Remote Plasma Nitridation of In-Situ Steam Generated (ISSG) Oxide
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REMOTE PLASMA NITRIDATION OF In-Situ STEAM GENERATED (ISSG) OXIDE
H.N. Al-Shareef, A. Karamcheti, T.Y. Luo, G.A. Brown,V.H.C. Watt, M.D. Jackson, and H.R. Huff, International Sematech, Inc., Austin, TX 78741 R. Jallepally, D. Noble, and N. Tam, and G. Miner, Applied Materials, Santa Clara, CA 95050
ABSTRACT
Electrical performance of in-situ steam generated (ISSG) oxide nitrided using remote plasma nitridation (RPN) has been evaluated. An equivalent oxide thickness (EOT) of 1.6 nm with gate leakage current around 5x10-3 A/cm2 (at –1.5V) has been achieved. The leakage current of remote plasma nitrided ISSG oxide is lower than that of ISSG only, where more than one order of magnitude leakage current reduction (at the same EOT) has been achieved for some RPN conditions. Moreover, it is observed that the extent to which the RPN process conditions modify device parameters such as EOT, flatband voltage (VFB), and time-to-breakdown (tbd) increases with decreasing ISSG thickness. The thinner ISSG oxides appear to be more susceptible to plasma damage and accumulation of positively charged nitrogen atoms at the oxide/Si interface. Therefore, RPN processes that use lower temperature and shorter time are preferred for very thin oxides. The nitrogen content and profile in the samples evaluated using SIMS analysis, indicate that RPN offers higher nitrogen content and better nitrogen profile compared to conventional nitrogen incorporation methods such as NO annealing [1].
INTRODUCTION Extensive efforts are currently underway to find alternative gate dielectrics for conventional silicon dioxide. The scaling of SiO2 thickness will most likely continue down to the 150 nm technology node. However, the required SiO2 thickness for the 130 nm node is projected to be 1.4-1.9 nm according to the International Technology Roadmap for Semiconductors (ITRS)[2]. At these thickness levels SiO2 may not work properly due to excessive tunneling leakage currents and boron penetration from the p+ polysilicon electrodes. It therefore appears that alternative gate dielectrics will be needed for the 130 nm node, and several have already been investigated. These include a silicon oxide/silicon nitride stack [3], remote plasma nitrided (RPN) silicon oxide [4,5], and jet vapor deposited (JVD) nitride [6]. In this work, we have evaluated remote plasma-nitrided (RPN) in-situ steam generated (ISSG) oxide as a gate dielectric for the 130 nm technology node. The choice of the RPN process has been driven by the apparent RPN process ability to introduce large amounts of [N] into the SiO2 film while carefully controlling the nitrogen depth profile [4]. However, care must be exercised as excessive amounts of [N] near the Si/SiO2 interface can lead to mobility degradation. EXPERIMENT MOS capacitor devices with oxide isolation were fabricated on high quality 200 mm EPI p/p+ (100) Si substrates. The wafers were cleaned in a 100:1 HF solution (DHF) prior to ISSG oxide
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growth. An AMAT Centura RTP system with in-situ steam generation capability was used to
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