JPS60189857A - Energy analyzer in electron microscope or the like - Google Patents

Abstract

PURPOSE:To invariably obtain a high-resolution energy spectrum or an electron microscope image by switching the exciting currents of a lens in response to the switching of energies. CONSTITUTION:A voltage signal proportional to the main exciting current Iso from a main power supply 10a and a voltage signal proportional to the sweep current Is from a sweep power supply 10b are fed to a dividing circuit 18. A voltage signal from the circuit 18 is fed to a multiplying circuit 19. A reference signal generating circuit 20 generates a reference voltage signal in response to the exciting current of an incident lens 16 when the energy of an incident electron beam is Eo. This reference voltage signal is fed to an adding circuit 21 to be added to the output voltage signal of the circuit 19, and an outgoing lens 16 is excited in proportion to the output voltage of the adding circuit 21. Accordingly, a high-resolution energy spectrum or an electron microspcope image can be invariably obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for analyzing the energy of an electron beam transmitted through sample 1'Nl and for displaying a sample image based on an energy-filtered electron beam.

Figure 1 IJ is an energy analyzer that shows the energy analysis device attached to a conventional electron microscope, etc., and focuses the electron beam 2 from the electron gun 1 to the sample 4. Teru QJ, trial 1
31 /I) is guided through the objective lens 5, the intermediate lens 6, and the projection lens 7 to the spectrum 1~['' meter 8, where the electron beam is energized. Distributed according to the issue, 1
! 10a is the main power supply for supplying the main current to the main coil 11ε1 of the spec l-1:1 meter 8, and 10b is This is a swinging power supply for supplying 1!l) bright current to the energy supply coil 11b.

From this oscillating current Δj;
If the output signal from the detector 13 associated with this L% discount is supplied to the recorder A112, and the recorder 12 is synchronized with this energy and UIM is subtracted, energy 1! −
Subekle can be displayed. In addition, 9 is the required aperture,
14 is an amplifier. C1 J5° to such a device
C is the energy dispersion power δ is the spectrum [L of 1 meter
J is determined by the following relational expression depending on the energy molecule ik function 1) and the width of the output aperture.

δ-=1. /D...Pa (1) However, 1μrTl culm stone is the limit due to the 1:N limit on the mechanical precision of t LL C1. 1, -me, δ is uniquely determined by D. That's the reality. Therefore, D
When using a high-acceleration electric current 1t11,'l or a small Svek 1-11 meter with a small / 'aHut''J. However, in such a conventional device, the excitation and current of the exit lens 16 are identified (therefore, when the energy selected by the spectrometer changes, the band (onto Surin 1-15 which emits electrons to form a spectral image)
There were cases in which A-resolution was not possible, and it was not possible to obtain a high-resolution spectrum.

As shown in Figure 2, the electron beam that forms 1-4 in the electron microscope image is guided into the spectrometer 8, and only electrons with a specific energy are selected. The electron microscope image 11J is magnified by the lens 16 and projected onto the fluorescent screen 17 to produce the electron microscope image K.
There is also a device t1 in which the excitation current of the exit lens 16 is fixed, so depending on the energy set by the sweep current 10b, the exit lens 1G is 2 to fluorescent screen 17
In some cases, it was not possible to form an image at 6F.

It is an object of the present invention to solve these conventional drawbacks and provide an energy analysis device for an electron microscope or the like that can obtain high-resolution spectra or electron microscope images.

The above explains the basic idea of the present invention.

If the negative and charge terms of the electron are 111 and e, respectively, and the strength of the magnetic field in the spectrometer is B, then the spectrum is 1.
- The ilA core radius r of an electron moving 1J to the right of the velocity peak V in the rometer is expressed as r= (mv)/(eB) (2)C. The IJI ratio of electron energy e and velocity V is c2/(mv) = - c/ (2mo V (1+9.787xlO-7V)
) - (3> and I'. However, mO is the rest mass of the electron, and ■ is the acceleration mass. What is the relationship between the magnetic field strength B in the spectrometer, I - excitation F1 current 1so? , /lO is the magnetic permeability of di°1, and 1- is the vA interpole distance island of the spectrometer ゛1.] is the number of excitation turns, then 1'3 = (tto / L-) IsoT...
(4) CJ is accepted. From equations (2>, (3), and (4), the energy of the electron λ() is calculated by using the above-mentioned main excitation current 1so of the Svek 1-I-1 meter in the name of the Adon λ・j theory abstraction. -C(μor-1-1so) 2/ (2mo L2
)-(5). Now, when the energy of the incident electron changes (S), the excitation current 11
In the electron lens used at
11 is the amount of change in excitation current, G[ is the longitudinal chromatic aberration coefficient, Cm
If is the 18th chromatic aberration coefficient, Cr is the rotational chromatic aberration coefficient, α is the listening angle of the electron, and LJa is the distance from the center of the electron orbit in the 11th plane, then the lens current is given by ΔE/Fo=2 ( Ilo-Tlo)/Ilo...
If the current 11 is changed to a value that satisfies (7), no chromatic aberration will occur. Now, if the current (111) supplied by the working power source of the spectrometer is equal to ISO, from equation (5), ΔE/Eo = (Is 2 - lSO2) / l5
o2... (8) Therefore, from formulas (7) and (8), the lens excitation current (1) to prevent chromatic aberration is If = Ilo + (Is'2 - l5o2)/
(21so2)...(9) It can be seen that it is given by the following. Therefore, by detecting the main excitation current ISO and sweep current IS of the spectrometer and supplying the lens current 11 calculated by equation (9) based on them to the lens, 61 will always be accurate no matter which energy is selected. A focused image can be obtained.

The present invention provides an electron gun, a means for transmitting an electron beam from the electron gun into a sample A: 1 in the air, and a means for transmitting an electron beam through the sample 1 and transmitting an electron beam rf'i. ! 'i, 1 spectral A'-meter for dispersing; a means for switching the energy of electrons to be selected for the spectral meter; - a device equipped with a lens etc. disposed after the chromometer and for enlarging the subekir image or the image based on the electron beam generated by the subek 1~rometer; The switching means is provided with means for switching the excitation current of the lens in conjunction with the switching of the energy.

1., -L 'rd'r shi/, : , then j,
(The following is an example of the present invention.

In FIG. 33 showing an embodiment of the present invention, 471. For component A;, the same number is set f]. What about 18? l'l "γ circuit is present, this divider circuit 18 has a main excitation current of 1s
Proportional to o
A voltage No. 45 proportional to the working current TS of , , and ri is supplied. The voltage 1 signal from this divided `lI 1 B is supplied to the 110) circuit 19. Reference numeral 20 denotes a reference signal generation circuit, and this reference signal generation circuit 20 is used to generate the lens 1 when the energy of the electron beam equal to 80.1 is [0].
A reference voltage signal corresponding to the excitation 711 flow 11o of No. 6 is generated. This lead; j t%1. The electric current fix is supplied to the adder circuit 2'1, where it is added to the output voltage im of the multiplier circuit 19, and the output voltage of the adder circuit 2'1 is proportional output q4 lens 16
is now energized.

411 like this. In H configuration (13 and 14) phase power supply 1
The energy of the selected electron is 1. ■It is pulled. Now, at this time, the output signal of the dividing circuit 18 is Is/IS
Since it is proportional to O, the multiplication circuit 19 has Is/
Since a voltage signal proportional to Iso and a voltage signal proportional to excitation current ■to from the reference signal generation circuit 20 are supplied, the output of the multiplication τ) circuit 19J is llo IS/IS.
It is proportional to O. On the other hand, the interference circuit 21 is supplied with a signal Y in proportion to the signal Y generation circuit 20J.
The output of h circuit 21, 10 is l 1o-i 1 lo・
A roar proportional to ls, /lso. Therefore, to set the circuit constants, the excitation current 11 flowing through the QJ lens 10 is expressed as l 1 = l to−+1to・
Is/Iso...(10) To take? (-Saru.

On the contrary, the right side of the above equation (9) becomes approximately 110+110・is/lso when Is is small. Even if the output slit 150 is employed, a band spectral image can always be focused on the exit slit 150. Therefore, a spectrum with a resolution of 1':i can be displayed on the recorder 12.

In addition, in the embodiment described above, a3 is shown in FIG.
An example in which the present invention is applied to an energy analysis device such as an electron microscope has been described. The present invention can be similarly applied to conventional devices of the type shown in FIG.

In addition, in the above explanation, an example in which the present invention was applied to a device using a so-called lid-type spectrum IJ meter was explained, but it can also be applied to a device using a so-called ω-type spectrum L1 meter. The present invention is equally applicable.

”It is clear from the explanation that J, uni, that the present invention has 1.
According to the L-based device, it is possible to always obtain an energy spectrum with an i:71 resolution or a microscopic image of 4.L electrons!!1 by switching the energy selected. .

[Brief explanation of the drawing]

Figures 1 and 32 are diagrams for explaining the conventional device;
FIG. 3 is a diagram showing one embodiment of this Y5 light. 1: Electron gun, 2: Electron beam, 3: Focusing lens system, 4: Testing, 5: Objective lens, 6: Intermediate lens, 7: Projection lens,
8: Spectrometer, 9: Inlet/1 aperture, 15: f
Fl! )l slit, 10a: main power supply, 10b: l
/i) Reference power source, 11a: Main coil, 11b Second reference coil, 12: Recorder, 13: Detector, 14: Amplifier, 1
6: Output lens, 17: Fluorescent plate, 18 20% bell circuit, 19
: Multiplication circuit, 20: Reference I5] generation circuit, 21: Addition circuit.

Claims (1)

[Claims] The electron gun and the electron gun J: Focus the electron beam of the sample
Nisho! A means for covering J=1, a spectrometer for transmitting the electric J-rays transmitted through the sample by 11'I, and a means for covering J: 1 to the spectrometer.
7. A means for switching the energy of the electrons to be produced, and a lens disposed after the spectrometer and for enlarging the image based on the electron beam selected by the spectrometer in the spectral image. ／、：
An energy analysis device for an electron microscope or the like, characterized in that the device includes a means for switching the excitation current of the lens in conjunction with switching of energy by the switching means.