TWI427821B - Method for fabricating planar conduction type light emitting diodes with thermal guide substrate - Google Patents

Description

Planar conductive light emitting diode with heat conducting substrate

The invention relates to a method for fabricating a light-emitting element, in particular to a method for fabricating a planar conductive light-emitting diode.

Referring to FIG. 1 , the planar light-emitting diode 1 includes an epitaxial substrate 11 , an epitaxial film unit 12 that is epitaxially grown upward from the epitaxial substrate 11 , and a phase of the epitaxial film unit 12 . An electrode unit 13 electrically connected to provide electrical energy.

The epitaxial substrate 11 is a material that is lattice-matched with a gallium nitride-based semiconductor material, such as sapphire or gallium arsenide (GaAs), so as to epitaxially grow the epitaxial film unit 12 with good quality.

The epitaxial film unit 12 is mainly formed by epitaxial epitaxy from the epitaxial substrate 11 by a gallium nitride-based semiconductor material, and has first and second cladding layers 121 and 122 which are respectively doped into n-type and p-type ( An n-type cladding layer, a p-type cladding layer, and an active layer 123 formed between the first and second cladding layers 121 and 122. The first and second cladding layers 121 and 122 are opposite to the active layer. 123 forms a carrier energy barrier and supplies electrical energy to the active layer 123 to generate electron-hole recombination, release energy, and convert it into light.

The electrode unit 13 includes two electrodes 131 and 132 for supplying electric energy, which are respectively connected to the first and second cladding layers 121 and 122 and are in ohmic contact, and can cooperate with each other to supply electric energy to the epitaxial film unit 12; When the two electrodes 131, 132 are applied with electric energy, the current dispersion flows through the active layer 123, so that the active layer 123 generates photons by the photoelectric effect, thereby emitting light outward.

In the present operation, the planar conductive light-emitting diode 1 is limited in operation, and nearly 70% of the electric power cannot be converted into light and converted into heat, resulting in an increase in the temperature of the operation junction of the planar-conducting light-emitting diode 1 Therefore, the carrier layer limitation effect of the active layer 123 is reduced, the carrier lifetime is shortened, and the carrier recombination efficiency is lowered, and the vicious cycle in which the thermal power is lowered to reduce the optical power is also caused. As the input current increases, the optical output power saturates or even decreases, which makes the component unstable and the actual working life is reduced. Therefore, how to reduce the junction temperature during operation has always been the planar conduction light-emitting diode 1 technology. One of the key points of field research.

In the case of the planar conduction light-emitting diode 1, the fastest and most effective way to reduce the junction temperature is to generate heat generated by the active layer 123, which is conducted to the outside through the epitaxial substrate 11 and is conducted to the outside. The epitaxial growth quality limited to the epitaxial film unit 12 is a necessary condition for the element to generate light by a quantum effect, and in order to grow the epitaxial film unit 12 having excellent crystal quality, it is necessary to use sapphire and arsenic with high lattice matching degree. Gallium or the like is used as the epitaxial substrate 11, but since the thermal conductivity of the sapphire material is only about 40 W/mK, the thermal conductivity of gallium arsenide is preferably about 50 W/mK, so the planar conduction light-emitting diode is In the case of the body 1, the heat generated during the operation cannot be effectively guided away from the element to maintain the stability and actual working life of the element when it is actuated.

Although it has been proposed to use a material having a higher thermal conductivity as the epitaxial substrate 11, a buffer layer is formed on the material having a lattice constant simultaneously matched with the substrate material and the gallium nitride-based semiconductor material ( Buffer layer), and then epitaxially grow the epitaxial film unit 12 to take into account the epitaxial film sheet The epitaxial quality and heat dissipation efficiency of element 12 improve the heat dissipation problem of the planar planar light-emitting diode 1 . However, such a method is still limited by the limitation of being used as the material of the epitaxial substrate 11 and the buffer layer - a material having a high thermal conductivity is selected as the epitaxial substrate 11, and the lattice matching degree is inevitably related to the gallium nitride-based semiconductor material. There is a considerable gap, even if the existence of the buffer layer, the epitaxial growth quality of the epitaxial film unit 12 is affected by the lattice matching degree; and at the same time, the planar conduction light-emitting light produced by such a process is The polar body, because there is a buffer layer on the structure, the heat conduction path must first pass through the buffer layer to be conducted to the outside through the substrate, and the heat dissipation efficiency is not significantly improved, but the process control of the epitaxial growth is increased. .

Therefore, the inventor is inspired by the current fabrication of a vertical-conducting light-emitting diode, and it is considered that the planar-conducting light-emitting diode can also remove the epitaxial substrate and replace the substrate composed of a material having a high heat transfer rate to achieve improvement. The problem of heat dissipation. However, the current vertical conduction light-emitting diodes are fabricated by laser lift-off technology to remove the epitaxial substrate. This technology is more expensive than the equipment, and the laser power is adjusted. Is the key to the success of the entire process - too high will damage the epitaxial film unit, too low to remove the epitaxial substrate - and the power modulation depends on experienced engineers, the technical level is too high, so The production experience of the vertical conduction light-emitting diode cannot be simply transferred to the production of the planar conductive light-emitting diode, and is not suitable for mass production, and must be re-improved.

After several experiments, the inventor proposed a planar guide with a thermally conductive substrate The manufacturing method of the light emitting diode includes the following five steps.

First, a sacrificial layer made of a material which is lattice-matched with a gallium nitride-based semiconductor material and has a high etching selectivity is grown on an epitaxial substrate for epitaxially growing a gallium nitride-based semiconductor material.

An epitaxial film unit mainly composed of a gallium nitride-based semiconductor material and generating light by a photoelectric effect when power is supplied is formed upward from the sacrificial layer.

Then, a temporary substrate supporting the epitaxial film unit is bonded to the epitaxial film unit.

A plurality of perforations through the epitaxial substrate are then formed.

The sacrificial layer is then etched away to separate the epitaxial substrate from the epitaxial film unit, and the epitaxial film unit is exposed opposite to the bottom surface to which the temporary substrate is bonded.

Finally, a thermal conductive substrate made of a material having a high thermal conductivity is attached to the bottom surface of the epitaxial film unit, and the temporary substrate is removed.

The effect of the present invention is to propose a complete production method suitable for mass production to produce a novel planar conductive light-emitting diode having a thermal conductive substrate, and at the same time, a planar guide method prepared by such a manufacturing method. The light-emitting diode has a stable performance due to high heat dissipation efficiency and a long practical working life.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Before the present invention is described in detail, it is to be noted that In the description, similar elements are denoted by the same reference numerals.

Referring to FIG. 2 and FIG. 3, a preferred embodiment of a method for fabricating a planar conductive light-emitting diode having a thermal conductive substrate is to produce a planar conductive light having a thermal conductive substrate as shown in FIG. Diode 3.

The manufacturing method of the present invention can be more clearly understood after understanding the structure of the produced product.

Referring to FIG. 3, the planar conductive LED 3 having a thermal conductive substrate comprises a thermal conductive substrate 4 and an epitaxial film unit 5 attached to the thermal conductive substrate.

The thermal conductive substrate 4 is selected from a material having a high thermal conductivity, such as ruthenium, a metal, an alloy, or the like, and is supported by the epitaxial film unit 5 to support the structure of the epitaxial film unit 5, At the same time, the heat generated by the operation of the epitaxial film unit 5 is quickly guided away to the outside, and the junction temperature is lowered to stabilize the operation of the epitaxial film unit 5.

The epitaxial film unit 5 is mainly formed by epitaxially epitaxially forming a gallium nitride-based semiconductor material from an epitaxial substrate, and then bonded to the heat dissipating substrate 4, and has a doped n and p type, respectively. One or two cladding layers 51, 52, a layer of active layer 53 formed between the first and second cladding layers, and two electrodes formed of conductive materials on the first and second cladding layers 51, 52, respectively 54. The first and second cladding layers 51 and 52 form a carrier energy barrier with respect to the active layer 53 to generate electron-hole recombination, release energy, and convert into light when power is supplied.

The two electrodes 54 are in ohmic contact with the first and second cladding layers 51 and 52, respectively, and can cooperate with the first and second cladding layers 51 and 52 and the active layer 53. Providing electrical energy; when electrical energy is applied from the two electrodes 54, the current dispersion flows through the active layer 53, causing the active layer 53 to generate photons by photoelectric effect, thereby emitting light outward; and the active layer 53 is not converted into light when actuated The converted waste heat is quickly guided from the epitaxial film unit 5 to the outside through the thermal conductive substrate 4, and can effectively maintain/lower the temperature of the operating junction, thereby enabling the component to stably operate and effectively extend the actual working life of the component. .

The above-mentioned planar conductive light-emitting diode 3 having a thermal conductive substrate is produced by a preferred embodiment of a method for fabricating a planar conductive light-emitting diode having a thermally conductive substrate of the present invention.

Referring to FIG. 2, first, step 21 is performed on a epitaxial substrate for epitaxially growing a gallium nitride-based semiconductor material, and a material having a lattice matching with a gallium nitride-based semiconductor material and having a high etching selectivity ratio is selected ( In the case of hydrofluoric acid (HF), the etching ratio is selected to be not less than 20) to form a sacrificial layer; here, a familiar sapphire substrate is selected as the epitaxial substrate, and zinc oxide (ZnO) is used as the sacrifice. As a constituent material of the layer, a zinc oxide film having a thickness of not more than 10 μm is deposited as a sacrificial layer, and of course, other non-nitrogen compounds such as ZnAlO, ZnMgO, and ZnBeO are also one of the material choices, and since such materials are variously selected, No more examples are given here.

Next, in step 22, the epitaxial film unit 5 is formed upward from the sacrificial layer; here, the first cladding layer 51, the active layer 53, and the second cladding layer 52 are sequentially epitaxially grown, and then conductive. The material deposits the two electrodes 54.

Next, in step 23, a temporary substrate (here, a glass substrate) capable of supporting the epitaxial film unit 5 is bonded to the epitaxial film unit 5 by wax. .

Step 24 is further performed, and the semi-finished product obtained in step 23 is immersed in an etching solution containing hydrogen fluoride to etch away the sacrificial layer, and the epitaxial substrate is separated from the epitaxial film unit 5 to which the temporary substrate is bonded, and the The bottom surface of the epitaxial film unit 5 is exposed.

Finally, in step 25, the thermal conductive substrate 4 pre-formed from the material having a high thermal conductivity is attached to the bottom surface of the epitaxial film unit 5, and the wax for fixing the temporary substrate is melted off and the temporary substrate is removed. Fabrication of a planar conduction light-emitting diode 3 having a thermally conductive substrate.

Preferably, before performing step 24, a step may be performed to thin the epitaxial substrate to a thickness of not more than 10 μm to accelerate the wet etching to remove the sacrificial layer structure; or to form a majority in one step. Punching through the epitaxial substrate (the process of forming the perforations may be performed before or after thinning the epitaxial substrate, or may be performed separately, and does not affect the process of thinning the epitaxial substrate) to simultaneously achieve Accelerating the wet etching to remove the sacrificial layer structure, and avoiding the stress damage of the epitaxial film unit 5 when thinning the epitaxial substrate, thereby achieving the effect of improving the process yield and reducing the time cost of the overall process.

In addition, in the overall implementation step, when the step 22 is performed, only the first and second cladding layers 51 and 52 and the active layer 53 are formed by epitaxy, and then the removal step is performed in step 25. After the substrate, the change of the two electrodes 54 is made. Since the fine adjustment of these implementation details is varied, no more description will be given here.

In addition, it is to be noted that although the above-mentioned planar conduction with the thermal conductive substrate is The light-emitting diode 3 is described by the most basic structure in which the epitaxial film unit 5 includes only the first and second cladding layers 51 and 52, the active layer 53, and the two electrodes 54. In fact, the epitaxial film unit is further The transparent conductive layer formed on the second cladding layer by using a transparent and electrically conductive metal oxide may be included. Of course, when corresponding to the structure, the two electrodes are respectively disposed on the first cladding layer and the transparent conductive layer. On the layer, the current through the active layer is uniformly diffused to enhance the quantum efficiency. Since these structures are well known in the art and are not the focus of the present invention, they are not described here. In the manufacturing process, it is similar to the foregoing manufacturing method. The only difference is that the transparent conductive layer can be epitaxially formed to form the first and second cladding layers 51 and 52 and the active layer 53 when the step 22 is performed. Thereafter, the transparent conductive layer is deposited, and then the second electrode 54 is deposited, or when the step 22 is performed, only the first and second cladding layers 51 and 52 and the active layer 53 are formed by epitaxy, and then After the temporary substrate is removed in the implementation step 25, the transparent conductive layer is formed to form the two electrodes 54. Since the fine adjustment of the implementation details is numerous, no further description will be given here.

Referring to FIG. 4, it is to be noted that the thermal conductive substrate 6 may include a substrate 61, a mirror 62 formed on the substrate 61 and connected to the bottom surface of the epitaxial film unit 5, and two connecting electrodes 63. In the complicated structure, the substrate 61 is a plate body made of a material having a high thermal conductivity coefficient, and the mirror 62 is made of a material having a high thermal conductivity and reflecting light, such as a metal, an alloy, or the like, or a plurality of layers stacked and having A dielectric material having a high refractive index and a low refractive index is formed for re-reflecting light generated by the epitaxial film unit 5 and traveling toward the thermally conductive substrate 6 to improve overall luminous efficiency. The two connection electrodes 63 At the same time, it is electrically connected to an external circuit or an external power supply device, and can be connected to, for example, a gold wire 7 to supply electric power to the epitaxial film unit 5, and the lifting device is lifted by the overall design of the thermal conductive substrate 6. The brightness of the light, while at the same time responding to the increasingly complex circuit requirements.

From the above description, it can be seen that the present invention mainly proposes a complete manufacturing method suitable for mass production and technical level is not high, and a sapphire substrate whose lattice constant is matched with a GaN semiconductor material is selected as an epitaxial substrate, and at the same time, A material in which a gallium nitride-based semiconductor material has a lattice matching and a high etching selectivity ratio, such as zinc oxide, first grows a sacrificial layer on an epitaxial substrate, and epitaxially grows an epitaxial film unit 5 having an excellent quality structure. The obtained component thus has high operating efficiency, and then the sacrificial layer is separated from the epitaxial film unit 5 by etching to remove the sacrificial substrate, and the thermal conductive substrate 4 having high heat conduction effect can be attached to the Lei On the crystal film unit 5, the completed planar conductive light-emitting diode can quickly guide the inner waste heat generated by the epitaxial film unit 5 to the outside through the thermal conductive substrate 4, and the active layer is surely maintained. The junction temperature makes the component operation stable and effectively extends the actual working life.

In addition, the manufacturing method of the present invention also improves the current vertical conduction light-emitting diode using the laser stripping technology, which relies on the experience of the operation engineer to adjust the laser power, and the technical level is too high to be mass-produced. A planar conduction light-emitting diode 3 having a heat-conducting substrate having a high light-emitting performance and a working life does achieve the inventive object of the present invention.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention cannot be limited thereto, that is, the patent application according to the present invention The scope of the invention and the equivalent equivalents and modifications of the invention are still within the scope of the invention.

1‧‧‧ Planar Guided Light Emitting Diode

11‧‧‧ Epitaxial substrate

12‧‧‧ epitaxial film unit

121‧‧‧First coating

122‧‧‧Second coating

123‧‧‧Active layer

13‧‧‧Electrode unit

131‧‧‧electrode

132‧‧‧ electrodes

21‧‧‧Steps

22‧‧‧Steps

23‧‧‧Steps

24‧‧‧Steps

25‧‧‧Steps

3‧‧‧Plane-conducting light-emitting diodes with thermal conducting substrates

4‧‧‧Hot conductive substrate

5‧‧‧ epitaxial film unit

51‧‧‧First coating

52‧‧‧Second coating

53‧‧‧ active layer

54‧‧‧Electrode

6‧‧‧Hot conductive substrate

61‧‧‧Base

62‧‧‧Mirror

63‧‧‧Connecting electrode

7‧‧‧ Gold wire

1 is a schematic cross-sectional view showing a conventional planar light-emitting diode; FIG. 2 is a flow chart showing a preferred embodiment of a method for fabricating a light-emitting diode having a heat-conductive substrate according to the present invention; Is a schematic cross-sectional view showing a planar conductive light-emitting diode having a thermally conductive substrate produced by the fabrication method of FIG. 2; and FIG. 4 is a schematic cross-sectional view showing the planar conductive light having the thermal conductive substrate of the present invention. The manufacturing method of the diode is to fabricate a light-emitting diode having a heat conducting substrate, which has a structure of a heat conducting substrate.

Step 21‧‧‧ Growing a sacrificial layer on the epitaxial substrate

Step 22‧‧‧ Epitaxially epitaxially forming from the sacrificial layer an epitaxial film unit that generates light by photoelectric effect when supplying electrical energy

Step 23‧‧‧ attaching the temporary substrate supporting the epitaxial film unit to the epitaxial film unit

Step 24‧‧‧ Etch the sacrificial layer to separate the epitaxial substrate from the epitaxial film unit and expose the bottom surface of the epitaxial film unit

Step 25‧‧‧After attaching the thermal conductive substrate made of a material with high thermal conductivity to the bottom surface of the epitaxial film unit, remove the temporary substrate

Claims (5)

A method for fabricating a planar conduction light-emitting diode having a thermal conductive substrate, comprising: (a) growing on a epitaxial substrate for epitaxially growing a gallium nitride-based semiconductor material, and growing gallium nitride a sacrificial layer composed of a material in which the semiconductor material phase is lattice-matched and etched with a high selectivity; (b) an epitaxial layer formed mainly of a gallium nitride-based semiconductor material and generating light by a photoelectric effect when supplying electric energy is formed upward from the sacrificial layer a film unit; (c) bonding a temporary substrate supporting the epitaxial film unit to the epitaxial film unit; (d) forming a plurality of perforations penetrating the epitaxial substrate; (e) the step (d) Thereafter, the sacrificial layer is etched away to separate the epitaxial substrate from the epitaxial film unit, and the epitaxial film unit is exposed opposite to the bottom surface to which the temporary substrate is bonded; and (f) a high thermal conductivity coefficient The thermal conductive substrate composed of the material is attached to the bottom surface of the epitaxial film unit to remove the temporary substrate. The method for fabricating a planar conductive light-emitting diode having a thermally conductive substrate according to claim 1, wherein the sacrificial layer is formed by zinc oxide deposition and has a thickness of not more than 10 μm, and the step (e) is The sacrificial layer is removed by etching using an etching solution containing hydrogen fluoride. The method for fabricating a planar conductive light-emitting diode having a thermally conductive substrate according to claim 1, wherein the step (d) further thins the epitaxial substrate to a thickness of not more than 10 μm. The method for fabricating a planar-conducting light-emitting diode having a thermally conductive substrate according to the first aspect of the invention, wherein the epitaxial film unit formed in the step (b) comprises a doped electrically opposite one. a first cladding layer, a second cladding layer, an active layer between the first and second cladding layers and forming a carrier barrier relative to the first and second cladding layers, and two formed of a conductive material And electrodes respectively ohmically contacting the first and second cladding layers to provide electrical energy. The method for fabricating a planar-conducting light-emitting diode having a thermally conductive substrate according to the first aspect of the invention, wherein the epitaxial film unit formed in the step (b) comprises a doped electrically opposite one. a first cladding layer, a second cladding layer, an active layer between the first and second cladding layers and forming a carrier barrier relative to the first and second cladding layers, and the layer is transparent and electrically conductive The metal oxide is a transparent conductive layer formed on the second cladding layer, and two electrodes formed of a conductive material and respectively in ohmic contact with the first cladding layer and the transparent conductive layer to provide electrical energy.