The ring focuses the plasma directly over the wafer to speed up the etching process and provide uniform plasma coverage.
Plasma cleaning technology provider Nordson March has rolled out a plasma confinement ring for wafer processing and wafer fan-out applications. The ring concentrates and focuses the plasma directly over the wafer to speed up the etching process, provide uniform plasma coverage and to isolate the plasma on the wafer itself rather than the area around or below it. Process temperatures can be kept low because the ring increases etch rate capability without the need to increase the electrode temperature or add bias to the chuck.
Using the confinement ring, there is a free conduction path between the upper and lower electrodes in the wafer region, but no conduction path in the adhesive tape and wafer frame area. The ring is made with an insulated, non-conductive material, while the aluminium-to-aluminium plasma conduction path is confined to the wafer area. There is a 2mm gap between the ring and the adhesive tape and wafer frame. Because there is no plasma generation or plasma to the bottom of the wafer and adhesive tape, undercutting and delaminating are minimised and there is no sputtering or adhesive tape deposition on the wafer surface.
The plasma confinement ring is available with Nordson March's Sphere series of plasma systems. Plasma applications include descum, ashing/photoresist/polymer stripping, dielectric etch, wafer bumping, organic contamination removal, and wafer destress.