JP5420239B2 - Resonance method for the production of atomic and molecular low-impurity strong ion beams. - Google Patents

Description

[Citation of related application]
This application claims priority from US Provisional Application No. 60 / 683,016 filed May 20, 2005 and US Patent Application No. 11 / 185,141 filed July 20, 2005. The disclosures of which are incorporated herein by reference.

[Field of the Invention]
It relates to accelerator mass spectrometry, isotope dating, high energy semiconductor implantation, low energy semiconductor ion implantation, molecular beam implantation, cluster beam ionization, decaborane ionization, isobaric particle rejection.

  The technology to be described has important applications in several areas of scientific research and in industry. These include molecular ion implantation, generation of directed neutral beams, generation of low energy electrons required for ion beam neutralization in a magnetic field, and unwanted isobaric nuclei during accelerator mass spectrometry (AMS) measurements. Attenuation is included. Such a process is briefly described below.

Molecular ion implantation in the semiconductor industry The formation of ultra-shallow junctions requires an ion beam having an energy between 2,300 electron volts and 3 keV. Although commercialization requires high beam currents to achieve useful manufacturing throughput, it is substantially difficult to extract and transport such low energy ion beams. The basic problem is to introduce and maintain a reasonable number of space charge neutralized electrons or negative ions in the ion beam to avoid beam “expansion”. A classic neutralization method known since the Second World War and the Manhattan Project involves the generation of electrons generated by ionization of molecules in the space charge well of the ion beam due to collisions of beam particles with residual gas molecules. It is. Unfortunately, this method becomes ineffective at low particle velocities and other techniques must be used.

An important proposal to avoid this problem was made in 1993 by Yamada et al. And reported in the journal Nuclear Instruments and Methods , 79, 223. Yamada's proposal suggests that the problem of low energy implantation will be substantially reduced if monovalent molecular clusters of desired ions are used instead of individual atoms of the desired atomic species. It was a thing. One such molecular replacement described by Jacobson et al. In IEEE Conference Report “IIT2000” accelerates to about 11 times greater kinetic energy than an implanted ion beam extracted from a suitable ion source and consisting only of individual B ⁺ atoms. An ionized molecular decaborane (B ₁₀ H ₁₄ ⁺ ) was used. As an example, during implantation of 500 eV boron atoms, the decaborane parent ion will be accelerated to an energy of 5.5 keV, that is, an energy that allows molecular ions to be easily transported through modern injectors. Obviously, the measured dose using charge collection is increased by a factor of 10 compared to that using conventional boron implantation, and the space charge force is correspondingly reduced.

To confirm the usefulness of this method for semiconductor fabrication, several researchers have demonstrated decaborane implantation in a specific device configuration. In page 304 of IEEE Conference Report “IIT2000” In one example reported by Perel, secondary ion mass spectrometry (SIMS) measurements were made to establish a deep distribution of boron atoms following cluster implantation into silicon. Perel's data showed no obvious distinction between the conventionally implanted deep distribution of boron atoms and the same rate of molecular B ₁₀ H ₁₄ ⁺ implantation.

A method and apparatus for using an electron beam to ionize decaborane without substantial dissociation of the decaborane molecular structure is described by Horsky in US Patents 6,452,338 and 6,686,595 . In addition, Vella in US Pat. No. 6,573,510 B1 describes a method and apparatus for a two-chamber charge exchange source capable of producing monovalent decaborane ions.

  In this disclosure, another highly efficient ionization method for producing monovalent molecular decaborane ions is described. The method uses the well-known phenomenon of resonant charge exchange between molecular or atomic ions, where an incident initial ion beam is passed through a region containing cluster molecules or atoms to be ionized and accelerated. While the immediate application is the production of high current monovalent decaborane ions, applications involving other atoms and molecular species will also become important as the demand for other beams required for low energy implantation grows. There is expected.

  Features that make this procedure more attractive than the devices described above by Horsky and Vella include (1) that higher current charged decaborane should be available using the resonance procedure, and (2) the interaction This includes that the background of undesirable material that is generated due to selective resonance should be smaller.

Accelerator mass spectrometry (AMS)
Although AMS has been described in detail by a number of authors, they are able to apply AMS technology to the detection of stable rare radioisotopes such as ¹⁰ Be, ¹⁴ C, ²⁶ Al, ³⁶ Cl, and ¹²⁹ I. Is provided. Such description includes " Supersensitive Particle Identification System Based on Electrostatic Accelerator" in US Pat. No. 4,037,100 to Purser, Journal, Nuclear Instruments and Methods , 162, 637, (1979). Purser, K. H. Literland, A .; E. And Gove, H .; E. The paper by is included. These publications dictate that using AMS, the detection limit ratio for many rare radionuclides is between 10 ⁻¹⁴ and 10 ⁻¹⁶ compared to the concentration of stable elemental isotopes. Pointed out. These ratios show a greater sensitivity than the 6th order than is possible using conventional mass spectrometry.

A major problem in detecting radioactive atoms at such low abundance is that the high beam current of the parent element is essential. For example, for a single atom detection of radioactive atoms, ^(as compared to the number of atoms of a parent element) 10 ^-16 of the parent element concentration of less than milliamperes beam is desirable. In addition, such beams should be as pure as possible with low amounts of molecular and isobaric contaminants.

For the purposes of AMS measurement, the present invention can take advantage of the difference between resonant and non-resonant processes to allow for the increase or decay of specific elemental species. For example, a beam of Cs ^- ions across a cell containing cesium atoms will transfer charge to Cs atoms much more efficiently than to non-identical atoms. Thus, stationary negative cesium ions formed in the cell can be extracted at the expense of other non-identical atoms that may be present.

Currently, most AMS instruments use a sputter source to generate negative ions, such sources being reported in Nuclear Instruments and Methods , 214, 214, (1983), “Negative Ion Cesium”. R. Sputter ion source " Described by Middleton. In general, the yield of negative ions from these sources decreases rapidly with negative ion mass and decreases with decreasing electron affinity. Physical Review B , 19, 5661, (1979), Norskov J. et al. K. According to “Secondary ion emission in sputtering”, the ratio of product negative ions to sputtered neutral atoms, ε, is given by:

Where β is a constant associated with that of Norskov and Lundquivst,
φ is the work function of the sputtered surface,
A is the electron affinity of the sputtered species,
M is the mass of the sputtered seed.

  From Equation 1, it can be seen that the yield of negative ions from the sputter source for heavy ions tends to be dramatically lower than the yield for carbon, ie, light atoms with high electron affinity. As a result, negative ions are omnipresent, but for species with low electron affinity, the beam is useful for many measurements because the rate of ion production from the sputter source can be very low. Absent.

  Using the near-resonance transition of the present invention, the above sputtering barrier no longer limits beam formation of weakly coupled negative ions. Furthermore, as will be discussed later, the exact equal electron affinity of both partners is not essential for efficient charge transfer.

Neutral beam technology An important group of implant materials includes ions with energies approaching one million electron volts. One reason for the growth of this high energy implantation was the miniaturization of the transistor. Over time, individual transistors are smaller and tighter, or operate at lower voltages. These changes have led to an increase in capacitance between elements, which may cause parasitic current coupling between individual circuits, which can cause circuit instability. To avoid these undesirable results, it is often useful to introduce barriers that electrically isolate the transistor circuits from each other and from the underlying substrate where parasitic currents may flow. Such substrate isolation can occur by embedding a low resistivity layer under the active circuit. In general, the energy required for such processing is in the range of 0.8-3.0 MeV, and uses higher acceleration voltages compared to those used during traditional embedded or complex radio frequency accelerator installations. I need.

  Commercially available high energy implanters use DC voltage and utilize tandem acceleration principles to generate ions with energies in the million electron volt range. During this process, negative ions are accelerated from ground to the positive terminal where the charge of the incident negatively charged ions is converted to a positive polarity by extracting electrons from the negative ions. The next acceleration phase returns these positive ions to ground potential.

  Unfortunately, the required negative ion production cross-section tends to be small and it is the limitations of this tandem acceleration system that often limit the beam current intensity. One way to avoid this problem is to use a neutral beam of ions that are in need of being swept through the first stage of a million volt dc tandem configuration without acceleration. The neutral beam carries neutral particles to a high voltage terminal where the neutral particles become positive polarity by removing one or more electrons as the ions pass through a suitable gas cell or foil. Charge conversion is performed. Effectively, this method generates positive ions in the positive terminal, from which the positive ions are accelerated to return to ground potential while gaining energy on the way. The importance of such a scheme is that the beam intensity of ions having an energy of ~ MeV can often be increased substantially by the order of magnitude.

The ¹¹ B beam neutralization study to generate such a neutral beam is Made by Tomski and reported in his Master of Science thesis he submitted to the University of Toronto in 1997. A feature of this study was the use of molecules to neutralize the fast beam of directed boron ions. These ions were passed through a cell filled with a low pressure vapor of the organic molecule anisole (C ₇ H ₈ O). The usefulness of anisole is that the ionization potential for boron is 8.29 eV, which provides an almost complete resonance ionization harmonic for boron. The cross-sectional areas were measured for three materials, water (ionization potential 12.612 eV), methanol (10.85 eV) and anisole (8.21 eV). The cross-sectional areas measured from B ⁺ to B ^{0 in} units of 10 ⁻¹⁵ cm ² at 10 keV are 2.1 +/− 0.2 for water and 2.7 +/− 0.2 for methanol. Anisole was 5.9 +/− 0.6, indicating an effect close to resonance.

Background underlying resonance interaction Although not intended to limit the scope, the charge transfer reaction between a positive atom or molecule and a neutral atom or neutral molecule can be written as I can do it.
Y ⁰ + X ⁺ → Y ⁺ + X ⁰ (1)

During such a reaction, the electrons that were originally part of the neutral target atom Y ⁰ are transferred to the moving charged incident particle X ⁺ , making the first charged X ⁺ electrically neutral, still atoms ^{Y 0} is positively charged ^{Y +.} Here, both X particles and Y particles can be atoms or molecules. The convention used is that X ⁺ refers to the atom or molecule of the incident particle that initiates the reaction, and Y ⁰ is the target atom or molecule. However, it should be noted that during the generation of a fast neutral beam, the incident positive ions X ⁺ can still be converted to neutral charges, allowing prefocused directed ions to be converted to directed neutral particle beams. I must. The same type of resonant interaction can also be used to create a resonant charge conversion between negative ions and neutral particles.

The dominant dominant parameter for estimating the cross-sectional area for such an interaction is the energy difference ΔE between the ionization potential or electron affinity of the neutral target atom Y ⁰ and that of the uncharged incident particle atom X ⁰ . If ΔE is small, the cross-sectional area for the reaction described by Equation 1 is large, which can provide a high possibility for resonant charge transfer.

  The physical basis for this effect is that when an atom or molecule passes through each other, the wave functions of both particles combine to induce electronic oscillations between the two particles. The cross-sectional area for this process increases when the difference in electronic bond energy between the particles is small and when the relative velocity is low. These are prerequisites for electron transfer that is resonant or close to resonance. In contrast, if the electron binding energies for each of both particles are substantially different, the resonance state will no longer dominate and the electron transfer cross section will be smaller.

  One skilled in the art will recognize that the above diatomic system is an atomic analog of a pair of weakly coupled oscillators tuned to the same frequency. In the case of two weakly coupled identical pendulums, it is well known that the oscillatory motion is transferred from the first pendulum to the second pendulum. If all of the energy of the first pendulum is transferred to the second pendulum, the process is reversed and the energy returns to the first pendulum. In this way, energy is transferred back and forth between the two components without limit. For atomic systems, electrons oscillate between two atoms or molecules, X and Y, and if ΔE is small, the “inversion” frequency for electron transfer is large. When the pair eventually separates, the electrons are trapped on one component or the other, resulting in a yield of about 50% of the incident charged particle intensity transferred to the other partner. An ion source designed to take advantage of this effect makes available a new area for generating both positive and negative ion beams.

A detailed theory describing such a resonance charge transfer process is described in the paper “Electron and Ion Collision Phenomenon” in Oxford University Press Vol. 4, 2579, (1974). S. W. Massey and H.M. B. See also, “Sections for Resonant Transfer Between Atoms and Their Positive Ions”, Sakabe, S., by Gilbody and also in Atomic and Nuclear Data Tables 49, 257-314 (1991). And Yazukazu, I .; Is provided by. If the base atoms are the same, or if the particles are different and the electronic binding energies are substantially the same, the possibility of resonant charge transfer is substantial even with high collision parameter values. A useful correction estimate for the change in cross-section for near-resonance electron transfer is published by Littleland et al. In a paper entitled "Ion Reactions for Isobaric Separation in Accelerator Mass Spectrometry", and also in the journal Nuclear Instruments and Methods. B , 204, 323-327, (2003).

Furthermore, it should be noted from the above-mentioned Literland reference that the exact equal ionization potential of both partners is not essential for efficient charge transfer. The uncertainty principle can roughly predict the size of the cross-sectional area for resonant ionization, but the principle is that if the product ΔExΔt is of order h / 2π, the cross-sectional area will be high. Show. Here, Δt is the order of D / v (v is the velocity of fast ions, and D is the “size” of the molecule). For example, if D is 1 nanometer and the translational energy E is 10 keV relative to the incident As ⁺ ion, then ΔE will be as large as 107 meV. However, those skilled in the art will recognize that D is not well defined and that the resonant cross section does not change suddenly but decreases smoothly as the ionization energy difference increases. If ΔE is several times larger than the estimated size, useful resonance ionization is still expected.

Although the mechanism of formation has not been clarified until recently, there is one well-known example in the knowledge of the production of heavy negative ions used in nuclear research to explain the above charge transfer mechanism between non-identical negative ions. . In geometry tolerated even ions, the vapor of neutral calcium atoms the He ^{- -} The generated becomes either want to Ca that as extracted as a separate ion beam by the measurements made when passed through a beam of ions The measured intensity of Ca ^- beam (~ 1 microamp) was shown to be surprisingly high. In the end, the results were considered unusual. For details, see K.K. A paper entitled “Development made at Rochester Tandem Laboratory” in Proceedings of the SNEAP Conference, Tallahassee Florida , page 1972, edited by Chapman and published by the University of Florida. H. Reported by Purser. The purpose of the experiment was the nuclear physical measuring high energy Ca ^- a generation of ions, since the there was about one ion current microamps too reasonable efforts to increase the output current above this value was not at all made . Recently, however, the electron affinity of He ⁻ is ~ 0.078 eV and the electron affinity of Ca is now ~ 0.022 eV, and the first He ⁻ ion and vaporous neutral Ca atom The reason for the high production rate became clear when it was recognized that resonant charge exchange during the process increased the cross-sectional area for Ca ⁻ production.

Although not intended to limit the scope, an important example of the usefulness of such a resonance process is the ionization of decaborane by a slow beam of arsenic atoms. As mentioned above, a clue to efficient movement is that the decaborane ionization potential must be close to that of the excitation beam. Experimentally, the ionization potential of B ₁₀ H ₁₄ has been accurately measured to be 9.88 +/− 0.03 eV. The closest atomic particle that matches this ionization potential is arsenic As, which has almost the same ionization potential -9.815 eV. Furthermore, the first excited state of As is 131.9 meV (millivolt) or only 30 meV away from resonance with the measured ionization potential of the decaborane molecule. Since the ionization potential difference ΔE between the two ground states is only ˜80 meV, strong resonance can be expected with the lowest energy. The calculated cross section for interaction with decaborane for incident As ⁺ ions with an energy of 10 keV is 2.77 × 10 ⁻¹⁵ cm ² , and the resonance effect is even more so with As ⁺ ions with an energy of 1 keV. Notably, the calculated exchange cross section is -3.94 × 10 ⁻¹⁵ cm ² , ie a substantial area on the atomic scale.

  An important feature of such a resonance ionization process is that the natural quantum mechanical frequency is well-defined and narrow, so that the reaction is selective, and there are few background dissociation products from other decaborane configurations. It is expected that the majority of the decaying particles will be hydrogen. Nevertheless, those skilled in the art have found that high energy incident arsenic ions sometimes collide head-on with decaborane molecules and crush the molecules to produce a background of particles that are subject to low separation field deflection or cross-domain velocity filtering. It will be appreciated that would have to be removed from the charged decaborane beam using.

The actual aspect that makes the above method very attractive to generate monovalent decaborane is, firstly, that the ionization energy is closely matched between As and decaborane, and secondly, This means that an As ⁺ 20-30 mA current can be easily generated in the form of a qualified ion beam. The energy required for boron implantation is accelerated to whatever energy is required for implantation by raising the decaborane source chamber to a potential ~ 11 times higher than the required final implantation energy. It can be adjusted by adjusting to. As an example, the decaborane source would be raised to a potential of ˜33 keV for the generation of boron implantation using atoms with an implantation energy of 3 keV. In practice, the incident As ⁺ ions will enter a decaborane cell with an energy close to 1 keV or any energy that is deemed most reasonable to maximize charge exchange resonance, but when this energy becomes an important parameter Is not expected.

  Obviously, different initial beams with different electron affinities are needed to make good use of the resonance effect to generate all ions with high intensity. Those skilled in the art will recognize that numerous experiments have been performed with rare gas atoms such as helium, neon, argon, krypton and xenon to produce low intensity beams and these atomic gases and their combinations. It will be appreciated that ion resonance transfer methods are well established using ion beams. However, high intensity (greater than 1 milliamp) beams have not been previously produced. Obviously, more research is needed for most other atoms. Although more research is needed to determine the ionization potential for both atomic and molecular groups, molecular and nuclear power that can be generated reliably and at an intensity that might be considered useful as an “initial beam” It will be apparent to those skilled in the art that a large number of atomic ions already exist.

[Detailed explanation]
Referring initially to the drawing, FIG. 1, there is shown an initial ion beam 101 that enters a cell 102 and passes through a gas or vapor 103 contained within the cell. The initial ion beam 101 can be negative or positive ions, which can be atomic or molecular. Within the cell 102, the sample 103 is maintained in a gaseous or vaporous state with an appropriate vapor pressure. If necessary, temperature control may be required using a suitable heater or cooler. The initial ion beam species 101 generally has the electron affinity or ionization potential of the ion species 101 and the electron affinity or ionization potential of atoms or molecules constituting the gas or vapor 103 to be converted into negative or positive ions. Selected to be equal. The obtained ions 106 are extracted in the vertical direction from the cell side opposite to the side where the initial ion beam enters, and are formed into an appropriate ion beam 107 using the extraction optical element. The design and operation of the optical element are as follows. Well known to those skilled in the art.

In the case of decaborane ionization using As ⁺ as the initial beam, the cross-sectional area is expected to be approximately 3.5 × 10 ⁻¹⁵ cm ² . If the integrated thickness of decaborane is adjusted to be 10 ¹⁵ / cm ² , the resonance charge exchange collision between As ⁺ ions and decaborane molecules will be about 3 times when arsenic ions pass through the cell. I will. Extraction of decaborane ions formed in the source box is accomplished by an electric field that enters the source box through the extraction port 108. Extraction can also be facilitated by the introduction of a small electric field within the source box, or by the use of ion motion induced by the crossing of the electric and magnetic fields producing ExB drift, as is well known to those skilled in the art.

  As shown in FIG. 2, in some cases it may be more convenient to extract the ions that are determined perpendicular to the direction of incidence of the initial ion beam 201. A vapor or gas sample in the center of the cell 202 that is raised to a positive potential is bombarded by the incident initial particle beam. Ions generated in the gas are separated from the incident initial ion beam by an appropriate electric field that directs the sought charged ions toward the region of the extraction optics. A stepwise extraction region of 2-3 volts / cm extending along the width of the cell, or the placement of crossed ExB regions, should allow efficient extraction of ions. When the ions reach the extraction port 204, they are accelerated and formed into a directed ion beam. If necessary, an appropriate electric field can be introduced into the cell 202 by a series of equipotential planes or from around the acceleration region penetrating through the extraction port 204.

  Alternatively, the apparatus of FIGS. 1 and 2 can be used to create a neutral beam. For example, the ionization initial beam 101 enters the cell 102 and passes through the gas or vapor 103 contained in the cell. Electrons from the gas or vapor are transferred to the initial ion beam 101, which converts the ionized beam into a neutral beam. The resulting neutral beam 106 then exits the cell 102 through the extraction port 108. In a specific embodiment, a boron ionization beam is used in conjunction with the target molecule of anisole.

FIG. 6 illustrates the operational details of the geometry where the desired extraction beam is directed along the direction of the incident initial ion beam. FIG. 5 illustrates the operational details of the extraction geometry where the extracted ion ejection direction is perpendicular to the direction of the incident initial ion beam.

Claims (31)

The species is sought for use in load electrostatic particle beam ions, helium, neon, argon, a method for producing from a group of target atoms or molecules excluding noble gas atoms krypton or xenon, high speed atom Passing an incident beam having a positive or negative ion in the form or molecule and passing through the group, wherein the incident ion beam of the desired species of ions desired to be produced in the group. The said manufacturing method which has ionization potential or electron affinity within 500 meV among ionization potential or electron affinity.   The method of claim 1, wherein the sought-after ion species can have a positive or negative polarity.   The method of claim 1, further comprising providing an electric field over the entire volume of the group.   The method of claim 1, comprising providing an ExB drift of the desired species.   4. The method of claim 3, wherein the electric field is provided substantially parallel to the direction of the incident beam of atomic or molecular ions.   4. The method of claim 3, wherein the electric field is provided substantially perpendicular to the direction of the incident beam of atomic or molecular ions.   The method of claim 1, wherein the target molecule to be ionized comprises decaborane and the incident beam of ionized atoms comprises a single charged arsenic atom. The species is sought for use in load electrostatic particle beam ions, a method for producing from a group of target atoms or molecules, an incident beam having a positive or negative ions at high velocity atomic or molecular The incident ion beam has an ionization potential or electron affinity that is within 500 meV of the ionization potential of the desired species of ions that are desired to be produced in the group. The manufacturing method.   9. The method of claim 8, wherein the sought-after ion species can have a positive or negative polarity.   The method of claim 8, further comprising providing an electric field across the entire volume of the group.   9. The method of claim 8, comprising providing the desired species of ExB drift.   The method of claim 10, wherein the electric field is provided substantially parallel to the direction of the incident beam of atomic or molecular ions.   The method of claim 10, wherein the electric field is provided substantially perpendicular to the direction of the incident beam of atomic or molecular ions. Helium, neon, argon, an apparatus for producing a directed beam of the group or Lion of atoms or molecules of the target atoms or molecules excluding noble gas atoms krypton or xenon,
A cell adapted to hold a group of said target atoms or molecules,
Means for ionizing said target atom or molecule by removing electrons from said target atom or molecule located in said cell by passing an initial beam of ionized atoms or molecules through said cell; Means wherein the initial ion beam has an ionization potential within 500 meV of the ionization potential of the ions desired to be produced in the cell; and the ionization atom or ion following the ionization of the target atom or molecule The apparatus comprising a combination of means for extracting molecules and converting the extracted ions and molecules into the ion beam.   The apparatus of claim 14, wherein the target molecule located in the cell comprises decaborane.   The apparatus of claim 14, wherein the initial beam comprises arsenic ions.   15. The apparatus of claim 14, wherein the atoms or molecules of the initial beam are not the same species as the target atoms or molecules.   The apparatus of claim 14, wherein the cell is temperature controlled. An apparatus for producing a directed beam of the group or Lion of atoms or molecules of the target atoms or molecules,
A cell adapted to hold a group of said target atoms or molecules,
Means for ionizing said target atom or molecule by removing electrons from said target atom or molecule located in said cell by passing an initial beam of ionized atoms or molecules through said cell; Means wherein the initial ion beam has an ionization potential within 500 meV of the ionization potential of the ions desired to be produced in the cell; and the ionization atom or ion following the ionization of the target atom or molecule The apparatus comprising a combination of means for extracting molecules and converting the extracted ions and molecules into the ion beam.   20. The apparatus of claim 19, wherein the target molecule located in the cell is selected from the group comprising helium, neon, argon, krypton and xenon.   The apparatus of claim 19, wherein the target molecule located in the cell comprises decaborane.   The apparatus of claim 19, wherein the initial beam comprises arsenic ions.   20. The apparatus of claim 19, wherein the atoms or molecules of the initial beam are not the same species as the target atoms or molecules.   The apparatus of claim 19, wherein the cell is temperature controlled. An apparatus for producing a directed beam of the group or al negatively charged atoms or molecules of the target atoms or molecules,
A cell adapted to hold a group of said target atoms or molecules,
Means for adding electrons to the target atom or molecule by passing an initial beam of negatively charged atoms or molecules through the cell to add electrons to the target atom or molecule located in the cell; Wherein the negative beam of negatively charged atoms or molecules has an electron affinity within 500 meV of the electron affinity of the ions desired to be produced in the cell, and the target atoms or molecules. The apparatus comprising a combination of means for extracting the negative atoms or molecules following the addition of electrons and converting the extracted negative atoms or molecules into the ion beam. An apparatus for producing a directed beam of neutral atoms or molecules having a monovalent grain equivalent current,
Cells adapted to hold a group of data Getto atoms or molecules,
By passing a charged particle beam of ionized atoms or molecules through the cell, the atoms or molecules in the charged particle beam are neutralized by adding electrons from the atoms or molecules located in the cell. Means for generating a beam of ionic atoms or molecules, wherein the ionized atom or molecule beam is within an ionization potential of an atom or molecule in the cell of the same type as the atom or molecule in the cell. And a combination of means having an ionization potential within 500 meV.   27. The apparatus of claim 26, wherein the charged particle beam comprises boron and the molecule located in the cell comprises anisole.   27. The apparatus of claim 26, wherein the atoms or molecules of the charged particle beam are not the same species as the atoms or molecules located in the cell. Using a group of target atoms or molecules, having a monovalent grain equivalent current, the sought species are neutral atoms or directed beam of molecules to a method for producing preferentially, are the calculated Passing an incident beam having high-speed atomic or molecular ions of a species through the group, and applying an ionization potential or electron affinity within 500 millielectron volts within the ionization potential of the target atom or molecule. The said manufacturing method which an ion beam has.   30. The method of claim 29, wherein the charged particle beam comprises boron and the target molecule comprises anisole.   30. The method of claim 29, wherein the atom or molecule of the charged particle beam is not the same species as the target atom or molecule.

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