• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.1-10
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• 1997

It is well-known that rectangular bulk-Si sensors prepared by etch or epi etch-stop micromachining technology are already in practical use today, but the conventional bulk-Si sensor shows some drawbacks such as large chip size and limited applications as silicon sensor device is to be miniaturized. We consider a circular-shape SOI(Silicon-On-Insulator) micro-cavity technology to facilitate multiple sensors on very small chip, to make device easier to package than conventional sensor like pressure sensor and to provide very high over-pressure capability. This paper demonstrates the cross-functional results for stress analyses(targeting $5{\mu}m$ deflection and 100MPa stress as maximum at various applicable pressure ranges), for finding permissible diaphragm dimension by output sensitivity, and piezoresistive sensor theory from two-type SOI structures where the double SOI structure shows the most feasible deflection and small stress at various ambient pressures. Those results can be compared with the ones of circular-shape bulk-Si based sensor$^{[17]}. The SOI micro-cavity formed the sensors is promising to integrate with calibration, gain stage and controller unit plus high current/high voltage CMOS drivers onto monolithic chip.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.65-70
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• 2006

Characteristics of thin-film NTC thermal sensors fabricated by micromachining technology were studied as a function of the thickness of membrane. The overall-structure of thermal sensor has a form of Au/Ti/NTC/$SiO_{X}$/(100)Si. NTC film of $Mn_{1.5}CoNi_{0.5}O_{4}$ with 0.5 mm in thickness was deposited on $SiO_{X}$ layer (1.2 mm) by PLD (pulsed laser deposition) and annealed at 873-1073 K in air for 1 hour. Au(200 nm)/Ti(100 nm) electrode was coated on NTC film by dc sputtering. By the results of microstructure, X-ray and NTC analysis, post-annealed NTC films at 973 K for 1 hour showed the best characteristics as NTC thermal sensing film. In order to reduce the thermal mass and thermal time constant of sensor, the sensing element was built-up on a thin membrane with the thickness of 20-65 mm. Sensors with thin sensing membrane showed the good detecting characteristics.

• Journal of the Semiconductor & Display Technology
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• v.11 no.4
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• pp.19-23
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• 2012

We report microbolometer characteristic with n-type and p-type amorphous silicon thin film. The n-type and p-type amorphous silicon thin films were made by PECVD. The electrical properties of n-type and p-type a-Si:H thin films were investigated as a function of doping gas flow rate. The doping gas used $B_2H_6/Ar$ (1:9) and $PH_3/Ar$ (1:9). In general, the conductivity of doping a-Si:H thin films increased as doping gas increase but the conductivity of a-Si:H thin films decreased as the doping gas increase because doping gas concentration increase led to dilution gas (Ar) increase as the same time. We fabricated an amorphous silicon microbolometer using surface micromachining technology. The fabricated microbolometer had a negative TCR of 2.3%. The p-type microbolometer had responsivity of $5{\times}10^4V/W$ and high detectivity of $3{\times}10^8cm(Hz)^{1/2}/W$. The p-type microbolometer had more detectivity than n-type for less noise value.

• Journal of Sensor Science and Technology
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• v.7 no.5
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• pp.356-363
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• 1998

Using the results analyzed by FEM(Finite Element Method). the microheaters with the stress-balanced $Si_3N_4$(150 nm)/$SiO_2$(300 nm)/$Si_3N_4$(150 nm) diaphragms were fabricated by silicon micromachining techniques. Pt was used as microheater materials. Pt temperature sensor was fabricated to measure the temperature of microheaters. Resistance of temperature sensor and power dissipation of microheater were measured and calculated at the various temperatures. The thermal distribution of heater was examined by a IR thermoviewer. Measured and simulated results are compared and analyzed. The temperature coefficient of resistance of heater was about $0.00379/^{\circ}C$. Pt heater showed the power dissipation of about 51 mW at $300^{\circ}C$ and a uniform thermal distribution on the surface.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.59.1-59.1
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• 2010

Aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) is studied with the structure of a glass/Al/$SiO_2$/a-Si, in which the $SiO_2$ layer has micron-sized laser holes in the stack. An oxide layer between aluminum and a-Si thin films plays a significant role in the metal-induced crystallization (MIC) process determining the properties such as grain size and preferential orientation. In our case, the crystallization of a-Si is carried out only through the key hole because the $SiO_2$ layer is substantially thick enough to prevent a-Si from contacting aluminum. The crystal growth is successfully realized toward the only vertical direction, resulting a crystalline silicon grain with a size of $3{\sim}4{\mu}m$ under the hole. Lateral growth seems to be not occurred. For the AIC experiment, the glass/Al/$SiO_2$/a-Si stacks were prepared where an Al layer was deposited on glass substrate by DC sputter, $SiO_2$ and a-Si films by PECVD method, respectively. Prior to the a-Si deposition, a $30{\times}30$ micron-sized hole array with a diameter of $1{\sim}2{\mu}m$ was fabricated utilizing the femtosecond laser pulses to induce the AIC process through the key holes and the prepared workpieces were annealed in a thermal chamber for 2 hours. After heat treatment, the surface morphology, grain size, and crystal orientation of the polycrystalline silicon (pc-Si) film were evaluated by scanning electron microscope, transmission electron microscope, and energy dispersive spectrometer. In conclusion, we observed that the vertical crystal growth was occurred in the case of the crystallization of a-Si with aluminum by the MIC process in a small area. The pc-Si grain grew under the key hole up to a size of $3{\sim}4{\mu}m$ with the workpiece.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1442-1444
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• 1995

In this study, we confirmed that the crystallinity and the mechanical properties of polycrystalline Silicon(poly-Si) deposited on the poly-oxide are better than those of poly-Si on the conventional sacrificial layers that is CVD oxide layer or PSG. But the etch rate of poly-oxide is poor than that of the CVD oxide layer or PSG. Therefore, to make the best use of small stress and fast etch rate, we fabricated the double oxide layer; 10%-thick poly-oxide on 90%-thick CVD oxide or PSG. To estimate structure deformation by stress, we fabricated the test structures; cantilever. bridge and ring/beam structure and estimated by SEM. As the results, all structure is expressed the deformed structure by residual stress(tensile stress) and the deformation of the structure layer on the double oxide layer is small compared with that of the structure layer on the CVD oxide layer or PSG. And, the etch rate of the double oxide layer is enhanced compared with that of the poly-oxide.

• Transactions on Electrical and Electronic Materials
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• v.7 no.4
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• pp.157-162
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• 2006

Chemical-mechanical polishing (CMP), one of the dominant technology for ULSI planarization, is used to flatten the micro electro-mechanical systems (MEMS) structures. The objective of this paper is to achieve good planarization of the deposited film and to improve deposition efficiency of subsequent layer structures by using surface-micromachining process in MEMS technology. Planarization characteristic of poly-Si film deposited on thin oxide layer with MEMS structures is evaluated with different slurries. Patterns used for this research have shapes of square, density, line, hole, pillar, and micro engine part. Advantages of CMP process for MEMS structures are observed respectively by using the test patterns with structures larger than 1 urn line width. Preliminary tests for material selectivity of poly-Si and oxide are conducted with two types of silica slurries: $ILD1300^{TM}\;and\;Nalco2371^{TM}$. And then, the experiments were conducted based on the pretest. A selectivity and pH adjustment of slurry affected largely step heights of MEMS structures. These results would be anticipated as an important bridge stone to manufacture MEMS CMP slurry.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.271-275
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• 2008

The MAM(Megasonic Agitated Module) has been fabricated for improving the characteristics of wet etching. The characteristics of the MAM are investigated during the wet etching with and without megasonic agitation in this paper. The adoption of the MAM has improved the characteristics of wet etching, such as the etch rate, etch uniformity, and surface roughness. Especially, the etching uniformity on the entire wafer was less than ${\pm}1%$ in both cases of Si and glass. Generally, the initial root-mean-square roughness($R_{rms}$) of the single crystal silicon was 0.23nm. Roughnesses of 566nm and 66nm have been achieved with magnetic stirring and ultrasonic agitation, respectively, by some researchers. In this paper, the roughness of the etched Si surface is less than 60 nm. Wet etching of silicon with megasonic agitation can maintain nearly the original surface roughness during etching. The results verified that megasonic agitation is an effective way to improve etching characteristics of the etch rate, etch uniformity, and surface roughness and that the developed micromachining system is suitable for the fabrication of devices with complex structures.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.20-23
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• 2003

Piezoelectric powder with the composition of PbTiO$_3$-PbZrO$_3$-Pb(Mn$\_$1/3/Nb$\_$2/3/)O$_3$ and small particle size of 0.3 $\mu\textrm{m}$ was investigated for low-temperature firing of PZT thick films. PbTiO$_3$-PbZrO$_3$-Pb(Mn$\_$1/3/Nb$\_$2/3)O$_3$ ceramics showed dense microstructure and superior piezoelectric properties, electromechanical coupling factor (k$\_$p/) of 0.501 and piezoelectric constant (d$\_$33/) of 224. The PZT paste was made of the powder and organic vehicles, and screen-printed on Pt(450nm)/YSZ(110nm)/SiO$_2$(300nm)/Si substrates and fired at 800∼900$^{\circ}C$. Any interface reaction between the PZT thick film and the bottom electrode was not observed in the PZT thick films. The PZT thick film fired at 800$^{\circ}C$ showed moderate electrical properties, the remanent polarization(p$\_$r/) of 16.0 ${\mu}$C/$\textrm{cm}^2$, the coercive field(E$\_$c/) of 36.7 ㎸/cm, and dielectric constant ($\varepsilon$$\_$r/) of 531. Low-temperature sinterable piezoelectric composition and high activity of fine particles reduced the sintering temperature of the thick film. This PZT thick film could be utilized for piezoelectric microactuators or microsensors that require Si micromachining technology.

• Journal of the Korean Vacuum Society
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• v.8 no.4A
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• pp.465-469
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• 1999

In this paper, spacer process for FED (Field Emission Display ) was developed with the glass to glass anodic bonding technology using Al film as an interlayer. Characteristics, current density-time curves and force of the anodic boding were measured on various thickness of Al film; 1000$\AA$, 2000$\AA$, 3000$\AA$, 4000$\AA$ and 500$\AA$. Holders for spacer were fabricated with photosensitive glass and (110) Si wafer by bulk micromachining. Spacers was formed on glass substrate by spacer glass to glass anodic bonding and an evacuated panel was fabricated to prove the potential of application for FED.