Mass-analyzed CFx+ (x=1,2,3) ion beam study on selectivity of SiO2-to-SiN etching and a-C:F film deposition

Abstract

To clarify the origins of high selectivity in SiO2-to-SiN etching in fluorocarbon gas plasma, mass-analyzed CFx+ (x=1,2,3) ions with a definite kinetic energy of 250–2000eV were irradiated on SiN and SiO2 surfaces. Selectivity in SiO2-to-SiN etching varies greatly for different CFx+ ions. For CF3+ ions, the etch yield of SiN is almost the same as that of SiO2, causing poor selectivity. For CF+ ions, on the other hand, the etch yield of SiN is much smaller than that of SiO2. An amorphous fluorinated carbon (a-C:F) film grows without any neutral radicals on the SiN surface at energies below 1250eV and on the SiO2 surface at energies below 500eV due to CF+ ion irradiation. The difference in threshold energy of a-C:F film deposition causes high selectivity in SiO2-to-SiN etching. Slight etching of substrate films first takes place at the initial stage of deposition, then etching stops, and a homogeneous a-C:F film is grown. Accumulated carbons during the initial etching reaction modify the surface reaction layer, which causes drastic changes in reactions such as etching to “etch stop” and a-C:F film growth.

Effects of hydrogen ion irradiation on zinc oxide etching

“…The mass selected ion beam system [35][36][37][38][39][40][41][42][43][44] used in this study can inject mass-selected ions with a specified energy. A schematic diagram of the ion beam system is given in Fig.…”

Characteristics of silicon etching by silicon chloride ions

“…In this study, we use a multibeam system that can irradiate a sample surface with a mass selected ion beam under ultrahigh vacuum conditions. [9][10][11] The mass-selected ion beam system consists of three parts-an ion source, a mass selecting magnet, and a reaction chamber. Ions were generated by arc discharge in a Freeman-type ion source and were first accelerated up to 25 keV.…”

Correlation between dry etching resistance of Ta masks and the oxidation states of the surface oxide layers

“…The mass-selected ion beam system used in this study allows ions of specific mass to be injected into a sample surface with specified incident energy. [25][26][27][28][29][30][31][32] In this system, ions are generated in an ion source and specific ions such as Ar þ or CO þ relevant for this study are selected by the mass analyzing magnet. Ions thus extracted and selected are then injected into the surface of a sample set in the ultrahigh vacuum chamber, where the gas pressure is typically kept in the range of 10 À8 Pa. With a rotatable sample holder, the ion incident angle can be varied from 0 (i.e., normal incidence) to about 80 .…”