Pure Appl. Chem., 2002, Vol. 74, No. 3, pp. 381-395
Study for plasma etching of dielectric film in semiconductor device manufacturing. Review of ASET research project
Abstract: Conventional developments were conducted in a very empirical way, such as a trial and error with many speculations using qualitative data. This approach requires more and more resources and time for the development of future devices with a design rule below 100 nm in the system on a chip (SOC) era. It is necessary to establish a systematic methodology for process development and qualification. ASET Plasma Laboratory had been found to research a basis for the systematic development of the plasma etching technology. Fluorocarbon (CF) plasma for the etching of high-aspect-ratio contact holes in SiO2 was investigated intensively in the 5-year program that finished in March 2001. They introduced 5 plasma sources that can etch 0.1-mm contact holes on a 200-mm wafer in production, and state-of-the-art diagnostics tools for the plasma and etched surface. The SiO2 etch mechanism was revealed from the etch species generation to the reaction in a deep hole. The number of electron collisions to fluorocarbon gas molecule is proposed as an important parameter to control the gas dissociation and etch species flux to the surface. An etch reaction model was also proposed using the estimated-surface-reaction probability that is a function of ion energy and CF polymer thickness that reduces the net ion energy to the reaction layer. The CF polymer thickness was determined by a balance equation of generation term (radical fluxes) and loss terms (etching by ions, radicals, and out-flux oxygen from SiO2). A program was developed and successfully predicts the etch rates of Si-containing materials, including organic dielectrics. Requirements for the next-generation plasma etch tools are also discussed.