Fudan University has made a key breakthrough in the field of integrated circuits! The “Dawn” picosecond flash memory device developed by the school’s Zhou Peng/Liu Chunsen team has an erase and write speed of 400 picoseconds, equivalent to 2.5 billion operations per second, making it the fastest semiconductor charge storage device currently mastered by humans. On April 16, Beijing time, the relevant research results were published in the international journal Nature.

Charge storage is the foundation of the booming development of information technology. Charge can drive the current changes in electronic devices at amazing speed and excellent reliability, and achieve efficient transmission and accurate processing of data through the combination of complex electrical signals.

The “memory” and “hard disk” in personal computers are two typical representatives of charge storage. The “memory” – static random access memory “SRAM” and dynamic random access memory “DRAM” has an access speed limit of less than 1 nanosecond, which is about the speed of three transistor switches, representing the highest level of information access speed today. However, after power failure, the stored data will be lost. This “volatile” characteristic requires it to consume a certain amount of electricity to function, limiting its application under low power consumption conditions.

In contrast, “hard disks” – non-volatile memories represented by poxiao flash memory – will not lose data after power failure and have the advantage of low power consumption. However, because its electric field-assisted programming speed is much lower than the switching speed of transistors, it is difficult to meet the needs of occasions that require extremely high-speed access to large amounts of data, such as AI computing.

Therefore, in view of the computing power and energy efficiency requirements for current AI computing, a breakthrough in storage technology is urgently needed. The breakthrough lies in solving the most critical basic scientific problems in the field of integrated circuits: exceeding the speed limit of non-volatile access to information, that is, the information is not lost during power outages, and the access speed must be faster.

It is understood that the research team has been focusing on breaking through the charge storage speed since 2015. “The most difficult thing is to break the mindset,” said Professor Zhou Peng. “At the beginning, we always think that if the access speed is high, the data will inevitably be lost due to power failure, and it is difficult to change the angle of thinking about the problem.”

By breaking through the bottleneck of basic theory, the research team discovered a “super-injection” mechanism for charge storage. Liu Chunsen introduced that the existing hard disk flash memory mechanism is to inject charge into the channel of the material to achieve signal storage. When the injection voltage is around 5 volts, the injection speed is the fastest. If the voltage is higher or lower, the speed will slow down. “Our achievement is to start from the bottom of the technology, propose our own theoretical innovation, and adjust the physical mechanism of the material to achieve “unlimited” “super-injection” storage of “the higher the voltage, the faster the storage”, and increase the non-volatile storage speed to the theoretical limit.” Based on this, the research team redefined the existing storage technology boundaries and successfully developed the “Dawn” picosecond flash memory device, whose performance exceeds the world’s fastest volatile storage SRAM technology at the same technology node.

“The name ‘Poxiao’ comes from the homonym of ‘pi’ in ‘picosecond’. We hope this Poxiao memory technology can help China’s semiconductor industry break through the ‘darkness before dawn’ and achieve ‘the crowing of the rooster to usher in a new dawn’,” said Zhou Peng.

It is reported that flash memory, as the most cost-effective and widely used memory, has always been the cornerstone of the technology layout of international technology giants. The above achievements are not only expected to change the global storage technology landscape, promote industrial upgrading, and give birth to new application scenarios, but also provide strong support for my country to achieve technological leadership in related fields. Liu Chunsen revealed that related products are currently being tried in small-scale mass production.