Etching Rate Selectivity Improvement Using a Novel Anti-Reflective Coating with KrF Deep UV Photoresist

摘要

We reported a process improvement of etching rate selectivity using polymeric bottom anti-reflective coating (PARC) over KrF deep UV photoresist on the polysilicon, oxide and metal films. The improvement of etching rate selectivity of PARC to photoresist versus organic bottom anti-reflective coating to the DUV photoresist is greater than unity. The extinction index, k, varies nearly linearly with the refractive in dex, n. By optimizing the values of n and k and the thickness of PARC, we are able to minimize the intensity of reflected light from the substrate. Good conformity of film deposition performs like oxynitride inorganic ARC. The forming rate of PARC could be controlled to as low as 4.3A per second and with very good film uniformity of less than 5%. We then apply the new PARC on the polysilicon, oxide and metal films for etching rate selectivity studies. For polysilicon line, the PARC etching selectivity over photoresist has 140%～214% improvement with for line spacing from 0.28um to 1.95 μm. The etching rate selectivity improvement for polysilicon is increased with decreasing polysilicon line spacing. The maximum improvement of etching rate selectivity is for 0.28μm space and it is larger than 200%. For oxide film, the contact hole pattern is used for the etching rate selectivity comparison. The PARC etching selectivity over DUV photoresist has 164%～200% improvement for contact size from 0.3μm to 0.6μm. For Al-Cu metal film, the PARC has the excellent performance of the aforementioned substrates. The etching rate selectivity improvement is in the range of 452%～568% on the metal line spacing from 0.28μm to 1.8μm. For Al-Cu metal bottom anti-reflective coating etching, this is extremely important for 0.18μm process and beyond because this novel PARC can be used instead of using oxide hard mask method. Using the oxide film as a hard mask might have issue of removal if lower dielectric constant is required for superior device performance with lower RC delay. The new PARC can be removed as the normal organic bottom anti-reflective coating by using the same regular ashing tool.