JPH0760659B2 - Deflection device for electron microscope - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in an electron beam deflector incorporated in an electron microscope.

[Problems to be Solved by the Invention] In a transmission electron microscope, normal sample irradiation is performed in which an electron beam diverging from an electron gun is irradiated as a parallel electron beam bundle along the optical axis of the electron optical system perpendicularly to the sample surface. Besides the mode,
There are several sample irradiation modes.

FIG. 4 is a schematic diagram showing the central path of the electron beam flux in the tilt mode. In the tilt mode, the electron beam 2 is applied to the sample 3 from the direction inclined by the angle α with respect to the optical axis 1. The electron beam is deflected in the opposite direction by the deflector A and the deflector B of the second stage. FIG. 5 is a schematic diagram showing the central path of the electron beam flux in the (field of view) movement mode. In the movement mode, the electron beam is moved while keeping parallel to the optical axis 1 to irradiate a desired region of the sample 3. Therefore, the electron beam 2 is deflected in the opposite direction by the first-stage deflector A and the second-stage deflector B, respectively.

The electron beam paths shown in FIGS. 4 and 5 are obtained when there is no electron lens field between the sample 3 and the deflector A. However, in an actual device, as shown in FIG. A pre-magnetic field 4 of the objective lens field and a mini-objective magnetic field 5 are often formed in the vicinity of 3. In such an optical system, in order to perform electron beam irradiation in the moving mode, a fixed point P on the optical axis 1 is used.
It is necessary to deflect the electron beam with the deflection fulcrum as the deflection fulcrum, and in order to perform the electron beam irradiation in the tilt mode, it is necessary to deflect the electron beam with the fixed point Q on the optical axis 1 as the deflection fulcrum. The positions of these deflection fulcrums P and Q move according to the excitation change of the objective lens or the mini objective lens.

By using the two-stage deflectors A and B, it is possible to deflect the electron beam incident along the optical axis with an arbitrary point on the optical axis as a deflection fulcrum. FIG. 7 is an optical diagram when the position 6 below the deflector B is used as a deflection fulcrum, with respect to the deflection angle β by the deflector A in the first stage and with respect to the deflector B.
If K1 is used as a constant and the deflection angle of Ka · β is given (when the deflection angle β is small), the deflection fulcrum can be kept constant. In this case, since the deflection angle of the electron beam deflected by each deflector is proportional to the signal intensity of the exciting current or the exciting voltage supplied to the deflector, the exciting signal supplied to the first-stage deflector A. By supplying an excitation signal, which is a constant Ka times the intensity I, to the deflector B, the target deflection can be performed. The deflection power supply for performing such deflection is
It is usual to provide control means for interlocking two constant current power supplies to adjust the output of one constant current power supply and control means for adjusting the output ratio of the two power supplies.

FIG. 8 is an optical diagram when the fixed point 7 above the deflector A is used as the deflection fulcrum, and Kb for the deflector B is a constant for the deflection angle γ by the deflector A in the first stage. It suffices to provide a deflection angle of Kb · γ, and if an excitation signal of a constant Kb times the excitation signal intensity I supplied to the first-stage deflector A is supplied to the deflector B, Deflection can be performed.

FIG. 9 is a schematic diagram showing the relationship between the position (coordinates) of the deflection fulcrum and the deflection signal intensity ratio supplied to the two-stage deflector, where the horizontal axis represents the coordinates of the deflection fulcrum and the vertical axis represents the deflection signal intensity ratio. (Coefficient). The curve a is used in the first-stage initiative mode in which the excitation signal Ib obtained by multiplying the deflection signal Ia supplied to the first-stage deflector A by a constant constant Ka is supplied to the second-stage deflector B. The change in the constant Ka (= Ib / Ia) is represented by the curve b
Is the excitation signal Ia obtained by multiplying the deflection signal Ib supplied to the deflector B of the second stage by a constant Kb.
Kb (= Ia) used in the second-stage initiative mode
/ Ib).

As is clear from FIG. 9, when the deflection fulcrum comes close to the deflector A, the value of Kb becomes extremely large, and it becomes difficult to calculate such a coefficient. Similarly, when the deflection fulcrum reaches the vicinity of the deflector B, the value of Ka becomes extremely large,
It becomes difficult to calculate such a coefficient. Therefore, in a deflection power source that operates only in the first-stage initiative mode or only in the second-stage initiative mode, it is difficult to deflect the electron beam with an arbitrary point as a deflection fulcrum. Must be configured to operate in either mode. However, the coordinates of the optimum deflection fulcrum change depending on the usage conditions of the electron lens as described above. Therefore, in order to prevent the constants Ka and Kb from taking too large values, the first-stage initiative mode and the second-stage mode are used. Since it is difficult to determine which of the lead modes should be used, and the operator selects the lead mode by trial and error, this has been a cause of making the operability of the electron microscope difficult.

[Problems to be Solved by the Invention] An object of the present invention is to more easily perform an electron beam deflection operation of a sample irradiation system in a transmission electron microscope.

[Means for Solving the Problem] In the transmission electron microscope of the present invention, a two-stage deflector provided between the electron gun and the observation sample position, and provided between the sample position and the deflector. An electron lens, a first-stage drive mode for supplying an excitation signal obtained by multiplying the excitation signal supplied to the first-stage deflector by a variable constant to the second-stage deflector,
In addition to the device provided with the deflection power supply having a function of switching the excitation signal obtained by multiplying the excitation signal supplied to the deflector of the first stage by the variable constant to the second stage initiative mode for supplying the deflector of the first stage, A means for obtaining the position of the electron beam deflection fulcrum necessary for performing an inclination mode for inclining the electron beam incident on the sample or a movement mode for moving the irradiation position of the electron beam incident on the sample from the intensity of the electron lens; The above-mentioned problem is solved by providing means for displaying which of the first-stage initiative mode and the second-stage initiative mode should be selected based on the output of the above.

[Operation] In the present invention, the deflection fulcrum position for performing the desired deflection is obtained from the intensity of the electron lens formed between the sample position and the deflector, and the optimum deflection mode by the two-stage deflector is obtained from the result. Since the calculation is performed, the electron beam deflection operation of the sample irradiation system in the transmission electron microscope can be performed more easily.

[Embodiment] FIG. 1 is a schematic view showing the structure of an embodiment of the present invention. On top of the vacuum housing 10 of the transmission electron microscope, an electron gun
11 is provided, and the electron beam emitted from the electron gun 11 is
The observation sample 15 placed in the magnetic field of the objective lens 14 is irradiated by being sequentially focused by the forward magnetic field of the focusing lens 12, the mini objective lens 13, and the objective lens 14. A first-stage deflector A and a second-stage deflector B are provided between the focusing lens 12 and the mini objective lens 13. Switching means 16 is provided for the deflectors A and B.
Is connected to the output terminal s or t of the deflection power supply 17 via the input terminal of the deflection power supply 17, and the deflection power supply 17 is supplied with a control signal from the deflection intensity designating means 18 and the coefficient designating means 19 via an input means such as a keyboard. A deflection signal Io designated by the deflection intensity adjusting means 18 is output to its output terminal s, and a deflection signal Ko × Io obtained by multiplying the deflection signal Io by the coefficient Ko designated by the coefficient adjusting means 19 is output to the output terminal t. Is output. By operating the switching means 16, either the first stage initiative mode or the second stage initiative mode is selected.

Lens power supply for mini-objective lens 13 and objective lens 14, 20, 21
A part of the output of is input to the arithmetic unit 22, together with the input signal from the irradiation mode designating means 23 for designating the mode of the moving mode or the tilt mode, and the coordinates of the deflection fulcrum based on the data stored in advance. To calculate. Next, when this coordinate value is above the intermediate point C between the deflector A and the deflector B in FIG. 9 (on the right side in the figure), the first stage initiative mode is set, and the coordinate value is the deflector A. When it is below the intermediate point C of the deflector B (on the left side in the figure), it is output to the switching display means 24 so as to display the second stage initiative mode. After the operator of the deflection system gives an instruction by the irradiation mode designating means 23, the switching indicating means
While observing the display of 24, the switching unit 16 selects the first stage initiative mode or the second stage initiative mode. Next, the deflection intensity adjusting means 18 and the coefficient adjusting means 19 are operated to perform the desired electron beam deflection. In this way, when switching between the first-step initiative mode and the second-step initiative mode depending on whether the coordinates of the deflection fulcrum are above or below the intermediate point C between the deflectors A and B, the coefficient value Is in the range between -1 and +1, so
The deflection power supply can be easily designed.

FIG. 2 is a schematic diagram showing a main part of an apparatus according to another embodiment of the present invention, in which the same reference numerals as those in FIG. 1 represent the same constituent elements. In the apparatus of FIG. 2, instead of displaying the result obtained by the arithmetic unit 22 on the switching display means 24 as in the apparatus of FIG. 1, the switching means 16 is directly controlled to automatically perform the first stage initiative mode. And the second stage initiative mode is switched.

FIG. 3 is a schematic view showing a device according to still another embodiment of the present invention. In the apparatus of the embodiment shown in FIG. 3, the instruction signal of the first stage initiative mode or the second stage initiative mode output from the arithmetic unit 22 is applied to the deflection controller 25. Deflection control device
The reference numeral 25 sends a control signal to the first deflection power source 26 and the second deflection power source 27 based on the input signals from the deflection intensity adjusting means 18 and the coefficient adjusting means 19 and the instruction signal from the arithmetic unit 22, and the first stage initiative mode. Alternatively, the control is performed so that the deflection is performed in the second stage initiative mode.

EFFECTS OF THE INVENTION According to the first aspect of the present invention, it is immediately known which of the first-stage initiative mode and the second-stage initiative mode should be selected, and the electron beam deflection operation with an arbitrary point as the electron beam deflection fulcrum. Will be easier. Further, according to the second aspect of the present invention, the selection between the first step initiative mode and the second step initiative mode is automatically performed, and the electron beam deflection operation with an arbitrary point as the electron beam deflection fulcrum becomes easier.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the construction of an apparatus according to an embodiment of the present invention.
FIGS. 3 and 4 are schematic diagrams showing another embodiment of the present invention, FIG. 4 is a schematic diagram for explaining a tilt mode for tilting an electron beam incident on a sample, and FIG. 5 is an electron incident on the sample. FIG. 6 is a schematic diagram for explaining a moving mode for moving a line, FIG. 6 is a schematic diagram for explaining a deflection fulcrum of an electron beam necessary for performing a tilt mode and a moving mode, and FIGS. 7 and 8 are two stages. FIG. 9 is a schematic diagram for explaining the optical system when arbitrarily selecting the deflection fulcrum of the electron beam by the deflector, and FIG. 9 is a schematic diagram for explaining the relationship between the deflection signal strength and the deflection fulcrum in the two-stage deflection system. . 1 ...... Optical axis 2 ...... Electron beam 3 ...... Sample 4 ...... Pre-magnetic field of objective lens 5 ...... Mini objective lens magnetic field 6, 7 ...... Deflection fulcrum 10 ...... Vacuum housing 11 ...... Electron gun 12 ...... Focusing lens 13 …… Mini objective lens 14 …… Objective lens 15 …… Sample 16 …… Switching means 17 …… Deflecting power supply 18 …… Deflection intensity adjusting means 19 …… Coefficient adjusting means 20 …… Mini objective lens power supply 21 …… Objective lens power supply 22 …… Computing device 23 …… Irradiation mode designating means 24 …… Switching display means 25 …… Deflection control device 26 …… First deflection power supply 27 …… Second deflection power supply

Claims (2)

[Claims] 1. A two-stage deflector provided between an electron gun and an observation sample position, an electron lens provided between the sample position and the deflector, and a first-stage deflector. The excitation signal obtained by multiplying the excitation signal obtained by multiplying the excitation signal by the variable constant to the second stage deflector and the excitation signal obtained by multiplying the excitation signal supplied to the second stage deflector by the variable constant are In an apparatus equipped with a deflection power source having a function of switching between a second-stage leading mode for supplying to the first-stage deflector, an inclination mode for inclining an electron beam incident on a sample or an irradiation position of an electron beam incident on the sample is set. A means for obtaining the position of the electron beam deflection fulcrum required to perform the movement mode for moving from the intensity of the electron lens, and which of the first-stage initiative mode and the second-stage initiative mode should be selected based on the output of the means. Characterized by providing a means to display the tick Electron microscope deflection apparatus. 2. A two-stage deflector provided between an electron gun and an observation sample position, an electron lens provided between the sample position and the deflector, and an excitation signal supplied to one of the deflectors. In a device equipped with a deflection power supply for supplying an excitation signal obtained by multiplying the desired variable constant to the other deflector, a tilt mode for tilting the electron beam incident on the sample or a movement for moving the position of the electron beam incident on the sample Means for obtaining the position of the electron beam deflection fulcrum necessary to perform the mode from the intensity of the electron lens,
Deflection for an electron microscope, characterized in that means for controlling switching of two deflection signals supplied from the deflection power source to the first-stage deflector and the second-stage deflector based on the result of the means is provided. apparatus.