Jung-Hyung Kim, Chang-Jin Kang, Joo-Tae Moon and Moon-Yong Lee

Semiconductor R & D center, Samsung Electronics
Kihueng, Yongin, Kyungki, Korea
helicon@samsung.co.kr

Characteristics of pulse modulated helicon wave plasma were studied. The rising time to get to the steady state of the plasma after turning on the source power was estimated by measurements of the ion saturation current and the optical emission intensity. The rising time for HBr, Cl, and Ar plasmas was 3 ms, 5 ms, and 1 ms, respectively. The self bias voltage induced on the wafer by rf bias of 300 kHz was directly measured with a Pt wafer, by high voltage probe. The self bias voltage induced on the wafer was strongly dependent on the plasma density. Even though the rf bias frequency of 300 kHz was less than the ion plasma frequency, the self bias voltage was induced due to the mobility difference between ion and electron. In the pulse mode, the weak plasma was sustained by the only rf bias power in the off period of the source power and the self bias was induced with a higher value than in the continuous mode. The resist erosion rate was higher in the pulse mode than in the continuous mode and proportional to the self bias voltage. The etchings were carried out in the modulation frequency range of 100 Hz ~ 20 kHz and the dependence of the etching characteristics on the modulation frequency was discussed, especially on the low modulation frequency.