JPH03180037A - Manufacture of quantum thin wire - Google Patents

Abstract

PURPOSE:To decrease the fluctuation of the width of a fine quantum thin wire and to suppress damages by performing inverted mesa etching with chemical etchant having anisotropy. CONSTITUTION:An InP buffer layer 2, an InGaAs quantum well layer 3 and an InP cap layer 4 are laminated on a (100) InP substrate 1 in this order. Then, a resist stripe pattern 5 is formed in the direction of <100> by an electron beam lithography method. Inverted mesa etching is performed for the cap layer 4 and the quantum well layer 3 by chemical etching. At this time, the width of a quantum thin wire is controlled with the orientation of the surface of the inverted mesa and the thickness of the cap layer 4. The thickness is not limited with the size of a resist pattern. Even if the resist pattern is fluctuated, the etching quickly progresses in the fluctuation in the direction other than a {111} surface. In this way, the fine quantum thin wire can be manufactured without machining damages, and the fluctuation in lithography can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a one-dimensional quantum wire structure applicable to optical devices, electronic devices, and the like.

(Prior Art) In recent years, several methods have been proposed and tried as means for producing one-dimensional quantum wire structures.

In particular, methods of forming quantum wires by processing quantum well structures using electron beam exposure have been intensively researched in recent years as lithography technology has progressed. In this method, a resist stripe pattern with a line width of approximately 300 mm is formed by electron beam exposure on a quantum well structure of a semiconductor fabricated using molecular beam epitaxial growth, etc., and this is etched by reactive ion etching, etc. Quantum wires are formed by transferring them onto a quantum well structure.

However, with the above method, fluctuations occur in the line width of the resist pattern formed due to electron beam exposure, the processing limit is currently about 300 people, and there are problems when transferring the resist pattern to the quantum well. , damage to the quantum well structure was a problem.

(Problems to be Solved by the Invention) The present invention reduces fluctuations in line width when transferring a resist pattern to a quantum well structure, and prevents damage to quantum wires that are thinner than the resist pattern formed by electron beam exposure. It is an object of the present invention to provide a method for manufacturing quantum wires that can be manufactured while keeping the amount of wires low.

(Means for Solving the Problems) The quantum wire manufacturing method of the present invention uses anisotropic etching instead of conventionally used dry etching such as reactive ion etching as a method for transferring a resist pattern to a quantum well. The method is to perform reverse mesa etching using a chemical etchant that has properties. By using anisotropic chemical etching, it is possible to reduce the resist pattern and transfer it to the quantum well structure, and at the same time, it is possible to reduce the fluctuation of the resist pattern with an orientation outside the chamfer that appears in the inverted mesa shape. It is also possible to reduce damage during processing.

(Example) The method for manufacturing a quantum wire of the present invention will be explained in detail below using the drawings. FIG. 1 shows a procedure for manufacturing a quantum wire in an embodiment of the present invention. First, as shown in FIG. 1(a), (100) InP was grown using a thin film growth method that allows film thickness control on the order of atomic layers, such as molecular beam epitaxy.
An InP buffer layer 2, an InGaAs quantum well layer 3, and an InP cap layer 4 are grown in this order on a substrate. Next, using a method such as electron beam lithography, the image shown in FIG. 1(b) is
As shown in , a resist stripe pattern is formed in the <011> direction. Thereafter, the InP cap layer 4 and the InGaAsfi child well layer 3 are subjected to reverse mesa etching using chemical etching, as shown in FIG. 1(C). During the etching shown in FIG. 1(C), side etching becomes a problem, so a dielectric mask (such as a silicon nitride film) is used.
A method in which the InP cap layer 4 is etched after being transferred to a semiconductor film (InGaAs thin film in the above case), or a method in which the InP cap layer 4 is etched using a selective etching solution after being transferred to an ultra-thin semiconductor film (InGaAs thin film in the above case) (Reference: H ,Te
mkinet al,^pplied Physics
Letters, vol, 52+ page 147
8 (1988)) is valid.

At this time, the surface that appears during reverse mesa etching is (111
) surface, the angle of the mesa slope is as shown in Figure 2.
It becomes 54.74 degrees. Therefore, if the width of the resist stripe is 500 and the thickness of the InP cap layer 4 is 200 Å, the width of the resulting InGaAs quantum wire will be about 200 Å. The width of the produced quantum wire can be controlled by the plane orientation of the appearing reverse mesa plane and the film thickness of the InP camp layer 4, and is not limited by the size of the resist pattern formed by electron beam exposure.

Furthermore, as shown in FIG. 3, if the resist stripe pattern has a certain fluctuation, etching progresses quickly for fluctuations in a direction other than (111) chamfering, so as the etching progresses, the lithography fluctuation is reduced. When ideal anisotropic etching is performed, even if the resist pattern formed by the initial lithography has fluctuations in the <O1b direction, the surface that appears by reverse mesa etching will be strictly (111).
Since only the surface is covered, the gaps in the resist pattern disappear.

In the above embodiment, <011 on the (100) substrate
Although the case where (111) facets appear using stripes in the > direction has been described, the present invention is generally applicable to cases where inverted mesas appear in etching. For example, when using a (111) substrate, the above explanation also applies when a high-order facet surface such as a (411) plane appears.

Furthermore, in the above embodiments, InGaAs/In
As mentioned in P-based materials, GaAs /^1GaA
This is also possible with materials such as s-based and InGaAs/1nAIAs-based materials.

(Effects of the Invention) According to the method for manufacturing quantum wires of the present invention, thin quantum wires that are not limited to lithography techniques such as electron beam exposure can be manufactured without being damaged by processing, and at the same time, stripes can be formed by lithography. Fluctuations can be eliminated by the characteristics of reverse mesa etching. Therefore, by the method of the present invention, it is possible to produce a quantum wire of extremely small size and with little size fluctuation, which can be expected to have a large quantum effect.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (C) are diagrams showing the steps for manufacturing a quantum wire in an embodiment of the present invention. FIG. 2 is a diagram for explaining the size of the quantum wire to be manufactured. The figure is a schematic diagram illustrating a mechanism in which fluctuations in a lithography pattern disappear by the method of the present invention. l...InP substrate 2...InPn substrate 9
Fufu 5...Resist

Claims (1)

[Claims] 1. In a method of fabricating quantum wires by subjecting a semiconductor single quantum well structure or multiple quantum well structure to fine processing using an electron beam or optical lithography, the processing of the quantum well structure is performed using an etching solution that has crystal plane orientation dependence. A method for producing a quantum thin wire that is smaller in size than a lithographic pattern and has smaller size fluctuation than a lithographic pattern by forming a lithographic pattern in a direction in which an inverted mesa structure appears.