Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

Österlund, Elmeri; Suihkonen, Sami; Ross, Glenn; Torkkeli, Altti; Kuisma, Heikki; Paulasto‐Kröckel, Mervi

doi:10.1016/j.jcrysgro.2019.125345

Cited by 12 publications

(13 citation statements)

References 122 publications

(182 reference statements)

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“…Despite the directionality added by the plasma steps, the ALA PEALD process retains the excellent conformal coverage of ALD and the coverage is significantly better than previously obtained using MOCVD, where the film thickness decreased from approximately 140 to 40 nm down a 100 μm deep trench. 13 The average thickness of the AlN film is 124 nm with a standard deviation of 14 nm and the film thickness does not decrease significantly down the sidewall, as can be seen in Fig. 5(a).…”

Section: Resultsmentioning

confidence: 69%

“…However, it is unlikely that the change in the measured film thickness down the sidewall is caused only by the measurement error and similar thickness profiles are observed in the MOCVD AlN films as well. 13 The uneven growth rates down the sidewall can be due to insufficient purge times causing precursors to linger in the trench and leading to a more CVD like growth. Another possibility is that AlN grows faster on the rougher etched surface due to the availability of terraces and other nucleation sites.…”

Section: Resultsmentioning

confidence: 99%

“…The conformal coverage of the ALD process was studied by using patterned Si substrates. 100 μm deep and 100 μm wide trenches were etched into 200 μm thick Si(110) substrates using a previously developed potassium hydroxide wet etching process, 13 which results in smooth and vertical sidewalls with Si(111) surfaces. The thickness of the AlN film on the sidewalls was measured by first cleaving samples perpendicular to the sidewalls and then imaging the formed cross section using scanning electron microscopy (SEM, Zeiss Supra 40) along the depth of the sidewall at 10 μm intervals.…”

Section: E Conformal Coveragementioning

confidence: 99%

“…Chemical vapor deposition (CVD) generally has better conformal coverage 12 and metal-organic CVD (MOCVD) has been used to grow high-quality AlN on vertical sidewalls. 13 However, MOCVD requires growth temperatures above 1000 C for high crystal quality AlN (Ref. 13) and results in residual stresses of more than 1.5 GPa, 8 both of which are a challenge for process integration.…”

Section: Introductionmentioning

confidence: 99%

“…13 However, MOCVD requires growth temperatures above 1000 C for high crystal quality AlN (Ref. 13) and results in residual stresses of more than 1.5 GPa, 8 both of which are a challenge for process integration. Atomic layer deposition (ALD), on the other hand, uses lower growth temperatures while being known for unparalleled conformal coverage.…”

Section: Introductionmentioning

confidence: 99%

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Atomic layer deposition of AlN using atomic layer annealing—Towards high-quality AlN on vertical sidewalls

Österlund

Seppänen

Bespalova

et al. 2021

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Atomic layer deposition (ALD) of aluminum nitride (AlN) using in situ atomic layer annealing (ALA) is studied for microelectromechanical systems (MEMS). Effective piezoelectric in-plane actuation and sensing requires deposition of high crystal quality and (0002) oriented AlN on vertical sidewalls of MEMS structures. Previous studies have shown that the crystal quality of ALD AlN can be significantly improved using ALA but have not studied the conformal coverage or crystal quality on metal electrodes, which are required for piezoelectric MEMS devices. In this study, AlN thin films are deposited on Si, Al, Pt, and on vertical sidewalls etched into Si. The AlN microstructure and properties are studied using x-ray diffraction methods, transmission electron microscopy, and Fourier transform infrared spectroscopy. The conformal coverage is evaluated by measuring the film thickness on the vertical sidewalls. The effects of postdeposition annealing are studied as well. This study aims to enable effective piezoelectric actuation and sensing for MEMS sensors. The conformal coverage of the ALA ALD process is excellent and AlN has the best crystal quality and degree of orientation when deposited on Al. The as-deposited films contain oxygen impurities, which might be detrimental to the piezoelectric properties of AlN. Annealing at high temperatures reduced the number of impurities but did not improve the crystal quality.

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Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Section: E Conformal Coveragementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Atomic layer deposition of AlN using atomic layer annealing—Towards high-quality AlN on vertical sidewalls

Österlund

Seppänen

Bespalova

et al. 2021

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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In‐Plane AlN‐based Actuator: Toward a New Generation of Piezoelectric MEMS

Bespalova

Nieminen

Gabrelian

et al. 2023

Adv Elect Materials

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A novel design that utilizes aluminum nitride (AlN) piezoelectric thin films deposited on vertical surfaces for lateral motion and sensing is a step toward emerging multi-axial microelectromechanical systems (MEMS). This work demonstrates the fabrication process and potential applications of an in-plane moving piezoactuator. The actuator is excited using the inverse piezoelectric effect of the AlN thin film grown on the vertical surfaces of a Si cantilever. Lateral motion of the actuator is enabled when a voltage is applied between the top and bottom electrodes of the device, which are highly doped Si and titanium nitride thin film. The motion of the actuator is captured using scanning electron microscope.

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Metalorganic Chemical Vapor Deposition of AlN on High Degree Roughness Vertical Surfaces for MEMS Fabrication

Bespalova,

Ross,

Suihkonen

et al. 2024

Adv Elect Materials

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Aluminum nitride (AlN) grown on vertical surfaces can be utilized for the fabrication of advanced piezoelectric microelectromechanical systems (MEMS). The in‐plane motion of the parts of a MEMS element is possible when AlN is deposited on the vertical surfaces of the moving structure. For the best device performance, AlN must have high crystal quality, uniform coverage of the vertical sidewalls, and c‐axis crystalline orientation perpendicular to the plane of a vertical surface. The impact of the surface roughness (Rq) of the vertical sidewalls formed in Si using wet and dry etching methods on the crystal quality, crystallographic orientation, and uniformity of the metalorganic chemical vapor deposited (MOCVD) AlN thin films is studied in this paper. In both cases, AlN films demonstrated full sidewall coverage and grew crystalline in the c‐axis direction. AlN films grown on vertical Si surfaces achieved using anisotropic wet etching are highly crystalline and oriented in [0001] direction, while the films grown on vertical surfaces achieved using dry etching displayed a lower level of alignment with the Si sidewalls.

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Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

Cited by 12 publications

References 122 publications

Atomic layer deposition of AlN using atomic layer annealing—Towards high-quality AlN on vertical sidewalls

Atomic layer deposition of AlN using atomic layer annealing—Towards high-quality AlN on vertical sidewalls

In‐Plane AlN‐based Actuator: Toward a New Generation of Piezoelectric MEMS

Metalorganic Chemical Vapor Deposition of AlN on High Degree Roughness Vertical Surfaces for MEMS Fabrication

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