KR20060055739A - Method for fabricating iii-v nitride compound flip-chip semiconductor light-emitting device using dry etching on the substrate to improve the extraction efficiency - Google Patents

Abstract

 According to the present invention, a lower contact layer made of n-AlxGayInzN (0 ≦ x, y, z ≦ 1, x + y + z = 1) and p-AlxGayInzN (0 ≦ x, y, z ≦ 1, An upper contact layer made of x + y + z = 1) is formed, and light emission made of AlxGayInzN (0 ≦ x, y, z ≦ 1, x + y + z = 1) between the lower contact layer and the upper contact layer. The present invention relates to a method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure having an active layer interposed therebetween, wherein the bottom surface of the transparent substrate in contact with air is bent through dry etching. According to the present invention, the external photon efficiency increases because the probability of photons satisfying a condition of a specific critical angle, that is, the probability that photons can escape to the outside due to the curvature of the substrate surface in contact with air, increases.

Luminous efficiency, dry etching, sapphire, bend, flip structure, nitride semiconductor

Description

Method for fabricating III-V nitride compound flip-chip semiconductor light-emitting device using dry etching on with improved light extraction efficiency by performing dry etching on substrate the substrate to improve the extraction efficiency}             

1 is a view for explaining a method of manufacturing a semiconductor light emitting device of a conventional III-V nitride flip chip structure;

2 is a view for explaining a method for manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure according to an embodiment of the present invention;

3 is a photograph showing a case where the shape of the etching pattern 14 is a mesh type;

Figure 4 is a graph measuring the bending of Figure 3 with an alpha step measurement equipment;

FIG. 5 is a graph showing current-emitting intensity characteristics for the case of FIG. 3 and the conventional case without dry etching according to the present invention; FIG.

FIG. 6 is a photograph showing a case where the shape of the etching pattern 14 is linear. FIG.

FIG. 7 is a graph measuring the curvature of FIG. 6 with an alpha step measuring apparatus; FIG.

FIG. 8 is a graph showing current-emitting intensity characteristics for the case of FIG. 6 and the conventional case without dry etching according to the present invention; FIG.

9 is a graph of current-emitting intensity characteristics for the conventional case without surface bending and the case of FIGS. 3 and 6 according to the present invention.

<Description of Reference Numbers for Main Parts of Drawings>

10: sapphire substrate 14: etching pattern

20: GaN nucleation layer 32: bottom contact layer

34: upper contact layer 40: light emitting active layer

52: p-type reflective electrode 54: n-type electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor light emitting device having a III-nitride-based flip chip structure. In particular, the present invention provides a semiconductor light emitting device having a III-V nitride flip chip structure, which improves light extraction efficiency by providing bending to a substrate surface in contact with air. It is about a method.

In the conventional planar top-emitting light emitting diode, light generated therein is emitted into the air through the p-AlGaInN layer. At this time. Due to the difference in the refractive index of the p-AlGaInN layer and air, light loss occurs at the interface, thereby lowering the light extraction efficiency. In other words, the internally generated quantum efficiency is almost 100%, but the efficiency of light that can escape to the outside is only about 3 to 30%.

In order to increase the external extraction efficiency of the lowered light, studies on increasing the probability of photons coming out of the outside air by forming curved nano or micro units by dry or wet etching the surface of the p-AlGaInN layer are as follows. It was introduced.

I.schnitzer and E. Yablonovitch and three others reported a method of increasing the external light emission efficiency by 30% by giving nanoscale roughness to the n-layer semiconductor layer of GaAs light emitting diodes using "natural lithography." (See Appl. Phys. Lett. 63, 2174, 1993).

Chul Huh and three others deposit a metal on the surface of the p-GaN layer of the nitride-based light emitting diode, heat-treat it at a high temperature to form a metal cluster, and then use it as an etching mask on the surface of the p-GaN layer. It has been reported that the light emission intensity has been increased by artificially forming micro roughening (see J. Appl. Phys. 93, 9383, 2003).

In addition, Youg-Jae Lee and seven others stacked photonic crystals on glass substrates to improve the light extraction efficiency of organic light-emitting diodes, and patterned them in nano units using photolithography technology (see Resources: Appl. Phys. Lett. 82, 3779, 2003), CW Liu and four others reported that the external quantum efficiency was increased by bending the silicon and Si / oxide interface (Ref .: IEEE Electron Device Lett. 21, 601, 2000). ).

However, the above methods all relate to top emitting light emitting diodes, and mainly form roughness or curvature on the p-GaN surface. One of the disadvantages of the top-emitting type light emitting diode is that the absorption of light from the metal electrode, the bonding pad, the trans layer, the wire line, etc. is large, and thus the constraint on the improvement of the light extraction efficiency is followed.

Therefore, in order to reduce the above absorption rate by forming a thick metal electrode 52 as a reflective layer of light on the upper contact layer 34 as shown in FIG. 1, the light is emitted to the outside through the sapphire substrate 10 This newly proposed. Such a light emitting diode is referred to as a light emitting diode having a flip-chip structure.

In this case, since light is extracted through the sapphire substrate 10 instead of being extracted through the upper contact layer 34, there is no absorption of light by a metal electrode, a bonding pad, a trans layer, or wire lines. Can increase the extraction efficiency of 2 ~ 3 times, and most companies are currently researching and developing the flip-chip light emitting diode.

The following study introduces that the flip-chip type light emitting diode has improved light extraction efficiency compared to the top type light emitting diode.

J.J. Wierer et al. Manufactured and compared top light emitting diodes and flip chip type light emitting diodes. In the case of flip chip light emitting diodes, the loss due to light absorption is reduced in metal electrodes, bonding pads, trans layers, and wires. It is reported that this has been improved. (Reference: J. Appl. Phys. 78, 22, 2001).

However, in the case of the flip chip type light emitting diode, when light passes through the interface between the sapphire substrate 10 and the air, there is a loss of light due to the difference in refractive index of the two materials, which causes the external extraction efficiency to be generated internally. It is considerably lowered compared to the efficiency of the light.

In the case of the semiconductor light emitting diode of III-V nitride flip chip structure, the refractive index of sapphire is 1.8 and the refractive index of air is 1, so that the light generated inside the light emitting diode is allowed to escape from the sapphire substrate 10 into the outside air. The critical angle of θ _c = sin ⁻¹ (n _air / n _sapphire ) is about 34.4 degrees. That is, the light emitted from the inside of the flip chip light emitting diode can escape to the outside only when it is incident at the interface between the sapphire substrate 10 and the air with an angle smaller than 34.4 degrees, and in the other cases, the sapphire substrate 10 As it is reflected back to the inside at the interface between the air and the air, the light extraction efficiency is still quite small.

Therefore, the technical problem to be achieved in the present invention, III to perform a structural treatment so that more light can be included in the critical angle at the interface of the substrate in contact with air in order to further increase the external photon efficiency in the flip-chip light emitting diode A semiconductor light emitting device having a -V nitride flip chip structure is provided.

In the semiconductor light emitting device manufacturing method of III-V nitride flip chip structure according to the present invention for achieving the above technical problem, n-AlxGayInzN (0≤x, y, z≤1, x + y + on a transparent substrate) a lower contact layer made of z = 1) and an upper contact layer made of p-AlxGayInzN (0 ≦ x, y, z ≦ 1, x + y + z = 1) are formed between the lower contact layer and the upper contact layer. A method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure, comprising a light emitting active layer composed of Al x Ga y In z N (0 ≦ x, y, z ≦ 1, x + y + z = 1), wherein the transparent material is in contact with air. The bottom surface of the substrate is characterized in that the bending through the dry etching.

It is preferable that the curvature has a periodicity.

The transparent substrate may be a sapphire substrate, and in this case, the dry etching is performed using a mixed gas containing methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), and argon (Ar). desirable. In this case, the dry etching may be performed in an inductively coupled plasma reactor, wherein the ICP output is 200 to 2000 W, the RF plasma output is 10 to 1000 W, and the pressure of the reactor may be 5 to 50 mbar. The supply flow rates of methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), and argon (Ar) are preferably 1 to 50 sccm, 10 to 100 sccm, 1 to 50 sccm, and 1 to 100 sccm, respectively. .

The shape of the bend may be square, circular, or line when viewed from above. And, the side surface of the bend may be a long trapezoid or triangle.

The surface area increase of the transparent substrate by the dry etching may be 10 to 70%.

The depth of the curve may be 100 ~ 100㎛.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. In the drawings, the same reference numerals as in FIG. 1 denote components that perform the same function, and a repetitive description thereof will be omitted. The following examples are only presented to understand the content of the present invention, and those skilled in the art will be capable of many modifications within the technical spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited to these embodiments.

2 is a view for explaining a method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure according to an embodiment of the present invention.

First, a GaN nucleation layer 20 is formed on the sapphire substrate 10 at 500 ° C. with a thickness of 300 GPa, and a lower contact layer 32 made of n-GaN with a thickness of 1.5 μm is formed on the GaN nucleation layer 20. ). Then, a light emitting active layer 40 formed by alternately stacking a GaN layer and an InGaN layer is formed to have a thickness of 1500 mW. Next, an upper contact layer 34 made of p-GaN is formed on the light emitting active layer 40 to a thickness of 0.25 탆.

After the upper contact layer 34 is formed, silicon oxide (SiO ₂ ) having a thickness of 1 μm is formed on the surface of the sapphire substrate 10 in contact with air, and then patterned. Such silicon oxide patterning may use BOE chemicals. Once the silicon oxide is patterned, the sapphire substrate 10 is dry-etched using this as an etching mask.

Dry etching of the sapphire substrate 10 is carried out in the methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), and argon (Ar) in an inductively coupled plasma reactor 30, 8, 8, And 16 sccm flow rate, the reactor pressure was 20 mTorr, the temperature was 20 ° C, the ICP output was 1000W, and the RF table output was 150W.

The etch pattern 14 of the sapphire substrate 10 has a similar shape depending on the pattern of the silicon oxide when viewed from above, and may be circular, rectangular, or line-shaped. Lateral sections usually have a long trapezoidal shape, which may be triangular (three-dimensionally equivalent to a horn). Since the etching pattern 14 of the sapphire substrate 10 can increase the probability that light can escape to the outside in the case of anisotropy than in the case of isotropy, it is preferable to pursue anisotropic bending formation.

After the bending is formed on the sapphire substrate 10 through dry etching, the stepped portion is formed by dry etching the upper contact layer 34, the light emitting active layer 40, and the lower contact layer 32 in the reactor. The p-type reflective electrode 52 and the n-type electrode 54 are formed on the upper contact layer 34 and the lower contact layer 32. The n-type electrode 54 may have a Ti / Al structure, and the p-type reflective electrode 52 should have a thickness sufficient to reflect light.

The use of BCl ₃ gas as an sapphire etching method has already been introduced as follows.

YJ Sung and 6 others introduced the possibility of sapphire etching with high etching rate by mixing BCl ₃ , Cl ₂ , and Ar gas (Ref. Materials Science and Engineering B82, 2001, p50-52). It is reported that BCl ₃ and HBr gases are used and higher etch rates can be obtained by applying an external magnetic field during etching (Ref. Thin Solid Films 435, 2003, p242-246).

However, the sapphire dry etching carried out in the above study is not intended to improve the light extraction efficiency, but is intended for polishing or cutting sapphire, and has been suggested as an alternative to mechanical cutting using diamond.

In particular, in the description above, studies to use the BCl ₃ gas to increase the etch rate, BCl ₃ gas is that it is difficult to store and manage its own, further heating the gas (heating gas) in accordance with the use of the BCl ₃ storage vessel and the pipe The need for pipes is expensive to manage.

However, the present invention using a mixed gas of methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), and argon (Ar) is bent to the sapphire surface at a desired etching rate without using BCl ₃ gas. Can be formed, and the light extraction efficiency can be improved. The use of BCl ₃ gas for the purpose of improving external light extraction is rather undesirable in terms of production costs and management time.

Since the dry etching of the sapphire substrate 10 is similar to the case of forming the n-type electrode 54 in the lower contact layer 32, there is no burden on additional processes, and the equipment, tools, and work used for manufacturing the light emitting diodes. Since the structural difficulty of the phase is not given, each dry type has a fluidity that can be performed anywhere in the entire light emitting diode fabrication process.

FIG. 3 shows a photograph of the etching pattern 14 formed on the sapphire substrate 14 from above. It can be seen that the square-shaped pattern is periodically and uniformly arranged in a mesh form.

FIG. 4 is a graph measuring the curvature of FIG. 3 with an alpha-step measuring apparatus. It can be seen that the etching depth is about 4000Å. The etching depth may have a range of 100 μm to 100 μm depending on the etching process.

FIG. 5 is a graph showing current-emitting intensity characteristics for the case of FIG. 3 and the conventional case where dry etching is not performed according to the present invention. FIG. In the case of FIG. 3 according to the present invention, it can be seen that the luminescence intensity is improved by about 1.3 times when the etching depth is 4000 kPa and about 1.5 times when the etching depth is 8000 kPa compared with the conventional art.

Through this, it can be seen that the probability of light being included within the critical angle in the sapphire substrate 10 and the air interface is increased by the formation of the bend by dry etching, and as the depth of the bend increases, the outside of the light in the side of the bend is increased. It can also be seen that the probability of exiting increases more.

FIG. 6 is a photograph showing a case where the shape of the etching pattern 14 is a line shape, and FIG. 7 is a graph measuring the bending of FIG. 6 by an alpha step measuring apparatus, and shows that the etching depth of this case is about 4000Å.

FIG. 8 is a graph showing current-emitting intensity characteristics of the case of FIG. 6 and the conventional case in which dry etching is not performed according to the present invention. In the case of FIG. 6 according to the present invention, it can be seen that the luminescence intensity is improved by about 1.2 times when the etching depth is 3000 Å and about 1.4 times when the etching depth is 8000 비 compared with the conventional art. In the case of the line pattern, as in the mesh form of FIG. 3, it can be seen that the emission intensity is improved as the formation of the bend and the depth of the bend are added.

9 is a graph of current-emitting intensity characteristics for the conventional case without surface bending and the case of FIGS. 3 and 6 according to the present invention. In the case of the present invention, it can be seen that the light emission intensity is improved as compared with the conventional case, and the light emission intensity is further improved in the case of the mesh pattern than the line pattern.

This is due to the fact that the mesh pattern has a higher periodicity than the line pattern, and thus the substrate surface area exposed to the air is wider, which releases the possibility of light exiting from the surface of the sapphire substrate. .

As described above, according to the present invention, the external photon efficiency is increased because the probability of photons satisfying a certain critical angle condition, that is, the probability that photons can escape to the outside due to the curvature of the substrate surface in contact with air increases. . In addition, in the sapphire dry etching process, by using gas such as methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), argon (Ar), etc., which are easy to manage and etch at low cost, instead of BCl ₃ gas. Even in mass production, high efficiency can be pursued at low cost.

Claims (9)

On the transparent substrate, a lower contact layer made of n-AlxGayInzN (0≤x, y, z≤1, x + y + z = 1) and p-AlxGayInzN (0≤x, y, z≤1, x + y An upper contact layer consisting of + z = 1) is formed, and a light emitting active layer consisting of AlxGayInzN (0 ≦ x, y, z ≦ 1, x + y + z = 1) is interposed between the lower contact layer and the upper contact layer. In the method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure, A method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure, wherein the bottom surface of the transparent substrate in contact with air is bent through dry etching. The semiconductor light emitting device of claim 1, wherein the bending has a periodicity. The method of claim 1, wherein the transparent substrate is a sapphire substrate, and the dry etching is performed using a mixed gas including methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), and argon (Ar). A method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure. The method of claim 3, wherein the dry etching is performed in an inductively coupled plasma reactor, wherein the ICP output is 200 ~ 2000W, RF plasma output is 10 ~ 1000W, the pressure of the reactor is 5 ~ 50mbar A method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure. According to claim 3, wherein the methane (CH ₄ ), chlorine (Cl ₂ ), hydrogen (H ₂ ), and argon (Ar) supply flow rate of 1 ~ 50sccm, 10 ~ 100sccm, 1 ~ 50sccm, 1 ~ 100sccm A method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure. The method of manufacturing a semiconductor light emitting device according to claim 1, wherein the curved shape has a square, circular, or line shape when viewed from above. The method of manufacturing a semiconductor light emitting device according to claim 1, wherein the side surface of the bend is a long trapezoid or a triangle. The method of claim 1, wherein the surface area of the transparent substrate is increased by 10 to 70% by dry etching. The method of manufacturing a semiconductor light emitting device having a III-V nitride flip chip structure according to claim 1, wherein the depth of the bend is 100 mW to 100 m.

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