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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.

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