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Chemically amplified photoresists where first created for broadband deep UV imaging, then used for monochromatic KrF excimer laser light, then ArF and now F2 for 157nm imaging. With this experience we may able to build The Perfect Photoresist. This may sound ridiculous, however, take a good look at the SIA roadmap, and the timing in which 157nm imaging will be needed. There are numerous arguments regarding 157nm insertion, some say 100nm and others say the 70nm node; regardless of the timing it is approaching quickly. The time allowed to develop such technology is decreasing. If we recall back to the early 1980's when deep UV (248nm) materials development started, it has taken nearly 10-12 years to perfect them. ArF materials, whose development began in the early 90's, will take approximately 8 years before reaching manufacturing (and there is still great improvement needed). Now let's focus on the timeline for 157nm resist: its development began in 1999 and it must be ready for early manufacturing by the end of 2004. Most, if not all, photoresist companies have plans to develop photoresist technology for 157nm. Many of these solutions are based on existing KrF or ArF materials technology with modifications to meet optical density requirements for 157nm. Considering the implementation node for this technology (let's assume 70nm), films thickness' will most likely not exceed 250nm and in most cases range from 150nm to 200nm. These films thicknesses bring on new and unique challenges, however, they can be managed. The authors will take into consideration three different types of device level imaging: gate, trench and contact holes for single layer imaging. Through the use of designed simulation experiments and existing data we will construct different photoresist models to meet the requirements for these device levels. We'll plan to test whether resist models calibrated at 248nm can be extrapolated to 157nm. The authors will also explore the question of optical density (B parameter), chemical contrast, exposed & unexposed film dissolution along with acid diffusion to provide the insight that can aid in developing materials for the photoresists composition. We will investigate the use of binary and attenuated reticles with various illumination conditions over several substrates, to provide insight into designing The Perfect Photoresist for 157nm Imaging.
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