KR100435039B1 - Fabrication Method of AlGaInP related LED - Google Patents

Abstract

PURPOSE: A method for fabricating an AlGaInP type LED(Light Emitting Diode) is provided to improve characteristics of an AlGaInP type LED and reduce a fabricating cost of the AlGaInP type LED by changing a structure of the AlGaInP type LED. CONSTITUTION: An LED wafer is formed by depositing sequentially an n-type etch stop layer(31), an n-type AlGaInP clad layer, an AlGaInP or a GaInP active layer and a barrier, a p-AlGaInP clad layer, and a p-contact layer on an n-type GaAs substrate. An etch process for the LED wafer is performed. A p-metal is deposited on a p-contact layer. An n-metal is deposited on the n-type AlGaInP clad layer. An insulating layer(41) is grown on a conductive silicon substrate(40). A p-metal, an n-metal(43), and a metal bump(44) are formed thereon. A metal side of the LED wafer is adhered to the silicon substrate(41). The n-type GaAs substrate is removed by using a dry etch method or a wet etch method.

Description

AlGaInP-based LED manufacturing method {Fabrication Method of AlGaInP related LED}

The present invention relates to a method of manufacturing an AlGaInP-based LED having a new structure for dramatically improving the light output, thermal characteristics and current uniformity of the current in the active layer of the light emitting diode (LED) of the conventional AlGaInP-based and to reduce the LED manufacturing cost .

A conventional AlGaInP-based light emitting diode (LED) is, as shown in FIG. 1, a distributed bragg reflector (DBR) layer 21 and an n-type AlGaInP clad layer 22 formed on one surface of a GaAs substrate 20. , GaAs composed of an AlGaInP (or GaInP) active layer 23, a p-type AlGaInP cladding layer 24, a window layer 25, an n-type metal electrode 26 and a p-type metal electrode 27. The n-type DBR layer 21, the n-type AlGaInP cladding layer 22, the AlGaInP (or GaInP) active layer 23, the p-type AlGaInP clad layer 24, and the window layer 25 on the substrate 20 are MOCVD ( After crystal growth sequentially according to the method of Metal Organic Chemical Vapor Deposition, a p-type metal electrode 27 is formed on the window layer 25, and then the n-type metal electrode 26 is formed on the other surface of the GaAs substrate 20. It is produced by vapor deposition.

Electrons and holes injected through the n-type and p-type electrodes 26 and 27, respectively, are combined in the active layer 23, and the light generated thereby is emitted into the air through the window layer 25. In this process, the external quantum efficiency is limited by absorption and reflection by the p-metal of the emission surface and absorption by the substrate 20. In particular, half of the amount of light generated in the active layer 23 proceeds toward the substrate 20 and is reflected by the DBR layer 21 to proceed to the LED surface. At this time, the DBR layer 21 is designed to reflect only light incident perpendicularly to the boundary surface, and in reality, a large amount of light passes through the DBR layer 21 to reach the substrate 20, in particular, a substrate made of GaAs. Since 20 absorbs light generated by the AlGaInP (or GaInP) active layer 23 well, most of the light is absorbed by the absorption effect in the substrate 20 and thus a large part of the light generated in the active layer 23. Will be lost.

In addition, in the conventional LED structure as shown in FIG. 1, as is well known, there is a problem of nonuniformity of current in the LED active layer due to local p metal formation and low doping concentration of the p-window layer. One distribution problem arises. In addition, the conventional LED has a problem that the thermal characteristics of the device is poor because the GaAs substrate is poor thermal conductivity is bonded to the submounter. This problem will seriously affect the device's performance as the device's operating current increases.

Therefore, in order to improve the performance of AlGaInP-based LED, it is absolutely necessary to improve the above problems.

The present invention has been made to solve the above problems, the technical problem of the present invention, by removing the substrate on which the AlGaInP-based LED is grown to remove the light absorption loss by the substrate to improve the external quantum efficiency, and also partially N-metal is formed on the exposed n-AlGaInP thin film, and p-AlGaInP side deposits p-metal on the entire surface to improve current uniformity, as well as n-metal and p-metal of the device formed on the same surface. In order to improve the thermal characteristics of the device by adhering to the silicon substrate having excellent thermal conductivity, another technical problem of the present invention is another n-metal, in which n-metal and p-metal are previously formed on the silicon substrate at the same time. And p-metals are also bonded to ensure ease of packaging process.

1 is a general structure of a conventional AlGaInP-based LED device;

2 is a conceptual diagram illustrating a thin film structure grown to fabricate an AlGaInP-based LED;

3 is a conceptual diagram of a unit device after etching an LED wafer;

4 is a conceptual diagram after depositing a metal on the etched LED structure;

5 is a conceptual diagram showing a dielectric film deposited on a p-type silicon substrate, a metal pattern, and metal bumps for flip chip bonding deposited thereon;

FIG. 6 is a conceptual view after the LED wafer fabricated as shown in FIG. 4 is inverted and pasted onto the silicon substrate prepared as shown in FIG.

7 is a conceptual diagram after removing the substrate on which the LED is grown using a dry or wet etching technique; And

8 is a conceptual diagram of an LED device fabricated using a conductive silicon substrate and an exposed n electrode.

<Description of the code | symbol about the principal part of drawing>

20.n-type GaAs substrate 21.DBR layer

22. n-AlGaInP clad layer 23. AlGaInP or GaInP active layer and barrier layer

24.p-AlGaInP Clad Layer 25.Window Layer

26. First n-metal 27. Second p-metal

31. Etch stop layer 32. P-contact layer

40. Conductive Silicon Substrate 41. Dielectric

42. Second p-metal 43. Second n-metal

44. Metal bump

50. p electrode of package mounter 51. n electrode of package mounter

52. Package submount 53. Bonding wire

In order to achieve the above object, the technical features of the etching of the LED wafer, the preparation of the silicon substrate, the bonding of the LED wafer and the silicon substrate, and the removal of the substrate used in the growth of the LED thin film are described. A method for fabricating an AlGaInP-based LED, comprising: sequentially forming an etch stop layer, an n-AlGaInP layer, an active layer made of AlGaInP or InGaP, a p-AlGaInP layer, and a p-contact layer on one surface of an n-type GaAs substrate; ; Etching a portion of the p-contact layer and a lower portion of the p-contact layer, wherein the n-AlGaInP layer is etched to a depth of a first depth; Etching a portion of the n-AlGaInP layer exposed by etching and a lower portion of the n-AlGaInP layer, wherein the n-type GaAs substrate is etched to a depth of a second depth; Forming a first p-metal on the unetched region of the p-contact layer; And forming a first n-metal on the exposed n-AlGaInP layer. In this case, the second depth at which the n-type GaAs substrate is etched is one surface of the n-type GaAs substrate. 0.01 micrometer or more, and 10 micrometers or more from the other surface of the said n-type GaAs substrate. Moreover, the said 1st depth by which the said n-AlGaInP layer is etched is 0.01 micrometer from the bottom surface of the active layer which consists of said AlGaInP or InGaP. The above-described method is preferably performed so as not to reach the etch stop layer. In the present invention, (a) a silicon substrate having a doping concentration of electrons or holes in the range of 10 ¹⁵ / cm 3 to 10 ²² / cm 3, and the silicon An insulating film located only in a portion of the substrate, a second p-metal located in an area of the silicon substrate where the insulating film does not exist, a second n-metal located on the insulating film, the second p-metal and a second n -metal The method comprising providing a bonded substrate comprising a metal in each of the bumps to claim 1 wherein the metal p- and n- claim 1 metal and alignment; (b) bonding the metal bumps of the bonded substrate and the first p-metal and the first n-metal to each other; (c) preferably removing the n-type GaAs substrate. In this case, the step (c) of removing the n-type GaAs substrate may be performed by any one of dry etching and wet etching, or a combination thereof. In addition, after the step (c) is completed, bonding the silicon substrate to the p-electrode of the LED package mounter; The method may further include connecting the second n-metal and the n-electrode of the LED package mounter by wire bonding.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 shows the structure of a thin film grown for an AlGaInP-based LED. Referring to FIG. 2, an n-type etch stop layer 31, an n-AlGaInP clad layer 22, an AlGaInP or GaInP active layer and a barrier layer 23 on one surface of an n-type GaAs substrate 20. It can be seen that the p-AlGaInP cladding layer 24 and the p-contacting layer 32 are sequentially formed. The holes supplied from the p-AlGaInP cladding layer 24 and the electrons supplied from the n-AlGaInP cladding layer 22 combine in the active layer so that the energy is transformed in the form of light to correspond to the energy bandgap of the material. To generate a wavelength of light. The n-type etch stop layer 31 is made of a material having sufficient etching selectivity with respect to the n-type GaAs substrate 20. AlAs or InGaP may be used as the material. The p-AlGaInP cladding layer 24 requires a p-contact layer 32 because it is difficult to form ohmic contact directly due to a large bandgap and low doping level. At this time, p-GaP, p-GaAs, and p-InGaP may be used as the material of the p-contact layer 32. Among these materials, p-GaAs and p-InGaP may be used to emit light generated from the InGaP or AlGaInP active layer 23. The thickness of the p-contact layer 32 should be minimized as it can absorb, usually 100 nm being suitable. Meanwhile, the LED epi wafer according to the present invention does not require the thick DBR layer and the window layer shown in FIG.

FIG. 3 is a view after etching the LED wafer grown as shown in FIG. 2, a part of which is n-AlGaInP 22, and a part of which is etched through the etch stop layer 31 to a part of the n-type GaAs substrate 20. . In more detail, first, a portion of the p-contact layer 32 and its lower portion are etched, and the etch is performed so that the n-AlGaInP layer 22 is recessed by the first depth. Subsequently, a portion of the n-AlGaInP layer 22 exposed by the etching and the lower portion of the n-AlGaInP layer 22 are etched, and the etching is performed so that the n-type GaAs substrate 20 is recessed by a second depth. At this time, the second depth at which the n-type GaAs substrate 20 is etched is set to be 0.01 μm or more from one surface of the n-type GaAs substrate 20 and 10 μm or more from the other surface of the n-type GaAs substrate 20. . In addition, the first depth at which the n-AlGaInP layer 22 is etched is set to 0.01 µm or more from the bottom of the active layer 23 made of AlGaInP or InGaP, but not to the etch stop layer 31.

FIG. 4 shows the first p-metal 27 (Ti / Pt / Au, etc.) exposed on the unetched region of the p-contact layer 32 for the etched and formed LED wafer as shown in FIG. The first n-metal 26 (AuGe / Ni / Au, etc.) is deposited on the AlGaInP layer 22, respectively.

FIG. 5 is a view illustrating a silicon substrate to be inverted and attached to an LED wafer formed as shown in FIG. 4. Referring to the method of forming a silicon substrate for bonding in detail as follows. First, a dielectric insulating film 41 such as SiO ₂ or SiN _x is grown on a conductive n-type or p-type silicon substrate 40 having an electron or hole doping concentration in the range of 10 ¹⁵ / cm 3 to 10 ²² / cm 3. The portions are etched away to form second p-metals 42, second n-metals 43, and metal bumps 44 on the resultant. The doping concentration should be in the above-described range because the electrical conductivity of the silicon substrate should be good enough to prevent the device from increasing the operating voltage or generating heat after the LED device is fabricated. In FIG. 5, the p-type silicon substrate 40 is used as the substrate. In more detail below, in the case of the second p-metal 42, a portion of the insulating layer is deposited on an etched or removed region, which is used to form a p contact of a LED to be manufactured through the conductive silicon substrate. The second n-metal 43 is deposited on the insulating film 41 to isolate the n contact and the p contact. Subsequently, metal bumps 44 to be used for flip chip bonding are formed on the second p-metal 42 and the second n-metal 43, wherein the formation positions of the metal bumps 44 are formed. These are determined to enable adhesion to the first p-metal 27 and the first n-metal 26 of FIG. 4, respectively. In addition, the second p-metal 42 may obtain good ohmic characteristics with the conductive silicon substrate 40, and the second n-metal 43 may be suitable for flip chip bonding described later in FIG. Is enough.

FIG. 6 shows a state after the metal surface of the LED wafer formed as shown in FIG. 4 is turned upside down on the silicon substrate for bonding as shown in FIG. 5. This is done by the same process as conventional flip chip bonding.

When the n-type GaAs substrate 20 is removed from the sample formed as shown in FIG. 6 by a wet etching method and a dry etching method, or a mixture thereof, the sample formed as shown in FIG. In the case of dry etching, an inductively coupled plasma etching method or a reactive ion etching method may be used. At this time. Since the etch stop layer 31 has an etching property different from that of the n-type GaAs substrate 20, the process of only etching the n-type GsAs substrate 20 is a relatively easy process. As such, when the n-type GaAs substrate 20 is removed, the portion that is etched from the LED wafer to the n-type GaAs substrate 20 is exposed to form a part of the second n-metal 43 as shown in FIG. 7. If a part of the exposed second n-metal 43 is used as an n-type electrode, it can be easily attached to a general LED package as shown in FIG. 8. FIG. 8 shows an LED wafer formed as shown in FIG. After a single LED chip is mounted on a typical LED package mounter. The silicon substrate surface of the device is bonded to the p electrode 52 of the LED package mounter, and the n-type electrode 43 of the device and the n electrode 51 of the LED package mounter are connected using a bonding wire 53. This completes the LED package process.

According to the present invention made as described above, by removing the substrate used for the LED thin film growth it is possible to eliminate the light loss due to light absorption by the substrate. In addition, by removing the substrate, the LED device becomes very thin, around a few μm, thereby increasing the Photon Recycling effect in the device, thereby finally improving the external quantum efficiency.

In addition, in the present invention, since the existing silicon substrate known to have very good thermal conductivity is used as the mount of the device, heat generated from the LED can be effectively removed, thereby improving the life and electrical characteristics of the device.

In addition, in the present invention, since p-metal is deposited on the entire surface of p-AlGaInP, which is generally known to be difficult to do high concentration, it is possible to reduce the serial resistance of the device, and also partially n on the n-AlGaInP which has excellent electrical conductivity. By forming the type electrode, the uniformity of the current density in the active layer can be greatly improved. This makes it possible to obtain a uniform light output over the entire light output surface of the LED element.

In addition, by using the device manufactured as described above, the LED package can be completed by only one wire bonding, thereby simplifying the LED package process and expecting a cost reduction effect.

Claims (6)

In the AlGaInP-based LED manufacturing method having a p-n junction diode structure, sequentially forming an etch stop layer, an n-AlGaInP layer, an active layer made of AlGaInP or InGaP, a p-AlGaInP layer, and a p-contact layer on one surface of the n-type GaAs substrate; Etching a portion of the p-contact layer and a lower portion of the p-contact layer, wherein the n-AlGaInP layer is etched to a depth of a first depth; Etching a portion of the n-AlGaInP layer exposed by etching and a lower portion of the n-AlGaInP layer, wherein the n-type GaAs substrate is etched to a depth of a second depth; Forming a first p-metal on the unetched region of the p-contact layer; Forming a first n-metal on the exposed n-AlGaInP layer; AlGaInP-based LED manufacturing method comprising a. 2. The AlGaInP according to claim 1, wherein the second depth of the n-type GaAs substrate is 0.01 μm or more from one surface of the n-type GaAs substrate and 10 μm or more from the other surface of the n-type GaAs substrate. How to make LED system. The AlGaInP type according to claim 1, wherein the first depth of the n-AlGaInP layer is etched to be 0.01 μm or more from the bottom of the active layer made of AlGaInP or InGaP, but not to the etch stop layer. How to make LED. The method of claim 1, (a) a silicon substrate having an electron or hole doping concentration in the range of 10 ¹⁵ / cm 3 to 10 ²² / cm 3, an insulating film located only in a partial region on the silicon substrate, and a region of the silicon substrate in which the insulating film does not exist A second p-metal, a second n-metal positioned on the insulating film, and the first p-metal and the first n-metal respectively positioned on the second p-metal and the second n-metal. Providing a bonded substrate including located metal bumps; (b) bonding the metal bumps of the bonded substrate and the first p-metal and the first n-metal to each other; (c) removing the n-type GaAs substrate; AlGaInP-based LED manufacturing method characterized in that it further comprises. The method of claim 4, wherein the step (c) of removing the n-type GaAs substrate is performed by any one of dry etching and wet etching, or a mixture thereof. The method of claim 4, wherein after step (c) is completed, Bonding the silicon substrate to the p-electrode of the LED package mounter; Connecting the second n-metal and the n-electrode of the LED package mounter by wire bonding; AlGaInP-based LED manufacturing method characterized in that it further comprises.