JPH0535541B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention measures the energy distribution of particles scattered from the material surface at a scattering angle of approximately 180° while scanning an incident ion beam two-dimensionally on the material surface. death,
This field relates to ion scattering spectroscopic microscopy for analyzing the local chemical composition and atomic arrangement of material surfaces.

[Conventional technology]

Conventionally used ion scattering spectrometers perform energy analysis of scattered ions by colliding an ion beam with a sample and deflecting the trajectory of the scattered ions generated by this using a magnetic field or an electric field. Ion scattering spectrometers that focus an ion beam and scan it over a material surface observe ions scattered at a scattering angle much smaller than 180° (maximum 135°).
In such a scanning type ion scattering spectrometer, the scattering angle is much smaller than 180°, so only ions that collide with a position shifted from the center of each atom on the surface can be observed at the scattering angle (≪180°). The ions that collide with the center of the atom are scattered at 180 degrees and are not observed. Therefore, with conventional devices, it is difficult to obtain direct information regarding the center position of surface atoms, which complicates the analysis of the atomic arrangement on the surface.

Further, typical instruments that can observe the composition distribution on the surface of a material include the scanning Auger electron microscope (SAM) and the electron probe microanalysis (EPMA). Both of these methods use electrons as incident particles; the former detects Auger electrons, and the latter detects characteristic It is obtained as an image. However, the former gives information about the composition averaged over a depth from the surface of about 10 Å and the latter about μm, so it is not possible to give accurate values about the composition of the outermost layer of the surface, and because of this, the structure of the surface It has the disadvantage that it is difficult to analyze.

[Means for solving problems]

The above problems are related to the pulsed ion beam generation means that generates the pulsed ion beam that is incident on the material surface, and the energy of particles (ions and neutral atoms) scattered at a scattering angle of approximately 180° with respect to the pulsed ion beam. a time-of-flight measurement type energy analyzer for measuring distribution; a focusing lens for focusing the pulsed ion beam; a scanning deflector for deflecting the pulsed ion beam to two-dimensionally scan the material surface; and the pulsed ion beam. a vacuum container having an opening through which the beam and the scattered particles pass, the pulsed ion beam generating means, a detection section of the energy analyzer that detects the scattered particles, the focusing lens, and the scanning deflector. This problem is solved by the ion scattering spectroscopic microscope of the present invention, in which the ion scattering spectroscope and the ion scattering spectroscope of the present invention are installed coaxially.

[Effect]

The ion beam focused by the focusing lens is deflected by the scanning deflector and spreads over the material surface in two directions.
Scan dimensions. At this time, an energy analyzer performs energy analysis of the particles scattered at a scattering angle of approximately 180° with respect to the incident ion beam.

〔Effect of the invention〕

(1) Ion scattering microscopy detects particles scattered on the material surface, so it is extremely sensitive to the outermost surface layer compared to scanning Augier electron microscopy (SAM) and electron microprobe analysis (EPMA). The local distribution of the composition of can be analyzed.

(2) Since the incident ion beam source and the detection part of the scattered particle energy analyzer are coaxially arranged, the device can be integrated into a compact unit, and only a single port into the sample chamber is required to view the sample. For example, the microscope of the present invention can be attached.

(3) Since particles scattered at the material surface are observed at a scattering angle extremely close to 180°, information about the center position of atoms on the surface can be obtained, making it easy to quantitatively analyze the structure of the surface. I can do it.
In addition, since we observe only the particles that are scattered by following the incident trajectory almost in the opposite direction, the scattering of the incident ions on the material surface can be regarded as one-time scattering.
Analysis becomes significantly easier.

〔Example〕

Hereinafter, the present invention will be explained in more detail according to Examples. FIG. 1 is a schematic diagram of an embodiment in which the energy distribution of scattered particles is measured using a time-of-flight energy analyzer. Inside the vacuum container 1 having an opening A at one end, there is an ion gun I which is an ion source that generates an ion beam IB, a detection part D of a time-of-flight energy analyzer whose axis is aligned with the ion gun I, and an ion gun I that is an ion source that generates an ion beam IB. An ion focusing lens EL and deflectors DX and DY for scanning in the X and Y directions perpendicular to the traveling direction of incident ions are housed. A time-of-flight energy analyzer consists of a detector that detects scattered particles, a drift tube DT, and electronics that measure the time it takes for the scattered particles to fly through the drift tube. Container 1 is connected at opening A to port P of sample chamber C. The ion gun I can generate rare gas ions such as He ⁺ , Ne ⁺ , Ar ^+, etc. or alkali metal ions such as Li ⁺ , Na ⁺ , K ^+, etc., and the ion energy is 100 ~
It is about 10000eV. Slits S ₁ and S ₂ are arranged between the ion gun I and the detection section D, and a beam chopping plate CP for pulsing the ion beam is further provided between these slits S ₁ and S ₂ . is set up. This beam jumping plate
The CP consists of parallel plate electrodes spaced about 5 mm apart, between which a pulsed square wave voltage of a constant frequency is applied by a pulse generator PG.
Therefore, the ion beam IB passing through the slit _S1
is periodically deflected and passes intermittently through the slit _S2 , thereby forming a pulsed ion beam. Deflection plates _D1 and _D2 are provided between the beam chopping plate CP and the slit _S2 , and the ion beam is deflected in the X and Y directions by changing the voltage of the deflector power supply DS. The trajectory of the ion beam is made to coincide with the approximately 0.5 mm small hole in the slit _S2 . The detection part D of the time-of-flight energy analyzer is 2 mm from the center axis.
Two microchannel plates 3 with holes are used. This microchannel plate 3 is a bundle of many thin glass tubes whose inner walls are coated with a secondary electron emitting material, and accelerates secondary electrons generated by the impact of scattered ions within the microchannel plate 3. Out of necessity,
A high voltage is applied to both ends of the microchannel plate 3 by a high voltage power supply 7. On the central axis of the detector D, there is a collimator 4 for introducing incident ions.
is inserted, and the collimator 4 is grounded to shield it from the electric field due to the above-mentioned high voltage, and is insulated from the detector D by an insulator. Furthermore, a grounded grid 2 is placed in front of the detector D, surrounding the collimator 4, so that the high electric field due to the above-mentioned high voltage does not act on the incident ion beam exiting the collimator 4. Note that the sample S is attached to a manipulator that can rotate on two axes.

The ion scattering spectroscopic microscope configured as described above operates as follows.

The ion beam IB emitted from the ion gun I is made into a pulse by a combination of a pulse generator PG, a beam chopping plate CP, and a slit _S2 , and a trigger circuit TC generates a square wave that is applied to the beam chopping plate CP. A start signal is input to the time-to-wave height converter 8 with the time at which the voltage generates a pulse of incident ions as the starting point for time-of-flight measurement. The pulse of incident ions passes through the collimator 4, is focused by the focusing lens EL in the drift tube DT, is deflected in the X and Y directions by the deflectors DX and DY, and is scanned over the surface of the sample S. Among the ions scattered by surface atoms of the sample, particles scattered at a scattering angle extremely close to 180° pass through the same drift tube DT as the incident ions, but in this case, the deflectors DX and DY and the focusing lens EL The voltage applied to these is made into a pulse by a gate circuit GC that controls switching of the beam scanning power source 11 and the focusing lens power source 12 so as not to affect the scattered ions. Figure 2 shows the focusing lens EL and deflector DX that operate in conjunction with the generation of pulses of incident ions.
A time correlation diagram of the voltage applied to DY is shown.
The focusing lens EL and deflectors DX and DY maintain the set voltage for the time T ₀ from when the pulse of incident ions leaves the beam chopping plate CP to when it reaches the sample S. After reaching the point, the gate circuit GC controls the voltage so that it remains zero until the next pulse of incident ions starts. The aforementioned scattered ions thus proceed through the electric field-free drift tube DT, pass through the grid 2, and are detected by the detection unit D, and this detection signal is sent to the time-to-wave height converter 8 via the amplifier AMP to the final point of time-of-flight measurement. It is input as a stop signal. The time difference between the start signal and the stop signal is measured as a time of flight T by the time-to-peak converter 8 as an analog quantity, which is converted from analog to digital in the pulse height analyzer 9, and the horizontal axis shows the time of flight T; The numbers are accumulated on a histogram with the number of scattered particles detected on the vertical axis.
The computer 10 reads these data and subtracts the known value of the flight time _T0 of the pulse of incident ions to the sample S from the flight time T, thereby obtaining a time-of-flight type from the sample S as shown in FIG. The flight time T _L of the scattered particles traveling the flight distance L to the detection part D of the energy analyzer is determined, and the flight time spectrum of the scattered particles with respect to the flight time T _L as shown in FIG. 3 is stored.

At the same time as the flight time measurement described above is carried out, the computer 10 controls the beam scanning power supply 11 every time a pulse of the incident ions is generated to scan the pulse of the incident ions on the sample S. By calculating the scanning position of the incident ion on the sample S by the computer 10 and recording the time-of-flight spectrum of the scattering particles at each minute part of the surface of the sample S together with the scanning position of the incident ion, the composition distribution on the sample surface can be determined. can be analyzed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of an ion scattering spectroscopic microscope according to the present invention, FIG. 2 is a timing diagram explaining the operation of the embodiment shown in FIG. 1, and FIG. Time-of-flight spectrum of the resulting scattering particles. I... Ion gun, IB... Incident ion beam,
S ₁ , S ₂ ... Slit, CP ... Beam chopping plate, D ₁ , D ₂ ... Deflector, S ... Sample,
EL... Lens for beam focusing, DX, DY... Deflector for beam scanning, D... Detection unit of energy analyzer, DT... Drift tube, L... Flight distance of scattered ions, C... Sample chamber, P...Port, A...Opening, PG...Pulse generator, TC...
...Trigger circuit, GC...gate circuit, AMP...amplifier, DC...power supply for deflector, 1...vacuum container,
_T0 ...Flight time for incident ions to reach the sample, T _L ...Flight time of scattered ions, 2...Grid, 3...Microchannel plate, 4
... Collimator, 7 ... High voltage power supply, 8 ... Time -
Wave height converter, 9... Wave height analyzer, 10... Computer, 11... Beam scanning power source, 12...
Power supply for lens.

Claims (1)

[Claims] 1 Pulsed ion beam generation means that generates a pulsed ion beam that is incident on the material surface, and time-of-flight energy analysis that measures the energy distribution of particles scattered at a scattering angle of approximately 180 degrees with respect to this pulsed ion beam. a focusing lens that focuses the pulsed ion beam, a scanning deflector that deflects the pulsed ion beam and scans the material surface in two dimensions, and the pulsed ion beam and the scattered particles pass through. A vacuum container having an opening, the pulsed ion beam generating means, the detection unit of the energy analyzer for detecting scattered particles, the focusing lens, and the scanning deflector being coaxially installed. Scattering spectroscopic microscope.