“Patterning at the Nanoscale using
Polymer Ultra-Thin Films:
Developing Advanced Materials and Processes to Overcome the Limits of Lithography”
Professor Cliff Henderson
School of Chemical & Biomolecular Engineering
Georgia Institute of Technology
DATE: Thursday, May 27, 2004
TIME: 4:00 p.m.
PLACE: Engineering II Room 3361
ABSTRACT
The meteoric rise in the functionality of semiconductor integrated circuits (IC’s) over the past 30 years has dramatically changed human lifestyles and living standards around the world. Alarmingly, the semiconductor industry today faces a significant number of technological roadblocks that threaten to halt such further advancements, and thus threaten the technologies and economies that rely on semiconductor technology. One of the primary challenges moving forward will be designing more advanced or completely new lithographic methods to create the small patterns (already <130 nm in size) that define the microelectronic device features such as the transistor gate.
This seminar will first provide a brief introduction to microelectronics fabrication and microlithography. Specifically, the major challenges and options for future lithographic technologies will be discussed as a motivation for some of the work currently in progress in our research group. One of the critical challenges to be faced in designing more advanced lithographic patterning technologies is the development of advanced photoresist materials that can enable sub-100nm patterning. A persistent roadblock to the rational design of such resist materials is the difficulty encountered in properly characterizing the photochemical, chemical, and physical events that lead to pattern formation in modern chemically amplified photoresists. For example, simply measuring the photochemical reaction rates of the photoacid generators (PAGs) that initiate the first step in the patterning process in chemically amplified photoresists (CARs) has historically been very difficult. Significant advancements have been made in our laboratories recently in this area by developing a variety of techniques for photoresist characterization. This talk will present a powerful new methodology for characterizing reaction rates and diffusion coefficients in thin polymer films based on the use of electrical measurements involving interdigitated electrode (IDE) sensors. These sensors are now helping us to gain a better understanding of the fundamental processes that control pattern formation in resist materials.
As each new lithography generation is introduced, one trend that is occurring as feature sizes decrease is that the film thickness of the polymeric photoresist films used for lithographic patterning is also decreasing. Resist films well below 200 nm in thickness will be needed in the near future. This nanometer scale confinement of the polymeric photoresist film can have a strong impact on the physical properties of the film which can in turn affect lithographic performance. A summary of recent results concerning the impact of such confinement effects on polymer thin film behavior and photoresist materials design and performance will also be presented. In particular, the impact of film thickness on the glass transition temperature, coefficient of thermal expansion, polymer dissolution rate, and the diffusion coefficient of small molecules, such as photoacids, in photoresist films will be discussed. It will be shown that certain nanoscale confinement effects may work to our advantage in continuing to make features below 100 nm in size.