You are seeing a problem with uneven solvent removal. Caused by variations in
hot plate uniformity and or variations in oven temperature. Suggest a vacuum
oven set to 65 with preheated Nitrogen at 65. Then run for 2 minutes of vacuum
to pull out solvent, then 2 minutes of preheated Nitrogen. This will replace the
lost solvent and warm the SU8 from the inside. Repeat as many times as needed to
get even soft bake. Bill Moffat

Sent from my iPad

> On Oct 27, 2014, at 7:48 AM, "KarthiKeyan K"  wrote:
>
> Dear sir,
>
> Thanks for your mail and information.
>
> Actually the SU8 photo resist is spined by spin coater at 2500rpm during
> this process I got uniform coating and then I goes to soft backing for 65c,
> when I put it on the hotplate or hot air oven (with in 2-3 min) the coated
> su 8 layer will be shrinkaged and or some times non uniform surface layer
> on su8 layer during soft backing process.
>
> Which one is prefereable for soft/hard backing whether hot plate or air
> oven???
>
> Looking forward to your suggestion.
>
> Thanking you,
>
> Best regards,
> Karthi
>
>> On Oct 24, 2014 12:55 AM, "Andrew Sarangan"  wrote:
>>
>> Can you elaborate how you are determining this shrinkage? During softbake
>> there will be loss of solvents and a change in thickness, but it should
> not
>> cause any stresses because the uncured SU8 should reflow above 65C.
> Perhaps
>> your ramp rate is too fast causing part of the SU8 to flow while other
>> parts are still solid?
>>
>> On Wed, Oct 22, 2014 at 10:49 PM, KarthiKeyan K 
>> wrote:
>>
>>> Dear All,
>>>
>>> I am facing shrinkage problem on SU8 2075 photoresist layer on Silicon
>>> Substrate. Actually this problem accruing on soft backing process at
> 65C on
>>> hotplate & hot air oven also.
>>>
>>> Kindly suggest to over come this problem.
>>>
>>> Thanking you,
>>>
>>> Best Regards,
>>> Karthi
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> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
> provider of MEMS and Nanotechnology design and fabrication services.
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