CN113437194A - Preparation method of high-reflection low-ohmic contact electrode - Google Patents
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- CN113437194A CN113437194A CN202110575377.XA CN202110575377A CN113437194A CN 113437194 A CN113437194 A CN 113437194A CN 202110575377 A CN202110575377 A CN 202110575377A CN 113437194 A CN113437194 A CN 113437194A
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- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000002184 metal Substances 0.000 claims abstract description 31
- 229910052751 metal Inorganic materials 0.000 claims abstract description 31
- 239000000758 substrate Substances 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 17
- 239000004065 semiconductor Substances 0.000 claims abstract description 12
- 150000004767 nitrides Chemical class 0.000 claims abstract description 6
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 229910052697 platinum Inorganic materials 0.000 claims description 6
- 239000013078 crystal Substances 0.000 abstract description 11
- 238000002310 reflectometry Methods 0.000 abstract description 6
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 79
- 238000005275 alloying Methods 0.000 description 6
- 238000000137 annealing Methods 0.000 description 6
- 238000001704 evaporation Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 230000010355 oscillation Effects 0.000 description 4
- 239000011241 protective layer Substances 0.000 description 4
- 239000000956 alloy Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 3
- 238000004806 packaging method and process Methods 0.000 description 3
- 239000002096 quantum dot Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000012876 topography Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
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- 238000004220 aggregation Methods 0.000 description 1
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- 229910052738 indium Inorganic materials 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
- H01L33/46—Reflective coating, e.g. dielectric Bragg reflector
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Abstract
The invention discloses a preparation method of a high-reflection low-ohmic contact electrode, which is mainly applied to a semiconductor light-emitting chip. During the fabrication process, a plurality of layers of nitride including an N-type layer, a light emitting layer, and a P-type layer are grown on a substrate. The high-reflection low-ohmic contact electrode is prepared on the nitride of the P-type layer and is of a double-layer structure of metal nano-dots and an Ag reflector which can form good ohmic contact with the P-type layer. The existence of the metal nano-point effectively improves the film crystal quality of the Ag reflector, obviously improves the reflectivity of the Ag reflector, and reduces the working voltage of the semiconductor light-emitting chip, thereby improving the electro-optic conversion efficiency of the semiconductor light-emitting chip.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a preparation method of a high-reflection low-ohmic contact electrode.
Background
In recent years, semiconductor Light Emitting Diodes (LEDs) have attracted attention for their wide application in the fields of lighting, display, medicine, animal husbandry, agriculture, and the like. The light emission of the LED originates from the light emitting layer between the P-type layer and the N-type layer inside the chip. When an external power source is turned on, the electron and hole pairs recombine in the light-emitting layer to emit light. However, when light is emitted toward the substrate layer, it is absorbed by the opaque substrate, causing significant light loss and heat generation, which adversely affects the device. As shown in fig. 1, in order to improve the light extraction efficiency, a mirror layer is generally fabricated on P-GaN, and light emitted toward the substrate is reflected to the light extraction layer, so that the light extraction efficiency of the device can be significantly improved. However, the reflector layer and the P-GaN are difficult to form good ohmic contact, and the higher potential barrier causes the voltage of the LED device to be increased. Therefore, the high-reflection low-ohmic contact electrode is prepared on the P-GaN, and the method plays a vital role in improving the photoelectric performance of the LED device.
At present, the P-surface reflecting electrode of the LED chip with the vertical structure mostly adopts structures such as Ni/Ag, NiO/Ag/Ni and the like. Methods for preparing reflective electrodes in flip-chip LED chips are also given in the patent literature [ CN110518105A, CN107968143A, CN106025010A ]. As shown in FIG. 2, in the prior art reflective electrode structure, the work function of Ni is 5.15eV, and the work function of Ag is only 4.26eV, so that the contact barrier between P-GaN and Ag can be reduced to a certain extent by the existence of the Ni contact layer, and the working voltage of the LED can be reduced. Patent document CN204118110U proposes that the metal thickness of the ohmic contact layer is 10 to 50 angstroms, but the metal of the ohmic contact layer is opaque, and an excessively thick metal layer causes a serious problem of light absorption, and reduces the reflectivity of the mirror. Moreover, because the surface migration capability of Ag atoms is very strong, the grooving of crystal boundaries is very easy to cause, and clusters are finally formed. The uneven surface appearance of the Ag reflector can change the distribution of surface electrons and the distribution of an electric field, and when light irradiates the surface of the Ag reflector, photons and the surface electrons generate violent plasma resonance to be absorbed, so that the reflectivity of the reflector layer is reduced. Therefore, obtaining the reflecting electrode with smooth and uniform surface appearance has important significance for improving the reflectivity. The industry has learned through the design of different mirror structures such as: the reflectivity is improved by methods of preparing a composite reflector, a laminated reflector and a back reflector with a periodic structure, doping In or Zn element In the Ag reflector, regulating stress based on different Ag reflector thicknesses and the like.
Disclosure of Invention
The invention aims to provide a preparation method of a high-reflection low-ohmic contact electrode, which is characterized in that a metal nano-point contact layer is prepared between a P-GaN reflector and an Ag reflector, so that the quality of a thin film crystal of the reflector is effectively improved, the light output power of an LED chip with a vertical structure is improved, the working voltage of the LED chip is reduced, and the electro-optic conversion efficiency of the LED chip is improved.
The purpose of the invention is realized as follows:
a preparation method of a high-reflection low-ohmic contact electrode comprises the following steps of growing a multilayer nitride semiconductor structure on a substrate, wherein the multilayer nitride semiconductor structure sequentially comprises an N-type layer, a light-emitting layer and a P-type layer, and is characterized in that: and sequentially preparing metal nano-dots capable of forming good ohmic contact with the P-type layer and an Ag reflector on the P-type layer as a reflecting electrode.
The metal nanodots are any one of Au, Pt and Ni, or any two of Au, Pt and Ni, or any three of Au, Pt and Ni.
The density of the metal nano dots is 2 multiplied by 107 ~1×108/cm2The height of the metal nanodots is 2-20 nm.
The thickness of the evaporated Ag reflector is 20-200 nm.
As shown in fig. 3, according to the present invention, based on the growth theory of the thin film, before the Ag mirror is prepared, a layer of metal nanodots is deposited as a nucleation seed layer of the Ag mirror, such that surface diffusion energy and mass transport of Ag atoms can be greatly reduced, Ag spheronization is inhibited, thereby forming a smooth surface topology and improving crystal quality of the Ag mirror. Meanwhile, because the aggregation of the Ag balls is inhibited, holes and grain boundaries in the Ag reflector are reduced, the absorption and scattering of electron transfer are reduced, and the conductivity of the Ag reflector is greatly improved.
The invention has the beneficial effects that:
(1) preparing metal nano-dots serving as a contact layer between the P-type layer and the Ag reflector by an electron beam evaporation method;
(2) the prepared contact layer based on the metal nano-dots effectively improves the quality of the film crystal of the Ag reflector, remarkably improves the reflectivity of the Ag reflector and the light output power of the semiconductor light-emitting chip, and reduces the working voltage of the semiconductor light-emitting chip, thereby improving the electro-optic conversion efficiency of the semiconductor light-emitting chip.
Drawings
Fig. 1 is a schematic diagram of a conventional vertical LED chip structure, wherein: 101-metal substrate, 102-reflector, 103-contact layer, 104-P type layer, 105-light emitting layer, 106-N type layer, 107-N electrode;
fig. 2 is a schematic diagram of a conventional LED chip reflective electrode structure, wherein: 201-substrate, 202-N-type layer, 203-light emitting layer, 204-P-type layer, 205-contact layer, 206-Ag mirror layer;
fig. 3 is a schematic structural diagram of an LED chip reflective electrode with a metal nano-point contact layer provided in the present invention, wherein: 301-substrate, 302-N type layer, 303-light emitting layer, 304-P type layer, 305-metal nanodot contact layer, 306-Ag mirror;
fig. 4 is a schematic structural diagram of an LED chip with a vertical structure of a reflective electrode and a metal nano-point contact layer, provided by the invention, wherein: 401-metal substrate, 402-bonding metal layer and protective layer, 403-Ag reflector, 404-metal nano point contact layer, 405-P-GaN layer, 406-light emitting layer, 407-N-GaN layer, 408-N electrode;
fig. 5 is an AFM topography of a metal nano-dot contact layer in an embodiment of the present invention, wherein: a is a two-dimensional plan view, and b is a three-dimensional perspective view;
FIG. 6 is an SEM topography of a metal nano-dot contact layer in an embodiment of the invention;
FIG. 7 is an AFM profile of a reflective electrode in an embodiment of the present invention, wherein: a is a two-dimensional plan view, and b is a three-dimensional perspective view.
Detailed Description
The present invention is described in further detail below with reference to the drawings and specific examples, but the embodiments of the present invention include but are not limited to the scope shown in the following examples.
Example 1:
the embodiment of the invention provides a method for preparing a high-reflection low-ohmic contact electrode on a vertical-structure LED, which comprises the following steps:
(1) carrying out epitaxial growth on a Si substrate by using MOCVD in sequence: an AlN buffer layer, a Si-doped N-GaN layer, an InGaN/GaN superlattice layer, an InGaN/GaN Multiple Quantum Well (MQWs) light-emitting layer and a Mg-doped P-GaN layer;
(2) and sequentially evaporating a Ni nano-point contact layer and two layers of metal of an Ag reflector on the surface of the P-GaN of the epitaxial layer to be used as a reflecting electrode, and performing high-temperature alloy by using a rapid annealing furnace. Wherein, when the Ni nano-point contact layer 404 is evaporated, the thickness recorded by the crystal oscillation sheet is 0.05nm, the speed is 0.001nm/s, and the density of the Ni nano-points measured by AFM is 5 multiplied by 107/cm2And the height is 10 nm. The surface topography is shown in fig. 5 and 6; when the Ag reflector layer 403 is evaporated, the thickness recorded by the crystal oscillator plate is 100nm, the speed is 0.5nm/s, and the surface appearance is shown in FIG. 7; the conditions for high-temperature alloying of the reflection electrode by using the rapid annealing furnace are as follows: n is a radical of2、O2Gas atmosphere, 385 ℃ temperature and alloying time of 25 seconds;
(3) after the preparation of the reflecting electrode is finished, evaporating a protective layer and a bonding layer 402; transferring the LED epitaxial wafer onto a metal substrate by using a bonding machine through high-temperature bonding 401; removing the Si substrate by using a thinning machine and a chemical corrosion method; then preparing an N electrode 408 on the N-GaN; finally, performing point measurement, scribing, sorting and packaging on the chip; thus, after the vertical structure LED with the high-reflection low-ohmic contact electrode is prepared, the chip structure is as shown in fig. 4.
Example 2:
the embodiment of the invention provides a method for preparing a high-reflection low-ohmic contact electrode on a vertical-structure LED, which comprises the following steps:
(1) carrying out epitaxial growth on a Si substrate by using MOCVD in sequence: an AlN buffer layer, a Si-doped N-GaN layer, an InGaN/GaN superlattice layer, an InGaN/GaN Multiple Quantum Well (MQWs) light-emitting layer and a Mg-doped P-GaN layer;
(2) and sequentially evaporating a Pt nano-point contact layer and two layers of metal of an Ag reflector on the surface of the P-GaN of the epitaxial layer to be used as a reflecting electrode, and performing high-temperature alloy by using a rapid annealing furnace. When the Pt nano point contact layer is evaporated, the thickness recorded by the crystal oscillation piece is 0.07nm, and the speed is as follows: 0.004 nm/s, density of Pt nanodots measured using AFM of 1X 108/cm2And the height is 18 nm. When the Ag reflector layer is evaporated, the thickness recorded by the crystal oscillation plate is 150nm, and the speed is 0.8 nm/s; the conditions for high-temperature alloying of the reflection electrode by using the rapid annealing furnace are as follows: n is a radical of2、O2Gas atmosphere, 385 ℃ temperature and alloying time of 25 seconds;
(3) after the preparation of the reflecting electrode is finished, evaporating a protective layer and a bonding layer; transferring the LED epitaxial wafer to a metal substrate by using a bonding machine through high-temperature bonding; removing the Si substrate by using a thinning machine and a chemical corrosion method; then preparing an N electrode on the N-GaN; finally, performing point measurement, scribing, sorting and packaging on the chip; thus, the preparation of the LED with the vertical structure of the high-reflection low-ohmic contact electrode is finished.
Example 3:
the embodiment of the invention provides a method for preparing a high-reflection low-ohmic contact electrode on a vertical-structure LED, which comprises the following steps:
(1) carrying out epitaxial growth on a Si substrate by using MOCVD in sequence: an AlN buffer layer, a Si-doped N-GaN layer, an InGaN/GaN superlattice layer, an InGaN/GaN Multiple Quantum Well (MQWs) light-emitting layer and a Mg-doped P-GaN layer;
(2) and sequentially evaporating an Au nano-point contact layer and an Ag reflector layer on the P-GaN surface of the epitaxial layer to be used as a reflecting electrode, and performing high-temperature alloy by using a rapid annealing furnace. When the Au nano-point contact layer is evaporated, the thickness recorded by the crystal oscillator plate is 0.03nm, and the speed is as follows: 0.001nm/s, and a density of Au nanodots measured using AFM of 3X 107/cm2And the height is 5 nm. When the Ag reflector layer is evaporated, the thickness recorded by the crystal oscillation piece is 60nm, and the speed is 0.4 nm/s; use the speed rapidlyThe conditions of the annealing furnace for carrying out high-temperature alloying on the reflecting electrode are as follows: n is a radical of2、O2Gas atmosphere, 385 ℃ temperature and alloying time of 25 seconds;
(3) after the preparation of the reflecting electrode is finished, evaporating a protective layer and a bonding layer; transferring the LED epitaxial wafer to a metal substrate by using a bonding machine through high-temperature bonding; removing the Si substrate by using a thinning machine and a chemical corrosion method; then preparing an N electrode on the N-GaN; finally, performing point measurement, scribing, sorting and packaging on the chip; thus, the preparation of the LED with the vertical structure of the high-reflection low-ohmic contact electrode is finished.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (4)
1. A preparation method of a high-reflection low-ohmic contact electrode comprises the following steps of growing a multilayer nitride semiconductor structure on a substrate, wherein the multilayer nitride semiconductor structure sequentially comprises an N-type layer, a light-emitting layer and a P-type layer, and is characterized in that: and sequentially preparing metal nano-dots capable of forming good ohmic contact with the P-type layer and an Ag reflector on the P-type layer as a reflecting electrode.
2. The method of claim 1, wherein the method comprises the steps of: the metal nanodots are any one of Au, Pt and Ni, or any two of Au, Pt and Ni, or any three of Au, Pt and Ni.
3. The method of claim 1, wherein the method comprises the steps of: the density of the metal nano dots is 2 multiplied by 107 ~1×108/cm2The height of the metal nano-dots is 2-20nm。
4. The method of claim 1, wherein the method comprises the steps of: the thickness of the evaporated Ag reflector is 20-200 nm.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1677703A (en) * | 2004-03-12 | 2005-10-05 | 三星电子株式会社 | Nitride-based light-emitting device and method of manufacturing the same |
| CN108305921A (en) * | 2017-12-21 | 2018-07-20 | 河源市众拓光电科技有限公司 | A kind of light emitting diode (LED) chip with vertical structure and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1677703A (en) * | 2004-03-12 | 2005-10-05 | 三星电子株式会社 | Nitride-based light-emitting device and method of manufacturing the same |
| CN108305921A (en) * | 2017-12-21 | 2018-07-20 | 河源市众拓光电科技有限公司 | A kind of light emitting diode (LED) chip with vertical structure and preparation method thereof |
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Application publication date: 20210924 |