Polymers for microelectronics and energy storage




Meyer, Paul William, Ph. D.

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This dissertation focuses on two different applications of polymers for use in electronic devices. The first is pitch division photoresists, employed to improve the resolution of current photolithography tools. The second application employs the self-assembly of di-block copolymers for membrane applications, with specific focus given to separators in batteries. The microelectronics industry has continually devised new ways of printing smaller features to increase the complexity of devices and drive down cost. Although 193 nm exposure tools are common for printing the smallest of features, they are expensive, and many processes still use patterning at 254 and 365 nm wavelengths for patterns with less stringent length scales. To further improve the feature density for these processes, manufacturers oftentimes must purchase a new tool, requiring significant capital investment. At the core of this printing process is a photoresist, a photosensitive resin that changes solubility upon exposure to light. Pitch division photoresists improve the resolution of these exposure tools through chemistry. By employing a photobase generator in combination with a photoacid generator, the feature density obtained can be doubled without changing the aerial image, effectively extending the lifetime of exposure tools. This dissertation specifically focuses on pitch division at wavelengths at 254, 265, 355, and 365 nm. With increasing demand in portable electronics, there is also demand for improvements in energy storage, with lithium-ion batteries having taken over this landscape. Within this class of batteries, lithium metal anodes have been proposed to further increase the storage capabilities of these devices. However, lithium metal is very unstable, sometimes leading to catastrophic failure due to dendritic growth. Several types of solid electrolytes have been proposed in order to suppress lithium dendrite formation. Among them, polymer electrolytes have become an intensely studied class of materials, but generally exhibit a tradeoff between mechanical strength and ionic conductivity. The second part of the dissertation leverages the self-assembly of block copolymers into an isoporous gyroid morphology. One of the blocks is mechanically strong while the other is a selectively degradable polylactide. Because the pores created by the polylactide block can be filled with another electrolyte, the mechanical and ionically-conductive properties have been decoupled. The fabrication of these gyroid membranes and preliminary investigations into their application are presented.


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