Characteristics of inverted pyramidal microdischarge devices operating in CHF3 and CHF3/Ar for maskless microplasma etching

In the SPM-based microplasma etching system proposed in our previous work, the stable discharge performance of microplasma device in reactive gases is the foundation of the following maskless scanning etching. In order to realize microplasma etching of SiO₂ or Si₃N₄, CHF₃ or CHF₃/Ar mixtures is chosen as the operating gas. Although discharge characteristics of microcavity plasma devices in rare gases have been widely studied, the microdischarge characteristics in CHF₃ reactive gases have been rarely reported up to date. In this paper, the inverted pyramidal microdischarge devices are successfully fabricated with good quality. Experiment results show that the devices can discharge stably in CHF₃ and CHF₃/Ar mixtures under dc excitation. The voltages-current (V-I) curves of micrplasma devices in CHF₃ and CHF₃/Ar gas mixtures exhibit negative differential resistance in a classical hollow cathode discharge mode. The pd scaling values ( p and d are the CHF₃ gas pressure and characteristic dimension of the microdischarge devices, respectively) for minimum ignition voltage are observed about 0.4Pa m. The results of this paper verify the feasibility of microplasma maskless etching of SiO₂ or Si₃N₄ and lay a foundation for upcoming experiments of SiO₂ or Si₃N₄ maskless etching.