Reducing costs and increasing throughput using model-based process control on sputtering systems

As the target within a sputter system erodes over time, the deposition rate decreases. In mass production semiconductor facilities, the sputter process is usually controlled by using monitor wafers and adjusting the deposition time or power to obtain a constant thickness. By modeling deposition rates with regard to target life, these costly monitor wafers can be removed; thereby increasing available time for product wafers. Using over a year of production data on the numerous sputter tools in several of Texas Instruments´ fabrication plants, quadratic models of AlCu and Ti deposition rates have been developed. These models, along with simple operator procedure and software changes, were implemented at one fab in less than six months with no added costs. Furthermore, the identified monitor wafer savings at all of Texas Instruments´ fabs account for a 79% reduction in pilot usage with a potential 4.9% capacity increase. Process control has also shown significant improvements