NEM Relay DRAM Cell for Leakage Reduction
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Solution Overview
Problem
Conventional DRAM cells face challenges in reducing standby power due to non-zero leakage currents, which increase with device scaling, leading to variability and limitations in performance and power dissipation, and are difficult to scale further without compromising power or performance.
Innovation Solution
The implementation of a nano-electro-mechanical (NEM) relay pass-gate in DRAM cells using a cantilever beam actuated by an electrostatic actuator, which eliminates off-currents and reduces variability, allowing for sub-1V operation and efficient charge storage without relying on stiction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If device dimensions are scaled down to increase memory density, then memory capacity is improved, but leakage currents increase due to short-channel effects, band-to-band tunneling, and gate oxide tunneling
Solution Approach 1:
The patent replaces the conventional MOSFET mechanical switching system with a NEM relay mechanical switching system. The NEM relay uses a cantilever beam that can be actuated to make or break electrical contacts, providing a mechanically-based switching mechanism that eliminates the subthreshold leakage inherent in MOSFETs while enabling continued device scaling for increased memory capacity.
Solution Approach 2:
The patent changes the fundamental switching parameter from electrical field control in MOSFETs to mechanical contact control in NEM relays. By using a cantilever beam that physically opens or closes the circuit, the system achieves near-zero off-state leakage current while maintaining the ability to scale dimensions for higher density memory arrays.
2Quantity of substance
If device dimensions are scaled down, then memory density is improved, but variability increases due to dopant fluctuations and manufacturing tolerances
Solution Approach 1:
The patent replaces the MOSFET electrical switching mechanism with a NEM relay mechanical switching system. The cantilever beam-based switching mechanism is inherently less sensitive to dopant fluctuations and manufacturing variations, providing more consistent and reliable operation across scaled device dimensions and reducing variability in the memory array.
3Productivity
If gate voltage is increased to compensate for Vt drop and maintain performance, then performance is improved, but power dissipation increases and oxide breakdown risk increases
Solution Approach 1:
The patent replaces the MOSFET electrical field-effect switching with a NEM relay mechanical contact switching system. The NEM relay achieves low-resistance on-state conduction through direct mechanical contact without requiring high gate voltages, thereby maintaining memory performance while significantly reducing power dissipation and eliminating oxide breakdown risks associated with high voltage operation.
4Ease of manufacture
If conventional MOSFET pass-gate is used, then device integration is simplified, but non-zero leakage current requires periodic refresh and consumes standby power
Solution Approach 1:
The patent replaces the MOSFET pass-gate with a NEM relay switch that uses a cantilever beam to make or break electrical contacts. This mechanical switching mechanism provides near-zero off-state leakage current, eliminating the need for periodic refresh operations and reducing standby power consumption while maintaining compatibility with existing memory cell architectures.
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 significantly reduces DRAM standby power and variability, enabling dramatic improvements in power dissipation and area efficiency, allowing for smaller storage capacitors and more bits per bit line, thus enhancing DRAM performance and scalability.
Implementation Method 1
a high voltage is applied to an actuator to induce electrostatic pull-in of a relay
Data Source
AI summary
A DRAM cell and method for storing information in a dynamic random access memory using an electrostatic actuator beam to make an electrical connection between a storage capacitor and a bit line.