Abstract: A method of providing particle deposition on a semiconductor wafer or other surface first provides a flow of clean gas into a deposition chamber that purges the chamber prior to introduction of the wafer, and after introduction, continues the flow of clean gas. An aerosol is mixed into the clean gas flow for a desired length of time, so that as the combined flow passes through the deposition chamber particles are deposited on the wafer supported in the chamber. After the deposition has continued for either a desired particle count or a length of time, the flow of aerosol is discontinued, and a clean gas flow sheath is provided over the wafer as it is removed from the chamber. The apparatus carries out this method by providing a source of a clean gas, valves for controlling aerosol introduction into the clean gas, and a support for the wafer in the path of gas introduced into the chamber.