Part of the  

Solid State Technology

  and   

The Confab

  Network

About  |  Contact

Posts Tagged ‘MOL’

Applied Materials Fields Cobalt Solution for MOL

Thursday, June 7th, 2018

thumbnail

By Pete Singer, Editor-in-Chief

Applied Materials has introduced a set of processes that enable cobalt to be used instead of tungsten and copper for contacts and middle-of-line interconnects. Higher levels of metal, which typically have wider dimensions, will still employ copper as the material of choice, but at more advanced nodes, cobalt will likely be the best option as linewidths continue to shrink. Tungsten will still be used at the gate contact level.

To enable the use of cobalt, Applied has combined several materials engineering steps – pre-clean, PVD, ALD and CVD – on the Endura® platform. Moreover, Applied has defined an integrated cobalt suite that includes anneal on the Producer® platform, planarization on the Reflexion® LK Prime CMP platform and e-beam inspection on the PROVision™ platform. The process flow is shown in FIGURE 1.

While challenging to integrate, cobalt brings significant benefits to chips and chip making: lower resistance and variability at small dimensions; improved gapfill at very fine dimensions; and improved reliability. The move to cobalt, which is underway at Intel, GlobalFoundries and other semiconductor manufacturing companies, is the first major change in materials used as conductors since copper dual damascene replaced aluminum in 1997. “You don’t see inflections this large very often,” said Jonathan Bakke, global product manager, Metal Deposition Products at Applied Materials. “This is a complete metallization change.”

At IEDM last year, Intel said it would use cobalt for its 10nm logic process for several of the lower metal levels, including a cobalt fill at the trench contacts and cobalt M0 and M1 wiring levels. The result was much-improved resistivity– a 60 percent reduction in line resistance and a 1.5X reduction in contact resistance – and improved reliability.

Today, critical dimensions of contacts and interconnects are about 20 nm, plus or minus a few nanometers depending on the customer and how it’s defined. “As you get smaller – and you typically get about 30% smaller with each node — you’re running out of room for tungsten. Copper is also facing challenges in both gap fill and electromigration,” Bakke said.

As shown in FIGURE 2, cobalt has advantages over copper when dimensions shrink to about 10nm. They are presently at 30 nm. It’s not yet clear when that cross-over point will arrive, but decisions will be based on how much resistivity and electromigration improvement can be gained.

Applied Materials started developing cobalt-based processes in the mid-2000s, and released the Volta CVD Cobalt system in 2013, which was designed to encapsulate copper interconnects in cobalt, which helped improve gap fill and electromigration. “It was shortly thereafter that we started depositing thick CVD cobalt films for metalization. We quickly realized that there’s a lot of challenges with doing this kind of metalization using cobalt because of its unique properties,” Bakke said. Cobalt can be reflowed and recrystallized, which eliminates seams and leads to larger grain sizes, which reduces resistivity. “We started looking at things like interfaces, adhesion and microstructure of the cobalt to make sure that it was an efficient material and it had very low resistance and high yield for in-device manufacturers,” he added. One perfected, it took several years before the processes were fully qualified at customers. “This year is when we start to see proliferation and expect HDM manufacturing of real devices with cobalt,” Bakke said.


Extension Media websites place cookies on your device to give you the best user experience. By using our websites, you agree to placement of these cookies and to our Privacy Policy. Please click here to accept.