Hybrid DHF and N2 jet spray cleaning for silicon nitride and metal layer DRAM patterns

Abstract

Cleaning different layers during dynamic random-access memory (DRAM) pattern making is critical to the re-moval of particles. Physical cleaning techniques such as deionized water (DIW) with N2spray and hybridcleaning using an ammonia and hydrogen peroxide mixture (APM) with N2spray have been employed. However,with the continuing shrinkage of device structures for the next generation technology nodes existing cleaningsystems could be problematic. DIW spray–based physical cleaning could cause pattern damage, whereas an APM-based hybrid system presents the threats of low particle removal efficiency (PRE) for silicon nitride (SiN) sur-faces and corrosion of metal layers. In this study, a hybrid DHF spray–cleaning process based on dilute hy-drofluoric acid (DHF) and N2was tested on a 40 nm scale DRAM pattern, and its cleaning performance ondifferent patterns of SiN and metal layers such as TiN and tungsten (W) was analyzed. In optimized conditions, aPRE of > 90% was achieved using DHF spray cleaning. The dominant mechanism responsible for the higher PREon SiN and metal layers was found to be slight surface etching. However, surface roughness did not change evenafter treatment with a DHF spray. Based on these observations, a DHF and N2jet spray system could be apromising method for particle removal from SiN and metalfilms during DRAM pattern-making.