You can use dot exposure. You can also use line exposure with large step size ex: 1 um, 2 um if that works for your pattern. Using line exposure to pattern dots/holes significantly reduces exposure time. In both cases, you need to do a dose test. To image, you can use SEM scanning electron microscopy: develop your sample then load again in the EBL system to observe. Hope this information helps.

Thanks a lot. I will try your suggestions.

Thanks again,

Salahuddin

Hi, as Devrim already say, I confirm that dot exposure mode is the best if you require good hole border shape: this because each single hole is written starting from his center and moving the beam in concentric manner. Just an addition: you can experience better results and less exposure duration if you take time to order the holes (I don't know which version of the software you are using, but in the GDS file editor should be the possibility to use CTRL+O in order to access to the order modality in wich every hole have a number on it. If not, eventually please ask to Raith helpdesk for software updates). The number represents the order of exposure: 1 is the first hole that is exposed; nearby holes should have sequential numbers and the beam should follow a regular pattern without jumps.

About the pattern, you can use also proximity correction to avoid overexposure of the central holes.

After developing you should be able to see the sample directly on SEM. If you have a profilometer or AFM you can check also the height of the holes and thus you can check if the resist is completely developed.

Hoping this information could be useful to you,

Vito

I would recommend you to go for a dose test with curved elements. I am not sure about getting circles with out enabling curved elements. Then deposit a thin metal ( say around 50 nm, Cr-Au or any metal available for you), do a lift-off. Remember the resist to metal thickness ratio for lift-off. I could succefully demonstrate a 100 nm Cr-Au with 400 nm thick PMMA.

Now you get an array of Metal circles, whcih can be seen via Optical Microscope, just for a quick look (works for even 100 nm patterns at 100x magnification with dark field mode). 

Go for a SEM to measure the dimensions. The advantage of doing lift-off is, you are sure about your developed patterns. If its not developed properly, you may not get a good lift-off. Direct imaging of resit (resist only, with out metal) in SEM, after development leads to charging and error in measurement.

Good Luck!

Hi Senthil,

Thanks a lot. I started trying direct imaging on resist and found it is not efficient as you suggested. One thing I would like to ask you just out of curiosity, does it make any difference which metal I deposit? Say, if I deposit Al instead of Au would it make much difference in case of SEM imaging?

Thanks again.

Salahuddin

Hi,

No issues. You can try with any metal. 

Good Luck!