3 years ago

Probing the Dielectric Properties of Ultrathin Al/Al2O3/Al Trilayers Fabricated Using in Situ Sputtering and Atomic Layer Deposition

the Dielectric Properties of Ultrathin Al/Al2O3/Al Trilayers Fabricated Using in Situ Sputtering
and Atomic Layer Deposition
Jagaran Acharya, Judy Wu, Bo Liu, Jamie Wilt
Dielectric properties of ultrathin Al2O3 (1.1–4.4 nm) in metal–insulator–metal (M–I–M) Al/Al2O3/Al trilayers fabricated in situ using an integrated sputtering and atomic layer deposition (ALD) system were investigated. An M–I interfacial layer (IL) formed during the pre-ALD sample transfer even under high vacuum has a profound effect on the dielectric properties of the Al2O3 with a significantly reduced dielectric constant (εr) of 0.5–3.3 as compared to the bulk εr ∼ 9.2. Moreover, the observed soft-type electric breakdown suggests defects in both the M–I interface and the Al2O3 film. By controlling the pre-ALD exposure to reduce the IL to a negligible level, a high εr up to 8.9 was obtained on the ALD Al2O3 films with thicknesses from 3.3 to 4.4 nm, corresponding to an effective oxide thickness (EOT) of ∼1.4–1.9 nm, respectively, which are comparable to the EOTs found in high-K dielectrics like HfO2 at 3–4 nm in thickness and further suggest that the ultrathin ALD Al2O3 produced in optimal conditions may provide a low-cost alternative gate dielectric for CMOS. While εr decreases at a smaller Al2O3 thickness, the hard-type dielectric breakdown at 32 MV/cm and in situ scanning tunneling spectroscopy revealed band gap ∼2.63 eV comparable to that of an epitaxial Al2O3 film. This suggests that the IL is unlikely a dominant reason for the reduced εr at the Al2O3 thickness of 1.1–2.2 nm but rather a consequence of the electron tunneling as confirmed in the transport measurement. This result demonstrates the critical importance in controlling the IL to achieving high-performance ultrathin dielectric in MIM structures.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b16506

DOI: 10.1021/acsami.7b16506

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.