JPH06242029A - Reflection electron diffraction intensity measuring equipment - Google Patents

Abstract

PURPOSE:To allow intensity measurement of diffraction spot while irradiating a sample with an electron beam by calculating the surface position of a rotating sample instantaneously and then irradiating the position thus calculated with an electron beam. CONSTITUTION:A sample 4 mounted on a sample holder 3 placed in a vacuum chamber 1 is scanned by means of an electron beam projected from a scanning electron gun 2 while being irradiated with a substance evaporated from an evaporation source 5. When a thin film is being formed thereat, surface of the sample 4 is scanned acutely by means of an electron beam projected from the electron gun 2 and a diffraction pattern, generated at the time of reflection or diffraction on the surface of the sample 4, is projected to a fluorescent screen 6 provided on the wall of the vacuum chamber 1. Thus projected diffraction pattern is then observed through a measuring means 7 disposed on the outside of the vacuum chamber 1. A sample rotation mechanism 8 is controlled by a signal delivered from a control means 9 comprising a computer to regulate the starting point of rotary movement or the rotational speed of the sample 4. The electron gun 2 and the means 7 are also controlled in synchronism with the mechanism 8 by a signal delivered from the means 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backscattered electron beam diffraction intensity measuring apparatus for accurately measuring the diffraction spot intensity of a high speed backscattered electron beam diffraction of a rotating sample by using a scanning electron gun.

[0002]

2. Description of the Related Art The necessity of rotating a sample in a vacuum chamber is mainly to rotate a substrate in a thin film forming apparatus such as a molecular beam epitaxy apparatus to improve the uniformity of film thickness and film quality. For the evaluation of the thin film, after forming the thin film on the substrate, the substrate was taken out from the vacuum chamber and the film thickness distribution, composition, crystal structure, surface structure, etc. were measured. As means for observing the microscopic image of the thin film surface, there are an optical microscope and a scanning electron microscope for detecting secondary electrons, but none of them is suitable for in-situ observation during growth of the thin film. The reason is that in the former case, since the distance between the objective lens and the surface of the substrate is short, it is difficult to put it in a vacuum chamber and observe it from the outside. The latter is because the secondary electron detector is sensitive to dirt and the scintillator contamination reduces the detection sensitivity, so that it is difficult to place it in a growth atmosphere. One of the means that enables microscopic observation of the surface of a growing thin film is a backscattered electron diffraction microscope apparatus. However, when this reflection electron beam diffraction microscope device rotates the substrate sample during thin film growth and observes its surface, the rotation mechanism and the diffraction spot intensity measuring mechanism on the fluorescent screen, which is the signal source of the device, are independent. It could not be realized because it had a structure.

In 1983, J. H. Neave et al. Discovered that the diffraction spot intensity of backscattered electron diffraction oscillates with the growth of one atomic layer or one molecular layer.
It is actively used in the thin film formation technology in the molecular beam epitaxy method. However, also in this case, it was impossible to measure the intensity while rotating the sample because the fluorescence intensity measuring mechanism and the substrate rotating mechanism had independent structures that were driven separately.

The conventional backscattered electron diffraction intensity measuring device depends on the atomic arrangement and geometric structure of the sample surface when the sample surface is irradiated with an electron beam from an electron gun in a vacuum chamber evacuated to a high vacuum. The diffraction pattern of the electron beam comes to appear as light emission on the fluorescent screen. At that time, the growth rate can be controlled by measuring the intensity of any part of the diffraction spots with a photomultiplier tube or a television camera. Furthermore, by using a scanning electron gun, the reflection diffraction electron beam image of the sample surface can be controlled. It will be possible to obtain. The former growth rate can be controlled by measuring the intensity oscillation accompanying the growth of the thin film, and the latter observation of the reflected diffraction electron beam image is possible by measuring the intensity change associated with the scanning of the electron beam.

The outline of the measurement of the reflected diffraction electron beam image is as follows. When a predetermined area is selected on the sample and an electron beam controlled by a computer is scanned in the predetermined area, the difference in atomic arrangement due to the location on the sample and the difference in geometric structure are reflected on the fluorescent screen. The fluorescence intensity or shape of the diffraction pattern changes, and the reflected diffraction electron beam image can be obtained by measuring the intensity change of a specific portion on the diffraction pattern at that time with an optical fiber or a television camera.

On the other hand, rotation of the substrate has been effectively applied as a means for improving the composition of the growing thin film and the uniformity of the film thickness distribution.

[0007]

However, the conventional backscattered electron diffraction intensity measuring device cannot continue to irradiate a predetermined position of the rotating sample with the electron beam, and the rotating mechanism of the sample and the electron Since the intensity measurement system including the gun is a different mechanism, it is not possible to measure the intensity in synchronization with the rotational movement. There was a problem that the strength measurement could not be performed.

An object of the present invention is to solve the conventional problems and to make it possible to measure the intensity of diffraction spots while irradiating the surface of a rotating sample with an electron beam. To provide.

[0009]

In order to achieve the above object, the present invention irradiates a sample mounted on a sample holder arranged in a vacuum chamber with an evaporated substance to form a thin film thereon. While scanning, an electron beam from a scanning electron gun irradiates the surface of the sample at an acute angle for scanning, and the diffraction pattern generated when reflected and diffracted on the surface of the sample is projected onto the fluorescent screen, and the projection is performed. In a backscattered electron diffraction intensity measuring device for observing the diffraction pattern thus formed with a measuring means outside the vacuum chamber, a sample rotating mechanism for rotating the sample holder to which the sample is attached, and the surface position of the rotating sample are instantaneously measured. It is characterized in that it is provided with a fluorescence intensity measuring mechanism for controlling the sample rotating mechanism, the scanning electron gun and the measuring means synchronously so as to irradiate an electron beam to the calculated position.

[0010]

In the present invention, the sample rotating mechanism is operated by the signal from the control means to rotate the sample. The scanning electron gun and the measuring means are controlled in synchronization with the signal for operating the sample rotating mechanism. Like Therefore, the control means instantly calculates the position of the rotating thin film on the sample to be irradiated with the electron beam, and the position is irradiated with the electron beam, so that the fluorescence intensity can be measured. Therefore, during the rotation of the sample, it is possible to observe not only the temporal change in the intensity of the diffraction spots (intensity vibration) but also the reflection diffraction electron beam image.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. A backscattered electron diffraction intensity measuring apparatus according to an embodiment of the present invention is shown in FIG. 1, in which a scanning electron gun 2 is attached to the wall of a vacuum chamber 1 and the scanning electron gun 2 The electron beam irradiates the sample 4 mounted on the sample holder 3 arranged in the vacuum chamber 1 with the evaporation material from the evaporation source 5 to form a thin film on the sample 4, and the electron beam is emitted from the scanning electron gun 2. The sample 4 is made to scan while irradiating the surface of the sample 4 at an acute angle, and the diffraction pattern generated when the sample 4 is reflected and diffracted on the surface of the sample 4 is projected on the fluorescent screen 6 on the wall of the vacuum chamber 1 and projected. Diffraction pattern in vacuum tank 1
The outside measuring means 7 is used for observation. Measuring means 7
Is a combination of optical fiber, optical lens, photomultiplier tube,
Alternatively, it is composed of a TV camera. The sample holder 3 is driven by a sample rotation mechanism 8 equipped with a vacuum-compatible stepping motor, and the sample rotation mechanism 8 is controlled by a signal from a control means 9 composed of a computer to rotate the sample 4. The starting point of the movement and the rotation speed are adjusted. Further, the scanning electron gun 2 and the measuring means 7 are also controlled by a signal from the control means 9 in synchronization with the sample rotating mechanism 8.

In such an embodiment, the sample rotating mechanism 8 is operated by the signal from the control means 9 to rotate the sample 4, but the scanning electron gun is synchronized with the signal for operating the sample rotating mechanism 8. 2 and the measuring means 7 come to be controlled. Therefore, the control means 9 instantaneously calculates the position to be irradiated with the electron beam on the sample 4 during the formation of the rotating thin film,
The position is irradiated with an electron beam, and the fluorescence intensity can be measured. Therefore, during the rotation of the sample 4, it is possible to observe not only the temporal change of the intensity of the diffraction spots (intensity vibration) but also the reflection diffraction electron beam image.

FIG. 2 shows how the surface of the sample 4 is scanned with the electron beam from the scanning electron gun 2. Now
Consider a case where the intensity of the diffraction spot is measured while scanning the sample 4 with an electron beam. The electron beam was irradiated from the upper part of the figure to the surface of the sample, and (1, 1) →
It is assumed that it is necessary to scan in the order of (2, 1) → ... (n, 1) → ... (n, n). It is assumed that the rotation axis is at the center of the sample, but whether or not it is at the center does not matter.

When the sample 4 is stationary without rotating, the electron beam is continuously scanned along the x-axis and the y-axis in the figure, and the strengthening change of the RHEED diffraction spots at that time may be monitored. . However, when the sample 4 is rotating, the next irradiation position on the sample 4 is also rotating, so it is necessary to obtain the irradiation position in accordance with the rotation. As a simple example, suppose that the (1,1) point in the observation area is irradiated, and then (2,1)
When irradiating a point, waiting for the sample 4 to make one rotation and returning makes it possible to observe the sample as if it were not rotating.

Further, as another observation method, it is also possible to calculate the irradiation position that changes by rotation and irradiate the electron beam. FIG. 3 shows the situation. The one shown in FIG.
Since the zero point of the rotational movement and the rotational speed can be controlled by the computer, the positional change of a certain point on the sample after starting the rotational movement can be accurately obtained.
Therefore, as in the previous example, after irradiating the (1,1) point, the position when irradiating the next (2,1) point is calculated and the timing is calculated, and if the electron beam is swung as it is, Good.
At this time, as shown in FIG. 3, the position of the reflection diffraction spot on the screen for measuring the intensity also changes with the rotation, so the position of the measurement point must also be calculated and the measurement probe must be made to follow it.

In the above embodiment, a vacuum-compatible stepping motor is used as the sample rotating mechanism 8, but instead of this, a normal rotation introducing terminal is used to rotate the atmosphere side rotating portion into a chain or a wire. It is also possible to control the rotational movement of the sample by connecting to the motor with. Further, the computer of the control means 9 need not be a general-purpose product with a CRT, but may be a board computer having a CPU. Further, the controller can be configured by an analog circuit without using a computer.

[0017]

Since the present invention has the above-mentioned structure, the control means instantly calculates the position to be irradiated with the electron beam on the sample during the formation of the rotating thin film, and the position is set to that position. The electron beam is emitted, and the fluorescence intensity can be measured. Therefore, during the rotation of the sample, it is possible to observe not only the temporal change of the diffraction spot intensity (intensity vibration) but also the reflection diffraction electron beam image.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing how a sample surface is scanned with an electron beam in an embodiment of the present invention.

FIG. 3 is an explanatory view showing a state of scanning the surface of a rotating sample with an electron beam in the embodiment of the invention.

[Explanation of Codes] 1 ... Vacuum tank 2 ... Scanning electron gun 3 ... Sample holder 4 ... Sample 5 ... Evaporation source 6 ... ..Fluorescent screen 7 ... Measuring means 8 ... Sample rotation mechanism 9 ... Control means

Front page continuation (72) Inventor Hiroshi Yanagida 2500 Hagien, Chigasaki City, Kanagawa Japan Vacuum Technology Co., Ltd.

Claims (1)

[Claims] 1. A sample mounted on a sample holder arranged in a vacuum chamber is irradiated with an evaporated substance to form a thin film thereon, and an electron beam from a scanning electron gun is applied to the sample. Backscattered electrons that are scanned while irradiating the surface at an acute angle, project the diffraction pattern generated when reflecting and diffracting on the surface of the sample onto a fluorescent screen, and observe the projected diffraction pattern with measuring means outside the vacuum chamber. In a line diffraction intensity measuring device, a sample rotation mechanism that rotates a sample holder to which the sample is attached, and the surface position of the rotating sample is instantly calculated, and the sample rotation is performed so that the position is irradiated with an electron beam. A backscattered electron beam diffraction intensity measuring apparatus, comprising: a mechanism, a scanning electron gun, and a fluorescence intensity measuring mechanism for synchronously controlling the measuring means.