## 2 Materials and Methods
### Destruction Removal Efficiency (DRE)
#### 2.2.3 Improving DRE Measurements  
To measure the DRE of the semiconductor and display manufacturing processes, the volume flow rate of the process gas was calculated by estimating the concentration of tracer gas, as mentioned in Section 2.2.2. Tracer gas is generally applied as an inert gas that interacts with other gases in the pipe and is not destroyed by the abatement system, and Kr (Krypton) gas is used among several inert gases because it must be applied as a gas that is not used in semiconductor and display manufacturing processes. Accordingly, tracer gas (Kr) is injected using a mass flow controller (MFC) at the front of the abatement system. However, an MFC is generally calibrated using nitrogen or compressed air and when an MFC is calibrated by nitrogen or when compressed air is used, the accuracy of the volume flow rate of Kr is decreased. Therefore, accurate measurements were only possible when the volume flow rate of Kr was corrected by applying the gas factor, as shown in Table 2, and the composition of internal process gas in the semiconductor and display industry is shown in Table S4. Accurate measurements of the QMS for estimating the volume flow rate of process gas are only possible when samples are manufactured and equipment is calibrated, similar to the configuration of the actual internal process gas. Accordingly, a mixed standard gas similar to the composition of the process gas is produced, and the Kr concentration to be measured is diluted with N\({}_{2}\), and then the true estimation values are calculated in Table 3 to draw comparisons with the measured values. When Kr (99.999%) was injected into 1 SLM by estimating the volume flow rate of the process gas through the concentration measurement of Kr, measured concentrations were used to calculate the volume flow rate, according to Equation (1). In Experiment 1, when the volume flow rate was calculated, after calibration in consideration of only Kr without the composition of the process gas, the estimated true error value rate was 1.8 to 4.37% (Figure 2 and Table 4). In Experiment 2, when all components of the mixed standard gas were calibrated to measure the Kr concentration, in light of the composition of the process gas, a normalization process was performed to estimate the volume flow rate of the process gas, and the error rate with true values was 0.74 to 2.26% (Table 5). \begin{table}
\begin{tabular}{c c} \hline
**Inert Gas** & **Gas Factors in Nitrogen** \\
**Calibration Standard** \\ \hline He & 1.386 \\ Ne & 1.398 \\ Kr & 1.382 \\ Xe & 1.383 \\ \hline \end{tabular}
\end{table} 
Table 2: Gas factors in nitrogen calibration standard using inert gas. Experiments 1 and 2 confirmed that the concentration of Kr and the volume flow rate of process gas calculated through calibration based on Kr alone were accurately measured compared to the volume flow rate of the process gas. In addition, in order to confirm the accuracy of measurements, the estimated true value was analyzed by adding He gas to the mixed standard gas, as shown in Experiment 3, and, as the injected concentration of He gas increased, the normalization rate was found to also increase (Table 6 and Table S3 and Figure 3). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**N\({}_{2}\)**} & \multirow{2}{*}{**STD Gas**} & \multirow{2}{*}{**
\begin{tabular}{c} **Pre-Set Kr** \\ **Concentration (\%)** \\ \end{tabular}**} & **Measured Kr** & \multirow{2}{*}{**Gas Factor**} & **Temperature and** & **Measured** & **Calculated True** & **Value of** & **Error Rate (\%)** \\  & & **Concentration (\%)** & & **Conservation (\%)** & & **Pressure Calibration** & **Rate (\$\$\$\$\$\$\)** & **Value Flow Rate** & **Error Rate (\%)** \\ \hline
7 & 3 & 0.6 & 0.627 & 1.382 & 1.073 & 236.413 & 247.2 & 4.37 \\
5 & 5 & 1.0 & 1.027 & 1.382 & 1.073 & 144.369 & 148.3 & 2.67 \\
3 & 7 & 1.4 & 1.425 & 1.382 & 1.073 & 104.036 & 105.9 & 1.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Arithmetic error rate values compared to true values in Experiment 1.