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mikas remeika | 2 Nov 2010 02:08
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Cryogenic chip holder

Dear, Everyone,

I imagine quite a few here deal with measurements at cryogenic
temperatures, so I hope that you might have some experience to share.

I am looking for a mounting socket similar to a DIP carrier but where
the sample would sit on a thick metal heatsink.  What we need to do is
mount a 5x7mm chip into an optical dilution refrigerator and also have
some electrical contact to the sample.  Currently we do this by gluing
the chip (with indium) into a DIP carrier (like these -
http://semipackages.com/images/thumb/c/c3/Lcc-from-corwil.jpg/200px-Lcc-from-corwil.jpg)
and then wire-bonding the contacts from the chip to the DIP carrier.

The problem is that the DIP carrier is made mostly of plastic with
only a thin layer of gold under the sample. The sample in this case
generates enough heat that the plastic cannot efficiently conduct it
away.

So the question is, is it possible to obtain a similar chip holder,
but where the chip would sit on a solid metal plate. The experiment is
electro-optical so the top part of the chip must remain exposed.

thank you in advance,
-mikas
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Dibyadeep Paul | 2 Nov 2010 09:43
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lithography on a wafer surface containing deep trenches

Hi,

I have a wafer, which contains some deep trenches. I fabricated these 250
micron deep trenches using DRIE, with AZ9260 as the mask layer. Now I have
to do a DRIE, to etch away 150 micron more, in the trenches already
fabricated as well as in some other regions.

In order to do this 2 level DRIE, I had grown an oxide layer 2 microns thick
to act as the masking layer for the second DRIE. I had planned to use 9260
as the masking layer for the first DRIE and the oxide as the masking layer
for the second DRIE. However after growing the oxide layer, and etching away
the unwanted regions, I found that some of the masking oxide layer has also
been removed.

As I said for the first DRIE, I used 9260, and the DRIE went fine. I had
initially thought that I would use the 9260 layer which would remain after
the DRIE and do a contact exposure-development, to expose the areas where I
wanted the next DRIE to happen. This would help me do the DRIE on regions I
wanted to expose, to circumvent the problem created by the presence of the
holes in oxide layer.

However after the first DRIE I found that the 9260 layer has become complete
inert to the the developer AZ 400K, even after multiple and long expsures.

Next, I removed the 9260 on one of the test wafers, and tried doing a
contact exposure-development with various photoresists in AZ and SC series.
In all of them I found that even after long exposures, some of the
photoresist always remains within the trenches, and I cannot remove that. I
am not sure why this happens.
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James Paul Grant | 2 Nov 2010 17:22
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Polyimide swelling

Hello all,

Doeas anyone have any experience of partially inidized polyimide? I have 
been using HD Microsystems PI2545 polyimide and been cutting a few 
corners by doing the final cure at 180oC in a nitrogen purged convection 
oven. However the PI2545 data sheets says to do a final cure for 1 hour 
at 400oC.

In subsequent lithography steps I have used lift-off using acetone and 
noted that the polyimide seems to swell in certain sections. After 
immersing the sample in acetone for 3 days at room temperature there are 
200-300 nm thick ridges visible all over the sample.

Anyone got any thoughts? I can provide more details/pictures if necessary.

Thanks,

James

--

-- 
Dr. James Paul Grant
Postdoctoral Research Associate
Microsystems Technology Group
76 Oakfield Avenue Room 205
School of Engineering
University of Glasgow
Glasgow
Scotland
G12 8LS
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Michael D Martin | 2 Nov 2010 19:26
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Re: Polyimide swelling

Polyimide swells in water, bases and organic solvents though we've often
done lift-off on it with no problems in acetone.  If you bake it (say
115C for 5 min) after the lift-off the swelling should go down.  Of
course, to maximize dimensional stability you should fully cure it.  If
you have a "dirty" tube furnace available, you can fully cure it in
there.  We've also cured it under a nitrogen blanket on a hotplate. 

Good luck, 

  Michael  

>>> James Paul Grant <j.grant <at> elec.gla.ac.uk> 11/2/2010 12:22 PM >>>
Hello all,

Doeas anyone have any experience of partially inidized polyimide? I
have been using HD Microsystems PI2545 polyimide and been cutting a few 
corners by doing the final cure at 180oC in a nitrogen purged convection 
oven. However the PI2545 data sheets says to do a final cure for 1 hour
at 400oC.

In subsequent lithography steps I have used lift-off using acetone and
noted that the polyimide seems to swell in certain sections. After 
immersing the sample in acetone for 3 days at room temperature there
are 200-300 nm thick ridges visible all over the sample.

Anyone got any thoughts? I can provide more details/pictures if
necessary.

Thanks,
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Hongzhi CHEN | 3 Nov 2010 17:30
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high dielectric strength insulator

Hi,

Does anyone know what kind of insulator has extremely high dielectric strength 
(the highest electric field before the material breakdown)?

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Nabhiraj Yalagoud | 3 Nov 2010 23:10
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Re: high dielectric strength insulator

hi,

Kapton, Alumina, Teflon
have very good dielectric strength

Nabhiraj

On Wed, Nov 3, 2010 at 10:00 PM, Hongzhi CHEN <cfzsg <at> yahoo.com> wrote:

> Hi,
>
> Does anyone know what kind of insulator has extremely high dielectric
> strength
> (the highest electric field before the material breakdown)?
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Joseph Peach | 4 Nov 2010 22:04
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Wafer holder/protector for backside during wet etching

Hello MEMS community,

I'm looking to order a wafer holder to protect the backside of wafers during
various wet etches. I have seen the AMMT "single series" wafer holders and
also an option from Silicet, "basic-g". Does anyone have experience using
either of these, or any other wafer holder? Any recommendations for which
might be better? I noticed that the specification sheat for the AMMT states
that "the holder tolerates wafers with a thickness of +/- 80um around the
specified target thickness", and I am processing 1mm as well as 500um
thickness wafers, so I was wondering if the Silicet option also has similar
limitations? Finally, both options are also from Europe, is the US provider
for wafer holders that for whatever reason just isn't coming up in my google
searches? (it would just would be nice to save time/money on shipping and so
I can more easily call them...)

Thanks in advance,
Joseph Peach
University of Washington
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LEE | 5 Nov 2010 17:01
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solvent that only removes shipley1813

I am looking for a high selective solvent, which only remove shipley1813  
with no affect on AZ4620. Does anybody use it before?

Btw, Does shipley 1813 stick well with SU-8?

Thanks very much!

LEE
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ketbra koukou | 5 Nov 2010 18:29
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Wire bonding on polymer substrate

Hello all,

I'm trying to make wire bonding on polyimide substrate. The thikness of the Layer path is 1µm.

I combined all parameters :

Temperature
Power
Strength
time

Both aluminium and gold wire 25 µm can not be soldered on the gold path.

Can some someone help me or suggest ideas for solving this problem?

thank you 		 	   		  
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Marcel Spurny | 5 Nov 2010 18:36
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Re: solvent that only removes shipley1813

Try acetone, depending on how you've treated your az it should do the job.

Cheers,
Marcel

Am 05/11/2010 16:01, schrieb LEE:
> I am looking for a high selective solvent, which only remove 
> shipley1813 with no affect on AZ4620. Does anybody use it before?
>
> Btw, Does shipley 1813 stick well with SU-8?
>
> Thanks very much!
>
> LEE

Marcel Spurny, Dipl. Phys. MPhys.
School of Physics&  Astronomy
University of St. Andrews
North Haugh
St. Andrews
KY16 9SS
Fife
Scotland, United Kingdom
Tel.: 01334 467336

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Gmane