Ottmar Dr. Rohde

Recent Advances In Photoimagable Polyimides

To date the use of photoimagable polyimide systems has been limited by lack of photo-speed, excessive volume contraction, and by shelf-life problems. These shortcomings have now been improved to the point where a practical, usable system has become available. Through the use of novel high quantum yield sensitizers, tailored to the g-line (436 nm) of the mercury spectrum, it is now possible to lower exposure times markedly and to reduce the amount of layer shrinkage that occurs in the final cure. Layers up to 70 microns and more of final cured polyimide can be photostructured at high resolution with an exposure energy of less than 1 J/cm2. The system presented is particularly useful for relatively thick layer applications as, for example, alpha particle protection, but can be used also for thin layer applications with accordingly shorter exposure times.

Structural design of ketal and acetal blocking groups in two-component chemically amplified positive DUV resists

In the present study, protecting groups of moderate stability, such as acetals and ketals, were investigated as pendant blocking groups in polyvinyl phenols. Polymers were obtained by reacting enol ethers with the phenolic side groups to form acetal or ketal blocked phenols. Decomposition temperatures, glass transition temperatures, and molecular weights of the resulting polymers were monitored and correlated with the protecting group structure. Stability of the protecting groups can be explained by protonation occurring at either of the two oxygen sites, making two cleavage routes possible. Secondary reactions of the released protecting groups in the resist film were investigated and discussed. The structure of the protecting group was designed in order to meet basic resist properties such as resolution/linearity, DOF, post exposure delay latitude and thermal stability. A Canon FPA 4500 (NA equals 0.37) and a GCA XLS exposure tool (NA equals 0.53) were used for the optimization process. A preoptimized resist formulation based on the above criteria exhibits 0.23 micrometers line/space resolution, 0.8 micrometers focus latitude at 0.25 micrometers resolution and approximately two hours post exposure delay latitude.