KR20050039098A - A method for fabricating gan device using iii metal layer - Google Patents

Abstract

The present invention is to solve the problems of the conventional method using a low temperature buffer layer, GaN device manufacturing method of the present invention, providing a substrate, and the step of changing the temperature of the substrate to 200 ℃ ~ 1300 ℃ and Depositing a Group III metal film on the substrate, raising the temperature of the substrate on which the Group III metal film is deposited to 900 ° C. to 1300 ° C. while supplying at least one of H 2 and N 2 gas; Supplying a nitrogen source gas to the substrate on which the metal film is deposited to nitride the surface, forming a u-GaN thin film on the nitrided substrate, and growing a GaN device on the grown GaN thin film. do.

Description

A method of fabricating gallium nitride devices using a Group 3 metal film {A METHOD FOR FABRICATING GaN DEVICE USING III METAL LAYER}

The present invention relates to a method for manufacturing a GaN light emitting diode (LED) device or a GaN laser diode (LD) device, and more particularly, to fabricate a GaN device having a better crystal structure by using a group III metal film. It is about a method.

GaN LED is a device that emits blue and ultraviolet light and has been used in recent years to make a backlight or white LED used in keypads of mobile phones. In addition, GaN LD is being actively studied for application to a DVD title having a large capacity because its oscillation wavelength is shorter than that of a conventional red laser.

In order to fabricate GaN devices with long lifetime, stable operation, and high brightness, it is very important how high quality crystal structure of epitaxial layer of each layer of device is grown. The lattice match with the GaN element has a great influence. However, since GaN has not yet found a substrate suitable for its lattice constant and crystal structure, sapphire, which has a relatively similar crystal structure to GaN, has been used as a GaN growth substrate. In the case of using a sapphire substrate, it is common to provide a low temperature GaN buffer layer between the GaN device and the sapphire substrate because the difference in lattice constant and thermal expansion coefficient between the two materials is eliminated to some extent.

However, GaN devices employing such buffer layers also have relatively high crystal defect densities, and the defect density of the GaN layer formed on the buffer layer varies depending on process conditions and conditions, but on average, about 1 × 10 ⁸ cm −2 to 1 × ¹⁰ 10 cm-2 are known dalhandago. These crystal defects interfere with the stable operation of the device, reduce the efficiency of hole-electron coupling in the active layer and the like, and cause an increase in operating voltage.

Therefore, a new method for growing a higher quality epitaxy layer than the low temperature buffer layer is required for efficient high luminance emission.

The present invention is to solve the problems of the conventional method using the low temperature buffer layer, and to provide a new GaN crystal growth method using a Group III metal film instead of the low temperature buffer layer.

Another object of the present invention is to provide a method for manufacturing a high quality GaN device through a crystal growth method using such a group III metal film.

The GaN device fabrication method of the present invention for achieving the above object comprises the steps of providing a substrate, changing the temperature of the substrate to 200 ℃ ~ 1300 ℃, and depositing a Group III metal film on the substrate And raising the temperature of the substrate on which the group III metal film is deposited to 900 ° C. to 1300 ° C. while supplying at least one of H ₂ and N ₂ , and supplying a nitrogen source gas to the substrate on which the group III metal film is deposited. And nitriding the surface, and growing u-GaN and GaN devices on the nitrided substrate.

Here, the group III metal film may be made of boron (B), aluminum (Al), gallium (Ga), indium (In), tantalum (Ta), or an alloy thereof, and the substrate may include sapphire, silicon carbide ( It may be a substrate made of any one of SiC) and silicon (Si). In addition, the nitrogen source gas may be composed of at least one material of ammonia, hydrazine (hydrazine).

Hereinafter, with reference to the drawings will be described embodiments of the present invention;

FIG. 1 is a flowchart illustrating a basic embodiment of the present invention, and FIG. 2 shows the flowchart of FIG. 1 on the time and temperature axes, and the same process is indicated by the same step symbols S1 to S10.

As the substrate used in the present invention, a substrate made of any one of sapphire, SiC, and Si may be used. Unlike the conventional method, the epitaxy growth method used in the present invention does not rely on the compatibility with the substrate, so that silicon carbide (SiC) or silicon in addition to sapphire can be used as the substrate.

The substrate is washed with acetone, etc., and then charged into a reactor, and then heated to a temperature of 1300 ° C. or lower in a hydrogen atmosphere (S1), and subjected to a pretreatment process of removing organic substances and other impurities adsorbed on the surface of the substrate ( S2). The pretreatment process can take about 1 to 10 minutes.

After the pretreatment process is finished, the substrate temperature is changed back to 200 ° C. to 1300 ° C. to perform a metal film forming step (S4). In the present embodiment, a group III metal film was formed while supplying Group III organometallic cause TMG (TrimethylGallium) and hydrogen and / or nitrogen in the reactor at about 200 ° C., about 580 ° C., and about 1300 ° C. (S4). . At this time, the pressure in the reactor was about 250 Torr. The metal film deposited at the above temperature was similar, but when the temperature was below 200 ° C., the TMG did not decompose well, and when the temperature was above 1300 ° C., the rate at which the metal film was formed was too slow to be substantially undesirable. In addition, since the appropriate deposition temperature is slightly different depending on the Group III metal element used, and recrystallization is performed again through a subsequent thermal etching process, it is not necessary to perform the process at a temperature outside this range. .

In the present embodiment, a gallium metal film using TMG is used as the Group III metal film. However, a metal organic source such as TEG or a chloride-based precursor may be used as the metal source, and the remaining Group III elements are boron (B). The same applies to a source source such as aluminum (Al), indium (In), or tantalum (Ta). The metal film may be any one of the group III elements, or a mixture thereof, and an alloyed metal film may be used when the metal film is mixed.

After the Ga metal film is formed at 580 ° C., which is one of the temperatures used in this embodiment, the supply of the Group III metal source gas that is supplied is stopped (S5). The temperature of the substrate is then maintained between about 900 ° C. and 1300 ° C., preferably between about 950 ° C. and 1100 ° C., more preferably about 1000 ° C., while supplying only hydrogen and / or nitrogen into the reactor. The film is etched (S6).

The etching of this step is a step in which the weakly bonded metal atoms on the surface of the group III metal film are broken at a high temperature, and the metal film is changed into a small and evenly dispersed metal particle layer, which is substantially different from the metal film forming step (S4). It may also be carried out continuously. That is, in the case of performing the metal film forming step S4 at, for example, about 1000 ° C., if the temperature is maintained in this state while the supply of the metal source gas such as TMG is stopped (S5), the etching step S6 is automatically performed. It may also proceed to.

This etching step (S6) may be performed while increasing the temperature, but of course, may be performed at a stop in any one of the above temperature range. It is sufficient that the etching time is such that the metal film is recrystallized into an island shape. In the present embodiment was performed for about 4 minutes to 5 minutes at the aforementioned 1000 ℃.

After etching the metal film using thermal energy, a nitriding treatment step of supplying ammonia or hydrazine gas into the reactor is performed (S7). This nitriding step is carried out at about 900 ° C to 1300 ° C, the final temperature of the temperature rise, at which time the pressure in the reactor is about 250 Torr. When the nitriding treatment is performed at 900 ° C. or lower, the Group III metal having FCC structure is not easily recrystallized into Group III nitride having HCP structure, and at 1300 ° C. or higher, it is not preferable in terms of equipment stability and efficiency.

After the nitriding treatment step, the dispersed metal particle layer is changed into a group III nitride particle layer evenly dispersed (S8).

The nitride particle layer after this nitriding step serves as a seed layer necessary for growing a GaN epitaxy layer having high quality crystalline in a subsequent process.

After the nitriding treatment step, the temperature is changed to about 950 ° C. to 1300 ° C., and an undoped-GaN layer (hereinafter referred to as u-GaN layer) which is not doped with impurities is grown (S9). It is possible to grow a high quality u-GaN layer, which is reduced by about 1/10 compared with that of FIG.

After the u-GaN is grown, n-GaN, an active layer, a p-GaN layer, a contact layer and an electrode are sequentially stacked to fabricate a GaN LED device or to form a cavity therein to form a GaN laser diode. Step S10 is the same as the existing process, so detailed description thereof will be omitted. However, when the active layer is formed, aluminum, indium, or the like may be included in gallium according to a required oscillation wavelength, and thus the oscillation wavelength may be variously changed from ultraviolet to bluish green series.

Since the temperature diagram of FIG. 2 schematically shows the temperature of some embodiments of the situation performed at the temperature of each step described above, a section in which the temperature appears to be falling or rising may not be substantially falling or rising. Therefore, Figure 2 is intended to help the understanding of the present invention and should not be used in the interpretation of the scope of the present invention.

Figure 3a is a photograph taken with the AFM surface of the nitrided substrate using the present invention, Figure 3b is a photograph taken a substrate having a GaN buffer layer of the prior art to contrast with the present invention. As can be seen from the figure, the particle distribution of the surface of the substrate of FIG. 3A using the present invention can be seen that a GaN particle layer composed of particles having relatively small and almost the same size is formed, whereas the surface roughness of the conventional GaN buffer layer is constant. It can be seen that not. Due to the difference in surface shape of these two substrates in the u-GaN deposition process described later, the present invention has a growth substrate completely different from the existing low temperature GaN buffer layer.

Hereinafter, the substrate of the present invention will be described in which the substrate of the present invention can grow an epitaxial layer having fewer crystal defects and an excellent epitaxial layer than the conventional GaN buffer layer. For reference, the description of the present invention is not based on accurate measurement, and the present invention is based on the above-described AFM photograph and visual measurement of defect density on the final surface.

FIG. 4 schematically shows the state of the surface of the substrate 10 that is assumed to occur between the above-described steps S4 to S8.

After the substrate is pretreated (S2), the substrate temperature is changed to 200 ° C. to 1300 ° C. (S3), and the metal film forming step is performed while supplying the group III metal source gas and hydrogen or nitrogen together. As shown in FIG. 4A, as the metal particles 20 are deposited, a metal film is formed over the entire surface of the substrate in the form of interspersing voids and amorphous particles.

After the metal film is formed, the supply of the metal source gas is stopped (S5). Then, the temperature of the substrate is maintained at 900 ° C to 1300 ° C in order to undergo a step of thermally etching and simultaneously recrystallizing the formed metal film (S6).

In the temperature rise step shown in FIG. 4B, the metal particles that are weakly bound to the surface are evaporated (20 ″) back into the atmosphere gas when the bond with the substrate surface is lost, or metal clusters formed around for thermodynamic stability. Adsorbed by (cluster, 400), it contributes to recrystallization (20 '). In the end, these steps are separated from each other by a certain distance, and the small and homogeneous metal clusters are spaced at almost uniform intervals from each other. Evenly formed on the surface This uniformity is naturally formed by enthalpy and entropy at the substrate surface.

When ammonia or hydrazine, which is a nitrogen source gas, is supplied to the substrate in this state, the metal clusters are combined with activated nitrogen (N *) and undergo a nitride particle layer forming step of changing into nitride 30 (S7). 4C schematically shows such a state, in which the cluster surface is all modified with nitride 30, and metal particles 20 not yet modified with nitride are mixed therein. Over time, all of these metals quickly denature to nitride. In the following, such modified nitride distributions are referred to as nitride seeds.

Through this nitride particle layer forming step, the layer originally formed of the metal film is changed into a small, uniformly dispersed nitride seed. 5 is a view for explaining how the nitride seeds formed by the above-described process contribute to the formation of high quality GaN crystals.

In FIG. 5A, it can be seen that the nitride seed 40 schematically shown is uniformly distributed on the surface of the substrate 10. When the nitride seed is formed, the temperature in the reactor is changed to about 950 ° C. to 1300 ° C., which is a GaN growth temperature, to form a full GaN layer, and then TMG and NH 3 gas for forming a u-GaN layer is introduced into the reactor. Supply (S9).

U-GaN formed at the beginning of the gas supply is preferentially grown since the nitride seed 40 is a nucleation site that is easily thermodynamically crystallized, and the growth method appears to mainly take the lateral growth method. That is, as shown in Figure 5b, the initial u-GaN (50) is a method of growing from side to side around the nitride seed, which is a group III nitride having the same or very similar chemical properties as the crystalline that is grown at this time Since silver nitride seeds are the same group III-V compounds, the lattice constants and structures are very similar to each other, so that stresses and defects hardly occur between them, especially when the nitride seeds start from the Ga metal film.

In addition, since the horizontal axis is the main growth axis, it is not influenced by the lower substrate and the distance between the seeds is not so long, and thus its size is not large. Thus, a perfect epitaxy layer with almost no crystal defects is believed to grow at this time.

As the growth phase continues (FIG. 5C), crystallines that have begun to grow from adjacent nitride seeds grow in size and impinge directly on each other to fill the gap between the nitride seeds, which occurs across the substrate front surface. An initial u-GaN layer 50 'covering is formed.

The initial u-GaN layer 50 'has a defect density that is incomparable with the conventional low temperature GaN buffer layer. Most of the defects occurring in this layer are stacking faults occurring at the interface 500 hit by the growth layers of FIG. 5B described above, the absolute number of which is small compared to the existing defect density and also occurs at high temperature. Many of them disappear due to rearrangement of dislocations. Therefore, the initial u-GaN (50 ') grown in the present invention has fewer defects than the existing low temperature buffer layer and has excellent surface morphology.

In FIG. 6, even after the initial growth of the u-GaN layer 50 ′, the growth time is continued to grow a thick u-GaN layer 60, and then n-GaN, indium or aluminum is not shown thereon. A GaN active layer, a p-GaN layer, an electrode layer, etc., which may be added, may be grown, and if necessary, an ohmic contact layer or a window layer may be further grown. In addition, when fabricating GaN LD, a Fabry-Perot resonator or the like is formed. Such LED or LD fabrication process is generally well known, and thus detailed description thereof will be omitted.

The present invention is to solve the problem of high density defects of the conventional low-temperature GaN buffer layer used for the substrate when manufacturing a GaN device, a method using a group III-V seed layer homogeneously dispersed on the substrate surface instead of the low-temperature buffer layer It is about.

By using the GaN growth method and device fabrication method provided in the present invention, it is possible to produce high quality GaN light emitting devices or GaN laser diodes, which have significantly fewer crystal defects and dramatically improved device lifetime and luminance, compared to conventional low temperature buffer layers. have.

Those of ordinary skill in the art who understand the technical spirit of the present invention can easily come up with various modifications in the above-described embodiments by changing the temperature of each process step slightly or adding doping elements. Could be. Therefore, since these modifications also belong to the scope of the present invention, the scope of the present invention should be defined by the following claims.

1 is a flow diagram illustrating a basic embodiment of the present invention.

FIG. 2 is a process diagram representing the flow chart of FIG. 1 with respect to time and temperature.

Figure 3 is a photograph of the surface of the nitrided Ga metal film of the present invention and a conventional low temperature GaN buffer layer.

4 is a view schematically showing a situation from the group III metal film forming step to the nitriding treatment step of the present invention.

5 is a diagram schematically illustrating a process of forming a u-GaN layer using a nitride seed layer.

Fig. 6 is a diagram schematically showing a state of a substrate formed up to a u-GaN layer using the present invention.

Claims (9)

In the GaN device manufacturing method, Providing a substrate, Changing the temperature of the substrate to 200 ° C to 1300 ° C; Depositing a group III metal film on the substrate; Changing the temperature of the substrate on which the Group III metal film is deposited to 900 ° C. to 1300 ° C. while supplying at least one of H 2 and N 2; Supplying a nitrogen source gas to the substrate on which the group III metal film is deposited, and nitriding a surface thereof; Growing a GaN device on the nitrided substrate GaN device manufacturing method comprising a. The method of claim 1, wherein the Group III metal film is made of at least one of B, Al, Ga, In, and Ta. The method of claim 1, wherein the substrate is a substrate made of any one of sapphire, SiC, and Si. The method of claim 1, wherein the nitrogen source gas is a gas composed of at least one material of ammonia and hydrazine. The GaN device manufacturing method of claim 1, wherein the depositing of the Group III metal film on the substrate is performed in at least one of hydrogen and nitrogen atmospheres. The method of claim 1, wherein the GaN device has an active layer composed of GaN, and the active layer further comprises at least one of Al and In as a compound. The method of claim 1, wherein the GaN device is any one of an LED and a laser diode. The method of claim 1, further comprising pretreating the provided substrate in a hydrogen atmosphere of 1300 ° C. or lower before the Group III metal film deposition step. The GaN device manufacturing method of claim 1, wherein the GaN device is grown at 950 ° C. or higher.