Enhancing Productivity for IC-substrate manufacturing by using a novel Copper Electrolyte for Semi Additive Plating

Abstract

The Semi Additive Process (SAP) has gained more attraction over the past years because it enables very fine lines and spaces for the production of IC-Substrates. When operating with lines and spaces (L/S) of $10/10 \mu \mathrm {m}$ and less the copper thickness variation is one of the critical parameters which has to be controlled within a tight range in order to avoid reliability problems in assembly or during the lifetime as described in several papers [1], [2]. The key process parameter here is called the copper thickness within-unit distribution (WUD) or copper thickness within-panel-distribution (WPD). Another important parameter is the current density used for the copper plating process. Higher current density operating range of an electrolyte results in in better productivity. But both parameters are usually influencing each other. The existing POR might operate at a current density at 1.5 A/dm2 but increasing the current density in order to improve the productivity means the copper thickness variation within the panel will increase. This is not beneficial for the quality of the product, as the market is looking for a tight control of the copper thickness variation on a IC substrate.Already in 2013 a SAP Electrolyte was introduced to the market which is established meanwhile as a POR at IC-substrate manufacturers. Now in 2017 an upgraded electrolyte was developed in order to overcome this conflict of productivity and copper thickness variation. The novel SAP Copper electrolyte was optimized in its formulation so that higher current densities may be applied while still keeping very good copper thickness within unit distribution (WUD) results. Continuity of innovation and invention as expected by Moore’s Law are needed to reduce cost and increase capability. Challenges like within-unit distribution become a critical factor for the subsequent processing steps.The technical paper will contain results of copper thickness and the copper thickness variation (WUD), microsection pictures, DOE Results, dimple results, filling performance and further data. The novel electrolyte shows capabilities to operate at > 3A/dm2 which brings almost an improvement of the productivity by a factor of 2! The new electrolyte also brings further improvement regarding the Cu thickness variation as tighter tolerances may be realized. This is important for the later process steps during package manufacturing. Other Parameters of the new electrolyte will be shown as well like ductility and copper crystal structures of the new electrolyte.