Chip quality in semiconductor fabrication processes is typically defined as the reduction of variability around target, or in other words, how well the distribution sets between the lower and upper specified limits. Critical to Quality (CTQ) and conformance to customer requirements also play a significant role. Too high variability in manufacturing quickly turns to product quality issues. To ensure a stable supply of good products to market, thorough quality metrics and process control are needed. One important part of product quality and manufacturing is chemistry. Semiconductor wafer plants consume tons of chemicals throughout the whole fab process. Repeatability and reproducibility of each process is a top concern of fabs, and even the slightest deviation from specification can result in expensive equipment contamination and wafer scrap.
Process monitoring and fault detection
From chemistry’s point of view, there are two distinct operations related directly to product quality: process monitoring and fault detection. In process monitoring applications, the desired chemistry must be maintained over time. In fault detection applications, the system must verify that the correct chemical is being dispensed to the process. With accurate monitoring, fabs know the composition of each given chemical stream. Without monitoring, wafers become the de facto chemical monitors. By that time, wafers have already been lost and large-scale equipment contamination may have occurred.
Vaisala K PATENTS® Semicon Refractometer offers real-time liquid monitoring and prevents wrong chemical concentrations from being dispensed onto wafers, indicates timing for spiking, e.g. for water in EKC at the post-etch residual removal, and indicates bath life and KOH concentration in the etching of silicon. The fully integratable Semicon Refractometer supports intelligent fabs and self-diagnosis.
