig. 5;

Fig. 7 shows the Axcel figure of the shaped electrode of 5mm under 250V;

Fig. 8 shows the Axcel emittance figure of the layout among Fig. 7;

Fig. 9 shows the Axcel figure of the shaped electrode of the 5mm that has strong acceleration-deceleration under 250V;

Figure 10 shows the Axcel emittance figure of the layout among Fig. 9;

Figure 11 shows the Axcel figure of the shaped electrode of the 8mm that has strong acceleration-deceleration under 250V; And

Figure 12 shows the Axcel emittance figure of the layout among Figure 11.

Embodiment

As shown in Figure 2, the invention provides a kind of ion accelerator 200 of triode form.Triode arrangement comprises: first beam forms electrode 202, second third electrode 206 that extracts electrode 204 and be known as grounding electrode.All electrodes all have the hole of passing it, and each Kong Jun is flat, and have circular symmetry or rotational symmetry about the center in hole.Electrode serial (in series) is arranged so that their hole is aimed at substantially.

The hole that beam forms electrode 202 comprises oblique angle (bevelled) or excision portion 203.So arrange oblique angle 203, make it have circular symmetry or rotational symmetry about the center that beam forms electrode hole.Oblique angle 203 is positioned at respect to beam and forms on the electrode side opposite with plasma generation place, source side.The oblique angle has four critical dimensions: hole inlet radius a, counterbore (counterbore) or hole exits radius s, the angle θ that forms angle of bevel and the thickness T of electrode material ₁Angle θ is defined as the angle in the metal, that is, and relatively perpendicular to the angle on the plane of the axle of ion beam.The fit value and the representative value of critical dimension have been shown in the following table 1.

Table 1-oblique angle size

Parameter	Fit value	Representative value
			θ	20 ° to 60 °	45°
s/a	1.1 to 1.7	1.3
			T 1/a	0.5 to 1	0.7

In table, the geometry of first grid is expressed as one group of dimensionless number.They first is angle θ, second be the counterbore radius divided by pore radius s/a, and the 3rd be that the thickness of electrode material is divided by pore radius T ₁/ a.Therefore, should be appreciated that optimum value and do not rely on the specific size in hole.

The position that the outward flange in hole 201 will be positioned at if dotted line 205 shows that the hole does not have the oblique angle.More specifically, the outer surface in the hole concordant extension of point that on whole hole, will limit with interior radially diameter (innerradial diameter) by the hole.

Because described oblique angle arranges that accelerator field forms the part of idealized spherical accelerator, thereby has almost eliminated spherical aberration.Secondly, whole extraction electrode hole 204 is used for not only producing useful beam at the core of electrode, thereby can use bigger hole.

The final beam energy of extracting from accelerator 200 is limited by the potential difference that beam forms between electrode 202 and the grounding electrode 206, and beam current is limited by the potential difference that beam forms between electrode 202 and the extraction electrode 204.Suppose grounding electrode 206 is defined as earth potential, then the current potential of beam formation electrode 202 is also determined.Thereby the current potential that extracts electrode 204 can be defined as the interior random desired value of constraints that beam collimation requires.Because beam is at first quickened strongly, almost slowed down (reduction of speed) consumingly then, so such accelerator is called the acceleration-deceleration accelerator.

For the current potential of the extraction electrode 204 revised and the order of severity of residual aberration are assessed,, can use ion optics sign indicating number (ion optics code) by space charge and plasma source emulation and electronics and ion temperature.Use is tested layout of the present invention by the Axcel sign indicating number that ING GmbH sells.

Fig. 3 shows the The ion extraction figure according to the non-shaping accelerator of prior art.Accelerator illustrates the ion trajectory of the integrated pattern that begins in plasma, in plasma, space charge is neutralized by plasma electron.For this reason, current potential has increased about 30V～80

V is to reach the plasma potential in the source.The beam in this yard permission accelerator downstream is by the space charge of other plasma neutralization.

As emittance figure, the order of severity of the aberration that is produced by the accelerator of this non-shaping has been shown among Fig. 4, wherein, every ray among Fig. 3 is by radius (x) and the point dispersed in (x ') face is represented.The outer wing of beam forms serpentine up and down.These are aberrations and form beam～40%.In above-mentioned application, this part of ion beam is useless substantially.

By replacing the extraction electrode that does not have the oblique angle of prior art with the extraction electrode that the oblique angle arranged, and the gap done the adjustment of some necessity, as understood by those skilled in the art,, produced the improvement shown in Fig. 5 and Fig. 6 in order to regulate electrode.Comparison diagram 4 and Fig. 6 can find that the minimizing of aberration is fairly obvious, because almost eliminated all aberrations.In addition, for identical gap, current potential and bore dia, beam current has risen to every hole 0.7mA from every hole 0.47mA.The effect of back is that the ray by the part that forms main beam at bore edges place causes that these rays carry the beam current of their corresponding shares.

Yet ultra low beam operation remains difficulty because electric current will drop to the beam energy of crossing over gaps between electrodes power 3/2.This as can be seen, wherein used the geometry identical with Fig. 5 and Fig. 6, but beam energy has dropped to 250V in Fig. 7 and Fig. 8.Beam current drops to 0.45mA, and aberration has increased.

The mode of operation of acceleration-deceleration has been avoided electric current decline problem under extremely low-yield with the arrangement of electrodes that the oblique angle is arranged, and it is low-level that aberration is remained on.This is shown in Fig. 9 and Figure 10, works under 250V in the hole that wherein shows the 5mm diameter.As shown in Figure 9, although be difficult to make beam not have aberration fully, though under low-yield, have higher this additional advantage of narrow beam electric current in this extremely low-yield maintenance down.

Additional advantage is that electrode is much firmer than the electrode of the geometry with prior art shown in Fig. 4, and this is because the ability by utilizing accelerator to work under high extraction electrode potential makes that present electrode is thicker.The gap also is increased to 3mm, and this makes accelerator more can resist high-voltage spark.

As Figure 11 and shown in Figure 12, the bore dia that beam can be formed electrode 202 is increased to 8mm.This selection allows electrode thicker higher with operating potential, makes that therefore particularly the beam formation electrode 202 of most fragile is very firm, is exposed under the plasma heat load because beam forms electrode 202, so be easy to bending when major diameter.The quantity in hole is less then to help reducing manufacturing cost.

Therefore as can be seen, the invention provides a kind of low emission, reduced the ion beam of spherical aberration, its power density with abundance is propagated.In addition, the invention provides a kind of firmer ion accelerator, it is not easy to be subjected to the influence of plasma source heat load.

Claims (17)

1. equipment that is used to quicken positive ion beam comprises:

First electrode, have nearside and distally, and have at least one hole of passing described first electrode, the shape of the wall in described hole forms and makes the radius in the described hole on the described distally be positioned at described first electrode greater than the radius in the described hole on the described nearside that is positioned at described electrode;

Second electrode is arranged so that adjacently but spaced apart with the described distally of described first electrode, and has at least one hole of passing described second electrode; And

Third electrode is arranged so that adjacently but spaced apart with described second electrode, and has at least one hole of passing described third electrode,

Described at least one hole in each electrode is aimed at the corresponding hole in other electrode;

Wherein, so arrange these electrodes, make between described first electrode and described second electrode, to have potential difference, and between described second electrode and described third electrode, have potential difference.

2. equipment according to claim 1, wherein, described first electrode is that beam forms electrode, described second electrode is to extract electrode, and described third electrode is a grounding electrode.

3. equipment according to claim 1, wherein, described second electrode is to disperse electrostatic lens, described third electrode is a focus electrostatic lens.

4. equipment according to claim 1, wherein, there is the oblique angle in the described hole of the shaping of described first electrode.

5. equipment according to claim 1, wherein, the hole of each electrode is flat at least a portion thickness of this electrode, and is outward-dipping with 20 °～60 ° angle then.

6. equipment according to claim 5, wherein, wherein the hole of each electrode is flat at least a portion thickness of this electrode, and is outward-dipping with 45 ° angle then.

7. equipment according to claim 1, wherein, the shape in the hole in each electrode is identical.

8. equipment according to claim 7, wherein, the hole in each electrode is circular.

9. equipment according to claim 1 wherein, is positioned at the pore radius of the pore radius in the described hole on the described nearside of described first electrode less than the described hole on the described distally that is positioned at described first electrode.

10. equipment according to claim 9, wherein, the ratio of the pore radius on the pore radius on the described distally of described first electrode and the described nearside of described first electrode is 1.1～1.7.

11. equipment according to claim 9, wherein, the ratio of the pore radius on the pore radius on the described distally of described first electrode and the described nearside of described first electrode is 1.2～1.4.

12. equipment according to claim 9, wherein, the ratio of the pore radius on the pore radius on the described distally of described first electrode and the described nearside of described first electrode is 1.3.

13. equipment according to claim 1, wherein, the ratio of the pore radius on the thickness from the described nearside of described first electrode to the described distally of described first electrode and the described nearside of described first electrode is 0.5～1.

14. equipment according to claim 13, wherein, the ratio of the pore radius on the thickness from the described nearside of described first electrode to the described distally of described first electrode and the described nearside of described first electrode is 0.7.

15. equipment according to claim 1, wherein, the potential difference between the potential difference between described first electrode and described second electrode and described second electrode and the described third electrode equates on magnitude but is opposite.

16. equipment according to claim 1 wherein, is crossed over the potential difference of described first electrode and described second gaps between electrodes and the ratio of final beam energy and was at least 2: 1.

17. an equipment that is used to produce low-yield charged particle beam comprises: plasma chamber, be used for producing the device of plasma at described plasma chamber, described plasma comprises the particle of the oppositely charged of the particle of first polarity and second polarity; Be used for the particle of described first polarity is limited in the device of described plasma chamber; And according to each described accelerator in the claim 1 to 16, wherein, the nearly face of described first electrode contacts with described plasma.

Images