Fine pitch RDL patterning characterization

Abstract

Lithography is a key enabling technology for semiconductor devices and circuits. The CMOS scaling continues to drive lithography to sub-10 nanometers resolution. The challenges of advanced wafer level packaging (WLP) are very different from CMOS technology. Generally, advanced WLP process requires not only good critical dimension control and nearly 90 degree vertical resist profile, but also requires scum free after photoresist development, good resist adhesion during electroplating and residual free resist stripping performance. In this paper we studied a new Redistribution layers (RDL) process based on 2um thickness chemical amplified resist (CAR) to resolve 1um post lithography critical dimension (CD) design. The performance comparison between our existing in house 2um thickness naphthoquinonediazide (NQD) and CAR photoresist were based on critical dimension uniformity (CDU) and Copper (Cu) electroplating performance. The final results were promising for printing RDL at 1um critical dimension (CD) and thickness with integrated solution for advanced WLP.