Implementation of sub-150 nm contact hole pattern by resist flow process

The characteristics and performance of the resist flow process (RFP), which is one of the contact hole (CM) shrinking technologies, were investigated for sub-150 nm C/H patterns using KrF (lambda = 248 nm) lithography. A fine C/H pattern was defined by adopting optimized process parameters at a high er baking temperature than the glass transition temperature of the used mat rix 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, howev er, the bowing profile of the C/H pattern was observed in the case of a shr inking bias larger than 50 nm. It was also found that the amount of shrinka ge of the C/H pattern was strongly dependent on the baking temperature, tot al 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 t he energy latitude (EL) were 1.6 mu m and 16%, respectively, and the critic al dimension (CD) uniformity in an 8-inch wafer was less than 25 nm. In thi s 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.