KR100822482B1 - Growing method for nitride based epitaxial layer and semiconductor device using the same - Google Patents

Abstract

A method for growing a nitride-based epitaxial layer is provided to embody crystallinity on a sapphire substrate and obtain chemical stability by forming a GaAs-based thin film layer on a substrate wherein a part of an As element is replaced by a nitrogen element and by growing a nitride-based epitaxial layer on the thin film layer. A thin film layer(115) is formed on a prepared substrate(100) wherein a part of an As element is replaced by a nitrogen element in the thin film. The thin film layer can include a thickness of 5-10000 Å. A nitride-based epitaxial layer(120) is grown on the thin film layer. The process for forming the thin film layer includes the following steps. An GaAs-based thin film layer is grown on the substrate. The substrate having the grown thin film layer is heat-treated in a nitrogen atmosphere to replace a part of the As element by a nitrogen element. The substrate can include a sapphire material.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of growing a nitride-based epitaxial layer and a semiconductor device using the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a method for growing a nitride-based epitaxial layer, and more particularly, to a method for growing a nitride compound semiconductor layer using a gallium arsenide (GaAs) based buffer layer on a sapphire substrate in a nitride- .

In general, light emitting diodes (LEDs), which are used as light emitting devices, are attracting attention as next generation light sources that replace incandescent lamps and fluorescent lamps. Particularly, blue light emitting diodes using nitride based compound semiconductors such as gallium nitride (GaN) have been developed, and all colors can be realized. Accordingly, demand is increasing in various directions.

In a compound semiconductor device typified by such a light emitting diode, gallium nitride or gallium nitride based compound semiconductor materials (for example, InGaN, AlGaN, etc.) are physically hardened on the bottom and chemically stable substrates (for example, sapphire substrate As shown in Fig.

In forming a compound semiconductor material such as gallium nitride on the substrate, an epitaxy growth method is generally used to form a thin film while maintaining material specific characteristics. In order to grow an epitaxial layer made of a material other than the substrate material on the substrate, it is necessary that the size of the lattice constant between the lower substrate and the upper epitaxial layer is similar and the crystallographic directions coincide with each other. Further, in order to prevent occurrence of cracking or peeling in a subsequent thermal process, the more the matching parameter such as the coefficient of thermal expansion is, the more advantageous the application is.

However, since the above-mentioned nitride-based compounds have a large lattice constant difference from sapphire used as a substrate, it is difficult to grow a high-purity epilayer by a general method. As an alternative, an epitaxial growth technique is used in which gallium nitride or an aluminum-gallium nitride (AlGaN) buffer layer is first formed at a low temperature, followed by high-temperature epitaxial growth on the buffer layer.

1 is a schematic cross-sectional view in a main process of a method for epitaxial growth of a nitride layer according to a conventional method.

First, as shown in FIG. 1A, a buffer layer 11 is formed on a prepared substrate 10 such as a sapphire substrate or a silicon carbide (SiC) substrate. The buffer layer 11 is made of gallium nitride or gallium nitride based compound semiconductor material (for example, AlGaN). The buffer layer 11 can be grown at a relatively low temperature because the buffer layer 11 can not be directly grown due to a difference in lattice constant at a high temperature at which epitaxial growth is performed.

Then, the gallium nitride or the compound semiconductor material in which the buffer layer 11 is formed is heat-treated at a high temperature. When the semiconductor material of the buffer layer is heat-treated, only the portion corresponding to the lattice constant and the substrate 10 such as the lower sapphire is left as shown in FIG. 1 (b) And removed from the substrate. The gallium nitride semiconductor material remaining on the lower substrate 10 through the heat treatment process is pyramid-shaped and crystallized. The crystallized pyramidal buffer layer is denoted by reference numeral 11a in order to distinguish it from the buffer layer 11 formed at a low temperature in the previous step.

Thereafter, as shown in Fig. 1C, a nitride-based compound semiconductor epitaxial layer 12 is grown on the crystallized pyramid-shaped buffer layer 11a. Since the epitaxial layers of the same series are grown at a high temperature on the buffer layer 11a ensuring high temperature stability and lattice mismatching with respect to the lower substrate 10, the lattice mismatch or the high temperature characteristic mismatch It is possible to reduce the defective interfacial property due to the contact resistance.

However, in the low-temperature buffer layer growth technique, since the crystallinity of the buffer layer 11 growing at a low temperature is lowered, the concentration of the dislocation indicating the crystallinity of the grown epitaxial layer based thereon is in the range of 10 ⁸ to 10 ¹⁰ / cm ³ < / RTI > Further, it is difficult to control the density of the buffer layer, which makes it difficult to control the tensile force (or stress) of the subsequently grown gallium nitride compound semiconductor epitaxial layer.

SUMMARY OF THE INVENTION The present invention provides a method for growing a nitride compound semiconductor epitaxy on a sapphire substrate which is excellent in crystallinity, chemically stable, and easy to control characteristics of each layer .

According to another aspect of the present invention, there is provided a method of growing a nitride-based epitaxy layer, comprising the steps of: preparing a gallium arsenide (GaAs) layer in which a part of arsenic (As) Forming a thin film layer on the substrate; And growing a nitride-based epitaxial layer on the thin film layer.

The forming of the thin film layer may include: growing a gallium arsenide thin film layer on the substrate; And a step of heat treating the substrate on which the thin film layer is grown in a nitriding atmosphere to replace a portion of the elemental nitrogen with a nitrogen element. In the step of growing the thin film layer of gallium arsenide type, the thin film layer may be grown to a thickness of 5 to 10000 angstroms And the heat treatment step may be performed in an atmosphere containing ammonia (NH ₃ ) and arsenic at a temperature of 500 to 1200 ° C. At this time, the substitution fraction of the gallium arsenide-based thin film layer can be controlled according to the heat treatment time and the partial pressure of the arsenic component contained in the atmosphere in replacing a part of the arsenic component with the nitrogen component.

The thin film layer of the gallium arsenide series may include at least one of an indium (In) element and an aluminum (Al) element, and the substrate may be made such that the material material thereof includes sapphire, is a material selected from the group consisting of _{GaN, AlN, InN, Al x} Ga 1-x N, in x Ga 1-x N, Al x in y Ga 1-y N ( from above 0 <x, y <1) As shown in FIG.

A semiconductor device according to another embodiment of the present invention is a semiconductor device including a nitride-based epitaxial layer, the semiconductor device comprising: a substrate; 0.0 &gt; _{1 & lt; /} RTI _{&gt; x} N _x (0 &lt; x &lt; 1) layer; And a nitride-based epitaxial layer overlying the GaAs _1-x N _x layer.

Hereinafter, a method of manufacturing a light emitting diode according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the element directly over another element, Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

2 (a) to 2 (d) are schematic cross-sectional views in a main process of a method for growing a nitride-based epitaxial layer according to an embodiment of the present invention.

First, as shown in Fig. 2A, a substrate 100 such as a sapphire substrate or a silicon carbide (SiC) substrate is prepared. The substrate 100 is preferably a sapphire substrate.

Then, as shown in FIG. 2 (b), a gallium arsenide-based thin film layer 110 is formed on the substrate 100. The gallium arsenide-based thin film layer 110 may be formed by a thin film forming method such as an MOCVD method or a molecular beam epitaxy (MBE) method.

Since the buffer layer formed of the gallium arsenide-based thin film layer, especially the gallium arsenide-based thin film layer substituted with nitrogen, has a higher wet etching rate than the gallium nitride layer formed thereon, the gallium nitride epitaxy But also has an advantage of being very easy in the step of separating the layers.

Thin-film layer of such a GaAs series, may be made in addition to pure gallium arsenide, a Group III element such as indium (In), aluminum (Al) to gallium element and a replacement material, and can also be represented by the formula, In _x Al _y Ga _{1 -xy} As (where 0? x, y, x + y? 1). The fraction of indium or aluminum to be added is determined in consideration of the composition of the nitride epitaxial layer 120 to be formed in the subsequent process, the crystal constant, and the coefficient of thermal expansion.

Although the degree of crystallization varies depending on the formation temperature of the thin film layer 110 and the process time, the In _x Al _y Ga _1-xy As thin film layer 110 can be grown at a relatively low temperature of 500 to 700 ° C, Can be obtained. In particular, the In _x Al _y Ga _{1 -x- y} As thin film has a thermal expansion coefficient similar to that of a sapphire substrate, unlike gallium nitride, and has an advantage of minimizing the occurrence of stress caused by a difference in thermal expansion coefficient in a subsequent thermal process .

The thickness of the gallium arsenide-based thin film layer 110 is determined in consideration of a subsequent process in a thickness range of 5 to 10,000 angstroms. Since the thin film layer 110 serves as a buffer layer in a subsequent process, the thin film layer 110 is determined in consideration of the degree of crystallization required for the epitaxial layer 120 to be formed thereon and the characteristics of the finally produced semiconductor device. That is, due to the characteristics of the buffer layer, it is advantageous to form the thin film layer 110 as thin as possible to the extent that the crystallization can be performed. However, when the upper epitaxial layer 120 is formed thick or requires high crystallization, It is necessary that the thickness of the substrate 110 also be thickened accordingly.

Thereafter, as shown in Fig. 2 (c), the In _x Al _y Ga _1-xy As thin film layer 110 is heat-treated in a nitriding atmosphere. The main purpose of the heat treatment of the thin film layer is to accelerate the crystallization of the gallium arsenide type compound and to nitride at high temperature to replace the arsenic element with the nitrogen element to form In _x Al _y Ga _1-xy As _z N _1-z , 0? X, y, x + y? 1, 0 <z <1).

The heat treatment atmosphere is preferably a heat treatment in an NH ₃ atmosphere in order to increase the reaction rate and cause a more stable nitridation reaction. More specifically, an NH ₃ atmosphere is first formed at a temperature of about 500 ° C or higher. In addition, arsenic (As) gas and nitrogen, hydrogen, and the like may be included. The substrate 100 on which the In _x Al _y Ga _1-xy As thin film layer 110 is formed is loaded on a thermal processing apparatus having an NH ₃ atmosphere as described above, and then heat treatment is performed at a temperature of 500 to 1200 ° C .

When the heat treatment is performed in such a nitriding atmosphere, the arsenic element starts to be replaced with the nitrogen element of the same Group 5 element, and a thin film layer of In _x Al _y Ga _{1 -x- y} As _z N _{1 -z} is formed. The crystallized In _x Al _y Ga _1-xy As _z N _{1 -z} thin film layer is denoted by reference numeral 115 to distinguish it from the In _x Al _y Ga _1-xy As thin film layer 110 formed in the previous step.

The heat treatment time is in consideration of the degree of crystallization required, the thickness of the In _x Al _y Ga _1-xy As _z N _{1 -z} thin film layer 115 to be crystallized, the fraction of nitrogen to be substituted, and the like. That is, a rapid thermal annealing (RTA) method, which is a method for minimizing a thermal budget, can be used, and an electric furnace heat treatment method having a relatively long process time can be applied. In addition, the composition ratio between As and N in the thin film layer 115 can be relatively easily adjusted according to the heat treatment temperature and time of the thin film layer. That is, the higher the heat treatment temperature and the longer the time, and the lower the fraction of As contained in the heat treatment atmosphere, the greater the amount of nitrogen to be substituted. The relative wet etch rate of the buffer layer in the case of forming a thin film layer having a high As content, that is, a buffer layer, is high, and thus the substrate and the gallium nitride epitaxial layer can be easily separated in a subsequent process. However, the higher the fraction of As, the smaller the bandgap, which can also absorb a part of the light emitted from the pn junction or the active layer. Therefore, it is desirable to consider the fraction of As in view of these advantages and disadvantages. That is, in the case where the step of separating the substrate is not applied, it is advantageous for the device characteristics to minimize the fraction of As and increase the fraction of the nitrogen component.

If the density and the composition ratio of the crystal are controlled as described above, the stress or tensile force applied to the nitride-based epitaxial film formed in the subsequent process also changes accordingly, so that the stress or tensile force required in the semiconductor device manufacturing process can be adjusted as needed There is an effect that can be.

Thereafter, the growth, the crystallization of _{In x Al y Ga 1 -x- y} As z N 1 -z thin film layer 115, the compound semiconductor epitaxial layer 120 of the nitride series over as shown in Fig. 2 (d) . The nitride-based materials described in this specification include not only gallium nitride (GaN) and compound semiconductors containing the same, but also nitride containing another group III element aluminum (Al) or indium (In) substituted nitride to be. Thus, the epitaxial layer of the GaN-based is _{GaN, AlN, InN, Al x} Ga 1-x N, In x Ga 1-x N, Al x In y Ga 1-y N (0 <x, y in the above &Lt; 1).

On the In _x Al _y Ga _1-xy As _z N _{1 -z} thin film layer 115 having high temperature stability and lattice mismatching through the heat treatment process, the Group III nitride compound semiconductor epitaxial layer, which is a material of the same series, It is possible to reduce interfacial characteristic defects due to lattice mismatch or high-temperature property mismatches, as compared with the case where there is no buffer layer, as well as the case where a conventional buffer layer is present.

When the In _x Al _y Ga _1-xy As _z N _1-z thin film layer 115 is applied as a buffer layer, the process is easier and less costly than the conventional technique, and the upper epitaxial layer 120 ) Is similar to the thermal expansion coefficient and lattice constant, and the chemical and mechanical stability can be maintained in the subsequent crystallization process.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Rather, the invention should be construed as including all modifications that are within the scope of the present invention as defined by the appended claims.

According to an embodiment of the present invention, on a thin film layer of In _x Al _y Ga _1-xy As _z N _{1-z having} high temperature stability and lattice composition, a group III nitride compound semiconductor epitaxial layer, which is a material of the same series, It is possible to reduce the interfacial characteristic defects due to the lattice mismatch between the substrate and the epitaxial layer or the mismatch of the high temperature characteristics.

In particular, even when a buffer layer is formed at a low temperature, it is possible to form a thin film of good crystallinity, so that the burden of crystallization due to a high-temperature heat treatment in a subsequent step can be reduced, and the density and degree of crystallization can be easily controlled. Thus, the deterioration of the characteristics of the epitaxial layer placed on the buffer layer can be minimized.

Since the above characteristics can be improved by a relatively simple modification of the conventional technique, it is possible to produce a semiconductor device which is suitable for mass production of a compound semiconductor device and in particular, does not cause characteristic deterioration due to stress in introduction of a large diameter substrate.

1 is a schematic cross-sectional view in a main process of a method for growing a nitride-based epitaxial layer according to a conventional method.

2 (a) to 2 (d) are schematic cross-sectional views in a main process of a method for growing a nitride-based epitaxial layer according to an embodiment of the present invention.

Claims (14)

In a method for growing a nitride-based epitaxy layer, Forming a thin film layer of gallium arsenide (GaAs) series in which a part of arsenic (As) element is substituted with nitrogen (N) element, on a prepared substrate; And And growing a nitride-based epitaxial layer on the thin film layer, Wherein forming the thin film layer comprises: Growing a gallium arsenide-based thin film layer on the substrate; And And a step of heat treating the substrate on which the thin film layer has been grown in a nitriding atmosphere to replace a part of the arsenic element with a nitrogen element. delete The method according to claim 1, Wherein the step of growing the gallium arsenide-based thin film layer comprises growing the thin film layer to a thickness of 5 to 10000 angstroms. The method according to claim 1, Wherein the annealing step is performed in an atmosphere containing ammonia (NH ₃ ) at a temperature of 500 to 1200 ° C. 5. The method of claim 4, Wherein the heat treatment step is performed in an atmosphere containing an arsenic (As) component. 6. The method of claim 5, Wherein the gallium arsenide-based thin film layer controls the substitution fraction according to a heat treatment time and a partial pressure of an arsenic component contained in the atmosphere in replacing a part of the arsenic component with a nitrogen component. The method according to claim 1, Wherein the gallium arsenide-based thin film layer comprises at least one of indium (In) and aluminum (Al) elements. The method according to claim 1, Wherein the substrate is characterized in that the material material comprises sapphire. The method according to claim 1, Epitaxial layer of the nitride series _{GaN, AlN, InN, Al x} Ga 1-x N, In x Ga 1-x N, Al x In y Ga 1-y N ( from above 0 <x, y <1) &Lt; / RTI &gt; and a material selected from the group consisting of &lt; RTI ID = 0.0 &gt; delete delete delete delete delete

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