Ozone Doesn’t Work? You’re Doing It Wrong.
The use of ozone in semiconductor wet processing surface preparation has gained new momentum as fabs pursue advanced cleans and strip steps that reduce chemical waste without compromising performance. In theory, ozone’s oxidation potential (2.07 V) makes it one of the strongest practical oxidizers — far exceeding hydrogen peroxide or sulfuric acid blends typically used for organic removal. But in practice, its full power is fundamentally constrained because ozone decomposes rapidly in water, drastically reducing its effectiveness at the wafer surface.
Why Conventional Ozone Baths Fall Short
The HydrOzone™ process from Shellback overcomes this limitation, delivering strip rates 10 to 20 times faster than conventional dissolved ozone methods. To see why this matters, it helps to understand what happens inside a traditional ozone bath. In a dissolved ozone system, once ozone is dissolved, it immediately begins to self-destruct through a chain of reactions:
- Ozone reacts with hydroxide ions (OH⁻)to form hydroperoxide:
O₃ + OH⁻ → HO₂⁻ + O₂ - Hydroperoxide ions react with more ozone, generating radicals that further degrade ozone:
HO₂⁻ + O₃ → O₂⁻ + O₂ + H⁺ O₂⁻ + H⁺ → HO₂•
- Hydroperoxyl radicals generate hydroxyl radicals, which accelerate ozone breakdown:
HO₂• → O₂ + •OH
These reactions propagate rapidly, consuming dissolved ozone before it can reach the wafer and deliver its oxidative punch. Under typical conditions, dissolved ozone has a half-life of just ~15 minutes at room temperature — and this shrinks dramatically at elevated bath temperatures.
The result is a fundamental double bind: ozone must dissolve to be usable, yet once dissolved, it is chemically unstable and self-limiting. Cooling the bath can extend ozone’s half-life — but only by slowing the reactions needed for effective strip and clean performance. In short, conventional dissolved ozone processes can never deliver ozone’s full theoretical oxidative power. They are always fighting against the molecule’s inherent instability in water.
HydrOzone Brings Ozone’s Full Power to the Wafer
HydrOzone breaks this deadlock by decoupling ozone’s effectiveness from bulk dissolution. Instead of saturating an entire bath, HydrOzone uses a precisely controlled spray of heated water onto a spinning wafer while the chamber is purged with a high concentration of gaseous ozone.
This creates a thin, fast-moving water film — just 5–20 microns thick — for gaseous ozone to diffuse through. An ozone molecule crosses this layer in 4–60 milliseconds, four to five orders of magnitude faster than ozone decomposes in bulk solution. This means more of ozone’s oxidative power reaches the wafer where it’s needed, instead of being wasted in the bath.
Equally important, because HydrOzone doesn’t rely on dissolving ozone into solution, its performance improves as process temperature rises — the opposite of conventional ozone baths, where higher temperatures accelerate decomposition and reduce effectiveness. With HydrOzone, higher temperatures increase mass transfer rates and chemical activity at the wafer surface.
No More Tradeoffs — Just Faster, Cleaner Results
Gone is the dependency on dissolution. Gone is the rapid loss of ozone to chain reactions. Gone is the harsh tradeoff between process temperature and strip rate. Gone is the wasted oxidative potential. The result: HydrOzone achieves strip rates up to 20 times faster than conventional dissolved ozone — while delivering on the industry’s growing need for greener, lower-waste solutions.
When fabs talk about leveraging ozone to meet real sustainability goals, the chemical fundamentals matter. With HydrOzone, Shellback finally unlocks the full promise of ozone — giving fabs an environmentally conscious process that delivers powerful on-wafer results without compromise.