JPH0478128A - Formation of fine structure of semiconductor - Google Patents

Abstract

PURPOSE:To easily form many quantum boxes with high precision, by selectively growing a semiconductor core layer in the inside of holes of a porous thin film, eliminating the porous thin film, and growing a buried layer in which the core layer is buried. CONSTITUTION:An undoped GaAs crystal layer 12 is grown on a substrate 1; a P-Si layer 13 is grown on the layer 12 and turned into a porous state; a plurality of holes 14 are formed; an SiO2 film 15 and a GaAs oxide film 16 are formed; the wafer is heated in a vacuum, thereby eliminating only the GaAs oxide film 16; a P-type Al0.3Ga0.7As layer 17 is crystal-grown on the wafer surface from which the GaAs oxide film 16 is eliminated; the wafer is dipped in a hydrofluoric acid solution and the like, thereby eliminating the SiO2 film 15; the Si layer 13 is eliminated by gas etching and like. Hence a plurality of columnar P-AlGaAs layer 17 protrude from the surface, and finally an undoped GaAs buried layer 18 is grown on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor fine structure manufacturing technique for manufacturing semiconductor fine structures used in semiconductor devices such as electronic devices and optical devices.

[Prior Art] In general, the following techniques such as etching or selective growth must be appropriately used to fabricate semiconductor fine structures.

These techniques can be broadly classified into methods that do not use a mask pattern and methods that use a mask pattern, and the methods are as follows.

Etching without using a mask pattern uses light, electromagnetic waves,
Focus electron beams, ion beams, etc. by appropriate means,
Direct irradiation is applied only to the area to be etched to provide some kind of excitation to promote etching in that area. Excitation here refers to, for example, an etching acceleration phenomenon that utilizes the excitation effect of reactive species due to the interaction between etching gas plasma and light, or a localized phenomenon in which a natural oxide film layer on a semiconductor surface is irradiated with an electron beam or an ion beam. It also includes the phenomenon of gas etching only the clean surface from which the oxide film has been removed.

Furthermore, when using a mask pattern, a solution, ion beam, gas, or the like is used. In this case, the etching phenomenon can be accelerated by light, electromagnetic waves, etc. (for example, reactive ion etching method, etc.), etching using sputtering effect by ion beam irradiation (ion milling), etc.
It is often accompanied by some form of excitation. When this mask pattern is used, excitation is not locally limited during microfabrication. That is, in this case, the location to be etched is designated by a mask pattern. Therefore, the method using a mask pattern has the characteristic that etching progresses over the entire wafer at once, and is suitable for mass production technology.

As a manufacturing technique for semiconductor fine structures other than these, there is a fine processing technique using selective growth.

This method is the opposite of the method using etching described above.
Crystals are grown only in predetermined locations. In the second method, there are cases where a mask pattern is used and cases where selective growth is performed by locally excitation without using a mask pattern.

Furthermore, as another technique for manufacturing semiconductor microstructures, a semiconductor wafer with a superlattice structure is subjected to a process that combines ion implantation and annealing to make the superlattice structure irregular.
A microstructure formation method that causes mixed crystallization in a predetermined region,
There is a method such as the Fvl BE method in which raw material species are alternately supplied onto a slightly inclined substrate and a fine structure is produced using the dependence of the adsorption state on the atomic species in the atomic layer step.

Conventionally, a fine structure is created on a semiconductor substrate using the above-mentioned technique, and then buried growth or the like is performed to obtain a semiconductor device.

[Problems to be Solved by the Invention] However, the conventional method has the following problems.

In etching and selective growth using mask patterns,
Since the accuracy depends on the accuracy of the mask pattern, there is a problem that it is not possible to achieve fineness beyond a certain level.

Etching methods and selective growth methods that do not use a mask pattern require a vibration isolator to irradiate a focused beam only to a predetermined area, a special beam scanning device or substrate holding device to scan a beam over a wide area, etc. There is a problem in that it requires complicated equipment. Another problem is that it takes time to scan the beam, making it unsuitable for mass production. Furthermore, when an ion beam is used, it is very difficult to recover from damage after etching, so there is concern about the effect it will have on the characteristics of the fabricated device.

The method of combining ion implantation and annealing in a semiconductor wafer with a superlattice structure to cause mixed crystal formation in a predetermined location has problems such as damage caused by ion sputtering and controllability of ion diffusion by annealing. There is.

The method using a slightly tilted substrate has problems in that it is sensitive to crystal growth conditions and it is difficult to form a uniform structure over a wide range and a fine structure with nanometer-order precision.

An object of the present invention is to provide a semiconductor microstructure fabrication method that does not require complicated equipment, has high processing accuracy, and is capable of mass production.

[Means for Solving the Problems] The present invention includes a first step of forming a porous thin film, and a second step of selectively growing a semiconductor core layer inside the pores of the porous thin film.
, a third step of removing the porous thin film, and a fourth step of growing a buried layer for burying the core layer.

[Example] The present invention will be described in detail below with reference to the drawings.

GaAs%Aj! A method for producing a so-called super atom using GaAs will be explained.

Here, a super atom is a type of quantum box. When an impurity is confined in an extremely narrow region made of a semiconductor with a large band gap, electrons equal to the number of impurities are bound around it by the Coulomb force, making it appear as if it had become gigantic. It works like an artificial atom.

First, as shown in FIG. 1(a), a P-GaAs substrate 1
1, a non-doped GaAs crystal layer 12 is grown to a thickness of several thousand as a buffer layer. Then, on the grown GaAs crystal layer 12, a p-5i layer 13 is grown at about 4 OA by a two-step growth method or the like.

Next, as shown in FIG. 1(b), p
-5i layer 13 is made porous and a plurality of holes 14 reaching buffer layer 12 are provided. The distribution of the holes 14 at this time is shown in FIG. 1(C).

The anodic oxidation method is the same as a method generally known as a film forming method. That is, in a hydrofluoric acid aqueous solution, p-8i
A positive direct current is passed through the layer 13 and a negative direct current is passed through the platinum layer. The diameter and depth of the holes 14 formed by this method and the distribution density of the holes 14 are determined by the electrical conductivity of the p-Si layer 13, the applied voltage and current, etc. For example, if the diameter of the holes 14 is ~40, the variation in the diameter of the holes 14 is about ±5 people, which is close to the theoretical limit for processing by electron beam lithography (theoretically, it is about several dozen people, In practice, an accuracy of about 100) can be achieved.

Next, the wafer having the porous p-5i layer 13 is placed in an oxygen atmosphere, and a 5in2 film 15 and a GaAs oxide film 16 are formed on the surface as shown in FIG. 1(d).

After forming the oxide film, when the temperature of the wafer is raised in a vacuum, only the GaAs oxide film 16 is removed at around 550°C.

After that, p-type All-in-all is formed on the wafer surface from which the GaAs oxide film 16 has been removed using MOMBE method or the like.

G a 0.7 A 5 layer 17 is grown as a crystal. At this time, as shown in FIG. 1(e), crystal growth does not occur on the 5in2 film, and growth progresses only on the GaAs buffer layer. That is, crystals grow only inside the holes 14.

This p-type ADO,3G ao,,A s layer 17 is
It becomes the core part of Super Atom.

Next, this wafer is immersed in a hydrofluoric acid solution etc. to form a 5in2 film 1.
5 is removed, and the Si layer 13 is further removed by CF4+O□-based gas etching or the like. As a result, multiple cylindrical p-Aj7G, which is the core part of the super atom,
The aAs layer 17 protrudes from the surface.

Finally, a non-doped GaAs buried layer 18 is grown on the surface, and as shown in FIG. 1(f'), p-11? GaAs
Layer 17 is embedded to form a super atom.

In this way, according to this embodiment, the diameter is ~40 people and the height is ~4
Super atoms (quantum boxes) having the 0A p-AgGaAs layer 17 as a core part can be manufactured in large quantities with high precision.

In addition, in the above embodiment, GaAs/Aj? Although the method for producing a super atom using GaAs-based material has been described, the method is not limited thereto.

Further, the thin film is not limited to a Si film, and may be any film that can be easily made porous with high precision, for example, a fluoride film such as CaF.

Furthermore, the method of making the thin film porous is not limited to anodization, as long as it is a method that can make the thin film porous with good control.

[Effects of the Invention] According to the present invention, after forming a porous thin film and selectively growing a semiconductor core layer inside the pores of the thin film, the porous thin film is removed, and then a buried layer in which the core layer is embedded is formed. By growing quantum boxes, it is possible to easily produce large quantities of quantum boxes with high precision without the need for complicated equipment.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the manufacturing process of an embodiment of the present invention. 11... p-GaAs substrate, 12... non-doped G
aAs buffer layer, 13.= p-type Si thin film, 14.
...hole, 15-5in2 film, 16-GaAs oxide film, 17-p type Ajto, iGao7As
layer, 18-=undoped GaAs buried layer. Section (a) 1 (b) (C) (d) (e) (f)

Claims (3)

[Claims] 1. a first step of forming a porous thin film; a second step of selectively growing a semiconductor core layer inside the pores of the porous thin film; a third step of removing the porous thin film; and a third step of removing the porous thin film. A method for manufacturing a semiconductor microstructure, comprising: a fourth step of growing a buried layer that embeds the . 2. 2. The method of manufacturing a semiconductor microstructure according to claim 1, wherein in the first step, after forming the thin film, the thin film is made porous by an anodic oxidation method. 3. Claim 2, wherein the thin film is a Si film.
A method for fabricating the semiconductor microstructure described.