IC testing is one of the crucial steps in the chip manufacturing process, aimed at verifying whether the chip meets design specifications, whether its functions are correct, and screening out unqualified chips. Digital Logic Testing is mainly used to detect the digital circuit part of a chip, ensuring its logic function, timing characteristics, and structural integrity.
Digital Logic Testing is mainly used to verify whether the digital circuits in the chip are working correctly according to the design specifications. The goal of testing is to ensure that the chip can output correctly under various input conditions, meet functional and timing requirements, and detect manufacturing defects.
1. Testing phase:
Wafer Test (CP): Testing is conducted at the wafer level to screen out significantly defective chips.
Final Test (FT): Conduct more comprehensive testing after packaging to ensure the reliability of the chip in practical applications.
2. The main methods of digital logic testing include logic function testing, structural testing, automatic test vector generation, timing testing, and on-chip self-test.
Objective of Functional Test: To verify whether the logic function of the chip works correctly according to the design requirements.
Method: Apply a test pattern and observe whether the output of the chip matches the expected value; It is necessary to comprehensively cover all functional modes of the chip, such as arithmetic unit (ALU), control unit (FSM), storage unit (register/cache), etc.
• Scan Chain Test objective: Improve test controllability and observability, and detect register level faults.
Method: Using Scan Chain technology, connect all Flip Flops in series to form a shift register; By inputting test data externally (Scan in), it is gradually transferred into the chip and output through logical operations (Scan out); Suitable for register level fault detection, such as trigger failure to flip, short circuit, open circuit, etc.
Automatic Test Pattern Generation (ATPG) aims to detect manufacturing defects such as short circuits, open circuits, and leakage.
Method: Fault Modeling is adopted:
Stuck at Fault: A node is fixed at 0 or 1 (SA0/SA1).
Transition Fault: Detecting delay issues during signal flipping.
Bridge Fault: Two signal lines accidentally short circuited.
Input the test vector into the chip for detection through the scanning chain.
Timing Test Objective: To ensure that the chip operates normally at the target clock frequency without any timing violations.
Method: Path Delay Test: Measure the propagation delay on the logical path;
Setup Time and Hold Time tests:
Setup Violation: Data failed to stabilize before the clock edge arrived, resulting in trigger sampling errors.
Hold Violation: Data failed to hold for enough time after the clock edge, resulting in trigger failure.
Built In Self Test (BIST) aims to reduce reliance on ATE (Automated Test Equipment) and improve testing efficiency.
Method: Integrate test circuits inside the chip, generate test vectors from the chip itself, and conduct testing; Mainly used for memory BIST, logic BIST, and scan chain testing.
3. Process of Digital Logic Testing
Test vector generation: Design functional test cases; Generate structural test vectors using ATPG; Design a timing testing mode.
ATE testing: loading test programs on ATE; Apply test vectors and collect outputs; Calculate the pass rate and determine whether it is qualified or failed (Pass/Tail).
Fault analysis: If the test fails, perform Fail Bin analysis; May involve logical simulation, physical analysis, and failure localization.
Yield optimization: Combining CP and FT data to analyze defect patterns; Adjust testing strategy to improve chip yield.
Digital logic testing is a crucial step in the chip manufacturing process, involving multiple aspects such as functional testing, structural testing, ATPG testing, timing testing, and BIST technology. With the increasing complexity and performance requirements of chips, testing technology continues to develop to improve fault detection rates and reduce testing costs. In the future, AI optimization, DFT enhancement, and BIST popularization will become important development directions for digital logic testing.

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