How a Chinese "core" was born Author 丨 Cao Wenmi
"The world power device market size of 22 billion US dollars, the domestic market accounted for more than half. But 90% rely on imports, especially high-end chips. Li Simin sighed that in the 1990s, there was still a big gap between domestic and international advanced semiconductor devices.
In the 1980s, China's semiconductor devices transitioned from the first generation of tubes to the second generation of transistors, and the world has entered the era of modern power electronic devices, and IGBT is about to become mainstream.
It was not until the 1990s that China's first high-voltage IGBT was born, which was designed by Huang Qin, an expert in power semiconductor devices, and Li Simin was responsible for the process.
The semiconductor industry is divided into two categories according to products, one is equivalent to the human brain nerve, which is the current shortage of integrated circuit chips (Integrated Circuit Chips), and the other is equivalent to human limbs, known as power semiconductor devices (Power Semiconductor Device), and high-end products are also highly dependent on imports.
IGBT, insulated gate bipolar transistor, small to welding machines, induction cookers, medium to new energy vehicle charging piles, large to rail transit, power grids, aerospace, wind power turbine operation of the "CPU" are it, a wide range of application scenarios.
In such important technical components as semiconductor chips, the more dependent on imports, the more likely it is to be "stuck neck" by importing countries.
In 2020, Sino-US relations fell into tension, the United States announced sanctions on some Chinese companies, close monitoring of chip exports to China, a war without smoke and smoke began. With the advent of the epidemic, the world has fallen into a chip shortage crisis, accelerating the pace of Power Chip Research in China.
Semiconductor chip technology is the basis of almost all modern technologies, and national pillar industries such as high-speed rail, rail transit, wind power, power grids, ships, military industry, and large equipment are inseparable from power chips.
However, the design and manufacture of a new type of chip often cost tens of millions and takes years.
The main difficulties are in architecture design, manufacturing process, and research and development cycle: designing a chip, researchers want the chip to "standardize", define key information such as instruction set, function, input and output pins, performance and power consumption, divide the circuit into multiple small modules, and clearly describe the requirements for each module. The "front-end" designer then designs the "circuit" according to the function of each module, uses the computer language to model and verify that its function is accurate. The "back-end" designer designs the "layout" according to the circuit, and regularly reprints hundreds of millions of circuits to a silicon wafer according to its connection relationship. At this point, the chip design is complete. Such a complex design, there can be no flaws, otherwise it can not be repaired, must start from scratch.
The manufacturing process is complex. A chip manufacturing production line involves about 50 industries, generally going through 2,000 to 5,000 processes.
The investment is large and the development cycle is long. A complex chip, from research and development to mass production, to invest a lot of manpower, material and financial resources, the time is at least 3 to 5 years, or even longer. This is true of ICs, and so is power chips.
The development of a new chip requires the cooperation of the R&D team, funds and industrial chain, among which the R & D personnel's judgment and adherence to the new technology route are particularly important.
"On the road to semiconductors, there is no shortcut, we can only go to the hardest road. Doing the hardest thing now will make it easy later. Li Simin's daughter Li Lianyu told the small dinner table.
- Range of applications for power semiconductors -
Li Simin is the first participating manufacturer of high-voltage insulated gate bipolar transistor (IGBT) in China, founded the semiconductor company Youjiemin, and has developed GAT tubes and GATH tubes, and obtained more than 10 Chinese patents. Now 82 years old, Li Simin is still tireless in technology research and development: his newly developed reverse conductive intergrid transistor (RCGAT) that replaces MOS tubes has entered the assembly line manufacturing stage.
82-year-old Li Simin with his chip dream
- Founder &CTO Li Simin -
Li Simin's chip dream is rooted in her teenage years. In 1956, at the age of 16, Li Simin was admitted to the Physics Department of Peking University to study semiconductor physics; in college, Li Simin and his classmates witnessed the artificial satellites of the former Soviet Union flying overhead, and in that era of lack of technology and weak industrial foundation, this group of young people silently planted the seeds of science and technology to serve the country in their hearts. For this seed, Li Simin gave half a life.
After graduating from university, Li Simin was assigned to the Beijing Radio Device Research Institute. In 1983, he participated in the work of the 8085 microprocessor jointly researched with the Institute of Microelectronics of Tsinghua University. His experience spans multiple product areas in the semiconductor industry.
In the early 1980s, the world's third-generation semiconductor power device research was in full swing. The rise of the third generation of power devices based on metal-oxide semiconductor field effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs), at that time, China was in the midst of a wave of reform and opening up, and semiconductor devices were still transitioning from the first generation of electron tubes to the second generation of transistors.
At that time, the core technology and industry of IGBT were controlled by most European, American and Japanese semiconductor manufacturers, and the import of IGBT chips around the world depended on it, and China was no exception.
During that period, China began to implement the "Eighth Five-Year" national key scientific and technological project (research) plan, striving for breakthroughs in power electronic devices and applications, and changing the situation of being subject to people in the development of electronic technology.
Through a friend's introduction, Huang Qin, an expert in semiconductor devices, met Li Simin, who was then deputy director of the high-tech laboratory of the Beijing Semiconductor Device Research Institute. In 1987, designed by Huang Qin and li Simin was responsible for the process production, the two cooperated to develop China's first high-voltage IGBT, breaking the international monopoly.
In 1988, the Office of the Beijing Electronics Revitalization Leading Group held a brainstorm to gather the best talents in the semiconductor industry and hold a China Power Electronics Seminar every half a month. At this grand event that brought together the best and most talented semiconductor research talents in China, Li Simin accepted advanced semiconductor research ideas from home and abroad. This academic journey has sown the seeds for his follow-up independent innovation GAT and GATH tubes.
In 1994, Li Simin was sent to the United States to learn the latest semiconductor device groove type IGBT full set of technologies, laying the foundation for research work after returning to China. After returning to China, just when Li Simin was preparing to show his skills in the art, he encountered the bank restructuring in the 90s. The original cooperative bank no longer invested in li Simin's company's electronic power research projects, and Li Simin's research path was interrupted.
In 1996, in order to improve the performance of domestic IGBTs, so that it can be quickly introduced to the market at lower cost and high adaptability, Li Simin began to optimize the existing IGBT structure, and then innovated another architecture - the grid power tube, invented a special fine cell (~10 micron) GAT (binary gate transistor). Compared with IGBTs, the advantages of GAT tubes are low heat generation, high energy efficiency and a large safe working area.
Between 1996 and 2012, Li Simin cooperated with Beijing Shanbei Company and Shenzhen Shengyuan Semiconductor Company to sell hundreds of millions of GAT tubes.
In 2012, Li Simin established Youjiemin Company, immersed in research and technology, hoping to break through the restrictions and allow Chinese companies to use domestic semiconductor chips with confidence. When Li Simin's daughter Li Lianyu ran for financing for her father's chip dream, a sentence from the investor made them enlightened, thus opening the road of transformation: "The characteristics of such a good product, high voltage and large current are also urgently needed by our country, energy-saving lamps do not need such good characteristics, why don't you do high voltage and large current in this technology?" Li Lianyu said.
Since then, Li Simin has begun to study high-voltage and high-current products. Under the premise that the early GAT tube technology has been very mature, Soon, Li Simin launched GATH (Gate Associated THyristor) in 2018. GATH breaks through the highest current density of IGBT, with high temperature resistance, high power, stronger robustness, low cost and other advantages, suitable for flexible HVDC transmission, rail transit, wind power and other high-voltage high-current scenarios, it is more durable under the condition of high voltage and large current, which is also the chinese chip industry urgently needs to solve the problem.
- Ujemin 1700V 100A Single Chip -
"Public information shows that the maximum current density of IGBT is 800A/cm2, and experimental data show that the current density of GATH with the same specification of 1200V has reached 25000A/C㎡. This shows that GATH has a strong resistance to current impact, just like the flood control embankment, IGBT is one floor, and the GATH anti-electric surge flood control embankment is ten stories high. Therefore, GATH is far more robust than IGBT. Li Simin described.
- Ujemin 1700V 400A GATH 6 Inch Tablet -
Since the cost is lower and the durability is stronger, why has the technology not been applied and promoted in China?
"What we do is fundamental innovation. An industry also needs collaborative innovation and system innovation. We only have the ability to make chips. Li Simin said that after the chip is developed, it is also necessary to package the module, develop the drive line, make it into a whole machine, test and identify, and then carry out market promotion.
"It's a big, complex ecosystem. There is nothing we can do about it. Li Simin said.
The system integration of flexible HVDC transmission, high-speed rail, wind power and other large projects can be done by no one on their own. "From the voltage type to the current type, the whole machine test of the line and the system needs the support of large companies or the state to do it." Li Si, who once went to the United States to study, has a deep sense of sensitivity, and the collaborative innovation of the industrial chain and system innovation in the United States have been very mature, and there is a lack of such collaborative innovation in China.
At present, the highest withstand voltage of GATH products has reached 1700V 400A, so Li Simin has obtained more than 10 Chinese invention patents and is applying for international invention patents. Li Simin believes that if there is financial support, it is easy to make 3300V, 6500V, and even 8000V 200A (8-inch line) GATH products. Li Simin believes that GATH will play an important role in the field of flexible HVDC transmission and UHV.
It is estimated that the total investment scale of HVDC transmission projects during the "14th Five-Year Plan" period is close to 400 billion yuan, of which power semiconductors (IGBT, thyristors) will invest 45 billion yuan. Flexible HVDC transmission is a structural opportunity in the construction of new power systems.
The development of flexible HVDC has placed new demands on power devices: higher voltages, higher currents, lower losses and higher junction temperatures. At present, IGBT is difficult to meet the needs of softness. Mainly IGBT is limited by the structural ceiling latch, the more high voltage, high current, high temperature, IGBT is about easy to cause overcurrent failure due to latching. Therefore, it is difficult for IGBT to make a larger power specification chip, and the power capacity of the IGBT module is difficult to increase. Due to latch-up, the avalanche resistance of high-voltage, high-current applications of IGBTs is also fragile. At present, flex-direct application 4500V/3000A IGBT module, series parallel connection of hundreds of IGBT modules, large loss, complex control, expensive cost. In order to control the overcurrent failure caused by IGBT due to latch-up, the fault branch used, the system control is complex, and the maintenance cost is high, so that the current cost of flexible HVDC transmission is 1.5 times that of HVDC transmission. Therefore, the ceiling of the IGBT latch restricts the development of flexible HVDC transmission.
GATH is an advanced IGCT, with the advantages of high voltage and high current, high reliability and low cost of thyristors, coupled with the linkage structure, the repeating unit is reduced, breaking through the limitations of IGCT due to the large cell size, di/dt dv/dt, the driving power consumption is IGCT 1/10, and the drive is much simpler than IGCT.
Taking the Zhangbei Flex Direct Project as an example, if the 8000V/6000A crimp GATH module is used instead of the 4500V/3000A crimped IGBT, the voltage output of the flexible straight grid can be doubled, from ±500KV to ±1000KV, and the rated output capacity of the flexographic grid of 4.5 million kilowatts can be increased by 3 times to 18 million kilowatts. And the failure rate will be greatly reduced, and it is expected to be reduced by 1-2 orders of magnitude. GATH meets the requirements of flexible HVDC transmission for high voltage and high power of power devices, strong avalanche resistance, higher junction temperature and lower loss, and will promote the faster development of flexible HVDC transmission.
GATH listed mass production difficulties The founder sold the house twice
There are only 3 members of the whole team of Youjiemin, and the founder Li Simin is now 82 years old and has not changed his original intention of technology. The CEO is the founder's daughter Li Lianyu, who has experienced a break in the capital chain and a split with cooperative companies, and has sold houses for the technology research and development of the father and daughter twice. In the 40-square-meter cottage, Li Simin created a domestic high-voltage high-current semiconductor device independently developed.
Li Simin's daughter Li Lianyu was a former university teacher who lived in the comfort zone of the campus environment. She has seen representatives of cooperative enterprises repeatedly go to the door to discuss equity cooperation in order to buy her father's technology, and finally ended in failure when her father insisted on himself; she also experienced the difficult moments when her father sold the house twice in order to support research, which made her more determined to pass on her father's semiconductor technology.
In 2012, Li Simin established Youjiemin Semiconductor Technology Company, and after three years, the technology matured and was ready to be pushed into the market. At that time, Li Lianyu's younger brother resigned from his post and was bent on running the market for his father, and Li Lianyu consulted with his husband to sell their own house and give his father start-up funds. Since 2015, Li Lianyu has also resigned from the university campus and began to help his father run the market full-time.
- Li Lianyu, CEO of Ujemin Semiconductor -
"Doing semiconductors is a very expensive thing, from personnel formation, product design, to factory processing, to delivery to cooperative enterprises, there are too many links in this chain, once there is a problem, the enterprise will be on the verge of life and death." Soon, the money from the sale of the house burned out. Li Lianyu recalled.
At that time, Youjiemin cooperated with a chip processing plant, although Youjiemin already had a part of the order, but due to the factory production capacity restrictions, there are requirements for the output of the product, if it is not met, it will consider cutting this production line, coupled with the shortage of funds of Youjiemin, there are some payments that cannot be paid, Li Simin weighed again and again, did not want to let his more than 20 years of hard work in vain, sold his house at that time.
After selling the house, Li Simin moved into a one-room cottage rented of more than 40 square meters in Beijing's North Third Ring Road, using it as his "research base" and continuing to "wrestle" with semiconductor technology. In order to devote himself to research, he refused his daughter's request to move in with him.
Li Lianyu recalls that when he was a university teacher, his father refused the cooperation of a company in Shenzhen because he wanted to concentrate on his own technology instead of making a profit quickly. Without any support or help, my father continued to think every day, read cutting-edge journals, buy materials at his own expense, and do experiments. Once she went to visit her father, talked until 11:30 p.m., and when she got up to leave, she looked back and saw her father, in his 70s, in the dim light, hunched over his back, doing experiments, like a lone soldier.
"As soon as he had a new idea in science, he was going to do experiments." Li Lianyu said, "When I look back at the moment when he was looking back, I thought I must help my father make this thing, this is my father's lifelong scientific research results, this is the core thing of our country, I must keep it." ”
Li Simin hopes that his technology can be applied to larger scenarios, such as flexible HVDC transmission, rail transit, photovoltaics, energy storage, wind power, new energy vehicles, etc.
Li Lianyu believes that the process, materials and design determine the quality of a chip.
"My father spent decades not making a single product, but developing an entire process platform."
The manufacturing process of the chip includes wet washing, lithography, ion implantation, etching, plasma cleaning, heat treatment, chemical vapor deposition, physical vapor deposition, electroplating treatment, chemical/mechanical surface treatment, wafer testing, wafer polishing, packaging and other links.
From the development of GAT in 1996 to the launch of GATH tube today, a complete set of complete process flow has been formed for more than 20 years.
After the process platform matures, the underlying structure of the chip does not need to be adjusted, and what remains is some fine-tuning. On the one hand, there are epitaxial tablets.
On the other hand, design, good design can maximize the efficiency of the chip, now, Professor Li Simin can generally use a week or two to do a good design.
Nowadays, Ujemin is no longer in the 0-1 research and development stage, and can now quickly launch new products based on the process platform.
Although the GATH tube performs well in experimental data, far stronger than IGBT, due to the lack of whole machine testing, extensive scene testing, limit testing, etc., no one has given accurate conclusions and clear prospects for the time being.
But fortunately, at the end of 2021, Youjiemin received the support of the State Grid and settled in the "Double Innovation Incubation Platform". With the support of the state, Li Simin was finally able to achieve the adjustment of the surrounding lines of GATH and test the various characteristics of the chip, and it was also with the support of the State Grid that Youjiemin began to produce prototypes in the field of photovoltaic and wind power. At the same time, Li Lianyu also continued to help his father find angel round financing, hoping to expand the team and expand production capacity.
"My father used to say that when I die, someone will do it. I used to wonder, if you die, how can anyone still do it? But he believes that the grid architecture is an innovation in the underlying architecture of power devices, and someone in this direction will continue to do it well. Li Lianyu said.
Li Simin firmly believes that the power tubes GATH and GAT of the joint gate architecture are superior to the power tubes IGBT, MOS and the third generation semiconductor SIC MOS of the insulated gate architecture. GATH is ten times more robust than IGBTs, and the high efficiency and high power density of GAT are comparable to SIC MOS at a cost of only 20%.
Li Simin has newly developed a reverse conductive intergrid transistor (RCGAT) that replaces MOS tubes, which has entered the assembly line manufacturing stage and will be available at the end of 2022. RCGAT is the core component of the charging pile of new energy electric vehicles, which can solve the problem of fast charging. GAT has the advantages of high frequency (100KHz), high power density, high energy efficiency and low cost, which can improve the power density of the whole machine, optimize the heat dissipation system, reduce the volume of the charging module, and will become a new technology path for power chips to solve the range anxiety of electric vehicles.
"There are no fast-charging power devices above 50kw in China." Li Simin said that some manufacturers in the Pearl River Delta have come to the door to wait for the tape-out.
Perhaps Youjiemin will not be the first company to complete the test of THE GATH tube machine, and Li Simin will not be the "first person to eat crabs", but on the road of domestic semiconductor power devices, there will always be their shadow.
* Zhang Yiwei also contributed to this article
Resources:
1Source: A new type of IGCT – GATH
https://www.dianyuan.com/article/57445.html
2Source: A new energy-efficient, low-cost power device, the GAT, a triangular transistor
https://www.dianyuan.com/article/59336.html