JPH0969630A - Single electron tunnel device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single electron tunnel element whose structure and characteristic are controlled and its manufacturing method. SOLUTION: The element has a multiple tunnel joint 6 wherein fine particles 6 made of metal or semiconductor are close to each other at 5nm in distance between particles and are dispersed in an electrical insulating film 4. The joint 6 is produced by accumulating an electrical insulating substance and a metal or semiconductor fine particle alternately or simultaneously through a sputtering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-electron tunnel device that utilizes multiple tunnel junctions and can operate in units of one electron, and a method for manufacturing the same.

[0002]

2. Description of the Related Art LSIs that support the information society have been highly integrated by miniaturizing semiconductor elements such as transistors. By miniaturizing the element, the traveling distance and capacity of the carrier can be reduced, and high performance of the LSI such as high speed can be achieved. The 16M DRAM currently in mass production has a gate length of 0.5 μm, and the 64 MDRAM that has begun to be sampled has a gate length of about 0.35 μm, which is 0.1 μm or less at the research stage. But the operation has been confirmed.

However, when such elements are further miniaturized, physical problems such as generation of tunnel leakage current between the gate electrode and the semiconductor substrate, and further, the number of electrons per operation are reduced. Therefore, there is a fundamental problem that the statistical fluctuation of the number of electrons is increased and a malfunction easily occurs. For this reason, there has been proposed a single-electron tunnel element that operates by controlling individual electrons, rather than using the statistical properties of electrons as the basis of operation, as in the current LSI. The feature of this device is that as the device becomes finer, the operation becomes complete and the ultimate characteristics can be obtained. For example, by applying this to a memory, it is 6 orders of magnitude faster than the human brain and 6 times faster than the current semiconductor memory.
It is possible to obtain a memory with a large number of digits.

[0004]

The single electron tunneling device is based on the Coulomb blockade effect. In order to bring out this effect, a multiple tunnel junction in which several tunnel junctions are connected in series becomes useful, and it is necessary to reduce the electrostatic capacitance of the island sandwiched by the tunnel junctions. Considering room temperature operation in particular, it is necessary to set the island capacitance to 1 aF or less, and in order to manufacture such a structure, a technology for forming a fine structure having a size of nanometer (nm) is necessary. Is.

At present, a technique for forming such a fine structure has not been put into practical use, and some devices utilizing a natural structure have been proposed. For example, "Appl. Phys. Lett., Vo
l.61, 1992, p3145 ", multiple tunnel junctions with side gates beside the atomic layer-doped GaAs wires, and poles as described in" Proc. IEDM, 1993, p541 ". Single electron memories have been fabricated using thin polysilicon as the channel.

However, the former uses a random arrangement of charged impurities existing in a GaAs thin wire to form a tunnel junction, and the latter uses grains in polysilicon as islands, and a portion where electrons easily flow is used as a channel. Therefore, it is difficult to manufacture the structure with good controllability, and the characteristics of the manufactured devices also vary.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a single electron tunnel device having a controlled structure and characteristics and a method for manufacturing the same.

[0008]

A single-electron tunneling device of the present invention comprises a multiple tunnel junction layer including multiple tunnel junctions, and a first tunnel layer for applying a voltage to the multiple tunnel junction layers.
And a second electrode, the multiple tunnel junction layer comprising:
The electrically insulating thin film and the metal fine particles and / or the semiconductor fine particles dispersed in the electrically insulating thin film are contained, whereby the above object is achieved.

In one embodiment, an electrically insulating layer in contact with the multiple tunnel junction layer and a third electrode for applying an electric field to the multiple tunnel layer via the electrically insulating layer are provided.

Preferably, the diameter of the fine particles is 50 nm or less.
It is the following.

Preferably, the average distance between the fine particles is 5
nm or less.

In one embodiment, the fine particles are dispersed in layers in the multiple tunnel layer.

Preferably, the electrically insulating thin film is formed of an oxide, and the fine particles are gold (Au), silver (Ag),
Copper (Cu), platinum (Pt), or palladium (Pd)
It is formed of at least one metal selected from the group consisting of:

Preferably, the electrically insulating thin film is made of silicon (Si), aluminum (Al), titanium (Ti), hafnium (Hf) oxide, silicon (Si), or aluminum (Al) nitride. The main component is at least one selected from the group.

The single-electron tunneling device of the present invention comprises a resistor layer and first and second resistor layers for applying a voltage to the resistor layer.
And a third electrode for adjusting an electric field formed by the first and second electrodes, wherein the resistor layer has an island-shaped potential potential. The lower regions are formed from the formed electrically insulating material, thereby achieving the above objectives.

In one embodiment, the first electrode is formed on a first main surface of the resistor layer, and the second electrode is formed on the first main surface of the resistor layer. Are formed on different second main surfaces.

In one embodiment, the first and second electrodes are formed on the same surface of the resistor layer.

Preferably, the distance between the closest portions between the first electrode and the second electrode is 1 μm or less, and the width of at least one of the first electrode and the second electrode is It is 100 nm or less.

In one embodiment, at least one of the first electrode and the second electrode has a sharpened portion, and the sharpened portion faces another adjacent electrode.

In one embodiment, the tip portion of the first electrode overlaps the tip portion of the second electrode, and the area of the overlapping portion of the tip portion is 1 square μ.
m or less.

In one embodiment, the resistor layer includes an electrically insulating thin film and metal fine particles and / or semiconductor fine particles dispersed in the electrically insulating thin film.

In one embodiment, in the resistor layer,
Metal fine particles and / or semiconductor fine particles are three-dimensionally dispersed.

Preferably, the fine particles have a diameter of 50 nm.
It is the following.

Preferably, the average distance between the fine particles is 5
nm or less.

In one embodiment, the fine particles are dispersed in layers in an electrically insulating material.

[0026] In one embodiment, the electrically insulating material is formed of an oxide or a nitride.

Preferably, the electrically insulating thin film is formed of an oxide, and the fine particles are gold (Au), silver (Ag),
Copper (Cu), platinum (Pt), or palladium (Pd)
It is formed of at least one metal selected from the group consisting of:

Preferably, the electrically insulating thin film is made of silicon (Si), aluminum (Al), titanium (Ti), hafnium (Hf) oxide, silicon (Si), or aluminum (Al) nitride. The main component is at least one selected from the group.

A method of manufacturing a single electron tunnel device according to the present invention comprises a multiple tunnel junction layer including multiple tunnel junctions, and first and second electrodes for applying a voltage to the multiple tunnel junction layer. The multiple tunnel junction layer is a method for manufacturing a single electron tunnel device including an electrically insulating thin film and metal fine particles and / or semiconductor fine particles dispersed in the electrically insulating thin film. And a sub-step of depositing an electrically insulating substance and a sub-step of forming metal and / or semiconductor fine particles are alternately repeated, whereby the above object is achieved.

In one embodiment, the step of forming the multiple tunnel junction layer forms the multiple tunnel junction layer by an alternating sputtering method.

[0031] In one embodiment, the step of heat-treating the multiple tunnel junction layer, thereby changing the size or density of the fine particles is included.

A method of manufacturing a single electron tunnel device according to the present invention comprises a multiple tunnel junction layer including multiple tunnel junctions, and first and second electrodes for applying a voltage to the multiple tunnel junction layer, The multiple tunnel junction layer is a method for manufacturing a single electron tunnel device including an electrically insulating thin film and metal fine particles and / or semiconductor fine particles dispersed in the electrically insulating thin film. The step of forming an electric insulating material and the deposition of the metal and / or semiconductor fine particles are carried out at the same time, whereby the above object is achieved.

In one embodiment, the step of forming the multiple tunnel junction layer forms the multiple tunnel junction layer by a co-sputtering method.

In one embodiment, the step of heat-treating the multi-tunnel junction layer, thereby changing the size or density of the fine particles, is included.

According to the structure of the present invention, the fine particles of metal or semiconductor are dispersed in the electrically insulating thin film at a high density. Therefore, when a voltage is applied between the fine particles of metal, the electrons flow between the fine particles of metal or semiconductor. It tunnels and a so-called tunnel current flows. Therefore, by providing electrodes on a thin film in which fine particles of metal or semiconductor are dispersed in an electrically insulating thin film, and applying a voltage between the electrodes, a plurality of tunnel junctions connected in series are used to connect the electrodes. Multiple tunnel junctions in which electrons flow are formed, and a single-electron tunneling device using the Coulomb blockade effect can be realized. Furthermore, since the metal or semiconductor fine particles can be dispersed relatively uniformly in the electrically insulating thin film, a multiple tunnel junction with a controlled structure can be easily obtained.

According to the structure of the present invention, since the pair of thin film electrodes facing each other is provided on either the upper surface or the lower surface of the resistor thin film layer, the channel portion formed in the resistor thin film layer has the most electric field. Electrons formed between the electrodes, which become higher, move in the channel portion between the metal or semiconductor fine particles inside the resistor thin film layer by the tunnel effect. Therefore, by performing processing such as sharpening the tip of the counter electrode, the width of the channel becomes narrower, and a single electron tunnel element utilizing the Coulomb blockade effect can be realized without using electron beam lithography technology.

Further, according to the structure in which the thin film electrodes are provided on the upper surface and the lower surface of the resistor thin film layer so that the resistor thin film is partially sandwiched, the channel portion formed in the resistor thin film layer has the highest electric field. Electrons are formed in the sandwiched portion and move in the channel portion between the metal or semiconductor fine particles inside the resistor thin film layer by the tunnel effect. Therefore, by performing processing such as sharpening the tip of the thin film electrode, the area of the sandwiched part becomes smaller, and a single electron tunnel element using the Coulomb blockade effect is realized without using electron beam lithography technology. it can.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(Embodiment 1) A cross section of a first embodiment of a single electron tunnel device according to the present invention will be described with reference to FIG.

The single-electron tunnel device of this embodiment comprises a multiple tunnel junction layer 6 including multiple tunnel junctions, a source electrode 2 and a drain electrode 3 for applying a voltage to the multiple tunnel junction layer 6, and an insulating film 7. And a gate electrode 1 for forming an electric field in the multiple tunnel junction layer 6 via the.

The multiple tunnel junction layer 6 has a large number of fine particles 5.
Are formed from the electrically insulating thin film 4 in which is dispersed. The gate electrode 1, the source electrode 2, and the drain electrode 3 are
It is formed of a conductive material such as metal or semiconductor. The fine particles 5 are formed of a metal or a semiconductor material. It is preferably formed of a thermally and chemically stable material, especially a noble metal. Electrically insulating thin film 4 and insulating film 7
The material may be an oxide, a nitride, an organic material, or the like, as long as the conductivity is low enough to detect a change in tunnel current.

It is important that the distance between the fine particles is adjusted so that a tunnel current flows in the electrically insulating thin film 4.

In order to observe the Coulomb-Brocket effect, the charging energy when one particle is charged with one electron needs to be larger than the thermal energy of the electron. FIG. 10 shows the relationship between the size of the particles and the temperature equivalent to the charging energy when one electron is injected into the particles. It can be seen that the size of the particles needs to be 50 nm or less in order to obtain a memory element which operates at room temperature (300 ° k).

The size of the fine particles 5 is preferably within the range of about 1 to 50 nm. When the volume ratio of the fine particles 5 to the electrically insulating thin film 4 was set to 5 to 70%, a single electron tunnel device operating at a relatively high temperature was obtained.

A method for forming the multiple tunnel junction layer 6 of this embodiment using the sputtering apparatus shown in FIG. 2 will be described below.

At least two kinds of sputtering targets are set in the chamber of the sputtering apparatus shown in FIG. In this example, a quartz (SiO ₂ ) glass target 8 and a gold (Au) target 9 are used as sputter targets.

As shown in FIG. 1, the substrate 10 having the gate electrode 1 and the insulating film 7 formed thereon is fixed to a substrate holder 12 having a heater 11. The substrate 10 can be moved to the vicinity of either the SiO ₂ glass target 8 or the Au target 9 by the rotation shaft directly connected to the substrate holder 12. The position of the substrate 10 and the staying time above each target are controlled by a computer. In order to prevent contamination during sputtering, the shield plate 13 is shaped so as to cover each target and its extension.
Is provided.

Argon is preferably used as the sputtering gas. The sputtering gas is the gas inlet port 14.
Gas exhaust port 15 is connected to a vacuum exhaust system. The gas pressure is, for example, 1.0 Pa, and the substrate temperature is 200.
C. is maintained. The power applied to the SiO ₂ target 8 is 250 W, for example, and the power applied to the Au target 9 is 10 W, for example.

Next, the process of forming the multiple tunnel junction layer 6 will be described.

First, the substrate 10 was allowed to stay on the Au target 9 for 20 seconds to deposit Au particles on the insulating film 7 of the substrate 10. Next, the substrate 10 is set to the SiO ₂ target
Of the SiO ₂ target 8 and allowed to stay for 5 minutes. Thus, this time, a SiO ₂ film having a thickness of 0.1 μm was deposited so as to cover the Au fine particles. Transmission electron microscope SiO ₂ film Au fine particles are dispersed (TE
When the cross section was observed with M), the average particle size of the Au fine particles was 5
It was found to be nm.

After the multiple tunnel junction layer 6 thus formed is patterned into an island shape, a conductive thin film (for example, with a thickness of 50) is formed so as to cover the multiple tunnel junction layer 6.
nm chromium film and 0.1 μm thick Au film). As the deposition method, for example, a vacuum vapor deposition method is used.
After that, if the source electrode 2 and the drain electrode 3 are formed by ordinary photolithography and etching techniques, a single electron tunnel element as shown in FIG. 1 is obtained. The distance between the source electrode 2 and the drain electrode 3 is 1
μm.

In this embodiment, aluminum (Al) is used for the gate electrode 1 and its oxide film is used for the insulating film 7.

FIG. 3 shows the voltage-current characteristics when a voltage (drain voltage) is applied between the source electrode 2 and the drain electrode 3 in the single electron tunnel element of this embodiment. It was observed that the current (drain current) flowing between the source electrode 2 and the drain electrode 3 increases stepwise as the drain voltage (the potential of the drain electrode 3 relative to the potential of the source electrode 2) increases. . It is considered that this is a result of Coulomb blockade, that is, a result of electrons moving one by one through the tunnel junction.

FIG. 4 shows how the drain current changes depending on the voltage applied to the gate electrode 1. The drain current changed periodically with the gate voltage, and it was possible to control the drain current using the gate electrode.

In this embodiment, the multiple tunnel junction layer 6 is formed by sputtering the Au target and the insulator target once, respectively.
For 5 seconds on the Au target and 2 on the insulator target.
By repeating the operation of staying for 2 seconds about 300 times, the Au fine particles having a uniform particle size are dispersed in the electrically insulating thin film 4 by 3 times.
You may form the multiple tunnel junction 6 distributed dimensionally (in layer form).

Further, the substrate 10 is provided with two targets 8, 9
The multi-tunnel junction layer 6 in which Au particles are three-dimensionally dispersed in the electrically insulating thin film 4 can also be formed by disposing the Au fine particles in the electrically insulating thin film 4 by spattering Au and an insulator at the same time.

The Au target is aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel. (Ni), copper (Cu), zinc (Z
n), gallium (Ga), germanium (Ge), arsenic (As), selenium (Se), palladium (Pd), silver (Ag), cadmium (Cd), indium (In),
Even if the target is made of at least one kind of metal or semiconductor selected from tin (Sn), antimony (Sb), tellurium (Te), platinum (Pt), gold (Au), or lead (Pb). A multiple tunnel junction in which fine particles of metal or semiconductor having a particle size of 1 to 50 nm were uniformly dispersed was obtained.

In this embodiment, SiO ₂ is used as the material of the electrically insulating thin film, but silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN ), Titanium oxide (TiO ₂ ), and hafnium oxide (HfO ₂ ), a multiple tunnel junction layer excellent in corrosion resistance could be formed. Among them, aluminum oxide (Al ₂ O ₃ ) is particularly dense, and thus has the effect of exhibiting stable characteristics with little change over time.

These electrically insulating thin films can be produced by sputtering oxides or nitrides, but can also be produced by sputtering a semiconductor material such as silicon or aluminum or a metal material in an atmosphere containing oxygen or nitrogen. I was able to.

When an oxide is used for the electrically insulating thin film, gold (Au), silver (Ag), copper (C
By using at least one metal selected from u), platinum (Pt), and palladium (Pd), a device having extremely excellent stability could be manufactured. This is because
It is considered that the interface between these metals and the oxide is steep and stable.

These multiple tunnel junction layers 6 are formed by increasing the substrate temperature during heat treatment or sputtering.
The characteristics of the device could be improved. The particle size was increased by the heat treatment, and the particle size was also uniform, and the corners of the particles were smooth and smooth. Smooth particles had better initial properties than angular particles. The tunnel current is easily affected by the state of the fine particle surface. This is because fine particles having a smooth surface have a stable surface, and thus a stable tunnel current flows. Further, it is considered that the characteristics are improved because the strain and defects in the crystal of the fine particles are removed by the heat treatment.

However, if the heat treatment temperature is set too high, the particle size of the fine particles will increase too much. FIG. 11 shows how the diameter of the fine gold particles changes depending on the temperature of the heat treatment. If the heat treatment temperature is raised above 700 ° C., the grain size increases sharply, which is not preferable. Therefore, the heat treatment temperature is preferably 700 ° C. or lower.

When a nitride material was used as the electrically insulating thin film, the grain size was slightly increased by the heat treatment, but the characteristics could be stabilized. In this case, the grain size could be controlled by the substrate temperature during sputtering.

By raising the substrate temperature during sputtering (to 200 to 400 ° C., for example) or performing heat treatment, the corners of the fine particles were removed and the particles became smooth. Smooth particles had better initial properties than angular particles. It is considered that this is because the tunnel current is easily affected by the state of the surface of the fine particles, and thus the fine particles having a smooth surface allow a stable tunnel current to flow easily.

(Second Embodiment) A second embodiment of the single-electron tunneling device according to the present invention will be described with reference to FIGS. 5 (a) and 5 (b).

First, the multiple tunnel junction layer 19 in which only one layer of the CdSe fine particles 17 is dispersed in the SiO ₂ film 18 is formed on the insulating substrate 16 by a method similar to that described in the first embodiment. To do. After that, the multiple tunnel junction layer 19 is patterned by using electron beam lithography and etching technology, and processed into a thin wire (strip) having a line width of 0.1 μm and a length of about 1.5 μm.

After that, the gate electrode 20, the source electrode 21, and the drain electrode 22 are formed by a known metallization technique. The distance between the gate electrode 20 and the multiple tunnel junction layer 19 was 0.1 μm. The distance between the source electrode 21 and the drain electrode 22 was 1 μm.

FIG. 6 schematically shows the in-plane distribution of the CdSe fine particles 17 dispersed in the multiple tunnel junction layer 19. There are many paths through which electrons can flow from the source electrode 21 to the drain electrode 22. When a voltage is applied to the gate electrode 20, a multiple tunnel junction where electrons easily flow is formed. By applying a voltage between the source electrode 21 and the drain electrode 22, the channel 23 is formed at the portion where electrons easily flow. Around channel 23,
There are isolated particles (potential islands) 24 that do not directly contribute to this current.

In this device, when the voltage applied to the gate electrode was gradually increased, it was observed that the electrons tunneled from the channel 23 to the isolated potential island 24 one by one. That is, it was possible to record information depending on whether or not there is one electron in the isolated island 24.

FIG. 12 shows the gate voltage-drain current characteristics when electrons are present in the isolated island 24 and when electrons are not present. In FIG. 12, the solid line shows the case where no electrons exist on the island 24, and the broken line shows the case where there are electrons on the island 24.

The change of the drain current is as follows.
This is because the electrons flowing in the channel 23 shown in FIG. 6 are affected by the Coulomb force of the electrons existing in the island 24. The gate voltage at which the drain current peaks varies from tens of millivolts to hundreds of millivolts depending on whether or not electrons are present in the island 24. For example, it is assumed that the drain current has a peak value when the gate voltage is 0.1 V in a state where no electrons are present on the island 24. Island 2 by electron tunneling
After changing to the state in which electrons exist in 4, the drain current hardly flows even if the gate voltage is 0.1 volt. Therefore, by measuring the drain current, it is possible to detect whether or not electrons are present in the island 24. Thus, according to the present invention, the storage operation can be performed for each electron.

In order to obtain a single-electron tunnel element having stable characteristics, it is preferable that the position where the channel 23 is formed in the multi-tunnel junction layer 19 is not largely changed. For this purpose, as shown in FIG. 5A, it is effective to make the line width of the multiple tunnel junction layer 19 as thin as about 0.1 μm. Further, it is preferable to narrow the distance between the source electrode 21 and the drain electrode 22 because the resistance of the multiple tunnel junction layer 19 decreases and the drain current increases.

Next, an improved example of the single electron tunnel device will be described with reference to FIG. In this example, FIG.
Similarly to the elements of (b) and (b), after forming the fine line-shaped multiple tunnel junction layer 26 in which fine particles of metal or semiconductor are three-dimensionally dispersed in the insulating thin film on the insulating substrate 25, the source electrode 27 and The drain electrode 28 was formed, and the gate electrode 30 was formed on the surface of the drain electrode 28 with the insulating film 29 interposed therebetween.

In the fabricated device, a channel and an isolated island can be formed by applying a voltage to the gate electrode similarly to the above device, and a single electron tunnel device having a memory function could be manufactured.

(Embodiment 3) A third embodiment of the single electron tunnel device according to the present invention will be described with reference to FIGS. 8A is a plan view, and FIGS. 8B and 8C are cross-sectional views.

The single-electron tunneling device of this embodiment is shown in FIG.
As shown in (b) and (c), the surface is a thermal oxide film 3
It is provided on the Si substrate 32 covered with 1. On the thermal oxide film 31, as shown in FIG. 8A, a source electrode 33 and a drain electrode 34 having a sharp pointed portion at one end are arranged so that the pointed portions face each other. The distance between the tips of the sharp edges of the electrodes 33 and 34 is
It is preferably set to about 100 nm to 1 μm. If this interval exceeds 1 μm and becomes large, the resistance value becomes large and it becomes difficult for the tunnel current to flow. The source electrode 33 and the drain electrode 34 of this embodiment are formed of Au / Cr thin films.

The resistor thin film layer (multi-tunnel junction layer) 35 in which Au particles are dispersed in the SiO ₂ film is used as the electrode 33.
And 34 are formed so as to cover them. Unlike the embodiment of FIG. 5A, the resistor thin film layer 35 is not patterned in a strip shape. The resistor thin film layer 35 is covered with a SiO ₂ thin film 36 which is an electrically insulating thin film, and S
A gate electrode 37 is formed on the iO ₂ thin film 36. The gate electrode 37 is formed of an Au / Cr thin film,
The source electrode 33 and the drain electrode 34 are patterned so as to cover at least part of the sharpened portions.

As described above, according to the present embodiment, the sharp portions of the pair of electrodes 33 and 34 are arranged so as to face each other, thereby locally strengthening the electric field formed in the resistor thin film layer 35. You can More specifically, the strongest electric field is formed on the straight line connecting the sharp tips of the electrodes 33 and 34. Therefore, the channel part where the tunnel current flows is
The electrodes 33 and 34 are always formed at positions close to the straight line connecting the sharp tips. Therefore, it is not necessary to pattern the resistor thin film layer 35 into a strip shape as in the embodiment of FIG. Therefore, the electron beam lithography process is unnecessary.

Source electrode 33 and drain electrode 34
Is to deposit a Cr thin film having a thickness of 10 nm and an Au thin film having a thickness of 0.1 μm on the Si thermal oxide film 31 by a vacuum deposition method, and then patterning these conductive thin films by photolithography and etching techniques. Can be formed by.

Further, the resistor thin film layer 35 was formed by the same method as described above using the sputtering apparatus shown in FIG. A 0.1 μm SiO ₂ thin film 36 is formed on the surface of the resistor thin film layer 35 thus formed, and a gate electrode 37 having a thickness of 0.1 μm is further formed by vacuum vapor deposition of Cr and Au and photolithography. A single electron tunnel device was completed by.

Source electrode 3 of this single electron tunnel device
It was observed that when a voltage (drain voltage) was applied between the drain electrode 3 and the drain electrode 34, the drain current increased stepwise as the drain voltage increased. This is considered to be a result of Coulomb blockade, that is, a result of electrons moving through the tunnel junction one by one. Further, FIG. 4 shows the result of measuring the drain current when a voltage is applied to the gate electrode. The drain current changed periodically with the gate voltage, and it was possible to control the drain current using the gate electrode.

Further, in the produced single-electron tunnel element, since the Au fine particles are two-dimensionally dispersed in the plane of the resistor thin film layer, electrons flow from the source electrode 3 to the drain electrode 34. The structure is such that isolated islands remain around the channel (that is, the metal particles existing in the vicinity of the channel part, not in the channel part of the metal particles, become isolated islands). In this device, when the gate electrode voltage was gradually increased, it was observed that electrons were tunneled from the above channel to the isolated islands one by one. That is, it becomes possible to record information depending on whether or not there is one electron in an isolated island, and application to a memory is possible.

In this embodiment, the source electrode 33, the drain electrode 34, and the gate electrode 37 are made of Au / Cr thin films, but various conductive materials such as metal and semiconductor can be used depending on the application. However, when Cr is used as described above, the adhesion to Au is excellent and it is effective. For example, if Si having a low resistance is used as the Si substrate 32 used in the present embodiment and this is used as a gate electrode, a simple element structure is obtained and the fabrication is easy.

Further, when the sharpened portion 38 is formed by the photolithography technique, the Au thin film is over-etched by using an isotropic etching solution such as aqua regia so that the curvature of the tip is made smaller than that of the formed resist thin film. Can be made smaller.

Further, in this embodiment, the resistor thin film layer 35 is formed on the upper surfaces of the source electrode 33 and the drain electrode 34. However, a resistor thin film layer as shown in FIG. 8C is formed on the Si thermal oxide film 31. The same effect was obtained by forming the source electrode 33 and the drain electrode 34 on the upper surface after the formation. However,
In the structure shown in FIG. 8B, SiO ₂ is continuously formed on the SiO ₂ thin film (resistor thin film layer 35) in which Au particles are dispersed.
It is efficient because a sputtering target can be continuously used to form a thin film.

Although the resistor thin film layer was manufactured by sputtering the Au target and the insulator target once each, the operation of alternately placing the substrate 32 on the Au target and the insulator target is repeated. As a result, the Au fine particles having a uniform particle size could be dispersed in the electrically insulating material. In addition, the resistor thin film layer in which Au fine particles are dispersed in the electrically insulating substance can be prepared by placing the substrate 32 above the two targets 9 and 10 and simultaneously sputtering Au and the insulator. did it.

Further, the resistor thin film layer may be a material having a structure in which metal or semiconductor fine particles are dispersed in an electrically insulating substance. In particular, it is desirable to use a noble metal, which is a thermally and chemically stable material, as the fine particles. This is because when a thermally or chemically stable element is used, deterioration of the element over time can be reduced. Further, it is desirable that the size of the fine particles is 50 nm or less in terms of production and in order to make the distance between the fine particles relatively uniform at the level of nm, but basically, the distance between the fine particles is set to a size at which a tunnel current flows. This is very important. A single electron tunnel device operating at a relatively high temperature was obtained in the region where the volume ratio of the fine particles to the electrically insulating substance in the resistor thin film layer 35 in which the tunnel current actually flows was 5 to 70%. If the volume ratio is 5% or less, the tunnel current does not flow. On the other hand, if the volume ratio exceeds 70%, adjacent metal fine particles stick to each other and the islands become large, so that the tunnel element cannot be used at room temperature. Therefore, it is desirable that the distance between the metal fine particles is 5 nm or less.

The materials of the electrically insulating substance and the electrically insulating thin film 36 may be oxides, nitrides, organic materials, etc., as long as they have low conductivity to the extent that changes in tunnel current can be detected.

The Au target is aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel. (Ni), copper (Cu), zinc (Z
n), gallium (Ga), germanium (Ge), arsenic (As), selenium (Se), palladium (Pd), silver (Ag), cadmium (Cd), indium (In),
Even if the target is made of at least one kind of metal or semiconductor selected from tin (Sn), antimony (Sb), tellurium (Te), platinum (Pt), gold (Au), or lead (Pb). A multiple tunnel junction in which fine particles of metal or semiconductor having a particle size of 1 to 50 nm were uniformly dispersed was obtained.

Further, in the present embodiment, the case where SiO ₂ is used as the electrically insulating substance is shown, but silicon nitride (S
i ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), titanium oxide (TiO ₂ ), and hafnium oxide (HfO ₂ ) can be used to manufacture the resistor thin film layer 35 having excellent corrosion resistance. It was These electrically insulating substances can be produced by sputtering an oxide or a nitride, but can also be produced by sputtering a semiconductor material such as silicon or aluminum or a metal material in an atmosphere containing oxygen or nitrogen. It was

Further, the characteristics of the single electron tunnel element could be improved by performing heat treatment. This heat treatment was suitably performed at a temperature between 1/5 and 3/5 of the melting point of the metal or semiconductor material used.
It is considered that the characteristics are improved because the grain size is increased and the grain size is made uniform by the heat treatment, and the strains and defects in the fine grain crystals are removed. When the nitride material was used as the electrically insulating substance, the grain size was slightly increased by the heat treatment, but the characteristics could be stabilized. In this case, the grain size could be controlled by the substrate temperature during sputtering.

By increasing the substrate temperature during sputtering or by performing heat treatment (performing before forming the gate electrode 37), the corners of the fine particles became smooth and smooth, but the smooth fine particles were finer. Initial characteristics were better than. It is considered that this is because the tunnel current is easily affected by the state of the surface of the fine particles, and therefore the fine particles having a smooth surface provide a more stable surface and a stable tunnel current flows.

(Embodiment 4) FIG. 9 shows a block diagram of a single electron tunnel element in the fourth embodiment of the present invention having the same operation principle as that of the single electron tunnel element in the above third embodiment. . FIG. 9B shows AA in FIG. 9A.
9C is a cross-sectional view, and FIG. 9C is B- in FIG. 9A.
It is B sectional drawing.

In the single-electron tunneling device of this embodiment, an Au / Cr thin film electrode (source electrode 41) having a sharp point and a SiO ₂ thin film 42 on the surface are formed on a Si substrate 40 whose surface is covered with a thermal oxide film 39. An Au / Cr thin film electrode (gate electrode 43) covered with is formed, and a resistor thin film layer 44 in which Au fine particles are dispersed in SiO ₂ is formed on the surface of the Au / Cr thin film electrode. The resistor thin film layer 4 has a structure in which a thin film electrode (drain electrode 45) is formed.
4 has a configuration sandwiched by the sharpened portions of the source electrode 41 and the drain electrode 45.

The source electrode 41 and the gate electrode 43 are
A Cr thin film having a thickness of 10 nm is vacuum-deposited on the Si thermal oxide film 39, and then an Au thin film having a thickness of 0.1 μm is vacuum-deposited and produced by photolithography. The surface of the gate electrode 43 has a thickness of 0.1 μm. It was covered with a SiO ₂ thin film 42.

The resistor thin film layer 44 is formed by repeating Au and SiO ₂ alternately for about 10 times by using the same apparatus as in the first embodiment, so that Au fine particles having a uniform particle size are made into Si.
It was three-dimensionally dispersed in O ₂ to be manufactured, and had a thickness of 50 nm.

A single electron tunnel element was completed by forming a 0.1 μm thick drain electrode 45 on the surface of the produced resistor thin film layer 44 by vacuum vapor deposition of Cr and Au and photolithography. The area of the portion where the resistor thin film layer 44 was sandwiched between the source electrode 41 and the drain electrode 45 was about 0.01 square μm. However, this area is 1
It is desirable to be less than square μm, and if it is more than this, the channel portion becomes too wide and controllability deteriorates.

In the manufactured element, as in the above-described element, by applying a voltage to the gate electrode, a channel 23 and an isolated island 24 can be formed as shown in FIG. 9D, which has a memory function. A single-electron tunneling device could be produced. As can be seen from this figure, when the resistor thin film 44 is thickened, the resistance increases and the drain current decreases. The thickness of the resistor thin film 44 is preferably set within the range of approximately 10 nm to 1 μm.

[0099]

As described above, according to the single-electron tunneling device having the structure according to the present invention, multiple tunnel junctions in which fine particles of metal or semiconductor are uniformly dispersed in an electrically insulating thin film with a gap of about 1 nm are provided. And a single-electron tunneling device whose characteristics can be controlled is obtained. Moreover, since an electrically insulating thin film having excellent corrosion resistance can be used,
It is possible to provide a single electron tunnel device having excellent reliability and long-term stability. This single electron tunnel element functions as a transistor or a memory by changing the electrode configuration, and can be applied to an analog circuit or a digital circuit.

Further, according to the method of manufacturing a single electron tunnel device of the present invention, the type of metal or semiconductor, the size of fine particles, the density, the distance between fine particles, etc. can be easily controlled, and the single electron tunnel having excellent characteristics can be easily controlled. The device can be manufactured with good reproducibility.

Further, according to the single-electron tunnel element of the present invention, a multi-tunnel in which fine particles of metal or semiconductor are uniformly dispersed in an electrically insulating material with a gap of about 1 nm without using a special fine processing technique. A single-electron tunneling device is obtained in which a junction is obtained and whose characteristics can be controlled.
Further, since an electrically insulating thin film having excellent corrosion resistance can be used, it is possible to provide a single electron tunnel element having excellent reliability and long-term stability.

These single-electron tunnel elements function as transistors and memories by changing the electrode structure, and can be applied to analog circuits or digital circuits. In addition, it is possible to easily control the type of metal or semiconductor, the size and density of fine particles, the distance between fine particles, and the like, and it is possible to reproducibly manufacture a single electron tunnel device having excellent characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a single electron tunnel device of the present invention.

FIG. 2 is a schematic cross-sectional view of a sputtering apparatus for manufacturing a single electron tunnel device of the present invention.

FIG. 3 is a diagram showing drain voltage-drain current characteristics in an example of a single electron tunnel device of the present invention.

FIG. 4 is a diagram showing gate voltage-drain current characteristics in an example of a single electron tunnel device of the present invention.

5A is a plan view of another embodiment of the single electron tunneling device of the present invention, and FIG. 5B is a schematic cross-sectional view thereof.

FIG. 6 is a cross-sectional view showing a thin-line multiple tunnel junction of a single-electron tunnel device of the present invention.

FIG. 7 is a cross-sectional view showing an improved example of the single electron tunnel device of the present invention.

8A is a plan view of still another embodiment of the single-electron tunneling device of the present invention, FIG. 8B is a sectional view taken along a source electrode 33 and a drain electrode 34, and FIG. Sectional view of another example

9A is a plan view of still another embodiment of the single-electron tunneling device of the present invention, FIG. 9B is a sectional view taken along the line AA, and FIG. -A sectional view taken along line B,
FIG. 3D is a cross-sectional view showing channels formed in the vertical direction.

FIG. 10 is a graph showing the relationship between the diameter of fine particles and the equivalent temperature.

FIG. 11 is a graph showing the relationship between heat treatment temperature and particle diameter.

FIG. 12 is a diagram showing that the gate voltage-drain current characteristics change depending on whether or not electrons are present in islands of isolated particles.

[Explanation of symbols]

1 Gate Electrode 2 Source Electrode 3 Drain Electrode 4 Electrically Insulating Thin Film 5 Fine Particles 6 Multiple Tunnel Junction 7 Insulating Film 8 Quartz Glass Target 9 Gold Target 10 Substrate 11 Heater 12 Substrate Holder 13 Shield Plate 14 Gas Inlet 15 Gas Outlet 16 Insulation Substrate 17 CdSe fine particles 18 SiO ₂ 19 multiple tunnel junction 20 gate electrode 21 source electrode 22 drain electrode 23 channel 24 isolated island 25 insulating substrate 26 multiple tunnel junction 27 source electrode 28 drain electrode 29 insulating film 30 gate electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 29/792 29/80 (72) Inventor Yoshio Manabe 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Within the corporation

Claims (27)

[Claims] 1. A multi-tunnel junction layer including a multi-tunnel junction, and first and second electrodes for applying a voltage to the multi-tunnel junction layer, wherein the multi-tunnel junction layer is electrically insulating. A single electron tunnel device comprising a thin film and metal fine particles and / or semiconductor fine particles dispersed in the electrically insulating thin film. 2. The electrically insulating layer in contact with the multiple tunnel junction layer, and a third electrode for applying an electric field to the multiple tunnel layer via the electrically insulating layer. Single electron tunnel device. 3. The single electron tunnel device according to claim 1, wherein the fine particles have a diameter of 50 nm or less. 4. The single electron tunnel device according to claim 1, wherein the average distance between the fine particles is 5 nm or less. 5. The single electron tunnel device according to claim 1, wherein the fine particles are dispersed in layers in the multiple tunnel layer. 6. The electrically insulating thin film is formed of an oxide, and the fine particles are selected from the group consisting of gold (Au), silver (Ag), copper (Cu), platinum (Pt), or palladium (Pd). A single-electron tunneling device according to claim 1, wherein the single-electron tunneling device is formed of at least one metal. 7. The electrically insulating thin film comprises silicon (Si), aluminum (Al), titanium (Ti), and hafnium (H).
f) oxide, silicon (Si), or aluminum (A
The single-electron tunneling device according to claim 1, which contains at least one selected from the group consisting of the nitrides of 1) as a main component. 8. A resistor layer, first and second electrodes for applying a voltage to the resistor layer, and a third for adjusting an electric field formed by the first and second electrodes. A single-electron tunnel element having an electrode of, wherein the resistor layer is formed of an electrically insulating material in which island-shaped regions having a low potential potential are formed. 9. The first electrode is a first electrode of the resistor layer.
9. The single electron according to claim 8, wherein the single electron is formed on a main surface of the resistor layer, and the second electrode is formed on a second main surface different from the first main surface of the resistor layer. Tunnel element. 10. The single electron tunnel element according to claim 8, wherein the first and second electrodes are formed on the same surface of the resistor layer. 11. The distance between the closest portions between the first electrode and the second electrode is 1 μm or less, and the width of at least one of the first electrode and the second electrode is 100 nm. The single-electron tunneling device according to claim 8, wherein: 12. The single electron tunnel device according to claim 8, wherein at least one of the first electrode and the second electrode has a sharpened portion, and the sharpened portion faces another adjacent electrode. 13. The tip portion of the first electrode is the second electrode.
10. The single-electron tunneling device according to claim 9, wherein the area of the overlapping portion of the electrode is 1 square μm or less. 14. The resistor layer includes an electrically insulating thin film,
The single electron tunnel device according to claim 8, comprising metal fine particles and / or semiconductor fine particles dispersed in the electrically insulating thin film. 15. The single electron tunnel device according to claim 8, wherein metal fine particles and / or semiconductor fine particles are three-dimensionally dispersed in the resistor layer. 16. The single electron tunnel device according to claim 14, wherein the fine particles have a diameter of 50 nm or less. 17. The single electron tunnel device according to claim 14, wherein the average distance between the fine particles is 5 nm or less. 18. The single electron tunnel device according to claim 14, wherein the fine particles are dispersed in a layered form in an electrically insulating material. 19. The single electron tunnel device according to claim 14, wherein the electrically insulating material is formed of an oxide or a nitride. 20. The electrically insulating thin film is formed of an oxide, and the fine particles are selected from the group consisting of gold (Au), silver (Ag), copper (Cu), platinum (Pt), or palladium (Pd). 15. The single electron tunnel device according to claim 14, wherein the single electron tunnel device is formed of at least one kind of metal. 21. The electrically insulating thin film is silicon (Si),
The method according to claim 14, wherein the main component is at least one selected from the group consisting of aluminum (Al), titanium (Ti), hafnium (Hf) oxide, silicon (Si), and aluminum (Al) nitride. Single electron tunneling device as described. 22. A multi-tunnel junction layer including a multi-tunnel junction and first and second electrodes for applying a voltage to the multi-tunnel junction layer, wherein the multi-tunnel junction layer is an electrically insulating thin film. And a metal fine particle and / or semiconductor fine particle dispersed in the electrically insulating thin film, the method including the step of forming the multiple tunnel junction layer, the step comprising: , A sub-step of depositing an electrically insulating material, metal and / or
Alternatively, a method of manufacturing a single-electron tunneling device, in which the sub-step of forming semiconductor particles is alternately repeated. 23. The method of manufacturing a single electron tunnel device according to claim 22, wherein in the step of forming the multiple tunnel junction layer, the multiple tunnel junction layer is formed by an alternating sputtering method. 24. Heat treating the multiple tunnel junction layer,
23. The method of manufacturing a single electron tunnel device according to claim 22, further comprising the step of changing the size or density of the fine particles. 25. A multi-tunnel junction layer including a multi-tunnel junction and first and second electrodes for applying a voltage to the multi-tunnel junction layer, wherein the multi-tunnel junction layer is an electrically insulating thin film. And a metal fine particle and / or semiconductor fine particle dispersed in the electrically insulating thin film, the method including the step of forming the multiple tunnel junction layer, the step comprising: A method for manufacturing a single-electron tunneling device, which comprises simultaneously depositing an electrically insulating substance and depositing metal and / or semiconductor fine particles. 26. The method of manufacturing a single electron tunnel device according to claim 25, wherein in the step of forming the multiple tunnel junction layer, the multiple tunnel junction layer is formed by a co-sputtering method. 27. Heat treating the multiple tunnel junction layer,
26. The method for manufacturing a single electron tunnel device according to claim 25, including the step of changing the size or density of the fine particles thereby.