Nanoelectromechanical Switch with Doubly-Supported Beam
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As CMOS transistors are scaled down, sub-threshold leakage power becomes a significant fraction of total power dissipation, prompting the need for alternative technologies that can reduce or eliminate this leakage, while also offering improved radiation hardness and higher temperature operation.
Innovation Solution
Nanoelectromechanical (NEM) switching devices with an electrically-conductive beam suspended above a substrate, anchored at each end, and utilizing ruthenium metal with a ruthenium oxide coating, which provides a higher restoring force, faster switching times, and reduced leakage current, allowing for the formation of logic circuits and memory cells with low standby power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If CMOS transistors are scaled down in size, then device density and integration are improved, but sub-threshold leakage power becomes a significant fraction of total power dissipation
Solution Approach 1:
The patent replaces the electrostatic field control mechanism of CMOS transistors with a mechanical NEM switch system. The NEM switch uses a movable beam that physically opens or closes electrical contacts mechanically, rather than relying on electric field modulation. This mechanical switching action completely disconnects the electrical path when open, eliminating the sub-threshold leakage mechanism inherent in CMOS transistors where small leakage currents flow through the channel even when the transistor is supposed to be off.
2Ease of operation
If NEM switching devices use cantilever arms, then device operation is achieved, but restoring force and resonant frequency are reduced, resulting in slower switching times
Solution Approach 1:
Instead of using a cantilever arm that is fixed at one end and free at the other, the patent inverts the support configuration by anchoring the beam at both ends. This creates a doubly-supported beam structure where the middle section can deflect upward or downward. This inversion provides greater structural stability and higher restoring force because both ends are constrained, preventing the beam from buckling or deforming excessively. The higher restoring force directly translates to faster switching times as the beam can more quickly return to its neutral position after actuation.
3Ease of operation
If NEM switching devices use cantilever arms, then device operation is achieved, but stiction and curl-up due to internal stress occur, reducing device reliability
Solution Approach 1:
The patent inverts the cantilever configuration to a doubly-supported beam anchored at both ends. This structural inversion eliminates the free end of the cantilever that is prone to curling up due to internal stresses during fabrication. With both ends constrained, the beam structure is much more resistant to stress-induced deformation. Additionally, the symmetric support configuration helps distribute and balance internal stresses, preventing the curl-up effect that plagues cantilever-based NEM devices and significantly improving fabrication yield and device reliability.
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 NEM switching devices achieve significantly reduced sub-threshold leakage power, increased radiation hardness, and higher temperature operation, enabling the creation of logic circuits and memory cells with near-zero standby power consumption and longer charge retention times.
Implementation Method 1
When a gate voltage is applied to the gate electrode, an electrostatic force is generated that attracts the beam towards the gate electrode
Implementation Method 2
a flow of electrical current between source and drain electrodes is controlled electrically and mechanically using a cantilever arm which moves in response to an applied gate voltage to make or break an electrical connection
Data Source
AI summary
A nanoelectromechanical (NEM) switch is formed on a substrate with a source electrode containing a suspended electrically-conductive beam which is anchored to the substrate at each end. This beam, which can be formed of ruthenium, bows laterally in response to a voltage applied between a pair of gate electrodes and the source electrode to form an electrical connection between the source electrode and a drain electrode located near a midpoint of the beam. Another pair of gate electrodes and another drain electrode can be located on an opposite side of the beam to allow for switching in an opposite direction. The NEM switch can be used to form digital logic circuits including NAND gates, NOR gates, programmable logic gates, and SRAM and DRAM memory cells which can be used in place of conventional CMOS circuits, or in combination therewith.