| Plasma etching is becoming an important part of the manufacturing process for ultra-large scale integrated circuits (ULSIs). Plasma processing is the only commercial technology that could make the mask pattern being faithfully transferred into the substrate. Plasma reactors are very important in plasma process. The reduction in ULSI feature size proposes higher and higher requirements on the plasma processing technology. There is a need to develop new type of plasma reactors. Thus, the dual-frequency capacitively coupled plasmas (DF-CCPs) driven with two different frequencies, were studied and hoped to be used in the microelectronic industry.In the DF-CCPs, it is expected that the ions energy is controlled by low frequency component while the ion flux by the high frequency. There are still a lot of problems need to be studied on the DF-CCPs, such as the mechanisms of discharge and etching. Using compensated Langmuir electrostatic probe, actinometrical optical emission spectroscopy and mass spectrometry, we investigated the characteristic and the control of discharge chemistry in DF-CCPs.(1) In Argon DF-CCPs driven with 60/13.56 MHz, the plasma characteristics was investigated using compensated Langmuir electrostatic probe. At the lower pressure (about 10 mTorr), it is possible to control the plasma density and the ion bombardment energy independently. That is, the high frequency (60 MHz) controls the plasma density and hence the ion flux while the low frequency component (13.56 MHz) controls the ions energy. At the pressure of 50 mTorr and higher, this independent control could not be achieved, because the low frequency power also affects the plasma characteristics, such as the electron energy probability functions (EEPFs), electron densities and electron temperatures. As the low-frequency power increases, the EEPF changes from Druyvesteyn-like to Maxwellian-like type at the pressure of 50 mTorr and higher, along with the drop in electron temperature and the rise in electron density. Compared with simulation results, this could be results of enhanced ionization by the low-frequency power and secondary electron emission.It can be seen from the variation of EEPF with the pressure that the stochastic heating is predominant in low pressure while the collision heating is predominant in high pressure. The distribution of plasma parameters showed that it was not uniform in radial position for some extent.(2) The discharge chemistry of CHF3 in 27/2, 60/2, 60/13.56 MHz DF-CCPs is studied with actinometrical optical emission spectroscopy. The effects of frequency and its power on the generation of reactive species were investigated. It is shown that the chosen of frequency is important in generation of reactive species. The reactive radicals and the density ratio of F/CF2 could be controlled by the 2 MHz rf power in 27/2 and 60/2 MHz DF-CCPs. This control could not be obtained in 60/13.56 MHz DF-CCP by adjusting the power of 13.56 MHz. This could be the result of the different EEPFs in different DF-CCPs. A change in EEPF could lead to radical changes in the plasma chemistry. The results show that the EEPFs in 27/2 MHz DF-CCP may be similar with that in 60/2 MHz DF-CCP, whereas may be quite different from that in 60/13.56 MHz DF-CCP.(3) The DF-CCPdischarge chemistry of CHF3 is also studied with mass spectrometry. It was shown that there are abundant HF radicals in CHF3 plasma. Moreover, the HF radicals are even more when the driven frequency and its power are higher.
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