Gate oxide damage: Testing approaches and methodologies

The main types of gate oxide damage measurement techniques are examined and compared, leading to a selection of "application-specific" damage measurem ent techniques. Each technique has strengths and weaknesses, so no single m easurement can completely characterize damage. Instead, a combination of me asurement approaches is needed, each one targeted to provide a piece of the damage puzzle. It is helpful to understand the different damage mechanisms when selecting a measurement technique, so a survey of mechanisms is given . Damage proceeds by either direct exposure of the gate oxide (through ion bombardment or ultraviolet radiation) or by indirect exposure (by charging from a nonuniform. plasma or from the presence-of high aspect ratio structu res on the wafer). The relative importance of each mechanism depends on pro cess technology and other factors. The most useful combination of damage me asurement techniques includes surface potential measurement, electrically e rasable read-only memory transistors, direct measurement of charging, anten na transistors, and passive voltage contrast. Damage measurements should be calibrated to device performance parameters such as yield or reliability. (C) 1999 American Vacuum Society. [S0734-2101(99)13404-3].