Monday, August 4, 2014

Edwards on the need for Vacuum Technologies for ALD and 3D Device Processing

A very interesting blog post on the need for Vacuum Technologies for ALD and 3D Device Processing. Thanks Toni Koblenz for the tip on this one!

Future ICs will use more 3D device structures such as finFETs and gate-all-around (GAA) transistors, and so vacuum deposition processes are needed that can produce conformal films on the tops, bottoms, and side-walls of features. New materials are needed as the commercial IC fabrication industry pushes the limits of device miniaturization, while industry consolidation drives the remaining players to use proprietary materials.

Even lithography needs more vacuum processing when double-, triple-, and quadruple-patterning schemes need sidewall spacer and sacrificial hard-mask depositions. Materials deposited in these process steps may not remain on the final chip, but they are nonetheless essential in sub-22nm node process flows.

All of this leads to a need for an unprecedented number of new chemical precursors for vacuum depositions to be simultaneously ramped into high-volume manufacturing (HVM) in fabs worldwide. “If you’re trying to deposit a metal nitride, for example, four different fabs may use four different precursors sets,” explained Kate Wilson, global applications director, Edwards Vacuum Ltd. in an exclusive interview with the Show Daily.
Pulsed precursors in a vacuum system.

For some ALD process there are conflicting challenges in configuring a vacuum solution, such as one using a MOCVD precursors and a chloride precursor. For the MOCVD molecule the general approach would be to lower temperatures to prevent decomposition, while for the chloride molecule it would be best to use high temperatures to prevent condensation. Some molecules polymerize more at higher temperatures, while condensing more at lower temperatures, so a strategic trade-off must be made.

“Chlorine-based precursors, for example, are quite challenging to abate without creating toxic by-products,” explained Wilson. “Most of the things we abate become a powder, so we have to deal with that powder to ensure that we don’t clog the system.”

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