Why is it necessary to remove ozone when cleaning silicon wafers?

In the semiconductor and photovoltaic manufacturing fields, silicon wafer cleaning is a critical process step. Ozone is widely used in cleaning processes due to its strong oxidizing properties to remove organic contamination. However, the ozone off-gas released during wafer cleaning produces a strong, irritating odor that not only affects operator health but also may cause potential corrosion to cleanroom equipment. Through practice and data analysis, using manganese dioxide or copper‑manganese composite oxide catalysts to decompose ozone under ambient conditions is currently the most effective, safe, and economical purification solution. This method achieves ozone decomposition efficiency above 99%, outlet ozone concentration below 0.1 ppm, no secondary pollution, simple operation, and low operating cost, making it the preferred choice for ozone abatement in silicon wafer cleaning workshops.

Reasons for Ozone Generation During Silicon Wafer Cleaning

In silicon wafer cleaning processes, ozone mainly originates from two types of processes: ozone water cleaning and ultraviolet ozone cleaning. Ozone water cleaning (O₃+H₂O) introduces ozone into deionized water to form ozone water, which cleans photoresist residues and organic contaminants from the wafer surface. The ozone dissolved in water continuously escapes during circulation, transport, and drainage, especially near the cleaning bath opening and drain port, where ozone concentrations are relatively high, creating noticeable odors.

Ultraviolet ozone cleaning (UVO) uses 185 nm UV light to photolyze oxygen (O₂) in air, generating highly reactive atomic oxygen, which further forms ozone. The ozone reacts with organic matter inside the chamber, oxidizing it to CO₂ and H₂O, completing the cleaning. However, after cleaning, residual ozone in the chamber is released into the workshop with the exhaust air, causing odors. Overall, ozone acts both as a green oxidizer in the cleaning process and as a source of odor and potential hazards.

Hazards of Ozone (Limited to Actual Hazards in This Application Case)

Ozone has strong oxidizing and irritating properties, posing potential risks to both human health and equipment. In silicon wafer cleaning workshops, operators may face the following hazards:

1. Respiratory irritation: Ozone concentrations above 0.1 ppm in air can cause coughing, chest tightness, throat dryness, and even difficulty breathing. If workshop ventilation is inadequate and ozone accumulates, operators may experience discomfort within a short period.
2. Precision equipment corrosion: The oxidizing nature of ozone can corrode metal components in cleanrooms, accelerate aging of seals, affect semiconductor equipment and wafer processing precision, and reduce yields.
3. Occupational health and safety risk: Chinese standards specify a maximum allowable concentration of ozone in the workplace of 0.15 ppm, while the U.S. NIOSH sets a TWA of 0.1 ppm. Long‑term exposure above these limits may cause lung tissue damage, thus requiring strict air quality control in the workshop.

It is worth noting that although ozone can naturally decompose into oxygen at ambient temperature, the closed environment of semiconductor cleanrooms makes it difficult for ozone to dissipate naturally, so active abatement measures must be taken.

Ozone Abatement Methods

For ozone issues in silicon wafer cleaning workshops, the industry has developed several abatement technologies. Each method has different characteristics, advantages, and disadvantages:

Advantages of Catalytic Decomposition

Catalytic decomposition is currently the mainstream solution for ozone abatement in silicon wafer cleaning workshops, with advantages as follows:

High Decomposition Efficiency, Extremely Low Residual Concentration

Copper‑manganese composite oxide catalysts rapidly decompose ozone under ambient temperature and pressure. Mature products achieve decomposition efficiencies of 95%–99.9%, with outlet ozone concentrations as low as below 0.1 ppm, fully meeting occupational safety standards.

Zero‑Energy Operation, Low Cost

The catalytic decomposition process requires no heating or chemical consumption; the only energy input is for fan power to move the air. Long‑term operating costs are much lower than those of thermal decomposition or chemical scrubbing.

Long Service Life and Regenerability

Catalyst life can reach 3–5 years, reducing equipment downtime and maintenance costs.

Wide Operating Range Adaptability

The catalyst maintains high activity across a relative humidity range of 0%–98% and can treat large‑volume, low‑concentration ozone exhaust with excellent stability.

Safe, Reliable, and No Secondary Pollution

Catalytic decomposition completely converts ozone to oxygen, generating no waste liquid or toxic byproducts, and presents no risk of flammable materials, fully complying with the stringent air quality requirements of semiconductor cleanrooms.