High speed through glass via manufacturing technology for interposer

Abstract

Silicon and organic materials are largely accepted as substrates for interposer. Glass outperforms the current interposer materials in a number of properties such as mechanical strength, low loss and chemical resistance. In addition it offers the potential of being a low cost but high density substrate material. As this is recognized glass is an emerging material for interposer application. While metallization is widely solved, via formation is still one of main drawbacks of glass interposers. Current glass drilling technologies lack either in speed, minimal diameter or quality for interposer application. In this paper a new high speed Through-Glass-Via (TGV) manufacturing process is presented. The new process is based on a laser induced chemical etching of the glass substrate. Laser induced glass etching technologies are known in the art. Using ultra short laser pulses a permanent modification of the glass is generated which triggers an anisotropic etching. In contrast to the state of the art, the presented process generates a modification from one surface of the glass substrate to the other with one shot only. Therefore the technology enables structuring on the fly. The speed of the on the fly process only depends on the dynamics of the base machine. Structuring speeds of around 5000 TGV/s can be achieved. The process works with standard glasses used for interposer. It does not depend on a special glass additive or additional thermal treatments of the glass before etching. Results are shown for glass thicknesses between 50 μm and 200 μm. Depending on the length of the etching step TGV diameter between 10 μm and 50 μm can be achieved. The TGVs have a small taper of below 5°.