Structural, Optical and Electrical Characteristics of Silicon Carbon Nitride
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SiO 2
( E -3.9) is currently the prevailing gate dielectric for Si-based metal-oxide-
semiconductor (MOS) devices due to its remarkable electronic properties that are unmatched by other materials. However, the continuous vertical scaling of the dielectric equivalent thickness in MOS-based devices to 3 nm and below may necessitate the use of thick, high-K dielectric materials such as Ta 2O5 ( E-25) and Si3N4 ( - -7.5). The deposition of Ta20 5 (or any other high-K oxides) and post-deposition annealing (to reduce defect density) is usually carried out in a strong oxidizing conditions which can lead to the formation of an appreciable thickness of Si0 2 under the Ta 2O5 layer [1]. This results in an increase in effective equivalent oxide thickness (therefore, decreased capacitance) and defeats the purpose of using a high-K dielectric in the first place. On the other hand, previous attempts to use non-oxide-based high-K gate dielectrics such as silicon nitride grown directly on Si have not been successful, primarily because of the poor interface quality and high density of bulk traps. Typical CVD nitride process involves the use of NH 3 in order to introduce nitrogen efficiently. However, the incorporation of hydrogen in the silicon nitride layer is inevitable in this process, thus producing the unwanted effect of electron trapping [2]. Recently, the jet vapor deposition (JVD) technique has been found to produce gatequality silicon nitride films [3]. The estimated hydrogen concentrations in JVD films are 219 Mat. Res. Soc. Symp. Proc. Vol. 592 ©2000 Materials Research Society
significantly lower in comparison to those in typical CVD nitrides, which may be partly responsible for the improved electrical properties of the JVD nitride [3]. In this context, it is thought worthwhile to explore other non-oxide high-K dielectrics, preferably those that can be prepared by a hydrogen-free process. In this paper, we examine the ternary SiCxNy films deposited by ion-beam sputtering process, which is a convenient and robust technique that has been employed in the industry. The crystalline SiCxNY material is a novel superhard and wide band gap semiconductor [4-6]. Since SiCXNY is fairly new to the electronic and optoelectronic industry, the research and development work in this system is still in its infant stage [7]. In this report, ultraviolet-visible (UV-Vis) spectrometry and spectroscopic ellipsometry were employed to study the optical characteristics of the amorphous SiCxN, films. The I-V curves with and without light illumination of the MNS are also reported.
EXPERIMENT Figure 1 depicts the schematic of the ion beam sputtering system equipped with a separate atomic nitrogen source and a boron nitride resistive heater for independent substrate temperature control. The target material consists of a 1-inch hot-pressed SiC sheet placed on top of 4-inch Si wafer or graphite plate. A 3-cm Kaufman-type ion source was used to sputter the SiC target with N 2' ions at a nitrogen flow rate of 2 sccm. The ion beam current was held con
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