TSV Leakage Measurement via BIST Sensing Circuits
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Solution Overview
Problem
Current methods for testing through silicon vias (TSVs) in semiconductor structures are limited by the need for direct probing, which can damage the TSVs and only allow for a small sample of TSVs to be tested for current leakage, using a binary classification that is inadequate for assessing shifts in leakage current over time.
Innovation Solution
A method involving a built-in self-test (BIST) engine and sensing circuits connected to substrate contacts and TSVs, allowing for non-destructive testing of all TSVs by applying a reference current and setting a leakage threshold, with outputs indicating current leakage exceeding the threshold, enabling precise detection and monitoring of TSVs in semiconductor substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct probing is used to test TSVs for current leakage, then leakage detection is possible, but the TSVs may be damaged and only a small sample can be tested
Solution Approach 1:
The patent introduces an intermediary measurement structure consisting of substrate contacts and sensing circuits that indirectly measure TSV leakage without direct probing of the TSVs themselves. The substrate contacts extend into the substrate and connect to the TSV bottoms, while sensing circuits detect leakage current through these contacts, thereby avoiding direct contact with and potential damage to the TSVs.
Solution Approach 2:
The measurement system is segmented into separate functional components: substrate contacts that physically extend into the substrate to reach TSV bottoms, sensing circuits that detect leakage current, and a BIST engine that controls the measurement process. This segmentation allows each component to perform its specific function without exposing the TSVs to damaging probing forces.
2Ease of manufacture
If binary classification is used for leakage detection, then simple pass/fail testing is achieved, but accurate assessment of leakage shifts over time is limited
Solution Approach 1:
The patent implements a dynamic leakage detection system where the BIST engine can selectively activate different sensing circuits to measure individual TSVs or groups of TSVs. The system dynamically adjusts which TSVs are tested and can compare leakage measurements across multiple TSVs to detect shifts and trends over time, moving beyond static binary classification to a more nuanced assessment capability.
Solution Approach 2:
The BIST engine provides feedback by comparing leakage measurements from multiple TSVs and detecting shifts in leakage current. The system can identify when leakage exceeds a threshold and provide information about which specific TSVs are affected, enabling continuous monitoring and assessment of TSV reliability over time rather than simple pass/fail outcomes.
3Reliability
If only kerf structures are tested, then TSV damage is prevented, but the number of TSVs tested is limited to a small sample
Solution Approach 1:
The measurement structure with substrate contacts and sensing circuits is designed to be universally applicable to multiple TSVs throughout the product area. The substrate contacts can be positioned to contact the bottoms of multiple TSVs, and the sensing circuits can be selectively activated to test different TSVs, enabling comprehensive testing of all TSVs in the chip without being limited to kerf structures.
Data Source
AI summary
A method of testing a semiconductor substrate having through substrate vias for current leakage which includes: forming a current leakage measurement structure that includes substrate contacts, sensing circuits to sense current leakage from the through substrate vias, the sensing circuits connected to the through substrate vias and to the substrate contacts so that there is a one-to-one correspondence of a substrate contact and sensing circuit to each through substrate via, and a built-in self test (BIST) engine to sense one of the through substrate vias for current leakage. A reference current is applied to the sensing circuits to set a current leakage threshold for the through substrate vias. A through substrate via is selected for sensing for current leakage. The sensing circuit senses the selected through substrate via to determine whether there is current leakage from the selected through substrate via.