Process integration issues for advanced contact etch of a .25 μm BiCMOS application in manufacturing

Abstract

The contact etch module for BiCMOS device is one of the most critical modules. The process window involves several steps, including insulator thickness and uniformity, photolithography, etch and post etch treatments used to make contact to the kont end devices. Due to the topography of the BiCMOS structure, the etch process requires high selectivity of oxide to nitride at 2O:land nitride to TiSi greater than 30:l. The highly polymerizing process requires chemicals such as C4F8 and CO. These chemicals have the tendency to cause etch stop if the process is not scrutinized frequently throughout ail steps. . After the etch, the post etch treatments are a critical component in removing the residues. Selecting the correct wet chemicals can improve the contact resistances significantly. This paper will examine the contact module process window for photolithography and etch and post etch treatments. It will illustrate how the yield was improved in a BiCMOS manufacturing environment.

Contact Etch Schemes at Advanced Logic Technology Nodes

“…CESL film has become thinner and thinner required by the continuously size-down pitch. High selectivity is required in the 2 nd etch step for contact holes landing on both gate and active area with different aspect ratio [2]. To balance contact open and salicide loss, CxFy will generate more polymer to achieve the high selectivity.…”