Claims
- 1. A method for isotopic ratio determination of elements on a metallic, semi-conducting or insulating surface, comprising the steps of:
- pulsing an ion beam of at least about 2 KeV at grazing incidence to impinge said surface; and
- detecting the ionized elements directly recoiled from the surface with a high resolution time-of-flight mass spectrometer comprised of at least one linear field free drift tube and at least one toroidal or spherical energy filter with a +/- V polarization to deflect positive or negative ions.
- 2. The method of claim 1, wherein the surface elements are selected from the group consisting of H, He, Li, Be, B, C, N, 0, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, Cs, Ba, La, Nd, Gd, Tb, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Th and U.
- 3. The method of claim 1, wherein said ion beam is selected from the group consisting of Cs, Na, Li, B, He, Ar, Ga, In, Kr, Xe, K, Rb, O.sub.2, N.sub.2 and Ne.
- 4. The method of claim 1, wherein said ion beam is at least about 15 KeV.
- 5. The method of claim 4, wherein said ion beam is Cs.
- 6. The method of claim 1, wherein said surface is coated with an overlayer.
- 7. The method of claim 6, wherein said overlayer is selected from the group consisting of hydrocarbons, carbon, gold, platinum, aluminum, oxides, frozen noble gases and molecular gases.
- 8. A method for determining elements on a surface with high pressure mass spectrometry, comprising the steps of:
- pulsing an ion beam of at least about 2 KeV at grazing incidence of between 45.degree. and 80.degree. to impinge said surface; and
- detecting the direct recoiled ions of element with a mass spectrometer having a time-of-flight sector comprising at least one linear field free drift tube and at least one toroidal or spherical energy filter with a +/- v polarization to deflect positive or negative ions; located at an elevation angle of about 0.degree. to 85.degree. and a channelplate detector for measurement of direct recoiled ions.
- 9. The method of claim 8, wherein said angle is 35.degree..
- 10. The method of claim 9, wherein said element measured is selected from the group consisting of H, He, Li, Be, B, C, N, 0, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, Cs, Ba, La, Nd, Gd, Tb, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Th and U.
- 11. The method of claim 8, wherein said pulsed ion beam is selected from the group consisting of Cs, Na, Li, B, He, Ar, Ga, In, Kr, Xe, K, Rb, O.sub.2, N.sub.2 and Ne.
- 12. The method of claim 8, wherein said pulsed ion beam is at least about 15 KeV.
- 13. The method of claim 12, wherein said ion beam is Cs.
- 14. The method of claim 8, wherein the pressure is from about 10.sup.-11 Torr to 1 Torr.
- 15. A method for quantitive measurement of elements on a surface with a high pressure mass spectrometer comprising the steps of:
- pulsing an ion beam of at least about 2 KeV at grazing incidence to impinge the surface;
- detecting positive or negative ions of elements recoiled from the surface with a first high resolution time-of-flight mass analyzer comprised of at least one linear field free drift tube and at least one toroidal or spherical energy filter with a +/- V polarization on the sectors of the filter to deflect positive or negative ions, wherein the outer sector of said filter contains a hole;
- detecting direct recoiled ions and neutrals with a second mass analyzer attached to the first mass analyzer and positioned to detect ions and neutrals exiting through said hole, wherein said second mass analyzer has a time-of-flight detector located at an elevation angle of 0.degree. to 85.degree., an electrostatic deflection plate to separate negative and positive ions and neutrals, and a channelplate detector with at least three anodes, said anodes detecting either direct recoiled negative or positive ions or neutrals;
- alternately collecting data on the first and second mass analyzers at time intervals ranging from 100 .mu.sec to 1 sec; and
- comparing the ion intensity from the first high resolution analyzer to the intensity of the neutrals and ions detected in the second analyzer used to obtain the ion fraction of the recoiled element.
- 16. The method of claim 15, wherein the elements are selected from the group consisting of H, He, Li, Be, B, C, N, 0, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, Cs, Ba, La, Nd, Gd, Tb, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Th and U.
- 17. The method of claim 15, wherein the angle is 35.degree..
- 18. The method of claim 15, wherein the pressure is 10.sup.-11 Torr to 1 Torr.
- 19. The method of claim 15, wherein said surface is coated with an overlayer.
- 20. The method of claim 19 wherein the overlayer is selected from the group consisting of hydrocarbons, carbon, gold, platinum, aluminum, oxides, frozen noble gases and molecular gases.
- 21. An apparatus for measuring recoiled and direct recoiled ions comprising:
- a sample chamber;
- an ion beam pulsing means for generating a pulsed ion beam, said pulsing means oriented at an angle to the sample chamber, wherein the pulsing ion beam impinges a surface of a sample in the sample chamber at a grazing incidence of about 45.degree. to 80.degree.;
- a first mass analyzer attached to the sample chamber at an elevation angle of about 0.degree. to 85.degree. relative to the sample and in the forward specular direction, said first mass analyzer having at least one field free drift tube and at least one toroidal or spherical energy filter with sector halves polarizable +/- V for the deflection of positive or negative ions and, wherein the outer sector of said filter includes a hole;
- a second mass analyzer for detecting direct recoiled ions and neutrals when the sectors of the first analyzer are grounded, said second analyzer having an electrostatic deflector and an ion detector containing three separate anodes, said ion detector attached to at least one field free drift tube of said first mass analyzer in a position to simultaneously detect ions and neutrals separated by the electrostatic detector, after said ions and neutrals exit through the hole in the outer sector of the first mass analyzer; and
- a computer system for regulating the frequency of pulsing and the collection of data from the first and second mass analyzers.
- 22. The apparatus of claim 21, comprising further at least one pulse sequencer attached to the first mass analyzer within at least one linear field free flight path.
- 23. The apparatus of claim 21, wherein the ion pulsing means includes at least about a 15 KeV alkali ion source, at least one adjustable slit attached between the ion source and the sample chamber for directing and focusing the ion beam emitted from the ion source and at least one pulser and lens attached between the ion source and sample chamber for generating a pulsed ion beam.
- 24. The method of claim 23, wherein said ion beam is selected from the group consisting of Cs, Na, Li, B, He, Ar, Ga, In, Kr, Xe, K, Rb, O.sub.2, N.sub.2 and Ne.
- 25. The apparatus of claim 23, further comprising a focusing lens to vary the divergence between 0.5.degree. to 3.degree., said lens attached between the pulser and the sample.
- 26. The apparatus of claim 21, wherein said second mass analyzer is at a scattering angle of 35.degree..
- 27. The apparatus of claim 21, further comprising a third mass analyzer for ion scattering spectroscopy said third mass analyzer having a time-of-flight tube with at least one channelplate detector attached to said sample chamber at a scattering angle of about 45.degree. to 180.degree..
- 28. The apparatus of claim 27, wherein said channelplate detector is at an angle of 78.degree..
- 29. The apparatus of claim 21, further comprising:
- a second ion beam; and
- at least one channelplate ring detector for detecting backscatter ions said channelplate ring detector positioned between the second ion beam source and sector containing a hole in the outer sector half and the sample, wherein direction of incidence of ion beam on the sample is normal to the midpoint of the diameter of said at least one anode ring of said channelplate ring.
- 30. The apparatus of claim 29 wherein said channelplate detector includes 10 concentric annuli rings, wherein each annular ring is 1/2 degree wide and said annular rings are positioned on a channelplate to detect 10 backscattering spectra covering an angle of about 165.degree. to 180.degree..
- 31. An apparatus of claim 21 further comprising:
- A fourth mass analyzer for detecting secondary ions at an angle of about +/- relative to the sample normal, said fourth mass analyzer having provisions for biasing the sample or analyzer to extract secondary ions and having at least one field free drift tube and at least one toroidal or spherical energy filter with sector halves polarizable +/- V for deflection of positive or negative ions, wherein the outer sector of said filter includes a hole; and
- A fifth mass analyzer for detecting scattered ions and neutrals, said fifth mass analyzer having an ion detector attached to at least one field free drift tube of the fourth mass analyzer in a position to detect ions and neutrals, exiting through the hole in the outer sector of the fourth mass analyzer.
- 32. The apparatus of claim 31, further comprising of at least one pulse sequencer attached to the fourth mass analyzer within at least one linear field free flight path.
- 33. An apparatus for ion scattering spectroscopy and secondary ion mass spectrometry comprising:
- a sample chamber;
- an ion beam pulsing means for generating a pulsed ion beam, said pulsing means oriented at an angle to the sample chamber, wherein the pulsing ion beam impinges a surface of a sample in the sample chamber at a grazing incidence of about 45.degree. to 80.degree.;
- a first mass analyzer for secondary ion mass spectrometry attached to the sample chamber at an angle of about 80.degree. to 180.degree. relative to the sample, said first mass analyzer having at least one toroidal or spherical field free drift tube and at least one toroidal or spherical energy filter with sector halves polarizable +/- V for the deflection of positive or negative ions, and wherein the outer sector of said filter includes a hole;
- a second mass analyzer for ion scattering spectroscopy, said second mass analyzer attached to at least one field free drift tube of said first mass analyzer in a position to detect ions and neutrals, exiting through the hole in the outer sector of the first analyzer; and
- a computer system for regulating the frequency of ion pulsing and the collection of data from the first and second mass analyzers.
- 34. The apparatus of claim 33, further comprising at least one pulse sequencer attached to the first mass analyzer within at least one linear field free flight path.
- 35. A device for high pressure real time stoichiometry measurements of a surface comprising:
- a sample chamber;
- an ion beam pulsing means oriented at an angle to the sample chamber generating a pulsed ion beam at a grazing incidence to impinge the surface of a sample in the sample chamber;
- a micro capillary gas doser to form a local area of high pressure on the surface;
- a first array of discrete detectors in the forward specular hemisphere to measure forward ion scatter from the ion beam impinging the surface, said first array including up to about 100 discrete detectors each defining a scattering angle of .+-.0.5.degree.;
- a second array of discrete detectors in the back specular hemisphere to measure the backward ion scatter from the ion beam impinging the surface, said second array including up to about 100 discrete detectors each defining a scattering angle of .+-.0.5.degree.; and
- a collection means to collect a multiplicity of time of flight data simultaneously from each detector in both the first and second array of discrete detectors.
- 36. The device of claim 35, wherein the primary angle of grazing incidence of the pulsed ion beam is about 45.degree. to 85.degree.; the angle of forward ion scatter is about 0.degree. to 90.degree. ; and the backward ion scatter is 90.degree. to 180.degree..
- 37. The device of claim 35, wherein the gas doser is of sufficient size to expose about a 100 .mu.diameter of the surface to a local pressure of up to about 100 Torr.
- 38. The device of claim 35 for determining the real time stoichiometry during high pressure surface modification, wherein the gas doser of claim 35 is replaced with a device for depositing thin films selected from the group consisting of elemental effusion source, molecular beam source, chemical beam source, sputter deposition source, laser ablation source, plasma assisted chemical vapor deposition source and atomic layer epitaxy source.
- 39. The device of claim 35 for determining the real time stoichiometry during high pressure modification, wherein the gas doses of claim 35 is replaced with an etching device selected from the group consisting of chemical beam source, ion sputtering source, plasma sputtering source, and laser ablation source.
- 40. The apparatus of claim 35 determining real time stoichiometry during the annealing process, further comprising a heating element in the sample chamber.
- 41. A device for performing DRS in a differentially pumped chamber comprising:
- a sample chamber, said chamber containing a first jacket with an entrance slit to allow access to the chamber by an ion beam and an exit slit to allow egress of the recoil or scattered ions, said slits further allow the sample chamber to maintain a pressure of 1 Torr; and
- a second jacket with entrance and exit slits similar to said slits in first jacket and, a pump to remove gas from the sample chamber and maintain differential pressure between the sample chamber and an ion beam and a detector chambers wherein said ion beam and detector chambers are less than 10.sup.-5 Torr.
- 42. A method of measuring elemental surface concentrations in real time comprising the steps of:
- impinging about a 100 .mu.diameter of a surface with a device for high pressure real time stoichiometry measurements, said device comprising a sample chamber, an ion beam pulsing means oriented at an angle to the sample chamber and generating a pulsed ion beam at a grazing incidence to impinge the surface of a sample in the sample chamber and a microcapillary gas doser to form a local area of high pressure on the surface;
- detecting the forward direct recoiled ion and neutral profile from the impinging step with a first array of discrete detectors in the forward specular hemisphere from the ion beam impinging surface, said first array including up to about 100 discrete detectors, each defining a scattering angle of .+-.0.50;
- detecting the low energy ion scattering from the surface with said first array of discrete detectors and with a second array of discrete detectors in the back specular hemisphere, said second array including up to about 100 discrete detectors, each defining in a scattering angle of .+-.0.50;
- sampling the ion scatter at the rate of about every 10 .mu.sec. to 1 sec. with a collection means that collects a multiplicity of time of flight data simultaneously from each detector in both the first and second array of discrete detectors; and
- analyzing the data selected from the group of direct recoil scattering, low energy ion scattering and a combination thereof.
- 43. The method of claim 42 for analyzing the real time stoichiometry during deposition of elements on the surface wherein the gas doser of the impinging step is replaced with a device for depositing thin films selected from the group consisting of elemental effusion source, molecular beam source, chemical beam source, sputter deposition source, laser ablation source, plasma assisted chemical vapor deposition source and atomic layer epitaxy source.
- 44. The method of claim 42 for analyzing the real time stoichiometry during etching of elements on the surface, wherein the gas doser of the impinging step is replaced with an etching device selected from the group consisting of chemical beam source, ion sputtering source, plasma sputtering source, and laser ablation source.
- 45. The method of claims 43 or 44 for the process control of surface modification, wherein the analysis is in real time stoichiometry during deposition or etching of elements on the surface and further comprising the step of:
- regulating the intensity of a plurality of deposition or etching sources by adjusting the intensity based on the real time stoichiometry sampling.
- 46. A method of determining the crystallography by blocking and shadowing analysis with a device for high pressure time stoichiometry measurements comprising the steps of:
- impinging a surface of a sample with said device, wherein said device comprises a sample chamber, an ion beam pulsing means oriented at an angle to the sample chamber and generating a pulsed ion beam at a grazing incidence to the surface of a sample in the sample chamber and a microcapillary gas doser to form a local area of high pressure on the surface;
- detecting the forward direct recoil ion and neutral profile from the impinging step with a first array of discrete detectors in the forward specular hemisphere, said first array including up to about 100 discrete detectors each defining a scattering angle of .+-.0.50;
- detecting the low energy ion scattering from said surface with a second array of discrete detectors in the back specular hemisphere, said second array including up to about 100 discrete detectors each defining a scattering angle of .+-.0.50;
- collecting the time of flight data simultaneously from each detector in both the first and second array of discrete detectors; and
- monitoring the ion beam scattering intensity as a function of scattering angle.
- 47. A method for calibrating a DRS or MSRI intensity comprising the steps of:
- inserting into a sample chamber a gas of known composition;
- pulsing an ion beam of at least about 2 KeV into said gas; and
- detecting the resultant ionized recoiled atoms of the gas.
CROSS REFERENCE TO RELATED APPLICATION
This Application is a continuation-in-part of Applicant's co-pending Application Ser. No. 433,482 filed Nov. 8, 1989 now abandoned.
FIELD OF THE INVENTION
The present invention relates generally to mass spectrometers for isotopic ratio determination, for measuring surface elements with and without contamination and for analysis in a high-pressure environment using time-of-flight instrumentation. The mass spectrometer measures both recoiled and direct recoiled ions. The invention also relates to the use of multiple time-of-flight mass spectrometers for simultaneously measuring and quantifying elements on the surface, for isotopic ratio determination, for secondary ion mass spectometry and for backscatter ion determination. The invention also relates to methods for measuring isotopic ratio determination, surface element measurements and quantitation using time-of-flight measurements and bombardment with a pulsed ion beam.
While secondary ion mass spectometry (SIMS) (particularly time-of-flight (TOF)/SIMS) is emerging as a powerful surface analytical tool, an inherent drawback for isotope identification results from isobaric interferences. Ubiquitous hydrocarbon signals, particularly from samples extracted from a biological milieu, provide signal at virtually every mass and make interpretation difficult. One does not know if the secondary ion intensity is from isotope or from hydrocarbon.
There are several other techniques being developed for measurement of isotopic abundances on surfaces. One is accelerator mass spectrometry. This technique avoids the complicated mass spectra associated with SIMS where a signal is seen at all masses from hydrocarbon fragments. Accelerator mass spectrometry strips the electrons from all molecular secondary ions resulting in their total fragmentation. Unfortunately accelerator mass spectrometry requires a fairly expensive and cumbersome apparatus.
Alternatives to accelerator mass spectrometry are laser based techniques for elemental identification. These experiments require vaporization of a solid material by either ion bombardment or laser ablation with subsequent photoionization of the vapor and mass analysis of the resulting elemental ions. The differences in the laser techniques for the vapor analysis depend upon the method of ionization, and upon the type of mass spectroscopy used. In one technique, a pulsed (10 Hz) high powered excimer laser is directed into the sputtered material. All atoms and molecules are ionized to some extent and mass analyzed by TOF. Although this approach ionizes the sputtered neutrals, its limitation with respect to isotope identification is identical to SIMS, for example, isobaric interferences.
A laser technique for specific elemental detection to circumvent isobaric interferences involves tuning a dye laser frequency until one or a multiple photon resonance with an electronic state of the desired element occurs. The photon absorption cross section, as resonance is approached, increases by orders of magnitude and subsequent photons can ionize all of the element in the laser focal volume (100% efficiency). Resonance ionization has been used to sensitively analyze for ppb levels of iron in silicon. While this is an elegant technique, one has several problems in applying this in a routine fashion. For one thing the apparatus is very complex and combines most of the hard experimental problems to be found in both surface science as well as laser physics. Another more subtle problem is that if a significant fraction of the element of interest is sputtered in molecular form, then it is invisible to the resonance technique. This can be a serious limitation. For example, during uranium (U) analyses in urine, as the ablation of the sample progresses, U changes oxidation state and is sputtered as UO.sub.2 instead of U. The resonance signal for U vanishes although uranium is still in the sample. An inherent limitation of the resonance ionization technique for isotopes is that the laser frequency must be changed to match each isotope of interest.
A criticism of TOF mass spectrometry is that in order to obtain high transmission and simultaneous identification of masses one sacrifices data throughput. If a narrow mass region is of interest, then the low duty cycle of TOF wastes a lot of time compared to a quadrupole or a magnetic sector instrument. The purging technique suggested in the present invention would seem to be particularly suitable as a way of eliminating this criticism. It will also be possible to perform this in other applications of doubly symmetric TOF systems such as TOF/SIMS.
All of our information about in-situ process chemistry has come from the gas phase (reactants), mostly using infrared spectroscopy. Previously, no method for observing reaction chemistry at the surface (products) was available. This is understandable, since surface science is difficult even under the best ultra high vacuum (UHV) conditions, and the electron-based surface spectroscopies (e.g. XPS, AES, UPS, HREELS) would be subject to scatter and attenuation by process gas. If implemented, the first three of these would be of little value because they are completely insensitive to hydrogen and isotopic variations, while the notoriously difficult HREELS is very slow, strictly qualitative and would be severely compromised b inelastic electron scattering by the gas ambient.
Typical conditions for diamond growth include a hydrogen:1% methane gas feed at 1 to 100 Torr, a substrate heated to about 950.degree. C., and "activation" by an incandescent filament or electric discharge. Generally accepted features of low pressure diamond process chemistry are that atomic hydrogen must be present, along with a small carbon bearing growth species. Methyl radical and acetylene appear from gas phase diagnostics to be the only growth candidates sufficiently abundant to account for observed growth rates. Speculations about the role of atomic hydrogen include (1) formation of methyl radical by abstraction, (2) suppressing formation of poly-aromatic hydrocarbons in the gas phase, and (3) etching graphitic deposits from the growth surface.
The critical role of the surface has largely been ignored theoretically, due to the lack of hard experimental data on it. The native surface of diamond is hydrogen terminated, and although UHV surface studies have shown diamond to desorb hydrogen and reconstruct at the usual growth temperatures, an implicit assumption in existing mechanistic theories is that diamond is fully hydrogen saturated under growth conditions. The degree of hydrogenation of the surface under process conditions has a large impact on growth mechanism theory, as the chemistry of saturated hydrocarbons and olefins are completely different. In keeping with this, atomic hydrogen has been assumed to activate the surface by H abstraction. Surface radical sites can reasonably react with either methyl radical (by recombination) or with acetylene (by polymerization). The subsequently required steps of cyclyzing pendant alkyl groups to extend the diamond lattice, and removing their excess hydrogen have also been ignored.
To solve the need for an efficient and inexpensive method, mass spectrometry of recoiled ions (MSRI) was developed into a general surface analysis technique. This method is complementary and in some ways superior to existing techniques for surface isotope and impurity analysis. MSRI should have a future in semiconductor analysis and in biomedical studies in which non-radioactive isotopic tracer analysis or trace elemental detection is desired.
The current understanding of the chemical mechanisms involved in low pressure chemical vapor deposition (LPCVD) of diamond is poor at best. In general, to characterize a chemical system, one needs information about both the reactants and the products. The present invention, high pressure direct recoil spectroscopy (DRS), solves these problems.
The inventors recognized that the energetic, massive particles used in ion beam analysis techniques would be relatively insensitive to gas phase attenuation. Thus, they developed DRS to observe the growing diamond surface in-situ, and resolve the above mechanistic issues.
An object of the present invention is a method for isotopic ratio determination on a surface.
An additional object of the present invention is detection of a variety of elements from the periodic table.
A further object of the present invention is the use of an ion beam of at least about 2 KeV to detect isotopic ratios on a surface of elements.
Further, an additional object of the present invention is a method of determining the elements on a surface with high pressure mass spectrometry.
Another object of the present invention is a device and method for measuring the surface during etching or deposition of the surface.
An additional object of the present invention is a method for the quantitative measurement of elements on the surface with a high pressure mass spectrometer.
A further object of the present invention is a method for process control during surface modification.
An additional object of the present invention is a mass spectrometer which simultaneously detects multiply recoiled and direct recoiled ions and neutrals, secondary ions, and back and forward scattered ions and neutrals.
A further object of the present invention is a method of determining crystallography by blocking and shadowing analysis.
Thus in accomplishing the foregoing objects, there is provided in accordance with one aspect of the present invention a method for isotopic ratio determination of elements on a metallic, semi-conducting or insulating surface comprising the steps of: pulsing an ion beam of at least about 2 KeV at grazing incidence between 45.degree. and 80.degree. measured relative to the surface normal to impinge said surface; and detecting the ionized elements directly recoiled from the surface with a high resolution time-of-flight mass spectrometer comprised of at least one linear field free drift tube and at least one toroidal or spherical energy filter with a +/- V polarization to deflect positive or negative ions. In the preferred embodiment, the ion beam is selected from the group of elements consisting of Cs, Na, Li, B, He, Ar, Ga, In, Kr, Xe, K, Rb, O.sub.2, N.sub.2 and Ne. In a more preferred embodiment, the ion beam is Cs and the ion beam is at least about 15 KeV. In another preferred embodiment, the surface which is being detected is coated with an overlayer and the overlayer is usually selected from the group consisting of hydrocarbons, gold, platinum, aluminum, oxides, frozen noble and molecular gases.
Another embodiment of the invention includes a method for determining the elements on a surface with high pressure mass spectrometry comprising the steps of: pulsing an ion beam of at least about 2 KeV at grazing incidence of between 45.degree. and 80.degree. to impinge said surface; and detecting the direct recoiled ions with a mass spectrometer having a time-of-flight sector located at an elevation angle of about 0.degree. to 85.degree. measured relative to the surface and in the forward direction and a channelplate detector for measurement of direct recoiled ions. In a preferred embodiment, the angle is 35.degree. and the pressure is from about 10.sup.-11 Torr to 1 Torr.
A further embodiment of the present invention is a method for quantitative measurement of elements on a surface with a high pressure mass spectrometer comprising the steps of: pulsing an ion beam of at least about 2 KeV at grazing incidence of between 45.degree. and 80.degree. to impinge the surface; detecting positive or negative ions of elements recoiled from the surface with a first high resolution time-of-flight mass analyzer comprised of at least one linear field free drift tube and at least one toroidal or spherical energy filter with a +/- V polarization on the sectors of the filter to deflect positive and negative ions, wherein the outer sector of said filter contains a hole; detecting direct recoiled ions and neutrals with a second mass analyzer attached to the first mass analyzer and positioned to detect ions and neutrals exiting through said hole, wherein said second mass analyzer has a time-of-flight detector located at an elevation angle of 0.degree. to 85.degree. and in the forward direction, an el deflection plate to separate negative and positive ions and neutrals, and a channelplate detector with at least three anodes, said anodes detecting either direct recoiled negative or positive ions or neutrals; and, alternately collecting data on the first and second mass analyzers at time intervals of 10 .mu.sec. to 1 sec. and comparing the neutrals and ions detected to obtain the ion fraction of the recoiled element.
In an alternative embodiment, a computer system is used for regulating the frequency of pulsing and the collection of data from the first and second analyzers.
In another preferred embodiment, a pulse sequencer can be attached to the first mass analyzer within at least one linear field free flight path.
A further embodiment of the present invention is an apparatus for measuring recoiled and direct recoiled ions comprising a sample chamber; an ion beam pulsing means for generating a pulsed ion beam, said pulsing means oriented at an angle to the sample chamber, wherein the pulsing ion beam impinges a surface of a sample in the sample chamber at a grazing incidence of about 45.degree. to 80.degree.; a first mass analyzer attached to the sample chamber at an elevation angle of about 0.degree. to 85.degree. relative to the sample surface and in the forward specular direction, said first analyzer having at least one field free drift tube and at least one toroidal or spherical energy filter with sector halves polarizable +/- V for the deflection of positive or negative ions and, wherein the outer sector of said filter includes a hole; a second mass analyzer for detecting direct recoiled ions and neutrals said second analyzer having an ion detector attached to at least one field free drift tube of said first analyzer in a position to detect ions and neutrals exiting through the hole in the outer sector of the first analyzer when the sector halves are both grounded; and a computer system for regulating the frequency of pulsing and collection of data from the first and second analyzers. In one preferred embodiment, the apparatus comprises further at least one pulse sequencer attached to the first mass analyzer within at least one linear field free flight path. Additional embodiments to enhance the system include: an ion pulsing means including at least about a 15 KeV alkali ion source; at least one adjustable slit attached between the ion source and the sample chamber for directing and focusing the ion beam emitted from the ion source and at least one pulser and lens attached between the ion source and sample chamber for generating a pulsed ion beam.
In one preferred embodiment, the apparatus includes a focusing lens to vary the divergence between 0.5.degree. to 3.degree., said lens attached between the pulser and the sample.
Another embodiment includes the apparatus with at least one additional mass analyzer for ion scattering spectroscopy, said mass analyzer having a time-of-flight tube with at least one channelplate detector attached to the sample chamber at a scattering angle of about 45.degree. to 180.degree..
An additional embodiment of this apparatus is the addition of at least one channelplate ring detector and a second ion beam source and sector containing a hole in the outer sector half positioned between the detector and the sample for detecting backscatter ions, wherein direction of incidence of ion beam on the sample is normal to the mid point of the diameter of said at least one channelplate ring. In the preferred embodiment, the channelplate detector includes an annuli of 10 concentric metal ring collectors where each annular ring is 1/2.degree. wide and said detector is positioned behind mounted dual channelplates to detect 10 backscattering spectra covering about 165.degree. to 180.degree..
In another embodiment, there is a fourth mass analyzer for detecting secondary ions at an angle of about .+-.30.degree. relative to the sample normal, said fourth analyzer having at least one field free drift tube and at least one toroidal or spherical energy filter with sector halves polarizable +/- V for deflection of positive or negative ions, wherein the outer sector of said filter includes a hole; and a fifth mass analyzer for detecting scattered ions and neutrals; said fifth analyzer having an ion detector attached to the at least one field free drift tube of the fourth analyzer in a position to detect ions and neutrals exiting through the hole in the outer sector of the fourth analyzer. This later embodiment can also have at least one pulse sequencer attached to the fourth mass analyzer within at least one linear field free flight path. In addition to this complete system of five analyzers, smaller systems including any combinations of the five analyzers can be added to form a system for detecting either ion scattering spectroscopy, secondary ion spectometry, direct and multiply recoiled ion spectroscopy and back scattering.
An additional embodiment is a device for high pressure real time stoichiometry measurements of a surface comprising: a sample chamber; an ion beam pulsing means oriented at an angle to the sample chamber generating a pulsed ion beam at a grazing incidence to impinge the surface of a sample in the sample chamber; a micro capillary gas doser to form a local area of high pressure on the surface; a first array of discrete detectors in the forward specular hemisphere to measure forward ion scatter from the ion beam impinging the surface, said first array including up to about 100 discrete detectors each defining a scattering angle of .+-.0.5.degree.; a second array of discrete detectors in the back specular hemisphere to measure the backward ion scatter from the ion beam impinging the surface, said second array including up to about 100 discrete detectors each defining a scattering angle of .+-.0.5.degree.; and a collection means to collect a multiplicity of time of flight data simultaneously from each detector in both the first and second array of discrete detectors.
Other embodiments of the above devices include replacing the gas doser with devices for depositing elements on the surface or devices for etching the surface. The chamber of the device can be differentially pumped.
A further embodiment is to use the devices to measure real time stoichiometry of the surface under various high pressure conditions which modify the surface being measured.
Other and further objects features and advantages will be apparent in the following description of present and preferred embodiments of the invention. Given for the purpose of disclosure and taken in conjunction with the accompanying drawings.
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Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
433482 |
Aug 1989 |
|
Patent Grant
5087815
