Abstract
It has been observed that the photoresist stripping rate in an oxygen plasma is slower for a full load of silcon wafers than it is for the center wafer of a three‐wafer array. For molecular oxygen flow rates of 500 cm3/min corresponding to reactor residence times of approximately 5 sec and substrate temperatures from 120° to 200°C, it is shown that 200 cm3/min of carbon monoxide or 15 cm3/min of water vapor reduces the atomic oxygen flow from about 33 cm3/min to about 15 cm3/min and reduces the stripping rate also by about a factor of two. If water vapor is added to a mixture of molecular oxygen and 200 cm3/min of carbon monoxide or if carbon monoxide is added to a mixture of molecular oxygen and 15 cm3/min of water vapor, the atomic oxygen concentration is not appreciably changed. However, the photoresist stripping rates are reduced by a factor of 1.5–2.0. A model is proposed which explains some aspects of the results, and it is shown that the difference in strip times between the full boat and three‐wafer array is in most current instances a thermal effect.
Published Version
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