Hierarchical Optimization in semiconductor manufacturing is a multi-level optimization approach that optimizes at different structural levels — from module-level recipe optimization, to integration-level process flow optimization, to fab-level throughput and cost optimization.

Optimization Levels

• Unit Process: Optimize individual recipes (etch rate, selectivity, uniformity) within each tool.
• Module: Optimize across the lithography-etch module or the CVD-CMP module jointly.
• Integration: Optimize the full process flow for electrical performance and yield.
• Factory: Optimize tool utilization, cycle time, throughput, and cost.

Why It Matters

• Decomposition: Breaking a 1000-variable problem into hierarchical sub-problems makes it solvable.
• Consistency: Each level's optimization must be consistent with the constraints from adjacent levels.
• Industry Practice: Real fab optimization is inherently hierarchical — process engineers → integration engineers → fab management.

Hierarchical Optimization is optimizing at every scale — from individual recipe parameters up through the entire factory, with each level informing the next.