IEICE Transactions on Electronics
Online ISSN : 1745-1353
Print ISSN : 0916-8524
Special Section on Solid-State Circuit Design - Architecture, Circuit, Device and Design Methodology
Single-Grain Si Thin-Film Transistors for Monolithic 3D-ICs and Flexible Electronics
Ryoichi ISHIHARAJin ZHANGMiki TRIFUNOVICJaber DERAKHSHANDEHNegin GOLSHANIDaniel M. R. TAJARI MOFRADTao CHENKees BEENAKKERTatsuya SHIMODA
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2014 Volume E97.C Issue 4 Pages 227-237

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Abstract

We review our recent achievements in monolithic 3D-ICs and flexible electronics based on single-grain Si TFTs that are fabricated inside a single-grain with a low-temperature process. Based on pulsed-laser crystallization and submicron sized cavities made in the substrate, amorphous-Si precursor film was converted into poly-Si having grains that are formed on predetermined positions. Using the method called µ-Czochralski process and LPCVD a-Si precursor film, two layers of the SG Si TFT layers with the grains having a diameter of 6µm were vertically stacked with a maximum process temperature of 550°C. Mobility for electrons and holes were 600cm2/Vs and 200cm2/Vs, respectively. As a demonstration of monolithic 3D-ICs, the two SG-TFT layers were successfully implemented into CMOS inverter, 3D 6T-SRAM and single-grain lateral PIN photo-diode with in-pixel amplifier. The SG Si TFTs were applied to flexible electronics. In this case, the a-Si precursor was prepared by doctor-blade coating of liquid-Si based on pure cyclopentasilane (CPS) on a polyimide (PI) substrate with maximum process temperature of 350°C. The µ-Czochralski process provided location-controlled Si grains with a diameter of 3µm and mobilities of 460 and 121cm2/Vs for electrons and holes, respectively, were obtained. The devices on PI were transferred to a plastic foil which can operate with a bending diameter of 6mm. Those results indicate that the SG TFTs are attractive for their use in both monolithic 3D-ICs and flexible electronics.

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© 2014 The Institute of Electronics, Information and Communication Engineers
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