Jae-Hyuk Ahn

Double-Gate Nanowire Field Effect Transistor for a Biosensor

A silicon nanowire field effect transistor (FET) straddled by the double-gate was demonstrated for biosensor application. The separated double-gates, G1 (primary) and G2 (secondary), allow independent voltage control to modulate channel potential. Therefore, the detection sensitivity was enhanced by the use of G2. By applying weakly positive bias to G2, the sensing window was significantly broadened compared to the case of employing G1 only, which is nominally used in conventional nanowire FET-based biosensors. The charge effect arising from biomolecules was also analyzed. Double-gate nanowire FET can pave the way for an electrically working biosensor without a labeling process.

Nanogap Field-Effect Transistor Biosensors for Electrical Detection of Avian Influenza

This work was supported by the National Research and Development Program for biomedical function-monitoring biosensor development, sponsored by the Korean Ministry of Education, Science and Technology (MEST) (Y.-K.C.), the NRL program of the KOSEF grant funded by MEST (Y.-K.C.), Grant No. 08K1401-00210 from the Center for Nanoscale Mechatronics & Manufacturing, one of the 21st Century Frontier Research Programs supported by MEST (Y.-K.C.), the World Class University (WCU) program through the KOSEF funded by the MEST (R32-2008-000-10142-0) (T.J.P. and S.Y.L.), and by the IT Leading R&D Support Project from the Ministry of Knowledge Economy through KEIT (T.J.P. and S.Y.L.). X.J.H. was supported by the Brain Korea 21 project, the School of Information Technology, and KAIST in 2007.

Energy band engineered unified-RAM (URAM) for multi-functioning 1T-DRAM and NVM

A novel fusion memory is proposed as a new paradigm of silicon based memory technology. An O/N/O gate dielectric and a floating body are combined with a FinFET, and the non-volatile memory (NVM) and high speed capacitorless 1T-DRAM are performed in a single transistor. A nitride trap layer is used as an electron storage node for NVM, and hetero-epitaxially grown Si/Si1-xGex energy band engineered bulk substrates allow excess hole storage for 1T-DRAM. Highly reliable 1T-DRAM and NVM are demonstrated.

Nonvolatile Memory by All-Around-Gate Junctionless Transistor Composed of Silicon Nanowire on Bulk Substrate

A junctionless transistor with a width of 10 nm and a length of 50 nm is demonstrated for the first time. A silicon nanowire (SiNW) channel is completely surrounded by a gate, and the SiNW is built onto the bulk substrate. The proposed junctionless transistor is applied to a Flash memory device composed of oxide/nitride/oxide gate dielectrics. Acceptable memory characteristics are achieved regarding the endurance, data retention, and dc performance of the device. It can be expected that the inherent advantages of the junctionless transistor can overcome the scaling limitations in Flash memory. Hence, the junctionless transistor is a strong candidate for the further scaling of NAND Flash memory below the 20-nm node.

A Bulk FinFET Unified-RAM (URAM) Cell for Multifunctioning NVM and Capacitorless 1T-DRAM

A bulk FinFET-based unified-RAM (URAM) cell technology is demonstrated for the fusion of a nonvolatile-memory (NVM) and capacitorless 1T-DRAM. An oxide/nitride/oxide layer and a floating-body are combined to perform a URAM operation in a single transistor. A buried n-well technology for NMOS allows hole accumulation for the 1T-DRAM operation in a p-type bulk substrate. The bulk FinFET URAM offers a cost-effective and fully compatible process with a conventional FinFET SONOS, and it also expedites heat dissipation. Highly reliable NVM and high-speed 1T-DRAM operation are confirmed, and it was also verified that there is no disturbance between the two memory functions.

An underlap field-effect transistor for electrical detection of influenza

An underlap channel-embedded field-effect transistor (FET) is proposed for label-free biomolecule detection. Specifically, silica binding protein fused with avian influenza (AI) surface antigen and avian influenza antibody (anti-AI) were designed as a receptor molecule and a target material, respectively. The drain current was significantly decreased after the binding of negatively charged anti-AI on the underlap channel. A set of control experiments supports that only the biomolecules on the underlap channel effectively modulate the drain current. With the merits of a simple fabrication process, complementary metal-oxide-semiconductor compatibility, and enhanced sensitivity, the underlap FET could be a promising candidate for a chip-based biosensor.

A self-heated silicon nanowire array: selective surface modification with catalytic nanoparticles by nanoscale Joule heating and its gas sensing applications

We demonstrated novel methods for selective surface modification of silicon nanowire (SiNW) devices with catalytic metal nanoparticles by nanoscale Joule heating and local chemical reaction. The Joule heating of a SiNW generated a localized heat along the SiNW and produced endothermic reactions such as hydrothermal synthesis of nanoparticles or thermal decomposition of polymer thin films. In the first method, palladium (Pd) nanoparticles could be selectively synthesized and directly coated on a SiNW by the reduction of the Pd precursor via Joule heating of the SiNW. In the second method, a sequential process composed of thermal decomposition of a polymer, evaporation of a Pd thin film, and a lift-off process was utilized. The selective decoration of Pd nanoparticles on SiNW was successfully accomplished by using both methods. Finally, we demonstrated the applications of SiNWs decorated with Pd nanoparticles as hydrogen detectors. We also investigated the effect of self-heating of the SiNW sensor on its sensing performance.

Palladium nanoparticle decorated silicon nanowire field-effect transistor with side-gates for hydrogen gas detection

A silicon nanowire field-effect transistor (SiNW FET) with local side-gates and Pd surface decoration is demonstrated for hydrogen (H2) detection. The SiNW FETs are fabricated by top-down method and functionalized with palladium nanoparticles (PdNPs) through electron beam evaporation for H2 detection. The drain current of the PdNP-decorated device reversibly responds to H2 at different concentrations. The local side-gates allow individual addressing of each sensor and enhance the sensitivity by adjusting the working region to the subthreshold regime. A control experiment using a non-functionalized device verifies that the hydrogen-sensitivity is originated from the PdNPs functionalized on the SiNW surface.

Electrical Biomolecule Detection Using Nanopatterned Silicon via Block Copolymer Lithography

An electrical biosensor exploiting a nanostructured semiconductor is a promising technology for the highly sensitive, label-free detection of biomolecules via a straightforward electronic signal. The facile and scalable production of a nanopatterned electrical silicon biosensor by block copolymer (BCP) nano-lithography is reported. A cost-effective and large-area nanofabrication, based on BCP self-assembly and single-step dry etching, is developed for the hexagonal nanohole patterning of thin silicon films. The resultant nanopatterned electrical channel modified with biotin molecules successfully detects the two proteins, streptavidin and avidin, down to nanoscale molarities (≈1 nm). The nanoscale pattern comparable to the Debye screening length and the large surface area of the three-dimensional silicon nanochannel enable excellent sensitivity and stability. A device simulation confirms that the nanopatterned structure used in this work is effective for biomolecule detection. This approach relying on the scalable self-assembly principle offers a high-throughput manufacturing process for clinical lab-on-a-chip diagnoses and relevant biomolecular studies.

A Universal Core Model for Multiple-Gate Field-Effect Transistors. Part I: Charge Model

A universal core model for multiple-gate field-effect transistors (Mug-FETs) is proposed. The proposed charge and drain current models are presented in Parts I and II, respectively. It is first demonstrated that an exact potential profile in the entire channel is not necessary for the derivation of accurate charge models in inversion-mode FETs. With application of this new concept, a universal charge model is derived for Mug-FETs by assuming an arbitrary channel potential profile, which simplifies the mathematical formulation. Thereafter, using the Pao-Sah integral, a drain current model is obtained from the charge model of Part I. The proposed model can be expressed as an explicit and continuous form for all operation regimes; therefore, it is well suited for compact modeling to support fast circuit simulations. The model shows good agreement with 2-D and 3-D numerical simulations for several multiple-gate structures, such as single-gate, double-gate, triple-gate, rectangular gate-all-around, and cylindrical gate-all-around FETs.