Micron has announced unit shipments for its first DRAM manufactured on the 1α (1 alpha) node. This new memory, which the company is building before it has deployed EUV for manufacturing, will offer a larger improvement in bit density and a modest decrease in power consumption.
Initially, 1α will be used for manufacturing DDR4 and LPDDR4. Over time, Micron expects to expand the use of the node to other products. The company is claiming a bit density improvement of 40 percent over products built using the 1z manufacturing node. Power consumption is said to have improved by “up to” 20 percent.
“The strong improvement on 1-alpha bit density is driven by combination of process technology improvement, as well as very strong improvement in array efficiency due to design improvements,” said Thy Tran, Micron vice president of DRAM process integration. “Array efficiency alone gave us approximately 10 percent of the design improvement.”
We normally talk about manufacturing nodes in numerical terms — 3nm, 5nm, 7nm, 20nm, and so on. But these conventions refer to the way TSMC, Samsung, and Intel number their various nodes. Because all process node names are arbitrary — there is no universal group or guide that sets a single metric for the industry — different companies can use different standards. Memory manufacturers opted to move away from straight numerical numbering after 20nm planar silicon and opted for metrics like 1X, 1Y, and 1Z. According to Blocks and Files, 1X was roughly equivalent to 17-19nm manufacturing, 1Y was 14-16nm, and 1Z was 11-13nm. The same site notes that 1Z manufacturing was 15 percent of Micron’s DRAM bit production in Q3 2020.
What’s impressive is that Micron is moving to manufacture these new chips without the use of EUV. Extreme Ultraviolet Lithography is a manufacturing method that uses much smaller wavelengths of ultraviolet light to etch wafers, as opposed to the 193nm ArF lasers that power DUV (Deep Ultraviolet Lithography). EUV has been making its way into the industry bit by bit for some years now, but it’s still not being used much for DRAM manufacturing. Samsung uses EUV for its own 1Z manufacturing, but it dedicates less of its own production in percentage terms to 1Z than Micron does (6 percent versus 15 percent). Micron, however, is the smaller company in terms of market share.
In the past, Micron has implied that it might wait until 1β or even 1γ (1 beta or 1 gamma, respectively) to introduce EUV. The company has previously said it would move to EUV only when it was beneficial, and it’s released slides implying the shift date could be 2023 or later.
According to Tran, Micron incorporated new materials, tools, and “novel techniques” to improve its multi-patterned alignment. The downside of not using EUV is that this increases the need for multi-patterning. Multi-patterning allows 193nm lithography to target smaller feature sizes than would otherwise be possible, even via immersion lithography, but it also comes with tradeoffs in terms of image quality.
Micron may be slow-walking its EUV transition due to the limited number of EUV tools being manufactured every year, or because its found alternate ways of improving yields and performance. In the long run, every leading-edge manufacturer is going to move to EUV, but Micron might not make the shift before 2022 or 2023 based on its current roadmaps.
To give you an idea just how long the road to EUV has been, here’s an EETimes piece noting that Micron has joined “a private industry group led by Intel, Advanced Micro Devices and Motorola… to develop next-generation lithography technology that will replace optical exposure tools in wafer fabs.”
Publication date: May 11, 2000.
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