JPS62143351A - Automatic optical axis adjuster - Google Patents

Abstract

PURPOSE:To aim at improvements in controllability of an electron microscope and maintenance efficiency, by shifting an electron source, a focusing lens and a diaphragm automatically to a position where an irradiation current quantity comes to the maximum. CONSTITUTION:An analog signal out of an irradiation current detector 15 is converted into a digital signal at an irradiation amperometric block 16 in a control circuit 14, and whether this signal is the maximum value or not is judged by a maximum value judging block 17. And, if it is not the maximum value, such an electric signal that is necessary for shifting an electron source 1, a focusing lens 4 and further a diaphragm 6 as far as a proper distance is generated by a driving current generating block 18, and it is transmitted to an electron source driving device 11, a focusing lens driving device 12 and a diaphragm transfer device 13, respectively. Driving devices 11-13 shift the focusing lens 4 and the diaphragm 6 as far as a proper distance in a direction vertical to an optical axis. With this movement, a charge quantity to be irradiated to a sample 10 or a manipulator 9 is varied. This charge quantity is detected again by the irradiation current detector 15, and fed back to the control circuit 14. After repeating suchlike feedback, the electron source 1, the focusing lens 4 and the diaphragm 6 are shifted to a position where the irradiation current quantity comes to the maximum, stopping, them.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic optical axis adjustment device that is applied to adjusting the optical axis during initial setting of an electron microscope or the like.

Conventional technology In recent years, electron microscopes have become popular in laboratories, factories, etc. as condition observation devices with better resolution and deeper depth of focus than optical microscopes. Demand for automated devices equipped with computers (hereinafter referred to as microcomputers) is increasing.

The configuration and operation of a conventional electron microscope will be described below.

FIG. 3 shows the configuration of a conventional electron microscope. In Figure 3, ■ is an electron source, 2 is an adjustment screw for manually moving the electron source l in a direction perpendicular to the optical axis, and 3 is an electron source l.
This is an anode that applies voltage to accelerate the electrons emitted from the 4 is an electromagnetic lens (hereinafter referred to as a focusing lens) for focusing the accelerated electrons, 5 is an adjustment screw for manually moving the focusing lens 4 in a direction perpendicular to the optical axis, and 6 is a passage through which the accelerated and focused electrons pass. This is an aperture to change the amount.

7 is a device for manually moving the diaphragm 6 in a direction perpendicular to the optical axis. 8 is an electromagnetic lens (hereinafter referred to as objective lens) for further focusing or deflecting the electrons that have passed through the aperture 6;
9 is a manipulator for fixing or moving the sample 10 within the apparatus. By irradiating a sample with this narrowly focused electron beam and detecting reflected electrons, transmitted electrons, secondary electrons, etc. generated from the sample, it is possible to observe and record the shape and structure of the sample. .

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the optical axis shifts when replacing the electron source I or the diaphragm 6, and the adjustment is manually performed using the electron source position adjustment screw as an initial setting for operation. 2, the focusing lens position adjustment screw 5, and the aperture position adjustment device 7 are complicated and time-consuming tasks. Furthermore, adjustment of the optical axis is a work related to resolution, which is the basic performance of an electron microscope, and requires practice.

The present invention solves the above-mentioned conventional problems, and aims to provide an automatic optical axis adjustment device that can automate optical axis adjustment, increase precision, and improve operability.

Means for Solving the Problems To achieve this objective, the automatic optical axis adjustment device of the present invention includes an electron microscope equipped with an irradiation current detector that detects the amount of charge (current amount) irradiated onto a sample or a manipulator, and an electron source. The irradiation current is It has a configuration of a control circuit that controls each of the drive devices described above based on the electrical signals obtained by the detector.

Function: With this configuration, the electron source, focusing lens, and diaphragm can be automatically moved to the position where the amount of irradiation current is maximum, that is, the optical axis from the electron source to the manipulator can be aligned, which improves the operability of the electron microscope. It is possible to improve the performance and maintenance efficiency.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the automatic optical axis ali in the first embodiment of the present invention.
1 shows the main configuration of the lfl device. In FIG. 1, 11 is an electron source driving device mechanically connected to the electron source 1, and 12 is a focusing lens driving device mechanically connected to the focusing lens 4. 13 is an aperture driving device mechanically connected to the aperture 6; 15 is an irradiation current detector electrically connected to the manipulator 9; 14 is a control circuit;
The amount of irradiation current received by the irradiation current detector 15 can be manually input and an appropriate electric signal can be output to each drive device 1112.13.

Note that 1, 3, 4, 6, 8, 9, and 10 in the same figure are the same as those in the conventional example shown in FIG. 3 with the same symbols.

FIG. 2 is a block diagram showing the operation contents of the control circuit 14. In FIG. 2, IG is 1((), which is an injection current estimation block that digitizes the analog signal of the irradiation current obtained by the irradiation current detector 15.

17 is the maximum value judgment block and the irradiation current measurement block 1
It is determined whether the electric signal from 6 is at the maximum value. 18 is a drive current generation block, which is electrically connected to send signals to the drive devices 11, 12, and 13. Note that 11 is an electron source drive device, 12 is a focusing lens drive device, 13 is an aperture drive device, and 15 is an irradiation current detector, which have the same configuration as in FIG.

The operation of the automatic optical axis adjustment device configured as described above will be described below.

First, when this apparatus is started, the irradiation current detector 15 detects the current irradiated to the sample IO or the manipulator 9, and this electric signal is input to the control circuit 14. An irradiation current measuring block 16 in the control circuit 14 converts the analog signal from the irradiation current detector 15 into a digital signal, and this digital signal is input to a maximum value determination block 17. In the maximum value judgment block 17, this signal is
It is determined whether the value is large, and if it is not the maximum, the driving current generation block 18 generates an electric signal necessary to move the electron source 1, the focusing lens 4, and the aperture 6 by an appropriate distance, and the electron source driving device 11. Focusing lens drive device 1
2. Send to the aperture moving device 13. Upon receiving this signal, each drive device 1112, 3 moves the focusing lens 4 and aperture 6 mechanically connected thereto by an appropriate distance in a direction perpendicular to the optical axis. As a result, the amount of charge applied to the sample 10 or the manipulator 9 changes. This amount of charge (
The amount of current) is detected again by the irradiation current detector 15 and fed back to the control circuit 14. By repeating the foot bank in this manner, the electron source 1, the focusing lens 4, and the aperture 6 are moved to the position where the amount of irradiation current is maximum, and then stopped. Note that, as a matter of course, the detected amount of irradiation current that is first input to the control circuit 14 is not determined to be the maximum value by the maximum value determination block 17.

Effects of the Invention As described above, the present invention provides a driving device capable of moving an electron source in a direction perpendicular to the optical axis, a driving device capable of moving a focusing lens perpendicular to the optical axis, and a driving device capable of moving an aperture perpendicular to the optical axis. By equipping the electron microscope with a detector that detects the device and the amount of irradiated current, and a control circuit that manually inputs the signals from this detector and outputs the appropriate output to each drive device, an automatic light beam with excellent operability and maintainability can be achieved. This makes it possible to realize an axis adjustment device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an automatic optical axis adjustment device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the operation contents of the control circuit I4, and FIG. & L) 1 is a configuration diagram. 11...Electron source drive device, 12...Focusing lens drive device, 13...Aperture drive device, 1
4...Control circuit, 15...Irradiation current detector, 16...Irradiation cloth/I! Current measurement block, 17...Maximum value determination block, 18...
...Drive current generation block. Name of agent: Patent attorney Toshio Nakao (Figure 2)

Claims (1)

[Claims] an electron source, a focusing lens for focusing electrons generated from the electron source, an aperture for further narrowing down the electron beam focused by the focusing lens, an objective electromagnetic lens, a manipulator for moving the sample, and the above. A drive device that moves the electron source in a direction perpendicular to the optical axis, a drive device that moves the focusing lens in a direction perpendicular to the optical axis, a drive device that moves the aperture in a direction perpendicular to the optical axis, and irradiation of the manipulator. An automatic optical axis adjustment device comprising: a detection circuit that detects a current; and a control circuit that feeds back an electric signal obtained by the detection circuit and controls each of the drive devices.