JPH11288679A - Automatic sample tilting device of transmission type electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically tilt a sample to an angle formed by mathematically calculated different orientations of the crystals of the sample and to automatically move the sample so that the mathematically calculated positional deviation of the sample is canceled out. SOLUTION: The electron diffraction pattern of a sample 4 is recognized by an image recognition means 11 via an image pickup TV 7, and cystal orientations and the orientation and the tilt angle of the required sample tilt in the target orientation from which to perform observation are calculated from the electron diffraction pattern by an analysis means 12. A sample tilting mechanism 9 is controlled by a position correcting means 14 to tilt an image of the sample 4 by a minute amount such that it does not go out of the screen of an image display means 13, the positional deviation of the sample 4 being calculated by the analysis means 12. Position correcting control is performed whereby a sample moving mechanism 8 and a deflection coil 6 are controlled by the position correcting means 14 so that the positional deviation is canceled out. Such tilting of the sample 4 and position correcting control are repeated until the calculated tilt angle is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a transmission electron microscope which irradiates a sample with an electron beam and obtains an image of the sample by transmitted electrons transmitted through the sample. It belongs to the technical field of automatic tilting devices in transmission electron microscopes.

[0002]

2. Description of the Related Art Transmission microscopes (hereinafter also referred to as TEMs).
In addition to observing the sample by irradiating the sample with an electron beam and obtaining a high-resolution transmission electron image of the sample using transmitted electrons transmitted through the sample, it is also possible to examine the arrangement of molecules and atoms in crystalline materials. An elemental analysis is also performed by obtaining a possible electron diffraction image, scanning transmission image or energy loss image. In recent years, using this transmission electron microscope, not only the image due to the transmitted electrons, but also the reflected electrons reflected from the sample, secondary electrons generated from the sample, Auger electrons, X-rays, etc. Various analyzes such as observation of a structure and elemental analysis of a sample are also performed.

In the TEM, when observing an electron diffraction pattern or the like, it is necessary to adjust the direction (azimuth) of the observation sample with respect to the incident electron beam. this is,
This is because observing one sample in different directions provides knowledge of the crystal structure of the sample. Conventionally, the orientation of the sample is adjusted by a mechanism (goniometer) that mechanically tilts the sample independently in the two x-axis and y-axis directions.

[0004]

However, if the sample does not ride on the tilt axis, the sample will be displaced when the sample tilts around the tilt axis. For this reason, when the sample is tilted, the target sample deviates from the observation visual field, and it takes much time and effort to adjust the orientation. In particular, it is extremely difficult to align the orientation of fine crystal grains of about several tens nm. Therefore, it is necessary to correct the position of the sample, but conventionally, the transmission microscope has not been provided with a means for positively correcting the position shift.

The present invention has been made in view of the above circumstances, and an object of the present invention is to mathematically determine an angle between different orientations of a crystal of a sample and a displacement of the sample caused by the inclination of the sample. Automatically tilting the sample to a desired tilt based on the angles formed by the different orientations of the crystal of the sample, and automatically and simply to eliminate the displacement of the sample caused by the tilt of the sample. It is an object of the present invention to provide an automatic sample tilting device in a transmission electron microscope which can be moved to a position.

[0006]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a sample moving mechanism for moving a sample in the front-rear, left-right, and up-down directions, and to tilt the sample at a predetermined tilt angle. A sample tilting mechanism, and at least an electronic control unit that controls the sample moving mechanism and the sample tilting mechanism, respectively, and adjusts the position of the sample by moving the sample in the front-rear, left-right, and vertical directions by the sample moving mechanism. At the same time, the sample is tilted to a predetermined tilt angle by the sample tilting mechanism, the sample is irradiated with an electron beam, and the transmitted electrons transmitted through the sample are deflection-controlled by a deflection coil to form an image on an imaging means. In a transmission electron microscope that obtains a high-resolution image of a sample by photographing an image of the sample with an imaging unit, the electronic control unit is configured to perform image processing based on an image signal from the imaging unit. Calculate the current crystal orientation and observe by analyzing the intensity distribution of the electron diffraction pattern from the image recognition device and the electron diffraction pattern obtained from the current crystal orientation of the sample. Calculating the tilt direction and tilt value of the sample tilt mechanism required to shift to the desired crystal orientation, and further generating a position after controlling the sample tilt by the sample tilt mechanism based on the calculated tilt direction and tilt value. Analysis means for calculating a shift; image display means for displaying an image of the sample based on an image signal from the imaging means; and the sample tilt mechanism based on the tilt direction and the tilt value calculated by the analysis means Is controlled so that the crystal orientation of the sample becomes the target crystal orientation to be observed, and the displacement calculated by the analysis means is At least one of the sample moving mechanism and the deflection coil Zui is characterized in that it comprises a position correcting means for position correction control as the positional deviation is eliminated.

Further, in the invention according to claim 2, when the position correction control by the position correction means is a position correction control with a coarser accuracy than a predetermined accuracy, the position correction control is performed by the sample moving mechanism and a fine accuracy of the predetermined accuracy or less. The position correction control is performed by the deflection coil.

Further, according to a third aspect of the present invention, the electronic control unit controls the image of the image display means by the sample tilt mechanism based on the tilt direction and the tilt value of the sample tilt mechanism calculated by the analysis means. The sample is slightly tilted to such an extent that the image of the sample does not deviate from the display screen, and at least one of the sample moving mechanism and the deflection coil is caused by the tilt and based on the displacement of the sample calculated by the analysis means. The method is characterized in that the position correction control of the sample is performed, and the minute tilt and position correction control of the sample are repeatedly performed until the tilt direction and the tilt value of the sample tilting mechanism calculated by the analysis unit are obtained.

[0009]

In the automatic sample tilting apparatus of the transmission electron microscope of the present invention having the above-described structure, when observing the electron diffraction pattern of the sample by TEM, the sample tilt angle required for crystal orientation alignment is mathematically determined. Is calculated. The sample is tilted based on the calculated sample tilt angle. At this time, the displacement of the sample caused by the sample tilt is calculated mathematically. Then, the sample is automatically moved so that the calculated displacement of the sample is eliminated.

In particular, according to the second aspect of the present invention, in the case of a relatively large displacement of the sample, the position correction control is mechanically performed by the sample moving mechanism with a coarser accuracy than a predetermined accuracy, and the minute position of the sample is finely adjusted. In the case of a deviation, the position correction control is electrically performed by the deflection coil with a fine precision equal to or less than a predetermined precision.

According to the third aspect of the present invention, the tilt of the sample is finely controlled so that the position of the sample does not deviate from the image display screen of the image display means. Position correction control is performed so that the positional shift of the sample caused by the minute sample tilt is eliminated. By repeating the micro sample tilt and position correction control, the sample tilt control and the position correction control can be automatically and easily performed without the sample image deviating from the image display screen of the image display means. You will be

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing an example of an embodiment of an automatic sample tilting device in a transmission electron microscope according to the present invention.

As shown in FIG. 1, a transmission electron microscope 1 of this embodiment comprises an electron gun 3 for emitting an electron beam into a lens barrel 2 and a sample 4 in the same manner as a conventionally known transmission electron microscope. A sample mounting table 5 for mounting and supporting, and a deflection coil 6 for focusing transmitted electrons transmitted through the sample 4 on an imaging television (TV) 7
A sample moving mechanism 8 for moving the sample mounting table 5 in the x, y directions and up and down z directions in a horizontal plane so that the sample 4 is at a desired position; And a sample tilting mechanism 9 for tilting the sample mounting table 5 around the x and y axes.

Further, the transmission electron microscope 1 of this embodiment includes:
A control computer 10 is provided. The control computer 10 includes an image recognition unit 11 that recognizes an image of the sample 4 based on an image signal from the imaging TV 7, and an analysis that calculates an azimuth angle based on the image recognition signal from the image recognition unit 11. Means 12, an image display means 13 for displaying a sample image and an azimuth angle based on an image recognition signal from the image recognition means 11 and an analysis signal from the analysis means 12, and a sample 4 based on the analysis signal from the analysis means 12. In order to perform the position correction, the position correction means 14 outputs a position correction signal to the polarizing coil 6, the sample moving mechanism 8 and the sample tilting mechanism 9, respectively, and controls them.

Next, the operation of the automatic sample tilting when observing the electron diffraction pattern using the transmission electron microscope 1 configured as described above will be described. (1) Recognize the electron diffraction pattern in the current crystal orientation. That is, the electron diffraction pattern obtained in the current crystal orientation is photographed on the photographing TV 7 in the same manner as in the related art, and is taken from the photographing TV 7 into the memory of the image recognition means 11 of the control computer 10 to recognize the electron diffraction pattern. . Although the capture of the electron diffraction pattern is not shown,
This is performed by hardware provided with a D converter. Further, the electron diffraction pattern taken in here is generally from an unspecified crystal orientation and not from a target crystal orientation to be observed.

(2) The current crystal orientation is calculated. That is, when the image recognition means 11 recognizes the electron diffraction pattern, it outputs an image recognition signal to the analysis means 12 and
By analyzing the intensity distribution of the electron diffraction pattern,
Calculate the current crystal orientation mathematically. There are various calculation methods. For example, when the operator specifies three spots satisfying the Bragg reflection, the following equation 1 between the azimuth vector v and each reflection vector g is obtained.

[0017]

(Equation 1)

The present invention can be applied to calculate the current crystal orientation. The direction and magnitude of each reflection vector are calculated by indexing the electron diffraction pattern based on the lattice constant, acceleration voltage, and camera length.

(3) The tilt angle required for observation is calculated. That is, after specifying the current crystal orientation from the relationship of Expression 1, the direction and the tilt angle of the sample tilting mechanism (goniometer) 9 necessary for shifting to the crystal orientation to be observed are mathematically calculated.

(4) The first capture of the real image of the sample 4 is performed. That is, a real image of the sample 4 under observation is taken into the memory of the image recognition means 11 of the control computer 10 via the photographing TV 7 to be an image 1 (IMG1), and the image 1 is displayed on the image display means 13. I do.

(5) Perform sample tilt control. That is, a small angle (1 degree to 3 degrees)
Degree of sample tilt is performed. At this time, since the sample 4 is generally not on the mechanical axis, the real image of the sample 4 moves on the observation screen of the image display means 13 with the tilt of the sample. Due to the inclination of 3 degrees), the amount of movement is such that it does not completely deviate from the observation screen, so that the real image of the sample 4 is maintained on the observation screen of the image display means 13.

(6) The second capture of the real image of the sample 4 is performed. That is, the image of the observation sample 4 that has been displaced due to the inclination of the sample at this minute angle (1 to 3 degrees) is stored in the memory of the image recognition unit 11 of the control computer 10 via the imaging TV 7 in the same manner as described above. Image 2 (IMG2)
And

(7) Calculate the image position shift. That is, by calculating the correlation function XCF (r) between the image 1 and the image 2, the displacement (direction, amount) of the sample due to the tilt is mathematically calculated. This correlation function is calculated by a Fourier transform using the following equation (2).

[0024]

(Equation 2)

The position vector R corresponding to the maximum point of the peak (P (r)) appearing in the correlation function calculated in this way corresponds to the amount of displacement and the direction between the image 1 and the image 2.

(8) The position is corrected. That is, the movement of the sample 4 is represented by the obtained position vector R,
That is, the correction is performed in accordance with the accuracy required for the correction so that the displacement caused by the sample tilt is canceled. In that case,
When an accuracy of about 0.1 μ is sufficient, the mechanical sample moving mechanism 8 is operated to coarsely move the sample 4 and
When an accuracy of about 0.1 μ or less is required, the sample 4 is finely moved by using the beam deflection function of the electric deflection coil 6.

(9) Perform an automatic tilt sequence. That is, the above-described processes (4) to (8) are repeatedly performed until the inclination angle required for shifting to the observation target direction is reached. In this way, the tilt of the sample 4 is automatically controlled so that the crystal orientation of the sample becomes the observation target direction.

According to the automatic sample tilting device in the transmission microscope 1 of this embodiment, the displacement of the sample 4 caused by the sample tilt is calculated by image analysis by a computer, and the position is calculated based on the calculated position shift, and the minute displacement is gradually reduced. By repeating the tilt and the position correction, the sample can be automatically and easily tilted without the sample 4 deviating from the observation screen of the image display means 13 up to the tilt angle necessary for obtaining the target orientation. become. And several tens n, which was very difficult in the past
This ease of orientation of the microcrystals of m makes the automatic sample tilter of this example very useful in the field of electron diffraction research.

[0029]

As is apparent from the above description, according to the automatic sample tilting apparatus in the transmission microscope of the present invention, the sample tilt angle required for the crystal orientation alignment and the sample displacement caused by the sample tilt are calculated mathematically. And automatically tilt the sample based on the calculated sample tilt angle,
Since the sample is automatically moved so that the calculated displacement of the sample is eliminated, it is possible to automatically and easily perform the position correction control for tilting the sample to the target direction and eliminating the displacement. Become like This makes it possible to easily align the orientation of microcrystals of several tens of nm, which has been very difficult in the past. Therefore, the automatic sample tilting apparatus in the transmission electron microscope of the present invention is extremely useful in the field of electron diffraction research. It becomes something.

In particular, according to the second aspect of the present invention, in the case of a relatively large displacement of the sample, the position correction control is performed mechanically by the sample moving mechanism, and in the case of a small displacement of the sample, Since the position correction control is electrically performed by the deflection coil, the position correction control can be performed more efficiently.

According to the third aspect of the present invention, the tilt control and the position correction control of the sample are automatically performed without the image of the sample deviating from the observation screen of the image display means. The azimuth adjustment and the positional deviation correction control can be performed with little effort, and the azimuth alignment and the positional deviation correction control of the sample can be performed more accurately.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of an embodiment of an automatic sample tilting device in a transmission electron microscope according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmission electron microscope, 2 ... Electron gun, 4 ... Sample, 5 ... Sample mounting table, 6 ... Deflection coil, 7 ... TV for imaging, 8 ... Sample moving mechanism, 9 ... Sample tilting mechanism, 10 ... Control computer, 11 image recognition means, 12 analysis means, 13 image display means, 14 position correction means

Claims (3)

[Claims] 1. A sample moving mechanism for moving a sample in the front-rear, left-right, and vertical directions, a sample tilting mechanism for tilting the sample at a predetermined tilt angle, and electronic control for controlling the sample moving mechanism and the sample tilting mechanism, respectively. At least a device for adjusting the position of the sample by moving the sample in the front-rear, left-right and up-down directions by the sample moving mechanism, and tilting the sample at a predetermined tilt angle by the sample tilting mechanism. A high resolution image of the sample is obtained by irradiating the sample with an electron beam, deflecting the transmitted electrons transmitted through the sample by a deflection coil to form an image on an imaging unit, and photographing the image of the sample with the imaging unit. In the transmission electron microscope, the electronic control unit is configured to obtain an electron diffraction pattern obtained in a current crystal orientation of the sample based on an image signal from the imaging unit. Means and the sample tilt mechanism required to calculate the current crystal orientation by analyzing the intensity distribution of the electron diffraction pattern from the image recognition means and to shift to the target crystal orientation to be observed. Analyzing means for calculating a tilt direction and a tilt value of the sample, further calculating a position shift generated after the sample tilt control by the sample tilt mechanism based on the calculated tilt direction and the tilt value, and an image signal from the imaging means. Image display means for displaying an image of the sample, the sample tilt mechanism based on the tilt direction and the tilt value calculated by the analysis means, the crystal orientation of the target crystal orientation to be observed and And at least one of the sample moving mechanism and the deflection coil based on the displacement calculated by the analysis means. An automatic sample tilting device for a transmission electron microscope, comprising: a position correcting means for performing position correction control so as to eliminate the positional deviation. 2. The position correction control by the position correction means is performed by the sample moving mechanism when the position correction control is coarser than a predetermined accuracy, and is performed when the position correction control is finer than the predetermined accuracy. 2. The automatic sample tilting device in a transmission electron microscope according to claim 1, wherein the tilting is performed by a deflection coil. 3. An electronic control unit according to claim 1, wherein said sample tilting mechanism converts an image of the sample from an image display screen of said image display means based on the tilt direction and tilt value of said sample tilting mechanism calculated by said analyzing means. The sample is tilted slightly to the extent that it does not deviate, and the position correction control of the sample is performed by at least one of the sample moving mechanism and the deflection coil based on the position shift of the sample caused by the tilt and calculated by the analysis means. 3. The transmission according to claim 1, wherein the control is performed repeatedly until the tilt and the tilt of the sample tilt mechanism are calculated by the analysis means. Automatic sample tilting device for scanning electron microscope.