Innovative Nitride Film Deposition on Copper Interconnects of MEMS Devices Using Plasma-Enhanced Chemical Vapor Deposition Techniques

Abstract

Advances in integrated circuit fabrication technology over the past two decades have resulted in integrated circuits with smaller device dimensions, larger area, and complexity. As the device size shrinks, process integration gets more complicated and interaction between the layers becomes very important. In this work, the silicon nitride layer is deposited on test wafers with different percentage of NH₃ to study the effect of NH₃ on film profile like step coverage and conformity. A stack of 5000 Å oxide was deposited on test wafers with low and H hydrogen nitride to study the effect of Cu diffusion and adhesion properties of nitride layer. The deposited wafers were etched to calculate the etch rate and etch rate dependence on hydrogen content. Furthermore, the low pressure CVD (LPCVD) process is used to deposit the nitride layer, and characteristics of low nitride with LPCVD layers are done using SEM analysis. Low H nitride developed in this work gives excellent copper diffusion resistance. Low H nitride gives good adhesion to the FSG layer. Low-H nitride film increases etch selectivity up to 30%. In addition, it also provides a larger process window for trench and via etching. In situ process developed in this work gives the highest productivity.