Selective functionalization of silicon nitride with a water-soluble etch-resistant polymer

Abstract

In semiconductor device manufacturing, it is typically necessary to process devices incorporating both Si3N4 and SiO2 with etching solutions. However, several commercially ubiquitous etchants affect both these dielectrics simultaneously; therefore, high-cost protection solutions or highly selective etchants are required to mitigate this issue. To address this problem, this study examined a simple method of selectively functionalizing Si3N4 with a protective polymer film, thus reducing its etching rate relative to that of SiO2. Several polymers were screened for their selectivity and resistance to buffered hydrofluoric acid (BHF) etching. A water-soluble cellulose-based polymer, DC01, was subsequently found to reduce the etching of Si3N4 selectively, owing to strong interactions between the polymer and underlying bulk material once the native oxide is removed. In addition, X-ray photoelectron spectroscopy results confirmed the retention of DC01 on this substrate after etching, while quartz crystal microbalance measurements indicated the stability of the polymer film after multiple rounds of rinsing with aqueous surfactant solutions. Thus, this polymer has considerable potential as an additive for the simplification of Si3N4/SiO2 composite processing.