Dear Pousali Ghosh,

You can use some tools similar to a doctor blade coating technique to coat your well structure substrates.

It could be a bar coating tool. Alternatively you could try a dip-coating.

The two main factors that define film thickness are the spin speed and the viscosity of the solution. Other factors considered include spin time, solution density, solvent evaporation rate, and surface wettability.

Hello Dr. Alagealy,

I am quite certain that the film thickness is just right, else the structures wouldn't form in the first place. My concern lies in having a complete coverage of the polymer solution on this 3x3 mm substrate having a thickness of 100 nm.

Hello Dr. Wang,

Thank you for your response. Our polymer solution(coating material) is way too dilute in order to coat the wafers using these alternative procedures. I appreciate your help.

Thank you,

Dear Pousali Ghosh ,

I would go empirical in your case.

You need to prepare two other thicknesses of the substrate wafer. and repeat the experiment to see if what you see is reproducible.

You can inspect the surface of the substrate directly before the coating.

You may have difference in the surface morphology.

You can also make a precoating with other material which is known with good surface property for spin on coating of your polymer.

You can use a second spin on after the first trial.

Note: The moisture in your laboratory may have been changed with time.

Please start with the last factor?

Best wishes