Effects of silicon via profile on passivation and metallization in TSV interposers for 2.5D integration

• The PECVD SiO2 passivation of the TSV vias is insensitive to scalloping pattern.
• The metallization with sputtering is quite sensitive to via profile.
• Tapered vias can be formed by Bosch process combination with isotropic etching.
• The scallops have significantly a “shadow effect” on sputtering.
• The metallization of TSV vias depends on AR instead of dimension.

In this paper, the influences of profile factors on passivation and metallization in deep vias of Through Silicon Vias (TSV) interposer, such as taper angle, scallops and aspect ratio (AR), were investigated for 2.5D integration. The diameter of vias was scaled from 40 μm to 100 μm. Conventional Plasma Enhanced Chemical Vapor Deposition (PECVD) deposition and Physical Vapor Deposition (PVD) metallization processes were used. Slightly tapered vias was formed by Bosch process combination with isotropic etching. This investigation shows that the SiO2 passivation of the TSV vias with PECVD deposition is completely insensitive to the factors related to via profile. But the metallization with sputtering is quite sensitive to taper angle, scallops and AR. A good trade-off between passivation and metallization can be realized to fabricate the TSV interposer by controlling the taper angle in the range of 1–3°. The TSV vias with scalloping pattern is difficult to achieve the continuous and conductive metal layer. The continuous metal layer can be successfully achieved to realize the conductive interconnection with front-side multi-level metallization (MLM) layers in a maximal AR of ∼3 for tapered vias.

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