The high complexity, high costs, short time frames, and rentless competition in semiconductor manufacturing make all errors potentially very costly and make problem solving efforts very valuable. The paper presents a low-cost strategy for managing tools and processes through modelling basic parameters and applying input SPC to both basic parameters and to relationship among basic parameters. This work is done at STMicroelectronics 200 mm fab at Phoenix, Arizona. The focus is on exploiting the existing measurements of basic process/tool parameters that are used for closed-loop control. By making use of existing measurements of process inputs, expensive, slow process measurements of process outputs such as thickness, resistivity, or critical dimension are avoided or reduced.