ELECTRICAL STUDIES OF THE REACTIONS BETWEEN ETHANOL VAPORS AND INVERSION MODE SI-THIN SIO2 STRUCTURES

Processes taking place in Si-thin SiO2 structures (oxide thickness 135 angstrom) after exposure to ethanol vapours have been investigated by measurements of the inversion channel I-V characteristics. It has bee n established that the changes in the Si-SiO2 structure under the acti on of ethanol vapours relax with time after their removing and the ext ent of relaxation depends on the drain voltage duration as well as on the time interval separation of the drain voltage pulses. The ID(t) de pendence obeys two exponents, reflecting the presence of two different processes (one of them being slower than the other one), characterize d with different time constants. They appear to be a unique function o f the ethanol vapour reaction with the oxide surface. It has been show n that the ethanol vapours action at certain drain voltage leads to th e introduction of defects in the Si-thin SiO2 structure. The defects a re a source of electrically active centres. The total value of these c harges originating after the interaction of ethanol vapours with the S iO2 surface is of the order of (1.5-1.7) x 10(11) cm-2. It is proposed that the surface oxide charge is mainly responsible for the ethanol v apours-introduced positive charge in the Si-SiO2 structure. The paper proposes some concepts for the interpretation of the results obtained. Adsorption of ethanol molecules, surface reaction and desorption of d ecomposition products are included.