Decapping and Chip-Documentation - Howto

[magic]

For large lenses you may need to use 28mm ring for that instead of 14mm as I did. Or maybe not, who knows, have fun
Mirror position and angle is quite important, otherwise the light goes somewhere to the side of the FOV. Infinity focus system seems to be somewhat less sensitive to that, so I am using it for now.

Further testing of my Hugin configuration revealed that Maxim definitely curses their ICs to thwart reverse engineering. Just when I thought I got a cleaner die than yours, I dropped an M42 tube on it

And there is more chromatic aberration due to brighter metal. I definitely need to fix illumination and get my webcam lens to work because it has virtually zero CA. I know it can be done because it was better in the matchbox than it is now. I may also try infinity focus with webcam, but I expect impractically high magnification.

Nevertheless, Hugin delivered. 18 frames with only 25% horizontal overlap, everything went smoothly and automatically. To recap, this is the flow that works:

0. Add a new control point finder in preferences; copy everything from "Hugin's CPFind (prealigned)" but change arguments to "--ransacmode rpy --prealigned blah blah blah". This only needs to be done once.
1. Load the images, specify HFOV as 1° or focal length as 9999 or something like that.
2. Run "manipulate image variables", load the "2 row panorama" preset, adjust for actual number of rows.
3. Select the customized control point finder and run it.
4. Manually add a pair of horizontal/vertical line control points on any image so the IC comes out rotated correctly.
5. Run the default geometric optimization.
6. Play with photometric optimizations if necessary (exposure, white balance).
7. Autosize, autocrop, stitch.
 

BTW, I think there may be some CMOS logic stuff on this reference, right under the output stage. The green rectangles further below also look like some bigger MOSFETs.

[mawyatt]

Been involved with chip imaging (mostly the chips we designed) since ~2000. We've done images as large a 30,000 by 20,000 pixels. There's lots to learn and here's some links that will help. Many world class macro/micro photographers are involved with these sites, especially the Photomacrography site hosted by the Rik the author of Zerene Stacker.

For a complete evaluation of potential lens be sure and visit Robert's site CloseUpPhotography.

Can post some of the setups we've developed over the years if folks are interested.

Best,

https://www.photomacrography.net/index.htm

http://zerenesystems.com/cms/stacker

https://www.closeuphotography.com

http://extreme-macro.co.uk

[Noopy]

You have a really nice setup but unfortunately over all it's quite expensive.  I wish I had unlimited credit... 

[mawyatt]

We developed some setups around the very affordable WeMacro stand. This is an excellent setup which can be utilized both vertically and horizontally, and with some simple and inexpensive modifications becomes a quite respectable setup for serious macro work. This became our "Go To" setup for most of our chip imaging work, highly recommended!!

https://www.wemacro.com

Note the 1st image that comes up on the WeMacro site was requested by William at WeMacro, it used his affordable microscope objective, stand and is part of a non-proprietary test chip we developed ~15 years ago.

Here's some links about the stand and some modifications.


https://www.photomacrography.net/forum/viewtopic.php?f=25&t=34617&hilit=Modified+WeMacro+Stand
https://www.photomacrography.net/forum/viewtopic.php?f=25&t=38353&hilit=Modified+WeMacro+Stand
https://www.photomacrography.net/forum/viewtopic.php?t=38838&highlight=wemacro
https://www.photomacrography.net/forum/viewtopic.php?t=38511&highlight=wemacro
http://www.photomacrography.net/forum/viewtopic.php?t=38353&start=0&postdays=0&postorder=asc&highlight=stack+stitch

Best,

[mawyatt]

Also, if you spend some serious time on the sites mentioned, including CloseUpMacro, you'll find some really good lenses at bargain prices. Lenses like the old Soviet Lomo 3.7, or some repurposed scanner lenses. The Minolta 5400 scanner lens became an overnight hit because it was so good, and the price shot up after others found out, fortunately we got one before the price went too far

The cheap AmScope 4X isn't bad either, sure it's not in the Mitutoyo class, but for the price quite a bargain 

https://www.closeuphotography.com/seventeen-dollar-plan-4x-objective

The message is spend some time researching on the sites mentioned, it will pay off

You can build a very good setup with lenses, mechanicals, and linear stepper based focus rail stages for a modest investment. Of course this just opens your pocket book since later after you've mastered the setup and imaging techniques, in pursuit of the perfect image you'll want better optics, focus rails and so on.

So please don't discount everything as being too expensive, if you follow the advise above you'll end up with a quality lens and setup for a very modest investment, however there's no free lunch as you must do your homework

Best,

[Noopy]

Probably you are right.
Perhaps I should do some more research.
I´m quite happy with my equipment (resolution/€) but a little more pictures quality would be nice of course. 

I have seen a lot of your pictures with tilted chips.
- Did you have a solution for tilting the die to get it flat parallel to the lens? Often such precision tilting blocks are 100€ to 300€...
- Did you have a solution for light through the lens? Or did you just do tilted pictures?

[mawyatt]

Probably you are right.
Perhaps I should do some more research.
I´m quite happy with my equipment (resolution/€) but a little more pictures quality would be nice of course. 

I have seen a lot of your pictures with tilted chips.
- Did you have a solution for tilting the die to get it flat parallel to the lens? Often such precision tilting blocks are 100€ to 300€...
- Did you have a solution for light through the lens? Or did you just do tilted pictures?

Your pictures are quite nice with good detail, sharpness and contrast 

If you are looking for a little better quality, maybe when shown much larger then I highly recommend studying Robert O'Tools site, he has put in an enormous amount of effort in lens tests. Note that he also uses silicon wafers as the target subject. Photomacrography also has lots of information on various lenses and combinations, many of which are not expensive.

Precision tilting blocks can be expensive, watch eBay for some bargains, I got a couple last year for ~$75 each, however I haven't used them yet.

For the chip mounting, the chip backside was glued to a pin head which was held in place by an alligator clip on a photographic ball head. The head was either mounted to a XY or XYR micrometer stage or a XY linear rail, shown in the old images below when we 1st starting venturing into Stack and Stitch territory. The XYR micrometer stage is an inexpensive clone off eBay, ~$70, the ball heads were $10~15. The XY linear rails are surplus THK KR15s, also ~$75 with NEMA 11 motor included. The stand is a WeMacro ~$130.

Have never used thru the lens lighting, all my lighting was done with highly diffused light from multiple strobes or LEDs. Cheap eBay light tents work well as diffusers, have even used two, one small tent inside a larger tent. White foam cups also work very well.

Tilted images can be difficult since you need significantly more depth, but add a degree of 3D like to the image. One issue is that the perspective can change as the distance between the subject and lens changes when doing image stacking. This can become extremely difficult with stitching, much more so than stitching an insect because the chip has straight and right angle edges which must align between tiles. Here is where the special class of "Telecentric Lenses" comes into play, these lenses have a unique property that the magnification does not change with subject to lens distance. Do a search over at Photomacrography for details.

Best,

[magic]

Lighting through the lens (or reflected off the lens) is relevant in that it is a straightforward way to avoid focus stacking altogether and a requirement for serious NA/resolution.

Extreme macro technology may be applicable to Noopy's closeups of package internals, bond wires and stuff like that, but detailed die imaging is strict microphotograhpy territory and the path has been shown by guys like Svarichevsky and Shirriff IMO. The EM crowd has some useful information about optical components, though.

And I wouldn't expect bargains once they find out about something

edit
Purely for science, I ran my MAX6250 project through Hugin on default settings. I tested:
- run CP find, run geometry optimization
- switch to beginner mode and just click "align"
- the "scanned images" assistant

All of them failed hard and produced the familiar "cubist mess", albeit a different mess each time.

[mawyatt]

Lighting through the lens (or reflected off the lens) is relevant in that it is a straightforward way to avoid focus stacking altogether and a requirement for serious NA/resolution.

This is incorrect, lighting of any kind has absolutely nothing to do with focus stacking, NA or resolution!! They are all lens dependent.

DoF ~= Lambda/NA^2  for small NA

Resolution = Lambda/(2*NA)

NA = {(1/(2*F))*(M/(M+1)}

Effective Aperture = F(M+1)

Where Lambda is wavelength (~550nm for green), F is lens aperture, M is magnification

Examples:

The Mitutoyo 5X Inf objective lens has a M of 5, NA of 0.14, DoF of 28um, Resolution of 2um, and Effective Aperture of 18

The Mitutoyo 20X has M=20, NA=0.42, DoF=3.2uM, R=0.7um and EA=24

So if you are after higher Resolution then you want a larger NA, which causes less DoF. Focus Stacking is simply a means to get around the shallow DoF caused by higher M and Resolution needs, and has created some excellent high resolution images of subjects with significant effective depth (like chips tilted for example).

Lighting is a completely independent subject of itself, many techniques are available and used. Each has pros and cons, but we've never needed to use thru the lens for any of our work (we mostly image the chips we designed, some even at 50X).

The tradeoff between M, DoF and Resolution creates a barrier called Diffraction which is being addressed with post techniques called Deconvolution, but that's another highly involved subject.

Best,

[magic]

Well, it does. With proper lighting DoF can be rendered irrelevant, as it should be with a flat subject

As for resolution, the problem is that high NA objectives tend to have short working distance and not much space is left for lighting. Surely you can spend four figures on ELWD objectives and precision macro rails, but not everybody will go that far. And if one does, it is not entirely clear why the same money wouldn't be better spent on a metallographic scope and ordinary WD optics with more NA.

If you have infinite money, I would bet on the latter setup winning too. I don't quite see combining 1.4NA oil immersion with ping-pong balls.

All of the above applies to subjects that are indeed flat, of course.

[Noopy]

That´s a complex topic. You have to built a setup that does most of the things you have on your wish list with the amount of money you can spend.
My wish list is quite long and calls for different solutions:

• big parts / dies
  I take my Canon 100m 2.8L Macro and take pictures with a magnifications of 1x or lower.
  For "parts" I use diffused light by putting a paper over the part and moving a CFL desktop lamp above it. Works quite well.
  For big dies I use light from behind the die to get the nice colors. I like those pictures to get an overview since pictures stacking consumes more time.
  Adjustments are done by holding the part with a third hand and bending the arm. That´s good enough for 1x and lower.
• die - flat
  I take my reversed 10-22mm and add the tubes I need to get the right magnification: For example i take 10mm+0 for an overview and 10mm+2 for details or a big stacked picture.
  Light comes from behind and I´m quite fast with changing the magnification.
  I own a small micro manipulator for x, y and tilting over the two axes. That´s makes it easy to adjust the alignment.
  The sharpness is controlled with the focus ring.
• die - tilted
  Side views and "3D structures" need "tilted pictures" and focus stacking. But tilted dies often give some more sharpness and details too. I don´t know why.
  I use the setup described above and vary the focus. That´s worse than moving the object because the magnification changes but I´m quite fast and moving the object needs a though construction.
  Lightning is a CFL desktop lamp. I can vary the light angle to get the best possible pictures.
  
• something for inbetween 
  Sometimes I use my new Canon MP-E 65mm 1-5x. That´s the magnification at which my 100mm Macro isn´t good enough (with distance rings). The 10-22mm retro at it´s "lowest" configuration 22mm+0 has quite some magnification, sometimes too much. And the Canon MP-E 65mm 1-5x is really sharp (at 1-5x). 
  The Canon MP-E 65mm 1-5x has no focus so I have to use a macro rail. Since I have only a cheap one it´s not possible to mount the camera on the rail: The rail moves sideways a little while moving forward and the mirror movement makes the picture blurred. Mounting the lens on the rail is bad and mounting the camera is bad also. Because of that I place the die on the rail (with my third hand). That looks strange but guarantees sufficient image quality.

My whole setup is placed on a esd pad. That seems to be a perfect support. The parts stick a little on the surface. The pad is hard enough that the parts don´t sink into the pad but does a little damping.


A change in my setup has to improve the already good quality. It has to fit into the rest and it must not slow down the process. That´s no easy task. 
I´m afraid changing something makes me change a lot and would consume a lot of money. And for some problems I still have no solution. For example the light through/from the lens with a vertical setup. Of course I can built something like magic but I´m afraid such a modification makes the new setup worse than the old one...

[magic]

But tilted dies often give some more sharpness and details too. I don´t know why.

Shadows of all the vertical steps on the surface, perhaps?
Colors also change so sometimes it could be down to that.

I´m afraid changing something makes me change a lot and would consume a lot of money.

That's why I play with cheap junk to roughly figure out what matters and what does not

Light through the lens may help with shadows in the center of a big die. Otherwise, I'm not sure if it will be any better than what you have.

[mawyatt]

Well, it does. With proper lighting DoF can be rendered irrelevant, as it should be with a flat subject

Now you've restricted yourself to flat images because of a shallow DoF. Flat images tend to be less artistic than images with some depth, most folks I know prefer a tilted chip subject which shows some of the features better and gives a sense that a chip isn't just a 2 dimensional object.

As for resolution, the problem is that high NA objectives tend to have short working distance and not much space is left for lighting. Surely you can spend four figures on ELWD objectives and precision macro rails, but not everybody will go that far. And if one does, it is not entirely clear why the same money wouldn't be better spent on a metallographic scope and ordinary WD optics with more NA.

If you know what you are doing getting sufficient illumination even at 20~50X can be done without the need for ELWD objectives, or thru the lens lighting. As mentioned spend some serious time over at Photomacrography and learn from some of the world class macro photographers there (I'm not one).

If you have infinite money, I would bet on the latter setup winning too. I don't quite see combining 1.4NA oil immersion with ping-pong balls.

And why would anyone that knows anything about chips, lenses and macrophotography use an oil immersion lens on a chip, seems like a very messy recipe??

BTW don't discount a ping pong ball or foam cup used as a diffuser, if you look at the results over a Photomacrography you'll soon realize just how good they are as diffusers!! Some of the images below likely used a foam cup, but can't remember details since these are almost 10 years old, or older.

All of the above applies to subjects that are indeed flat, of course.

What about a die that has wire-bonds, how do you propose to show such a subject with a shallow DoF, yet the wire-bonds add depth?? The wire-bonds would come into the die image as a surrounding massive blurry mess, but utilizing focus stacking you can create an image like these very low resolution versions which shows the die and the wire bonds both with reasonable clarity.

Also, note the last image below used the $17 AmScope 4X we mentioned earlier, not an expensive lens at all 

Anyway, most will prefer the focus stacking rendered image IMO and why we went to all the effort to do such. Folks at IBM, Cornell, USC, MIT-LL, DARPA, Keysight, Harris, Excelis, ITT and a few others I can't mention thought so too

BTW our images have been printed or displayed in very large format (some 2 meters across), and inspected in detail, so they needed to be accurate and have very high resolution

Noopy's images are all very good and he sure does quite a few, my notes were if certain images of particular interest were to be enlarged then he might want to consider alternative techniques, including focus stacking. If he were here is the US and came by, I'd probably help him with some things, and even donate some equipment.

Best,

[mawyatt]

Noopy,

Your images and techniques are fine, producing nice images without much addition effort

Don't want to imply anything else, the equipment and technique I mentioned were just as information that you might find useful.

Your use of the stacked lenses (100mm and 10-22mm) is an excellent way to get around some of the diffraction limits imposed, see details over at PM, lots of  discussions on this stacked lens topic.

If you look at the last image I posed above, reposted here in slightly higher resolution, this is from an AmScope $17 4X lens than Robert O'Tool discovered a number of years ago. If you decide to acquire this lenses be very careful, lots of sub-par clones showed up after this was discovered.

Best,

[mawyatt]

One of the more difficult chip related things to image we discovered a number of years ago is new chip solder balls. These are like tiny (40~100um) bright spherical mirrors before they oxidize and reflect everything, especially the illumination sources. All sorts of illumination technique were tried and the highly diffused (usually 3 or 4 levels of diffusion) multiple strobes proved acceptable. This produces a very uniform illumination from all directions, without significant specular artifacts which detract from the final rendered image.

Best,

[Noopy]

magic, mawyatt I highly appreciate your knowledge and experiences! 
It´s a complex topic and the solution can be different for different requirements.
I like my setup but getting better is always a good thing. 

But tilted dies often give some more sharpness and details too. I don´t know why.

Shadows of all the vertical steps on the surface, perhaps?
Colors also change so sometimes it could be down to that.

I´m not sure... ...it´s different, sometimes better.





The 3D effect helps but it seems like it´s a little sharper too.

Your images and techniques are fine, producing nice images without much addition effort

Don't want to imply anything else, the equipment and technique I mentioned were just as information that you might find useful.

Your use of the stacked lenses (100mm and 10-22mm) is an excellent way to get around some of the diffraction limits imposed, see details over at PM, lots of  discussions on this stacked lens topic.

I appreciate your hints! 

But I don´t  use stacked lenses. I just use reversed lenses, mostly the 10-22mm.



Works fine! 

One of the more difficult chip related things to image we discovered a number of years ago is new chip solder balls.

Yeah, solder balls are wierd. 

[magic]

Flat images tend to be less artistic than images with some depth, most folks I know prefer a tilted chip subject which shows some of the features better and gives a sense that a chip isn't just a 2 dimensional object.

I repeatedly tried to make it clear that I am after transistors, not solder balls and bond wires. Those I would rather tear off so they don't obstruct the view

Your cheap 4x achromats would struggle to produce the LF357 image that I posted recently and this is 1980s technology. The Maxim is 1990s technology and my 10x achromat struggles to resolve some details. And there are chips from the 2000s that I would like to see. With the <2mm working distance of common high mag objectives I can only imagine external illumination as nothing but a massive PITA. Epi at least stays attached to the optics - mount it once and it keeps working, chip after chip.

And why would anyone that knows anything about chips, lenses and macrophotography use an oil immersion lens on a chip, seems like a very messy recipe??

Because the formula for resolution that you posted is incomplete and I'm sure you know it

The 3D effect helps but it seems like it´s a little sharper too.

It does look sharper indeed. It could be due to hard shadows, or I'm not sure what else. I presume it's the same optics, subject distance and magnification in each case?

At any rate, I applied some fake sharpness and contrast to it. I don't know if it's better, but it's different

But I don´t  use stacked lenses. I just use reversed lenses, mostly the 10-22mm.

You could. It really is as simple as getting a different kind of passive reverse mount adapter (<$5 delivered here) and replacing the extension tubes with a telephoto lens. You get the benefit of both lenses working near infinity focus, which most photographic lenses are optimized for. AF can be used for fine-tuning focus. And some gain in NA if working near unity magnification, but I don't know what magnification you use.

edit
Although it must be said that not all tele lenses are suitable for this job. Vignetting or all sorts of distortion around the edges is a possibility. But reverse mounting rings are cheap to try...

I'm sure I have seen a post explaining what sort of lens to look for on some internet forum. You could try to find it - it was photomacrography most likely. I think the first rule was that front element diameter is not supposed to be much larger than absolute aperture diameter (= focal length / F-number).

[RoGeorge]

The oil immersed objective is a trick used in microscopy.  It shows more details for the same optics.

At minute 4:35 there is an image with and without oil, side by side.

[magic]

It shows more detail with different optics. It's not just about sealing to keep oil from leaking into the objective as they say on the video, but the whole objective is designed for light coming at different angles and refracting differently.

In fact, immersion oils are produced to have similar refractive index as glass, so that the borders between the cover slip, the oil and the front surface of the objective almost disappear. Serious refraction starts to occur on internal surfaces of the objective, which can be ground precisely, aligned and then left alone undisturbed by external factors.

For that reason I wonder if biological oil objectives could actually be usable without covers slip, but I'm not rushing to buy one because I doubt I would be able to provide necessary focusing precision and illumination quality. To collect a wide cone of light from a reflective surface one has to first project an equally wide cone from above.

Once upon a time, Zeptobars posted photographs of some submicron CMOS stuff using oil immersion on a proper microscope.

[mawyatt]

Your cheap 4x achromats would struggle to produce the LF357 image that I posted recently and this is 1980s technology. The Maxim is 1990s technology and my 10x achromat struggles to resolve some details. And there are chips from the 2000s that I would like to see. With the <2mm working distance of common high mag objectives I can only imagine external illumination as nothing but a massive PITA. Epi at least stays attached to the optics - mount it once and it keeps working, chip after chip.

First off, these are not MY cheap achromats, ones I learned about from Robert O'Tool at Close-up Photography and Photomacrography, not a bad lenses for $17 back then. Second, we have no problems even at 20X with diffused illumination, or resolving detail

Because the formula for resolution that you posted is incorrect and I'm sure you know it

Seems Microscopy University at Nikon, Wiki (Optical Resolution), Leica, Zeiss must all be incorrect then, as they Refer to Resolution (r) = Lambda/(2NA) which is the generally accepted criteria, although some use Resolution (r) = 0.61*Lambda/NA based upon Rayleigh criteria. However, I'm sure you know much more about this than all the folks at Nikon Microscopy University, Wiki, Leica, and Zeiss 


Best,

[magic]

Upon some consideration I have already changed "incorrect" to "incomplete" while you were writing your post

Come on, we both know what monsters hide in that "NA" thing that you talk about and we both know that we know

[mawyatt]

Noopy,

Using stacked lenses rather than a revered lens, has some very useful benefits regarding diffusion, which becomes the ultimate limit in achieving quality images at higher magnification. Folks strive to keep the Effective Aperture, which is Lens Aperture*(1+Magnification), as low as possible to keep diffusion at bay, even at F10 diffusion starts to degrade things. Most of the higher end objectives are designed for a lower EF for this very reason. PM has some very useful information on stacked lenses.

For example, a typical 50mm lens stacked onto your 100mm usually produces a very good 2X combination. With your 22mm and the 100mm you might have a good ~5X and likely much better than using the 22mm alone, reversed.

I'll wager a Brewisky that if you give this lens stacking technique a try you'll be pleasantly surprised   

Hey, how come we don't have Brewisky icon?

Best,

[mawyatt]

Upon some consideration I have already changed "incorrect" to "incomplete" while you were writing your post

Come on, we both know what monsters hide in that "NA" thing that you talk about and we both know that we know

Yup, and a lot more "Monsters" hide in the forests of detail

Murphy is also on the same team as the "Monsters"

Best,

[mawyatt]

The oil immersed objective is a trick used in microscopy.  It shows more details for the same optics.

At minute 4:35 there is an image with and without oil, side by side.

A little familiar with this technique, but never wanted to get the chips covered in oil since keeping the surface clean is already a chore, and adding oil they'll become a dust magnet

The typical oil has an index of ~1.5 which is highly benefical. The semiconductor fabrication process has used this "trick" for a long time now, and one of the many means they use to defy diffraction physics

Best,

[Noopy]

The 3D effect helps but it seems like it´s a little sharper too.

It does look sharper indeed. It could be due to hard shadows, or I'm not sure what else. I presume it's the same optics, subject distance and magnification in each case?

At any rate, I applied some fake sharpness and contrast to it. I don't know if it's better, but it's different

Yes, it was the same optics, the same subject distance and magnification. I just tilted the die a bit and adjusted the light.
It´s annoying not to know what is happening but I´m happy to have a second possibility to get nice pictures. ...better than some fake sharpness and contrast. 



I have already bought an adapter to test stacked lenses. I wanted to try that earlier but somehow forgot about it.
I have quite some lenses here. First I will try 100mm + 10-22mm. Better or worse I will drink a beer afterwards. 
It´s a pity I´m no optics expert...  But I highly regards your advices!