JPS5854463B2 - electronic probe device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the irradiation current to a sample of an electron probe device such as an X-ray microanalyzer or a scanning electron microscope.

In devices such as X-ray microanalyzers and scanning electron microscopes, the range of acceleration voltage used and beam current for irradiating the sample is from several KV to several tens of KV and 10 KV, respectively.
It covers a very wide range from 'A' to 10'A.

Under a certain accelerating voltage, the current value of the electron beam that irradiates the sample is determined by the excitation conditions of the converging lens and the diameter of the slit. You need to choose what you can.

In the past, fixed apertures were used in some cases to suit the conditions of use most frequently used, but normally apertures with several different hole diameters were prepared and the most suitable one was selected according to the conditions. .

In particular, in X-ray microanalyzers, conditions such as accelerating voltage and probe current are changed frequently and widely depending on the type and concentration of the element to be analyzed, the composition of the sample, etc. It is necessary to observe secondary electron beam images and reflected electron beam images, which have very different usage conditions.

Therefore, in the past, in order to always use the device under optimal conditions, the relationship between the optimal aperture diameter according to accelerating voltage, probe current, etc. was calculated theoretically, and the results were calculated in several stages by referring to tables or graphs showing the results one by one. Among the apertures with different hole diameters,
The device is operated to select the most suitable one and install it.

Therefore, in the past, not only did the operation require skill and experience, but it was also very complicated.

The present invention has been made to solve the drawbacks of conventional devices, and provides irradiation current control for electronic probe devices that makes it possible to easily use the device under optimal conditions without complicated operations. An embodiment of the present invention will be described below in detail with reference to FIG. 1.

In FIG. 1, reference numeral 1 denotes a housing of an electron probe device that is kept in a vacuum, and an electron gun 2 is disposed in the upper part of the housing 1.

3 is a high voltage power supply for the electron gun.

An electron beam 4 generated by the electron gun 2 is converged by a converging lens 5.

Reference numeral 6 denotes a converging lens power source, and a signal corresponding to the accelerating voltage set in the high voltage power source 3 is supplied to the converging lens power source.

An auxiliary converging lens I is provided near the converging lens 4, and the auxiliary converging lens I is excited by an excitation power source from an auxiliary converging lens power source 8.

The electron beam focused by the converging lens is further focused onto the sample 10 by the objective lens 9.

11 is an objective lens power supply.

The objective lens power supply 11 is supplied with a signal corresponding to the accelerating voltage from the high voltage power supply 3, and the excitation current of the objective lens is such a current that the electron beam is always focused on the sample 10, regardless of the accelerating voltage. controlled by.

12 is, for example, four slits 13a, 1 with different hole diameters.
It is a slit plate having 3b, 13c, and 13d.

The slits 13a and 13b. It is assumed that holes 13c and 13d have an optimum hole diameter for the probe current range as shown below.

10-10 A, 13a 10-1OA, 13b 10-9-10"A: 13c 10"A or less: 13d The slit plate is connected to a moving shaft 14 taken out of the vacuum casing, and the moving shaft 14 By moving the slit, any one of the slits can be placed on the optical axis 15.

Reference numeral 16 denotes a vacuum seal member for allowing the movement of the moving shaft 14 to be carried out while keeping it airtight.

The moving shaft 14 is mechanically connected to a slit detection circuit 17.

The slit detection circuit 11 detects the position of the moving axis 14 to detect slits 13a, 13b,
A signal indicating which slit among slits 13c and 13d is placed is output.

The output signal of the slit detection circuit 1γ is supplied to the converging lens power supply 6.

In the above-described configuration, the high-voltage power supply 3 is operated to set the acceleration voltage to a desired value.

Thereafter, a slit is selected according to the current value of the probe irradiated onto the sample, and the moving shaft 14 is operated so that the selected slit is located on the optical axis 15.

As a result, the high-voltage power supply 3 supplies a signal corresponding to the set acceleration voltage, and the slit detection circuit 17 supplies a signal corresponding to the selected slit to the converging lens power supply 6.

As a result, under the selected Kato voltage and slit conditions, the excitation current supplied from the converging lens power supply 5 to the converging lens 4 is automatically adjusted so that the thinnest electron beam probe is formed. .

In this way, according to the present invention, the combination of the excitation current of the converging lens and the aperture diameter of the slit that can minimize the electron probe diameter can be set with a simple operation for a desired acceleration voltage and beam current. I can do it.

The auxiliary converging lens power supply 8 may be operated to finely adjust the excitation intensity of the converging lens according to special requirements of the measurement.

FIG. 2 shows a further detailed explanation of another embodiment, and in FIG. 2, the same components as in FIG.

One difference from FIG. 1 is that the converging lens power source 6 is equipped with an electron beam current setting section 18, and the converging lens power source 6 receives the electron beam instead of a signal corresponding to the accelerating voltage from the high voltage power source 3. It is controlled by a signal from the current setting section 18.

When the operator sets the electron beam current to a desired electron beam current, the electron beam current setting section 18 gives a signal corresponding to the set electron beam current to the converging lens power supply 6 to optimize the converging lens current. It is for.

Furthermore, the moving shaft 14 is mechanically connected to a slit exchange device 19.

The slit exchange device 19 is supplied with a signal from the electron beam current setting section 18, and the slit exchange device 19 automatically selects the optimum slit based on the signal from the electron beam current setting section 18. Optical axis 15
It includes a drive motor and the like for moving the moving shaft 14.

In the above-described configuration, the slit can be replaced by first adjusting the acceleration voltage by adjusting the high-voltage power supply 3 and setting it to a desired value, and then operating the electron beam current setting section 18 according to the desired value of the electron beam current irradiated onto the sample. The device 19 operates to move the slit plate 12, and a slit having the optimum hole diameter is automatically placed on the optical axis 15.

Therefore, in this case as well, it is possible to select the optimum combination of the excitation current of the converging lens and the slit diameter under a specific accelerating voltage and electron beam current, and as a result, the thinnest electron beam probe can be obtained. The sample can be irradiated.

In the above-mentioned embodiment, a slit plate was used in which the diameter of the slits was changed stepwise, but if a continuously variable slit is used, the diameter of the slits can be continuously controlled at all times, making it more precise. control becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates one embodiment of the present invention, and FIG. 2 illustrates another embodiment of the present invention in detail. 1: Housing, 2: Electron gun, 3: High voltage power supply, 4: Electron beam, 5: Converging lens, 6: Converging lens power supply, T: Auxiliary converging lens, 8: Auxiliary converging lens power supply, 9: Objective lens, 1
0: sample, 11: objective lens power supply, 12 Nislit plate,
13a, 13b, 13c. 13d Nislit, 14: Moving axis, 15: Optical axis, 16:
Vacuum seal member, 17: Slit detection circuit, 18: Electron beam current setting section, 19 Nislit exchange device.

Claims (1)

[Claims] 1. A convergent lens and an objective lens for irradiating an electron beam generated from an electron gun onto a sample, a slit means arranged near the objective lens and capable of changing the aperture diameter, and a convergent lens for exciting the convergent lens. What is claimed is: 1. An electron probe device comprising: a power source; the apparatus further comprising means for controlling the slit means and the converging lens power source according to a desired beam current value of an electron beam irradiating the sample.