Influences of metal, non-metal precursors, and substrates on atomic layer deposition processes for the growth of selected functional electronic materials

Lee, S.W.,Choi, B.J.,Eom, T.,Han, J.H.,Kim, S.K.,Song, S.J.,Lee, W.,Hwang, C.S. Elsevier Publishing Company 2013 Coordination chemistry reviews Vol.257 No.23

Atomic layer deposition (ALD) is known for its self-limiting reaction, which offers atomic-level controllability of the growth of thin films for a wide range of applications. The self-limiting mechanism leads to very useful properties, such as excellent uniformity over a large area and superior conformality on complex structures. These unique features of ALD provide promising opportunities for future electronics. Though the ALD of Al<SUB>2</SUB>O<SUB>3</SUB> film (using trimethyl-aluminum and water as a metal precursor and oxygen source, respectively) can be regarded as a representative example of an ideal ALD based on the completely self-limiting reaction, there are many cases deviating from the ideal ALD reaction in recently developed ALD processes. The nonconventional aspects of the ALD reactions may strongly influence the various properties of the functional materials grown by ALD, and the lack of comprehension of these aspects has made ALD difficult to control. In this respect, several dominant factors that complicate ALD reactions, including the types of metal precursors, non-metal precursors (oxygen sources or reducing agents), and substrates, are discussed in this review. The examination of such aspects may contribute to the further understanding of non-ideal ALD reactions. Several functional materials for future electronics, such as higher-k dielectrics (TiO<SUB>2</SUB>, SrTiO<SUB>3</SUB>), phase change materials (Ge-Sb-Te solid solution), noble metal electrodes (Ru, RuO<SUB>2</SUB>), and resistive switching materials (NiO), are addressed in this review. Finally, desirable directions of ALD are suggested with consideration of the uncommon and non-ideal aspects of the ALD reactions.

원자층증착 기술: 개요 및 응용분야

신석윤,함기열,전희영,박진규,장우출,전형탁,Shin, Seokyoon,Ham, Giyul,Jeon, Heeyoung,Park, Jingyu,Jang, Woochool,Jeon, Hyeongtag 한국재료학회 2013 한국재료학회지 Vol.23 No.8

Atomic layer deposition(ALD) is a promising deposition method and has been studied and used in many different areas, such as displays, semiconductors, batteries, and solar cells. This method, which is based on a self-limiting growth mechanism, facilitates precise control of film thickness at an atomic level and enables deposition on large and three dimensionally complex surfaces. For instance, ALD technology is very useful for 3D and high aspect ratio structures such as dynamic random access memory(DRAM) and other non-volatile memories(NVMs). In addition, a variety of materials can be deposited using ALD, oxides, nitrides, sulfides, metals, and so on. In conventional ALD, the source and reactant are pulsed into the reaction chamber alternately, one at a time, separated by purging or evacuation periods. Thermal ALD and metal organic ALD are also used, but these have their own advantages and disadvantages. Furthermore, plasma-enhanced ALD has come into the spotlight because it has more freedom in processing conditions; it uses highly reactive radicals and ions and for a wider range of material properties than the conventional thermal ALD, which uses $H_2O$ and $O_3$ as an oxygen reactant. However, the throughput is still a challenge for a current time divided ALD system. Therefore, a new concept of ALD, fast ALD or spatial ALD, which separate half-reactions spatially, has been extensively under development. In this paper, we reviewed these various kinds of ALD equipment, possible materials using ALD, and recent ALD research applications mainly focused on materials required in microelectronics.

ALD와 RF 마그네트론 스퍼터링을 이용한 FBAR 소자의 ZnO 박막증착 및 특성

신영화,권상직,윤영수,Shin, Young-Hwa,Kwon, Sang-Jik,Yoon, Young-Soo 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.2

Piezoelectric ZnO thin films were for the first time formed on SiO$_2$/Si(100) substrate using 2-step deposition, atomic layer deposition(ALD) and RF magnetron sputtering deposition, for film bulk acoustic resonator(FBAR) applications. The ZnO buffer layer by ALD was deposited using alternating diethyl zinc(DEZn)/$H_2O$ exposures and ultrahigh purity argon gas for purging. The ZnO films by 2-step deposition revealed stronger c-axis-preferred orientation and smoother surface than those by the conventional RF sputtering method. The solidly mounted resonator(SMR)-typed FBAR fabricated by using 2-step deposition method revealed higher quality factor of 580 and lower return loss of -17.35dB. Therefore the 2-step deposition method in this study could be applied to the FBAR device fabrication.

High-performing and durable MgO/Ni catalysts via atomic layer deposition for CO₂ reforming of methane (CRM)

Jeong, M.G.,Kim, S.Y.,Kim, D.H.,Han, S.W.,Kim, I.H.,Lee, M.,Hwang, Y.K.,Kim, Y.D. Elsevier 2016 Applied Catalysis A Vol.515 No.-

<P>MgO-coated Ni catalysts with two different shell thicknesses were prepared using atomic layer deposition (ALD) and their catalytic activities for the CO2 reforming of CH4 (CRM) were compared with that of bare Ni catalyst. Conversion of CO2 and CH4 in the CRM reaction at 800 degrees C was enhanced with increasing thickness of the ALD-deposited MgO shells. In particular, the catalytic activity of MgO/Ni catalyst prepared using 200 ALD MgO deposition cycles was fairly durable, with negligible deactivation during a 72 h CRM reaction. We suggest that the MgO shell, which is highly basic and has high affinity to CO2, likely, accelerated the reverse CO disproportionation, thereby reducing the poisoning of Ni active sites during the CRM reaction. Furthermore, the 200-cycled MgO shell destroyed ensemble of Ni catalysts surface, allowing preservation of Ni active sites with preferential growth of filamentous carbon to layered graphitic ones. We suggest that the preparation of core-shell structures using ALD can be a promising strategy for fabricating highly active and durable catalysts that are operable at relatively high temperatures. (C) 2016 Elsevier B.V. All rights reserved.</P>

원자층 증착장치에 의한 TiO2 박막 코팅된 폴리머 절연체의 표면 및 전기적 특성의 향상

박용섭,김남훈 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.7

Titanium oxide (TiO2) thin films were synthesized on polymer insulator and Si substrates by atomic layer deposition (ALD) method. The surface and electrical properties of TiO2 films synthesized at various ALD cycle numbers were investigated. The synthesized TiO2 films exhibited higher contact angle and smooth surface. The contact angle of TiO2 films was increased with the increase of ALD-cycle number. Also, the rms surface roughness of films was slightly rough with the increase of ALD-cycle number. The leakage current on TiO2 film surface synthesized at various conditions were uniformed, and the values were decreased with the increase of ALD-cycle number. In the results, the performance of TiO2 films for self-cleaning critically depended on a number of ALD-cycle. TiO2 박막은 원자층 증착 장치(ALD)를 이용하여 폴리머 절연체와 실리콘 기판위에 합성하였다. 다양한 ALD 사이클 수에 따라 제작되어진 TiO2 박막의 표면과 전기적 특성이 고찰되었다. 합성되어진 TiO2 박막은 높은 접촉각과 부드러운 표면을 나타내었다. 도한 TiO2 박막의 접촉각은 ALD 사이클 수가 증가함에 따라 증가하였다. 박막의 rms 표면 거칠기 값은 ALD 사이클 수의 증가에 따라 약간 거칠어 졌다. 다양한 조건에서 합성되어진 TiO2 박막 표면에서 누설전류 값은 균일하였고, 이 값은 ALD 사이클 수의 증가에 따라 감소하였다. 결과로서 자기세정 응용을 위한 TiO2 박막의 특성들은 ALD 사이클 수에 의존하는 것을 확인하였다.

Plasma Assisted ALD 장비를 이용한 니켈 박막 증착과 Ti 캡핑 레이어에 의한 니켈 실리사이드 형성 효과

윤상원,이우영,양충모,하종봉,나경일,조현익,남기홍,서화일,이정희,Yun, Sang-Won,Lee, Woo-Young,Yang, Chung-Mo,Ha, Jong-Bong,Na, Kyoung-Il,Cho, Hyun-Ick,Nam, Ki-Hong,Seo, Hwa-Il,Lee, Jung-Hee 한국반도체디스플레이기술학회 2007 반도체디스플레이기술학회지 Vol.6 No.3

The NiSi is very promising candidate for the metallization in 45 nm CMOS process such as FUSI(fully silicided) gate and source/drain contact because it exhibits non-size dependent resistance, low silicon consumption and mid-gap workfunction. Ni film was first deposited by using ALD (atomic layer deposition) technique with Bis-Ni precursor and $H_2$ reactant gas at $220^{\circ}C$ with deposition rate of $1.25\;{\AA}/cycle$. The as-deposited Ni film exhibited a sheet resistance of $5\;{\Omega}/{\square}$. RTP (repaid thermal process) was then performed by varying temperature from $400^{\circ}C$ to $900^{\circ}C$ in $N_2$ ambient for the formation of NiSi. The process temperature window for the formation of low-resistance NiSi was estimated from $600^{\circ}C$ to $800^{\circ}C$ and from $700^{\circ}C$ to $800^{\circ}C$ with and without Ti capping layer. The respective sheet resistance of the films was changed to $2.5\;{\Omega}/{\square}$ and $3\;{\Omega}/{\square}$ after silicidation. This is because Ti capping layer increases reaction between Ni and Si and suppresses the oxidation and impurity incorporation into Ni film during silicidation process. The NiSi films were treated by additional thermal stress in a resistively heated furnace for test of thermal stability, showing that the film heat-treated at $800^{\circ}C$ was more stable than that at $700^{\circ}C$ due to better crystallinity.

원자층 증착장치에 의한 TiO₂ 박막 코팅된 폴리머 절연체의 표면 및 전기적 특성의 향상

김남훈,박용섭,Kim, Nam-Hoon,Park, Yong Seob 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.7

Titanium oxide ($TiO_2$) thin films were synthesized on polymer insulator and Si substrates by atomic layer deposition (ALD) method. The surface and electrical properties of $TiO_2$ films synthesized at various ALD cycle numbers were investigated. The synthesized $TiO_2$ films exhibited higher contact angle and smooth surface. The contact angle of $TiO_2$ films was increased with the increase of ALD-cycle number. Also, the rms surface roughness of films was slightly rough with the increase of ALD-cycle number. The leakage current on $TiO_2$ film surface synthesized at various conditions were uniformed, and the values were decreased with the increase of ALD-cycle number. In the results, the performance of $TiO_2$ films for self-cleaning critically depended on a number of ALD-cycle.

Organic/inorganic multilayer thin film encapsulation via initiated chemical vapor deposition and atomic layer deposition for its application to organic solar cells

김봉준,한동근,유승협,임성갑 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.3

A thin film encapsulation (TFE) was fabricated by alternating deposition of organic and inorganic layers via initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD). A highly crosslinked organosilicone polymer, poly(1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane) (pV3D3) was successfully adopted as the organic layer for the fabrication of TFE. The film formed a stable and smooth interface with ALD Al2O3 layer. The multilayer TFE consisting of pV3D3 and Al2O3 alternating layers exhibited outstanding optical transparency as well as excellent barrier property. Finally, the multilayer TFE was applied monolithically to organic solar cells (OSCs), and the shelf life of the cells was increased immensely, suggesting that the developed organic/inorganic multilayer TFE is an efficient barrier film for elongating the lifetime of organic electronics.

Ultra Thin Film Encapsulation of OLED on Plastic Substrate

Sang-Hee Ko Park,강광용,양용석,이정익,Jiyoung Oh,황치선,Hye Yong Chu 한국전자통신연구원 2005 ETRI Journal Vol.27 No.5

We have carried out the fabrications of a barrier layer on a polyethersulfon (PES) film and organic light emitting diode (OLED) based on a plastic substrate by means of atomic layer deposition (ALD). Simultaneous deposition of 30 nm AlOx film on both sides of the PES film gave a water vapor transition rate (WVTR) of 0.062 g/m2/day (@38°C, 100% R.H.). Further, the double layer of 200 nm SiNx film deposited by plasma enhanced chemical vapor deposition (PECVD) and 20 nm AlOx film by ALD resulted in a WVTR value lower than the detection limit of MOCON. We have investigated the OLED encapsulation performance of the double layer using the OLED structure of ITO / MTDATA (20 nm) / NPD (40 nm) / AlQ (60 nm) / LiF (1 nm) / Al (75 nm) on a plastic substrate. The preliminary life time to reach 91% of the initial luminance (1300 cd/m2) was 260 hours for the OLED encapsulated with 100 nm of PECVD-deposited SiNx and 30 nm of ALD-deposited AlOx.

Staggered and Inverted Staggered Type Organic-Inorganic Hybrid TFTs with ZnO Channel Layer Deposited by Atomic Layer Deposition

Gong, Su-Cheol,Ryu, Sang-Ouk,Bang, Seok-Hwan,Jung, Woo-Ho,Jeon, Hyeong-Tag,Kim, Hyun-Chul,Choi, Young-Jun,Park, Hyung-Ho,Chang, Ho-Jung The Korean Microelectronics and Packaging Society 2009 마이크로전자 및 패키징학회지 Vol.16 No.4

Two different organic-inorganic hybrid thin film transistors (OITFTs) with the structures of glass/ITO/ZnO/PMMA/Al (staggered structure) and glass/ITO/PMMA/ZnO/Al (inverted staggered structure), were fabricated and their electrical and structural properties were compared. The ZnO thin films used as active channel layers were deposited by the atomic layer deposition (ALD) method at a temperature of $100^{\circ}C$. To investigate the effect of the substrates on their properties, the ZnO films were deposited on bare glass, PMMA/glass and ITO/glass substrates and their crystal properties and surface morphologies were analyzed. The structural properties of the ZnO films varied with the substrate conditions. The ZnO film deposited on the ITO/glass substrate showed better crystallinity and morphologies, such as a higher preferred c-axis orientation, lower FWHM value and larger particle size compared with the one deposited on the PMMA/glass substrate. The field effect mobility ($\mu$), threshold voltage ($V_T$) and $I_{on/off}$ switching ratio for the OITFT with the staggered structure were about $0.61\;cm^2/V{\cdot}s$, 5.5 V and $10^2$, whereas those of the OITFT with the inverted staggered structure were found to be $0.31\;cm^2/V{\cdot}s$, 6.8 V and 10, respectively. The improved electrical properties for the staggered OITFTs may originate from the improved crystal properties and larger particle size of the ZnO active layer.