Recently, the SSMB-EUV light source technology proposed by Tsinghua University has attracted great public interest. One claim is that China can build accelerators to generate EUV light sources, and different frequencies of light sources can be used for various chip processes such as 28nm, 14nm, 7nm, and 5nm. Instead of relying on ASML's EUV lithography machines, the idea is to use "light source factories" to break the U.S. blockade with unexpected innovative thinking. This concept is "easy to understand," and it feels like there is hope for advanced domestic lithography machines.

The public's interest in the complex synchronization radiation light source, SSMB-EUV, is fundamentally driven by the desire to break the U.S. technological blockade and industrialize Tsinghua's research, thereby helping to produce high-performance domestic chips.

This article focuses on the industrial engineering perspective to introduce some relevant technical details of chip manufacturing and lithography. It also explains the scientific principles behind SSMB, EUV, and synchronization radiation. After understanding sufficient engineering technical details and scientific principles, we can properly evaluate interesting concepts like the "light source factory."

Key points of this article:

1. SSMB-EUV lithography machines have a technological background. China has already made actual R&D investments, and it is indeed a development direction for future lithography machines.

2. Analyzing the process of chip manufacturing using DUV and EUV lithography machines, the requirements for lithography machine performance in industrial production are beyond ordinary people's imagination.

3. What are the technical difficulties that SSMB-EUV lithography machines need to overcome? We should not assume that finding a good direction will make breaking through the lithography machine technology easy.

I. Knowledge about chip manufacturing industry 

To make a certain type of transistor, we introduce tetravalent silicon doped with a small amount of trivalent boron and pentavalent phosphorus to create a PN junction, and then add a metal oxide as a control gate. By arranging a large number of transistors densely on a wafer and connecting them according to a specific design, we can create a chip. The most critical step in chip manufacturing is wafer processing, which takes place in a FAB factory. On a highly pure silicon wafer, identical bare chips (dies) are produced one by one. Prior to that, the silicon wafer needs to be manufactured, and afterwards, the dies are cut, packaged, tested, and assembled with pins. The difficulty of these processes is relatively low.

First and foremost, it is important to understand that chip production in industrial applications is massive in scale to keep costs low. For example, the recent popular smartphone chip has an estimated quantity of 10 million units. Due to increased demand, this quantity has risen to 15-17 million units, and further increased to 20 million units.

How can tens of millions of chips be manufactured in a relatively short period of time? The key lies in the ability to produce a large number of identical dies on a single wafer. Taking a 12-inch wafer (referring to inches, there are also 8-inch and 6-inch ones) as an example, its diameter is approximately 300 millimeters, with an area of 70,659 square millimeters. Advanced chips can achieve a stunning transistor density of 100 million transistors per square millimeter. A single chip contains billions of transistors and performs complex functions such as 5G baseband and mobile SOC. Assuming the area of a die is 140 square millimeters, a wafer can accommodate around 500 dies.

The concept of "yield" is crucial in chip manufacturing. Simply put, if out of these 500 dies, 400 are found to be functional and qualified after processing in the FAB factory, the yield is 80%. Although the yield of advanced chip fabrication is sometimes not very high, it is also not too low, as that would render it commercially impractical. Assuming a conservative estimate of 50%, a wafer should still have over 200 functional dies.

The production capacity of a FAB factory is generally measured by how many thousands of wafers it can process per month, ranging from 10,000 to 100,000 wafers. If the capacity is 10,000 wafers per month, with 200 functional dies per wafer, it means there will be 2 million chips produced in a month, resulting in over 20 million chips in a year.

To be continued...