CN1369920A - Light-emitting diode and its manufacturing method - Google Patents

Abstract

A light emitting diode and a manufacturing method thereof, comprising providing a light emitting diode epitaxial wafer, on which a light emitting diode structure formed by multiple aluminum gallium arsenide epitaxial layers is grown on a light absorbing substrate; and the transparent substrate and the surface of the light emitting diode epitaxial layer are bonded together through a soft transparent adhesive layer. The light emitting efficiency of the light emitting diode is greatly improved.

Description

Light-emitting diode and its manufacturing method

The present invention relates to a light emitting diode (Light Emitting Diode; LED) chip structure and a manufacturing method thereof, in particular to a structure of an aluminum gallium indium phosphide (AIGaln P) light emitting diode and a manufacturing method thereof.

The commonly used aluminum gallium indium phosphide light-emitting diode has a double heterostructure (DoubleHeterostructure; DH), as shown in Figure 6, is grown on an n-type gallium arsenide (GaAs) substrate 3 with an aluminum content of 70-100%. n-type (Al _x Ga _1-X ) _0.5 ln _0.5 P lower cladding layer 4, (Al _x Ga _1-X ) _0.5 ln _0.5 P active layer 5, a p-type (Al _x Ga _1-X ) _0.5 ln _0.5 P upper cladding layer 6 and a p-type high energy gap current spreading layer (Current Spreading Layer) 7, the material of this layer can be gallium phosphide, phosphorus arsenide, phosphide Indium gallium or aluminum gallium arsenide, etc., by changing the composition of the active layer, the light-emitting wavelength of the light-emitting diode can be changed, so that it can produce a wavelength from 650nm red to 555nm pure green. However, this commonly used light-emitting diode has a disadvantage, that is, when the light generated by the active layer is incident on the gallium arsenide substrate, the light incident on the gallium arsenide substrate will be eliminated due to the small energy gap of the gallium arsenide substrate. Absorbed, and cannot produce high-efficiency light-emitting diodes.

In order to avoid the light absorption of the substrate, there are some literatures disclosing LED technologies, but these technologies have their disadvantages and limitations. For example, Sugawara et al. published in [Appl.PhysLett.Vol.61, 1775-1777 (1992)] disclosed a method of adding a layer of Distributed Bragg Reflector (Distributed Bragg Reflector; DBR) on the gallium arsenide substrate, In order to reflect the light incident on the GaAs substrate and reduce the absorption of the Arsenide grafted substrate, however, since the DBR reflective layer can only effectively reflect the light energy that is close to the vertical incidence on the GaAs substrate, the practical effect is not great.

Kish et al. published in [Appl.Phys Lett.VOl.64, NO.21, 2839, (1994) document titled "Very high-efficiency semiconductor wafer-bonded transparent-substrate (Al _x Ga _1-X ) _0.5 ln _0.5 P/GaP"] discloses a transparent-substrate (Transparent-Substrate; TS) (Al _x Ga _1-X ) _0.5 ln _0.5 P/GaP light-emitting diode for wafer bonding. This TSAIGalnP LED uses vapor phase epitaxy (VPE) to form a relatively thick (about 50 μm) P-type gallium phosphide (GaP) window layer, and then selectively removes N-type arsenic by commonly used chemical etching methods. Gallium (GaAs) substrates. The exposed N-type (Al _x Ga _1-X ) _0.5 ln _0.5 P lower cladding layer is then bonded to an n-type GaP substrate with a thickness of about 8-10 mils. Since the wafer bonding (Wafer Bonding) is to directly bond two III-V compound semiconductors together, it needs to be heated and pressed at a relatively high temperature for a period of time to complete. In terms of luminous brightness, the TS AIGalnP LED obtained in this way is more than twice as large as the commonly used Absorbing-Substrate (AS) AIGalnP LED. However, the disadvantage of this TS AIGalnP LED is that the manufacturing process is too complicated, and usually has a non-ohmic contact with high resistance characteristics at the bonding interface, therefore, it is difficult to obtain high yield of production and it is difficult to reduce the manufacturing cost.

Another commonly used technique, such as Horng et al. published in [Appl.Phys.Lett.Vol.75, No.20, 3054 (1999)] literature, named "AIGalnP light-emitting dlodes with mirror substrates fabricated by wafer bonding"] . Horng et al. taught a chip fusion technology to form a mirror-substrate (Mirror-Substrate; MS) AlGaInP/Metal/SiO2/Si LED. It uses AuBe/Au as adhesive material to bond silicon substrate and LED epitaxial layer. However, at an operating current of 20mA, the luminous intensity of this MSAIGalnP LED is only about 90med, which is still at least 40% less than that of the TS AIGalnP LED, so its luminous intensity is not satisfactory.

The purpose of the present invention is to provide a light-emitting diode structure, which includes a multi-layer epitaxial structure with a light-emitting layer, combined with a transparent substrate through an adhesive layer, to overcome the disadvantages of the prior art, and to improve the efficiency of light-emitting diodes. The purpose of luminous efficiency. The light-emitting layer of this diode includes homostructure (Homostructure), single heterostructure (Single heterostructure, SH), double heterostructure (Double heterostructure, DH) or multiple quantum well structure (Multi quantum wells, MQWs): also includes the second An ohmic contact metal electrode layer and a second ohmic contact metal electrode layer are respectively in contact with the first conductivity type epitaxial layer and the second conductivity type epitaxial layer, and the first ohmic contact metal electrode layer and the second ohmic contact metal electrode layer The layers are all on the same side.

The second object of the present invention is to provide a method of manufacturing a light-emitting diode, through a transparent adhesive layer, such as BCB (B-staged bisbenzocyclobutene BCB) resin, the light-emitting diode epitaxial layer and the transparent substrate are combined, and the light-emitting diode substrate Removing to the first conductive type etch stop layer to form a first ohmic contact metal electrode layer, while partially etching to the second conductive type epitaxial layer to form a second ohmic contact metal electrode layer, and the first ohmic contact metal electrode layer is located on the same side as the second ohmic contact metal electrode layer. The material of the adhesive layer used in the present invention is not limited to BCB resin, and other adhesive substances that can form a transparent state, such as epoxy resin (EpOXy), are suitable for the present invention.

The object of the present invention is achieved in the following way: a light emitting diode, comprising a light emitting diode epitaxial wafer, characterized in that: the epitaxial wafer is provided with a multilayer aluminum gallium indium phosphide epitaxial layer to form a light emitting diode structure grown on a light absorbing substrate ; The transparent substrate and the surface of the epitaxial layer of the light-emitting diode are bonded together through a soft transparent adhesive layer.

The substrate is gallium arsenide. The LED is aluminum gallium indium phosphide. The light-emitting diode is a single heterostructure of aluminum gallium indium phosphide. The light-emitting diode is an AlGaIn double heterostructure. The light-emitting diode is an aluminum gallium indium phosphide quantum well structure. The material of the transparent adhesive layer includes BCB resin. The material of the soft transparent adhesive layer includes epoxy resin. The light-absorbing substrate is removed after the transparent substrate is bonded to the light-emitting diode. The transparent substrate is sapphire. The transparent substrate is glass. The transparent substrate is gallium phosphide or gallium arsenide phosphide. The transparent substrate is GaSe, ZnS or ZnS. The transparent substrate is silicon carbide. The method of bonding the transparent substrate and the surface of the epitaxial layer of the light-emitting diode to the transparent adhesive layer at least includes: the first stage includes pressing and heating in the range of 60-100°C; the second stage includes pressing and heating at 200-100°C; Pressurized and heated within 600°C.

A method for manufacturing a light-emitting diode, comprising providing a light-emitting diode epitaxial wafer, characterized in that: the epitaxial wafer is provided with a multi-layer aluminum gallium arsenide epitaxial layer to form a light-emitting diode structure grown on a light-absorbing substrate; through a soft transparent The adhesive layer joins the transparent substrate and the surface of the epitaxial layer of the light emitting diode together.

The substrate is gallium arsenide. The light emitting diode is aluminum gallium arsenide. The LED is an aluminum gallium arsenide single heterostructure. The LED is an aluminum gallium arsenide double heterostructure. The LED is an aluminum gallium arsenide quantum well structure. The material of the transparent adhesive layer includes BCB resin. The material of the transparent adhesive layer includes epoxy resin. After the transparent substrate is bonded to the LED, the light-absorbing substrate is removed. The transparent substrate is sapphire. The transparent substrate is glass. The transparent substrate is gallium phosphide or gallium arsenide phosphide. The transparent substrate is gallium selenide, zinc sulfide or zinc selenide sulfur. The transparent substrate is silicon carbide. The step of using the transparent adhesive layer to bond the transparent substrate and the surface of the epitaxial layer of the light-emitting diode at least includes the following methods: the first stage includes pressing and heating in the range of 60-100°C; The second stage includes pressurization and heating in the range of 200-600°C.

The main advantages of the present invention are:

1. Provide a simple LED chip bonding structure, which can carry out chip bonding at a lower temperature and reduce the volatilization of group V elements during the bonding process. And because there is no disadvantage of base being light-absorbed, the luminous efficiency of the LED can be greatly improved.

2. The manufacturing process is simple, and low-cost transparent substrates such as glass can be used, so the effect of high yield and low cost can be obtained.

3. The light-emitting diode of the present invention uses a soft transparent adhesive layer to join the light-emitting diode and a transparent substrate. Therefore, even if the surface of the light-emitting diode epitaxial wafer is uneven, it can be tightly bonded together by the adhesive layer .

Further description will be given below in conjunction with preferred embodiments and accompanying drawings.

Fig. 1 is a schematic diagram of a manufacturing process of a light-emitting diode of the present invention;

Fig. 2 is a schematic diagram of the second manufacturing process of the light-emitting diode of the present invention;

Fig. 3 is a schematic diagram of the third manufacturing process of the light-emitting diode of the present invention;

Fig. 4 is a structural schematic diagram of a light emitting diode of the present invention;

Fig. 5 is a schematic structural diagram of another light-emitting diode of the present invention;

Fig. 6 is a schematic diagram of the structure of a commonly used light-emitting diode;

Referring to FIGS. 1-3 , the present invention discloses a light emitting diode structure and a manufacturing method thereof. The epitaxial structure of the light-emitting diode of the present invention includes an N-type gallium arsenide substrate 26, an etching stop layer 24, and an N-type aluminum gallium indium phosphide (Al _x Ga _1-X ) _0.5 ln _0.5 P lower cladding layer stacked in sequence 22 and aluminum gallium indium phosphide (Al _x Ga _1-X ) _0.5 ln _0.5 P active layer (Active Layer) 20, P-type aluminum gallium indium phosphide (Al _x Ga _1-X ) _0.5 ln _0.5 P upper cladding layer 18 and a P-type ohmic contact epitaxial layer (Ohmic Contact Epitaxial Layer) 16 .

The material of the P-type ohmic contact epitaxial layer can be aluminum gallium arsenide or aluminum gallium indium phosphide or phosphorus gallium arsenide, as long as its energy gap is larger than the active layer, it will not absorb the light generated by the active layer, but it must have high Carrier concentration, in order to facilitate the formation of ohmic contact, can be selected as a P-type ohmic contact epitaxial layer.

The aluminum content of the above-mentioned active layer is in the range of x=0-0.45, and the aluminum content of the upper and lower cladding layers is controlled at X=0.5-1.0. When the aluminum content of the active layer X=0, the active layer The composition is Ga _0.5 ln _0.5 P, and the wavelength of the light-emitting diode is about 635nm.

The compound ratio mentioned above, for example, the active layer (Al _x Ga _1-X ) _0.5 ln _0.5 P is just a preferred example and is not intended to limit the present invention, and the present invention is also applicable to other ratios. In addition, in the present invention, the structure of the AIGalnP active layer 20 can be a commonly used homogeneous structure, single heterostructure, double heterostructure or multiple quantum wells. The so-called double heterostructure (DH) includes an N-type aluminum gallium indium phosphide (Al _x Ga _1-X ) _0.5 ln _0.5 P lower cladding layer 22 and an aluminum gallium indium phosphide (Al _x Ga 1-X ) shown in FIG. _1-X ) _0.5 ln _0.5 P active layer 20, a P-type aluminum gallium indium phosphide (Al _x Ga _1-X ) _0.5 ln _0.5 P upper cladding layer 18, wherein the preferred thicknesses of these three layers are respectively 0.5 -3.0μm, 0.5-2.0μm, 0.5-3.0μm.

In the present invention, the material of the etch stop layer 24 can be any compound semiconductor of III-V elements, as long as its lattice constant can be matched with the gallium arsenide substrate 26 to avoid misalignment, and the etching rate is much lower than that made by arsenic The substrate 26 composed of GaN material can be used as an etching stop layer. In the present invention, a preferred material of the etch stop layer 24 may be indium gallium phosphide (InGaP) or aluminum gallium arsenide (AIGaAs). In this embodiment, the etching rate of the N-type AlGaInP lower cladding layer is also much lower than that of the GaAs substrate. Therefore, another epitaxial layer with a different composition may not be needed as an etch stop layer as long as it is thicker.

The structure shown in FIG. 2 includes a transparent adhesive layer 14 made of BCB (B-staged bisbenzocy clobu tene: BCB) resin and a transparent substrate TS 10. The material of the adhesive layer 14 used in the present invention is not limited to BCB resin, and other adhesive substances with similar properties that can form a transparent state, such as epoxy resin, are suitable for the present invention. Transparent substrates can be made of glass, sapphire (Sapphire) wafers, silicon carbide (SiC) chips, gallium phosphide (GaP) chips, gallium arsenide phosphide (GaAsP) wafers, zinc selenide (ZnSe) wafers, zinc sulfide (ZnS) Wafers and zinc selenium sulfide (ZnSSe) wafers, etc., as long as these chips do not have a large absorption for the light emitted by the light-emitting layer, they can be used as the transparent substrate of the present invention, and another advantage of the present invention is that the used The transparent substrate does not have to be a single wafer, because the current does not pass through the transparent substrate when the LED emits light, the purpose of the transparent substrate is only as a mechanical support to prevent the LED epitaxial layer from breaking during the process of manufacturing crystal grains. Therefore, polycrystalline (POlycrysta) substrates or amorphous (Amorphous) substrates can also be used, thereby greatly reducing production costs.

Referring to the light-emitting diode epiwafer in Figure 1 and the transparent substrate in Figure 2, they are bonded together through the BCB adhesive layer, and the bonding process is completed at a high temperature of about 250°C, pressurized and heated for a period of time. In order to improve the bonding characteristics between the LED epitaxial wafer and the transparent substrate, a layer of bonding accelerator can also be coated on the surface of the LED epitaxial wafer and the transparent substrate, and then coated with BCB, and then heated at a high temperature of about 250°C Pressing and heating for a period of time to complete the bonding of the epitaxial wafer and the transparent substrate. In order to make the bonding effect better, the light-emitting diode epiwafer and transparent substrate bonded by BCB can also be heated at a low temperature of 60-100°C for a period of time to drive off the organic solvent in the BCB, and then increase the temperature. When the temperature reaches the range of 200-600°C, the BCB is closely bonded with the LED epiwafer and the transparent substrate. The adhered epiwafer is then etched with an etching solution such as (5H ₃ PO ₄ : 3H ₂ O ₂ : 3H ₂ O or INH ₄ OH: 35H ₂ O ₂ ) to remove the opaque N-type GaAs substrate . If the etch stop layer is InGaP or AIGaAs, it will still absorb the light generated by the active layer. Therefore, it must be completely removed with an etching solution or only the part in contact with the N-type ohmic contact metal electrode layer will be left. Then use dry etching method such as RIE to remove part of the N-type AlGaInP lower cladding layer, the AlGaInP active layer and the P-type AlGaInP upper cladding layer, and expose the P-type ohmic contact Epitaxial layer, then form a P-type ohmic contact metal electrode layer 28 on the P-type ohmic contact epitaxial layer 16, and form an N-type ohmic contact metal electrode layer 30 on the N-type aluminum gallium indium phosphide lower cladding layer 22 , thus forming a light-emitting diode structure in which P and N ohmic contact metal electrode layers are on the same side, as shown in FIG. 3 .

The wavelength of light emitted by the aluminum gallium indium phosphide light-emitting diode obtained according to the present invention is about 635nm, and under the operating current of 20mA, its light output power is about 4mW, which is the highest of the commonly used absorption type substrate aluminum gallium indium phosphide light-emitting diode. More than 2 times the optical output power.

The present invention is not limited to be applicable only to high-brightness AlGaInP light-emitting diodes, and the present invention is also applicable to other light-emitting diode materials, such as AlGaAs red and infrared light-emitting diodes. FIG. 4 is a schematic diagram of another epitaxial structure of the present invention. The epitaxial structure of the 650nm aluminum gallium arsenide red light-emitting diode of the present invention includes an N-type gallium arsenide substrate 51 and an N-type aluminum gallium arsenide lower cladding layer 52 (the aluminum content is 70-80% and the thickness is 0.5 -3 μm), an AlGaAs active layer 53 (with an aluminum content of about 35% and a thickness of about 0.5-2.0 μm), and a P-type AlGaAs upper cladding layer 54 (with an aluminum content of about 70-80% and a thickness of about 0.5-3.0μm). Then, the above-mentioned AlGaAs red light-emitting diode epitaxial wafer and a transparent substrate 56 (such as a sapphire wafer) are bonded together with BCB silicone resin 55 . The adhered epiwafer is then etched with an etching solution (eg, NH ₄ OH:H ₂ O ₂ =1.7:1) to remove the opaque N-type GaAs substrate. Then, a part of the N-type AlGaAs lower cladding layer and the AlGaAs active layer are removed by wet etching or dry etching, and the P-type AlGaAs upper cladding layer is exposed. Next, a P-type ohmic contact metal electrode layer 57 is formed on the P-type AlGaAs upper cladding layer 54, and an N-type ohmic contact metal electrode layer 58 is formed on the N-type AlGaAs lower cladding layer 52. A light emitting diode with P and N ohmic contact metal electrode body layers on the same side is formed, as shown in FIG. 5 .

The wavelength of light emitted by the red aluminum gallium arsenide light-emitting diode obtained according to the present invention is about 650nm, and under the operating current of 20mA, its light output power is 2 times that of the common absorption type substrate aluminum gallium arsenide light-emitting diode. times.

Since the light-emitting diode of the present invention adopts a transparent substrate, and the P and N ohmic contact metal electrodes are located on the other side of the transparent substrate, it can be packaged in a flip-chip manner without the need for commonly used metal bonding wires. better. And because the transparent substrate does not absorb light, the brightness of the light-emitting diode can be significantly increased. In addition, if the transparent substrate is made of sapphire, glass or silicon carbide, etc., because these materials are very hard, the thickness of the substrate can be reduced to about 100 microns without cracking during the grain process or packaging process, and thinner substrates can be manufactured. And smaller light-emitting diodes.

The light-emitting diode of the present invention uses a soft transparent adhesive layer to join the light-emitting diode and a transparent substrate. Therefore, even if the surface of the light-emitting diode epiwafer is uneven, the adhesive layer can be used to tightly bond them together.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. All other equivalent changes or modifications that do not deviate from the spirit disclosed in the present invention should be included in the scope of the present invention. within the scope of protection.

Claims (30)

1. a light-emitting diode comprises light-emitting diode chip, it is characterized in that: this wafer of heap of stone is provided with the light emitting diode construction of multilayer AlGaInP epitaxial layer formation and grows up on the extinction substrate; Transparency carrier and this light-emitting diode epitaxial layer surface are bonded together by soft clear adhesive.

2. as claim 1 a described light-emitting diode, it is characterized in that: this substrate is a GaAs.

3. as claim 1 a described light-emitting diode, it is characterized in that: this light-emitting diode is an AlGaInP.

4. as claim 1 a described light-emitting diode, it is characterized in that: this light-emitting diode is an AlGaInP single heterojunction structure.

5. as claim 1 a described light-emitting diode, it is characterized in that: this light-emitting diode is that aluminum phosphate is sowed the indium double-heterostructure.

6. as claim 1 a described light-emitting diode, it is characterized in that: this light-emitting diode is the AlGaInP quantum well structures.

7. as claim 1 a described light-emitting diode, it is characterized in that: the material of the clear adhesive of this matter comprises the BCB resin.

8. as claim 1 a described light-emitting diode, it is characterized in that: the material of the clear adhesive that this is soft comprises epoxy resin.

9. as claim 1 a described light-emitting diode, it is characterized in that: this transparency carrier with this extinction substrate is removed after light-emitting diode engages.

10. as claim 1 a described light-emitting diode, it is characterized in that: this transparency carrier is a sapphire.

11. as claim 1 a described light-emitting diode, it is characterized in that: this transparency carrier is a glass.

12. as claim 1 a described light-emitting diode, it is characterized in that: this transparency carrier is gallium phosphide or gallium arsenide phosphide.

13. as claim 1 a described light-emitting diode, it is characterized in that: this transparency carrier is gallium selenide, zinc sulphide or tin zinc sulphur.

14. as claim 1 a described light-emitting diode, it is characterized in that: this transparency carrier is a carborundum.

15. as claim 1 a described light-emitting diode, it is characterized in that: this clear adhesive comprises this transparency carrier and light-emitting diode epitaxial layer surface engagement mode together at least: the phase I is included in to pressurize in the 60-100 ℃ of scope and heat and forms; Second stage is included in to pressurize in the 200-600 ℃ of scope and heat and forms.

16. the manufacturing method for LED of a claim 1 comprises light-emitting diode chip is provided, and it is characterized in that: this wafer of heap of stone is provided with the light emitting diode construction of multilayer aluminum gallium arsenide epitaxial layer formation and grows up on the extinction substrate; By soft clear adhesive together with transparency carrier and light-emitting diode epitaxial layer surface engagement.

17. as claim 16 a described manufacturing method for LED, it is characterized in that: this substrate is a GaAs.

18. as claim 16 a described manufacturing method for LED, it is characterized in that: this light-emitting diode is an aluminum gallium arsenide.

19. as claim 16 a described manufacturing method for LED, it is characterized in that: this light-emitting diode is an aluminum gallium arsenide single heterojunction structure.

20. as claim 16 a described manufacturing method for LED, it is characterized in that: this light-emitting diode is the aluminum gallium arsenide double-heterostructure.

21. as claim 16 a described manufacturing method for LED, it is characterized in that: this light-emitting diode is the aluminum gallium arsenide quantum well structures.

22. as claim 16 a described manufacturing method for LED, it is characterized in that: the material of this clear adhesive comprises the BCB resin.

23. as claim 16 a described manufacturing method for LED, it is characterized in that: the material of this clear adhesive comprises epoxy resin.

24., it is characterized in that as claim 16 a described manufacturing method for LED: transparency carrier with the substrate of extinction is removed after light-emitting diode engages.

25. as claim 16 a described manufacturing method for LED, it is characterized in that: this transparency carrier is a sapphire.

26. as claim 16 a described manufacturing method for LED, it is characterized in that: this transparency carrier is a glass.

27. as claim 16 a described manufacturing method for LED, it is characterized in that: this transparency carrier is gallium phosphide or gallium arsenide phosphide.

28. as claim 16 a described manufacturing method for LED, it is characterized in that: this transparency carrier is gallium selenide, zinc sulphide or zinc selenide sulphur.

29. as claim 16 a described manufacturing method for LED, it is characterized in that: this transparency carrier is a carborundum.

30. as claim 16 a described manufacturing method for LED, it is characterized in that: described this clear adhesive of utilizing comprises following manner at least with this transparency carrier and light-emitting diode epitaxial layer surface engagement step together: the phase I is included in to pressurize in the 60-100 ℃ of scope and heat and forms; Second stage is included in to pressurize in the 200-600 ℃ of scope and heat and forms.

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