Plasma characterization and correlation with the etch rate and via sidewall angle in a deep reactive ion etch system using Langmuir probe and optical emission spectroscopy.

摘要

In this study, the plasma parameters were investigated in an Ar/SF 6 plasma in a deep reactive ion etching system. The dilution effects of Ar and SF6 plasma were studied by using a Langmuir probe. The plasma parameters were investigated in the modified Bosch process using a Langmuir probe and optical emission spectroscopy.;When Ar flow rate was increased, the average electron temperature decreased while the electron density increased, as expected. In a marked contrast, the average electron temperature increased with the increase in SF6 flow rate This result was due to the attachment of low energy electrons. In addition, the increase of SF6 flow rate in an Ar plasma resulted in the decrease of the average electron temperature and reached a minimum value of 3.25 eV when the SF6 content was approximately 20%. On further increasing the flow rate, the average electron energy increased and was attributed to the variation of the negative ion density, which is consistent with the literature.;Moreover, the plasma parameters such as electron density, ion density, average electron energy, electron energy distribution function, argon and fluorine emission intensity were investigated using a Langmuir probe and optical emission spectroscopy. The data were obtained by varying coil power, pressure, and platen power in an Ar/SF6 plasma. The plasma was characterized, and the plasma parameters were correlated with etch rates and via sidewall angles from a previous study. The results showed that the etch rate correlated with all the plasma parameters except argon emission intensity. The etch rate increased with the increase in fluorine emission intensity, electron density, and ion density. In contrast, the etch rate decreased with the increase in the average electron energy and was due to collision processes. The argon emission exhibited a double-valued relation with the etch rate, which increased or decreased with emission intensity as a result of changes in power coupling efficiency. Moreover, the via sidewall angle did not show any correlation with the plasma parameters but instead correlated with the variation in the passivation cycle.