• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2453-2458
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• 2007

The performance of polysilicon thin film transistor (p-Si TFT) has an important role in the operation of active matrix liquid crystal displays. To fabricate the p-Si TFTs that have uniform characteristics, understanding of the recrystallization mechanism of silicon is crucial. Especially, the analysis of the transient temperature variation and the liquid-solid interface motion is required to find the mechanism. The thermal conductivity is one of the most important parameters to understand the mechanism. In this work, a KrF eximer laser beam was irradiated to amorphous silicon thin films. We measured the transient reflectivity at the wavelength of 633 nm. We carried out the numerical simulation of one dimension conduction equation so that we determined the most well-fitted thermal conductivity by comparing the numerically obtained transient reflectivity with the experimentally measured one. The experimentally determined thermal conductivity of amorphous silicon thin films is 1.5 W/mK.

• 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.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.117-123
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• 2014

The fabrication and characterization of a Si/ZnO thin film heterojunction ultraviolet photodiode has been presented in this paper. ZnO thin film of ~100 nm thick was deposited on <100> Silicon (Si) wafer by atomic layer deposition (ALD) technique. The Photoluminescence spectroscopy confirms that as-deposited ZnO thin film has excellent visible-blind UV response with almost no defects in the visible region. The room temperature current-voltage characteristics of the n-ZnO thin film/p-Si photodiodes are measured under an UV illumination of $650{\mu}W$ at 365 nm in the applied voltage range of ${\pm}2V$. The current-voltage characteristics demonstrate an excellent UV photoresponse of the device in its reverse bias operation with a contrast ratio of ~ 1115 and responsivity of ~0.075 A/W at 2 V reverse bias voltage.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.06a
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• pp.121-147
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• 1996

Since 1980, the water quality of ultra-pure water has been rapidly improved, and presently ultra-pore water producing equipment for 64Mbit is in operation. Table 1 shows the degree of integration of DRM and required water quality exlmple. The requirements of the ultra-pure water for 64Mbit are resistivity: 18.2 MQ/cm or higher, number of particulates: 1 pc/ml or less (0.05 $\mu$m or larger). bacteria count: 0.1 pc/l or less. TOC (Total Organic Carbon, index of organic snbstance) : 1ppb or less, dissolved oxygen: 5ppb or less, silica: 0.5ppb or less, heavy metal ions: 5ppb or less. The effect of metals on the silicon wafer has been well known, and recently it has been reported that the existence of organic substance in ultra-pure water is closely related to the device defect, drawing attention. It is reported that if organic substance sticks to the natural oxidation film, the oxide film remaims on the organic substance attachment in the hydrofluoric acid treatment (removal of natural oxidation film). The organic substance forms film on the silicon wafer, and harmful elements such as metals and N.P.S., components contained in the organic substance and the bad effect due to the generatinn of silicon carbide cannot be forgotten. In order to remove various impurities in raw water, many technological develoments (membrane, ion exchange, TOC removal, piping material, microanalysis, etc.) have been made with ultra-pure water producing equipment and put to practical use. In this paper, technologies put to practical use in recent ultra-pure vater producing equimeut are introduced.

• Advances in nano research
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• v.2 no.1
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• pp.23-56
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• 2014

The significant growth of the Si photovoltaic industry has been so far limited due to the high cost of the Si photovoltaic system. In this regard, the most expensive factors are the intrinsic cost of silicon material and the Si solar cell fabrication processes. Conventional Si solar cells have p-n junctions inside for an efficient extraction of light-generated charge carriers. However, the p-n junction is normally formed through very expensive processes requiring very high temperature (${\sim}1000^{\circ}C$). Therefore, several systems are currently under study to form heterojunctions at low temperatures. Among them, carbon nanotube (CNT)/Si hybrid solar cells are very promising, with power conversion efficiency up to 15%. In these cells, the p-type Si layer is replaced by a semitransparent CNT film deposited at room temperature on the n-doped Si wafer, thus giving rise to an overall reduction of the total Si thickness and to the fabrication of a device with cheaper methods at low temperatures. In particular, the CNT film coating the Si wafer acts as a conductive electrode for charge carrier collection and establishes a built-in voltage for separating photocarriers. Moreover, due to the CNT film optical semitransparency, most of the incoming light is absorbed in Si; thus the efficiency of the CNT/Si device is in principle comparable to that of a conventional Si one. In this paper an overview of several factors at the basis of this device operation and of the suggested improvements to its architecture is given. In addition, still open physical/technological issues are also addressed.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.56-60
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• 2006

We review our studies on the growth of microcrystalline silicon films by the standard PECVD technique. In situ spectroscopic ellipsometry studies allow the optimization of the complex film structure with respect to competing aspects of the growth process. Fine tuning the hydrogen flux, the ion energy, and the nature of the species contributing to deposition produces unique films with a fully crystallized interface with silicon nitride. These materials have been successfully incorporated in bottom gate TFTs which present mobility values in the range of 1 to 3 $cm^2/V.s$, and stable characteristics when submitted to a bias stress. The stability of these TFTs makes them suitable for driver applications in AMLCDs as well as pixel elements in OLED displays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.332-333
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• 2008

DC magnetron sputtering was used to deposit p-type polycrystalline silicon on n-type Si(100) wafer. The influence of film microstructure properties on deposition parameters (DC power, substrate temperature, pressure) was investigated. The substrate temperature and pressure have the important influence on depositing the poly-Si thin films. Smooth ploy-Si films were obtained in (331) orientation and the average grain sizes are ranged in 25-30nm. The grain sizes of films deposited at low pressure of 10mTorr are a little larger than those deposited at high pressure of 15mTorr.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.48-53
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• 1996

We present a microscopic description for generation of 1/f noise in interfaces between cobalt thin film and silicon substrate. Along with surface resistance measurements and transmission electron diffraction observations. 1/f noise power spectral density has been measured for the interfacial structures at the liquid nitrogen temperature . The cobalt films have been deposited by the electron-beam evaporation technique onto p-type (100) silicon in the high vacuum condition. The measured noise power spectral density shows highest magnitude near the structural transition and metallization transition region. The noise magnitude rapidly decreased after the cobalt silicide nucleation. The noise parameter is concluded to be originated form the structural fluctuations.

• Journal of Surface Science and Engineering
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• v.23 no.1
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• pp.34-43
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• 1990

Al-Si piston alloys such as AlS10CuMg have been anodized to examine apossibility of forming a hard film aat relatively higher temperatures compard with those in conventional sulfuric acid processes. Three types of electrolytes have been employed in this study ; electrolyte A(15% H2SO4, $0^{\circ}C$), electrolyte B(12% H2SO4, 1% oxalic, $10^{\circ}C$), electrolyte C(tartaric acid 125g/L+oxalic 75g/L+aluminum sulfate 225g/L, $25^{\circ}C$). Hard anodisine process in electrolyte B at a current density of 1.54A/dm2 produced a harder film of VHN 396 at a relatibely low film forming voltage compared with those obtained in other electrolyte at equivalent current density. A liner relationship between hardness and abrasion resistance exists for Al-Si piston alloys. The hardness of anodized film decreasees with increasing silicon content in Al-Si alloys and also with bath temperature. The film hardeness of Na-modified alloy os higher than that of P-modified alloy due to its finer microstructre. The film on the silicon phase in Al-Si alloys is observed to be formed by lateral growth of oxide film nucleated at surroundings.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.130-136
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• 1989

Electrical transport and thermally induced metastability in hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) using boron-doped amorphous silicon as an active layer have been studied. The device characteristics n-channel and p-channel operations. The thermal quenching experiments on amorphous silicon-silicon nitride ambipolar TFT give clear evidence for the co-existence of two distinct metastable changes. The densities of metastable active dopants and dangling bonds increase with the quenching temperature. On the other hand, the interface state density appears to decrease with increasing quenching temperature.