Understanding and controlling high-density fluorocarbon plasmas for dielectric etching has been requiring innovative tools for plasma diagnostics. First, I present a novel and simple probe called plasma absorption probe (PAP), which enables one to measure the local electron density even when the probe surface is soiled with processing plasmas.@footnote 1@ The PAP is based on the resonant absorption of surface wave excited in a "cavity" at the probe head. Second, I describe a new technique for measuring electron energy distribution function (EEDF), i.e., RF-biased optical probe (RF-BOP).@footnote 2@ These new tools reveal a clear difference between high-density ICP and surface wave plasma in their EEDFs, radical and ionic compositions. In the latter half of presentation, I focus on plasma wall interactions. Steady-state radical density profiles near the wall suggests that radical production on surfaces often exceeds the production by electron-impact dissociation of parent molecule. To give an insight into the mechanism, the time/space resolved measurement of radical density is made in a source gas puffed out repeatedly. This experiment allows us to separate the gas phase from the surface processes in time space. Another approach of ion-beam surface experiment is challenged: an ion beam of fluorocarbon species is injected to a substrate at the energies from 10 to 200 eV, and the radicals produced on the surface are detected as a function of the ion energy. For example, SiF@sub 2@, CF@sub 2@ and CF with less CF@sub 3@ are observed desorbing from silicon surface bombarded with CF@sub 3@@super +@ ion. The relevant fluorocarbon chemistry will be discussed combining the beam study with the plasma experiment. @FootnoteText@ @footnote 1@H. Kokura, K. Nakamura, I. Ghanashev and H. Sugai, to be published in Jpn. J. Appl. Phys. @footnote 2@H. Toyoda et al., Extended Abstract of Int. Conf. Reactive Plasmas / GEC (Maui, 1998) p.27.