No abstract

No abstract

Processes for PECVD SiON Anti-Reflective Layer (ARL) films are currently being developed for application to DUV lithography (exposure wavelength of248nm). The shorter wavelength (compared to g-line at 436nm or i-line at 365nm) allows for higher pattern resolution. Anti-reflective films are needed to reduce thin film interference (TFI) effects and reflective notching, which limit the control of critical dimension (CD) variations. The refractive index (n) and extinction coefficient (k) at the exposure wavelength, in addition to the film thickness (t), are needed to predict the film's anti-reflective property.Broadband ultra-violet spectroscopic ellipsometry (SE) is uniquely capable of directly measuring the refractive index dispersion (n and k versus wavelength) and thickness of single layer thin films (and films within multilayer thin film stacks), especially in the critical UV region. The refractive index (RI) dispersion is physically determined by the compositional characteristics ofthe film. This paper evaluates the robustness of various RI dispersion models (harmonic oscillator, Bruggeman effective medium approximation (BEMA) and Cauchy polynomial) in relation to the compositional variations of the SiON films. The n and k values (at 248nm) are correlated with the SiON stoichiometry, including hydrogen concentration from Rutherford Backscattering Spectrometry (RBS) measurements. Moreover, it is found that the UV RI's (n and k at 248nm in the range of I .9 to 2.2 and0.4 to 0.6 respectively) are better able to track small stoichiometry variations than conventional RI at 633nm.

No abstract

No abstract