Ultra-Low energy Ion Implantation of Si into HfO 2 -based layers for Non Volatile Memory Applications
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1160-H01-03
Ultra-Low Energy Ion Implantation of Si into HfO2-based layers for Non Volatile Memory Applications P. E. Coulon1, K. Chan Shin Yu1*, S. Schamm1, G. Ben Assayag1, B. Pecassou1, A. Slaoui2, S. Bhabani2, M. Carrada2, S. Lhostis3 and C. Bonafos1 1 Groupe Nanomat – CEMES-CNRS – 29 rue J. Marvig - BP 94347 - 31055 Toulouse Cedex 4 – Université de Toulouse 2 InESS – CNRS, 23 rue du Loess, 67037 Strasbourg, France 3 ST Microelectronics, 850 rue Jean Monnet, 38926 Crolles * now at LAAS-CNRS, Université de Toulouse
ABSTRACT The fabrication of NCs is carried out using an innovative method, ultra-low energy (≤5 keV) ion implantation (ULE-II) into thin (6-9 nm) HfO2–based layers in order to form after subsequent annealing a controlled 2D array of Si NCs. The implantation of Si into HfO2 leads to the formation of SiO2–rich regions at the projected range due to the oxidation of the implanted Si atoms. This anomalous oxidation that takes place at room temperature is mainly due to humidity penetration in damaged layers. Different solutions are investigated here in order to avoid this oxidation process and stabilize the Si-phase. Finally, unexpected structures as HfO2 NCs embedded with SiO2 matrix are obtained and show interesting memory characteristics. Interestingly, a large memory window of 1.18 V has been achieved at relatively low sweeping voltage of ± 6 V for these samples, indicating their utility for low operating voltage memory device. INTRODUCTION Nanocrystal memory (NCM) devices are competitive candidates for extending further the scalability of Flash-type memories [1-3]. Various process/materials alternatives have been suggested recently to establish a proven NCM technology in the timeframe required by the industry roadmap. In this direction, the fabrication of NCs into high-k dielectric matrices instead of SiO2 materials has retained particular attention for achieving NCMs with low programming voltages and improved data retention. Indeed, a dielectric with a higher dielectric constant allows, in principle, to use a thicker tunnel oxide reducing leakage currents and, because of the smaller conduction band offset between the high-k film and the silicon substrate, to achieve the goal of a low voltage non-volatile memory device. Among the different high-k materials under investigation, HfO2 and their alloys are probably the most widely studied and are considered as very promising candidates for the integration in ultra-scaled commercial devices. Most of the data reported in literature on the synthesis of metallic and semiconducting nanocrystals for memory device application focus on the possibility to integrate the nanocrystals in these materials. Very few data are available on the synthesis of Si nanocrystals in a high-k matrix, especially in Hafnium oxide alloys. Superior programming efficiency and data retention characteristics have been obtained for systems described by Si nanocrystals deposited on HfO2 films by LPCVD with SiH4 at 600°C followed by in-situ HfO2 deposition of the control dielectric [4-5]. P
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