There are many methods for cleaning substrate materials. One method that many people use is to place the wafer in acetone and use ultrasonication for at least 15 minutes. Then, when the film is removed from the acetone, it should be IMMEDIATELY rinsed with ethanol and/or methanol and dried with a dry N2 gun, if possible. Compressed air can also be used for drying, but I think the N2 gun is better. When using this method, you must watch for residue left on the surface by the solvents - this can be an issue.

If you are using spin-coating, I would recommend "spin-cleaning." In this method, a few drops of a strong solvent (such as 2-methoxyethanol) are dropped onto the wafer using a syringe, and then the wafer is spun to remove the excess solvent and dried on a hot plate to remove any remaining organics. I like this method; however, make sure you are doing this in a fume hood as stronger solvents (like 2-methoxyethanol) are quite toxic.

There are many other methods out there, and the best one for you will depend on your deposition technique, materials, applications, etc.

Good luck!

There are many methods for cleaning substrate materials. One method that many people use is to place the wafer in acetone and use ultrasonication for at least 15 minutes. Then, when the film is removed from the acetone, it should be IMMEDIATELY rinsed with ethanol and/or methanol and dried with a dry N2 gun, if possible. Compressed air can also be used for drying, but I think the N2 gun is better. When using this method, you must watch for residue left on the surface by the solvents - this can be an issue.

If you are using spin-coating, I would recommend "spin-cleaning." In this method, a few drops of a strong solvent (such as 2-methoxyethanol) are dropped onto the wafer using a syringe, and then the wafer is spun to remove the excess solvent and dried on a hot plate to remove any remaining organics. I like this method; however, make sure you are doing this in a fume hood as stronger solvents (like 2-methoxyethanol) are quite toxic.

There are many other methods out there, and the best one for you will depend on your deposition technique, materials, applications, etc.

Good luck!

Dear Dr Rao, are you talking about loosely bound contaminants such as adsorbed carbon, nitrogen and oxygen from the ambient atmosphere? If cleaning in an ultrasonic bath using ethanol/acetone doesn't do the job, you might consider argon ion sputtering in a vacuum chamber prior to transferring your sample into the deposition chamber. This will erode the top layer, so it may or may not be possible depending on the thickness and quality of your gold/platinum coating, but it might be worth considering. Kind regards, Marco Wisse

With respect to Ar ion etching/sputtering it may be useful to anneal the sample after sputtering or to apply cicles of sputtering and subsequent annealing. In case that the Au or Pt coatings are very thin you can also think of tilting the sample (i.e. increasing the angle between surface normal and ion momentum) in order to reduce the transfer of momentum perpendicular to the surface.

Dear Dr. Weiss, Dr. Wisse, and Dr.Muller thanks for your reply.

i am using RF sputtering to deposit ceramic oxide thin films.

To improve adhesion i want to remove contaminants on the wafer..

thank you all once again..

UV-ozone cleaning is one of the most efficient method to remove any organic contaminant. It works perfectly on gold for thin film deposition.

In our lab. the gold wafers we usully clean them by diping 5 min into piranha solution [3:1 mixture of concentrated sulfuric acid (H2SO4) with hydrogen peroxide (H2O2)], then rinsing with ultrapure water and drying with a strem of N2.

The comments given by researchers...are marvelous. Nevertheless, we need to investigated the substrate that we use...cause different substrates will have different physical and chemical reaction. Example...the surface charge could be different for glass, silicon or titanium. Therefore, my advice is...understand your substrate before proceed to other manipulation....

Deposited thin films typically are best removed from solvent they were deposited initially. If you want the gold also removed use piranha then rinse copiously with water.

I use about 20 rinsings with ultrapure water, than 10% Nitric acid solution, sonication, rinsing with water...sonication, rinsing with water...then drying in oven or blown dry with N2 if urgently needed. The surface seem to work fine for any new deposition or surface chemical modification.

About the substrate:

Silicon water works fine with piranha solution

Glass or quartz: use piranha to a minimum, works better with 10% nitric. If you use piranha on glass, it will etch the surface and from 20 nm surface roughness you can easily get to 100 nm which in turn is a mess for ultrathin film deposition (such as LB films) or surface chemical attachment.

Thank you so much dear all for thought provoking suggestions...

Will ultrasonication remove an e beam evaporated Ni film of 50 nm on Si/SiO2 substrate

Dear Dr. Weiss, for cleaning other chemicals from the gold-coated Si wafer can I use your first described method? I mean the method that one can use by placing the wafer in acetone and use ultrasonication for at least 15 minutes. Then, the gold-coated Si wafer  should be IMMEDIATELY rinsed with ethanol and/or methanol and dried with a dry N2 gun. If I follow this method does it remove the gold thin electroplating from the Si wafer?

I prefer UV/Ozone (UVO) treatment. Commonly used for removing unwanted vapours that readily deposit on Au coated wafers when exposed to air. O2 plasma ashing works well but not effective as UVO treatment.

I would go for Oxygen plasma ashing

Do you want to remove gold and platinum contaminants or do you want to coat on gold and platinum and clean the surface of contaminants before?

Why people using Piranha solution ? Are there any other methods to clean Au surface ?

Cleaning substrates, is vital, the routes used including chemical, ultrasonic, reactive ion etching, etc. You need to know, what kind of interaction between your substrates with your working environment. If you used ambient condition, you know contamination of organic matters are possible. If you are using vacuum environment, contaminations are reduced, but still, we need to realize other things could happened, such as re-arrangement of atoms, or the chemisorption has occurred during sample preparation. So, it is not enough, if you just saying you are cleaning the substrate with piranha solution,...etc. More things need to be mentioned, before any conclusion can be made that your substrates are contaminated free.