Why is the Resistivity of Water so Small When Wafer Dicing?

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This article explains the concept, how, and why water is involved in the wafer dicing process.

The resistance law of water during wafer dicing < 1 MΩ·m, but the resistivity of ultrapure water is 18.3 MΩ·m, so why use water with such a small resistivity? How do you achieve resistivity drop?

What is wafer dicing (dicing)?
Wafer dicing, Wafer dicing, after the wafer has completed all the manufacturing processes, needs to cut the wafer into chips for further packaging and testing.
How many ways are there for wafer dicing (dicing)?
Generally includes mechanical cutting, laser cutting, plasma cutting, etc. The participant's question mainly concerned mechanical cutting, i.e. diamond blade cutting, i.e. cutting semiconductor wafers and separating individual chips using a high-speed rotating diamond blade.
Why is there water involved in wafer dicing (dicing)?
1. Cooling: When the blade is cut, a lot of heat will be generated, which will lead to deformation and even cracks of the wafer. Water impingements on the surface of the wafer and is able to remove the heat generated during the dicing process, keeping the temperature of the wafer in a low range. 2. Remove cutting chips: A large amount of cutting chips will inevitably be generated when the blade is cutting. If these chips are not removed in time, they can lead to damage to the cutting tool, affect the cutting accuracy, and cause scratching of the wafer.

3. Reduce friction: If there is no lubrication of water, the wear of the blade will be very fast, and the damage to the surface of the wafer will also be great. Water reduces the friction between the blade and the wafer, extending the life of the blade.
Why is the resistivity of water so small when wafer dicing?
During dicing, the high-speed friction between the wafer and the blade can lead to the accumulation of static electricity, which can damage the wafer and attract more dicing debris. Therefore, CO2 is injected into ultrapure water, and CO₂ can be dissolved in the water and carbonic acid (H₂CO₃) is formed. Carbonic acid is a weak acid that decomposes into hydrogen ions and bicarbonate ions (HCO₃⁻) in the middle of water, the presence of which increases the conductivity of water, thereby reducing the resistivity of water to prevent the accumulation of static electricity.