KOH based selective wet chemical etching of AlN, AlxGa1−xN, and GaN crystals: A way towards substrate removal in deep ultraviolet-light emitting diode

Guo, Wei; Kirste, Ronny; Bryan, Isaac; Bryan, Zachary; Hussey, Lindsay; Reddy, Pramod; Tweedie, James; Collazo, Ramón; Sitar, Zlatko

doi:10.1063/1.4913705

Cited by 81 publications

(62 citation statements)

References 24 publications

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“…16,21 Bulk AlN which shows N-polarity is etched faster in a wet-chemical etching solution (KOH, H3PO4) than AlN with Al-polarity. 14 The considerable lower |d33| values of the AlN synthesized on Ti films support the assumption of a mixed Al-and N-polarity of the layer. As a consequence, we expect that the porous etching behavior from Figure 1a-d follows from the different etching rates of N-polar and Al-polar grains 14,22,23 in combination with the higher surface roughness of the layer.…”

Section: Resultsmentioning

confidence: 81%

“…14 The considerable lower |d33| values of the AlN synthesized on Ti films support the assumption of a mixed Al-and N-polarity of the layer. As a consequence, we expect that the porous etching behavior from Figure 1a-d follows from the different etching rates of N-polar and Al-polar grains 14,22,23 in combination with the higher surface roughness of the layer. This would also explain the etching behavior observed on Si substrates (Figure 1e-h).…”

Section: Resultsmentioning

confidence: 81%

“…potassium hydroxide (KOH), tetramethylammonium hydroxid (TMAH) or phosphoric acid (H3PO4) as etchants for patterning. [12][13][14][15] In this work we investigate in the wet chemical etching performance of highly c-axis oriented AlN on sputter-deposited Ti layers or on pure Si substrates with phosphoric acid based etch solutions. Furthermore, to evaluate the impact on the electro-mechanical properties of the AlN layers, piezoelectric response measurements are performed providing the absolute value of the piezoelectric coefficient |d33|.…”

Section: Introductionmentioning

confidence: 99%

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Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

2015

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Highly c-axis orientated sputter deposited aluminium nitride (AlN) thin films are widely used as piezoelectric layers in micro-electro-mechanical systems (MEMS). Therefore, stable and reliable deposition and patterning of the AlN thin films in the fabrication process of such devices is of utmost importance. In this work, we study the wet chemical etching behavior of highly c-axis oriented AlN layers as well as the film-related residuals after the etching procedure. To investigate the impact of the underlying material on the quality of the AlN films they are either deposited on pure silicon (Si) substrates or on Si substrates covered with a sputter-deposited thin titanium (Ti) film. The 620 nm thin AlN layers are synthesized simultaneously onto both substrate types and subsequently wet-chemical etched in a phosphorous acid based etching solution at a temperature of 80°C. We demonstrate a significant difference in surface roughness of the untreated AlN films when sputter-deposited on Ti or pure Si. Furthermore, we analyze the piezoelectric properties of the deposited films. Although the XRD analyses indicate a high c-axis orientated wurtzite structure for all deposited films, the absolute value of the piezoelectric coefficients |d33| of AlN thin films synthesized on Ti are 0.4-4.3 pC/N, whereas corresponding values of 5.2-6 pC/N are determined at those deposited on pure Si substrates,. Finally, after wet chemically etching a porous, but homogeneous AlN microstructure is observed for samples synthesized onto Ti layers, whereas AlN layers deposited directly on Si substrate are either etched very inhomogenously or almost completely with some etch resistant pyramidal-shaped residues. This might be due to a local change in polarity within the AlN layer.

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Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

2015

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“…All samples of the AlN layers were N‐polar, implying that, for growing N‐polar AlN, it is not necessary to change the growth conditions when the misorientation angle of the sapphire substrate is from 0.2° to 5.0°. It has been proved that the etch rate of the N‐polar surface of AlN is very fast, whereas the etch rate for the Al‐polar AlN surface is extremely slow . All the residual parts on the sapphire substrates in the SEM images after KOH etching could be Al‐polar AlN.…”

Section: Resultsmentioning

confidence: 99%

Growth of N‐Polar Aluminum Nitride on Vicinal Sapphire Substrates and Aluminum Nitride Bulk Substrates

Isono

Ito

Sakamoto

et al. 2020

Physica Status Solidi (b)

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Herein, nitrogen‐polar (N‐polar, (000‐1)) aluminum nitride (AlN) is grown on sapphire substrates with various misorientation angles through metal‐organic vapor phase epitaxy. Moreover, the effect of the sapphire substrates’ misorientation angle on the surface flatness and the crystal quality of N‐polar AlN is studied. The results demonstrate that the surface flatness of the AlN layer improves as the misorientation angle of the sapphire substrates increases. Further, the root mean square of the AlN layer significantly improves to a maximum of 1 nm, in the range of the misorientation angles between 2° and 4°, as compared with the misorientation angle of 0.2° of a conventional substrate. No deterioration in crystallinity is confirmed when an AlN layer is grown on an N‐polar AlN substrate under the same growth conditions as those for the sapphire substrates.

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“…The polarity of all the N-polar AlGaN epi-layer samples was verified with KOH solution etching method. In terms of this method, the as-grown AlGaN film was identified to be N-polar epi-layer if it could be removed completely without any residual Ga-polar inversion domains after etched in 5 mol/ L KOH solution under 100 ℃ for at least 3 min [19][20][21].…”

Section: Methodsmentioning

confidence: 99%

Influence of nitridation process on characteristics of N-polar AlGaN films grown by MOCVD

Wang

Zhang

et al. 2017

Materials Science in Semiconductor Processing

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KOH based selective wet chemical etching of AlN, AlxGa1−xN, and GaN crystals: A way towards substrate removal in deep ultraviolet-light emitting diode

Abstract: Articles you may be interested inEffects of double layer AlN buffer layers on properties of Si-doped AlxGa1−xN for improved performance of deep ultraviolet light emitting diodes

Cited by 81 publications

References 24 publications

Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

Growth of N‐Polar Aluminum Nitride on Vicinal Sapphire Substrates and Aluminum Nitride Bulk Substrates

Influence of nitridation process on characteristics of N-polar AlGaN films grown by MOCVD

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