Dear all,
Thank you for all the comments. I had gotten straight profile for my played
gold, so I assumed my photoresist profile is also straight. However I realized
that pattern at wafer edges is not straight somehow.
I suspect it's due to non-uniformity of my photoresist across the wafer. Is
there any way to determine and ensure the SU-8 photoresist is uniform across the
wafer?
Thank you.
Best Regards,
Siew Mun
Sent from my iPhone
On 23 Jan, 2013, at 2:32, Brubaker Chad wrote:
> If your soft bake only occurs at 65C, then you could be retaining significant
amounts of solvent in the film - this could probably cause the polymer to have
weakness to the developer, most likely resulting in a positive slope.
>
> Best Regards,
>
> Chad Brubaker
>
> EV Group
> invent * innovate * implement
> Senior Process Technology Engineer - Direct: +1 (480) 305 2414, Main: +1 (480)
305 2400 Fax: +1 (480) 305 2401
> Cell: +1 (602) 321 6071
> E-Mail: C.Brubaker@EVGroup.com, Web: www.EVGroup.com
>
>
> This message and any attachments contain confidential or privileged
information, which is intended for the named addressee(s) only. If you have
received it in error, please notify the sender immediately and then delete this
e-mail. Please note that unauthorized review, copying, disclosing, distributing
or otherwise making use of the information is strictly prohibited.
>
> Save paper and trees! Please consider the environment before printing this
e-mail.
>
> -----Original Message-----
> From: mems-talk-bounces+c.brubaker=evgroup.com@memsnet.org [mailto:mems-talk-
bounces+c.brubaker=evgroup.com@memsnet.org] On Behalf Of Jocelyn Ng
> Sent: Monday, January 21, 2013 4:22 PM
> To: General MEMS discussion
> Cc: Brubaker Chad; General MEMS discussion
> Subject: Re: [mems-talk] SU-8 2005 overexposed?
>
> Thank you so much for your insights and comments.
> Ya that was a typo, I meant post bake at 95C for 120S. In your opinion, does
the soft bake temperature affect much? Is there a minimum temperature?
>
> Thank you very much.
>
> Best Regards,
> Siew Mun
>
> Sent from my iPhone
>
> On 22 Jan, 2013, at 5:21, Brubaker Chad wrote:
>
>> Also, I would also look into your exposure source - as Gareth mentions in an
earlier message in this thread, SU-8 is very sensitive to DUV (exposure <350 nm
wavelength) - many broadband exposure sources (i.e., 350 - 450 nm) will have a
small amount of "leakage" below 350 nm (depends on the quality of the cut-off
filter) - SU-8 rapidly absorbs these wavelengths will little to no transparency
or bleaching - ultimately this leads to a T-topped profile (which, when viewed
from above, can have the appearance of dark edges).
>>
>> On the other hand, if the film is underexposed, but uses the proper
wavelength band, the profile can slope in either direction (positive slope due
to longer developer attack to the upper regions, or negative slope, due to top
surface being exposed, and bottom not - this is less likely, due to the
transparency of the SU-8).
>>
>> Regarding the bake parameters you are currently using, I almost think I could
read it as "95 seconds at 120 C" or "95C for 120 seconds).
>>
>> If you are PEB at 120C, then underexposure is not your concern - SU-8 uses a
catalyzed photo-acid - the exposure product is not a reactant for the cross-
linking process, it's a catalyst. Longer exposures simply increase the
concentration of the catalyst, which influences reaction rate. Variation in PEB
temperature will also influence the reaction rate (similar to exposure - the
higher the temperature, the higher the reaction rate). In general, SU-8, once
exposed, will crosslink to near-completion; its just a question of "how long".
>>
>> Considering
>>
>> Best Regards,
>>
>> Chad Brubaker
>>
>> EV Group
>> invent * innovate * implement
>> Senior Process Technology Engineer - Direct: +1 (480) 305 2414, Main: +1
(480) 305 2400 Fax: +1 (480) 305 2401
>> Cell: +1 (602) 321 6071
>> E-Mail: C.Brubaker@EVGroup.com, Web: www.EVGroup.com
>>
>>
>> This message and any attachments contain confidential or privileged
information, which is intended for the named addressee(s) only. If you have
received it in error, please notify the sender immediately and then delete this
e-mail. Please note that unauthorized review, copying, disclosing, distributing
or otherwise making use of the information is strictly prohibited.
>>
>> Save paper and trees! Please consider the environment before printing this
e-mail.
>> -----Original Message-----
>> From: mems-talk-bounces+c.brubaker=evgroup.com@memsnet.org [mailto:mems-talk-
bounces+c.brubaker=evgroup.com@memsnet.org] On Behalf Of Gareth Jenkins
>> Sent: Saturday, January 19, 2013 5:38 PM
>> To: General MEMS discussion
>> Subject: Re: [mems-talk] SU-8 2005 overexposed?
>>
>> Your bake parameters do not sound right. The datasheets recommend only
>> about 2mins softbake at 95C for this thickness and 3-4mins post exposure
>> bake at 95C (120C is too high).
>> Looking at the datasheet, I think Andrew may be correct that it is also
>> underexposed - 2 or three times the dose may be required. This would lead
>> to the profile not being straight (if the top of the structure is equal or
>> less than the size of the mask feature then this would confirm it).
>>
>>
>> On 19 January 2013 22:17, Jocelyn Ng wrote:
>>
>>> After post exposure bake, still no darkening, but after developing,
>>> darkening occurs. After seeing the profile using SEM, the profile is not
>>> straight. I soft bake it at 65C for about 9mins, 95C at 120C for post
>>> exposé bake. Or does it require higher soft bake temperature for this
>>> photoresists?
>>> Thank you.
>>>
>>> Best Regards,
>>> Siew Mun
>>>
>>> Sent from my iPhone
>>>
>>> On 18 Jan, 2013, at 10:24, Gareth Jenkins wrote:
>>>
>>>> Deep UV or heating of the wafer may also cause the problem. When does the
>>>> darkening occur? (Is it immediately visible after exposure or at some
>>> other
>>>> point in the process)? Do your structures look overexposed after
>>>> development?
>>>>
>>>>
>>>> On 17 January 2013 11:11, Jocelyn Ng wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> I'm doing single layer SU8 2005, thickness ~6-7um. I use 60mJ/cm^-2 on
>>>>> sputtered gold surface. But somehow sometimes I notice that the edges
>>> of my
>>>>> pattern darkens, I suspect it's due to overexposed. But 60mJ is quite a
>>> low
>>>>> dose compared to the recommended one. I would appreciate any comments
>>>>> given. Thank you.
>>>>>
>>>>> Best Regards,
>>>>> Jocelyn
>>>>>
>>>>> Sent from my iPhone
>> _______________________________________________
>> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
>> provider of MEMS and Nanotechnology design and fabrication services.
>> Visit us at http://www.mems-exchange.org
>>
>> Want to advertise to this community? See http://www.memsnet.org
>>
>> To unsubscribe:
>> http://mail.mems-exchange.org/mailman/listinfo/mems-talk
> _______________________________________________
> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
> provider of MEMS and Nanotechnology design and fabrication services.
> Visit us at http://www.mems-exchange.org
>
> Want to advertise to this community? See http://www.memsnet.org
>
> To unsubscribe:
> http://mail.mems-exchange.org/mailman/listinfo/mems-talk
> _______________________________________________
> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
> provider of MEMS and Nanotechnology design and fabrication services.
> Visit us at http://www.mems-exchange.org
>
> Want to advertise to this community? See http://www.memsnet.org
>
> To unsubscribe:
> http://mail.mems-exchange.org/mailman/listinfo/mems-talk
_______________________________________________
Hosted by the MEMS and Nanotechnology Exchange, the country's leading
provider of MEMS and Nanotechnology design and fabrication services.
Visit us at http://www.mems-exchange.org
Want to advertise to this community? See http://www.memsnet.org
To unsubscribe:
http://mail.mems-exchange.org/mailman/listinfo/mems-talk