Peter K. Loewenhardt

Plasma Diagnostics: Use and Justification in an Industrial Environment

The importance of plasma diagnostics at semiconductor equipment manufacturers has increased steadily over the past decade. The design and procurement of advanced etching tools now require a full host of plasma diagnostics and modeling capability. Examples of these activities at a semiconductor equipment manufacturer will be given, with specifics of significant and useful results. Examples include the development and optimization of an inductive plasma source, trend analysis and hardware effects on ion energy distributions, and mass spectrometry influences on process development. Discussion will focus on plasma diagnostics for in-house development and proliferation in an environment with strong financial justification requirements.

The sensitivity of electron shading damage to electron temperature, electron density and the plasma-to-wafer electron energy threshold

The electron temperature, T/sub e/, is a well known critical parameter affecting electron shading damage (ESD). This parameter is considered important because the damaging part of the electron density comes from high energy tail of the electron energy distribution. As the size of the high energy tail is dependent upon T/sub e/, obtaining low T/sub e/ in plasma processing is considered an important approach to reducing ESD. Recent results in metal etching (Tokashiki et al., 1998) suggest that ESD not only depends on T/sub e/ as previously suspected but also that the electron density, n/sub e/, may play an important role. We introduce a new parameter, the electron energy threshold, and demonstrate that it may be as important as T/sub e/ or n/sub e/ in the mechanism for electron shading damage. This new parameter, E/sub th/, is the energy threshold for electrons to reach the wafer surface and is related to the plasma potential as well as the wafer DC bias. This threshold aspect of electron shading damage could explain why a particular class of recipes (high bias power/low source power) show improved damage performance in inductively coupled plasma (ICP) etching tools (Tokashiki et al, 1998; Tabara, 1997; Hashimoto et al., 1997; Karzhavin and Wu, 1998). In addition, we provide experimental evidence obtained on an Applied Materials DPS Metal Etch Centura which supports this explanation.