• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.75.2-75.2
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• 2010

We studied the fabrication of polycrystalline silicon (pc-Si) films as seed layers for application of pc-Si thin film solar cells, in which amorphous silicon (a-Si) films in a structure of glass/Al/$Al_2O_3$/a-Si are crystallized by the aluminum-induced layer exchange (ALILE) process. The properties of pc-Si films formed by the ALILE process are strongly determined by the oxide layer as well as the various process parameters like annealing temperature, time, etc. In this study, the effects of the oxide film thickness on the crystallization of a-Si in the ALILE process, where the thickness of $Al_2O_3$ layer was varied from 4 to 50 nm. For preparation of the experimental film structure, aluminum (~300 nm thickness) and a-Si (~300 nm thickness) layers were deposited using DC sputtering and PECVD method, respectively, and $Al_2O_3$ layer with the various thicknesses by RF sputtering. The crystallization of a-Si was then carried out by the thermal annealing process using a furnace with the in-situ microscope. The characteristics of the produced pc-Si films were analyzed by optical microscope (OM), scanning electron microscope (SEM), Raman spectrometer, and X-ray diffractometer (XRD). As results, the crystallinity was exponentially decayed with the increase of $Al_2O_3$ thickness and the grain size showed the similar tendency. The maximum pc-Si grain size fabricated by ALILE process was about $45{\mu}m$ at the $Al_2O_3$ layer thickness of 4 nm. The preferential crystal orientation was <111> and more dominant with the thinner $Al_2O_3$ layer. In summary, we obtained a pc-Si film not only with ${\sim}45{\mu}m$ grain size but also with the crystallinity of about 75% at 4 nm $Al_2O_3$ layer thickness by ALILE process with the structure of a glass/Al/$Al_2O_3$/a-Si.

• 한국재료학회지
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• 제22권4호
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• pp.190-194
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• 2012

The formation of high-quality polycrystalline silicon (poly-Si) on relatively low cost substrate has been an important issue in the development of thin film solar cells. Poly-Si seed layers were fabricated by an inverse aluminum-induced crystallization (I-AIC) process and the properties of the resulting layer were characterized. The I-AIC process has an advantage of being able to continue the epitaxial growth without an Al layer removing process. An amorphous Si precursor layer was deposited on Corning glass substrates by RF magnetron sputtering system with Ar plasma. Then, Al thin film was deposited by thermal evaporation. An $SiO_2$ diffusion barrier layer was formed between Si and Al layers to control the surface orientation of seed layer. The crystallinity of the poly-Si seed layer was analyzed by Raman spectroscopy and x-ray diffraction (XRD). The grain size and orientation of the poly-Si seed layer were determined by electron back scattering diffraction (EBSD) method. The prepared poly-Si seed layer showed high volume fraction of crystalline Si and <100> orientation. The diffusion barrier layer and processing temperature significantly affected the grain size and orientation of the poly Si seed layer. The shorter oxidation time and lower processing temperature led to a better orientation of the poly-Si seed layer. This study presents the formation mechanism of a poly seed layer by inverse aluminum-induced crystallization.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1116-1118
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• 2005

We studied laser crystallization of amorphous silicon films prepared at ultra low temperatures ($<150^{\circ}C$). Amorphous silicon films having a low content of hydrogen were deposited by using catalytic chemical vapor deposition method. Influence of process parameters on the hydrogen content was investigated. Laser crystallization was performed dispensing with the preliminary dehydrogenation process. Crystallization took place at a laser energy density value as low as $70\;mJ/cm^2$, and the grain size increased with increasing the laser energy. The ELA crystallization of Catalytic CVD a-Si film is a promising candidate for Poly-Si TFT in active-matrix flexible display on plastic substrates.

• 전자공학회논문지D
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• 제34D권5호
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• pp.45-51
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• 1997

Low temperature activation of dopants which were doped using ion mass doping system in amorphous silicon(a-Si) thin films was investigated. With a 20.angs.-thick Ni film on top of the a-Si thin film, the activation temperature of dopants lowered to 500.deg. C. When the doping was performaed after the deposition of Ni thin film on the a-Si thin films (post-doping), the activation time was shorter than that of dopants mass, the activation time of the dopants doped by pre-doping method increased. It turned NiSi2 formation, while the decrease of activation time was mainly due to the enhancement of the NiSi2 formation by mixing of Ni and a-Si at the interface of Ni and a -Si thin during the ion doping process.

• 한국전기전자재료학회논문지
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• 제13권2호
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• pp.95-100
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• 2000

For the well-controlled growing in-situ heavily phosphorus doped polycrystalline Si films directly on Si wafer by reduced pressure chemical vapor deposition, a study is made of the two step growth. When in-situ heavily phosphorus doped Si films were deposited directly on Si (100) wafer, crystal structure in the film is not unique, that is, the single crystal to polycrystalline phase transition occurs at a certain thickness. However, the well-controlled polycrtstalline Si films deposited by two step growth grew directly on Si wafers. Moreover, the two step growth, which employs crystallization of grew directly on Si wafers. Moreover, the two step growth which employs crystallization of amorphous silicon layer grown at low temperature, reveals crucial advantages in manipulating polycrystal structures of in-situ phosphorous doped silicon.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.396-396
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• 2007

Highly ordered pore structures as a template for formation of seeds have been prepared by the self-organization process of aluminum oxidation. The a-Si films were deposited on the anodic alumina films and crystallized by laser irradiation. It was found that un-melted part of fine poly-Si grain formed by explosive crystallization (EX) lead super lateral growth(SLG) and occluded with neighbor grains. The crystallized grains along the distribution of seeds were obtained. This results show a great potential for use in novel crystallization for decently uniform polycrystalline Si thin film transistors (poly-Si TFTs).

• 센서학회지
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• 제6권6호
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• pp.483-490
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• 1997

Thin film Si has been used in sensors, radiation detectors, and solar cells. The carrier mobility of thin film Si influences the device behavior through its frequency response or time response. Since poly-Si shows the higher mobility value, a-Si:H films on Mo substrate were subjected to various crystallization treatments. Consequently, we need to find an appropriate method in mobility measurement before and after the anneal treatment. This paper investigates the carrier mobility improvement with anneal treatments and summarizes the mobility measurement methods of the a-Si:H and poly-Si film. Various techniques were investigated for the mobility determination such as Hall mobility, HS, TOF, SCLC, TFT, and TCO method. We learned that TFT and TCO method are suitable for the mobility determination of a-Si:H and poly-Si film. The measured mobility was improved by $2{\sim}3$ orders after high temperature anneal above $700^{\circ}C$ and grain boundary passivation using an RF plasma rehydrogenation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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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.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.65-66
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• 2000

Various fluoride films on a glass substrate were prepared and characterized to provide a seed layer for crystalline Si film growth. The XRD analysis on $CaF_2/glass$ illustrated (220) preferential orientation and showed lattice mismatch less than 5 % with Si. We achieved a fluoride film with breakdown electric field of 1.27 MV/cm, leakage current density about $10^{-6}$ $A/cm^2$, and relative dielectric constant less than 5.6. This paper demonstrates microcrystalline silicon $({\mu}c-Si)$ film growth by using a $CaF_2/glass$ substrate. The ${\mu}c-Si$ films exhibited crystallization in (111) and (220) planes, grain size of $700\;{\AA}$, crystalline volume fraction over 65 %, dark- and photo-conductivity ratio of 124, activation energy of 0.49 eV, and dark conductivity less than $4{\times}10^{-7}$ S/cm.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1329-1333
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• 2018

We investigated the mechanism of mobility enhancement after the dehydrogenation process in polycrystalline silicon (poly-Si) thin films. The dehydrogenation process was performed by using an in-situ CVD chamber in a $N_2$ ambient or an ex-situ furnace in air ambient. We observed that the dehydrogenated poly-Si in a $N_2$ ambient had a lower oxygen concentration than the dehydrogenated poly-Si annealed in an air ambient. The in-situ dehydrogenation increased the (111) preferred orientation of poly-Si and reduced the oxygen concentration in poly-Si thin films, leading to a reduction of the trap density near the valence band. This phenomenon gave rise to an increase of the field-effect mobility of the poly-Si thin film transistor.