Selective surface exposure, cleans, and conditioning of the germanium film in a Ge photodetector

A method, comprising:

• forming a first layer over a substrate, the first layer sensitive to a first chemistry;
• forming a second layer on the first layer, the second layer formed to a first thickness and the second layer not sensitive to the first chemistry;
• forming a third layer over the second layer, the third layer removable by the first chemistry;
• patterning the third layer to have an opening;
• etching a substantial thickness of the second layer through the opening, leaving a thin, unetched portion of the second layer on the first layer, the thin unetched portion having a second thickness;
• removing the third layer using the first chemistry, the thin, unetched portion of the second layer protecting the first layer from the first chemistry;
• removing the thin, unetched portion of the second layer using a second chemistry to which the first layer is not sensitive to provide an exposed first layer;
• and
• conditioning a surface of the exposed first layer with a third chemistry after removing the thin, unetched portion of the second layer, the conditioning to terminate the surface of the exposed first layer with primarily the same atomic termini.