JP2541456B2 - Microstructure fabrication method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the selective fabrication of semiconductor microstructures on the surface of crystalline substrates.

[0002]

2. Description of the Related Art A semiconductor fine structure fabrication technique is important in the development of high-speed transistors and devices utilizing the quantum effect. In particular, the production of quantum wires, which is the basic element, is important, and it is desired to have no crystal defects. In the microfabrication method that combines electron beam writing and dry etching, which has been generally used up to now, in order to induce crystal defects, in recent years, a method of self-forming a quantum wire using a growth technique has been popular. is there. This method is described, for example, by Tsukamoto et al. In "Fabrication of Journal of Applied Physics".
f GaAs quantum wires on e
pitaxially grown Vgrooves
by metal-organic chemicala
l-vapor deposition ", S. Tsu
kamoto et al. , Journal of
Applied Physics, Vol. 71, N
o. 1, pp. 533-535, 1992).

FIG. 2 is a process drawing of a conventional quantum wire fabrication. In FIG. 2, (a) shows a step of forming a mask material on the crystal substrate, (b) shows a step of growing a separation layer on the substrate and the mask material, and (c) shows a step of forming a buffer layer and a buried layer. 1 is a crystal substrate, 4 is a buried layer, 5 is a mask, 6 is a separation layer, and 7 is a buffer layer.

Regarding this conventional method for producing a fine structure,
GaAs on the substrate 1, GaAs on the buried layer 4, mask 5
To SiO ₂ , separation layer 6 to GaAs, buffer layer 7 to Al
This will be described using GaAs. First, S on the GaAs substrate
An iO ₂ film is deposited, a photoresist is applied thereon, and a mask pattern is formed by electron beam drawing. After that, the etching resist of SiO ₂ is removed to complete the mask (FIG. 2A). Next, GaAs is grown in an organic source vapor deposition (MOCVD) apparatus, and (11
1) A separation layer having a surface is formed (FIG. 2B). After growing the AlGaAs buffer layer in the same growth apparatus, GaA
s A buried layer is formed. At this time, the GaAs burying layer is scarcely formed on the (111) plane, but is mainly formed in the V-shaped groove. Thus, the fine structure of GaAs is completed.

[0005]

According to this conventional method,
It is possible to form a fine structure with less crystal damage, but the height of the separation layer is determined by the dimensions of the mask.
If the mask size is large, the height of the separation layer becomes high, and it becomes difficult to perform subsequent fine processing. In addition, it is necessary to form a mask in advance before crystal growth,
The process is complicated, for example, it is necessary to pay attention to cleaning the substrate before growth.

An object of the present invention is to provide a method for easily producing a fine structure of good quality without requiring such a complicated process.

[0007]

The method for producing a fine structure according to the present invention comprises the steps of breaking a bond between crystal constituent atoms on a crystal substrate surface and selectively implanting accelerated ions in an amount that does not cause sputtering. It is characterized in that a heat treatment for recovering crystallinity is applied to the substrate to form a selective groove, and a crystal is selectively embedded in this groove.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments. FIG. 1 is a process drawing showing an embodiment of the present invention. 1, the same symbols as those in FIG. 2 are equivalent to those in FIG. 2 and have the same functions. Further, (A) shows a substrate after ion irradiation, (B) shows a substrate after heat treatment, and (C) shows a substrate after burying crystals, 2 is a focused ion, and 3 is an ion implantation region.

[0009] A method for manufacturing a fine structure of the present invention, GaAs substrate 1, Si ⁺ in ion 2, illustrating the InAs the buried layer 4 as an example. First, focused Si ⁺ ions 2 are implanted on the GaAs substrate 1. The ions that have been implanted into the substrate lose their energy due to collision with crystal atoms inside the substrate and stop. In this process, the bonds of the atoms constituting the crystal are broken, so that the substrate becomes amorphous in the ion-implanted region 3 into which the ions have been implanted (FIG. 1A). Since the atoms in the amorphized region are broken, the volume thereof expands more than that of the crystalline region. Therefore, a raised region is formed on the ion implantation region 3. Of course, some of the substrate surface atoms jump out, but in the method of the present invention, the mass and energy of the ions to be implanted are large enough to penetrate deeply into the substrate, and the amount of ions to be implanted is much smaller than that of ion milling. The atoms that jump out to can be almost ignored. In this step, it is necessary to set the optimum ion implantation amount. If the amount of ions to be implanted is small as in the case of ordinary impurity doping, the crystal bonds cannot be sufficiently broken, so that it cannot be made amorphous and the surface does not rise. Further, when the amount of ions is too large to be used for ion milling, the surface is scraped off by sputtering, and the crystal surface is not raised. As described above, in the ion implantation step of the present invention, in order to raise the crystal surface, it is necessary to carefully set the amount of implanted ions to be in the middle thereof.

Next, when a heat treatment is performed at a temperature at which the crystallinity of the amorphized ion-implanted region 3 is restored, the amorphized portion begins to crystallize again and the raised region decreases. Go. Further, since the atom whose bond has been broken is easy to move and has high reactivity, the atom in the ion-implanted region 3 moves to its periphery, evaporates, or is taken into the heat treatment atmosphere. As a result, the number of atoms in the ion-implanted region 3 is reduced, and a groove is formed there (FIG. 1 (B)). By this heat treatment, most of the amorphized region disappears, and the periphery of the ion-implanted region containing crystal defects is also annealed to improve the crystallinity.

Finally, the material for the buried layer is crystal-grown on this structure. When the substrate surface orientation is selected, the growth on the inclined surface can be delayed similarly to the growth of the buried layer 4 in FIG. 2C, so that the growth at the bottom of the groove is remarkable and a fine buried layer is formed.

A Si ⁺ focused ion beam having a diameter of 100 nm was applied to a GaAs substrate at an acceleration voltage of 260 keV and a linear density of 10.
^{When the} line was injected at ¹⁰ cm ^-1 , the surface of the injected region was raised by 20 nm. Subsequently, when this substrate was heat-treated at 650 ° C. for 15 minutes while flowing an arsine gas, a V-shaped groove having a width of 200 nm and a depth of 25 nm was formed. This structure has InA formed by MOCVD.
s was grown to form a wedge-shaped quantum wire structure having a width of 80 nm and a depth of 10 nm.

In the above-described embodiments of the present invention, only formation of a groove having a depth of about 25 nm was shown. However, the depth and shape of the groove can be adjusted by selecting the mass, acceleration energy and distribution of implanted ions. it can. Also, the depth and shape of the groove can be adjusted by adjusting the heat treatment temperature and time. Of course, the size and shape of the fine structure can be controlled by appropriately selecting the growth conditions of the buried layer.

Although only single-crystal GaAs is shown as the substrate, it is obvious that the present invention can be applied to other semiconductor single-crystal substrates such as Si, Ge, InP and GaSb and polycrystalline substrates. It is also clear that the present invention can be applied to single crystal substrates and polycrystal substrates other than semiconductors such as insulators and metals.

Although only InAs is shown as the buried layer, it is obvious that other materials such as GaAs in which the bottom of the groove is preferentially grown may be used. It is also apparent that another material may be sandwiched between the substrate and the buried layer as in the conventional example.

Although only Si ⁺ is shown as the ion to be implanted, it is also clear that other ions such as Au ⁺ , Ga ⁺ As ⁺ Sb ⁺ may be used.

Further, although only arsine gas was shown as the atmosphere for the heat treatment, other gases may be used, and it is also clear that the atmosphere may be pressurized, depressurized or vacuum.

In the present invention, it is desirable to use a focused ion beam in order to facilitate the fine structure manufacturing process, but when processing a large area at once, a spread ion beam is used and placed on the substrate surface. It is also apparent that the ions may be selectively implanted through the mask.

[0019]

According to the method for producing a fine structure of the present invention, a fine structure can be selectively produced on the crystal surface, and it becomes possible to incorporate fine semiconductor elements into a high density.

[Brief description of drawings]

FIG. 1 is a process drawing showing an example of the present invention. (A) shows the state during the ion irradiation, (B) after the heat treatment, and (C) shows the state after the buried layer is formed.

FIG. 2 is a process drawing of fine structure fabrication by a conventional method. (A) is after mask formation, (b) is after separation layer growth,
(C) shows the state after the formation of the buffer layer and the buried layer.

[Explanation of symbols]

 1 Crystal Substrate 2 Ion 3 Ion Implantation Region 4 Buried Layer 5 Mask 6 Separation Layer 7 Buffer Layer

Claims (1)

(57) [Claims] 1. A surface of a crystal substrate is selectively implanted with an amount of accelerated ions that break bonds between crystal constituent atoms and do not cause sputtering, and then subject the substrate to a heat treatment to recover crystallinity to selectively A method for producing a fine structure, characterized in that a fine groove is formed and crystals are selectively embedded in the groove.