September 19, 2012 - SPTS Technologies has introduced a low-temperature plasma-enhanced chemical vapor deposition (PECVD) system for via-reveal passivation in 3D IC packaging. The Delta fxP cluster system deposits dielectric layers onto bonded substrates at wafer temperatures below 200°C, with what the company claims is up to twice the throughput up competitors' systems.
Via reveal occurs after the through-silicon vias (TSV) are formed -- wafers are temporarily bonded face-down to a carrier and thinned from the backside to reveal the vias, which are then passivated (typically with a combination of silicon nitride and oxide) before final redistribution metallization. The adhesive used for temporary bonding, though, creates two challenges to PECVD passivation: passivation film properties have to accommodate temperatures >200°C to maintain the temporary bond integrity, and the bonding adhesive will outgas inside the PECVD vacuum chamber, affecting the film growth quality.
To solve these challenges, the Delta fxP cluster system incorporates "a number of hardware and process innovations" that achieve low-leakage current, high-breakdown voltage deposition of TEOS oxides and nitrides at a peak deposition temperature of <190°C, the company explains. Addressing the outgassing problem, for example: an integrated batch Multi-Wafer Degas (MWD) outgasses multiple wafers at the same time. The low-temperature limit of bonded wafers can require as little as 15min degas times for some adhesives -- but the MWD capability outgases multiple wafers at a time to achieve up to 1hr degas times without affecting system throughput.
"The combination of leading film properties and highest system throughput on bonded wafers addresses two of major obstacles in productionizing post-TSV packaging," stated Keith Buchanan, marketing manager for advanced deposition products.
PECVD via reveal. (Source: SPTS)