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Fluorine implantation for effective work function control in p-type metal-oxide-semiconductor high-k metal gate stacks

: Fet, A.; Häublein, V.; Bauer, A.J.; Ryssel, H.; Frey, L.


Journal of vacuum science and technology B. Microelectronics and nanometer structures 29 (2011), No.1, Art. 01A905, 5 pp.
ISSN: 0734-211X
ISSN: 1071-1023
ISSN: 2166-2746
ISSN: 2166-2754
Workshop on Dielectrics in Microelectronics (WoDiM) <16, 2010, Bratislava>
Journal Article, Conference Paper
Fraunhofer IISB ()

The instability of the p -type metal effective work function of high- k /metal gate metal-oxide-semiconductor stacks after high temperature treatment results in device threshold voltage shifts and is one of the big challenges for the gate-first integration of high- k dielectrics in the future complementary metal-oxide semiconductor process flow. The exact cause of this instability is a subject of intense debate. In this article, it is shown that by implanting the gate stack with a fluorine dose of 1015 cm-2, it is possible to achieve an appropriate silicon valence band-edge effective work function of 5.1 eV for p -type metal-oxide-semiconductor devices. It is also shown that the fluorine doping can be accomplished not only with F+, but also with BF 2+ ions. The influence of the implantation energy on the obtained effective work function is demonstrated and discussed. The origin of the induced shift is also discussed. Leakage current measurements show that the leakage pr operties of high- k stacks are not worsened by F implantation, while the implantation of BF2 slightly affects the leakage currents.