Nanusens Solves the Problem of Stiction in MEMS Inertial Sensors
August 3, 2017 | NanusensEstimated reading time: 3 minutes
Nanusens has announced that its CMOS nano-sensor technology has been successfully used to solve the problem of stiction in MEMS inertial sensors, which is a major source of failure for this type of sensor.
"Our first silicon nano-sensor samples from GLOBALFOUNDRIES exceeded our expectations showing outstanding resilience to stiction, with the devices going through more than 10,000 switching cycles, each equivalent to more than 1000G shocks," explained Nanusens' CEO, Dr Josep Montanyà i Silvestre. "And the sensitivity is an order of magnitude above what is needed for a motion sensor in most applications."
The problem of stiction in MEMS is caused by attractive forces that occur on microscopic levels such as Van der Waals and Casimir. These are surface area dependant and not mass dependant. In an inertial sensor design, there is a proof mass connected to a spring. This mass moves when there is an acceleration and the movement is detected by the mass acting as one electrode and the change in capacitance is measured relative to a second fixed electrode. However, if there is a large movement such as from a shock or collision, the mass goes beyond the normal range of travelling and touches a surface enclosing the sensor where it 'sticks' due to the attractive forces and stops working. This can be countered by having stronger springs but this reduces the sensitivity of the sensor. A solution to increase the sensitivity could be to increase the mass but this results in a greater surface area for the mass and so, unfortunately, more attractive forces.
Nanusens NEMS motion sensor
Close up of spring
The approach used by Nanusens is to reduce the sensor design by an order of magnitude from Micro ElectroMechanical Systems (MEMS) with linear feature sizes of 1-2um to Nano ElectroMechanical Systems (NEMS) where the features are 0.3um. This reduces the attractive forces significantly as the surface area reduction is in two dimensions, i.e. almost two orders of magnitude reduction. Reducing the proof mass could result in decreased sensitivity except this is offset by reducing the gap between it and the fixed electrode. The size reduction also means that the energy stored on the proof mass when it hits the surface in case of a shock, it is much less and the travelling gap is also small. A shock with less energy is also easier to detach.
"Therefore, by reducing all the dimensions of the device, we keep the sensitivity and we increase the reliability," added Dr Montanyà. "In fact, we have such a gain in reliability, that we can increase sensitivity and still have a very reliable device."
The new nano-sensors are made using standard CMOS processes and mask techniques. The Inter Metal Dielectric (IMD) is etched away through the pad openings in the passivation layer using vapour HF (vHF) to create the nano-sensor structures. The holes are then sealed and the chip packaged as necessary. As only standard CMOS processes are used, and the sensors can be directly integrated with active circuitry as required, the sensors can potentially have high yields similar to CMOS devices.
Nanusens has perfected this CMOS nano-sensor technology over the past year based on developments that the key staff had done when working at Baolab Microsystems, which closed in 2014. It was the success of this previous work that has enabled Nanusens to partner with GLOBALFOUNDRIES (GF).
Rajesh Nair, vice president of product management at GF, commented, "We have built a strong relationship with Nanusens and we look forward to advance this new generation of sensor designs using our standard 0.18um processes."
Dr Montanyà concluded, "Nanusens decided to partner with GF to develop its nano-sensors due to the outstanding technical expertise and quality of service received from their teams, together with such a large variety of CMOS nodes where we plan to move some of the devices in the future including many RF options. In addition to this, producing our nano-sensors at GF, with their huge volume capacities that keep growing due to their continuous investment in their global footprint ensures that Nanusens will have all the required production capacity that it will need in the future, and that there will never be a shortage in supplying our products to the customers. This large volume capacity is key to serve the consumer market, where demand can fluctuate very quickly, and there can be unexpected peaks."
About Nanusens
Founded in 2014, Nanusens is pioneering the development of nano-scale sensors that overcome a major problem of MEMS inertial sensors - stiction - by two orders of magnitude by reducing the sensor size by an order of magnitude into the nano-realm. For more information click here.
Suggested Items
NASA, Japan Advance Space Cooperation, Sign Agreement for Lunar Rover
04/11/2024 | NASANASA Administrator Bill Nelson and Japan’s Minister of Education, Culture, Sports, Science and Technology (MEXT) Masahito Moriyama have signed an agreement to advance sustainable human exploration of the Moon.
Lockheed Martin Conducts Historic LRASM Flight Test
04/04/2024 | Lockheed MartinThe U.S. Navy in partnership with Lockheed Martin [NYSE: LMT] successfully conducted a historic Long-Range Anti-Ship Missile (LRASM) flight test with four missiles simultaneously in flight.
Ynvisible Appoints Felix Karlsson as Director
04/02/2024 | Ynvisible Interactive Inc.Ynvisible Interactive Inc. is pleased to announce the appointment of Felix Karlsson as a Director of the Company effective immediately.
Plasmatreat at IPC APEX EXPO 2024
04/02/2024 | PlasmatreatFor the pretreatment of highly sensitive electronic components, Plasmatreat will present a real innovation at the IPC APEX Expo in Anaheim 2024: The new REDOX tool safely and effectively reduces oxide layers on electronic components in an inline process.
NASA Selects First Lunar Instruments for Artemis Astronaut Deployment
03/27/2024 | NASANASA has chosen the first science instruments designed for astronauts to deploy on the surface of the Moon during Artemis III. Once installed near the lunar South Pole, the three instruments will collect valuable scientific data about the lunar environment, the lunar interior, and how to sustain a long-duration human presence on the Moon, which will help prepare NASA to send astronauts to Mars.