Secondary electron deposition mechanism of carbon contamination

Deposition of a carbonaceous contaminant layer on surfaces exposed to radiation exceeding 7–10 eV is ubiquitous in many fields of research. The mechanism of this deposition process is still debated. A scanning transmission x-ray microscope has been used to create and interrogate carbonaceous deposits with photon energies spanning the C 1s ionization edge. For equal fluence, the rate of carbon deposition is proportional to the x-ray absorption spectrum of the deposited material. The results are consistent with a deposition mechanism involving secondary electrons. Implications of this measurement with regard to future generations of high volume photolithography are discussed.