Can you add Cl2 to the recipe? In this case you could look at a Cl2 + O2 etch process.

O2 plasma is most often used to etch organic layers.

More importantly, can you please explain what your objective is? What are you planning to use the metal for? There may be a far simpler strategy to achieve the end result.

What exactly is the underlying layer? Preventing damage of this will likely be difficult, especially for thicker metal films. How thick does the metal layer need to be? Will you remove all of this metal layer or pattern it?

Metals will be very slow to etch using an oxygen plasma (see attached article). What plasma system are you using? Can you use an alternative etch recipe where you can tune the physical/chemical etch processes (e.g., SF6 + O2)? You state "except noble metals" - is there a reason for this?

Thank you Jules Lloyd Hammond , yes I have already read this article, but I wanted to hear about someone else's experience, since not everything, that is described in the articles can be made as easy as it is written.

No, I can't add no other gases to the etch processes.

Since the plasma system I use is quite simplified, because here is possible to etch only with one tipe of plasma: with oxygen or with argon plasma. I can tune only flow rate of the working gass, anode voltage and filament current.

The reason for not wanting to use noble metals is related to their high cost, which, in turn, will increase the cost of fabrication.

The metal layer will be aproximetly 100 nm thick and used as an intermediate layer between the polymer (bottom layer) and photoresist AZ (top layer). It will be removed after oxygen-plasma etching of the top layer - AZ photoresist (pattern).

But now I am a little concerned about the quality of the lower layer (polymer), i.e. will it not become rough after the oxygen-plasma etching of metal, in consequence of the fact that in the process of thermally deposited the metal can penetrate in the polymer layer. (I have recently checked, that in my plasma system oxygen plasma do not etched used polymers or etched them so negligibly that it cant be detected).

Hello Julija Pervenecka ,

I still don't understand the overall objective. What is the final "stack" of the completed device? And of this stack, which layers need to be patterned individually? Is the metal intended to protect the underlying polymer temporarily or do you plan to retain some of the metal (you state that the metal will be etched away with oxygen plasma, after another oxygen plasma etching of the AZ resist layer)? Again, what is the polymer layer and what is its thickness?

In my mind, it may make more sense to either try and pattern the metal layer via a lift-off process, or to explore a wet etch provided you can achieve suitable selectivity. Of course, it will depend on the nature of the underlying polymer and the crtical feature sizes.

You state that you plan to also etch the AZ photoresist using an oxygen plasma process... Is there a reason the PR layer cannot be patterned during the exposure/development stages? The etch rate of the AZ photoresist is likely to be MUCH higher than that of a metal. Using a PR as a soft mask for physical plasma etching (as opposed to chemical) of a metal is an unusual approach.

I should state that I find the concept of avoiding the use of a noble metal layer, due to cost of material, quite amusing. Surely the cost of steps associated with equipment, maintenance and human salary for oxygen plasma etching, deposition of metal layer, etc. for a more complicated process will be more substantial?

Jules Lloyd Hammond

Completed device will be the microstructe of the polymer (PMMA, PSU or PVK). The thickness of the polymer is approximately 300 nm. Through all these stages of etching layer by layer, the pattern which is lithographed in a photoresist should be transferred on the polymer.

After lithography will folows etching(?) of the metal that is not covered with the PR, then using selective wet etching or some other technique polymer which is not coated with the metal pattern, will be removed ... but to get the requred microstructure of the polymer device from the polymer need to be removed top layer of the metal. But if you say that etch rate of the AZ photoresist is MUCH higher than that of a metal. I'll try to use another etching metods and vary with the layers in a different a sequence. May be you could sugest something about lift-off process for remove the metal, or about wet etch. I will try to use other etching methods and vary with the layers in a slightly different sequence.

But what about metals? Which metals can be comparably fast and good etched with the oxygen plasma?