• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.65-66
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• 2008

The realization and origin of p-type ZnO are main issue for photoelectronic devices based on ZnO material. N-doped and nominally undoped p-type ZnO films were achieved on silicon (100) and homo-buffer layers by RF magnetron sputtering and post in-situ annealing. The undoped film shows high hole mobility of 1201 $cm^2V^{-1}s^{-1}$ and low resistivity of $0.0454\Omega{\cdot}cm$ with hole concentration of $1.145\times10^{17}cm^{-3}$. The photoluminescence(PL) spectra show the emissions related to FE, DAP and defects of $V_{Zn}$, $V_O$, $Zn_O$, $O_i$ and $O_{Zn}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.418-418
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• 2008

The electrochemical etching of silicon in HF-based solutions is known to form various types of porous structures. Porous structures are generally classified into three categories according to pore sizes: micropore (below 2 nm in size), mesopore (2 ~ 50 nm), and macropore (above 50 nm). Recently, the formation of macropores has attracted increasing interest because of their promising characteristics for an wide scope of applications such as microelectromechanical systems (MEMS), chemical sensors, biotechnology, photonic crystals, and photovoltaic application. One of the promising applications of macropores is in the field of MEMS. Anisotropic etching is essential step for fabrication of MEMS. Conventional wet etching has advantages such as low processing cost and high throughput, but it is unsuitable to fabricate high-aspect-ratio structures with vertical sidewalls due to its inherent etching characteristics along certain crystal orientations. Reactive ion dry etching is another technique of anisotropic etching. This has excellent ability to fabricate high-aspect-ratio structures with vertical sidewalls and high accuracy. However, its high processing cost is one of the bottlenecks for widely successful commercialization of MEMS. In contrast, by using electrochemical etching method together with pre-patterning by lithographic step, regular macropore arrays with very high-aspect-ratio up to 250 can be obtained. The formed macropores have very smooth surface and side, unlike deep reactive ion etching where surfaces are damaged and wavy. Especially, to make vertical microwire or nanowire arrays (aspect ratio = over 1:100) on silicon wafer with top-down photolithography, it is very difficult to fabricate them with conventional dry etching. The electrochemical etching is the most proper candidate to do it. The pillar structures are demonstrated for n-type silicon and the formation mechanism is well explained, while such a experimental results are few for p-type silicon. In this report, In order to understand the roles played by the kinds of etching solution and mask patterns in the formation of microwire arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, dimethyl sulfoxide (DMSO), iso-propanol, and mixtures of HF with water on the structure formation on monocrystalline p-type silicon with a resistivity with 10 ~ 20 $\Omega{\cdot}cm$. The different morphological results are presented according to mask patterns and etching solutions.

• Journal of Integrative Natural Science
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• v.3 no.3
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• pp.168-173
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• 2010

Novel porous silicon chip exhibiting dual optical properties, both Frbry-Perot fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type sillicon wafer (boron-doped, <100> orientation, resistivity 1 - 10 ${\Omega}$). The ething solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF (48% by weight). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Ething was carried out as a two-electrode Kithley 2420 preocedure at an anodic current. The surface of porous silicon was characterized by FT-IR instrument. The porosity of samples was about 80%. Three different types of porous silicon, fresh porous silicon (Si-H termianated), oxidized porous silicon (Si-OH terminated), and surface-derivatized porous silicon (Si-R terminated), were prepared by the thermal oxidation and hydrosilylation. Then the samples were exposed to the wapor of various organics vapors. such as chloroform, hexane, methanol, benzene, isopropanol, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic wapors.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1049-1055
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• 1999

Electrochemical oxidation of silicon (p-type Si(100)) at room temperature in ethylene glycol and in aqueous solutions has been performed by applying constant low current densities for the preparation of thin SiO2 layers. In-situ ac impedance spectroscopic methods have been employed to characterize the interfaces of electrolyte/oxide/semiconductor and to estimate the thickness of the oxide layer. The thicknesses of SiO2 layers calculated from the capacitive impedance were in the range of 25-100Å depending on the experimental conditions. The anodic polarization resistance parallel with the oxide layer capacitance increased continuously to a very large value in ethylene glycol solution. However, it decreased above 4 V in aqueous solutions, where oxygen evolved through the oxidation of water. Interstitially dissolved oxygen molecules in SiO2 layer at above the oxygen evolution potential were expected to facilitate the formation of SiO2 at the interfaces. Thin SiO2 films grew efficiently at a controlled rate during the application of low anodization currents in aqueous solutions.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.169-172
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• 2003

Silicon nanocrystalline thin films on p-type (100) silicon substrate have been fabricated by pulsed laser deposition technique using a Nd:YAG laser with the wavelength of 355, 532, and 1064 nm. The base vacuum in the chamber was down to $10^-6$ Torr and the laser energy densities were 1.0~3.0 J/$\textrm{cm}^2$ After deposition, silicon nanocrystalline thin films have been annealed at nitrogen gas. Strong Blue and green luminescence from silicon nanocrystalline thin films have been observed at room temperature by photoluminescence and its peak energies shift to green when the wavelength is increased from 355 to 1064 nm.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.465-468
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• 1998

For porous silicon layer to be used as active layer in various devices, it is necessary to be formed locally along with a designed pattern on the wafer. However, there is still no suitable masking layer to withstand against the high concentration of HF for a time of some minutes up to some hours during the anodic process effectively. In this work, we investigated the property of selectivity between p$^{+}$ and n layers to form localized porous silicon even without a mask by the difference of the anodic I-V characteristics on the doping level and doping type. The width of the pattern made in the sample was 2mm, and the formed porous silicon layer was observed by SEM to see the morphology on the cross section below the surface. As the results, it was found that the selectivity was reasonable for the pattern size over 100.mu.m.m.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.4
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• pp.361-364
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• 2008

Tips of probe card were fabricated using MEMS technology. P-type silicon wafer with $SiO_2$ layer was used as a substrate for fabricating the probe card. Ni-Cr and Au used as seed layer for electroplating Ni were deposited on the silicon wafer. Line patterns for probing devices were formed on silicon wafer by electroplating Ni through mold which formed by MEMS technology. Bridge structure was formed by wet-etching the silicon substrate. AZ-1512 photoresist was used for protection layer of back side and DNB-H100PL-40 photoresist was used for patterning of the front side. The mold with the thickness of $60{\mu}m$ was also formed using THB-120N photoresist and probe tip with thickness of $50{\mu}m$ was fabricated by electroplating process.

• Mass Spectrometry Letters
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• v.12 no.2
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• pp.47-52
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• 2021

Evaluating the impurity concentrations in semiconductor thin films using time of flight secondary ion mass spectrometry (ToF-SIMS) is an effective technique. The mass interference between isotopes and matrix element in data interpretation makes the process complex. In this study, we have investigated the doping concentration of phosphorus in, phosphorus doped silicon thin film on glass using ToF-SIMS in the dynamic mode of operation. To overcome the mass interference between phosphorus and silicon isotopes, the quantitative analysis of counts to concentration conversion was done following two routes, standard relative sensitivity factor (RSF) and SIMetric software estimation. Phosphorus doped silicon thin film of 180 nm was grown on glass substrate using hot wire chemical vapor deposition technique for possible applications in optoelectronic devices. Using ToF-SIMS, the phosphorus-31 isotopes were detected in the range of 10¹~10⁴ counts. The silicon isotopes matrix element was measured from p-type silicon wafer from a separate measurement to avoid mass interference. For the both procedures, the phosphorus concentration versus depth profiles were plotted which agree with a percent difference of about 3% at 100 nm depth. The concentration of phosphorus in silicon was determined in the range of 10¹⁹~10²¹ atoms/cm³. The technique will be useful for estimating distributions of various dopants in the silicon thin film grown on glass using ToF-SIMS overcoming the mass interference between isotopes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.754-759
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• 2013

Aluminum oxide($Al_2O_3$) film deposited by atomic layer deposition (ALD) is known to supply excellent surface passivation properties on crystalline Si surfaces. Since $Al_2O_3$ has fixed negative charge, it forms effective surface passivation by field effect passivation on the rear side in p-type silicon solar cell. However, $Al_2O_3$ layer formed by ALD process needs very long process time, which is not applicable in mass production of silicon solar cells. In this paper, plasma-assisted ALD(PA-ALD) was applied to form $Al_2O_3$ to reduce the process time. $Al_2O_3$ synthesized by ALD on c-Si (100) wafers contains a very thin interfacial $SiO_2$ layer, which was confirmed by FTIR and TEM. To improve passivation quality of $Al_2O_3$ layer, the deposition temperature was changed in range of $150{\sim}350^{\circ}C$, then the annealing temperature and time were varied. As a result, the silicon wafer with aluminum oxide film formed in $250^{\circ}C$, $400^{\circ}C$ and 10 min for the deposition temperature, the annealing temperature and time, respectively, showed the best lifetime of 1.6ms. We also observed blistering with nanometer size during firing of $Al_2O_3$ deposited on p-type silicon.

• New & Renewable Energy
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• v.2 no.2 s.6
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• pp.4-8
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• 2006

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layer were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The surface morphology of porous Si layers were investigated using SEM. The formation of a porous Si layer about $0.1{\mu}m$ thick on the textured silicon wafer result in an effective reflectance coefficient Reff lower than 5% in the wavelength region from 400 to 1000nm. Such a surface modification allows improving the Si solar cell characteristics.