CN101673793B - Preparation method of GaN-based LED chip - Google Patents
Preparation method of GaN-based LED chip Download PDFInfo
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- CN101673793B CN101673793B CN2009101126133A CN200910112613A CN101673793B CN 101673793 B CN101673793 B CN 101673793B CN 2009101126133 A CN2009101126133 A CN 2009101126133A CN 200910112613 A CN200910112613 A CN 200910112613A CN 101673793 B CN101673793 B CN 101673793B
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Abstract
The invention discloses a preparation method of a GaN-based LED chip, relates to an LED chip, and provides a preparation method of the GaN-based LED chip which has obvious effect, simple operation, compatibility with general component technology, low series resistance and good P-type ohmic contact. The method comprises the steps of depositing a layer of metal Zn film on the P-GaN surface of an LED epitaxial wafer in a sputtering or evaporating method; irradiating the Zn/P-GaN surface of the sample by a laser; eating off the residual Zn on the surface of the sample, drying after cleaning; conducting ICP corrosion on the well-treated sample to lead the n-type GaN layer to be exposed, photoetching and sputtering a Ti/Al metal layer, forming an n-type electrode after stripping, and annealing; and photoetching the sample again and sputtering a Ni/Au metal layer on the surface, forming a p-type electrode after stripping, and annealing.
Description
Technical field
The present invention relates to a kind of led chip, especially relate to a kind of method that adopts the induced with laser doping of Zn to prepare the GaN base LED chip.
Background technology
GaN based light-emitting diode (LED) has extensively applied to numeral and image and has shown the field owing to the advantage of aspects such as it is efficient, energy-saving and environmental protection.In recent years, because the research of GaN sill has obtained breakthrough, developed high efficiency white light and blue-ray LED, the colour that not only can be used in large-screen shows the field, and probably replaces illuminating engineerings such as existing incandescent lamp, fluorescent lamp and get their way into people's lives.Yet up to the present, GaN base LED device still has many technical barriers that do not solved fully, and wherein restricting it, to develop a topmost difficult problem be exactly that the high effective doping content of P-GaN is difficult to realize, good P type GaN ohmic contact prepares difficulty etc.Usually the P-GaN of GaN base LED epitaxial wafer mixes, and generally is to mix Mg when MOCVD grows, and passes through high-temperature annealing activation Mg then; Or the annealing of employing ion implantation high temperature, codoping technology etc.; But the effective doping content of GaN material P type that these technology can be accomplished generally only is 10
17Cm
-3Magnitude.The effective doping content of P type of GaN material is not high, and its chief reason has the following aspects: during the MOCVD growing GaN, be subjected to main Mg easily and H form electroneutral Mg-H complex compound, make Mg can not effectively replace the Ga position; Be easy to generate the N room during next growing GaN, the N room is the alms giver source, just shows the n type so the GaN material mixes; The energy level of Mg in the GaN material is darker in addition, the most shallow general energy level 170mev that also has an appointment, at room temperature more difficult ionization.The effective doping content of P type is not high, and then good P type ohmic contact preparation is difficult.For GaN base LED device, bad P type ohmic contact has improved the series resistance of device.And higher P type series resistance not only makes LED device heating and charge carrier injection efficiency reduce, and heating when making device work, reduce device luminous efficiency, reduce the reliability of device, thereby shorten the life-span of device.
Publication number provides a kind of method that improves external quantum efficiency of GaN based LED chip of great power for the application for a patent for invention of CN101290956, be characterized in adopting hemisphere sapphire or GaN substrate, growth hemisphere GaN film and the active illuminating layer in the middle of the GaN film on substrate, the light that active illuminating layer sent allows the critical angle of incidence angle less than total reflection when the outgoing of GaN film surface.Because substrate is a hemisphere, can adopt the MOCVD technology growth to go out hemispheric GaN and hemispheric active illuminating layer thereof thereon, when enough hour of the radius of ball, the light that sends from active layer is when the outgoing of hemisphere GaN surface, because incidence angle is less than the critical angle of total reflection, so total reflection can not take place, most of light can be gone out from transmission on this sphere, thereby the external quantum efficiency that makes chip obtains to improve, and can reduce the working temperature of chip simultaneously, improves chip performance.
Publication number provides a kind of power-type LED chip for preparing the laser lift-off substrate on metal heat sink and preparation method thereof, large tracts of land evaporation transparency electrode Ni/Au on Sapphire Substrate GaN epitaxial wafer for the application for a patent for invention of CN1779996; Evaporation Ni/Ag/Ti/Au reflector on transparency electrode; On the reflector, electroplate smooth, periodic metal heat sink unit, more than the thickness 50 μ m; The heat sink epitaxial wafer of plating is peeled off Sapphire Substrate under the irradiation of Kr excimer laser, obtain n towards the last epitaxial wafer that is bonded in metal heat sink; Use plasma etching on n-GaN surface, evaporating n face electrode then, electrode structure is Ti/Al/Ni/Au; LED epitaxial wafer n face is sticked blue film, obtain the GaN base LED epitaxial wafer that metal heat sink supports, and make the tube core cellular spliting open.
Publication number provides a kind of led chip and preparation method thereof for the application for a patent for invention of CN101471406, and the side that makes a circle in ICP chip after etching week slopes inwardly, and is the shape of falling from power.The preparation method of led chip may further comprise the steps: growing GaN based LED construction epitaxial wafer on Sapphire Substrate; The GaN epitaxial wafer is at N
2The atmosphere high annealing; With solvent that GaN epitaxial wafer surface clean is clean; On the GaN epitaxial wafer, make figure by lithography; Evaporation Cr/Ni mask layer on the GaN epitaxial wafer after the photoetching; Photoresist is removed clean with solvent; Then epitaxial wafer is etched into the n-GaN layer with ICP, and the shape of falling from power in the chip after etching side being sloped inwardly be, wherein the ICP etching condition is that 1500～2000W, RF power are that 20～40W, chamber pressure are 40～80mTorr, etching gas flow-rate ratio Cl for ICP power
2: Cl
3=(3～6): 1.
Summary of the invention
The present invention aim to provide a kind of not only effect obvious, easy and simple to handle, with the conventional device process compatible, and have the preparation method of the GaN base LED chip of low series resistance and good P-type ohmic contact.
The present invention adopts the method for induced with laser doping of Zn to prepare the GaN base LED chip.
The present invention includes following steps:
1) with the method for sputter or evaporation at LED epitaxial wafer P-GaN surface deposition layer of metal Zn film;
2) the Zn/P-GaN surface of usefulness laser irradiation sample;
3) the remaining Zn of sample surfaces is eroded, clean the back oven dry;
4) sample of handling well is carried out the ICP etching, expose n type GaN layer, photoetching and sputtered with Ti/Al metal level is peeled off the back and is formed n type electrode, annealing;
5) sample is carried out photoetching once more and, peel off back formation p type electrode, annealing at surface sputtering Ni/Au metal level.
In step 1), the thickness of described metal Zn film is preferably 50～300nm.
In step 2) in, the excimer laser irradiation of the most handy wavelength 248nm of described laser irradiation, the time on the Zn/P-GaN surface of irradiation sample is preferably 1～6s, and the single pulse energy of laser is preferably 100～600mJ, and pulse frequency is preferably 10～30Hz.
In step 3), washed with de-ionized water is preferably used in described cleaning, describedly the remaining Zn of sample surfaces is eroded the most handy hydrochloric acid the remaining Zn of sample surfaces is eroded.
In step 4), described annealing is preferably in 600～750 ℃ the nitrogen atmosphere and anneals.
In step 5), described annealing is preferably in 450～600 ℃ the nitrogen atmosphere and anneals.
The method that the present invention adopts induced with laser to mix Zn prepares the GaN base LED chip, its equipment is simple, easy and simple to handle, with conventional device technology compatibility.The prepared GaN base LED chip of the present invention has low, the good P-type of series resistance ohmic contact, advantages such as the forward operating voltage is low, thermal resistance is little, luminous efficiency is high, device long working life.The preparation method of the GaN base LED chip of good P-type ohmic contact.
Description of drawings
Fig. 1 measures through induced with laser with Electrochemical C-V and mixes the variation relation of the hole concentration of the LED epitaxial wafer of Zn and conventional LED epitaxial wafer P-GaN layer with thickness.Laser pulse frequency: 20Hz, single pulse energy: 300mJ, exposure time: 2.5s.The Zn film thickness of sputter is 200nm, and abscissa is thickness/nm, and ordinate is hole concentration/10
18Cm
-3, ■ is the laser doping epitaxial wafer, zero is conventional epitaxial wafer.
Fig. 2 is for mixing the LED of Chip Packaging of Zn and the I-V curve of conventional LED through laser.In Fig. 2, abscissa is voltage/V, and ordinate is electric current/mA; ■ is a common LED, I=20mA, V=3.33V; is laser doping LED, I=20mA, V=3.13V.
Fig. 3 mixes the LED of Zn and the decline curve under the conventional LED room temperature through laser.In Fig. 3, abscissa is operating time/h, and ordinate is normalization Output optical power P/%; ■ is a common LED, and is laser doping LED.
Fig. 4 mixes the relation of the LED of Zn and the conventional LED reverse leakage current under-5V with the operating time through laser.In Fig. 4, abscissa is operating time/h, and ordinate is reverse leakage current/μ A; ■ is a common LED, and is laser doping LED.
Fig. 5 mixes the chip thermal resistance contrast of LED and the conventional LED of Zn through laser.In Fig. 5, abscissa is R
Th/ (K/W), ordinate is K/ (W
2S/K
2); ■ is a common LED, R
Th=18.6K/W; is laser doping LED, R
Th=9.7K/W.
Embodiment
The thick Zn film of conventional LED epitaxial wafer P-GaN surface deposition one deck 200nm that is cleaning up with the method for sputter, Zn/P-GaN surface with excimer laser irradiation sample under the environment of atmosphere of wavelength 248nm, the pulse frequency of laser is 20Hz, single pulse energy is 300mJ, exposure time 2.5s.Erode remaining Zn with watery hydrochloric acid, the deionized water rinsing oven dry.The sample of handling well is carried out the ICP etching expose n type GaN layer, photoetching and sputtered with Ti (60nm)/Al (2nm) metal level is peeled off the back and is formed n type electrode, and 2min anneals in 700 ℃ nitrogen atmosphere; Sample is carried out photoetching once more and at surface sputtering Ni/Au metal level, peels off back formation p type electrode, and 2min anneals in 550 ℃ nitrogen atmosphere.
The thick Zn film of conventional LED epitaxial wafer P-GaN surface deposition one deck 300nm that is cleaning up with the method for sputter, Zn/P-GaN surface with KrF excimer laser irradiation sample under the environment of atmosphere, the pulse frequency of laser is 25Hz, and single pulse energy is 350mJ, exposure time 2s.Erode remaining Zn with watery hydrochloric acid, the deionized water rinsing oven dry.The sample of handling well is carried out the ICP etching expose n type GaN layer, photoetching and sputtered with Ti (60nm)/Al (2nm) metal level is peeled off the back and is formed n type electrode, and 4min anneals in 600 ℃ nitrogen atmosphere; Sample is carried out photoetching once more and at surface sputtering Ni/Au metal level, peels off back formation p type electrode, and 3min anneals in 500 ℃ nitrogen atmosphere.
The thick Zn film of conventional LED epitaxial wafer P-GaN surface deposition one deck 100nm that is cleaning up with the method for sputter, Zn/P-GaN surface with KrF excimer laser irradiation sample under the environment of atmosphere, the pulse frequency of laser is 30Hz, and single pulse energy is 250mJ, exposure time 3s.Erode remaining Zn with watery hydrochloric acid, the deionized water rinsing oven dry.The sample of handling well is carried out the ICP etching expose n type GaN layer, photoetching and sputtered with Ti (60nm)/Al (2nm) metal level is peeled off the back and is formed n type electrode, and 5min anneals in 650 ℃ nitrogen atmosphere; Sample is carried out photoetching once more and at surface sputtering Ni/Au metal level, peels off back formation p type electrode, and 2min anneals in 600 ℃ nitrogen atmosphere.
Embodiment 4
The thick Zn film of conventional LED epitaxial wafer P-GaN surface deposition one deck 100m that is cleaning up with the method for sputter, Zn/P-GaN surface with KrF excimer laser irradiation sample under the environment of atmosphere, the pulse frequency of laser is 15Hz, and single pulse energy is 400mJ, exposure time 3s.Erode remaining Zn with watery hydrochloric acid, the deionized water rinsing oven dry.The sample of handling well is carried out the ICP etching expose n type GaN layer, photoetching and sputtered with Ti (60nm)/Al (2nm) metal level is peeled off the back and is formed n type electrode, and 1min anneals in 750 ℃ nitrogen atmosphere; Sample is carried out photoetching once more and at surface sputtering Ni/Au metal level, peels off back formation p type electrode, and 5min anneals in 450 ℃ nitrogen atmosphere.
With the method for Electrochemical C-V the hole concentration of the sample surfaces P-GaN layer handled well is measured in the experiment, measurement result (as Fig. 1) shows that the P-GaN layer has reached 10 near the hole concentration of surperficial annex
18Cm
-3～10
19Cm
-3Magnitude.With the Chip Packaging handled well the low-power LED device that becomes to emit white light, compare with the white light low-power LED device of routine, the performance of this device has obtained tangible improvement: forward voltage drops to 3.13V (as Fig. 2) from 3.33V, and this has illustrated that the series resistance of chip has reduced 10 Ω; Decline coefficient under the room temperature is from 1.68 * 10
-4Drop to 1.34 * 10
-4, luminous efficiency raising, life-span have also prolonged 41%; Fig. 3 provides through laser and mixes the LED of Zn and the decline curve under the conventional LED room temperature.The reverse leakage current of device is also less than conventional device (as Fig. 4).
From the foregoing description as can be seen, compare with the GaN base LED chip preparation method of routine, the present invention has following outstanding advantage:
1) equipment is simple, and method is easy, with the device technology compatibility of routine
The P-GaN of conventional LED epitaxial wafer mixes, and mixes Mg when generally adopting MOCVD growing GaN layer, and will pass through high-temperature annealing activation Mg; Or the annealing of employing ion implantation high temperature, codoping technology etc.And the present invention adopts the method for induced with laser doping of Zn to improve the hole concentration of P-GaN, need not to use the technology such as MOCVD growing technology, ion injection of complex and expensive, only need to increase sputter Zn and induced with laser twice technology, equipment is simple, easy and simple to handle, and compatible fully with the device making technics of routine.
2) the effective doping content of P type improves, and chip performance improves obviously
After induced with laser was mixed Zn as can be seen through the measurement of Electrochemical C-V, the hole concentration of the P-GaN layer of LED epitaxial wafer brought up to 10
18Cm
-3～10
19Cm
-3Magnitude (as Fig. 1), and the hole concentration of the P-GaN layer of conventional LED epitaxial wafer is only 10
17Cm
-3Magnitude.Measurement result by experiment shows that the method with the induced with laser doping of Zn prepares the GaN base LED chip, the series resistance of chip has reduced by 10 Ω, the thermal resistance of chip drops to 9.7K/W (as first peak position of Fig. 5) from 18.6K/W, and the forward operating voltage has reduced 0.2V, charge carrier injection efficiency and luminous efficiency and has improved for GaN base LED, and the life-span of device has prolonged 41%.
Claims (6)
1. the preparation method of a GaN base LED chip is characterized in that may further comprise the steps:
1) with the method for sputter or evaporation at LED epitaxial wafer P-GaN surface deposition layer of metal Zn film;
2) the Zn/P-GaN surface of usefulness laser irradiation sample, the described laser irradiation excimer laser irradiation of wavelength 248nm, the time on the Zn/P-GaN surface of irradiation sample is 1～6s, and the single pulse energy of laser is 100～600mJ, and pulse frequency is 10～30Hz;
3) the remaining Zn of sample surfaces is eroded, clean the back oven dry;
4) sample of handling well is carried out the ICP etching, expose n type GaN layer, photoetching and sputtered with Ti/Al metal level is peeled off the back and is formed n type electrode, annealing;
5) sample is carried out photoetching once more and, peel off back formation p type electrode, annealing at surface sputtering Ni/Au metal level.
2. the preparation method of a kind of GaN base LED chip as claimed in claim 1 is characterized in that in step 1), and the thickness of described metal Zn film is 50～300nm.
3. the preparation method of a kind of GaN base LED chip as claimed in claim 1 is characterized in that in step 3), described cleaning washed with de-ionized water.
4. the preparation method of a kind of GaN base LED chip as claimed in claim 1 is characterized in that in step 3), and the described remaining Zn of sample surfaces is eroded with hydrochloric acid erodes the remaining Zn of sample surfaces.
5. the preparation method of a kind of GaN base LED chip as claimed in claim 1 is characterized in that in step 4) described annealing is annealed in 600～750 ℃ nitrogen atmosphere.
6. the preparation method of a kind of GaN base LED chip as claimed in claim 1 is characterized in that in step 5) described annealing is annealed in 450～600 ℃ nitrogen atmosphere.
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|---|---|---|---|
| CN2009101126133A CN101673793B (en) | 2009-10-01 | 2009-10-01 | Preparation method of GaN-based LED chip |
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|---|---|---|---|
| CN2009101126133A CN101673793B (en) | 2009-10-01 | 2009-10-01 | Preparation method of GaN-based LED chip |
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| CN101673793B true CN101673793B (en) | 2011-12-28 |
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Effective date of registration: 20161122 Address after: Jinyuan Road in Jimei District of Xiamen City, Fujian Province, No. 469 361000 Patentee after: Xiamen Mai keepsake Polytron Technologies Inc Address before: Xiamen City, Fujian Province, 361005 South Siming Road No. 422 Patentee before: Xiamen University |
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Address after: 361000 room 772, Pioneer Building, Pioneer Park, torch hi tech Zone, Xiamen City, Fujian Province Patentee after: Xiamen Maixin Zhinong Wulian Technology Co.,Ltd. Address before: 361000 No. 469, Jinyuan West Road, Jimei District, Xiamen City, Fujian Province Patentee before: XIAMEN TOP-SUCCEED ELECTRONICS TECHNOLOGY CO.,LTD. |