Third-Generation Precursors Enable Advancement
Applied Materials announced on July 12 that it has integrated chemical-vapor deposition (CVD) and UV-cure steps to reduce the dielectric constant (k) of multi-layer interconnects on 22nm node chips. Using a new organometallic precursor for porous CVD, the “Black Diamond” brand name has been extended to the ultra-low k (ULK) level as low as 2.2 for the final film. However, like all ULK films, the as-deposited film requires an ultra-violet (UV) cure to stabilize the pores, so the company has also upgraded the “Nanocure” chamber that also runs on the “Producer” hardware platform.
Increasing the porosity of the dielectric helps reduce its k value, but also renders the film susceptible to downstream plasma damage or physical damage during packaging steps.
Applied Materials says that the generation three precursor uses a patented molecule where the pore is grafted to the organometallic backbone. This seems to be a version of the molecular pore stacking (MPS) CVD processes that have been touted by Fujitsu and NEC at technical conferences in recent years. Using MPS, the maximum porosity is built-in from the “bottom-up,” instead of having to control porosity from the “top-down” like Black Diamond 2 low-k films using multiple precursors and chamber parameters. The company is attractively pricing the purportedly proprietary precursor. “The chemical cost per wafer will be equal or less than Black Diamond 2,” said Russ Perry, global product manager for dielectric depositions for Applied Materials, in an interview with the SEMICON Show Daily.
The upgrade to the UV-cure chamber includes newly designed optical and chamber components plus real-time UV intensity monitoring that improves yields. AMAT claims that 22nm node processing will require post-processing steps at the interface layers within the on-chip multilevel interconnect stack, as well as to the ULK material to improve mechanical properties. The result is a dramatic increase in the number of UV-cure steps needed in a logic manufacturing process flow, up to supposedly greater than 49 UV cure steps at 22/20nm.