CN102185046A

CN102185046A - Method for manufacturing gallium nitride-based LED (Light Emitting Diode) with vertical structure

Info

Publication number: CN102185046A
Application number: CN 201110088004
Authority: CN
Inventors: 李云; 王静辉; 任继民; 苏银涛; 肖国华; 徐海洲; 李兴
Original assignee: TONGHUI ELECTRONICS Corp CO Ltd
Current assignee: TONGHUI ELECTRONICS Corp CO Ltd
Priority date: 2011-04-08
Filing date: 2011-04-08
Publication date: 2011-09-14

Abstract

The invention discloses a method for manufacturing a gallium nitride-based LED (Light Emitting Diode) with a vertical structure. The method comprises the following steps of: (1) extending an n-type semiconductor layer and a p-type semiconductor layer on a sapphire substrate in sequence to form an LED wafer, performing metal evaporation on the surface of the LED wafer and treating in a nitrogen atmosphere at the temperature between 200 DEG C and 400 DEG C for 1-10 minutes to form a p electrode, and partitioning the LED wafer into independent LED chips; (2) evaporating gold layers on the upper surface and the lower surface of a composite metal substrate respectively, wherein the composite metal substrate is made of a copper-molybdenum alloy or an aluminum-silicon alloy; (3) reversely welding the independent LED chips obtained in the step (1) onto the upper surface of the composite metal substrate respectively; (4) stripping substrates of the LED chips; and (5) manufacturing an n-type electrode on an n-type semiconductor material of each LED chip. In the method, a CuMo or AlSi composite metal substrate with high thermal conductivity is taken as a transfer substrate and has a small thermal expansion coefficient difference from a transferred LED chip, the thermal stress is small, and the bonding yield is increased.

Description

The manufacture method of vertical stratification gallium nitride based LED

Technical field

The present invention relates to the preparation method of a kind of LED, especially a kind of preparation method of vertical stratification gallium nitride based LED.

Background technology

China is one of the fastest country of present global urban process, can expect in the many decades in future, and the market demand for high-power, high brightness, energy-conservation LED street lamp product in all parts of the country is extremely huge.According to national street lamp industry statistic, China's city illumination has the street lamp more than 1,500 ten thousand, and growth rate in recent years is more than 20%.Estimation like this, the market scale of national annual illuminating street lamp is not less than 5,000,000,000 yuan, as using the LED street lamp, can economize on electricity every year more than 2,000,000,000 degree.One of core technology of LED street lamp is exactly the blue light high-power LED chip, and each big well-known LED enterprise of the whole world all drops into a large amount of man power and materials to make every effort to solve high light efficiency, problem cheaply.

Power such as American-European-Japanese all classifies the solid state lighting technology one of as direction of following energy-conservation development.The high-power blue-light LED chip of vertical injection is the technology of studying in the world, its advantage is under the prerequisite that guarantees certain luminous efficiency (lm/W), inject bigger electric current by the direction vertical with the luminous zone, improve the electrical power that single chip can bear, improve the luminous flux of single chip, reach same chip and send than traditional die and more many purpose of light, be equivalent to reduce the cost of each lumen, have higher reliability simultaneously again.

The substrate transfer technology and the shortcoming of making the employing of vertical injection led chip at present are as follows:

1. transfer base substrate generally adopts semi-conducting material such as Si or metal such as Cu.Its deficiency mainly shows the thermal coefficient of expansion gap big (greater than more than 30%) of substrate with the wafer that is transferred of transfer, cause existing between latter two wafer of bonding big stress, thereby reduce the bonding rate of finished products, and the vertical injection chip of Zhi Zuoing might come off or the local rosin joint that forms from translate substrate afterwards, causes reliability to reduce;

2. full wafer bonding promptly at substrate surface evaporation or the metallizing or the metal binding agent of the wafer of wanting translate substrate and transfer, and then adds certain pressure, temperature, time, and two wafers are combined.Owing to be full wafer bonding (bonding), be easy to generate bubble between the wafer of two bondings, cause local bonding not firmly, make the decrease in yield of back chip, reliability reduces;

3. the size of translate substrate can not be too big (they generally be round, and diameter being less than 100 centimetres), can not make other shapes of removing the circle.

Summary of the invention

The technical problem to be solved in the present invention provides the preparation method of a kind of rate of finished products height, vertical stratification gallium nitride based LED that reliability is high.

For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of preparation method of vertical stratification gallium nitride based LED, carry out according to following step:

1. extension n type GaN layer and p type GaN layer successively on Sapphire Substrate form GaN-based LED epitaxial wafer; At the surperficial evaporation metal of GaN-based LED epitaxial wafer, and in nitrogen atmosphere, 200-400 ℃ handles 1-10min, forms the p electrode, then the LED wafer is divided into discrete led chip;

2. the processing of composite metal substrate

At the upper surface and the lower surface difference gold evaporation layer of composite metal substrate, described composite metal substrate is copper molybdenum alloy or alusil alloy;

3. with step 1. in independently led chip respectively flip chip bonding be connected to the upper surface of composite metal substrate;

4. peel off the Sapphire Substrate of removing led chip;

5. on the n of led chip type GaN layer, prepare the n electrode.

Step 2. described in the thickness of gold layer be not less than 5 μ m.

The step 1. metal of middle evaporation is ITO, NiAg or NiAu.

The present invention adopts discrete led chip is transferred to method on the composite metal substrate one by one, when having overcome the whole LED wafer bonding, causes local bonding not firm easily, decrease in yield, the shortcoming that reliability reduces; Owing to be that single chip shifts one by one, so the transfer base substrate of led chip can be large scale (diameter is greater than 100 centimetres) circle, also can be square (length of side is greater than 100 centimetres); And the substrate that shifts in the prior art is generally diameter less than 100 centimetres circular substrate; Composite metal substrate, as the thermal coefficient of expansion gap of CuMo or AlSi and the led chip that is transferred less than 30%.

Adopt the beneficial effect that technique scheme produced to be: 1) the present invention adopts the high composite metal substrate of thermal conductivity as translate substrate, has improved the heat conductivility of LED lamp; 2) adopt the composite metal substrate of CuMo or AlSi and the led chip that is transferred between the thermal coefficient of expansion gap little, thermal stress is little, has improved the bonding rate of finished products; 3) wafer is divided into discrete chip, transfers to one by one on the composite metal substrate, improved the rate of finished products of bonding; 4) adopt two electrodes of LED lamp to adopt the mode of the upper and lower surface that is distributed in led chip to be arranged vertically, electric current circulates up and down.

Description of drawings

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

Fig. 1 is the schematic top plan view of the present invention's GaN-based LED epitaxial wafer of growing;

Fig. 2 be single led chip along A-A to cutaway view;

Fig. 3 is soldered to structural representation on the composite metal substrate with single led flip-chip;

Fig. 4 is the structural representation after led chip is removed Sapphire Substrate;

Fig. 5 is the structural representation behind the making n electrode;

Fig. 6 is the topology view of the single gallium nitride based LED after cutting apart;

Wherein, 1, Sapphire Substrate, 2, led chip, 3, n type GaN layer, 4, p type GaN layer, 5, the p electrode, 6, composite metal substrate, 7, the gold layer, 8, n electrode.

Embodiment

Embodiment 1

1. prepare led chip

Extension n type GaN layer 3 and p type GaN layer 4 successively on Sapphire Substrate 1 form separate led chip 2 through chemical wet etching technology in Sapphire Substrate 1, referring to Fig. 1; Evaporation metal ITO, NiAg or NiAu on the surface of led chip 2, and in nitrogen atmosphere, 200-400 ℃ handles 1-10min, forms p electrode 5; Then with Sapphire Substrate 1 attenuate:, Sapphire Substrate 1 is thinned to 70-120 μ m with diamantiferous emery wheel corase grind, again with the polishing fluid polishing that contains diamond dust; With cutting modes such as laser, diamant or abrasive cutoff saws Sapphire Substrate is divided into single led chip independently mutually according to led chip 2 at last, the cross-sectional view of single led chip is referring to Fig. 2.

2. the processing of composite metal substrate

The upper surface gold evaporation layer 7 of the composite metal substrate of copper molybdenum alloy or the composite metal substrate of alusil alloy 6, the thickness of described gold layer is not less than 5 μ m.

3. with step 1. in independently led chip 2 respectively flip chip bonding be connected to the upper surface of composite metal substrate 6.

With the p electrode surface of led chip 2 down, weld or be bonded on the gold layer 7 of composite metal substrate 6, referring to Fig. 3.Independently led chip 2 is transferred on the composite metal substrate 6 one by one, forms array.

4. peel off the substrate of led chip

With the Sapphire Substrate 1 of 248nm excimer laser irradiation led chip 2 or with the method for chemical corrosion Sapphire Substrate 1 is removed, referring to Fig. 4.

Removing Sapphire Substrate 1 is in order to make the n electrode of LED, to be arranged vertically, being convenient to electric current and circulating up and down.And removal Sapphire Substrate 1 has also solved the heat dissipation problem of LED.

5. on the n of led chip N-type semiconductor N material, prepare the n electrode.

Respectively soaked 3-5 minute with acetone and isopropyl alcohol then, clean with high purity deionized water, nitrogen dries up; On n type GaN layer 3, make the electrode pattern window by lithography, evaporated metal Cr, Pt and Au or Ti, Pt and Au successively in above-mentioned electrode pattern window, the thickness of metal is not less than 1 μ m; Remove photoresist at last, form n electrode 8, referring to Fig. 5.

With cutting modes such as laser, diamant or abrasive cutoff saws composite metal substrate 7 is cut into needed size according to the distribution of led chip 2 again, referring to Fig. 6.

The present invention adopts the composite metal substrate of copper molybdenum alloy or adopts the composite metal substrate of alusil alloy, close with the thermal coefficient of expansion of led chip, the rosin joint of avoiding the thermal stress between led chip and the substrate to cause has greatly improved the rate of finished products of LED, and has improved the reliability of LED; The mode that led chip is shifted has one by one overcome the local bonding not firm shortcoming that causes when entire wafer shifts.

Claims

1. the preparation method of a vertical stratification gallium nitride based LED is characterized in that carrying out according to following step:

1. prepare discrete led chip

Extension n type GaN layer and p type GaN layer successively on Sapphire Substrate, the preparation GaN-based LED epitaxial wafer; At the surperficial evaporation metal of GaN-based LED epitaxial wafer, and in nitrogen atmosphere, 200-400 ℃ handles 1-10min, forms the p electrode, then GaN-based LED epitaxial wafer is divided into discrete led chip;

2. the processing of composite metal substrate

3. with step in 1. discrete led chip respectively flip chip bonding be connected to the upper surface of composite metal substrate;

4. peel off the Sapphire Substrate of removing led chip;

5. on the n of led chip type GaN layer, prepare the n electrode.

2. the preparation method of vertical stratification gallium nitride based LED according to claim 1 is characterized in that the thickness of the layer of gold described in step 2. is not less than 5 μ m.

3. the preparation method of vertical stratification gallium nitride based LED according to claim 1 is characterized in that the metal of evaporation was ITO, NiAg or NiAu during step 1..