Specific Process Knowledge/Lithography/Coaters: Difference between revisions
| Line 258: | Line 258: | ||
===Backside rinse=== | ===Backside rinse=== | ||
Dependent on the spin speeds used in the various steps of the spin coating, resist may creep over the edge of the wafer and onto the backside. Also, some resists tend to leave fine strings of resist protruding from the edge of the wafer, or folded onto the backside, an effect sometimes referred to as "cotton candy". This resist will contaminate the | Dependent on the spin speeds used in the various steps of the spin coating, resist may creep over the edge of the wafer and onto the backside. Also, some resists tend to leave fine strings of resist protruding from the edge of the wafer, or folded onto the backside, an effect sometimes referred to as "cotton candy". This resist will contaminate the softbake hotplate, and thus subsequent wafers with resist. In a backside rinse step, solvent administered through a nozzle to the backside of the wafer while spinning at low or medium spin speed dissolves the resist and washes it away. After the rinse, a short spin at medium spin speed dries the wafer before the softbake. During the backside rinse solvent inevitably creeps onto the front side of the wafer. This effect may be used to dissolve and subsequently remove an edge-bead, but it may also leave the rim of the wafer exposed. As an alternative to backside rinse, a wafer which is left dirty on the backside by the spin coat process may be softbaked in proximity in order to protect the hotplate from contamination. This leaves front side coating intact, but also leaves the backside dirty. | ||
===Edge bead=== | ===Edge bead=== | ||