KR101316118B1 - Method of fomring nitride semiconducter layer on a substrate and lihgt emitting diode having the layer - Google Patents

Abstract

The present invention relates to a method of forming a nitride semiconductor layer on a substrate, by using a method of forming a recess in a GaN-based epi layer on a substrate and at least partially transversely growing a GaN-based material within the recess, There is a technical problem to provide a method for implementing a good flat surface, which can greatly reduce the defect density without including an unnecessary dielectric layer therein.

According to an aspect of the present invention, a GaN-based first epitaxial section is formed on the upper surface of the substrate in a layered manner, a plurality of recesses are formed on the upper surface of the first epitaxial portion, and within the recesses. Through at least partial lateral growth, a GaN-based second epitaxial layer is formed in the concave portions, and a GaN-based third epitaxial layer is layered on an upper surface of the first and second epitaxial surfaces adjacent to each other. A method of forming is provided.

Epi, Sapphire, Transverse, Defect, GaN, Sapphire, Pattern

Description

FIELD OF THE INVENTION A method of forming a nitride semiconductor layer on a substrate, and a light emitting diode having the same, and a light emitting diode having the same.

1 is a cross-sectional view showing a sapphire substrate used in the embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a state in which an epitaxial layer of GaN is formed on an upper surface of the sapphire substrate shown in FIG. 1. FIG.

3 and 4 are cross-sectional views for explaining a step of forming a mask on the upper surface of the epi part shown in FIG. 2 and forming a plurality of recesses on the upper surface of the epi part using the mask.

FIG. 5 is a sectional view for explaining a step of forming another epitaxial part in the concave part shown in FIG. 4. FIG.

6 is a cross-sectional view illustrating a nitride semiconductor layer formed on a substrate in accordance with an embodiment of the present invention.

<Code Description of Main Parts of Drawing>

10: sapphire substrate 12: pattern

22: first epitaxial 222: recess

24: Second Epi 26: Third Epi

The present invention relates to a method of forming a nitride semiconductor layer on a substrate and a light emitting diode having the nitride semiconductor layer.

In general, GaN-based light emitting diodes are manufactured by growing nitride semiconductor crystals on a sapphire substrate or a heterogeneous substrate such as SiC. In particular, sapphire substrate is most commonly used because of the advantage that the quality is good compared to the SiC substrate and the price is also appropriate.

However, the sapphire substrate and the nitride semiconductor layer formed thereon have a large difference in coefficient of thermal expansion and lattice constant, causing high defect density. These dense defects exist in the form of propagation potentials or cracks, which propagate to the growing layer when another nitride semiconductor layer is grown thereon. The propagation potential as described above reduces the electron mobility, and also causes the performance of the light emitting diode to be degraded in that it serves as a passage for non-light emitting sites or current leakage of the light emitting diode. Therefore, forming nitride semiconductor layers on the nitride substrate has been considered, but in the current technology, there is a big limitation in manufacturing a large-area substrate made of nitride single crystal.

Conventionally, a dielectric layer defining an opening for exposing the substrate is formed on a surface of a substrate of sapphire or SiC material, the GaN-based material is vertically grown in the opening, and the GaN-based material is laterally stacked over the dielectric layer after the opening is filled. A technique for forming a GaN epitaxial layer having a low defect density by directional growth has been proposed. According to the conventional technology proposed, since the same type of GaN semiconductor layers are formed on the surface of the GaN epitaxial layer, the defect density in the GaN based semiconductor layer to be grown can be reduced.

However, the above conventional technique causes a steep inclination between two neighboring portions where lateral growth occurs, and this inclination makes it impossible to obtain a flat substrate surface. In addition, since the conventional technology inevitably includes a heterogeneous dielectric material, its performance is poor and its manufacturing process is complicated.

The present invention utilizes a method of forming a plurality of recesses in a GaN-based epi layer on a substrate and at least partially transversely growing a GaN-based material within the recesses, thereby reducing defect density without including unnecessary dielectric layers therein. There is a technical problem to provide a light emitting diode including the nitride semiconductor layer growth method and a method of growing a nitride semiconductor layer that can be greatly reduced, a good flat surface.

According to an aspect of the present invention, a GaN-based first epitaxial section is formed on the upper surface of the substrate in a layered manner, a plurality of recesses are formed on the upper surface of the first epitaxial portion, and within the recesses. At least in part through lateral growth, a GaN-based second epitaxial layer is formed in the concave portions, and a GaN-based third epitaxial layer is layered on top surfaces of the first and second epitaxial surfaces adjacent to each other. A method of forming is provided.

Preferably, the substrate is a sapphire substrate formed with an uneven pattern on the upper surface.

Preferably, the forming of the plurality of recesses on an upper surface of the first epitaxial part includes forming a mask having a plurality of openings on an upper surface of the first epitaxial part, and a part of the first epitaxial part corresponding to the openings. Etching to form a plurality of recesses.

Advantageously, forming said second epitaxial portion comprises removing said mask from an upper surface of said second epitaxial portion after said recesses are filled to a predetermined height in said recesses. In this case, the second epitaxial portion is preferably formed in the concave portions such that its upper surface is coplanar with the upper surface of the first epitaxial portion.

The mask is preferably made of silicon oxide or silicon nitride.

According to another aspect of the present invention, the GaN-based first epitaxially formed on the upper surface of the substrate, a plurality of recesses are formed on the upper surface, and through the lateral growth made at least partially within the recesses, A nitride semiconductor layer comprising a GaN-based second epitaxial part filled in concave portions, and a GaN-based third epitaxial layer formed on a top surface of the first and second epitaxial surfaces adjacent to each other; A light emitting diode is provided.

Example

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that the spirit of the invention to those skilled in the art can fully convey. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, and the like of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

6 is a cross-sectional view illustrating nitride semiconductor layers formed on a substrate according to the present invention. Referring to FIG. 6, a plurality of epitaxial parts 22, 24, and 26 are formed on the substrate 10.

According to the exemplary embodiment of the present invention, the substrate 10 is made of sapphire, and an uneven pattern 12 is formed on an upper surface thereof. The pattern 12, when used in the manufacture of a light emitting diode, is caused by a difference in refractive index between the substrate 10 (hereinafter referred to as a sapphire substrate) and a nitride semiconductor layer formed thereon and thereby an increase in total internal reflection. Contributes greatly to mitigating light extraction efficiency degradation. Although the cross-sectional shape of the pattern 12 is shown to be approximately square in FIG. 6, it may be a circular, trapezoidal or other geometric pattern.

On the upper surface of the sapphire substrate 10, that is, the pattern 12, a GaN-based first epitaxial portion 22 made of GaN-based semiconductor crystals is formed in a layered manner with respect to the sapphire substrate 10. In addition, a plurality of recesses 222 are formed on an upper surface of the first epitaxial part 22. Each of the recesses 222 has a bottom surface 222a and a side surface 222b. It is preferable that the cross-sectional shape of each of the recesses 222 is rectangular, but other shapes are also possible.

GaN-based second epitaxial portions 24 formed by growing GaN-based materials in the transverse and vertical directions are formed in the recesses 222. The second epitaxial portion 24 may lower the density of defects such as dislocations or cracks by the lateral growth mainly formed from the side surface 222b of the concave portion 222. In this case, it is preferable that the upper surface of the second epitaxial part 24 is located on the same plane as the upper surface of the first epitaxial part 22, whereby the third epitaxial part 26 thereon is disposed. It is easy to form to have a flat surface.

The third epitaxial part 26 is made of GaN and is commonly formed on the upper surface of the first epitaxial part 22 and the upper surface of the second epitaxial part 24. In addition, an upper surface of the third epitaxial part 26 is formed of an approximately flat surface, and the remaining nitride semiconductor layers forming light emitting cells of the light emitting diodes are sequentially formed on the upper surface of the third third epitaxial part 26, for example. When the third epitaxial part 26 is an N-GaN semiconductor layer, an active semiconductor layer and a P-GaN semiconductor layer are sequentially formed on the third epitaxial part 26.

According to the embodiment of the present invention, although the growth surface for the nitride semiconductor layers is GaN-based, it can be formed in a large area, a plurality of light emitting cells are formed on one substrate and the plurality of light emitting cells are AC power It can be usefully used to manufacture an AC light emitting diode operated by. As described above, the AC light emitting diode is disclosed in International Publication WO2004 / 023568 (A1) by SAKAI et. Al. Under the title of LIGTH-EMITTING DEVICE HAVING LIGHT-EMITTING ELEMENT. There is a bar.

The first, second and third epitaxial parts may be formed by growing a GaN-based material having Al _x In _y Ga _{1 −x− y} N (0 ≦ x, y, x + y ≦ 1). In addition, the first, second, and third epi portions may be made of the same component GaN-based material, and may be made of other components GaN-based material.

A method of forming a nitride semiconductor layer according to an embodiment of the present invention will now be described with reference to FIGS. 1 to 6.

First, a sapphire substrate 10 as shown in FIG. 1 in which a pattern 12 is formed on an upper surface is prepared. The pattern 12 serves to improve light extraction efficiency in the light emitting diode. Then, as illustrated in Figure 2, to a GaN-based material on the upper surface of the sapphire substrate 10 is epitaxially grown (epitaxial), Al _x In _y Ga _{1 -x- y} N (0≤x, y, x A first epitaxial part 22 having + y ≦ 1) is formed.

3, a mask 30 made of silicon oxide or silicon nitride having a plurality of openings 32 is formed on the first epitaxial portion 22. In this case, forming the opening 32 of the mask 30 and forming the concave portion 222 on the first epitaxial part 22, which is a subsequent process, may be performed continuously.

The first epitaxial part 22 is exposed to the outside by the opening 32, and a plurality of concave parts 222 as illustrated in FIG. 4 are formed by etching the exposed part. 1 may be formed on the surface of the epitaxial part 22. Each of the recesses 222 has a bottom surface 222a and a side surface 222b, and in particular, from the side surface 222b the lateral growth of the second epitaxial portion 24 (see FIG. 5) described below It is mainly done.

Said second epitaxial portion (24) is made of a material which may be represented by _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), such as that illustrated in Figure 5 The upper surface of the first epitaxial part 22 is formed to grow in the concave part 222 and form a substantially same plane as the upper surface of the first epitaxial part 22. Next, the mask 30 located on the upper surface of the first epitaxial part 22 is removed from the upper surface of the first epitaxial part 22. Here, the first epitaxial part 22 and the second epitaxial part 24, in which careful consideration of defect density is particularly required, have a coarse growth method, that is, a 3D (3D) growth method, which can reduce the defects. The third epitaxial part 26 (refer FIG. 6) formed after that is formed in the compact growth method which is easy to obtain the flat surface, ie, the 2D (2D) growth method. The conditions of 2D growth and the conditions of 3D growth can be determined by the pressure conditions and / or the amount of Ga. In particular, 3D growth is mainly performed under relatively high pressure conditions.

A common upper surface of the mask 30, the first and second epitaxial portion (22, 24) is roughly removed, and a flat surface, on top of that, Al _x In _y Ga _{1 -x- y} N (0≤x, A third epitaxial part 26 with y, x + y ≦ 1) is formed. As mentioned above, the third epitaxial part 26 is preferably densely grown by a 3D growth method.

When the substrate described in the above embodiments and the nitride semiconductor layer formed thereon are used for manufacturing the light emitting diode, the light emitting diode can be manufactured with fewer defects, lower internal stress, and excellent surface smoothness.

In the manufacture of light emitting diodes, the present invention utilizes a method of forming recesses in a GaN-based epilayer on a substrate, particularly a sapphire substrate on which a pattern is formed, and at least partially laterally growing a GaN-based material within the recesses. The defect density can be greatly reduced without unnecessary dielectric layers contained therein, and a nitride semiconductor layer having a good flat surface can be formed on the substrate.

Claims (11)

Forming a GaN-based first epitaxial layer on an upper surface of the substrate; Forming a mask having an opening on an upper surface of the first epitaxial portion to form a plurality of recesses in an area corresponding to the opening; Forming a GaN-based second epitaxial portion in the recesses, through lateral growth at least partially formed in the recesses; Removing the mask and forming a GaN-based third epitaxial layer on an upper surface of the first and second epitaxial portions adjacent to each other; A method of forming a nitride semiconductor layer. The method of forming a nitride semiconductor layer according to claim 1, wherein the substrate is a sapphire substrate having an uneven pattern formed on an upper surface thereof. The method of claim 1, wherein the forming of the plurality of recesses on the upper surface of the first epi, And etching away a portion of the first epitaxial part corresponding to the opening to form the plurality of recesses on the top surface of the first epitaxial part. The method of claim 3, wherein the forming of the second epitaxial portion comprises removing the mask from an upper surface of the first epitaxial portion after the second epitaxial portion is filled to a predetermined height in the recesses. A method of forming a nitride semiconductor layer. The method of claim 1, wherein the second epitaxial portion is formed in the concave portions such that an upper surface thereof is coplanar with an upper surface of the first epitaxial portion. The method of claim 3, wherein the mask is made of silicon oxide or silicon nitride. The method of claim 1, wherein the third epitaxial part is formed by coarse crystal growth compared to the first and second epitaxial parts. A first epitaxial portion formed of GaN based on a top surface of the substrate and having a plurality of recesses formed thereon; A GaN-based second epitaxial portion formed by filling the concave portions through lateral growth at least partially formed in the concave portions; A third epitaxial layer formed on a top surface of the first and second epitaxial portions adjacent to each other; Including, And the third epitaxial part has a nitride semiconductor layer formed on the second epitaxial part. The light emitting diode of claim 8, wherein the substrate is a sapphire substrate having an uneven pattern formed on an upper surface thereof. The light emitting diode of claim 8, wherein the second epitaxial portion is formed in the concave portions such that an upper surface thereof is coplanar with an upper surface of the first epitaxial portion. The light emitting diode of claim 8, wherein the entirety of the second epitaxial portion has a nitride semiconductor layer having a top surface coplanar with the top surface of the first epitaxial portion.

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