Ultraviolet Photoelectron Spectroscopy, Any data for polymers?

Was wondering if there was any data from anywhere on ultraviolet photoelectron spectroscopy (UPS) for polymeric materials and specifically photoresists. It seems this can be used to study chemical changes induced by process.

Thanks in advance.

Here is one paper you can check out: http://mat.chem.nagoya-u.ac.jp/info/newpub...st/1998/257.pdf

J. Appl. Phys. vol. 83, 4292-4298 (1998).

Hope it is useful.

Thanks for the link/reference. I hope to find more articles such as above.

Rgds

When doing the spectroscopy, it is important to select a light source so that you get adequate energy scanning above the ionization potential. Polymers have ionization potentials of ~ 8eV, so as long as you are using a wavelength sufficiently shorter than 155 nm (which corresponds to 8 eV energy) you should be able to get a decent spectrum.

The photoelectron fog has always been a problem for insulating samples.

If lithographers had known anything about UPS, they wouldn't be backing EUV or any NGL using ionizing radiation. So we have lots of ignorant lithographers.

There could also be a lot of denial going on.

Fortunately there is immersion lithography using non-ionizing radiation (I guess ArF doesn't ionize!) in the near-term. Then afterwards you have other options like imprint and near-field contact lithography, or direct deposition.

Up until now, the electron fog was mostly known to electron-beam lithographers, and consisted of backscattered and reflected as well as secondary electrons. Similarly, photoelectron emission was well-known to X-ray lithographers. Why this knowledge was not passed on to EUV research is not known. But this is a real effect with lots of surface potential data available in the literature.

XPS seems like a more widely used technique than UPS, but is less sensitive to lower binding energies.

One should wonder where those secondary electrons go after EUV bombardment...

The EUV absorption cross section is larger for inner electrons, in which case an inner electron should be kicked out, followed by a second one (the Auger one). If a valence electron is removed directly, it will have a higher kinetic energy. These removed electrons can leave the sample or scatter and produce more electrons ("secondary electrons" or "secondaries"). These secondaries can also scatter and produce more electrons or leave the surface.

The surface potential in this case will depend totally on the number of electrons that exit the surface. If the sample is insulating, it will be impossible to expect to balance the charge except by having electrons re-enter the surface. This is not a reliable mechanism either; a flood e-gun is usually used to achieve the same end.

EUV has energy of 92.5 eV. Carbon has ionization potential of ~11 eV. So we can estimate ~ 80 eV electrons released from EUV bombardment of Carbon.

Ironically, such electrons are involved in the process of EUV multilayer contamination.

Actually, I am not so sure about this statement.

I am reading a paper from the 1998 IEEE Conference on Conduction and Breakdown in Solid Dielectrics.

There is a paper titled "Electronic Levels in Insulating Polymers Estimated by XPS and UPS" by A. Kawamoto, Y. Suzuoki, T. Ikejiri, T. Mitzutani, and M. Ieda. Four polymers were tested: PVP (Poly-2-vinyl pyridine-co-styrene), PVK (Poly-N-vinylcarbazole), PMMA (polymethyl-methacrylate) and PS (polystyrene).

All of them ionized via photoelectric emission below 6 eV during UPS in air. ArF is 6.4 eV. I don't think the released photoelectrons are much more than 1 eV in energy.

Looks like you got your reference !

Wow, if this is true for ArF photoresists as well (possibly so if methacrylate-based), that is definitely something new I learned today . This is the stuff that should be talked about at lithography conferences, but at all the ones I've been to, it's never been mentioned.

Still, it seems the photoelectrons will not be lithographically significant (too low in energy to re-expose the photoresist). Also, it looks like they won't go far before hitting the immersion medium.

UPS is an effective tool to study photodegradation of polymer compounds.

Some pesticide compounds apparently are also photodegraded by ArF photoionization: http://www.ch.ic.ac.uk/ectoc/echet98/pub/108/index.htm

One example is UV photon iduced electric field poling of a ferroelectric molecule used as a voltage charged refractive molecule could have hundreds of applications.

Also, we will start to see polymers, ceramics, carbon, and even metals take on new properties as we explore the possibility of using combinations of heat, vibration, light, electric curent, magnetic fields, and electric fields to influence nano molecular geometry structures.

For you holoman, in case you are interested:

http://www.ssl.physics.ncsu.edu/publicatio...r-rodriguez.ppt

"Direct observation and characterization of domain-patterned ferroelectrics by UV Photo-Electron Emission Microscopy"

Woochul Yang, Brian J. Rodriguez, Alexei Gruverman, and Robert J. Nemanich
Department of Physics, and Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-8202