Leakage Current Detection Using FEOL PN Junction Diodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for detecting leakage current in metal layers of semiconductor ICs face challenges in achieving high accuracy due to the small size of the leakage current, requiring multiple detecting elements that increase the test layout area, which is undesirable as chip size decreases.
Innovation Solution
A system comprising a test layout module with PN junction diodes formed in the FEOL process parallel-connected to classical leakage current test units in the metal layer, where P-regions are connected to a high potential and N-regions to a low potential, allowing for enhanced detection accuracy by calculating the final leakage value through the leakage values of each PN junction diode and classical test units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple detecting elements are paralleled to increase total current for accurate leakage detection, then measurement precision is improved, but test layout area increases
Solution Approach 1:
The patent combines FEOL process-formed PN junction diodes with BEOL metal layer test structures into a unified test layout module. The PN junction diodes are formed in the same substrate during front-end processing, and their leakage current paths are merged with the metal layer leakage detection paths through shared contact holes and metal interconnects. This integration allows simultaneous detection of both FEOL and BEOL leakage currents using a single compact test structure, resolving the contradiction between measurement precision and layout area.
Solution Approach 2:
The test layout module serves multiple functions: it detects leakage current in the metal layer (BEOL), detects leakage current in the PN junction diodes (FEOL), and provides a unified measurement interface. By making the test structure multi-functional, the patent eliminates the need for separate detection circuits for different leakage sources, thereby reducing overall test layout area while maintaining comprehensive detection capability.
2Reliability
If more detecting elements are used to monitor short circuit occurrence, then reliability is improved, but test layout area increases
Solution Approach 1:
The patent divides the leakage detection function into multiple independent detection paths within a compact module. Each PN junction diode creates a separate leakage current path that can be individually monitored, while sharing common measurement infrastructure (contact holes, metal interconnects, measurement terminals). This segmentation provides comprehensive short circuit monitoring capability across different regions while maintaining a compact overall structure.
Solution Approach 2:
The test layout module employs a nested structure where PN junction diodes are formed within the substrate, their contact holes are nested within the metal layer structure, and multiple detection functions are nested within a single unified test interface. This nested arrangement allows multiple detection elements to be packed into a minimal area while maintaining full monitoring capability.
Data Source
AI summary
A test layout, a system, and a method for detecting leakage current are disclosed. The test layout module includes M PN junction diode leakage current test units formed in the FEOL process, parallel-connect with a classical leakage current test unit formed in the metal layer; wherein, P-regions of the PN junction diodes are connected to a high potential, N-regions of the PN junction diodes are connected to a low potential, the junction areas of the PN junction diodes are different each other, each of the PN junction diode leakage current test units is controlled by one switch respectively, the positive integer M is greater than or equal to 1. Through paralleling the PN junction diodes formed in the FEOL process with the classical leakage current test unit in the metal layer, not only the required test layout area utilized to detect the leakage current in the metal layer is reduced, but also the detecting accuracy is further enhanced.