JPH0831304A - Electron beam source, and electron beam application device and electronic device usinging the source - Google Patents

Abstract

PURPOSE:To provide an electron beam source which generates an electron beam having a narrow energy width and which can favorably be used in forming a high performance, milti-funstional electron beam application device using a monochromatic electron beam by selecting a specific electron beam source. CONSTITUTION:An electron beam source is selected which has a double barrier type quantum well layer and which is structured so that the electron transmission probability of the double barrier layer including the quantum well layer becomes approx. one. Preferably, the double barrier layer is structured so that the electron permiation lengths into the two barrier layers are identical substantially. For example, a barrier layer 12 of a single crystal AlAs film with a film thickness less than the permeation length of electron wave is grown by a molecular beam epitaxy method on the surface of a needle 11 which is made of n<+> type GaAs single crystal and whose radius of curvature at the tip is 0.1mum, and thereover a quantum well layer 13 of a single crystal GaAs film is grown, and thereby an electron beam source is accomplished which generates an electron beam by impressing a negative voltage on the opposing electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam source and an electron beam application apparatus, and more particularly, to an ultra-monochromatic electron beam source suitable for an electron microscope having a high resolution and an analysis apparatus for evaluating materials by energy analysis and the same. The present invention relates to an electron beam application device and an electronic device using.

[0002]

2. Description of the Related Art A field emission type electron gun is widely used as a conventional electron beam source having a narrow energy width, and the principle of this is described in, for example, Japan Society for the Promotion of Science. The 132nd Committee edition, Electron / Ion Beam Handbook 2nd Edition (1986 Nikkan Kogyo Shimbun), pp. 145-151. In this electron beam source, the tip of the tungsten (W) cathode is
By sharpening the diameter to about 00 nm, the electric field is concentrated on the tip portion, and as a result, the electrons that are field-emitted from the tip portion into the vacuum are used.

Further, in an analyzer using a monochromatic electron beam, in order to obtain an electron beam with a narrow energy width,
An electron beam generated from a conventional electron beam source is passed through an energy analyzer, energy is dispersed by a magnetic field or an electric field, and a very small part thereof is taken out by a slit or the like.

Further, conventional metal / insulator / metal (MI
M) structure cathode instead of semiconductor / insulator / semiconductor (S
IS) The idea of using the resonant tunneling phenomenon as a multi-layered structure was introduced in Takeuchi and Mikoshiba's "Physics and Applications of the Tunneling Phenomenon" by Yokoo and Ono in "Chapter 6 Tunnel Emission Issues", published by Baifukan (1987). ~ Page 90. However, the specific structure and voltage application method are not described. As an example of forming a double barrier structure by using a SIS multilayer film in a conventional MIM structure, what is easily analogized is shown in FIG. MIM
At the cathode, a voltage is applied between the substrate and the upper electrode, and electrons in the substrate are pulled out by the tunnel effect. And
When this potential difference becomes larger than the work function, the extracted electrons are easily emitted into the vacuum.

Further, the structure of an electron source for obtaining an electron beam by the resonant tunneling phenomenon using a quantum well layer is disclosed in Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent Publication No.-74333.

[0006]

However, JP-A-5-7
In the structure disclosed in Japanese Patent No. 4333, a sufficient transmission probability cannot be obtained, so that there is a problem that the current density is small and it is difficult to use as an electron beam source.

There is a potential energy difference called a work function between the electrons inside W and the free electrons in vacuum, and the electrons inside W do not go out at room temperature. In the conventional example, when the vacuum level is bent by applying a high electric field to form a thin triangular potential barrier as shown in FIG. 2A, some of the electrons in W pass through this potential barrier by the tunnel effect. , Released into a vacuum.
The energy distribution of the electron beam in this case is the product of the energy distribution of the electrons inside W and the transmittance of the potential barrier, and becomes the distribution shown in FIG. As a result, the energy full width at half maximum of the emitted electrons becomes about 0.26 eV at room temperature. When the temperature is lowered, the Fermi distribution of electrons becomes steeper so that the spread on the high energy side becomes smaller, but the half value width is about 0.2 eV even at absolute zero. This is because the spread on the low energy side from the peak is determined by the transmittance of the potential barrier, and this transmittance does not change even at low temperatures. Therefore, in the conventional example, there is a problem that further monochromaticization cannot be expected and a significant improvement in the resolution of the microscope cannot be expected.

Further, in an analyzer using a monochromatic electron beam, since an energy analyzer is used in the electron optical system, there are problems that the electron dose is reduced and it is difficult to downsize the device. In particular, in the case of a high resolution electron energy loss spectroscopy (EELS) device, a high resolution energy analyzer is used to obtain an electron beam with an energy width of several tens of meV or less. Took a long time. Also in this case,
There is a problem that a lot of labor is required for assembling a high-resolution energy analyzer, alignment, adjustment of an electron beam, and the like. Further, in this case, since the analyzer becomes large when the focal length of the analyzer is long, the degree of freedom in arranging the sample, the electron beam source, etc. is small, and downsizing of the device is difficult, and it becomes multifunctional in combination with other devices. There was a problem that it was difficult.

Further, in the example shown in FIG.
Under the operating conditions, as shown in FIG. 12 (b), a high electric field is generated in the insulator, so that the energy structure of the double barrier is not symmetrical, and a resonance condition in which the transmission probability is 1 is completely obtained. Absent. Further, near the upper electrode, electrons having a large kinetic energy called hot electrons become lost due to scattering in a solid, and the energy distribution of emitted electrons is widened.

The main object of the present invention is to solve the above problems and to provide an electron beam source for generating an electron beam having a narrow energy width according to a new principle, and to provide a high-performance electron beam using a monochromatic electron beam. It is to provide a wire application device and an electronic device.

[0011]

In order to form an electron beam source having a narrow energy distribution, only electrons having a specific energy level among the electrons in a solid are used and a double barrier type quantum well layer is used. The resonance tunneling phenomenon may be used for selective extraction. The narrower this selection is, the smaller the energy width of the electron beam can be obtained.

Further, high performance using a monochromatic electron beam,
In order to form a multifunctional device, an electron beam source having a narrow energy distribution may be used. As a result, it is possible to eliminate the use of an energy analyzer having a high resolution, which has many restrictions in use.

[0013]

In order to achieve the above-mentioned means for selectively extracting only the electrons of a specific energy level among the electrons in the solid, two energy barrier layers for the electrons are provided in the electron emission path. A quantum well layer surrounded by the double barrier is formed, and the resonance tunnel phenomenon due to this double barrier structure is utilized. That is, when an electron having an energy matching the quantum level in the quantum well enters the double barrier layer, it is transmitted with a very high probability. This resonance condition is present everywhere according to the quantum level, and the energy band with high transmission probability is extremely narrow. It is, so to speak, an electron wave interference filter. Here, in order to set the resonance condition such that the transmission probability is completely 1, it is sufficient to make the structure symmetrical about the quantum well. In particular, the two barriers have the same barrier height, effective electron mass, and thickness. It can be realized by

In the present invention, in order to apply this resonance tunnel phenomenon to the electron beam source, a double barrier structure is provided between the solid and the vacuum. As shown in FIG. 3A, a triangular potential barrier 3 formed by a vacuum level under a high electric field.
1 is one of the double barriers, and the other barrier is a thin film 12 formed inside the electron beam source. The quantum well is the thin film 13. In the case of this electron beam source, since one of the barriers is vacuum and the other is solid and the two barriers are not the same material, ideal resonance conditions cannot be obtained, but conditions close to it can be selected. it can.

The electron transmittance D for one potential barrier can be written as follows using the WKB approximation.

D = exp {2∫k (x) dx} (Equation 1) where x is a variable representing a position, integral is a definite integral over the thickness of the barrier layer, and k (x) is represented by the following equation. .

K (x) = [√ {2m (V (x) −E)}] 2π / h (Equation 2) where m is the effective mass of the electron, V (x) is the barrier height, and E
Is the electron energy and h is Planck's constant.

The reciprocal of k (x) corresponds to the length of penetration of the electron wave into the barrier, and the value of D becomes larger as the film thickness becomes thinner and the penetration length becomes longer. Then, in order to obtain a condition close to an ideal resonance state, it is desirable that the value of D be substantially the same in both barriers and be larger than one millionth order. This condition is achieved by controlling the potential barrier 31 formed in vacuum with an external electric field. That is, the electric field strength is 3 to 10
V / nm is required. This condition is achieved by using a structure having a convex tip like a field emission electron source.

The barrier layer 1 provided in the electron beam source
Regarding No. 2, the condition can be achieved by making the film thickness equal to or less than the permeation length determined by the effective mass m of electrons, the barrier height V, and the electron energy E. That is, it is possible to provide a monochromatic electron beam source having an extremely small energy width, which is the object of the present invention.

As described above, according to the present invention, a resonance tunnel phenomenon occurs between a solid and a vacuum, which is different from the example shown in FIG. Moreover, there is an advantage that an electron beam having a sufficiently large current amount can be obtained.

By using an electron beam source having an extremely narrow energy distribution, the high-resolution energy analyzer used in the conventional electron beam monochromatizer becomes unnecessary, and the structure is simpler and the electron dose does not decrease. Since the sample reaches the sample surface, it is possible to provide an analyzer capable of measuring in a short time.

The present invention will be described in detail below with reference to examples.

[0023]

【Example】

(Embodiment 1) FIG. 1 shows one embodiment of the present invention. A needle 11 having a tip of n + type GaAs single crystal extending in the (111) direction and having a radius of curvature of 0.1 μm was used as the first material, and a 1.4 nm single crystal was formed near the tip by molecular beam epitaxy (MBE). A crystalline AlAs film 12 is used as a second material, and a 7 nm single crystal GaAs film 13 is grown thereon as a third material. This results in the formation of the energy structure shown in Figure 1b. After introducing this into a vacuum device and cleaning the surface by heating at 540 ° C. for 5 minutes, the electric field near the tip is 3 to 10 V with respect to the opposing anode.
When a negative voltage is applied up to about / nm, the structure shown in FIG.
Moreover, since the electron transmittance has energy dependence as shown in FIG. 3b, an electron beam having an extremely narrow energy width can be obtained. 26m of heat energy at room temperature
The width is about eV. Furthermore, by mounting a cryostat on this electron beam source, the liquid nitrogen temperature (77
7 meV at K), 1 meV at liquid helium temperature (4 K)
An electron beam with an energy width of about a degree can be obtained.

In this embodiment, the GaAs quantum well layer 13, which is the outer third material, is not doped with impurities. However, when the operating condition becomes unstable due to the presence of the surface level, the GaAs quantum well layer 13 is used. Doping about 10 ^{12 of} Si, which is an n-type impurity, in the well layer 13 per square centimeter has an advantage that the surface potential is fixed and stable operation is obtained.

In this embodiment, n + type GaA is used as the first material of the electron beam source base material 11, the second material of the barrier layer 12, and the third material of the quantum well layer 13, respectively.
s, 1.4 nm AlAs, and 7 nm GaAs are used, but n + type GaAs, AlGaAs, and G are also used.
aAs combination, or other III-V group compound semiconductor, for example, lattice mismatched system combination such as InGaAsP mixed crystal, or II-VI group compound semiconductor, for example n +.
Type ZnSe, ZnS, combination of ZnSe, or
Even if a group IV semiconductor such as a combination of n + type Ge, Si-Ge, and Ge is used, if the thickness of the barrier layer and the quantum well layer is adjusted by the effective mass of each material and the electron potential, the material having the same physical properties can be obtained. Since it is a combination, the same effect can be obtained.

In the case of an indirect transition type semiconductor such as Ge, it is more effective to select an azimuth having a small effective mass as the electron traveling direction. Also, if the electron traveling direction is selected to be a crystal orientation with a small work function of the surface material, an electron beam with a small divergence angle and good convergence can be obtained, which is advantageous for high resolution when applied to an electron microscope or the like. .

Further, in this embodiment, the semiconductor is used as the combination of materials, but if the first material is metal, metalloid or the like as the base material of the electron beam source, the electron density is higher than that of the semiconductor. An electron beam source with a large amount of current can be obtained. For example, if single crystal NiAl is used, n + type GaAs, ALGaAs, and
GaAs-based single crystal can be grown, and single crystal CoSi ₂ can be used to grow Si and Ge-based single crystals. Further, even if an insulator having a thickness of about 1 nm or less is used as the second material for the barrier layer, the same effect as that of the embodiment is obtained. For example, single crystal CaF
₂ combined with Si and GaAs, and single crystal Al
2O3 is capable of single crystal growth in combination with Si,
In this case, the heat resistance is higher than that of a semiconductor, and there is an advantage that it operates even at a large current density. Therefore, it is more effective to use these metals, insulators and semiconductors in combination.

MBE is used here as a crystal growth method.
Although the method is used, similar effects can be obtained as long as it is a method capable of growing a single crystal thin film, such as MOCVD (metal organic chemical vapor deposition) method and CVD (vapor phase growth) method.

In this embodiment, a single crystal is used as the material, but the same effect can be obtained by using an amorphous material having a thickness of about 1 nm or less. In this case, an existing needle-shaped W electron beam source is used. There is an advantage that it can be easily formed by a plasma CVD method or a low temperature vapor deposition method. As the amorphous material, for example, aS
i, a-Si-C, a-Si-N, a-Si-Ge, etc.
A combination of group IV type or S-Se-Te type chalcogen and the like is used.

In this embodiment, one set of barrier layer and quantum well layer is used, but the same effect can be obtained by forming a plurality of sets. In that case, if the materials of the outer barrier layer and the quantum well layer are made to have a higher electron potential, that is, a smaller work function than that of the inner one, there is an advantage that an electron beam can be obtained at a lower extraction voltage. Also,
If the peak energy of the density of states of the inner quantum well layer, which has an extremely narrow energy width, is made to coincide with the electron wave interference filter formed by the outer barrier layer and the quantum well layer by applying voltage, etc., the energy width will be further improved. There is an advantage that a narrow and large-current electron beam can be obtained.

In this embodiment, the tip is formed into a needle shape to concentrate the electric field to form the thin potential barrier 31 in vacuum. However, the same effect can be obtained even with a blade shape. A radiation source is obtained. Further, although the radius of curvature of the tip is set to 0.1 μm, the same effect can be obtained even when the counter electrode is moved to about 10 μm even if the radius is larger than 3 μm.

(Embodiment 2) FIG. 4 shows an embodiment in which the electron beam source of the present invention is applied to an analyzer.

An electron beam 42 is emitted from the electron beam source 41 by the voltage V1 (about 2.5 kV) applied to the first anode 431 of the acceleration lens 43. Next, a voltage V ₀ (= 100V) is applied to the second anode 432 to obtain an electron beam having a desired acceleration voltage. The electron beam 42 passing through the acceleration lens 43 is narrowed down by a condenser lens 44 and an objective lens 45,
The sample 47 is irradiated. Secondary electrons 480 generated at this time
Is detected by the secondary electron detector 48, and the detected signal strength is
If the electron beam 42 is displayed on the CRT in synchronization with the deflection signal of the deflector 46 that two-dimensionally scans the surface of the sample 47,
An SEM image is obtained. In this embodiment, the electrostatic energy analyzer 49 is arranged so that the reflected electrons 490 reflected and emitted from the sample 47 can be subjected to energy analysis. This is to know the surface state of the sample 47 by measuring the energy lost by the electron beam 42 in the sample 47. For example, the electronic state of the surface chemical species can be known in the range of loss energy several eV to several hundred meV, and the vibrational state of the surface chemical species can be known in the region of loss energy several tens meV. This has the advantage that, for example, the type of element or adsorbed molecule on the sample surface first layer and the adsorption state can be locally analyzed. Further, compared to a conventional monochromatic electron beam apparatus using a high-resolution energy analyzer, it has a simple structure and reaches the sample surface without a decrease in electron dose, which is advantageous in that measurement can be performed in a short time. .

In this embodiment, since the energy width of the electron beam 42 is as small as about 25 meV, chromatic aberration can be suppressed even when the accelerating voltage V0 is as low as 100 V, and the electron beam 42 on the sample 47 can be reduced. It was possible to narrow down to 20 nm. That is, even if it is judged that the conventional field emission electron beam source has an acceleration voltage of about 0.1 μm, the electron beam source of the present invention is an electron beam source suitable for high spatial resolution. I understand. On the other hand, also in the energy analysis, since the energy width was as small as about 25 meV, it was possible to accurately measure the energy loss up to about 30 meV. When this analysis was carried out with a conventional field emission electron beam source, only a loss energy of about 0.5 eV could be measured. Therefore, the electron beam source of the present invention has high energy resolution in such an analyzer. It turns out to be extremely effective.

If a rotation mechanism of the sample 47 and the energy analyzer 49 is added and the measurement is performed by changing the incident angle of electrons, the direction of a specific chemical bond can be known. If an electron lens is added to the entrance of the energy analyzer 49 and the electron is measured from a wider range, a two-dimensional image of the surface chemical state can be obtained.

The above is an example of a device using the present electron beam source. In the present embodiment, the number and arrangement of lenses and deflectors are not limited to those in this embodiment, and the analyzer is not limited to the electrostatic type, and needless to say, the present invention can be implemented.

In this embodiment, a combination of a high resolution scanning electron microscope and an electron spectroscopic device is used by focusing on the advantage of an electron beam source having good monochromaticity, but it is also useful when used alone. Needless to say. When used as an electron spectroscope, an energy analyzer can be provided between the electron beam source and the sample to obtain an analyzer with higher energy resolution. In addition, in the present embodiment, an electron beam source with good monochromaticity was used for high spatial resolution and high energy resolution, but focusing on high coherence, for example, when applied to a reflection electron beam diffractometer, an atomic array of There is also an advantage that the interval can be precisely measured.

In this embodiment, taking a scanning electron microscope as an example, if the energy width of the electron beam is narrow, chromatic aberration can be suppressed even if the acceleration voltage is low, and the electron beam can be narrowed down on the sample. However, this electron gun is also useful when applied to an electron beam drawing apparatus used in a semiconductor production process. In the electron beam drawing method, an electron beam is applied to the organic resist film applied to the surface of the substrate to locally change the resist film chemically to form a fine pattern. In the conventional electron beam source, an accelerating voltage of several k to several tens of keV or more is required to reduce the chromatic aberration and narrow the electron beam. The high-speed electrons generate a large amount of secondary electrons in the substrate to chemically change the resist film, and the resulting resist pattern becomes thicker than the electron beam diameter, so that miniaturization is limited. Further, since high-speed electrons have a small scattering cross section with respect to the resist material, a high current density of about 1 mA / sr in terms of the radiation angle current density of the electron beam source is required for high-speed writing. There was a problem of causing instability and deterioration of the. With the electron beam source according to the present invention,
These problems are due to the low acceleration voltage.
Easily resolved. In particular, if it is used in the range of accelerating voltage of several eV to several tens of eV, it directly acts on the chemical bond of the resist material and the scattering cross section becomes extremely large. There is an advantage that you can. Further, since the generation of secondary electrons is almost suppressed, there is an advantage that a finer pattern can be formed.

(Embodiment 3) FIG. 5 shows one embodiment of the present invention. The first material, n + type GaAs (111) B
On the surface substrate 51, 1.4 of the second material is formed by the MBE method.
nm AlAs layer 52 and 3 nm 7 nm GaAs
Layer 53 is single crystal grown (FIG. 5a). Next, a 200 nm SiO2 layer 54 is deposited by the CVD method (FIG. 5b).
A photoresist film 55 having a diameter of about 100 μm is formed on a desired region of the surface (FIG. 5c). The SiO2 layer 54 is etched by the HF-NH4OF mixed solution using the photoresist film 55 as a mask (FIG. 5d). SiO2 formed
H2SO4-H kept at 60 ° C. using layer 54 as a mask
GaAs layer 53, AlAs layer 52,
The n + type GaAs (100) substrate 51 is etched.
Since this solution isotropically etches GaAs, it simultaneously etches the substrate downward and at the same time Ga under the SiO2 layer is etched.
When As is laterally etched and etching is stopped at an appropriate time, a needle-like structure with a GaAs / AlAs thin film at the tip is obtained (FIG. 5e). After that, the SiO ₂ layer 54 remaining on the upper portion is removed by ultrasonic cleaning or the like to obtain an electron beam source having the same structure as that of the first embodiment. According to this embodiment, there is an advantage that a large number of electron beam sources can be obtained at one time with good reproducibility.

When this is used alone, the back surface of the substrate 51 is thinly shaved, an ohmic contact layer such as an Au-Ge-Ni film and an adhesive layer such as solder or Au are formed, and then they are cut off one by one, and are separated on a metal base. Heat bonding.

In this embodiment, GaA is used as an example of the material.
Although s and AlAs are used, similar effects can be obtained even if another material system as shown in Example 1 is used if similar steps are performed.

(Embodiment 4) FIG. 6 shows one embodiment of the present invention. 2 μm on n + type GaAs (111) substrate 51
The SiO ₂ layer 54 and the W layer 60 having a thickness of 500 nm are deposited by the CVD method (FIG. 6a). Next, using a photoresist film having a hole with a diameter of about 2 μm as a mask, a hole is made in the W layer 60 with an NH ₄ OH—H ₂ O ₂ aqueous solution, and further, HF—NH ₄ O
The SiO ₂ layer 54 is etched with the F mixed aqueous solution.
At this time, the etching time is set to be long to form a hole larger than the W layer 60 (FIG. 6B). After removing and cleaning the photoresist film, it is introduced into an ultrahigh vacuum and heated at 540 ° C. for about 5 minutes
The surface of the aAs substrate is cleaned, the substrate temperature is kept at about 540 ° C., and NiAl is added at a rate of about 0.1 nm / sec for 1.5 nm.
Deposit about μm. As a result, polycrystalline NiAl is formed on the W layer.
The film 62 is a conical single crystal NiA on the GaAs substrate 51.
l61 is formed as the first material (Fig. 6c). Then, a 1.4 nm AlAs-7 nm GaAs multilayer film is vapor-deposited as a second material and a third material to form a single crystal NiAl.
61 The surface is covered with a single crystal AlAs-GaAs multilayer film 63 (FIG. 6d). The other region becomes the polycrystalline body 64. As a result, an electron beam source having the same structure as in Example 1 can be obtained. According to this embodiment, there is an advantage that a large number of electron beam sources can be obtained at one time with good reproducibility. Further, when the W layer 60 is used as an electron extraction electrode, there is an advantage that a monochromatic electron beam can be obtained with a small extraction voltage because the cathode and the anode are close to about 1 μm, and a small monochromatic electron beam source device can be obtained.

In this embodiment, NiA is used as an example of the material.
Although I, GaAs, and AlAs were used, similar effects can be obtained by using other material systems as shown in Example 1 if the same steps are performed.

If a similar structure can be obtained by using a method other than the forming process used in this embodiment, the same effect can be obtained.

By using a large number of electron beam sources formed on the substrate of this embodiment, a multi-beam of monochromatic electron beams can be obtained, and the throughput of the electron beam drawing apparatus can be increased and the speed of the CRT display can be increased or increased. It is effective for miniaturization and miniaturization.

(Embodiment 5) FIG. 7 shows one embodiment of the present invention.

The W needle 71 is obtained by electrolytically etching a W single crystal in a KOH aqueous solution. The W needle 71 is used as a probe of a scanning tunneling microscope, and is brought close to a distance of about 1 nm with respect to the Au substrate 73, and a pulse of -7 to -15 V is applied to the needle.
As a result, as shown in FIG. 7A, the Au adsorption layer 72 of about one atomic layer is formed in the extremely narrow region of the tip of the W needle. Next, this W needle 71 is put in a reaction vessel as a first material, heated to 400 ° C. to 500 ° C., and trimethylaluminum (TMA) and trimethylgallium (TM) are added.
G) and arsine (AsH ₃ ) with a flow rate of 10 ^-6 mo, respectively
When introduced at a rate of about 1 / s, a 2 nm Al _0.4 Ga _0.6 As film 74 grows as a second material only in the portion where the Au adsorption layer 72 is present. Then, TMG and AsH ₃ were introduced, and 8
A GaAs film 75 nm having a thickness of 3 nm was grown as a third material to obtain the structure shown in FIG. If you use this needle as a cathode,
An electron beam can be obtained only from an extremely narrow region of the needle tip, and not only monochromatic but also high brightness of the radiation source was achieved. Therefore, the resolution of the electron microscope can be further increased by using this embodiment.

In this embodiment, the semiconductor is grown on the W needle formed by etching. However, the tip of the crystallographic layer is crystallized by a process such as heating once in a high vacuum at about 1000.degree. It is even more effective to grow the semiconductor after forming a stable surface on it, because the conditions for the tunnel effect are adjusted.

In this embodiment, as the barrier layer and the quantum well layer, an AlGaAs-GaAs system with a gas source that selectively grows when an Au adsorption layer is used is used, but the same structure is obtained. If so, the same effect can be obtained by using the various material systems shown in the first embodiment.

In this embodiment, as an example for selectively growing the barrier layer and the quantum well layer at the needle tip,
Although a surfactant (surfactant) effect by Au attached to the tip by a scanning tunneling microscope was used, other materials exhibiting the same effect may be used. The same effect as in the present embodiment can be obtained by selectively growing the W needle tip by a method such as applying a high electric field at the tip to dissociate the material gas.

(Embodiment 6) FIG. 8 shows an embodiment in which the present invention is applied to a surface analyzer.

The surface of the sample 47 placed in an ultrahigh vacuum is irradiated with the electron beam 42 from the electron gun 84, and the reflected electrons 490 reflected and emitted from the sample 47 are converted into electrons by the electrostatic energy analyzer 49. The energy lost by line 42 is measured. In the electron gun 84, the electron beam source 82 having good monochromaticity
The electron beam 42 generated by the accelerating lens 43 is converged on the sample surface by the electrostatic electron lens 81, and the converged position is adjusted by the electrostatic deflector 83. Thereby, the surface condition of the sample can be known. In Example 2, it was shown that the same surface analysis function can be added to the scanning electron microscope by using the monochromatic electron beam source. In this embodiment, a monochromatic electron beam can be obtained without using a high-resolution energy analyzer, so that surface analysis can be performed with an extremely small electron gun. For example, there is an advantage that it can be installed as a surface monitor device in a molecular beam epitaxy (MBE) device. The electron beam source 82 having a good monochromaticity has an energy width corresponding to the required information. For example, if you want to know the surface elements,
Since the loss energy is in the range of several eV to several hundred eV,
A needle-like W field emission electron beam source may be used. More specifically, when it is desired to know the type of adsorbed molecule, the adsorbed state, etc., the loss energy is in the region of several tens of meV. An electron beam source using the resonance tunnel effect as shown may be used.

In this embodiment, the electrostatic energy analyzer 49 is used as a means for measuring the energy lost by the electron beam 42, but other means may be used, such as a Schottky diode energy analyzer. Can be further miniaturized.

Further, in the case of high-accuracy measurement, application of an electron beam source utilizing the resonance tunnel effect and use of an energy analyzer as shown in FIG. 9 enable downsizing. This energy analyzer includes an electron beam source 41, a first anode 431, a second anode 432, and an electrostatic electron lens 81. Electrons 490 reflected on the surface of the sample 47 are converged by the electrostatic electron lens 81. It reaches the electron beam source 41. By the constant voltage (about 2.5 kV) applied to the electron beam source 41 and the first anode 431, an electron wave interference filter by the resonance tunnel effect as shown in FIG. 3 is formed. , Function independent of the direction of electron movement. In this case, only electrons matching the quantum level in the quantum well (13 in FIG. 3) are allowed to enter the solid from the vacuum. Therefore, the potential of the electron beam source 41 is swept in the vicinity of the energy of the reflected electron 490, and the current change is measured, whereby the reflected electron 4
The energy distribution of 90 can be measured with high accuracy. The quantum well width of the electron beam source 41 is made narrower than that of the first embodiment. For example, when the GaAs layer having a thickness of 7 nm in the first embodiment is 4 nm, the energy of the quantum level in the quantum well increases. This is effective because it is possible to suppress the electron emission from the electron beam source 41 and measure the incident electrons.

Note that the energy analyzer to which the electron wave interference filter is applied has the same structure as the monochromatic electron gun shown in FIG. An electron beam resonator can be formed. In this case, if the potentials of both electron beam sources are adjusted to match the emitted electron energies, the current between the two becomes 0 when there is no loss, and a standing wave of electrons can be easily formed in the vacuum. it can.

(Embodiment 7) FIG. 11 shows an embodiment in which the electron beam source of the present invention is applied to an analyzer.

As in Example 1, the first material (11
Using the n + type GaAs single crystal needle 11 extending in the 1) direction, by a molecular beam epitaxy (MBE) method, a 1.4 nm single crystal AlAs film 12 as a second material is further provided near this tip, and the A material obtained by growing a 2 nm single crystal GaAs film 13 is used as a probe of a scanning tunneling microscope. When approaching a distance of about 1 nm, an energy level as shown in FIG. 11B is formed. When the voltage is swept here, the electron transmittance increases due to the resonance tunnel effect at the location where the energy level on the surface of the sample 110 and the quantum level 14 in the GaAs film 13 coincide with each other. You can know the electronic state of the surface. Similar to the energy loss spectroscopy of backscattered electrons shown in Examples 2 and 6, it is possible to know the type of surface element, the type of adsorbed molecule, the adsorption state, and the like.
In addition, when the probe has a negative potential with respect to the substrate, the sample 110
Among the energy levels on the surface, vacant levels of electrons are measured, and when a positive potential is applied, the levels at which electrons are present are measured, so that the surface potential and the band structure of the surface can be known. Furthermore, since the scanning tunneling microscope has a very high spatial resolution in the lateral direction, by combining and measuring it,
There is an advantage that individual atoms and molecules can be directly measured.

Although the scanning tunneling microscope is used in this embodiment, the same effect can be obtained by using an atomic force microscope or the like as long as the needle is brought close to the surface.

[0059]

As described above with reference to the embodiments, by using the present invention, an electron beam source which emits an electron beam having an extremely narrow energy width can be obtained. As a result, a high-resolution electron microscope, a high-performance electron spectroscope, an electron beam diffractometer, and an electronic device can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure (a) and an energy structure (b) of Example 1 of the present invention.

FIG. 2 is a diagram showing an energy structure (a) and an explanation (b) of an energy distribution of emitted electrons in a conventional example.

FIG. 3 is a diagram showing an explanation (a) of the operating principle of Embodiment 1 of the present invention and an explanation (b) of the energy distribution of emitted electrons.

FIG. 4 is a diagram showing a structure of a second embodiment of the present invention.

FIG. 5 is a process drawing of a third embodiment of the present invention.

FIG. 6 is a process chart of forming a fourth embodiment of the present invention.

FIG. 7 is a process chart of forming a fifth embodiment of the present invention.

FIG. 8 is a diagram showing the structure of Example 6 of the present invention.

FIG. 9 is a diagram showing the structure of Example 6 of the present invention.

FIG. 10 is a diagram showing the structure of Example 6 of the present invention.

FIG. 11 is a diagram showing a structure (a) and an energy structure (b) of Example 7 of the present invention.

FIG. 12 is an energy structure (a) of a structure that is easily analogized as an example of forming a double barrier structure using a SIS multilayer film in a conventional MIM structure when no voltage is applied.
FIG. 3 is a diagram showing an energy structure (b) when a voltage is applied.

[Explanation of symbols]

11 ... First material, 12 ... Barrier layer of second material,
13 ... Quantum well layer made of third material, 14 ... Quantum level in quantum well layer, 31 ... Triangular potential barrier formed by vacuum level, 41 ... Electron beam source according to the present invention, 42
... electron gun, 43 ... accelerating lens, 44 ... condenser lens, 45 ... objective lens, 46 ... deflector, 48 ... secondary electron detector, 49 ... energy analyzer, 51 ... n + type GaA
s (100) substrate, 52 ... AlAs layer, 53 ... GaAs
Layers, 54 ... SiO ₂ layers, 60 ... W layers, 61 ... Conical single crystal NiAl, 63 ... Single crystal AlAs-GaAs multilayer film, 71 ... W needles, 72 ... Au adsorption layer, 74 ... Al _0.4
Ga _0.6 As film, 75 ... GaAs film, 81 ... Electrostatic electron lens, 82 ... Electron beam source with good monochromaticity, 83 ... Electrostatic deflector, 84 ... Monochromatic electron gun, 110 ... Sample.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Mitsuhiro Mori 1-280 Higashi Koikeku, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd. (72) Inventor Takeyuki Hiruma 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Inside the Central Research Laboratory (72) Inventor Masakuni Okamoto 1-280, Higashi Koikeku, Kokubunji City, Tokyo Inside Hitachi Central Research Institute (72) Inventor Kiyokazu Nakagawa 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi Central Research Co., Ltd. (72) Inventor Masanobu Miyao 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (19)

[Claims] 1. An electron beam source having a double-barrier quantum well layer and having a structure such that the double barrier layer including the quantum well layer has an electron transmission probability of approximately 1. 2. The electron beam source according to claim 1, wherein the double barrier layer has a structure in which penetration lengths of electrons into the respective barrier layers are substantially the same. 3. The double barrier layer controls the thickness and height of the barrier and the effective mass of electrons, and has a structure in which the permeation lengths of the symmetrically formed structures of the electrons with respect to the respective barrier layers are substantially the same. The electron beam source according to claim 1, wherein the electron beam source comprises. 4. The first material is a protrusion having a height H, and
At least one set is formed on the surface of the first material, having a shape having a flat or convex region with a width d at the tip of the protrusion, and satisfying the relationship that the height H and the width d are H> 10d. A quantum well layer made of the third material and a barrier layer for electrons made of the second material between the first material and the quantum well layer are present. An electron beam source having a structure having a permeation length of less than or equal to, and applying a negative voltage to the first material as compared with the displacement of the facing anode to emit an electron beam from the first material. 5. The electron beam source according to claim 4, wherein the width d is 3 μm or less. 6. The structure of the cathode is formed in a needle shape, and a tip portion of the cathode that emits electrons is a hemisphere having a radius of 1.5 μm or less or a convex shape that does not protrude therefrom, and the structure is a conductor. The surface of the first material is at least one set of the second material and the third material, which are sequentially laminated and coated, and the first material is a material having a density of states near the Fermi level. And the second material is a material that has no electron level within ± 30 meV with respect to the Fermi level of the first material when in contact with the first material,
And the thickness of the third material is not more than the permeation length of the electron wave, and the third material is at least 30 meV more than the lowest level of the second material in which no electrons are contained when it comes into contact with the second material. The electron beam source according to claim 4, wherein the electron beam source is a material having a level of conduction electrons at a low energy, and has a film thickness of about the de Broglie wavelength of conduction electrons. 7. In a system in which there are two or more pairs of structures for sequentially laminating and coating the second and third materials on the surface of the first material which is the conductor, the laminated coating structure of the second and subsequent pairs. 7. The electron beam source according to claim 4, wherein at least one kind of the materials constituting the above is different from the first set. 8. The first material, wherein all of the first, second, and third materials forming the electron beam source are semiconductor single crystals, and the crystals of the second material are base materials. 8. The electron beam source according to claim 4, wherein the crystal of the third material is epitaxially grown, and the crystal of the third material is epitaxially grown on the crystal of the second material. 9. The first material is a single crystal metal or semimetal, and the crystal of the second material is epitaxially grown on the crystal of the first material which is a base material. 9. The electron beam source according to claim 4, wherein the crystal of the material of 3 is epitaxially grown on the crystal of the second material. 10. The electron beam source according to claim 4, wherein at least one of the first, second and third materials is an amorphous material or a microcrystalline material. The electron beam source described in. 11. An electron beam source according to any one of claims 4 to 10, wherein a plurality of at least one type of electron beam source are formed on the same substrate, and an anode corresponding to the plurality of electron beam sources. An electron beam source characterized in that it is also formed on the same substrate. 12. The second and third materials are laminated and coated on the first material, which is a substrate, and then welding, gas,
The electron beam source according to claim 4, wherein the entire structure is formed into a needle shape by etching using plasma or the like. 13. The electron according to claim 4, wherein a thin film made of the second and third materials is formed in layers on the needle-shaped first material. Radiation source. 14. GaA as the second and third materials
The electron beam source according to claim 4, wherein a combination of III-V group compound semiconductors such as s-AlAs system is used. 15. GaAs and Al _X G as the semiconductor
15. The electron beam source according to claim 14, wherein a direct transition type material such as a mixed crystal system in which x of a _(1-X) As is 0.4 or less is used. 16. An electron beam application apparatus, wherein at least one electron beam source is used as an electron beam source among the electron beam sources according to claims 1 to 15. 17. An electron optical system comprising an electron beam source, an electron lens, a deflector, and the like, and an electron energy analyzer. The sample surface is irradiated with an electron beam emitted from the electron beam source. The electron beam application apparatus according to claim 16, wherein the electrons reflected from the surface of the sample are subjected to energy analysis by the electron energy analyzer. 18. The same structure as at least one of the electron beam sources according to any one of claims 1 to 11 and claims 14 to 15, and an electron beam flying from the outside to the quantum well layer in the structure. A means for converging and irradiating the laminated coating layer made of the second material is provided, and by changing the potential of the structure, only electrons having a specific energy among the electron beams are absorbed in the structure. An electron beam application device characterized by measuring. 19. An electron beam source having the same structure as at least one of the electron beam sources according to any one of claims 1 to 11 and 14 to 15 and having a needle-like structure having a tip diameter of 500 nm or less. A means for bringing the tip of the structure close to 10 nm or less of the sample surface, a means for changing the potential of the needle-like structure with respect to the sample surface, and a means for measuring a change in current flowing in the needle-like structure. Characterized electronic device.