SELF-LIMITED LAYER-BY-LAYER ETCHING OF SI BY ALTERNATED CHLORINE ADSORPTION AND AR+ ION IRRADIATION

We report the observation of self-limited layer-by-layer etching of Si by alternated chlorine adsorption and low energy Ar+ ion irradiation using an ultraclean electron-cyclotron-resonance plasma apparatus. The etch rate per cycle increased with the chlorine supplying time and sa turated to a constant value of about 1/2 atomic layer per cycle for Si (100) and 1/3 for Si(lll), which was independent of the chlorine parti al pressure in the range of 1.3-6.7 mPa. These results indicate that e tching was determined by self-limited adsorption of chlorine. Moreover , the chlorine adsorption rate was found to be described by a Langmuir -type equation with an adsorption rate constant k=83 and 110 (Pa s)(-1 ) for Si(100) and Si(111), respectively.