• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.581-588
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• 2013

This paper presents a study of the process temperature dependence of $Al_2O_3$ film grown by thermal atomic layer deposition (ALD) as a passivation layer in the crystalline Si (c-Si) solar cells. The deposition rate of $Al_2O_3$ film maintained almost the same until $250^{\circ}C$, but decreased from $300^{\circ}C$. $Al_2O_3$ film deposited at $250^{\circ}C$ was found to have the highest negative fixed oxide charge density ($Q_f$) due to its O-rich condition and low hydroxyl group (-OH) density. After post-metallization annealing (PMA), $Al_2O_3$ film deposited at $250^{\circ}C$ had the lowest slow and fast interface trap density. Actually, $Al_2O_3$ film deposited at $250^{\circ}C$ showed the best passivation effects, that is, the highest excess carrier lifetime (${\tau}_{PCD}$) and lowest surface recombination velocity ($S_{eff}$) than other conditions. Therefore, $Al_2O_3$ film deposited at $250^{\circ}C$ exhibited excellent chemical and field-effect passivation properties for p-type c-Si solar cells.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.53-60
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• 2014

Different kinds of post-deposition annealing (PDA) by a rapid thermal process (RTP) are used to enhance the field-effect passivation of $Al_2O_3$ film in crystal Si solar cells. To characterize the effects of PDA on $Al_2O_3$ and the interface, metal-insulator semiconductor (MIS) devices were fabricated. The effects of PDA were characterized as functions of RTP temperature from $400{\sim}700^{\circ}C$ and RTP time from 30~120 s. A high temperature PDA can retard the passivation of thin $Al_2O_3$ film in c-Si solar cells. PDA by RTP at $400^{\circ}C$ results in better passivation than a PDA at $400^{\circ}C$ in forming gas ($H_2$ 4% in $N_2$) for 30 minutes. A high thermal budget causes blistering on $Al_2O_3$ film, which degrades its thermal stability and effective lifetime. It is related to the film structure, deposition temperature, thickness of the film, and annealing temperature. RTP shows the possibility of being applied to the PDA of $Al_2O_3$ film. Optimal PDA conditions should be studied for specific $Al_2O_3$ films, considering blistering.

• Journal of Korean Vacuum Science & Technology
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• v.5 no.1
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• pp.11-18
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• 2001

Dielectric passivation effects on the EM(electromigration) have been a great interest with recent ULSI and multilevel structure tends in thin film interconnections of a microelectronic device. SiO$_2$, PSG(phosphosilicate glass), and Si$_3$N$_4$ passivation materials effects on the EM resistance were investigated by utilizing widely used Al-1%Si thin film interconnections. A standard photolithography process was applied for the fabrication of 0.7㎛ thick 3㎛ wide, and 200㎛ ~1600㎛ long Al-1%Si EM test patterns. SiO$_2$, PSG, and Si$_3$N$_4$ dielectric passivation with the thickness of 300 nm were singly deposited onto the Al-1%Si thin film interconnections by using an APCVD(atmospheric pressure chemical vapor deposition) and a PECVD(plasma enhanced chemical vapor deposition) in order to investigate the passivation materials effects on the EM characteristics. EM tests were performed at the direct current densities of 3.2 $\times$ 10$\^$6/∼4.5 $\times$ 10$\^$6/ A/cm$^2$ and at the temperatures of 180 $\^{C}$, 210$\^{C}$, 240$\^{C}$, and 270$\^{C}$ for measuring the activation energies(Q) and for accelerated test conditions. Activation energies were calculated from the measured MTF(mean-time-to-failure) values. The calculated activation energies for the electromigration were 0.44 eV, 0.45 eV, and 0.50 eV, and 0.66 eV for the case of nonpassivated-, Si$_3$N$_4$passivated-, PSG passivated-, and SiO$_2$ passivated Al-1%Si thin film interconnections, respectively. Thus SiO$_2$ passivation showed the best characteristics on the EM resistance followed by the order of PSG, Si$_3$N$_4$ and nonpassivation. It is believed that the passivation sequences as well as the passivation materials also influence on the EM characteristics in multilevel passivation structures.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.339-344
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• 2017

Highly corrosion resistance performance of CrAlSiN coatings were obtained by applying ultrathin $Al_2O_3$ thin films using atomic layer deposition (ALD) method. CrAlSiN coatings were prepared on Cr adhesion layer/SUS304 substrates by a hybrid coating system of arc ion plating and high power impulse magnetron sputtering (HiPIMS) method. And, ultrathin $Al_2O_3$ passivation layer was deposited on the CrAlSiN/Cr adhesion layer/SUS304 sample to protect CrAlSiN coatings by encapsulating the whole surface defects of coating using ALD. Here, the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray spectrometry (EDX) analysis revealed that the ALD $Al_2O_3$ thin films uniformly covered the inner and outer surface of CrAlSiN coatings. Also, the potentiodynamic and potentiostatic polarization test revealed that the corrosion protection properties of CrAlSiN coatings/Cr/SUS304 sample was greatly improved by ALD encapsulation with 50 nm-thick $Al_2O_3$ thin films, which implies that ALD-$Al_2O_3$ passivation layer can be used as an effect barrier layer of corrosion.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.40-47
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• 2014

In this paper, $Al_2O_3$ film deposited by thermal atomic layer deposition (ALD) with diluted $NH_4OH$ instead of $H_2O$ was suggested for passivation layer and anti-reflection (AR) coating of the p-type crystalline Si (c-Si) solar cell application. It was confirmed that the deposition rate and refractive index of $Al_2O_3$ film was proportional to the $NH_4OH$ concentration. $Al_2O_3$ film deposited with 5 % $NH_4OH$ has the greatest negative fixed oxide charge density ($Q_f$), which can be explained by aluminum vacancies ($V_{Al}$) or oxygen interstitials ($O_i$) under O-rich condition. $Al_2O_3$ film deposited with $NH_4OH$ 5 % condition also shows lower interface trap density ($D_{it}$) distribution than those of other conditions. At $NH_4OH$ 5 % condition, moreover, $Al_2O_3$ film shows the highest excess carrier lifetime (${\tau}_{PCD}$) and the lowest surface recombination velocity ($S_{eff}$), which are linked with its passivation properties. The proposed $Al_2O_3$ film deposited with diluted $NH_4OH$ is very promising for passivation layer and AR coating of the p-type c-Si solar cell.

• Journal of the Semiconductor & Display Technology
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• v.12 no.3
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• pp.41-46
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• 2013

Efficient and inexpensive solar cells are necessary for photo-voltaic to be widely adopted for mainstream electricity generation. For this to occur, the recombination losses of charge carriers (i.e. electrons or holes) must be minimized using a surface passivation technique suitable for manufacturing. Recently it has been shown that aluminum oxide thin films are negatively charged dielectrics that provide excellent surface passivation of silicon solar cells to attract positive-charged holes. Especially aluminum oxide thin film is a quite suitable passivation on the rear side of p-type silicon solar cells. This paper, it demonstrate the interfacial microstructure and electrical properties of mono-crystalline silicon surface passivated by $Al_2O_3$ films during firing process as applied for screen-printed solar cells. The first task is a comparison of the interfacial microstructure and chemical bonds of PECVD $Al_2O_3$ and of PEALD $Al_2O_3$ films for the surface passivation of silicon. The second is to study electrical properties of double-stacked layers of PEALD $Al_2O_3$/PECVD SiN films after firing process in the temperature range of $650{\sim}950^{\circ}C$.

• Journal of the Semiconductor & Display Technology
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• v.12 no.3
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• pp.47-51
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• 2013

Current research trends of solar cells has focused on the high conversion efficiency and low-cost production technology. Passivation technology that can be easily adapted to mass production. Therefore, this study conducted experiments with aim of the following two methods for the fabrication of high-efficiency crystalline silicon solar cells. In the first task, an attempt is formation of local Al-BSF to a number of locally doped dots to increase the conversion efficiency of solar cells to reduce the loss of $V_{oc}$ overcome. The second major task, rear surface apply in $Al_2O_3/SiN_x$ stack layer, $Al_2O_3$ prominent negative fixed charge characteristics. As the result of task, Local Al-BSF and $Al_2O_3/SiN_x$ stack layer applied to the p-type single crystalline silicon solar cells, the average $V_{oc}$ of 644mV, $I_{sc}$ of 918mV and conversion efficiency of 18.70% were obtained.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.219-224
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• 2017

The K gettering in $SiO_2/PSG/SiO_2/Al-1%Si$ multilevel thin films was investigated using SIMS(secondary ion mass spectrometry) and XPS(X-ray Photoelectron Spectroscopy) analysis. DC magnetron sputter techniques and APCVD(atmosphere pressure chemical vapor deposition) were utilized for the deposition of Al-1%Si thin films and $SiO_2/PSG/SiO_2$ passivations, respectively. Heat treatment was carried out at $400^{\circ}C$ for 5 h in air. SIMS depth profiling was used to determine the distribution of K, Al, Si, P and other elements throughout the $SiO_2/PSG/SiO_2/Al-1%Si$ multilevel thin films. XPS was used to analyze binding energies of Si and P elements in PSG passivation layers. K peaks were observed throughout the $PSG/SiO_2$ passivation layers on the Al-1%Si thin films and especially at the $PSG/SiO_2$ interfaces. K gettering in $SiO_2/PSG/SiO_2/Al-1%Si$ multilevel thin films is considered to be caused by a segregation type of gettering. The chemical state of Si and P elements in PSG passivation appears to be $SiO_2$ and $P_2O_5$, respectively

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.6-9
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• 2020

Thin film transistors (TFTs) with large-area, high mobility, and high reliability are important factors for next-generation displays. In particular, thin transistors based on IGZO oxide semiconductors are being actively researched for this application. In this study, several methods for improving the reliability of a-IGZO TFTs by applying various materials on a passivation layer are investigated. In the literature, inorganic SiO₂, TiO₂, Al₂O₃, ZTSO, and organic CYTOP have been used for passivation. In the case of Al₂O₃, excellent stability is exhibited compared to the non-passivation TFT under the conditions of negative bias illumination stress (NBIS) for 3 wavelengths (R, G, B). When CYTOP passivation, SiO₂ passivation, and non-passivation devices were compared under the same positive bias temperature stress (PBTS), the Vth shifts were 2.8 V, 3.3 V, and 4.5 V, respectively. The Vth shifts of TiO₂ passivation and non-passivation devices under the same NBTS were -2.2 V and -3.8 V, respectively. It is expected that the presented results will form the basis for further research to improve the reliability of a-IGZO TFT.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.418.2-418.2
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• 2016

$Al_2O_3$ passivation layer has excellent passivation properties at p-type Si surface. This $Al_2O_3$ layer forms thin $SiO_2$ layer at the interface. There were some studies about inserting thermal oxidation process to replace naturally grown oxide during $Al_2O_3$ deposition. They showed improving passivation properties. However, thermal oxidation process has disadvantage of expensive equipment and difficult control of thin layer formation. Wet chemical oxidation has advantages of low cost and easy thin oxide formation. In this study, $Al_2O_3$/$SiO_2/Si(100)$ interface was formed by wet chemical oxidation and PA-ALD process. $SiO_2$ layer at Si wafer was formed by $HCl/H_2O_2$, $H_2SO_4/H_2O_2$ and $HNO_3$, respectively. 20nm $Al_2O_3$ layer on $SiO_2/Si$ was deposited by PA-ALD. This $Al_2O_3/SiO_2/Si(100)$ interface were characterized by capacitance-voltage characteristics and quasi-steady-state photoconductance decay method.