KR20080017173A - Fabrication method of nitride semiconductor light emitting device - Google Patents

Abstract

A fabricating method of a nitride semiconductor light emitting device is provided to suppress a merged effect of a pyramid crystal structure by adjusting a window interval of a mask. A mask(23) having windows is formed on an upper surface of a base layer(22) including a first conductive type nitride semiconductor. A first conductive type nitride semiconductor crystal(24) of a hexagonal pyramid structure having an inclined crystal surface to an upper surface of the base layer is selectively grown on each of base layer regions exposed by the windows. An active layer(25) and a second conductive type nitride semiconductor layer(26) are sequentially grown on a surface of the first conductive type nitride semiconductor crystal. The mask is divided into at least two regions. The windows positioned on at least two regions are arranged at different intervals.

Description

TECHNICAL MANUFACTURING METHOD OF NITRIDUM SEMICONDUCTOR LIGHT EMITTING DEVICE {FABRICATION METHOD OF NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

1A and 1B are perspective and partial detailed views of a conventional hexagonal pyramidal nitride light emitting device, respectively.

2A to 2D are cross-sectional views illustrating a method of manufacturing a hexagonal pyramidal nitride light emitting device according to one embodiment of the present invention, respectively.

3A to 3C are plan views showing masks of various patterns that can be employed in the present invention, respectively.

4 is a side cross-sectional view showing an example of a nitride light emitting device that can be manufactured from the structure of FIG. 2d.

<Code Description of Main Parts of Drawing>

11,21: substrate 12,22: first conductivity type nitride base layer

13,23: mask W: Windows

14,24: first conductivity type nitride crystal structure

15,25: active layer 16,26: second conductivity type nitride semiconductor layer

27: transparent electrode layers 29a, 26b: first and second electrodes

The present invention relates to a nitride semiconductor light emitting device, and more particularly to a method of manufacturing a nitride light emitting device having a plurality of hexagonal pyramidal light emitting structure using the selective growth method.

Research into semiconductor light emitting devices has been actively conducted as a new light source to replace bulb-type bulbs and fluorescent lamps using filaments. Recently, a method of providing a high quality nitride light emitting device by forming a hexagonal pyramid light emitting structure using a selective growth method has been developed.

The nitride single crystal obtained by the selective growth method has a large number of defects that grow in the horizontal direction during the growth process in the lateral direction and thus hardly affects the active layer, and the hexagonal pyramid-shaped LED structure obtained by the selective growth method has a nonpolar plane. Having a photographic side, the piezo-electric field effect can be mitigated. In addition, from the geometric point of view, the hexagonal pyramid-shaped LED structure has a wider effective light emitting area compared to the same area due to the inclined side surface, and therefore, an improvement effect of luminance characteristics can be expected.

However, in the process of forming a plurality of hexagonal pyramidal light emitting structure arrays for nitride light emitting devices, there is a problem that relatively overgrowth occurs in a specific region due to the difference in the gradient of the source gas for nitride growth in the reaction chamber. This problem can be explained with reference to Figs. 1A and 1B.

1A shows an array of hexagonal pyramid crystal structures 14 selectively grown on base layer 12. On the substrate 11, a base layer 12 of a first conductivity type nitride is formed. A mask 13 having a plurality of windows W formed on the base layer 12 is formed, and the first conductivity type nitride crystals 14 having a plurality of hexagonal pyramid structures are grown through the windows W.

In this selective growth process, since the source gas for nitride growth may be preferentially provided in the corner region rather than the center region, as shown in FIG. 1A, the hexagonal pyramid crystal structure 14 in the corner region is more than in the center region. Can grow at a rapid rate.

As a result, a merged area M in which adjacent hexagonal pyramid crystal structures 14 are connected to each other may be formed in a region having a high growth rate such as in an edge region. This merge region M is very low in crystallinity and may even have voids or the like.

As a result, as shown in FIG. 1B (sectional view of region A of FIG. 1A), the thickness or In content of the active layer 15 subsequently grown on the hexagonal pyramid crystal structure 14 surface becomes uneven, and the active layer 15 is formed on the merge region M. FIG. ) May not be properly grown, which may cause serious short defects in direct contact with the first conductive nitride layer 16, which is the hexagonal pyramid crystal structure 14, which is the second conductive nitride semiconductor.

The present invention is to solve the above problems of the prior art, an object thereof is to provide a method for manufacturing a nitride semiconductor light emitting device improved the arrangement of the windows for a plurality of hexagonal pyramidal light emitting structure in consideration of the growth rate difference according to the region. It is.

In order to achieve the above technical problem, the present invention

Forming a mask having a plurality of windows on an upper surface of the base layer formed of a first conductivity type nitride semiconductor, and forming a mask having a crystal plane inclined with respect to the upper surface of the base layer on each of the base layer regions exposed to the plurality of windows. Selectively growing a first conductivity type nitride semiconductor crystal and sequentially growing an active layer and a second conductivity type nitride semiconductor layer on a surface of the first conductivity type nitride semiconductor crystal, wherein the mask comprises at least two regions The window is located in the at least two areas is provided with a nitride semiconductor light emitting device manufacturing method, characterized in that each arranged to have a different interval.

The at least two regions of the mask include a first region adjacent to the supply position of the nitride source gas and a second region spaced apart from the supply position of the nitride source gas, wherein the window located in the first region is the It may be arranged to have a larger interval than the interval of the window located in the second area.

In addition, when the at least two regions of the mask include a first region adjacent to the edge region of the mask and a second region surrounded by the first region, the window located in the first region may be the second region. It may be arranged to have a larger interval than the interval of the window located in the area.

In this case, the windows located in the first region are preferably arranged to have a spacing 1.2 to 3 times larger than the spacing of the windows located in the second region.

If necessary, the plurality of windows may be arranged such that the distance gradually decreases along the center direction of the edge region of the mask. In addition, the plurality of windows positioned in the at least two regions may be formed to have the same size as each other.

In a specific embodiment of the present invention, forming a transparent conductive layer on the second conductivity type nitride semiconductor layer, performing a mesa etching so as to expose a region of the upper surface of the base layer, and the exposed base layer The method may further include forming first and second electrodes in one region of an upper surface and one region of the light transmissive conductive layer, respectively.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail.

2A to 2D are cross-sectional views illustrating a method of manufacturing a hexagonal pyramidal nitride light emitting device according to one embodiment of the present invention, respectively.

As shown in FIG. 2A, the method may begin with forming a base layer of a first conductivity type nitride semiconductor on a substrate.

The substrate 21 usable in this embodiment may be made of a material selected from the group consisting of sapphire, SiC, Si, ZnO, MgAl ₂ O ₄ , MgO, LiAlO ₂ , Ga ₂ O ₃ and LiGaO ₂ . A base layer 22 made of a first conductivity type nitride semiconductor crystal is formed on the substrate 21. Although not shown, a low temperature nitride buffer layer (not shown) such as AlN or GaN may be additionally formed on the surface of the substrate 21 on which the base layer 22 is formed.

Subsequently, as shown in FIG. 2B, a mask 23 having a plurality of windows W is formed on the upper surface of the base layer 22.

The mask 23 is not limited thereto, but may be formed of a silicon oxide film or a silicon nitride film. The plurality of windows W formed in the mask 13 define a region in which nitride semiconductor crystals (see 24 in FIG. 2C) of the hexagonal pyramid start to grow.

The windows W formed in the mask 23 employed in the present invention are arranged to have different intervals. In the present embodiment, the plurality of window W arrays have different spacings d1> d2 in the first region I and the second region II therein, which are defined as adjacent edges of the mask 23. Is arranged to have In the first region I of the mask 23, a source gas for nitride growth is preferentially provided than the second region II of the mask 13, so that a lot of reaction occurs and the second region II is relatively in the second region II. Since the amount of source gas that reaches is reduced, the nitride single crystal in the first region (I) grows at a higher speed than the speed in the second region (II).

In order to prevent the merging phenomenon due to the growth rate, the plurality of windows W may have a distance d1 of a window located in the first region I and a distance d2 of a window located in the second region II. Is arranged to be greater than). The window (W) may be formed to have the same size (S1 = S2), that is, the same diameter in the case of a circular, without being separated by the area, but is not limited thereto.

Next, as shown in FIG. 2C, a first conductivity type nitride semiconductor crystal 24 having a hexagonal pyramid structure is selectively grown in each of the base layer 23 regions exposed to the plurality of windows W. As shown in FIG. Here, the first conductivity type nitride semiconductor crystal 24 of the hexagonal pyramid structure has a crystal plane inclined with respect to the upper surface of the base layer 22, the inclination angle can be appropriately controlled according to the growth conditions such as the growth rate.

As described above, even in the same growth conditions, the hexagonal pyramid crystal structure 24 grown in the first region (I) having a high growth rate is relatively hexagonal pyramid crystal structure 24 growing in the second region (II). Even if it is grown to have a size of, the distance d1 of the window located in the first area I is arranged to have a larger distance d2 than the second area II, as described above in FIG. 2B. The possibility that the hexagonal pyramid crystal structures 24 of (I) are connected to each other can be greatly reduced.

The window spacing d1 of the first region I may be overgrown in the first region I even though the window spacing d1 proceeds according to the growth conditions matched by the desired hexagonal pyramid crystal structure 24 in the second region II. It is set so that the pyramid crystals 24 are not connected to each other. Although the window spacing d1 of the first region I is somewhat different depending on the reactor and the overall growth area and the process conditions, the window W of the first region I is preferably the second. It may be arranged to have an interval d1 that is 1.2 to 3 times larger than the window interval d2 of the region II.

As shown in FIG. 2D, the active layer 25 and the second conductivity type nitride semiconductor layer 26 are sequentially grown on the surface of the first conductivity type nitride semiconductor crystal 24.

In this embodiment, since the first conductivity type nitride crystals 24 having a hexagonal pyramid structure may not be connected to each other by adjusting the window spacing of the mask 23, the active layer 25 formed thereon is a nonpolar plane. It can be stably formed on the inclined surface, and the second conductivity type nitride semiconductor layer 26 formed on the active layer 25 is also not shorted with the first conductivity type nitride crystal structure 25 as illustrated in FIG. Can be.

The mask 23 employed in this embodiment can be understood in the form of a mask 33 similar to FIG. 3A. That is, the mask 33 shown in FIG. 3A has a window W of a predetermined size S exposing the first conductivity type nitride semiconductor layer 32, and the first region I adjacent to the corner and the first region I and its first portion. It is divided into 2nd area | region II surrounded by 1 area | region I. As described above, in the first region (I), since the amount of source gas for nitride growth is easily reached in comparison with the second region (II), the growth rate may proceed rapidly. Due to this difference in growth rate, in order to prevent interconnection of hexagonal pyramid crystal structures grown in the first region (I), the window (W) located in the first region (I) is spaced apart from the second region (II). It is formed to have an interval d1 larger than (d2).

It can be understood that the design criteria related to the spacing of the windows in the present invention depend on the growth rate difference due to the gradient of the source gas in the reaction chamber. Since the nonuniform growth rate in the total area may vary depending on the shape and size of the reaction equipment, the growth conditions and the growth area, the window arrangement in the mask according to the present invention may be implemented in various forms to suit the conditions.

Another example is shown in FIG. 3B. The mask 43 has a window W of a predetermined size S exposing the first conductivity type nitride semiconductor layer 42. In the mask 43 according to the present example, when the source gas supply path for the reaction is located on one side of the substrate having a relatively large growth area, the concentration gradient of the source gas is adjacent to the source gas supply path. Focused on (I), it will show a rapid growth rate in the first region (I), while the second region (II), which is relatively far from the source gas supply path, will exhibit a relatively slow growth rate. Therefore, as shown in FIG. 3B, the distance d1 of the window located in the first area I adjacent to the supply path may be larger than the window distance d2 located in the other second area II.

In addition, the mask according to the present invention may be divided into three or more regions as shown in FIG. 3C and may be designed to have different window spacings in each region. Similarly to the previous example, the mask 53 shown in FIG. 3C also has a window W of constant size S exposing the first conductivity type nitride semiconductor layer 52.

The window arrangement of the mask 53 can be usefully employed in a nitride semiconductor device manufacturing process using a substrate having a relatively large area. That is, the mask 53 shown in FIG. 3C is divided into first to third regions I, II, and III in the order from the corner to the center region. The first region I is the region closest to the corner and is the region having the fastest growth rate, and is arranged such that its window spacing d1 also has the largest spacing. In addition, the growth rate in the second region (II) is faster than in the center region of the third region (III) even though the growth rate is smaller than the growth rate in the first region (I). It has a spacing d2 smaller than (d1) but larger than the window spacing d3 of the third region III.

As illustrated in FIG. 3C, when the difference in growth conditions in the total growth area is required to be further subdivided, the window gap may be further subdivided. Further, the mask may be designed such that the window spacing gradually decreases along the smallest position at the position where the source supply amount is high. For example, if necessary, the mask may be designed such that the window spacing gradually decreases from the edge area to the center area.

The nitride semiconductor light emitting structure manufactured as described above may be implemented as a light emitting device having various types of electrode array structures. As an example, FIG. 4 shows a nitride semiconductor light emitting device 20 that can be manufactured from the structure of FIG.

The nitride semiconductor light emitting device 20 shown in Fig. 4 can be obtained from a nitride semiconductor light emitting structure having a hexagonal pyramid structure obtained in Fig. 2D.

More specifically, after the light-transmissive conductive layer 27 is formed on the second conductivity type nitride semiconductor layer 26 of the light emitting structure shown in FIG. 2D, mesa etching is performed on a portion of the first conductivity type. One region of the upper surface of the base layer 22, which is a nitride semiconductor, is exposed. Subsequently, first and second electrodes 29a and 29b are formed in one region of the exposed upper layer 22 and one region of the light transmissive conductive layer 27, respectively.

In the resultant nitride semiconductor light emitting device 20, the hexagonal pyramid crystal structure 24 grown in a specific region (in the corner region in the present embodiment) exhibiting a rapid growth rate is larger than that in other regions (inner region in the present embodiment). Although it has a large size, it can be seen that the distance of the window may be a structural feature that is designed to be larger than the internal area.

As described above, this prevents local merging due to uneven pyramid growth due to the difference in source concentrations in the reaction chamber, thereby ensuring an active layer 25 having a uniform thickness and providing a first and second conductivity type nitride layer ( 24, 26) provides the advantage that can prevent the short.

As such, the present invention is not limited by the above-described embodiments and the accompanying drawings, and is intended to be limited by the appended claims, and various forms of substitution may be made without departing from the technical spirit of the present invention described in the claims. It will be apparent to one of ordinary skill in the art that modifications, variations and variations are possible.

As described above, according to the present invention, by adjusting the window spacing of the mask used in the selective epitaxial growth process for forming the hexagonal pyramid crystal structure, a pyramid that can be caused in a region where a relatively large amount of source gas is supplied Merge of the crystal structure can be suppressed. As a result, it is possible to provide a reliable nitride light emitting device that solves the problem of non-uniformity of the active layer thickness and In content and prevents defects such as shorts.

Claims (8)

Forming a mask having a plurality of windows on an upper surface of the base layer formed of the first conductivity type nitride semiconductor; Selectively growing a first conductivity type nitride semiconductor crystal having a hexagonal pyramid structure having a crystal plane inclined with respect to the base layer in each of the base layer regions exposed to the plurality of windows; And Sequentially growing an active layer and a second conductivity type nitride semiconductor layer on the first conductivity type nitride semiconductor crystal surface, The mask is divided into at least two areas, and the windows located in the at least two areas are arranged to have a different distance from each other, the method of manufacturing a nitride semiconductor light emitting device. The method of claim 1, At least two regions of the mask include a first region adjacent to a supply position of the nitride source gas and a second region spaced apart from the supply position of the nitride source gas, The method of claim 1, wherein the windows positioned in the first region are arranged to have a larger interval than the intervals of the windows positioned in the second region. The method of claim 1, At least two regions of the mask include a first region adjacent to an edge region of the mask and a second region surrounded by the first region, The method of claim 1, wherein the windows positioned in the first region are arranged to have a larger interval than the intervals of the windows positioned in the second region. The method according to claim 2 or 3, The method of claim 1, wherein the windows positioned in the first region are arranged to have a spacing of 1.2 to 3 times larger than an interval of the windows positioned in the second region. The method of claim 1, And the plurality of windows are arranged in the edge region of the mask so that the intervals thereof become smaller along the center direction thereof. The method of claim 1, And a plurality of windows disposed in the at least two regions to have the same size as each other. The method of claim 1, Forming a transparent conductive layer on the second conductive nitride semiconductor layer; Performing mesa etching to expose a region of the upper surface of the base layer; And forming first and second electrodes in one region of the exposed base layer and one region of the transparent conductive layer, respectively. A nitride semiconductor light emitting device manufactured by any one of claims 1 to 7.

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