## 7 Case Analysis and Discussion  
An Optical Measuring Machines (OMM) dimensional measurement precision microscope was used at 2500 \(\upmu\)m for the BM photoresist ADI, as shown in Figure 3.  
Current condition measurement: The present \(C_{pk}\) process capability of BM photoresist build-up dimension was analyzed. The key success factors shown are the study design and the results, as shown in Table 1. \begin{table}
\begin{tabular}{l c c c c c} \hline Control Factor & Range & Current Level & Level 1 & Level 2 & Level 3 \\ \hline A. Target material temperature (\({}^{\circ}\)C) & 40–350 & 170 & 150 & 170 & - \\ B. Toor (\%) & 10 \({}^{1}\) & 10 \({}^{8}\) & 0.0001 & 0.001 & 0.000001 \\ C. Prebaking time (S) & 100–350 & 120 & 120 & 130 & 140 \\ D. Exposure (m) & 100–450 & 400 & 360 & 380 & 400 \\ E. Rate of development (M/min) & 2.5-4 & 2.8 & 2.7 & 2.8 & 2.9 \\ F. Post-baking time (S) & 7300 & 1800 & 1700 & 1800 & 1900 \\ G. Post-baking temperature (\({}^{\circ}\)C) & 350 & 240 & 230 & 240 & 250 \\ H. Exposure GAP (\(\upmu\)m) & 20–400 & 150 & 140 & 150 & 160 \\ \hline \end{tabular}
\end{table} 
Table 1: Factor level setting for control factors. Figure 3: The BM photoresist build-up dimension (nominal-the-best: diameter: 2500 \(\upmu\)m). The dimension process capability index \(C_{pk}=0.9<1.33\), meaning the process is unstable. Because the process capability is insufficient, there is large room for improvement. In this study, human factors include immature skill, insufficient training, and misoperation: environmental factors include temperature, humidity, and light rays; material factors include exposure, overtime, concentration, and temperature; method factors include exposure, development rate, and pre-baking time; machine factors include feed rate, part failure, and vacuum pressure. All of these factors may cause problems in the lithography BM photoresist operation build-up dimension. Data analysis: The factors were analyzed and confirmed by interviews with experts, and the factors that influence the BM negative photoresist build-up dimension ADI were determined by interviewing photolithography process engineers and process integration engineers, so as to remove the unnecessary factors in implementing the analysis of the hybrid Taguchi-genetic algorithm. The factors and levels influencing the BM photoresist build-up dimension were analyzed according to the lithographic photoresist operating conditions influencing ADI, as shown in Table 1.  
After fmGA analysis, the two-level and three-level factors were collected simultaneously, while the experimental data were collected by an orthogonal array of mixed level \(L_{18}\left(2^{1}\quad 3^{7}\right)\). According to the results in Table 2, the root mean square error (RMSE) [11] value of training examples ranges from 0.039 to 0.058, as the input variable and output variable were normalized to 0 to 1. This result is fairly good. The RMSE of the test examples ranges from 0.012 to 0.031, which is a better result than that of the training examples. The experiment was conducted and the data were collected according to the orthogonal array configuration, with limited samples used for the experiment. This experiment hopes to optimize the BM photoresist build-up dimension, but the quality characteristic of Toor is in percentage form in this study. If the quality characteristic is in percentage form, then, when the value approaches 0 or 100, the additivity is very bad, so the deficiency is remedied. The Taguchi method implements \(\Omega\) transformation (Omega transformation) for the quality characteristics in percentage form. The experimental data with additivity are obtained by \(\Omega\) transformation, and the signal/noise (SN) ratio was worked out of these data. When the experimental control factor and level table were completed, the orthogonal array was created. The two-level and three-level factors were collected simultaneously in this experiment.