Radiation Damage of SiO 2 /Si By Energetic Neutral Beam and Vjuv Photons
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RADIATION DAMAGE OF SiO /Si BY ENERGETIC NEUTRAL BEAM AND VJUV PHOTONS
Tatsumi Mizutani, Shigeru Nishimatsu and Takashi Yunogami Central Research Laboratory, Hitachi Ltd. Kokubunji, Tokyo 185, Japan
ABSTRACT To clarify the generation mechanism of radiation damage induced in SiO2 /Si by plasma processes, effects of three different beams, i.e., ions, neutrals and vacuum ultraviolet (VUV) photons have been evaluated independently. The radiation damage caused by these energetic bombardments has been measured by capacitance-voltage (C-V) Teasurements. These reveal that bombardments with a 250 eV Ne neutral beam generate + far less flat-band voltage shifts ( 4V R) than those with a Ne ion beam of equal kinetic energy. This c n be interpreted in terms of the differences in charge build-up and in hole production upon the incidence of these particles. VUV photons produced in the plasma are also responsible for large AVFB.
INTRODUCTION Plasma processes are now indispensable technologies in the current VLSI fabrication processes. Plasma etching can delineate extremely fine patterns down to deep submicron range by virtue of directional ion-assisted etching mechanism [1,2]. It has been applied successfully to almost every kind of microelectronics fabrication including VLSI's, magnetic bubble devices and surface acoustic wave devices. This technology, however, has a potential disadvantage since it utilizes glow discharge plasma which contains a lot of energetic particles generating radiation damage within solid state devices. These radiation damage will prohibit or at least limit the wide application of plasma processes. It is then needed to improve the current plasma process or to develop low damage surface processes. Among the many kinds of radiation damage we are particularly interested in charge-associated damage[3] and in vacuum ultraviolet (VUV) induced damage[4] since we believe that these would be fatal to thin insulators such as MOSFET's gate dielectrics and capacitor insulators. In order to understand the generation mechanism of the damage stated above, we constructed a beam-irradiation apparatus which can independently generate ion beams, neutral beams and VUV photons and we measured the corresponding radiation damage. Here we during demonstrate that the radiation damage induced in SiO plasma processes is mainly due to ionic charge and VUV Ihotons. Mat. Res. Soc. Symp. Proc. Vol. 128. 41989 Materials Research Society
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EXPERIMENTAL A. Generation of energetic particles from a plasma neutral beams and VUV photons were Low energy ion beams, The low energy produced from a magneto-microwave plasma [5]. ion beams were extracted through two multiaperture electrodes at 1. desired energies ranging from 100 to 500 eV as shown in Fig. Typicgl ion current densities were in the range of 0.1-0.3 beams were produced by charge exchange Neutral mA/cm . neutrals between extracted ions and background reactions Retarding Background gas pressures were 0.09-0.10 Pa. [6,7,8]. potentials were applied to the grids set up in front of t
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