Tamae Haruki

Simple Method of Correcting Optical Proximity Effect for 0.35 µm Logic LSI Circuits

We propose a practical optical proximity correction (OPC) system, whose characteristics are simple and effective, for logic LSI circuits and outline all the steps for OPC. We also report the improvement of gate length deviations in a logic device with OPC.

Algorithm for shifter placement with flexible order prioritizing

Alternating phase shifting masks have been investigated as a method for forming the devices of 0.18 μm or less. To design these mask patterns, the phase difference between adjacent apertures should be 180°. However, it is theoretically impossible to accomplish this without phase conflicts. Therefore, design modifications at each conflicting portion is necessary after the shifter placement. On the basis of our investigations, modifying the design layout can be facilitated by reflecting the designers’ various demands in the shifter layout that is designed by the automated computer-aided design (CAD). We formulated an evaluation function by taking the priorities for designers’ demands into account and developed a model of the design layout and a resolution method implemented by a genetic algorithm. Then, a shifter placement CAD was made available on the layout editor. We confirmed that the various demands of designer are satisfied and that the computational performance is satisfactory for practical use.

MASCOT: Mask Pattern Correction Tool Using Genetic Algorithm

We propose a new optical proximity correction (OPC) method using a polygonal mask model and a genetic algorithm (GA). With the polygonal mask model, our method can generate simple and practical masks that satisfy the constraints arising from manufacturing requirements. A robust optimization method, the genetic algorithm was adopted for obtaining adequate modifying ability for a given arbitrary mask pattern. For some of these mask patterns, the characteristics of distortion due to the optical proximity effects (OPE) are not well-known. GAs simulate the free-competition among animals through generation alternation is recognized as the algorithm that can avoid being stuck in local optima in multi-modal optimization problems. We developed our mask pattern correction tool (MASCOT) using the mask model and the optimization method. Experimental results showed great improvement in the generated resist pattern. Satisfactorily practical computational performance was obtained in our experiments with a workstation.

Development of a total CAD system for alternate-type PSMs with optical proximity correction

Alternate-type phase shifting masks (PSMs) have been investigated as a methods used to fabricate 0.18 micrometer and smaller rule devices. For practical use, an automatic shifter placement CAD, a DRC for the indicating errors in rules for alternate-type PSMs, and an optical proximity correction (OPC) tool are indispensable. We previously reported on the algorithm for the shifter placement and the DRC for alternate-type PSMs and the OPC tool. We now report that these tools enhance the practical CAD system, fully supporting the entire process from designing the physical layout to adjusting the mask patterns in order to prevent the optical proximity effects. First, the phase shifting patterns are generated automatically. Next, the DRC tool indicates rule errors for the design of alternate-type PSMs. The Designers must modify the indicated portions and replace the shifters or DRC until there are no errors. In order to be more general than our previous tools, it is important that the delivering data between the layout editor and the program be GDS formatted data. Following the designing of the PSMs, the OPC tool, which was developed on parallel processor units, adjusts the designed patterns. Our system was actually used to fabricate 0.18 micrometer rule full-chip devices, and thus we confirmed that the computing performance is satisfactorily practical and that the CAD system shows promises as a means of fabricating rule devices beyond current rules.