Novel metal-oxide photoresist materials for extreme UV lithography

A major current trend in lithography is the development of exposure tools that have ever-shorter wavelengths, with the overall aim of achieving mass production of devices with sub-10nm feature sizes. Extreme UV lithography (EUVL) at a wavelength of 13.5nm is the main candidate for next-generation lithography technology.1 Highly sensitive resist materials, however, are required for EUVL so that its high-power exposure source requirements can be reduced.2

Until now, chemically amplified resists (CARs) have been used in EUVL.3 CARs are formulated by adding an organic polymer, a photoacid generator, and a quencher species together (see Figure 1). Although such resists have good sensitivity, they also have a number of associated problems. For example, the resolution of chemically amplified resists is strongly affected by pattern collapse, which becomes increasingly important as feature sizes approach the nanometer scale.4 Furthermore, it is challenging to reduce the aspect ratio (film thickness/critical dimension) of CARs because of their high susceptibility to the non-uniform distribution of components in the film. As a result, poor imaging performance tends to be obtained.

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