Abstract:

Nanoimprint lithography (NIL) has developed into an increasingly mature technology with applications in many different areas. This dissertation work focuses on the application of NIL in fabricating electronic devices with nanometer size features.

Lithography patterns in electronic devices are complex and can have elements of very different sizes ranging from tens of nanometers to tens of micrometers. Nonetheless, the total foot print area of each individual device pattern is relatively small. Thus, NIL mold patterns for electronic devices are best generated by electron beam lithography (EBL). In this thesis I first discuss the patterning and fabrication of NIL mold using EBL and reactive ion etching (RIE) in chapter 2.

Alignment is essential to fabricating devices with more than one lithography levels. With resolution better than 10 nm, NIL should ideally have alignment accuracy no worse than a few nanometers to match its superb resolution. An alignment method based on interferential Moir? pattern is explored and the result is presented in chapter 3.

With these technologies at disposal, I fabricated organic thin film transistors (OTFT) with channel lengths as short as 20 nm. An ultra-thin gate oxide was used to minimize the short-channel effects and reduce operating voltage. The OTFTs demonstrated normal field-effect transistor characteristics. Detail of this work is in chapter 4.

Another device fabricated and studied is gold-nanowire based organic molecule detectors, with nanowire dimension of 25-200 nm wide and 10-30 nm thick. The resistance change of the nanowires caused by the formation of n-alkanethiol molecule self-assembly monolayers (SAM) on the nanowire surfaces was found to depend on the geometric dimension of the nanowires. The sensitivity of the detector was improved by increasing the surface-to-volume ratio of individual nanowire.

To investigate the scalability of chalcogenide based phase change memory (PCM) devices I fabricated PCM devices with vertical pore-like structure. Their contact hole diameters are as small as 20 nm. The performances of the devices were tested and very low power consumption and fast switching operation were realized in the smaller devices. Devices with different contact hole sizes also demonstrated clear scaling behavior in their operating currents.