Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Fu, Dejun; Lei, Dan; Li, Zhe; Zhang, Gang; Huang, Jiali; Sun, Xueqing; Wang, Qikun; Li, Dabing; Wang, Jiang; Wu, Liang

doi:10.1021/acs.cgd.2c00240

Cited by 24 publications

(14 citation statements)

References 43 publications

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“…Based on the crystallinity of AlN/Al 1−x Sc x N, several methods can be used for film growth. Single-crystal AlN can be grown via physical vapor transport (PVT) on substrates up to 60 mm in diameter [ 34 , 35 , 36 ]. Single-crystal Al 1−x Sc x N can be grown by molecular beam epitaxy (MBE) [ 9 ] on 100 mm wafers [ 37 ] with scandium concentration x from 0.06 to 0.36 [ 38 ].…”

Section: Methodsmentioning

confidence: 99%

Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions

et al. 2022

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Due to their favorable electromechanical properties, such as high sound velocity, low dielectric permittivity and high electromechanical coupling, Aluminum Nitride (AlN) and Aluminum Scandium Nitride (Al1−xScxN) thin films have achieved widespread application in radio frequency (RF) acoustic devices. The resistance to etching at high scandium alloying, however, has inhibited the realization of devices able to exploit the highest electromechanical coupling coefficients. In this work, we investigated the vertical and lateral etch rates of sputtered AlN and Al1−xScxN with Sc concentration x ranging from 0 to 0.42 in aqueous potassium hydroxide (KOH). Etch rates and the sidewall angles were reported at different temperatures and KOH concentrations. We found that the trends of the etch rate were unanimous: while the vertical etch rate decreases with increasing Sc alloying, the lateral etch rate exhibits a V-shaped transition with a minimum etch rate at x = 0.125. By performing an etch on an 800 nm thick Al0.875Sc0.125N film with 10 wt% KOH at 65 °C for 20 min, a vertical sidewall was formed by exploiting the ratio of the 1011¯ planes and 11¯00 planes etch rates. This method does not require preliminary processing and is potentially beneficial for the fabrication of lamb wave resonators (LWRs) or other microelectromechanical systems (MEMS) structures, laser mirrors and Ultraviolet Light-Emitting Diodes (UV-LEDs). It was demonstrated that the sidewall angle tracks the trajectory that follows the 1¯212¯ of the hexagonal crystal structure when different c/a ratios were considered for elevated Sc alloying levels, which may be used as a convenient tool for structure/composition analysis.

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Section: Methodsmentioning

confidence: 99%

Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions

et al. 2022

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“…Physical vapor transport (PVT) is considered the most suitable method now for AlN bulk growth with a high growth rate and easy control of dislocation density [11,12]. In the past two decades, many research groups have tried to develop PVT-AlN growth technology [13][14][15][16], the current purity of PVT-AlN is not sufficient, which makes industrial applications still difficult. In the process of PVT-AlN growth, it is difficult to achieve a growth environment with no impurity pollution, because all the source powder and heating systems are under high-temperature above 2000 • C and the Al atoms are chemically active at the temperature.…”

Section: Introductionmentioning

confidence: 99%

Oxygen reduction through specific surface area control of AlN powder for AlN single-crystal growth by physical vapor transport

Wang,

Zhu,

Zhao

et al. 2024

Semicond. Sci. Technol.

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In the physical vapor transport (PVT) growth of AlN, re-oxidation of aluminum nitride (AlN) source powder happening in the process of setting seed crystal into crucible seems to be unavoidable. This process introduces oxygen just before AlN growth and has a significant impact on the crystal quality. In this paper, a high and low-temperature alternative sintering method (HLAS) is proposed based on the idea of specific surface area control to reduce the re-oxidation of AlN source powder. This method introduces cyclic sintering between 1500°C and 1900°C to the conventional three-step treatment repeatedly, which utilizes possible phase-transition along with the processes of powder sintering back and forth to increase the particle size and decrease the specific surface area significantly. The SEM (Scanning electron microscope) and BET (Brunauer, Emmett, and Teller) results showed that the specific surface area of AlN powder treated with the HLAS method can be reduced to one-third of that with the conventional method. Thus, the SIMS (secondary ion mass spectrometry) confirmed the reduction of oxygen impurity in AlN single-crystals to a good level of 1.5×1017cm-3. It is clear that this HLAS process is an effective way of controlling the specific surface area of AlN source powder, which contributes to the suppression of oxygen influence on PVT-AlN growth.

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“…Considering crystal quality and growth rate, the PVT technique has emerged as the most suitable growth method for AlN substrates. For acquiring large-size AlN substrates, two common technical routes of PVT have been developed. , One is to prepare high-quality AlN crystal nuclei by spontaneous nucleation, and then to expand the diameter at an appropriate thermal field, − which requires large amounts of repeated runs and intermediate processing steps. It took a long time to expand crystal size to 2 in.…”

Section: Introductionmentioning

confidence: 99%

“…of diameter through this route, and reaching larger sizes is even harder. It imposes extremely high quality standards on seed crystals, 14 bringing about high costs and significant challenges in industrial manufacture. The other is to grow thick AlN layers heterogeneously on large SiC single crystals of a desired diameter, and optimize the crystal quality of AlN in subsequent homogeneous growth, 1 which can take advantage of the large size and high quality of SiC seed crystals.…”

Section: Introductionmentioning

confidence: 99%

Surface Control of AlN Single Crystal Growth on SiC Substrate

Chen,

Zhao,

Zhang

et al. 2024

Crystal Growth & Design

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In this study, the process of surface morphology control was researched by combining the computation fluid dynamics (CFD) simulations and physical vapor transport (PVT) growth experiments. The results indicate the essentiality of preserving the surface structure of SiC substrate with macroscopic steps at the initial stage of the heterogeneous PVT growth. We identified an optimal range of growth temperature (T g) and pressure to maintain the active Al vapor below a critical threshold. In the subsequent process, the pivotal factor for controlling the surface morphology of the AlN layer is identified as the supersaturation near the growing surface. Excessive supersaturation leads to a transition from a 2D to a 3D growth mode, resulting in a shift from a smooth to a rough surface morphology. An appropriate level of supersaturation can be achieved by carefully controlling the T g, striking a balance between high surface quality and growth rate. Herein, we proposed a two-step PVT method for cultivating high-surface-quality AlN crystals on SiC substrates. At the first stage, the T g is maintained below a threshold corresponding to the critical Al vapor pressure to preserve the surface structure until the SiC surface is completely covered by AlN. Then, T g is elevated to near transition temperature (T tran) to continue AlN single crystal growth at a proper rate for a long time, where T tran is defined as the growth temperature at which the transition of the dominant mode from step growth to 3D growth happens. Two-inch-diameter AlN single crystals of thicknesses of nearly 1 mm with a smooth and lustrous surface have been obtained on SiC substrate by the two-step method.

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Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Cited by 24 publications

References 43 publications

Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions

Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions

Oxygen reduction through specific surface area control of AlN powder for AlN single-crystal growth by physical vapor transport

Surface Control of AlN Single Crystal Growth on SiC Substrate

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