Progressive hierarchical deep reinforcement learning for defect wafer test

Wafer testing plays a critical role in the wafer fabrication process. It involves using a probe to inspect all the wafers on a map, which presents a Coverage Path Planning (CPP) problem. Deep Reinforcement Learning (DRL) has emerged as a state-of-the-art (SOTA) solution for automating regular wafer testing. However, in the presence of production defects, the wafer maps become irregular, requiring more advanced probe strategies. Unfortunately, SOTA DRL methods cannot be directly applied to defect wafer testing due to high computational complexity, low sample efficiency, and limited transferability between tasks. To address these challenges, we propose a novel DRL solution called the Progressive Hierarchical DRL method for automated defect wafer testing. Specifically, our method utilizes a Visual Memory Attention Model (VMAM) to create a high-level strategy, referred to as a manager, which generates a goal specifying the most crucial image region for the task. Subsequently, a low-level strategy, referred to as a worker, generates precise cruising actions to navigate to the designated area. Additionally, we employ transfer learning to generalize the method to handle more complex defect wafer maps. Our approach outperforms seven SOTA DRL baselines in the domains of CPP and wafer testing. It achieves significant improvements in task duration and wafer visit overlap, ranging from 6.0% to 30.5%. Furthermore, we explore the application of our method to a dual-probe defect wafer testing system.