Presentation Information
[10p-E218-13]Dependence of Time Interval Between High-Voltage Application and Microwave Irradiation on Plasma Generation Probability in High-Pressure Microwave Excited Oxygen Plasma
〇(M2)Thiha Kyawswar1, Yusuke Nakano1, Yasunori Tanaka1, Tatsuo Ishijima1, Noriko Miura2, Shinichi Ikeda2, Shiro Hara2,4, Takeshi Aizawa3, Mitsunori Nogawa3, Yasuhiro Oonishi3, Hiroshi Sugiyama4, Fumito Imura4 (1.Kanazawa Univ., 2.AIST, 3.Yonekura MFG, 4.Hundred Semicon Inc)
Keywords:
Microwave plasma,Plasma generation probability,High voltage application
Precise photoresist removal using microwave-excited water plasma ashers requires instantaneous plasma ignition upon microwave irradiation. Since ignition depends on the availability of free electrons capable of avalanche multiplication, insufficient free electron density introduces ignition delay, compromising reliability under high-pressure conditions. A high-voltage unit (HVU, ±34 kV) was installed near the antenna to enhance plasma generation probability. This study systematically characterizes ignition delay time (td) as a function of the time interval (tint) between HVU termination and microwave irradiation onset. Experiments were conducted in a 2.44 GHz microwave plasma system at 200 W peak power (30% duty), with O2 at 20 sccm and ~6.8 kPa. Seven tint values (0.25–1.0 s) were tested over 100 trials each. Results show that increasing tint elevates average td and markedly reduces ignition probability, attributed to progressive free electron decay with time. These findings establish quantitative guidelines for HVU–microwave timing optimization.