A new supermagnetron plasma etcher remarkably suited for high performance etching

Abstract

A new type of plasma etcher named a supermagnetron plasma etcher equipped with two parallel cathodes and an annular permanent magnet was developed. Using the supermagnetron plasma etcher, two kinds of experiments for the high rate etching of SiO2 and the highly uniform etching of photoresist and SiO2 under a stationary magnetic field were investigated. In the etchings of 6-in.-diam bare and patterned SiO2 wafers, high etch rates of 570 and 710 nm/min were obtained, respectively, using C2F6 gas of 7.5 mTorr. The etch selectivities of SiO2 to Si became as high as 6–15 using CHF3 gas at 3–6 mTorr. In a stationary magnetic field, the highly uniform etching of photoresist and SiO2 were also obtained using two types of supermagnetron plasma etchers. The etch uniformities depend on rf powers supplied to the upper and lower cathodes, gas pressure, and the position of a magnet, etc. High etch uniformities of ±5% were obtained without the rotation of a magnetic field in the etching of 3-in.-diam photoresist film and 6-in.-diam SiO2 at phase differences of rf voltages of about 180 and 250 degrees, respectively. Applying the CHF3 and O2 supermagnetron plasmas to submicron pattern etchings, SiO2 contact holes with tapered side walls and photoresist lines with vertical side walls were obtained, respectively.