Bubbles in my SU-8

[frank berisford]

Hello all,

I've been trying several different techniques in an attempt to minimize bubbles
in my SU-8. At first I tried pippeting it onto my substrate using a large bore
pippette. I also tried dispensing from a syringe and pouring straight from
the bottle. The pouring seems to work best but I still get a sizable bubble
count. From here I've tried sucking the bubbles out with a needle and syringe
but to no avail.

I've read of others wiping the SU-8 across the wafers but have yet to try this
method for fear of destroying the substrate. For what it's worth I'm using
SU-8 2035 with a target thickness of 50microns but I think I've got my spin
recipe locked down.

Thanks for your time,
Frank Berisford




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[Christopher F. Blanford]

Dear Frank Berisford

I put the SU-8 resist into a sonic bath with a degas cycle to removed
dissolved gases. This cycle pulses the sonics, assisting the nucleation
of these gases. About 5 minutes of pulsed sonics at full power and 40
C, gives (nearly) bubble-free coatings.

Regards,

Chris Blanford

Post by frank berisford
I've been trying several different techniques in an attempt to
minimize bubbles
in my SU-8. At first I tried pippeting it onto my substrate using a large bore
pippette. I also tried dispensing from a syringe and pouring straight from
the bottle. The pouring seems to work best but I still get a sizable bubble
count. From here I've tried sucking the bubbles out with a needle and syringe
but to no avail.

--
Christopher F. Blanford
Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK
Phone: [phone]; Fax: [phone]
PGP keyID: 8D830BC9 http://pgp.mit.edu/


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[Jennifer Pagan]

Frank,

I used glass syringes and put them in an oven between 40-60C for
5-10 minutes to get rid of bubbles.

Jennifer Pagan
Senior Process Engineer
WaveguideSolutions, Inc.
***@WaveguideSolutions.com
Phone: [phone]
Fax: [phone]


-----Original Message-----
From: mems-talk-***@memsnet.org
[mailto:mems-talk-***@memsnet.org] On Behalf Of Christopher F.
Blanford
Sent: Monday, March 17, 2003 8:25 AM
To: ***@email.uah.edu; General MEMS discussion
Subject: Re: [mems-talk] Bubbles in my SU-8

Dear Frank Berisford

I put the SU-8 resist into a sonic bath with a degas cycle to removed
dissolved gases. This cycle pulses the sonics, assisting the nucleation
of these gases. About 5 minutes of pulsed sonics at full power and 40
C, gives (nearly) bubble-free coatings.

Regards,

Chris Blanford

Post by frank berisford
I've been trying several different techniques in an attempt to
minimize bubbles
in my SU-8. At first I tried pippeting it onto my substrate using a large bore
pippette. I also tried dispensing from a syringe and pouring straight
from
the bottle. The pouring seems to work best but I still get a sizable bubble
count. From here I've tried sucking the bubbles out with a needle and
syringe
but to no avail.

--
Christopher F. Blanford
Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK
Phone: [phone]; Fax: [phone]
PGP keyID: 8D830BC9 http://pgp.mit.edu/


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Visit us at http://www.memsnet.org/




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[Runkel, Frank]

Frank,

first of all you must avoid any bubbles when dispensing the SU-8 onto the
wafer. When you do a manual dispense, pour the resist carefully from a
bottle or a beaker with a wide opening only in the center of the substrate.
Use a moderate spinning speed to spread the SU-8 over the wafer before you
ramp up to the final coating speed. This should help to spin a defect free
layer, but bubbles may also appear during the soft bake step. When the
initial bake temperature is too high, the solvent is driven out of the
resist too fast and creates bubbles as well. For this reason, it is
essential to ramp up the bake temperature smoothly.

Another possible reason for bubbles in the resist layer is a rough or even
topographic surface of the substrate you are trying to coat, but I cannot
give process recommendations in this case without knowing more details.

Best Regards,

Frank.

--------------------------------------------
SUSS MicroTec
Applications Center Europe
Frank Runkel
Schleissheimer Str. 90
85748 Garching
Germany
Fon [phone] - 302
Fax [phone] - 390

------------------------------
Message: 6
Date: Fri, 14 Mar 2003 11:07:41 cst
Subject: [mems-talk] Bubbles in my SU-8
Content-Type: text/plain; charset="iso-8859-1"
Hello all,
I've been trying several different techniques in an attempt to minimize
bubbles
in my SU-8. At first I tried pippeting it onto my substrate using a large
bore
pippette. I also tried dispensing from a syringe and pouring straight
from
the bottle. The pouring seems to work best but I still get a sizable
bubble
count. From here I've tried sucking the bubbles out with a needle and
syringe
but to no avail.
I've read of others wiping the SU-8 across the wafers but have yet to try
this
method for fear of destroying the substrate. For what it's worth I'm
using
SU-8 2035 with a target thickness of 50microns but I think I've got my
spin
recipe locked down.
Thanks for your time,
Frank Berisford
------------------------------

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[Josef Kouba]

It is a question of how handy you are... There are many techniques, I
would say one per user.. I usually use a small cup and pour the resist
into it first. You can remove the bubbles from the cup already, if there
are any, but I usually don't have them. Then pour the resist on the
substrate.. Using a plastic pipette (I'm using one with about 1 mm
diameter), you can again remove the bubbles, if you see some. After
spinning, you can use a blade or any other sharp object... Also, placing
the sample on well-leveled plate and heating up to around 60 deg will
remove few bubbles as the resist becomes more liquid.

Good luck!

J.

-----Original Message-----
From: mems-talk-***@memsnet.org
[mailto:mems-talk-***@memsnet.org] On Behalf Of frank berisford
Sent: Friday, March 14, 2003 11:08 AM
To: mems-***@memsnet.org
Subject: [mems-talk] Bubbles in my SU-8



Hello all,

I've been trying several different techniques in an attempt to minimize
bubbles in my SU-8. At first I tried pippeting it onto my substrate
using a large bore pippette. I also tried dispensing from a syringe and
pouring straight from the bottle. The pouring seems to work best but I
still get a sizable bubble count. From here I've tried sucking the
bubbles out with a needle and syringe but to no avail.

I've read of others wiping the SU-8 across the wafers but have yet to
try this method for fear of destroying the substrate. For what it's
worth I'm using SU-8 2035 with a target thickness of 50microns but I
think I've got my spin recipe locked down.

Thanks for your time,
Frank Berisford




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options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
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Visit us at http://www.memsnet.org/


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[Mark Shaw]

Dear All,

I have been reading the various comments on bubbles in SU-8 coatings and I wanted to offer some suggestions, as well as raise some additional questions....

As the manufacturer of SU-8 we are focused on evaluating and solving the various processing issues associated with this unique material...In the past we have had reports of bubbling in the SU-8 films and have investigated the root causes of the problem and by far the dispensing method was found to be the largest contributing factor, followed closely by the fact that the sample had bubbles in it before actually dispensing the material onto the substrate surface...

We have found that the best way to generate high quality coatings with SU-8 is to use an Eppendorf Repeating Pipettor which incorporates a syringe type plunger and the ability to repeatably dispense the same volume to the surface... These Eppendorf Pipettor's are available from most laboratory supply companies and are priced at around
$300.00.....On filling of the syringe adapter some air may become entrapped and if so these can be removed very easily by placing the syringe into an oven/heated environment set at around 60C for several minutes....This same method should be used if bubbles are seen in the bottle prior to dispensing....This heating step reduces the viscosity of the SU-8 and allows the bubbles to rise to the surface and extinguish....Following this heating cycle the SU-8 should be allowed to attain room temperature before processing in order to attain the targeted film thicknesses....

Recently, I have found that some of these bubbles were in fact particulates caused by 'dried' SU-8 being dispensed onto the wafer surface when pouring directly from the bottle, therefore I would recommend that the opening of the bottle be wiped down prior to dispensing with a clean room wipe containing a small amount of the SU-8 Developer....Just a word of advice.....

I can concur with some of the comments about the effect of the 65C bake on the removal of bubbles, this happens due to the fact that the glass transition temperature of the material (prior to exposure and PEB) is around 55C, therefore the material will soften and planarise slightly due to the reduction in the viscosity and hence the bubbles will extinguish...However, if the bubbles are being produced during the bake step another issue is involved and is most commonly associated with substrate cleanliness...

The questions I have revolve around what specific formulations are more prone to 'bubbling', is it the original SU-8 formulation or the improved SU-8 2000 family ? Is there a particular film thickness that is more prone to this than others ?

I appreciate any feedback and the opportunity to assist any of the SU-8 users who are experiencing problems in solving the issues...

Best regards,

Mark Shaw
Technical Sales & Applications Support
MicroChem Corp.

email: ***@microchem.com
url: www.microchem.com


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[weiwei2]

i fabricated some cantilevers 500um-1000um long using MUMPS. (curled bimorgh
cantilever ---> gold ontop of poly2)

i die attach the entire die + wire bond it

during die attach, i use thermal cure epoxy which is treated at 150C. i
tried vary time from 1 hour to 1.5 hour

all my cantilever experienced "extra curling" after die attach. How to solve
this? Any paper which explain or model this problem? how to take into
account the extra curling in my design + modeling?

Leow
Universiti Teknologi Malaysia
Malaysia


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