In order for EUV plasma sources to become the next-generation lithographic (NGL) source, significant obstacles still need to be overcome. Improvements in conversion efficiency (CE), plasma stability, and component lifetimes are required. Although the final goal is to produce a suitable 13.5-nm light source, solving the full range of problems will require a more thorough understanding of the plasma than just the EUV optical emission. Because of the complex nature and extreme conditions produced in the EUV plasma sources, many different plasma diagnostics are needed to fully characterize these EUVL sources.
Although the development of EUVL light sources is a relatively recent endeavor, similar plasmas have been utilized for many years for other applications. LPPs have been used for applications ranging from laser drilling to x-ray lasers. DPPs have been investigated as potential nuclear fusion sources and also as x-ray sources. Consequently, suitable plasma diagnostics have been developed over many years for the study of these types of plasma sources.
This chapter will concentrate on plasma diagnostics not based on optical-emission measurements. Although measurements of the optical emissions from these plasmas provide a great deal of information, many of these techniques have been discussed previously in Chapter 27. Consequently, this chapter will concentrate mainly on diagnostics of emitted plasma debris and other basic plasma properties such as electron density and temperature.
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