Integration of Electrografted Layers for the Metallization of Deep TSVs

Abstract

Electrografting (eG) is a molecular engineering technology delivering high-quality films for Through Silicon Vias (TSVs). It generates surface-initiated conformal films which are thin, continuous, adherent and uniform. It is a wet-process technique, operated in standard plating tools, and is used on (semi)-conductive surfaces. Chemical grafting (cG) is a similar technology, used to graft films on non-conductive surfaces. A wet deposition of insulator, barrier and copper seed layers inside deep TSVs using a combination of electrografting and chemical grafting techniques has already been demonstrated [1, 2]. Electrografting and chemical grafting formulations and processes have been developed and specifically tailored for TSV diameters ranging from 1 to 200 μm, covering a depth/diameter Aspect Ratio (AR) range from 2:1 to 20:1. Film thickness can be controlled to any value from 50nm to few microns, depending on the layer, with 5% 3ó in-wafer non-uniformity, providing a step coverage (bottom/top thickness ratio) value of up to 90%. Adhesion of all layers is measured using a 16-square scribe tape test method: all layers successfully pass the test. The presentation will focus on film properties and show how TSV formed using these layers meet all key process requirements such as conformality, uniformity, adhesion, reliability and industrial compatibility for cost-effective high volume manufacturing of TSV wafers. A comprehensive set of film properties and reliability data characterized on blanket and pattern 200-mm Si wafers will be discussed. Integration schemes of electrografted layers within current 3D packaging process flows will be presented.