View All Items
(1 - 3 of 3)
- Title
- EFFECTS OF DEPOSITION TEMPERATURE AND POST DEPOSITION ANNEALING ON THE ELECTRICAL PROPERTIES OF BARIUM STRONTIUM TITANATE THIN FILM FOR EMBEDDED CAPACITOR APPLICATIONS.
- Creator
-
Peelamedu Ranganathan, Raviprakash, Kalpathy. B, Sundaram, University of Central Florida
- Abstract / Description
-
A higher degree of system level integration can be achieved by integrating the passive components into semiconductor devices, which seem to be an enabling technology for portable communication and modern electronic devices. Greater functionality, higher performance and increase in reliability can be achieved by miniaturizing and reducing the number of components in integrated circuits. The functional potential of small electronic devices can be enormously increased by implementing the...
Show moreA higher degree of system level integration can be achieved by integrating the passive components into semiconductor devices, which seem to be an enabling technology for portable communication and modern electronic devices. Greater functionality, higher performance and increase in reliability can be achieved by miniaturizing and reducing the number of components in integrated circuits. The functional potential of small electronic devices can be enormously increased by implementing the embedded capacitors, resistors and inductors. This would free up surface real estate allowing either a smaller footprint or more silicon devices to be placed on the same sized substrate. This thesis focuses on the effect of deposition temperature and post deposition annealing (PDA) in different gas ambient on the electrical properties of sputter deposited ferroelectric Barium Strontium Titanate (Ba0.5St0.5) TiO3 thin film capacitors. Approximately 2000Å of Barium Strontium Titanate (BST) thin film was deposited at different substrate temperatures (400,450,500 and 550◦C) on cleaned silicon substrates. These BST films were then annealed separately in 100% N2, 100% O2 and 10% O2 + 90% N2 at 575◦C in sputtering machine (PVD anneal) and a three zone annealing Lindberg furnace. The objective of this thesis was to compare the effect of PDA on the electrical properties of BST films deposited at different substrate temperatures between PVD annealing and furnace annealing. For this work, tantalum thin film was used as top and bottom electrode to fabricate the capacitors. BST thin film capacitors were fabricated and characterized for leakage current and dielectric breakdown. Roughness study on pre and post annealed BST films were done using optical profilometer. The capacitors were tested using HP impedance analyzer in the frequency range from 10Hz through 1 MHz. From the experiments, 100% O2 annealed furnace annealed BST thin film seem to have better dielectric constant, higher breakdown voltage and nominal capacitance density.
Show less - Date Issued
- 2004
- Identifier
- CFE0000314, ucf:46310
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000314
- Title
- BEAM-STEERABLE AND RECONFIGURABLE REFLECTARRAY ANTENNAS FOR HIGH GAIN SPACE APPLICATIONS.
- Creator
-
Karnati, Kalyan, Gong, Xun, Wahid, Parveen, Jones, W Linwood, Wu, Thomas, Cho, Hyoung Jin, University of Central Florida
- Abstract / Description
-
Reflectarray antennas uniquely combine the advantages of parabolic reflectors and phased array antennas. Comprised of planar structures similar to phased arrays and utilizing quasi-optical excitation similar to parabolic reflectors, reflectarray antennas provide beam steering without the need of complex and lossy feed networks. Chapter 1 discusses the basic theory of reflectarray and its design. A brief summary of previous work and current research status is also presented. The inherent...
Show moreReflectarray antennas uniquely combine the advantages of parabolic reflectors and phased array antennas. Comprised of planar structures similar to phased arrays and utilizing quasi-optical excitation similar to parabolic reflectors, reflectarray antennas provide beam steering without the need of complex and lossy feed networks. Chapter 1 discusses the basic theory of reflectarray and its design. A brief summary of previous work and current research status is also presented. The inherent advantages and drawbacks of the reflectarray are discussed.In chapter 2, a novel theoretical approach to extract the reflection coefficient of reflectarray unit cells is developed. The approach is applied to single-resonance unit cell elements under normal and waveguide incidences. The developed theory is also utilized to understand the difference between the TEM and TE10 mode of excitation. Using this theory, effects of different physical parameters on reflection properties of unit cells are studied without the need of full-wave simulations. Detailed analysis is performed for Ka-band reflectarray unit cells and verified by full-wave simulations. In addition, an approach to extract the Q factors using full-wave simulations is also presented. Lastly, a detailed study on the effects of inter-element spacing is discussed.Q factor theory discussed in chapter 2 is extended to account for the varying incidence angles and polarizations in chapter 3 utilizing Floquet modes. Emphasis is laid on elements located on planes where extremities in performance tend to occur. The antenna element properties are assessed in terms of maximum reflection loss and slope of the reflection phase. A thorough analysis is performed at Ka band and the results obtained are verified using full-wave simulations. Reflection coefficients over a 749-element reflectarray aperture for a broadside radiation pattern are presented for a couple of cases and the effects of coupling conditions in conjunction with incidence angles are demonstrated. The presented theory provides explicit physical intuition and guidelines for efficient and accurate reflectarray design.In chapter 4, tunable reflectarray elements capacitively loaded with Barium Strontium Titanate (BST) thin film are shown. The effects of substrate thickness, operating frequency and deposition pressure are shown utilizing coupling conditions and the performance is optimized. To ensure minimum affects from biasing, optimized biasing schemes are discussed. The proposed unit cells are fabricated and measured, demonstrating the reconfigurability by varying the applied E-field. To demonstrate the concept, a 45 element array is also designed and fabricated. Using anechoic chamber measurements, far-field patterns are obtained and a beam scan up to 25o is shown on the E-plane.Overall, novel theoretical approaches to analyze the reflection properties of the reflectarray elements using Q factors are developed. The proposed theoretical models provide valuable physical insight utilizing coupling conditions and aid in efficient reflectarray design. In addition, for the first time a continuously tunable reflectarray operating at Ka-band is presented using BST technology. Due to monolithic integration, the technique can be extended to higher frequencies such as V-band and above.
Show less - Date Issued
- 2015
- Identifier
- CFE0006040, ucf:50963
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006040
- Title
- BST-Inspired Smart Flexible Electronics.
- Creator
-
Shen, Ya, Gong, Xun, Wahid, Parveen, Sundaram, Kalpathy, Coffey, Kevin, University of Central Florida
- Abstract / Description
-
The advances in modern communication systems have brought about devices with more functionality, better performance, smaller size, lighter weight and lower cost. Meanwhile, the requirement for newer devices has become more demanding than ever. Tunability and flexibility are both long-desired features. Tunable devices are 'smart' in the sense that they can adapt to the dynamic environment or varying user demand as well as correct the minor deviations due to manufacturing fluctuations,...
Show moreThe advances in modern communication systems have brought about devices with more functionality, better performance, smaller size, lighter weight and lower cost. Meanwhile, the requirement for newer devices has become more demanding than ever. Tunability and flexibility are both long-desired features. Tunable devices are 'smart' in the sense that they can adapt to the dynamic environment or varying user demand as well as correct the minor deviations due to manufacturing fluctuations, therefore making it possible to reduce system complexity and overall cost. It is also desired that electronics be flexible to provide conformability and portability.Previously, tunable devices on flexible substrates have been realized mainly by dicing and assembling. This approach is straightforward and easy to carry out. However, it will become a (")mission impossible(") when it comes to assembling a large amount of rigid devices on a flexible substrate. Moreover, the operating frequency is often limited by the parasitic effect of the interconnection between the diced device and the rest of the circuit on the flexible substrate. A recent effort utilized a strain-sharing Si/SiGe/Si nanomembrane to transfer a device onto a flexible substrate. This approach works very well for silicon based devices with small dimensions, such as transistors and varactor diodes. Large-scale fabrication capability is still under investigation.A new transfer technique is proposed and studied in this research. Tunable BST (Barium Strontium Titanate) IDCs (inter-digital capacitors) are first fabricated on a silicon substrate. The devices are then transferred onto a flexible LCP (liquid crystalline polymer) substrate using wafer bonding of the silicon substrate to the LCP substrate, followed by silicon etching. This approach allows for monolithic fabrication so that the transferred devices can operate in millimeter wave frequency. The tunability, capacitance, Q factor and equivalent circuit are studied. The simulated and measured performances are compared. BST capacitors on LCP substrates are also compared with those on sapphire substrates to prove that this transfer process does not impair the performance.A primary study of a reflectarray antenna unit cell is also conducted for loss and phase swing performance. The BST thin film layout and bias line positions are studied in order to reduce the total loss. Transferring a full-size BST-based reflectarray antenna onto an LCP substrate is the ultimate goal, and this work is ongoing at the University of Central Florida (UCF).HFSS is used to simulate the devices and to prove the concept. All of the devices are fabricated in the clean room at UCF. Probe station measurements and waveguide measurements are performed on the capacitors and reflectarray antenna unit cells respectively.This work is the first comprehensive demonstration of this novel transfer technique.
Show less - Date Issued
- 2012
- Identifier
- CFE0004439, ucf:49339
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004439
