The In - Film Etching Barrier Layer Structure For Double Mosaic Etching Process Of Research

With the continuous development of the IC (Integrated Circuit) technology, copper interconnect has replaced the aluminum interconnect. Different from aluminum, copper cannot react with etching gas to produce volatile by-product. Then copper damascene process was developed, including single damascene and dual damascene process and the latter is more widely employed. This thesis studies the dual damascene etching process based on the application of in-film etching stop layer, including three important sections.Via etching process:Photo resist is used as the mask in via etching process. The most important point in this section is that via profile must be well controlled. For a deep via (～1.7um), no striation is allowed at the top of via. A slight bowing profile could be acceptable but need to be well controlled. Via bottom profile must be vertical (>87°) and etch needs to stop on bottom NDC layer.Photo resist etch back (PREB) process:After via etching process is finished, a layer of photo resist will be coated on wafer. Both wafer surface and via will be filled with photo resist. The difficulty of PREB step is to precisely control the amounts of the remaining photo resist within via.Trench etching process:This section is the most difficult one. Both oxide film (SiO2) and PR will be etched during trench etching process. The etching selectivity must be well designed, i.e., the top of PR plug in via must be lower than the in-film stop layer of SiN. After SiO2etching stops on SiN, PR strip begins. All the PR on wafer surface and within via must be fully stripped. The last step is to etch bottom NDC, DARC and SiN in the meanwhile. The etching selectivity between SiN, SiO2and PR of each step must be well controlled.The most important achievement of this study is that Via, PREB and Trench etching process recipe as well as the very large process window has been obtained, allowing the smooth development of55nm technology. Besides, a project research and development framework was systematically proposed, which will be a good reference for other process development.