JPH11274470A - Manufacture of single electronic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a highly integrated single electronic element by a simple method. SOLUTION: This method includes the processes of: first mask forming process for forming a patterned first resist film 13 on a first conductive film 9 on an insulating substrate 1; first etching process for dry-etching the first conductive film 9; first oxide film forming process for oxidizing the first conductive film 9 to form a first oxide film 10 having a predetermined thickness on the side wall of the first conductive film 9; second conductive film forming process for forming a second conductive film 11; second oxide film forming process for forming a second oxide film 12 on the exposed surface of the second conductive film 11; second mask forming process for forming a band-like mask crossing the first resist film 13; and second etching process for etching the first and second conductive films 9, 11 and the first and second oxide films 10, 12, and forming an island made of the first conductive film 9 and two leads 7 extending from the island via the first oxide film 10 in the direction opposite to each other to limit the extension of a single electronic element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a single electronic device, and more particularly, to a method for manufacturing a single electronic device, in which a single electronic device formed with high integration is manufactured by a simple method. Things.

[0002]

2. Description of the Related Art Single electron device (single electron tunnel device)
When manufacturing a semiconductor device, lithography technology is indispensable for forming a minute tunnel junction which is a component of the semiconductor device. The most commonly used lithography method for forming a metal-based small tunnel junction is a double vapor deposition method using a suspended mask. Hereinafter, a conventional method for manufacturing a single electronic device will be described with reference to the drawings. FIG. 13 is a perspective view showing a state in which a single electronic device is manufactured by the above-described double vapor deposition method. First, as shown in FIG.
Thus, the suspension mask 3 is lifted from the base 1 and partially suspended in the air. Thereafter, as shown in FIG. 13, a first metal film is deposited from a direction U that forms a predetermined angle with respect to the base, and then the first metal film is oxidized to form an oxide film barrier. Further, a second metal film is vapor-deposited from the V direction intersecting with U to form a minute tunnel junction 4 at an overlapping portion of the two metal films.

[0003] A method for manufacturing a single-electron device will be described below by taking a single-electron transistor having the simplest structure and a single-electron transistor having two tunnel junctions as an example. FIG. 14 is a plan view of a mask used when depositing a metal film, and an open portion indicates an opening. The first mask having a pattern as shown in FIG.
Is formed. After that, when a second metal film is formed from the V direction crossing the U direction, as shown in FIG.
A single electron transistor having two lead electrodes 7, an island 8, and two tunnel junctions 4 formed between the island and the lead electrode is formed. In FIG. 16, the description of the gate electrode is omitted for simplicity. In this specification, an island means an isolated electrode connected to an external electrode (lead electrode 7) by a tunnel junction.

[0004]

When a single electronic device is manufactured by the conventional double vapor deposition method, a so-called double pattern is formed on a substrate (FIG. 16). Half is unnecessary. In addition, the size of the mask pattern having openings is forced to take an extra area as compared with the size of a single electronic element, that is, is significantly large (FIG. 14). For this reason, there has been a first problem that the increase in the degree of integration is limited. Further, since the direction in which the element is formed is uniquely determined by the film forming direction with respect to the film formation target, there is a second problem that the degree of freedom in circuit design and the like is limited. Further, there is a third problem that the procedure for preparing the suspension mask is complicated. In view of the circumstances as described above, an object of the present invention is to provide a method of manufacturing a single electronic device, which manufactures a highly integrated single electronic device by a simple method.

[0005]

In order to achieve the above object, a method for manufacturing a single electronic device according to the present invention comprises forming an oxidizable first conductive film on an insulating substrate. A first conductive film forming step, a first mask forming step of forming a first resist film on the first conductive film and patterning to form a strip-shaped mask, and a first resist film A first etching step of dry-etching the first conductive film using as a mask, and then oxidizing the first conductive film while controlling the state quantity of the surrounding gas atmosphere,
A first oxide film forming step of forming a first oxide film having a predetermined thickness on a side wall surface of the first conductive film, and after the first oxide film forming step,
A second conductive film forming step of forming an oxidizable second conductive film, and oxidizing the second conductive film to form a second oxide film on an exposed surface of the second conductive film. Forming a second resist film, forming a second resist film after the second oxide film forming process, and patterning the second resist film to form a strip-shaped mask crossing the first resist film. A mask forming step, and etching the first and second conductive films and the first and second oxide films using the second resist film as a mask;
A second etching step of forming an island made of the first conductive film and two leads extending from the island in a direction opposite to each other via the first oxide film to limit the spread of the single electronic device; And is characterized by having.

The state quantity of the gas atmosphere is the oxygen gas concentration,
It means a state quantity such as gas temperature. The predetermined thickness of the first oxide film is determined in consideration of various parameters such as a tunnel junction to be formed and a material of the first oxide film. Between the second oxide film forming step and the second mask forming step, a lift-off step of performing lift-off with the first resist film may be provided.

Further, instead of the first mask forming step and the first etching step, a first conductive film is formed, a first insulating film is formed on the first conductive film, and the first conductive film is formed. Forming a first resist film on the insulating film, further comprising a step of patterning the first resist film and the first insulating film into a band shape, and following the second etching step, A step of forming a second insulating film and further forming a gate electrode thereon may be provided. In the second oxide film forming step, the second oxide film may be formed by oxidizing the substrate by exposing it to the air, or the second oxide film may be formed by anodizing or plasma oxidizing the second conductive film. An oxide film may be formed. Thereby, when manufacturing a single-electron memory element, the floating gate electrode can be formed in a self-aligned manner.

Preferably, an etching contamination removing step is provided between the first etching step and the first oxide film forming step to remove contaminants on the substrate surface by the first etching step by increasing the substrate temperature. I have.

A step of forming carbon nanotubes may be provided instead of the first mask forming step, and the first etching step may use carbon nanotubes as a mask instead of the first resist film. The method may further include forming a first resist film or a second carbon nanotube crossing the carbon nanotube according to claim 6 in place of the second mask forming step. The second carbon nanotubes may be used as a mask instead of the resist film described above. The carbon nanotube is formed, for example, by a spin method in which carbon is self-organized. This results in smaller sized islands.

Hereinafter, the basic operation of the method of the present invention will be described with reference to the drawings. FIG. 1 is a view for explaining the method of the present invention, and is a cross-sectional side view of a substrate for each step. A first conductive film 9 is formed on the substrate 1, and a first resist film 13 is formed thereon by lithography. The area of the first resist film is expanded so that it can be processed to a fine size required for a single electronic element by various lithography techniques (FIG. 1A). Next, dry etching is performed in the vertical direction on the basis of the first conductive film 9 using the first resist film 13 as a mask (FIG. 1B). Subsequently, the first oxide film 10 having a desired thickness is formed by controlling the state quantity of the surrounding gas atmosphere (mainly, oxygen) using, for example, the same apparatus as that used for the dry etching (FIG. 1C). )). Further, a second conductive film 11 is formed from a direction perpendicular to the substrate (FIG. 1).
(D)). Next, the surface of the second conductive film 11 is oxidized to form a second oxide film 12 (FIG. 1E). Due to this oxidation, the portion of the second conductive film 11 attached to the side wall of the first resist film 13 is entirely oxidized to become an insulator. The thickness t of the film attached to the side wall and the second conductive film 1
The ratio t / T to the film thickness T of 1 is, for example, the size of the evaporation source at the time of film formation (for example, the diameter when the exposed surface of the evaporation source is circular) D
It is equal to the ratio D / L of the distance L between the evaporation source and the substrate. Therefore, assuming that the thickness of the oxide film is s, this can be achieved by forming the second conductive film 11 under the condition of DT / L = t <s. This oxidation can be achieved by taking it out into the atmosphere, and furthermore, artificial means such as anodic oxidation and plasma oxidation may be used.

Thereafter, for example, fine islands 8 connected to the lead electrodes 7 are formed by bonding (4). This is already a single electron charge meter. In addition, as can be seen from FIG.
Another floating island is formed at the top of the island 8, which does not affect the operation of the charge meter. Further, the first resist film 1 can be formed without forming the second oxide film 12 as described above.
3 is lifted off to form the first resist film 13
The short circuit between the lead electrodes is prevented via the second conductive film 11 formed on the side wall of the single electron charge meter, and the single electron charge meter as described above is formed.

The device manufactured in this manner is a device having a small effective area suitable for manufacturing an integrated circuit, as compared with a conventional device.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 Embodiment 1 is an embodiment of the present invention. FIG.
(A) to (g) are cross-sectional side views of the substrate in each step of the embodiment. 3 and 4 are perspective views showing the configuration of the base shown in FIGS. 2A and 2G, respectively. In the present embodiment, the same components as those described in the basic operation of the present invention are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, first, the insulating substrate 1
Then, a first conductive film forming step of forming an oxidizable first conductive film 9 is performed thereon. The film is desirably a metallic film such as aluminum, for example, on which a high-quality oxide film can easily grow. Next, a first mask forming step of forming a first resist film 13 on the first conductive film 9 and patterning by lithography to form a strip-shaped mask is performed (FIG. 2).
(a), FIG. 3). The strip-shaped resist formed as a mask is formed by various lithography techniques so as to have a fine width of, for example, several tens of nanometers required for a single electronic device. Next, a first etching step of dry-etching the first conductive film 9 in a direction perpendicular to the substrate surface is performed using the first resist film as a mask (FIG. 2).
(b)). Subsequently, the first conductive film is oxidized in the same vacuum processing apparatus that has performed the dry etching while controlling the state quantity (mainly the state quantity of oxygen) of the gas atmosphere around the substrate, so that the first conductive film is oxidized. A first oxide film forming step of forming a first oxide film 10 having a desired thickness on the side wall surface of the conductive film is performed (FIG. 2C). After the first oxide film forming step, a second conductive film forming step of forming an oxidizing second conductive film in a direction perpendicular to the substrate in the same vacuum apparatus is performed (FIG. 2D). . Further, a second oxide film forming step of naturally oxidizing the surface of the second conductive film by removing the substrate from the vacuum processing apparatus is performed (FIG. 2E).

Further, a lift-off step of lifting off the first resist film 13 with an organic solvent or the like is performed (FIG. 2F).
By this step, a short circuit due to the “side wall portion” of the film 2 is removed. Next, a second mask forming step of forming and patterning a second resist film to form a strip-shaped mask crossing the first resist film is performed (FIGS. 2G and 4). Further, using the second resist film as a mask, the first and second conductive films and the first and second oxide films are etched to form an island 8 made of the first conductive film; First
Extending in opposite directions from the island via the oxide film of
After forming the lead electrodes 7, a second etching step for limiting the spread of the single electronic element is performed. Thereafter, unnecessary portions are removed by an etching process, and the second resist film is removed. FIG. 5 is a perspective view showing a configuration of a substrate obtained by removing the second resist film. The circuit formed in this way is a single electron charge meter,
And two lead electrodes 7 connected to each other via two tunnel junctions 4. The junction 4 is formed by the first oxide film 10 formed by controlling, and is a high-quality tunnel junction.

Embodiment 2 FIG. 6 is a perspective view of a single electronic device formed according to this embodiment. The process of manufacturing the single electronic device shown in FIG. 6 is the same as the process described in the first embodiment, except that the lift-off process (FIG. 2F) is omitted. 6, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the second conductive film 11 formed on the side wall of the first resist film 13 is entirely oxidized into the second oxide film 12, that is, changed to an insulator. This sufficiently prevents the second conductive film 11 attached to the side wall of the first resist film from short-circuiting the lead electrode 7. The thickness t of the second conductive film attached to the side wall and the thickness of the second conductive film formed on the substrate
The ratio t / T to T is, for example, equal to the ratio D / L between the size D of the evaporation source during film formation and the distance L between the evaporation source and the substrate. Assuming that the thickness of the second oxide film is s, the second conductive film is formed so as to satisfy the condition of DT / L = t <s. Can be completely oxidized. The oxidation step of forming the second oxide film having the thickness s can be spontaneously achieved by removing the substrate into the atmosphere. Further, as shown in FIG. 6, fine islands 8 connected to the external lead electrodes 7 via the tunnel junctions 4 are formed. This is already a single electron charge meter. Another floating island is formed at the top of the island 8, which does not affect the operation of the charge meter. In this embodiment, since the lift-off process is not performed, silicon, polysilicon, or the like can be used as a material of the first conductive film and the second conductive film.

Embodiment 3 FIGS. 7 (a) to 7 (g) are cross-sectional side views of a substrate in each step of this embodiment, and FIG.
It is a perspective view showing composition of a base shown in (g). In this embodiment, the same components as those in the first or second embodiment are denoted by the same reference numerals, and the description thereof is omitted. In this embodiment, a first conductive film is formed, a first insulating film is formed on the first conductive film, and a first resist film 13 is formed on the first insulating film. Then, the first resist film is patterned into a belt shape (FIG. 7A). Further, using the first resist film as a mask, the first insulating film 16 is patterned into a band by dry etching from the vertical direction of the substrate, and the first resist film is removed with an organic solvent or the like. (FIG. 7 (b)). Further, dry etching is performed vertically on the first conductive film 9 as a base using the first insulating film 16 as a mask (FIG. 7C). Subsequently, the first oxide film 10 having a desired thickness is formed while controlling the state quantity of the surrounding gas atmosphere (FIG. 7D). The film is formed from the direction (FIG. 7E). Then, the surface of the second conductive film 11 is naturally oxidized by removing the substrate from the vacuum device and exposing the substrate to the atmosphere (FIG. 7F).
In the present embodiment, as in the second embodiment, the entire portion of the second conductive film 11 attached to the side wall of the first insulating film 16 is oxidized to form an insulating second oxide film. 12 is formed. Next, in the same manner as in the formation of the substrate shown in FIG. 2G in the first embodiment, a second mask forming step of forming a second resist film and performing an etching process is performed. Obtain a charge meter. Thereafter, a second insulating film 17 is formed on the entire surface, and a gate electrode 15 is formed thereon.
(g), FIG. 8).

As a result, a single-electron memory cell having the floating gate 18 and performing reading with a single-electron charge meter is manufactured. Since the floating gate 18 is automatically formed on a single electron charge meter in a self-aligned manner, lithographic alignment is not required. Also, the first insulating film 16
When the thickness is several nanometers or more, a nonvolatile storage operation can be performed. In this embodiment, since the lift-off process is not performed, silicon, polysilicon, or the like can be used as a material of the first conductive film and the second conductive film.

Fourth Embodiment In the fourth embodiment, when forming the second oxide film 12 in the manufacturing process of the second or third embodiment, artificial oxidation such as anodic oxidation or plasma oxidation is used. This is an example of forming a film. FIGS. 9 and 10 are side sectional views of a substrate obtained by growing the artificial oxide film 12a as a second oxide film in the second and third embodiments, respectively. According to this embodiment, an oxide film thicker than a natural oxide film can be grown. Therefore, the thickness t of the film attached to the side wall of the first resist film 13 or the first insulating film 16
Even if the second conductive film 12 is formed under the condition that the thickness is larger than the thickness s of the natural oxide film, a normal element can be formed. Therefore, the conditions for forming the second conductive film 12 are milder than the aforementioned conditions of DT / L = t <s.

Fifth Embodiment In this fifth embodiment, as compared with the fourth embodiment, a step of performing a vacuum heating process on the substrate immediately before forming the first oxide film 10 is performed. Thereby, the residue of the etching gas attached to the side wall of the first conductive film 9 can be removed. Therefore, it is possible to prevent the possibility that the tunnel characteristic of the tunnel junction is deteriorated.

Embodiment 6 This embodiment is an example in which carbon nanotubes are formed instead of the first resist film 13 and the second resist film 14 as compared with the first embodiment. FIG. 11 is a perspective view showing a state in which a carbon nanotube 13a is formed instead of forming the patterned first resist film 13 when a single electronic device is manufactured in this embodiment. FIG. 12 shows that when a single electronic device is manufactured in this embodiment, the carbon nanotubes 1 are formed instead of forming the patterned second resist film 14.
It is a perspective view showing signs that 4a was formed. 11 and 12 correspond to FIGS. 3 and 4, respectively. In the present embodiment, the etching is performed using the carbon nanotubes having a minute self-organized structure as a mask, and a much smaller island can be obtained as compared with the case of forming a resist patterned by electron beam exposure lithography. Therefore, it is possible to realize an element having a higher operating temperature.
Incidentally, the carbon nanotubes can be arranged in a film shape by a spin method or the like.

[0022]

According to the present invention, a first conductive film forming step of forming a first conductive film and a first conductive film forming step of forming a patterned resist film on the first conductive film are performed. A mask forming step, a first etching step of dry-etching the first conductive film, and a first oxide film having a predetermined thickness on a side wall surface of the first conductive film by oxidizing the first conductive film. Forming the first
An oxide film forming step, a second conductive film forming step of forming a second conductive film, and a second oxide film forming step of forming a second oxide film on an exposed surface of the second conductive film A second mask forming step of forming a strip-shaped mask crossing the first resist film; and etching the first and second conductive films and the first and second oxide films to form a first mask. A second etching step of forming an island made of a conductive film and two leads extending in a direction opposite to each other from the island via the first oxide film to limit the spread of the single electronic element. ing. This allows
A single electronic device with a small effective area and thus suitable for fabricating integrated circuits can be manufactured. Moreover, when manufacturing, a complicated procedure such as a suspension mask is not required.

Preferably, a first conductive film is formed instead of the first mask forming step and the first etching step.
Forming a first insulating film on the first conductive film, forming a first resist film on the first insulating film, and patterning the first resist film and the first insulating film. And a step of forming a second insulating film subsequent to the second etching step, and further forming a gate electrode thereon. This makes it possible to realize a single-electron nonvolatile memory cell that is fast, has good controllability, and requires no lithography alignment.

[Brief description of the drawings]

FIG. 1 is a view for explaining the method of the present invention, and is a cross-sectional side view of a substrate for each step.

FIGS. 2 (a) to 2 (g) are cross-sectional side views of a substrate in each step of the first embodiment.

FIG. 3 is a perspective view showing a configuration of a base shown in FIG. 2 (a).

FIG. 4 is a perspective view showing a configuration of a base shown in FIG. 2 (g).

FIG. 5 is a perspective view showing a configuration of a base obtained by further processing the base shown in FIG. 2 (g).

FIG. 6 is a perspective view of a single electronic device formed in a second embodiment.

FIGS. 7A to 7G are cross-sectional side views of the substrate in each step of the embodiment of the present invention.

FIG. 8 is a perspective view showing a configuration of the base board shown in FIG. 7 (g).

FIG. 9 is a side sectional view of a substrate obtained by growing the artificial oxide film as a second oxide film in the fourth embodiment.

FIG. 10 is a side sectional view of a substrate obtained by growing the above-described artificial oxide film as a second oxide film in the fourth embodiment.

FIG. 11 is a perspective view showing a state in which carbon nanotubes are formed in a sixth embodiment.

FIG. 12 is a perspective view showing a state in which carbon nanotubes are formed in a sixth embodiment.

FIG. 13 is a perspective view showing a state in which a single electronic device is manufactured by a conventional method.

FIG. 14 is a plan view of a mask used when depositing a metal film by a conventional method.

FIG. 15 is a plan view showing a state where a metal film is formed by a conventional method.

FIG. 16 is a plan view showing a state where a metal film is formed by a conventional method.

[Explanation of symbols]

 1. Base 2. Spacer 3. Suspension mask 4. Junction (tunnel junction) 7. Lead electrode 8. Island 9. First conductive film 10. First oxide film 11. Second conductive film 12. 2 oxide film 12a. Artificial oxide film 13. first resist film 13a. Carbon nanotube 14. second resist film 14a. Carbon nanotube 15. gate electrode 16. first insulating film 17. second insulating film 18 . Floating gate

Claims (7)

[Claims] A first conductive film forming step of forming an oxidizable first conductive film on an insulating substrate; and forming a first resist film on the first conductive film. A first mask forming step of forming a strip-shaped mask by filming and patterning; a first etching step of dry-etching the first conductive film using the first resist film as a mask; A first oxide film having a predetermined thickness formed on a side wall surface of the first conductive film by oxidizing the first conductive film while controlling a state quantity of a surrounding gas atmosphere; Forming a second conductive film after forming the first oxide film, forming a second conductive film having an oxidizing property, and oxidizing the second conductive film to form a second conductive film. Forming a second oxide film on the exposed surface of the conductive film; forming a second oxide film on the exposed surface of the conductive film; A second mask forming step of forming a strip film and patterning the same to form a strip-shaped mask crossing the first resist film; and forming a first and second mask using the second resist film as a mask.
The first conductive film and the first and second oxide films are etched to form an island made of the first conductive film, and two leads extending from the island through the first oxide film so as to face each other. And a second etching step for limiting the spread of the single electronic device. 2. The single electronic device according to claim 1, further comprising a lift-off step of performing a lift-off with a first resist film between the second oxide film forming step and the second mask forming step. A method for manufacturing a single electronic device, comprising: 3. The method for manufacturing a single electronic device according to claim 1, wherein the first mask forming step and the first etching step are replaced with a first mask forming step and a first etching step.
A first conductive film is formed; a first insulating film is formed on the first conductive film; a first resist film is formed on the first insulating film; Patterning the resist film and the first insulating film into a band shape, and forming a second insulating film following the second etching process, and further forming a gate electrode thereon. A method for manufacturing a single electronic device, comprising the steps of: 4. The method for manufacturing a single electronic device according to claim 1, wherein the second conductive film is formed by anodizing or plasma oxidizing the second conductive film in the second oxide film forming step. A method for manufacturing a single electronic device, comprising forming an oxide film. 5. The single electronic device according to claim 1, wherein the substrate temperature is increased between the first etching step and the first oxide film forming step by increasing the substrate temperature. A method for manufacturing a single electronic device, comprising: an etching contamination removing step of removing contaminants on a substrate surface by an etching step. 6. The method of manufacturing a single electronic device according to claim 2, further comprising a step of forming a carbon nanotube instead of the first mask forming step, wherein the first etching step includes the step of forming a first resist film. A method of manufacturing a single electronic device, wherein a carbon nanotube is used as a mask instead. 7. The method for manufacturing a single electronic device according to claim 2 or 6, wherein the first resist film or the carbon nanotube according to claim 6 is used instead of the second mask forming step. Forming a crossing second carbon nanotube, wherein in the second etching step, the second carbon nanotube is used as a mask instead of the second resist film. .