posted by Bryon Moyer
MEMS technology is providing new ways to generate reliable frequencies that conventionally require bulky LC tanks and crystals. Granted, it’s early days (as other monolithic ideas are commercialized), but research proceeds apace, with bulk acoustic wave (BAW) technology now being added to the use of actual mechanical moving parts as candidates for commercialization.
The challenge with an approach requiring a moving part can be summed up in one word: release. While release is required for most MEMS, it’s always extra work to do, and avoiding it is tempting. The alternative to a moving mass is the use of waves transported in a solid, which is the BAW approach. The simplest such device involves two reflectors, top and bottom, but that involves back- and front-side etching.
So-called Bragg reflectors* eliminate the need for so-called “free surface” reflectors by using an sequence of two materials with different acoustic velocities. You typically have them alternating at quarter-wavelength distances, and, if you have enough layers, it acts like a reflector. This can be used at the bottom, for instance, to eliminate the need for all the backside work to get a “real” reflector in there. This is built using alternating thin films in a stack.
In that configuration, the waves travel vertically; there have also been attempts to do this laterally, some of which have challenges and some of which still require release. But a paper at IEDM takes a slightly different approach, using deep-trench capacitors to create the Bragg reflectors and the drive and sense elements.
The good news is that the spacing of the trenches can establish the frequency – that is, lithography provides flexible target frequency design (as opposed to having to rely on a deposited film thickness or etch depth). However, quality is somewhat traded off for manufacturability in that the spacing doesn’t necessarily follow the ideal quarter-wavelength target.
The other piece of good news is, of course, that the manufacturing steps are common for creating shallow-trench isolation (STI) on ICs. (I know, there’s the obvious question: make up your mind, is it deep trench or shallow trench? I guess that, by capacitor standards, it’s a deep trench; by isolation standards, it’s a shallow trench.)
Despite this tradeoff, the researchers claimed that their 3.3-GHz resonator, built on an IBM 32-nm SOI technology, approached the performance of similar suspended-mass resonators. If you have the IEDM proceedings, you can find the details in paper # 15.1.
*If you’re unfamiliar with Acoustic Bragg Reflectors, as I was, and want to Google it, be aware… most useful information appears to be locked behind the infamous pay walls. There were some bits and pieces I could salvage, but apparently such knowledge isn’t for us, the hoi polloi…
posted by Bryon Moyer
A while back, MIG director Karen Lightman posted a blog entry about life without MEMS (if you haven’t read it, I’d recommend doing so before proceeding). After a chuckle, my first thought was, “Wow, how the hell did we ever live five years ago without dying of anxiety??” Then it occurred to me to take things back further than five years. What would the life of a caveman (or –woman) be like given the opportunity for tools to improve their existence? While not specifically relevant to us today, seemed a worthy Friday Fun exercise.
So I did some research on this to see if any evidence existed that might shine light on the matter. Turns out that there were some vague scribings on a cave in Altamira that suggest that the kinds of anxious moments Karen experienced may not be unique to our time. It’s a little hard to discern what’s going on – this is pre-Sumeria, pre-oracle-bones, when there was no organized civilization, no structured leisure or entertainment as we know it; there wasn’t even any Hollywood. So writing hasn’t been invented yet, making interpretation difficult. But what follows is my crude attempt at an Englishesque rendition that maintains the stilted style of the time. Any of you better versed in archeology or paleoanthropology might be able to shed more light on my meager attempts.
- [hmmmmngh]* Wake up, big noise. Bash Rocks** broken, kids bored. Daughter dragging little brother by hair. Go pound head on wall to gauge stress, but forgot iCudgel***, not know stress now. [hmmmmngh]
- Weather? Look outside, too much berry juice**** last night. Horizon flip regular, sideways, regular, sideways. [hmmmmngh] Bad belly. Look through hole in iCudgel instead. No help. [hmmmmngh]
- Late for hunting. [hmmmmngh] Which way go? Drop iCudgel, see which way pointing, go that way. But point to cave. Not helpful. Must go without guidance. [hmmmmngh]
- Go to birthday. Record drawing on wall with iCudgel, but blurry. Use rock, still blurry. Bad berries… [hmmmmngh] Maybe take home to improve… whack around picture with iCudgel to break free so can take home. No work. Foiled again. [hmmmmngh]
- Big sneeze. Whack nose with iCudgel to fix. No work, more sneeze. [hmmmmngh] Maybe take pill? But how know when to take pill? Write on iCudgel? But pill not invented yet. Never mind. Remove pterodactyl feather from nose by hand. [hmmmmngh]
- Go drive PieceOfSchist*****. Have big block of chalk on steering wheel so when crash, head hit nice soft chalk, not steering wheel. But chalk no there. [hmmmmngh] Now weather bad, big floppy snow ice rain mix bits. Whack wheel with iCudgel so no slide off road. No work. [hmmmmngh] Also test wheel to see if chunk about to fall off. Whack with iCudgel. Not sure if worked. [hmmmmngh]
- Wife must cook nice organic free-range pterodactyl hunted today. She too far away, no hear. Yell through hole in iCudgel to make louder. No work. Need yell extra big loud. [hmmmmngh]
- Need wake-up. Take PieceOfSchist to place where civet cat eat shiny red berry and get all giggety. But on hill, PieceOfSchist will roll down hill. Put iCudgel under wheel to stop. No work. [hmmmmngh]
Beyond this point, the images fade too much to be intelligible. But it does give us something of a “day in the life”; perhaps our toys and stresses aren’t as unique to our time as we might think.
*I’m totally taking a wild-ass guess at this one. It seems to be a recurrent interjection of some sort, but based on context, I’m hearing it as some sort of low growl/grumble kind of thing. Kind of like the croonings of a Phil Hartman Frankenstein.
**Seems to be some sort of game where they toss boulders at each other to see who can pin whom to the cave wall first.
***This appears to be some ubiquitous club-like device that features in pretty much every activity. In this case, it would appear that they measure stress by pounding their heads against the wall. By pounding the iCudgel along with it, they can count the number of hits – more hits, more stress.
****This would seem to be some kind of drink made with fermented berries.
***** I’m picturing a Flintstone-mobile here. They had a poor reliability record, hence the deprecating nickname.
posted by Bryon Moyer
I don’t know this for sure, but I can imagine that some marketing folks at STMicroelectronics were less than thrilled by the high-profile Java issues ricocheting through the airwaves a couple weeks ago. My colleague Jim Turley engendered some back-and-forth with his analysis of the appropriateness of Java in embedded systems in particular.
It was not but a few days after this had barely disappeared from the headlines that ST announced their STM32Java development kit for developing Java applications on embedded systems. Such an announcement might have been routine on any other week. (Of course, had it been routine, you might not be reading about it here…)
I just had to check in with ST’s Michael Markowitz; the question was just sitting there like a lonely technical support hotline agent with no calls in the queue: “Ask me!” The issue, of course, is security. Will using Java in white goods ultimately allow the dryer to infect the washing machine? Could a WiFi-enabled cordless drill be instructed by a trench-coat-wearing lurker behind the boxwood to stop drilling the furniture and turn on its master instead? Could a smart showerhead be maliciously configured by an unauthorized plumber to broadcast pictures to the Internet?
OK, I didn’t ask those questions specifically. It’s early, OK? I’m still not far into my cuppa Joe, blundering about a bit in that happy gray zone between waking and sleeping. But I did ask for comment regarding the blaring warnings that were still echoing off the hillsides. Having checked with the team, Michael responded that, as far as they could tell, the issue wasn’t intrinsic to Java specifically, but rather was related to “a badly programmed library, that… allows a program to access another program on the host machine,... crossing the ‘sand box.’" Having no such concept in its architecture, STM32Java would therefore not be affected.
So the simple answer would then be, “Not an issue.” Of course, this deals specifically with the one vulnerability identified in the latest brouhaha. There are those that take issue with Java generically: this doesn’t address that. But, given the amount of opinion and philosophy that accompanies this debate, I can only conclude that there are no fundamental facts to settle the issue one way or another. It would seem that abandoning Java on computers would be reasonably disruptive; if it migrates onto embedded systems in a universal way, we’ll be just that much more strongly wedded to it.
ST, at the very least, is moving forward undeterred. You can read more about it in their release.