PEALD-Grown Crystalline AlN Films on Si (100) with Sharp Interface and Good Uniformity
© The Author(s). 2017
Received: 31 December 2016
Accepted: 5 April 2017
Published: 18 April 2017
Aluminum nitride (AlN) thin films were deposited on Si (100) substrates by using plasma-enhanced atomic layer deposition method (PEALD). Optimal PEALD parameters for AlN deposition were investigated. Under saturated deposition conditions, the clearly resolved fringes are observed from X-ray reflectivity (XRR) measurements, showing the perfectly smooth interface between the AlN film and Si (100). It is consistent with high-resolution image of the sharp interface analyzed by transmission electron microscope (TEM). The highly uniform thickness throughout the 2-inch size AlN film with blue covered surface was determined by spectroscopic ellipsometry (SE). Grazing incident X-ray diffraction (GIXRD) patterns indicate that the AlN films are polycrystalline with wurtzite structure and have a tendency to form (002) preferential orientation with increasing of the thickness. The obtained AlN films could open up a new approach of research in the use of AlN as the template to support gallium nitride (GaN) growth on silicon substrates.
KeywordsAluminum nitride PEALD Sharp interface Good uniformity
With a direct wide bandgap of 6.2 eV , high resistivity and resistance of breakdown voltage, and good thermal conductivity and stability , aluminum nitride (AlN) is suitable for various applications, such as photodetectors, ultraviolet light-emitting diodes, complementary metal-oxide-semiconductor (CMOS), and solar cells. As we know, low-temperature prepared AlN was used as a critical buffer layer for the growth of epitaxial gallium nitride (GaN) layers on sapphire substrates [3–5], which contributed to the development of GaN electronic and optoelectronic devices. Since large and high-quality silicon wafers are readily available at relatively low cost, AlN films grown on silicon substrates are highly desirable and have the potential to develop GaN electronic and optoelectronic devices on silicon substrates in future. Recently, ultrathin AlN films deposited at low temperatures were widely applied for passivation layers on high electron mobility transistors (HEMTs) by controlling their thickness at atomic level [6–11]. Therefore, great efforts have been carried out for fabricating high-quality AlN growth at low temperature. It is well known that plasma-enhanced atomic layer deposition (PEALD) is a low-temperature growth method based on self-limiting growth mechanism, which can deposit highly uniform and conformal angstrom-scale thin films. In the literatures, Alevli et al.  fabricated polycrystalline AlN films using PEALD, and the polar (002)-preferred orientation appeared with increasing the temperature up to 400 °C. Ozgit et al.  obtained (100)-oriented polycrystalline AlN films on Si (100) substrates. Epitaxial growth of (002)-oriented crystalline AlN films on GaN and sapphire were achieved [14, 15]. However, high-quality (002)-preferred orientation AlN films on silicon substrates have not been realized at low temperature up to now.
In this work, we have deposited polycrystalline hexagonal AlN films with (002) preferential orientation on Si (100) substrates at temperature as low as 300 °C. Interface between the AlN film and Si (100) has been investigated. AlN films with sharp interface and good uniformity are obtained.
Deposition conditions of the AlN films by PEALD
Gas line temperature
Flow rate of carrier gas (UHP Ar)
Flow rate of N precursor
RF plasma frequency
After deposition, the thickness and the optical constants of AlN films were measured by spectroscopic ellipsometer (SE) in the energy range of 1.5–4.5 eV at incidence angle of 70°. X-ray reflectivity (XRR) with a PANalytical system X-ray reflectometry was used to study the interface between the films and substrates. The crystallinity of the as-deposited AlN was analyzed by grazing incidence X-ray diffraction (GIXRD) measurement. The thickness, uniformity, and interface of the as-deposited AlN films were further characterized by transmission electron microscope (TEM).
Results and Discussion
The extracted thickness of the 2-inch size AlN film at different points
where η and d are the non-uniformity and thickness of the film, respectively, the non-uniformity η of around 1% is calculated, suggesting that the AlN nucleation on Si (100) is highly uniform. Deposition of large-size uniform AlN films by PEALD at low temperatures broadens application of AlN in the areas that require uniform growth at low temperature with thickness controlled at the atomic level.
In summary, polycrystalline hexagonal AlN films with sharp interface and good uniformity have been deposited on Si (100) at 300 °C by PEALD. Increasing the thickness of AlN films promotes crystallization in (002) orientation. AlN films exhibit a high transparency in the visible region of the spectrum, which can be utilized in solar photovoltaic technology. The achieved AlN films are not only potential buffer layer materials for GaN growth but also promising materials for applications in other microelectronic and optoelectronic devices.
This work was supported by the National Nature Science Foundation of China (Grant Nos. 61274134, 51402064), USTB Start-up Program (Grant No. 06105033), Beijing Innovation and Research Base (Grant No. Z161100005016095), Fundamental Research Funds for the Central Universities (Grant No. FRF-UM-15-032, 06400071), and Youth Innovation Promotion Association of Chinese Academy of Sciences (2015387). Authors would like to acknowledge Yuanjun Song from USTB for TEM measurements and thank Yangfeng Li from Institute of Physics CAS for the XRR measurements. Authors would also like to acknowledge Zhengwei Chen from Saga University for his useful comments and suggestions.
SJL designed and performed the experiments, analyzed the data, and drafted the manuscript. XHZ and MZP supervised this study. All authors read and approved the manuscript.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
- Yamashita H, Fukui K, Misawa S, Yoshida S (1979) Optical properties of AlN epitaxial thin films in the vacuum ultraviolet region. J Appl Phys 50:896–898View ArticleGoogle Scholar
- Junior AF, Shanafield DJ (2004) Thermal conductivity of polycrystalline aluminum nitride (AlN) ceramics. Cerâmica 50:247–253Google Scholar
- Akasaki I, Amano H, Koide Y, Hiramatsu K, Sawaki N (1989) Effects of AlN buffer layer on crystallographic structure and on electrical and optical properties of GaN and Ga1−xAlxN (0
≦ 0.4) films grown on sapphire substrate by MOVPE. J Cryst Growth 98:209–219View ArticleGoogle Scholar
- Hiramatsu K, Itoh S, Amano H, Akasaki I, Kuwano N, Shiraishi T, Oki K (1991) Growth mechanism of GaN grown on sapphire with AlN buffer layer by MOVPE. J Cryst Growth 115:628–633View ArticleGoogle Scholar
- Nakamura S (1991) In situ monitoring of GaN growth using interference effects. Jpn J Appl Phys 30:1620–1627View ArticleGoogle Scholar
- Koehler AD, Nepal N, Anderson TJ, Tadjer MJ, Hobart KD, Eddy CR Jr, Kub FJ (2013) Atomic layer epitaxy AlN for enhanced AlGaN/GaN HEMT passivation. Electron Device Letters, IEEE 34:1115–1117View ArticleGoogle Scholar
- Huang S, Jiang Q, Yang S, Zhou C, Chen KJ (2012) Effective passivation of AlGaN/GaN HEMTs by ALD-grown AlN thin film. Electron Device Letters, IEEE 33:516–518View ArticleGoogle Scholar
- Huang S, Jiang Q, Yang S, Tang Z, Chen KJ (2013) Mechanism of PEALD-grown AlN passivation for AlGaN/GaN HEMTs: compensation of interface traps by polarization charges. Electron Device Letters, IEEE 34:193–195View ArticleGoogle Scholar
- Tang ZK, Huang S, Jiang Q, Liu SG, Liu C, Chen KJ (2013) High-voltage (600-V) low-leakage low-current-collapse AlGaN/GaN HEMTs with AlN/SiNx passivation. Electron Device Letters, IEEE 34:366–368View ArticleGoogle Scholar
- Liu XY, Zhao SX, Zhang LQ, Huang HF, Shi JS, Zhang CM, Lu HL, Wang PF, Zhang DW (2015) AlGaN/GaN MISHEMTs with AlN gate dielectric grown by thermal ALD technique. Nanoscale Res Lett 10:109View ArticleGoogle Scholar
- Chen KJ, Huang S (2013) AlN passivation by plasma-enhanced atomic layer deposition for GaN-based power switches and power amplifiers. Semicond Sci Technol 28:074015View ArticleGoogle Scholar
- Alevli M, Ozgit C, Donmez I, Biyikli N (2012) Structural properties of AlN films deposited by plasma-enhanced atomic layer deposition at different growth temperatures. Phys Status Solidi A 209:266–271View ArticleGoogle Scholar
- Ozgit C, Donmez I, Alevli M, Biyikli N (2012) Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition. Thin Solid Films 520:2750–2755View ArticleGoogle Scholar
- Nepal N, Qadri SB, Hite JK, Mahadik NA, Mastro MA, Eddy CR (2013) Epitaxial growth of AlN films via plasma-assisted atomic layer epitaxy. Appl Phys Lett 103:082110View ArticleGoogle Scholar
- Tarala V, Ambartsumov M, Altakhov A, Martens V, Shevchenko M (2016) Growing c-axis oriented aluminum nitride films by plasma-enhanced atomic layer deposition at low temperatures. J Cryst Growth 455:157–160View ArticleGoogle Scholar
- Danielsson Q, Janzen E (2003) Using N2 as precursor gas in III-nitride CVD growth. J Cryst Growth 253:26–37View ArticleGoogle Scholar
- Riihela D, Ritala M, Matero R, Leskela M, Jokinen J, Haussalo P (1996) Low temperature deposition of AIN films by an alternate supply of trimethyl aluminum and ammonia. Cherc Vap Deposition 6:277–283View ArticleGoogle Scholar
- Puurunen RL (2005) Surface chemistry of atomic layer deposition: a case study for the trimethylaluminum/water process. J Appl Phys 97:121301View ArticleGoogle Scholar
- Kim KH, Kwak NW, Lee SH (2009) Fabrication and properties of AlN film on GaN substrate by using remote plasma atomic layer deposition method. Electron Mater Let 5:83–86View ArticleGoogle Scholar
- Alevli M, Ozgit C, Donmez I, Biyikli N (2011) The influence of N2/H2 and ammonia N source materials on optical and structural properties of AlN films grown by plasma enhanced atomic layer deposition. J Cryst Growth 335:51–57View ArticleGoogle Scholar
- Bui HV, Wiggers FB, Gupta A, Nguyen MD, Aarnink AAI, Jong MP, Kovalgin AY (2015) Initial growth, refractive index, and crystallinity of thermal and plasma-enhanced atomic layer deposition AlN films. J Vac Sci Technol A 33:01A111Google Scholar
- Goerkea S, Zieglera M, Ihringa A, Dellitha J, Undiszb A, Diegela M, Andersa S, Huebnera U, Rettenmayrb M, Meyer HG (2015) Atomic layer deposition of AlN for thin membranes using trimethylaluminum and H2/N2 plasma. Appl Surf Sci 338:35–41View ArticleGoogle Scholar
- Ozgit C, Goldenberg E, Okyay AK, Biyikli N (2014) Hollow cathode plasma-assisted atomic layer deposition of crystalline AlN, GaN and AlxGa1−XN thin films at low temperatures. J Mater Chem C 2:2123–2136View ArticleGoogle Scholar
- Bosund M, Sajavaara T, Laitinen M, Huhtio T, Putkonen M, Airaksinen VM, Lipsanen H (2011) Properties of AlN grown by plasma enhanced atomic layer deposition. Appl Surf Sci 257:7827–7830View ArticleGoogle Scholar
- Motamedi P, Cadien K (2015) Structural and optical characterization of low-temperature ALD crystalline AlN. J Cryst Growth 421:45–52View ArticleGoogle Scholar
- Barshilia HC, Deepthi B, Rajam KS (2008) Growth and characterization of aluminum nitride coatings prepared by pulsed-direct current reactive unbalanced magnetron sputtering. Thin Solid Films 516:4168–4174View ArticleGoogle Scholar