Phosphoric Acid in Semiconductor Production
The production of Semiconductor Grade H₃PO₄
Phosphoric Acid is used in Semiconductor Production. In the semiconductor manufacturing process, phosphoric acid can be used as a solvent for etching, for example: a mixture of phosphoric acid and hydrogen peroxide can convert InGaAs to InP to achieve the purpose of etching.
Due to the extremely strict requirements for impurity control, all semiconductor-grade phosphoric acid is produced from elemental phosphorus (P₄) via the thermal process. When qualified raw materials are used, this process does not introduce unwanted impurities.
In contrast, wet-process phosphoric acid contains a high level of impurities, and purifying it to meet technical, food, or semiconductor standards presents significant technological and engineering challenges. Numerous attempts to upgrade wet-process phosphoric acid have failed. A well-known example is a project in Idaho, where engineers adopted European purification technology designed for wet-process phosphoric acid produced from North African phosphate rock. Despite repeated efforts, they were unable to consistently achieve qualified food-grade acid. Ultimately, the project was forced to shift production to agricultural-grade phosphoric acid instead.
For this reason, thermal-process phosphoric acid remains the only viable option for producing semiconductor-grade phosphoric acid.
Another critical challenge lies in materials compatibility. All equipment in contact with phosphoric acid must not introduce any contaminants. As phosphoric acid is a moderately strong acid, production systems for semiconductor-grade phosphoric acid typically rely on high-purity glass or ceramic materials for pipes, pumps, and storage tanks to ensure contamination-free processing.