Semiconductor wet process drying

1 Drying Technology Classification and Principles

1.1 Spin Drying

Principle: Utilizing centrifugal force generated by high-speed rotation to remove surface moisture, supplemented by hot nitrogen gas blowing to enhance drying effect.

Process Flow: Drug solution/deionized water spraying → High-speed spin drying (1000–3000 rpm) → Hot nitrogen gas assisted dehydration.

Advantages: Mature technology, good surface uniformity, no watermark residue.

Disadvantages:

Only suitable for wafers/epitaxial wafers, poor effect on deep and narrow grooves;

High-speed rotation is easy to damage the mechanical strength of ultra-thin wafers.

Key parameters: Rotation speed, nitrogen gas flow rate, chamber sealing, resonance control.

1.2 IPA Drying

Principle: Utilizing the volatility and low surface tension of isopropyl alcohol (IPA) to replace water, achieving drying through steam condensation-volatilization.

Equipment Composition: Steam tank (heating IPA), steam zone (stabilizing steam), condensation tank (cooling water pipe).

Process Flow: Wafer immersion in IPA liquid → Rise to steam zone (steam condensation washing) → Enter condensation zone (IPA volatilization drying).

Disadvantages:

High IPA consumption, high cost, flammable and explosive;

Easy to leave organic residue, gradually being replaced by new technologies.

1.3 Marangoni Drying

Principle: Based on the surface tension difference between IPA and water, water molecules migrate to the liquid phase, achieving rotation-free dehydration.

Applicable Scenarios: 150mm and above wafers, especially deep and narrow groove structures.

Equipment Composition: Lifting mechanism, drying chamber, translation mechanism, drying tank, atomization tank.

Process Flow:

Wafer dehydration: DI water overflow rinsing → Slow water injection to form IPA gas environment → Slow pull-up dehydration with Dryknife;

Basket dehydration: Nitrogen/IPA mixed gas injection → Dehydration using surface tension;

Vacuum exhaust: Emptying the tank → Removing residual IPA gas.

Advantages: Low IPA consumption, high cleanliness, no watermarks.

1.4 Slow Pull-IR Drying

Principle:

Dehydration stage: Slow pull-up with hot water to reduce surface moisture;

Drying stage: Infrared radiation heating (45–50℃) to evaporate residual moisture.

Equipment Composition: Infrared heating system, temperature probe, quartz tank (anti-pollution), reflector.

Advantages:

No chemical reagents, safe and environmentally friendly;

Completely avoid watermark defects, high particle cleanliness;

Low-temperature drying protects wafer structure.

Key Design:

Cassette removed, reducing contact area;

Optimized drying tank airflow field (multi-directional nitrogen gas coverage).

2. Technology Comparison and Challenges

In general, wet cleaning is the core process of semiconductor wafer surface treatment, and drying, as its final step, is crucial to wafer cleanliness, defect control, and the stability of subsequent processes. It is the last step in the wet cleaning process, ultimately determining the surface quality of wafer cleaning.

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