Evaluation of TOC of Sulfuric Acid using Wet Oxidation TOC Analyzer

Importance of the Topic

Sulfuric acid is widely used in semiconductor surface cleaning and stringent control of organic contaminants is essential to maintain process integrity and product quality in advanced integrated circuit fabrication.

Objectives and Study Overview

This study demonstrates the feasibility of using the Shimadzu Wet Oxidation Total Organic Carbon Analyzer TOC-V to quantify low levels of total organic carbon (TOC) in a 10 % sulfuric acid solution, addressing the need for reliable quality assessment in semiconductor manufacturing.

Methodology and Instrumentation

The non-purgeable organic carbon (NPOC) method was employed: samples were sparged to remove inorganic carbon without additional acidification due to the inherent acidity of the matrix. Calibration was performed using potassium hydrogen phthalate standards at 0, 0.1, 0.5, and 1 mgC/L with an origin shift to account for baseline TOC in the diluent. Key parameters included a 3000 μL injection volume and wet oxidation via sodium peroxodisulfate with UV irradiation and heating.

Instrumentation Used

• Shimadzu TOC-Vwp Wet Oxidation Total Organic Carbon Analyzer
• Autosampler for unattended multi-sample analysis
• Sodium peroxodisulfate oxidant with UV and thermal modules

Main Results and Discussion

Measurement of a blank 10 % sulfuric acid solution yielded 0.0185 mgC/L TOC (CV 1.88 %). Spiked samples at 0.1–0.5 mgC/L exhibited recoveries between 99.3 % and 103 % with coefficients of variation below 2 %. A calibration plot of added versus measured TOC showed excellent linearity (R²=0.9999), confirming accurate quantification across the tested range.

Benefits and Practical Applications

• Precise detection of trace organic carbon in aggressive acid matrices
• Enhanced quality control for semiconductor-grade reagents
• High throughput via automatic sampling

Future Trends and Applications

Emerging developments may focus on further sensitivity improvements, integration of TOC analysis into process analytical technology (PAT) frameworks, expansion to other aggressive matrices, and hybrid methods combining TOC with other analytical techniques to broaden application scope.

Conclusion

The Shimadzu TOC-V analyzer effectively measures low-level TOC in strong sulfuric acid solutions, providing a robust tool for quality management in semiconductor cleaning processes and potentially extending to various industrial acid analyses.