JPH11289079A - Single electronic element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single electronic element with a small effective area in a structure suitable for constituting an integrated circuit, and a method for manufacturing this. SOLUTION: In this single electronic element 1, an island-shaped electrode 32 arranged in a recessed part 11 formed on the surface (basement face) of a basement 10 is connected through a tunnel junction 22 formed oh the side face of the island-shaped electrode 32 with a lead electrode 33 formed on the basement face. In a method for manufacturing this single electronic element 1, a recessed part is formed on the basement face, a first conductive film is formed on the basement face, a first conductive film 33a on the basement face and the first conductive film 32 in the recessed part 11, are formed so as to be separated from each other, the tunnel junction 22 is formed on the side face of the recessed part 11, a second conductive film is formed on the basement face, and the first conducive film and the second conductive film are patterned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single electronic device and a method of manufacturing the same, and more particularly, to a single electronic device having a small effective area and suitable for forming an integrated circuit, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A single electronic device has its operating principle based on the Coulomb blockade effect. This is a phenomenon in which when the capacitance of an extremely fine tunnel junction becomes extremely small, a difference appears in the electrostatic energy depending on whether the tunnel junction stores one electron or not. Single electronic devices can form various devices such as three-terminal transistors, memories, and the like. In general, there has been proposed a transistor structure in which two small tunnel junctions are connected in series, and a gate electrode is electrostatically connected via a capacitor to an intermediate island electrode having a very small capacitance. I have.

[0003] A lithography technique is indispensable for producing a minute tunnel junction which is a component of such a single electron tunneling device. As a conventional method for forming a metal-based minute tunnel junction, there is a double vapor deposition method using a suspension mask. In this double vapor deposition method, as shown in FIG. 6, first, a suspension mask 102 which is lifted above a substrate 101 by a spacer 100 and partially floats in the air is produced. Thereafter, a first deposition of a metal film is performed, and the surface of the metal film is oxidized to form a metal oxide film barrier. Then, the second deposition of the metal film is performed at an angle different from that of the first deposition.
An overlapping portion of the two deposition films is formed, and a minute tunnel junction 103 is formed at the overlapping portion.

A mask pattern and steps will be described with reference to FIG. 7 taking a simple electron transistor having two junctions, which is the simplest single electron element, as an example. A mask 200 having holes 201 for lead electrodes and holes 202 for island electrodes as shown in FIG. 7A is prepared. Such a mask 2
The metal film of the lead electrode pattern 210 and the island pattern 211 as shown in FIG. Next, after oxidizing the surfaces of the metal films 210 and 211 to form oxide films, as shown in FIG. 7C, a second metal film is formed by shifting the film forming angle in the horizontal direction, and the lead is formed. The electrode 220 and the island 221 are formed. Thus, a single electron transistor including the two junctions 222 and the island 221 can be manufactured. In this figure, the gate electrode is omitted.

[0005]

However, in the conventional double vapor deposition method using a suspended mask, a suspended mask must be formed around the device, and unnecessary by-products are required as the device. I can't increase the degree. Further, since the direction in which the element is formed is uniquely determined by the film forming angle, there is a problem that the degree of freedom in circuit design is limited. Furthermore, the procedure for manufacturing the suspension mask is complicated, and in any case, this method is not suitable for an integrated circuit.

In the method shown in FIG. 7, the finally formed device has a double pattern, and half of the device is unnecessary and is an unnecessary by-product. Further, the mask pattern shown in FIG. 7A is also required to have an extra area than the size of the element which is really required. Therefore, the degree of integration cannot be increased, and this is an element manufacturing method that is not suitable for an integrated circuit.

The present invention has been made in view of the above problems, and has as its object to provide a single electronic device having a small effective area and a structure suitable for forming an integrated circuit, and a method of manufacturing the same. I do.

[0008]

According to a first aspect of the present invention, there is provided a single electronic device comprising: an island-shaped electrode disposed in a recess formed in a base surface; and a lead formed in the base surface. The electrode has a structure in which it is connected via a tunnel junction formed on a side surface of the island-shaped electrode.

According to the invention having such a configuration, the surface of the substrate and the conductive film formed in the concave portion are electrically connected to each other by utilizing the step of the concave portion formed in the substrate in the first conductive film formation. In addition to forming a tunnel junction by oxidizing a conductive film formed on the step side wall and forming a second conductive film, an island-like electrode can be formed in the base recess, A structure in which the conductive film on the substrate surface and the island-shaped electrode are connected by a tunnel junction can be obtained. Therefore, performing the film formation twice is the same as the conventional one, but since the film is formed in a stacked manner, the structure has no useless area, the effective area is small, and the integration degree can be improved. .

[0010] The single electronic device according to the second aspect is the first aspect.
In the single electronic device described above, the island-shaped electrode has a laminated structure laminated on a conductor through an insulating film, and the lead electrode is formed of a double-sided conductor through an insulating film. The stacked structure of these island-shaped electrodes and the stacked structure of the lead electrodes are formed in the same process. According to the invention having such a configuration, since the island-shaped electrode and the lead electrode are manufactured in the same process, a structure that does not cause useless area is obtained.

According to a third aspect of the present invention, there is provided a single electronic device.
Alternatively, in the single electronic device according to Item 2, the concave portion formed in the base surface is a groove formed in a direction intersecting with a lead electrode. According to the invention having such a configuration, by forming the lead electrode in a direction orthogonal to the groove formed in the base, a single electronic element can be formed along the groove, and the degree of integration can be increased. .

According to a fourth aspect of the present invention, there is provided a single electronic device.
4. The single electronic device according to any one of the above-described items, wherein the single electronic device has a structure in which a gate electrode is arranged on a side. According to the invention having such a configuration, the so-called side gate electrode can be formed of the same conductive film as the lead electrode, and the lead electrode and the gate electrode can be simultaneously manufactured, so that productivity is high.

According to a fifth aspect of the present invention, there is provided a single electronic device according to the first aspect.
5. The single electronic device according to any one of items 4 to 4, wherein a gate electrode is arranged above the island-shaped electrode with an insulating film interposed therebetween. According to the invention having such a configuration, the degree of integration can be improved by the so-called overlap gate electrode structure.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a single electronic device, comprising the steps of: forming a concave portion on a base surface;
Forming a first conductive film on the substrate surface and the first conductive film in the concave portion separately from each other; forming a tunnel junction on the side wall of the concave portion; (2) forming a conductive film, patterning the first conductive film and the second conductive film, and forming an island-shaped electrode composed of the second conductive film disposed in the concave portion and the base surface; This is a method for forming a structure in which the formed first conductive film and a lead electrode formed of the second conductive film are connected via the tunnel junction.

According to the invention, the surface of the substrate is electrically separated from the conductive film formed in the concave portion by the first deposition of the conductive film by utilizing the step of the concave portion formed in the substrate. Let
In addition, a tunnel oxide film is formed by oxidizing the conductive film formed on the step side wall, and after forming a second conductive film, the first conductive film and the second conductive film are patterned together. Thus, the single electronic device according to claim 1 can be manufactured. Therefore, although the film formation is performed twice, which is the same as the conventional method, the pattern is formed after the film formation is performed in an overlapping manner, so that a wasteful area is not generated and the degree of integration can be improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an elevation view showing one embodiment of the single electronic device of the present invention. This single electronic device 1 is
The floating conductor 31 is provided at the bottom of the recess 11 formed in a groove shape on the surface 0 (base surface), and from the surface of the substrate 10 from the groove 11 via the first oxide film 21 on the floating conductor 31. An island-shaped electrode 32 is formed projecting upward. Two lead electrodes 33 sandwiching the island-shaped electrode 32 via the tunnel oxide film 22 formed on the side surface of the island-shaped electrode 32 are formed on the surface of the base 10. The lead electrode 33 is connected to the lower first conductor 33a and the upper second conductor 33b via the first oxide film 21 formed integrally with the tunnel oxide film 22.
Are laminated, and the upper surface and the end surface of the second conductor 33b are covered with the second dioxide film 24.

The entire surface of the island-shaped electrode 32 is an oxide film 21 or 2.
2 and 24, and the first conductor 33a of the lead electrode 33
And a tunnel oxide film (tunnel junction) 22. Although not shown, the base 10 is provided with a gate electrode.

The width of the island-shaped electrode 32, that is, the width of the groove 11 formed in the base 10 is a fine dimension of about several tens of nm, and the thickness of the tunnel oxide film 22 is about 5 nm. The island-shaped electrode 32 is formed in the same process as the second conductor 33b, and is made of a conductive material such as aluminum or polysilicon doped with impurities. Also, the first conductor 33a
The second conductor 33b is made of a material capable of forming a high-quality tunnel oxide film by oxidation, for example, aluminum or polysilicon doped with impurities.

The conductive films 33a, 3a, 3
Since the oxide film 21 separating 3b is extremely thin, and the upper and lower conductive films 33a and 33b are connected through this oxide film 21 in a wide area, they can be regarded as one electrode at substantially the same potential. It is a structure that can be done. In addition, another floating conductor 31 is formed below the island-shaped electrode 32, but this does not affect the operation of the single electronic device.

When a voltage is applied to a gate electrode (not shown), a current flows to the lead electrode 33 via the island electrode 32 from a certain threshold value. Since this threshold value varies depending on whether or not there is one electron in the island electrode, a three-terminal transistor can be formed. Further, a single-electron nonvolatile memory can be realized.

Next, a first manufacturing process of the single electronic device shown in FIG. 1 will be described with reference to FIG.

First, a side view of FIG. 2A and FIG.
As shown in the elevation view of 1), a resist film R1 is formed on the surface of the substrate 10, and a groove is formed in the resist film R1 with a fine dimension of several tens of nm by electron beam lithography or the like. afterwards,
Using the resist film R1 as a mask, the substrate is vertically etched by RIE (reactive ion etching) to form a groove (recess) 11 having a depth h.

Next, as shown in FIG. 2B, after the resist film R1 is removed by ashing or the like, a conductive material is formed in a thickness T1 in a direction perpendicular to the substrate 10 to form a first conductive film C.
Form one. The conductive material is preferably a metal on which a high-quality oxide film can easily grow, and specific examples thereof include aluminum and polysilicon doped with impurities. The thickness T1 of the first conductive film C1 is smaller than the depth h of the groove 11. As a result, the surface of the first conductive film C1 formed in the groove 11 becomes lower than the surface of the substrate,
The first conductive film is slightly deposited on the side wall of the first.

Since the side wall portion C11 of the first conductive film is entirely oxidized to form a tunnel barrier, the side wall portion C11 of the first conductive film is formed.
The thickness t ′ of 11 is an important parameter and needs to be a predetermined thickness. The ratio t ′ / T of the thickness t ′ of the side wall portion C11 of the first conductive film to the thickness T of the first conductive film C1 is, for example, the size D of the deposition source at the time of film formation, the deposition source and the base 10. It is equal to the ratio D / L to the distance L. Therefore, if the film is formed under the condition of DT / L> t ', the thickness of the side wall portion C1 of the first conductive film C1 can be controlled to be smaller than t'.

Next, as shown in FIG. 2C, a first oxide film 21 having a desired thickness is formed by controlling oxygen and the like in the same vacuum film forming apparatus as used for forming the first conductive film C1. I do. If the first conductive film C1 is polysilicon, a silicon oxide film is formed, and if the first conductive film C2 is aluminum, an aluminum oxide film is formed. At this time, the first conductive film C1
Are oxidized to become an insulator and become a tunnel oxide film 22. Assuming that the thickness of the tunnel oxide film 22 is t, the thickness t ′ of the side wall portion C11 of the first conductor is increased by oxidation. , This increase will be taken into account.

Next, as shown in FIG. 2D, a second conductive film C2 is formed with a thickness T2. The thickness T2 of the second conductive film C2 is equal to the thickness T1 obtained by adding the thickness T1 of the first conductive film C1.
+ T2 needs to be larger than the depth h of the groove 11.
As a result, as shown in FIG. 2D, the upper surface of the second conductive film C2 formed in the groove 11 protrudes from the surface of the substrate 10, and the first conductive film C2 on the substrate 10 via the tunnel oxide film 22. It can be opposed to the conductive film C1. Also, the second conductive film C
2 cannot be greater than the difference in height between the upper surface of the first oxide film 21 in the trench 11 and the first oxide film 21 on the upper surface of the first conductive film C1 on the base surface. Further, a thin side wall portion C21 of the second conductive film C2 is formed on the side wall of the groove 11.
The thickness of the side wall portion C21 of the second conductive film can also be controlled as described above.

Next, the surface of the second conductive film C2 is oxidized,
The surface of the second conductive film C2 is covered with the second dioxide film 24. This oxidation can also be achieved by taking it out to the atmosphere. At this time, the entire side wall portion C21 of the second conductive film C2 is oxidized.
As a result, the second conductive film C2 on the base 10 and the second conductive film C2 in the groove 11 are electrically separated, and the second conductive film C2 in the groove 11
The conductive film C2 becomes an isolated island-shaped electrode 32 all around which is covered with an oxide film. On the other hand, the first conductive film C1 on the surface of the substrate 11
The second conductive film C2 and the second conductive film C2 form a lead electrode 33, and the island-shaped electrode 32 and the first conductive film C1 of the lead electrode are connected via a tunnel oxide film (tunnel junction) 22.

Finally, after forming the second resist film R2, as shown in the side view of FIG. 2F and the elevation view of FIG. 2F, the second resist film R2 is linearly formed in a direction orthogonal to the groove 11. Perform patterning. Then, using the second resist film R2 as a mask, the second dioxide film 24, the second conductive film C2, the first oxide film 21,
Patterning is performed by performing anisotropic etching in the order of the conductors C1. Thereafter, by removing the second resist film R2, the single electronic device shown in FIG. 1 can be obtained.

According to such a method of manufacturing a single electronic device, the conductive film is formed twice, but is formed in a superimposed manner and is patterned in one etching step, which is different from the conventional manufacturing method. The device occupies a minimum area, and a single electronic device having a small effective area suitable for manufacturing an integrated circuit can be manufactured. In addition, since the manufacturing process is simple and does not include complicated procedures such as a suspended mask, the productivity is good and a fine pattern can be formed. Therefore, for example, a single-electron nonvolatile memory with high speed and good controllability can be realized.

Next, a second manufacturing process of the single electronic device shown in FIG. 1 will be described with reference to FIG.
In this manufacturing process, a lead electrode and an island electrode are formed by a lift-off method.

First, a first resist film R11 is formed on the surface of the substrate 10.
Then, as shown in the side view of FIG. 3A and the elevation view of FIG. 3A1, the first resist film R11 is patterned in a linear shape having a width to be a concave portion of the single electronic element. Thereafter, the base film 12 that is easy to form, for example, silicon oxide, is
The film is formed to have the same thickness as the depth h of the groove in the manufacturing process. next,
When the first resist film R11 is removed, a trench 11 having an insulator on the side and a base on the bottom is formed by a lift-off method.

Next, a side view of FIG. 3B and FIG.
As shown in the elevation view of 1), after the second resist film R12 is formed, a groove R12 ′ is formed in the second resist film R12 in a width perpendicular to the groove 11 to form a lead electrode and an island electrode. Perform patterning.

Next, as in the first manufacturing process, the film thickness T
After forming the first conductive film C1 over the entire surface of the substrate in step 1, the surface of the first conductive film C1 is oxidized to form a tunnel oxide film (junction) 22 and a first oxide film 21. Next, after forming the second conductive film C2 with a thickness T2, the surface of the second conductive film C2 is oxidized to form the second dioxide film 24. In this case, T1 <h, T1 +
Observe the condition T2> h. Further, the thickness of the side wall of the first conductive film C1 can be controlled similarly to the first manufacturing process.

Finally, by removing the second resist film R12, the film on the second resist film R12 is also removed, leaving only the groove R12 'of the second resist film.
The single electronic device shown in FIG. 1 can be manufactured by the lift-off method.

According to the second manufacturing process, a single electronic element having a small effective area and suitable for manufacturing an integrated circuit can be manufactured with a simple process with high productivity by the lift-off method.

FIG. 4 is an elevation view of a single electronic device according to another embodiment of the present invention. The single-electron element 2 is a single-electron transistor to which a gate electrode 34 is added as a side gate. Gate electrode 3 formed on the surface of substrate 10
4 is separated by an insulator between the gate electrode 34 and the island-shaped electrode 32. The gate electrode 34 is connected to the first
In both the manufacturing process and the second manufacturing process,
When the second resist films R2 and R12 are exposed,
By adding the pattern of the gate electrode 34 in addition to the pattern of 3 and the island-shaped electrode 32, the gate electrode 34 can be added without increasing the number of steps. Therefore, a gate electrode can be added while maintaining a simple manufacturing process of the single electronic device of the present invention.

FIG. 5 is an elevation view of a single electronic device according to still another embodiment of the present invention. The single element 3 is a single electron transistor having a structure in which a gate electrode 35 is added as a top gate via an insulating film 25.

In the single-electron transistor 3, after the structure shown in FIG. 1 is manufactured, an insulating film 25 is formed, and further, a conductive film is formed on the insulating film 25 and a gate electrode 35 is formed by patterning. It can be manufactured by the following.

In the top-gate single-electron transistor 3, since the gate electrode 35 can be disposed so as to overlap with the upper part, the degree of integration of elements is not reduced. Therefore, the gate electrode structure has a small effective area and is suitable for the single electronic device of the present invention suitable for manufacturing an integrated circuit.

[0041]

As described above, the single electronic device of the present invention has a small effective area and has a structure suitable for manufacturing an integrated circuit.

According to the method for manufacturing a single electronic device of the present invention, a single electronic device having a small effective area and a structure suitable for manufacturing an integrated circuit can be manufactured in a simple process with high productivity.

[Brief description of the drawings]

FIG. 1 is an elevation view showing one embodiment of a single electronic device of the present invention.

2 (a) to 2 (f) are side views, and FIG. 2 (a1) is an elevational view of the same step as in FIG. 1 (a). The figure, (f1), shows an elevation view of the same step as (f).

3 (a) and 3 (b) are side views, and FIG. 3 (a1) is an elevation view of the same step as in FIG. 1 (a). FIG. 1 (b1) is an elevational view of the same step as (b), and FIG. 1 (c) is an elevational view showing a finally obtained single electronic device.

FIG. 4 is an elevation view showing another embodiment of the single electronic device of the present invention.

5A and 5B show still another embodiment of the single electronic device of the present invention, wherein FIG. 5A is a sectional view and FIG. 5B is an elevation view.

FIG. 6 is an elevation view illustrating a conventional manufacturing process using a suspended mask for a single electronic device.

FIG. 7 is an explanatory view illustrating another manufacturing process of a conventional single electronic device.

[Explanation of symbols]

 Reference Signs List 10 base 11 groove (recess) 21 first oxide film 22 tunnel junction (tunnel oxide film) 24 second dioxide film 32 island electrode 33 lead electrode 33a first conductor 33b second conductor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 29/788 29/792

Claims (6)

[Claims] 1. An island-shaped electrode disposed in a concave portion formed on a substrate surface and a lead electrode formed on the substrate surface are connected via a tunnel junction formed on a side surface of the island-shaped electrode. A single electronic device having a structured structure. 2. The single electronic device according to claim 1, wherein the island-shaped electrode has a laminated structure laminated on a conductor via an insulating film, and the lead electrode is vertically arranged via an insulating film. A single electronic device having a laminated structure composed of a double conductor, wherein the laminated structure of these island-shaped electrodes and the laminated structure of the lead electrodes are formed in the same process. 3. The single electronic device according to claim 1, wherein said recess formed in said base surface is a groove formed in a direction intersecting with a lead electrode. Electronic element. 4. The single electronic device according to claim 1, wherein the single electronic device has a structure in which a gate electrode is arranged on a side. 5. The single electronic device according to claim 1, wherein said single electronic device has a structure in which a gate electrode is disposed above an island-shaped electrode via an insulating film. 6. A step of forming a concave portion on the substrate surface, forming a first conductive film on the substrate surface, and forming the first conductive film on the substrate surface and the first conductive film in the concave portion separately. Forming a tunnel junction on the side wall of the concave portion; forming a second conductive film on the base surface; and patterning the first conductive film and the second conductive film to form the inside of the concave portion. An island-shaped electrode formed of the second conductive film disposed on the first conductive film and a second conductive film formed on the base surface;
A method for manufacturing a single electronic device, comprising forming a structure in which a lead electrode made of a conductive film is connected via the tunnel junction.