One-Time Programmable Memory Cell Reverse Bias Programming
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Solution Overview
Problem
Non-volatile memory arrays with passive element memory cells face challenges in endurance due to high bias conditions, leading to leakage currents and program disturbances, which restrict bandwidth and reliability.
Innovation Solution
A one-time field-programmable memory cell with a resistance change element in series with a steering element is field-programmed using a reverse bias operation, reducing leakage currents and voltage levels, allowing for controlled programming and read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high bias conditions are applied to program memory cells, then programming speed is improved, but leakage currents increase and reliability deteriorates
Solution Approach 1:
The patent inverts the conventional programming approach by applying reverse bias conditions instead of forward bias. This inversion allows programming to occur through a different physical mechanism that does not rely on high forward current, thereby achieving fast programming speeds while maintaining low leakage currents and high reliability during read operations.
Solution Approach 2:
The patent changes the bias parameter from forward bias to reverse bias during programming operations. This parameter change enables the memory cells to be programmed through reverse breakdown or tunneling mechanisms, which achieve rapid state changes without the harmful side effects of high forward bias conditions, thus resolving the contradiction between speed and reliability.
2Productivity
If high bias conditions are applied to program memory cells, then programming capability is improved, but leakage currents increase and bandwidth is restricted
Solution Approach 1:
By inverting the bias polarity to reverse bias during programming, the patent eliminates the need for high forward currents that cause leakage. This allows a larger number of memory cells to be simultaneously addressed and programmed without generating harmful leakage currents, thereby increasing bandwidth while maintaining low leakage levels.
Solution Approach 2:
The patent converts the typically harmful reverse breakdown phenomenon into a beneficial programming mechanism. By utilizing reverse bias conditions to program the cells, the harmful leakage currents associated with forward bias are eliminated, and the reverse bias itself becomes the useful mechanism for achieving fast, high-bandwidth programming with minimal leakage.
3Device complexity
If conventional forward bias programming is used, then programming operations are simple, but voltage levels required by driver circuitry are high
Solution Approach 1:
The patent inverts the programming bias from forward to reverse, which fundamentally changes the electrical stress characteristics. Reverse bias programming allows the use of lower voltage levels because the programming mechanism occurs through reverse breakdown or tunneling at lower voltages compared to forward conduction, thereby reducing voltage stress on driver circuitry while maintaining programming capability.
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
The reverse bias programming method minimizes leakage currents, enabling more memory cells to be simultaneously addressed, improving operational reliability and reducing programming times.
Implementation Method 1
passive element memory cells which utilize a state change element such as a resistance change material or phase change material
Implementation Method 2
Materials having a memory effect such as a detectable level of resistance are often placed in series with a steering element to form a memory device. Diodes or other devices having a non-linear conduction current are typically used as the steering element.
Implementation Method 3
An OTP memory cell in accordance with one embodiment includes at least one resistance change element in series with a steering element. The memory cell is field programmed using a reverse bias operation that can reduce leakage currents through the array
Data Source
AI summary
A one-time field programmable (OTP) memory cell with related manufacturing and programming techniques is disclosed. An OTP memory cell in accordance with one embodiment includes at least one resistance change element in series with a steering element. The memory cell is field programmed using a reverse bias operation that can reduce leakage currents through the array as well as decrease voltage levels that driver circuitry must normally produce in program operations. An array of memory cells can be fabricated by switching the memory cells from their initial virgin state to a second resistance state during the manufacturing process. In one embodiment, the factory switching operation can include popping an anti-fuse of each memory cell to set them into the second resistance state. The array of memory cells in the second resistance state are provided to an end-user. Control circuitry is also provided with the memory array that can switch the resistance of selected cells back toward their initial resistance state to program the array in accordance with data received from a user or host device.