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Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
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Posts: 143
I run across http://spie.org/x8622.xml?ArticleID=x8622, there is long time I try to find some way to make less expensive thermal imaging ,I had some result with thermocromic paper and silicon lens,but it always lack sensibilities. now ,dlp technologies for video projector use much more complex electromechanics system than those from above,how difficult would it be to build microcantilaver at home ,using basic chemistry and lithography? also ,dlp chips are probably build to be only moderately affected by temperature ,on the other and ,they rest on a piece of copper ,so the temperature difference spread evenly,I suppose those chip are build on a silicon wafer witch is transparent to mild infrared ,so if the chip where remove from there heat sink ,and a thermal image where projected from behind ,it might be that the mirror could experience minute variation of angle (for example du to expansion of there inches),I have a dlp chip at home ,if I was to try this ,what would be the best way to remove it from it heat sink?(with out breaking it)
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
wrote ... dlp technologies for video projector use much more complex electromechanics system than those from above,how difficult would it be to build microcantilaver at home ,using basic chemistry and lithography?
To get a dense array I think you'll need the high aspect ratio (large height to width ratio) posts which in your link are fabricated with reactive ion etching (RIE) which would be difficult to DIY. With a less dense array you might be able to get away a more isotropic wet etch process, possibly with a series of masks. Or maybe you can try to do something clever with a KOH etch. The CMP step would also be nice to have but challenging to DIY. Without it you'll have to do a wet etch after the oxidation to expose the posts.
I have seen silicon oxidation DIY'd by Jeri, and aluminum deposition DIY'd in the homemade telescope community.
So, it's possible but tricky to replicate what they've done in your link without a fair amount of equipment and experience.
PS: Commas go before the space, not after. So "a, then b" is correct while "a ,then b" is wrong. Not trying to be rude but it would make your post much easier to read.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
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Posts: 143
Mattski wrote ...
wrote ... dlp technologies for video projector use much more complex electromechanics system than those from above,how difficult would it be to build microcantilaver at home ,using basic chemistry and lithography?
To get a dense array I think you'll need the high aspect ratio (large height to width ratio) posts which in your link are fabricated with reactive ion etching (RIE) which would be difficult to DIY. With a less dense array you might be able to get away a more isotropic wet etch process, possibly with a series of masks. Or maybe you can try to do something clever with a KOH etch. The CMP step would also be nice to have but challenging to DIY. Without it you'll have to do a wet etch after the oxidation to expose the posts.
I have seen silicon oxidation DIY'd by Jeri, and aluminum deposition DIY'd in the homemade telescope community.
So, it's possible but tricky to replicate what they've done in your link without a fair amount of equipment and experience.
PS: Commas go before the space, not after. So "a, then b" is correct while "a ,then b" is wrong. Not trying to be rude but it would make your post much easier to read.
Well , sputtering is in reach of diy , the only difficult part are to get a good vacuum pomp and some argon , I think it should be possible to make fine lithography using a lens system , (let say you use a slr camera , you replace the film by your wafer with light sensitive coating on it , than you take long exposure "picture" of a transparent on witch you have printed the line you want to each.) I should be able to reach a precision of 0.01 mm . One of the difficulty (beside getting those technique to work together ) is to find an organic material that is easy to dissolve , the photo sensitive resin might do the job . I suppose the surface of the chip once finish is extremely sensitive to even a breath of air and should be protected by a piece of glass.
ps: Sorry for the syntax error , I am finitely bad at it , I guess they never teach it to me at school , or I wasn't listening ...
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
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Posts: 527
cedric wrote ...
Well , sputtering is in reach of diy , the only difficult part are to get a good vacuum pomp and some argon ,
It's do-able, but to get a highly anisotropic etch to machine the pillars in the article you linked will take some work. Vacuum pumps are easy to find though you generally get what you pay for. Argon is available from welding shops, probably not the purest grade but that's probably alright.
wrote ...
I think it should be possible to make fine lithography using a lens system , (let say you use a slr camera , you replace the film by your wafer with light sensitive coating on it , than you take long exposure "picture" of a transparent on witch you have printed the line you want to each.) I should be able to reach a precision of 0.01 mm .
That might be doable. Some things to consider is that generally photoresist (PR) is exposed with UV, which may behave a little differently in the lens than visible light, I think a lot of glass blocks UV. Also keep in mind the angle of the light incident on your PR, if there is a substantial angle then you'll have a lot of partially exposed PR. Oh, and you'll want a collimated light source. And the higher resolution you want the thinner your PR has to be also, because when the light hits the PR the light spreads out and diffuses.
wrote ... One of the difficulty (beside getting those technique to work together ) is to find an organic material that is easy to dissolve , the photo sensitive resin might do the job .
I'm not following, what organic material are you looking for? Are you planning to make your own liquid photoresist?
wrote ... I suppose the surface of the chip once finish is extremely sensitive to even a breath of air and should be protected by a piece of glass.
Seems reasonable. Depending on the metals used you might also need an inert gas.
wrote ... ps: Sorry for the syntax error , I am finitely bad at it , I guess they never teach it to me at school , or I wasn't listening ...
Well you're halfway there, but now you have two spaces instead of one between words with commas
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
[quote]
cedric wrote ...
Well , sputtering is in reach of diy , the only difficult part are to get a good vacuum pomp and some argon ,
It's do-able, but to get a highly anisotropic etch to machine the pillars in the article you linked will take some work. .[quote]
[/quote1312632386]
I think this involves an RF (inductively coupled) plasma, and electrostatic (capacitatively coupled) electrodes (grids), the workpiece being one, driven by high frequency AC, super-imposed onto a DC component. The grids are generally aligned using electron microscopes (eg MEMS). Molybdenum or inconel is usually used for the grids. I think it also utilises fluorine ions to do the etching.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
I'm not super familiar with RIE processes but I think that's the basic idea Ash, a plasma is ignited with an AC signal which can probably be either inductively or capacitively coupled, which turns some of the etching gas (it's still near vacuum) to ions. A voltage difference is applied between the top of the chamber and the substrate being etched which accelerates the gas ions towards the substrate. The R in RIE stands for reactive, so the gas is often something containing flourine and chlorine both of which are very reactive, but you could also do non-reactive ion etching using something like argon where the electrical and kinetic energy of the ion just knocks out some atoms from the etching target.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I understand that a lot of current/recent research is aimed at getting the ions to move perpendicular to the workpiece, in order to reduce undercutting (This is the main reason for the move from 'wet chemistry' to plasma technology in the first place) which enables more components per unit area. I believe RIE also has advantages here over non-reactive etching. I think this is due to the lower energy levels required, but I'm not certain.
As far as this thread is concerned, 'wet chemistry' may well provide acceptable results. The resolution of the masks employed obviously also plays a part here, as has already been discussed.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
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I only south of using sputtering as a mean to deposit fine layer of metal on the substrate only to be each latter by chemical ( not as a etching process). Sputtering is a very develop sciences and some good second hand machine can be found around 2 or 3000 euro, some of them use microwave and magnetic field to uniform the deposition, but in it simplest form it's really just a target material on the cathode and some anode some where to close the circuit, and it's possible to have a reasonably uniform deposition if the geometry of the target and the wafer (in front of the target) coincide, the only limitation is that it's difficult to sputter something witch is not conductive.
For a microcantilaver the process should be made in few step: first deposition of a very fine film of metal oxide (to absorb the ir) with a little oxygen mix with the argon, than two metals have to be deposit in a much thicker layer and with out oxygen, and then a 4 fine layer of reflective material like aluminum or gold, it might be possible to reduce the number of layer if some metal can have double function, once it's done a mask is applied and the cantilever are etch free from each other ...
I try to extract the silicon chip from the dlp projector and I fail badly. The micro-mirror are only protected by the front windows witch is extremely thick so breaking the glass to access it is definitely a no-go..
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a low cost thermal imager...
