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Nanofluidic channels are useful for many biological and chemical applications, such as DNA sequencing, drug delivery, blood cell sorting and molecular sensing and detection. But in the effort to build a versatile lab-on-a-chip, it has been challenging to develop a wafer-scale nanochannel fabrication process compatible with CMOS technology.

At the upcoming International Electron Devices Meeting (IEDM), to be held December 9-11 in Washington, D.C., IBM researchers will report on a CMOS-compatible 200 mm wafer-scale sub-20nm nanochannel fabrication method that enables stretching, translocation and real-time fluorescence microscopy imaging of single DNA molecules.

Through the use of sacrificial XeF2 etching and various UV and e-beam lithography methods, sub-20-nm patterns in silicon were converted into macro-scale fluidic ports, micro-scale fluidic feed channels, and nano-scale channels for DNA imaging. Gradient nanopillars were located in the channels to stretch DNA molecules prior to imaging them. Fluid wasn’t pumped through the channels, but instead was transported by the force of gravity. The researchers say their techniques lead to highly manufacturable structures and can produce chips for a variety of biological applications.

A schematic of the nanochannel architecture. Grey represents silicon layers, while blue represents SiO2. The silicon layers serve as sacrificial material.

A schematic of the nanochannel architecture. Grey represents silicon layers, while blue represents SiO2. The silicon layers serve as sacrificial material.

The etching sequence of the silicon layers is shown: A) silicon-patterning with sub-20 nm features (note the inset SEM electron microscope photo); B) capping-oxide deposition followed by vent-hole patterning: and C) XeF2 gas-phase etching of silicon patterns embedded in SiO2.

The etching sequence of the silicon layers is shown: A) silicon-patterning with sub-20 nm features (note the inset SEM electron microscope photo); B) capping-oxide deposition followed by vent-hole patterning: and C) XeF2 gas-phase etching of silicon patterns embedded in SiO2.

SEM electron microscope photo of silicon nanochannels.

SEM electron microscope photo of silicon nanochannels.

Optical photos showing A,B) nanochannels with vent holes on 1-2 µm SiO2 capping layer, on top of silicon patterns; and C,D) following gas etching and removal of silicon patterns.

Optical photos showing A,B) nanochannels with vent holes on 1-2 µm SiO2 capping layer, on top of silicon patterns; and C,D) following gas etching and removal of silicon patterns.

Wang (14.1) Fig.12 (450x338)

 

An alternative to scaling is to expand vertically, by thinning, stacking and interconnecting ICs, commonly called 3D integration. Chip-to-chip Interconnections are are typically made with through-silicon vias (TSVs), but some TSVs also have major disadvantages, including relatively large dimensions, parasitic capacitances and thermal mismatch issues.

At the upcoming International Electron Devices Meeting (IEDM) in December, researchers from Taiwan’s National Nano Device Laboratories avoided the use of TSVs by fabricating a monolithic sub-50nm 3D chip, which integrates high-speed logic and nonvolatile and SRAM memories. They built it from ultrathin-body MOSFETs isolated by 300-nm-thick interlayer dielectric layers.

To build the device layers, the researchers deposited amorphous silicon and crystallized it with laser pulses. They then used a novel low-temperature chemical mechanical planarization (CMP) technique to thin and planarize the silicon, enabling the fabrication of ultrathin, ultraflat devices. The monolithic 3D architecture demonstrated high performance – 3-ps logic circuits, 1-T 500ns nonvolatile memories and 6T SRAMs with low noise and small footprints, making it potentially suitable for compact, energy-efficient mobile products.

The process flow used to fabricate the 3D IC without TSVs.

The process flow used to fabricate the 3D IC without TSVs.

A TEM electron microscope view of the 3D chip.

A TEM electron microscope view of the 3D chip.

 

It’s apparent that the world’s appetite for electronics has never been greater. That has increasingly taken the form of mobile electronics, including smartphones, tablets and tablets and the new “phablets.” People want to watch movies and live sports on their phones. They want their mobile devices to be “situationally aware” and even capable of monitoring their health through sensors. That drives higher bandwidth (6G is on the drawing board), faster data rates and a demand for reduced power consumption to conserve battery life. At the same time, “big data” and the internet of things (IoT) are here, which drives the demand for server networks and high performance semiconductors, as well as integrated sensors and inventive gadgets such as flexible displays and human biosensor networks.

All of this is pushing the semiconductor manufacturing industry and related industry (MEMS, displays, packaging and integration, batteries, etc.) in new directions. The tradeoffs that chipmakers must manager between power, performance, area and cost/complexity (PPAC) are now driven not by PCs, but by mobile devices.

In a keynote address at Semicon West 2013, Ajit Monacha, CEO of Global Foundries, expanded on his Foundry 2.0 concept, talking about how the requirements of mobile devices were, in fact, changing the entire semiconductor industry. He noted that the mobile business is forecast to be double the size of the PC market in 2016. The mobile business drives many new requirements, said Manocha, including power, performance and features, higher data rates, high resolution multicore processors and thinner form factors.

Manocha presented the audience with what he sees as today’s Big Five Challenges: cost, device architectures, lithography and EUV, packaging and the 450mm wafer transition. I don’t recall when cost wasn’t an issue, but an audience poll revealed that most people believe economic challenges will be the main factor limiting industry growth, not technical challenges. I agree, but I’m also thinking new applications will emerge particularly in the health field that could push the industry in yet another new direction.

Peter Singer, Editor-in-Chief