Process flow is the complete sequence of process steps required to build a semiconductor device from bare wafer to finished chip. Scope: Hundreds to over 1000 individual process steps for advanced logic chips. Major modules: Front-end (transistors), back-end (interconnects), packaging. Flow document: Defines sequence, tool types, target specifications for each step. Typical sequence: Oxidation, lithography, etch, implant, deposition, CMP, metallization, test, packaging. Loops: Front-end builds transistors layer by layer. Back-end adds metal layers iteratively. Cycle time: Weeks to months from start to finish depending on complexity. Technology definition: Process flow largely defines the technology node and device characteristics. Variants: Same base flow with variations for different products (logic, memory, RF). Control points: Metrology steps between processes verify quality. Flow optimization: Reduce steps, cycle time, cost while maintaining quality. Design rules: Dictate what the flow must achieve for device functionality.