KR100622819B1 - Fabricating method of patterned substrate and fabricating method of light emitting diode of using the substrate - Google Patents

Abstract

The present invention relates to a method of manufacturing a patterned substrate and a method of manufacturing a light emitting diode using the substrate, wherein the nitride semiconductor layer is grown after forming a nanoscale pattern on the substrate using nano powder, It is characterized by increasing the critical angle by forming a nano-scale pattern.

According to the present invention, by forming a nanoscale pattern on the substrate, dislocations, defects, and the like in the nitride-based semiconductor layer growing on the substrate can be reduced, thereby obtaining a high quality nitride-based semiconductor crystalline. In addition, by forming a nanoscale pattern on the surface of the nitride semiconductor layer of the light emitting diode to increase the critical angle of the surface, when the light generated in the active layer reaches the nitride semiconductor layer, it is possible to reduce the probability of being totally reflected inside the device again and consumed It becomes possible to improve the light extraction efficiency of a light emitting diode.

Nano powder, jig, light extraction efficiency, light emitting diode, potential

Description

Fabrication method of patterned substrate and fabricating method of light emitting diode of using the substrate}

1 is a cross-sectional view of a conventional nitride based light emitting diode.

2A to 2E are cross-sectional views showing an embodiment of a method of manufacturing a patterned substrate of the present invention.

3A to 3C are views illustrating a nanoscale pattern formed on a photoresist.

4A to 4H are cross-sectional views showing an embodiment of a method of manufacturing a light emitting diode using the patterned substrate of the present invention.

Explanation of symbols on the main parts of the drawings

100 substrate 110 silicon oxide film

120: photoresist 130: nano powder

140: jig 300: substrate

310: n-type nitride semiconductor layer 320: active layer

330 p-type nitride semiconductor layer 340 conductive support film

350: photoresist 360: nano powder

370: jig 380: n-electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to light emitting devices, and more particularly, to a method of manufacturing a patterned substrate and a method of manufacturing a light emitting diode using the substrate.

Nitride-based semiconductors are direct-transition semiconductors that have a wide spectrum of emission spectrum from ultraviolet to infrared, and are widely used in light emitting devices such as light emitting diodes (LEDs) and laser diodes (LDs).

In addition, since the energy band gap is wide and stable operation can be expected at a higher temperature than devices using other semiconductors, applications to transistors such as field effect transistors (FETs) are also in full swing.

In addition, since nitride-based semiconductors do not use arsenic (As) as a main component, they have high responses in terms of environmental friendliness.

However, in the case of the nitride semiconductor, since the dissociation pressure of nitrogen reaches as high as 2000 atm at the growth temperature of the single crystal, it is difficult to grow the nitride semiconductor into a single crystal, and sapphire (Al ₂ O ₃ ) is usually used for epitaxial growth. It is formed as a substrate to be used.

However, a large lattice mismatch and a difference in coefficient of thermal expansion appear between the sapphire (Al ₂ O ₃ ) and the nitride-based semiconductor crystal epitaxially grown on the substrate.

That is, sapphire (Al ₂ O ₃ ) and gallium nitride (GaN) as an example, sapphire (Al ₂ O ₃ ) has a lattice constant of a: 4.758 (Å), c: 12.991 (Å), the thermal expansion coefficient is a and ^{7.5 (× 10 -6 / K)} , c:: 8.5 (× 10 -6 / K) inde contrast, GaN has the lattice constant a: 3.189 (Å), and, c: is 5.185 (Å), the thermal expansion coefficient is a: and ^{5.59 (× 10 -6 / K)} , c: 3.17 (× 10 -6 / K) a, the difference in lattice constant (16.02%) and thermal expansion coefficient (35.5%) between the sapphire and gallium nitride (GaN) Will come out.

Dislocations occur at the interface between the sapphire and the nitride-based semiconductor due to the difference in lattice constant and thermal expansion coefficient between the sapphire and the nitride-based semiconductor, thereby lowering the electrical characteristics of the device.

The dislocation due to the lattice mismatch is a threading dislocation that penetrates the semiconductor layer in the longitudinal direction, that is, the direction perpendicular to the substrate plane, and causes a problem that a dislocation of about 10 ⁹ cm ^-3 propagates in the nitride-based semiconductor. have.

The penetrating potential propagates to the top layer of each of the nitride-based semiconductors having different compositions. As a result, for example, in the case of a light emitting device, a threshold current value of a laser diode (LD), and an element lifetime of an LD and a light emitting diode (LED) There is a problem in that device characteristics such as these are deteriorated.

On the other hand, in the case of light emitting diodes, as the field of application is expanded, high power and high brightness light emitting diodes are required. In the high power and high brightness light emitting diodes, light extraction efficiency serves as an important variable for determining the light emission efficiency.

Here, light extraction efficiency is determined by the ratio of electrons injected into the light emitting diode to photons emitted out of the light emitting diode, and the higher the extraction efficiency, the brighter the light emitting diode.

Since the light extraction efficiency of the light emitting diode is greatly influenced by the shape or surface shape of the chip, the structure of the chip, and the packaging type, great care must be taken when designing the light emitting diode. By the way, there is a limit in light extraction efficiency in the conventional manufacturing method of the nitride-based light emitting diode.

1 is a cross-sectional view of a conventional nitride based light emitting diode. As shown therein, the buffer layer 11, the n-type nitride semiconductor layer 12, the active layer 13, and the p-type nitride semiconductor layer 14 are sequentially stacked on the substrate 10.

Mesa etching is performed from the p-type nitride semiconductor layer 14 to a portion of the n-type nitride semiconductor layer 12 to expose a portion of the n-type nitride semiconductor layer 12,

The n-electrode 15 is formed on the exposed n-type nitride semiconductor layer 12, and the p-electrode 16 is formed on the p-type nitride semiconductor layer 14.

In the nitride-based light emitting diode configured as described above, light generated in the active layer 13 is absorbed by the substrate 10 or inside the device at an interface between the substrate 10 and the p-type nitride semiconductor layer 14. Is totally reflected and consumed, which causes a problem of lowering the light extraction efficiency of the device as light loss.

Accordingly, an object of the present invention is to form a nanoscale pattern on a substrate on which a nitride-based semiconductor is grown, thereby reducing the dislocations and defects to grow a high quality semiconductor crystalline. To provide.

Another object of the present invention is to grow a nitride semiconductor layer using the patterned substrate, and to form a nano-scale pattern on the surface of the nitride semiconductor layer, the light generated in the active layer from the interface of the nitride semiconductor layer into the device The present invention provides a method of manufacturing a light emitting diode using a patterned substrate which reduces the total reflection and improves the light extraction efficiency.

An embodiment of the method of manufacturing a patterned substrate of the present invention includes the steps of sequentially forming a silicon oxide film and a photoresist on the substrate, and mixing the nanopowder in a solvent and applying on the photoresist, and then removing the solvent And mounting a jig on the nanopowder, forming a nanoscale pattern on the photoresist by irradiating a laser between the photoresist and the jig, and masking the photoresist on which the nanoscale pattern is formed. Etching the silicon oxide film, and etching the substrate using the etched silicon oxide film as a mask to form a nanoscale pattern on the substrate.

In the embodiment of the method of manufacturing a light emitting diode using the patterned substrate of the present invention, a light emitting structure is formed by sequentially stacking an n-type nitride semiconductor layer, an active layer, a p-type nitride semiconductor layer, and a conductive support layer on a substrate on which a nanoscale pattern is formed. Forming a photoresist, separating the substrate from the light emitting structure, forming a photoresist under the n-type nitride semiconductor layer, and mixing nanopowder with a solvent and applying the photoresist onto the photoresist. Removing a solvent, mounting a jig under the nanopowder, and irradiating a laser between the photoresist and the jig to form a nanoscale pattern in the photoresist, and the nanoscale pattern is The n-type nitride semiconductor layer is etched using the formed photoresist as a mask to form the n-type nitride Including the step of forming the pattern of the nanoscale to the conductive layer, characterized in that formed.

Hereinafter, a method of manufacturing a patterned substrate and a method of manufacturing a light emitting diode using the substrate will be described in detail with reference to FIGS. 2 to 4. 2A to 2E are cross-sectional views showing an embodiment of a method of manufacturing a patterned substrate of the present invention.

As shown in the drawing, first, a silicon oxide film (SiO ₂ ) 110 and a photo resist 120 are sequentially formed on the substrate 100 (FIG. 2A).

Here, as the substrate 100, a sapphire substrate, a silicon carbide substrate, a silicon substrate, a gallium arsenide substrate, or the like is used. In particular, a sapphire substrate is typically used.

Next, the nano powder 130 is dispersed in a solvent, and the solvent in which the nano powder is dispersed is applied onto the photoresist 120, and then the solvent is removed (FIG. 2B).

Here, the nano powder 130 may be silver (Ag), nickel (Ni), gold (Au), ceramics (Ceramics) and the like.

In addition, the diameter of the nano powder 130 has a size of 100 ~ 500 nm usually, the size of the pattern to be formed on the substrate 100 is determined according to the size of the nano powder 130.

Subsequently, the substrate 100 is fixed by mounting a jig 140 on the nano powder 130, and then irradiates a laser between the photoresist 120 and the jig 140 (FIG. 2C). ).

As such, when the laser is irradiated between the photoresist 120 and the jig 140, the energy of the irradiated laser is transmitted to the photoresist 120 through the nanopowder 130 to thereby transmit the photoresist 120. The nanoscale pattern is formed on the substrate.

That is, the laser irradiated between the photoresist 120 and the jig 140 collides with the nanopowder 130 while passing between the nanopowder 130, whereby heat is generated due to the collision, which is a photograph. It serves as an exposure in the etching process.

Therefore, heat is transferred to the photoresist 120 which is in contact with the nanopowder 130 so that the photoresist 120 reacts, and the photoresist 120 has a smaller size than the nanopowder 130. The pattern of is formed. That is, the pattern formed in the photoresist 120 has a size of about 50 ~ 200nm.

Thereafter, after the jig 140 is removed, the silicon oxide film 110 is etched using the photoresist 120 having the nanoscale pattern formed thereon as an etch mask (FIG. 2D).

Here, when the silicon oxide film 110 is etched using the photoresist 120 having the nanoscale pattern formed as an etch mask, the pattern formed on the photoresist 120 is transferred to the silicon oxide film 110. Will appear.

Therefore, a pattern having a size of about 50 to 200 nm is formed in the silicon oxide film 110.

Next, the substrate 100 is etched using the silicon oxide film 110 having the nanoscale pattern formed thereon as an etch mask, thereby forming a nanoscale pattern on the substrate 100 (FIG. 2E).

The etching of the silicon oxide film 110 and the substrate 100 may be performed using an inductively coupled plasma / reactive ion etching (ICP / RIE) method.

As such, after forming the silicon oxide film 110 and the photoresist 120 on the substrate 100 and forming the nano powder 130 thereon, after irradiating the laser using a laser jig 140, When the photoresist 120 and the silicon oxide layer 110 are etched, a nanoscale pattern is formed on the substrate 100.

In this case, the size of the nanoscale pattern formed on the substrate 100 may vary depending on the size of the nanopowder 130 deposited on the photoresist 120.

When the nitride-based semiconductor layer is grown on the nano-scale patterned substrate 100, dislocations or defects in the nitride-based semiconductor layer may be reduced due to the laterally grown effect. Therefore, high quality nitride semiconductor crystalline can be obtained.

3A to 3C are diagrams illustrating a pattern in which nanoscale patterns are formed in a photoresist. As shown in the drawing, the photoresist 210 is formed on the substrate 200 and the nano powder 220 is formed on the photoresist 210.

After fixing the substrate 200 by mounting the jig 230 on the nano powder 220, the laser is irradiated between the substrate 200 and the jig 230.

Then, the irradiated laser hits the nanopowder 220 to generate heat, and the heat is transferred to the photoresist 210 in contact with the nanopowder 220 so that the photoresist 210 reacts. Will cause.

That is, as shown in FIG. 3B, when a laser having a wavelength of 410 nm collides with silver (Ag) nanopowder, heat is generated, and this heat acts as a kind of exposure to the photoresist and the silver (Ag) nanopowder The photoresist being in contact with each other reacts, thereby forming a pattern having a smaller size than the silver (Ag) nanopowder.

3C shows a state in which a nanoscale pattern is formed on the photoresist. After the nano powder is dispersed in a solvent and the solvent in which the nano powder is dispersed is applied onto the photoresist 210, the solvent is removed, so that the nano powder is randomly distributed on the photo resist 210. In addition, nanoscale patterns 215 formed on the photoresist 210 are also irregularly spaced apart from each other.

4A to 4H are cross-sectional views showing an embodiment of a method of manufacturing a light emitting diode using the patterned substrate of the present invention.

As shown in FIG. 2, first, a substrate 300 having a nanoscale pattern is prepared by performing the process of FIGS. 2A to 2E (FIG. 4A).

Here, as the substrate 300, a sapphire substrate, a silicon carbide substrate, a silicon substrate, a gallium arsenide substrate, and the like are used. In particular, a sapphire substrate is typically used.

Next, the n-type nitride semiconductor layer 310, the active layer 320, and the p-type nitride semiconductor layer 330 are sequentially stacked on the substrate 300 (FIG. 4B).

The n-type nitride semiconductor layer 310 formed on the substrate 300 has an Al _x In _y Ga _(1-xy) N composition formula (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y). ≦ 1), and in particular GaN is widely used.

The active layer 320 formed on the n-type nitride semiconductor layer 310 has a quantum well structure and may be formed of GaN or InGaN.

The p-type nitride semiconductor layer 330 formed on the active layer 320 is the same as the n-type nitride semiconductor layer 310, Al _x In _y Ga _(1-xy) N composition formula (where 0≤x≤1 , 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and p-doped.

A buffer layer is further formed between the substrate 300 and the n-type nitride semiconductor layer 310 to mitigate a difference in lattice mismatch and thermal expansion coefficient between the substrate 300 and the n-type nitride semiconductor layer 310. The buffer layer may be formed of a low temperature growth GaN layer or an AlN layer.

The n-type nitride semiconductor layer 310, the active layer 320, and the p-type nitride semiconductor layer 330 may be deposited using a deposition process such as a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method. It is preferable to grow, but especially by MOCVD.

As such, when the nitride-based semiconductor layer is grown on the nano-scale patterned substrate 300, dislocations or defects in the nitride-based semiconductor layer may be removed due to the laterally grown effect. Can be reduced.

Subsequently, a light emitting structure is formed by forming a conductive support layer 340 on the p-type nitride semiconductor layer 330 (FIG. 4C).

Here, since the conductive support layer 340 serves as a p-electrode, it is preferable to use a metal having excellent electrical conductivity.

In addition, since the heat generated during the operation of the light emitting diode should be sufficiently dissipated, a metal having high thermal conductivity should be used, and scribing without bringing warp to the entire wafer when forming the conductive support layer 340. In order to separate well into separate chips through the process and breaking process, it must have some mechanical strength.

Therefore, as the conductive support layer 340, a soft metal having good thermal conductivity, such as gold (Au), copper (Cu), silver (Ag), and aluminum (Al), a crystal structure, and a crystal lattice constant Similarly, it is preferable to form an alloy of light metal such as nickel (Ni), cobalt (Co), platinum (Pt), and palladium (Pd) having mechanical strength while minimizing the generation of internal stress in the alloy.

Here, before the conductive support layer 340 is formed, an ohmic layer and a reflective layer may be further formed on the p-type nitride semiconductor layer 330. The reflective layer may include light emitted from the active layer 320. In order to prevent the light amount of the light emitting diode from being reduced by being attenuated therein, the light generated from the active layer 320 is reflected to the outside.

In this case, the reflective film is made of one metal selected from Ag, Al, Au, Ni, Ti, or an alloy of two or more metals selected from the metals.

The ohmic layer is used to form ohmic contact with the p-type nitride semiconductor layer 330. The ohmic layer is a metal thin film of indium tin oxide (ITO) or nickel (Ni) / gold (Au). Is done.

When the ohmic layer is formed of a metal thin film of nickel (Ni) / gold (Au), ohmic contact having a specific contact resistance of about 10 ⁻³ to 10 ⁻⁴ Ωcm ² may be formed.

In addition, when the ohmic layer is formed of a metal thin film of nickel (Ni) / gold (Au), since the reflectance is high, the light emitted from the active layer 320 can be effectively reflected, so that a separate reflector is not formed. The advantage is that even if the reflection effect can be obtained.

Thereafter, the substrate 300 is removed from the light emitting structure (FIG. 4D). Here, the substrate 300 may be removed by a laser lift off (LLO) method using an excimer laser or the like, or may be a dry or wet etching method.

In particular, the removal of the substrate 300 is preferably performed by a laser lift-off method. That is, when focusing and irradiating excimer laser light having a wavelength of a predetermined region to the substrate 300, thermal energy is concentrated on the interface between the substrate 300 and the n-type nitride semiconductor layer 310 As the interface of the n-type nitride semiconductor layer 310 is separated into gallium and nitrogen molecules, the substrate 300 is instantaneously separated at the portion where the laser light passes.

After the laser lift-off process, the roughened surface of the n-type nitride semiconductor layer 310 may be polished by an ICP / RIE (Inductively Coupled Plasma / Reactive Ion Etching) method.

Next, after the photoresist 350 is formed under the n-type nitride semiconductor layer 310, the nano powder 360 is dispersed under the photoresist 350, and the nano powder 360 ) Mount a Zig 370 on the bottom (FIG. 4E).

Here, as the nano powder 360, silver (Ag), nickel (Ni), gold (Au), ceramics (Ceramics), etc. may be used, and the nano powder 360 has a diameter of about 100 to 500 nm. Has a size.

Subsequently, a laser is irradiated between the photoresist 350 and the jig 370 (FIG. 4F).

When the laser is irradiated between the photoresist 350 and the jig 370, the irradiated laser collides with the nano powder 360 to generate heat, which is in contact with the nano powder 360. The photoresist 350 is transferred to the photoresist 350, which reacts with the photoresist 350, and a pattern of a nano scale having a smaller size than the nanopowder 360 is formed on the photoresist 350. .

Thereafter, after the jig 370 is removed, the n-type nitride semiconductor layer 310 is etched by the ICP / RIE method using the photoresist 350 having the nanoscale pattern formed thereon as an etch mask, thereby providing the n-type. A nanoscale pattern is formed on the nitride semiconductor layer 310 (FIG. 4G).

Next, an n-electrode 380 is formed under the n-type nitride semiconductor layer 310 (FIG. 4H). Here, the n-electrode 380 is made of any one metal selected from chromium (Cr), nickel (Ni), and gold (Au).

As such, when the nitride semiconductor layer is grown using a substrate on which a nanoscale pattern is formed, it is possible to obtain a high quality nitride semiconductor crystalline having reduced potential or defect due to side growth effects.

In addition, by forming a nano-scale pattern on the n-type nitride semiconductor layer to increase the critical angle of the surface, when the light generated in the active layer reaches the n-type nitride semiconductor layer, it is possible to reduce the probability of total reflection is consumed inside the device again This makes it possible to improve the light extraction efficiency of the light emitting diode.

In the present embodiment, the manufacturing method of the vertical light emitting diode has been described, but the same may be applied to the manufacturing method of the horizontal light emitting diode.

That is, after preparing a substrate having a nanoscale pattern by performing the process of FIGS. 2A to 2E, a nitride semiconductor layer is grown on the substrate, and a process as illustrated in FIGS. 4E to 4G is performed on the surface of the nitride semiconductor layer. Nanoscale patterns can be formed.

According to the present invention, by forming a nanoscale pattern on the substrate, dislocations, defects, and the like in the nitride-based semiconductor layer growing on the substrate can be reduced, thereby obtaining a high quality nitride-based semiconductor crystalline. have.

In addition, by forming a nanoscale pattern on the surface of the nitride semiconductor layer of the light emitting diode to increase the critical angle of the surface, when the light generated in the active layer reaches the nitride semiconductor layer, it is possible to reduce the probability of total reflection is consumed inside the device again This makes it possible to improve the light extraction efficiency of the light emitting diode.

On the other hand, while the present invention has been shown and described with respect to specific preferred embodiments, various modifications and variations of the present invention without departing from the spirit or field of the invention provided by the claims below It will be readily apparent to one of ordinary skill in the art that it can be used.

Claims (8)

Sequentially forming a silicon oxide film and a photoresist on the substrate; Mixing the nanopowder with a solvent and applying it onto the photoresist, and then removing the solvent; Mounting a jig on the nanopowder, and then irradiating a laser between the photoresist and the jig to form a nanoscale pattern on the photoresist; Etching the silicon oxide film using a photoresist on which the nanoscale pattern is formed as a mask; And Forming a nanoscale pattern on the substrate by etching the substrate using the etched silicon oxide film as a mask. The method of claim 1, wherein the nano powder is one selected from silver (Ag), nickel (Ni), gold (Au), and ceramics. The method of claim 1, wherein the silicon oxide layer and the substrate are etched by an inductively coupled plasma / reactive ion etching (ICP / RIE) method. Sequentially forming an n-type nitride semiconductor layer, an active layer, a p-type nitride semiconductor layer, and a conductive support layer on the substrate on which the nanoscale pattern is formed to form a light emitting structure; Separating the substrate from the light emitting structure; Forming a photoresist under the n-type nitride semiconductor layer; Mixing the nanopowder with a solvent and applying it onto the photoresist, and then removing the solvent; Mounting a jig under the nanopowder, and then irradiating a laser between the photoresist and the jig to form a nanoscale pattern on the photoresist; And Forming a nanoscale pattern on the n-type nitride semiconductor layer by etching the n-type nitride semiconductor layer by using the photoresist on which the nano-scale pattern is formed as a mask. Way. The method of claim 4, wherein the light emitting structure further comprises an ohmic layer and a reflective film on the p-type nitride semiconductor layer. The method of claim 5, wherein the ohmic layer is made of a metal thin film of indium tin oxide (ITO) or nickel (Ni) / gold (Au). The method of claim 5, wherein the reflective film is made of any one metal selected from Ag, Al, Au, Ni, Ti or an alloy of two or more metals selected from the above metal manufacturing of a light emitting diode using a patterned substrate Way. 5. The method of claim 4, wherein the nano powder is one selected from silver (Ag), nickel (Ni), gold (Au), and ceramics. 6.

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