Semi-floating gate transistor industry prospects 100 billion yuan

In the latest issue of the "Science" magazine published on August 9, the research and development achievements of Chinese scientists' semi-floating-gate transistor (SFGT) attracted worldwide attention because it promises to achieve a breakthrough in the performance of electronic chips. This latest research paper published by Prof. Zhang Wei of the School of Microelectronics of Fudan University is the first original microelectronic device field in China published in this academic journal.

Semiconductor processing faces physical limitations, semi-floating gate transistors speed up energy savings, or break the bottleneck

Metal-oxide-semiconductor field-effect transistors (MOSFETs) are the most basic devices in current integrated circuits. The advances in technology have led to the shrinking size of MOSFETs and their power density has been increasing. Low-power tunneling field effect transistors (TFETs) are considered to be a major future technological development of the device. Our flash memory chips, such as U-disk, use another device called floating-gate transistor. It requires a higher operating voltage (approximately 20 volts) and a longer time (microseconds) for writing and erasing. level). According to experts, as the device size approaches its physical limit, transistors based on new structures and new principles have become an urgent need in the industry.

Zhang Wei’s team of scientists tried to combine a TFET with a floating gate device to form a new “half-floating-gate” structure device called a semi-floating-gate transistor, which has the characteristics of a compact structure and high performance. It creates the conditions for low power consumption of the chip.

"Silicon-based TFETs use the quantum tunneling effect in silicon, while the traditional erasing operation of floating-gate transistors is to make the electron tunneling through the insulating medium." The first author of the paper, Wang Pengfei, explained that. "Tunnelling" is a common phenomenon in the quantum world. It can "magicly" pass through solids as if it had a wall-through technique. The lower the "tunneling" barrier, the thinner the "wall" and the lower the voltage required to tunnel the device. Combining the TFET with the floating gate, the TFET charges and discharges the floating gate and completes the “data erasing” operation. The “half floating gate” realizes the function of “data storage and readout”. Zhang Wei said that the traditional floating-gate transistor is a silicon dioxide insulating medium that tunnels electrons through a high barrier (with a band gap of approximately 8.9 eV), while tunneling of semi-floating-gate transistors occurs at a bandgap width of only 1.1 eV. In silicon materials, the tunneling barrier is greatly reduced. This allows the data erasure of the semi-floating gate transistor to be easier and faster, and the entire process can be completed under low voltage conditions, which creates the conditions for low-power operation of the chip.

As a new type of basic device, semi-floating gate transistors can be applied to different integrated circuits. It can replace a portion of static random access memory (SRAM) to improve the performance of high-speed processors. It can also be applied to the dynamic random access memory (DRAM) field to improve computer memory functions. The density of SRAM composed of half-floating-gate transistors can be increased by approximately 10 times compared with conventional SRAMs. The DRAM formed by the DRAMs can realize all the functions of conventional DRAMs without capacitors, not only greatly reducing the cost, but also increasing the integration and reading and writing speeds.

The semi-floating gate transistor can also be applied to an active image sensor chip (APS). The new image sensor unit can be reduced in area by more than 20%, and the density of the photosensitive unit is increased, so that the resolution and sensitivity of the image sensor chip can be improved. .

The compatibility with the existing manufacturing process is high and the faster industrialization still requires the government to support the team led by Zhang Wei has long been engaged in the research and development of integrated circuit technology and new semiconductor devices. The team studies backbones to join Fudan University from all over the world for the common research interests and goals. In the past five years, the team has published a number of research results in the "Science" and top international journals in this field. It has obtained more than 30 patents from China and the United States.

Zhang Wei said that the core patents for DRAM, SRAM, and image sensor technologies are basically controlled by foreign companies such as Micron, Samsung, Intel, and Sony. “In these areas, there are almost no products with independent intellectual property rights and applicable in mainland China.” It is estimated that semi-floating-gate transistors, as a basic electronic device, have a potential market size of 300 in the fields of storage and image sensing. Billion dollars or more.

Unlike transistors based on new materials such as carbon nanotubes and graphene researched in the laboratory, the semi-floating gate transistor is a microelectronic device based on standard silicon CMOS technology. It is compatible with existing mainstream silicon integrated circuit manufacturing processes and has a very good Industrialization foundation. Professor Zhang Wei said that semi-floating gate transistors do not require major changes to the existing integrated circuit manufacturing process. However, new devices also require a lot of work to gradually realize industrialization.

Zhang Wei said that China’s integrated circuit technology is not far from the international advanced level. The industry mainly relies on the introduction and absorption of mature technologies from abroad, but lacks core technologies. Foreign integrated circuit manufacturers will often phase out one or two generations of technology at a high price to Chinese companies. The invention and industrialization of the semi-floating gate transistor is actually to make up for the gap in the core technology of China's integrated circuit companies through the technical advantages of the new basic device. If the new device technology is transformed into productivity, Chinese IC companies can significantly reduce their dependence on foreign technology in certain application areas and form their own highly competitive and autonomous core technologies. This requires the strong support of the government and relevant departments. In addition, to achieve industrialization and promotion of semi-floating-gate transistor technology, it is also necessary to strengthen the close cooperation between production, education and research.

Having a core patent does not mean having a vast market in the future. Although semi-floating-gate transistor applications have a broad market, the premise is the optimized layout of the core patents. "Our layout is going to be faster and avoid being overtaken by big foreign companies quickly." Zhang Wei is not worried. Their future research work focuses on the optimization and further improvement of device performance.