Joon-Tae Song

An effective method to prevent stiction problems using a photoresist sacrificial layer

An effective method to prevent stiction problems is presented for surface micromachined suspended structures using a photoresist sacrificial layer. This technique is based on a photoresist sacrificial layer and supporting posts to prevent a stiction problem. The processes of coating and patterning were able to be condensed using photoresist as a sacrificial layer. Photoresist posts were easily fabricated using only one additional exposure process. To measure the effectiveness of this technique, the posts were designed under the condition of the calculated maximum spacing distance. For a 120 nm thick aluminum structure, the theoretically calculated dmax was about 30 µm. The sacrificial layer was removed using a developer and then the posts were removed using an oxygen plasma asher. This technique may be a more useful method to fabricate big suspended platforms. From 100 × 100 µm2 cantilevers to 1000 × 1000 µm2 big platforms, various types of micromachined structures were easily suspended using this technique without a stiction problem or any damage.

Implementation of Electrical Property Assessment System for Overhead Contact Lines

Currently in Korea, the simple catenary type overhead contact line system is being applied to both conventional lines and high speed lines of electric railway, and circulation current flowing into the catenary system frequently bring undesirable consequences. Namely, the connector wire has many problems according to a flow of excessive circulation current and arc current on catenary when an electric train runs at high speed. This paper presents the development and application of a real-time data acquisition system designed to measure the electrical characteristics of an overhead catenary system in electric railways. The developed system is capable of storing data of a 25 kV power source in a live wire state through a telemetry environment. The field test results show that the proposed technique and the developed system can be practically applied to measure characteristics of current of an overhead catenary system.

Mechanism and CHARM2 Evaluation of P-Channel Metal Oxide Semiconductor Threshold Voltage Drop during High Density Plasma Heat-up Process

Plasma damage during the plasma deposition process is one of the most critical device characteristic issues facing complementary metal oxide semiconductor field effect transistor (CMOSFET) technology. In this paper, the CHARM2 monitoring system is used to evaluate UV damage and plasma charging damage during a high density plasma chemical vapor deposition (HDP-CVD) heat-up process. As a result, the amount of UV damage and negative charging damage is increased as the HDP-CVD heat-up process source power is increased. The main cause of P-channel metal oxide semiconductor field effect transistor (PMOSFET) threshold voltage drop is UV photon facilitated gate oxide electron trapping at the gate oxide and substrate P-channel interface during the HDP-CVD heat-up process. In N-channel metal oxide semiconductor field effect transistor (NMOSFET), when negative gate voltage stress is increased, gate oxide energy bend is flattened. Electrons cannot be trapped at the gate oxide and substrate N-channel interface. Therefore, the NMOSFET threshold voltage is constant during the HDP-CVD heat-up plasma process.

Effect of Annealing Temperature on the Properties of Sputtered Bi 3.25 La 0.75 Ti 3 O 12 Thin Films

(BLT) thin films were prepared on the Pt(150 nm)/Ti(50 nm)//Si substrate using the rf magnetron sputtering method. The BLT thin films were annealed at temperatures ranging from to using the rapid thermal annealing. The structure and surface morphology of the thin films were characterized by x-ray diffraction and field emission scanning electron microscopy. The hysteresis loop of the BLT thin films showed that the remanent polarization (2Pr) of the film annealed at was 10.92 . The fatigue characteristic of the BLT thin film annealed at was shown change polarization up to switching cycles. We confirmed the excellent remnant polarization (Pr) and fatigue properties compared with other fabrication methods and suggested a good method for BLT thin films fabrications.

Properties of the Various Power Ratio in GZOB/AU Multilayers

We investigated the effects of power ratio on the electrical and optical properties of Au based Ga-, B- codoped ZnO(GZOB) thin films. GZOB thin films were deposited on Au based poly carbonate(PC) substrate with various power in the range from 60 to 120 W by DC magnetron sputtering. In the result, GZOB films at 100 W exhibited a low resistivity value of , and a visible transmission of 80 % with a thickness of 300 nm. This result indicated that the addition of Ga and B in ZnO films leads to the improvement of conductivity and transparent. From the result, we can confirm the possibility of the application as transparent conductive electrodes.

The Characteristics of Ga-doped ZnO Transparent Thin Films by using Multilayer

With development of electronic products the demands for miniaturization and weight-lightening have increased until a recent date. Accordingly, The effort to substitute glass substrates was widely made. However, polymer substrates have weak point that substrates were damaged at high temperature. In this paper, we deposited transparent conductive film at low temperature. And we inserted Au thin film between oxide to compensate for deteriorated electrical characteristics. Ga-doped ZnO(GZO) multilayer coatings were deposited on glass substrate by DC sputtering. The optimization of deposition conditions of both AZO and Au layers were performed to obtain better electrical and optical characteristics in advance. We presumed that the properties of multilayer were affected by the deposition process of both GZO and Au layers. The best multilayer coating exhibited the resistivity of and transmittance of 77 %. From these results, we can confirm a possibility of the application as transparent conductive electrodes.

Study of Effect of PZT Thin Film Prepared in Different Post-Annealing Temperature Using SIMS

The effect of various post-annealing temperature to sputtered Pb(Zr,Ti) (PZT) thin films was investigated. The crystallization process, surface morphology and the electrical characteristics strongly depends on the rapid thermal annealing (RTA). In radio frequency (RF) sputtering methods, there were many papers mostly forcing on the crystal forming and the surface variations with different elements distribution (Pb, Ti, Zr, O) on the surface of the PZT layer. In this experiment, the post-annealing treatment promoted the Pb volatilization in PZT thin film and affected the Ti diffused throughout the Pt layer into the PZT layer. Second ion mass spectroscopy (SIMS) analysis was employed to show that the Pb element in the PZT layer was decreased at the same time the Ti element mass was slight decreased than Pb with increasing RTA temperature. That result prove the content of Pb affect the PZT thin film property.

Effects of Sputtering Condition on Structural Properties of PZT Thin Films on LTCC Substrate by RF Magnetron Sputtering

Recently, low temperature co-fired ceramic (LTCC) technology is widely used in sensors, actuators and microsystems fields because of its very good electrical and mechanical properties, high reliability and stability as well as possibility of making 3D micro structures. In this study, we investigated the effects of sputtering gas ratio and annealing temperature on the crystal structure of (PZT) thin films deposited on LTCC substrate. The LTCC substrate with thickness of were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. The PZT thin films were deposited on Pt / Ti / LTCC substrates by RF magnetron sputtering method. The results showed that the crystallization of the films were enhanced as increasing mixing ratio. At about 25% mixing ratio, was well crystallized in the perovskite structure. PZT thin films was annealed at various temperatures. When the annealing temperature is lower, the PZT thin films become a phyrochlore phase. However, when the annealing temperature is higher than , the PZT thin films become a perovskite phase. At the annealing temperature of , perovskite PZT thin films with good quality structure was obtained.

A Study on Efficiency of Energy Conversion for a Piezoelectric Power Harvesting Using Polyvinylidene Fluorid Film

Piezoelectric materials can be used to convert mechanical energy into electrical energy. In this study, we investigated the possibility of harvesting from mechanical vibration force using a high efficient piezoelectric material-polyvinylidene fluoride (PVDF). A piezoelectric energy harvesting system consists of rectifier, filter capacitor, resistance. The experiments were carried out with impacting force to PVDF film with the thickness of 1 . The output power was measured with change in the load resistance value from 100 to 2.2 . The highest power was obtained under optimization by selection of suitable resistive load and capacitance. A power of 0.3082 was generated at the external vibration force of 5 N (10 Hz) across a 1 optimal resistor. Also, the maximum power of 0.345 was generated at 22 and 1 . The developed system was expected at a solution to overcome the critical problem of making up small size energy harvester.

Leakage current characteristics by ion-bombardment physical damage during pulse-time modulated plasma process

The pulse-time modulated plasma etching technology, developed more than a decade ago [1], has been considered as one of the best solutions to the plasma-process-induced charging damage on the gate oxide of the MOSFET.[2–3] Mieno et al., reported that, in the plasma-off state, the generation of the negative ion due to a low temperature electron attachment to the neutral radical, helps in reducing the plasma-process-induced charging damage.[4] However, the plasma-process-induced physical damages that are generated by highly energetic ion-bombardment during the pulse-time modulated plasma process have not been evaluated yet. As illustrated in Fig. 1, highly energetic ions can make trap sites in the depleted gate-drain overlap region and in the space-charge-region (SCR) between drain and substrate. The gate induced drain leakage (GIDL) can be increased substantially when the trap-site concentrations increase in the depleted gate-drain-overlap region through the trap assisted tunneling (TAT).[5] In this paper, we evaluated the plasma physical damages during pulse-time modulated plasma-gate etching process by measuring GIDL current.