process flow

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.