Hsin-Chiang You

Advanced Cu chemical displacement technique for SiO2-based electrochemical metallization ReRAM application

This study investigates an advanced copper (Cu) chemical displacement technique (CDT) with varying the chemical displacement time for fabricating Cu/SiO2-stacked resistive random-access memory (ReRAM). Compared with other Cu deposition methods, this CDT easily controls the interface of the Cu-insulator, the switching layer thickness, and the immunity of the Cu etching process, assisting the 1-transistor-1-ReRAM (1T-1R) structure and system-on-chip integration. The modulated shape of the Cu-SiO2 interface and the thickness of the SiO2 layer obtained by CDT-based Cu deposition on SiO2 were confirmed by scanning electron microscopy and atomic force microscopy. The CDT-fabricated Cu/SiO2-stacked ReRAM exhibited lower operation voltages and more stable data retention characteristics than the control Cu/SiO2-stacked sample. As the Cu CDT processing time increased, the forming and set voltages of the CDT-fabricated Cu/SiO2-stacked ReRAM decreased. Conversely, decreasing the processing time reduced the on-state current and reset voltage while increasing the endurance switching cycle time. Therefore, the switching characteristics were easily modulated by Cu CDT, yielding a high performance electrochemical metallization (ECM)-type ReRAM.

Improving the operational characteristic stability in Al/Au/ZnO/Al resistive random access memory devices

Resistive random access memory (ReRAM) devices are considered to be one of the most promising candidates for the next generation of nonvolatile memory devices because of their superior properties such as low power consumption, simple structure, high integration density, and fast operation speed. In this study, we used zinc oxide (ZnO) thin films to fabricate ReRAM devices comprising Au/ZnO/Al and Al/Au/ZnO/Al structures. We observed that the operating stability of the device containing the Al/Au/ZnO/Al structure improved. The devices displayed effective and stable operational characteristics. The operational voltage of the ZnO ReRAM devices was less than 3 V, and the reset operational voltage was less than −1.5 V.

Fabricating zinc oxide semiconductor device of flexible substrate by using the spin-coating method

In recent years, zinc oxide (ZnO) semiconductor have attracted much attention. Amorphous silicon thin film transistors are currently processed at a high temperature (>600 °C), with low mobility, but cannot be used in flexible electronics. Other organic thin film transistors were fabricated at a low temperature with middle mobility, but had a short life. This study used a bottom gate structure, low temperature (<400 °C) and spin-coating method to achieve the ZnO device with the on-off ratio = 107. The future study will focus on reducing channel width and length of devices, and the flexible substrate to make better flexible devices.

The Transistor Characteristics of Zinc Oxide Active Layer with Different Thickness of Zinc Oxide Thin-Film

ZnO is a wide band gap semiconductor which is used as transparent electrode in solar cells, chemical and gas sensors and light emitting diodes etc. This study examines the semiconductor layers produced by ZnO solution with sol-gel method and spin-coating in zinc oxide (ZnO) thin-film transistors (TFTs). By using spin coating method, the films are deposited on Si substrates. Compared with other methods, the method used in this study can be made at low annealing temperature of 300°C. We have investigated the electrical characteristics of ZnO thin film transistors with respect to the different thickness of ZnO active layers: 3.7 nm and 11.7 nm. The film thickness is controlled by the number of spin-coatings. In this study the VDS-IDS curve was consistent with ideal metal-oxide-semiconductor field-effect-transistor equation, on-off ratio = 106. The ZnO channel layer with 11.7 mm thickness has the best performance.

Fabrication of sol-gel-derived zinc oxide thin-film transistor

In this paper, a zinc oxide (ZnO) thin-film transistor (TFT) has been developed by using the sol-gel method with spin coating. Solution-processed thin-film deposition method is used to overcome the drawback of other vacuum deposition techniques in which process needs high temperature coating and expensive equipment. In order to analyze the characteristics of ZnO film, atomic force microscopy (AFM) is used to investigate the roughness of ZnO film. The experimental results show that the thickness of ZnO film is ranging from 5 nm to 10 nm with mean roughness 0.683 nm. The I–V characteristic of ZnO thin film transistor shows high current on-to-off ratio up to 106.

Investigating the Main Operating Mechanism of the Zinc Oxide Layer of ZnO RRAM

This study is to investigate the main operating mechanism of zinc oxide layer of ZnO RRAM (Resistance Random Access Memory). This experiment prepared four types of ZnO RRAM under different thermal annealing temperatures, Keithley 4200 measurement system was used to measure the operating voltage and current under a high impedance state and a low resistance state into the dielectric layer transmission mechanism analysis. This study found that the operating mechanism of a zinc oxide layer under the low-resistance state is mainly ohm conduction state. However, the operating mechanism of a zinc oxide layer under the high-resistance state is Poole-Frenkel Emission.

Controllable Ink-Jet Printing Technique on Various Channel Width Designs toward Zinc Oxide-Based Thin Film Transistor

Ink-jet printed (IJP) thin-film transistor (TFT) electronics employing solution processed materials is considered to be the key technique to achieve mask-less, low-cost, large-area, and low temperature fabrication systems. We propose an approach for a direct printing highly transparent conducting oxide material of zinc oxide (ZnO) which the use of semiconductor layer with different transistor channel widths without any photolithography process defined. In this work, we describe the ink-jet printing ZnO TFT with three-types channel widths, and electrical characteristics with low voltage operation, high performance of switch on/off state and low temperature fabrication (200~300°C). These printed TFT thus represent an uniquely attractive path for realizing high flexibility printed electronics.

Temperature Effects on Resistance of Power Devices

In recent years, due to the rapid development of integrated circuits, the demand of power devices is increasing. These power devices are often used in mobile phones, power supplies, and computer motherboards. However, for power devices design requirements today, the Withstanding voltage and on-resistance of devices are first required in design. When the device is in operation, the operating environment will cause a rise in temperature. When the temperature rises, the breakdown voltage and on-resistance of a device will change. This paper discusses the structure of device built on a BULK substrate to withstand a breakdown voltage of 200V or more, which is compared with the device built on a SOI substrate. And breakdown voltage and on-resistance of devices are analyzed at various temperatures. It is found that when the device built on a BLUK substrate is tested under a high temperature, it likely causes the high resistance state, this state will cause the device breakdown voltage rapidly declining.

The effect of X-ray irradiation on the novella type photoresist

As a result of the rapid development of lithography, it enables semiconductor technology to design more devices in the same area, which therefore makes electronic products faster, more functional, and hold more components. The photoresist, playing an important role in lithography, constantly develops with light wavelength used for exposure, from early entire wavelengths to present optical and non-optical lithography. The light sources of optical lithography have moved from the early 436nm and 365nm wavelength to short-wavelength light gradually. It is a big issue to find a suitable photoresist under the exposure of 0.578nm X-Ray light source. In this paper we first proposed to use DNQ / Novolak photoresist sold in the market for the 0.578nm X-Ray lithography. Due to the good resolution of NQ / Novolak photoresists, we obtained a 30nm line width as shown in Figure 1.In the experiment, it was discover that the exposure amount of X-Ray can determine if the photoresist is positive or negative; in low doses, when the photoresist film thickness is increased with the reduced exposure time, and a critical level is reached, the Novolak liquid will become positive photoresist after it is exposed in certain time. The high-dose X-Ray beam will make Novolak resin bond break and result in free radicals, which, through resin crosslinking, can improve the internal strength, and reduce developer solubility so the Novolak liquid can become to be a negative photoresist as shown in figure 2. By using synthesized DNQ / Novolak photoresist, under X-Ray exposure, we can reduce process line width, and explore principles of photoresist imaging analysis under the different exposure doses.