CN101315882A - A method for positioning and growing quantum dots using silicon dioxide as a mask - Google Patents

Abstract

A method for positioning and growing quantum dots with silicon dioxide as a mask, characterized in that the method comprises the following preparation steps: Step 1: select a substrate, and vapor-deposit a silicon dioxide layer on the substrate; Step 2: Coat a layer of photoresist on top of the silicon dioxide layer, and engrave the required pattern structure on the photoresist by electron beam exposure; Step 3: Carry out dry etching on the sample, and transfer the required pattern structure to the silicon dioxide The surface of the layer; step 4: remove the photoresist and clean the sample; step 5: put the processed sample into the growth chamber to grow GaAs material; step 6: corrode the grown sample with hydrofluoric acid solution, Remove the remaining silicon dioxide layer.

Description

A method for positioning and growing quantum dots using silicon dioxide as a mask

technical field

The invention relates to the technical field of semiconductors, and is a growth technology for quantum dot materials, in particular to a method for positioning and growing quantum dots using silicon dioxide as a mask.

Background technique

In the field of semiconductor materials, quantum dots have many unique optical and electrical properties, such as sharper light absorption, light gain and light reflection spectrum, increased binding energy of excitons and impurities, quantum interference effect, quantum tunneling effect and Coulomb Blocking effect (Columbblaskade) and so on. These properties make quantum dots have great application potential in the field of optoelectronics and microelectronics, such as the development of quantum dot lasers with lower threshold, higher efficiency and better thermal stability, and higher speed microelectronic devices (HEMT, FET) and single-electron memory devices. In the preparation of quantum dot materials, the usual method is to grow quantum dots by self-assembly. The strained self-assembly method can produce high-density, defect-free quantum dots, but there are also disadvantages such as insufficient size uniformity and random distribution. Some devices have special requirements for the distribution of quantum dots, such as quantum cellular automata, single-electron transistors, and single-electron memories, which require quantum dots to grow at specific locations, and these devices are important devices for the development of nanoelectronics. Therefore, how to realize the positioning and controllable growth of quantum dots is becoming a hot spot in the research of quantum dot materials. In recent years, there have been many studies on the method of positioning and growing quantum dots, such as using the dislocation grid of the buried layer to affect the nucleation position of quantum dots, so that the quantum dots can be distributed along the dislocations to achieve the purpose of controlling the growth of quantum dots; growing multi-layer quantum dots Dots make quantum dots distributed in an orderly manner after multi-layer stacking growth; growth on the adjacent crystal surface uses atomic steps on the adjacent crystal surface to control the growth of quantum dots, etc. However, the effect of these methods for positioning and growing quantum dots is not good, but the positioning and growth of quantum dots on the substrate is still a complicated process, and it is necessary to provide an effective method to realize the selective positioning of quantum dots.

Contents of the invention

The object of the present invention is to provide a method for positioning and growing quantum dots using silicon dioxide as a mask, which adopts patterned silicon dioxide mask technology on a GaAs substrate to precisely control the growth position of quantum dots.

The invention provides a method for positioning and growing quantum dots using silicon dioxide as a mask, characterized in that the method comprises the following preparation steps:

Step 1: select a substrate, and vapor-deposit a silicon dioxide layer on the substrate;

Step 2: Coating a layer of photoresist on the silicon dioxide layer, and engraving the required pattern structure on the photoresist by electron beam exposure;

Step 3: Perform dry etching on the sample, and transfer the desired pattern structure to the surface of the silicon dioxide layer;

Step 4: removing photoresist and cleaning the sample;

Step 5: Put the processed sample into the growth chamber to grow GaAs material;

Step 6: Etching the grown sample with a hydrofluoric acid solution to remove the remaining silicon dioxide layer.

The material of the substrate is GaAs.

Wherein the thickness of the silicon dioxide layer vapor-deposited on the substrate in step 1 is 50nm.

Wherein the diameter of the pattern engraved by the electron beam exposure described in the second step is less than 100nm.

The degumming and cleaning treatment of the sample described in step 4 means that after the photoresist on the surface of the sample is removed by the degumming solution, the organic matter and impurities are removed in the boiling organic solvent in the following order, and this process is cycled for 2 times, including: petroleum ether for 2-3 minutes, absolute ethanol for 2-3 minutes, acetone for 2-3 minutes, trichloroethylene for 8 minutes-2 times, acetone for 2-3 minutes, absolute ethanol for 2-3 minutes, and then Rinse with high-purity deionized water several times.

Among them, the step five is to put the sample into the growth chamber to grow the GaAs material, which is grown at high temperature by solid-state molecular beam epitaxy, the growth temperature is 620°C, the growth rate is 0.09 μm/h, and the As pressure is maintained at 4×10 -6Pa, the growth thickness is 30nm.

Description of drawings

In order to further illustrate the features and effects of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments, wherein:

Fig. 1 is a structural schematic diagram of engraving patterns on the photoresist;

Fig. 2 is a schematic diagram of the structure of the substrate and the silicon dioxide mask before growing the GaAs material.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings.

Please refer to Fig. 1 and Fig. 2, the method for positioning and growing quantum dots of the present invention using silicon dioxide as a mask includes:

(1) Firstly, a silicon dioxide layer 20 of about 50 nm is vapor-deposited on the semi-insulating planar GaAs substrate 10 by plasma-enhanced chemical vapor deposition (PECVD). The purpose of vapor-depositing the silicon dioxide layer 20 is to provide a mask for positioning and growing quantum dots, and the purpose of vapor-depositing the silicon dioxide layer 20 by PECVD technology is to obtain a flat mask.

(2) Coat the photoresist layer 30 on the GaAs substrate 10 deposited with the silicon dioxide layer 20 , and engrave circular holes with a diameter of about 90 nm and a center-to-center distance of about 200 nm by electron beam exposure technology. The purpose is to provide a window for positioning grown quantum dots, as shown in Figure 1.

(3) Dry etching and degumming and cleaning treatment are adopted, wherein the silicon dioxide layer 20 in the graphic window is etched away by dry etching, and the graphic structure is transferred to the surface of the silicon dioxide layer 20 . The gas used for dry etching is a mixed gas of silicon tetrachloride and argon, and then the photoresist 30 is removed, so that the GaAs in the pattern window is exposed to the growth surface, as shown in Figure 2; wherein the sample is cleaned , means that after removing the photoresist 30 on the surface of the sample by using the glue remover, the organic matter and impurities are removed in a boiled organic solvent in the following order, and this process is cycled twice, including: petroleum ether for 2-3 minutes, no Water ethanol for 2-3 minutes, acetone for 2-3 minutes, trichlorethylene for 8 minutes-twice, acetone for 2-3 minutes, absolute ethanol for 2-3 minutes, and then rinse with high-purity deionized water several times.

(4) After the substrate 10 with the silicon dioxide layer 20 is cleaned, it is sent to the growth chamber of the molecular beam epitaxy equipment for growth. The growth temperature was 620° C., the growth rate was 0.09 μm/h, and 30 nm of GaAs was grown. Since GaAs is grown at a high temperature of 620°C, the adsorption of GaAs on the silicon dioxide layer 20 is very small, and the adsorption on the GaAs exposed to the growth surface through the opened window is very large, and the migration of Ga atoms on the surface , GaAs will be mainly deposited in the graphics window to realize the positioning growth of GaAs quantum dots.

(5) Take out the sample after growth, and use hydrofluoric acid solution to etch, because hydrofluoric acid solution has good selectivity for silicon dioxide layer 20 and GaAs, promptly can with very fast speed silicon dioxide layer 20 etch away, but not corrode the GaAs substrate 10 and the grown quantum dots. Therefore, after the silicon dioxide layer 20 is completely corroded by the hydrofluoric acid solution, only the GaAs quantum dots positioned and grown in the graphics window are left. Positional growth of quantum dots is realized in the pattern window of the engraved silicon dioxide layer 20 .

Claims (6)

1. a method for mask positioning growth quantum dots with silicon dioxide, is characterized in that, the method comprises the following preparation steps: Step 1: select a substrate, and vapor-deposit a silicon dioxide layer on the substrate; Step 2: Coating a layer of photoresist on the silicon dioxide layer, and engraving the required pattern structure on the photoresist by electron beam exposure; Step 3: Perform dry etching on the sample, and transfer the desired pattern structure to the surface of the silicon dioxide layer; Step 4: removing photoresist and cleaning the sample; Step 5: Put the processed sample into the growth chamber to grow GaAs material; Step 6: Etching the grown sample with a hydrofluoric acid solution to remove the remaining silicon dioxide layer. 2. The method for positioning and growing quantum dots using silicon dioxide as a mask according to claim 1, wherein the material of the substrate is GaAs. 3. The method for positioning and growing quantum dots using silicon dioxide as a mask according to claim 1, wherein the thickness of the silicon dioxide layer vapor-deposited on the substrate in step 1 is 50 nm. 4. The method for positioning and growing quantum dots using silicon dioxide as a mask according to claim 1, wherein the diameter of the pattern engraved by the electron beam exposure described in step 2 is less than 100 nm. 5. the method for positioning and growing quantum dots with silicon dioxide as a mask according to claim 1 is characterized in that, wherein the sample described in step 4 is carried out to degumming and cleaning treatment, refers to the use of degumming solution to remove the sample After the photoresist on the surface, remove the organic matter and impurities in the boiling organic solvent in the following order, and cycle this process twice, including: petroleum ether for 2-3 minutes, absolute ethanol for 2-3 minutes, acetone for 2- 3 minutes, trichlorethylene for 8 minutes-2 times, acetone for 2-3 minutes, absolute ethanol for 2-3 minutes, and then rinse with high-purity deionized water several times. 6. the method for positioning and growing quantum dots with silicon dioxide as a mask according to claim 1, characterized in that, wherein said sample in step 5 is put into a growth chamber to grow GaAs material, it adopts solid-state molecular beam epitaxy The growth is carried out at high temperature, the growth temperature is 620°C, the growth rate is 0.09μm/h, the As pressure is kept at 4×10-6Pa, and the growth thickness is 30nm.

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