DEVELOPMENT AND PLASMA CHARACTERISTICS MEASUREMENT OF PLANAR-TYPE MAGNETIC NEUTRAL LOOP DISCHARGE ETCHER

A low-pressure and high-density plasma source, called a planar-type ma gnetic neutral loop discharge (NLD), has been developed for a single-w afer etching process, employing a pair of permanent magnet rings and a single-turn RF antenna on the quartz plate. First, the plasma charact eristics of planar-type NLD were compared with those of a planar-type inductively coupled plasma (ICP) using the prototype etcher with a lar ge magnetic neutral loop (MNL) of 230 mm diameter. The results of prob e measurements in Ar plasmas have revealed that a planar-type NLD can be sustained at low pressures of 0.1-10 mTorr with higher plasma densi ty and lower electron energy than a planar-type ICP. The depletion of high-energy electrons in NLD was revealed by the direct measurement of electron energy distribution function (EEDF) and optical emission spe ctroscopy. Next, for the purpose of uniform and large-diameter NLD gen eration, effects of magnetic field strength and the gap between an ant enna and a wafer stage on the plasma uniformity have been investigated . By reducing the magnetic field strength that suppresses plasma diffu sion, an ion current uniformity within +/-2.5% and a high ion current density of 13 mA/cm(2) was obtained over a 240 mm diameter in the down stream Ar plasma. As for C4F8 + 90% Ar plasmas, preferable gas phase c hemistry of ion and neutral species for highly selective SiO2/Si etchi ng was attained due to relatively low electron energy, and a uniformit y within +/-2% was also achieved over a diameter of 240 mm.