On-chip sub-terahertz surface plasmon polariton transmission lines in CMOS.

Yuan Liang,Tie Jun Cui,Hao Chi Zhang,Hao Yu,Chang Yang

doi:10.1038/srep14853

Yuan Liang, Tie Jun Cui + Show 3 more

Open Access

https://doi.org/10.1038/srep14853

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Abstract

A low-loss and low-crosstalk surface-wave transmission line (T-line) is demonstrated at sub-THz in CMOS. By introducing periodical sub-wavelength structures onto the metal transmission line, surface plasmon polaritons (SPP) are excited and propagate signals via a strongly localized surface wave. Two coupled SPP T-lines and two quasi-TEM T-lines are both fabricated on-chip, each with a separation distance of 2.4 μm using standard 65 nm CMOS technology. Measurement results show that the SPP T-lines achieve wideband reflection coefficient lower than −14 dB and crosstalk ratio better than −24 dB, which is 19 dB lower on average than the traditional T-lines from 220 GHz to 325 GHz. The demonstrated compact and wideband SPP T-lines have shown great potential for future realization of highly dense on-chip sub-THz communications in CMOS.

Highlights

A low-loss and low-crosstalk surface-wave transmission line (T-line) is demonstrated at sub-THz in CMOS
In what follows, for ease of impedance matching at the injection interface as well, we investigate the surface plasmon polariton (SPP) property by designing a compact SPP T-line structure operating at frequencies that are lower than asymptote frequency
The crosstalk in multi-channel series link is quantized for 10-mm interconnect in 0.13 μ m CMOS41, in which both the adjacent crosstalk-to-signal ratio (ACSR) and distant crosstalk-to-signal ratio

Summary

Result

By properly structuring the top metal, the loss of SPP T-line can be minimized across wideband, which cannot be achieved by a bare T-line in CMOS at sub-THz. Further observation of Fig. 4b implies a vanishing of superiority on transmission by SPP T-line regardless of trace length, revealing another feature of surface mode adapted to the periodical sub-wavelength grooves: localization decreases for frequencies lower than 200 GHz (ω ω p), where β → k0 due to their large free electron density. The surface mode is obviously excited and more restricted within the grooves, and the resulting E-field is tightly confined as well In this scenario, the propagation constant is much larger than ω /c, leading to an increase of wave vector with the dispersion curve bending more strongly away from the light line. During the circuit design phase this spacing is not necessary to be such narrow

Discussion

Findings

Methods