Series MTJ Antifuse Bitcells for Wider Sensing Windows
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Solution Overview
Problem
In magnetoresistive tunnel junction (MTJ) antifuse circuitry designs, the window between the programmed state and the unprogrammed low state is too small when using large diameter MTJs or low resistance area products, making it difficult to place a reference resistor for high yield sensing operations.
Innovation Solution
The use of two MTJs in series for each antifuse bitcell, instead of a single MTJ, increases the sensing window for antifuse read operations by doubling the resistance values, allowing for a more reliable sensor measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single MTJ is used in each antifuse bitcell, then the device complexity is low, but the sensing window is too small to accommodate a reference resistor for high yield sensing operations
Solution Approach 1:
The patent divides the antifuse bitcell into multiple segments by using two MTJs in series instead of a single MTJ. This segmentation increases the total resistance and creates a larger sensing window that can accommodate reference resistors, thereby improving sensing reliability while managing device complexity through systematic design
Solution Approach 2:
The patent combines multiple MTJs (two or more) in series within each antifuse bitcell to achieve the desired sensing window. By merging these components, the total resistance increases, creating sufficient margin to place reference resistors and enabling high yield sensing operations
2Reliability
If two or more MTJs are used in series for each antifuse bitcell, then the sensing window is increased, but the device complexity increases
Solution Approach 1:
The antifuse bitcell is segmented into multiple MTJ components connected in series, where each MTJ contributes to the total resistance. This segmentation strategy increases the sensing window by doubling or tripling the resistance values while maintaining a structured, manageable device architecture
Solution Approach 2:
The patent changes the electrical parameters of the antifuse bitcell by using multiple MTJs in series, which doubles or triples the resistance values. This parameter change creates a larger sensing window that accommodates reference resistors, balancing improved reliability with controlled device complexity
3Reliability
If large diameter MTJ or low resistance area product MTJ is used, then the MTJ resistance is reduced, but the window between programmed state and unprogrammed low state becomes too small for high yield sensing
Solution Approach 1:
The patent applies segmentation by using multiple MTJs in series to compensate for the reduced resistance of large diameter or low RA product MTJs. This creates sufficient total resistance and sensing window despite using smaller resistance individual MTJ components, enabling high yield sensing operations
Solution Approach 2:
Multiple MTJs are merged in series to achieve the required total resistance level. This merging compensates for the lower resistance of individual large diameter or low RA product MTJs, creating an adequate sensing window that maintains manufacturing precision and sensing yield
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
This approach effectively increases the sensing window for low resistance MTJ antifuse read operations, enabling more reliable sensing and accommodating variations in MTJ resistance, thereby improving the yield of sensing operations.
Implementation Method 1
magnetoresistive tunnel junction (MTJ) antifuse circuitry designs
Data Source
AI summary
The present disclosure is drawn to, among other things, an antifuse circuit. The antifuse circuit includes a plurality of antifuse bitcells and a reference resistor. Each antifuse bitcell includes two or more memory bits and a reference resistor. The two or more memory bits are configured to be in a programmed state and at least one unprogrammed state.