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September 2007

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Subject:
From:
Hernefjord Ingemar <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Hernefjord Ingemar <[log in to unmask]>
Date:
Wed, 12 Sep 2007 13:28:22 +0200
Content-Type:
text/plain
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text/plain (248 lines)
Hi Leo,

your reputation is in danger (kidding). I pasted your comment in a
document for our purchaser. Says "if you don't believe me, see what Dr
Higgins says! Basta! ". Now, little more seriously...I got kind of
confirmation on your comments regarding circumperiferical microcracks.
There ARE cracks, all around! Must be caused by mismatching materials.
Your insight in semi world is worth a lot, I've placed your name on a
map  named 'semi mysteries'.
I'll send a SEM image asap to Steve for publication, depends on when I
get a longdistance pigeon.

Have a nice day, sir!

/Inge
 

-----Original Message-----
From: Leo Higgins [mailto:[log in to unmask]] 
Sent: den 12 september 2007 12:12
To: Hernefjord Ingemar; TechNet E-Mail Forum
Subject: RE: [TN] Semi guys, need support, conclusion

Hi Inge,
    Last comment after your last bit of info.  Al-1%Cu bond pads can
require more care and control of wire bonding process parameters than Al
or Al-1% Si bond pads to be sure to form an intermetallic layer at the
Au ball to pad interface.  Even though the solubility of Cu in Al is
supposed to be about 5%, the Cu does tend to collect at microstructural
triple points, where it effectively hardens the Al and reduces the
lateral deformation of the Al pad during bonding.  The presence of the
Al and Cu in the very thin pad layer can result in a very nice galvanic
cell during dicing due to the cooling water, or due to environmental
humidity, leading to corrosion which is aggravated by the presence of
halogens.  Your supplier A appears to be using pure Al pads and supplier
B appears to be using Al + x%Cu pads.  As previously noted the fluorine
could be a contaminant from plasma processing, or could be from a
fluorinated passivation layer, if present.  I also think the C level
shown of the spectrum could be a contributor to the poor bonding.
     The link below provides connection to a short app note on scanning
Auger depth profiling on a good and a bad bond pad, and may represent a
similar problem.

http://www.eaglabs.com/files/appnotes/AN332.pdf



Best regards,
Leo

          
Leo M. Higgins III, Ph.D.
Sr. Vice President, Engg and Technology
ASAT, Inc. 
13809 Research Blvd., Suite 635
Austin, Texas     78750

office phone   512-249-4758
mobile           512-423-2002
[log in to unmask]
www.asat.com



-----Original Message-----
From: Hernefjord Ingemar [mailto:[log in to unmask]]
Sent: Wednesday, September 12, 2007 1:16 AM
To: TechNet E-Mail Forum; Leo Higgins
Subject: RE: [TN] Semi guys, need support, conclusion



 Thanks all for your help,
especially from Leo.
We found that we had two batches from the semi suppliers. The chips
ought to have same semi manufacturer's part number, but the two chip
houses had different codes. Supplier A had no Fluorine peaks, nor
Copper. Supplier B had both Fluorine and Copper peaks (quantification
was not done). Supplier A was excellent for wire bonding, supplier B was
hopelessly bad. So, the conclusion is, that the presence of F and Cu was
the reason for bad bondability. I can still not explain the exact cause
for bond lifting, think Leo's fluorine/fluorid explanation may be
correct. If the Copper added to the bad bondability, I don't know. The
Copper presence was percentage rather than ppm, which may have
reinforced the problem.
Anyway, one batch is scrapped, the other is used, production is started
again.
Sensmoral: use F for your teeth and avoid bad coppers...
/Inge




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins
Sent: den 6 september 2007 22:17
To: [log in to unmask]
Subject: Re: [TN] Semi guys, need support


Based upon a quick look at the photos and spectrum:

1. Fluorine peak in the spectrum is not desirable but some F is often
seen so formation of fluorides does not appear to be the main concern.

2. Photo 20b shows what appears to be cracking of a layer of material
overlaying the surface of the pad.  Cracking is clearly visible around
the inside edge of the bond pad and this seems to clearly indicate a
considerable amount, and a nearly continuous layer of contamination
across the bond pad. The photo indicates the use of a backscattered
electron detector, and this type of image shows an enhanced sensitivity
to atomic number, so the very dark surface of the bond pad makes me
believe a low atomic number film is on the surface.  I do not know from
which sample and from which location the spectrum was taken, but if
taken from somewhere on this bond pad, the high Carbon peak makes
organic contamination appear to be a big problem.  

2. It would be very helpful to know from what sample and sample site the
EDX data was collected.  The spectrum shows a fairly large Cl peak.
Photo 9 shows what appears to be corrosion sites or etch pits.  So
perhaps this is related to the Cl due to formation and dissolution of
AlCl3.  

3.  Photos 4 and 25b show pads that appear to exhibit scattered, and
widespread contaminated corrosion sites.  

4.  Is it possible the contamination came from the "chip trays"?  Off
gassing of anti-ESD materials and surfactants could be a source of some
contamination.

This is all I can say without further input. 





Best regards,
Leo

          
Leo M. Higgins III, Ph.D.
Sr. Vice President, Engg and Technology
ASAT, Inc. 
13809 Research Blvd., Suite 635
Austin, Texas     78750

office phone   512-249-4758
mobile           512-423-2002
[log in to unmask]
www.asat.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Steve Gregory
Sent: Thursday, September 06, 2007 10:16 AM
To: [log in to unmask]
Subject: Re: [TN] Semi guys, need support


Hi Inge and Everyone!

I've got your pictures up. Go to:

http://stevezeva.homestead.com/files/RYT809205_25b.jpg

http://stevezeva.homestead.com/files/RYT809205_20b.jpg

http://stevezeva.homestead.com/files/RYT809205_4.jpg

http://stevezeva.homestead.com/files/RYT809205_9.jpg

http://stevezeva.homestead.com/files/Spectrum_RYT809205_flat.jpg

Sorry I can't help with any input, but this kind of stuff is w-a-a-a-y
out of my league...

Steve

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Thursday, September 06, 2007 9:01 AM
To: [log in to unmask]
Subject: [TN] Semi guys, need support

 25 micron gold ball bonding bad yield, ball lifts, poor adhesion on Al
pads. Triple diff line tranceiver chip. Weird micrographic exteriour,
EDAX gives C,F,O, Cl,Cu,Al,Fe. Cu can be ppm alloy but the others
unwanted on semi chip bond pads I think. 1kV SEI SEM reveals strange
superficial structure. Chip not contaminated by us, fresh opened chip
trays show this face. Question: what semi manufacturing problem can this
be? Will post a few pics to Steve's gallery.

TrikeMan? 

/Inge

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