JP2000088560A - Method and apparatus for measurement of film thickness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which a film thickness can be measured by using a phenomenon that, while a thin film sample is being manufactured by a vacuum evaporation operation, the degree of polarization of secondary electrons emitted by irradiating the surface of the sample with primary electrons generates a kink in every thickness of one atomic layer as a function of the film thickness of the sample. SOLUTION: While a nonmagnetic-substance sample is being vacuum-evaporated by using a vacuum evaporation device 13, a magnetic-substance substrate 11 is irradiated with primary electrons having an energy of about 100 eV by an electron gun 12. At this time, the degree of polarization of secondary electrons emitted from the surface of the sample is measured by a degree-of-polarization measuring device 14, and it is attenuated as a function of the film thickness of the nonmagnetic-substance sample formed on the substrate 11. At this time, regarding the degree of polarization of the secondary electrons during the vacuum evaporation operation, its grade is changed discontinuously when the formation of every layer is completed, and a kink is generated in the film thickness. Iron is used as the substrate 11, and gold is used as the nonmagnetic-substance sample. At this time, the kink is equal to the thickness of one atomic layer of the gold. As a result, when the film thickness of the gold can be calibrated by using the kink, the thickness of a gold thin film can be detected precisely. By using this phenomenon, the film thickness can be measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a film thickness, and more particularly to a method and an apparatus for measuring a film thickness suitable for measuring a sample film thickness at an atomic level.

[0002]

2. Description of the Related Art When a material different from the above-mentioned substrate is formed on a substrate by a vacuum deposition method, the phenomenon that the Auger signal intensity causes a kink for every one atomic layer as a function of the film thickness of the sample is measured. The method used for thin solid films (Thin Solid Films) Vol. 188 (1990), No. 10
It is reported from pages 9 to 122.

A method of measuring the thickness of a sample based on the Auger signal intensity can be explained by the following principle.

Now, consider a case where a thin film having a thickness of one atomic layer d is present on a substrate. The signal intensity Is of Auger electrons from the substrate decreases when passing through the thin film, and Is = Is
0exp (-d / As). On the other hand, the signal intensity Id of Auger electrons from the thin film is Id = Id0 (1-exp (-d
/ Ad)). Here, Is0 and Id0 are the values of Is and Id for a sufficiently thick substrate and thin film, respectively, and As and Ad are the average escape depths of Auger electrons, respectively. In other words, the signal intensity of Auger electrons emitted from inside the sample attenuates when passing through the upper layer,
The signal intensity of Auger electrons from the substrate and the thin film when the layered thin film having the n-th layer coverage r is present on the substrate is Isn (r) = Is0 ((Is1 / Is0) ^ (n -1)) (1+
(Is1 / Is0−1) r), Idn (r) = Id0 (1 − ((Id1 / Id0) ^ (n−
1)) (1− (Id1 / Id0) r)). Here, Is1 and Id1 are the signal intensities of Auger electrons from substrate atoms and adatoms when a thin film of one atomic layer exists.

As is apparent from this equation, the signal intensity of Auger electrons during the formation of each layer changes linearly during the deposition of the thin film sample on the substrate, but upon completion of the formation of each layer, The gradient changes discontinuously. Therefore, the film thickness can be measured at an atomic level from the discontinuous change of the gradient.

[0006]

However, in the above-mentioned prior art, since only minute Auger electrons are selectively collected from all the electrons emitted from the vicinity of the sample surface, sufficient brightness and high brightness for detecting Auger electrons are obtained. It is necessary to bring the electron optical system having energy resolution sufficiently close to the sample surface. For this reason, there is a problem in that a special sample stage that does not prevent the deposition material from being incident on the substrate is required.

Furthermore, in the above prior art, an electron optical system having sufficient brightness and high energy resolution necessary for selecting only minute Auger electrons from all the electrons emitted from a sample has an expensive and complicated structure. There is a problem in point.

Further, the above-mentioned prior art has a problem in that the configuration around the sample becomes complicated in realizing the above-mentioned prior art due to the above two problems, so that handling of the apparatus becomes difficult.

Further, in the above-mentioned prior art, since Auger electrons having a weak signal intensity are used, it takes a long time to measure a signal, thereby taking a long time to measure a film thickness. Therefore, there is also a problem that the vapor deposition rate of the sample in the vacuum vapor deposition method cannot be increased.

An object of the present invention is to provide a method and an apparatus for measuring the film thickness which do not require the electron optical system to be sufficiently close to the surface of the sample, whereby a special sample which does not prevent the deposition material from entering the substrate. An object of the present invention is to provide a method and an apparatus for measuring a film thickness which do not require a table.

Another object of the present invention is to eliminate the necessity of selecting only minute Auger electrons from all the electrons emitted from a sample, so that an electron optical system having sufficient brightness and high energy resolution becomes unnecessary. It is to provide a measuring method and an apparatus.

Another object of the present invention is to provide a method and an apparatus for measuring a film thickness, in which the structure around a sample is simple and the handling of the apparatus is easy.

Another object of the present invention is to provide a method and an apparatus for measuring the thickness of a film, which can increase the vapor deposition rate of a sample in a vacuum vapor deposition method as compared with the case of using Auger electrons.

[0014]

The problem described above is based on the phenomenon that the degree of polarization of secondary electrons emitted from the surface of a sample during vacuum deposition causes a kink per atomic layer thickness as a function of the film thickness of the sample. It can be solved by using it.

The phenomenon that the degree of polarization of secondary electrons shows a kink for each atomic layer can be explained by the following principle.

Consider a case where a non-magnetic material having a thickness of one atomic layer T is vacuum-deposited on a magnetic substrate. Secondary electrons emitted when the surface of a magnetic material is irradiated with primary electrons are polarized. However, when a non-magnetic material is deposited on this surface, the degree of polarization of the secondary electrons is reduced by the thickness of the non-magnetic material. Decreases gradually as a function. Now, assuming that a non-magnetic thin film is deposited by one atomic layer on the magnetic substrate by the vacuum deposition, the degree of polarization P of the secondary electrons emitted from the sample surface is approximately P = P0exp (−T /
L). Here, P0 is the degree of polarization of the secondary electrons emitted from the surface of the magnetic substrate when the thickness of the nonmagnetic thin film is 0, and L is the amount called the magnetization information depth with respect to the nonmagnetic material. It is given as the thickness of the nonmagnetic material at which the value of P0 becomes 1 / e by vapor deposition of the nonmagnetic material on top. Also,
For simplicity, secondary electron yields for magnetic and non-magnetic materials were assumed to be equal.

Therefore, when a nonmagnetic thin film composed of m layers is present on the magnetic substrate and the coverage of the m-th layer, which is the uppermost layer, is q, the secondary electrons emitted from the sample surface Is P (q) = P0exp (− (m−1) T / L) (1
− (1-exp (−T / L)) q). Thus, the degree of polarization of secondary electrons during actual vacuum deposition is
While each layer changes linearly during its formation, the gradient changes discontinuously when the formation of each layer is completed.

In the above example, the case where a non-magnetic material sample is deposited on a magnetic substrate is considered. Conversely, even when a magnetic material sample is vacuum-deposited on a non-magnetic substrate, kinks may occur due to the same concept. Explain.

As described above, the phenomenon in which the degree of polarization of secondary electrons shows a kink for each atomic layer can be explained. This makes it possible to know the thickness of the sample during vacuum deposition with an accuracy of one atomic layer thickness or less. Furthermore, since the measurement sensitivity of the degree of polarization of the secondary electrons is superior to that of the Auger electron signal intensity, when forming a sample by the vacuum evaporation method, a film with high accuracy can be obtained even at a higher deposition rate. Thickness measurement becomes possible. Where 1
The energy of the secondary electron may be larger than about 10 eV, which is the minimum energy at which secondary electron excitation is possible, but is preferably 100 eV or less in order to more clearly see the kink.

[0020]

FIG. 1 is a diagram showing a first basic configuration of an embodiment of a film thickness measuring method and apparatus according to the present invention.
This configuration includes a magnetic substrate 11, an electron gun 12 for irradiating the magnetic substrate 11 with primary electrons, and a magnetic substrate 11.
The apparatus comprises a vapor deposition device 13 for vapor-depositing a non-magnetic sample thereon, and a polarization measuring device 14 for measuring the polarization of secondary electrons hit by primary electrons. Here, the electron gun 12 has a function of freely setting the energy of primary electrons from about 10 eV to about 5 keV.

In this configuration, the electron gun 1 is deposited while depositing a non-magnetic sample on the magnetic substrate 11 using the deposition device 13.
2 irradiates primary electrons having an energy of about 100 eV. At this time, the polarization degree of the secondary electrons emitted from the sample surface is measured by the polarization degree measuring device 14. The measured degree of polarization of the secondary electrons attenuates as a function of the thickness of the non-magnetic sample formed on the magnetic substrate 11. At this time, as described above, the degree of polarization of the secondary electrons during the vacuum deposition changes linearly during the formation of each layer, but the gradient changes discontinuously when the formation of each layer is completed. And kink occurs at the film thickness.

FIG. 2 shows how the degree of polarization of secondary electrons attenuates when iron is used as the magnetic substrate 11 and gold is used as the non-magnetic sample. Since the kink appearing here is equal to the thickness of one atomic layer of gold, the gold film thickness on the horizontal axis can be calibrated using this kink, and the accurate thickness of the gold thin film can be known. Therefore, the use of this phenomenon enables highly accurate film thickness measurement.

Further, the energy of the primary electrons, in which the kink of the degree of polarization of the secondary electrons is most remarkable, may be different depending on the kind of the sample and the plane orientation. In this embodiment, the primary electron energy is set to about 100 eV as an example. However, the kink of the degree of polarization of the secondary electrons appears most remarkably by changing the energy of the primary electrons according to the type of sample and the plane orientation. This method may be used under optimal conditions.

FIG. 3 is a diagram showing a second basic configuration of the embodiment of the film thickness measuring method and apparatus according to the present invention. This configuration includes a magnetic substrate 11, an electron gun 12 for irradiating the magnetic substrate 11 with primary electrons, and a magnetic substrate 11.
A vapor deposition device 13 for vapor-depositing a non-magnetic material sample thereon, a polarimeter 31 for measuring the polarization of secondary electrons hit by primary electrons, and a direction of a spin magnetic moment 32 of secondary electrons. Consists of a spin rotator 33 that can rotate freely. Here, as in the first embodiment, the electron gun 12 has a function of freely setting the energy of primary electrons from about 10 eV to about 5 keV. Further, it is assumed that the polarization measuring device 31 in the present embodiment detects a component perpendicular to the secondary electron orbit 34 of the spin magnetic moment 32 of the secondary electron.

In this configuration, the electron gun 1 is deposited on the magnetic substrate 11 while the non-magnetic sample is deposited by the deposition device 13.
2 irradiates primary electrons having an energy of about 100 eV. At this time, the polarization degree of the secondary electrons emitted from the sample surface is measured by the polarization degree measuring device 31. At this time, since the spin magnetic moment 32 of the secondary electrons is emitted in the same direction as the direction of the magnetization 35 of the magnetic substrate 11, the spin magnetic moment 32 of the secondary electrons emitted from the magnetic substrate 11 is The direction is at an angle A with respect to the secondary electron trajectory 34.

Accordingly, the direction of the spin magnetic moment 32 of the secondary electron is changed by the spin rotator 33 to the secondary electron orbit 3
By rotating the polarizer 4 in a direction perpendicular to the direction 4 and thereafter making it incident on the polarimeter 31, the polarimeter 31 can measure the degree of polarization of the secondary electrons with the highest efficiency. The measured degree of polarization of the secondary electrons attenuates as a function of the film thickness of the non-magnetic sample formed on the magnetic substrate 11, as in the first embodiment. Here, the degree of polarization of the secondary electrons during the vacuum deposition changes linearly during the formation of each layer, but upon completion of the formation of each layer, the gradient changes discontinuously. Kink occurs in the film thickness. Since the kink is generated for each atomic layer of the non-magnetic material sample, the film thickness can be measured with high accuracy.

Further, in the present embodiment, as in the first embodiment, the energy of the primary electrons in which the kink of the degree of polarization of the secondary electrons appears most remarkably may vary depending on the type of sample and the plane orientation. Also, in this embodiment, the method may be used under the optimal condition in which the kink of the degree of polarization of the secondary electron appears most remarkably by adjusting the energy of the primary electron according to the kind and the plane orientation of the sample.

Further, in this embodiment, the case where the angle A is not 90 degrees has been described. However, when the angle A is 90 degrees from the beginning, the spin rotator 33 becomes unnecessary, and the entire configuration can be simplified. .

FIG. 4 is a diagram showing a third basic configuration of an embodiment of the film thickness measuring method and apparatus according to the present invention. This configuration includes a magnetic substrate 11, an electron gun 12 for irradiating the magnetic substrate 11 with primary electrons, a vapor deposition device 13 for vapor-depositing a non-magnetic sample on the magnetic substrate 11, and a strike by primary electrons. It comprises a polarimeter 14 for measuring the degree of polarization of the secondary electrons thus obtained, and a computer 41 for controlling these devices and collecting data. Further, the electron gun 12 reduces the energy of the primary electrons to 10 e as in the first embodiment.
It has a function that can be freely set from about V to about 5 keV.

In this configuration, the non-magnetic sample is vapor-deposited on the magnetic substrate 11 by the vapor
Irradiates primary electrons having an energy of about 100 eV. At this time, the polarization degree of the secondary electrons emitted from the sample surface is measured by the polarization degree measuring device 14. The measured degree of polarization of the secondary electrons attenuates as a function of the film thickness of the non-magnetic sample formed on the magnetic substrate 11, as in the first embodiment. Here, the degree of polarization of the secondary electrons during the vapor deposition changes linearly during the formation of each layer, but upon completion of the formation of each layer, the gradient changes discontinuously, and the film becomes thin. Kink at thickness. Since the kink is generated for each atomic layer of the non-magnetic material sample, the film thickness can be measured with high accuracy. By monitoring the kink position of the degree of polarization of the secondary electrons by the computer 41, the film thickness measurement is automated.

Further, in the present embodiment, as in the first embodiment, the energy of the primary electron in which the kink of the degree of polarization of the secondary electron appears most remarkably may vary depending on the type of sample, the plane orientation, and the like. Also, in this embodiment, the method may be used under the optimal condition in which the kink of the degree of polarization of the secondary electron appears most remarkably by adjusting the energy of the primary electron according to the kind and the plane orientation of the sample. At this time, the kink measurement of the degree of polarization of the secondary electrons and the control of the electron gun 12 are performed by the computer 41, thereby enabling automation.

Further, in this embodiment, the control of the vapor deposition rate can be automated by monitoring the film thickness with respect to the vapor deposition time by the computer 41 and controlling the vapor deposition apparatus 13 so that the vapor deposition rate becomes an arbitrary velocity.

Further, in this embodiment, the film thickness with respect to the vapor deposition time is monitored by the computer 41, and when the target film thickness is obtained, the vapor deposition is automatically stopped by the computer 41, so that an arbitrary film thickness is obtained. Sample preparation can be performed automatically. At this time, information on the target film thickness may be input to the computer 41 in advance.

Further, in this embodiment, it has been shown that various measurements can be automated by the computer 41 based on the first embodiment. However, in the second embodiment, various kinds of measurement can be performed by using the computer 41. It is possible to automate the measurement and control of the device.

[0035]

According to the present invention, since it is not necessary to select and collect only minute Auger electrons from all the electrons emitted from the vicinity of the sample surface, it is necessary to bring the electron optical system sufficiently close to the substrate surface. There is an effect that it is possible to provide a method and an apparatus for measuring a film thickness that does not occur. Further, according to the present invention, there is an effect that a special sample stage that does not prevent the deposition material from being incident on the substrate becomes unnecessary.

Further, according to the present invention, it is not necessary to select only small Auger electrons from all the electrons emitted from the sample, so that an electron optical system having sufficient brightness and high energy resolution is not required. . Further, according to the present invention, there is an effect that the configuration around the sample is simplified, thereby facilitating the handling of the apparatus. Further, according to the present invention, there is an effect that the vapor deposition rate of the sample in the vacuum vapor deposition method can be made higher than in the case of using Auger electrons. The application of these effects to academic fields, and their industrial value, is very high.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a basic configuration of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a measurement diagram showing an example of a kink of the degree of polarization of secondary electrons obtained by the present invention.

FIG. 3 is a perspective view illustrating a basic configuration of an apparatus according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing an embodiment of the present invention in which automatic control of vapor deposition by a computer is enabled.

[Explanation of symbols]

11: magnetic substrate, 12: electron gun, 13: vapor deposition device, 1
4. Polarization measuring device, 31: Polarization measuring device, 32: Spin magnetic moment, 33: Spin rotator, 34: Secondary electron orbit, 35: Magnetization, 41: Computer.

Claims (7)

[Claims] 1. During the preparation of a thin film sample by vacuum deposition, the degree of polarization of secondary electrons emitted by irradiating the sample surface with primary electrons is kinked at every atomic layer thickness as a function of the sample film thickness. A film thickness measuring method characterized by utilizing a phenomenon that causes the film thickness. 2. The method according to claim 1, wherein the use of an electron gun having a function of setting the primary electron energy to an arbitrary value reduces the energy of the primary electron in which the kink of the degree of polarization of the secondary electron appears most clearly. A film thickness measuring method characterized by selecting and using. 3. A magnetic substrate, an electron gun for irradiating the magnetic substrate with primary electrons, a vapor deposition device for vapor-depositing a non-magnetic sample on the magnetic substrate, and A polarization measuring device for measuring the degree of polarization of the knocked out secondary electrons, and the energy of the primary electrons is increased from about 10 eV to 5 k.
A film thickness measuring device comprising means for setting the voltage to about eV. 4. A magnetic substrate, an electron gun for irradiating the magnetic substrate with primary electrons, a vapor deposition device for vapor-depositing a non-magnetic sample on the magnetic substrate, A polarimeter for measuring the degree of polarization of the ejected secondary electron, a spin rotator capable of rotating the direction of the spin magnetic moment of the secondary electron in an arbitrary direction, and an energy of 10 eV for the primary electron. A film thickness measuring device comprising means for setting the pressure from about 5 keV to about 5 keV. 5. The apparatus according to claim 3, wherein the polarization measuring device is means for detecting a component perpendicular to the secondary electron orbit with respect to the spin magnetic moment of the secondary electron. Film thickness measuring device. 6. A film thickness measuring apparatus according to claim 3, wherein said polarization degree measuring device is arranged in a direction perpendicular to an incident secondary electron orbit. 7. The method according to claim 4, wherein the spin rotator comprises:
A film thickness measuring apparatus characterized in that it is means for rotating the direction of the spin magnetic moment of the secondary electron in an arbitrary direction without changing the orbit of the incident secondary electron.