JPH04330781A - Selective growth method - Google Patents

Abstract

PURPOSE:To make it possible to manufacture easily a high-efficiency electron emission source and to make it possible to form easily a thin wire of a structure, wherein the part excluding the support parts of the wire floats in the air, and of a fine diameter. CONSTITUTION:Sharp-pointed electrodes 1 and 2 are formed and a voltage is applied between these electrodes 1 and 2 in an atmosphere containing a gaseous raw material to cause discharge, whereby electrons are made to emit from the tip of the electrode 1. These electrons collide with the electrode 2, whereby decomposition of the molecules of the raw material adsorbed on the surface of this electrode 2 is generated. Thereby, a substance layer 4 is selectively grown on the tip part of this electrode 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective growth method, and is suitable for use, for example, in manufacturing highly efficient electron emission sources.

0002

2. Description of the Related Art In vacuum microelectronics, it is necessary to form highly efficient electron emission sources and thin wires with minute diameters in which the portions excluding the supporting portions are suspended in the air.

0003

In order to improve the efficiency of an electron emission source, efforts have been made to sharpen the tip of the electron emission source, but it is difficult to achieve a sufficiently high efficiency with this alone. Therefore, attempts have been made to increase the electron emission efficiency by selectively growing cesium (Cs) or the like on the tip of the electron emission source. A conceivable method for performing such selective growth is to irradiate the tip of an electron emission source with an electron beam from the outside with a raw material containing Cs adsorbed onto the surface of the tip. However, it is difficult to use this method when the electron emission source is located in a location that cannot be seen from the outside, as shown in FIG. 7, for example. That is, in FIG. 7, reference numeral 101 indicates a semi-insulating gallium arsenide (GaAs) substrate, and reference numeral 102 indicates an n-type GaAs layer. Reference numerals 103 and 104 indicate electron emission sources. In this case, since these electron emission sources 103 and 104 are located at a considerable depth when viewed from the surface of the n-type GaAs layer 102, these electron emission sources 103 and 104 can be accessed from the outside.
It is difficult to irradiate the tips of these electron emission sources 103 and 104 with an electron beam.
It is difficult to grow layers selectively.

On the other hand, the limit of the size of a structure that can be formed using conventional microfabrication techniques such as dry etching is about 0.5 μm, and therefore it is difficult to form fine wires with a diameter of about 0.5 μm or less by microfabrication. It is. Recently, attempts have been made to form finer structures using epitaxial growth technology, but with normal epitaxial growth, epitaxial growth basically grows over the entire surface, although there are some growth rate differences depending on the location. It is impossible to form thin lines with suspended structures, as this will occur. Therefore, an object of the present invention is to provide a selective growth method that can easily produce a highly efficient electron emission source. Another object of the present invention is to provide a selective growth method that can easily form a thin wire with a fine diameter and a structure in which the portion excluding the supporting portion is suspended in the air.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a first electrode (1) and a second electrode (2) with sharp tips in a selective growth method, and a gas between the first electrode (1) and the second electrode (2) in an atmosphere containing raw materials such that the potential of the first electrode (1) is lower than the potential of the second electrode (2). Electrons are emitted from the tip of the first electrode (1) by applying a voltage to the second electrode (1) along the electron path from the first electrode (1) to the second electrode (2). 2) A material layer (4) made of a material produced from the raw material is selectively grown thereon.

[0006]

[Operation] Between the first electrode (1) and the second electrode (2) with sharp tips, the distance between the first electrode (1) and the second electrode (2) and the When a voltage higher than the voltage determined depending on the sharpness of the tips of the first electrode (1) and the second electrode (2) is applied, an electric field is emitted from the tip of the first electrode (1), which has a lower potential. electrons are emitted. These electrons are collected at the second electrode (2), which has a higher potential. The electrons collected on the second electrode (2) collide with the raw material molecules adsorbed on the surface of the second electrode (2) in an atmosphere containing the gaseous raw material to decompose the raw material molecules. This causes the second electrode (
2) A material layer (4) consisting of the material produced by this decomposition is selectively grown on top. In this case, a Cs layer or the like can be grown at the tip of the second electrode (2) by using a substance that has the effect of increasing electron emission efficiency, such as a compound containing Cs, as a raw material. The second electrode (2) on which a Cs layer or the like is grown serves as a highly efficient electron emission source. In this way, a highly efficient electron emission source can be easily manufactured. Moreover, this is also possible even when the second electrode (2) is located at a location that cannot be seen from the outside. Further, by growing the material layer (4) until it reaches the first electrode (1), the first electrode (1) and the second electrode (2) are grown.
In between, fine diameter thin wires with a suspended structure can be formed.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A to 1E show a first embodiment of the invention. In this first embodiment, as shown in FIG. 1A, first, a pair of electrodes 1 and 2 each having a square columnar shape with pointed tips, for example, are placed on a substrate (not shown) so that their tips face each other. Form it like this. here,
The tips of these electrodes 1 and 2 have, for example, a quadrangular pyramid shape. Such electrodes 1 and 2 can be formed by dry etching, epitaxial growth, or the like. Further, as the material of these electrodes 1 and 2, for example, GaA
Semiconductors such as S or metals such as tungsten can be used. Although it depends on the distance between electrodes 1 and 2, if the tips of electrodes 1 and 2 are simply pointed as described above, an electric current must be applied between these electrodes 1 and 2 to cause electron emission. The voltage usually needs to be quite high.

Next, the substrate on which the electrodes 1 and 2 are formed is placed in a vacuum chamber, and then a raw material gas of a substance to be grown is introduced into the vacuum chamber. As a result, these electrodes 1, 2
Raw material molecules are adsorbed on the surface of the material, and as shown in FIG. 1B, an adsorbed molecule layer 3 consisting of the adsorbed raw material molecules is formed. After this, a sufficiently large voltage V is applied between these electrodes 1 and 2.
= V1 is applied to cause discharge. by this,
Electrons (e-) are emitted from the tip of the electrode 1 that has a lower potential. These emitted electrons are transferred to the electrode 2, which has a higher potential.
are collected in. In this case, the electrons tend to concentrate near the tip of the electrode 2, where the electric field strength is highest. In this way, electrons collide with the adsorbed molecule layer 3 on the surface of the tip of the electrode 2, causing decomposition of the adsorbed molecules. As a result, as shown in FIG. 1C, a material layer 4 made of the material produced by this decomposition selectively grows on the tip of the electrode 2. Here, this material layer 4 tends to become thicker where the number of colliding electrons is greater. The number of colliding electrons is greatest at the tip of the electrode 2 and decreases as the distance from there increases.
has a more pointed shape than the tip of the electrode 2.

[0009] As described above, the material layer 4 having a more pointed shape than the tip of the electrode 2 grows at the tip of the electrode 2, and the distance between the electrodes 1 and 2 becomes shorter due to the growth of the material layer 4. In order to cause electron emission, the electrode 1,
The voltage V applied between the electrodes 2 causes a material layer 4 at the tip of the electrode 2
is lower than before it was formed. Therefore, electrodes 1 and 2
When the voltage V applied during this period is set to a voltage V2 slightly lower than the initial voltage V1 to cause a discharge, the growth of the material layer 4 further progresses, and as shown in FIG. 1D, the tip of the material layer 2 becomes more It has a pointed shape. As a result, the voltage V applied between the electrodes 1 and 2 to cause electron emission becomes even lower. In this way, the material layer 4 continues to grow while gradually lowering the voltage V applied between the electrodes 1 and 2, and when the material layer 4 reaches the desired thickness and shape, the voltage V
The growth of the material layer 4 is completed by stopping the application of the .

In this case, as the growth of the material layer 4 continues, the material layer 4 gradually grows toward the tip of the electrode 1 and finally reaches the tip of the electrode 1. Then, as shown in FIG. 1E, the tips of the electrodes 1 and 2 are connected with this material layer 4. In this case, the material layer 4 has an elongated columnar shape, and its diameter is very small compared to the cross-sectional dimensions of the electrodes 1 and 2. In this way, a fine-diameter thin wire made of the material layer 4 is formed, with the portion excluding the supporting portion floating in the air. In this case, by using, for example, a Cs compound as a raw material for growing the material layer 4, a Cs layer can be grown as the material layer 4 at the tip of the electrode 2, thereby manufacturing a highly efficient electron emission source. be able to. Further, by using a semiconductor compound as a raw material for growing the material layer 4, it is possible to form a semiconductor thin wire with a structure in which the portion excluding the supporting portion is suspended in the air.

As described above, according to the first embodiment,
The material layer 4 is selectively grown at the tip of the electrode 2 by applying a voltage between the electrodes 1 and 2 in an atmosphere containing source gas to cause a discharge. By growing a Cs layer as a material, a highly efficient electron emission source can be easily manufactured. Further, by growing until the tips of the electrodes 1 and 2 are connected to each other by the material layer 4, a thin wire with a fine diameter and a floating structure can be formed.

Next, a second embodiment of the present invention will be explained. In this second embodiment, the present invention is applied to the formation of a micro solenoid coil. In this second embodiment, first, a structure as shown in FIG. 2 is formed on a substrate (not shown) by dry etching, epitaxial growth, or the like. In FIG. 2, reference numerals 11 and 12 denote a pair of electrodes 1 and 1 similar to electrodes 1 and 2 in the first embodiment.
3 represents an intermediate electrode, 14 represents a lower electrode, and 15 represents an insulating layer.

In the second embodiment, a substrate having the above-described structure is placed in a vacuum chamber, and a source gas is introduced into the vacuum chamber. Then, by applying a voltage between the electrodes 11 and 12 with a constant magnetic field B applied in the z-axis direction in FIG. to be released. In this case, assuming that the electric field E between the electrodes 11 and 12 is perpendicular to the magnetic field B, the electrons emitted from the tip of the electrode 11 have a Lorentzian force in the direction perpendicular to both the magnetic field B and the electric field E. Because of the force acting on it, these electrons perform rotational motion. At this time, if the potential of the intermediate electrode 13 is biased to be higher than the potential of the electrode 11, the electrons emitted from the tip of the electrode 11 are drawn downward in FIG. As a result, the electrons fall while performing a spiral motion in the z-axis direction. Here, if the potential of the lower electrode 14 is biased to be sufficiently higher than the potential of the electrode 11, the electrons will collide with this lower electrode 14.

Due to this collision of electrons, this lower electrode 14
decomposition of raw material molecules adsorbed on the surface of the material occurs. As a result, as shown in FIG. 3, a material layer 16 made of a material produced by this decomposition grows on the surface of the lower electrode 14 at the portion where the electrons collided. In this case, this material layer 16
has a sharp shape reflecting the distribution of electrons colliding with the lower electrode 14. When the material layer 16 with a pointed shape grows on the lower electrode 14 in this manner, the electric field near the material layer 16 becomes stronger, so that electrons tend to gather at the tip of the material layer 16. And, as shown in Figure 4,
This material layer 16 grows along the path of the electrons in a direction opposite to the direction of movement of the electrons. Such growth is performed until the tip of the material layer 16 reaches the tip of the electrode 11. As a result, as shown in FIG. 5, the electrode 11 and the lower electrode 14
A micro solenoid coil 17 made of a thin wire-like material layer 16 with a minute diameter is formed between the two.

An example of the magnitude of the magnetic field B applied in the z-axis direction in the second embodiment is as follows. That is, if the radius of the spiral motion of an electron is r, the equation of motion of this electron is evB=mv2/r. However, e is the absolute value of the electron charge, m is the mass of the electron, and v is the velocity of the electron. Further, the kinetic energy K of electrons emitted from the electrode 11 is K=(1/2)mv2. Calculating B from these formulas, B=(2mK)1/2/er
becomes. Now, if r ~ 1 μm and K ~ 1 eV, then m ~ 9 x 10-
Since it is 31 kg, it becomes B~3T (Tesla). Further, when K~(2~3)eV, it becomes B~10T.

Next, a third embodiment of the present invention will be described. This third embodiment is based on the magnetic field Aharonov (Aharonov).
The present invention is applied to the manufacture of a transistor using the Bohm effect (hereinafter referred to as a magnetic field AB effect transistor). In this third embodiment, first, as shown in FIG. 6A, five electrodes 21, 22, 23 each having a sharp tip are formed on a substrate (not shown) by dry etching or epitaxial growth.
, 24, 25 are formed. Here, the electrodes 21 and 22 are formed such that their sharp tips face each other. The same applies to the electrodes 23 and 24. On the other hand, the electrode 25
is formed such that its tip faces the center between the electrodes 21 and 22 and the center between the electrodes 23 and 24, for example.

Next, a micro solenoid coil is formed between the electrodes 21 and 25 by a method similar to that described in the second embodiment. That is, after placing the substrate on which the above-described structure is formed into a vacuum chamber, a source gas is introduced into the vacuum chamber, and a constant magnetic field B is applied in the z-axis direction.
By applying a voltage between the electrodes 21 and 22 so that the potential of the electrode 21 is lower than the potential of the electrode 22, electrons are emitted from the tip of the electrode 21. At this time, the electrode 25
When the potential of the electrode 21 is biased to be higher than the potential of the electrode 21, the electrons proceed toward the electrode 25 while performing a spiral motion in the z-axis direction, and collide with the tip of the electrode 25. As a result, the raw material molecules adsorbed on the surface of the tip of the electrode 25 are decomposed, and a material layer (not shown) made of the substance produced by this decomposition selectively grows on the surface of the tip. This growth is prevented by the electrode 21
The material layer continues along the path of the electrons from the material layer to the electrode 25 in a direction opposite to the direction of movement of the electrons, and stops growing when the tip of the material layer reaches the tip of the electrode 25. As a result, as shown in FIG. 6B, a micro solenoid coil 26 made of a thin wire with a minute diameter is formed between the electrodes 21 and 25, and the intended magnetic field AB effect transistor is completed.

The operation of the magnetic field AB effect transistor according to the third embodiment will be explained as follows. In this magnetic field AB effect transistor, the micro solenoid coil 26 is biased negatively with respect to the electrode 23, and a voltage is applied between the electrodes 23 and 24 so that the potential of the electrode 23 is lower than the potential of the electrode 24, for example. By applying this, electrons are emitted from the tip of the electrode 23. The path of the emitted electrons is divided by the micro solenoid coil 26 into a path passing above the micro solenoid coil 26 and a path passing below the micro solenoid coil 26. That is, the electron wave emitted from the tip of the electrode 23 is divided into an electron wave passing above the micro solenoid coil 26 and an electron wave passing below the micro solenoid coil 26.

On the other hand, this micro solenoid coil 26
When a current I is applied to the micro solenoid coil 26, a magnetic flux Φ=μ0 is generated in the axial direction of the micro solenoid coil 26, that is, in the z-axis direction.
nIS occurs. However, μ0 is the vacuum permeability,
n is the number of turns of the coil per unit length, and S is the cross-sectional area of the coil. Due to this magnetic flux Φ, the phases of the electronic waves passing above and below the micro-solenoid coil 26 change in opposite directions by eΦ/(h/2π), respectively. Therefore, by controlling the phase of these electron waves with the current I flowing through the micro solenoid coil 26, the current flowing between the electrodes 23 and 24 can be turned on/off.

Assuming that the magnetic field B applied when forming the micro-solenoid coil 26 has the energy of electrons emitted from the electrode 21 ~1 eV and the radius of the coil ~0.5 μm,
B ~ 6.7T. Assuming that the number of turns n of the micro solenoid coil 26 formed under this condition is several turns/μm, the micro solenoid coil 26 is
The current I that needs to be passed can be determined as follows. That is, in order to turn off this magnetic field AB effect transistor, the phase difference between the electron wave passing above the micro solenoid coil 26 and the electron wave passing below the micro solenoid coil 26 may be set to π. This corresponds to the fact that the phase change of these electron waves is π/2. Therefore, eΦ/(h/2
From the relationship π)=eμ0 nIS/(h/2π)=π/2, I~10-9A, that is, about 1 nA. As described above, according to the third embodiment, it is possible to easily manufacture a magnetic field AB effect transistor that controls the phase of an electron wave using the micro solenoid coil 26 formed between the electrodes 21 and 25. can.

The magnetic field AB effect transistor according to the third embodiment has high modulation efficiency because even though the energy of the electrons emitted from the tip of the electrode 23 is not constant, the same phase change occurs in each electron. For this reason, while conventionally proposed AB effect transistors had to be operated at extremely low temperatures, the magnetic field AB effect transistor according to the third embodiment can operate at higher temperatures and can be operated at room temperature. This operation is also possible. Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the technical idea of the present invention.

[0022]

Effects of the Invention As explained above, according to the present invention, a highly efficient electron emission source can be easily manufactured, and a thin wire with a fine diameter having a structure in which the part excluding the supporting part is suspended in the air. can be easily formed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining a first embodiment of the invention.

FIG. 2 is a sectional view for explaining a second embodiment of the invention.

FIG. 3 is a partial cross-sectional view for explaining a second embodiment of the invention.

FIG. 4 is a partial cross-sectional view for explaining a second embodiment of the invention.

FIG. 5 is a sectional view for explaining a second embodiment of the invention.

FIG. 6 is a sectional view for explaining a third embodiment of the invention.

[Explanation of symbols]

1 Electrode 2 Electrode 3 Adsorbed molecule layer 4 Material layer 17 Micro solenoid coil

Claims (1)

[Claims] 1. A first electrode and a second electrode having sharp tips are formed, and the first electrode is disposed between the first electrode and the second electrode in an atmosphere containing a gaseous raw material. Electrons are emitted from the tip of the first electrode by applying a voltage such that the potential of A selective growth method, wherein a material layer made of a material produced from the raw material is selectively grown on the second electrode along the path of electrons.