JP2000323082A - Transmission electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize damage of a sample caused by a long-term radiation of an electron beam by arbitrarily automatically controlling electron beam strength when no operation of this microscope continues for a certain period. SOLUTION: When no command other than a preset command is transmitted in a certain period, it is determined by an interface portion 15 that no operation of a TEM is performed. At this time, a command for controlling bias voltage is transmitted so that electron beam strength for a high voltage control portion 3 is equal to 0 or any electron beam strength set by an operator. Simultaneously, a command for turning off all of high voltage, lens current impressed for radiation of an electron beam 2, deflecting coil current and mirror-body-cooling water current is transmitted to respective control portions of the high voltage control portion 3, a lens control portion 7, a deflecting coil control portion 8, and a mirror-body-cooling device control portion 17. Thus, a function of the mirror body can be substantially stopped simultaneously to the control of filament current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission electron microscope (hereinafter abbreviated as TEM), and more particularly to reduction of damage to a sample and a fluorescent plate due to electron irradiation, protection of a filament life of an electron gun, and reduction of power consumption.

[0002]

2. Description of the Related Art In image observation using a TEM, usually, once an electron beam is irradiated on a sample, the apparatus is often left while being irradiated with the electron beam during observation. When the electron beam is irradiated for a long time, the sample and the fluorescent plate are damaged. As a method of controlling the electron beam, Japanese Patent Application Laid-Open No. Hei 8-264148 discloses a method of irradiating a sample with an electron beam by using a phosphor fluorescent plate having a spectral sensitivity suitable for observation of a TEM image of a fluorescent plate and shooting of a TV camera. Has been shown to minimize electron beam damage to the sample.

In Japanese Patent Application Laid-Open No. 9-69352, by synchronizing the scanning cycle of an electron beam with the scanning cycle of a TV camera,
There has been disclosed a method capable of obtaining a TEM image that is not different from a normal one and constantly changing an electron beam irradiation position, thereby making it possible to suppress damage of a sample by an electron beam to a low level.

[0004]

However, since the above-mentioned means targets a TEM equipped with a TV camera, there is a problem that this means cannot be used in a TEM without a TV camera. In addition, a phosphor phosphor plate having a different spectral sensitivity from a normal one, and a means for synchronizing a scanning cycle of an electron beam with a scanning cycle of a TV camera are newly provided.
There is a problem that it needs to be added to a normal TEM. Further, although the time for irradiating the sample with the electron beam can be shortened, there is a problem that the life of the filament itself is shortened because current is continuously supplied to the filament in the electron gun for a long time.

An object of the present invention is to minimize damage to a sample due to prolonged irradiation of an electron beam without adding equipment to a conventional TEM. When the number of exchanges is reduced, the burden on the electron microscope user such as the operator is reduced, the cost caused by filament exchange is suppressed, and when the electron beam intensity becomes 0 or the electron beam intensity set arbitrarily by the operator, It is an object of the present invention to provide a transmission electron microscope capable of reducing power consumption due to a lens current, a deflection coil current, and a mirror cooling water flow which are unnecessary in function.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a transmission electron microscope in which the electron beam intensity is automatically set to 0 or the operator is automatically turned off when no operation continues for a certain period of time while emitting the electron beam. This is achieved by controlling the electron beam intensity to an arbitrary set value and simultaneously turning off the lens, the deflection coil current, and the mirror cooling water flow.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an electron beam control method in the TEM of the present invention. The electron beam 2 emitted from the electron gun 1 is turned on / off by the high voltage control unit 3.
Control such as F and intensity is performed. The electron beam 2 emitted from the electron gun 1 is focused by a lens 4 and adjusted by a deflection coil 5 to adjust the position of the electron beam 2 on the sample surface, so that the electron beam 2 is emitted to an arbitrary position on the surface of the sample 6. The lens 4 and the deflection coil 5 are controlled by a lens controller 7 and a deflection coil controller 8, respectively. The TEM image is formed on the fluorescent plate 9, and when the fluorescent plate 9 moves to a position where the electron beam 2 does not completely hit, the TEM image is formed on the film 11 in the camera 10 therebelow, and the TEM image is taken. You. The camera 10 is controlled by a camera control unit 12.

The high voltage control unit 3, the lens control unit 7, the deflection coil control unit 8, and the camera control unit 12 are connected to a personal computer 13, an operation panel 14, and an interface unit 1.
5 are connected. This TEM transmits operation information input on the screen of the personal computer 13 or from the operation panel 14 to the respective control units as commands via the interface unit 15 with the personal computer 13 at the center. Manipulate,
Such control is performed.

The personal computer 13 sends to each control unit a predetermined command which does not affect other controls (for example, a command for a software version request written in the microcomputer of each control unit). When the personal computer 13 receives a reply from each control unit in response to the
The operation of performing a communication check between the control units is performed. At this time, different commands are returned from the respective control units to the interface unit 15 depending on whether the command transmitted from the personal computer 13 is correct or not. By recognizing which reply command is used, it is always checked whether or not each other is normally connected and communicated. When any operation information is input, a command for control transmitted to each control unit is sent via the interface unit 15 in addition to the communication check command. The interface unit control software written in the microprocessor in the interface unit 15 has a timer function, and allows an operator to arbitrarily determine a time and monitor commands communicated within the time. The command monitoring time can be set to two or more patterns.

First, it is assumed that no command other than a preset command has been transmitted within a predetermined time (for example, 5 minutes) initially set (that is, only a version request command has been transmitted). Since the interface unit 15 does not detect any command other than the predetermined command, it determines that the TEM operation has not been performed. At this time, a command for controlling the bias voltage is transmitted to the high voltage control unit 3 so that the electron beam intensity is set to 0 or an arbitrary electron beam intensity set by the operator.

Also, when the transmission and reception of commands for communication check from the personal computer 13 to each control unit are not performed, the transmission and reception of commands related to control between the control units are monitored by the interface unit 15 and set first. When a command related to control between the control units is not detected in the interface unit 15 within a certain fixed time (for example, 5 minutes), the electron beam intensity is set to 0 or the operator sets the high voltage control unit 3. A command for controlling the bias voltage so as to have an arbitrary electron beam intensity is transmitted. This makes it possible to control the electron gun 1 so that the electron beam intensity becomes 0 or a beam intensity arbitrarily set by an operator in advance.

Next, if no communication is made within the second set time (for example, 10 minutes) as in the case of the first set time, a command is transmitted to the interface unit 15. Then, a command for controlling the filament current is transmitted to the high voltage control unit 3 so that the electron beam intensity is set to 0 or an arbitrary electron beam intensity set by the operator. As a result, the filament current can be controlled. At the same time, the high voltage, lens current, deflection coil current,
A command to turn off the mirror cooling water flow 16 is transmitted to each of the high voltage control unit 3, the lens control unit 7, the deflection coil control unit 8, and the cooling device control unit 17. Thereby, when the filament current is controlled to the electron beam intensity of 0 or an arbitrary electron beam intensity set by the operator, the function of the mirror can be almost stopped at the same time.

Immediately before a series of operations performed when no operation information is input within a certain period of time, all conditions such as bias voltage, filament current, lens current, deflection coil current, etc., which have been operating until then, are all set. It is stored in the storage device 18.

After that, when some operation information is input to the TEM and a command related to some operation is transmitted from the operation panel 14 and the personal computer 13, a command for returning to the state stored in the storage device 18 is transmitted. Is transmitted from the storage device 18 to each control unit. Thereby, it is possible to return to the state at the time of observation.

An electron dosimeter 19 is connected to the fluorescent plate 9 of the TEM. This electron dosimeter 19
Is further connected to the interface unit 15, and the electron dose measured by the electron dosimeter 19 is constantly monitored. When this value changes, the TEM is operated, and when it does not change, the TEM is operated. It is determined that they are not. This is the interface unit 15
It is linked with the timer function of the control software written in the microprocessor inside, and monitors the value of the electron dose periodically at the same interval as the time for monitoring the communication command, within the arbitrary fixed time set by the operator. When the value has not changed, the bias voltage and the filament current are controlled in a manner similar to the command monitoring. This makes it possible to control the electron gun 1 so that the electron beam intensity becomes 0 or a beam intensity arbitrarily set by an operator in advance.

When the value of the electron dose changes, a command for returning to the state stored in the storage device 18 is transmitted from the storage device 18 to each control unit. Thereby, it is possible to return to the state at the time of observation.

Further, by switching the ON / OFF switch 20, ON / OFF control of this function can be performed. The ON / OFF switch 20 is a 1-bit I / O port of the microprocessor in the interface unit 15.
It is connected to the. By switching the ON / OFF switch 20, "0" or "1" is set in this bit. Therefore, when the operator intentionally wants to keep the state where the electron beam 2 is emitted, it is possible to maintain the state where the electron beam 2 is emitted.

By utilizing these, the conventional TE
The irradiation time of the electron beam without adding equipment to M
At this time, the power ON / OFF of the functionally unnecessary part can be automatically controlled to be short.

[0020]

As described above, according to the present invention, the following effects are achieved.

Without adding equipment to the conventional TEM,
Since the intensity of the electron beam to be irradiated is automatically controlled, it is possible to minimize damage to the sample due to long-time irradiation. In addition, it is possible to extend the life of the electron gun in order to shorten the time for passing the current through the filament,
It is possible to reduce the number of times of filament exchange, reduce the burden on the user of the electron microscope such as the operator, and to suppress the cost caused by filament exchange. Further, the control of the electron beam intensity is divided into two stages of the bias voltage and the filament current according to the length of the monitoring time, first the bias voltage and then the filament current, and at the same time, the current of the lens, the deflection coil and the mirror side cooling device. Is turned off, the return of the electron beam is quick when the time during which no operation is performed is short, and the power consumption can be reduced when the time is long.

[Brief description of the drawings]

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Electron beam, 3 ... High voltage control part, 4 ...
Lens 5, deflection coil, 6 sample, 7 lens control unit, 8 deflection coil control unit, 9 fluorescent plate, 10 camera, 11 film, 12 camera control unit, 13 personal computer, 14 control Panel, 15: Interface unit, 16: Water flow for cooling mirror, 17: Control unit for cooling device of mirror, 18: Storage device, 19: Electronic dosimeter, 20
... ON / OFF switch.

Claims (7)

[Claims] In a transmission electron microscope, a means for controlling the intensity of an electron beam irradiating a sample, a means for setting the intensity, and an input related to the operation of the transmission electron microscope during a certain period of time are measured. A means capable of monitoring input information from the control unit, wherein when no operation information is input within a certain period of time, the transmission electron microscope sets the electron beam intensity to 0 or an arbitrary preset value; A transmission electron microscope characterized in that a bias voltage is controlled so that the electron beam intensity becomes as high as possible. 2. A means for controlling the intensity of an electron beam irradiating a sample in a transmission electron microscope, a means for setting the intensity, and an input relating to the operation of the transmission electron microscope during a certain period of time. A means capable of monitoring input information from the control unit, wherein when no operation information is input within a certain period of time, the transmission electron microscope sets the electron beam intensity to 0 or an arbitrary preset value; A transmission electron microscope characterized in that the filament current is controlled so that the electron beam intensity becomes as high as possible. 3. A means for controlling the intensity of an electron beam irradiating a sample in a transmission electron microscope, a means for setting the intensity, and an input related to the operation of the transmission electron microscope during a certain period of time. A means capable of monitoring input information from a control unit, wherein when no operation information is input within a certain period of time of the transmission electron microscope, a bias voltage or a filament current of the transmission electron microscope; Is controlled to 0 or an arbitrary value set by an operator, and when no operation information is input within a certain period of time, the bias voltage or filament current of the transmission electron microscope is set to 0 or an arbitrary value set by the operator. It is necessary to control the electron beam intensity to 0 or to an arbitrary predetermined electron beam intensity in a plurality of stages, such as controlling the electron beam intensity to a predetermined value. Transmission electron microscope according to symptoms. 4. A transmission electron microscope, means for controlling the intensity of an electron beam irradiating a sample, means for setting the intensity, and an input relating to operation of the transmission electron microscope during a certain period of time. A means capable of monitoring input information from a control unit, wherein when no operation information is input within a certain period of time, the transmission electron microscope automatically switches to a high voltage. A transmission electron microscope, wherein a lens current and a deflection coil current are turned off or controlled to predetermined voltage values and current values. 5. A transmission electron microscope, a means for controlling the intensity of an electron beam irradiating a sample, a means for setting the intensity, and an input relating to the operation of the transmission electron microscope during a certain period of time measured during the measurement. A means capable of monitoring input information from a control unit, wherein when no operation information is input within a certain period of time, the transmission electron microscope is automatically turned into a mirror body; O for cooling water flow
A transmission electron microscope characterized by being able to perform FF. 6. The transmission electron microscope according to claim 1, wherein when the transmission electron microscope has not been operated for a certain period of time, the transmission electron microscope is once turned off or set in a preset state. The bias voltage, the filament current, the lens current, the deflection coil current, and the turned off mirror cooling water flow return to the original state when the operator performs any operation of the transmission electron microscope. Transmission electron microscope. 7. The transmission electron microscope according to claim 1, wherein an operator can arbitrarily set a time for monitoring the operation of the transmission electron microscope. electronic microscope.