KR100643155B1 - Method for producing a silicon substrate-monocrystalline thin film laminate - Google Patents

Abstract

A method for producing a silicon substrate-monocrystalline GaN thin film laminate is provided.

Method for producing a silicon substrate-monocrystalline GaN thin film laminate according to the present invention comprises the steps of (a) injecting a silicon single crystal substrate into the reactor; (b) thermally cleaning the silicon single crystal substrate; (c) pretreatment by adding an organic gallium compound alone; (d) adding an organic gallium compound and ammonia together to form a polycrystalline GaN buffer layer; And (e) injecting the organic gallium compound and ammonia together to form a single crystal GaN thin film at a high temperature, which uses a silicon single crystal substrate instead of a sapphire single crystal substrate, thereby reducing manufacturing costs and increasing crystallinity. By directly stacking an excellent GaN epi thin film on a silicon single crystal substrate, it can be used as a vertical light emitting device. Since the buffer layer is not used, the operation start voltage can be lowered and process reproducibility due to contamination of the susceptor in the reactor can be reduced. Prevent and reduce manufacturing costs.

Description

Method of preparing silicon substrate-gallium nitride thin film laminated body}

1 is a schematic cross-sectional view of an example in which a GaN thin film is deposited on a silicon substrate by using a buffer layer according to the prior art.

2 is a schematic cross-sectional view of a laminate in which a single crystal GaN thin film is directly laminated on a silicon single crystal substrate according to the present invention.

3 is a flowchart sequentially illustrating a method of manufacturing a silicon substrate-monocrystalline GaN thin film laminate according to the present invention.

<Description of the symbols for the main parts of the drawings>

200 Silicon single crystal substrate 210 buffer layer

220 ... GaN thin film

The present invention relates to a method for manufacturing a silicon substrate-monocrystalline GaN thin film laminate, and more particularly, to a method for growing an epitaxial layer of GaN having excellent crystallinity directly on a silicon single crystal substrate.

GaN is a direct transition wide band gap semiconductor having a band gap energy of 3.39 eV, and is a useful material for manufacturing a light emitting device having a short wavelength region. This is a compound semiconductor that can be used for a light emitting diode device, a short wavelength laser diode, an ultraviolet detector, and the like, which operate at the wavelength of all visible light.

However, since GaN has a high nitrogen vapor pressure at the melting point, the general liquid crystal growth requires a high pressure of 1500 ° C. or higher and a high pressure of nitrogen, thus making mass production difficult. In addition, since the size of the crystals that are currently available is about 80 mm 2, it is difficult to use them in device fabrication. Therefore, GaN-based devices can be applied to vapor growth methods such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride or halide vapor phase epitaxy (HVPE), and sublimitation vapor phase epitaxy (SVPE) on heterogeneous substrates. To prepare a thin film.

At this time, SiC or sapphire single crystal has been used as a heterogeneous substrate. SiC is stable at high temperature and has the same hexagonal structure as GaN, and the difference in lattice constant and thermal expansion coefficient with GaN is smaller than that of sapphire, and has excellent thermal and electrical conductivity. However, the price is more expensive than sapphire, and the micropipes in the SiC substrate are propagated to the GaN thin film, thereby degrading the characteristics of the GaN device.

On the other hand, sapphire, like SiC, is stable at high temperature, has a hexagonal structure, and is relatively inexpensive, so that sapphire can be widely used in the manufacture of GaN thin films. About 35%) causes strain on the interface with GaN, which in turn causes lattice defects in the crystal, making it difficult to manufacture high quality GaN thin films, thereby shortening the lifespan of the fabricated device. The increase in manufacturing cost due to reduced production yield.

However, in the case of silicon single crystal substrates, high-quality single crystals with a large area can be obtained at a low price so as to be incomparable with other substrate materials among all semiconductor substrates, and the integrated electronic devices of silicon semiconductors, such as memories, and the optoelectronic devices of nitride semiconductors The advantage is that bonding is possible on the same substrate. In addition, it is also an advantage that it is possible to manufacture a vertical light emitting device that was not possible when a sapphire substrate is used as a non-conductor.

However, conventionally, the epitaxial growth of GaN on a silicon single crystal substrate is due to problems such as different crystal structures between the two materials, differences in lattice constants, differences in thermal expansion coefficients, and degradation of wetting of GaN on the silicon substrate. Direct epitaxial growth of the GaN film on the substrate was not satisfactory. Therefore, inevitably, the above problems have been solved by stacking heterogeneous materials such as a crystalline or amorphous buffer layer between the silicon single crystal substrate and the GaN film. In this case, the material used as the material of the buffer layer is 3C-SiC, low temperature. Growth GaN, AlN, GaAs, AlOx, Si ₃ N ₄ and the like. 1 illustrates an example in which a GaN thin film 220 is stacked on a silicon substrate by using such a buffer layer according to the prior art. The buffer layer may be formed using MOCVD, MBE, HVPE, SVPE, or the like. However, when the buffer layer 210 is stacked on the silicon single crystal substrate 200 as described above, a turn-on voltage of a light emitting device such as a light emitting diode is increased due to the high specific resistance of the buffer layer 210. ), Especially when AlN is used as a buffer layer material, contaminates the susceptor surface inside the reactor, increasing maintenance costs due to poor process reproducibility and reduced internal reactor cell replacement cycles. There was a problem.

Korean Laid-Open Patent Publication No. 2001-38505 discloses a method of laminating a film made of silicon oxide or silicon nitride as an insulator on a silicon substrate, then laminating a low temperature GaN film thereon, and finally manufacturing a GaN single crystal. Since too many processes are employed to obtain single crystal GaN, there is a problem in that process efficiency is low, and since the silicon substrate and the GaN thin film are insulated, there is a disadvantage that the utilization as an electronic device is low.

In addition, the Republic of Korea Patent Publication No. 388011 has a ??? Al ₂ O ₃ substrate having any one of (0001), (1102), (1120), and any one of (100), (111) Any one selected from the group consisting of a silicon substrate, a SiC substrate, an MgAl ₂ O ₄ substrate, a GaN single crystal substrate, and a GaN thin film having a surface; A GaN single crystal thin film (0001) formed on the substrate at a thickness of 0.3 to 1000 µm; And a SAW filter of a GaN thin film including an IDT electrode pattern formed on the GaN single crystal thin film, but actually used as a substrate is only an α-Al ₂ O ₃ substrate (sapphire substrate) having a (0001) plane. There is no mention as to which technical means can form an excellent single crystal GaN thin film on a silicon substrate.

The technical problem to be achieved by the present invention is to reduce the manufacturing cost by using a silicon single crystal substrate instead of the conventional SiC or sapphire (sapphire) single crystal substrate in order to solve the problems of the prior art as described above, the production of a vertical light emitting device It is to provide a method for producing a silicon substrate-single crystal GaN thin film laminate that facilitates this.

The present invention to achieve the above technical problem,

(a) introducing a silicon single crystal substrate into the reactor; (b) thermally cleaning the silicon single crystal substrate; (c) pretreatment by adding an organic gallium compound alone; (d) adding an organic gallium compound and ammonia together to form a polycrystalline GaN buffer layer; And (e) injecting an organic gallium compound and ammonia together to form a single crystal GaN thin film at a high temperature.

Hereinafter, the present invention will be described in more detail.

In the method for manufacturing a silicon substrate-monocrystalline GaN thin film laminate according to the present invention, a high-quality single crystal GaN thin film is directly deposited on a silicon substrate so that the combination of an integrated electronic device of a silicon semiconductor such as a memory and an optoelectronic device of a nitride semiconductor is the same. It is possible in the above, it is possible to manufacture a vertical light emitting device.

2 is a schematic diagram of a silicon substrate-monocrystalline GaN thin film laminate prepared according to the present invention. Referring to FIG. 2, it can be seen that in the silicon substrate-monocrystalline GaN thin film laminate according to the present invention, no buffer layer is laminated and the single crystal GaN thin film is directly laminated on the silicon single crystal substrate.

3 is a flowchart illustrating a method of manufacturing a silicon substrate ?? single crystal GaN thin film laminate according to an embodiment of the present invention.

Referring to FIG. 3, the silicon single crystal substrate 200 is introduced into a reactor (step S1), the silicon single crystal substrate 200 is thermally cleaned (step S2), and the organic gallium compound is added alone to pretreat the silicon. Forming a Ga metal layer on the single crystal substrate 200 (step S3), forming a polycrystalline GaN buffer layer on the Ga metal layer (step S4), and finally forming a single crystal GaN thin film (step S5). .

In the step S1, a GaN film is generally deposited using metal organic chemical vapor deposition (MOCVD) equipment, molecular beam epitaxy (MBE) equipment, vapor phase epitaxy (VPE) equipment, or hydride vapor phase epitaxy (HVPE) equipment. However, in this embodiment, metal organic chemical vapor deposition (MOCVD) equipment was used. The silicon single crystal substrate 111 introduced into the internal reactor of the equipment is not particularly limited as long as it is commonly used in the art and may be purchased through a conventional vendor. Since the silicon single crystal substrate 111 needs to be kept in an uncontaminated state for the lamination of the GaN film 002, it is necessary to wash the silicon single crystal substrate 111 before entering the reactor.

Next, in step S2, the silicon single crystal substrate 111 is thermally cleaned, and the substrate is fixed to a susceptor in the reactor, and the reactor is maintained at a vacuum pressure of 3 × 10 ^-2 torr and exhausted sufficiently. After that, hydrogen gas is injected. Such thermal cleaning may remove physical contaminants such as fine organic foreign substances and at the same time, physically and chemically modify the surface on which the GaN film of the silicon single crystal substrate is stacked.

     The organic gallium compound that can be used in the step S3 is used as a gallium source and is not particularly limited as long as it is commonly used in the art, for example, may be trimethylgallium (TMGa) or triethylgallium (TEGa). According to the prior art, the sapphire substrate is nitrided by using ammonia in this step. If the silicon substrate is nitrided using ammonia, ammonia and silicon are directly reacted to form a silicon nitride film, thereby increasing the growth of high quality GaN. In the present invention, the organic gallium compound is used instead of the nitriding treatment. In the pretreatment step, the organic gallium compound is decomposed to induce a physical chemical adsorption of a thin metallic Ga layer on the surface of the silicon substrate. The role of the metallic Ga layer is wettability between the silicon substrate and the single crystal GaN thin film to be deposited later. It is possible to form high quality GaN epitaxial films on silicon substrates by improving wetting, relieving stress, and changing nucleation mechanisms. Since the metallic Ga layer is later diffused and absorbed into the GaN layer when the high temperature GaN layer is grown, the final laminated structure becomes a silicon substrate / single crystal GaN thin film stacked structure.

The pretreatment temperature of the step S3 is 450 ~ 550 ℃ and the pretreatment time may be 10 minutes or less, the temperature range is to increase the process efficiency by the same as the temperature of step S4, the next step of the S3 step, the pretreatment time When the amount exceeds 10 minutes, the amount of metallic Ga generated is too large and the thickness becomes too thick, which is not preferable.

Next, in step S4, an organic gallium compound is used as a Ga source, and ammonia is used as an N source to form a polycrystalline GaN buffer layer on the Ga metal layer. The temperature of this step is also preferably 450 ~ 550 ℃, when the temperature is less than 450 ℃ nucleation density is too high or the amorphous layer is deposited, when the temperature exceeds 550 ℃ nucleation density is too low to wet and surface There is a risk of roughness.

Finally, in the S5 step, the GaN layer is grown at high temperature on the polycrystalline GaN buffer layer by using an organic gallium compound and ammonia under high temperature to perform epitaxial growth. It is preferable that the temperature of this step is 800 degreeC or more, but when the temperature is less than 800 degreeC, since the quality of crystallinity, optical, and electrical property becomes low, it is not preferable. Through this step, the metallic Ga layer, the polycrystalline GaN buffer layer and the final high temperature grown GaN layer are integrated and have the same single crystal structure.

On the other hand, the present invention may further comprise the step of laminating an amorphous GaN layer by adding an organic gallium compound and ammonia together at a low temperature of 250 ~ 350 ℃ after step S3, in which case the amorphous GaN layer is a silicon substrate surface Nitride or the formation of Si ₃ N ₄ can be effectively suppressed, and the wettability of GaN on the surface of the silicon substrate can be increased. That is, since the wettability of the amorphous GaN layer on the silicon substrate is superior to that of the polycrystalline GaN layer, the wettability can be improved by generating such an amorphous GaN layer.

Hereinafter, the present invention will be described in more detail with reference to preferred examples, but the present invention is not limited thereto.

Example 1

A susceptor in the interior of the apparatus is used using a silicon single crystal substrate having an organometallic chemical vapor deposition (MOCVD) apparatus (VTS, SOLOMON HR1010M) and having dimensions of 10 mm, 10 mm, and 0.4-0.7 mm in height. Susceptor). After the exhaust gas was sufficiently discharged while maintaining the pressure inside the reactor at 3 × 10 ⁻² torr, hydrogen (H ₂ ) gas (flow rate 2.4 slm) was injected, and the susceptor temperature was 1100 ° C. for 5 minutes. Heated. Subsequently, trimethylgallium (TMGa) gas was supplied at a flow rate of 7 sccm to pretreat the silicon substrate. The process conditions at this time was a temperature of 500 ℃ and the pressure was 300 Torr. Next, deposition was performed for 3 minutes while supplying trimethylgallium (TMGa) gas (flow rate 7 sccm) and ammonia gas (flow rate 1 slm) at the same temperature to deposit a polycrystalline GaN buffer layer on the metallic Ga layer in a thickness of 30 nm. It was. Finally, the trimethylgallium (TMGa) gas (flow rate 14 sccm) and ammonia gas (flow rate 1 slm) were continuously supplied, and the temperature in the reactor was raised to 800 ° C. to form a single crystal GaN thin film of 1 μm or more. A single crystal GaN thin film laminate was prepared.

Example 2

A silicon substrate-single crystal GaN thin film laminate was prepared in the same manner as in Example 1 except that the pretreatment of the silicon substrate was performed with triethylgallium (TEGa) (flow rate of 7 sccm).

Example 3

After pretreatment of the silicon substrate, a trimethylgallium (TMGa) gas (flow rate of 7 sccm) and ammonia gas (flow rate of 1 sml) were supplied at 300 ° C. in the same manner as in Example 1 except that an amorphous GaN layer was further formed. A silicon substrate-monocrystalline GaN thin film laminate was prepared.

Comparative Example 1

A susceptor in the interior of the apparatus is used using a silicon single crystal substrate having an organometallic chemical vapor deposition (MOCVD) apparatus (VTS, SOLOMON HR1010M) and having dimensions of 10 mm horizontal, 10 mm vertical and 0.4-0.7 mm high. Susceptor). After exhausting sufficiently while maintaining the pressure inside the reactor of the apparatus at 300 torr, hydrogen (H ₂ ) gas (flow rate 2.4 slm) was injected, and the susceptor was heated at 1100 ° C. for 5 minutes. Subsequently, the silicon substrate is nitrided using ammonia gas (flow rate 1 slm) at 500 ° C, and then trimethylgallium (TMGa) gas (flow rate 7 sccm) and ammonia gas (flow rate 1 slm) are supplied and the temperature in the reactor is 800. The GaN thin film was formed to be 1 μm or more by increasing to ℃.

Test Example 1

The X-ray (X-ray Diffraction, X-ray diffraction analysis) is incident on the single crystal surface grown in Examples 1 to 3 and Comparative Example 1 and characterized by the value of the full width half maximum (FWHM) of the diffraction peak Was determined. Lower half width indicates better crystallinity. In the case of GaN, a half width of about 200 to 500 arcsec is considered to have excellent crystallinity. In addition, the crystal growth direction can be measured simultaneously. GaN single crystal thin films are grown in the (0001) c-axis direction. Poor crystallinity may ideally determine that growth did not occur properly in the (0001) c-axis direction.

Example 1 Example 2 Example 3 Comparative Example 1 Crystallinity 400 arcsec 400 arcsec 400 arcsec 2000 arcsec

As can be seen in Table 1, according to the manufacturing method according to the present invention it can be produced a GaN thin film with excellent crystallinity on a silicon single crystal substrate.

The manufacturing method according to the present invention can reduce the manufacturing cost by using a silicon single crystal substrate instead of a sapphire single crystal substrate, and can be used as a vertical light emitting device by directly depositing a GaN epi thin film having excellent crystallinity on a silicon single crystal substrate. Since the buffer layer is not used, the starting voltage can be lowered, and the process reproducibility can be prevented due to contamination of the susceptor in the reactor and the manufacturing cost can be reduced.

Claims (5)

(a) introducing a silicon single crystal substrate into the reactor; (b) thermally cleaning the silicon single crystal substrate; (c) pretreatment by adding an organic gallium compound alone; (d) adding an organic gallium compound and ammonia together to form a polycrystalline GaN buffer layer; And (e) Injecting an organic gallium compound and ammonia together to form a single crystal GaN thin film at a high temperature manufacturing method of a silicon substrate-monocrystalline GaN thin film laminate. The method of claim 1, wherein the organic gallium compound is trimethylgallium (TMGa) or triethylgallium (TEGa), the pretreatment temperature of step (c) is 450 ~ 550 ℃, the pretreatment time is 10 minutes or less, the silicon after pretreatment A method for producing a silicon substrate-single crystal GaN thin film laminate, wherein a Ga metal layer is formed on the substrate. The method of claim 1, wherein the temperature in the step (d) is 450 to 550 ° C. The method of claim 1, wherein the temperature of the step (e) is 800 ° C. or higher. The silicon substrate-monocrystalline GaN thin film according to claim 1, further comprising laminating an amorphous GaN layer by injecting an organic gallium compound and ammonia together at a low temperature of 250 to 350 ° C. after the step (c). The manufacturing method of a laminated body.

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