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Radio on paper

English title Radio on paper
Applicant Ionescu Mihai Adrian
Number 113780
Funding scheme Project funding
Research institution Laboratoire de microsystèmes 1 EPFL - STI - IMT - LMIS1
Institution of higher education EPF Lausanne - EPFL
Main discipline Microelectronics. Optoelectronics
Start/End 01.10.2006 - 30.09.2008
Approved amount 218'056.00
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Keywords (6)

Organic semiconductors; Organic Thin Film Transistors (OTFT); pentacene; shadow masking; flexible substrate; RFID

Lay Summary (English)

Lay summary
This project proposes an ambitious goal, the realization of RF circuits on flexible substrates as a key enabler for almost transparent electronic circuits for future ambient intelligence. Functional low cost transceivers on flexible substrates, able to communicate amounts of data within a range of a few meters would also have a strong impact on the everyday life and on the society, in general.

To achieve significant technical and scientific progress compared to the mentioned goal, thin film transistors (TFTs) based on organic semiconductors layers fabricated at low temperature will be developed and used to demonstrate basic blocks for RF transceivers. The scientific project is structured in two main phases:
?the first will identify, develop and study various organic transistordevice architectures on flexible substrates (including vertical devices) and compare them with devices build on standard silicon substrates, as basic cell for organic circuit device,

?the second phase will consist in building first functional RF circuitsworking at few of MHz for the “radio on paper” concept. The project is simply planned on a two-year basis and, in case of success, an extension of two years will be asked as a new proposal dealing with building more complex radio architectures. As useful outputs, physical compact models for field effect organic transistors will be developed and grouped in a design library that can be then used for circuit designers.

From the beginning, the project proposes a fabrication approach that is based on a low temperature processing (compatible with paper and plastic substrates that will be temporarily ported on silicon wafers) exploiting the most advanced existing stencil and shadow mask processing that enables deposition of multiple and various layers such as metals, organic materials and dielectrics. This an original and different approach compared with lithographic or nanoimprint techniques that were explored until now. Technology development and device and RF circuit design and testing will be carried out as a collaborative work between two laboratories of EPFL: LMIS and LEG, that have recognized experience in the respective fields. We expect that this project will have significant results not only in the fundamental aspects concerning electronic transport in nanolayer organic transistor but also being a promising source of new patents in the field and generating new types of applications.

We expect to obtain a clear view on the performances of these non-conventional plastic technologies and their use to obtain future applications. The first part of the study will reveal first which planar architecture delivers the best performances not only in terms of current and mobility, but also in terms of degradation function of stress and temperature. The influence of contact resistances and the dielectric-semiconductor interface will be also preferentially studied for future organic device optimisation. The influence of other environment conditions on device performances will be also tested. We will test the dependence of the device characteristics when exposed to the light or humidity. This will provide useful information for future applications of these devices in the domain of optical and chemical sensors.

Another benefit from this project consists in the study of the vertical transistors. A vertical organic nano-MOS transistor seems to be well fitted for the exploration of the charge transport in the domain of intramolecular conduction. For instance, if we consider pentacene, a 30nm vertical channel corresponds to a stack of 20 molecules. The objective is to produce vertical sub-50nm channels. The scaling of this device with the channel length will directly relate the electrical characteristics with the number of molecules along the channel. To our best knowledge, this study has never been performed before. Concerning the electrical characteristics, by exploiting the conduction along the long axis of the molecule, we expect a significant mobility improvement. Finally, it is worth noting that the potential impact of a successful organic nano-MOS transistor technology could be large on many electronic products such as:applications of OTFT (like active matrix displays), chemical sensors and low cost microelectronics will be surely boosted.

Regarding applications and circuit design the main target is to provide not only functional individual blocks but also a combination of such blocks for RF applications, like simple radio receivers or RFID tags. In the case where vertical devices with improved performances are realized this will be a substantial step forward for RF applications on organic layers. The study of the reliability of the devices will be extended to the study of the reliability of whole circuits. Proposing design solutions for ameliorated tolerance to device characteristics instabilities is also an important as well as challenging goal to achieve. So far there are few published studies on reliability of organic-layer circuits and on design methods for improving their long-term stability so the field is open for new ideas and solutions.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
122134 Radio Flexible 01.10.2008 Project funding