Felix Lu | 1 Apr 04:04 2011
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Re: [mems-talk] Platinum e-beam evap liftoff

Andrew,

I would guess that the damage is worse now because you increased the  
thermal gradient across the resist by cooling down the substrate.
If you could heat up the substrate holder or evaporate the Pt in  
shorter cycles, I'd guess you'd see an improvement.

My 2 cents.

Felix

Felix Lu, Ph.D.
Applied Quantum Technologies, Inc.
Durham, NC

On Mar 31, 2011, at 5:07 PM, Andrew Sarangan wrote:

> I've been having trouble e-beam evaporating Pt on photoresist for
> lift-off, at 0.5A/s. The resist seemed to be cracking and/or reflowing
> after a few minutes, but it was ok since we only needed about 200A of
> Pt. The substrate temperature also rises pretty quickly, to about
> 150C. Assuming the resist damage was due to excessive heat damage, I
> installed a water-cooled substrate holder. Strangely, the resist
> damage is significantly worse now. It takes just 10 seconds before the
> resist becomes completely deformed, which can be visually seen through
> the viewport. Except for the substrate temperature, which is at 30C,
> everything else is identical during evaporation. Anyone has clues on
> what this could be due to?

_______________________________________________
(Continue reading)

Μπάμπης Πιτσ | 1 Apr 10:48 2011
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[mems-talk] Organic Transistors-Dopant type in Si thermal oxide wafers

Hello all,

Recently I purchased, heavily p-doped thermal Si oxide wafers, in order to prepare some organic
transistor (OTFT) samples. Some of these samples are based on pentacene organic semiconductor. In most
publications, similar devices, using n-doped SiO2 wafers. However some papers refer to p-doped SiO2
wafers for pentacene and other p-type organic semiconductors OTFT's. I would like to know if the doping
type affects the functionality of the devices?  

I would appreciate if you could help me.

Best Regards
Babis
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Christian Engel | 4 Apr 00:09 2011
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[mems-talk] Contact of 2 Al-Layers

Hello everybody,

I have 2 substrates, each with structured metal-layers. I want to bond the
substrates together. There are Pads on each surface for an electric contact
between the two metal-layers. The pads are a little bit recessed in
cavities. First we tried electroless plating for forming the
metal-structures but soon we faced heavy problems that aren't solved yet. So
we tried thick PVD Aluminium and thin PVD Gold on top as oxidation barrier.
Wet etching of this metal-combination failed because etching Gold in aqua
regia strongly attacked the Aluminium. Because time is running we decided to
use aluminium only because we can handle this material without problems.
Except its problematic native oxide. I don't really have an idea how to
avoid electrical contact problems because of this oxide. Even if I do a
short etch-dip for removing the oxide I am afraid that evacuating the bonder
takes too much time and the oxide will be there again before bonding starts.
Perhaps anybody has a great idea about how to handle this sorrowful
situation. Perhaps I can use some kind of conductive glue and get the
substrates together without bonding? Unfortunately the process needs a real
bond because there will be cavities between the two substrates that should
be "filled" with vacuum...

Thanks a lot and best regards, Chris

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righeira carnegie | 4 Apr 12:14 2011
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[mems-talk] Is it possible to make PDMS mold in room temperature?

Hi, we are been trying to make PDMS mold from sylgard 184. instead of the
curing temperature with the same mixture of ODMS and curing agent, Is it
possible to make PDMS mold in room temperature, just skipping the heating
process after pouring the mixture into the mold. We tried once, there is so
much  of difference when followed heating process. The structures where not
defined properly. Is this due to effect of temperature, but the dowcorning
people claim it should not change. they say the heating process is only for
making the procedure faster, so if the heating procedure is not followed
then it might take ,ore than one day to cure. But in our case we cured ot
for three days but the structure has changed when compared. The change in
structure is the height profile of the photonic crystal. has anyone tried
these things.

Thanks!
RIGHEIRA
IMEC
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petrulp | 4 Apr 13:42 2011
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Re: [mems-talk] Is it possible to make PDMS mold in room temperature?

Hi,

I have done a PDMS mold without baking. I left it one day at RT and it works  
well. Pdms channel height was around 30 microns.

Check your expiration dates on both agents and be careful about mixing.

Ratios

On Apr 4, 2011 12:14pm, righeira carnegie <righeira029 <at> gmail.com> wrote:

> Hi, we are been trying to make PDMS mold from sylgard 184. instead of the
> curing temperature with the same mixture of ODMS and curing agent, Is it
> possible to make PDMS mold in room temperature, just skipping the heating
> process after pouring the mixture into the mold. We tried once, there is so
> much of difference when followed heating process. The structures where not
> defined properly. Is this due to effect of temperature, but the dowcorning
> people claim it should not change. they say the heating process is only for
> making the procedure faster, so if the heating procedure is not followed
> then it might take ,ore than one day to cure. But in our case we cured ot
> for three days but the structure has changed when compared. The change in
> structure is the height profile of the photonic crystal. has anyone tried
> these things.

_______________________________________________
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Kumar, Parshant | 4 Apr 17:25 2011

Re: [mems-talk] Is it possible to make PDMS mold in room temperature?

Right, if you are working with the photonics crystal, I would say that
the dimensions are in sub micron range, even if you are in few micron
range. 

Two things, you can try out. The PDMS should not change either doing the
curing at room temperature or at high temperature for rapid curing. 

First, Pour the PDMS in the vacuum as well cure it in vacuum chamber for
the best results so that air trap into the holes not let the fill the
holes , and second, use appropriate release agent so that while
releasing the structures , they are not breaking at the tip to change
the height of the structures.

Good luck!

 
Parshant Kumar Ph.D.|    
The Charles Stark Draper Laboratory |MS37|555 Technology Square |
Cambridge. MA, 02139-3563|Tel: 617-258-4417|Fax: 617-258-4238 |
Email:- pkumar <at> draper.com |www.draper.com
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첸로 | 4 Apr 17:59 2011

[mems-talk] Is it possible to make PDMS mold in room temperature?

hi,

I did that before with no problem.
It can keep a good feature when peeling off so it is feasible in theory.

Regards,


At 2011-04-04 18:14:10,"righeira carnegie" <righeira029 <at> gmail.com> wrote:

>Hi, we are been trying to make PDMS mold from sylgard 184. instead of the
>curing temperature with the same mixture of ODMS and curing agent, Is it
>possible to make PDMS mold in room temperature, just skipping the heating
>process after pouring the mixture into the mold. We tried once, there is so
>much  of difference when followed heating process. The structures where not
>defined properly. Is this due to effect of temperature, but the dowcorning
>people claim it should not change. they say the heating process is only for
>making the procedure faster, so if the heating procedure is not followed
>then it might take ,ore than one day to cure. But in our case we cured ot
>for three days but the structure has changed when compared. The change in
>structure is the height profile of the photonic crystal. has anyone tried
>these things.
>
>Thanks!
>RIGHEIRA
>IMEC
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Jesse D Fowler | 4 Apr 18:03 2011

Re: [mems-talk] Platinum e-beam evap liftoff

I've had this trouble with platinum before, as well. In my case, it was 
because the deposition pressure was too high. 

My source had been contaminated (likely with carbon), and it was 
evaporating at 10^-5 torr. It had to be cooked for a good long while to 
get down to 10^-6 torr. 

Even at that pressure, I had to stop every 500 A to let the PR cool down. 

Lower pressure means lower temperature of the source. 

What was your deposition pressure?

Jesse Fowler

From:   Andrew Sarangan <asarangan <at> gmail.com>
To:     General MEMS discussion <mems-talk <at> memsnet.org>
Date:   03/31/2011 15:55
Subject:        [mems-talk] Platinum e-beam evap liftoff
Sent by:        mems-talk-bounces+jesse.d.fowler=aero.org <at> memsnet.org

I've been having trouble e-beam evaporating Pt on photoresist for
lift-off, at 0.5A/s. The resist seemed to be cracking and/or reflowing
after a few minutes, but it was ok since we only needed about 200A of
Pt. The substrate temperature also rises pretty quickly, to about
150C. Assuming the resist damage was due to excessive heat damage, I
installed a water-cooled substrate holder. Strangely, the resist
damage is significantly worse now. It takes just 10 seconds before the
resist becomes completely deformed, which can be visually seen through
the viewport. Except for the substrate temperature, which is at 30C,
everything else is identical during evaporation. Anyone has clues on
what this could be due to?
_______________________________________________
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Kirt Williams | 4 Apr 18:25 2011
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Re: [mems-talk] Platinum e-beam evap liftoff

Platinum has relatively melting and boiling points, so it must be heated
hotter than many other common metals for the same vapor pressure and hence
deposition rate. Because of this, at one place I worked, we evaporated just
100 A at a time, at 0.5-1.5 A/s. After each 100 A, we let the system cool
for about 30 minutes. I would guess that with your water-cooled substrate
holder, the holder might be running cooler, but there is probably a poor
thermal contact between the wafer and the holder.

For cleanliness, we always pumped to below 1e-6 Torr before the deposition.
We followed the standard practice of doing some evaporation with the
"shutter" over the sample to collect evaporated impurities before opening it
and exposing the substrate.

    --Kirt Williams

-----Original Message-----
From: mems-talk-bounces+kirt_williams=ieee.org <at> memsnet.org
[mailto:mems-talk-bounces+kirt_williams=ieee.org <at> memsnet.org] On Behalf Of
Andrew Sarangan
Sent: Thursday, March 31, 2011 2:08 PM
To: General MEMS discussion
Subject: [mems-talk] Platinum e-beam evap liftoff

I've been having trouble e-beam evaporating Pt on photoresist for
lift-off, at 0.5A/s. The resist seemed to be cracking and/or reflowing
after a few minutes, but it was ok since we only needed about 200A of
Pt. The substrate temperature also rises pretty quickly, to about
150C. Assuming the resist damage was due to excessive heat damage, I
installed a water-cooled substrate holder. Strangely, the resist
damage is significantly worse now. It takes just 10 seconds before the
resist becomes completely deformed, which can be visually seen through
the viewport. Except for the substrate temperature, which is at 30C,
everything else is identical during evaporation. Anyone has clues on
what this could be due to?
_______________________________________________
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provider of MEMS and Nanotechnology design and fabrication services.
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Gmane