Characteristics of Inter Poly Dielectric (IPD) Prepared by Plasma Oxidation Treatment of LP-CVD SiO2 Film
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1108-A09-05
Characteristics of the Inter Poly Dielectric (IPD) Prepared by Plasma Oxidation Treatment of LP-CVD SiO2 Film J. H. Kim, Y. S. Kim, B. H. Jang, H. Namkoong, W. S. Lee, H. H. Lim, S. W. Nam, C. J. Kang and T. H. Ahn Process Development Team, Memory Division, Semiconductor Business, Samsung Electronics Co., LTD San#16 Banwol-Ri, Taean-Eup, Hwaseong-City, Gyeonggi-Do, Korea. ABSTRACT To improve the IPD reliability of NAND flash memory, plasma oxidation was introduced as the post-treatment process of ONO (Oxide/Nitride/Oxide) IPD. The LP-CVD SiO2 modified by plasma oxidation showed the excellent electrical properties. e.g., low leakage current, high breakdown voltage etc. By the analysis of Tof-SIMS and XRR, we could observe the several changes of physical characteristics such as the reduction of impurities (H, N etc.), the increase of oxide density, and the improvement of oxide surface roughness. We found out the appropriate treatment condition to be able to densify oxide layer without the addition of ONO Equivalent Oxide Thickness (EOT). The LP-CVD SiO2 prepared by plasma oxidation was used for the ONO IPD of 50nm NAND flash device and also compared with the conventional LP-CVD SiO2 in the aspect of the IPD reliability. INTRODUCTION The Oxide/Nitride/Oxide (ONO) structure has been generally used as IPD material of NAND flash memory. However, as the design rule of device shrinks, the reduction of operation voltage is required due to the increase of parasitic capacitance between the adjacent cells.[1] So, it is necessary that the IPD and tunnel oxide EOT scale down without the degradation of charge retention capability.[2,3] Recently, there are two approaches to reduce IPD EOT in order to increase the gate coupling ratio. The one method is to decrease the physical thickness of ONO IPD through improving the leakage current of ONO oxide.[4] The other method is to increase the dielectric constant of IPD materials.[5] But, appropriate high-k dielectrics should be stable, reliable and suitable for mass production. There are still some integration problems to replace ONO IPD with high-k IPD (OAO). In this paper, we investigated the physical and electrical characteristics of LP-CVD SiO2 modified by plasma oxidation and also compared the dielectric properties of ONO IPD according to with and without plasma oxidation. EXPERIMENT In this experiment, we made use of the LP-CVD SiO2 that was deposited by using SiH4 / N2O mixture gas as reaction species at 0.5Torr and 750 . Plasma oxidation was conducted in TEL Ltd.’s TrasSPA, which generated plasma by using microware and Slot Plane Antenna (SPA). To observe the characteristic change of LP-CVD SiO2 according to the plasma oxidation treatment, the oxide density and surface roughness were respectively investigated by the analysis of wet etch rate for 200:1 HF etchant and X-Ray Reflectivity (XRR). We also inspected the
amount of impurity species (H, N etc.) in oxide layer through Time of Flight – Secondary Ion Mass Spectrometry (Tof-SIMS) measurement. For monitoring the l
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