JPH10172912A - Quantum structure forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a fine quantum structure with good productivity on a board, by emitting a reactive gas locally onto a mask provided on the board and forming a fine opening in the mask, and then feeding a material gas to this fine opening. SOLUTION: A semiconductor substrate 8 of GaAs, etc., provided with a mask 10 of SiO2 etc., is put on a susceptor 3. AsBr3 is led into a heating molecular beam cell 1 as a reactive gas, and a nozzle is heated to a hot temperature, and AsBr3 is heated and decomposed into a gas such as As2 , Br2 , Br radical, etc. A reactive gas decomposed in this way is emitted onto a mask 10 through openings 2a, 4a, and a mask 10 is etched and an opening is formed in the mask 10. Following this, TMG of group III material and AsH3 of group V material are led into the heating molecular beam cell 1 in turn, heated and decomposed and emitted on a board. A Ga layer and an As layer is crystal-grown on a mask opening, and a GaAs layer is laminated selectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a fine quantum structure such as a quantum wire or a quantum box.

[0002]

2. Description of the Related Art Attention has been focused on the development of devices utilizing nano-level fine quantum structures such as quantum wires and quantum well boxes. . Conventionally, as a method for forming a fine quantum structure, for example, a mask having a fine opening of SiO ₂ is formed on a Group 3-5 compound semiconductor substrate, and only a mask having the fine opening is formed by an alternate supply atomic growth method. Selectively 3-
A group V compound semiconductor is grown to form a quantum structure. Here, the atom alternate supply epitaxial growth method is a growth method based on the MBE method. For example, materials of group 3 and group 5 are alternately supplied to the substrate in a pulsed manner by a shutter operation.
A group compound semiconductor is grown. This growth method is characterized in that a crystal with high integrity can be obtained even when the growth temperature is relatively low. For example, GaAs
In the case of using trimethylgallium, arsine, etc. as raw materials, these gases are alternately supplied in a pulsed manner,
By setting the substrate temperature to a relatively low temperature of 450 to 550 ° C.,
And As atoms can be alternately stacked on the substrate one by one.

[0003]

However, the above-described method for forming a fine quantum structure has the following problems. 1) Although a fine opening pattern is formed on a mask by chemical etching or the like, there is a limit to miniaturization of the pattern by etching. 2) Since the process of forming the mask pattern and the process of growing the crystal are performed by separate apparatuses, there is a limit in improving the productivity.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a reactive gas is locally applied to a mask provided on a substrate to form a fine opening in the mask. Then, a raw material gas is supplied to the fine opening to form a fine quantum structure on the substrate.

The present invention has been obtained as a result of intensive studies. That is, when the reactive gas is irradiated on the mask on the substrate, the mask can be etched, so that the reactive gas is squeezed by passing through a sufficiently fine opening or the like,
By irradiating the mask locally, a fine opening having a desired size can be formed in the mask. As the reactive gas, for example, a mask made of SiO ₂ , GaN, or the like may be used, for example, AsBr ₃ , PBr ₃ , AsCl ₃ , PC
a gas such as l ₃ were pyrolyzed at a high temperature, it is possible to use a highly corrosive gas. Further, when a raw material gas is supplied to the fine opening of the mask formed as described above, a fine quantum structure can be vapor-phase grown on the substrate. As the vapor phase growth method, the above-described alternate supply epitaxial growth method or MBE method can be used. Further, when a reaction gas supply source and a source gas supply source are provided in the same ultra-high vacuum apparatus, a step of forming a fine opening in a mask and a step of forming a quantum structure in the fine opening are continuously performed in the same apparatus. Productivity can be improved.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a partial explanatory view of an apparatus used in one embodiment of a method for forming a quantum structure according to the present invention. In this apparatus, a susceptor 3 on which a heated molecular beam cell 1, a skimmer 2, and a substrate 8 are placed is provided in an ultra-high vacuum apparatus. In this apparatus, a reactive gas for forming a fine structure and a source gas for forming a quantum structure are supplied using the same heated molecular beam cell 1. The heated molecular beam cell 1 is composed of a thin nozzle 4 made of quartz glass having an opening 4a having a diameter of 500 mm at the tip and a heat shield tube 5 covering the outer periphery thereof. A porous rod-shaped ceramic body 6 for improving heat transfer to the supplied gas is inserted into the nozzle 4, and tungsten outside the nozzle 4 for heating the nozzle 4 is inserted outside the nozzle 4. The heater 7 is wound. Also, the skimmer (a jig with a very fine hole) 2 has an opening 2a having a diameter of 500 mm, and is located between the nozzle 4 and the substrate 8 at a distance of 100 mm or less from the substrate 8.
In addition, in order to prevent contamination of the substrate surface, it is installed so as not to contact the substrate 8. The alignment between the opening 2a of the skimmer 2 and the opening 4a of the nozzle 4 is performed by irradiating the inside of the nozzle 4 with a laser beam in the supply gas introducing direction (to the left in FIG. 1). This is performed so that the intensity of the passing light is maximized. Further, the susceptor 3 is mounted on the substrate 8
Has a built-in heater 9 for heating.

Using this device, a quantum structure is produced, for example, by the following procedure. That is, as shown in FIG. 2, 1) A semiconductor substrate 8 such as GaAs with a mask 10 made of SiO ₂ or GaN is placed on the susceptor 3 (FIG. 2A). 2) AsBr ₃ is introduced as a reactive gas into the heated molecular beam cell 1 and the nozzle 4 is heated to a temperature of 800 ° C. or higher,
AsBr ₃ is thermally decomposed into gases such as As ₂ , Br ₂ , and Br radicals. The mask 10 is irradiated with the reactive gas decomposed in this manner through the openings 2a and 4a, and the mask 10 is etched.
0a is formed (FIG. 2B). The substrate temperature during this etching is 200 to 400 ° C. When the mask 10 is completely etched, the reactive gas is stopped. 3) Next, a GaAs crystal is grown by the alternately supplying epitaxial growth method under the following conditions. That is, the nozzle temperature is set to 900 ° C., and trimethyl gallium (TMG) as a Group ₃ raw material and AsH ₃ as a Group 5 raw material are alternately introduced into the heated molecular beam cell 1 and thermally decomposed to irradiate a substrate at 450 to 550 ° C. Then, a Ga layer and an As layer are crystal-grown one by one in the opening 10a of the mask in the atomic order, and GaAs is selectively formed.
Stack the layers. Next, trimethylaluminum (TMA) is introduced instead of TMG, an Al layer and an As layer are crystal-grown one by one in the atomic order, and an AlAs layer is selectively laminated. By repeating such material supply, a fine quantum structure 11 in which GaAs layers and AlAs layers are alternately stacked is grown on the substrate 8 (FIG. 2C).

The above embodiments embody the present invention.
It is an example that limits the technical scope of the present invention.
Not. For example, only reactive gas has fine openings.
To supply microscopic openings to the mask
It may be formed and the quantum structure may be grown by MBE. Ma
As a reactive gas, an As-based quantum structure was grown.
AsBr _ThreeInstead of AsCl_ThreeUsing
When growing a P-based quantum structure, PBr
_Three, PCl_ThreeCan be used. In addition, raw material gas
Therefore, dimethyl aluminum halide is used for Al
You may. Also, a source gas of an InP / GaP quantum structure
Use trimethyl indium (TMI) and TMG
Can be. In addition, group 3 source gas and reactive gas
By changing the combination of AlGaAs, InGaAs
A quantum structure such as GaP or GaAsP can be formed.
Wear.

[0009]

According to the present invention, there is an excellent effect that a fine quantum structure can be formed with high productivity.

[Brief description of the drawings]

FIG. 1 is a partial explanatory view of an apparatus used in an embodiment of a method for forming a quantum structure according to the present invention.

FIGS. 2A to 2C are explanatory diagrams of a method for forming a quantum structure using the above-described device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heated molecular beam cell 2 Skimmer 2a, 4a, 10a Opening 3 Susceptor 4 Nozzle 5 Heat shielding tube 6 Ceramics body 7, 9 Heater 8 Substrate 10 Mask 11 Quantum structure

Claims (1)

[Claims] 1. A mask provided on a substrate is locally irradiated with a reactive gas to form a fine opening in the mask, and then a raw material gas is supplied to the fine opening to form a fine gas on the substrate. A method for forming a quantum structure, comprising forming a simple quantum structure.