The semiconductor industry fabricates chipsets, wafers, and printed circuit boards. These processes require ultrapure water for cleaning, rinsing, etching, and surface conditioning. pH measurement is one of key parameters monitored to ensure the purity and utility of water in this application.
The pH of ultrapure water can trend more acidic over time if not treated properly. Dropping pH values are typically attributed to the tendency for ultrapure water to absorb carbon dioxide from the air which creates carbonic acid. The equipment used to produce ultrapure water employ pH sensors in the process to ensure the finished or process water is of the expected quality.
The measurement of pH can be challenging due to the inherent low-ionic strength of the solution. Features such as low impedance sensor glass, fast temperature response, and reference junctions with consistent flow rates need to be considered in the design of an appropriate pH sensor.