Electromechanical memory cell with torsional movement

• US 20070002604A1
• Filed: 06/24/2005
• Published: 01/04/2007
• Est. Priority Date: 06/24/2005
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Ma, Jun, Lin, Pinyen, Chen, Jingkuang
• Granted Patent: US 7,349,236 B2
• Time in Patent Office: Days
• US Class Current: 365/129
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G11B 9/04 using record carriers having variable electric resistance; Record carriers therefor
• CPC Class Codes: G11B 9/06 using record carriers having variable electrical capacitance; Record carriers therefor G11B9/02 takes precedence
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor

Abstract

A memory cell uses a pair of cantilevers to store a bit of information. Changing the relative position of the cantilevers determines whether they are electrically conducting or not. The on and off state of this mechanical latch is switched by using, for example, electrostatic, electromagnetic or thermal forces applied sequentially on the two cantilevers to change their relative position. The amount of power required to change the state of the cell is reduced by supporting at least one of the cantilevers with at least one lateral projection that is placed in torsion during cantilever displacement. After a bit of data is written, the cantilevers are locked by mechanical forces inherent in the cantilevers and will not change state unless a sequential electrical writing signal is applied. The sequential nature of the required writing signal makes inadvertent, radiation or noise related data corruption unlikely.

Claims

1. A memory cell operative to store data, the memory cell comprising:

a first cantilever including a conductive portion; and

a second cantilever having and insulated portion and a conductive portion, the second cantilever positioned, at least in part, in overlapping relation to the first cantilever,

wherein at least one of the first and second cantilevers includes at least one lateral support projection extending from a respective at least one side thereof, whereby when an actuating force is applied to at least one of the first and second cantilevers the respective at least one lateral support projection is placed in torsion.

2. The memory cell of claim 1 further comprising an actuator operative to selectively cause the first cantilever to move away from the overlapping relationship by applying the actuating force to the first cantilever.

3. The memory cell of claim 2 wherein the actuator is an electrostatic actuator.

4. The memory cell of claim 1 further comprising an actuator operative to selectively cause the second cantilever to move away from the overlapping relationship by applying the actuating force to the second cantilever.

5. The memory cell of claim 4 wherein the actuator is an electrostatic actuator.

6. The memory cell of claim 1 further comprising:

a gate operative as an electrostatic reference, toward which attractive electrostatic forces act, when at least one of the first cantilever and the second cantilever is electrically charged in relation to the gate.

7. The memory cell of claim 1 further comprising:

a first gate operative to cause the first cantilever to move away from the first natural position when the first gate is charged in reference to the first cantilever; and

a second gate operative to cause the second cantilever to move away from the second natural position when the second gate is charged in reference to the first cantilever.

8. A memory cell operative to store data, the memory cell comprising:

a substrate;

a first cantilever having a supported portion and a free end, the supported portion being supported by at least one lateral support projection projecting along a lateral support projection axis of the first cantilever, the at least one laterally projecting support projection having a fixed end that is fixed in position relative to the substrate, the first cantilever having a first natural position;

a second cantilever having a supported portion and a free end, the supported portion being supported by at least one lateral support projection projecting along a support projection axis of the second cantilever, the at least one laterally projecting support projection having a fixed end that is fixed in position relative to the substrate, the second cantilever having a second natural position, a portion of the second cantilever being in overlapping relation with the first cantilever when the first cantilever is in the first natural position and the second cantilever is in the second natural position; and

an actuating system for sequentially applying torque to and releasing the first and second cantilevers, wherein the torque is sequentially applied about the support projection axes of the first and second cantilevers, whereby the cantilevers are placed in one of two steady state orientations.

9. The memory cell of claim 8 wherein the substrate includes a V-shaped groove and wherein:

the first cantilever includes a first groove following portion that is substantially parallel to a first leg of the V-shaped groove; and

the second cantilever includes a second groove following portion that is substantially parallel to a second leg of the V-shaped groove.

10. The memory cell of claim 8 wherein the actuating system comprises:

a gate operative as an electrostatic reference, toward which attractive electrostatic forces act, when at least one of the first cantilever and the second cantilever is electrically charged in relation to the gate.

11. The memory cell of claim 8 wherein the actuating system comprises:

a first gate operative to cause the first cantilever to move away from the first natural position when the first gate is charged in reference to the first cantilever; and

a second gate operative to cause the second cantilever to move away from the second natural position when the second gate is charged in reference to the first cantilever.

12. A memory device comprising:

a plurality of memory cells, each memory cell comprising a first cantilever, a second cantilever and a cantilever actuator wherein at least one of the first and second cantilever is supported by at least one laterally projecting support projection thereof; and

a control circuit operative to drive the cantilever actuators to sequentially displace and release the first and second cantilevers so as to place the first and second cantilevers in one of a first overlapping relation and a second overlapping relation.

13. The memory device of claim 12 wherein the first overlapping relation provides for a relatively low resistance path from one cantilever to the other, and wherein the second overlapping relation provides for a relatively high resistance path from one cantilever to the other, the memory device further comprising:

a cell reading circuit that is operative to measure the resistance from one cantilever to the other and report the results of the measurement as one of two binary states.

14. The memory device of claim 12 wherein the first overlapping relation and the second overlapping relation are natural, stable positions of the first and second cantilevers which are substantially unaffected by temperature variation and radiation.

15. An electronic device comprising:

at least one memory device, the at least one memory device comprising a plurality of memory cells, each memory cell comprising a first cantilever, a second cantilever and a cantilever actuator, wherein at least one of the first and second cantilevers is supported by at least one laterally projecting support projection thereof;

computational hardware operative to, at least one of, read data from and write data to, the at least one memory device; and

an output device operative to present a work product of the computational hardware.

16. The electronic device of claim 15 wherein the output device comprises a print engine.

17. The electronic device of claim 15 wherein the output device comprises a xerographic print engine.

18. The electronic device of claim 15 wherein the at least one memory device, computational device and output device are included in a device built for operation in an environment having ionizing radiation and/or temperature variations.

19. The electronic device of claim 18 wherein the device built for operation in the environment having ionizing radiation and/or temperature variations comprises:

at least one of spacecraft, probe, or satellite.

20. A method for writing data to a MEMS memory cell, the cell comprising a first cantilever and a second cantilever positioned in an overlapping relationship with the first cantilever wherein the first cantilever starts out as an upper cantilever and the second cantilever starts out as a lower cantilever and wherein at least one of the first and second cantilevers is supported by at least one lateral projection extending from a side and along a support projection axis thereof, the method comprising:

displacing the second cantilever out of a displacement path of the first cantilever;

displacing the first cantilever out of a returning path of the second cantilever;

releasing the second cantilever, allowing the second cantilever to follow the returning path of the second cantilever; and

releasing the first cantilever, allowing the first cantilever to follow a return path of the first cantilever, whereby the first cantilever becomes a lower cantilever and the second cantilever becomes an upper cantilever,

wherein displacing at least one of the first and second cantilevers includes applying a torque to at least one of the first and second cantilevers, the torque being applied about the support projection axis thereof, wherein the applied torque places the at least one lateral projection in torsion, thereby causing the at least one lateral projection to twist.