We present the FinFET process integration technology including improved sidewall transfer (SWT) process applicable to both fins and gates. Using this process, the uniform electrical characteristics of the ultra-small FinFETs of 15nm gate length and 10nm fin width have been demonstrated.A new process technique for the selective gate sidewall spacer formation (spacer formation only on the gate sidewall, no spacer on the fin sidewall) is also demonstrated for realizing low-resistance elevated source/drain (S/D) extension.
IntroductionFinFETs are promising candidates for sub-20nm scale CMOS devices because of their excellent scalability [1-8]. Primary challenges for FinFETs are the formation of uniform and narrow fins and the reduction of S/D series resistance. The sidewall transfer (SWT) process was proposed to form sub-lithographic fins and reduce the line edge roughness of the fins (Fig.1) [1]. However, the integration technology for the application of SWT process to both fin and gate formation has not been reported yet. On the other hand, it is necessary to deposit silicon selectively on the narrow fins for the reduction of the series resistance by increasing the fin width in S/D regions. However, this process has been very difficult because of the residue of gate sidewall spacer material left on the fin sidewall and the agglomeration of narrow fins.In this paper, we report the FinFET process integration technology including improved SWT process applied to both fins and gates. We also present the device characteristics of the ultra-small FinFET with 15nm gate length and 10nm fin width. A new process technique for the selective gate sidewall spacer formation is also proposed and the advantages of this new approach are experimentally demonstrated.
Dramatic advances are being made in dry processing technologies. Atomic scale precision below 10 nm is now possible with fine patterning technologies for high-volume manufacturing of semiconductor devices. The isotropic and anisotropic nature of both film deposition and etching is versatile for nanoscale fabrication of three-dimensional features, such as high-aspect-ratio (HAR) features. Here we conduct a systematic review of the literature over the last 40 years to evaluate the history and progress of dry processes with regard to fine pattern transfer, HAR feature formation, and multiple patterning as lithographic techniques. Finally, we address the major challenges shared across the plasma science and technology community.
We investigated the formation mechanism of sidewall striations in etched holes with high aspect ratios, with focus on the roles of energetic ions and fluorocarbon radicals. Striations were observed on the sidewalls of holes with high aspect ratios in stacked dielectric films, despite the smooth sidewall of the mask. Argon plasma treatment increased the degree of striation on the carbon mask, while striation was prevented with a cyclic process consisting of a fluorocarbon deposition step and an argon plasma treatment step. The blanket films were irradiated with oblique ion beams in order to simulate the surface reactions on the sidewalls of high aspect ratio holes. Argon ion beams oriented 85° from the surface normal formed severe striations on the blanket fluorocarbon film surface, despite the low roughness of the SiO2 film surface. A thicker fluorocarbon film was observed in regions with striations than deeper regions with smooth sidewalls. The striations formed on the fluorocarbon films at the sidewalls of high aspect ratio holes and transferred to the dielectric films laterally as the hole diameters increased. In addition, as etching proceeded, striations began to form at the deeper regions, depending on the aspect ratios.
Selective etching of LaAlSiOx to Si has been studied in inductively coupled BCl3 plasma using a hot cathode, and in capacitively coupled C4F8/Ar and C4F8/Ar/H2 plasmas. In BCl3 high-temperature etching, the etch selectivity of LaAlSiOx to Si was 0.05 at 210 °C. It was found that increasing the bias power using capacitively coupled C4F8/Ar plasma enhanced LaAlSiOx etching. Furthermore, the etch rate of LaAlSiOx increased and that of Si decreased upon the addition of H2. As a result, a high LaAlSiOx-to-Si selectivity of 6.7 was obtained when using C4F8/Ar/H2 plasma at an H2 flow rate ratio of 13%. We confirmed that H2 played different roles on the LaAlSiOx surface and on the Si surface. H2 suppressed Si etching by forming a high-C/F-ratio polymer on the Si surface, while it enhanced LaAlSiOx etching by breaking the stable metal–oxygen bonds of LaAlSiOx.
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