The Measurement And Analysis Of Capacitive Coupled Plasma Driven By Very High Frequency

In the modern semiconductor industry, cold plasma is commonly used in thin film deposition, etching and surface modification. In comparison with the inductively coupled plasma, the capacitive coupled plasma has a simple structure, so it is easy to generate large area plasma which is widely used in the semiconductor industry. Recently, capacitive coupled plasma driven by dual-frequency further expands its function, where the higher frequency is used to generate the plasma, while the lower to induce ions from the plasma to bombard the wafer. The independent control of ion flux and energy power greatly broadens the process window of this kind capacitively coupled plasma, and thus takes on a new future for the trench etching with ultra-fine feature size in semiconductor fabrications.In this thesis, the driving frequency in the concerned capacitively coupled plasma is generated from radio frequency signal generator, the desired radio frequency (RF) signal direct transmits to the RF match after magnified by RF power amplifier, the output of RF power from match box is connected to electrode, the driving frequency is ranged and adjusted continuously from 5MHz to 150MHz.We use high voltage probe, current probe and Langmuir probe techniques to measure the characteristics of capacitively coupled plasma driven by RF. We mainly focus on the relation of RF voltage vs. RF input power under the different driving frequency, the relation of RF current and Ar pressure and the influences of frequency and pressure on self-bias of the powered electrode.Frequencies of 60MHz and 13.56MHz are used to drive the capacitively coupled plasmas, the coupling between them are illustrated by the influences of their RF input powers on their self-bias of electrodes. The discharge characteristics driven by 60MHz and its electron behavior are investigated by using current and voltage probes and Langmuir probe diagnostics. The experimental results show that equivalent resistance increases while capacitance decreases with the increasing of input RF power. It is also shown that electron behavior in the plasma is not only related with RF input power but also with discharge pressure closely. Increasing pressure causes a transition of electron energy distribution function from Bi-Maxwellian type to Druyvesteyn type, with its transition pressure much less than that reported by others. This contributes to a great drop in efficiency of electron bounced resonance heating in CCP driven by 60MHz.