Method for reducing the microloading effect in a chemical vapor deposition reactor

摘要

A method is provided for reducing the microloading effect in a CVD process for depositing a film on a substrate. This method is particularly useful in a single-wafer CVD reactor. The microloading effect is reduced by identifying a growth-rate-limiting reactant; calculating a dilution factor (the ratio of the gas flow rate of the growth-rate-limiting reactant to the total gas flow rate in the reactor); and adjusting the film growth rate and/or the dilution factor to satisfy a numerical criterion for reducing the microloading effect. The criterion is satisfied when the film growth rate is reduced, or the dilution factor is increased, so that the dilution factor is equal to or greater than a quantity which includes the film growth rate as a factor. The film growth rate and dilution factor may be adjusted independently. The gap between the showerhead and the substrate in the CVD reactor may be adjusted to satisfy the numerical criterion. The gap may advantageously be reduced to less than 5 mm, preferably to about 100 mum. A gap in the range 50 mum-5 mm reduces a characteristic distance which is a factor in the above-mentioned quantity, so that the criterion becomes easier to meet.