Here is a systematic summary of common issues and corresponding handling methods in semiconductor wafer wet cleaning processes, integrating process principles and practical applications:

I. Surface Particle Residue

Problem Causes:Environmental particles (insufficient cleanroom grade), equipment wear debris, chemical impurities, or incomplete drying leading to water mark crystallization. Particle size must be less than half of the minimum feature size of the device; otherwise, it will cause circuit short circuits/open circuits.

Handling Methods:

1.Optimization of Chemical Cleaning:Use SC-1 solution (NH₄OH/H₂O₂/H₂O) to strip particles via oxidation decomposition and electrostatic repulsion effects. Dilute the ratio to 1:4:50 to reduce surface roughness (Ra value by 40%).

2.Physical Enhancement Techniques:Megasonic cleaning (0.8–1.2 MHz): Utilize non-contact cavitation effects to remove 0.1 μm particles while avoiding micro-damage. Combine with rotational spray (300–800 rpm) to improve coverage uniformity.

II. Metal Contamination (Fe, Cu, Al, etc.)

Problem Causes:Corrosion of chemical lines, ion implantation residues, or cross-contamination. Metal ion migration leads to PN junction leakage and reduces carrier lifetime.

Handling Methods:

1.Targeted Cleaning Solutions:

•SC-2 solution (HCl/H₂O₂/H₂O): Complex and dissolve alkali metals (Na⁺, K⁺) and heavy metals (Cu, Ni).

•HF/O₃ alternative: Avoid SC-2 crystallization issues and enhance metal oxide dissolution.

2.Chelating Agent Reinforcement:

Add EDTA or GLDA (green chelating agent) to increase copper ion solubility by 3 orders of magnitude.

III. Organic Contaminants (Photoresist, Grease)

Problem Causes:Human skin grease or photoresist residues form films that block contact between cleaning solutions and the surface.

Handling Methods:

1.Oxidative Decomposition:SPM solution (H₂SO₄/H₂O₂): Decompose organic matter at 120–150°C with a removal rate of 99.9%.

2.Dry-Assisted Method:Ozone water cleaning (O₃/H₂O): Hydroxyl radicals oxidize organics, reducing sulfuric acid usage by 95%.

IV. Water Mark Defects (Incomplete Drying)

Problem Causes:Residual moisture reacts with silicon to form metasilicic acid (H₂SiO₃), creating granular water marks that affect etching integrity.

Handling Methods:

1.Advanced Drying Technologies:

•Marangoni drying: Use the surface tension difference between isopropyl alcohol (IPA) and water to draw back moisture.

•Supercritical CO₂ drying: Eliminate trench moisture completely under conditions of 55°C and 1.2 MPa.

2.Emergency Treatment:If water marks remain, etch the oxide layer with hot phosphoric acid (selectivity >100:1).

V. Surface Roughness and Corrosion

Problem Causes:Excessive HF corrosion of the silicon substrate or micro-pitting induced by the alkaline SC-1 solution.

Handling Methods:

1.Concentration and Time Control:Keep dilute hydrofluoric acid (DHF) concentration ≤1% and exposure time ≤5 minutes. Add surfactants to SC-1 to reduce interfacial tension.

VI. Cross-Contamination and Process Control Failure

Problem Causes:Tank residue, incomplete rinsing, or parameter fluctuations (temperature, concentration) leading to secondary contamination.

Handling Methods:

1.Closed-Loop Control System:Real-time monitoring of pH, conductivity (accuracy 0.1 μS/cm), and particle count to dynamically adjust cleaning parameters.

2.Cascade Rinse Design:Multi-stage deionized water (DIW, 18.2 MΩ·cm) rinsing combined with nitrogen purging to minimize residue.