Development of scan coating by using parameter design of the Taguchi method

The HALCA project developed a new commercially feasible scan-coating technology. At the development stage, the parameter design of the Taguchi method was used as a technique to evaluate and modify various characteristics. The result is that we were able to perform experiments efficiently and quickly and that we were able to gain considerable knowledge and achieve improvements in intrawafer uniformity. Namely, in scan coating, there is a time difference between the starting point and the finishing point, which is significantly different from conventional spin coating. The time difference yields unevenness in drying and deteriorates intrawafer uniformity. To avoid the deterioration, it must take a short time to coat a wafer from start to finish. Further, the gap between a wafer and a dryness control plate must be optimized. By applying these factors, we achieved fair improvements on intrawafer uniformity to the level of 0.96%(3σ/ average^*100%) from the conventional 3.85%(3σ/ average^*100%), which is equivalent to the uniformity of spin coating. The efficiency of materials consumption in scan coating is fairly high as compared with that in spin coating, which achieved around 80%. Therefore, commercially practical scan coating can be promised, attaining a cost reduction in the semiconductor manufacturing process.