DTFab: A Digital Twin based Approach for Optimal Reticle Management in Semiconductor Photolithography

Photolithography is among the key phases in chip manufacturing. It is also among the most expensive with manufacturing equipment valued at the hundreds of millions of dollars. It is paramount that the process is ran efficiently, guaranteeing high resource utilization and low product cycle times. A key element in the operation of a photolithography system is the effective management of the reticles that are responsible for the imprinting of the circuit path on the wafers. Managing reticles means determining which are appropriate to mount on the very expensive scanners as a function of the product types being released to the system. Given the importance of the problem, several heuristic policies have been developed in the industry practice in an attempt to guarantee that the expensive tools are never idle. However, such policies have difficulties reacting to unforeseen events (e.g., unplanned failures, unavailability of reticles). On the other hand, the technological advance of the semiconductor industry in sensing at system and process level should be harnessed to improve on these “expert policies”. In this manuscript, we develop a system for the real time reticle management that not only is able to retrieve information from the real system, but also is able to embed commonly used policies to improve upon them. We develop a new digital twin for the photolithography process that efficiently and accurately predicts the system performance, thus allowing our system to make predictions for future behaviors as a function of possible decisions. Our results demonstrate the validity of the developed model, and the feasibility of the overall approach demonstrating a statistically significant improvement of performance as compared to the current policy.