KR102712378B1 - Single crystal growth method of Si group materials - Google Patents

Abstract

The present invention relates to a method for growing a single crystal silicon-based material by recrystallizing a silicon-based material on magnesium oxide using a magnesium oxide substrate and a line beam. The method for growing a single crystal of a silicon-based material can recrystallize a single crystal silicon-based material at a low temperature by irradiating a laser in the form of a line beam, and can also form a single crystal of a material different from the substrate through epitaxial growth.

Description

Single crystal growth method of Si group materials

The present invention relates to a method for growing a single crystal silicon-based material by recrystallizing an amorphous silicon-based material on magnesium oxide using a magnesium oxide substrate and a line beam.

The performance of devices used in semiconductor devices, displays, solar cells, sensors, etc. is determined by the semiconductor active layer. The semiconductor active layer of the existing silicon-based Complement Metal-Oxide-Semiconductor Field-Effect-Transistor (CMOS) device is formed by melting polycrystalline silicon at high temperature (>1400 ℃) to make it liquid, then contacting a single-crystal silicon seed and cutting the ingot grown in the direction of the seed and using it as a substrate, or the Homogeneous Epitaxy thin film growth method in which it grows in the same direction as the substrate. The single-crystal silicon formed in this way is very uniform and has excellent characteristics. In addition, when forming devices on substrates other than silicon, such as displays, through a low-temperature process, a method of inducing recrystallization of amorphous silicon using metal ions, a Low Temperature Poly Silicon (LTPS) method that recrystallizes polycrystalline silicon using excimer laser annealing, or oxide semiconductors such as InGaZnO (IGZO) and SnO are used as the active layer.

However, since the Czochralski method must be performed at a high temperature of 600℃ or higher, it is not suitable for forming low-temperature active layers in 3D integrated semiconductor devices, flat panel displays, solar cells, etc., which are sensitive to lower layer degradation, and the Homogeneous Epitaxy thin film growth method has a limitation that epitaxy growth is only possible on the same material as the substrate.

Wafer bonding technology has problems such as reduced yield due to surface roughness of the lower layer and reduced adhesion of the upper active layer due to subsequent processes. In addition, Metal-induced Crystallization technology that recrystallizes amorphous silicon has limitations in grain size growth and reduced device performance due to contamination by metal ions, and polycrystalline silicon recrystallization technology using Gaussian energy profile laser has poor performance of polycrystalline silicon formed by melting & re-growth compared to single crystal, and does not implement uniform performance among devices.

Therefore, a technology is needed to form single-crystal silicon-based materials at low temperatures with minimal contamination from impurities and no degradation of the lower layers, which can meet compatibility with existing CMOS processes.

Republic of Korea Publication Patent No. 10-2013-0044124 (Published on May 2, 2013)

The purpose of the present invention is to provide a method for controlling the crystal orientation of a silicon-based material and growing it into a single crystal using a magnesium oxide substrate to make a semiconductor active layer of a device used in a semiconductor device, display, solar cell, sensor, etc. into a single crystal.

In order to achieve the above-mentioned object, the present invention includes a first step of forming an amorphous silicon-based material layer formed on a magnesium oxide substrate; a second step of forming a capping layer on the silicon-based material layer; and a third step of irradiating a line beam laser onto the capping layer to recrystallize the silicon-based material; wherein the magnesium oxide substrate includes single crystal magnesium oxide, and the line beam type laser is irradiated under a scanning condition at a power higher than a critical power for crystallization and lower than a power at which ablation does not occur, a method for growing a single crystal of a silicon-based material is included.

In addition, the present invention provides an active layer including a single crystal silicon-based material manufactured by the single crystal growth method of the silicon-based material described above.

The single crystal growth method of a silicon-based material according to the present invention can recrystallize a single crystal silicon-based material at a low temperature by irradiating a laser in the form of a line beam, and can also form a single crystal of a material different from the substrate through epitaxial growth.

Figure 1 is a schematic diagram showing a method for manufacturing a single crystal silicon-based material according to the present invention.
FIG. 2 is an X-ray diffraction analysis (XRD) pattern graph (a) of a magnesium oxide substrate used in a single crystal growth method of a silicon-based material according to an embodiment of the present invention, and reflection high-energy electron diffraction (RHEED) patterns (b,c) of the magnesium oxide substrate before and after annealing.
Figure 3 shows the results of electron backscatter diffraction (EBSD IPF Mapping) analysis of germanium (Ge) on magnesium oxide (001), where (a) is the general direction (ND), (b) is the rolling direction (RD), (c) is the transverse direction (TD), and (d) is the grain boundary (GB).
Figure 4 shows the results of electron backscatter diffraction (EBSD IPF Mapping) analysis of germanium (Ge) on silicon dioxide (SiO ₂ ), where (a) is the general direction (ND), (b) is the rolling direction (RD), (c) is the transverse direction (TD), and (d) is the grain boundary (GB).
Figure 5 is a transmission electron microscope (TEM) image (a) of a cross-section of a germanium (Ge)/magnesium oxide (MgO) interface, and a fast Fourier transformation (FFT) image of magnesium oxide (MgO)[001] (b) and germanium (Ge)[110] (c).
Figure 6 is an image (a) showing the epitaxial relationship between germanium (Ge) and magnesium oxide (MgO) (001) and an image (b) showing a unit cell of germanium (Ge).

Hereinafter, in order to explain the present invention more specifically, preferred embodiments according to the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

The present invention is a technology for growing a single crystal by controlling the crystal direction of a silicon-based material on an MgO Seed to form a single crystal semiconductor active layer of a device used in a semiconductor device, display, solar cell, sensor, etc. More specifically, it is a technology for forming a low-temperature silicon-based (Ge) active layer whose crystal direction can be controlled without inducing thermal deterioration therebelow by depositing a silicon-based (Ge) material on an MgO Seed and then recrystallizing it in the direction of the Seed using a flat-top CW laser to form an active layer of a semiconductor device.

The present invention provides a method for growing a single crystal of a silicon-based material, comprising: a first step of forming an amorphous silicon-based material layer formed on a magnesium oxide substrate; a second step of forming a capping layer on the silicon-based material layer; and a third step of irradiating the capping layer with a line beam laser to recrystallize the silicon-based material.

The above first step is a step of forming a silicon-based material layer by depositing an amorphous silicon-based material on a magnesium oxide substrate.

The above silicon-based material layer may include at least one selected from the group consisting of germanium (Ge), gallium arsenide (GaAs), and indium arsenide (InAs), and specifically may be formed of amorphous germanium.

The above magnesium oxide substrate may include single crystal magnesium oxide.

The first step may form a silicon-based material layer by depositing an amorphous silicon-based material with a thickness of 30 nm or more or 30 nm to 2000 nm on a magnesium oxide substrate. When the thickness of the silicon-based material layer increases, the thickness of the capping layer and the laser power may be increased. The deposition method may be performed by a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, or a spin-on-glass (SOG) method.

The above first step may additionally include annealing the magnesium oxide substrate at a temperature of 300 to 800° C. for 30 minutes to 2 hours before forming the amorphous silicon-based material layer. Through the annealing process as described above, loss of crystallinity due to the high hygroscopicity of magnesium oxide can be prevented.

The second step is a step of forming a capping layer by depositing a capping material on a silicon-based material layer formed on a magnesium oxide substrate.

The above capping material may include silicon dioxide, and specifically may be made of amorphous silicon dioxide.

The second step may form a capping layer by depositing an amorphous capping material on the silicon-based material layer to a thickness of at least four times or four to ten times the thickness of the silicon-based material layer. The deposition method may be performed by a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, or a spin-on-glass (SOG) method.

By forming a capping layer as described above, when irradiating a laser for recrystallization, the heat energy of the irradiated laser is not rapidly released, and the energy is helped to stably reach the interface between the magnesium oxide substrate and the silicon-based material layer.

The third step is a step of forming a single crystal silicon semiconductor by recrystallizing an amorphous silicon-based material by irradiating a laser in the form of a line beam.

The above line beam type laser may be a continuous wave laser.

Specifically, the laser in the form of the line beam is irradiated under scanning conditions at a power higher than the critical power for crystallization and lower than the power at which ablation does not occur, and by irradiating with a critical power near the melting point (600 to 800°C) of the silicon-based material, recrystallization is caused from the interface between the magnesium oxide and silicon-based material layers, thereby preventing recrystallization on the surface of the silicon-based material, and due to high transmittance, loss of the irradiated laser energy may not occur.

For example, the critical power for the crystallization refers to the crystallization critical power density (I), and the crystallization critical power density may vary depending on the thickness and material of the silicon-based material layer and/or the capping layer, but specifically, the crystallization critical power density may be 0.01 to 0.09 W/㎛ ² , 0.01 to 0.05 W/㎛ ² , or 0.02 to 0.04 W/㎛ ² . When the thickness of the silicon-based material layer is 30 to 100 nm and the thickness of the capping layer is formed to be 100 to 500 nm, the crystallization critical power density may be 0.02 to 0.03 W/㎛ ² .

In the third step, when a laser is irradiated, the temperature at the interface between the magnesium oxide substrate and the silicon-based material layer is lower than the temperature at the surface of the silicon-based material layer due to the presence of the capping layer, so that crystallization can begin from the magnesium oxide substrate.

As described above, by irradiating the line beam laser to the melting point of the silicon-based material, the crystal grain growth direction of the melted silicon-based material is aligned in the same direction as that of the magnesium oxide and recrystallized, and the silicon-based material formed during recrystallization can be formed perpendicular to the magnesium oxide.

After the third step, a step of removing the capping layer through a visual process may be additionally performed, and the step of removing the capping layer may include removing a portion of the capping layer and the surface of the recrystallized silicon-based material through an etching process. The etching process is not particularly limited as long as it is a method used in an etching process of a semiconductor device.

In addition, the present invention provides an active layer including a silicon-based material manufactured by the single crystal growth method of the silicon-based material described above.

The above silicon-based material is a single-crystal silicon-based material and may include at least one selected from the group consisting of germanium (Ge), gallium arsenide (GaAs), and indium arsenide (InAs). In addition, the crystal boundary inclination of the silicon-based material may be 15° or less.

Specifically, the silicon-based material may be recrystallized and aligned along the crystal direction of magnesium oxide.

Hereinafter, in order to help understand the present invention, examples will be given and described in detail. However, the following examples are only intended to illustrate the content of the present invention, and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to a person having average knowledge in the art.

Example 1

Magnesium oxide (MgO) (001)-oriented substrates use a polished area where only the (001) pattern of X-ray Diffraction (XRD) is confirmed, and the average roughness (Ra) within the analysis area of 1 μm x 1 μm is less than 0.25 nm, the root-mean-square (RMS) is less than 0.35 nm, and the maximum pit-to-valley range (P-V) is less than 3 nm. To prevent crystallinity loss due to high hygroscopicity of magnesium oxide (MgO), it is annealed in-situ at 500 °C for 1 hour before germanium (Ge) deposition, and then single-crystal MgO (001) is confirmed before germanium (Ge) deposition.

A SiO 2 capping layer is deposited to prevent recrystallization (or ablation) from the Ge surface rather than the MgO/Ge interface during laser recrystallization after germanium (Ge) deposition, to prevent loss of irradiated laser energy due to high transmittance, and to stably reach the MgO/Ge interface without rapidly releasing the irradiated laser heat energy due to low thermal conductivity, acting as a _heat sink.

After forming a layered structure as in the structure of Fig. 1, a CW laser in the form of a line beam was used to irradiate the laser at a critical power near the melting point of amorphous germanium (a-Ge) to cause recrystallization, thereby producing a single crystal germanium.

Experimental Example 1

In order to confirm that the magnesium oxide substrate used in the present invention is a single crystal, X-ray diffraction (XRD) analysis and reflection high-energy electron diffraction (RHEED) analysis were performed, and the results are shown in Fig. 2.

X-ray diffraction analysis is a method in which when X-rays are irradiated on a sample, the X-rays scattered by the atoms in the sample interfere with each other to generate strong diffracted X-rays in a specific direction. The diffraction pattern of the X-rays generated at this time has a unique value that is different for each substance and is used for qualitative and quantitative analysis of the sample. The crystallinity of the MgO substrate was analyzed using grazing-incidence XRD at an angle of 0.5。 of Cu Kα in a range of 10 to 90 degrees, showing that only the peak in the (001) direction exists. (Model name: X’Pert PRO MRD, Manufacturer: Phillips, Country of manufacture: USA)

Reflection high-energy electron diffraction is an analytical method to characterize the top surface of a crystalline material by incident an electron beam on the sample surface at an angle of 1-2°, and projecting the diffracted electron beam from the sample surface onto the opposite fluorescent screen. It can be seen that the Kikuchi lines of RHEED become sharper after in-situ annealing of the MgO substrate to wash away the Mg(OH)2 and carbon contamination generated on the surface due to the high hygroscopicity of MgO.

Looking at Fig. 2 (a), only the (001) pattern of X-ray Diffraction (XRD) was confirmed for the magnesium oxide (MgO) (001)-oriented substrate.

Figures 2 (b) and (c) show reflection high energy electron diffraction (RHEED) patterns, which show the characteristics of magnesium oxide (MgO) after in-situ annealing at 500°C for 1 hour before germanium (Ge) deposition to prevent loss of crystallinity due to high hygroscopicity of MgO, and confirm that it is a single crystal magnesium oxide (MgO) (001).

Experimental example 2

In order to confirm the characteristics of the silicon-based material manufactured by the single crystal growth method of the silicon-based material according to the present invention, electron backscatter diffraction (EBSD) analysis, transmission electron microscopy (TEM), and fast Fourier transformation (FFT) analysis were performed, and the results are shown in FIGS. 3 to 5.

Electron backscatter diffraction analysis is an analytical method that characterizes various crystallographic information of a sample, such as crystal orientation, grain size, and grain boundaries, by collecting backscattered electrons from a depth of 30 to 50 nm from the sample surface with a measuring device located inside a field emission scanning electron microscope (FE-SEM). At this time, the stage where the sample is placed is tilted at 70。 for analysis to increase the yield of backscattered electrons. The recrystallized Ge was analyzed with an EBSD camera (Model: Hikari, Manufacturer: EDAX, Country of Manufacture: USA) of an FE-SEM (Model: SU-70, Manufacturer: Hitachi, Country of Manufacture: Japan) driven at 15 kV accelerating voltage and 36 μA electron current.

A transmission electron microscope is an electron microscope that uses an electron beam to pass through a sample, magnifies the electron beam with an electron lens, and observes it. Therefore, the sample must be prepared thin enough for the electron beam to pass through, and only a two-dimensional image can be observed. The sample was prepared by thinly cutting only the area irradiated with a laser using a dual beam focused ion beam (model name: Nova 200, manufacturer: FEI, country of manufacture: Netherlands). The sample was observed as a cross-section of Ge recrystallized along the MgO direction in the TEM mode of a field emission scanning transmission electron microscope (FE-STEM, model name: HD-2300A, manufacturer: Hitachi, country of manufacture: Japan).

Figures 3 and 4 show the crystal orientation of the recrystallized Ge on a magnesium oxide (MgO) (001) substrate and an amorphous SiO ₂ film, which was recrystallized using a CW laser and the SiO ₂ capping layer was removed, and then the crystal orientation of the recrystallized Ge was mapped using electron backscatter diffraction (EBSD) analysis.

As shown in (a) of the above Fig. 3, Ge recrystallized on a magnesium oxide (001) substrate formed crystals (grains) in the same [001] direction as the magnesium oxide seed, and as shown in (b) of Fig. 3, the Ge (001) crystals (grains) were aligned in the [110] direction. In addition, as shown in (d) of Fig. 3, large crystals (grains) were formed with a grain boundary tilt of 15˚ or less.

On the other hand, Ge recrystallized on SiO ₂ as shown in (a), (b), and (c) of Fig. 4 was not affected by the underlying amorphous SiO ₂ and formed polycrystalline Ge with random orientation. In addition, the crystals formed as shown in (d) of Fig. 4 were formed as small crystals with a grain boundary tilt of 15˚ or more.

Through the above Figures 3 and 4, it can be seen that the presence or absence of a lower seed controls the directionality of recrystallized Ge.

Fig. 5 (a) is a cross-section of the boundary between recrystallized Ge and the underlying magnesium oxide (MgO) seed, taken by transmission electron microscopy (TEM). Figs. 5 (b) and (c) show patterns analyzed by fast Fourier transform (FFT) that are Ge [110] and MgO [001] zone axes, respectively, indicating that the Ge is a single crystal. At this time, the lattice of germanium (Ge) in Fig. 5 (a) forms a 1:1 ratio with the underlying magnesium oxide (MgO), because the germanium (Ge) (001) plane is rotated 45˚ in the [110] direction, as shown in Fig. 6 (a) and (b).

Through the above Figures 3 to 7, it can be seen that the silicon-based (Ge) semiconductor material recrystallized by the laser grows into a single crystal with the (001) plane aligned in the [110] direction along the lower magnesium oxide (MgO) (001) seed direction.

While the specific parts of the present invention have been described in detail above, it is obvious to those skilled in the art that such specific description is merely a preferred embodiment and that the scope of the present invention is not limited thereby. In other words, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

A first step of forming an amorphous silicon-based material layer formed on a magnesium oxide substrate;
A second step of forming a capping layer on the silicon-based material layer; and
A third step of recrystallizing a silicon-based material by irradiating a continuous wave laser in the form of a line beam on the capping layer; and
A fourth step of removing the surface area of the capping layer and the recrystallized silicon-based material layer adjacent to the capping layer;
The above magnesium oxide substrate comprises single crystal magnesium oxide,
The above silicon-based material layer includes one material selected from the group consisting of germanium (Ge), gallium arsenide (GaAs), and indium arsenide (InAs).
A method for growing a single crystal of a silicon-based material, characterized in that during the third step, the silicon-based material is crystallized from the interface with the magnesium oxide substrate in the direction of the capping layer, such that the recrystallization growth direction of the silicon-based material is the same as the crystal direction of the magnesium oxide. delete In the first paragraph,
A method for growing a single crystal of a silicon-based material, characterized in that the first step is to form a silicon-based material layer by depositing an amorphous silicon-based material with a thickness of 30 nm or more on a magnesium oxide substrate. In the first paragraph,
The above capping layer is a single crystal growth method of a crystalline silicon material including amorphous silicon dioxide (SiO ₂ ). In the first paragraph,
The third step is a method for growing a single crystal of a silicon-based material, characterized in that crystallization starts from a magnesium oxide substrate when a laser is irradiated. In paragraph 1,
A method for growing a single crystal of a silicon-based material, characterized in that the first step additionally performs a process of annealing the magnesium oxide substrate at a temperature of 300 to 800° C. for 30 minutes to 2 hours before forming an amorphous silicon-based material layer. delete An active layer comprising a silicon-based material manufactured by a single crystal growth method of a silicon-based material according to any one of claims 1 and 3 to 6. In Article 8,
An active layer characterized in that the crystal boundary slope of the silicon-based material is 15° or less.