Wafer-Level Packaging Plasma Treatment
As semiconductor device manufacturers further shrink the size and increase the reliability of packaged devices, plasma treatment is increasingly used for advanced applications during wafer level packaging. Nordson MARCH treatment systems are capable of handling multiple wafer sizes and high-throughput, automated processing.
Wafer Cleaning - Plasma cleaning has traditionally been applied to remove contamination generated during a process in the device fabrication at the wafer level, or generated during an upstream assembly process. In either case, cleaning the product to remove contamination such a fluorine, oxides or metals significantly enhances the yield, reliability and performance of the integrated circuit.
Descum for WLP - Photoresist residue sometimes remains after development, processing, and resist strip. Plasma treatment provides uniform removal of small quantities of resist over the entire surface of the wafer prior to further post processing.
Stripping & Etch for WLP - Dry plasma processing is an efficient method for bulk stripping and etching of materials including photoresist, oxides, nitrides, and dielectrics. Etch rates in excess of one micron per minute with uniformities greater than 95% can be achieved. Stripping and etching processes can be applied in wafer level packaging, MEMS manufacture and disk drive processing.
Wafer Pre-Treatment - Plasma processing removes contamination and oxidation for increased reliability and bonding yields. Plasma also micro-roughens the wafer passivation layer for improved adhesion between the wafer passivation layer and BCB.
BCB & UBM Adhesion - Plasma treatment alters the topography and wettability of the wafer's original passivation layer to promote adhesion. Polymers, such as benzocyclobutene (BCB) and UBM, are dispensed on the wafer and act as a dielectric for the redistribution layer. Plasma treatment alters the topography and wettability of the wafer's original passivation layer to promote adhesion.
Dielectric Patterning - Typical methods of forming the redistribution layer include patterning the dielectric redistribution material using typical photolithography methods. Plasma treatment is a viable alternative for dielectric patterning where typical wet processing methods can be avoided.
Via Cleaning for WLP - Small vias, formed in the wafer for stacked die applications, often have residue remaining as a result of the via-formation process. Optimized plasma configurations can effectively treat the vias without damaging the wafer surface.
Bump Adhesion - Plasma cleaning can improve bump adhesion and increase bump shear strength. Plasma cleaning of the wafer surface improves bump adhesion and has been demonstrated to increase bump shear strength dramatically. Bump materials include solder of varying compositions and gold studs.