Dependence of thin-oxide films quality on surface microroughness

The effects of silicon surface microroughness on electrical properties of thin-oxide films, such as breakdown electric field intensity (E/sub BD/) and time-dependent dielectric breakdown (Q/sub BD/), have been studied, where the microroughnesses of silicon and silicon dioxide surfaces are evaluated by the scanning tunneling microscope (STM) and the atomic force microscope (AFM), respectively. An increase of surface microroughness has been confirmed to severely degrade the E/sub BD/ and Q/sub BD/ characteristics of thin-oxide films with thicknesses of 8-10 nm and to simultaneously decrease channel electron mobility. An increase of surface microroughness has been demonstrated to originate mainly from wet chemical cleaning processing based on the RCA cleaning concept, particularly the ammonium-hydrogen-peroxide cleaning step. In order to keep the surface microroughness at an initial level, the content ratio of NH/sub 4/OH/H/sub 2/O/sub 2//H/sub 2/O solution has been set at 0.05:1:5 and the room-temperature DI water rinsing has been introduced right after the NH/sub 4/OH/H/sub 2/O/sub 2//H/sub 2/O cleaning step in conventional RCA cleaning procedure.<
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