Dear Iva,

I want to make silver nano disks (dia 100-200nm) on the glass substrate. After developing the structure using EBL on PMMA, my plan is to coat silver by using DC sputtering techniques and then lift off the PMMA using Acetone. But I am worried that sputtering could damage the PMMA while coating ,as it uses the plasma for deposition.  I have tried it, but I am not sure if PMMA has damaged or my lift off technique has some issue.

What is the thickness of PMMA in your case ? Which PMMA  are you using ?

Please check the thickness of the deposited metal. In lift off resist should be sufficiently thicker as compared to deposited layer (generally ~3 times). 

Why are you using PMMA? You could use a general purpose photoresist such as Shipley AZ1400, which easily stands sputtering temperatures around ~100°C and can be easily lift-off in acetone.

I have used Shipley AZ1xxx for years with RF and DC sputtering systems with very little problems, and usually no damage to photoresist due to deposition, provided that the sputtering parameters are OK.

Thank you Dr. Maggi for you suggestion. I have also used S18xx series PPR and got the lift-off without any problem.

However, in his earlier post Mr. Kumar has already mentioned that he want to make 'silver nano disks (dia 100-200nm) on the glass substrate'. I think that is why he is using PMMA. 

I overlooked that post. Many thanks for pointing that out.

However, are you sure it is possible to make nanostructures on glass substrates? Wouldn't quartz or silicon substrates be better than glass?

Another point. From my past experience I believe it could be quite difficult to use lift-off for defining such small areas. Maybe a shadowing technique could be better, and in that case one could try to use AZ/S18xx (or similar) photoresists which work very well with lift-off on sputtered films.

My 2 cents.

Thank you for you suggestions Dr.Maggi. I want to make this on glass substrate because i am going to use this structure for the plasmonic application. I want to illuminate the light from the bottom of  the glass substrate . and one more thing i want to ask that the photoresist which you mentioned earlier .Can I use it for EBL? as I am very new in this field I know only  that PMMA is used for EBL writing and want to know any other varient.

Dear Gourab.

I am using PMMA(996k) and after spin coating I am getting about 200 nm thickness of PMMA on glass. I deposited 50nm thick layer of silver after making the pattern on PMMA using Dc sputtering.

@Kumar: As far as I know you cannot use AZ/S18xx for EBL, only with uv exposure. PMMA is ok with EBL, but you get problems with lift-off.

@Sunil, I have tried PMMA A4 (~240 nm) and did lift-off (of structure size 400 nm) of Cr/Au (~75 nm) which was deposited by E-beam evaporation. The lift off was good.

I have used S1813 PPR to lift-off sputtering deposited material. It worked fine. I have not tried PMMA in sputtering and am not sure about the effect of plasma on PMMA. 

However, you can try this: use the same PMMA and same dose (for exposure) what you are using earlier and try to do the the lift-off of ~50 nm (your Ag thickness) of a metal deposited by other deposition process (thermal or E-beam). If you are getting the proper lift-off in this case, then you can conclude that plasma is changing the PMMA property and you can think of using an alternate deposition process of Ag. If not, then you can change the dose and developing time for e-beam lithography. If PMMA in the exposed region is not completely removed during developing, then metal in that region will also go away.