Dynamic simulation and optimization of Cu CVD unit process for environmentally benign manufacturing

Environmentally benign semiconductor manufacturing requires methodologies which enable cooptimization of multiple objectives, namely environmental metrics (e.g., precursor utilization efficiency, energy consumption) simultaneously with metrics for manufacturing productivity (e.g., process cycle time) and technology performance (e.g., material or product quality). We used dynamic simulation to investigate this challenge at the unit process level, incorporating essential characteristics of physical and chemical behavior of the equipment, the process, and their dynamics for a prototype system. This enabled the evaluation of multiple metrics as a function of process recipe specifications and equipment design parameters, namely the extraction of process cycle time, reactant utilization, and energy consumption as metrics for a Cu chemical vapor deposition (CVD) unit process as the prototype. Higher temperature and pressure resulted in reduced process cycle time and increased precursor utilization efficiency, producing a "win-win" situation for the manufacturing and environmental metrics. In contrast, variation in precursor flow rate produced a tradeoff situation between these metrics, which could be quantified in different process parameter regimes by the simulation. Energy consumption is dominated by vacuum pump operation, placing a premium on short cycle times. In addition, energy requirements for wafer heating are reduced at higher wafer temperature because the deposition rate of the thermally activated CVD process increases rapidly with temperature, reducing the cycle time and, therefore, the energy used. These results illustrate that dynamic simulation provides a valuable guide in design-for-environment efforts which seek cooptimization of multiple metrics, win-win situations, and quantification of tradeoffs between metrics.