Comparative study of deep-UV resist processes for 0.35-um technology

Deep UV lithography at 248 nm has shown resolution down to 0.3 micrometers on flat substrates by using wet developable resists. However, due to higher reflectivity at this wavelength, interference effects are enhanced and CD variations have been observed on topography. Different approaches can be used to decrease these effects. In this paper we propose to study two processes related to this problem: (1) a dyed monolayer wet developable resist, and (2) a bilayer system, including a dry developable organic antireflective coating. Several dyed versions of XP 89131 resist from Shipley were studied first, on flat substrates and then on wafers with topography. On flat substrates, the influence of different parameters, such as resist absorption, solubility, bake temperatures, and development time for a given exposure dose on CD, slope, and process latitude have been quantified for 0.3 and 0.35 micrometers . The resist profile modification on reflective topography is discussed. In the case of a bilayer system, a deep UV transparent layer can be used as the top layer (XP 89131). The bottom antireflective (ARC) layer is the resist XP 91218 from Shipley. Dry anisotropic etching of this ARC has been studied by screening of plasma parameters (gas pressure, ion energy, gas type) in various etching equipments (DECR and RIE).