Key Measures for Particle Control in Wet Cleaning Equipment - Process Control

In the wet cleaning process of semiconductor manufacturing, effective control of particle contamination is a core challenge to ensure wafer yield and device performance. Particles can cause device shorts, opens, or performance degradation. Achieving low particle levels requires a systematic approach from multiple dimensions, including source prevention and cleaning process optimization.

Process Control: Efficient Removal and Inhibition of Particle Adsorption

• Chemical Formulation Optimization: Select chemical solutions that can effectively remove contaminants (organics, metals, particles) and inhibit particle re-adsorption, such as SC1 (optimize ratio/temperature/time to prevent metal contamination and roughness), DHF (control concentration/time to prevent adsorption), and add surfactants if necessary to reduce surface tension.
• Precise Control of Process Parameters: Precisely control the concentration, temperature, and duration of chemical solutions to maximize cleaning effectiveness while minimizing surface damage and the risk of particle redeposition.
• Megasonic Physical Cleaning: Apply high-frequency sound waves to generate cavitation effects and acoustic streaming, providing a strong physical force to efficiently peel off sub-micron particles. Precise control of power, frequency, and uniformity of action is required.
• Spray System Optimization: Design optimized nozzles, spray pressure, and angles to ensure effective impact on the wafer surface to remove particles, avoid damage to patterns or splashing; prioritize laminar flow spraying to reduce re-deposition caused by turbulence.
• Rotational Spin-Drying Assistance: Utilize centrifugal force generated by high-speed rotation during cleaning and drying steps to assist in the removal of particles and droplets.
• High-Efficiency Overflow Rinsing: Use continuous, large amounts of high-purity UPW for overflow rinsing in the tank to continuously dilute and remove contaminants and particles.
• Rapid Fluid Displacement: Design efficient drainage and filling systems to shorten liquid residence time and prevent particles from settling in low-flow areas.
• Multi-Stage/Cascade Rinsing: Use multi-stage rinsing tanks or multiple water changes in a single tank to gradually reduce contaminant concentration; cascade rinsing (using dirty water first, then clean water) can save water.
• Real-Time Monitoring of UPW Quality: Monitor the resistivity, TOC, and particle content of the rinsing water online.
• Optimize Drying Process: Optimize the rotation speed curve and nitrogen purge to prevent streaks during spin-drying; Marangoni drying (using IPA vapor surface tension gradient) has good results on patterned wafers and low residual risk; Isopropyl alcohol (IPA) dehydration uses its low surface tension characteristics to reduce water marks and particles; hot nitrogen drying requires ensuring high gas cleanliness.

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