The Role of Ultra Pure Water in the Semiconductor Industry

The semiconductor industry relies on precise and clean environments to ensure the production of high-quality microchips. Aqueous chemistry has played a significant role in the fabrication process, particularly in etching and cleaning steps. Ultra pure water (UPW) plays a critical role in ensuring the purity and reliability of the semiconductor devices being produced. This article explores the specific roles of UPW in the semiconductor industry and the challenges associated with maintaining a clean and uncontaminated environment.

The Significance of Ultra Pure Water in Semiconductor Fabrication

Ultra pure water (UPW) is used extensively in the semiconductor industry as a cleaning agent. The purification process involves removing ions, solid particles, and other contaminants from the water. These contaminants can include particles from the water itself, as well as dissolved impurities from various sources. If these contaminants are allowed to contaminate the wafers or the integrated circuits, they can cause significant defects and failures, leading to substandard products and increased costs for manufacturers.

Challenges in Maintaining Purity

The recent trend in semiconductor fabrication has been towards minimizing the use of aqueous chemistry steps and moving towards "dry processing" with low-pressure gas plasma. This shift is driven by the need for a cleaner and more controlled environment. While dry processing offers certain advantages, it also presents new challenges in maintaining the integrity of the process.

One of the primary challenges is the behavior of water at smaller feature sizes. As the size of transistors and other components continues to shrink, the surface tension of water becomes a significant issue. Hydrophobic materials, such as photoresist features, can make it difficult for water to effectively wet these surfaces. This can lead to incomplete cleaning and the formation of unwanted residues, which can compromise the integrity of the final product.

Ultra Pure Water in Semiconductor Fabrication

Ultra pure water is essential in the semiconductor industry for maintaining the cleanliness and purity of the manufacturing process. The purification process typically involves a series of steps, including deionization and ultrafiltration. Deionization removes dissolved ions from the water, while ultrafiltration removes any solid particles that could potentially become embedded in the wafer and cause defects.

How is UPW produced? UPW is typically produced through a multi-stage process that includes:

Reverse Osmosis (RO) to desalinate water and remove large colloidal particles Ion Exchange to remove dissolved ions Deionized Water Treatment including ultraviolet (UV) or hydrogen peroxide (H2O2) treatment to remove any remaining contaminants

Once the water has been purified to the required standard, it is commonly stored in tank farms protected from contamination with dedicated transfer and distribution systems. The use of UPW in the semiconductor industry is not limited to cleaning; it is also used in chemical solutions, as a carrier for various chemicals, and in other critical processes that require high purity water.

Conclusion

The role of ultra pure water (UPW) in the semiconductor industry is crucial for ensuring the production of reliable and high-quality microchips. The challenges of maintaining a clean and uncontaminated environment, particularly with the miniaturization of components, highlight the importance of using UPW in the semiconductor fabrication process. By understanding the importance of UPW and the challenges associated with maintaining purity, manufacturers can continue to produce advanced semiconductor devices that meet the high standards demanded by the industry.

As the industry continues to evolve, the demand for ultra pure water will likely increase, pushing for even more advanced purification technologies and stricter quality control measures. Ensuring the purity of UPW will remain a critical factor in the success of semiconductor manufacturers.