KR101025980B1 - Method of manufacturing nitride-based semiconductor light emitting device - Google Patents

Abstract

The present invention relates to a method of manufacturing a nitride-based semiconductor light emitting device, comprising: forming a light emitting structure in which a first conductive nitride layer, an active layer, and a second conductive nitride layer are sequentially stacked on a growth substrate; Bonding a support substrate to the second conductive nitride layer; Separating the growth substrate from the light emitting structure; Forming a polymer mask layer on a surface of the first conductive nitride layer on which the growth substrate is separated; Forming a mask pattern by heat-treating the polymer mask layer to disperse aggregate; Irradiating a laser beam to an area exposed by the mask pattern in the first conductive nitride layer to form an etch stop region; Forming an uneven structure by etching the region except the etch stop region of the first conductive nitride layer using the etch stop region as an etch mask; And forming a first conductive electrode to be electrically connected to the first conductive nitride layer.

Vertical structure, uneven structure, laser

Description

Method of manufacturing nitride-based semiconductor light emitting device

The present invention relates to a method for manufacturing a nitride-based semiconductor light emitting device, and more particularly to a method for manufacturing a nitride-based semiconductor light emitting device having an improved light extraction efficiency by forming an uneven structure on the light emitting surface.

Recently, a nitride-based semiconductor light emitting device is a light emitting device capable of generating light of a wide wavelength band including short wavelength light such as blue or green, and is gradually moving away from the market for conventional simple displays or portable liquid crystal displays. ), Electric field, lighting, etc., has gained much attention in the related technical field.

Such nitride semiconductor light emitting devices may be generally manufactured in a horizontal structure and a vertical structure. Since the p- and n-electrodes have a parallel horizontal structure instead of a vertical structure, a horizontal structure LED has a reduced light emitting area, and thus brightness is reduced, and reliability problems vulnerable to electrostatic discharge (ESD) due to poor current spreading. In addition to causing a problem, there is a problem that the yield is reduced by reducing the number of chips on the same wafer.

In order to solve the problem of the horizontal LED, a vertical LED has been proposed. In the case of the vertical LED, it is important to increase the light extraction efficiency in the same area.

In general, the light efficiency of a nitride semiconductor light emitting device is determined by internal quantum efficiency and light extraction efficiency (also called external quantum efficiency). In particular, the light extraction efficiency is determined by the optical factors of the light emitting device, that is, the refractive index of each structure and the flatness of the interface.

In light extraction efficiency, nitride semiconductor light emitting devices have fundamental limitations. That is, since the semiconductor layer constituting the semiconductor light emitting device has a larger refractive index than the external atmosphere or the substrate, the critical angle that determines the range of incidence angles of light emission becomes small, and as a result, a large part of the light generated from the active layer is totally reflected internally. It is propagated in a substantially undesired direction or lost in the total reflection process, the light extraction efficiency is low.

In order to solve this problem, a method of forming an uneven structure on the surface through which light is transmitted to the outside has been proposed. The method of forming the uneven structure is to apply reactive ion etching (RIE) to an n-type nitride semiconductor layer. In general, however, there is a problem that the region around the uneven structure suffers from plasma damage and the light extraction efficiency is still lowered.

The present invention is to solve the above problems, an object of the present invention is to form an uneven structure on the light emitting surface, it is possible to easily control the size and shape without compromising the crystallinity of the semiconductor single crystal It is to provide a method of manufacturing a nitride-based semiconductor light emitting device.

According to an aspect of the present invention, there is provided a light emitting structure in which a first conductive nitride layer, an active layer, and a second conductive nitride layer are sequentially stacked on a growth substrate; Bonding a support substrate to the second conductive nitride layer; Separating the growth substrate from the light emitting structure; Forming a polymer mask layer on a surface of the first conductive nitride layer on which the growth substrate is separated; Forming a mask pattern by heat-treating the polymer mask layer to disperse aggregate; Irradiating a laser beam to an area exposed by the mask pattern in the first conductive nitride layer to form an etch stop region; Forming an uneven structure by etching the region except the etch stop region of the first conductive nitride layer using the etch stop region as an etch mask; And forming a first conductive electrode to be electrically connected to the first conductive nitride layer.

At this time, the step of forming a polymer-based mask layer on the surface on which the growth substrate is separated in the first conductive nitride layer, characterized in that it is performed by spin coating a solution in which a dispersant is added to the polymer powder. .

The heat treatment of the mask layer of the polymer series to form a mask pattern may be performed by volatilization of the dispersant according to the heat treatment.

The mask pattern is in the form of a dot, and the size of the mask pattern is determined by the size of the polymer powder. The uneven structure has a pyramid shape.

The first conductive nitride layer is a gallium nitride-based semiconductor layer, the surface on which the mask pattern is formed among the first conductive nitride layers is a nitrogen-rich nitrogen polar surface (000-1), and is irradiated with the laser beam. Nitrogen polar surface (000-1) is converted to gallium-rich gallium polar surface (0001), the etch stop region is characterized in that the gallium polar surface.

After the forming of the etch stop region by irradiating a laser beam to the region exposed by the mask pattern of the first conductive nitride layer, the mask pattern is removed using an etchant that selectively removes the polymer-based material. Removing; characterized in that it further comprises.

The step of forming the uneven structure by etching the region except the etch stop region of the first conductive nitride layer is performed by chemical etching, the chemical etching is HF, KOH, H ₂ SO ₄ and H ₂ PO Characterized in that the wet etching using any one of the _four materials.

The method may further include removing the etch stop region formed on the first conductive nitride layer before forming the first conductive electrode.

And forming a highly reflective ohmic contact layer on the second conductive nitride layer before the bonding of the support substrate on the second conductive nitride layer.

Separating the growth substrate from the light emitting structure is characterized in that performed by a laser lift off or chemical lift off process.

According to the present invention, the uneven structure for extracting light having a uniform density and desired size can be formed on the upper surface of the first conductive nitride layer, which is the light emitting surface, without impairing the crystallinity of the semiconductor single crystal by using the polymer mask layer. . This improves the light extraction efficiency of the nitride semiconductor light emitting device.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

1 is a side cross-sectional view showing a nitride semiconductor light emitting device according to an embodiment of the present invention.

As shown in FIG. 1, the nitride-based semiconductor light emitting device 100 according to the present exemplary embodiment includes a support substrate 140, a light emitting structure 120 formed on the support substrate 140, and a light emitting structure 120 formed on the light emitting structure 120. The one conductive electrode 170 is provided. In addition, the nitride-based semiconductor light emitting device 100 further includes a highly reflective ohmic contact layer 130 between the support substrate 140 and the light emitting structure 120.

Herein, the light emitting structure 120 includes the first conductive nitride layer 121, the active layer 123 formed on one surface of the first conductive nitride layer 121, and the second conductive nitride layer 125 formed on one surface of the active layer 123. The second conductive nitride layer 125, the active layer 123, and the first conductive nitride layer 121 are sequentially formed on the support substrate 140.

In the present exemplary embodiment, the first conductive type and the second conductive type nitride layers 121 and 125 constituting the light emitting structure 120 have an Al _x In _y Ga _(1-xy) N composition formula, where 0 ≦ x ≦ 1 , 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1), and a semiconductor material doped with a first conductive impurity and a second conductive impurity, typically GaN, AlGaN, InGaN. In addition, Si, Ge, Se, Te, or C may be used as the first conductivity type impurity, and Mg, Zn, or Be, and the like are representative of the p-type impurity.

The active layer 123 is a layer in which light is generated by recombination of electrons and holes, and may be formed of a nitride semiconductor layer having a single or multiple quantum well structure. In the present embodiment, a nitride semiconductor is used, but the present invention is not limited thereto, and other kinds of semiconductor materials known in the art may be used.

The light emitting structure 120 has a plurality of light extracting concave-convex structures A formed on the upper surface of the first conductive nitride layer 121 serving as the light emitting surface, and the concave-convex structure A for extracting light has a pyramidal shape and It has a similar shape.

The uneven structure A for light extraction is formed by etching the first conductive type nitride layer 121, and an air layer is formed around the uneven structure A for light extraction.

In addition, the support substrate 140 is a substrate having excellent thermal conductivity and electrical conductivity, and serves as a support for supporting the light emitting structure 120 together with the role of the second conductive electrode, and is Si, Cu, Ni, Au, W And a material selected from the group consisting of Ti.

FIG. 2 is a side cross-sectional view for each process for explaining a method of manufacturing a nitride-based semiconductor light emitting device according to an embodiment of the present invention shown in FIG. 1. Here, the manufacturing method of the gallium nitride-based semiconductor light emitting device of the vertical structure is manufactured in plural using a predetermined wafer, Figure 2 shows a method of manufacturing only one light emitting device for convenience of description.

First, as shown in FIG. 2 (a), the light emitting structure 120 is formed on the growth substrate 110. Here, the light emitting structure 120 is a structure formed by sequentially stacking the first conductive nitride layer 121, the active layer 123 and the second conductive nitride layer 125, the light emitting structure 120 is a first The conductive nitride layer 121 is laminated to contact the growth substrate 110.

In this case, the first conductive type and the second conductive type nitride layers 121 and 125 may have an Al _x In _y Ga _(1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x +. y ≦ 1) and doped with a first conductive impurity and a second conductive impurity, respectively, and typically GaN, AlGaN, and InGaN. In addition, Si, Ge, Se, Te, or C may be used as the first conductive impurity, and Mg, Zn, or Be is representative as the second conductive impurity.

The active layer 123 is a layer in which light is generated by recombination of electrons and holes, and is formed of a nitride semiconductor layer having a single or multiple quantum well structure.

The first conductive nitride layer 121, the active layer 123, and the second conductive nitride layer 125 may be formed by organometallic vapor deposition (MOCVD), molecular beam growth (MBE), hybrid vapor deposition (HVPE), or the like. Can be grown.

Although not shown separately, the buffer layer may be preferentially grown before the first conductive nitride layer 121 is grown.

Thereafter, a highly reflective ohmic contact layer 130 is further formed on the second conductive nitride layer 125 of the light emitting structure 120. The highly reflective ohmic contact layer 130 is not a necessary component in the present invention, but the ohmic contact function of the second conductive nitride layer 125 together with the light emitted from the active layer 123 is used as the first conductive nitride layer. A function of reflecting toward (121) may be performed to contribute to luminous efficiency.

To this end, the highly reflective ohmic contact layer 130 preferably has a reflectance of 80% or more, for example, metals such as Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and the like. It may be formed of at least one layer of a material selected from the group consisting of combinations thereof.

Subsequently, as illustrated in FIG. 2B, the support substrate 140 is bonded to the highly reflective ohmic contact layer 130.

Here, the support substrate 140 is an element included in the final vertical structure light emitting device, and serves as a support for supporting the light emitting structure together with the role of the second conductive electrode. In particular, when the growth substrate 110 is removed by a laser lift-off process or a chemical lift-off process to be described later, the light-emitting structure having a relatively thin thickness can be more easily handled by bonding the support substrate 140.

In one embodiment of the present invention, the support substrate 140 is bonded through a wafer bonding process, but is not limited thereto, and a metal may be deposited on the highly reflective ohmic contact layer. For example, when the support substrate is formed of a metal, plating, vapor deposition, sputtering, or the like may be performed, but a plating process is preferable in terms of process efficiency. The plating process includes a known plating process used to form a metal layer, such as electroplating, non-plating, and deposition plating, and among these, it is preferable to use an electroplating method that requires a short plating time.

Thereafter, the growth substrate is separated from the light emitting structure 120 by a laser lift off process or a chemical lift off process. For example, when using a laser lift-off process, the growth substrate 110 is separated by irradiating a laser beam on the entire surface of the growth substrate 110. Meanwhile, when using the chemical lift-off process, a sacrificial layer may be further provided between the growth substrate 110 and the light emitting structure 120 by using wet etching, and the etching solution may be selectively removed. The growth substrate 110 is separated.

By the lift-off process, the surface of the first conductive nitride layer 121 that is in contact with the growth substrate 110 is exposed to the outside.

Subsequently, as shown in FIG. 2C, the mask pattern is formed by forming a polymer mask layer on the surface of the first conductive nitride layer 121 exposed as the growth substrate 110 is removed and then heat-treating the mask pattern. 150 is formed. Here, the polymer mask layer is formed by dispersing a solution in which a dispersant is added to the polymer powder through spin coating. In this case, polyethylene or the like may be used as the polymer powder.

When the mask layer is heat-treated, the dispersant is volatilized and the remaining polymer powder is agglomerated to form a nano patterned dot pattern mask 150. The size of the mask pattern 150 formed according to the size of the polymer powder is determined, and by using the polymer powder, the mask pattern 150 uniformly dispersed on the first conductive nitride layer 121 may be formed. .

The size and arrangement interval of this mask pattern then determines the shape, arrangement interval and size of the irregular structure when forming the uneven structure. For example, as the size of the mask pattern 150 decreases, the area of the area absorbing the laser decreases, so that the density of the unevenness increases.

Subsequently, as illustrated in FIG. 2D, an etch stop region 160 is formed by irradiating a laser beam to the region exposed by the mask pattern 150 of the first conductive nitride layer 121. In this case, the depth of formation of the etch stop region 160 may be controlled by adjusting the intensity of the laser beam.

Here, the surface of the first conductive nitride layer 121 on which the mask pattern 150 is formed is a surface (000-1) having nitrogen-rich nitrogen polarity, and a laser beam is provided on the surface (000-1) having nitrogen polarity. When irradiated, the nitrogen polarity is converted to the polarity of another element, for example, the polarity of the Group 3 element, to form a surface (0001) which is difficult to etch.

For example, if the first conductive nitride layer 121 is a gallium nitride-based semiconductor layer, the region having nitrogen polarity is converted into a region having gallium-rich gallium polarity by the energy of the irradiated laser beam. The region having gallium polarity is difficult to etch and is used as an etch stop region.

That is, the surface of the first conductive nitride layer 121 includes a region having a nitrogen polarity and a region having a polarity of another element, so that two polarities exist on one surface.

Therefore, the region in which the mask pattern 150 is formed absorbs the laser beam to which the mask pattern 150 is irradiated, and in the region in which the mask pattern 150 is not formed, the polarity is converted by the irradiated laser beam, thereby preventing the etch stop region. To form 160.

Subsequently, as shown in FIG. 2E, an area except the etch stop region of the first conductive nitride layer 121 is used by using the etch stop region 160 formed as a result of FIG. 2D as an etch mask. Is etched to form the uneven structure (A).

Here, the method may further include removing the mask pattern 150 from the first conductive nitride layer 121 before the uneven structure A is formed. In this case, an etchant that selectively removes a polymer-based material used for the mask pattern 150 is used, and the etchant does not have any effect on the surface of the first conductive nitride layer 121.

Thereafter, the etch stop region 160 is used as an etch mask to wet-etch an area except the etch stop region of the first conductive nitride layer 121 to form an uneven structure A. FIG.

Specifically, the region except for the etch stop region 160 is selectively wet etched through a chemical etching process using any one of HF, KOH, H ₂ PO _4, and H ₂ PO ₄ . In this case, the etch stop region 160 may be used as an etch mask during etching because it does not react with the etchant, and the region except the etch stop region 160 is etched by reacting with the etchant.

As a result, an uneven structure A having a pyramid shape or similar shape is formed. By using the chemical etching process, damage to the semiconductor single crystal due to the high temperature heat treatment generated in the region around the uneven structure may be minimized as compared with the case of using dry etching such as RIE. And, the etching depth for forming the uneven structure (A) can be adjusted by the molar concentration of the etchant, the etching temperature and the etching time, and particularly easily by adjusting the etching time.

Then, the etch stop region 160 remaining on the first conductive nitride layer 121 on which the uneven structure A is formed is removed by surface treatment.

Subsequently, as shown in FIG. 2F, the first conductive electrode 170 is formed on the surface of the first conductive nitride layer 121 from which the etch stop region 160 is removed through surface treatment. The first conductive electrode 170 is formed to be electrically connected to the type nitride layer. Although not illustrated, a second conductive electrode may be formed on the surface of the support substrate 140 opposite to the surface to which the highly reflective ohmic contact layer 130 is bonded.

As described above, the present invention can form the uneven structure through a simpler process by forming the uneven structure on the nitride-based semiconductor layer using the laser beam irradiation and the mask layer absorbing the laser beam, By using the mask layer, high density and uneven structure of desired size can be formed.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

1 is a side cross-sectional view showing a nitride semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a side cross-sectional view for each process for explaining a method of manufacturing a nitride-based semiconductor light emitting device according to an embodiment of the present invention shown in FIG. 1.

Claims (14)

Forming a light emitting structure in which a first conductive nitride layer, an active layer, and a second conductive nitride layer are sequentially stacked on the growth substrate; Bonding a support substrate to the second conductive nitride layer; Separating the growth substrate from the light emitting structure; Forming a polymer mask layer on a surface of the first conductive nitride layer on which the growth substrate is separated; Forming a mask pattern by heat-treating the polymer mask layer to disperse aggregate; Irradiating a laser beam to an area exposed by the mask pattern in the first conductive nitride layer to form an etch stop region; Forming an uneven structure by etching the region except the etch stop region of the first conductive nitride layer using the etch stop region as an etch mask; And And forming a first conductive electrode to be electrically connected to the first conductive nitride layer. The first conductive nitride layer is a gallium nitride-based semiconductor layer, the surface on which the mask pattern is formed among the first conductive nitride layers is a nitrogen-rich nitrogen polar surface (000-1), and is irradiated with the laser beam. A method of manufacturing a nitride-based semiconductor light emitting device, characterized in that the nitrogen polarization surface (000-1) is converted to gallium-rich gallium polarization surface (0001). The method of claim 1, The forming of the polymer mask layer on the surface of the first conductive nitride layer on which the growth substrate is separated is performed by spin coating a solution in which a dispersant is added to the polymer powder. Method of manufacturing a semiconductor light emitting device. The method of claim 2, Forming a mask pattern by heat-treating the mask layer of the polymer series, the method of manufacturing a nitride-based semiconductor light emitting device, characterized in that performed by volatilization of the dispersant according to the heat treatment. The method of claim 3, The mask pattern is a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that the dot (dot) form. The method of claim 3, The size of the mask pattern is a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that determined by the size of the polymer powder. delete The method of claim 1, The etch stop region is a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that the gallium polar surface. The method of claim 1, After the forming of the etch stop region by irradiating a laser beam to a region of the first conductive nitride layer exposed by the mask pattern, the mask pattern is removed using an etchant that selectively removes the polymer-based material. The manufacturing method of the nitride-based semiconductor light-emitting device further comprising. The method of claim 1, Forming a concave-convex structure by etching a region other than the etch stop region of the first conductive nitride layer, which is performed by chemical etching. 10. The method of claim 9, The chemical etching is a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that performed by wet etching using any one of HF, KOH, H ₂ SO ₄ and H ₂ PO ₄ material. 10. The method of claim 9, The uneven structure has a pyramid shape manufacturing method of a nitride-based semiconductor light emitting device, characterized in that. The method of claim 1, And removing the etch stop region formed on the first conductive nitride layer before forming the first conductive electrode. The method of claim 1, And forming a highly reflective ohmic contact layer on the second conductive nitride layer before the step of bonding the supporting substrate on the second conductive nitride layer. . The method of claim 1, And separating the growth substrate from the light emitting structure is performed by a laser lift off or chemical lift off process.

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