High-quality testing cannot be an afterthought; it must be an integral part of the design flow. Design for Testability (DFT) modifies the hardware architecture to make it easier, faster, and more thorough to verify the chip’s integrity.
Testing operates at the fault level because physical defects are too numerous to model individually.
High-quality testing requires fault models that correlate highly with real physical defects. While "Stuck-at" models cover 70-80% of defects, modern high-quality solutions require Transition Delay (for timing), Cell-Aware (for internal transistor defects), and Bridge models. High-quality testing cannot be an afterthought; it must
Detects delay faults and timing violations using capture cycles at system clock speed. Requires careful handling of clock skew and power droop.
The backbone of high-quality digital testing is Scan Design. This technique involves replacing standard flip-flops with scannable flip-flops and chaining them together during testing. This allows the ATE to access internal nodes of the circuit, drastically improving controllability (the ability to set internal states) and observability (the ability to read internal states). Requires careful handling of clock skew and power droop
Acceptance criteria:
The solution to this crisis was the adoption of Design for Testability (DfT). DfT is not merely a testing technique; it is a design philosophy where testing requirements are considered alongside functional requirements during the architecture phase. Cell-Aware (for internal transistor defects)
A high-quality DfT solution incorporates several key strategies: