JPH07161963A - Manufacture of quantum wire structure - Google Patents

Abstract

PURPOSE:To form a quantum wire structure, by utilizing a stress generated in case of the oxidizing of a thick film, and by making the thermal oxide film present near the end of the oxide film of the thick film into a thin film, and further, by utilizing silicon present below the part made into a thin film as a part of a quantum wire. CONSTITUTION:By the thermal oxidation of a silicon substrate 1, a silicon oxide film 2 is formed, and thereafter, a silicon nitride film is formed on the film 2. By the etching of this silicon nitride film, a new silicon nitride film 3 is formed, and thereafter, by the thermal oxidation of the silicon oxide film 2, a first oxide film 4 is formed out of a part of the film 2. Hereupon, in case of the forming of the first oxide film 4, a local stress is generated in a silicon crystal present below the end part of the first oxide film 4. By the further heat treatment of the same, this stress is further increased. By this stress, the diffusions of oxidation seeds are suppressed, and thereby, the oxidizing rate of the same is changed. Therefore, in case of the performing of this thermal oxidation, a part 6 made into a thin film and a protruding part 7 of silicon are formed respectively in the end part of the first oxide film 4. Still, after the forming of the first oxide film 4, a second oxide film 5 is formed by a thermal oxidation. In this way, both a gate oxide film which has along the shape of the first oxide film 4 and the protruding part 7 of silicon are utilized, and thereby, a quantum wire structure can be formed.

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 quantum wire structure.

[0002]

2. Description of the Related Art In recent years, the progress of semiconductor devices has led to higher integration and finer design rules. With the progress of such miniaturization, there is an increasing need to develop a new device structure different from the conventional transistor structure. Devices using the quantum effect have been studied as such new devices (Journal of the Institute of Electronics, Information and Communication Engineers Vol.7).
2, No12, pp1387 to 1391, December 1989).

In order to induce the quantum effect, it is necessary to develop a technique for forming dots or fine lines having dimensions on the order of the wavelength of electrons, and a technique for connecting them to form a circuit.

FIG. 5 shows a schematic view of a method attempted as a conventional method for manufacturing a quantum wire structure. Hereinafter, a method for manufacturing a quantum wire structure of a conventional example will be described with reference to FIG.

In FIG. 5A, a silicon oxide film 2 is formed on a silicon substrate 1. In FIG. 5B, the silicon nitride film 3 is deposited and processed into a predetermined shape. Figure 5 (c)
At 1000 ° C., thermal oxidation at 600 nm is performed in a pyrooxidizing atmosphere to form a first oxide film 4. In FIG. 5 (d),
The silicon nitride film 3 is removed to obtain the fine line region 31. According to this method, the thin wire region 31 is formed in the region sandwiched by the two first oxide films 4, and the quantum wire can be formed by utilizing this.

[0006]

In the conventional method of manufacturing a quantum wire structure having the above-described structure, the width of the wire region 31 is determined by the oxidation of the first oxide film 4, so that the width can be controlled. It had a problem of poor sex.

In view of the above points, the present invention has an object to provide a method for manufacturing a quantum wire structure which solves the above problems by utilizing the stress generated during thick film oxidation.

[0008]

A method for manufacturing a quantum wire structure according to the present invention utilizes a stress generated during thick film oxidation to thin a thermal oxide film near an edge of a thick film oxide film, and to reduce a thickness of a lower portion of a thinned portion. By using the silicon of as part of the quantum wire,
(EN) A method for manufacturing a quantum wire structure, which solves the problem that the controllability of the wire width is poor.

[0009]

With the above-described structure, the present invention makes it possible to manufacture a quantum wire structure in which the width of the quantum wire is easily controlled.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a quantum wire structure according to a first embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a process flow showing a method of manufacturing a quantum wire structure in a first embodiment of the present invention, and FIG. 2 is a sectional view of the process. The manufacturing flow of the method for manufacturing the quantum wire structure as described above will be described below.

In FIGS. 1A and 2A, the silicon substrate 1 is thermally oxidized to form a silicon oxide film 2 having a film thickness of 10 nm.
To form. In FIG. 1B, a silicon nitride film having a film thickness of 120 nm is deposited. 1C and 2B, the nitride film is etched to form the silicon nitride film 3 having a predetermined shape. In FIG. 1 (d) and FIG. 2 (c), the film thickness 60
Thermal oxidation of 0 nm is performed to form the first oxide film 4. 1E and 2D, the silicon nitride film 3 is removed with a phosphoric acid solution. In FIG. 1 (f), heat treatment is performed at 1100 ° C. for 16 hours in a nitrogen atmosphere. 1 (g) and 2 (e), the oxide film is etched with a hydrofluoric acid solution to remove the silicon oxide film 2. In FIG. 1 (h) and FIG. 2 (f), a second oxide film 5 having a film thickness of 12 nm is formed by thermal oxidation.

At this time, when the first oxide film 4 is formed, a local stress is generated in the silicon crystal below the end portion of the first oxide film 4. By further subjecting this to the heat treatment of FIG. 1 (f), this stress is further increased. In general, when a stress-applied silicon crystal is oxidized, the stress suppresses the diffusion of oxidizing species and changes the oxidation rate. Therefore, when thermal oxidation is performed from the state of Fig. 2 (e),
As shown in FIG. 5, the thinned portion 6 and the silicon protrusion 7 are formed on the end portion of the first oxide film 4. The film thickness of the thinned portion 6 is about 5 nm in this embodiment.

As described above, according to this embodiment, the gate oxide film having the thinned portion along the shape of the first oxide film 4,
And it becomes possible to form a silicon protrusion,
By utilizing this, it becomes possible to form a quantum wire structure.

In this embodiment, the removal of the nitride film and the
It is also possible to change the order of heat treatment in a nitrogen atmosphere at 1100 ° C for 16 hours.

In the present embodiment, the second oxide film 5
In the thermal oxidation step for forming the film, since the diffusion of the oxidizing species due to the stress in the silicon is suppressed, the oxidation rate becomes slower, and the thinned portion 6 is formed at the end of the first oxide film 4. If the second oxide film 5 is formed by dry oxidation, the diffusion rate of which is slower than that of pyrooxidation, the thinning becomes more remarkable. In the case of use as shown in the following examples, it is advantageous that the film thickness difference between the thinned portion 6 and the second oxide film 5 portion is large, and therefore, in the present embodiment,
By using dry oxidation when forming the oxide film 5, the more excellent quantum wire structure can be formed.

(Embodiment 2) A method of manufacturing a quantum wire structure according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a process sectional view, a perspective view and an operation explanatory view showing a method of manufacturing a quantum wire structure in a second embodiment of the present invention. The manufacturing flow of the quantum wire structure having the above-described structure will be described below.

By the manufacturing method shown in the first embodiment, a shape having a thinned portion 6 as shown in FIG. 1 (f) is formed.
After that, in FIG. 3A, a polycrystalline silicon film is deposited and phosphorus is diffused by a CVD method, and the polycrystalline silicon film is etched into a predetermined shape to form a gate electrode 11. A perspective view at this time is shown in FIG. In FIG. 3B, the thinned portion and the protrusion have a thin line shape extending in the direction indicated by the thin line direction 13.

In the second embodiment shown in FIG. 3 (a),
A voltage is applied to the gate electrode 11 with the silicon substrate 1 as ground. When the applied voltage is set to have an inversion polarity determined by the substrate type of the silicon substrate 1, when the applied voltage becomes equal to or higher than the threshold value, the channel region 1 is formed below the thinned portion 6.
2 is formed. The width of the channel region 12 is determined by the width, the film thickness, and the applied voltage of the thinned portion 6, but under the conditions shown in the first embodiment, the thinned portion 6 has a width of about 20 nm. It is a dimension. The depth of the inversion layer is about several nm although it depends on the impurity concentration in the silicon substrate 1, the applied voltage and the like. Therefore, the channel region 12 is quantized in the width direction and the depth direction, and the thin line direction 13
Is a quantum wire along. When a voltage is applied to both ends of the channel region 12 extending in the thin line direction 13 and the voltage is increased, as shown in FIG. An electric current having

(Embodiment 3) A method of manufacturing a quantum wire structure according to a third embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a process sectional view and a perspective view showing a method of manufacturing a quantum wire structure according to a third embodiment of the present invention. The manufacturing flow of the quantum wire structure having the above-described structure will be described below.

By the manufacturing method shown in the first embodiment, a shape having a thinned portion 6 as shown in FIG. 1 (f) is formed.
After that, as shown in FIG. 4A, a predetermined thickness not less than the film thickness of the thinned portion 6 and not more than the thickness of the second oxide film 5 is removed by etching with a hydrofluoric acid aqueous solution. At this time, the protruding portion 7 of silicon is exposed. In FIG. 4 (b),
Arsenic ions are implanted by the ion implantation method to form the impurity-implanted layer 21 on the protruding portion 7. A perspective view at this time is shown in FIG. In FIG. 4C, the impurity implantation layer 21 has a thin line shape extending in the direction indicated by the thin line direction 22.

In the third embodiment shown in FIG. 4 (c),
When a voltage is applied to both ends of the impurity injection layer 21 extending in the thin line direction 22 and the voltage is increased, as shown in FIG. A current having resistance flows.

[0025]

INDUSTRIAL APPLICABILITY As described above, the present invention can provide a method for manufacturing a quantum wire structure having simple steps and excellent controllability.

[Brief description of drawings]

FIG. 1 is a diagram showing a process flow in a first embodiment of the present invention.

FIG. 2 is a process sectional view in the first embodiment of the present invention.

3A is a cross-sectional view of the second embodiment of the present invention, FIG. 3B is a perspective view of the second embodiment of the present invention, and FIG. 3C is an operation explanatory view of the second embodiment of the present invention.

4A is a process sectional view in a third embodiment of the present invention. FIG. 4B is a process sectional view in a third embodiment of the present invention. FIG. 4C is a perspective view of the third embodiment of the present invention.

FIG. 5 is a process sectional view showing a method of manufacturing a quantum wire structure of a conventional example.

[Explanation of Codes] 1 Silicon substrate 2 Silicon oxide film 3 Silicon nitride film 4 First oxide film 5 Second oxide film 6 Thinned portion 7 Projection portion 11 Gate electrode 12 Channel region 13 Fine line direction 21 Impurity injection layer 22 Fine line Direction 31 Fine line area

Claims (10)

[Claims] 1. A first step of forming an oxidation suppressing mask on silicon, a second step of performing thermal oxidation to a predetermined film thickness, and a third step of removing the oxidation suppressing mask. Ten
Manufacturing a quantum wire structure characterized by including a fourth step of performing a heat treatment in an inert gas atmosphere at a temperature of 50 ° C. or more for 3 hours or more, and a fifth step of thermally oxidizing to a predetermined film thickness. Method. 2. A first step of forming an oxidation suppressing mask on silicon, a second step of performing thermal oxidation to a predetermined film thickness, and an inert gas atmosphere at a temperature of 1050 ° C. or higher for 3 hours or longer. Manufacturing a quantum wire structure comprising: a third step of performing heat treatment below; a fourth step of removing the oxidation suppressing mask; and a fifth step of thermally oxidizing the film to a predetermined film thickness. Method. 3. The method of manufacturing a quantum wire structure according to claim 1, wherein the thermal oxidation in the fifth step is performed in a dry oxidizing atmosphere. 4. The method of manufacturing a quantum wire structure according to claim 1, further comprising a sixth step of forming an electrode made of a conductive material, following the fifth step. 5. The method of manufacturing a quantum wire structure according to claim 1, wherein impurities are introduced by an ion implantation method after the fifth step. 6. The method for producing a quantum wire structure according to claim 1, wherein impurities are introduced by a diffusion method subsequent to the fifth step. 7. A sixth step, which follows the fifth step, has a sixth step of removing a part or all of silicon by removing a predetermined thickness of the silicon oxide film formed by the fifth step. The method for manufacturing the quantum wire structure according to claim 1. 8. The method of manufacturing a quantum wire structure according to claim 7, further comprising a seventh step of forming an electrode made of a conductive material after the sixth step. 9. The method for producing a quantum wire structure according to claim 7, wherein impurities are introduced by an ion implantation method after the sixth step. 10. The method for producing a quantum wire structure according to claim 7, wherein impurities are introduced by a diffusion method subsequent to the sixth step.