• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.8
• /
• pp.1227-1234
• /
• 2013

An analog array with a 1.2 double poly floating gate transistor has been developed with a standard CMOS fabrication process. The programming of each cell by means of an efficient control circuit eliminates the unnecessary erasing operation which has been widely used in conventional analog memories. It is seen that the path of the signal for both the programming and the reading is almost exactly the same since just one comparator supports both operations. It helps to eliminate the effects of the amplifier input-offset voltage problem on the output voltage for the read operation. In the array, there is no pass transistor isolating a cell of interest from the adjacent cells in the array. Instead of the extra transistors, one extra bias voltage, Vmid, is employed. The experimental results from the memory shows that the resolution of the memory is equivalent to the information content of at least six digital cells. Programming/erasing of each cell is achieved with no detectable disturbance of adjacent cells. Finally, the unique shape of the injector structure in a EEPROM is adopted as a cell of analog array. It reduces the programming voltage below the transistor breakdown voltage without any special fabrication process.

• Journal of the Korean Institute of Telematics and Electronics C
• /
• v.35C no.10
• /
• pp.30-37
• /
• 1998

An analog array with a 1.2 $\mu\textrm{m}$ double poly floating gate transistor has been developed with a standard CMOS fabrication process. The programming of each cell by means of an efficient control circuit eliminates the unnecessary erasing operation which has been widely used in conventional analog memories. It is seen that the path of the signal for both the programming and the reading is almost exactly the same since just one comparator supports both operations. It helps to eliminate the effects of the amplifier input-offset voltage problem on the output voltage for the read operation. In the array, there is no pass transistor isolating a cell of interest from the adjacent cells in the array. Instead of the extra transistors, one extra bias voltage, Vmid, is employed. The experimental results from the memory shows that the resolution of the memory is equivalent to the information content of at least six digital cells. Programming/erasing of each cell is achieved with no detectable disturbance of adjacent cells. Finally, the unique shape of the injector structure in a EEPROM is adopted as a cell of analog array. It reduces the programming voltage below the transistor breakdown voltage without any special fabrication process.

• Journal of the Semiconductor & Display Technology
• /
• v.16 no.2
• /
• pp.94-97
• /
• 2017

Amorphous Si has been used for data processing circuits in flat panel displays. However, low mobility of the amorphous Si is a limiting factor for the data transmission speed. Metal oxides such as ZnO have been studied to replace the amorphous Si. ZnO is a wide bandgap (3.3 eV) semiconductor with high mobility and good optical transparency. When ZnO is grown by sputtering with $O_2$ as an oxidizer, there can be many ion species arising from $O_2$ decomposition. $O^+$, $O_2{^+}$, and $O^-$ ions are expected to be the most abundant species, and it is not clear which one contributes to the ZnO growth. We applied alternating substrate voltage (0 V and -70 V) during sputtering growth. We studied changes in transistor characteristics induced by the voltage switching. We also compared ZnO grown by dc and rf sputtering. ZnO film was grown at $450^{\circ}C$ substrate temperature. ZnO thin-film transistor grown with these methods showed $7.5cm^2/Vsec$ mobility, $10^6$ on-off ratio, and -2 V threshold voltage.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.180-180
• /
• 2000

Plasma source ion implantation is a new doping technique for the formation of shallow junction with the merits of high dose rate, low-cost and minimal wafer charging damage. In plasma source ion implantation process, the wafer is placed directly in the plasma of the appropriate dopant ions. Negative pulse bias is applied to the wafer, causing the dopant ions to be accelerated toward the wafer and implanted below the surface. In this work, inductively couples plasma was generated by anodized Al antenna that was located inside the vacuum chamber. The outside wall of Al chamber was surrounded by Nd-Fe-B permanent magnets to confine the plasma and to enhance the uniformity. Before implantation, the wafer was pre-sputtered using DC bias of 300B in Ar plasma in order to eliminate the native oxide. After cleaning, B2H6 (5%)/H2 plasma and negative pulse bias of -1kV to 5 kV were used to form shallow p+/n junction at the boron dose of 1$\times$1015 to 5$\times$1016 #/cm2. The as-implanted samples were annealed at 90$0^{\circ}C$, 95$0^{\circ}C$ and 100$0^{\circ}C$during various annealing time with rapid thermal process. After annealing, the sheet resistance and the junction depth were measured with four point probe and secondary ion mass spectroscopy, respectively. The doping uniformity was also investigated. In addition, the electrical characteristics were measured for Schottky diode with a current-voltage meter.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.11
• /
• pp.18-24
• /
• 2000

(Ba,Sr)$TiO_3$ thin films have attracted great interest as new dielectric materials of capacitors for ultra-large-scale integrated dynamic random access memories (ULSI-DRAMs) such as 1 Gbit or 4 Gbit. In this study, inductively coupled $BCl_3/Cl_2/Ar$ plasmas was used to etch (Ba,Sr)$TiO_3$ thin films. RF power/dc bias voltage=600 W/-250 V and chamber pressure was 10 mTorr. The $Cl_2/(Cl_2+Ar)$ was fixed at 0.2 the (Ba,Sr)$TiO_3$ thin films were etched adding $BCl_3$. The highest (Ba,Sr)$TiO_3$ etch rate is $480{\AA}/min$ at 10 % $BCl_3$ to $Cl_2/Ar$. The change of Cl, B radical density measured by optical emission spectroscopy(OES) as a function of $BCl_3$ percentage in $Cl_2/Ar$. The highest Cl radical density was shown at the addition of 10% $BCl_3$ to $Cl_2/Ar$. To study on the surface reaction of (Ba, Sr)$TiO_3$ thin films was investigated by XPS analysis. Ion bombardment etching is necessary to break Ba-O bond and to remove $BaCl_2$. There is a little chemical reaction between Sr and Cl, but Sr is removed by physical sputtering. There is a chemical reaction between Ti and Cl, and $TiCl_4$ is removed with ease. The cross-sectional of (Ba,Sr)$TiO_3$ thin film was investigated by scanning electron microscopy (SEM), the etch slope is about 65~70$^{\circ}$.

• Journal of the Korean Vacuum Society
• /
• v.7 no.3
• /
• pp.242-247
• /
• 1998

Hydrogenated amorphous carbon nitride[a-C:H(N)] films were deposited on p-type Si(100) at room temperature with bias voltage of 200 V by DC saddle-field plasma-enhanced chemical vapor deposition. Effects of the ratio of $N_2$ to $CH_4$($N_2/CH_4$), in the range of 0 and 4 on such properties as optical properties, microstucture, relative fraction of nitrogen and carbon, etc. of the films have been investigated. The thickness of the a-C:H(N) film was abruptly decreased with the addition of nitrogen, but at $N_2/CH_4$>0.5, the thickness of the film gradually decreased with the increase of the $N_2/CH_4$. The ratio of N to C(N/C) of the films was saturated at 0.25 with the increase of $N_2CH_4$. N-H, C≡N bonds of the films increased but C-H bond decreased with the increase of $N_2CH_4$.Optical band gap energy of the film decreased from 2.53 eV at the ratio of $N_2CH_4$=4.

• Journal of Navigation and Port Research
• /
• v.28 no.5
• /
• pp.429-434
• /
• 2004

In this paper, we designed a reconfigurable slot antenna using sequentially voltage-applied RF MEMS switches. In order to obtain pull-in voltage and maximum stress of the MEMS switches, the switch structures in accordance with airgap height was analyzed by ANSYS simulation A actuation voltage of MEMS switches can be determined by switch geometry and airgap height between a movable plate and a bottom plate. The designed lengths of MEMS switches were 240 $\mu\textrm{m}$, 320 $\mu\textrm{m}$, 400 $\mu\textrm{m}$, respectively and the airgap was 6$\mu\textrm{m}$. The total size of the designed slot antenna was 10 mm x 10 mm and the slot length and width were 500 $\mu\textrm{m}$ and 200 $\mu\textrm{m}$, respectively. The length and size of the CPW feedline were 5 mm and 30-80-30 $\mu\textrm{m}$, respectively. and then the size of the CPW in the slot was 50-300-150 $\mu\textrm{m}$. The tuning of the resonant frequency of the proposed device is realized by varying the electrical length of the antenna, which is controlled by applying the DC bias voltages to the RF MEMS switches. The designed slot antenna has been simulated, fabricated and measured.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.211-211
• /
• 1999

Titanium nitride (TiN) thin films have useful properties including high hardness, good electrical conductivity, high melting point, and chemical inertness. The applications have included wear-resistant hard coatings on machine tools and bearings, decorative coating making use of the golden color, thermal control coatings for widows, and erosion resistant coatings for spacecraft plasma probes. For all these applications as feature sizes shrink and aspect ratios grow, the issue of good step coverage becomes increasingly important. It is therefore essential to manufacture conformal coatings of TiN. The growth of TiN thin films by chemical vapor deposition (CVD) is of great interest for achieving conformal deposition. The most widely used precursor for TiN is TiCl4 and NH3. However, chlorine impurity in the as-grown films and relatively high deposition temperature (>$600^{\circ}C$) are considered major drawbacks from actual device fabrication. To overcome these problems, recently, MOCVD processes including plasma assisted have been suggested. In this study, therefore, we have doposited Ti(C, N) thin films on Si(100) and D2 steel substrates in the temperature range of 150-30$0^{\circ}C$ using tetrakis diethylamido titanium (TDEAT) and titanium isopropoxide (TIP) by pulsed DC plamsa enhanced metal-organic chemical vapor deposition (PEMOCVD) method. Polycrystalline Ti(C, N) thin films were successfully grown on either D2 steel or Si(100) surfaces at temperature as low as 15$0^{\circ}C$. Compositions of the as-grown films were determined with XPS and RBS. From XPS analysis, thin films of Ti(C, N) with low oxygen concentration were obtained. RBS data were also confirmed the changes of stoichiometry and microhardness of our films. Radical formation and ionization behaviors in plasma are analyzed by optical emission spectroscopy (OES) at various pulsed bias and gases conditions. H2 and He+H2 gases are used as carrier gases to compare plasma parameter and the effect of N2 and NH3 gases as reactive gas is also evaluated in reduction of C content of the films. In this study, we fond that He and H2 mixture gas is very effective in enhancing ionization of radicals, especially N resulting is high hardness. The higher hardness of film is obtained to be ca. 1700 HK 0.01 but it depends on gas species and bias voltage. The proper process is evident for H and N2 gas atmosphere and bias voltage of 600V. However, NH3 gas highly reduces formation of CN radical, thereby decreasing C content of Ti(C, N) thin films in a great deal. Compared to PVD TiN films, the Ti(C, N) film grown by PEMOCVD has very good conformability; the step coverage exceeds 85% with an aspect ratio of more than 3.

• Journal of the Korean institute of surface engineering
• /
• v.34 no.5
• /
• pp.465-474
• /
• 2001

Type 304SS coatings were performed at 200$\square$ onto AISI 1045 carbon steel substrate using unbalanced magnetron sputtering (UBMS) with an austenitic AISI 304 stainless steel (SS) target of 100mm diameter. The total deposition pressure in the active Ar gas was 2$\times$10$^{-3}$ Torr. Coatings were done at various target power densities and bias voltages. Chemical compositions of metallic elements of the coatings were measured by energy dispersive X-rays spectroscopy (EDS). The structure and the morphology of Type 304SS coatings were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Corrosion properties of the coated specimens were examined using electrochemical polarization measurements and electrochemical impedance spectroscopy in a deaerated 3.5% NaCl solution. The porosity rate was obtained from a comparison of the dc polarization resistance of the uncoated and coated substrates. Scratch adhesion testing was used to compare the critical loads for different coatings. XRD results showed that the sputtered films exhibit a ferritic b.c.c. $\alpha$-phase. Potentiodynamic polarization curves indicated that all samples had much higher corrosion potential and better corrosion resistance than the bare steel substrate. The corrosion performance increased with increasing power density and the adhesion was enhanced at the bias voltage of -50V. An improvement in the corrosion resistance can be obtained with a better coating adhesion. Finally, an optimized deposition condition for corrosion protection was found as $40W/cm^2$ and -50V.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.7
• /
• pp.620-624
• /
• 2016

In this paper we designed a current mode logic frequency divider to transmit a baseband amplitude modulated signal. From simulation result, we studied input and output waveforms according to the variation of input bias voltage. For the purpose of the verification of the study, we designed a current mode logic frequency divider at 1,400 MHz. The designed frequency divider operates between 100 MHz and 3,000 MHz, for -33 dBm input power. The circuit draws $I_{total}=30mA$ from $V_{DD}=3V$ supply, and the simulation result shows that an amplitude modulated signal at 1,400 MHz with the modulation index of 0.5 was successfully downconverted to 700 MHz.