Production method of silicon-based chip and carbon-based chip
There are two main strategies for manufacturing the Wiener structure of chips in the world:
1. Top-down: Top-down method
The manufacturing of silicon-based chips adopts micro-nano processing technology from top to bottom, and the equipment used is mask aligner, ASML. Mask aligner is like a meat cleaver, using light to carve the devices on the chip design onto the silicon chip.
2. Bottom-up: bottom-up approach
The manufacture of carbon-based chips uses this bottom-up micro-nano processing technology, just like building a house. To build a house, we use bricks first, and then use bricks to build a house from bottom to top. The bricks used to build houses in carbon-based chips are carbon nanotubes.
Summary: The biggest difference between the two chips is that the silicon-based chip carves a complex chip structure on the silicon wafer through lithography and etching, while the carbon-based chip uses a large number of carbon nanotubes to build a macro chip device structure from bottom to top, just like assembling with Lego bricks. It boils down to two words: silicon-based chip engraving, carbon-based chip making!
Development status of carbon-based chips
At present, China and the United States are two leading scientific and technological powers in the world, and China and the United States have been catching up with each other in the research of carbon-based chips for more than ten years. It is said that the competition between China and the United States is actually the competition between two top universities in the world: Peking University and Massachusetts Institute of Technology.
Peking University Laboratory, led by Academician Peng Lianmao, started the project of carbon-based integrated circuits in 2007. They creatively developed a set of undoped manufacturing methods for high-performance carbon tube cmos devices from the aspects of carbon tube manufacturing, assembly technology and device structure, and realized the control of device polarity by adjusting the work function of contact metal. Simply put, it is to change the contact electrode material of carbon nanotubes, using metal as the source and drain electrode with high work function and aluminum as the source and drain electrode with low work function.
On 20 17, the experimental team led by Academician Peng of Peking University made breakthrough progress in carbon tube manufacturing technology, carbon tube device physics and performance limit exploration. And a 5nm gate carbon nanotube CMOS device is fabricated, which works twice as fast as Intel's latest commercial silicon transistor, but the energy consumption is only 1/4. This shows that carbon nanotube cmos devices below 10nm have obvious performance advantages over silicon-based cmos devices. This research achievement was published in the journal Science, and the breakthrough research of Peking University experimental team proved the feasibility and superiority of carbon-based chips. However, successful research and large-scale commercial production still have a long way to go, and the problem of Huawei's chip production capacity will not be solved for a while.
Besides, MIT, led by Professor Schuraker, is conducting research on carbon-based chips in Hello. In 20 19, Science, the world's top magazine, published a paper by Schuraker's team, introducing a carbon-based microprocessor with 14000 carbon transistors. This microprocessor with only 16 bits is based on RISC-V open source organization.
They adopted a technique called MIXED, which is similar to the method of the experimental team of Peking University. The function of transistor is realized by controlling the deposition of electrode materials such as metal. The Shulaker team is more concerned about compatibility with existing silicon-based chip technology. They use the current standard EDA chip design software, which is prepared by using materials and processes compatible with silicon-based chips. In this way, an integrated circuit consisting of 14000 carbon-based transistors is obtained. This method can realize industrial application faster, which is basically the technical level of silicon-based chips 30 years ago. There is still a long way to go to realize commercial mass production.
In this future technological battlefield, China is slightly ahead of its competitors.
Different from the practical utilitarian thinking of the Massachusetts team, the goal of the Peking University experimental team is to surpass the innovative thinking of silicon-based chips in an all-round way. In May 2020, Peking University's experimental team made another breakthrough in Science magazine. They solved an important problem, how to realize the orderly arrangement and construction of high-purity carbon nanotubes. They innovatively prepared a carbon nanotube solution with a purity higher than 99.9999%, and assembled it with a high-purity solution through size limitation, and prepared a well-arranged high-density carbon nanotube structure on a 4-inch silicon wafer.
The microprocessors they made through this distribution are smaller than those made in Massachusetts laboratory, but carbon-based transistors show better performance than silicon transistors with similar feature lengths.
Final summary:
The manufacture of carbon-based chips requires the preparation of large-area, high-density and high-purity carbon tube arrays on the wafer. At present, the related research technology of Peking University has been ahead of the world. Over time, I believe that the research of carbon-based chips in China will definitely make a breakthrough in commercial application, break through foreign technical barriers as soon as possible, and produce high-end advanced carbon-based chips.