QUANTIFICATION OF ADDITIVES IN A COMMERCIAL CMP SAMPLE USING HPLC WITH PHOTODIODE ARRAY AND MASS DETECTION

Significance of the Topic

The reliability of chemical mechanical polishing (CMP) slurries directly impacts semiconductor fabrication yield and device performance. Accurate monitoring of key additives prevents defects arising from friction, heat, oxidation and pH drift, making rapid, routine analysis essential for both formulation and quality control in advanced manufacturing.

Objectives and Study Overview

This study presents a streamlined 15-minute HPLC method combining photodiode array (PDA) detection with single quadrupole mass detection (QDa) for quantitative and qualitative analysis of four common CMP slurry additives: citric acid, benzotriazole, polyethylene glycol (PEG) and phosphoric acid. The goal is to enable efficient routine testing without complex sample preparation or multiple instruments.

Methodology and Instrumentation

Sample Preparation:

• Centrifugation of slurry at 4 °C, 2 200 rpm for 20 minutes.
• Dilution of supernatant in 10 mM ammonium formate buffer to 6.5 mg/mL.
• Preparation of individual calibration standards (0.01–1 mg/mL) and mixed additive series.

Instrument Configuration:

• Waters Arc HPLC system with in-system upgrade path to UHPLC.
• Waters XBridge BEH 5 µm column, gradient elution over 15 minutes.
• Photodiode array detector for UV-active analytes.
• ACQUITY QDa single quadrupole mass detector for m/z confirmation.
• Empower 3 Chromatography Data System for unified PDA and MS data processing.

Main Results and Discussion

Separation Performance:

• Baseline separation of all four additives in under 15 minutes.
• Retention time precision with %RSD < 0.1% (n=10).
• Peak area precision between 0.04% and 9.75% RSD.

Calibration and Linearity:

• Excellent linearity for individual standards (R² > 0.995).
• PEG in the mixture showed slightly lower linearity (R² = 0.98), likely due to matrix interactions.

Recovery and Matrix Effects:

• Benzotriazole recovery 99–101%.
• Citric acid recovery 78–83%, indicating moderate matrix suppression.
• PEG recovery 81–111%, with enhanced UV response via phosphoric acid interaction.

Mass Detection Confirmation:

• Positive and negative electrospray ionization provided unique m/z values for each additive.
• QDa data supported qualitative identification of challenging components.

Benefits and Practical Applications

• Rapid, robust QC method for CMP additive quantification.
• Minimal sample preparation compared to GC/MS, NMR or FTIR approaches.
• System flexibility allows upgrade to UHPLC without revalidation.
• Consolidated data analysis of PDA and MS outputs in Empower 3 CDS.

Future Trends and Potential Applications

• Expansion to wider panels of CMP additives and impurity profiling.
• Integration with automated sampling and inline process analytical technology (PAT).
• Coupling with UHPLC and high-resolution MS for enhanced sensitivity and selectivity.
• Application to next-generation materials and advanced semiconductor process development.

Conclusion

The combined HPLC-PDA/QDa method provides a straightforward, precise and confident workflow for quantitative and qualitative analysis of CMP slurry additives. This approach supports efficient formulation development and routine quality control in semiconductor manufacturing.

Reference

1. Raghavan S, Keswani M, Jia R. Particulate Science and Technology in the Engineering of Slurries for Chemical Mechanical Planarization. Kona Powder and Particle Journal 2008;26(1):94-105.
2. Nagarjuna Prasad Y, Ramanathan S. Role of Amino-Acid Adsorption on Silica and Silicon Nitride Surfaces during STI CMP. Electrochemical and Solid-State Letters 2006;9(12):G337.
3. Chempoint. Ludox™ TM-50 Colloidal Silica Technical Data Sheet. 2021.
4. Toray Research Center. Analysis of Organic Additives in CMP Slurry. Technical Data S00194E. 2020.
5. Rodrigues PCA, Beyer U, Schumacher P, et al. Acid-sensitive Polyethylene Glycol Conjugates of Doxorubicin: Preparation, In Vitro Efficacy and Intracellular Distribution. Bioorganic & Medicinal Chemistry 1999;7(11):2517-2524.
6. Waters Corporation. Arc™ HPLC System Brochure. 2022.
7. Waters Corporation. Empower™ 3 Tips and Tricks. 2021.