  Over the past decades industries have had to tackle the issue of
sustainability as a matter of increasing urgency to mitigate greenhouse gas
emissions and abide by government regulation policies. The semiconductor
industry has come under scrutiny for its significant carbon and water
footprints, largely attributed to substantial energy consumption. Notably,
machine utilisation accounts for a major portion of this consumption, while the
rest is shared by factory facilities. Thus, it is critical to optimise machine
utilisation to attain desired throughput while minimising energy consumption. A
flexible job shop model is developed for the six step Intel Mini fab using a
discretised time approach to find an optimal schedule. A multi objective
formulation is solved using the epsilon constraint method to minimise energy
consumption and make-span for a constant throughput. This approach affords
stakeholders the flexibility in choosing machine combinations based on energy
implications, a crucial consideration, especially in situations of machine
unavailability. Modifying this formulation, the throughput is varied, and an
additional objective is incorporated to maximise it. The energy-throughput
trade-off is critically analysed, and the effect of dynamically switching off
machines is well demonstrated. Energy consumed per unit wafer is observed to
decrease non-linearly with make-span. The effect of optimal scheduling on
energy consumption is highlighted using the FIFO heuristic strategy. When
employing optimal scheduling, there was a marked reduction of 26.72 percent in
energy consumption compared to the maximum energy consumed in the FIFO
approach.
