Etch rate, etch rate uniformity, linewidth uniformity, and microloading in tungsten, molybdenum, and niobium plasma etching have been studied. Electrical linewidth data with typically 100–300 measured lines/wafer have been used. Relation between linewidth uniformity and etched depth uniformity (as measured by profilometer) has been explored. Effects of tungsten film deposition processes (oxygen contamination) have been studied. Tungsten etch rate maximum in SF6/O2 is at 85/15 ratio for the oxygen contaminated films, but higher oxygen percentage in SF6/O2 is required for maximum etch rate of pure films. Oxygen impurities in the tungsten film affect the etch rate but neither linewidth nor linewidth uniformity. In molybdenum etching in Cl2/O2 plasma the etched depth uniformity gives an overly pessimistic uniformity value even though linewidth uniformity is acceptable 12% (3σ). Addition of 3%–6% of CHF3 to Cl2/O2 is shown to change microloading characteristics and to improve linewidth uniformity. On 100 mm wafers, 6%–12% (3σ) linewidth uniformities were obtained for the different metals. Linewidth differences between isolated and array lines were 4%–8%.
|Journal||Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures|
|Publication status||Published - 1994|
|MoE publication type||A1 Journal article-refereed|