Cheol Kyu Bok

The Implementation Of Sub-150nm Contact Hole Pattern By Resist Flow Process

The characteristics and performance of the resist flow process (RFP), which is one of the contact hole (C/H) shrinking technologies, were investigated for sub-150 nm C/H patterns using KrF (λ=248 nm) lithography. A fine C/H pattern was defined by adopting optimized process parameters at a higher baking temperature than the glass transition temperature of the used matrix material. The shrinking limit of the C/H pattern was in the range of 40–50 nm without any deformation in profile from the original C/H size, however, the bowing profile of the C/H pattern was observed in the case of a shrinking bias larger than 50 nm. It was also found that the amount of shrinkage of the C/H pattern was strongly dependent on the baking temperature, total quantity of the resist surrounding the C/H pattern, and resist thickness. When the 150 nm C/H pattern was formed by RFP from a 180 nm C/H generated by an attenuated phase shifting mask (PSM), the depth of focus (DOF) and the energy latitude (EL) were 1.6 µm and 16%, respectively, and the critical dimension (CD) uniformity in an 8-inch wafer was less than 25 nm. In this study, in spite of baking to enable resist flow, the etch selectivity of resist on silicon substrates was not changed and the C/H pattern on silicon oxide after the etching process showed a vertical profile. Based on these results, it is believed that the RFP for a sub-150 nm C/H pattern will be a very promising candidate for the mass production of gigabit devices.

Analysis of multilayer structure for reflection of extreme ultra-violet wavelength

Extreme ultraviolet lithography (EUVL) is considered to be one of the most competitive next generation lithography (NGL) technologies (Gwyn et al, 1998). In EUVL, reflective multilayers are used for mask and mirror applications in the exposure system. The reflectivity of these multilayers, which is a critical factor for throughput of EUVL, is dependent on structural factors as well as the materials. Even though the at-wavelength reflectivity should be measured, we usually use other characterization techniques (e.g. cross sectional TEM or low angle XRD) when we optimize the deposition conditions. In this paper, we deposited several Mo/Si multilayers and compared the structural factors extracted from various characterization techniques.