JP2000187078A - Radiation detecting device, electron microscope and measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting device which reduces the influence of an external noise and whose sensitivity is high by a method wherein a signal processing circuit is controlled and the input of a signal from a preamplifier circuit is inhibited temporarily. SOLUTION: Whenever X-rays are incident on a detecting element 101 and a detecting element 102, the waveform of the output voltage of a preamplifier circuit 31 and that of the output voltage of a preamplifier circuit 32 rise stepwise. When the voltages become 0 V, they are reset to a certain negative value so as to become a sawtooth waveform. The waveform of the output voltage of the preamplifier circuit 31 and that of the voltage of the preamplifier circuit 32 are differentiated by a differentiating circuit 61 and a differentiating circuit 62. A control-signal generation circuit 71 generates a control signal used to operate a pulse-height analytical circuit 53 and a pulse-height analytical circuit 54. That is to say, when the preamplifier circuits 31, 32 are in a reset state, or when a vibration level detected by a vibration detector 65 becomes a set level or higher, the input processing operation of the pulse-height analytical circuit 53 and that of the pulse-height analytical circuit 54 are inhibited temporarily, and signal information which is input is ignored. Thereby, in a resetting operation, an unexpected electromagnetic radiation noise or the like is excluded, and an intrinsic spectrum is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for irradiating a sample with charged particles such as an electron beam or X-rays and detecting or analyzing characteristic X-rays or fluorescent X-rays generated with high sensitivity and high accuracy.

[0002]

2. Description of the Related Art Characteristic X-rays or fluorescent X-rays have the characteristic energy of the elements constituting a sample, and are irradiated with charged particles such as electron beams or X-rays to the sample, and the characteristic X-rays emitted from the sample are emitted. There is a method of performing elemental analysis of a sample by detecting X-rays or fluorescent X-rays. In order to perform elemental analysis, it is necessary to count the number of X-rays generated per unit time for each X-ray energy. As a means for detecting X-rays, a semiconductor detection element using a semiconductor crystal such as silicon or germanium is generally used at present.

FIG. 10 shows a typical configuration of a radiation detecting apparatus using the above semiconductor detecting element. Here, the section of the storage container 231 is shown in a cross section to clearly show the internal structure. The radiation detecting apparatus includes a storage container 231, a semiconductor X-ray detection element 101 installed in the storage container 231,
A preamplifier circuit (not shown) including a circuit stored in the preamplifier circuit box 33, a field effect transistor, a light emitting diode, and a feedback capacitor stored in a ceramic container 238; a cooling device 70; a cooling rod 234; It comprises a metal net 235, a shaping amplifier circuit 51, and a wave height analyzer 53.

In FIG. 10, the inside of the storage container 231 is sealed in a vacuum. The detecting element 101 and the ceramic container 32 are cooled to less than minus 150 degrees Celsius. The semiconductor detection element 101 has a diode structure having electrodes facing each other, and a voltage is applied in the opposite direction. A depletion layer is formed inside the detection element 101 by the reverse voltage.

By irradiating the sample 299 with the electron beam 202, the sample emits the characteristic X-ray 1. Characteristic X-ray 1
Is transmitted through the X-ray transmission window 232 and enters the depletion layer, thereby generating secondary electrons (not shown). The secondary electrons lose energy, and a number proportional to the energy of the incident X-rays is lost. Generate electron-hole pairs. The generated electron-hole pairs move toward the electrodes due to the electric field between the electrodes, and are extracted as signals. The number of electron-hole pairs generated is from 200 electron volts to 20 kiloelectron volts energy X
About 50 to 5000 lines.

Hereinafter, a method of processing a signal obtained by the detection element 101 will be described. The electrons reaching the electrodes of the detection element 101 are converted into voltage pulses 220 having a height proportional to the number thereof by a charge integration type preamplifier circuit. It is filtered high and shaped into a voltage pulse 310. The voltage pulse 310 is subjected to wave height analysis by the wave height analyzer 53, and is converted into an X-ray spectrum 400.

[0007] Due to the statistical fluctuation of the generated electron-hole logarithm and the noise of the preamplifier circuit, the height of the voltage pulse 310 for X-rays of a certain energy is not constant but varies. Therefore, the spectrum 400 obtained by the wave height analyzer 53 has a certain width 410. Spectrum 4
The width 410 of the spectrum at half the value of the peak value of 00 is called energy resolution. High energy resolution,
In other words, the smaller the width, the higher the signal-to-noise ratio and the better the separability of the spectrum from various elements, enabling more precise elemental analysis.

FIG. 11 is a circuit diagram of a preamplifier circuit, which shows IEEE Transaction on Nuclear Science.
Science) 1971, Vol. 18, No. 1, pp. 115-124. 11, 1 is an incident X-ray, 2 is a field effect transistor, 4 is a light emitting diode, 6 is a feedback capacitor, 8 is an operational amplifier circuit, 41 is a power supply, 55 is a gain adjustment circuit, 101 is a detection element, and 115 is a transistor 2 , The drain 116 is the gate of the transistor 2, 11
7 is the source of transistor 2, 118 is ground, 150
Is the light from the light emitting diode 4, and 200 is the output point of the preamplifier circuit.

As shown in FIG. 11, the preamplifier circuit according to the above-described method includes a field effect transistor 2 which is an input stage of a signal from a detection element 101 for detecting an X-ray 1, a light emitting diode 4 disposed in the vicinity thereof. It comprises a feedback capacitor 6, an amplifier circuit 8 for amplifying a signal from the field effect transistor 2, and a comparator circuit 55.

FIG. 12 is a waveform diagram showing the output of the preamplifier circuit according to the above-mentioned method with respect to a certain X-ray input. In FIG. 12, 110 is an X-ray incident waveform, 220 is a preamplifier output signal, 221 is a step, and 223 is a reset signal. The operation principle of the preamplifier circuit will be described with reference to FIG.
Consider the incidence of X-rays shown in waveform 110. The waveform 110 indicates that X-rays are incident when the line is standing. The charge generated by the detection element 101 due to the X-ray incidence is accumulated in the feedback capacitor 6, and the voltage at the output point 200 of the preamplifier increases stepwise as shown by the waveform 220. The step 2 of the step-like waveform 220 is determined by the circuit at the subsequent stage.
21 is extracted as a signal corresponding to X-ray energy.

Since the waveform 220 increases each time X-rays enter, the waveform 220 rises to near the power supply voltage supplied to the circuit and saturates. To prevent this, the charge accumulated in the feedback capacitor 6 by the comparison circuit 55 is released by the following method. When the output of the preamplifier circuit shown by the waveform 220 reaches a certain voltage 222, the comparison circuit 55
Generates a reset signal 223, as shown in FIG.
The light emitting diode 4 emits light 150 to the field effect transistor 2.
Irradiation. The irradiation of the light 150 causes a current to flow between the gate 116 and the source 117 of the field-effect transistor 2 in the field-effect transistor 2, in which current does not normally flow. The charge accumulated in the feedback capacitor 6 is discharged through the path between the gate 116 and the source 117, and the voltage at the output point 200 is returned to the initial state (reset). With this method, high energy resolution can be obtained.

Although it has already been mentioned that the number of electron-hole pairs generated is about 50 to 5000 for X-rays having an energy of 200 to 20 kiloelectron volts, the preamplifier circuit for this has The output level is determined by the value of the feedback capacitor 6. A typical value of the feedback capacitor 6 that can be realized is 50 femtofarads.
0.16 to 16 millivolts. Since the voltage level is low, it is necessary to detect a signal with low noise. For this reason, it has been devised to cool the detection element and the detection element in the input stage to a low temperature, and further reduce the thermal noise as much as possible by using a special reset type circuit as described above.

The detecting element 101 and the field effect transistor 2
There are two types of cooling devices 70 that cool liquid crystal, a method using liquid nitrogen stored in a dewar and a method using the Peltier effect. The detection signal is susceptible to mechanical vibration due to the low signal level.To reduce the effects of vibration due to boiling of liquid nitrogen and vibration of the heat exchanger pump,
The cooling path using the metal mesh wire 235 and the fixing with a support that easily absorbs vibration are devised.

As the shaping amplifier 51, Semiconductor Detectors G. Bertoli
edited by ni, A. Coche 1968 North Holland (North H
olland), Amsterdam As described on pages 232 to 236, the one using a semi-Gaussian filter combining an analog differentiating circuit and a multi-stage integrating circuit is generally used because of its easy configuration. Have been.

Nuclear filter system
Instrument and Method in Physics Research (Nuclear Instruments And Method I
n Physics Research) 1990 A297 467
As described from page 478 to page 478, a system called a cusp filter is ideal, and can improve the energy resolution by 16% as compared with the above semi-Gaussian filter. However, it is difficult to realize the cusp filter, and a triangular filter system having an intermediate performance between them is practically used. In recent years, realizing an ideal filter has been disclosed in US Pat.
As described in US Pat. No. 9193, a digital signal processing system in which an output from a preamplifier circuit is converted into a digital signal by an analog-to-digital converter (ADC) and digitally filtered has appeared.

On the other hand, it is also effective to detect X-rays from a sample to be measured efficiently, that is, at a large detection solid angle, in order to increase the analysis sensitivity in elemental analysis or the like. The detection solid angle is determined by the distance from the sample to the detection element and the sensitive area of the detection element. The shorter the distance and the larger the sensitive area, the larger the detected solid angle. The distance is determined based on damage to the detection element and restrictions on the space in which the detector can be installed. About the sensitive area,
If the sensitive area is increased, the energy resolution is deteriorated, the fabrication becomes difficult, and the like, so the sensitive area of several tens of square millimeters is the limit. For this reason, the detected solid angle of the energy dispersive X-ray analyzer used in the electron microscope remains at about 0.1 to 0.3 radian.

As another method for increasing the sensitivity of the analysis, it is conceivable to increase the dose of charged particles and X-rays irradiated to the sample to be measured to increase the amount of X-rays generated from the sample. Since it takes time to prevent pulse overlap and convert to pulse height, several thousand X / s
The line is the limit that can be processed. Also, the irradiation amount on the sample is
The amount of irradiation is limited by the damage to the sample, and particularly in the analysis of a biological sample or a minute area of 1 nanometer, the damage becomes severe.

Although one detecting element has been described above, another method for increasing the detected solid angle is disclosed in
As described in US Pat. No. 2,468,862, a method of arranging two radiation detecting apparatuses 101, a method of
It is known to dispose a plurality of detection elements in one storage container as described in (1).

[0019]

In the radiation detection apparatus described in the section of the prior art, measures are taken to reduce the adverse effects of boiling of liquid nitrogen used for cooling and vibration caused by a Peltier element heat exchange pump. However, in the case where ice is formed in liquid nitrogen, the ice hits the liquid nitrogen tank, so that vibration having a larger amplitude than normal vibration is generated.
In this case, there is a problem that noise due to the vibration is mixed into the output signal of the preamplifier circuit, thereby deteriorating the energy resolution and generating a false spectrum peak. The same applies to the case where the door of the measurement room is opened and closed, vibration caused by sound such as the voice of the measurer, sudden electromagnetic noise generated from a motor or a computer, and the like. When the peaks due to these phenomena appear, there is a problem that it is difficult to distinguish from the peak of the trace element from the beginning, especially when measuring the trace element contained in the sample.

Next, in the method of arranging a plurality of radiation detecting devices described in the section of the prior art in order to realize a highly sensitive measurement, a plurality of containers for storing the detecting elements and a plurality of cooling devices are required. Therefore, the volume occupied by the device increases, the operability deteriorates, and the price is the same as the number of arranged devices,
There was a problem that it was expensive. On the other hand, the method of arranging a plurality of detection elements in one storage container is affected by the interaction between signal lines from each element, in addition to the noise caused by the external factors described above. Resets, noise enters the signal line of another preamplifier circuit,
There has been a problem that the energy resolution is deteriorated and a false spectrum peak appears. In other words, by taking the sum of the spectra from a plurality of detection elements, it is possible to detect about a multiple of the signal amount in the same measurement time as compared with the case of one detection element. There was a problem that it was easy to observe, the result of misinterpretation was obtained, and it became impossible to measure due to the overlap with the spectrum of the element to be examined.

An object of the present invention is to provide a high-sensitivity radiation detecting apparatus in which a plurality of detecting elements are arranged in one container and the influence of external noise is reduced.

[0022]

According to the present invention, in order to achieve the above object, a radiation detecting element and a signal from the radiation detecting element are converted into a voltage signal, and when the output voltage reaches a certain value, an initial value is obtained. In a parallel radiation detection apparatus having a preamplifier circuit returning to a state, a means for measuring vibration and electromagnetic waves is provided, and a control signal generation capable of recognizing signals from the measuring means and the preamplifier circuit and correcting time timing is provided. Providing a circuit, controlling the signal processing circuit from the circuit,
Means are provided for temporarily inhibiting signal take-in from the preamplifier circuit.

According to the present invention, the collection of the input signal is prohibited each time vibration or electromagnetic noise is generated or each time the preamplifier circuit is reset to the initial state. The effect of mixing can be eliminated. Further, in a detection device including a plurality of detection elements,
When a certain preamplifier circuit is reset to an initial state, noise is mixed into the remaining preamplifier circuits, and an accurate signal cannot be obtained.However, according to the present invention, when a certain preamplifier circuit is reset, Since the collection of output signals from the remaining preamplifier circuits can be prohibited, it is possible to eliminate the influence of noise contamination, which has been a problem in the past, and to achieve highly sensitive and highly accurate X-ray detection. Become.

[0024]

(Embodiment 1) FIG. 1 is a block diagram of a circuit configuration of a radiation detecting apparatus according to one embodiment of the present invention, and FIG. 2 shows a configuration of a preamplifier circuit in one embodiment of the present invention. FIG. 3 is a circuit diagram, FIG. 3 is a signal waveform diagram for explaining the operation of the radiation detecting apparatus according to one embodiment of the present invention, FIG. 4 is a diagram showing an X-ray spectrum obtained in one embodiment of the present invention, and FIG. FIG. 6 is a diagram showing an X-ray spectrum obtained under a certain condition in one embodiment, and FIG. 6 is a waveform diagram illustrating the origin of the X-ray spectrum obtained under a certain condition in one embodiment of the present invention. FIG. 7 is a configuration diagram when the radiation detection apparatus according to the present invention is applied to a scanning electron microscope, and FIG. 8 is a cross-sectional view showing a part of the radiation detection apparatus according to the present invention in an enlarged manner.

The configuration of the radiation detecting apparatus according to the present embodiment will be described with reference to FIGS. In FIG. 7, an electron beam 202 generated by an electron gun section 201 of an electron microscope is
03, the sample chamber vacuum vessel 25 passing through the objective lens 204
The sample 299 placed on the sample No. 3 is irradiated. And electron beam 2
02 scans the sample 299 by traversing the trajectory by the scanning coil 206 in accordance with the conditions input from the terminal 255.

The position of the sample 299 can be changed by the sample stage 212. Secondary electrons emitted from the sample 299 by irradiating the scanned electron beam 202 are detected by the secondary electron detector 211, and a secondary electron image of the sample 299 is obtained. A radiation detection device including a preamplifier circuit box 33, a liquid nitrogen tank 208, a storage container 231, an X-ray transmission window 232, and a backscattered electron remover 233 is provided in the sample chamber vacuum container 253. The signal obtained by the preamplifier circuit box 33 is sent to a radiation detection control device 240 including a wave height analysis circuit, a bias power supply, and a drive power supply, and a calculation such as a sum operation is performed. Further, calculation and display of element types, element concentrations, two-dimensional concentration distributions, and the like included in the sample 299 can be performed together with information from the electron beam scanning coil control device 252 in the electron microscope main control device 510. ing.

On the side surface of the preamplifier circuit box 33, the electromagnetic wave detector 64 and the vibration detector 6 which are the first features of the present invention are provided.
5 are provided, and respective detection signals are sent to the radiation detection control device 240. In this embodiment, the electromagnetic wave detector 64 detects electromagnetic waves based on the principle of a loop antenna.
As the vibration detector 65, one that detects vibration by detecting sound with a microphone was used.

FIG. 8 is a sectional view showing the internal structure of the storage container 231 of the radiation detector. A holding plate 2 in which detection elements 101 and 102 made of two high-purity silicon semiconductor crystals have holes for transmitting X-rays made of aluminum.
41, a conductor terminal 243 for extracting a signal from the detection element, and an insulating plate 242 made of boron nitride. The X-rays 1 emitted from the sample 299 are reflected by the backscattered electron remover 233, the aperture 236, and the X-ray transmission window 23.
2, the light enters the detection elements 101 and 102. A voltage can be applied to the holding plate 241 to form a depletion layer in the detection elements 101 and 102. The conductor terminal 243 is connected to a gate of a field effect transistor (not shown) provided inside a ceramic container 238 made of boron nitride.

The ceramic container 238 is fixed to a fixing base 235 by a fixing jig 244, and incorporates a light emitting diode (not shown) and a feedback capacitor (not shown) in addition to a field effect transistor. The circuit components in the ceramic container 238 and the preamplifier circuit box 33 constitute a preamplifier circuit. The temperature of the ceramic container 238 is adjusted to an optimum temperature (about -150 degrees Celsius) by a heater resistor 245 attached to the outside. Detecting elements 101, 102,
The ceramic container 238 is cooled by a cooling rod 234 connected to liquid nitrogen in the liquid nitrogen tank 208. The inside of the storage container 231 is vacuum-sealed.

Next, the configuration of the electric circuit in this embodiment will be described with reference to FIG. A voltage is applied to the two detection elements 101 and 102 from the power supply 41 in the reverse bias direction. The fluctuation of the voltage of the power supply 41 is reduced by a stabilizing circuit 42 composed of a resistor and a capacitor. The other ends of the detection elements 101 and 102 are connected to respective preamplifier circuits 31 and 32. Two preamplifier circuits 3
The outputs of 1, 32 are input to shaping amplifier circuits 51, 52,
At the same time, the signal is filtered so as to increase the signal-to-noise ratio, and at the same time, is amplified to an optimum amplitude so as to be input to the next-stage wave height analyzing circuits 53 and 54.

The signals from the shaping amplifier circuits 51 and 52 are composed of pulse trains having a height proportional to the energy of characteristic X-rays of the element species contained in the sample. Wave height analysis circuits 53, 5
Numeral 4 discriminates the height of the pulse train and examines the relationship between the pulse height and the number. The results processed by the wave height analysis circuits 53 and 54 are subjected to data processing and an input / output control unit 300 to calculate the element type of the sample, the element concentration ratio, and the like, and to display, print, and save the result. The data processing and input / output control device 300 is capable of inputting conditions such as a measurement start time and an end time using a keyboard (not shown) or the like, and controlling the device based on the above settings.

The output signals of the preamplifier circuits 31 and 32 are also input to differentiating circuits 61 and 62. The differentiated signal is sent to the control signal generation circuit 71. The above differentiating circuit is a second feature of the present invention. Further, the control signal generation circuit 7
1, an electromagnetic wave detector 64, which is a first feature of the present invention,
A signal from the vibration detector 65 is input. The control signal generation circuit 71 generates a control signal in accordance with the states of the four input signals, and controls the operations of the wave height analysis circuits 53 and 54.
The circuit configuration after the preamplifier circuit is built in the radiation detection control device 240 shown in FIG.

Next, details of two sets of preamplifier circuits in this embodiment are shown in FIG. The preamplifier circuits 31 and 32 are input stages of field effect transistors 2 and 3, light emitting diodes 4 and 5, feedback capacitors 6 and 7, operational amplifier circuits 8 and 9,
Comparing circuits 55 and 56, a fixed resistor 63 'and a variable resistor 63 are provided. The comparison circuits 55 and 56 monitor the voltage level of the output point 200 of the preamplifier circuit, and when the voltage reaches 0 V, the light emitting diodes 4 and 5 emit light, and as described in the section of the prior art, store in the feedback capacitors 6 and 7. The voltage and time applied to the light emitting diodes 4 and 5 are set so that the generated electric charges are discharged and the output voltage drops to about -1.5 V. The emission time was about 5 μs.

The fixed resistor 63 'and the variable resistor 63 have a function of a gain adjusting circuit. When the MnK line emitted from a sealed iron source having a mass number of 55 is incident, the output voltage from the two detecting elements is adjusted. Are adjusted so that the values are substantially equal to each other. This makes it easy to adjust the gain after the preamplifier circuit.

Here, the circuit on the left side of the boundary line 43 in FIG. 2 is in a vacuum, and the circuit on the right side is in the atmosphere. The preamplifier circuit box 33 shown in FIG. 7 is an aluminum box having a single wiring board in which two operational amplifier circuits 8, 9 and two stabilizer circuits 42 are mounted.

Hereinafter, the operation of the radiation detecting apparatus according to the present embodiment will be described with reference to FIG. Waveforms 11 and 11 'are examples of voltage waveforms at the output point 200 of the preamplifier circuits 31 and 32. Each time the X-rays enter the detection elements 101 and 102, the X-rays rise stepwise by a height proportional to the magnitude of the energy. When the X-rays reach zero volts, the X-rays are reset to a certain negative value and shown in waveforms 11 and 11 '. Thus, a sawtooth waveform is shown. Output voltage waveform 1 of preamplifier circuits 31, 32
Differentiating 1,11 'by differentiating circuits 61 and 62 results in waveforms 12 and 12'. The spike-shaped waveform appearing on the upper side of the waveforms 12 and 12 'is a waveform corresponding to the incident X-ray. A large amplitude pulse appearing on the lower side corresponds to a reset of the preamplifier circuit.

A waveform 13 is an example of a waveform from the vibration detector 65. The control signal generating circuit 71 includes differentiating circuits 61 and 6
2. With respect to the signal from the electromagnetic wave detector 64, the waveform 14,
Waveforms 14 'and 15 are generated by a comparison circuit. Further, a sum signal of the waveforms 14, 14 ', and 15 is obtained, and a waveform 16 is obtained.
Is generated, and the operation of the wave height analyzing circuits 53 and 54 is controlled by this signal.

That is, when the preamplifier circuits 31 and 32 are in a reset state, or when the vibration detected by the vibration detector 65 has exceeded a certain level, the input processing of the pulse height analyzing circuits 53 and 54 is temporarily stopped. It is banned. When the input processing is temporarily prohibited, the input signal information is ignored.

In this embodiment, the control signal generating circuit 71 has a time adjusting circuit (not shown), so that a time longer than the reset time (about 10 μsec), that is, noise at the time of reset is completely reduced. Ignored the input signal until it disappeared.

Hereinafter, the radiation detecting apparatus of this embodiment is
The results evaluated by X-rays from the sealed radiation source No. 5 will be described. From the sealed source, a manganese silicon alpha (MnKα) line is used when iron 55 is broken down by electron capture.
X-rays called manganese silicate beta (MnKβ) rays are emitted. The energy of each of the two X-rays is 5.9
Kiloelectron volts, 6.5 kiloelectron volts.

FIGS. 4 and 5 show the control signal generating circuit 7 respectively.
7 shows X-ray spectra obtained when there is no control signal from No. 1 and in some cases. As shown in FIG. 4, when there is no control signal from the control signal generation circuit 71, two peaks 31 corresponding to the MnKα line and the MnKβ line from the sealed radiation source.
A peak 313 was observed in addition to 1,312.

FIG. 6 shows a measurement example of the output voltage waveforms of the preamplifier circuits 31, 32. Output waveform 14 of preamplifier circuit 31
Is reset, the output waveform 14 'of the preamplifier circuit 32 is
It was observed that the noise shown in waveform 140 was parasitic. The signal mixed with the noise passes through the shaping circuit 52,
When processed by the wave height analysis circuit 54, it was found that the peak 313 was observed. Actually, as shown in FIG.
By controlling the peak analysis circuit 54 using the control signal from the control signal generation circuit 71, a spectrum without the peak 313 was obtained.

In the parallel radiation detection apparatus according to the present embodiment, the original spectrum can be obtained because the influence of noise due to noise caused by electromagnetic radiation noise and noise at the time of resetting and sudden noise which has been a problem in the conventional method can be excluded. Was. Further, by simultaneously detecting the signals from the two detection elements, the detection solid angle is approximately doubled, so that the measurement time required to obtain the analysis sensitivity in the case of one detection element can be reduced by half.
In addition, it was possible to improve the analysis sensitivity by a factor of 1.4 at the same measurement time.

In this embodiment, an example in which two detecting elements are used has been described. However, the number of detecting elements is not particularly limited, and the present invention is also effective in the case of one or more detecting elements. A method of taking out signals from the comparison circuits 55 and 56 of the preamplifier circuit and controlling them is also conceivable.
The number of wires from each preamplifier circuit is one more. If the number of detection elements increases, the size of the preamplifier circuit box 33 increases in order to secure the space required for the wiring connector. There is a problem that the wiring between the radiation detection control device 33 and the radiation detection control device 240 becomes thick, and the present invention is also effective for this problem.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIG. In this embodiment, a digital signal processing circuit is used. The same signals from the preamplifier circuits 31 and 32 used in the first embodiment are cut by an anti-aliasing amplifier 601 to remove high-frequency components of 5 MHz or more and amplified to an input level of an analog-to-digital converter (ADC) 602. . In this embodiment, the signal is amplified about five times, and the sawtooth waveform having an amplitude of 1.5 volts is converted into a waveform having a maximum amplitude of 8 volts. This signal is converted by the ADC 602, and the digitized data is temporarily stored in the ring memory 603. In this embodiment, the sampling frequency of the ADC 602 is set to 10 megahertz and the resolution is set to 16 bits.

The signal stored in the memory 603 is digitally differentiated by the signal recognizing circuit 605 to recognize a step-like step and reset accompanying X-ray incidence. The digital signal processing circuit 604 receives the result from the recognition circuit 605 and calculates the data stored in the ring memory 603. That is, when a step is recognized, the height of the previous step is calculated using the data up to the previous two steps.

The calculated result is sent to the data processing and input / output control device 300 and stored as data for obtaining an X-ray spectrum. If the reset is recognized, the corresponding data in the ring memory is ignored. The digital signal processing circuit 604 multiplies the digital data before and after the immediately preceding step by a predetermined weight to obtain a sum. The way of weighting can be freely set by rewriting the program in the digital signal processing unit via the data processing and input / output control device 300.

When the rate of incidence of X-rays is small and the capacity of the ring memory 603 is insufficient, the time from the latest step is detected, and after a certain time, a pseudo step signal is generated, and the pseudo step signal is generated. Calculate using digital data up to. Also, when the time between step signals, that is, the time from one X-ray incidence to the next X-ray incidence is shorter than the processing time of the digital signal processing unit, a prohibition signal is generated to skip the signal processing. ing.

Further, the control signal generation circuit 71, which is a feature of the present invention, generates a control signal by analyzing the reset signal from the two signal recognition circuits 605 and the signals from the electromagnetic wave detector 64 and the vibration detector 65. And controls the two digital signal processing circuits 604. That is, when reset, sudden electromagnetic wave noise, or vibration noise occurs, a signal for inhibiting signal processing is generated.

In this embodiment as well, collection of all signals is prohibited when each preamplifier circuit is reset, and signal collection is also prohibited when sudden electromagnetic wave noise or vibration noise occurs.
This eliminates the influence of noise on the output signal of the preamplifier circuit, which has been a problem in the past, and allows the original spectrum to be obtained.

In the first and second embodiments of the present invention, an example using a high-purity silicon detecting element has been described. However, a crystal in which lithium is diffused in silicon, a high-purity germanium crystal, or the like may be used.
It is obvious that the present invention can be applied to a detection element using another semiconductor material.

[0052]

As described above in detail, according to the present invention, sudden electromagnetic noise or vibration noise is generated, or when another preamplifier circuit returns to the initial state, it is mixed with the output signal of the preamplifier circuit. Since the adverse effect of the noise is automatically eliminated by stopping the signal collection, X-ray detection with higher accuracy than in the related art can be realized. In addition, this makes it possible to detect X-rays with high accuracy using a plurality of detection elements, realize a large solid angle and increase the amount of X-ray that can be detected in a unit time, shorten the measurement time, and improve the analysis sensitivity. It became.

Further, since no mounting measures are required to prevent noise from being mixed, a plurality of detecting elements can be arranged at high density in one storage container, and the apparatus can be reduced in size and inexpensive. Easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a block diagram of a radiation detecting apparatus according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the radiation detection apparatus according to the first embodiment of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the radiation detecting apparatus according to the first embodiment of the present invention.

FIG. 4 is an X-ray spectrum diagram obtained in the first example of the present invention.

FIG. 5 is an X-ray spectrum diagram obtained in the first example of the present invention.

FIG. 6 is a waveform chart for explaining the origin of an X-ray spectrum obtained in the first embodiment of the present invention.

FIG. 7 is a longitudinal sectional view of an embodiment in which the radiation detection device of the present invention is applied to a scanning electron microscope.

FIG. 8 is a cross-sectional view showing the internal structure of the storage container of the radiation detector of the present invention.

FIG. 9 is a block diagram of a radiation detecting apparatus according to a second embodiment of the present invention.

FIG. 10 is a configuration diagram illustrating a conventional radiation detection device.

FIG. 11 is a circuit diagram showing a conventional preamplifier circuit.

FIG. 12 is a signal waveform diagram illustrating an operation of a conventional preamplifier circuit.

[Explanation of symbols]

1 X-ray, 2, 3 field-effect transistor, 4, 5 light-emitting diode, 6, 7 feedback capacitor, 8, 9 operational amplifier circuit, 11, 11 'output voltage waveform of preamplifier circuit,
12, 12 ': differential waveform, 13: electromagnetic noise waveform, 1
4, 14 ', 15 ... internal signal waveforms of the control signal generation circuit,
16 output signal waveforms of the control signal generation circuit, 31, 32 ...
Preamplifier circuit, 33 Preamplifier circuit box, 41 Power supply, 42 Stabilization circuit, 43 Boundary line, 51, 52 Shaping amplifier circuit, 53, 54 Wave height analysis circuit, 55, 56 Comparison circuit, 61, 62: Differentiating circuit, 63: Variable resistor, 6
3 ': fixed resistance, 64: electromagnetic wave detector, 65: vibration detector, 70: cooling device, 71: control signal generation circuit, 10
1, 102: detection element, 110: X-ray incident waveform, 200
... Output point of the preamplifier circuit, 201: electron gun section, 202: electron beam, 203: convergent lens, 204: objective lens, 20
6 scanning coil, 208 liquid nitrogen tank, 211 secondary electron detector, 212 sample stage, 220 preamplifier circuit output signal, 221 step difference, 223 reset signal, 231
Storage container, 232 X-ray transmission window, 233 reflected electron remover, 234 cooling rod, 235 fixed base, 238 ceramic container, 240 radiation detection control device, 241 holding plate, 242 insulating plate, 243 ... conductor terminals, 244 ... fixing jig, 245 ... heater resistance, 250 ... electron gun controller, 251 ... electron lens controller, 252 ... scanning coil controller, 253 ... sample chamber vacuum container, 255 ... terminal, 2
99: sample, 300: data processing and input / output controller, 510: electron microscope main controller, 601: anti-aliasing amplifier, 602: analog-to-digital converter, 603: ring memory, 604: digital signal processing circuit, 605: signal Recognition circuit.

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Claims (11)

[Claims] 1. A radiation detecting element, a preamplifier circuit for converting a signal from the radiation detecting element to a voltage signal, and a signal processing device for filtering, amplifying, and analyzing a signal waveform from the preamplifier circuit. A main control device for analyzing a signal from the signal processing device and an output device for outputting and storing the analysis result, a radiation detection device including a storage device,
A radiation detection apparatus comprising means for temporarily inhibiting signal processing from the preamplifier circuit. 2. A radiation detection apparatus comprising one or more of the radiation detection element according to claim 1 and a preamplifier circuit. 3. A radiation detecting apparatus according to claim 1, wherein said means for temporarily inhibiting signal processing uses a signal obtained by transforming a radiation signal from a preamplifier circuit. 4. A radiation detecting apparatus according to claim 1, wherein said means for temporarily inhibiting signal processing of said signal processing apparatus uses an external signal. 5. The signal processing device according to claim 1, wherein the means for temporarily inhibiting signal processing uses a sum signal of a signal obtained by transforming a signal from the preamplifier circuit and an external signal. A radiation detection device characterized by the above-mentioned. 6. A radiation detecting apparatus according to claim 4, wherein said external signal is generated by means for detecting electromagnetic waves and vibrations around the apparatus. 7. A radiation detecting apparatus according to claim 2, wherein said means for temporarily inhibiting signal processing is a signal obtained by transforming a signal from each preamplifier circuit. A radiation detection apparatus characterized by using a signal obtained by combining the above. 8. A radiation detecting apparatus according to claim 3, wherein the transformation of the radiation signal from the preamplifier circuit is performed by an arithmetic processing including differentiation. 9. The signal processing device according to claim 1, further comprising a plurality of analog-to-digital converters, converting a signal from the preamplifier circuit into a digital signal, and inputting the digital signal by the plurality of digital signal processing devices. A radiation detection apparatus for obtaining X-ray energy. 10. An electron microscope equipped with the radiation detecting device according to claim 1. 11. A measuring device equipped with the radiation detecting device according to claim 1.