A Dual BARC method for Lithography and Etch for Dual Damascene with LowK

A new method using dual bottom anti-reflective coating (BARC) is described in this paper for reducing critical dimension (CD) variation across wafer and improving Dual Damascene (DD) profiles. Combined use of conformal and planarizing BARC together, is investigated for Low K intermetal dielectric. Schemes that involve coat of planarizing BARC before conformal BARC and the other with coat of conformal BARC before planarizing BARC are investigated. Amount of BARC fill in the via and the sequence of BARC coat were both found to influence fence generation around via boundary during a subsequent etch process. Dual BARC also showed better via corner protection and smaller faceting after trench etch. BARC etch time was found to influence the amount of fence generation and circular step formation after etch. Electrical test results showed significant improvements of via yield for the dual BARC process that used conformal BARC coat followed by planarizing BARC coat.