半导体制备技术简介CH12.ppt

Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm Chapter 12Chemical Mechanical Polishing Objectives List applications of CMP Describe basic structure of a CMP system Describe slurries for oxide and metal CMP Describe oxide CMP process. Describe metal polishing process. Explain the post-CMP clean Overview Multi layer metal interconnection Planarization of dielectric layers Depth of focus require flat surface to achieve high resolution The rough dielectric surface can also cause problems in metallization Tungsten CMP Tungsten has been used to form metal plugs CVD tungsten fills contact/via holes and covers the whole wafer. Need to remove the bulk tungsten film from the surface Fluorine based plasma etchback processes Tungsten CMP replaced etchback Definition of Planarization Planarization is a process that removes the surface topologies, smoothes and flattens the surface The degree of planarization indicates the flatness and the smoothness of the surface Definition of Planarization Definition of Planarization Degrees of Planarity Definition of Planarity Planarization Smoothing and local planarization can be achieved by thermal flow or etchback Global planarization is required for the feature size smaller than 0.35 mm, which can only be achieved by CMP Other Planarization Methods Thermal flow Sputtering etchback Photoresist etchback, Spin-on glass (SOG) etchback Thermal Flow Dielectric planarization Pre-metal dielectric High temperature, ~1000 ?C PSG or BPSG, become soft and start to flow due to the surface tension Smooth and local planarization As Deposited After Thermal Flow Etch Back Reflow temperature is too high for IMD can melt aluminum Other planarization method is needed for IMD Sputtering etch back and reactive etch back Etch Back Argon sputtering etchback chip off dielectric at corner of the gap and taper the openings Subsequent CVD process easily fills the gap with a reasonable planarized surface Reactive ion etchback process with CF4/O2 c