Samsung Shipping First GAAFET Silicon; 3nm and 4nm Yields Are Improving - Report

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Currently, only two foundries offer their customers 3 nm and 4 nm-class process technologies: TSMC and Samsung Foundry. But business media sometimes blames Samsung Foundry for mediocre yields on leading-edge nodes, which cannot be verified. But a set of recent reports claim that Samsung is now at a point where they are shipping their first GAAFET-based 3 nm chips to commercial customers, and that the yields of Samsung's 3 nm and 4 nm-class nodes are in decent shape overall.

www.anandtech.com/, Jul. 18, 2023 – 

Samsung Foundry's 4 nm-class process technology yield is now higher than 75%. In contrast, yields of chips on SF3E (3nm-class, gate-all-around early) now exceeds 60%, according to estimates in a report from Hi Investment & Securities, a member of DGB Financial Group, reports Kmib.co.kr. The same report claims that TSMC's yields at its N4 node approach 80%, but again, this is an estimate by a researcher.

In general, information about yields at foundries cannot be verified since contract fabs almost never publicly talk about yields. They sometimes disclose defect density publicly compared to previous nodes, but this is hardly the case for Samsung Foundry's SF4E, SF4, SF4P, and SF3E.

Officially, Samsung Foundry only says that its SF3E process technology is in high-volume production with stable yields (possibly to address a media report from late last year which said that SF's yields on SF3E were unstable), and the development of refined SF3 is ongoing.

Meanwhile, TechInsights found one of the first chips made on Samsung's SF3E process. This is the Whatsminer M56S++ which is apparently a cryptocurrency mining chip from MicroBT, a Chinese developer. Mining chips are relatively simplistic devices with loads of regular structures and few SRAM bit cells. Such chips are easy to build and make for great pipe cleaners for the latest process technologies, so it is not surprising that Samsung Foundry is making them rather than large ASICs on its SF3E. Though as a reminder, smaller chips have intrinsically higher yield rates than large ASICs (lower odds of any given chip covering a flawed spot on a wafer), so the commercial viability of the Whatsminer M56S++ does not mean that a relatively large smartphone or PC SoC would hit the same yields or be equally as viable at this time.

There is an indirect confirmation that yields of Samsung's 5 nm and 7 nm-class fabrication processes are improving. The utilization rate of Samsung Foundry's for 5 nm-capable lines increased to 80%, and the combined utilization rate of 5nm and 7 nm-capable fabs climbed to 90% recently, up from 60% in 2022, according to a DigiTimes story that cites ET News. Again, the information comes from an unofficial source.

Typically, fabless chip designers are not inclined to use nodes with high defect densities, so if the utilization rate of 5 nm-class (Samsung's SF4 derived from SF5) gets higher, this may indicate that they are now more intensively used by Samsung's customers. Alternatively, this may be a sign that Samsung Foundry has customers desperate enough to increase production despite low yields due to high demand. Yet, given the current market conditions, this may not be the case.

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