Patterning of Read Head Track by Alternating Phase Shifted Mask
Original Publication Date: 2002-May-05
Included in the Prior Art Database: 2003-Jun-20
A novel application of existing technology is disclosed: additional process latitude (depth of focus (DOF) and exposure latitude (EL)) and resolving capability are achieved by use of an alternating phase shifted mask (alt-PSM) to pattern read head tracks of thin-film recording heads (TFH). Manufacturing costs are reduced by improving yield and delaying the need for more expensive exposure tooling upgrades. The typical read track defining mask (two adjacent openings separated by a narrow isolated opaque strip which forms the track width) is a perfect candidate for the alternating phase-shift approach. It is o easily modified such that one of the openings shifts the phase of transmitted light by 180 using established methods involving etching the transparent material in the opening to be shifted to a precise depth, determined by the exposure wavelength, for which the mask is intended. A schematic drawing of the mask pattern is shown in Fig. 1: 0O Phase 180 O Phase Figure 1 The conventional binary mask uses the same shapes but both openings are unshifted. The increase in process latitude can be seen as the difference between sizes of the boxes in Fig. 2 (conventional) and Fig. 3 (alt-PSM), which represent allowable fluctuations in defocus and exposure dose resulting in within-tolerance line sizes. The alt-PSM approach nearly doubles the allowable depth of focus of the printing process.