Thanks for your suggestion. Unfortunately， I don't have phase contrast
microscope. In addition, the first layer structure was not clear to see and
difficult to observe both the alignment mark on the first layer and on the mask
clearly at the same time. Are there any usual practice to locate and align the
second layer with high accuracy? I am using Karl Suss MA6. Thanks.

Regards,

Bill


------ 原有訊息------
寄件者： Gareth Jenkins
日期: 週四, 2014年5月15日 8:30
收件者： General MEMS discussion;
主旨：Re: [mems-talk] Alignment problem with Multilayer SU-8 fabrication

I used to use a phase contrast microscope to align layers.
Once I found the alignment marks under the microscope, I would manually
scratch the resist with a scalpel (which needs a steady hand). Then I could
align the second layer to the scratches on the mask aligner.


On 14 May 2014 17:14, Bill Chow  wrote:

> Dear all,
>
> Recently, I am working on a two layer SU-8 structure. All the process are
> followed with the suggested procedures. However, the problem appeared when
> I try to look for the alignment mark, after I have spin coated and prebaked
> the second layer of SU-8, it is difficult to locate the first layer exposed
> features.
>
> First layer thickness : 3.7um
> Second layer thickness : 17 - 20um
>
> I found that it is extremely difficult to locate the first layer pattern
> under the microscope after I have coated the second layer, despite it can
> be seen be naked eye.... Sometimes if there are some defect or bump in the
> 2nd layer above the alignment mark, then it can be seen clearly. However,
> it  is a random process and will affect my pattern. Are there any ways to
> improve the visiblity of the alignment mark after I have coated the 2nd
> layer? Thanks.
>
> Regards,
>
> Bill
>
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