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Shrinking device geometry and differing material properties pose challenges for the gate etch process at 130 nm and below. A 300 mm hardmask (HM) WSix gate etch process is developed that achieves the desired WSix and poly profiles, good selectivity to the HM, and CD bias uniformity of < 3 nm (3ó). A CF4/Cl2/N2 chemistry main etch (ME) etches the Wsix layer to endpoint plus a certain over-etch percentage. The remaining poly film is etched with a HBr/Cl2/HeO2 chemistry soft-landing (SL) step until the poly layer starts to clear. Poly residue is removed using a HBr/HeO2/He over etch (OE). The eff Critical dimension (CD) bias uniformity of < 3 nm is commonly required for gate lengths of approximately 130 nm with a 1- to-1 line-to-space (LS) ratio. Yet as the LS ratio approaches 1, it becomes extremely difficult to minimize profile microloading between dense and isolated lines. Other challenges include HM selectivity, profile loading, selectivity to gate oxide, and CD bias uniformity.
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