In advanced semiconductor manufacturing and packaging, electroplating is a cornerstone process for key steps such as metal interconnects, TSVs (Through-Silicon Vias), and RDLs (Redistribution Layers). Wet electroplating equipment, with its fully automated process chain, high-precision parameter control, and intelligent fault diagnosis system, provides reliable metallization solutions for 5G chips, AI processors, and 3D packaging. The following sections offer a comprehensive analysis of its technical advantages, covering process flow, chemical management, parameter optimization, and problem resolution.
I. Core Equipment Process Flow
A three-step closed-loop process achieves nanoscale coating uniformity.
Pre-treatment
Descaling Cleaning: Acidic solution (H₂SO₄/H₂O₂) removes oxides and organic residues from the wafer surface.
Micro-etching Activation: Dilute hydrochloric acid (HCl) etches the surface to enhance coating adhesion.
Electroplating
Pulse Plating Technology: Periodic Reverse Current (PRC) fills high-aspect-ratio vias, preventing void defects.
Dynamic Flow Control: Multi-zone spray design ensures uniform chemical distribution, with edge-to-center thickness variation <3%.
Post-treatment
Deionized Water (DIW) Rinse: Multi-stage counter-current cleaning reduces chemical cross-contamination.
Drying: Nitrogen blow-off + infrared drying eliminates water stain residue.
II. Key Chemicals and Environmental Solutions
| Process Stage | Chemical | Concentration Range | Function |
|---|---|---|---|
| Pre-treatment | Sulfuric Acid (H₂SO₄) | 10-15% vol | Oxide layer stripping |
| Hydrogen Peroxide (H₂O₂) | 5-8% vol | Organic contaminant decomposition | |
| Electroplating | Copper Sulfate (CuSO₄) | 40-60 g/L | Metal ion source |
| Brightener (PEG/Cl⁻) | 50-200 ppm | Coating grain refinement and leveling | |
| Post-treatment | Citric Acid (C₆H₈O₇) | 2-5% wt | Neutralizes residual acid, prevents oxidation |
III. Core Process Parameters and Stability Control
| Parameter | Setting Range | Precision Control | Impact Indicator |
|---|---|---|---|
| Plating Temperature | 22±0.5℃ | PID Constant Temperature System | Coating crystallization speed & density |
| Current Density | 3-8 ASD | Multi-zone Independent Adjustment | Via filling capability |
| Fluid Velocity | 1.5-3.0 m/s | Closed-loop Flow Sensors | Boundary layer thickness, suppresses concentration polarization |
| pH Value | 1.2-1.5 (CuSO₄ system) | Online pH Meter + Auto Dosing | Bath stability & deposition rate |
IV. Typical Process Issues & Solutions
Issue: Coating Thickness Non-uniformity (Edge-Edge Variation)
Cause: Excessive edge current density or uneven fluid distribution.
Solution: Activate "edge shield ring" design coupled with a multi-zone adaptive flow control algorithm.
Issue: Voids inside TSVs (Void Formation)
Cause: Abnormal additive consumption or mismatched pulse current parameters.
Solution: Integrate online CVS (Cyclic Voltammetric Stripping) to monitor additive concentration and dynamically adjust duty cycle.
Issue: Particle Contamination
Cause: Insufficient fluid filtration efficiency or wafer holder wear.
Solution: Employ a 0.1μm dual-stage filtration system equipped with a particle counter linked to an alarm.
V. Core Equipment Value
High Efficiency & Stability: UPH (Units Per Hour) reaches 300 wafers (300mm), yield >99.5%.
High Precision & Compatibility: Supports sub-10nm processes and 2.5D/3D packaging structures.
Intelligent Operation: AI-based process parameter self-learning system reduces failure rate by 40%.
Conclusion
Wet electroplating equipment, with its core competencies of process traceability, zero chemical waste, and real-time defect interception, empowers customers to push the boundaries of Moore's Law.
