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--- cleaning [2012/06/24 01:12] – [Fingerprints] mcmaster
+++ cleaning [2013/11/17 07:18] (current) – mcmaster
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 Optics cleaning gives a lot of general guidelines on cleaning, consider consulting a textbook for more detail.
 ====== Choice of solvent ======
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   * Alcohols, especially isopropanol (isopropyl alcohol) and ethanol
   * Acetone
+====== JM chip cleaning procedure as of 03/09/2013 ======
+  * Fill 10 mL glass vial w/ polyprolyene cap about 2/3 full with acetone
+    * Glass has better acoustic coupling than plastic and removes a lot more
+  * Place chip in above vial and sonicate for 1 minute
+  * Empty acetone out into second identical vial, leaving the chip behind
+  * Fill 50 mL polypropylene (PP) vial with 30 mL water + detergent
+    * glass vial would probably work just as well if not better
+  * Shake chip from glass vial into PP vial
+  * Sonicate for 1 minute
+  * Pour solution from 50 mL PP into second identical PP, leaving chip behind
+  * Flood chip with water in vial, letting it fill past the top and refilling a few times until all suds are removed
+  * Fill another 50 mL PP with 30 mL acetone
+  * Shake chip from empty suds vial into final wash acetone vial
+  * Sonicate for one minute
+  * Pour most of acetone, leaving a few drops, into yet another 50 mL bottle
+  * With lid closed, shake chip so that its near mouth of vial with die facing up
+    * Alternatively carefully slosh it up there before pouring
+  * Use carbon fiber tweezers to grab die and place face up in PP sealable petri dish
+  * Seal petri dish
+Other notes:
+  * All vials are labeled to easily tell apart solutions
+  * The final acetone vial should have a flat surface near the lid to make it easy to grab
+  * Don't use the same acetone solution or vial for the initial and final wash
 ====== Ultrasound ======
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   * Higher initial cost than other techniques presented here
   * Takes a few minutes (but hopefully you aren't THAT impatient)
+===== Choice of container =====
+{{::cleaning:ultrasound:corner_noultra.jpg?300|}}
+{{::cleaning:ultrasound:corner_ultra.jpg?300|}}
+Using a glass container with strong ultrasound cleans the chip well, but may be stronger than needed.  Above left: chip from lot that was not ultrasonic cleaned.  Above right: chip from same lot that was ultrasonic cleaned for 1 minute in glass 10 mL vial.  The corners have been chipped off
 ===== Case study =====
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 Shame on you if you picked up a die with your bare hands but things do happen.  Acetone does not clean off fingerprints very well but soapy water does.  The above picture was taken after putting a fingerprint on a slide and sonicating in acetone for a few minutes.  It has little to no effect.  Fingerprint oils do not respond to polarized light (ie will black out).
 ===== Polymide passivation =====
-Can be removed with strong acids (eg RFNA)
+General reccomendations:
+  * Oxygen plasma is probably best if you have access to it
+  * If you can deal with safety issues, ethylendiamine may be next best
+  * Fuming nitric aicd works but takes a while.  This can potentially cause chip damage but shouldn't hurt Cu/Al if you keep the concentration high
+  * Piranha eats it quickly but it eats other metals nearly as quickly so its probably best avoided
+==== Ethylendiamine ====
+"find a polyimide layer that was not entirely removed by HNO3 but which can be dissolved with ethylendiamine" ([[http://static.usenix.org/publications/library/proceedings/smartcard99/full_papers/kommerling/kommerling_html/|ref]])
+Rest from [Beck 23]
+Procedure:
+  * Use straight (how much?)
+  * 100° C for 15-60
+==== Ethylendiamine + hydrazine monohydrate ====
+"Ethylenediamine readily reacts with moisture in humid air to produce a corrosive, toxic and irritating mist, to which even short exposures can cause serious damage to health (see safety)." [Wikipedia]
+From [Beck 23].  Use this if plain ethylendiamine does not work.  Unclear if it has a higher corrosion potential, but heed the safety warning
+Procedure:
+  * Mix (how much?)
+    * 7 mL 80% hydrazine monohydrate
+    * 1 mL ethylendiamine
+  * 100° C for 15-60?
+Notes:
+  * WARNING: spontaneous combustion can occur over 120° C
+==== Ethylendiamine + hydrazine monohydrate ====
+[Beck 23]
+Procedure:
+  * Mix
+    * 3 mL ethylendiamine
+    * 1 mL 98% acetic acid
+  * Cook 120-130° C for 10-30 minutes
+Notes:
+  * Mix slowly (or what?)
+  * Stir vigorously
+==== Caro's acid ====
+[Beck 23]
+Procedure:
+  * Mix
+    * 7 mL (98%?) H2SO4
+    * 1 mL 30% H2O2
+  * Cook at 80° C
+Notes:
+  * Seems like this is same thing as [[Piranha solution]]?  In any case see notes there
+==== Fuming nitric acid (FNA) ====
+When decapping part with WFNA/RFNA the amide layer will usually be simply dissolved [Beck 23, personal experience]
+Beck mentions "imide"?
+==== Oxygen plasma ====
+"Polymides can usually be removed gently without leaving residues by incineration in the oxygen plasma" [Beck 23]
+==== Dimethyl sulphoxide + ethanolamine ====
+[Beck 23]
+Procedure:
+  * Mix
+    * 3 mL dimethyl sulphoxide
+    * 1 mL part ethanolamine
+  * Cook at 110° C
+WARNING:
+  *  Spontaneous combustion above 120° C
 ===== Gel passivation =====
+Chip with some damaged gel:
+{{:mcmaster:passivation:gel:xc3090_low_res.jpg?300|}}
+{{:mcmaster:passivation:gel:xc3090_sticky_tweezers.jpg?300|}}
 Some chips have what I believe to be silica gel passivation.  Unfortunately, this can be rather difficult to remove chemically without damaging the chip.  However, it can be wiped off easily if you are fine destroying bond wires.