Matching Items (4)
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- All Subjects: Organic Light Emitting Diodes
- All Subjects: Semiconductors
- Creators: Adams, James
Description
Electromigration in metal interconnects is the most pernicious failure mechanism in semiconductor integrated circuits (ICs). Early electromigration investigations were primarily focused on aluminum interconnects for silicon-based ICs. An alternative metallization compatible with gallium arsenide (GaAs) was required in the development of high-powered radio frequency (RF) compound semiconductor devices operating at higher current densities and elevated temperatures. Gold-based metallization was implemented on GaAs devices because it uniquely forms a very low resistance ohmic contact and gold interconnects have superior electrical and thermal conductivity properties. Gold (Au) was also believed to have improved resistance to electromigration due to its higher melting temperature, yet electromigration reliability data on passivated Au interconnects is scarce and inadequate in the literature. Therefore, the objective of this research was to characterize the electromigration lifetimes of passivated Au interconnects under precisely controlled stress conditions with statistically relevant quantities to obtain accurate model parameters essential for extrapolation to normal operational conditions. This research objective was accomplished through measurement of electromigration lifetimes of large quantities of passivated electroplated Au interconnects utilizing high-resolution in-situ resistance monitoring equipment. Application of moderate accelerated stress conditions with a current density limited to 2 MA/cm2 and oven temperatures in the range of 300°C to 375°C avoided electrical overstress and severe Joule-heated temperature gradients. Temperature coefficients of resistance (TCRs) were measured to determine accurate Joule-heated Au interconnect film temperatures. A failure criterion of 50% resistance degradation was selected to prevent thermal runaway and catastrophic metal ruptures that are problematic of open circuit failure tests. Test structure design was optimized to reduce resistance variation and facilitate failure analysis. Characterization of the Au microstructure yielded a median grain size of 0.91 ìm. All Au lifetime distributions followed log-normal distributions and Black's model was found to be applicable. An activation energy of 0.80 ± 0.05 eV was measured from constant current electromigration tests at multiple temperatures. A current density exponent of 1.91 was extracted from multiple current densities at a constant temperature. Electromigration-induced void morphology along with these model parameters indicated grain boundary diffusion is dominant and the void nucleation mechanism controlled the failure time.
ContributorsKilgore, Stephen (Author) / Adams, James (Thesis advisor) / Schroder, Dieter (Thesis advisor) / Krause, Stephen (Committee member) / Gaw, Craig (Committee member) / Arizona State University (Publisher)
Created2013
Description
White organic light emitting diodes (WOLEDs) are currently being developed as the next generation of solid state lighting sources. Although, there has been considerable improvements in device efficiency from the early days up until now, there are still major drawbacks for the implementation of WOLEDs to commercial markets. These drawbacks include short lifetimes associated with highly efficient and easier to fabricate device structures. Platinum (II) complexes are been explored as emitters for single emissive layer WOLEDs, due to their higher efficiencies and stability in device configurations. These properties have been attributed to their square planar nature. Tetradentate platinum (II) complexes in particular have been shown to be more rigid and thus more stable than their other multidentate counterparts. This thesis aims to explore the different pathways via molecular design of tetradentate platinum II complexes and in particular the percipient engineering of a highly efficient and stable device structure. Previous works have been able to obtain either highly efficient devices or stable devices in different device configurations. In this work, we demonstrate a device structure employing Pt2O2 as the emitter using mCBP as a host with EQE of above 20% and lifetime values (LT80) exceeding 6000hours at practical luminance of 100cd/m2. These results open up the pathway towards the commercialization of white organic light emitting diodes as a solid state lighting source.
ContributorsOloye, Temidayo Abiola (Author) / Li, Jian (Thesis advisor) / Alford, Terry (Committee member) / Adams, James (Committee member) / Arizona State University (Publisher)
Created2016
Description
Research and development of organic materials and devices for electronic applications has become an increasingly active area. Display and solid-state lighting are the most mature applications and, and products have been commercially available for several years as of this writing. Significant efforts also focus on materials for organic photovoltaic applications. Some of the newest work is in devices for medical, sensor and prosthetic applications.
Worldwide energy demand is increasing as the population grows and the standard of living in developing countries improves. Some studies estimate as much as 20% of annual energy usage is consumed by lighting. Improvements are being made in lightweight, flexible, rugged panels that use organic light emitting diodes (OLEDs), which are particularly useful in developing regions with limited energy availability and harsh environments.
Displays also benefit from more efficient materials as well as the lighter weight and ruggedness enabled by flexible substrates. Displays may require different emission characteristics compared with solid-state lighting. Some display technologies use a white OLED (WOLED) backlight with a color filter, but these are more complex and less efficient than displays that use separate emissive materials that produce the saturated colors needed to reproduce the entire color gamut. Saturated colors require narrow-band emitters. Full-color OLED displays up to and including television size are now commercially available from several suppliers, but research continues to develop more efficient and more stable materials.
This research program investigates several topics relevant to solid-state lighting and display applications. One project is development of a device structure to optimize performance of a new stable Pt-based red emitter developed in Prof Jian Li's group. Another project investigates new Pt-based red, green and blue emitters for lighting applications and compares a red/blue structure with a red/green/blue structure to produce light with high color rendering index. Another part of this work describes the fabrication of a 14.7" diagonal full color active-matrix OLED display on plastic substrate. The backplanes were designed and fabricated in the ASU Flexible Display Center and required significant engineering to develop; a discussion of that process is also included.
Worldwide energy demand is increasing as the population grows and the standard of living in developing countries improves. Some studies estimate as much as 20% of annual energy usage is consumed by lighting. Improvements are being made in lightweight, flexible, rugged panels that use organic light emitting diodes (OLEDs), which are particularly useful in developing regions with limited energy availability and harsh environments.
Displays also benefit from more efficient materials as well as the lighter weight and ruggedness enabled by flexible substrates. Displays may require different emission characteristics compared with solid-state lighting. Some display technologies use a white OLED (WOLED) backlight with a color filter, but these are more complex and less efficient than displays that use separate emissive materials that produce the saturated colors needed to reproduce the entire color gamut. Saturated colors require narrow-band emitters. Full-color OLED displays up to and including television size are now commercially available from several suppliers, but research continues to develop more efficient and more stable materials.
This research program investigates several topics relevant to solid-state lighting and display applications. One project is development of a device structure to optimize performance of a new stable Pt-based red emitter developed in Prof Jian Li's group. Another project investigates new Pt-based red, green and blue emitters for lighting applications and compares a red/blue structure with a red/green/blue structure to produce light with high color rendering index. Another part of this work describes the fabrication of a 14.7" diagonal full color active-matrix OLED display on plastic substrate. The backplanes were designed and fabricated in the ASU Flexible Display Center and required significant engineering to develop; a discussion of that process is also included.
ContributorsO'Brien, Barry Patrick (Author) / Li, Jian (Thesis advisor) / Adams, James (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2017
Description
The semiconductor industry looks to constantly improve the efficiency of research and development in order to reduce costs and time to market. One such method was designed in order to decrease time spent inducing warpage in integrated circuits in an Intel research process. Intel's Atom product line seeks to compete with ARM architecture by entering the mobile devices CPU market. Due to the fundamental differences between the Atom's Bonnell architecture and the ARM architecture, the Intel Atom product line must utilize such improved research and development methods. Until power consumption is drastically lowered while maintaining processing speed, the Atom product line will not be able to effectively break into the mobile devices CPU market.
ContributorsLandseidel, Jack Adam (Author) / Adams, James (Thesis director) / Krause, Stephen (Committee member) / Anwar, Shahriar (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Materials Science and Engineering Program (Contributor)
Created2013-05