Wed, Mar 15, 2023 page8

• China is countering US chip ban

  • By Chiueh Tzi-cker 闕志克
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  In 2020, then-US president Donald Trump’s administration banned Taiwan Semiconductor Manufacturing Co and Samsung from manufacturing advanced chips for Chinese companies on the Entity List such as Huawei.

  Last year, US President Joe Biden’s administration announced that exports of high-performance computing chips from the US to China require approval; sales of semiconductor manufacturing equipment to China that can be used to produce logic chips at or below the 14/16-nanometer technology node, DRAM chips with a half-pitch less than or equal to 18 nanometers and NAND chips with 128 or more layers also require approval; and all US citizens or permanent residents working for Chinese semiconductor firms need to obtain explicit permission from the US government before they can continue to do so.

  These measures mean that the US does not allow China to purchase the highest-end computing chips from the outside, outsource their production or manufacture them domestically, dealing a blow to the development of China’s semiconductor industry. How can and does China fight back?

  Although Washington’s ban on exports of high-end computing chips to China might slow the development of the latter’s technology in advanced fields, it also eradicates all foreign competitors, leaving the corresponding market segment wide open to China’s domestic high-end computer chip companies.

  Before the ban, because of inferior technology, it might have taken local companies at least 10 years to catch up and gain a foothold in the segment. Today, Chinese users of high-end computing chips have no choice but to test-drive domestic chips, even though their quality and performance are far from state-of-the-art. As a result, the amount of time required by these domestic companies to develop competitive world-class products might be reduced by 30 to 50 percent.

  In other words, the US ban on semiconductor technology forces Chinese chip users to step up the process of substituting domestic products for imported ones, thus inadvertently helping the Chinese government accelerate the “import substitution” policy.

  The most high-profile sanction is perhaps the sale ban on extreme ultraviolet lithography machines. Does it completely prevent Chinese IC fabs from manufacturing chips more advanced than 14/16-nanometer nodes? The answer is no.

  By decomposing a chip’s physical layout into multiple patterns and making a separate mask for each of them, it is possible to carve out a higher-resolution circuit structure by exposing a chip multiple times using a lower-resolution photolithography machine.

  The technical feasibility of this multi-patterning approach has been empirically demonstrated for some time: The 7-nanometer chips that China’s Semiconductor Manufacturing International Corp produced last year were based on this technology. Although multi-patterning is more expensive, because it requires multiple masks and its yield rate is lower, given China’s current situation, it is nonetheless an acceptable compromise to those domestic IC companies that need to access advanced technology node fabrication processes but have no other options.

  At the same time, Chinese IC design companies are also trying to develop more innovative chip architectures and circuit designs that could enable, using only lower-end fabrication processes, the kind of chip performance that previously was only possible with higher-end fabrication processes.

  One such approach is to leverage the chiplet packaging technology to cut down the communication delay and power requirement between chips in a multi-chip system, thereby improving performance and power consumption at the system or application level. That is, although a lower-end fabrication process entails performance loss within individual chips, directly interconnecting chips as chiplets on a package makes up for those losses by speeding up the data exchanges between them.

  In August last year, Shanghai Birentech announced a chiplet-based graphics processor chip, BR100, whose performance is claimed to be three times that of a similar product from a leading US company.

  In the next few years, China is determined to fully focus on the development of semiconductor fabrication processes less advanced than 14 nanometers and chips made with such processes. For China this development strategy is practical and sustainable, but for Taiwan and other countries, it represents a threat, because more than 90 percent of the world’s chips are manufactured using such processes.

  The worry is that once China masters the technologies and business logic in this segment, it could use its domestic market’s scale to gain global dominance, repeating the same excruciating process of market cleansing that occurred previously in the solar panel, LCD and lithium battery industries.

  Chiueh Tzi-cker is a joint appointment professor in the Institute of Information Security at National Tsing Hua University.
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