With all the rapid progress going on in research and commercialization of flexible and transparent electronics, the obvious question is not if, but when it will be possible to build a flexible and transparent truly high performance computer.
Already, plastic-based organic electronics (whose inherent mobility is extremely low compared to traditional silicon); transferred silicon layers from expensive silicon-on-insulator or unconventional silicon (111); back side grinding of regular bulk wafers (abrasive and expensive as the process wastes a bulk portion of the whole wafer); and expensive high energy implantation and stress based exfoliation (possible damage can happen for abrasive nature of the process and does not provide transparency) have shown interesting application opportunities.
Todays computers use high-k/metal gate based planar and non-planar transistors for high performance computations (at a 3.1 GHz or higher switching frequency) and multi-tasking operations (a cell phone runs at a speed of 1.8 GHz). Our digital life and the devices supporting it are changing at a high pace, but still, all these devices are built on mono-crystalline silicon wafers, which is the most popular choice because of its controllable semiconducting characteristics, favorable mechanical properties and affordability.
A research team at the Integrated Nanotechnology Lab at King Abdullah University of Science and Technology (KAUST), led by Muhammad Mustafa Hussain, an Assistant Professor of Electrical Engineering, has now shown, for the first time, a generic batch fabrication process to obtain mechanically flexible and transparent mono-crystalline silicon (100) from bulk wafers.
Reporting their results in two recent papers in Applied Physics Letters (“Structural and electrical characteristics of high-k/metal gate metal oxide semiconductor capacitors fabricated on flexible, semi-transparent silicon (100) fabric”) and in physica status solidi (“Flexible semi-transparent silicon (100) fabric with high-k/metal gate devices”), the team has demonstrated a pragmatic pathway for a truly high performance computation systems on flexible and transparent platform.
(a) Scanning electron microscopic (SEM) images of top, crosssection, and bottom view of a released sample. The top view shows the capacitors geometries (blue), the bottom shows ALD-spacers regularity, and the cross-section shows thickness uniformity; (b) released sample wrapped around a finger, displaying great flexibility; (c) minimum bending radius before fracture; (d) semi-transparent sample covering portion of a LED screen with KAUST logo. (Reprinted with permission from American Institute of Physics)
“With the fabrication technique that we developed, we build devices following state-of-the-art CMOS compatible processes and then etch trenches through the silicons unused real estate in between devices followed by a vertical sidewall formation to protect the devices and the underlying silicon,” Hussain explains the fabrication process to Nanowerk. “We then perform an isotropic silicon etching to remove the silicon from the inner portion of the substrate, forming caves which – when interconnecting with others – eventually release the top portion of the substrate so that the devices can be peeled off.”
He points out that, unlike in MEMS processes where a sacrificial layer is removed to free the top layer which we term as silicon fabric, in their case no sacrificial layer is needed but rather they use a hard top mask to shield the top surface (where the devices are located) and a spacer-like protection technique to protect the holes integrity from the chemical effect of the subsequent releasing isotropic-etching step.
“The released silicon wafer – we have demonstrated up to 4 diameter silicon wafer – is mechanically flexible and optically transparent,” says Hussain. “This process allows to maintain the same performance level required for high performance computation and it does not compromise ultra-high resolution lithographic demand for billions of transistor integration; multi-level interconnects for complex circuitry fabrication; and affordability.”
In addition, the researchers have also tested that the remaining substrate is reusable after a chemical mechanical polishing (CMP).
“Although it is true that organic electronics can be fabricated using low-cost ‘garage fabrication’, the per-bit information/area cost is much lower in silicon chips,” says Hussain. “Therefore, our work shows a pragmatic path to building such advanced devices on a flexible as well as transparent platform of silicon – the most common and friendly name in electronics.”
By Michael Berger. Copyright © Nanowerk
A new generation of programmable shape-memory micro-optics
Posted: Mar 4th, 2013
Posted: Mar 1st, 2013
Designing nanogenerators for large-scale energy harvesting
Posted: Feb 28th, 2013
Graphene helps to unravel the mystery of 1/f noise in electronic devices
Posted: Feb 27th, 2013
Nanopaper transistors for the coming age of flexible and transparent electronics
Posted: Feb 21st, 2013
Replacing antibiotics with graphene-based photothermal agents
Posted: Feb 19th, 2013
Nanotoxicity research needs to target the endocrine system
Posted: Feb 18th, 2013
Sculpting silicon structures in three dimensions down to single nanometers
Posted: Feb 15th, 2013
A carbon nanotube synapse with dynamic logic and learning
Posted: Feb 12th, 2013
Silicon LEDS are an alternative to toxic quantum dot LEDs
Posted: Feb 8th, 2013
Posted: Feb 7th, 2013
The EU code of conduct for nanosciences and nanotechnologies research
Posted: Feb 5th, 2013
Opening band gaps in graphene and silicene via CH-Pi interactions
Posted: Feb 1st, 2013
Printable photonic devices with resolution below 10 nanometers
Posted: Jan 29th, 2013
Nanotechnology sensors for the detection of trace explosives
Posted: Jan 28th, 2013
Quantitative visualization of nanoparticles in cells and tissues
Posted: Jan 25th, 2013
The state of nanoimprinted polymer organic solar cell technology
Posted: Jan 24th, 2013
Twisted carbon nanotube yarns with unique mechanical properties
Posted: Jan 22nd, 2013
Nanotechnology in the media
Posted: Jan 21st, 2013
Almost 250 nanomedicine products approved or in clinical study
Posted: Jan 17th, 2013
Concept nanocars – off to the races?
Posted: Jan 15th, 2013
Nanotechnology and the environment – transformation of nanomaterials
Posted: Jan 10th, 2013
Nanomaterial platform captures and releases circulating tumor cells
Posted: Jan 8th, 2013
Metal oxide based breath nanosensors for diagnosis of diabetes
Posted: Jan 7th, 2013
Read more Spotlights
The contents of this site are copyright ©2012 Nanowerk. All Rights Reserved