Cho-Lun Hsu

9nm half-pitch functional resistive memory cell with <1µA programming current using thermally oxidized sub-stoichiometric WO x film

Record 9nm half-pitch functional Transition-Metal-Oxide based Resistive Random Access Memory (TMORRAM) cell and the lowest reported 1µA programming current (Iprog, both Set and Reset) have been achieved with thermally oxidized sub-stoichiometric WOx and Nano Injection Lithography (NIL) technique [1]. The unexpectedly low programming current at 9nm diameter has been examined in-depth, it offers potential for scaling low power non-volatile memory. This small device shows Reset/Set resistance ratio around 10, stability during read operation, and good data-retention. A switching mechanism based on oxygen-ion dynamics can account for the observed device characteristics as discussed in this work.

Utilizing Sub-5 nm sidewall electrode technology for atomic-scale resistive memory fabrication

A sidewall electrode technology was successfully developed for the first time in this study, improving the understanding of the working mechanism in an ultra small, functional HfO₂-based resistive random access memory (RRAM) device (<; 1 × 3 nm²). This technology exhibits potential for application in atomic-scale memories. The 1 × 3 nm² RRAM device exhibited an excellent performance, featuring a high endurance of more than 10⁴ cycles, a large on/off verified window (>100), and reasonable reliability (stress time > 10³ s, 2 × 10⁴ h at 250 °C). Furthermore, the 1 × 3 nm² RRAM device exhibited distinctive unipolar behavior when a high voltage and rapid switching operation (7 V, 50 ns) were applied, and a switching mechanism model is proposed.

MoS 2 U-shape MOSFET with 10 nm channel length and poly-Si source/drain serving as seed for full wafer CVD MoS 2 availability

A U-shape MoS2 pMOSFET with 10nm channel and poly-Si source/drain is demonstrated. The fabrication process is simple. Because the Si S/D serves as the nucleation seed for CVD MoS2 deposition, thin MoS2 is well deposited in the channel region any where over the fully scale oxide coated Si wafer. This is a big step forward toward a low cost multi-layer stacked TMD IC technology.

Threshold Vacuum Switch (TVS) on 3D-stackable and 4F 2 cross-point bipolar and unipolar resistive random access memory

A 3D stackable and bidirectional Threshold Vacuum Switching (TVS) selector using the same WOx material as the RRAM element is reported. It provides the highest reported current density of >108 A/cm2 and the highest selectivity of >105. Stress test at high current density indicates >108 cycle capability for Reset/Set operation. A mechanism based on recombination of oxygen-ions and vacancies is proposed for the observed volatile switching of TVS. Utilizing the threshold characteristics of the TVS selector, a two-step reading waveform offers potential for 3D-stackable and 4F2 cross-point RRAM applications.

Study of sub-5 nm RRAM, tunneling selector and selector less device

By using sidewall electrode technology, both record small functional TiO₂ selection device (1 × 5 nm²) and HfO₂ based RRAM device (1 × 3 nm²) were for the first time successfully demonstrated in this work, improving the understanding of the switching mechanism in an ultra-small, functional resistive random access memory (RRAM) device. The tunneling based low temperature back-end selection devices show high driving current density of > 10 MA/cm² and selectivity of > 10³. The pulse driven cycle endurance of sub-5nm selection device and RRAM device reaches 10⁶ and 10³, respectively. Well controlled TiO₂ barrier produced with conformal plasma oxidation exhibits tight uniformity. The 1 × 3 nm² RRAM device exhibited an excellent performance, featuring a large on/off verified window (>100), and reasonable reliability (stress time > 10³ s). Furthermore, the 1 × 3 nm² RRAM device exhibited distinctive unipolar behavior when a high voltage and rapid switching operation (7 V, 50 ns) were applied. We also study on double oxide layer device and propose a physical mechanism picture to compare with previous study. This technology demonstrates the potential of future atomic-scale memories.

Efficiency enhancement and sensitive broadband 1Hz ∼ 1kHz of power generator by recycling vibration energy on Automobile

Based on novel design of moveable magnet between two mutually inimical magnetic forces without strict fabrication, for the first time, we demonstrate successfully a producible power generator with significant efficiency enhancement at broadband frequency range of 1 Hz ~ 1 kHz, 3D-colis stack-ability for output voltage improvement, and recycling vibration energy on automobile simultaneously. Even though the vibration frequency is as low as 1 Hz, two orders-of-magnitude improvements in normalized power (the ratio of power to product of external force and coil turns) provided from previous reports can be obtained. Further, comparing our device with maturely accelerometer chip (MMA7361) indicates that proposed strategies benefit harvesting vibration energy on driving automobile indeed. This vibrated power generator inturn provides high potential for applications, such as human motion (1 Hz ~ 2 Hz), sporting (5 Hz ~ 10 Hz), and automotive (10 Hz ~ 1 kHz) etc.

High sensitivity DNA sieving technology by entropic trapping in 3D artificial nano-channel matrices

The highest reported sensitivity (35%) of DNA sieving by entropic trapping has been achieved with a low operation voltage of 8V, and short time of 6 minutes. Wafer scale fabrication of 3D artificial nano-channel matrices is based on proven NEMS, MEMS, and Through-Si-Via (TSV) semiconductor technologies and offers high potential for application in portable bioelectronic instruments. A mechanism based on entropic trapping is proposed for the observed high DNA sieving sensitivity by 3D artificial nano-channel matrices.

Device modeling of a micromorph tandem solar cell using AMPS-1D

This work first theoretically optimize the amorphous (a-Si:H) and the microcrystalline (μc-Si:H) devices characteristics, and then perform studies for micromorph tandem solar cells. The studies calculated by AMPS-1D show that the TCO work function has obvious influence on the open-circuit voltage. Moreover, the power conversion efficiency of an a-Si:H cell is optimized by changing the absorbers layer thickness and mobility gap. Furthermore, a critical doping concentration of μc-Si:H films limiting the barrier height of a grain boundary (GB) is observed. After optimizing sub cell mutually, we combine the individual junctions to construct a micromorph cell which has an efficiency of 9.24%.