Leakage Detector Circuit for Non-Volatile Memory Arrays
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Solution Overview
Problem
Conventional methods for detecting process defects in non-volatile memory arrays, such as excess leakage current through row decoders, word-lines, and bit-lines, require external testing equipment and consume on-chip area, making them inefficient for large-scale testing.
Innovation Solution
An integrated circuit die with a voltage regulator and a leakage detector circuit that generates a gate voltage based on a difference between a constant current and leakage current, allowing for selective detection of excess leakage within memory sectors using a selection circuit and leakage detection signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional external testing equipment is used to detect leakage current, then measurement capability is achieved, but device complexity and testing efficiency are reduced
Solution Approach 1:
The patent combines the leakage detection functionality with the existing voltage regulator circuit by integrating a leakage detector that shares the gate voltage generation path. The detector circuit is merged into the regulator block, allowing leakage measurement without requiring separate external testing equipment, thus reducing system complexity while maintaining measurement capability.
Solution Approach 2:
The voltage regulator circuit performs self-diagnosis by incorporating a leakage detector that monitors its own output current. The detector uses the regulator's internal components (transistors, current mirrors) to measure leakage current without external intervention, enabling the system to self-test and reduce dependency on external testing equipment.
2Measurement precision
If external read voltage is applied through an extra pad, then leakage detection is enabled, but on-chip area is consumed
Solution Approach 1:
The voltage regulator circuit is designed to serve dual purposes: normal voltage regulation operation and leakage current detection. The same output voltage node and transistor components are used for both regulating the word line voltage and measuring leakage current, eliminating the need for dedicated test pads or separate measurement circuits, thus saving on-chip area.
Solution Approach 2:
The patent uses the existing output voltage node of the regulator as an intermediary measurement point. Instead of applying external voltage through a new pad, the detector circuit taps into the regulator's output to measure leakage current, using the regulator's own output as the measurement intermediary and avoiding additional on-chip area consumption.
3Measurement precision
If external test apparatus is used for wafer sort testing, then defect detection is achieved, but testing speed and efficiency are reduced
Solution Approach 1:
The memory device performs self-testing during normal operation by incorporating the leakage detector into the voltage regulator. This eliminates the need for external test apparatus during wafer sort, allowing rapid in-circuit testing that significantly increases throughput and productivity while maintaining defect detection capability.
Solution Approach 2:
The leakage detector is designed to perform measurements during the normal voltage regulation operation before the device is shipped. By having the detection capability built-in and operational during standard testing phases, the system enables preliminary defect detection without requiring separate, time-consuming external testing steps, thus improving overall testing efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient on-chip testing of non-volatile memory arrays for process defects, reducing the need for external equipment and minimizing on-chip area, thereby facilitating faster and more efficient detection of defects during the wafer sort stage of fabrication.
Implementation Method 1
a first transistor driven by an output voltage to thereby generate a gate voltage, the output voltage being generated based upon a difference between a constant current and a leakage current
Implementation Method 2
drive a second transistor with the output voltage to thereby generate a copy voltage based upon a difference between a variable current and a replica of the constant current
Data Source
AI summary
An integrated circuit die includes memory sectors, each memory sector including a memory array. The die includes a voltage regulator with a first transistor driven by an output voltage to thereby generate a gate voltage, the output voltage being generated based upon a difference between a constant current and a leakage current. A selection circuit selectively couples the gate voltage to a selected one of the plurality of memory sectors. A leakage detector circuit drives a second transistor with the output voltage to thereby generate a copy voltage based upon a difference between a variable current and a replica of the constant current, increases the variable current in response to the copy voltage being greater than the gate voltage, and asserts a leakage detection signal in response to the copy voltage being less than the gate voltage, the leakage detection signal indicating excess leakage within the memory array.