Recently, China has established its own Chiplet (small chip, or core) consortium consisting of chip design, IP, and packaging, testing, and assembly service companies, and has launched a corresponding interconnection interface standard, ACC 1.0.
At a time when China is seeking autonomy and control of key links in the semiconductor industry chain under the pressure of the United States, the establishment of this alliance is quite a counterpoint to the UCIe alliance led by AMD, Arm, Intel, Taiwan Semiconductor Manufacturing and ASE. From a technical perspective, the value and development prospect of Chiplet has been widely recognized in the global semiconductor community.
Chiplet is not an innovative concept -- it was conceived early on, but the need for it didn't reach that point, so it's been "invisible" for a long time. The main reason for its popularity in recent years is that the cost of advanced manufacturing processes (5nm and below) is surprisingly high, which is difficult for most chip companies to afford. Chiplet can solve this problem in large part.
01. Why should Chiplet promote the change of industrial chain?
Chiplet can be transformed from a traditional single-chip design into a multi-chip (Die) design and integrated using an advanced packaging process. Its main advantages are as follows:
1. Improve chip performance and integration
By means of 2.5D/3D stacking, the number of transistors per unit area can be increased to improve the computing power. At the same time, the heterogeneous interconnection can further meet the complexity requirements of the chip and improve the integration degree.
2. Reduce the complexity of chip design
Modularized design can reduce the complexity of the overall design of the chip, thus speeding up the cycle of the product to market. And for some system-level manufacturers, it can lower the entry threshold of their own chips. In addition, chip I/O augmentation becomes easier due to the use of integrated heterogeneity and dielectric layer rewiring.
3. Reduce chip power consumption
Power consumption is also a problem as the chip gets bigger and wires move from one end to the other, and Chiplet can help solve that problem.
For China, Chiplet, in addition to the advantages mentioned above, has been given another layer of mission -- to help Chinese semiconductors achieve more localization of chip design and manufacturing in a deglobalized reality. Despite these advantages, Chiplet technology is not mature. Various dies, interface I/O, buses, etc. are very different from conventional SoC. A unified standard needs to be established so that design, manufacturing, packaging and other manufacturers in the industrial chain can operate according to the standard, so as to achieve efficient and large-scale production. As a result, industry specifications such as UCIe and ACC 1.0 have been introduced.
02. The challenges Chiplet faced
Not all types of chips are suitable for Chiplet. Currently, cpus, Gpus and other processors are most suitable for Chiplet, and they are used in high-performance applications, such as smart phones and other consumer electronic devices, which rarely need Chiplet design.
Switching to a Chiplet design only makes sense when the cost of traditional SOCs reaches a certain magnitude.
When a chip that adopts Chiplet architecture completes the encapsulation, due to the internal multiple dies, some chip internal functional blocks are numerous and complex, the processor, memory and I/O control are combined together, there may be more than 100 dies. Assuming that the yield of one Die is more than 90%, then the yield of the whole chip combined by them is definitely less than 90%. And the more Die, the lower the overall yield.
In most cases, it is difficult to tell if the Die will work properly before the package is complete. When different Dies are placed side by side, the I/O pad on the top of the chip is small and extremely difficult to test directly. Considerable pressure needs to be applied in order to make good contact with the probe, which can damage the contacts and chip internal structure. While foundries do test wafers, such tests are rarely exhaustive and are really just designed to screen out obvious defects. At present, in the face of this testing problem, well-known closed test factories in the industry, as well as top scientific research institutions have put forward solutions, but all belong to the exploratory stage, not mature.
03. Is Chiplet a "lifesaver" for Chinese semiconductor?
Not only internationally, Chiplet has also become very popular in mainland China in recent years, especially since the US began to crack down on the Chinese semiconductor industry. Chiplet, which can reduce the amount of advanced process while enjoying the benefits of advanced process, is highly anticipated.
The first thing to be sure of is that China is doing the right thing in developing Chiplet, and it represents the future, both in terms of the technology itself and the need for the app. But placing too much hope on Chiplet to solve key problems is a bit off the mark. As for China's development of the Chiplet, Wei Shaojun, a professor at Tsinghua University and vice president of the China Semiconductor Industry Association, said that no matter how the Chiplet develops, it still has to have a Chip first, so the goal is still heterogeneous integration at a controlled cost, which can only be a complement to advanced processes.
Wei believes that China's IC industry as a whole is still in the process of catching up, and Chiplet's presence cannot fundamentally change that. If we rely on foreign IP and EDA tools for chip design today, in the Chiplet era, the core and EDA tools we use are likely to rely on foreign vendors. However, Wei points out that Chiplet can also be used by a Chinese company. For example, Chiplet can be used by a Chinese company to grow apps more quickly.
The presence of Chiplet has broken new ground in the chip industry, and it is likely that a new business model will emerge that will build specialized chips by integrating standard cores, which is why the Chiplet standard has been created by several major international companies. Through the establishment of the standard, the chip produced by Chiplet can become a "standard product" used by Chiplet enterprise, which can be continuously integrated into various final applications, thus expanding its market.
Many people believe that Chiplet is an opportunity for our country to overtake in the corner of the chip field when the chip technology is "stuck" abroad. But don't forget that in actual driving, overtaking on a corner is something to avoid, and speeding up to overtake on a straight line is the correct behavior.
The accumulation of the chip industry can not be completed in a short time, nor can it be achieved by cutting corners and opportunism. And domestic manufacturers to take the "all self-research" route, still need to polish for a long time.