The reduction of line width roughness (LWR) remains a difficult issue for very fine patterns obtained with extreme ultraviolet (EUV) lithography. Thus, the investigation of LWR-reduction from the viewpoint of resist processing has become necessary. Alternative bake processes, such as the flash-lamp (FL) has been proven feasible as for application in EUV resists. This work focuses on initial investigations for its use in post-development bake (post bake or PB). A polyhydroxystyrene-acryl hybrid EUV model resist was utilized and comparisons with 'no bake' and conventional hot-plate PB conditions were made. As a result, relatively improved LWR was obtained with FL PB with minimal effect on lithographic performance. Moreover, in the course of these experiments, two types of resist reflow mechanisms assumed to be the primary basis for the LWR improvement achieved, are discussed.
We developed a pattern collapse prevention method which does not use a surfactant rinse agent. The pattern collapse phenomenon is commonly expressed by the stress applied on the pattern with key components including "the surface tension of the rinse agent" and "contact angle between pattern surface and rinse agent." Using a surfactant as a rinse agent is targeted at reducing "the surface tension of the rinse agent."The pattern collapse prevention method of focus in this report evaluates the "the drying rate of a rinse agent" and "the accumulated stress on a pattern" in relation to the pattern collapse phenomenon.By increasing the drying rate of the rinse agent, the integrated stress on the pattern is reduced allowing for the pattern collapse prevention. Dramatically speeding-up the drying rate of rinse agent by Accelerated Purge (AP) drying integrated into a photolithography track develop module and without using a surfactant rinse agent we have confirmed the ability to control the pattern collapse phenomenon. With AP drying we have also confirmed further defect reduction that would normally result from rinse agent remaining on a wafer, which has been significantly improved by the super-fast drying process. AP drying is a promising technology which can control pattern collapse phenomenon without using a surfactant rinse agent with advantages in yield improvement, process time reduction and chemical cost reduction.
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