A Novel Deep Hole Etching in NLD Plasma Low GWP Gases
As for etching of quartz or glass, CF<sub>4</sub> and C<sub>3</sub>F<sub>8</sub> and C<sub>4</sub>F<sub>8</sub> are mainly used. And, much SF<sub>6</sub> gas is used for etching of silicon. The case that uses together a C<sub>4</sub>F<sub>8</sub>-CVD method is also in sidewall protection film formation. However, these gases have a very large GWP. Since a MEMS market becomes larger in the future, the gas used by DRIE needs the reduction in GWP. This research is developing quartz etching technology, and succeeded in etching of the GWP free etching of Pyrex glass via using C<sub>3</sub>F<sub>7</sub>I. Furthermore, the method of performing anisotropic deep silicon etching by introducing a sputtering system into DRIE technology was invented, and C<sub>4</sub>F<sub>8</sub> free etching anisotropic etching was also successful. Therefore, the NLD etching in the MEMS field is very useful equipment, which can realize drastic GWP reduction and can propose highly efficient etching technology.
Magnetically neutral loop discharged plasma sources and system
The magnetically neutral loop discharged (NLD) plasma was applied first for a processing use with a machine composed of three steady current coils and an alternating induction coil. This demonstrated the NLD plasma is much more useful than the inductive coupling plasma for Si/SiO2 etching processes using Ar, C3F8, C4F8, and H2 gases. A remarkable feature of the NLD plasma method is that a high density plasma with a doughnut-shaped distribution in any size on both radii of the major and minor axes can be generated at any distance apart from wafer. Second, the NLD high density plasma is generated at a rather low gas pressure range of 10−2 Pa with the characteristic that thermalization of the electrons is easier when the stronger alternating induction power is supplied. Sufficiently high etching rates with high selectivity were realized in a uniform manner by control of the characteristics on the NLD plasma. Furthermore, anisotropic etching was also achieved. The NLD is based on an unusual mechanism of power...
Collisionless Heating of Electrons by Meandering Chaos and Its Application to a Low-Pressure Plasma Source
Near a magnetic neutral line, where the magnetic field vanishes, the adiabatic invariants of charged particle motion are destroyed, and hence the number of degrees of freedom increases. When a radio-frequency electric field is applied to the system, the particle motion becomes strongly chaotic. This effect can be used to produce heat in a plasma in the absence of any collisional process. The kinetic entropy of an electron orbit increases very rapidly by the mixing effect. The velocity distribution is approximated by a Gaussian function, so the thermodynamic entropy production can also be estimated. This collisionless heating mechanism enables high-efficiency plasma production at a low gas pressure.