July 22, 2011 -- ASM International's Bob Hollands, director of technical marketing, thermal products, discussed the challenges of making FinFET structures using both epitaxial and high-k/metal gate (HKMG) atomic layer deposition (ALD) processes, speaking with Solid State Technology during SEMICON West 2011. "With epi, the challenges on the fin itself will be getting conformal coverage," explained Hollands. Epitaxial deposition is more of a challenge with the vertical structure, "since you're depositing on the sidewall, its majority orientation is (110), which requires reengineering of the epi process to make it successful in terms of the performance requirements." To accommodate the overall reduction in thermal budget, the company is working on new precursors that operate at lower temperatures to control the very thin layers that are needed for these structures.
Hollands explained that as the industry moves to 15nm and beyond, there will be other issues with the HK gate stack. As the layers require higher-k materials, the material will get thinner noted Hollands. "We may still be using a basic hafnium oxide material -- but adding a higher-k cap layer that would be very thin -- on the order of several Angstroms, instead of the 15-20Ǻ (that is used now)." The requirements on conformality will be even more critical and will drive ALD reqs, he said.
The bigger transition with the FinFET structure will be the metal gates; the work function depends on the material's thickness. "It's critical to get conformality around the entire fin using ALD," explained Hollands. "If you don't get the same thickness around the fin, and fin to fin, across the device, then you will have variations in performance."
ASM International N.V. (NASDAQ:ASMI and Euronext Exchange in Amsterdam: ASM) design and manufacture equipment and materials used to produce semiconductor devices. For more information, visit ASMI's website at www.asm.com.
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