• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.131-137
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• 2009

In this paper, we have manufactured hole type PRAM unit cell using phase change material $Ge_2Sb_2Te_5$. The phase change material $Ge_2Sb_2Te_5$ was deposited on hole of 500 nm size using sputtering method. Reset current of PRAM unit cell was confirmed by measuring R-V characteristic curve. Reset current of manufactured hole type PRAM unit cell is 15 mA, 100 ns. And electro and thermal characteristics of hole type PRAM unit cell were analyzed by 3-D finite element analysis. From simulation temperature of PRAM unit cell was $705^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.120-122
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• 2003

We have been investigated phase-change with temperature and electric field in chalcogenide $Ge_2Sb_2Te_5$ thin film. $T_c$(crystallization temperature) is confirmed by measuring the resistance and conductivity with the varying temperature on the hotplate. We have measured I-V characteristics with $Ge_2Sb_2Te_5$ chalcogenide thin film. It is compared with I-V characteristics after impress the variable pulse. The pulse has variable height and duration that used voltage and current source.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.203-206
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• 2004

For the realization of PRAM, $Ge_2Sb_2Te_5$ (GST) has been employed for the phase transition between the crystal and amorphous states by electrical joule heating. Although there has been a vast amount of results concerning the GST in material aspect for the laser-induced optical storage disc applications, the process-related issues of GST for the PRAM applications have not been reported. In this work, the etching behaviors of GST were investigated when the processing conditions were varied in the high-density helicon plasma. The etching parameters of RF main power, RF bias power, and chamber pressure were fixed at 600 W, 150 W, and 5 mTorr, respectively. For the etching processes, gas mixtures of $Ar/Cl_2$, $Ar/CF_4$, and $Ar/CHF_3$ were employed, in which the etching rates and etching selectivities of GST thin film in given gas mixtures were evaluated. From obtained results, it is found that we can arbitrarily design the etching process according to given cell structures and material combinations for PRAM cell fabrications.

• 한국세라믹학회지
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• 제33권8호
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• pp.855-862
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• 1996

The nucleation and the crystal growth rates of Ge-Se-Te chalcogenide glass by two step heat-treatment and its effect on the mechanical optical properties and water-resistance were determined. The maximum nuclea-tion and crystal growth rate were 2.1$\times$103/mm3 .min at 28$0^{\circ}C$ and 0.4${\mu}{\textrm}{m}$/min at 33$0^{\circ}C$ respectively. When the crystal volume fraction with crystal size $1.5mutextrm{m}$ was about 4% the (hardness and fracture toughness were about 117kg/mm2 and 6.0 MPa.mm1/2)respectively. The weight loss of crystallized glass in water was lower than parent glass($25^{\circ}C$ for 32 hrs : 0.03% 8$0^{\circ}C$ for 16 hrs : 0.1%) as 0.01% at $25^{\circ}C$, 0.03% at 8$0^{\circ}C$ for 16 hrs : 0.1%) at $25^{\circ}C$ 0.03% at 8$0^{\circ}C$ respectively. The IR-transmittance decreased with increasing crystal size and crystal volume fraction. The IR-transmittance of crystallized glass with the crystal size of $1.5mutextrm{m}$ (crystal volume fraction : 4%) presented 56% which was about 4% lower than that of parent glass.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.19.1-19.1
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• 2009

Phase change random access memory (PRAM)은 large sensing signal margin, fast programming speed, low operation voltage, high speed operation, good data retention, high scalability등을 가지는 가장 유망한 차세대 비휘발성 메모리이다. 현재 PRAM용 상변화 재료로는 주로 Ge2Sb2Te5가 사용되고 있지만 reset 전류가 높고 reliability 가 좋지 않아서 새로운 상변화 물질 연구가 필요하다. AgInSbTe (AIST)는 GST와 더불어 열에 의한 가역적 상변화를 하는 소재로 광기록 매체에서는 기록 속도가 빠르고 동작 특성이 우수하다는 특징이 있다. 본 연구에서는 XRD, 비저항측정등을 통해 온도에 따른 AIST의 물성 및 결정화 특성을 분석하고 나노 소자제작을 통해 그 전기적 특성을 평가하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.52-52
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• 2009

To date, chalcogenide alloy such as $Ge_2Sb_2Te_5$(GST) have not only been rigorously studied for use in Phase Change Random Access Memory(PRAM) applications, but also temperature gap to make different states is not enough to apply to device between amorphous and crystalline state. In this study, we have investigated a new system of phase change media based on the In-Sb-Te(IST) ternary alloys for PRAM. IST chalcogenide thin films were prepared in trench structure (aspect ratio 5:1 of length=500nm, width=100nm) using Tri methyl Indium $(In(CH_3)_4$), $Sb(iPr)_3$ $(Sb(C_3H_7)_3)$ and $Te(iPr)_2(Te(C_3H_7)_2)$ precursors. MOCVD process is very powerful system to deposit in ultra integrated device like 100nm scaled trench structure. And IST materials for PRAM can be grown at low deposition temperature below $200^{\circ}C$ in comparison with GST materials. Although Melting temperature of 1ST materials was $\sim 630^{\circ}C$ like GST, Crystalline temperature of them was ~$290^{\circ}C$; one of GST were $130^{\circ}C$. In-Sb-Te materials will be good candidate materials for PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

• 한국세라믹학회지
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• 제45권5호
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• pp.276-279
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• 2008

In this research, properties of $N_2$-doped $Sb_2Te_3$ thin film were evaluated using 4-point probe, XRD and AFM. $Sb_2Te_3$ material has faster crystallization rate than $Ge_2Sb_2Te_5$, but sheet resistance difference between amorphous and crystallization state is very low. This low sheet resistance difference decreases sensing margin in reading operation at PRAM device operation. Therefore, in order to overcome this weak point, $N_2$ gas was doped on $Sb_2Te_3$ thin film. Sheet resistance difference between amorphous and crystallized state of $N_2$-doped $Sb_2Te_3$ thin film showed about $10^4$ times higher than Un-doped $Sb_2Te_3$ thin film because of the grain boundary scattering.

• 대한전자공학회논문지
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• 제23권1호
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• pp.50-57
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• 1986

The fabricatoin sequence of GaAs MIS type diode and its electrical characteristics are presented. Used wafers were undoped GaAS wafer adn Te-doped GaAs wafer. Au and AuGe/Ni was used as schottky contact metal and ohmic contact metal respectively. Oxide layer on GaAs surface was formed by water vapor saturated oxide growth technique and dry oxidation technique. In Te-doped GaAs wafer, cutin voltage of MIS type diode was enhanced about 3V comparing with non-oxide layer diode. From light I-V characteristics fill factor of MIS type Te-doped GaAs diode was about 64%, Voc(open circuit voltage) was 0.67V.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.210-213
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• 2004

The phase transition between amorphous and crystalline states in chalcogenide semiconductor films can controlled by electric pulses or pulsed laser beam; hence some chalcogenide semiconductor films can be applied to electrically write/erase nonvolatile memory devices, where the low conductive amorphous state and the high conductive crystalline state are assigned to binary states. Memory switching in chalcogenides is mostly a thermal process, which involves phase transformation from amorphous to crystalline state. The nonvolatile memory cells are composed of a simple sandwich (metal/chalcogenide/metal). It was formed that the threshold voltage depends on thickness, electrode distance, annealing time and temperature, respectively.

• ETRI Journal
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• 제39권3호
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• pp.390-397
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• 2017

In this paper, we propose a scheme for designing a tunable pixel layer based on a $Ge_2Sb_2Te_5$ (GST) alloy thin film. We show that the phase change of GST can significantly affect the reflection characteristic when the GST film is embedded into a dielectric encapsulation layer. We investigate the appropriate positions of the GST film within the dielectric layer for high diffraction efficiency, and we prove that they are antinodes of Fabry-Perot resonance inside the dielectric layer. Using the proposed scheme, we can increase the diffraction efficiency by about ten times compared to a bare GST film pixel, and 80 times for the first-to-zeroth-order diffraction power ratio. We show that the proposed scheme can be designed alternatively for a broadband or wavelength-selective type by tuning the dielectric thickness, and we discuss a multi-phase example with a double-stack structure.