Wednesday, December 9, 2020

ALD to take over more and more as CVD and spin-on processes no longer are viable for 3D NAND

EE Times reports [LINK] about the recently announced Striker FE from Lam Research, an enhanced atomic layer deposition (ALD) platform addresses semiconductor manufacturing challenges for 3D NAND as well as DRAM. It employs advanced dielectric gapfill technology the company has dubbed “ICEFill” for filling 3D NAND and DRAM structures — as well as logic devices — in emerging nodes. 

Lam Research’s recently announced Striker FE enhanced atomic layer deposition (ALD) platform addresses semiconductor manufacturing challenges for 3D NAND as well as DRAM
Lam Research Striker FE - Key applications (LINK):
  • Gapfill dielectrics
  • Conformal liners
  • Patterning spacers and masks
  • Hermetic encapsulation
  • Etch stop layers
  • Optical films
The need for gapfill methods isn’t new, said Aaron Fellis, vice president and general manager of Dielectric ALD products, but the traditional ones no longer meet today’s needs, especially as 3D NAND is stacked higher. “They’re so tall and they have a number of different features that get etched through them to enable the integration of different steps,” he said. “Ultimately, they need to get filled back up with a dielectric material, most commonly silicon oxide.”

Legacy techniques, such as chemical vapor deposition, diffusion/furnace, and spin-on processes that are normally used as gapfill for semiconductor manufacturing are no longer viable for 3D NAND, Fellis said, due to trade-offs between quality, shrinkage, and gapfill voids. “They tend to shrink and distort the actual structure that the customer is building and designing.”

According to Risto Puhakka, president of VLSIresearch, Lam Research is a dominant player for ALD technology, and the demands of its technology reflect those placed on memory. It’s all about increasing density for applications, such as artificial intelligence, that require more bits while keeping costs the same, and that includes gapfill capabilities as the memories such as 3D NAND are stacked higher, he said. “The stacking becomes more and more challenging from the manufacturing perspective, but the chip makers themselves get it a little bit little anxious about how much they have to spend.” Sticking with a known material such as silicon oxide adds some predictability because it’s well understood

But just as 3D NAND stacking will eventually hit limits, so will the gapfill techniques and ALD technology, added Puhakka. “It has its own roadmap and limitations.”

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