OTP Memory Cell Reverse Bias Programming Leakage Reduction
Solution Overview
Problem
Non-volatile memory arrays with passive element memory cells face challenges in reducing leakage currents and maintaining endurance due to high bias conditions during read and write operations, limiting the number of cells that can be simultaneously addressed and affecting system performance.
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 decreasing the voltage levels required by driver circuitry, allowing for reliable fabrication, programming, and reading of memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high bias conditions are applied during read and write operations, then programming capability is achieved, but leakage currents increase and endurance decreases
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 while minimizing leakage currents through the steering element, thereby improving endurance without sacrificing programming capability. The reverse bias operation changes the resistance state of the memory cell through a different physical mechanism that does not heavily stress the steering element.
Solution Approach 2:
The patent changes the bias parameter from conventional forward bias to reverse bias during programming operations. This parameter change enables the system to achieve programming functionality while operating under conditions that reduce leakage currents and minimize degradation of the steering element, thus improving overall reliability and endurance.
2Productivity
If high bias conditions are applied during programming, then memory cells can be programmed, but the number of cells that can be simultaneously addressed is limited
Solution Approach 1:
By inverting the bias condition to reverse bias, the patent enables a larger number of memory cells to be simultaneously addressed for programming. The reverse bias operation produces significantly lower leakage currents compared to forward bias, allowing the system to scale up the number of concurrently programmed cells without being constrained by excessive current consumption or thermal effects.
3Power
If conventional forward bias programming is used, then memory cells can be programmed, but driver circuitry requires high voltage levels
Solution Approach 1:
The patent inverts the programming approach by using reverse bias instead of forward bias. This inversion reduces the voltage stress on the memory cell components during programming operations, thereby improving device reliability. The reverse bias operation achieves the desired resistance state change with lower voltage levels, reducing the risk of breakdown or damage to the steering element and other cell components.
Solution Approach 2:
The patent changes the voltage parameter applied during programming from high forward bias voltage to lower reverse bias voltage. This parameter change reduces the electrical stress on the memory cell components, improving reliability while still achieving effective programming through the reverse bias mechanism that alters the resistance state of the memory element.
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 selected for programming, improving operational specifications and device reliability by reducing programming times and normalizing device performance.
Implementation Method 1
Materials having a detectable level of change in state, such as a resistance or phase change, are used to form various types of non-volatile semiconductor based memory devices
Implementation Method 2
An OTP 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
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.