RF Test Chips Under The Microscope - Page 1
Forum section: electronics / general

author: ericloewe
author_rank: Unknown
timestamp: May 18, 2017, 11:26:05 pm
content: AMS is almost certainly the fab, austriamicrosystems.https://en.wikipedia.org/wiki/Ams_AG

author: AF6LJ
author_rank: Unknown
timestamp: May 19, 2017, 01:01:07 am
content: Cool.

author: Razor512
author_rank: Regular Contributor
timestamp: May 19, 2017, 02:35:04 am
content: I wonder, for that microscope, if a standard camera can be used, it may be possible to take high res pics and do focus stacking to get a high res image with lots of depth of field.

author: Brumby
author_rank: Unknown
timestamp: May 19, 2017, 02:42:10 am
content: Quote from: Razor512 on May 19, 2017, 02:35:04 amIf you want to go down that route - what about generating a 3D model?

author: Brumby
author_rank: Unknown
timestamp: May 19, 2017, 03:08:53 am
content: I'd be curious about looking at something like an LM358 and comparing it to the functional diagram in the datasheet.

author: free_electron
author_rank: Super Contributor
timestamp: May 19, 2017, 03:07:58 pm
content: The structures between the bondpads are the protection diodes. you see that there are two rails ( one left , one right ) of the bondpads. That is power and ground. there is a diode , anode to bondpad, cathode to power , and another diode cathode to bondpad and anode to ground. these typically are shottky diodes ( not p-n , but metal diffused into the well. )most of those chips look digital to me. that horizontal bus with the attached logic looks like a decoder to me. a control word is set on the bus and depending on the value one or more outputs of the logic turn on.

author: vlad777
author_rank: Frequent Contributor
timestamp: May 19, 2017, 03:39:47 pm
content: This guy knows his silicon components:http://www.righto.com/2014/09/reverse-engineering-counterfeit-7805.html

author: lpickup
author_rank: Regular Contributor
timestamp: May 19, 2017, 05:23:34 pm
content: Cool video!Couple of comments on some of the structures shown:The large wires on the around the outside of this circuit is a typical power ring. One would be ground and the other power. Notice the 4x4 array of vias to via down to the next lowest level to pass under the inner ring. Typically wires would have a preferred direction: horizontal wires on odd metal layers and vertical on even (or vice versa) so you would actually see via arrays in the corners of the ring, but it looks like they didn't bother sticking with that rule for the ring itself as they are on the same level all the way around.Notice the taper down of this wire...again, likely a power or ground wire. The circuits above probably don't need a lot of power, but the groundrules for the bottom metal layer are probably such that it is minimum width (the top metal layers are very thick, and therefore have to be drawn very wide). They via-ed down to the next lowest layer and then were able to run a thinner wire for the rest of the run.The circuits shown here are pretty interesting. Yes, this looks digital, but "custom" digital as opposed to standard cells that would look far more regular. You can see that the pattern is repeated, but moved up slightly, and wired together in a cascading fashion. I wonder if this is some kind of frequency divider circuit where each stage is basically a flip flop that triggers the next stage on every other transition. If this is CMOS logic, then the PMOS devices are likely where I've outlined in red (the horiztonal wires are probably Metal1 with contacts (vias) down to the diffusion (source/drain) and the gates are in between. The NMOS devices would be where I've highlighted in green. Although this seems like an enormous P/N ratio. If that's the case, then the vertical wire to the left of the green box is probably GND (notice it comes from another power ring type structure above) and the vertical wire to the right of the red box (that looks somewhat translucent like it's on a different layer, but that would be pretty atypical) would be VDD. If this were a true standard cell based design those power and ground busses would be VERY regular and immediately obvious.

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 19, 2017, 05:30:41 pm
content: It doesn't look RF at all to me, you don't cross and loop wires but you create a clear signal path. It might be high speed logic, but I wouldn't call that RF.

author: lpickup
author_rank: Regular Contributor
timestamp: May 19, 2017, 06:03:54 pm
content: And while we didn't get a complete "tour" of the chips, if they had any significant amount of RF circuitry on them I would expect to see some spiral inductors and big interdigitated caps that would certainly be noticeable in the zoomed out pictures.

author: Brumby
author_rank: Unknown
timestamp: May 20, 2017, 12:09:52 am
content: I'm wondering if we are taking the description RF test chips too literally.Could these be high speed digital circuits of a prototype nature fabricated for the purpose of testing RF related issues?

author: Kilrah
author_rank: Unknown
timestamp: May 22, 2017, 01:34:32 pm
content: Nice!The colors are likely a mix of chromatic aberration and aliasing interference with the camera since they change when shifting the sample, if you turn the chip a bit so that traces are not aligned with the pixels it might turn out better. What kind of camera/recording system are you using?Reminds me I have a few old CPUs I had always wanted to crack open but never managed to unsolder the lid... now that I have a CNC router it should be a piece of cake, I need to have a go again. No microscope though so high-res macro photo is the best I can do.

author: etelmo
author_rank: Newbie
timestamp: June 16, 2017, 01:59:09 am
content: I didn't see this thread and posted in an older microscope thread...After you finished cleaning the microscope did you regrease it?Given the magnification some lash and play is to be expected (and vibration will be easily noticed) however it would be exacerbated if all of the old grease was removed in cleaning and none was reapplied as a small amount of grease is typically used to dampen movement. I don't know what product would be specified by Olympus however a small amount (less is more) of NyoGel 774H (heavy) or 774VH (very heavy) on the rack would probably help, it's a pretty generic damping grease (it's also hydrocarbon not silicone so it's less likely to spread).If someone knows the exact grease (or perhaps it was designed for none at all to avoid contamination? I haven't used this type at all and would love to be corrected) it would be interesting to know for in future reference.

author: aqarwaen
author_rank: Regular Contributor
timestamp: August 22, 2017, 11:02:20 am
content: i found this youtube channel............i it got also lots intersting chips under microscope........have fun guys watching theys videos......electronupdatehttps://www.youtube.com/channel/UCqp2_p4YjtaTKiHuNZv0mAQ

author: TheAmmoniacal
author_rank: Unknown
timestamp: August 26, 2017, 03:42:36 pm
content: How far have you come in making the automated microscope photo jig?I'd be happy to send a couple of dies if you want/could do photograph it all, I want to make a poster like the one attached.