Contact hole metrology study: understand the electron beam interaction with photoresist and how to minimize its impact

BackgroundContact hole (CH) features have been widely patterned in high-volume manufacturing in the semiconductor industry. E-beam metrology is the mainstream technique for inline metrology of such features. Yet, there are phenomena impacting accuracy and precision.AimWe aim to understand the e-beam interaction with the resist at different measurement conditions of critical dimension scanning electron microscope (CDSEM) and different resist materials.ApproachAn array of resist materials at different feature sizes and pitches have been measured using CDSEM under various conditions and methods. Three additional complementary metrology techniques have been used to characterize the 3D resist profile before and after irradiation. In addition, Monte Carlo simulations were used to further investigate charging effects induced by the CDSEM.ResultsThe results show that there are different critical dimension (CD) trends depending on the resist materials. There is a regime where the surface charging dominates the CD measurements and a regime where the thickness reduction along with the sloped resist profile effect dominates the CD measurements. Monte Carlo simulations show a positive charge on the top surface at lower primary electron beam energies and a negative charge at high primary beam energy, and this depends on the material properties.ConclusionsWe demonstrated the impact of e-beam metrology parameters on CH metrology. Complementary metrology techniques and Monte Carlo simulations assist in achieving a comprehensive interpretation of the CDSEM trends.