Kienemund, Daniel (2019)
High-Power Varactors for Fast Adaptive Impedance Matching at 13.56 MHz.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Solid state varactors, applicable in rapidly adjustable high-power impedance matching circuits at 13.56MHz are presented in this work. Tunable impedance matching networks are necessary for RF based plasma processes in the semiconductor industry. With increasing integration level, the speed at which the matching circuit can be adjusted gains impact as constant power transfer is pivotal during ignition and extinction of the plasma. State-of-the-art mechanical vacuum varactors have a limited tuning time of minimum 1ms but are hardly replaceable, as they introduce lower losses and higher linearity compared to solid state varactors. However, as tuning speed gains impact, the substitution with fast but lossy solid state varactors becomes feasible. Within the group of tunable high-power compatible solids, barium strontium titanate (BST) is a possible candidate, due to its high tunability and low dielectric losses in the desired frequency range. The material gains its tunability from an electric field dependent permittivity, which can be adjusted with a DC biasing voltage. When biased, BST exhibits piezoelectricity, resulting in acoustical excitation with an applied RF voltage. As a result, the electrical Q-factor locally decreases and additional losses are introduced. At high-power operation, this property represents a significant problem. In this work, novel fully-printed BST thick film and bulk ceramic disk varactors are presented and evaluated in regard to their compatibility in high-power impedance matching networks. The general applicability of thick film based varactors under high-power conditions up to 1kW is shown. At this power level, an acoustically optimized varactor design achieves a 63% dissipated power reduction from 37.1W to 13.5W, while remaining electrically tunable with 18%. By transient characterization, a response time for thick film varactors of less than 1.5μs is demonstrated in the range of C(0V) to C(120V). Bulk ceramic disk varactors are presented, employed on a printed circuit board for high-power operation. For that, a composite material comprised of BST and a nontunable, low loss, magnesium based metal oxide dielectric shows favorable properties, with a significantly reduced acoustic activity above the single digit MHz region. The feasibility, however, is shown with a thermally stabilized varactor module, employing bulk ceramic pellets based on a commercially available dielectric. At 700W input power a tunability of 12% is obtained with an input power and biasing voltage independent relative loss of 1.8%. A transient response time of less than 1.2μs is measured for a tuning range of C(0V) to C(1.1 kV).
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2019 | ||||
Autor(en): | Kienemund, Daniel | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | High-Power Varactors for Fast Adaptive Impedance Matching at 13.56 MHz | ||||
Sprache: | Englisch | ||||
Referenten: | Jakoby, Prof. Dr. Rolf ; Kölpin, Prof. Dr. Alexander | ||||
Publikationsjahr: | 2019 | ||||
Ort: | Darmstadt | ||||
Datum der mündlichen Prüfung: | 9 Juli 2019 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/8860 | ||||
Kurzbeschreibung (Abstract): | Solid state varactors, applicable in rapidly adjustable high-power impedance matching circuits at 13.56MHz are presented in this work. Tunable impedance matching networks are necessary for RF based plasma processes in the semiconductor industry. With increasing integration level, the speed at which the matching circuit can be adjusted gains impact as constant power transfer is pivotal during ignition and extinction of the plasma. State-of-the-art mechanical vacuum varactors have a limited tuning time of minimum 1ms but are hardly replaceable, as they introduce lower losses and higher linearity compared to solid state varactors. However, as tuning speed gains impact, the substitution with fast but lossy solid state varactors becomes feasible. Within the group of tunable high-power compatible solids, barium strontium titanate (BST) is a possible candidate, due to its high tunability and low dielectric losses in the desired frequency range. The material gains its tunability from an electric field dependent permittivity, which can be adjusted with a DC biasing voltage. When biased, BST exhibits piezoelectricity, resulting in acoustical excitation with an applied RF voltage. As a result, the electrical Q-factor locally decreases and additional losses are introduced. At high-power operation, this property represents a significant problem. In this work, novel fully-printed BST thick film and bulk ceramic disk varactors are presented and evaluated in regard to their compatibility in high-power impedance matching networks. The general applicability of thick film based varactors under high-power conditions up to 1kW is shown. At this power level, an acoustically optimized varactor design achieves a 63% dissipated power reduction from 37.1W to 13.5W, while remaining electrically tunable with 18%. By transient characterization, a response time for thick film varactors of less than 1.5μs is demonstrated in the range of C(0V) to C(120V). Bulk ceramic disk varactors are presented, employed on a printed circuit board for high-power operation. For that, a composite material comprised of BST and a nontunable, low loss, magnesium based metal oxide dielectric shows favorable properties, with a significantly reduced acoustic activity above the single digit MHz region. The feasibility, however, is shown with a thermally stabilized varactor module, employing bulk ceramic pellets based on a commercially available dielectric. At 700W input power a tunability of 12% is obtained with an input power and biasing voltage independent relative loss of 1.8%. A transient response time of less than 1.2μs is measured for a tuning range of C(0V) to C(1.1 kV). |
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URN: | urn:nbn:de:tuda-tuprints-88601 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau | ||||
Fachbereich(e)/-gebiet(e): | 18 Fachbereich Elektrotechnik und Informationstechnik 18 Fachbereich Elektrotechnik und Informationstechnik > Institut für Mikrowellentechnik und Photonik (IMP) > Mikrowellentechnik 18 Fachbereich Elektrotechnik und Informationstechnik > Institut für Mikrowellentechnik und Photonik (IMP) |
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Hinterlegungsdatum: | 11 Aug 2019 19:55 | ||||
Letzte Änderung: | 13 Dez 2019 09:57 | ||||
PPN: | |||||
Referenten: | Jakoby, Prof. Dr. Rolf ; Kölpin, Prof. Dr. Alexander | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 9 Juli 2019 | ||||
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