What kinds of yields are the manufacturers seeing (or accept to go into full production)?
When you mentioned Moore's law does not apply, it is from the physical (mechanical) rather than electrical issue with the device, I would expect given the types of materials available one reaches a physical/mechanical limitation.
Good presentation. Still digesting the phenomena ...
I would have to say that my personal exposure is predominantly with MEMS accelerometers rather than gyroscopes, but I didn't know that until this lecture.
Interesting series. Interested in most of the mems sensor. I use them for low frequency noise detection. Seismic waves, Low Frequency Noise (LFN or Infrasound) from Wind Turbines, trains, roadway vibration etc.
There were about 10 posts below, before the lecture started, and there wasn't a single response saying they HAD received one. Surely it's not just a marketing trick to get us Engineering types to attend.
Alex, Still there? Did you notice all the concerns about the promised Gift Card? It isn't why I attend, but I must say I've been to at least 5 of these that promised a gift card, including a few over a month ago and never have received one.
someone asked about specs - all manufacturers list their tested specs, but the problem is there is no current standard for testing MEMS motion sensors. So you need to read the data sheet with a skeptical eye, and many system integrators choose to evaluate the MEMS motion sensors themselves instead of believing the spec sheet. I'm not saying the mfgs are dishonest, just that there can be a bit of specmanship.
More on caps to create hermetic cavities: polymer bonds are not hermetic enough for motion sensors, but might be ok for other sensor types. Most motion sensors are bonded via anodic bonding (glass to silicon) or gold-gold thermocompression. Some use glass frit, too. Temps are generally under 400C, but depends on bond type.
@ttodorov, who asked about power generation - yes, people are exploring MEMS as energy harvesters. Most approaches incorporate piezoelectric materials, which can transduce motion/strain into voltage. These type of harvesters can only produce nW, so not super useful at this point, until electronics become even lower power.
Regarding caps - is cathodic bonding the dominant mechanism of attachment, or can one use a low temp glass frit? What temp ranges are we speaking of during cathodic bonding and how low can the frits go? 250-300°C?
Do they use a polymer seal and call it 'hermetic'?
@eviscito, who asked about MEMS integration in ASICs - it can be done, but it depends on the MEMS architecture. Some MEMS can not be easily integrated with a CMOS process. Analog Devices has very successfully come up with a MEMS design that is integrated with their BiCMOS electronics. Ultimately, it's a cost and yield question. Most mfgrs. choose to process MEMS and CMOS wafers separately and then integrate at the package level, because it's cheaper!
@Alissa - I wonder if somebody is researching using MEMS (as mechanical devices) to generate electricity for picopower applications - like from wind or fluid motion, to work in difficult to reach areas (can't just go and replace the battery at the bottom of the ocean)
@GeoSei: yes, there has been a lot of work on MEMS accels for geo applications - seismometers and down-hole applications. I can't think of any mfgrs off hand, but they are definitely out there.
@naperlou, who asked about outputs: most MEMS accels and gyros have standard digital outputs, and i think you can get some accels to provide analog output. Most mfgrs these days are trying to make their sensors as "application ready" as possible, so they are providing firmware along with the sensors.
@Steven who posed a question about caps: all MEMS motion sensors need to be in a sealed, partial pressure environment. The easiest way to create a hermetic cavity is by bonding a rigid cap. there are some MEMS process methods whereby you can create very shallow cavities, but these approaches do not work for motion sensors. So generally, you're stuck bonding on another piece of silicon or glass to seal in the motion sensor.
The freescale sensor i just received does a lot of processing within the sensor package so that the device puts out usable values. Is this true of most of the other brands as well?
@Alissa - It sure would be nice to have a face to go with the voice. We have only two sessions left this week. Will you consider posting your photo for us? Please?
For the majority of the MEMS devices shown in your presentation, is a Si 'cap' bonded to the peripheral face of the MEMS chip thereby creating the hermetic package which is subsequently wirebonded to a leadframe and over-molded - or is there another cheaper way to create the cavity in the molded package interior.
If not using a 'cap', is it really 'hermetic' and what might be the use environment limitations?
@Alex question: The most fascinating so far for me are the automotive performance computers.Push the suction cups onto the windshield, enter the car's weight and go.0-60 mph time, quarter mile time and much more...Great!
Consumers have no sense of sensors or what they are or whether or not they are in devices. My two cents. They just want to shift to landscape mode, for example, when they rotate their phone or tablets.
TRANSCENDING AGE: We won't be able to distinguish who are cenile or not when they speak and gesture apparently to themselves. That might bring us close to the perfect world.
Can I measure repeated shocks with a MEMS accelerometer without reducing its life? The shocks would be within the measurment range of the accelerometer.
I just got a kit from Freescale which combines an accelerometer and a magnetometor (sp?) to make a compass. Applications will be more for new product development.
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