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The energy transfer from a plasma to a surface always plays an important role in low pressure plasma material processing (deposition, etching, surface treatment...) [1, 2]. Three different types of plasma species interact with the surface: charge carriers, neutrals and photons [3]. The energy due to charged particles (mainly ions and electrons) represents a significant contribution, especially when the substrate is biased. The energy coming from neutrals can be divided into different contributions: gas conduction, metastable deexcitation, fast neutrals (sputtered atoms, charge transfer mechanisms,... ) and reactions at the surface (e.g. chemical etching...) In argon, for example, the energy due to neutrals is shared between gas conduction and metastable de-excitation since no reaction occurs at the surface. In reactive plasmas, the energy contribution of chemical reactions between radicals and substrate materials can be very high and has to be considered as well. From the results of conventional plasma diagnostics (knowledge of flux and energy carried by interacting species), it is possible to estimate the maximum energy that can be transferred to a surface through energy balances. But the true energy delivered during plasma/surface interaction is difficult to evaluate. Thus, it might be more accurate to perform direct measurements of the energy influx. Most of the techniques used until now only lead to indirect estimations (eg. time evolution of the substrate temperature) [3]. These methods only gives a posteriori values averaged over several minutes, although for most processes (especially time resolved ones) real time measurement of the energy flux would be of interest. To make direct heat flux measurements in plasma processes, we proposed to use a commercially available heat flux microsensor (HFM) [4]. This HFM is composed of hundreds of integrated micro thermocouples, which form a thin thermopile having a very good time resolution (<10 ms). In the following section, we present in details the diagnostic and the experimental setup we used to make measurements. Then, we will explain the method we used to calibrate it. The third section will describe the different contributions in the total energy transfer from a plasma to a surface. In the fourth section, measurements of the energy transfer from an inductively coupled plasma of argon to the HFM will be presented. Special diagnostics such as Langmuir probe and diode laser absorption have been used to evaluate the contribution of the different species (eg. charged particles, neutrals, metastables,...) in the total measured energy flux. In section five, we show an example of the evaluation of the energy flux due to chemical reactions between fluorine

A Heat Flux Microsensor for Direct Measurements in Plasma Surface Interactions