A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits
The heterogeneous integration of ferroelectric thin films on silicon- or silicon nitride-based platforms for photonic integrated circuits plays a crucial role in the development of nanophotonic thin film modulators. For this purpose, an ultrathin seed film was recently introduced as an integration m...
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MDPI AG
2025-03-01
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| author | Enes Lievens Kobe De Geest Ewout Picavet Liesbet Van Landschoot Henk Vrielinck Gilles Freddy Feutmba Hannes Rijckaert Klaartje De Buysser Dries Van Thourhout Peter Bienstman Jeroen Beeckman |
| author_facet | Enes Lievens Kobe De Geest Ewout Picavet Liesbet Van Landschoot Henk Vrielinck Gilles Freddy Feutmba Hannes Rijckaert Klaartje De Buysser Dries Van Thourhout Peter Bienstman Jeroen Beeckman |
| author_sort | Enes Lievens |
| collection | DOAJ |
| description | The heterogeneous integration of ferroelectric thin films on silicon- or silicon nitride-based platforms for photonic integrated circuits plays a crucial role in the development of nanophotonic thin film modulators. For this purpose, an ultrathin seed film was recently introduced as an integration method for ferroelectric thin films such as BaTiO<sub>3</sub> and Pb(Zr,Ti)O<sub>3</sub>. One issue with this self-orienting seed film is that for non-planarized circuits, it fails to act as a template film for the thin films. To circumvent this problem, we propose a method of planarization without the need for wafer-scale chemical mechanical polishing by using hydrogen silsesquioxane as a precursor to forming amorphous silica, in order to create an oxide cladding similar to the thermal oxide often present on silicon-based platforms. Additionally, this oxide cladding is compatible with the high annealing temperatures usually required for the deposition of these novel ferroelectric thin films (600–800 °C). The thickness of this silica film can be controlled through a dry etch process, giving rise to a versatile platform for integrating nanophotonic thin film modulators on a wider variety of substrates. Using this method, we successfully demonstrate a hybrid BaTiO<sub>3</sub>-Si ring modulator with a high Pockels coefficient of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>r</mi><mrow><mi>w</mi><mi>g</mi></mrow></msub><mo>=</mo><mn>155.57</mn><mo>±</mo><mn>10.91</mn></mrow></semantics></math></inline-formula> pm V<sup>−1</sup> and a half-wave voltage-length product of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>V</mi><mi>π</mi></msub><mi>L</mi><mo>=</mo><mn>2.638</mn><mo>±</mo><mn>0.084</mn></mrow></semantics></math></inline-formula> V cm, confirming the integration of ferroelectric thin films on an initially non-planar substrate. |
| format | Article |
| id | doaj-art-2491047bc6dd4e05bb258507db2e7d4a |
| institution | DOAJ |
| issn | 2072-666X |
| language | English |
| publishDate | 2025-03-01 |
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| spelling | doaj-art-2491047bc6dd4e05bb258507db2e7d4a2025-08-20T02:42:22ZengMDPI AGMicromachines2072-666X2025-03-0116333410.3390/mi16030334A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated CircuitsEnes Lievens0Kobe De Geest1Ewout Picavet2Liesbet Van Landschoot3Henk Vrielinck4Gilles Freddy Feutmba5Hannes Rijckaert6Klaartje De Buysser7Dries Van Thourhout8Peter Bienstman9Jeroen Beeckman10LCP Group, Department of Electronics and Information Systems, Ghent University, Technologiepark-Zwijnaarde 126, 9052 Gent, BelgiumLCP Group, Department of Electronics and Information Systems, Ghent University, Technologiepark-Zwijnaarde 126, 9052 Gent, BelgiumLCP Group, Department of Electronics and Information Systems, Ghent University, Technologiepark-Zwijnaarde 126, 9052 Gent, BelgiumPRG Group, Department of Information Technology, Ghent University—imec, Technologiepark-Zwijnaarde 126, 9052 Ghent, BelgiumDiSC, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Ghent, BelgiumLCP Group, Department of Electronics and Information Systems, Ghent University, Technologiepark-Zwijnaarde 126, 9052 Gent, BelgiumSCRiPTS, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Ghent, BelgiumSCRiPTS, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Ghent, BelgiumPRG Group, Department of Information Technology, Ghent University—imec, Technologiepark-Zwijnaarde 126, 9052 Ghent, BelgiumPRG Group, Department of Information Technology, Ghent University—imec, Technologiepark-Zwijnaarde 126, 9052 Ghent, BelgiumLCP Group, Department of Electronics and Information Systems, Ghent University, Technologiepark-Zwijnaarde 126, 9052 Gent, BelgiumThe heterogeneous integration of ferroelectric thin films on silicon- or silicon nitride-based platforms for photonic integrated circuits plays a crucial role in the development of nanophotonic thin film modulators. For this purpose, an ultrathin seed film was recently introduced as an integration method for ferroelectric thin films such as BaTiO<sub>3</sub> and Pb(Zr,Ti)O<sub>3</sub>. One issue with this self-orienting seed film is that for non-planarized circuits, it fails to act as a template film for the thin films. To circumvent this problem, we propose a method of planarization without the need for wafer-scale chemical mechanical polishing by using hydrogen silsesquioxane as a precursor to forming amorphous silica, in order to create an oxide cladding similar to the thermal oxide often present on silicon-based platforms. Additionally, this oxide cladding is compatible with the high annealing temperatures usually required for the deposition of these novel ferroelectric thin films (600–800 °C). The thickness of this silica film can be controlled through a dry etch process, giving rise to a versatile platform for integrating nanophotonic thin film modulators on a wider variety of substrates. Using this method, we successfully demonstrate a hybrid BaTiO<sub>3</sub>-Si ring modulator with a high Pockels coefficient of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>r</mi><mrow><mi>w</mi><mi>g</mi></mrow></msub><mo>=</mo><mn>155.57</mn><mo>±</mo><mn>10.91</mn></mrow></semantics></math></inline-formula> pm V<sup>−1</sup> and a half-wave voltage-length product of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>V</mi><mi>π</mi></msub><mi>L</mi><mo>=</mo><mn>2.638</mn><mo>±</mo><mn>0.084</mn></mrow></semantics></math></inline-formula> V cm, confirming the integration of ferroelectric thin films on an initially non-planar substrate.https://www.mdpi.com/2072-666X/16/3/334hydrogen silsesquioxaneplanarizationferroelectric thin filmsheterogeneous integrationchemical solution depositionPockels modulator |
| spellingShingle | Enes Lievens Kobe De Geest Ewout Picavet Liesbet Van Landschoot Henk Vrielinck Gilles Freddy Feutmba Hannes Rijckaert Klaartje De Buysser Dries Van Thourhout Peter Bienstman Jeroen Beeckman A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits Micromachines hydrogen silsesquioxane planarization ferroelectric thin films heterogeneous integration chemical solution deposition Pockels modulator |
| title | A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits |
| title_full | A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits |
| title_fullStr | A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits |
| title_full_unstemmed | A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits |
| title_short | A Pathway for the Integration of Novel Ferroelectric Thin Films on Non-Planar Photonic Integrated Circuits |
| title_sort | pathway for the integration of novel ferroelectric thin films on non planar photonic integrated circuits |
| topic | hydrogen silsesquioxane planarization ferroelectric thin films heterogeneous integration chemical solution deposition Pockels modulator |
| url | https://www.mdpi.com/2072-666X/16/3/334 |
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