JPH06310063A - Parallel detection type energy loss analyzer - Google Patents

Abstract

PURPOSE:To measure an energy loss spectrum simultaneously with simple constitution by arranging a quadrupole lens at an inlet and an outlet of a magnetic field sector type prism, and dispersing and converging the energy loss spectrum. CONSTITUTION:An electron emitted from an electron source passes through a sample, and is made incident on a magnetic field sector type prism 6 through a quadrupole lens 5. The prism 6 has a magnetic field in the vertical direction to space, and as for an electron 15 whose energy loss is large, an orbit is bent in a small radius of curvature, and as for an electron 16 whose energy loss is small, an orbit is bent in a large radius of curvature, and the electron is dispersed by the energy loss. A quadrupole lens 7 regulates dispersion of a spectrum optionally, and projects it on a parallel detector 8. The lens 5 adjusts the focus on the detector 8. In this way, since the quadrupole lens is arranged at an inlet and an outlet of the sector type prism, an energy loss spectrum can be measured simultaneously with simple constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an electron beam source such as a transmission electron microscope, a scanning transmission electron microscope and an electron beam diffractometer, which irradiates a sample with electrons emitted from the electron beam source and transmits the sample. The present invention also relates to a device for performing image formation, analysis, etc. by utilizing electrons that have been elastically scattered or inelastically scattered.

[0002]

2. Description of the Related Art A successive detection type energy loss analyzer uses a magnetic field sector type prism to disperse an electron beam by its energy loss. A slit is provided at the exit of the prism so that only electrons with a specific energy loss can pass through. The magnetic field generated by the prism was sequentially changed, and the energy loss spectrum was measured while dividing each channel. 1 if the entire spectrum is 1024 channels
The signals for the other 1023 channels were discarded while the channel was being measured, which was very inefficient.

To overcome this shortcoming, a parallel detection energy loss analyzer has been developed as shown in US Pat. No. 4,743,756. The analyzer is a sector type prism that disperses the electron beam by energy loss. The exit of the prism is equipped with a plurality of quadrupole lenses, at least two of which adjust the energy width of the spectrum, and the other lens reduces the detection efficiency by converging electrons to the width of one channel of the detector. It is functioning to prevent it. In this way, the energy loss spectrum is imaged on the parallel detector and simultaneously measured.

The energy loss spectrum is roughly divided into a zero loss peak (energy loss = 0 eV), a low energy region (energy loss <50 eV) and a high energy region (energy loss ≧ 50 eV). Zero loss
The peak is a peak due to the electrons that have passed through the sample without losing energy. In the low energy region, plasmon peaks appear due to the structure of bound electrons in the valence band and ionization, and collective excitation of conduction electrons. Structures such as peaks and edges due to ionization of inner-shell electrons appear in the high energy region. Usually, the zero intensity peak is the strongest, which is about 10 times that of the next strongest plasmon, which may reach 10 ⁷ times the core excitation spectrum. The intensity distribution of the energy loss spectrum exceeds the dynamic range of the detector. Although there is no problem in measuring the inner shell excitation spectrum, when measuring the zero loss peak and plasmon, the detector was saturated and the spectrum of the correct shape could not be measured in some cases.

To solve this problem, the device (attenuator) shown in US Pat. No. 4,831,255 is attached. This device is installed between the final quadrupole lens and the parallel detector, and the AC magnetic field or the electric field causes the spectrum to be largely deflected vertically to the detector array, and the time during which the detector is substantially irradiated is 1 mse.
c. By adjusting the value to a certain level, it is possible to measure the spectrum without strong spectrum saturation. The device also serves to prevent detector burnout by the intense beam.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a parallel detection type energy loss analysis instrument having a simpler structure.

[0007]

The present invention is provided with an electron beam source such as a transmission electron microscope, a scanning transmission electron microscope, and an electron beam diffractometer, and irradiates the sample with electrons emitted from the electron beam source. A device for imaging, analysis, etc. using transmitted, elastically scattered, or inelastically scattered electrons is used in a magnetic field type sector type prism placed at the place where those electrons pass. One quadrupole lens is installed at the entrance and one at the exit. The spectrum detection is
It is carried out by means of detecting the energy loss spectrum in parallel, such as a diode array or CCD linear sensor.

[0008]

[Function] A sector type of magnetic field type equipped with an electron beam source, which irradiates the sample with electrons emitted from the sample, is transmitted through the sample, and is placed in the path of the elastically scattered or inelastically scattered electrons. The prism disperses the electron beam by its energy loss.

One quadrupole lens is attached to each of the entrance and the exit of the prism, and the quadrupole lens at the exit has a function of adjusting the dispersion by diverging a spectrum in the direction of the detector array. The polar lens has a function of converging the spectrum in the width direction of one channel of the detector (the vertical direction of the channels).

In the case where the zero loss peak or plasmon is saturated, in order to compensate for the lack of the dynamic range of the detector, the quadrupole lens is strongly excited, and the energy dispersion is the same, but the direction perpendicular to the dispersion. Is one of the detectors
It can diverge the spectrum over a wider range of channels.

When the spectrum is measured, the saturation of the detector can be avoided by measuring the spectrum with the shortest integration time peculiar to the detector regardless of the integration time set by the operator. This method may be used in combination if necessary.

The beam current on the detector is detected, and when the current exceeds the threshold value, the quadrupole lens is automatically excited strongly,
It is possible to diverge the spectrum over a wider range than the width of one channel of the detector. This makes it possible to protect the detector.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. The electrons emitted from the electron source 1 are controlled by the irradiation system 2 and irradiated onto the sample 3. The electrons transmitted through the sample 3 are magnified and imaged by the imaging system 4 in some cases. The main part of the energy loss analyzer is also shown in FIG. The magnetic field type sector type prism 6 generates a magnetic field in a direction perpendicular to the paper surface. Due to the magnetic field, the electrons 15 having a large loss of energy have a small radius of curvature, and the electrons 16 having a small loss of energy have their orbits bent with a large radius of curvature. The quadrupole lens 7 arbitrarily adjusts the dispersion of the spectrum and projects it on the parallel detector 8. The quadrupole lens 5 is focused on the parallel detector 8. FIG. 3 shows a ray diagram in the direction perpendicular to the energy dispersion.

The parallel detector 8 has a structure in which detector elements such as a photo diode array are arranged in a line, and it is possible to simultaneously measure the entire spectrum.

The magnetic field type sector type prism 6, quadrupole lens 5 and quadrupole lens 7 are integrated by a computer 11 by a prism controller 13, a prism entrance quadrupole lens controller 12 and a prism exit quadrupole lens controller 14, respectively. It is controlled under optimal conditions.

FIG. 4 shows an example of the relationship between excitation of a quadrupole lens and velocity dispersion. Energy dispersion has a lens constant of -3
It increases until it reaches a maximum at 50, and decreases under stronger conditions. Therefore, for example, −310 and −400 take the same value of velocity dispersion.

FIG. 5 shows an example of the relationship between the excitation of the quadrupole lens and the aberration coefficient in the direction perpendicular to the energy dispersion. It can be seen that the aberration is small up to a lens constant of −350, but increases sharply when it exceeds that. Since the aberration is small at −310, the spectrum fits within the width of the detector 8. However-
At 400, the aberration is considerably large, and the spectrum is detected by the detector 8
Will diverge more than the width of. Therefore, when the spectrum is measured with this dispersion, the lens constant is usually set to −310. However, if the intensity of the spectrum is too strong and the detector saturates, set the lens constant to −
It is also possible to switch to 400 and measure so that most of the signal does not enter the detector.

In the embodiment of FIG. 1, the beam current on the parallel detector 8 is detected by the minute ammeter 10 through the amplifier 9 and used as a control signal for switching the lens condition. The lens conditions may be switched manually.

[0019]

INDUSTRIAL APPLICABILITY The present invention has a simpler structure than that described in US Pat. No. 4,743,756 and enables simultaneous measurement of energy loss spectra.
Even if the device as described in US Pat. No. 4,831,255 is not attached, the same function can be obtained only by the quadrupole lens condition.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of an energy loss analyzer.

FIG. 3 is a diagram showing a horizontal ray diagram in a normal state.

FIG. 4 is a diagram showing an example of a relationship between excitation of a quadrupole lens and velocity dispersion.

FIG. 5 is a diagram showing an example of a relationship between excitation of a quadrupole lens and an aberration coefficient in a direction perpendicular to dispersion.

[Explanation of symbols]

1 ... Electron source, 2 ... Irradiation system, 3 ... Sample, 4 ... Imaging system, 5 ...
Quadrupole lens, 6 ... Magnetic field type sector type prism, 7 ... Quadrupole lens, 8 ... Parallel detector, 9 ... Amplifier,
10 ... Micro ammeter, 11 ... Computer, 12 ... Prism entrance quadrupole lens control device, 13 ... Prism control device, 14 ... Prism exit quadrupole lens control device, 15 ...
Electron beam with large energy loss, 16 ... Electron beam with small energy loss.

Claims (7)

[Claims] 1. A quadrupole lens is provided at each of the entrance and exit of a sector type prism, and means for detecting the energy loss spectrum in parallel, such as a photodiode array or a CCD linear sensor, is provided. Characteristic parallel detection type energy loss analyzer. 2. The quadrupole lens at the exit has a function of adjusting the dispersion by diverging the spectrum in the direction of the detector row, and the quadrupole lens at the entrance has a width of one channel of the detector. A parallel detection type energy loss analyzer having a function of converging a spectrum in a direction (vertical direction of channels). 3. The lens condition according to claim 2, wherein when the quadrupole lens is further strongly excited, a spectrum can be broadly diverged in the width direction of one channel of the detector,
A parallel detection type energy loss analyzer characterized by utilizing such a lens condition. 4. The lens condition of claim 3 having the same energy dispersion as the lens condition of claim 2 is stored as a pair, and the former is used in the normal case, but the latter condition is used when the spectral intensity is too strong. A parallel detection type energy loss analyzer having a switchable function. 5. The parallel detection type energy according to claim 3, wherein when the spectrum is measured, the spectrum is measured with the shortest integration time peculiar to the detector regardless of the integration time set by the operator. Loss analyzer. 6. A parallel detection type energy loss analyzer characterized in that the lens condition of claim 3 and the integration time of claim 4 are used together. 7. The parallel detection type energy loss analysis according to claim 1, wherein the beam current on the detector is detected, and when the current exceeds a threshold value, the function of claim 3 is automatically activated. vessel.