KR20150106568A - Method for growing epitaxial layer and semiconductor structure - Google Patents

Abstract

Provided in an embodiment is a method for growing an epitaxial layer, which comprises the following steps: preparing a substrate including protrusions on the surface; amorphizing a part of the protrusions; and growing an epitaxial layer on the substrate.

Description

METHOD FOR GROWING EPITAXIAL LAYER AND SEMICONDUCTOR STRUCTURE < RTI ID = 0.0 >

Embodiments relate to a method of growing an epitaxial layer and a semiconductor structure, and more particularly, to a method and a grown semiconductor structure for reducing the occurrence of crystal defects during growth of an epitaxial layer.

BACKGROUND ART Light emitting devices such as light emitting diodes and laser diodes using semiconductor materials of Group 3-5 or 2-6 group semiconductors have been widely used for various colors such as red, green, blue, and ultraviolet And it is possible to realize white light rays with high efficiency by using fluorescent materials or colors, and it is possible to realize low energy consumption, semi-permanent life time, quick response speed, safety and environment friendliness compared to conventional light sources such as fluorescent lamps and incandescent lamps .

Therefore, a transmission module of the optical communication means, a light emitting diode backlight replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of an LCD (Liquid Crystal Display) display device, a white light emitting element capable of replacing a fluorescent lamp or an incandescent lamp Diode lighting, automotive headlights, and traffic lights.

The light emitting diode and the laser diode (LD) described above are manufactured by growing a semiconductor structure on the surface of a single crystal semiconductor substrate through epitaxial growth.

Since the thin film for the epitaxial layer growth is very difficult to be manufactured into a bulk monocrystal substrate such as an ingot due to the nature of the material, it is difficult to fabricate the epitaxial layer by using the hybrid vapor phase epitaxy (HVPE), the molecular beam epitaxy : MBE) and metal organic chemical vapor deposition (MOCVD). The most widely used method is the metal organic vapor phase growth method.

The epitaxial layer growth method on a single crystal substrate by the metal organic vapor phase epitaxy (MOVPE) method is most widely used in the field of light emitting diodes. When the growth of a single crystal substrate is the same, the process is called homoepitaxy, When the material of the substrate and the substrate are different, it is called heteroepitaxy. Typical epitaxial growth materials include gallium nitride (GaN), aluminum nitride (AlN), and the like.

Sapphire (a-Al2O3) and SiC substrates are typical examples of monocrystalline substrates used for epitaxial layer growth. However, due to the difference in lattice mismatch at the time of thin film growth, misfit dislocation, threading dislocation, A defect such as an Inversion Domain Boundary (IDB) is observed.

Since these defects are very important factors for determining the lifetime and luminous efficiency of the device, various efforts have been made to improve defects. Among them, Epitaxial Lateral Overgrowth (ELOG) is used as a representative method have.

1A is a view showing a conventional light emitting device.

The light emitting structure 120 including the first conductivity type semiconductor layer 122, the active layer 124 and the second conductivity type semiconductor layer 126 is grown on the substrate 110 made of sapphire or the like, A first electrode 162 and a second electrode 164 are formed on the semiconductor layer 122 and the second conductivity type semiconductor layer 126, respectively.

At this time, as shown in the figure, the surface of the substrate 110 may be formed with a concave-convex pattern. When a patterned substrate 110 is used, the density of threading dislocations can be reduced during growth of the epitaxial layer to increase the internal quantum efficiency (MQW), and the active layer 124) toward the substrate 110, thereby improving light extraction efficiency.

However, the conventional light emitting device described above has the following problems.

FIG. 1B is a view showing crystal defects in FIG. 1A.

The irregularities on the surface of the substrate 110 are composed of concave and convex portions, and crystal defects may occur between the epitaxial layer (b) grown on the flat concave portion and the epitaxial layer (a) grown on the convex portion particularly above the convex portion .

That is, when two phases are formed in one single crystal substrate 100 and growth is performed at different speeds and modes, degradation of the epitaxial layer may occur. More specifically, in the case of the above- Dislocations may occur between the epitaxial layer (a) grown in the horizontal direction and the epitaxial layer (b) grown in the flat recess after the nuclei are grown.

The embodiment attempts to reduce the occurrence of crystal defects when growing a semiconductor structure with an epitaxial layer of different materials on a substrate.

An embodiment of the present invention provides a method of manufacturing a semiconductor device, Amorphizing a part of the irregularities of the irregularities; And growing an epitaxial layer on the substrate.

The step of amorphizing a part of the concavities and convexities includes the steps of applying a mask to the surface of the substrate and removing a part of the mask to expose a part of the concavities and convexities, To thereby amorphize the amorphous semiconductor layer.

The step of applying the mask can be carried out so as to cover the recessed portion and the convex portion of the substrate with silicon oxide.

The step of removing the mask may remove the mask covering at least a part of the convex portion of the substrate by a dry etching method.

The amorphizing step may be performed by implanting ions into the exposed convex portions of the substrate.

The substrate is a sapphire substrate, and the step of implanting ions may inject nitrogen into the substrate.

Ions can be implanted at a depth of at least 100 nanometers from the surface of the convex portion of the substrate.

Ions at a density of 1 x 10 < ¹⁷ > / cm < ³ >.

Ions can be injected perpendicular to the upper surface of the convex portion of the irregularities.

Removing the mask, and cleaning and drying the substrate.

The step of applying the mask can grow the mask with the same composition as the epitaxial layer.

The mask can be applied with silicon oxide or silicon oxide.

Another embodiment includes a substrate having a surface with concave and convex portions formed thereon; An amorphous layer formed on the convex portion of the convexo-concave portion; And an epitaxial layer formed on top of the substrate.

The substrate is a sapphire substrate, the epitaxial layer is a GaN layer, and the amorphous layer can be injected with nitrogen ions into the substrate.

The thickness of the amorphous layer may be greater than 100 nanometers.

Ions can be implanted into the amorphous layer at a density of 1 x 10 < ¹⁷ > / cm < ³ >

The thickness of the amorphous layer may be thickest in the upper region of the convex portions of the irregularities.

The method of growing an epitaxial layer according to an embodiment of the present invention and the semiconductor structure grown by the method have an advantage that ions are selectively implanted into a substrate to form an amorphous layer and nucleation of a source material occurs in regions other than the amorphous layer, In the single crystal substrate, one phase is grown at the same speed and mode, crystal defects of the epitaxial layer due to dislocation do not occur, the quality of the epitaxial layer is excellent, and the light extraction efficiency Can be improved.

1A is a view showing a conventional light emitting device,
FIG. 1B is a view showing crystal defects in FIG. 1A,
2A and 2B are diagrams showing the principle of an embodiment of a growth method of an epitaxial layer,
3A to 3F are views showing an embodiment of a method of growing an epitaxial layer,
4 is a view showing an embodiment of a light emitting device.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

In the description of embodiments according to the present invention, in the case of being described as being formed "on or under" of each element, the upper (upper) or lower (lower) or under are all such that two elements are in direct contact with each other or one or more other elements are indirectly formed between the two elements. Also, when expressed as "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

2A and 2B are diagrams illustrating the principle of an embodiment of a method of growing an epitaxial layer.

2A, an amorphous region is formed on the convex and concave portions of a substrate having concave and convex portions formed on the surface thereof, as shown in FIG. 2A, and then the epitaxial layer is grown on the substrate except for the amorphous region, Lt; RTI ID = 0.0 > a < / RTI >

At this time, the nucleation is suppressed in the amorphous region of the substrate, the nuclei are grown from the recess of the substrate, the epitaxial layer is grown through the horizontal growth, and the dislocation density is decreased, so that the epitaxial layer can be stably grown in the horizontal direction.

3A to 3F are views showing an embodiment of a method of growing an epitaxial layer. Hereinafter, one embodiment of a method of growing an epitaxial layer according to the above-described principle will be described with reference to FIGS. 3A to 3F.

As shown in FIG. 3A, a substrate 210 having unevenness on its surface is prepared.

The irregularities are composed of concave and convex portions. The arrangement of the concave portions and the convex portions may be regular or irregular. The shape of the convex portions may be other than the hemispherical shape shown in the drawing, and the convex portions may be arranged in different shapes irregularly. .

As shown in FIG. 3B, the mask 300 is disposed on the surface of the substrate 210.

The mask 300 may be coated to cover both the recess and the recess. In particular, the recess must be shielded by the mask 300 since it is a region where the ion implantation for amorphization is not to be performed.

For example, the mask 300 may be formed by applying silicon nitride, silicon oxide, photoresist, or the like so as to cover both the recessed portion and the convex portion of the substrate 210.

As shown in FIG. 3C, the mask 300 is partially removed to expose most of the convex portions of the substrate 210, but the concave portions of the substrate 210 are not exposed. Through this process, the convex portion of the substrate 210 may be irregularized and amorphous by selective ion implantation described later may be possible.

In the case of a mask made of, for example, silicon oxide, the mask 300 is anisotropically etched to expose only the upper portion of the concavo-convex pattern using a dry etching equipment. The substrate on which only the convex portion on the upper part of the substrate 210 is partially exposed may be cleaned with deionized water and then dried using nitrogen gas.

3B and 3C, the mask 300 is left only on the surface of the concave portion of the substrate 210, but may be applied only to the concave portion of the substrate 210 during the application of the mask 300, The etching process of one mask may be omitted, and when the mask is grown by the same material as the epitaxial layer to be grown later, for example, GaN, the mask may not be removed after the formation of the amorphous layer as well as the selective etching of the mask.

As shown in FIG. 3D, ions 310a are implanted into the exposed surface of the substrate 210. At this time, the ions 310a may be injected into the region where the mask 300 is not disposed, that is, the convex portion, on the substrate 210, and ions may not be injected into the C-plane of the bottom surface of the substrate 210.

The ion may be implanted with, for example, nitrogen (N) ions, the supply density of nitrogen may be 5 x 10 ¹⁷ ions / cm ³ , and the ion implantation energy should be 67.5 KeV . The ion implantation energy can be increased to implant ions larger or heavier than nitrogen ions. At this time, if the ion implantation energy is increased, even if the amount of ions supplied decreases, the ions can be penetrated into the inside of the substrate.

When the amount of nitrogen is less than 1 x 10 < ¹⁷ > atoms / cm < ³ >, the ions can not be penetrated into the substrate 210 and adsorbed only on the surface of the substrate 210 to form an AlN layer. .

When the mask 300 is removed after the ion implantation process is completed, as shown in FIG. 3E, the amorphous layer 310 is disposed on the convex portion of the concave-convex structure of the substrate 210. The amorphous layer 310 is an amorphous layer implanted with ions and the thickness t ₁ of the upper region of the amorphous layer 310 may be thicker than the thickness t ₂ of the lower region. That is, the ions are vertically incident on the upper region of the amorphous layer 310 and injected relatively deeply, and the ions may be injected obliquely into the lower region to be injected relatively shallowly.

The depth at which the ions are implanted may be the thickest in the upper region of the amorphous layer 310, as described above. For example, the thickness t ₁ in the upper region of the amorphous layer 310 may be greater than 100 nanometers, If the depth at which the ions are implanted is shallow, the ions are not sufficiently injected, so that the amorphization does not occur and the AlN layer can be formed as described above.

The above-described values are obtained when ions are vertically implanted into the surface at the top of the convex portion of the substrate 210, and when the oblique implantation is performed, the implantation depth of the ions may be shallower, so that a larger number of ions and / Energy may be needed.

Alternatively, the substrate 210 may be washed with acetone, methanol, pure water, and then dried using a nitrogen gas, for example, .

Then, an epitaxial layer may be grown on the substrate 210 as shown in FIG. 3F. At this time, nucleation of the epitaxial layer may not occur in the amorphous layer 310. That is, the region in which the ions are selectively implanted in the substrate 210 is amorphized due to a shock due to the impact of the lattice, so that even if a source for epitaxial layer growth is supplied, nucleation may not occur.

The epitaxial layer is grown by depositing a substrate 210 of FIG. 3E in a MOCVD reactor, forming low-temperature gallium nitride (GeN) nuclei, and then using a horizontal growth method to grow a gallium nitride (GaN) .

At this time, horizontal growth occurs in the other region of the substrate 210 except the amorphous layer 310, that is, in the recessed structure, after the nucleation, and the epitaxial layer can be grown in all the recesses and convex portions of the substrate 210.

As described above, since the epitaxial layer is horizontally grown after nucleation only in the recesses of the substrate 210, crystals that can be generated when the epitaxial layer is grown after nucleation and nucleation in the recesses and recesses of the conventional substrate, respectively Since defects do not occur, the quality of the epitaxial layer can be improved as compared with the prior art.

4 is a view showing an embodiment of a light emitting device.

The light emitting device 200 according to the embodiment may include the substrate 210, the amorphous layer 310, the light emitting structure 220, the first electrode 262, and the second electrode 264, It is a semiconductor structure.

The substrate 210 may be formed of a material suitable for semiconductor material growth or a carrier wafer, may be formed of a material having excellent thermal conductivity, and may include a conductive substrate or a cut-away substrate. For example, at least one of sapphire (Al ₂ O ₃ ), SiO ₂ , SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge and Ga ₂ O ₃ can be used.

The lattice mismatch between GaN and AlGaN superfine light may occur when the substrate 210 is formed of sapphire or the like and the light emitting structure 220 in which GaN or AlGaN is grown as an epitaxial layer is disposed on the substrate 210. [ Melt-back, crack, pit, surface morphology, and the like, which deteriorate the crystallinity, because of the very large difference in the thermal expansion coefficient between them. A buffer layer (not shown) may be formed using AlN or the like, or an undoped semiconductor layer (not shown) may be formed.

A concave-convex structure may be formed on the surface of the substrate 210 to refract the light emitted from the light emitting structure 220 to the substrate 210.

The amorphous layer 310 is an amorphized region formed by implanting ions into the substrate 210. The amorphous layer 310 may be formed on the surface of the convex portion of the substrate 210. When measured using a TEM, The contrast difference can be observed in another area of the display unit 210. When analyzing with XPS or the like, AlN or the like can be detected when nitrogen ions are injected.

The light emitting structure 120 may include an epitaxial layer of GaN or the like. More specifically, the light emitting structure 120 may include a first conductive semiconductor layer 122, an active layer 124, and a second conductive semiconductor layer 126.

The first conductive semiconductor layer 122 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a first conductive dopant to form a first conductive semiconductor layer. The first conductivity type semiconductor layer 122 is made of a semiconductor material having a composition formula of Al _x In _y Ga _(1-xy) N (0? X? 1, 0? _Y? 1, 0? _X + And may be formed of any one or more of AlGaN, GaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP, for example.

When the first conductive semiconductor layer 122 is an n-type semiconductor layer, the first conductive dopant may include n-type dopants such as Si, Ge, Sn, Se, and Te. The first conductive semiconductor layer 122 may be formed as a single layer or a multilayer, but is not limited thereto.

The active layer 124 is disposed on the upper surface of the first conductive semiconductor layer 122 and may have a multi quantum well (MQW) structure. In order to relax the piezoelectric field, a quantum well A first doped region and a second doped region may be formed as described below.

InGaN / InGaN, InGaN / InGaN, AlGaN / GaN, InAlGaN / GaN, GaAs (InGaAs), and AlGaN / AlGaN / InGaN / / AlGaAs, GaP (InGaP) / AlGaP, but is not limited thereto. The well layer may be formed of a material having an energy band gap smaller than the energy band gap of the barrier layer.

The second conductive semiconductor layer 126 may be formed of a semiconductor compound on the surface of the active layer 124. The second conductive semiconductor layer 126 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a second conductive dopant. The second conductivity type semiconductor layer 126 may be a semiconductor material having a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + And may be formed of any one or more of AlGaN, GaN AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

The second conductive type semiconductor layer 126 may be a second conductive type semiconductor layer doped with a second conductive type dopant. If the second conductive type semiconductor layer 126 is a p-type semiconductor layer, the second conductive type dopant may be Mg , Zn, Ca, Sr, Ba, and the like. The second conductive semiconductor layer 126 may be formed as a single layer or a multilayer, but the present invention is not limited thereto.

A part of the active layer 124 and the first conductivity type semiconductor layer 122 are mesa-etched from the second conductivity type semiconductor layer 126 in a part of the light emitting structure 120 to form the first conductivity type semiconductor layer 122 The surface is exposed.

A light transmitting conductive layer (not shown) may be disposed on the second conductive semiconductor layer 126. The light transmitting conductive layer may be formed of ITO (Indium-Tin-Oxide) The current spreading characteristic of the transmissive conductive layer 250 is poor and the current can be supplied from the second electrode 160 to the transmissive conductive layer 250.

The first electrode 162 and the second electrode 160 are disposed on the exposed surface of the first conductive type semiconductor layer 122 and the second conductive type semiconductor layer 126, The two electrodes 160 may be formed as a single layer or a multilayer structure including at least one of aluminum (Al), titanium (Ti), chrome (Cr), nickel (Ni), copper (Cu) , Respectively, to a wire (not shown).

Although not shown, a passivation layer may be formed around the light emitting structure 220. The passivation layer may be formed of an insulating material, specifically, an oxide or a nitride, and more specifically, a silicon oxide (SiO ₂ ) layer, an oxynitride layer, and an aluminum oxide layer.

The light emitting devices described above can be mounted in the light emitting device package in one or a plurality of them, but the invention is not limited thereto.

The light emitting device package described above can be used in an illumination system, for example, in an image display device and a lighting device.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

100, 200: light emitting device 110, 210:
120, 220: Light emitting structure
122, 222: first conductivity type semiconductor layers 124, 224: active layer
126, 226: second conductivity type semiconductor layer 162, 262: first electrode
164, 264: second electrode 300: mask
310: amorphous layer 310a: ion

Claims (17)

Preparing a substrate having surface irregularities formed thereon;
Amorphizing a part of the concavities and convexities; And
And growing an epitaxial layer on the substrate. The method according to claim 1,
Wherein the step of amorphizing a part of the concavities and convexities comprises:
Applying a mask to a surface of the substrate;
Removing a part of the mask to expose a part of the concavities and convexities,
And treating the exposed portion of the substrate to amorphize the epitaxial layer. 3. The method of claim 2,
Wherein applying the mask comprises:
Wherein the silicon oxide is applied so as to cover the recessed portion and the convex portion of the substrate. 3. The method of claim 2,
Wherein the removing the mask comprises:
And removing the mask covering at least a part of the convex portion of the substrate by a dry etching method. 3. The method of claim 2,
Wherein the amorphizing step comprises:
And implanting ions into the exposed convex portions of the substrate. 6. The method of claim 5,
Wherein the substrate is a sapphire substrate, and the step of implanting ions includes injecting nitrogen into the substrate. 6. The method of claim 5,
Wherein the ions are implanted at a depth of at least 100 nanometers from the surface of the convex portion of the substrate. 6. The method of claim 5,
Wherein the ions are implanted at a density of 1 x 10 < ¹⁷ > / cm < ³ >. 6. The method of claim 5,
And implanting the ions perpendicularly to the upper surface of the convex portions of the irregularities. 3. The method of claim 2,
Removing the mask, and cleaning and drying the substrate. ≪ Desc / Clms Page number 19 > 3. The method of claim 2,
Wherein applying the mask comprises:
Wherein the mask is grown in the same composition as the epitaxial layer. 3. The method of claim 2,
Wherein said mask is applied with silicon nitride or silicon oxide. A substrate having an uneven surface formed thereon;
An amorphous layer formed on the convex portion of the convexo-concave portion; And
And an epitaxial layer formed on the substrate. 14. The method of claim 13,
Wherein the substrate is a sapphire substrate, the epitaxial layer is a GaN layer, and the amorphous layer is formed by implanting nitrogen ions into the substrate. 14. The method of claim 13,
Wherein the amorphous layer has a thickness of at least 100 nanometers. 14. The method of claim 13,
Wherein the amorphous layer is doped with ions at a density of 1 x 10 < ¹⁷ > / cm < ³ > 14. The method of claim 13,
Wherein the thickness of the amorphous layer is the thickest in the upper region of the convex portion of the irregularities.

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