SRT 3

Controlled surface roughness

Main objectives are to develop knowledge on how to

• Modify the surface roughness of the wafer clamp while maintaining the overall flatness
• Modify the surface to minimize the van der Waals forces between the wafer and the wafer chuck without compromising chuck flatness
• Limit the wear on the wafer-chuck surface keeping production efficiency over the lifetime of the wafer-chuck under a 2000 wafers per day load

For this topic, a research method will be set up, aimed at explaining unwanted phenomena. The first focus is the deformation of the wafer. When the wafer is loaded on the wafer chuck, it is not able to completely relax due to sticking effects between the wafer and the wafer table. The determining sticking force is the van de Waals force between the chuck and wafer materials. To minimize this force, the surface contact area between wafer and chuck should be minimized. Conventional methods to roughen surfaces also compromise surface flatness. At first sight this seems easy; in practice this is a complicated task: the roughening should be uniform and be in the 5 to 10 nm range and should not comprise the chuck flatness (better then 100 nm).