Spin coating is one possibility

How about masking and spin coating?

One can try this. Take a Si wafer, cover one half with a aluminum foil and tape exactly in the center. Heat the Silicon substrate from 100-200C (if an alcoholic/aqueous solution; can increase the temperature if needed) and use a atomizing nozzle (similar to spray pyrolysis) to spray the solution A on the open side. After the solution dries up to form a coating remove the foil and cover the other side (do not tape as it might damage the coating A). On the other side spray the solution B and let it dry to form a coating B. For uniform coating, spray the solutions in same number of passes.

Solutions should contain same stoichiometries of A and B compounds.

Dear

I think it is not possible because Si wafer is available in market are used in only one side which has finishing and the back side of wafer has not any finishing i.e. it is rough surface, so if you try to deposit on both side then the thickness will not be same and uniformity also vanish.

You could do photolithography and spin coating.

1. Protect half wafer with resist

2. Spin nanoparticles at speed needed for desired thickness.

3. Remove resist.

4. Protect other half wafer with resist (on top of nanoparticles).

5. Spin on solution at speed needed for desired thickness.

6. Remove resist.

Of course this method will only work if there is good adhesion between the nanoparticles and wafer, and that the resist won't affect your films.

The way that Nathanael Sieb explained is the classical one for making a number of different films beside each other on the same substrate. Cheers, Andrew

Nathanael's method would be a precise one but you did not write degree of precision you want to achieve. Cheaper technique would be to go with some kind of masking as Raghavendar suggested

Nathanael Sieb explained the procedure very well, but I suggest to use gelatin instead resist.

Gelatin can be removed easily with hot water from Si wafer, and from dried A film.

So, first gelatin layer, next, remove half of it, clean and dry the surface, spin coating A film on the top.

Next, remove half of A film coating, which is placed on gelatin, with hot water.

Next, spin coating gelatin on top of wafer (one half, Si wafer and second half, A film).

Remove half of gelatin coating with hot water (where B layer should be placed).

Spin coating with B layer, and remove rest half of B layer (with gelatin layer on the top of A layer) with hot water.

Gelatin definitely does not affect nanoparticle films and (with some additions) can be used

in photo-lithography. Large surface of gelatin can be solved in hot water, but during rather long time.

Here there is a problem, how to make a boundary between A and B films.

You can try spray coating or dip coating

You should be more specific.What the nature of the films? What do you intend to do further?

using hot water may effect the film if their is any tendency to reaction between them.I wish their are two methods

-electrochimical deposition with good masking on side B to prevent exposure to the solution, then good masking on side A and deposit the other film

-using PECVD which is the simplest one and doesn't need any masking, only the side adjacent to plasma will get deposition film. this depend on the material film and if it is possible to use PECVD to deposit it.

Ok, now probably the time to look at easy way of doing this :-)

1. Take your Si wafer;

2. Cover part of the wafer with another piece of wafer and hold it with Kapton tape;

3. Deposit your layer A;

4. Move that piece of wafer on top of your film A;

5. Deposit your film B on the area which is not covered with the piece of wafer;

6. Remove the piece of wafer and enjoy your two different films on the same Si wafer.

PS: you can make as many as you want different films on the same Si wafer and at the same time to enjoy your life :-)

Hi All. Just for information - a typical 300 mm Si wafer used in the semiconductor industry is double polished.

Concerning the question I guess it is difficult to give a good advice untill you really know what is intended. There are many ways to deposit films and as was pointed out the precision is not mentioned as well. I guess Jimmy has to be a bit more specific at least what deposition techniques he can use.

I personally like dip coating like Chaoyang Feng suggested : not that messy, rather good thickness control (I hope we are not talking down to nm here), and gives you a sharp border. Flip the sample upside down and here you have your two layers next to each other. Also suggested covering teqhniques should work here pretty well.

Cheers, Andriy

Yes,

You can paste adhesive tape on one of the wafer and dip it in solution A

After "A" is on the wafer, take the tape of and dip only the clean side of the wafer in solution B. It will cause some overlapping between A and B, but maybe it is good enough

One more idea:

Use photo lithography to expose different sides of the wafer to different solutions , that way you will get a cleaner interface between A and B

wow, thanks for all the suggestions. As I wrote above, these films will be prepared from nanoparticle solutions (in various solvents), therefore my head hurts thinking of any possible things that have gone wrong when I looked at the poor quality of the film. I will consider all the suggestions, and if I found a working one, I would let you all know.

The usage of material is important here too, although spraying is interesting, spraying NP can be less practical. So far I am leaning to either spin coating or some sort of spincoating+covering.

In the meantime, feel free to any further ideas. Thanks in advance to all commenters here.

Mainly the method would depend on what material you want to coat, solvent system and what thickness you want. However combination of covering with tape and dip or spin coating as other have suggested would be best. From experience using Teflon tape (inert to solvent) to cover one side then spin coat, take tape of and dip coat other side without disturbing the other side now.

Jimmy, another possible way would be depositing selective adhesion agents on top of Si. That would work if i) you have a native oxide layer on top of Si, ii) you can disperse your NP systems in two different types of solvents, such as water and chloroform. This technique will only require you to use masking before you deposit NPs and will result in far better quality large area NP films. You need to have two different types of adhesion agents, like perfluorooctyltrichlorosilane (or any other long alkyl chain silanes, for NPs dispersed in chloroform) and N1-(3-trimethoxysilylpropyl)diethylenetriamine (or a simpler shorter chain amine like APTES, for NPs dispersed in water, alcohol) and put them in two halves of your substrate. Clean the substrate, use any of the masking techniques you are comfortable with, and dip it in a