Pattern collapse solution for asymmetric pattern

One of the most critical issues associate with decreasing photo-resist feature size is pattern collapse, and more serious pattern collapse can be easily observed especially in asymmetric pitch environment due to unbalanced capillary stress acting on photo-resist pattern during development rinse step. The pattern collapse would kill product yield in the worse condition. This work investigates the approaches of mitigating the asymmetric pattern collapse behavior, such as adjusting photoresist pattern aspect ratio, applying surfactant during development rinse to reduce the solution surface tension, and altering underlying anti-reflection coating and hard-mask combinations to tailor the photo-resist bottom profile as well as decreasing developer permeation into photo-resist interface. Pattern sizing to resist unbalanced capillary force is also explored in the asymmetric pattern region. Two novel layout methods to mitigate asymmetric dummy pattern collapse were demonstrated and both methods were confirmed to have higher immunity against pattern collapse in asymmetric pitch environment.