KR100334085B1 - Two Chambered Chemical Vapor Deposition Apparatus for Producing Quantum Dots - Google Patents

Abstract

The present invention relates to a dual chamber chemical vapor deposition apparatus for forming a quantum dot, comprising: a reaction chamber having an inlet through which a precursor is introduced, and a reactant through which the precursor introduced through the inlet reacts to generate charged clusters; And an adjustable orifice for passing charged clusters falling to the lower end of the reaction chamber, a shutter unit mounted at the lower end of the orifice to block or pass charged clusters passing through the orifice, passing through the shutter unit. It is characterized in that it comprises a deposition chamber having a stand on which the substrate on which one charged cluster is deposited is placed. The dual chamber chemical vapor deposition apparatus for forming a quantum dot according to the present invention can not only form a quantum dot having a uniform size distribution in a single process using a double chamber without undergoing a multi-step process, There is an advantage to control the density.

Description

Two Chambered Chemical Vapor Deposition Apparatus for Producing Quantum Dots}

The current semiconductor industry is growing rapidly in line with high integration and miniaturization technology based on silicon (Si), and its area is expanding not only in the electronic industry but also almost all industries. In addition, research on optical communication devices through active compound semiconductors, which will be the core of the information and communication industry, is being actively conducted.

A quantum dot is a particle whose size is smaller than the length of the quantum mechanical wavelength of the electron in all directions. Such zero-dimensional quantum structures are known to fall in size in the range of approximately 2-50 nm. Because quantum dots have specific energy levels, they are likely to be applied to many electronic and optical devices. In particular, research on the application to single-electron transistors has been very intensive.

A quantum dot is a semiconductor composed of many atoms surrounded by a material with a larger bandgap energy. The quantum structure is characterized by three-dimensional quantum confinement, indicating that the density of the energy levels is delta-functional, resulting in electrical and optical properties. It is an excellent structure. The use of a quantum dot structure has the advantage of enabling the implementation of ultra-high speed devices at room temperature due to the large optical gain and excellent stability at high temperatures.

The quantum well structure growth technology has already developed a lot of advances to control the interfacial structure at the monolayer level, but commercialized devices are being manufactured, but next-generation optical communication devices and single-electron devices require more low power and ultra high speed characteristics. The quantum dot structure growth technology necessary to realize the quantum dot structure growth technology is still inadequate despite significant advantages, and the quantum dot structure growth technology is an essential core technology for the fabrication of next generation information communication devices. In dressmaking growth technology, controlling the size of quantum dots, controlling the uniform distribution of sizes, and controlling the number of quantum dots per unit area are key factors.

The present invention relates to a quantum dot forming apparatus based on a charged cluster model of chemical vapor deposition (CVD). In the charged cluster model, after the clusters charged with vapor nucleation are formed, deposition takes place on the substrate surface. Such nucleated charged clusters are known as growth units.

In this charged cluster model, since the charge is present, the nucleated clusters are not aggregated due to the coulomb repulsion, so there are small clusters having a narrow size distribution. This cluster can be the respective quantum dot.

Conventional techniques related to chemical vapor deposition have problems in quantum dot formation because it is difficult to control the size distribution and particle density in the process because a single process chamber is used to increase the efficiency of thin film formation. In addition, since the prior art of forming quantum dots tends to go through several processes, there is a need for a simple process methodology that satisfies most of the conditions for forming quantum dots.

The present invention is to solve the problems of the prior art as described above, and to provide a device that can form a quantum dot uniform size distribution in one process using a double chamber without going through a multi-step process.

The present invention also provides a quantum dot forming apparatus that can adjust the size and density of the quantum dots.

1 is a block diagram of a double chamber chemical vapor deposition apparatus for forming a quantum dot according to the present invention,

2 is a transmission electron micrograph of a silicon quantum dot formed according to a first embodiment of the present invention;

3 is a transmission electron micrograph of a gold quantum dot formed by a second embodiment of the present invention,

4 is a transmission electron micrograph of a gold quantum dot formed by a third embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1: reaction chamber 2: deposition chamber

11 inlet 12: reaction unit

21: Orifice 22: Shutter part

23: stand 24: bias voltage

25: substrate heating part

In order to achieve the object as described above, the dual chamber chemical vapor deposition apparatus for forming a quantum dot according to the present invention, the reaction in which the precursor introduced through the precursor, the precursor introduced through the inlet reacts to generate a charged cluster A reaction chamber having a portion; A scalable orifice for passing charged clusters falling to the bottom of the reaction chamber, a shutter mounted to the bottom of the orifice to block or pass charged clusters passing through the orifice, passing through the shutter And a deposition chamber having a stand on which the substrate on which the charged clusters are deposited is placed.

Hereinafter, a dual chamber chemical vapor deposition apparatus for forming a quantum dot according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a dual chamber chemical vapor deposition machine for forming quantum dots according to the present invention.

As shown in FIG. 1, the dual chamber chemical vapor deposition machine according to the present invention is largely composed of a reaction chamber 1 and a deposition chamber 2. The reaction chamber 1 and the deposition chamber 2 are each connected to a vacuum pump and operate at a pressure of 760 torr at 10 ⁻⁴ torr.

In the reaction chamber 1, where the introduced precursor reacts to generate charged clusters, the reaction chamber 1 includes an inlet 11 through which the precursor flows, and a reaction part 12 through which the introduced precursor reacts.

Precursors introduced through inlet 11 may be controlled in concentration and, if desired, may be introduced into the chamber in solid phase as in standard chemical vapor deposition processes. The size of the generated clusters can be adjusted according to the concentration of the incoming precursor. The greater the concentration of precursor, the larger the resulting cluster size.

The reaction unit 12 uses a high temperature filament or a high temperature plasma system such as microwave CVD. Specifically, processes such as hot filament CVD, plasma CVD, thermal CVD, metal-organic CVD and thermal evaporation are used. The high temperature filament applicable to the reaction part 12 is a metal such as tungsten (W), molybdenum (Mo), or tantalum (Ta) having a high melting point. The charge density may be adjusted according to the temperature of the filament or the plasma of the reaction unit 12, and the size of the generated clusters may be controlled. The higher the charge density, the smaller the size of the resulting clusters.

The deposition chamber 2 includes an adjustable orifice 21 for passing a cluster falling to a lower end of the reaction chamber, and a shutter unit mounted at a lower end of the orifice to block or pass a cluster passing through the orifice 21 ( 22) and a stand 23 on which a substrate on which charged clusters passing through the shutter unit 22 are deposited is raised.

The size of the orifice 21 can be adjusted and the shutter device 22 can be used to accurately control the time that the substrate placed on the stand 23 is exposed to the cluster falling from the reaction chamber. This is directly related to the density of the quantum dots formed on the substrate, and is deposited on the substrate using the shutter device 22 and the size control of the orifice 21 in the deposition chamber 2 of the dual chamber chemical vapor deposition apparatus according to the present invention. Quantum dot density by clusters can be accurately controlled.

In addition, by applying a bias voltage 24 to the deposition chamber, the moving speed of the charged cluster can be controlled, and the height of the stand 23 on which the substrate is placed is adjusted to adjust the distance of the substrate from the orifice 21 to the reaction chamber. The quantum dot density can be controlled by controlling the degree of dispersion (spreading) in which the cluster generated in (1) is deposited on the substrate.

The substrate lying on the stand 23 may be an electrically conductive, semiconductive or insulating surface. The conductive substrate is a metal, for example Pd, Pt, Rh, Ir, Ni, Fe, Mo, Fe, Mo, Cu, Ti, graphite or conductive polymer. Semiconducting substrates are materials whose electrical conductivity increases with increasing temperature, and examples thereof include Si, Ge, and barium titanate (BaTiO ₃ ), which is a semiconducting ceramic. A nonconductive substrate is an insulator with low electrical conductivity, such as silicon oxide (SiO ₂ ).

Such a substrate is heated to the required temperature by the substrate heating unit 25. The heating temperature is adjusted by changing the voltage of the substrate heating section 25.

Using the dual chamber chemical vapor deposition apparatus according to the present invention, the size of the quantum dots formed on the substrate can be adjusted to 1 nm to 25 nm according to the conditions of the process. The size of the quantum dot is determined according to the charge density, reaction pressure, temperature, and precursor concentration in the reaction chamber 1, and the density of the quantum dot is determined by the size of the orifice 21 and the shutter portion 22 of the deposition chamber 2. It is determined by the substrate exposure time that is controlled.

The following examples illustrate specific examples of quantum dot generation using a dual chamber chemical vapor deposition machine according to the present invention.

<First Embodiment>

Silicon quantum dots

As a reaction part of the reaction chamber, tungsten filament doped with 2% thoria is used. The precursor concentration is set to SiH ₄ : HCl: H ₂ = 1: 1: 98, the pressure in the reaction chamber is adjusted to 100 Torr, and the pressure in the deposition chamber is adjusted to 0.001 Torr.

The orifice is 3 cm in size, and through the orifice, nucleated silicon particles in the upper reaction chamber move to the lower deposition chamber. The exposure time by the shutter unit is 30 seconds. In this case, since a large diameter orifice of 3 cm is used, the conditions are substantially the same as that of depositing a single chamber using only one.

In the deposition chamber, a substrate is placed on a stand, or a viewing grid of a transmission electron microscope is placed for observation. The distance between the orifice and the grid is 10 mm, the substrate heating temperature is 630 ° C and the filament temperature is 1800 ° C.

2 is a transmission electron micrograph of the silicon quantum dots thus formed. As shown in Fig. 2, the particle size of the silicon quantum dot has a range of 8 nm to 10 nm, and the density is 350 / mm 2.

Second Embodiment

Gold quantum dots (3 cm orifice)

In order to make gold quantum dots, 4 cm of gold wire is placed on the tungsten filament in the reaction chamber. The initial pressure is 0.050 Torr for the reaction chamber, 0.001 Torr for the deposition chamber, and the temperature is maintained at 1250 ± 3 ° C. During the deposition, the gold evaporated, increasing the pressure in the reaction chamber to 0.1 Torr. The size of the orifice is 3 cm, the opening time of the shutter portion is 10 seconds, and the distance from the orifice to the substrate is 2.5 cm.

3 is a transmission electron micrograph of the gold quantum dots thus formed. As shown in Fig. 3, the size of the quantum dot is 2.5 ± 0.3 nm, and the number density is about 10 ¹¹ / mm 2.

Third Embodiment

Gold quantum dots (1 mm orifice)

In order to make gold quantum dots, 4 cm of gold wire is placed on the tungsten filament in the reaction chamber. The initial pressure is 0.050 Torr for the reaction chamber, 0.001 Torr for the deposition chamber, and the temperature is maintained at 1250 ± 3 ° C. During the deposition, the gold evaporated, increasing the pressure in the reaction chamber to 0.1 Torr. The size of the orifice is 1 mm, the opening time of the shutter section is 30 seconds, and the distance from the orifice to the substrate is 2.5 cm.

4 is a transmission electron micrograph of the gold quantum dots thus formed. As shown in Figure 3, the size of the quantum dot is 2.5 ± 0.3 nm, the number density is about 10 / mm2.

As can be seen from the second and third embodiments described above, it can be seen that the number density of the quantum dots is controlled by adjusting the size of the orifice and the substrate exposure time by the shutter unit. Specifically, since the reaction pressure, temperature, and the like of the reaction chamber are the same in the second embodiment and the third embodiment, the size of the quantum dot is 2.5 ± 0.3 nm. However, with respect to the density of the quantum dots, when the size of the orifice was 3 cm in the second embodiment and the substrate exposure time was 10 seconds, the density of the quantum dots was about 10 ¹¹ / mm 2, and the size of the orifice in the third embodiment Was 1 mm and the substrate exposure time was 30 seconds. The density of the quantum dots was about 10 / mm 2.

As described above, the dual chamber chemical vapor deposition apparatus for forming a quantum dot according to the present invention may not only form a quantum dot having a uniform size distribution in one process using a dual chamber without undergoing a multi-step process, There is an advantage of controlling the size of the quantum dot and the density of the quantum dot.

Claims (11)

A reaction chamber having an inlet through which the precursor is introduced, and a reaction unit through which the precursor introduced through the inlet reacts to generate a charged cluster; And A scalable orifice for passing charged clusters falling to the bottom of the reaction chamber, a shutter mounted to the bottom of the orifice to block or pass charged clusters passing through the orifice, passing through the shutter And a deposition chamber having a stand on which the substrate on which the charged clusters are to be deposited comprises a deposition chamber. The method of claim 1, The reaction unit is formed of a quantum dot characterized in that the process of hot filament CVD, plasma CVD, thermal CVD, metal-organic CVD or thermal evaporation is applied. Dual chamber chemical vapor deposition machine. The method of claim 2, Wherein said high temperature filament is tungsten (W), molybdenum (Mo) or tantalum (Ta). The method of claim 1, Wherein the reaction chamber and the deposition chamber are connected to a vacuum pump to operate at a pressure of 760 torr at 10 ⁻⁴ torr. The method of claim 1, And a bias voltage applying means in the deposition chamber to control the rate of movement of the charged clusters. The method of claim 1, Wherein the stand is height-adjusted to adjust the distance of the substrate on the stand from an orifice. The method of claim 1, Wherein said substrate is a conductive substrate, a semiconductive substrate, or a non-conductive substrate. The method of claim 7, wherein Wherein the conductive substrate is one of Pd, Pt, Rh, Ir, Ni, Fe, Mo, Fe, Mo, Cu, Ti, graphite, or a conductive polymer. The method of claim 7, wherein Wherein the semiconductive substrate is Si, Ge or barium titanate (BaTiO ₃ ). The method of claim 7, wherein The non-conductive substrate is silicon oxide (SiO ₂ ), characterized in that the dual chamber chemical vapor deposition for quantum dot formation. The method of claim 1, And a substrate heating unit for heating the substrate placed on the stand.