Silicon substrate LED research and development documentary

In the past 2015, the once-famous LED industry was as fierce as the previous two years. In one year, the number of LED companies has decreased by 20%, and about 4,000 companies have withdrawn from the market.
However, there is still a "black horse" behind the "downturn" that is one after another. In Nanchang, Jingneng Optoelectronics (Jiangxi) Co., Ltd. not only has annual sales all the way, but also has a new technology road.
"Our goal is to become a world-class semiconductor lighting company and become the pride of the Chinese!" CEO Dr. Wang Min is full of enthusiasm. Workers must first sharpen their tools in order to do their best. Wang Min's bottom gas comes from the world's leading silicon substrate LED technology (silicon substrate high-efficiency GaN-based blue light-emitting diode) with independent intellectual property rights. This technology also took the first place in the National Science and Technology Awards Conference this year.

"Eggs also touch the stone"
Isn't it a silicon substrate LED technology? But if you know the history of LED development, you may be sighed with sincerity. Because this is a disruptive new technology that rewrites the history of semiconductor lighting.
"Using ordinary equipment, lower cost process to produce LED", in the "Top 50 Most Innovative Enterprises in the World" selected by MIT Technology Entrepreneurship magazine in 2011, Jingneng Optoelectronics and Appple, IBM, etc. The company is on the list together;
"This technology has changed the situation in which Japanese companies monopolize sapphire substrates and US companies monopolize silicon carbide substrate semiconductor lighting technology, forming a situation of sapphire, silicon carbide, and silicon-based semiconductor lighting technology solutions." National 863 Expert Group If it is evaluation...
Why did a little-known LED company win this award, causing widespread concern inside and outside the industry? Things have to start with the preparation of blue LED chips.
In general, the white LEDs we see are inspired by blue LED chips that excite yellow fluorescent materials. Previously, there were two main technical routes for blue LED chips, one was a sapphire substrate and the other was on a silicon carbide substrate. Among them, the three inventors of the sapphire substrate technology route won the 2014 Nobel Prize in Physics, and the inventor of the silicon carbide substrate technology route won the US Presidential Technology Invention Award.
The preparation of high-efficiency LED chips on silicon substrates has always been the goal of the academic world. After more than forty years of research, researchers all over the world have not found an ideal solution to overcome the key technical difficulties.
“Difficult!” This is the first reaction of LED experts to the preparation of blue LED chips on silicon substrates! Where is it difficult? To prepare an LED chip, a gallium nitride light-emitting film is first grown on the substrate. The problem is that high-quality gallium nitride light-emitting films have not been available for a long time due to thermal mismatch and lattice mismatch of silicon and gallium nitride materials. As a result, the preparation of silicon substrate LED chips is naturally impossible.
"Eggs also have to touch the stone." When the technical route of silicon substrate was declared "death penalty" by the industry, in 2003, the R&D team led by Professor Jiang Fengyi of Nanchang University turned its way to aiming at the silicon substrate LED technology and struggling!
Not a moment of fever. Before choosing silicon as the substrate, Jiang Fengyi team has been tracking sapphire substrate technology for 10 years. However, they know that although the sapphire substrate is the mainstream technology route in the current market, it is difficult to achieve large-scale extensions such as 8-12吋 due to the limitation of materials. It also has certain limitations in large-scale automated manufacturing; and because of sapphire heat dissipation Poor performance and difficulty in stripping the substrate, so it has performance limitations in high-power LEDs. The performance of silicon carbide is obvious to all. It can be taken away from the “noble route”, which is costly and not suitable for mass popularization.
"Si as a substrate material, silicon has the advantages of low cost, large size, high quality, and electrical conductivity compared with sapphire and silicon carbide. It is considered to be the most promising substrate material for growing gallium nitride blue LEDs. The future lighting market will tend to choose this kind of technical route with high performance, high reliability and low cost." Jiang Fengyi is full of confidence.
It is also fortunate that Wang Min and others who worked side by side with Jiang Fengyi are also very optimistic about this technical route. "China is a veritable LED product manufacturing country. Domestic LED companies all adopt sapphire technology routes, which are covered with patent mines carefully buried by LED giants. In the past 10 years, many LED companies have swallowed bitter results for this." The low discourse is Wang Min’s heavy sense of responsibility. In Wang Min's view, DVD is subject to the teachings of other countries to alert us. The efforts of foreign LED manufacturers to "water and fish" have been in full swing. The LED patent warfare is ready at any time. "The silicon substrate technology route is the only possibility to break through." Opportunities for foreign patent blockades."
Unswerving. In 2004, the R&D team took the lead in internationally to overcome the gallium nitride-based LED materials and device technology on silicon substrates. In 2005, the laboratory produced samples. In 2006, Jingneng Optoelectronics was founded. In 2007, the pilot test was successful. In 2008, small batch trial production, mass production in 2009... years of arduous research and development, crystalline silicon substrate LED technology is maturing.
More importantly, with this technology as the core, Jingneng Optoelectronics has applied for more than 330 international and domestic patents (including authorization), and has layout in the fields of LED epitaxial growth, chip manufacturing, packaging and application, and successfully avoided many foreign countries. LED company's patent blockade. And the facts prove that the life of the silicon substrate LED exceeds 60,000 hours, and the performance is comparable to that of the international manufacturers, and the cost is the lowest! According to calculations, the manufacturing cost ratio of a thin film type LED chip made of a silicon substrate, a sapphire substrate, and a silicon carbide substrate is 1:1.3:3.6.

"The groping in the dark"
Looking at the success of today's crystal energy silicon substrate LED technology, many people are envious. But little is known about the fact that they chose the silicon substrate technology route and were dismissed as whimsical.
Questioning is not without reason. Compared with well-known institutions such as IBM and the University of Marburg, which have studied silicon substrates more than 40 years ago, this R&D team, which initially had only a few people, is not a little disparate in terms of financial strength and R&D strength. "This technology, there is no breakthrough in foreign countries, why can you succeed?" "It will not take long, the silicon substrate technology will be 'fetal death'." From the day of the selection of the silicon substrate technology route, similar sounds are heard.
Looking back, Wang Min said that it was a history of "exploring in the dark." However, in the face of the sneer of rushing, he smiled lightly - no counterattacks or evasive. He said that it is normal to have doubts. "Question is another kind of motivation. The best answer is to get things done and speak with facts."
For silicon substrate LED technology, the biggest “blocker” is the thermal mismatch and lattice mismatch between silicon and gallium nitride materials: the difference in thermal expansion coefficient between silicon and gallium nitride is as high as 57%, and gallium nitride on silicon When the film material suddenly drops to room temperature after more than 1000 degrees of growth, it is subjected to huge tensile stress and cracks, which cannot meet the basic needs of the device; the lattice mismatch between silicon and gallium nitride is as high as 19%. This causes an excessively high dislocation density in the epitaxial film, which in turn leads to poor crystal quality and high quality LEDs cannot be obtained.
How to overcome this world-class problem? Jiang Fengyi, who suffered from severe lumbar disc herniation, had a bed in the laboratory. He slept there and slept there for more than ten hours a day. After more than 3,000 attempts, they finally ushered in the “Rainbow after the Rain”: successfully developed a gallium nitride light-emitting film on silicon to reach a practical level.
"The next step is to industrialize! In the new era, we have no reason to order foreign semiconductor lamps!" Jiang Fengyi, who first tasted the fruits of joy, is looking forward to the future.
"Ideal is full, the reality is very skinny". Recalling that Jingneng Optoelectronics has been on the verge of life and death on the LED industrialization road several times, now the hair color has gradually changed to the "grandmother ash" Wang Sen. "The choice of the year is based on a bloody blood, if you anticipate early There will be all kinds of things after this, and you may be scared."
Indeed, the silicon substrate LED technology laboratory stage was successful, but the long march took the first step. As Zhao Hanmin, the current chief technology officer of Jingneng Optoelectronics, said, the success of research and development and mass production are two completely different stages. In the research and development stage, one of the 100 samples is qualified, but to achieve industrialization, you have to To ensure that 100 are qualified, the gap between the two is unimaginable.
Take silicon substrate processing as an example. "It is feasible in the laboratory stage, but it is 'failed' in the trial production stage." Zhao Hanmin told reporters that in the laboratory stage, because the amount of products used for the processing of silicon substrates is easy to control, the liquid concentration and time are easy to control. In the production stage, on the one hand, the number of silicon substrates immersed is large, and on the other hand, there is no equipment matching the silicon substrate on the market, which leads to a significant drop in product yield. “In the beginning, the yield was only 5%, which was much worse than in the lab. At the moment of seeing the results, the whole person was stupid.” Wang Min recalled. "Open the bow without turning back the arrow", can only buy back similar equipment, and explore a little bit of transformation. "This change is more than a year!"
It’s not difficult to win a technical battle. There are more than 350 steps in making silicon substrate LED chips, and every step will encounter various problems. For example, although the thickness of a gallium nitride light-emitting film is only a few micrometers (the hair filament diameter is about 50-100 micrometers), it is composed of dozens of different structures. How to ensure that each layer is intact? How to improve the light efficiency of silicon substrate LED chips? How to reduce the dislocation to ensure the light output rate? ... The first "eat crab", a series of endless technology "hard ice" blocked in front of Jingneng photoelectric people.
At this time, some people said, "The success of silicon substrate LED technology is hopeless"; even more, it is asserted that "Crystal Optoelectronics is a 'hot potato', and the money it will throw will be watered." However, "We have been sighing from beginning to end, determined to fight for the tone, and do a good job of silicon substrate technology." Feng Bo, a young engineer who grew up with Jingneng Optoelectronics, said with deep feelings.
There is no relevant literature for reference. There is no experience to learn from. Every step must be “crossing the river by feeling the stones”. The annual “tuition fee” due to trial and error is as high as tens of millions of yuan. More than 100 million loans are heavy, but the company's executives take the lead in taking low wages and ensure that the annual R&D investment is around 80 million yuan... firmly open up a new LED road, and Jingneng Optoelectronics insists on it.
Hardships and hardships, Yu Yu Yucheng. In 2009, the silicon substrate was mass-produced with low-power LED chips. In June 2012, large-capacity LED chips were mass-produced. On the way of silicon substrate LED technology, Jingneng Photoelectricity walked in front.
With the maturity of blue- and white-light LED products and processes on silicon substrates, Crystal Energy has begun to develop new plans, "developing silicon-based violet LED technology, and new technologies such as silicon-based GaN-based power devices." ."

In the "cold winter"
On another historical axis parallel to the silicon-based LED technology, its industrialization journey has become more and more smooth: in 2012, the operating rate of enterprises in the whole industry was less than 60%, and the crystallized photovoltaics were fully sold and sold for the first time. Balance; 2013 sales revenue of 33 million US dollars; 2014 sales revenue of 60.99 million US dollars.
In the cold winter of LED, the secret weapon of Jingneng Optoelectronics is the leading silicon substrate LED technology -
From the device point of view, the silicon substrate has good heat dissipation performance and stress relief by peeling, so the product has good antistatic performance, long life, and high current density, and is more suitable for high-power LED lighting;
From the point of view of the substrate stripping method, the cost of the silicon substrate is much lower than that of the sapphire substrate when preparing the thin film type chip. Since the chemical etching method is used for the peeling, the efficiency and the yield are higher than the sapphire using the laser stripping. a substrate product to obtain a high quality, low cost vertical structure chip;
From the perspective of mass production, future technological advances can well combine the advantages of large-size silicon substrates with mature automation equipment and production lines in the integrated circuit industry, greatly improving the industrial maturity of the existing LED industry and rapidly forming The scale effect has further reduced the overall cost of LED lighting;
From the perspective of product characteristics, the single-sided light-emitting vertical structure chip combined with the white light chip process can obtain a chip with good directionality and good light quality, and also allows the silicon substrate LED to be in a small angle spotlight, car lighting, mobile phone flash, etc. The application of quality and directional lighting is more advantageous.
What does this specifically mean? For example, Wang Min, the headlight illumination of the car is mainly based on high-power LED. The design of the lamp is required in a limited space to solve the requirements of high optical density and good directionality. At the same time, the energy consumption of the whole lamp should be reduced as much as possible. The advantages of single-sided high-density light output on silicon substrate LEDs become very obvious.
For this reason, in the domestic high-end lighting application market such as motorcycle lights, electric lights, mobile lighting, etc., Jingneng Optoelectronics has occupied a large share, and its lighting products are also exported to the United States, Brazil, Japan, Italy and other countries.
IHS, the US economic advisory body, predicts that "the market share of silicon substrate LEDs will reach 40% by 2020."
"Now, the LED industry's general trend is to go to the large-size substrate." Jiang Fengyi explained that the current price of silicon carbide substrate is still high; the larger the size of the sapphire substrate, the price per unit area does not fall, 6 sapphire The substrate price is about $240; by contrast, 6 or even çš„8 silicon substrates are under $50. "It is foreseeable that if the silicon substrate achieves a larger size, the cost advantage will be more obvious," he said.
“The cake looks beautiful, but for Jingneng Optoelectronics, the pressure still exists. In recent years, with the confirmation of the feasibility of the crystal production of silicon substrate LED technology by Crystal Energy Optoelectronics, many international companies with skepticism have turned to develop silicon substrate LED technology, and they are making rapid progress. "And after the technical optimization of hundreds of companies, sapphire LED technology is quite mature, and will remain the mainstream route for a period of time." Wang Min analysis.
However, silicon-based LED technology is now in the midst of a young age, and they are confident that the silicon substrate LED will illuminate the world!

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