Hi everyone. I hope you won't mind reading such a long question post...
I am trying to sputter gold electrodes on glass substrate and I was stuck at the problem of photoresist SPR660 (for patterning) adhesion.The problem can somehow be easily fixed by replacing different types of glass, but I would like to know more cause it seems quite fundamental. I am new to nanofabrication so I hope you could give me some insights on this matter:
I have been using the glass substrates that remain in our lab's stock. They work pretty well, no matter how I pre-treat them (RCA, sulfuric clean or simply DIW rinsing), they could be patterned with fine feature and resolution. But when I used the glass substrates bought from elsewhere (even for display grade ones) with the same protocol, I couldn't obtain the good features as the previous one. I tried to fine-tune the experimental parameters, e.g. extension of bake time and reduction in developing time (from 1 min to 30s). They might be improved a bit, like the edges of PR become more straight, but still some PR in smaller feature size (i.e. 5-10 um) peeled off.
Please don't ask why I did not continue to use the "good" glass substrate, it was a very long story, haha. But one thing I could tell is that the appearances of the glass subs look different: the edges for the good one are white, while the others are green. After all these, I was told that the "good" glass substrate is called Corning Glass. But I could not find much info from the Internet about its data or material.
So here comes to my questions:
1. I could understand why the extension of baking time would help. But I don't understand why the reduction of developing time would help too. What will be the possible reasons?
2. How do the glass material or their parameters in material science would affect the adhesion of photoresist (including the processes that might take into account, like photolithography and priming?) What would you recommend me to consider when choosing the suitable type of glass substrate?
3. If you have heard of, what is the "magic" actually in Corning glass that makes it so suitable for the captioned process? Is there any clue from its quality/treatment?
4. What would contribute to the difference of colors in the edge of glass? From what I have searched, it seems to be related to the concentration of iron. Please let me know if there is any other parameters.
I apologize for making the post so long. But I would be very very grateful if you could answer me some of the questions.
Thank you so so much!
Dear Ada, there are many reasons that interfere adhesion, for my opinion most important to check local humidity because most resist are very sensitive, and apply adhesion primer treatment before resist application, for instance, hexamethyldisiloxane primer.
https://amolf.nl/wp-content/uploads/2016/09/datasheets_MCC_primer.pdf
http://www.microchemicals.com/technical_information/resist_adhesion.pdf
May be try XPS techique to recognize elemental composition of the different glasses surface. For problematic glasses try alkali-based cleaning (e.g. concentrated NH4OH) followed by oxygen plasma ashing treatment. Some organic residues can hardly affect the adhesion.
For Q4 if you mean the color of glass covered by resist, it is resist thickness variation related effect, doesn't connected with glass nonuniformity. Glasses usually have good uniformity.
Good luck!
Dear Ada,
I assume that the effect may be optical rather than chemical. May be such colored glass diffracts more light at the edges of the photo resist. i mean the light will be more scattered at the edges in case of colored glass. One can observe how much light coming out of the glass edges when illuminating specific resist windows in the two materials.
The other effect may be chemical etching of glass itself by the developer. This can be investigated by studying the effect of the developer on both types of glasses.
Best wishes
Ada, see if oxygen plasma process on your glass could do better job. Good luck!
Thank you for the answer, Vasil’evskii. I was doing both experiments with HMDS in controlled room, one type of glass subs work pretty well and the other one is not working the same - so I guess the humidity might not be the main reason.
I have also tried alkaline cleaning but still the results are not good, so if this is the way to prevent most of the organic residue contamination, the adhesion issue might be most likely due to the glass material/type then.
It's so great that you have suggested me the way to analyse the glass, I will try later soon. Hope it can tell me what's the clue inside the "good" subs.
Thanks for your suggestions, Abdelhalim. The problem really seems to come from the glass itself.
I don't quite understand the first method you mentioned. May I ask for a further explanation (Observation of light across the glass edges)? Thanks!
Dear Ada,
It is very nice from you to give some some feedback about the results of our proposals.
Many researchers do not respond on the commentors on their questions.
Any how, the glass plate has a face and side walls. If you made a photo resist window, and illuminated this window only, you may observe light coming from the sidewalls. If this happens means that the light in the window will be scattered at the edges pf the window. I hope this time i could describe the phenomenon well.
Best wishes
Hi , i have tried TI Prime before spin coating AZ5214E , i UV fused glass substrate,
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