Yoon-ho Son

Integration and Electrical Properties of Carbon Nanotube Array for Interconnect Applications

Carbon nanotube (CNT) vertical integration and electrical properties are presented in full 6-inch wafer for interconnect applications. Series array of 1000 vias made of vertically grown CNTs is obtained with uniform electrical resistances within the wafer. Integration processes are implemented by following sequential steps: bottom electrode and via hole patterning, CNT growth and planarization, and top electrode patterning in a 6-inch wafer. Multiwall carbon nanotubes (MWNTs) are used for interconnection, titanium nitride for the bottom electrode, and aluminum with titanium adhesion layer for the top electrode. We have demonstrated well-defined CNT via series interconnection with 700 nm via diameters within the full wafer. Via resistance of 1.2 kΩ with CNT density of 2.7×1010/cm2is obtained with small resistance variation within the wafer, which also corresponds to 176 kΩ per one MWNT with 10 nm diameters. The possible approaches for further decrease of electrical resistance will be suggested.

Integration of ferroelectric random access memory devices with Ir/IrO2/Pb(ZrxTi1-x)O3/Ir capacitors formed by metalorganic chemical vapor deposition-grown Pb(ZrxTi1-x)O3

Metal organic chemical vapor deposition (MOCVD) of Pb(ZrxTi1-x)O3 (PZT) and its capacitor module process were established for ferroelectric memory device integration. The 130 nm-thick PZT films were deposited on Ir layers at 530°C or 550°C. The remnant polarization of the Ir/IrO2/PZT/Ir capacitors is in the range of 15 to 21 µC/cm2, and their leakage current is 10-5 A/cm2 at 2.5 V without additional annealing. The degradation in their switching endurance is less than 5% after 1010 cycles, indicating that the interfaces formed between the PZT and Ir layers can be optimized to improve their fatigue properties. To evaluate the capacitors on the devices, the conventional backend process was performed after encapsulating the capacitors with AlOx/TiOx layers located on the poly-Si plug. High charge separation and fully functional bit activities were obtained, demonstrating that this MOCVD-PZT process is a reliable integration scheme for high-density ferroelectric memory devices.

Plasma-assisted dry etching of ferroelectric capacitor modules and application to a 32M ferroelectric random access memory devices with submicron feature sizes

In the manufacturing of a 32M ferroelectric random access memory (FRAM) device on the basis of 0.25 design rule (D/R), one of the most difficult processes is to pattern a submicron capacitor module while retaining good ferroelectric properties. In this paper, we report the ferroelectric property of patterned submicron capacitor modules with a stack height of 380 nm, where the 100 nm-thick Pb(Zr, Ti)O3 (PZT) films were prepared by the sol-gel method. After patterning, overall sidewall slope was approximately 70° and cell-to-cell node separation was made to be 80 nm to prevent possible twin-bit failure in the device. Finally, several heat treatment conditions were investigated to retain the ferroelectric property of the patterned capacitor. It was found that rapid thermal processing (RTP) treatment yields better properties than conventional furnace annealing. This result is directly related to the near-surface chemistry of the PZT films, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The resultant switching polarization value of the submicron capacitor was approximately 30 µC/cm2 measured at 3 V.

Effect of Ashing, Strip and Annealing Process on the Dopant Concentration of Silicon

Introduction Silicon has been used successfully for semiconductor material because it can have a high degree of purity at a low cost, and shows the good mechanical, chemical and electrical properties. In the respect of electrical properties, the pure silicon is an insulator, thus the ion implantation process is necessary to make insulating silicon into semiconductor. Generally, the electrical properties of silicon based semiconductors are determined by the characteristics of dopant. Hence the study for the change of dopants concentration in following process such as ashing, strip, and annealing, is very important. (Shown in Figure 1.) In this study, we will discuss about the loss of dopant by strip process using fluorine-based stripper and annealing.