We have developed a high-quality gate oxide on Si 0.6 Ge 0.4 with a 30 Å Si top layer. The good oxide integrity comparable to conventional thermal oxide is demonstrated by the low interface trap density of 6.2 ϫ 10 10 eV Ϫ1 cm Ϫ2 , low oxide charge of 5.8 ϫ 10 10 cm Ϫ2 , small leakage current at 3.3 V of 4.2 ϫ 10 Ϫ8 A/cm 2 , high breakdown field of 13.8 MV/cm, good charge-to-breakdown of 5.2 C/cm 2 , and small stress-induced leakage current. This good oxide integrity is directly related to our previously developed SiGe formed by solid phase epitaxy at high temperatures that is stable during thermal oxidation. This simple process is fully compatible with existing very large scale integration technology. Figure 5. SILC effect of 50 Å thermal oxide grown on 30 Å Si/350 Å Si 0.6 Ge 0.4 measured under Ϫ5 V for 10,000 s.Figure 6. AFM surface morphology (a) before and (b) after 50 Å thermally oxide grown on 30 Å Si/350 Å Si 0.6 Ge 0.4 .
We have characterized the radio frequency ͑rf͒ noise in high-k Al 2 O 3 and AlTiO x gate dielectrics, which have respective effective oxide thickness ͑EOT͒ of 17.2 and 12.5 Å. The measured noise figure in gate dielectric is material dependent and sensitive to dielectric defect after stress. Although the high-k AlTiO x gate dielectric has lower EOT, it has a higher noise figure than others. From the simulation in our proposed equivalent circuit model, the dominant noise is thermal noise and the reason for increasing noise figure after stress is due to additional parallel resistance by trap-assisted tunneling.One important direction of next generation metal-oxide semiconductor field effect transistors ͑MOSFETs͒ is the replacement of thermal oxide with high-k dielectrics. However, the scaling of complementary metal oxide semiconductors ͑CMOS͒ has resulted in a strong improvement in the radio frequency ͑rf͒ characteristics that causes Si-based CMOS devices currently to be used in rf front-end integrated circuits ͑ICs͒ for wireless communication applications. Unfortunately, in spite of the fast progress and good achievement in high-k gate dielectric, 1-4 there is no rf performance of high-k gate dielectric reported so far. Among various rf performance characteristics, rf noise is one of the important factors for Si MOSFETs because noise is the key characteristic for some rf circuits, such as low-noise amplifiers in rf receivers. 5,6 In addition to channel thermal noise, it is suspected that the noise originating from the large gate leakage current in either conventional SiO 2 or high-k gate dielectric may be a serious concern in the noise performance of MOSFETs. In this paper, we have characterized the rf performances of high-k Al 2 O 3 and AlTiO x capacitors and compared with thermal SiO 2 . The measured noise figure is dependent on material and very sensitive to the existing dielectric defects and stress-induced defects. From analysis using an equivalent circuit model, the noise source is thermal noise and the stress effect generates additional shunt resistance in parallel with capacitor that increases the thermal noise. Therefore, achieving good rf noise characteristics is another important consideration for choosing suitable high-k dielectric materials. ExperimentalHigh-k Al 2 O 3 and AlTiO x capacitors with coplanar transmission lines 7,8 fabricated on Si substrates are used for rf noise characterization. First, the n ϩ Si bottom transmission line is formed. Then high-k Al 2 O 3 or AlTiO x is formed by depositing Al or Ti/Al on HF-vapor passivated Si 9 followed by oxidation and annealing. A more detailed fabrication process of high-k Al 2 O 3 dielectric can be found elsewhere. 4 It is found in our previous study that the self-limiting oxidation mechanism is one of the important merits of Al 2 O 3 for either reproducibility or uniformity control. The advantages of adding Ti-O into Al 2 O 3 is to reduce effective oxide thickness ͑EOT͒ by adding the very high-k TiO x and at the same time preserve the slow oxygen dif...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.