Editing Photolithography (section)

=== Preparation ===
The wafer is initially heated to a temperature sufficient to drive off any moisture that may be present on the wafer surface; 150&nbsp;°C for ten minutes is sufficient. Wafers that have been in storage must be chemically cleaned to remove [[contamination]]. A [[liquid]] or [[gas]]eous "adhesion promoter", such as [[Bis(trimethylsilyl)amine|Bis(trimethylsilyl)amine ("hexamethyldisilazane", HMDS)]], is applied to promote adhesion of the photoresist to the wafer.  The surface layer of silicon dioxide on the wafer reacts with HMDS to form tri-methylated silicon-dioxide, a highly water repellent layer not unlike the layer of wax on a car's paint. This water repellent layer prevents the aqueous developer from penetrating between the photoresist layer and the wafer's surface, thus preventing so-called lifting of small photoresist structures in the (developing) pattern. In order to ensure the development of the image, it is best covered and placed over a hot plate and let it dry while stabilizing the temperature at 120&nbsp;°C.<ref>{{cite web | title=Semiconductor Lithography (Photolithography) - The Basic Process | url=http://www.lithoguru.com/scientist/lithobasics.html}}</ref>