| The most advanced microelectronic devices of today are manufactured using photoresists that rely on the design concept of "chemical amplification". Rather than using exposure energy to directly cause a solubility switch, chemically amplified photoresists use exposure energy only to generate a catalytic species. The photogenerated catalyst then promotes a solubility-switching chemical reaction in the exposed regions of the photoresist. In this manner, lithographic imaging can be accomplished with very low exposure doses, saving time and money in manufacturing. While chemically amplified resists have many advantages, they have one potential limitation or drawback. It is possible in chemically amplified systems for catalyst generated in exposed regions to diffuse into unexposed regions, causing blurring of the deposited latent image. This blurring effect is an observed fact in microelectronic processing and becomes of increasing concern as feature sizes shrink. The topic of catalyst diffusion (often referred to as "acid diffusion" because the catalyst in all practical systems has been an acid) has been of concern to microlithography community since the introduction of chemically amplified photoresists in the late 1980's. Since that time it has been a well studied, but poorly understood, phenomenon. This work is an attempt to develop a fundamental, mechanistic understanding of catalyst transport processes in chemically amplified photoresist. It is hoped that a better understanding of the fundamentals of resist performance will eventually lead to better photoresist designs and formulations and thus, faster and cheaper microelectronic devices. |
